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Entropy, Volume 17, Issue 4 (April 2015) , Pages 1549-2555

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Open AccessArticle
Thermodynamic Analysis of Double-Stage Compression Transcritical CO2 Refrigeration Cycles with an Expander
Entropy 2015, 17(4), 2544-2555; https://doi.org/10.3390/e17042544 - 22 Apr 2015
Cited by 10 | Viewed by 2319
Abstract
Four different double-compression CO2 transcritical refrigeration cycles are studied: double-compression external intercooler cycle (DCEI), double-compression external intercooler cycle with an expander (DCEIE), double-compression flash intercooler cycle (DCFI), double-compression flash intercooler cycle with an expander (DCFIE). The results showed that the optimum gas [...] Read more.
Four different double-compression CO2 transcritical refrigeration cycles are studied: double-compression external intercooler cycle (DCEI), double-compression external intercooler cycle with an expander (DCEIE), double-compression flash intercooler cycle (DCFI), double-compression flash intercooler cycle with an expander (DCFIE). The results showed that the optimum gas cooler pressure and optimum intermediate pressure of the flash intercooler cycles are lower than that of the external intercooler cycle. The use of an expander in the DCEI cycle leads to a decrease of the optimum gas cooler pressure and little variation of the optimum intermediate pressure. However, the replacement of the throttle valve with an expander in the DCFI cycle results in little variation of the optimal gas cooler pressure and an increase of the optimum intermediate pressure. The DCFI cycle outperforms the DCEI cycle under all the chosen operating conditions. The DCEIE cycle outperforms the DCFIE cycle when the evaporating temperature exceeds 0 °C or the gas cooler outlet temperature surpasses 35 °C. When the gas cooler exit temperature varies from 32 °C to 48 °C, the DCEI cycle, DCEIE cycle, DCFI cycle and DCFIE cycle yield averaged 4.6%, 29.2%, 12.9% and 22.3% COP improvement, respectively, over the basic cycle. Full article
(This article belongs to the Section Thermodynamics)
Open AccessArticle
Justifying Objective Bayesianism on Predicate Languages
Entropy 2015, 17(4), 2459-2543; https://doi.org/10.3390/e17042459 - 22 Apr 2015
Cited by 2 | Viewed by 2141
Abstract
Objective Bayesianism says that the strengths of one’s beliefs ought to be probabilities, calibrated to physical probabilities insofar as one has evidence of them, and otherwise sufficiently equivocal. These norms of belief are often explicated using the maximum entropy principle. In this paper [...] Read more.
Objective Bayesianism says that the strengths of one’s beliefs ought to be probabilities, calibrated to physical probabilities insofar as one has evidence of them, and otherwise sufficiently equivocal. These norms of belief are often explicated using the maximum entropy principle. In this paper we investigate the extent to which one can provide a unified justification of the objective Bayesian norms in the case in which the background language is a first-order predicate language, with a view to applying the resulting formalism to inductive logic. We show that the maximum entropy principle can be motivated largely in terms of minimising worst-case expected loss. Full article
(This article belongs to the Special Issue Maximum Entropy Applied to Inductive Logic and Reasoning)
Open AccessArticle
Information Geometry on Complexity and Stochastic Interaction
Entropy 2015, 17(4), 2432-2458; https://doi.org/10.3390/e17042432 - 21 Apr 2015
Cited by 30 | Viewed by 4122
Abstract
Interdependencies of stochastically interacting units are usually quantified by the Kullback-Leibler divergence of a stationary joint probability distribution on the set of all configurations from the corresponding factorized distribution. This is a spatial approach which does not describe the intrinsically temporal aspects of [...] Read more.
Interdependencies of stochastically interacting units are usually quantified by the Kullback-Leibler divergence of a stationary joint probability distribution on the set of all configurations from the corresponding factorized distribution. This is a spatial approach which does not describe the intrinsically temporal aspects of interaction. In the present paper, the setting is extended to a dynamical version where temporal interdependencies are also captured by using information geometry of Markov chain manifolds. Full article
(This article belongs to the Special Issue Information Theoretic Incentives for Cognitive Systems)
Open AccessArticle
Collaborative Performance Research on Multi-level Hospital Management Based on Synergy Entropy-HoQ
Entropy 2015, 17(4), 2409-2431; https://doi.org/10.3390/e17042409 - 20 Apr 2015
Cited by 3 | Viewed by 2060
Abstract
Because of the general lack of multi-level hospital management collaboration performance effectiveness research, this paper proposes a multi-level hospital management Synergy Entropy-House of Quality (HoQ) Measurement Model by innovatively combining the House of Quality (HoQ) measure model with a Synergy Entropy computing principle. [...] Read more.
