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Appl. Sci., Volume 7, Issue 12 (December 2017)

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Cover Story (view full-size image) The Bloch Surface Wave (BSW) is an evanescent electromagnetic mode found on the surface of a [...] Read more.
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Open AccessArticle A Bibliometric Study to Assess Bioprinting Evolution
Appl. Sci. 2017, 7(12), 1331; https://doi.org/10.3390/app7121331
Received: 20 October 2017 / Revised: 11 December 2017 / Accepted: 14 December 2017 / Published: 20 December 2017
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Abstract
Bioprinting as a tissue engineering tool is one of the most promising technologies for overcoming organ shortage. However, the spread of populist articles among on this technology could potentially lead public opinion to idealize its readiness. This bibliometric study aimed to trace the
[...] Read more.
Bioprinting as a tissue engineering tool is one of the most promising technologies for overcoming organ shortage. However, the spread of populist articles among on this technology could potentially lead public opinion to idealize its readiness. This bibliometric study aimed to trace the evolution of bioprinting literature over the past decade (i.e., 2000 to 2015) using the SCI-expanded database of Web of Science® (WoS, Thomson Reuters). The articles were analyzed by combining various bibliometric tools, such as science mapping and topic analysis, and a Technology Readiness Scale was adapted to assess the evolution of this emerging field. The number of analyzed publications was low (231), but the literature grew exceptionally fast. The “Engineering, Biomedical” was still the most represented WoS category. Some of the recent fronts were “hydrogels” and “stem cells”, while “in vitro” remained one of the most used keywords. The number of countries and journals involved in bioprinting literature grew substantially in one decade, also supporting the idea of an increasing community. Neither the United States’ leadership in bioprinting productivity nor the role of universities in publications were challenged. “Biofabrication” and “Biomaterials” journals were still the leaders of the bioprinting field. Bioprinting is a young but promising technology. Full article
(This article belongs to the Special Issue Biofabrication: from Additive Bio-Manufacturing to Bioprinting)
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Open AccessArticle Production and Characterization of Glass-Ceramic Materials for Potential Use in Dental Applications: Thermal and Mechanical Properties, Microstructure, and In Vitro Bioactivity
Appl. Sci. 2017, 7(12), 1330; https://doi.org/10.3390/app7121330
Received: 19 November 2017 / Revised: 11 December 2017 / Accepted: 18 December 2017 / Published: 20 December 2017
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Abstract
Multicomponent silicate glasses and their corresponding glass-ceramic derivatives were prepared and tested for potential applications in dentistry. The glasses were produced via a melting-quenching process, ground and sieved to obtain fine-grained powders that were pressed in the form of small cylinders and thermally
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Multicomponent silicate glasses and their corresponding glass-ceramic derivatives were prepared and tested for potential applications in dentistry. The glasses were produced via a melting-quenching process, ground and sieved to obtain fine-grained powders that were pressed in the form of small cylinders and thermally treated to obtain sintered glass-ceramic samples. X-ray diffraction investigations were carried out on the materials before and after sintering to detect the presence of crystalline phases. Thermal analyses, mechanical characterizations (assessment of bending strength, Young’s modulus, Vickers hardness, fracture toughness), and in vitro bioactivity tests in simulated body fluid were performed. On the basis of the acquired results, different potential applications in the dental field were discussed for the proposed glass-ceramics. The use of such materials can be suggested for either restorative dentistry or dental implantology, mainly depending on their peculiar bioactive and mechanical properties. At the end of the work, the feasibility of a novel full-ceramic bilayered implant was explored and discussed. This implant, comprising a highly bioactive layer expected to promote osteointegration and another one mimicking the features of tooth enamel, can have an interesting potential for whole tooth substitution. Full article
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Open AccessArticle Populating the Mix Space: Parametric Methods for Generating Multitrack Audio Mixtures
Appl. Sci. 2017, 7(12), 1329; https://doi.org/10.3390/app7121329
Received: 31 October 2017 / Revised: 24 November 2017 / Accepted: 4 December 2017 / Published: 20 December 2017
Cited by 1 | PDF Full-text (1375 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The creation of multitrack mixes by audio engineers is a time-consuming activity and creating high-quality mixes requires a great deal of knowledge and experience. Previous studies on the perception of music mixes have been limited by the relatively small number of human-made mixes
