Computer Science & Mathematics
http://www.mdpi.com/journal/computer-math
Latest open access articles published in Computer Science & Mathematics at http://www.mdpi.com/journal/computer-math<![CDATA[JRFM, Vol. 8, Pages 227-265: Dependency Relations among International Stock Market Indices]]>
http://www.mdpi.com/1911-8074/8/2/227
We develop networks of international stock market indices using information and correlation based measures. We use 83 stock market indices of a diversity of countries, as well as their single day lagged values, to probe the correlation and the flow of information from one stock index to another taking into account different operating hours. Additionally, we apply the formalism of partial correlations to build the dependency network of the data, and calculate the partial Transfer Entropy to quantify the indirect influence that indices have on one another. We find that Transfer Entropy is an effective way to quantify the flow of information between indices, and that a high degree of information flow between indices lagged by one day coincides to same day correlation between them.Journal of Risk and Financial Management2015-05-2982Article10.3390/jrfm80202272272651911-80742015-05-29doi: 10.3390/jrfm8020227Leonidas JuniorAsher MullokandovDror Kenett<![CDATA[Symmetry, Vol. 7, Pages 815-842: Cosmological Probes for Supersymmetry]]>
http://www.mdpi.com/2073-8994/7/2/815
The multi-parameter character of supersymmetric dark-matter models implies the combination of their experimental studies with astrophysical and cosmological probes. The physics of the early Universe provides nontrivial effects of non-equilibrium particles and primordial cosmological structures. Primordial black holes (PBHs) are a profound signature of such structures that may arise as a cosmological consequence of supersymmetric (SUSY) models. SUSY-based mechanisms of baryosynthesis can lead to the possibility of antimatter domains in a baryon asymmetric Universe. In the context of cosmoparticle physics, which studies the fundamental relationship of the micro- and macro-worlds, the development of SUSY illustrates the main principles of this approach, as the physical basis of the modern cosmology provides cross-disciplinary tests in physical and astronomical studies.Symmetry2015-05-2972Review10.3390/sym70208158158422073-89942015-05-29doi: 10.3390/sym7020815Maxim Khlopov<![CDATA[Electronics, Vol. 4, Pages 303-310: A Theoretical Study on the Operation Principle of Hybrid Solar Cells]]>
http://www.mdpi.com/2079-9292/4/2/303
In this work, the operation mechanism of hybrid solar cells is studied explicitly. The excitation, diffusion and dissociation of singlet and triplet excitons and charge transport of free charge carriers are studied and their corresponding rates are calculated for a flexible P3HT:SiNW hybrid solar cell. The rates are found to be faster for singlet than triplet excitons. Possible loss mechanisms in hybrid solar cells have also been highlighted.Electronics2015-05-2942Article10.3390/electronics40203033033102079-92922015-05-29doi: 10.3390/electronics4020303Monishka NarayanJai Singh<![CDATA[Symmetry, Vol. 7, Pages 788-814: Supersymmetry with Radiatively-Driven Naturalness: Implications for WIMP and Axion Searches]]>
http://www.mdpi.com/2073-8994/7/2/788
By insisting on naturalness in both the electroweak and quantum chromodynamics (QCD) sectors of the minimal supersymmetric standard model (MSSM), the portrait for dark matter production is seriously modified from the usual weakly interacting massive particle (WIMP) miracle picture. In supersymmetry (SUSY) models with radiatively-driven naturalness (radiative natural SUSY or radiative natural SUSY (RNS)) which include a Dine–Fischler–Srednicki–Zhitnitsky (DFSZ)-like solution to the strong charge-conjugation-parity (CP) and SUSY \(\mu\) problems, dark matter is expected to be an admixture of both axions and higgsino-like WIMPs. The WIMP/axion abundance calculation requires simultaneous solution of a set of coupled Boltzmann equations which describe quasi-stable axinos and saxions. In most of parameter space, axions make up the dominant contribution of dark matter although regions of WIMP dominance also occur. We show the allowed range of Peccei-Quinn (PQ) scale \(f_a\) and compare to the values expected to be probed by the axion dark matter search experiment (ADMX) axion detector in the near future. We also show WIMP detection rates, which are suppressed from usual expectations, because now WIMPs comprise only a fraction of the total dark matter. Nonetheless, ton-scale noble liquid detectors should be able to probe the entirety of RNS parameter space. Indirect WIMP detection rates are less propitious since they are reduced by the square of the depleted WIMP abundance.Symmetry2015-05-2872Article10.3390/sym70207887888142073-89942015-05-28doi: 10.3390/sym7020788Kyu BaeHoward BaerVernon BargerMichael SavoyHasan Serce<![CDATA[Symmetry, Vol. 7, Pages 774-787: Flexible Polyhedral Surfaces with Two Flat Poses]]>
http://www.mdpi.com/2073-8994/7/2/774
We present three types of polyhedral surfaces, which are continuously flexible and have not only an initial pose, where all faces are coplanar, but pass during their self-motion through another pose with coplanar faces (“flat pose”). These surfaces are examples of so-called rigid origami, since we only admit exact flexions, i.e., each face remains rigid during the motion; only the dihedral angles vary. We analyze the geometry behind Miura-ori and address Kokotsakis’ example of a flexible tessellation with the particular case of a cyclic quadrangle. Finally, we recall Bricard’s octahedra of Type 3 and their relation to strophoids.Symmetry2015-05-2772Article10.3390/sym70207747747872073-89942015-05-27doi: 10.3390/sym7020774Hellmuth Stachel<![CDATA[Future Internet, Vol. 7, Pages 152-169: Receiver-Triggered Handshake Protocol for DTN in Disaster Area]]>
http://www.mdpi.com/1999-5903/7/2/152
When a disaster hits a wide area, communication services for public use will be rendered unavailable. This will make it difficult to confirm the safety of people in the disaster area. A solution to this problem is to form delay/disruption tolerant networks (DTN) using mobile terminals of victims, those of rescuers, who serve as information carriers, and terminals (servers) in shelters. In this paper, we propose using a receiver-triggered handshake protocol for communication between these terminals. We have developed the bundle layer protocol for this handshake method. The proposed method has been implemented on a network simulator to build an evaluation environment. The disaster area has been modeled on an area around Shinjuku Station in Tokyo. Victims are randomly distributed in the area. We have compared the proposed method with Epidemic Routing and Spray and Wait in terms of the delivery rate at which messages reach their destinations, and the length of time taken for messages to reach their destinations. We have found that the delivery rate of the three methods are, more or less, the same, but that the proposed method is superior to the other two methods in terms of storage usage and battery consumption of terminals, and the number of bundles generated in the network.Future Internet2015-05-2772Article10.3390/fi70201521521691999-59032015-05-27doi: 10.3390/fi7020152Ryoma YamashitaKazumasa Takami<![CDATA[Computation, Vol. 3, Pages 262-273: LES: Unsteady Atmospheric Turbulent Layer Inlet. A Precursor Method Application and Its Quality Check]]>
http://www.mdpi.com/2079-3197/3/2/262
The motivation of this work is to bridge the gap between experimental approaches in wind tunnel testing and numerical computations, in the field of structural design against strong winds. This paper focuses on the generation of an unsteady flow field, representative of a natural wind field, but still compatible with Computational Fluid Dynamics inlet requirements. A simple and “naive” procedure is explained, and the results are in good agreement with some international standards.Computation2015-05-2632Article10.3390/computation30202622622732079-31972015-05-26doi: 10.3390/computation3020262Julien Berthaut-GerentesDidier Delaunay<![CDATA[Mathematics, Vol. 3, Pages 412-427: Subordination Principle for a Class of Fractional Order Differential Equations]]>
http://www.mdpi.com/2227-7390/3/2/412
The fractional order differential equation \(u'(t)=Au(t)+\gamma D_t^{\alpha} Au(t)+f(t), \ t&gt;0\), \(u(0)=a\in X\) is studied, where \(A\) is an operator generating a strongly continuous one-parameter semigroup on a Banach space \(X\), \(D_t^{\alpha}\) is the Riemann–Liouville fractional derivative of order \(\alpha \in (0,1)\), \(\gamma&gt;0\) and \(f\) is an \(X\)-valued function. Equations of this type appear in the modeling of unidirectional viscoelastic flows. Well-posedness is proven, and a subordination identity is obtained relating the solution operator of the considered problem and the \(C_{0}\)-semigroup, generated by the operator \(A\). As an example, the Rayleigh–Stokes problem for a generalized second-grade fluid is considered.Mathematics2015-05-2632Article10.3390/math30204124124272227-73902015-05-26doi: 10.3390/math3020412Emilia Bazhlekova<![CDATA[Algorithms, Vol. 8, Pages 248-270: On String Matching with Mismatches]]>
http://www.mdpi.com/1999-4893/8/2/248
In this paper, we consider several variants of the pattern matching with mismatches problem. In particular, given a text \(T=t_1 t_2\cdots t_n\) and a pattern \(P=p_1p_2\cdots p_m\), we investigate the following problems: (1) pattern matching with mismatches: for every \(i, 1\leq i \leq n-m+1\) output, the distance between \(P\) and \(t_i t_{i+1}\cdots t_{i+m-1}\); and (2) pattern matching with \(k\) mismatches: output those positions \(i\) where the distance between \(P\) and \(t_i t_{i+1}\cdots t_{i+m-1}\) is less than a given threshold \(k\). The distance metric used is the Hamming distance. We present some novel algorithms and techniques for solving these problems. We offer deterministic, randomized and approximation algorithms. We consider variants of these problems where there could be wild cards in either the text or the pattern or both. We also present an experimental evaluation of these algorithms. The source code is available at http://www.engr.uconn.edu/\(\sim\)man09004/kmis.zip.Algorithms2015-05-2682Article10.3390/a80202482482701999-48932015-05-26doi: 10.3390/a8020248Marius NicolaeSanguthevar Rajasekaran<![CDATA[IJGI, Vol. 4, Pages 900-927: Mapping the Socio-Economic and Ecological Resilience of Japanese Coral Reefscapes across a Decade]]>
http://www.mdpi.com/2220-9964/4/2/900
Shallow coral reefs threatened by climate change must be spatio-temporally analyzed in terms of their protection of coastal human populations. This study combines Japanese spatio-temporal gradients of population/asset and coral buffering exposure to stress-inducing and stress-mitigating factors so that the socio-economic and ecological (SEE) resilience tied to coral reefscapes can be regionally mapped (1200 km) at a fine resolution (1 arcsec) over a decade (11 years). Fuzzy logic was employed to associated environmental factors based on the related population/asset/coral buffering responses, as found in the literature. Once the factors were weighted according to their resilience contributions, temporally static patterns were evident: (1) a negative correlation occurs between coral buffering resilience and latitude; (2) the least resilient islands are low-lying, deprived of wide reef barriers, and located on the eastern and southern boundaries of the Nansei archipelago; (3) the southwestern-most, middle and northeastern-most islands have the same SEE resilience; and (4) Sekisei Lagoon islands have a very high coral buffering resilience. To overcome uncertainty, future studies should focus on the socio-ecological adaptive capacity, fine-scale ecological processes (such as coral and fish functional groups) and the prediction of the flood risks in the coming decades.ISPRS International Journal of Geo-Information2015-05-2642Article10.3390/ijgi40209009009272220-99642015-05-26doi: 10.3390/ijgi4020900Antoine CollinKazuo NadaokaLawrence Bernardo<![CDATA[Symmetry, Vol. 7, Pages 726-773: Probing Majorana Neutrinos and their CP Violation in Decays of Charged Scalar Mesons π, K, D, Ds, B, Bc]]>
http://www.mdpi.com/2073-8994/7/2/726
Some of the outstanding questions of particle physics today concern the neutrino sector, in particular whether there are more neutrinos than those already known and whether they are Dirac or Majorana particles. There are different ways to explore these issues. In this article we describe neutrino-mediated decays of charged pseudoscalar mesons such as π± ,K± and B±, in scenarios where extra neutrinos are heavy and can be on their mass shell. We discuss semileptonic and leptonic decays of such kinds. We investigate possible ways of using these decays in order to distinguish between the Dirac and Majorana character of neutrinos. Further, we argue that there are significant possibilities of detecting CP violation in such decays when there are at least two almost degenerate Majorana neutrinos involved. This latter type of scenario fits well into the known neutrino minimal standard model (MSM) which could simultaneously explain the Dark Matter and Baryon Asymmetry of the Universe.Symmetry2015-05-2672Article10.3390/sym70207267267732073-89942015-05-26doi: 10.3390/sym7020726Gorazd CvetičClaudio DibChoong KimJilberto Zamora-Saá<![CDATA[Mathematics, Vol. 3, Pages 398-411: Implicit Fractional Differential Equations via the Liouville–Caputo Derivative]]>
http://www.mdpi.com/2227-7390/3/2/398
We study an initial value problem for an implicit fractional differential equation with the Liouville–Caputo fractional derivative. By using fixed point theory and an approximation method, we obtain some existence and uniqueness results.Mathematics2015-05-2532Article10.3390/math30203983984112227-73902015-05-25doi: 10.3390/math3020398Juan NietoAbelghani OuahabVenktesh Venktesh<![CDATA[Computation, Vol. 3, Pages 235-261: Engineering-Based Thermal CFD Simulations on Massive Parallel Systems]]>
http://www.mdpi.com/2079-3197/3/2/235
The development of parallel Computational Fluid Dynamics (CFD) codes is a challenging task that entails efficient parallelization concepts and strategies in order to achieve good scalability values when running those codes on modern supercomputers with several thousands to millions of cores. In this paper, we present a hierarchical data structure for massive parallel computations that supports the coupling of a Navier–Stokes-based fluid flow code with the Boussinesq approximation in order to address complex thermal scenarios for energy-related assessments. The newly designed data structure is specifically designed with the idea of interactive data exploration and visualization during runtime of the simulation code; a major shortcoming of traditional high-performance computing (HPC) simulation codes. We further show and discuss speed-up values obtained on one of Germany’s top-ranked supercomputers with up to 140,000 processes and present simulation results for different engineering-based thermal problems.Computation2015-05-2232Article10.3390/computation30202352352612079-31972015-05-22doi: 10.3390/computation3020235Jérôme FrischRalf-Peter MundaniErnst RankChristoph van Treeck<![CDATA[Computation, Vol. 3, Pages 222-234: Computational Approach to 3D Modeling of the Lymph Node Geometry]]>
http://www.mdpi.com/2079-3197/3/2/222
In this study we present a computational approach to the generation of the major geometric structures of an idealized murine lymph node (LN). In this generation, we consider the major compartments such as the subcapsular sinus, B cell follicles, trabecular and medullar sinuses, blood vessels and the T cell zone with a primary focus on the fibroblastic reticular cell (FRC) network. Confocal microscopy data of LN macroscopic structures and structural properties of the FRC network have been generated and utilized in the present model. The methodology sets a library of modules that can be used to assemble a solid geometric LN model and subsequently generate an adaptive mesh model capable of implementing transport phenomena. Overall, based on the use of high-resolution confocal microscopy and morphological analysis of cell 3D reconstructions, we have developed a computational model of the LN geometry, suitable for further investigation in studies of fluid transport and cell migration in this immunologically essential organ.Computation2015-05-2232Communication10.3390/computation30202222222342079-31972015-05-22doi: 10.3390/computation3020222Alexey KislitsynRostislav SavinkovMario NovkovicLucas OnderGennady Bocharov<![CDATA[Algorithms, Vol. 8, Pages 234-247: An Optimization Clustering Algorithm Based on Texture Feature Fusion for Color Image Segmentation]]>