Because of the general lack of multi-level hospital management collaboration performance effectiveness research, this paper proposes a multi-level hospital management Synergy Entropy-House of Quality (HoQ) Measurement Model by innovatively combining the House of Quality (HoQ) measure model with a Synergy Entropy computing principle. Triangular fuzzy functions are used to determine the importance degree parameter of each hospital management element which combined with the results from the Synergy Entropy evaluation of the hospital management elements, arrive at a comprehensive collaborative computation result for the various elements, ensuring results objectivity. Finally, the analysis of the collaborative research on multi-level hospital management demonstrated the scientific effectiveness of the hospital management Synergy Entropy-House of Quality (HoQ) Measurement Model. Full article
(This article belongs to the Special Issue Entropy, Utility, and Logical Reasoning)
Open AccessArticle
An Entropy-Based Network Anomaly Detection Method
Entropy 2015, 17(4), 2367-2408; https://doi.org/10.3390/e17042367 - 20 Apr 2015
Cited by 59 | Viewed by 4007
Abstract
Data mining is an interdisciplinary subfield of computer science involving methods at the intersection of artificial intelligence, machine learning and statistics. One of the data mining tasks is anomaly detection which is the analysis of large quantities of data to identify items, events [...] Read more.
Data mining is an interdisciplinary subfield of computer science involving methods at the intersection of artificial intelligence, machine learning and statistics. One of the data mining tasks is anomaly detection which is the analysis of large quantities of data to identify items, events or observations which do not conform to an expected pattern. Anomaly detection is applicable in a variety of domains, e.g., fraud detection, fault detection, system health monitoring but this article focuses on application of anomaly detection in the field of network intrusion detection.The main goal of the article is to prove that an entropy-based approach is suitable to detect modern botnet-like malware based on anomalous patterns in network. This aim is achieved by realization of the following points: (i) preparation of a concept of original entropy-based network anomaly detection method, (ii) implementation of the method, (iii) preparation of original dataset, (iv) evaluation of the method. Full article
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Open AccessArticle
A Criterion for Topological Close-Packed Phase Formation in High Entropy Alloys
Entropy 2015, 17(4), 2355-2366; https://doi.org/10.3390/e17042355 - 20 Apr 2015
Cited by 32 | Viewed by 2502
Abstract
The stability of topological close-packed (TCP) phases were found to be well related to the average value of the d-orbital energy level \( \overline{Md} \) for most reported high entropy alloys (HEAs). Excluding some HEAs that contain high levels of the elements aluminum [...] Read more.
The stability of topological close-packed (TCP) phases were found to be well related to the average value of the d-orbital energy level \( \overline{Md} \) for most reported high entropy alloys (HEAs). Excluding some HEAs that contain high levels of the elements aluminum and vanadium, the results of this study indicated that the TCP phases form at \( \overline{Md} \) > 1.09. This criterion, as a semi-empirical method, can play a key role in designing and preparing HEAs with high amounts of transitional elements. Full article
Open AccessArticle
Multi-State Quantum Dissipative Dynamics in Sub-Ohmic Environment: The Strong Coupling Regime
Entropy 2015, 17(4), 2341-2354; https://doi.org/10.3390/e17042341 - 17 Apr 2015
Cited by 17 | Viewed by 2096
Abstract
We study the dissipative quantum dynamics and the asymptotic behavior of a particle in a bistable potential interacting with a sub-Ohmic broadband environment. The reduced dynamics, in the intermediate to strong dissipation regime, is obtained beyond the two-level system approximation by using a [...] Read more.
We study the dissipative quantum dynamics and the asymptotic behavior of a particle in a bistable potential interacting with a sub-Ohmic broadband environment. The reduced dynamics, in the intermediate to strong dissipation regime, is obtained beyond the two-level system approximation by using a real-time path integral approach. We find a crossover dynamic regime with damped intra-well oscillations and incoherent tunneling and a completely incoherent regime at strong damping. Moreover, a nonmonotonic behavior of the left/right well population difference is found as a function of the damping strength. Full article
(This article belongs to the Special Issue Quantum Computation and Information: Multi-Particle Aspects)
Open AccessArticle
Exergy Analysis of a Ground-Coupled Heat Pump Heating System with Different Terminals
Entropy 2015, 17(4), 2328-2340; https://doi.org/10.3390/e17042328 - 17 Apr 2015
Cited by 7 | Viewed by 2571
Abstract
In order to evaluate and improve the performance of a ground-coupled heat pump (GCHP) heating system with radiant floors as terminals, an exergy analysis based on test results is performed in this study. The system is divided into four subsystems, and the exergy [...] Read more.