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The creation of multitrack mixes by audio engineers is a time-consuming activity and creating high-quality mixes requires a great deal of knowledge and experience. Previous studies on the perception of music mixes have been limited by the relatively small number of human-made mixes analysed. This paper describes a novel “mix-space”, a parameter space which contains all possible mixes using a finite set of tools, as well as methods for the parametric generation of artificial mixes in this space. Mixes that use track gain, panning and equalisation are considered. This allows statistical methods to be used in the study of music mixing practice, such as Monte Carlo simulations or population-based optimisation methods. Two applications are described: an investigation into the robustness and accuracy of tempo-estimation algorithms and an experiment to estimate distributions of spectral centroid values within sets of mixes. The potential for further work is also described. Full article
(This article belongs to the Special Issue Sound and Music Computing) Printed Edition available
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Open AccessFeature PaperArticle Virtual Analog Models of the Lockhart and Serge Wavefolders
Appl. Sci. 2017, 7(12), 1328; https://doi.org/10.3390/app7121328
Received: 12 October 2017 / Revised: 10 November 2017 / Accepted: 13 December 2017 / Published: 20 December 2017
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Abstract
Wavefolders are a particular class of nonlinear waveshaping circuits, and a staple of the “West Coast” tradition of analog sound synthesis. In this paper, we present analyses of two popular wavefolding circuits—the Lockhart and Serge wavefolders—and show that they achieve a very similar
[...] Read more.
Wavefolders are a particular class of nonlinear waveshaping circuits, and a staple of the “West Coast” tradition of analog sound synthesis. In this paper, we present analyses of two popular wavefolding circuits—the Lockhart and Serge wavefolders—and show that they achieve a very similar audio effect. We digitally model the input–output relationship of both circuits using the Lambert-W function, and examine their time- and frequency-domain behavior. To ameliorate the issue of aliasing distortion introduced by the nonlinear nature of wavefolding, we propose the use of the first-order antiderivative method. This method allows us to implement the proposed digital models in real-time without having to resort to high oversampling factors. The practical synthesis usage of both circuits is discussed by considering the case of multiple wavefolder stages arranged in series. Full article
(This article belongs to the Special Issue Sound and Music Computing) Printed Edition available
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Open AccessArticle Day-Ahead Dispatch Model of Electro-Thermal Integrated Energy System with Power to Gas Function
Appl. Sci. 2017, 7(12), 1326; https://doi.org/10.3390/app7121326
Received: 28 October 2017 / Revised: 13 December 2017 / Accepted: 14 December 2017 / Published: 20 December 2017
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Abstract
The application of power to gas (P2G) provides a new way to absorb intermittent renewable energy generation, which improves the efficiency of renewable energy utilization and provides the necessary flexibility for operating the integrated energy system. The electro-thermal integrated energy system with P2G
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The application of power to gas (P2G) provides a new way to absorb intermittent renewable energy generation, which improves the efficiency of renewable energy utilization and provides the necessary flexibility for operating the integrated energy system. The electro-thermal integrated energy system with P2G is a new form of using energy efficiently. In this paper, we first introduce the technology and application of P2G. On the basis of considering the characteristics of P2G facilities, power systems, natural gas systems and heating systems, an optimal dispatching model of electro-thermal multi-energy system with P2G facilities is proposed. Particle swarm optimization is used to solve the optimal scheduling model. The simulation results are discussed for the six-bus and six-node integration system and show that when the volume fraction of hydrogen does not exceed 20% in the gas network, for the same operating mode, an integrated energy grid with P2G function will save about 20 tons of standard coal per day and the abandoned wind rate can be regarded as 0. Full article
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Open AccessFeature PaperArticle An Accurate Perception Method for Low Contrast Bright Field Microscopy in Heterogeneous Microenvironments
Appl. Sci. 2017, 7(12), 1327; https://doi.org/10.3390/app7121327
Received: 21 November 2017 / Revised: 15 December 2017 / Accepted: 15 December 2017 / Published: 19 December 2017
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Abstract
Automated optical tweezers-based robotic manipulation of microscale objects requires real-time visual perception for estimating the states, i.e., positions and orientations, of the objects. Such visual perception is particularly challenging in heterogeneous environments comprising mixtures of biological and colloidal objects, such as cells and
[...] Read more.