http://www.mdpi.com/1999-4893/8/2/234
We introduce a multi-feature optimization clustering algorithm for color image segmentation. The local binary pattern, the mean of the min-max difference, and the color components are combined as feature vectors to describe the magnitude change of grey value and the contrastive information of neighbor pixels. In clustering stage, it gets the initial clustering center and avoids getting into local optimization by adding mutation operator of genetic algorithm to particle swarm optimization. Compared with well-known methods, the proposed method has an overall better segmentation performance and can segment image more accurately by evaluating the ratio of misclassification.Algorithms2015-05-2282Article10.3390/a80202342342471999-48932015-05-22doi: 10.3390/a8020234Gaihua WangYang LiuCaiquan Xiong<![CDATA[Symmetry, Vol. 7, Pages 714-725: Conservation Laws of Discrete Evolution Equations by Symmetries and Adjoint Symmetries]]>
http://www.mdpi.com/2073-8994/7/2/714
A direct approach is proposed for constructing conservation laws of discrete evolution equations, regardless of the existence of a Lagrangian. The approach utilizes pairs of symmetries and adjoint symmetries, in which adjoint symmetries make up for the disadvantage of non-Lagrangian structures in presenting a correspondence between symmetries and conservation laws. Applications are made for the construction of conservation laws of the Volterra lattice equation.Symmetry2015-05-2272Article10.3390/sym70207147147252073-89942015-05-22doi: 10.3390/sym7020714Wen-Xiu Ma<![CDATA[Computers, Vol. 4, Pages 155-175: A Reference Point Construction Method Using Mobile Terminals and the Indoor Localization Evaluation in the Centroid Method]]>
http://www.mdpi.com/2073-431X/4/2/155
As smartphones become widespread, a variety of smartphone applications are being developed. This paper proposes a method for indoor localization (i.e., positioning) that uses only smartphones, which are general-purpose mobile terminals, as reference point devices. This method has the following features: (a) the localization system is built with smartphones whose movements are confined to respective limited areas. No fixed reference point devices are used; (b) the method does not depend on the wireless performance of smartphones and does not require information about the propagation characteristics of the radio waves sent from reference point devices, and (c) the method determines the location at the application layer, at which location information can be easily incorporated into high-level services. We have evaluated the level of localization accuracy of the proposed method by building a software emulator that modeled an underground shopping mall. We have confirmed that the determined location is within a small area in which the user can find target objects visually.Computers2015-05-2242Article10.3390/computers40201551551752073-431X2015-05-22doi: 10.3390/computers4020155Takahiro YamaguchiKazumasa Takami<![CDATA[Econometrics, Vol. 3, Pages 376-411: Asymptotic Distribution and Finite Sample Bias Correction of QML Estimators for Spatial Error Dependence Model]]>
http://www.mdpi.com/2225-1146/3/2/376
In studying the asymptotic and finite sample properties of quasi-maximum likelihood (QML) estimators for the spatial linear regression models, much attention has been paid to the spatial lag dependence (SLD) model; little has been given to its companion, the spatial error dependence (SED) model. In particular, the effect of spatial dependence on the convergence rate of the QML estimators has not been formally studied, and methods for correcting finite sample bias of the QML estimators have not been given. This paper fills in these gaps. Of the two, bias correction is particularly important to the applications of this model, as it leads potentially to much improved inferences for the regression coefficients. Contrary to the common perceptions, both the large and small sample behaviors of the QML estimators for the SED model can be different from those for the SLD model in terms of the rate of convergence and the magnitude of bias. Monte Carlo results show that the bias can be severe, and the proposed bias correction procedure is very effective.Econometrics2015-05-2132Article10.3390/econometrics30203763764112225-11462015-05-21doi: 10.3390/econometrics3020376Shew LiuZhenlin Yang<![CDATA[IJGI, Vol. 4, Pages 883-899: Using Multi-Attribute Decision Factors for a Modified All-or-Nothing Traffic Assignment]]>
http://www.mdpi.com/2220-9964/4/2/883
To elucidate a realistic traffic assignment scenario, a multi-criterion decision system is essential. A traffic assignment model designed to simulate real-life situation may therefore utilize absolute and/or relative impedance. Ideally, the decision-making process should identify a set of traffic impedances (factors working against the smooth flow of traffic) along with pertinent parameters in order for the decision system to select the most optimal or the least-impeded route. In this study, we developed geospatial algorithms that consider multiple impedances. The impedances utilized in this study included, traffic patterns, capacity and congestion. The attributes of the decision-making process also prioritize multi-traffic scenarios by adopting first-in-first-out prioritization method. We also further subdivided classical impedance into either relative impedance or absolute impedance. The main advantage of this innovative multi-attribute, impedance-based trip assignment model is that it can be implemented in a manner of algebraic approach to utilize shortest path algorithm embedded in a Geographic Information Systems (GIS)—Graphical User Interface tool. Thus, the GIS package can therefore handle the multi-attribute impedance effectively. Furthermore, the method utilized in this paper displays flexibility and better adaptation to a multi-modal transportation system. Transportation, logistics, and random events, such as terrorism, can be easily analyzed with pertinent impedance.ISPRS International Journal of Geo-Information2015-05-2142Article10.3390/ijgi40208838838992220-99642015-05-21doi: 10.3390/ijgi4020883EunSu LeePeter Oduor<![CDATA[Risks, Vol. 3, Pages 139-163: Interconnectedness of Financial Conglomerates]]>
http://www.mdpi.com/2227-9091/3/2/139
Being active in both the insurance sector and the banking sector, financial conglomerates intrinsically increase the interconnections between the banking sector and the insurance sector. We address two main concerns about financial conglomerates using a unique database on bilateral exposures between 21 French financial institutions. First, we investigate to what extent to which the insurers that are part of financial conglomerates differ from pure insurers. Second, we show that in the presence of sovereign risk, the components of a financial conglomerate are better off than if they were distinct entities. Our empirical findings bring a new perspective to the previous results of the literature based on using different types of data.Risks2015-05-2132Article10.3390/risks30201391391632227-90912015-05-21doi: 10.3390/risks3020139Gaël HautonJean-Cyprien Héam<![CDATA[Symmetry, Vol. 7, Pages 689-713: Sensitivity of High-Scale SUSY in Low Energy Hadronic FCNC]]>
http://www.mdpi.com/2073-8994/7/2/689
We discuss the sensitivity of the high-scale supersymmetry (SUSY) at \(10\)–\(1000\) TeV in \(B^0\), \(B_s\), \(K^0\) and \(D\) meson systems together with the neutron electric dipole moment (EDM) and the mercury EDM. In order to estimate the contribution of the squark flavor mixing to these flavor changing neutral currents (FCNCs), we calculate the squark mass spectrum, which is consistent with the recent Higgs discovery. The SUSY contribution in \(\epsilon_K\) could be large, around \(40\%\) in the region of the SUSY scale \(10\)–\(100\) TeV. The neutron EDM and the mercury EDM are also sensitive to the SUSY contribution induced by the gluino-squark interaction. The predicted EDMs are roughly proportional to \(|\epsilon_K^{\rm SUSY}|\). If the SUSY contribution is the level of \({\cal O}(10\%)\) for \(\epsilon_K\), the neutron EDM is expected to be discovered in the region of \(10^{-28}\)–\(10^{-26}\) ecm. The mercury EDM also gives a strong constraint for the gluino-squark interaction. The SUSY contribution of \(\Delta M_D\) is also discussed.Symmetry2015-05-2172Article10.3390/sym70206896897132073-89942015-05-21doi: 10.3390/sym7020689Morimitsu TanimotoKei Yamamoto<![CDATA[Technologies, Vol. 3, Pages 126-141: Medical Image Processing for Fully Integrated Subject Specific Whole Brain Mesh Generation]]>
http://www.mdpi.com/2227-7080/3/2/126
Currently, anatomically consistent segmentation of vascular trees acquired with magnetic resonance imaging requires the use of multiple image processing steps, which, in turn, depend on manual intervention. In effect, segmentation of vascular trees from medical images is time consuming and error prone due to the tortuous geometry and weak signal in small blood vessels. To overcome errors and accelerate the image processing time, we introduce an automatic image processing pipeline for constructing subject specific computational meshes for entire cerebral vasculature, including segmentation of ancillary structures; the grey and white matter, cerebrospinal fluid space, skull, and scalp. To demonstrate the validity of the new pipeline, we segmented the entire intracranial compartment with special attention of the angioarchitecture from magnetic resonance imaging acquired for two healthy volunteers. The raw images were processed through our pipeline for automatic segmentation and mesh generation. Due to partial volume effect and finite resolution, the computational meshes intersect with each other at respective interfaces. To eliminate anatomically inconsistent overlap, we utilized morphological operations to separate the structures with a physiologically sound gap spaces. The resulting meshes exhibit anatomically correct spatial extent and relative positions without intersections. For validation, we computed critical biometrics of the angioarchitecture, the cortical surfaces, ventricular system, and cerebrospinal fluid (CSF) spaces and compared against literature values. Volumina and surface areas of the computational mesh were found to be in physiological ranges. In conclusion, we present an automatic image processing pipeline to automate the segmentation of the main intracranial compartments including a subject-specific vascular trees. These computational meshes can be used in 3D immersive visualization for diagnosis, surgery planning with haptics control in virtual reality. Subject-specific computational meshes are also a prerequisite for computer simulations of cerebral hemodynamics and the effects of traumatic brain injury.Technologies2015-05-2132Article10.3390/technologies30201261261412227-70802015-05-21doi: 10.3390/technologies3020126Chih-Yang HsuBen SchnellerMahsa GhaffariAli AlarajAndreas Linninger<![CDATA[Risks, Vol. 3, Pages 112-138: Custom v. Standardized Risk Models]]>
http://www.mdpi.com/2227-9091/3/2/112
We discuss when and why custom multi-factor risk models are warranted and give source code for computing some risk factors. Pension/mutual funds do not require customization but standardization. However, using standardized risk models in quant trading with much shorter holding horizons is suboptimal: (1) longer horizon risk factors (value, growth, etc.) increase noise trades and trading costs; (2) arbitrary risk factors can neutralize alpha; (3) “standardized” industries are artificial and insufficiently granular; (4) normalization of style risk factors is lost for the trading universe; (5) diversifying risk models lowers P&amp;L correlations, reduces turnover and market impact, and increases capacity. We discuss various aspects of custom risk model building.Risks2015-05-2032Article10.3390/risks30201121121382227-90912015-05-20doi: 10.3390/risks3020112Zura KakushadzeJim Liew<![CDATA[Risks, Vol. 3, Pages 103-111: Rationality Parameter for Exercising American Put]]>
http://www.mdpi.com/2227-9091/3/2/103
In this paper, irrational exercise behavior of the buyer of an American put is characterized by a single parameter. We model irrational exercise rules as the first jump time of a point processes with stochastic intensity. By the rationality parameter, we parameterize a family of stochastic intensities that depends on the value of the put itself. We present a probabilistic proof that the value of the American put using the irrational exercise rule converges to the arbitrage-free price as the rationality parameter converges to infinity. Another application of this result is the penalty method for approximating the price of an American put.Risks2015-05-2032Article10.3390/risks30201031031112227-90912015-05-20doi: 10.3390/risks3020103Kamille GadJesper Pedersen<![CDATA[IJGI, Vol. 4, Pages 858-882: Characterization of Black Spot Zones for Vulnerable Road Users in São Paulo (Brazil) and Rome (Italy)]]>
http://www.mdpi.com/2220-9964/4/2/858
Non-motorized transportation modes, especially cycling and walking, offer numerous benefits, including improvements in the livability of cities, healthy physical activity, efficient urban transportation systems, less traffic congestion, less noise pollution, clean air, less impact on climate change and decreases in the incidence of diseases related to vehicular emissions. Considering the substantial number of short-distance trips, the time consumed in traffic jams, the higher costs for parking vehicles and restrictions in central business districts, many commuters have found that non-motorized modes of transportation serve as viable and economical transport alternatives. Thus, local governments should encourage and stimulate non-motorized modes of transportation. In return, governments must provide safe conditions for these forms of transportation, and motorized vehicle users must respect and coexist with pedestrians and cyclists, which are the most vulnerable users of the transportation system. Although current trends in sustainable transport aim to encourage and stimulate non-motorized modes of transportation that are socially more efficient than motorized transportation, few to no safety policies have been implemented regarding vulnerable road users (VRU), mainly in large urban centers. Due to the spatial nature of the data used in transport-related studies, geospatial technologies provide a powerful analytical method for studying VRU safety frameworks through the use of spatial analysis. In this article, spatial analysis is used to determine the locations of regions that are characterized by a concentration of traffic accidents (black zones) involving VRU (injuries and casualties) in São Paulo, Brazil (developing country), and Rome, Italy (developed country). The black zones are investigated to obtain spatial patterns that can cause multiple accidents. A method based on kernel density estimation (KDE) is used to compare the two cities and show economic, social, cultural, demographic and geographic differences and/or similarities and how these factors are linked to the locations of VRU traffic accidents. Multivariate regression analyses (ordinary least squares (OLS) models and spatial regression models) are performed to investigate spatial correlations, to understand the dynamics of VRU road accidents in São Paulo and Rome and to detect factors (variables) that contribute to the occurrences of these events, such as the presence of trip generator hubs (TGH), the number of generated urban trips and demographic data. The adopted methodology presents satisfactory results for identifying and delimiting black spots and establishing a link between VRU traffic accident rates and TGH (hospitals, universities and retail shopping centers) and demographic and transport-related data.ISPRS International Journal of Geo-Information2015-05-2042Article10.3390/ijgi40208588588822220-99642015-05-20doi: 10.3390/ijgi4020858Cláudia MachadoMariana GiannottiFrancisco NetoAntonino TripodiLuca PersiaJosé Quintanilha<![CDATA[Econometrics, Vol. 3, Pages 355-375: A Jackknife Correction to a Test for Cointegration Rank]]>