In order to evaluate and improve the performance of a ground-coupled heat pump (GCHP) heating system with radiant floors as terminals, an exergy analysis based on test results is performed in this study. The system is divided into four subsystems, and the exergy loss and exergy efficiency of each subsystem are calculated using the expressions derived based on exergy balance equations. The average values of the measured parameters are used for the exergy analysis. The analysis results show that the two largest exergy losses occur in the heat pump and terminals, with losses of 55.3% and 22.06%, respectively, and the lowest exergy efficiency occurs in the ground heat exchange system. Therefore, GCHP system designers should pay close attention to the selection of heat pumps and terminals, especially in the design of ground heat exchange systems. Compared with the scenario system in which fan coil units (FCUs) are substituted for the radiant floors, the adoption of radiant floors can result in a decrease of 12% in heating load, an increase of 3.24% in exergy efficiency of terminals and an increase of 1.18% in total exergy efficiency of the system. The results may point out the direction and ways of optimizing GCHP systems. Full article
(This article belongs to the Special Issue Exergy: Analysis and Applications)
Open AccessArticle
Information-Theoretic Inference of Common Ancestors
Entropy 2015, 17(4), 2304-2327; https://doi.org/10.3390/e17042304 - 16 Apr 2015
Cited by 13 | Viewed by 3226
Abstract
A directed acyclic graph (DAG) partially represents the conditional independence structure among observations of a system if the local Markov condition holds, that is if every variable is independent of its non-descendants given its parents. In general, there is a whole class of [...] Read more.
A directed acyclic graph (DAG) partially represents the conditional independence structure among observations of a system if the local Markov condition holds, that is if every variable is independent of its non-descendants given its parents. In general, there is a whole class of DAGs that represents a given set of conditional independence relations. We are interested in properties of this class that can be derived from observations of a subsystem only. To this end, we prove an information-theoretic inequality that allows for the inference of common ancestors of observed parts in any DAG representing some unknown larger system. More explicitly, we show that a large amount of dependence in terms of mutual information among the observations implies the existence of a common ancestor that distributes this information. Within the causal interpretation of DAGs, our result can be seen as a quantitative extension of Reichenbach’s principle of common cause to more than two variables. Our conclusions are valid also for non-probabilistic observations, such as binary strings, since we state the proof for an axiomatized notion of “mutual information” that includes the stochastic as well as the algorithmic version. Full article
(This article belongs to the Special Issue Information Processing in Complex Systems)
Open AccessArticle
Some Comments on the Entropy-Based Criteria for Piping
Entropy 2015, 17(4), 2281-2303; https://doi.org/10.3390/e17042281 - 15 Apr 2015
Cited by 2 | Viewed by 2344
Abstract
This paper is an extension of previous work which characterises soil behaviours using the grading entropy diagram. The present work looks at the piping process in granular soils, by considering some new data from flood-protection dikes. The piping process is divided into three [...] Read more.
This paper is an extension of previous work which characterises soil behaviours using the grading entropy diagram. The present work looks at the piping process in granular soils, by considering some new data from flood-protection dikes. The piping process is divided into three parts here: particle movement at the micro scale to segregate free water; sand boil development (which is the initiation of the pipe), and pipe growth. In the first part of the process, which occurs during the rising flood, the increase in shear stress along the dike base may cause segregation of water into micro pipes if the subsoil in the dike base is relatively loose. This occurs at the maximum dike base shear stress level (ratio of shear stress and strength) zone which is close to the toe. In the second part of the process, the shear strain increment causes a sudden, asymmetric slide and cracking of the dike leading to the localized excess pore pressure, liquefaction and the formation of a sand boil. In the third part of the process, the soil erosion initiated through the sand boil continues, and the pipe grows. The piping in the Hungarian dikes often occurs in a two-layer system; where the base layer is coarser with higher permeability and the cover layer is finer with lower permeability. The new data presented here show that the soils ejected from the sand boils are generally silty sands and sands, which are prone to both erosion (on the basis of the entropy criterion) and liquefaction. They originate from the cover layer which is basically identical to the soil used in the Dutch backward erosion experiments. Full article
Open AccessReview
Integrating Entropy and Copula Theories for Hydrologic Modeling and Analysis
Entropy 2015, 17(4), 2253-2280; https://doi.org/10.3390/e17042253 - 15 Apr 2015
Cited by 22 | Viewed by 2667
Abstract
Entropy is a measure of uncertainty and has been commonly used for various applications, including probability inferences in hydrology. Copula has been widely used for constructing joint distributions to model the dependence structure of multivariate hydrological random variables. Integration of entropy and copula [...] Read more.