Automated optical tweezers-based robotic manipulation of microscale objects requires real-time visual perception for estimating the states, i.e., positions and orientations, of the objects. Such visual perception is particularly challenging in heterogeneous environments comprising mixtures of biological and colloidal objects, such as cells and microspheres, when the popular imaging modality of low contrast bright field microscopy is used. In this paper, we present an accurate method to address this challenge. Our method combines many well-established image processing techniques such as blob detection, histogram equalization, erosion, and dilation with a convolutional neural network in a novel manner. We demonstrate the effectiveness of our processing pipeline in perceiving objects of both regular and irregular shapes in heterogeneous microenvironments of varying compositions. The neural network, in particular, helps in distinguishing the individual microspheres present in dense clusters. Full article
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Open AccessArticle Fog over Virtualized IoT: New Opportunity for Context-Aware Networked Applications and a Case Study
Appl. Sci. 2017, 7(12), 1325; https://doi.org/10.3390/app7121325
Received: 19 November 2017 / Revised: 2 December 2017 / Accepted: 13 December 2017 / Published: 19 December 2017
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Abstract
In this paper, we discuss the most significant application opportunities and outline the challenges in real-time and energy-efficient management of the distributed resources available in mobile devices and at the Internet-to-Data Center. We also present an energy-efficient adaptive scheduler for Vehicular Fog Computing
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In this paper, we discuss the most significant application opportunities and outline the challenges in real-time and energy-efficient management of the distributed resources available in mobile devices and at the Internet-to-Data Center. We also present an energy-efficient adaptive scheduler for Vehicular Fog Computing (VFC) that operates at the edge of a vehicular network, connected to the served Vehicular Clients (VCs) through an Infrastructure-to-Vehicular (I2V) over multiple Foglets (Fls). The scheduler optimizes the energy by leveraging the heterogeneity of Fls, where the Fl provider shapes the system workload by maximizing the task admission rate over data transfer and computation. The presented scheduling algorithm demonstrates that the resulting adaptive scheduler allows scalable and distributed implementation. Full article
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Open AccessArticle Bandwidth Widening of Piezoelectric Cantilever Beam Arrays by Mass-Tip Tuning for Low-Frequency Vibration Energy Harvesting
Appl. Sci. 2017, 7(12), 1324; https://doi.org/10.3390/app7121324
Received: 18 November 2017 / Revised: 11 December 2017 / Accepted: 14 December 2017 / Published: 19 December 2017
Cited by 2 | PDF Full-text (4759 KB) | HTML Full-text | XML Full-text
Abstract
Wireless sensor networks usually rely on internal permanent or rechargeable batteries as a power supply, causing high maintenance efforts. An alternative solution is to supply the entire system by harvesting the ambient energy, for example, by transducing ambient vibrations into electric energy by
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Wireless sensor networks usually rely on internal permanent or rechargeable batteries as a power supply, causing high maintenance efforts. An alternative solution is to supply the entire system by harvesting the ambient energy, for example, by transducing ambient vibrations into electric energy by virtue of the piezoelectric effect. The purpose of this paper is to present a simple engineering approach for the bandwidth optimization of vibration energy harvesting systems comprising multiple piezoelectric cantilevers (PECs). The frequency tuning of a particular cantilever is achieved