http://www.mdpi.com/2225-1146/3/2/355
This paper investigates the performance of a jackknife correction to a test for cointegration rank in a vector autoregressive system. The limiting distributions of the jackknife-corrected statistics are derived and the critical values of these distributions are tabulated. Based on these critical values the finite sample size and power properties of the jackknife-corrected tests are compared with the usual rank test statistic as well as statistics involving a small sample correction and a Bartlett correction, in addition to a bootstrap method. The simulations reveal that all of the corrected tests can provide finite sample size improvements, while maintaining power, although the bootstrap procedure is the most robust across the simulation designs considered.Econometrics2015-05-2032Article10.3390/econometrics30203553553752225-11462015-05-20doi: 10.3390/econometrics3020355Marcus Chambers<![CDATA[Robotics, Vol. 4, Pages 141-168: DOF Decoupling Task Graph Model: Reducing the Complexity of Touch-Based Active Sensing]]>
http://www.mdpi.com/2218-6581/4/2/141
This article presents: (i) a formal, generic model for active sensing tasks; (ii) the insight that active sensing actions can very often be searched on less than six-dimensional configuration spaces (bringing an exponential reduction in the computational costs involved in the search); (iii) an algorithm for selecting actions explicitly trading off information gain, execution time and computational cost; and (iv) experimental results of touch-based localization in an industrial setting. Generalizing from prior work, the formal model represents an active sensing task by six primitives: configuration space, information space, object model, action space, inference scheme and action-selection scheme; prior work applications conform to the model as illustrated by four concrete examples. On top of the mentioned primitives, the task graph is then introduced as the relationship to represent an active sensing task as a sequence of low-complexity actions defined over different configuration spaces of the object. The presented act-reason algorithm is an action selection scheme to maximize the expected information gain of each action, explicitly constraining the time allocated to compute and execute the actions. The experimental contributions include localization of objects with: (1) a force-controlled robot equipped with a spherical touch probe; (2) a geometric complexity of the to-be-localized objects up to industrial relevance; (3) an initial uncertainty of (0.4 m, 0.4 m, 2Π); and (4) a configuration of act-reason to constrain the allocated time to compute and execute the next action as a function of the current uncertainty. Localization is accomplished when the probability mass within a 5-mm tolerance reaches a specified threshold of 80%. Four objects are localized with final {mean; standard-deviation} error spanning from {0.0043 m; 0.0034 m} to {0.0073 m; 0.0048 m}.Robotics2015-05-1942Article10.3390/robotics40201411411682218-65812015-05-19doi: 10.3390/robotics4020141Niccoló TosiOlivier DavidHerman Bruyninckx<![CDATA[Technologies, Vol. 3, Pages 111-125: Microwave Absorption of Barium Borosilicate, Zinc Borate, Fe-Doped Alumino-Phosphate Glasses and Its Raw Materials]]>
http://www.mdpi.com/2227-7080/3/2/111
This study presents microwave absorption of raw materials used in barium borosilicate, Fe-doped alumina phosphate and zinc borate glass. Microwave absorption was investigated for the raw materials SiO2, Na2CO3, BaCO3, BPO4, Al(PO3)3, Mg(PO3)2, Al(OH)3, TiO2. The study shows that SiO2 could be heated directly above 1000 °C within 30 min at 1.5 kW microwave output (MW) power and 0.8 kW MW power is necessary to initiate heating (from 260 °C). Microwave heating of material with low dielectric loss has been investigated by increasing MW power. Microwave absorption of above glass systems has also been investigated. Dielectric properties such as loss tangent of glass as a function of temperature are presented. Glass melting under direct microwave heating was demonstrated for the studied glass systems. Temperature-Microwave power-Time (T-P-t) profiles for the three glasses indicate maximum MW output power ~1 kW, 0.65 kW and ~1 kW for barium borosilicate, zinc borate glass and alumino-phosphate glass for 60 g glass melting.Technologies2015-05-1932Article10.3390/technologies30201111111252227-70802015-05-19doi: 10.3390/technologies3020111Ashis MandalRanjan Sen<![CDATA[IJFS, Vol. 3, Pages 153-161: Purchasing Power Parity in Transition Countries: Panel Stationary Test with Smooth and Sharp Breaks]]>
http://www.mdpi.com/2227-7072/3/2/153
This study examines whether the long-run purchasing power parity (PPP) holds in transition economies (Bulgaria, the Czech Republic, Hungary, Latvia, Lithuania, Poland, Romania and Russia) using monthly data over the 1995–2011 period. We apply a recently introduced panel stationary test, which accounts for sharp breaks and smooth shifts. The results indicate that the PPP holds only in two countries (i.e., Lithuania and Poland).International Journal of Financial Studies2015-05-1932Article10.3390/ijfs30201531531612227-70722015-05-19doi: 10.3390/ijfs3020153Mohsen Bahmani-OskooeeTsangyao ChangTsung-Pao Wu<![CDATA[IJGI, Vol. 4, Pages 837-857: Intelligent Open Data 3D Maps in a Collaborative Virtual World]]>
http://www.mdpi.com/2220-9964/4/2/837
Three-dimensional (3D) maps have many potential applications, such as navigation and urban planning. In this article, we present the use of a 3D virtual world platform Meshmoon to create intelligent open data 3D maps. A processing method is developed to enable the generation of 3D virtual environments from the open data of the National Land Survey of Finland. The article combines the elements needed in contemporary smart city concepts, such as the connection between attribute information and 3D objects, and the creation of collaborative virtual worlds from open data. By using our 3D virtual world platform, it is possible to create up-to-date, collaborative 3D virtual models, which are automatically updated on all viewers. In the scenes, all users are able to interact with the model, and with each other. With the developed processing methods, the creation of virtual world scenes was partially automated for collaboration activities.ISPRS International Journal of Geo-Information2015-05-1842Article10.3390/ijgi40208378378572220-99642015-05-18doi: 10.3390/ijgi4020837Juho-Pekka VirtanenHannu HyyppäAli KämäräinenTommi HollströmMikko VastarantaJuha Hyyppä<![CDATA[Information, Vol. 6, Pages 183-211: The Role of Malware in Reported Cyber Espionage: A Review of the Impact and Mechanism]]>
http://www.mdpi.com/2078-2489/6/2/183
The recent emergence of the targeted use of malware in cyber espionage versus industry requires a systematic review for better understanding of its impact and mechanism. This paper proposes a basic taxonomy to document major cyber espionage incidents, describing and comparing their impacts (geographic or political targets, origins and motivations) and their mechanisms (dropper, propagation, types of operating systems and infection rates). This taxonomy provides information on recent cyber espionage attacks that can aid in defense against cyber espionage by providing both scholars and experts a solid foundation of knowledge about the topic. The classification also provides a systematic way to document known and future attacks to facilitate research activities. Geopolitical and international relations researchers can focus on the impacts, and malware and security experts can focus on the mechanisms. We identify several dominant patterns (e.g., the prevalent use of remote access Trojan and social engineering). This article concludes that the research and professional community should collaborate to build an open data set to facilitate the geopolitical and/or technical analysis and synthesis of the role of malware in cyber espionage.Information2015-05-1862Article10.3390/info60201831832112078-24892015-05-18doi: 10.3390/info6020183Gaute Wangen<![CDATA[Technologies, Vol. 3, Pages 103-110: A Hybrid Feature Extractor using Fast Hessian Detector and SIFT]]>
http://www.mdpi.com/2227-7080/3/2/103
This paper addresses a new hybrid feature extractor algorithm, which in essence integrates a Fast-Hessian detector into the SIFT (Scale Invariant Feature Transform) algorithm. Feature extractors mainly consist of two essential parts: feature detector and descriptor extractor. This study proposes to integrate (Speeded-Up Robust Features) SURF’s hessian detector into the SIFT algorithm so as to boost the total number of true matched pairs. This is a critical requirement in image processing and widely used in various corresponding fields from image stitching to object recognition. The proposed hybrid algorithm has been tested under different experimental conditions and results are quite encouraging in terms of obtaining higher matched pairs and precision score.Technologies2015-05-1532Article10.3390/technologies30201031031102227-70802015-05-15doi: 10.3390/technologies3020103Mehmet Güzel<![CDATA[Future Internet, Vol. 7, Pages 140-151: Quantitative Analysis of the Usage of a Pedagogical Tool Combining Questions Listed as Learning Objectives and Answers Provided as Online Videos]]>
http://www.mdpi.com/1999-5903/7/2/140
To improve the learning of basic concepts in molecular biology of an undergraduate science class, a pedagogical tool was developed, consisting of learning objectives listed at the end of each lecture and answers to those objectives made available as videos online. The aim of this study was to determine if the pedagogical tool was used by students as instructed, and to explore students’ perception of its usefulness. A combination of quantitative survey data and measures of online viewing was used to evaluate the usage of the pedagogical practice. A total of 77 short videos linked to 11 lectures were made available to 71 students, and 64 completed the survey. Using online tracking tools, a total of 7046 views were recorded. Survey data indicated that most students (73.4%) accessed all videos, and the majority (98.4%) found the videos to be useful in assisting their learning. Interestingly, approximately half of the students (53.1%) always or most of the time used the pedagogical tool as recommended, and consistently answered the learning objectives before watching the videos. While the proposed pedagogical tool was used by the majority of students outside the classroom, only half used it as recommended limiting the impact on students’ involvement in the learning of the material presented in class. Future Internet2015-05-1572Article10.3390/fi70201401401511999-59032015-05-15doi: 10.3390/fi7020140Odette LaneuvilleDorota Sikora<![CDATA[Economies, Vol. 3, Pages 72-99: How Offshoring Can Affect the Industries’ Skill Composition]]>
http://www.mdpi.com/2227-7099/3/2/72
While most of the offshoring literature focuses on the effects on relative wages, other implications do not receive the necessary attention. This paper investigates the effects on the industries’ skill ratio. It summarizes the empirical literature, discusses theoretical findings, and provides empirical evidence for Germany. As results show, effects are mainly driven by the industry where offshoring takes place. If offshoring takes place in high-skill intensive industries, the high-skill labor ratio increases (vice versa if offshoring takes place in low-skill intensive industries). Results are in line with other empirical findings, however, they seem to contradict theoretical causalities. Thus, we additionally discuss possible explanations.Economies2015-05-1532Article10.3390/economies302007272992227-70992015-05-15doi: 10.3390/economies3020072Daniel HorgosLucia Tajoli<![CDATA[Symmetry, Vol. 7, Pages 675-688: Secure Cooperative Spectrum Sensing via a Novel User-Classification Scheme in Cognitive Radios for Future Communication Technologies]]>
http://www.mdpi.com/2073-8994/7/2/675
Future communication networks would be required to deliver data on a far greater scale than is known to us today, thus mandating the maximal utilization of the available radio spectrum using cognitive radios. In this paper, we have proposed a novel cooperative spectrum sensing approach for cognitive radios. In cooperative spectrum sensing, the fusion center relies on reports of the cognitive users to make a global decision. The global decision is obtained by assigning weights to the reports received from cognitive users. Computation of such weights requires prior information of the probability of detection and the probability of false alarms, which are not readily available in real scenarios. Further, the cognitive users are divided into reliable and unreliable categories based on their weighted energy by using some empirical threshold. In this paper, we propose a method to classify the cognitive users into reliable, neutral and unreliable categories without using any pre-defined or empirically-obtained threshold. Moreover, the computation of weights does not require the detection, or false alarm probabilities, or an estimate of these probabilities. Reliable cognitive users are assigned the highest weights; neutral cognitive users are assigned medium weights (less than the reliable and higher than the unreliable cognitive users’ weights); and unreliable users are assigned the least weights. We show the performance improvement of our proposed method through simulations by comparing it with the conventional cooperative spectrum sensing scheme through different metrics, like receiver operating characteristic (ROC) curve and mean square error. For clarity, we also show the effect of malicious users on detection probability and false alarm probability individually through simulations.Symmetry2015-05-1472Article10.3390/sym70206756756882073-89942015-05-14doi: 10.3390/sym7020675Muhammad UsmanKoo Insoo<![CDATA[Mathematics, Vol. 3, Pages 382-397: The Spectral Connection Matrix for Any Change of Basis within the Classical Real Orthogonal Polynomials]]>
http://www.mdpi.com/2227-7390/3/2/382
The connection problem for orthogonal polynomials is, given a polynomial expressed in the basis of one set of orthogonal polynomials, computing the coefficients with respect to a different set of orthogonal polynomials. Expansions in terms of orthogonal polynomials are very common in many applications. While the connection problem may be solved by directly computing the change–of–basis matrix, this approach is computationally expensive. A recent approach to solving the connection problem involves the use of the spectral connection matrix, which is a matrix whose eigenvector matrix is the desired change–of–basis matrix. In Bella and Reis (2014), it is shown that for the connection problem between any two different classical real orthogonal polynomials of the Hermite, Laguerre, and Gegenbauer families, the related spectral connection matrix has quasiseparable structure. This result is limited to the case where both the source and target families are one of the Hermite, Laguerre, or Gegenbauer families, which are each defined by at most a single parameter. In particular, this excludes the large and common class of Jacobi polynomials, defined by two parameters, both as a source and as a target family. In this paper, we continue the study of the spectral connection matrix for connections between real orthogonal polynomial families. In particular, for the connection problem between any two families of the Hermite, Laguerre, or Jacobi type (including Chebyshev, Legendre, and Gegenbauer), we prove that the spectral connection matrix has quasiseparable structure. In addition, our results also show the quasiseparable structure of the spectral connection matrix from the Bessel polynomials, which are orthogonal on the unit circle, to any of the Hermite, Laguerre, and Jacobi types. Additionally, the generators of the spectral connection matrix are provided explicitly for each of these cases, allowing a fast algorithm to be implemented following that in Bella and Reis (2014).Mathematics2015-05-1432Article10.3390/math30203823823972227-73902015-05-14doi: 10.3390/math3020382Tom BellaJenna Reis<![CDATA[Econometrics, Vol. 3, Pages 339-354: The Seasonal KPSS Test: Examining Possible Applications with Monthly Data and Additional Deterministic Terms]]>