Entropy is a measure of uncertainty and has been commonly used for various applications, including probability inferences in hydrology. Copula has been widely used for constructing joint distributions to model the dependence structure of multivariate hydrological random variables. Integration of entropy and copula theories provides new insights in hydrologic modeling and analysis, for which the development and application are still in infancy. Two broad branches of integration of the two concepts, entropy copula and copula entropy, are introduced in this study. On the one hand, the entropy theory can be used to derive new families of copulas based on information content matching. On the other hand, the copula entropy provides attractive alternatives in the nonlinear dependence measurement even in higher dimensions. We introduce in this study the integration of entropy and copula theories in the dependence modeling and analysis to illustrate the potential applications in hydrology and water resources. Full article
(This article belongs to the Special Issue Entropy in Hydrology)
Open AccessArticle
A Community-Based Approach to Identifying Influential Spreaders
Entropy 2015, 17(4), 2228-2252; https://doi.org/10.3390/e17042228 - 14 Apr 2015
Cited by 20 | Viewed by 2728
Abstract
Identifying influential spreaders in complex networks has a significant impact on understanding and control of spreading process in networks. In this paper, we introduce a new centrality index to identify influential spreaders in a network based on the community structure of the network. [...] Read more.
Identifying influential spreaders in complex networks has a significant impact on understanding and control of spreading process in networks. In this paper, we introduce a new centrality index to identify influential spreaders in a network based on the community structure of the network. The community-based centrality (CbC) considers both the number and sizes of communities that are directly linked by a node. We discuss correlations between CbC and other classical centrality indices. Based on simulations of the single source of infection with the Susceptible-Infected-Recovered (SIR) model, we find that CbC can help to identify some critical influential nodes that other indices cannot find. We also investigate the stability of CbC. Full article
(This article belongs to the Special Issue Recent Advances in Chaos Theory and Complex Networks)
Open AccessArticle
Cryptographic Aspects of Quantum Reading
Entropy 2015, 17(4), 2218-2227; https://doi.org/10.3390/e17042218 - 13 Apr 2015
Cited by 7 | Viewed by 1823
Abstract
Besides achieving secure communication between two spatially-separated parties,another important issue in modern cryptography is related to secure communication intime, i.e., the possibility to confidentially store information on a memory for later retrieval.Here we explore this possibility in the setting of quantum reading, which [...] Read more.
Besides achieving secure communication between two spatially-separated parties,another important issue in modern cryptography is related to secure communication intime, i.e., the possibility to confidentially store information on a memory for later retrieval.Here we explore this possibility in the setting of quantum reading, which exploits quantumentanglement to efficiently read data from a memory whereas classical strategies (e.g., basedon coherent states or their mixtures) cannot retrieve any information. From this point ofview, the technique of quantum reading can provide a new form of technological security fordata storage. Full article
(This article belongs to the Special Issue Quantum Cryptography)
Open AccessArticle
Entropic-Skins Geometry to Describe Wall Turbulence Intermittency
Entropy 2015, 17(4), 2198-2217; https://doi.org/10.3390/e17042198 - 13 Apr 2015
Cited by 2 | Viewed by 1973
Abstract
In order to describe the phenomenon of intermittency in wall turbulence and, more particularly, the behaviour of moments and and intermittency exponents ζP with the order p and distance to the wall, we developed a new geometrical framework called “entropic-skins geometry” based [...] Read more.
In order to describe the phenomenon of intermittency in wall turbulence and, more particularly, the behaviour of moments and and intermittency exponents ζP with the order p and distance to the wall, we developed a new geometrical framework called “entropic-skins geometry” based on the notion of scale-entropy which is here applied to an experimental database of boundary layer flows. Each moment has its own spatial multi-scale support Ωp (“skin”). The model assumes the existence of a hierarchy of multi-scale sets Ωp ranged from the “bulk” to the “crest”. The crest noted characterizes the geometrical support where the most intermittent (the highest) fluctuations in energy dissipation occur; the bulk is the geometrical support for the whole range of fluctuations. The model assumes then the existence of a dynamical flux through the hierarchy of skins. The specific case where skins display a fractal structure is investigated. Bulk fractal dimension and crest dimension are linked by a scale-entropy flux defining a reversibility efficiency (d is the embedding dimension). The model, initially developed for homogeneous and isotropic turbulent flows, is applied here to wall bounded turbulence where intermittency exponents are measured by extended self-similarity. We obtained for intermittency exponents the analytical expression with γ ≈ 0.36 in agreement with experimental results. Full article
Open AccessArticle
Implications of Non-Differentiable Entropy on a Space-Time Manifold
Entropy 2015, 17(4), 2184-2197; https://doi.org/10.3390/e17042184 - 13 Apr 2015
Cited by 9 | Viewed by 1680
Abstract
Assuming that the motions of a complex system structural units take place on continuous, but non-differentiable curves of a space-time manifold, the scale relativity model with arbitrary constant fractal dimension (the hydrodynamic and wave function versions) is built. For non-differentiability through stochastic processes [...] Read more.