by changing the tip mass. It is shown that the bandwidth enhancement by mass tuning is limited and requires several PECs with close resonance frequencies. At a fixed frequency detuning between subsequent PECs, the achievable bandwidth shows a saturation behavior as a function of the number of cantilevers used. Since the resonance frequency of each PEC is different, the output voltages at a particular excitation frequency have different amplitudes and phases. A simple power-transfer circuit where several PECs with an individual full wave bridge rectifier are connected in parallel allows one to extract the electrical power close to the theoretical maximum excluding the diode losses. The experiments performed on two- and three-PEC arrays show reasonable agreement with simulations and demonstrate that this power-transfer circuit additionally influences the frequency dependence of the harvested electrical power. Full article
(This article belongs to the Special Issue Piezoelectric Energy Harvesting: Materials, Devices and Application)
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Open AccessArticle Evaluating the High Frequency Behavior of the Modified Grounding Scheme in Wind Farms
Appl. Sci. 2017, 7(12), 1323; https://doi.org/10.3390/app7121323
Received: 11 November 2017 / Revised: 6 December 2017 / Accepted: 13 December 2017 / Published: 19 December 2017
Cited by 4 | PDF Full-text (2961 KB) | HTML Full-text | XML Full-text
Abstract
Wind generators are exposed to numerous destructive forces such as lightning and are therefore vulnerable to these phenomena. To evaluate the transient behavior of a wind power plant during direct and indirect strikes, modeling of all relevant components is required. Among the protective
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Wind generators are exposed to numerous destructive forces such as lightning and are therefore vulnerable to these phenomena. To evaluate the transient behavior of a wind power plant during direct and indirect strikes, modeling of all relevant components is required. Among the protective and control components of wind turbines, the grounding system is the most important element for protection against lightning strikes. This paper examines the impact of nonlinear soil ionization behavior and frequency dependency on a wind turbine in order to model a sufficient protection scheme to reduce overvoltage and make the system tolerable against transitions. The high frequency models of other equipment such as transformers, horizontal conductors, vertical rods, surge arresters and underground cables must also be taken into account to design the grounding system. Our Proposed Modified Grounding Scheme (PMGS) is to reduce the maximum transient overvoltages. We simulate the model in a restructured version of the Electromagnetic Transient Program (EMTP-RV) software to examine the effectiveness of the system. We then apply the simulated results to pair of turbines that are interconnected with a frequency-dependent cable. We carry out the simulation for direct and indirect lightning strikes. The results indicate that the MGS can lead to considerably more than a 50% reduction in transient voltages for lightning and thus leads to more reliable networks. Full article
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Open AccessArticle Current-Fluctuation Mechanism of Field Emitters Using Metallic Single-Walled Carbon Nanotubes with High Crystallinity
Appl. Sci. 2017, 7(12), 1322; https://doi.org/10.3390/app7121322
Received: 17 November 2017 / Revised: 13 December 2017 / Accepted: 14 December 2017 / Published: 19 December 2017
Cited by 1 | PDF Full-text (2502 KB) | HTML Full-text | XML Full-text
Abstract
Field emitters can be used as a cathode electrode in a cathodoluminescence device, and single-walled carbon nanotubes (SWCNTs) that are synthesized by arc discharge are expected to exhibit good field emission (FE) properties. However, a cathodoluminescence device that uses field emitters radiates rays
[...] Read more.