http://www.mdpi.com/2225-1146/3/2/339
The literature has been notably less definitive in distinguishing between finite sample studies of seasonal stationarity than in seasonal unit root tests. Although the use of seasonal stationarity and unit root tests is advised to determine correctly the most appropriate form of the trend in a seasonal time series, such a use is rarely noted in the relevant studies on this topic. Recently, the seasonal KPSS test, with a null hypothesis of no seasonal unit roots, and based on quarterly data, has been introduced in the literature. The asymptotic theory of the seasonal KPSS test depends on whether data have been filtered by a preliminary regression. More specifically, one may proceed to extracting deterministic components, such as the mean and trend, from the data before testing. In this paper, we examine the effects of de-trending on the properties of the seasonal KPSS test in finite samples. A sketch of the test’s limit theory is subsequently provided. Moreover, a Monte Carlo study is conducted to analyze the behavior of the test for a monthly time series. The focus on this time-frequency is significant because, as we mentioned above, it was introduced for quarterly data. Overall, the results indicated that the seasonal KPSS test preserved its good size and power properties. Furthermore, our results corroborate those reported elsewhere in the literature for conventional stationarity tests. These subsequent results assumed that the nonparametric corrections of residual variances may lead to better in-sample properties of the seasonal KPSS test. Next, the seasonal KPSS test is applied to a monthly series of the United States (US) consumer price index. We were able to identify a number of seasonal unit roots in this time series. [1] [1] Table 1 in this paper is copyrighted and initially published by JMASM in 2012, Volume 11, Issue 1, pp. 69–77, ISSN: 1538–9472, JMASM Inc., PO Box 48023, Oak Park, MI 48237, USA, ea@jmasm.com.Econometrics2015-05-1332Article10.3390/econometrics30203393393542225-11462015-05-13doi: 10.3390/econometrics3020339Ghassen Montasser<![CDATA[IJFS, Vol. 3, Pages 151-152: Special Issue: Recent Developments in Finance and Banking after the 2008 Crisis]]>
http://www.mdpi.com/2227-7072/3/2/151
The sub-prime financial crisis was not simply the result of excessive leverage and inadequate capital, but it was brewing for some time as a result of a gradual deterioration of business leadership, lapses in governance and in the regulatory framework (particularly in derivatives markets), and an ineffective risk-management framework.[...]International Journal of Financial Studies2015-05-1332Editorial10.3390/ijfs30201511511522227-70722015-05-13doi: 10.3390/ijfs3020151Nicholas ApergisJames Payne<![CDATA[IJGI, Vol. 4, Pages 815-836: Open Geospatial Analytics with PySAL]]>
http://www.mdpi.com/2220-9964/4/2/815
This article reviews the range of delivery platforms that have been developed for the PySAL open source Python library for spatial analysis. This includes traditional desktop software (with a graphical user interface, command line or embedded in a computational notebook), open spatial analytics middleware, and web, cloud and distributed open geospatial analytics for decision support. A common thread throughout the discussion is the emphasis on openness, interoperability, and provenance management in a scientific workflow. The code base of the PySAL library provides the common computing framework underlying all delivery mechanisms.ISPRS International Journal of Geo-Information2015-05-1342Article10.3390/ijgi40208158158362220-99642015-05-13doi: 10.3390/ijgi4020815Sergio ReyLuc AnselinXun LiRobert PahleJason LauraWenwen LiJulia Koschinsky<![CDATA[Mathematics, Vol. 3, Pages 368-381: The Role of the Mittag-Leffler Function in Fractional Modeling]]>
http://www.mdpi.com/2227-7390/3/2/368
This is a survey paper illuminating the distinguished role of the Mittag-Leffler function and its generalizations in fractional analysis and fractional modeling. The content of the paper is connected to the recently published monograph by Rudolf Gorenflo, Anatoly Kilbas, Francesco Mainardi and Sergei Rogosin.Mathematics2015-05-1332Article10.3390/math30203683683812227-73902015-05-13doi: 10.3390/math3020368Sergei Rogosin<![CDATA[Future Internet, Vol. 7, Pages 110-139: Dynamis: Effective Context-Aware Web Service Selection Using Dynamic Attributes]]>
http://www.mdpi.com/1999-5903/7/2/110
Quality web service discovery requires narrowing the search space from an overwhelming set of services down to the most relevant ones, while matching the consumer’s request. Today, the ranking of services only considers static attributes or snapshots of current attribute values, resulting in low-quality search results. To satisfy the user’s need for timely, well-chosen web services, we ought to consider quality of service attributes. The problem is that dynamic attributes can be difficult to measure, frequently fluctuate, are context-sensitive and depend on environmental factors, such as network availability at query time. In this paper, we propose the Dynamis algorithm to address these challenges effectively. Dynamis is based on well-established database techniques, such as skyline and aggregation. We illustrate our approach using observatory telescope web services and experimentally evaluate it using stock market data. In our evaluation, we show significant improvement in service selection over existing techniques.Future Internet2015-05-1272Article10.3390/fi70201101101391999-59032015-05-12doi: 10.3390/fi7020110Atousa PahlevanJean-Luc DupratAlex ThomoHausi Müller<![CDATA[Mathematics, Vol. 3, Pages 337-367: High-Precision Arithmetic in Mathematical Physics]]>
http://www.mdpi.com/2227-7390/3/2/337
For many scientific calculations, particularly those involving empirical data, IEEE 32-bit floating-point arithmetic produces results of sufficient accuracy, while for other applications IEEE 64-bit floating-point is more appropriate. But for some very demanding applications, even higher levels of precision are often required. This article discusses the challenge of high-precision computation, in the context of mathematical physics, and highlights what facilities are required to support future computation, in light of emerging developments in computer architecture.Mathematics2015-05-1232Article10.3390/math30203373373672227-73902015-05-12doi: 10.3390/math3020337David BaileyJonathan Borwein<![CDATA[Symmetry, Vol. 7, Pages 651-674: Harmonic Maps and Biharmonic Maps]]>
http://www.mdpi.com/2073-8994/7/2/651
This is a survey on harmonic maps and biharmonic maps into (1) Riemannian manifolds of non-positive curvature, (2) compact Lie groups or (3) compact symmetric spaces, based mainly on my recent works on these topics.Symmetry2015-05-1272Article10.3390/sym70206516516742073-89942015-05-12doi: 10.3390/sym7020651Hajime Urakawa<![CDATA[Electronics, Vol. 4, Pages 283-302: A Flexible Power Electronics Configuration for Coupling Renewable Energy Sources]]>
http://www.mdpi.com/2079-9292/4/2/283
A combination of series, parallel and multilevel power electronics has been investigated as a potential interface for two different types of renewable energy sources and in order to reach higher power levels. Renewable energy sources are typically dispersed in a territory, and sources, like wind and solar, allow small to medium-scale generation of electricity. The configuration investigated in this article aims at adapting the coupling solution to the specific generation characteristics of the renewable energy source to make it fit the electrical network. The configuration consists of a combination of three-phase multilevel converters and single-phase inverters, which are designed to provide flexibility, high power quality and high efficiency. A detailed analysis and simulation is performed to identify the properties in conjunction with the electrical grid requirements and the potential challenges encountered during operation. An optimized operation example of wind generation combined with solar PV generation is presented to exemplify the flexibility and benefits of the proposed configuration.Electronics2015-05-1142Article10.3390/electronics40202832833022079-92922015-05-11doi: 10.3390/electronics4020283Mattia FilippiniMarta MolinasEneko Oregi<![CDATA[Symmetry, Vol. 7, Pages 625-650: Coupled SU(3)-Structures and Supersymmetry]]>
http://www.mdpi.com/2073-8994/7/2/625
We review coupled SU(3)-structures, also known in the literature as restricted half-flat structures, in relation to supersymmetry. In particular, we study special classes of examples admitting such structures and the behavior of flows of SU(3)-structures with respect to the coupled condition.Symmetry2015-05-1172Article10.3390/sym70206256256502073-89942015-05-11doi: 10.3390/sym7020625Anna FinoAlberto Raffero<![CDATA[Econometrics, Vol. 3, Pages 317-338: The SAR Model for Very Large Datasets: A Reduced Rank Approach]]>
http://www.mdpi.com/2225-1146/3/2/317
The SAR model is widely used in spatial econometrics to model Gaussian processes on a discrete spatial lattice, but for large datasets, fitting it becomes computationally prohibitive, and hence, its usefulness can be limited. A computationally-efficient spatial model is the spatial random effects (SRE) model, and in this article, we calibrate it to the SAR model of interest using a generalisation of the Moran operator that allows for heteroskedasticity and an asymmetric SAR spatial dependence matrix. In general, spatial data have a measurement-error component, which we model, and we use restricted maximum likelihood to estimate the SRE model covariance parameters; its required computational time is only the order of the size of the dataset. Our implementation is demonstrated using mean usual weekly income data from the 2011 Australian Census.Econometrics2015-05-1132Article10.3390/econometrics30203173173382225-11462015-05-11doi: 10.3390/econometrics3020317Sandy BurdenNoel CressieDavid Steel<![CDATA[Econometrics, Vol. 3, Pages 289-316: Selection Criteria in Regime Switching Conditional Volatility Models]]>
http://www.mdpi.com/2225-1146/3/2/289
A large number of nonlinear conditional heteroskedastic models have been proposed in the literature. Model selection is crucial to any statistical data analysis. In this article, we investigate whether the most commonly used selection criteria lead to choice of the right specification in a regime switching framework. We focus on two types of models: the Logistic Smooth Transition GARCH and the Markov-Switching GARCH models. Simulation experiments reveal that information criteria and loss functions can lead to misspecification ; BIC sometimes indicates the wrong regime switching framework. Depending on the Data Generating Process used in the experiments, great care is needed when choosing a criterion.Econometrics2015-05-1132Article10.3390/econometrics30202892893162225-11462015-05-11doi: 10.3390/econometrics3020289Thomas Chuffart<![CDATA[Administrative Sciences, Vol. 5, Pages 71-87: Is the Asset Transfer of Public Leisure Facilities in England an Example of Associative Democracy?]]>
http://www.mdpi.com/2076-3387/5/2/71
In England, public sports facilities and libraries provided by local government are being transferred to management and delivery by volunteers. The catalyst for this development has been reductions in local government budgets. However, case studies explore if this asset transfer “offers a way of restoring the ideal of committed public service in the face of widespread bureaucratic failure and retreat”, as a form of associative democracy and empowerment of both the volunteers and those for whom the services are provided.Administrative Sciences2015-05-1152Article10.3390/admsci502007171872076-33872015-05-11doi: 10.3390/admsci5020071Geoff NicholsDeborah ForbesLindsay Findlay-KingGordon Macfadyen<![CDATA[Algorithms, Vol. 8, Pages 224-233: Numerical Solution of Turbulence Problems by Solving Burgers’ Equation]]>
http://www.mdpi.com/1999-4893/8/2/224
In this work we generate the numerical solutions of Burgers’ equation by applying the Crank-Nicholson method and different schemes for solving nonlinear systems, instead of using Hopf-Cole transformation to reduce Burgers’ equation into the linear heat equation. The method is analyzed on two test problems in order to check its efficiency on different kinds of initial conditions. Numerical solutions as well as exact solutions for different values of viscosity are calculated, concluding that the numerical results are very close to the exact solution.Algorithms2015-05-0882Article10.3390/a80202242242331999-48932015-05-08doi: 10.3390/a8020224Alicia CorderoAntonio FranquesJuan Torregrosa<![CDATA[Algorithms, Vol. 8, Pages 209-223: Pulmonary Nodule Detection from X-ray CT Images Based on Region Shape Analysis and Appearance-based Clustering]]>
http://www.mdpi.com/1999-4893/8/2/209
In this paper, we propose a detection method of pulmonary nodules in X-ray computed tomography (CT) scans by use of three image filters and appearance-based k-means clustering. First, voxel values are suppressed in radial directions so as to eliminate extra regions in the volumes of interest (VOIs). Globular regions are enhanced by moment-of-inertia tensors where the voxel values in the VOIs are regarded as mass. Excessively enhanced voxels are reduced based on displacement between the VOI centers and the gravity points of the voxel values in the VOIs. Initial nodule candidates are determined by these filtering processings. False positives are reduced by, first, normalizing the directions of intensity distributions in the VOIs by rotating the VOIs based on the eigenvectors of the moment-of-inertia tensors, and then applying an appearance-based two-step k-means clustering technique to the rotated VOIs. The proposed method is applied to actual CT scans and experimental results are shown.Algorithms2015-05-0882Article10.3390/a80202092092231999-48932015-05-08doi: 10.3390/a8020209Takanobu YanagiharaHotaka Takizawa<![CDATA[Algorithms, Vol. 8, Pages 190-208: From Enumerating to Generating: A Linear Time Algorithm for Generating 2D Lattice Paths with a Given Number of Turns]]>
http://www.mdpi.com/1999-4893/8/2/190
We propose a linear time algorithm, called G2DLP, for generating 2D lattice L(n1, n2) paths, equivalent to two-item multiset permutations, with a given number of turns. The usage of turn has three meanings: in the context of multiset permutations, it means that two consecutive elements of a permutation belong to two different items; in lattice path enumerations, it means that the path changes its direction, either from eastward to northward or from northward to eastward; in open shop scheduling, it means that we transfer a job from one type of machine to another. The strategy of G2DLP is divide-and-combine; the division is based on the enumeration results of a previous study and is achieved by aid of an integer partition algorithm and a multiset permutation algorithm; the combination is accomplished by a concatenation algorithm that constructs the paths we require. The advantage of G2DLP is twofold. First, it is optimal in the sense that it directly generates all feasible paths without visiting an infeasible one. Second, it can generate all paths in any specified order of turns, for example, a decreasing order or an increasing order. In practice, two applications, scheduling and cryptography, are discussed.Algorithms2015-05-0882Article10.3390/a80201901902081999-48932015-05-08doi: 10.3390/a8020190Ting Kuo<![CDATA[Axioms, Vol. 4, Pages 177-193: Generalized Yang–Baxter Operators for Dieudonné Modules]]>