Assuming that the motions of a complex system structural units take place on continuous, but non-differentiable curves of a space-time manifold, the scale relativity model with arbitrary constant fractal dimension (the hydrodynamic and wave function versions) is built. For non-differentiability through stochastic processes of the Markov type, the non-differentiable entropy concept on a space-time manifold in the hydrodynamic version and its correspondence with motion variables (energy, momentum, etc.) are established. Moreover, for the same non-differentiability type, through a scale resolution dependence of a fundamental length and wave function independence with respect to the proper time, a non-differentiable Klein–Gordon-type equation in the wave function version is obtained. For a phase-amplitude functional dependence on the wave function, the non-differentiable spontaneous symmetry breaking mechanism implies pattern generation in the form of Cooper non-differentiable-type pairs, while its non-differentiable topology implies some fractal logic elements (fractal bit, fractal gates, etc.). Full article
(This article belongs to the Section Complexity)
Open AccessArticle
High-Speed Spindle Fault Diagnosis with the Empirical Mode Decomposition and Multiscale Entropy Method
Entropy 2015, 17(4), 2170-2183; https://doi.org/10.3390/e17042170 - 13 Apr 2015
Cited by 12 | Viewed by 2122
Abstract
The root mean square (RMS) value of a vibration signal is an important indicator used to represent the amplitude of vibrations in evaluating the quality of high-speed spindles. However, RMS is unable to detect a number of common fault characteristics that occur prior [...] Read more.
The root mean square (RMS) value of a vibration signal is an important indicator used to represent the amplitude of vibrations in evaluating the quality of high-speed spindles. However, RMS is unable to detect a number of common fault characteristics that occur prior to bearing failure. Extending the operational life and quality of spindles requires reliable fault diagnosis techniques for the analysis of vibration signals from three axes. This study used empirical mode decomposition to decompose signals into intrinsic mode functions containing a zero-crossing rate and energy to represent the characteristics of rotating elements. The MSE curve was then used to identify a number of characteristic defects. The purpose of this research was to obtain vibration signals along three axes with the aim of extending the operational life of devices included in the product line of an actual spindle manufacturing company. Full article
Open AccessArticle
Deep Belief Network-Based Approaches for Link Prediction in Signed Social Networks
Entropy 2015, 17(4), 2140-2169; https://doi.org/10.3390/e17042140 - 10 Apr 2015
Cited by 26 | Viewed by 3261
Abstract
In some online social network services (SNSs), the members are allowed to label their relationships with others, and such relationships can be represented as the links with signed values (positive or negative). The networks containing such relations are named signed social networks (SSNs), [...] Read more.
In some online social network services (SNSs), the members are allowed to label their relationships with others, and such relationships can be represented as the links with signed values (positive or negative). The networks containing such relations are named signed social networks (SSNs), and some real-world complex systems can be also modeled with SSNs. Given the information of the observed structure of an SSN, the link prediction aims to estimate the values of the unobserved links. Noticing that most of the previous approaches for link prediction are based on the members’ similarity and the supervised learning method, however, research work on the investigation of the hidden principles that drive the behaviors of social members are rarely conducted. In this paper, the deep belief network (DBN)-based approaches for link prediction are proposed. Including an unsupervised link prediction model, a feature representation method and a DBN-based link prediction method are introduced. The experiments are done on the datasets from three SNSs (social networking services) in different domains, and the results show that our methods can predict the values of the links with high performance and have a good generalization ability across these datasets. Full article
Open AccessArticle
Image Encryption Using Chebyshev Map and Rotation Equation
Entropy 2015, 17(4), 2117-2139; https://doi.org/10.3390/e17042117 - 09 Apr 2015
Cited by 36 | Viewed by 2624
Abstract
We propose a novel image encryption algorithm based on two pseudorandom bit generators: Chebyshev map based and rotation equation based. The first is used for permutation, and the second one for substitution operations. Detailed security analysis has been provided on the novel image [...] Read more.
We propose a novel image encryption algorithm based on two pseudorandom bit generators: Chebyshev map based and rotation equation based. The first is used for permutation, and the second one for substitution operations. Detailed security analysis has been provided on the novel image encryption algorithm using visual testing, key space evaluation, histogram analysis, information entropy calculation, correlation coefficient analysis, differential analysis, key sensitivity test, and computational and complexity analysis. Based on the theoretical and empirical results the novel image encryption scheme demonstrates an excellent level of security. Full article
(This article belongs to the Special Issue Recent Advances in Chaos Theory and Complex Networks)
Open AccessArticle
Research and Measurement of Software Complexity Based on Wuli, Shili, Renli (WSR) and Information Entropy
Entropy 2015, 17(4), 2094-2116; https://doi.org/10.3390/e17042094 - 08 Apr 2015
Cited by 1 | Viewed by 2006
Abstract
Complexity is an important factor throughout the software life cycle. It is increasingly difficult to guarantee software quality, cost and development progress with the increase in complexity. Excessive complexity is one of the main reasons for the failure of software projects, so effective [...] Read more.