Field emitters can be used as a cathode electrode in a cathodoluminescence device, and single-walled carbon nanotubes (SWCNTs) that are synthesized by arc discharge are expected to exhibit good field emission (FE) properties. However, a cathodoluminescence device that uses field emitters radiates rays whose intensity considerably fluctuates at a low frequency, and the radiant fluctuation is caused by FE current fluctuation. To solve this problem, is very important to obtain a stable output for field emitters in a cathodoluminescence device. The authors consider that the electron-emission fluctuation is caused by Fowler–Nordheim electron tunneling and that the electrons in the Fowler–Nordheim regime pass through an inelastic potential barrier. We attempted to develop a theoretical model to analyze the power spectrum of the FE current fluctuation using metallic SWCNTs as field emitters, owing to their electrical conductivity by determining their FE properties. Field emitters that use metallic SWCNTs with high crystallinity were successfully developed to achieve a fluctuating FE current from field emitters at a low frequency by employing inelastic electron tunneling. This paper is the first report of the successful development of an inelastic-electron-tunneling model with a Wentzel–Kramers–Brillouin approximation for metallic SWCNTs based on the evaluation of FE properties. Full article
(This article belongs to the Special Issue Field Emission from Graphene and other Nanostructures)
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Open AccessArticle Playing for a Virtual Audience: The Impact of a Social Factor on Gestures, Sounds and Expressive Intents
Appl. Sci. 2017, 7(12), 1321; https://doi.org/10.3390/app7121321
Received: 30 October 2017 / Revised: 14 November 2017 / Accepted: 13 December 2017 / Published: 19 December 2017
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Abstract
Can we measure the impact of the presence of an audience on musicians’ performances? By exploring both acoustic and motion features for performances in Immersive Virtual Environments (IVEs), this study highlights the impact of the presence of a virtual audience on both the
[...] Read more.
Can we measure the impact of the presence of an audience on musicians’ performances? By exploring both acoustic and motion features for performances in Immersive Virtual Environments (IVEs), this study highlights the impact of the presence of a virtual audience on both the performance and the perception of authenticity and emotional intensity by listeners. Gestures and sounds produced were impacted differently when musicians performed at different expressive intents. The social factor made features converge towards values related to a habitual way of playing regardless of the expressive intent. This could be due to musicians’ habits to perform in a certain way in front of a crowd. On the listeners’ side, when comparing different expressive conditions, only one congruent condition (projected expressive intent in front of an audience) boosted the participants’ ratings for both authenticity and emotional intensity. At different values for kinetic energy and metrical centroid, stimuli recorded with an audience showed a different distribution of ratings, challenging the ecological validity of artificially created expressive intents. Finally, this study highlights the use of IVEs as a research tool and a training assistant for musicians who are eager to learn how to cope with their anxiety in front of an audience. Full article
(This article belongs to the Special Issue Sound and Music Computing) Printed Edition available
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Open AccessReview Wavefront Shaping and Its Application to Enhance Photoacoustic Imaging
Appl. Sci. 2017, 7(12), 1320; https://doi.org/10.3390/app7121320
Received: 14 October 2017 / Revised: 29 October 2017 / Accepted: 30 October 2017 / Published: 19 December 2017
Cited by 2 | PDF Full-text (3246 KB) | HTML Full-text | XML Full-text
Abstract
Since its introduction to the field in mid-1990s, photoacoustic imaging has become a fast-developing biomedical imaging modality with many promising potentials. By converting absorbed diffused light energy into not-so-diffused ultrasonic waves, the reconstruction of the ultrasonic waves from the targeted area in photoacoustic
[...] Read more.
Since its introduction to the field in mid-1990s, photoacoustic imaging has become a fast-developing biomedical imaging modality with many promising potentials. By converting absorbed diffused light energy into not-so-diffused ultrasonic waves, the reconstruction of the ultrasonic waves from the targeted area in photoacoustic imaging leads to a high-contrast sensing of optical absorption with ultrasonic resolution in deep tissue, overcoming the optical diffusion limit from the signal detection perspective. The generation of photoacoustic signals, however, is still throttled by the attenuation of photon flux due to the strong diffusion effect of light in tissue. Recently, optical wavefront shaping has demonstrated that multiply scattered light could be manipulated so as to refocus inside a complex medium, opening up new hope to tackle the fundamental limitation. In this paper, the principle and recent development of photoacoustic imaging and optical wavefront shaping are briefly introduced. Then we describe how photoacoustic signals can be used as a guide star for in-tissue optical focusing, and how such focusing can be exploited for further enhancing photoacoustic imaging in terms of sensitivity and penetration depth. Finally, the existing challenges and further directions towards in vivo applications are discussed. Full article
(This article belongs to the Special Issue Biomedical Photoacoustic and Thermoacoustic Imaging)
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Open AccessArticle Estimation of Tendon Force Distribution in Prestressed Concrete Girders Using Smart Strand
Appl. Sci. 2017, 7(12), 1319; https://doi.org/10.3390/app7121319
Received: 25 October 2017 / Revised: 8 December 2017 / Accepted: 13 December 2017 / Published: 19 December 2017
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Abstract
The recently developed smart strand offers the possibility of measuring the prestress force of the tendon from jacking and all along its service life. In the present study, a method estimating the force distribution in all the tendons of a prestressed concrete (PSC)
[...] Read more.