http://www.mdpi.com/2075-1680/4/2/177
An enrichment of a category of Dieudonné modules is made by considering Yang–Baxter conditions, and these are used to obtain ring and coring operations on the corresponding Hopf algebras. Some examples of these induced structures are discussed, including those relating to the Morava K-theory of Eilenberg–MacLane spaces.Axioms2015-05-0842Article10.3390/axioms40201771771932075-16802015-05-08doi: 10.3390/axioms4020177Rui Saramago<![CDATA[Algorithms, Vol. 8, Pages 177-189: An Adaptive Spectral Clustering Algorithm Based on the Importance of Shared Nearest Neighbors]]>
http://www.mdpi.com/1999-4893/8/2/177
The construction of a similarity matrix is one significant step for the spectral clustering algorithm; while the Gaussian kernel function is one of the most common measures for constructing the similarity matrix. However, with a fixed scaling parameter, the similarity between two data points is not adaptive and appropriate for multi-scale datasets. In this paper, through quantitating the value of the importance for each vertex of the similarity graph, the Gaussian kernel function is scaled, and an adaptive Gaussian kernel similarity measure is proposed. Then, an adaptive spectral clustering algorithm is gotten based on the importance of shared nearest neighbors. The idea is that the greater the importance of the shared neighbors between two vertexes, the more possible it is that these two vertexes belong to the same cluster; and the importance value of the shared neighbors is obtained with an iterative method, which considers both the local structural information and the distance similarity information, so as to improve the algorithm’s performance. Experimental results on different datasets show that our spectral clustering algorithm outperforms the other spectral clustering algorithms, such as the self-tuning spectral clustering and the adaptive spectral clustering based on shared nearest neighbors in clustering accuracy on most datasets.Algorithms2015-05-0782Article10.3390/a80201771771891999-48932015-05-07doi: 10.3390/a8020177Xiaoqi HeSheng ZhangYangguang Liu<![CDATA[Symmetry, Vol. 7, Pages 599-624: Reduction by Lie Group Symmetries in Diffeomorphic Image Registration and Deformation Modelling]]>
http://www.mdpi.com/2073-8994/7/2/599
We survey the role of reduction by symmetry in the large deformation diffeomorphic metric mapping framework for registration of a variety of data types (landmarks, curves, surfaces, images and higher-order derivative data). Particle relabelling symmetry allows the equations of motion to be reduced to the Lie algebra allowing the equations to be written purely in terms of the Eulerian velocity field. As a second use of symmetry, the infinite dimensional problem of finding correspondences between objects can be reduced for a range of concrete data types, resulting in compact representations of shape and spatial structure. Using reduction by symmetry, we describe these models in a common theoretical framework that draws on links between the registration problem and geometric mechanics. We outline these constructions and further cases where reduction by symmetry promises new approaches to the registration of complex data types.Symmetry2015-05-0772Article10.3390/sym70205995996242073-89942015-05-07doi: 10.3390/sym7020599Stefan SommerHenry Jacobs<![CDATA[Computers, Vol. 4, Pages 142-154: Semi-Automatic Image Labelling Using Depth Information]]>
http://www.mdpi.com/2073-431X/4/2/142
Image labeling tools help to extract objects within images to be used as ground truth for learning and testing in object detection processes. The inputs for such tools are usually RGB images. However with new widely available low-cost sensors like Microsoft Kinect it is possible to use depth images in addition to RGB images. Despite many existing powerful tools for image labeling, there is a need for RGB-depth adapted tools. We present a new interactive labeling tool that partially automates image labeling, with two major contributions. First, the method extends the concept of image segmentation from RGB to RGB-depth using Fuzzy C-Means clustering, connected component labeling and superpixels, and generates bounding pixels to extract the desired objects. Second, it minimizes the interaction time needed for object extraction by doing an efficient segmentation in RGB-depth space. Very few clicks are needed for the entire procedure compared to existing, tools. When the desired object is the closest object to the camera, which is often the case in robotics applications, no clicks at all are required to accurately extract the object.Computers2015-05-0642Article10.3390/computers40201421421542073-431X2015-05-06doi: 10.3390/computers4020142Mostafa PordelThomas Hellström<![CDATA[Future Internet, Vol. 7, Pages 94-109: Inefficiency of IDS Static Anomaly Detectors in Real-World Networks]]>
http://www.mdpi.com/1999-5903/7/2/94
A wide range of IDS implementations with anomaly detection modules have been deployed. In general, those modules depend on intrusion knowledge databases, such as Knowledge Discovery Dataset (KDD99), Center for Applied Internet Data Analysis (CAIDA) or Community Resource for Archiving Wireless Data at Dartmouth (CRAWDAD), among others. Once the database is analyzed and a machine learning method is employed to generate detectors, some classes of new detectors are created. Thereafter, detectors are supposed to be deployed in real network environments in order to achieve detection with good results for false positives and detection rates. Since the traffic behavior is quite different according to the user’s network activities over available services, restrictions and applications, it is supposed that behavioral-based detectors are not well suited to all kind of networks. This paper presents the differences of detection results between some network scenarios by applying traditional detectors that were calculated with artificial neural networks. The same detector is deployed in different scenarios to measure the efficiency or inefficiency of static training detectors.Future Internet2015-05-0672Article10.3390/fi7020094941091999-59032015-05-06doi: 10.3390/fi7020094Edward GuillenJeisson SánchezRafael Paez<![CDATA[Mathematics, Vol. 3, Pages 329-336: Action at a Distance in Quantum Theory]]>
http://www.mdpi.com/2227-7390/3/2/329
The purpose of this paper is to present a consistent mathematical framework that shows how the EPR (Einstein. Podolsky, Rosen) phenomenon fits into our view of space time. To resolve the differences between the Hilbert space structure of quantum theory and the manifold structure of classical physics, the manifold is taken as a partial representation of the Hilbert space. It is the partial nature of the representation that allows for action at a distance and the failure of the manifold picture.Mathematics2015-05-0632Article10.3390/math30203293293362227-73902015-05-06doi: 10.3390/math3020329Jerome Blackman<![CDATA[Symmetry, Vol. 7, Pages 561-598: Group Theory of Wannier Functions Providing the Basis for a Deeper Understanding of Magnetism and Superconductivity]]>
http://www.mdpi.com/2073-8994/7/2/561
The paper presents the group theory of optimally-localized and symmetry-adapted Wannier functions in a crystal of any given space group G or magnetic group M. Provided that the calculated band structure of the considered material is given and that the symmetry of the Bloch functions at all of the points of symmetry in the Brillouin zone is known, the paper details whether or not the Bloch functions of particular energy bands can be unitarily transformed into optimally-localized Wannier functions symmetry-adapted to the space group G, to the magnetic group M or to a subgroup of G or M. In this context, the paper considers usual, as well as spin-dependent Wannier functions, the latter representing the most general definition of Wannier functions. The presented group theory is a review of the theory published by one of the authors (Ekkehard Krüger) in several former papers and is independent of any physical model of magnetism or superconductivity. However, it is suggested to interpret the special symmetry of the optimally-localized Wannier functions in the framework of a nonadiabatic extension of the Heisenberg model, the nonadiabatic Heisenberg model. On the basis of the symmetry of the Wannier functions, this model of strongly-correlated localized electrons makes clear predictions of whether or not the system can possess superconducting or magnetic eigenstates.Symmetry2015-05-0572Review10.3390/sym70205615615982073-89942015-05-05doi: 10.3390/sym7020561Ekkehard KrügerHorst Strunk<![CDATA[IJGI, Vol. 4, Pages 799-814: Contextualized Relevance Evaluation of Geographic Information for Mobile Users in Location-Based Social Networks]]>
http://www.mdpi.com/2220-9964/4/2/799
The relevance of geographic information to mobile users must be evaluated by taking into account the usage context. This paper assumes that emerging Location-based Social Networks (LBSNs) contain contextual information rich enough to be used in order to contextualize such an evaluation process. This assumption is demonstrated through an exploratory analysis of a Foursquare check-in dataset, which reveals the impacts of two contextual factors—temporal and spatial—on mobility patterns. This paper then proposes an approach that may be used to contextualize the evaluation of geographic information’s relevance. The proposed algorithm links a priori relevance to the contextualized relevance using the hidden impacts of contextual factors. Improved performance from the experiments carried out confirms the validity of the proposed approach, as well as the benefits of utilizing contextual information within the relevance evaluation process.ISPRS International Journal of Geo-Information2015-05-0542Article10.3390/ijgi40207997998142220-99642015-05-05doi: 10.3390/ijgi4020799Ming LiYeran SunHongchao Fan<![CDATA[IJGI, Vol. 4, Pages 783-798: Exploring Spatial Scale, Autocorrelation and Nonstationarity of Bird Species Richness Patterns]]>
http://www.mdpi.com/2220-9964/4/2/783
In this paper we explore relationships between bird species richness and environmental factors in New York State, focusing particularly on how spatial scale, autocorrelation and nonstationarity affect these relationships. We used spatial statistics, Getis-Ord Gi*(d), to investigate how spatial scale affects the measurement of richness “hot-spots” and “cold-spots” (clusters of high and low species richness, respectively) and geographically weighted regression (GWR) to explore scale dependencies and nonstationarity in the relationships between richness and environmental variables such as climate and plant productivity. Finally, we introduce a geovisualization approach to show how these relationships are affected by spatial scale in order to understand the complex spatial patterns of species richness.ISPRS International Journal of Geo-Information2015-05-0542Article10.3390/ijgi40207837837982220-99642015-05-05doi: 10.3390/ijgi4020783Paul HollowayJennifer Miller<![CDATA[IJGI, Vol. 4, Pages 754-782: HybVOR: A Voronoi-Based 3D GIS Approach for Camera Surveillance Network Placement]]>
http://www.mdpi.com/2220-9964/4/2/754
As a consequence of increasing safety concerns, camera surveillance has been widely adopted as a way to monitor public spaces. One of the major challenges of camera surveillance is to design an optimal method for camera network placement in order to ensure the greater possible coverage. In addition, this method must consider the landscape of the monitored environment to take into account the existing objects that may influence the deployment of such a network. In this paper, a new Voronoi-based 3D GIS oriented approach named “HybVOR” is proposed for surveillance camera network placement. The “HybVOR” approach aims to achieve a coverage near 100% through three main phases. First, a Voronoi Diagram from buildings’ footprints is generated and cameras are placed on the Voronoi Edges. Second, the level of coverage is assessed by calculating a viewshed based on a raster Digital Surface Model of the region of interest. Finally, the visibility of the main buildings’ entrances is evaluated based on a 3D vector model that contains these features. The effectiveness of the “HybVOR” approach is demonstrated through a case study that corresponds to an area of interest in Jeddah Seaport in the Kingdom of Saudi Arabia.ISPRS International Journal of Geo-Information2015-05-0542Article10.3390/ijgi40207547547822220-99642015-05-05doi: 10.3390/ijgi4020754Reda YaagoubiMabrouk YarmaniAbdullah KamelWalid Khemiri<![CDATA[Mathematics, Vol. 3, Pages 319-328: There Are Quantum Jumps]]>
http://www.mdpi.com/2227-7390/3/2/319
In this communication we take up the age-old problem of the possibility to incorporate quantum jumps. Unusually, we investigate quantum jumps in an extended quantum setting, but one of rigorous mathematical significance. The general background for this formulation originates in the Balslev-Combes theorem for dilatation analytic Hamiltonians and associated complex symmetric representations. The actual jump is mapped into a Jordan block of order two and a detailed derivation is discussed for the case of the emission of a photon by an atom. The result can be easily reassigned to analogous cases as well as generalized to Segrè characteristics of arbitrary order.Mathematics2015-05-0532Article10.3390/math30203193193282227-73902015-05-05doi: 10.3390/math3020319Erkki Brändas<![CDATA[IJFS, Vol. 3, Pages 136-150: Convergence Studies on Monte Carlo Methods for Pricing Mortgage-Backed Securities]]>
http://www.mdpi.com/2227-7072/3/2/136
Monte Carlo methods are widely-used simulation tools for market practitioners from trading to risk management. When pricing complex instruments, like mortgage-backed securities (MBS), strong path-dependency and high dimensionality make the Monte Carlo method the most suitable, if not the only, numerical method. In practice, while simulation processes in option-adjusted valuation can be relatively easy to implement, it is a well-known challenge that the convergence and the desired accuracy can only be achieved at the cost of lengthy computational times. In this paper, we study the convergence of Monte Carlo methods in calculating the option-adjusted spread (OAS), effective duration (DUR) and effective convexity (CNVX) of MBS instruments. We further define two new concepts, absolute convergence and relative convergence, and show that while the convergence of OAS requires thousands of simulation paths (absolute convergence), only hundreds of paths may be needed to obtain the desired accuracy for effective duration and effective convexity (relative convergence). These results suggest that practitioners can reduce the computational time substantially without sacrificing simulation accuracy.International Journal of Financial Studies2015-05-0532Article10.3390/ijfs30201361361502227-70722015-05-05doi: 10.3390/ijfs3020136Tao PangYipeng YangDai Zhao<![CDATA[Systems, Vol. 3, Pages 27-44: An Integrated Architecture, Methods and Some Tools for Enhancing Sustainable Enterprises and Systems]]>
http://www.mdpi.com/2079-8954/3/2/27
Sustainability and, in particular, green sustainability are very complex subjects, because they typically include several integrated sub-systems. Many of these contain dynamically changing objects and variables, which are often difficult to measure and calibrate. Green sustainability means waste reduction and optimization with a non-toxic process focus that can be maintained over time, for a very long time. Furthermore, it means the ability of an ecosystem to maintain ecological processes and functions, biological diversity and productivity over time. Sustainable, green engineering design, manufacturing, demanufacturing and re-engineering are changing every aspect of our lives. In this paper, we offer an overview, a systems engineering framework, as well as some methodology and concrete results.Systems2015-05-0432Article10.3390/systems302002727442079-89542015-05-04doi: 10.3390/systems3020027Paul Ranky<![CDATA[Information, Vol. 6, Pages 162-182: Analysis of Scholarly Communication Activities in Buddhism and Buddhist Studies]]>