Complexity is an important factor throughout the software life cycle. It is increasingly difficult to guarantee software quality, cost and development progress with the increase in complexity. Excessive complexity is one of the main reasons for the failure of software projects, so effective recognition, measurement and control of complexity becomes the key of project management. At first, this paper analyzes the current research situation of software complexity systematically and points out existing problems in current research. Then, it proposes a WSR framework of software complexity, which divides the complexity of software into three levels of Wuli (WL), Shili (SL) and Renli (RL), so that the staff in different roles may have a better understanding of complexity. Man is the main source of complexity, but the current research focuses on WL complexity, and the research of RL complexity is extremely scarce, so this paper emphasizes the research of RL complexity of software projects. This paper not only analyzes the composing factors of RL complexity, but also provides the definition of RL complexity. Moreover, it puts forward a quantitative measurement method of the complexity of personnel organization hierarchy and the complexity of personnel communication information based on information entropy first and analyzes and validates the scientificity and rationality of this measurement method through a large number of cases. Full article
Open AccessArticle
Target Detection and Ranging through Lossy Media using Chaotic Radar
Entropy 2015, 17(4), 2082-2093; https://doi.org/10.3390/e17042082 - 08 Apr 2015
Cited by 14 | Viewed by 2227
Abstract
A chaotic radar system has been developed for through-wall detection and ranging of targets. The chaotic signal generated by an improved Colpitts oscillator is designed as a probe signal. Ranging to target is achieved by the cross-correlation between the time-delayed reflected return signal [...] Read more.
A chaotic radar system has been developed for through-wall detection and ranging of targets. The chaotic signal generated by an improved Colpitts oscillator is designed as a probe signal. Ranging to target is achieved by the cross-correlation between the time-delayed reflected return signal and the replica of the transmitted chaotic signal. In this paper, we explore the performance of the chaotic radar system for target detection and ranging through lossy media. Experimental results show that the designed chaotic radar has the advantages of high range resolution, unambiguous correlation profile, and can be used for through wall target detection and sensing. Full article
(This article belongs to the Special Issue Recent Advances in Chaos Theory and Complex Networks)
Open AccessArticle
Kappa and q Indices: Dependence on the Degrees of Freedom
Entropy 2015, 17(4), 2062-2081; https://doi.org/10.3390/e17042062 - 08 Apr 2015
Cited by 26 | Viewed by 2340
Abstract
The kappa distributions, or their equivalent, the q-exponential distributions, are the natural generalization of the classical Boltzmann-Maxwell distributions, applied to the study of the particle populations in collisionless space plasmas. A huge step in the development of the theory of kappa distributions [...] Read more.
The kappa distributions, or their equivalent, the q-exponential distributions, are the natural generalization of the classical Boltzmann-Maxwell distributions, applied to the study of the particle populations in collisionless space plasmas. A huge step in the development of the theory of kappa distributions and their applications in space plasma physics has been achieved with the discovery that the observed kappa distributions are connected with the solid statistical background of non-extensive statistical mechanics. Now that the statistical framework has been identified, it is straightforward to improve our understanding of the nature of the kappa index (or the entropic q-index) that governs these distributions. One critical topic is the dependence of the kappa index on the degrees of freedom. In this paper, we first show how this specific dependence is naturally emerged, using the formalism of the N-particle kappa distribution of velocities. Then, the result is extended in the presence of potential energies. It is shown that the kappa index is simply related to the kinetic and potential degrees of freedom. In addition, it is shown that various problems of non-extensive statistical mechanics, such as (i) the correlation dependence on the total number of particles; and (ii) the normalization divergence for finite kappa indices, are resolved considering the kappa index dependence on the degrees of freedom. Full article
(This article belongs to the Special Issue Entropic Aspects in Statistical Physics of Complex Systems)
Open AccessArticle
Experimental and Thermoeconomic Analysis of Small-Scale Solar Organic Rankine Cycle (SORC) System
Entropy 2015, 17(4), 2039-2061; https://doi.org/10.3390/e17042039 - 07 Apr 2015
Cited by 31 | Viewed by 3333
Abstract
A small-scale solar organic Rankine cycle (ORC) is a promising renewable energy-driven power generation technology that can be used in the rural areas of developing countries. A prototype was developed and tested for its performance characteristics under a range of solar source temperatures. [...] Read more.