The recently developed smart strand offers the possibility of measuring the prestress force of the tendon from jacking and all along its service life. In the present study, a method estimating the force distribution in all the tendons of a prestressed concrete (PSC) girder installed with one smart strand is proposed. The force distribution in the prestressed tendons is formulated by the friction and the anchorage slip, and is obtained through an optimization process with respect to the compatibility conditions and equilibrium of the forces in the section of the PSC girder. The validation of the proposed method through a numerical example and experiment shows that it can be used to estimate the force developed in the tendon. Full article
(This article belongs to the Section Mechanical Engineering)
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Open AccessArticle Mobile Music, Sensors, Physical Modeling, and Digital Fabrication: Articulating the Augmented Mobile Instrument
Appl. Sci. 2017, 7(12), 1311; https://doi.org/10.3390/app7121311
Received: 31 October 2017 / Revised: 12 December 2017 / Accepted: 13 December 2017 / Published: 19 December 2017
Cited by 1 | PDF Full-text (1524 KB) | HTML Full-text | XML Full-text
Abstract
Two concepts are presented, extended, and unified in this paper: mobile device augmentation towards musical instruments design and the concept of hybrid instruments. The first consists of using mobile devices at the heart of novel musical instruments. Smartphones and tablets are augmented with
[...] Read more.
Two concepts are presented, extended, and unified in this paper: mobile device augmentation towards musical instruments design and the concept of hybrid instruments. The first consists of using mobile devices at the heart of novel musical instruments. Smartphones and tablets are augmented with passive and active elements that can take part in the production of sound (e.g., resonators, exciter, etc.), add new affordances to the device, or change its global aesthetics and shape. Hybrid instruments combine physical/acoustical and “physically informed” virtual/digital elements. Recent progress in physical modeling of musical instruments and digital fabrication is exploited to treat instrument parts in a multidimensional way, allowing any physical element to be substituted with a virtual one and vice versa (as long as it is physically possible). A wide range of tools to design mobile hybrid instruments is introduced and evaluated. Aesthetic and design considerations when making such instruments are also presented through a series of examples. Full article
(This article belongs to the Special Issue Sound and Music Computing) Printed Edition available
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Open AccessArticle Multi-Fidelity Multi-Objective Efficient Global Optimization Applied to Airfoil Design Problems
Appl. Sci. 2017, 7(12), 1318; https://doi.org/10.3390/app7121318
Received: 30 October 2017 / Revised: 29 November 2017 / Accepted: 15 December 2017 / Published: 18 December 2017
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Abstract
In this study, efficient global optimization (EGO) with a multi-fidelity hybrid surrogate model for multi-objective optimization is proposed to solve multi-objective real-world design problems. In the proposed approach, a design exploration is carried out assisted by surrogate models, which are constructed by adding
[...] Read more.