http://www.mdpi.com/2078-2489/6/2/162
There is little knowledge regarding the exchange of academic information on religious contexts. The objective of this informational study was to perform an overall analysis of all Buddhism-related communications collected in the Web of Science (WoS) from 1993 to 2011. The studied informational parameters include the growth in number of the scholarly communications, as well as the language-, document-, subject category-, source-, country-, and organization-wise distribution of the communications. A total of 5407 scholarly communications in this field of study were published in the selected time range. The most preferred WoS subject category was Asian Studies with 1773 communications (22.81%), followed by Religion with 1425 communications (18.33%) and Philosophy with 680 communications (8.75%). The journal with the highest mean number of citations is Numen: International Review for the History of Religions—with 2.09 citations in average per communication. The United States was the top productive country with 2159 communications (50%), where Harvard University topped the list of organization with 85 communications (12%).Information2015-05-0462Article10.3390/info60201621621822078-24892015-05-04doi: 10.3390/info6020162Edoardo Magnone<![CDATA[IJGI, Vol. 4, Pages 741-753: Real-Time Sidewalk Slope Calculation through Integration of GPS Trajectory and Image Data to Assist People with Disabilities in Navigation]]>
http://www.mdpi.com/2220-9964/4/2/741
People with disabilities face many obstacles in everyday outdoor travels. One of the most notable obstacles is steep slope on sidewalk segments. Current navigation systems/services do not all support map databases with slope attributes and cannot calculate sidewalk slope in real time. In this paper, we present a technique for calculating slopes of sidewalk segments by image data and predict the most suitable route for each individual user through integration with GPS trajectory. In our technique we make use of GPS trajectory data, to identify the sidewalk segment on which the traveler will most probably pass, and images of the identified sidewalk segment. Through edge detection techniques we detect edges of objects, such as buildings, billboards, and walls, in the background. Slope of the segment is then calculated by comparing its line representation in the map with the detected edges. Our experiment result indicates effective calculation of sidewalk slopes.ISPRS International Journal of Geo-Information2015-05-0442Article10.3390/ijgi40207417417532220-99642015-05-04doi: 10.3390/ijgi4020741Yihan LuHassan. Karimi<![CDATA[IJGI, Vol. 4, Pages 725-740: The House Crow (Corvus splendens): A Threat to New Zealand?]]>
http://www.mdpi.com/2220-9964/4/2/725
The house crow (Corvus splendens), a native of the Indian subcontinent, has shown a rapid expansion of habitat range across Eastern Africa, the Arabian Peninsula, Europe and Asia. It is an adaptable, gregarious commensal bird which is regarded globally as an important pest species due to its impacts on livestock, agricultural and horticultural crops and indigenous fauna and as a fecal contaminator of human environments and water resources. Two Maxent (v3.3.3k) models (A) with presence data in Australia and (B) with simulated entry data locations in New Zealand) and a third ArcGIS model (C) with environmental and social layers) are used to determine an overall suitability index and establish a niche-based model of the potential spatial distribution for C. splendens within New Zealand. The results show that New Zealand, particularly the northern regions of North Island, has suitable environments for the establishment of the house crow. In order of suitability Model B showed highest potential land area suitability (31.84%) followed by Model A (13.79%) and Model C (10.89%). The potential for further expansion of this bird’s invasive range is high and, if New Zealand is invaded, impacts are likely to be significant.ISPRS International Journal of Geo-Information2015-05-0442Article10.3390/ijgi40207257257402220-99642015-05-04doi: 10.3390/ijgi4020725Diane FraserGlenn AguilarWilliam NagleMel GalbraithColin Ryall<![CDATA[Symmetry, Vol. 7, Pages 546-560: Online Social Snapshots of a Generic Facebook Session Based on Digital Insight Data for a Secure Future IT Environment]]>
http://www.mdpi.com/2073-8994/7/2/546
Physical memory acquisition has been an import facet for digital forensics (DF) specialists due to its volatile characteristics. Nowadays, thousands of millions of global participants utilize online social networking (OSN) mechanisms to expand their social lives, ranging from business-oriented purposes to leisure motivations. Facebook (FB) is one of the most dominant social networking sites (SNS) available today. Unfortunately, it has been a major avenue for cybercriminals to commit illegal activities. Therefore, the digital traces of previous sessions of an FB user play an essential role as the first step for DF experts to pursue the disclosure of the identity of the suspect who was exploiting FB. In this research work, we provide a systematic methodology to reveal a previous session of an FB identity, as well as his/her partial social circle via collecting, analyzing, preserving and presenting the associated digital traces to obtain the online social snapshots of a specific FB user who was utilizing a computing device with Internet Explorer (IE) 10 without turning off the power of the gadget. This novel approach can be a paradigm for how DF specialists ponder the crime scene to conduct the first response in order to avoid the permanent loss of the precious digital evidence in previous FB sessions. The hash values of the image files of the random access memory (RAM) of the computing device have proven to be identical before and after forensics operations, which could be probative evidence in a court of law.Symmetry2015-05-0472Article10.3390/sym70205465465602073-89942015-05-04doi: 10.3390/sym7020546Hai-Cheng ChuJong Park<![CDATA[Symmetry, Vol. 7, Pages 515-545: Some Elementary Aspects of 4-Dimensional Geometry]]>
http://www.mdpi.com/2073-8994/7/2/515
We indicate that Heron’s formula (which relates the square of the area of a triangle to a quartic function of its edge lengths) can be interpreted as a scissors congruence in four-dimensional space. In the process of demonstrating this, we examine a number of decompositions of hypercubes, hyper-parallelograms and other elementary four-dimensional solids.Symmetry2015-05-0472Article10.3390/sym70205155155452073-89942015-05-04doi: 10.3390/sym7020515J. CarterDavid Mullens<![CDATA[IJGI, Vol. 4, Pages 711-724: Solar Irradiance Modelling with NASA WW GIS Environment]]>
http://www.mdpi.com/2220-9964/4/2/711
In this work we present preliminary results regarding a proof-of-concept project which aims to provide tools for mapping the amount of solar radiation reaching surfaces of objects, accounting for obstructions between objects themselves. The implementation uses the NASA World Wind development platform (NASA WW) to model the different physical phenomena that participate in the process, from the calculation of the Sun’s position relative to the area that is being considered, to the interaction between atmosphere and solid obstructions, e.g., terrain or buildings. A more complete understanding of the distribution of energy from the Sun illuminating elements on the Earth’s surface adds value to applications ranging from planning the renewable energy potential of an area to ecological analyses.ISPRS International Journal of Geo-Information2015-04-3042Article10.3390/ijgi40207117117242220-99642015-04-30doi: 10.3390/ijgi4020711Marco PiragnoloAndrea MasieroFrancesca FissoreFrancesco Pirotti<![CDATA[Electronics, Vol. 4, Pages 274-282: A 0.8–8 GHz Multi-Section Coupled Line Balun]]>
http://www.mdpi.com/2079-9292/4/2/274
In this work, we propose a wideband multi-section transforming coupled-line balun using near equal length transmission line elements. The resulting design is realized by cascading several coupled-lines with minimal discontinuities. The multi-section Chebyshev matching optimizes bandwidth at the expense of passband ripple. The proposed design delivers good impedance matching and consistent 180° phase shift over 0.8–8 GHz frequency spectrum. Furthermore, the need for vias in conventional balun designs is relaxed by replacing the short-circuited (SC) terminal by its equivalent dual open-circuited (OC) element. The proposed design is simulated, fabricated, and measured. Both simulated and measured results are in a good agreement, and show an input port matching of below −9.7 dB over the design bandwidth, with a maximum phase and amplitude imbalance of 2.1° and 0.9 dB, respectively.Electronics2015-04-3042Article10.3390/electronics40202742742822079-92922015-04-30doi: 10.3390/electronics4020274Srikanth ItapuMohammad AlmalkawiVijay Devabhaktuni<![CDATA[Mathematics, Vol. 3, Pages 299-318: On the Duality of Discrete and Periodic Functions]]>
http://www.mdpi.com/2227-7390/3/2/299
Although versions of Poisson’s Summation Formula (PSF) have already been studied extensively, there seems to be no theorem that relates discretization to periodization and periodization to discretization in a simple manner. In this study, we show that two complementary formulas, both closely related to the classical Poisson Summation Formula, are needed to form a reciprocal Discretization-Periodization Theorem on generalized functions. We define discretization and periodization on generalized functions and show that the Fourier transform of periodic functions are discrete functions and, vice versa, the Fourier transform of discrete functions are periodic functions.Mathematics2015-04-3032Article10.3390/math30202992993182227-73902015-04-30doi: 10.3390/math3020299Jens Fischer<![CDATA[Technologies, Vol. 3, Pages 94-102: A Study on the Effect of Nano Alumina Particles on Fracture Behavior of PMMA]]>
http://www.mdpi.com/2227-7080/3/2/94
In the current research, the role of nano-sized alumina on deformation and fracture mechanism of Poly Methyl Methacrylate (PMMA) was investigated. For this purpose, PMMA matrix nanocomposite reinforced with different wt% of alumina (i.e., 5, 10 and 15) were fabricated using the compression molding technique. Tensile properties of produced nanocomposites were studied using Zwick Z250 apparatus at cross head speed of about 5 mm/min. In order to specify the role of alumina nanoparticles on deformation and fracture mechanism of PMMA, microscopic evaluation was performed using scanning electron microscope (SEM). The achieved results prove that tensile properties of PMMA depend on alumina wt%. For example, addition of 15 wt% alumina to PMMA causes an increase of about 25% modulus of elasticity. Micrographs taken from the fracture surface of PMMA and its nanocomposites show deformation and fracture mechanism of PMMA changes as alumina is added to it.Technologies2015-04-3032Article10.3390/technologies3020094941022227-70802015-04-30doi: 10.3390/technologies3020094Arezou SezavarSeyed ZebarjadSeyed Sajjadi<![CDATA[Symmetry, Vol. 7, Pages 488-514: Fluctuating and Directional Asymmetry of the Blue Mussel (Mytilus edulis): Improving Methods of Morphological Analysis to Explore Species Performance at the Northern Border of Its Range]]>
http://www.mdpi.com/2073-8994/7/2/488
In this work we examined morphological variation at different levels to study performance and population structuring of the blue mussel Mytilus edulis. Our objectives were: (i) to develop an integrated technique for analyzing morphological variation in blue mussels and, based on this technique; (ii) to perform a morphometric description of mussels from the northern part of their range; and (iii) to verify the hypothesis that populations at the outer range of their distribution have reduced performance due to harsh climatic conditions. Means, directional asymmetry (i.e., systematic differences between left and right structures), fluctuating asymmetry (random deviations from perfect symmetry, a measure of developmental instability), factorial variation (difference between total variance and variance of fluctuating asymmetry, an indirect index of genotypic variation), and measurement error were examined for 14 bilateral characters of muscle scars on mussel shells. Also, we analyzed one non-bilateral character. For the first time directional asymmetry—approaching 13% of the right:left ratio—was described in blue mussels. Measurement error, often ignored in morphometric studies, contributed 26% of total variance. Accurately addressing these methodical challenges is key to further and improved ecological interpretations. Morphological differences were found between (i) samples from estuarine areas in the White and Pechora Seas and (ii) samples from Barents Sea areas with oceanic salinity. Samples from the first group exhibited lower fluctuating asymmetry, indicating higher developmental stability likely due to better feeding conditions and lower factorial variation, which may result from lower genotypic variation. Absence of correlation between fluctuating asymmetry and temperature suggests that low temperatures in the northern border of their range do not degrade the performance of adult blue mussels in this region.Symmetry2015-04-2972Article10.3390/sym70204884885142073-89942015-04-29doi: 10.3390/sym7020488Dmitry LajusMarina KatolikovaPetr StrelkovHerman Hummel<![CDATA[Symmetry, Vol. 7, Pages 464-487: Provable Fair Document Exchange Protocol with Transaction Privacy for E-Commerce]]>
http://www.mdpi.com/2073-8994/7/2/464
Transaction privacy has attracted a lot of attention in the e-commerce. This study proposes an efficient and provable fair document exchange protocol with transaction privacy. Using the proposed protocol, any untrusted parties can fairly exchange documents without the assistance of online, trusted third parties. Moreover, a notary only notarizes each document once. The authorized document owner can exchange a notarized document with different parties repeatedly without disclosing the origin of the document or the identities of transaction participants. Security and performance analyses indicate that the proposed protocol not only provides strong fairness, non-repudiation of origin, non-repudiation of receipt, and message confidentiality, but also enhances forward secrecy, transaction privacy, and authorized exchange. The proposed protocol is more efficient than other works.Symmetry2015-04-2872Article10.3390/sym70204644644872073-89942015-04-28doi: 10.3390/sym7020464Ren-Junn HwangChih-Hua Lai<![CDATA[Administrative Sciences, Vol. 5, Pages 46-70: Understanding Cultural Difference Management through Charles Taylor’s Philosophy: Case Studies from the Food Processing Industry]]>
http://www.mdpi.com/2076-3387/5/2/46
In this paper, we use the work of the philosopher, Charles Taylor, to investigate the role of culture on internationalization decisions. Using parameters related to key constructs such as positive liberty, social ontology, expressivism, civic republicanism and common spaces, we look at how culture influences the decisions regarding corporate international expansion. This framework was applied in a multi-interview design in four firms from the food processing industry from France and Canada. Results showed an obvious sensitivity to cultural difference and that managerial practices surrounding this issue tended to be intuitive and emergent. These practices were not crystallized in the form of a conscious and deliberate organizational strategy for dealing with cultural difference when planning foreign market entry. Our findings triggered further reflections on managerial implications such as the importance of searching more explicitly for cultural and organizational anchors when reviewing location factors.Administrative Sciences2015-04-2852Article10.3390/admsci502004646702076-33872015-04-28doi: 10.3390/admsci5020046Samuel OuelletJoseph FacalLouis Hébert<![CDATA[Symmetry, Vol. 7, Pages 450-463: On Charge Conjugation, Chirality and Helicity of the Dirac and Majorana Equation for Massive Leptons]]>
http://www.mdpi.com/2073-8994/7/2/450