A small-scale solar organic Rankine cycle (ORC) is a promising renewable energy-driven power generation technology that can be used in the rural areas of developing countries. A prototype was developed and tested for its performance characteristics under a range of solar source temperatures. The solar ORC system power output was calculated based on the thermal and solar collector efficiency. The maximum solar power output was observed in April. The solar ORC unit power output ranged from 0.4 kW to 1.38 kW during the year. The highest power output was obtained when the expander inlet pressure was 13 bar and the solar source temperature was 120 °C. The area of the collector for the investigation was calculated based on the meteorological conditions of Busan City (South Korea). In the second part, economic and thermoeconomic analyses were carried out to determine the cost of energy per kWh from the solar ORC. The selling price of electricity generation was found to be $0.68/kWh and $0.39/kWh for the prototype and low cost solar ORC, respectively. The sensitivity analysis was carried out in order to find the influencing economic parameters for the change in NPV. Finally, the sustainability index was calculated to assess the sustainable development of the solar ORC system. Full article
(This article belongs to the Special Issue Exergy: Analysis and Applications)
Open AccessArticle
A Method to Derive the Definition of Generalized Entropy from Generalized Exergy for Any State in Many-Particle Systems
Entropy 2015, 17(4), 2025-2038; https://doi.org/10.3390/e17042025 - 07 Apr 2015
Cited by 4 | Viewed by 1919
Abstract
The literature reports the proofs that entropy is an inherent property of any system in any state and governs thermal energy, which depends on temperature and is transferred by heat interactions. A first novelty proposed in the present study is that mechanical energy, [...] Read more.
The literature reports the proofs that entropy is an inherent property of any system in any state and governs thermal energy, which depends on temperature and is transferred by heat interactions. A first novelty proposed in the present study is that mechanical energy, determined by pressure and transferred by work interactions, is also characterized by the entropy property. The second novelty is that a generalized definition of entropy relating to temperature, chemical potential and pressure of many-particle systems, is established to calculate the thermal, chemical and mechanical entropy contribution due to heat, mass and work interactions. The expression of generalized entropy is derived from generalized exergy, which in turn depends on temperature, chemical potential and pressure of the system, and by the entropy-exergy relationship constituting the basis of the method adopted to analyze the available energy and its transfer interactions with a reference system which may be external or constitute a subsystem. This method is underpinned by the Second Law statement enunciated in terms of existence and uniqueness of stable equilibrium for each value of energy content of the system. The equality of chemical potential and equality of pressure are assumed, in addition to equality of temperature, to be necessary conditions for stable equilibrium. Full article
(This article belongs to the Special Issue Exergy: Analysis and Applications)
Open AccessArticle
Resource Requirements and Speed versus Geometry of Unconditionally Secure Physical Key Exchanges
Entropy 2015, 17(4), 2010-2024; https://doi.org/10.3390/e17042010 - 03 Apr 2015
Cited by 4 | Viewed by 2441
Abstract
The imperative need for unconditional secure key exchange is expounded by the increasing connectivity of networks and by the increasing number and level of sophistication of cyberattacks. Two concepts that are theoretically information-secure are quantum key distribution (QKD) and Kirchoff-Law-Johnson-Noise (KLJN). However, these [...] Read more.
The imperative need for unconditional secure key exchange is expounded by the increasing connectivity of networks and by the increasing number and level of sophistication of cyberattacks. Two concepts that are theoretically information-secure are quantum key distribution (QKD) and Kirchoff-Law-Johnson-Noise (KLJN). However, these concepts require a dedicated connection between hosts in peer-to-peer (P2P) networks which can be impractical and or cost prohibitive. A practical and cost effective method is to have each host share their respective cable(s) with other hosts such that two remote hosts can realize a secure key exchange without the need of an additional cable or key exchanger. In this article we analyze the cost complexities of cable, key exchangers, and time required in the star network. We mentioned the reliability of the star network and compare it with other network geometries. We also conceived a protocol and equation for the number of secure bit exchange periods needed in a star network. We then outline other network geometries and trade-off possibilities that seem interesting to explore. Full article
(This article belongs to the Special Issue Quantum Cryptography)
Open AccessArticle
Translation of Ludwig Boltzmann’s Paper “On the Relationship between the Second Fundamental Theorem of the Mechanical Theory of Heat and Probability Calculations Regarding the Conditions for Thermal Equilibrium” Sitzungberichte der Kaiserlichen Akademie der Wissenschaften. Mathematisch-Naturwissen Classe. Abt. II, LXXVI 1877, pp 373-435 (Wien. Ber. 1877, 76:373-435). Reprinted in Wiss. Abhandlungen, Vol. II, reprint 42, p. 164-223, Barth, Leipzig, 1909
Entropy 2015, 17(4), 1971-2009; https://doi.org/10.3390/e17041971 - 02 Apr 2015
Cited by 22 | Viewed by 4746
Abstract
Translation of the seminal 1877 paper by Ludwig Boltzmann which for the first time established the probabilistic basis of entropy. Includes a scientific commentary. Full article
(This article belongs to the Section Statistical Physics)
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Open AccessArticle
Assessing Coupling Dynamics from an Ensemble of Time Series
Entropy 2015, 17(4), 1958-1970; https://doi.org/10.3390/e17041958 - 02 Apr 2015
Cited by 25 | Viewed by 3288
Abstract
Finding interdependency relations between time series provides valuable knowledge about the processes that generated the signals. Information theory sets a natural framework for important classes of statistical dependencies. However, a reliable estimation from information-theoretic functionals is hampered when the dependency to be assessed [...] Read more.