In this study, efficient global optimization (EGO) with a multi-fidelity hybrid surrogate model for multi-objective optimization is proposed to solve multi-objective real-world design problems. In the proposed approach, a design exploration is carried out assisted by surrogate models, which are constructed by adding a local deviation estimated by the kriging method and a global model approximated by a radial basis function. An expected hypervolume improvement is then computed on the basis of the model uncertainty to determine additional samples that could improve the model accuracy. In the investigation, the proposed approach is applied to two-objective and three-objective optimization test functions. Then, it is applied to aerodynamic airfoil design optimization with two objective functions, namely minimization of aerodynamic drag and maximization of airfoil thickness at the trailing edge. Finally, the proposed method is applied to aerodynamic airfoil design optimization with three objective functions, namely minimization of aerodynamic drag at cruising speed, maximization of airfoil thickness at the trialing edge and maximization of lift at low speed assuming a landing attitude. XFOILis used to investigate the low-fidelity aerodynamic force, and a Reynolds-averaged Navier–Stokes simulation is applied for high-fidelity aerodynamics in conjunction with a high-cost approach. For comparison, multi-objective optimization is carried out using a kriging model only with a high-fidelity solver (single fidelity). The design results indicate that the non-dominated solutions of the proposed method achieve greater data diversity than the optimal solutions of the kriging method. Moreover, the proposed method gives a smaller error than the kriging method. Full article
(This article belongs to the Special Issue Soft Computing Techniques in Structural Engineering and Materials)
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Open AccessReview Inorganic Salt Hydrate for Thermal Energy Storage
Appl. Sci. 2017, 7(12), 1317; https://doi.org/10.3390/app7121317
Received: 31 October 2017 / Revised: 6 December 2017 / Accepted: 14 December 2017 / Published: 18 December 2017
Cited by 1 | PDF Full-text (4219 KB) | HTML Full-text | XML Full-text
Abstract
Using phase change materials (PCMs) for thermal energy storage has always been a hot topic within the research community due to their excellent performance on energy conservation such as energy efficiency in buildings, solar domestic hot water systems, textile industry, biomedical and food
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Using phase change materials (PCMs) for thermal energy storage has always been a hot topic within the research community due to their excellent performance on energy conservation such as energy efficiency in buildings, solar domestic hot water systems, textile industry, biomedical and food agroindustry. Several literatures have reported phase change materials concerning various aspects. Among these materials, salt hydrates are worthy of exploring due to their high-energy storage density, rational price, multiple sources and relatively good thermal conductivity. This paper reviews the present state of salt hydrates PCMs targeting classification, properties, defects, possible solutions as well as their idiographic features which are suitable for applications. In addition, new trends of future research are also indicated. Full article
(This article belongs to the Section Energy)
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Open AccessReview Bibliometric Analysis of Social Robotics Research: Identifying Research Trends and Knowledgebase
Appl. Sci. 2017, 7(12), 1316; https://doi.org/10.3390/app7121316
Received: 10 October 2017 / Revised: 24 November 2017 / Accepted: 13 December 2017 / Published: 18 December 2017
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Abstract
As robotics becomes ubiquitous, there is increasing interest in understanding how to develop robots that better respond to social needs, as well as how robotics impacts society. This is evidenced by the growing rate of publications on social robotics. In this article, we
[...] Read more.