We revisit the charge-conjugation operation for the Dirac equation in its chiral representation. A new decomposition of the Dirac spinor field is suggested and achieved by means of projection operators based on charge conjugation, which is discussed here in a non-standard way. Thus, two separate two-component Majorana-type field equations for the eigenfields of the charge-conjugation operator are obtained. The corresponding free fields are entirely separated without a gauge field, but remain mixed and coupled together through an electromagnetic field term. For fermions that are charged and, thus, subjected to the gauge field of electrodynamics, these two Majorana fields can be reassembled into a doublet, which is equivalent to a standard four-component Dirac spinor field. In this way, the Dirac equation is retained in a new guise, which is fully equivalent to that equation in its chiral form.Symmetry2015-04-2772Article10.3390/sym70204504504632073-89942015-04-27doi: 10.3390/sym7020450Eckart Marsch<![CDATA[IJGI, Vol. 4, Pages 697-710: Open Geospatial Education]]>
http://www.mdpi.com/2220-9964/4/2/697
The advances in open data, free and open source software solutions and open access to research publications have influenced the emergence of open educational resources (OER) initiatives. These initiatives permit access to openly licensed learning resources including courses, webinars, training materials and textbooks. Thereby, an increasing number of users has the opportunity to broaden their knowledge and gain new skills. The goal of this paper is to evaluate open education initiatives in the geospatial domain and its synergies with open spatial data and software movements. The paper is focusing on the Massive Open Online Course (MOOCs) movement. The advantages and challenges of open geospatial education will be thoroughly discussed.ISPRS International Journal of Geo-Information2015-04-2442Article10.3390/ijgi40206976977102220-99642015-04-24doi: 10.3390/ijgi4020697Mariana BelgiuJosef StroblGudrun Wallentin<![CDATA[IJGI, Vol. 4, Pages 677-696: Remotely Sensed Soil Data Analysis Using Artificial Neural Networks: A Case Study of El-Fayoum Depression, Egypt]]>
http://www.mdpi.com/2220-9964/4/2/677
Earth observation and monitoring of soil quality, long term changes of soil characteristics and deterioration processes such as degradation or desertification are among the most important objectives of remote sensing. The georeferenciation of such information contributes to the development and progress of the Digital Earth project in the framework of the information globalization process. Earth observation and soil quality monitoring via remote sensing are mostly based on the use of satellite spectral data. Advanced techniques are available to predict the soil or land use/cover categories from satellite imagery data. Artificial Neural Networks (ANNs) are among the most widely used tools for modeling and prediction purposes in various fields of science. The assessment of satellite image quality and suitability for analysing the soil conditions (e.g., soil classification, land use/cover estimation, etc.) is fundamental. In this paper, methodology for data screening and subsequent application of ANNs in remote sensing is presented. The first stage is achieved via: (i) elimination of outliers, (ii) data pre-processing and (iii) the determination of the number of distinguishable soil “classes” via Eigenvalues Analysis (EA) and Principal Components Analysis (PCA). The next stage of ANNs use consists of: (i) building the training database, (ii) optimization of ANN architecture and database cleaning, and (iii) training and verification of the network. Application of the proposed methodology is shown.ISPRS International Journal of Geo-Information2015-04-2442Article10.3390/ijgi40206776776962220-99642015-04-24doi: 10.3390/ijgi4020677Filippo AmatoJosef HavelAbd-Alla GadAhmed El-Zeiny<![CDATA[IJFS, Vol. 3, Pages 102-135: On Transaction-Cost Models in Continuous-Time Markets]]>
http://www.mdpi.com/2227-7072/3/2/102
Transaction-cost models in continuous-time markets are considered. Given that investors decide to buy or sell at certain time instants, we study the existence of trading strategies that reach a certain final wealth level in continuous-time markets, under the assumption that transaction costs, built in certain recommended ways, have to be paid. Markets prove to behave in manners that resemble those of complete ones for a wide variety of transaction-cost types. The results are important, but not exclusively, for the pricing of options with transaction costs.International Journal of Financial Studies2015-04-2432Article10.3390/ijfs30201021021352227-70722015-04-24doi: 10.3390/ijfs3020102Thomas Poufinas<![CDATA[IJFS, Vol. 3, Pages 84-101: Financial Reforms and Financial Fragility: A Panel Data Analysis]]>
http://www.mdpi.com/2227-7072/3/2/84
This paper explores the relationship between financial reforms, financial liberalization and the quality of banking regulation and supervision for financial fragility by applying a dynamic two-step system generalized method of moments GMM panel estimator technique. The finding of this study is that the financial vulnerability of the banking sector could be affected, not only by bank-specific and macro-specific variables; but also by financial liberalization and banking regulations and supervision policies. The empirical results of this study confirm the evidence that financial reforms and financial liberalization significantly enhance the likelihood of financial fragility while strong banking regulations and supervision have an inverse relationship with financial fragility. The results of this study also explain that the lag value of loan growth and unemployment contribute to enhancing financial fragility while equity to assets ratio, natural log of total assets and share of foreign banks reduce financial vulnerability.International Journal of Financial Studies2015-04-2432Article10.3390/ijfs3020084841012227-70722015-04-24doi: 10.3390/ijfs3020084Syed Iftikhar<![CDATA[Information, Vol. 6, Pages 152-161: Graph Regularized Within-Class Sparsity Preserving Projection for Face Recognition]]>
http://www.mdpi.com/2078-2489/6/2/152
As a dominant method for face recognition, the subspace learning algorithm shows desirable performance. Manifold learning can deal with the nonlinearity hidden in the data, and can project high dimensional data onto low dimensional data while preserving manifold structure. Sparse representation shows its robustness for noises and is very practical for face recognition. In order to extract the facial features from face images effectively and robustly, in this paper, a method called graph regularized within-class sparsity preserving analysis (GRWSPA) is proposed, which can preserve the within-class sparse reconstructive relationship and enhances separatability for different classes. Specifically, for each sample, we use the samples in the same class (except itself) to represent it, and keep the reconstructive weight unchanged during projection. To preserve the manifold geometry structure of the original space, one adjacency graph is constructed to characterize the interclass separability and is incorporated into its criteria equation as a constraint in a supervised manner. As a result, the features extracted are sparse and discriminative and helpful for classification. Experiments are conducted on the two open face databases, the ORL and YALE face databases, and the results show that the proposed method can effectively and correctly find the key facial features from face images and can achieve better recognition rate compared with other existing ones.Information2015-04-2462Article10.3390/info60201521521612078-24892015-04-24doi: 10.3390/info6020152Songjiang LouXiaoming ZhaoWenping GuoYing Chen<![CDATA[Computation, Vol. 3, Pages 197-221: Simulation Frameworks for Morphogenetic Problems]]>
http://www.mdpi.com/2079-3197/3/2/197
Morphogenetic modelling and simulation help to understand the processes by which the form and shapes of organs (organogenesis) and organisms (embryogenesis) emerge. This requires two mutually coupled entities: the biomolecular signalling network and the tissue. Whereas the modelling of the signalling has been discussed and used in a multitude of works, the realistic modelling of the tissue has only started on a larger scale in the last decade. Here, common tissue modelling techniques are reviewed. Besides the continuum approach, the principles and main applications of the spheroid, vertex, Cellular Potts, Immersed Boundary and Subcellular Element models are discussed in detail. In recent years, many software frameworks, implementing the aforementioned methods, have been developed. The most widely used frameworks and modelling markup languages and standards are presented.Computation2015-04-2432Review10.3390/computation30201971972212079-31972015-04-24doi: 10.3390/computation3020197Simon Tanaka<![CDATA[Symmetry, Vol. 7, Pages 427-449: Unsupervised Object Modeling and Segmentation with Symmetry Detection for Human Activity Recognition]]>
http://www.mdpi.com/2073-8994/7/2/427
In this paper we present a novel unsupervised approach to detecting and segmenting objects as well as their constituent symmetric parts in an image. Traditional unsupervised image segmentation is limited by two obvious deficiencies: the object detection accuracy degrades with the misaligned boundaries between the segmented regions and the target, and pre-learned models are required to group regions into meaningful objects. To tackle these difficulties, the proposed approach aims at incorporating the pair-wise detection of symmetric patches to achieve the goal of segmenting images into symmetric parts. The skeletons of these symmetric parts then provide estimates of the bounding boxes to locate the target objects. Finally, for each detected object, the graphcut-based segmentation algorithm is applied to find its contour. The proposed approach has significant advantages: no a priori object models are used, and multiple objects are detected. To verify the effectiveness of the approach based on the cues that a face part contains an oval shape and skin colors, human objects are extracted from among the detected objects. The detected human objects and their parts are finally tracked across video frames to capture the object part movements for learning the human activity models from video clips. Experimental results show that the proposed method gives good performance on publicly available datasets.Symmetry2015-04-2372Article10.3390/sym70204274274492073-89942015-04-23doi: 10.3390/sym7020427Jui-Yuan SuShyi-Chyi ChengDe-Kai Huang<![CDATA[Electronics, Vol. 4, Pages 261-273: Heterojunction Diodes and Solar Cells Fabricated by Sputtering of GaAs on Single Crystalline Si]]>
http://www.mdpi.com/2079-9292/4/2/261
This work reports fabrication details of heterojunction diodes and solar cells obtained by sputter deposition of amorphous GaAs on p-doped single crystalline Si. The effects of two additional process steps were investigated: A hydrofluoric acid (HF) etching treatment of the Si substrate prior to the GaAs sputter deposition and a subsequent annealing treatment of the complete layered system. A transmission electron microscopy (TEM) exploration of the interface reveals the formation of a few nanometer thick SiO2 interface layer and some crystallinity degree of the GaAs layer close to the interface. It was shown that an additional HF etching treatment of the Si substrate improves the short circuit current and degrades the open circuit voltage of the solar cells. Furthermore, an additional thermal annealing step was performed on some selected samples before and after the deposition of an indium tin oxide (ITO) film on top of the a-GaAs layer. It was found that the occurrence of surface related defects is reduced in case of a heat treatment performed after the deposition of the ITO layer, which also results in a reduction of the dark saturation current density and resistive losses.Electronics2015-04-2342Article10.3390/electronics40202612612732079-92922015-04-23doi: 10.3390/electronics4020261Santiago SilvestreAlfredo Boronat<![CDATA[Algorithms, Vol. 8, Pages 157-176: Multiobjective Cloud Particle Optimization Algorithm Based on Decomposition]]>
http://www.mdpi.com/1999-4893/8/2/157
The multiobjective evolutionary algorithm based on decomposition (MOEA/D) has received attention from researchers in recent years. This paper presents a new multiobjective algorithm based on decomposition and the cloud model called multiobjective decomposition evolutionary algorithm based on Cloud Particle Differential Evolution (MOEA/D-CPDE). In the proposed method, the best solution found so far acts as a seed in each generation and evolves two individuals by cloud generator. A new individual is produced by updating the current individual with the position vector difference of these two individuals. The performance of the proposed algorithm is carried on 16 well-known multi-objective problems. The experimental results indicate that MOEA/D-CPDE is competitive.Algorithms2015-04-2382Article10.3390/a80201571571761999-48932015-04-23doi: 10.3390/a8020157Wei LiLei WangQiaoyong JiangXinhong HeiBin Wang<![CDATA[Algorithms, Vol. 8, Pages 144-156: The Auxiliary Problem Principle with Self-Adaptive Penalty Parameter for Multi-Area Economic Dispatch Problem]]>
http://www.mdpi.com/1999-4893/8/2/144
The auxiliary problem principle is a powerful tool for solving multi-area economic dispatch problem. One of the main drawbacks of the auxiliary problem principle method is that the convergence performance depends on the selection of penalty parameter. In this paper, we propose a self-adaptive strategy to adjust penalty parameter based on the iterative information, the proposed approach is verified by two given test systems. The corresponding simulation results demonstrate that the proposed self-adaptive auxiliary problem principle iterative scheme is robust in terms of the selection of penalty parameter and has better convergence rate compared with the traditional auxiliary problem principle method.Algorithms2015-04-2282Article10.3390/a80201441441561999-48932015-04-22doi: 10.3390/a8020144Yaming RenShumin Fei<![CDATA[Mathematics, Vol. 3, Pages 273-298: The Fractional Orthogonal Derivative]]>
http://www.mdpi.com/2227-7390/3/2/273
This paper builds on the notion of the so-called orthogonal derivative, where an n-th order derivative is approximated by an integral involving an orthogonal polynomial of degree n. This notion was reviewed in great detail in a paper by the author and Koornwinder in 2012. Here, an approximation of the Weyl or Riemann–Liouville fractional derivative is considered by replacing the n-th derivative by its approximation in the formula for the fractional derivative. In the case of, for instance, Jacobi polynomials, an explicit formula for the kernel of this approximate fractional derivative can be given. Next, we consider the fractional derivative as a filter and compute the frequency response in the continuous case for the Jacobi polynomials and in the discrete case for the Hahn polynomials. The frequency response in this case is a confluent hypergeometric function. A different approach is discussed, which starts with this explicit frequency response and then obtains the approximate fractional derivative by taking the inverse Fourier transform.Mathematics2015-04-2232Article10.3390/math30202732732982227-73902015-04-22doi: 10.3390/math3020273Enno Diekema<![CDATA[Symmetry, Vol. 7, Pages 412-426: Confluent Supersymmetric Partners of Quantum Systems Emerging from the Spheroidal Equation]]>
http://www.mdpi.com/2073-8994/7/2/412
We construct confluent supersymmetric partners of quantum systems that emerge from the spheroidal equation. Properties of the systems and of their transformed counterparts are discussed.Symmetry2015-04-2272Article10.3390/sym70204124124262073-89942015-04-22doi: 10.3390/sym7020412Axel Schulze-HalbergJie Wang<![CDATA[Information, Vol. 6, Pages 134-151: Analysis and Visualization for Hot Spot Based Route Recommendation Using Short-Dated Taxi GPS Traces]]>
http://www.mdpi.com/2078-2489/6/2/134