Finding interdependency relations between time series provides valuable knowledge about the processes that generated the signals. Information theory sets a natural framework for important classes of statistical dependencies. However, a reliable estimation from information-theoretic functionals is hampered when the dependency to be assessed is brief or evolves in time. Here, we show that these limitations can be partly alleviated when we have access to an ensemble of independent repetitions of the time series. In particular, we gear a data-efficient estimator of probability densities to make use of the full structure of trial-based measures. By doing so, we can obtain time-resolved estimates for a family of entropy combinations (including mutual information, transfer entropy and their conditional counterparts), which are more accurate than the simple average of individual estimates over trials. We show with simulated and real data generated by coupled electronic circuits that the proposed approach allows one to recover the time-resolved dynamics of the coupling between different subsystems. Full article
(This article belongs to the Special Issue Transfer Entropy) Printed Edition available
Open AccessArticle
A Simple Decoder for Topological Codes
Entropy 2015, 17(4), 1946-1957; https://doi.org/10.3390/e17041946 - 01 Apr 2015
Cited by 14 | Viewed by 2106
Abstract
Here we study an efficient algorithm for decoding topological codes. It is a simple form of HDRG decoder, which could be straightforwardly generalized to complex decoding problems. Specific results are obtained for the planar code with both i.i.d. and spatially correlated errors. The [...] Read more.
Here we study an efficient algorithm for decoding topological codes. It is a simple form of HDRG decoder, which could be straightforwardly generalized to complex decoding problems. Specific results are obtained for the planar code with both i.i.d. and spatially correlated errors. The method is shown to compare well with existing ones, despite its simplicity. Full article
(This article belongs to the Special Issue Quantum Computation and Information: Multi-Particle Aspects)
Open AccessArticle
On Nonlinear Complexity and Shannon’s Entropy of Finite Length Random Sequences
Entropy 2015, 17(4), 1936-1945; https://doi.org/10.3390/e17041936 - 01 Apr 2015
Cited by 4 | Viewed by 1896
Abstract
Pseudorandom binary sequences have important uses in many fields, such as spread spectrum communications, statistical sampling and cryptography. There are two kinds of method in evaluating the properties of sequences, one is based on the probability measure, and the other is based on [...] Read more.
Pseudorandom binary sequences have important uses in many fields, such as spread spectrum communications, statistical sampling and cryptography. There are two kinds of method in evaluating the properties of sequences, one is based on the probability measure, and the other is based on the deterministic complexity measures. However, the relationship between these two methods still remains an interesting open problem. In this paper, we mainly focus on the widely used nonlinear complexity of random sequences, study on its distribution, expectation and variance of memoryless sources. Furthermore, the relationship between nonlinear complexity and Shannon’s entropy is also established here. The results show that the Shannon’s entropy is strictly monotonically decreased with nonlinear complexity. Full article
(This article belongs to the Section Complexity)
Open AccessArticle
Pressure Tensor of Nanoscopic Liquid Drops
Entropy 2015, 17(4), 1916-1935; https://doi.org/10.3390/e17041916 - 01 Apr 2015
Cited by 1 | Viewed by 1559
Abstract
This study describes the structure of an inhomogeneous fluid of one or several components that forms a spherical interface. Using the stress tensor of Percus–Romero, which depends on the density of one particle and the intermolecular potential, it provides an analytical development leading [...] Read more.
This study describes the structure of an inhomogeneous fluid of one or several components that forms a spherical interface. Using the stress tensor of Percus–Romero, which depends on the density of one particle and the intermolecular potential, it provides an analytical development leading to the microscopic expressions of the pressure differences and the interfacial properties of both systems. The results are compared with a previous study and agree with the description of the mean field. Full article
(This article belongs to the Section Statistical Physics)
Open AccessArticle
Kinetic Theory Modeling and Efficient Numerical Simulation of Gene Regulatory Networks Based on Qualitative Descriptions
Entropy 2015, 17(4), 1896-1915; https://doi.org/10.3390/e17041896 - 01 Apr 2015
Cited by 4 | Viewed by 2425
Abstract
In this work, we begin by considering the qualitative modeling of biological regulatory systems using process hitting, from which we define its probabilistic counterpart by considering the chemical master equation within a kinetic theory framework. The last equation is efficiently solved by considering [...] Read more.
In this work, we begin by considering the qualitative modeling of biological regulatory systems using process hitting, from which we define its probabilistic counterpart by considering the chemical master equation within a kinetic theory framework. The last equation is efficiently solved by considering a separated representation within the proper generalized decomposition framework that allows circumventing the so-called curse of dimensionality. Finally, model parameters can be added as extra-coordinates in order to obtain a parametric solution of the model. Full article
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