Taxi GPS traces, which contain a great deal of valuable information as regards to human mobility and city traffic, can be extracted to improve the quality of our lives. Since the method of visualized analysis is believed to be an effective way to present information vividly, we develop our analysis and visualization method based on a city’s short-dated taxi GPS traces, which can provide recommendation to help cruising taxi drivers to find potential passengers with optimal routes. With our approach, hot spots for loading and unloading passenger(s) are extracted using an improved DBSCAN algorithm after data preprocessing including cleaning and filtering. Then, this paper describes the start-end point-based similar trajectory method to get coarse-level trajectories clusters, together with the density-based ε distance trajectory clustering algorithm to identify recommended potential routes. A weighted tree is defined including such factors as driving time, velocity, distance and endpoint attractiveness for optimal route evaluation from vacant to occupied hot spots. An example is presented to show the effectiveness of our visualization method.Information2015-04-2162Article10.3390/info60201341341512078-24892015-04-21doi: 10.3390/info6020134Ying ShenLigang ZhaoJing Fan<![CDATA[Symmetry, Vol. 7, Pages 395-411: Motion Key-Frame Extraction by Using Optimized t-Stochastic Neighbor Embedding]]>
http://www.mdpi.com/2073-8994/7/2/395
Key-frame extracting technology has been widely used in the field of human motion synthesis. Efficient and accurate key frames extraction methods can improve the accuracy of motion synthesis. In this paper, we use an optimized t-Stochastic Neighbor Embedding (t-SNE for short) algorithm to reduce the data and on this basis extract the key frames. The experimental results show that the validity of this method is better than the existing methods under the same experimental data.Symmetry2015-04-2172Technical Note10.3390/sym70203953954112073-89942015-04-21doi: 10.3390/sym7020395Qiang ZhangYi YaoDongsheng ZhouRui Liu<![CDATA[Computers, Vol. 4, Pages 113-141: Error and Congestion Resilient Video Streaming over Broadband Wireless]]>
http://www.mdpi.com/2073-431X/4/2/113
In this paper, error resilience is achieved by adaptive, application-layer rateless channel coding, which is used to protect H.264/Advanced Video Coding (AVC) codec data-partitioned videos. A packetization strategy is an effective tool to control error rates and, in the paper, source-coded data partitioning serves to allocate smaller packets to more important compressed video data. The scheme for doing this is applied to real-time streaming across a broadband wireless link. The advantages of rateless code rate adaptivity are then demonstrated in the paper. Because the data partitions of a video slice are each assigned to different network packets, in congestion-prone wireless networks the increased number of packets per slice and their size disparity may increase the packet loss rate from buffer overflows. As a form of congestion resilience, this paper recommends packet-size dependent scheduling as a relatively simple way of alleviating the buffer-overflow problem arising from data-partitioned packets. The paper also contributes an analysis of data partitioning and packet sizes as a prelude to considering scheduling regimes. The combination of adaptive channel coding and prioritized packetization for error resilience with packet-size dependent packet scheduling results in a robust streaming scheme specialized for broadband wireless and real-time streaming applications such as video conferencing, video telephony, and telemedicine.Computers2015-04-2142Article10.3390/computers40201131131412073-431X2015-04-21doi: 10.3390/computers4020113Laith Al-JobouriIsmail AliMartin FleuryMohammed Ghanbari<![CDATA[Electronics, Vol. 4, Pages 239-260: Analysis of a Multilevel Dual Active Bridge (ML-DAB) DC-DC Converter Using Symmetric Modulation]]>
http://www.mdpi.com/2079-9292/4/2/239
Dual active bridge (DAB) converters have been popular in high voltage, low and medium power DC-DC applications, as well as an intermediate high frequency link in solid state transformers. In this paper, a multilevel DAB (ML-DAB) has been proposed in which two active bridges produce two-level (2L)-5L, 5L-2L and 3L-5L voltage waveforms across the high frequency transformer. The proposed ML-DAB has the advantage of being used in high step-up/down converters, which deal with higher voltages, as compared to conventional two-level DABs. A three-level neutral point diode clamped (NPC) topology has been used in the high voltage bridge, which enables the semiconductor switches to be operated within a higher voltage range without the need for cascaded bridges or multiple two-level DAB converters. A symmetric modulation scheme, based on the least number of angular parameters rather than the duty-ratio, has been proposed for a different combination of bridge voltages. This ML-DAB is also suitable for maximum power point tracking (MPPT) control in photovoltaic applications. Steady-state analysis of the converter with symmetric phase-shift modulation is presented and verified using simulation and hardware experiments.Electronics2015-04-2042Article10.3390/electronics40202392392602079-92922015-04-20doi: 10.3390/electronics4020239M. MoonemC. PechacekR. HernandezH. Krishnaswami<![CDATA[Mathematics, Vol. 3, Pages 258-272: Fractional Euler-Lagrange Equations Applied to Oscillatory Systems]]>
http://www.mdpi.com/2227-7390/3/2/258
In this paper, we applied the Riemann-Liouville approach and the fractional Euler-Lagrange equations in order to obtain the fractional nonlinear dynamic equations involving two classical physical applications: “Simple Pendulum” and the “Spring-Mass-Damper System” to both integer order calculus (IOC) and fractional order calculus (FOC) approaches. The numerical simulations were conducted and the time histories and pseudo-phase portraits presented. Both systems, the one that already had a damping behavior (Spring-Mass-Damper) and the system that did not present any sort of damping behavior (Simple Pendulum), showed signs indicating a possible better capacity of attenuation of their respective oscillation amplitudes. This implication could mean that if the selection of the order of the derivative is conveniently made, systems that need greater intensities of damping or vibrating absorbers may benefit from using fractional order in dynamics and possibly in control of the aforementioned systems. Thereafter, we believe that the results described in this paper may offer greater insights into the complex behavior of these systems, and thus instigate more research efforts in this direction.Mathematics2015-04-2032Article10.3390/math30202582582722227-73902015-04-20doi: 10.3390/math3020258Sergio DavidCarlos Valentim<![CDATA[IJGI, Vol. 4, Pages 661-676: GIS-Based Borderlands Modeling and Understanding: A Perspective]]>
http://www.mdpi.com/2220-9964/4/2/661
Borderland regions are special areas and deserve more attention in global sustainable development. Reliable geo-information and effective analysis tools are requested to support borderlands studies through the integrated utilization of geospatial analysis, web service, as well as the other domain-specific expertise. This paper has reviewed the state-of-the-art of geospatial information sciences, (GIS)-based borderlands modeling, and understanding. From the perspective of GIS, integrated data modeling, comprehensive analysis, and collaborative information service are identified as the three major challenges in this filed. A research agenda is further proposed with four topics, i.e., classification and representation of borderland information, derivation of neighborhood information, development of synergetic analysis, and design and development of a geo-portal for borderlands studies. This interdisciplinary study requires a closer and in-depth collaboration of geopolitics, international relation, geography and geo-spatial information sciences.ISPRS International Journal of Geo-Information2015-04-2042Article10.3390/ijgi40206616616762220-99642015-04-20doi: 10.3390/ijgi4020661Jun ChenRan LiWeihua DongYuejing GeHua LiaoYang Cheng<![CDATA[IJGI, Vol. 4, Pages 647-660: Architecture of a Process Broker for Interoperable Geospatial Modeling on the Web]]>
http://www.mdpi.com/2220-9964/4/2/647
The identification of appropriate mechanisms for process sharing and reuse by means of composition is considered a key enabler for the effective uptake of a global Earth Observation infrastructure, currently pursued by the international geospatial research community. Modelers in need of running complex workflows may benefit from outsourcing process composition to a dedicated external service, according to the brokering approach. This work introduces our architecture of a process broker, as a distributed information system for creating, validating, editing, storing, publishing and executing geospatial-modeling workflows. The broker provides a service framework for adaptation, reuse and complementation of existing processing resources (including models and geospatial services in general) in the form of interoperable, executable workflows. The described solution has been experimentally applied in several use scenarios in the context of EU-funded projects and the Global Earth Observation System of Systems.ISPRS International Journal of Geo-Information2015-04-2042Article10.3390/ijgi40206476476602220-99642015-04-20doi: 10.3390/ijgi4020647Lorenzo BigagliMattia SantoroPaolo MazzettiStefano Nativi<![CDATA[IJGI, Vol. 4, Pages 626-646: Discriminating Irrigated and Rainfed Maize with Diurnal Fluorescence and Canopy Temperature Airborne Maps]]>
http://www.mdpi.com/2220-9964/4/2/626
This study evaluates the potential of airborne remote sensing images to detect water stress in maize. Visible and near infrared CASI (Itres Research Ltd., Calgary, AL, Canada) and thermal AHS-160 (Sensytech Inc., Beverly, MA, USA) data were acquired at three different times during the day on a maize field (Zea mays L.) grown with three different irrigation treatments. An intensive field campaign was also conducted concurrently with image acquisition to measure leaf ecophysiological parameters and the leaf area index. The analysis of the field data showed that maize plants were experiencing moderate to severe water stress in rainfed plots and a weaker stress condition in the plots with a water deficit imposed between stem elongation and flowering. Vegetation indices including the normalized difference vegetation index (NDVI) and the photochemical reflectance index (PRI) computed from the CASI images, sun-induced chlorophyll fluorescence (F760) and canopy temperature (Tc) showed different performances in describing the water stress during the day. During the morning overpass, NDVI was the index with the highest discriminant power due to the sensitivity of NDVI to maize canopy structure, affected by the water irrigation treatment. As the day progressed, processes related to heat dissipation through plant transpiration became more and more important and at midday Tc showed the best performances. Furthermore, Tc retrieved from the midday image was the only index able to distinguish all the three classes of water status. Finally, during the afternoon, PRI and F760 showed the best performances. These results demonstrate the feasibility to detect water stress using thermal and optical airborne data, pointing out the importance of careful planning of the airborne surveys as a function of the specific aims of the study.ISPRS International Journal of Geo-Information2015-04-2042Article10.3390/ijgi40206266266462220-99642015-04-20doi: 10.3390/ijgi4020626Micol RossiniCinzia PanigadaChiara CiliaMichele MeroniLorenzo BusettoSergio CogliatiStefano AmaducciRoberto Colombo<![CDATA[Mathematics, Vol. 3, Pages 190-257: Maxwell–Lorentz Electrodynamics Revisited via the Lagrangian Formalism and Feynman Proper Time Paradigm]]>
http://www.mdpi.com/2227-7390/3/2/190
We review new electrodynamics models of interacting charged point particles and related fundamental physical aspects, motivated by the classical A.M. Ampère magnetic and H. Lorentz force laws electromagnetic field expressions. Based on the Feynman proper time paradigm and a recently devised vacuum field theory approach to the Lagrangian and Hamiltonian, the formulations of alternative classical electrodynamics models are analyzed in detail and their Dirac type quantization is suggested. Problems closely related to the radiation reaction force and electron mass inertia are analyzed. The validity of the Abraham-Lorentz electromagnetic electron mass origin hypothesis is argued. The related electromagnetic Dirac–Fock–Podolsky problem and symplectic properties of the Maxwell and Yang–Mills type dynamical systems are analyzed. The crucial importance of the remaining reference systems, with respect to which the dynamics of charged point particles is framed, is explained and emphasized.Mathematics2015-04-1732Article10.3390/math30201901902572227-73902015-04-17doi: 10.3390/math3020190Nikolai BogolubovAnatolij PrykarpatskiDenis Blackmore<![CDATA[Computers, Vol. 4, Pages 87-112: A Dynamic Reputation Management System for Mobile Ad Hoc Networks]]>
http://www.mdpi.com/2073-431X/4/2/87
Nodes in mobile ad hoc networks (MANETs) are mandated to utilize their limited energy resources in forwarding routing control and data packets for other nodes. Since a MANET lacks a centralized administration and control, a node may decide to act selfishly, either by refusing to respond to route requests from other nodes or deceitfully by responding to some route requests, but dropping the corresponding data packets that are presented for forwarding. A significant increase in the presence of these misbehaving nodes in a MANET can subsequently degrade network performance. In this paper, we propose a dynamic reputation management system for detecting and isolating misbehaving nodes in MANETs. Our model employs a novel direct monitoring technique to evaluate the reputation of a node in the network, which ensures that nodes that expend their energy in transmitting data and routing control packets for others are allowed to carry out their network activities while the misbehaving nodes are detected and isolated from the network. Simulation results show that our model is effective at curbing and mitigating the effects of misbehaving nodes in the network.Computers2015-04-1742Article10.3390/computers4020087871122073-431X2015-04-17doi: 10.3390/computers4020087Eric ChiejinaHannan XiaoBruce Christianson<![CDATA[Economies, Vol. 3, Pages 55-71: Estimating Interest Rate Setting Behavior in Brazil: A LSTR Model Approach]]>
http://www.mdpi.com/2227-7099/3/2/55
Given limited research on monetary policy rules in emerging markets, this paper challenges the applicability of a nonlinear Taylor rule in characterizing the monetary policy behavior of the Brazilian Central Bank. It also investigates whether and how the process of setting interest rates has been developed in response to contingencies and special events. We extend the linear Taylor rule to a regime-switching framework, where the transition from one regime to another occurs in a smooth way, using a Logistic Smooth Transition Regression (LSTR) approach. In this sense, we empirically analyze the movement of the nominal short term interest rate of the Brazilian Central Bank using quarterly data, covering the period 1994.Q4–2012.Q2. We find that the nonlinear Taylor rule provides a better description of the Brazilian interest rate setting and is consistent with historical macroeconomic events. In particular, our results show that adopting a nonlinear specification, instead of the linear, leads to a costs reduction in terms of ﬁt: 190 basis points in 1995 and 140 basis points in the mid-2002 presidential election campaign in Brazil. Moreover, the Brazilian monetary policy exhibits nonlinear patterns that better captures special events and may contain relevant information rendering it applicable to unusual conditions, i.e., a financial crisis, which require disconnection from the automatic pilot rule and use of judgement to make decision.Economies2015-04-1732Article10.3390/economies302005555712227-70992015-04-17doi: 10.3390/economies3020055Yosra Baaziz