As robotics becomes ubiquitous, there is increasing interest in understanding how to develop robots that better respond to social needs, as well as how robotics impacts society. This is evidenced by the growing rate of publications on social robotics. In this article, we analyze the citation network of academic articles on social robotics to understand its structure, reveal research trends and expose its knowledgebase. We found eight major clusters, namely robots as social partners, human factors and ergonomics on human robot interaction, robotics for children’s development, swarm robotics, emotion detection, assessment of robotic surgery, robots for the elderly and telepresence and human robot interaction in rescue robots. In addition, despite its social focus, social science literature as a source of knowledge is barely present. Research trends point to studies on applications, rather than to specific technologies or morphologies, and in particular, towards robots as partners, for child development and assistance for the elderly. Full article
(This article belongs to the Special Issue Social Robotics)
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Open AccessFeature PaperArticle Plasmon Modulation Spectroscopy of Noble Metals to Reveal the Distribution of the Fermi Surface Electrons in the Conduction Band
Appl. Sci. 2017, 7(12), 1315; https://doi.org/10.3390/app7121315
Received: 15 November 2017 / Revised: 14 December 2017 / Accepted: 15 December 2017 / Published: 18 December 2017
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Abstract
To directly access the dynamics of electron distribution near the Fermi-surface after plasmon excitation, pump-probe spectroscopy was performed by pumping plasmons on noble-metal films and probing the interband transition. Spectral change in the interband transitions is sensitive to the electron distribution near the
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To directly access the dynamics of electron distribution near the Fermi-surface after plasmon excitation, pump-probe spectroscopy was performed by pumping plasmons on noble-metal films and probing the interband transition. Spectral change in the interband transitions is sensitive to the electron distribution near the Fermi-surface, because it involves the d valence-band to the conduction band transitions and should reflect the k-space distribution dynamics of electrons. For the continuous-wave pump and probe experiment, the plasmon modulation spectra are found to differ from both the current modulation and temperature difference spectra, possibly reflecting signatures of the plasmon wave function. For the femtosecond-pulse pump and probe experiment, the transient spectra agree well with the known spectra upon the excitation of the respective electrons resulting from plasmon relaxation, probably because the lifetime of plasmons is shorter than the pulse duration. Full article
(This article belongs to the Special Issue Laser Interaction with Plasmonic Nanostructures)
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Open AccessArticle Investigation into the Fire Hazards of Lithium-Ion Batteries under Overcharging
Appl. Sci. 2017, 7(12), 1314; https://doi.org/10.3390/app7121314
Received: 24 November 2017 / Revised: 14 December 2017 / Accepted: 15 December 2017 / Published: 18 December 2017
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Abstract
Numerous lithium-ion battery (LIB) fires and explosions have raised serious concerns about the safety issued associated with LIBs; some of these incidents were mainly caused by overcharging of LIBs. Therefore, to have a better understanding of the fire hazards caused by LIB overcharging,
[...] Read more.
Numerous lithium-ion battery (LIB) fires and explosions have raised serious concerns about the safety issued associated with LIBs; some of these incidents were mainly caused by overcharging of LIBs. Therefore, to have a better understanding of the fire hazards caused by LIB overcharging, two widely used commercial LIBs, nickel manganese cobalt oxide (NMC) and lithium iron phosphate (LFP), with different cut-off voltages (4.2 V, 4.5 V, 4.8 V and 5.0 V), were tested in this work. Some parameters including the surface temperature, the flame temperature, voltage, and radiative heat flux were measured and analyzed. The results indicate that the initial discharging voltage increases with the growth of charge cut-off voltage. Moreover, the higher the cut-off voltage, the longer the discharging time to reach 2.5 V. An overcharged LIB will undergo a more violent combustion process and has lower stability than a normal one, and the increasing cut-off voltage aggravates the severity. In addition, it is also revealed that the NMC fails earlier than the LFP under the same condition. The temperatures for safety vent cracking, ignition, and thermal runaway of LIBs exhibit similar values for the same condition, which demonstrates that the LIB will fail at a certain temperature. Finally, the peak heat flux, total radiative heat flux, and total radiative heat will rise with the increase in voltage. Full article
(This article belongs to the Special Issue Advanced Materials for Rechargeable Lithium Batteries)
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Open AccessFeature PaperArticle A Neural Parametric Singing Synthesizer Modeling Timbre and Expression from Natural Songs
Appl. Sci. 2017, 7(12), 1313; https://doi.org/10.3390/app7121313
Received: 3 November 2017 / Revised: 30 November 2017 / Accepted: 12 December 2017 / Published: 18 December 2017
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Abstract
We recently presented a new model for singing synthesis based on a modified version of the WaveNet architecture. Instead of modeling raw waveform, we model features produced by a parametric vocoder that separates the influence of pitch and timbre. This allows conveniently modifying
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We recently presented a new model for singing synthesis based on a modified version of the WaveNet architecture. Instead of modeling raw waveform, we model features produced by a parametric vocoder that separates the influence of pitch and timbre. This allows conveniently modifying pitch to match any target melody, facilitates training on more modest dataset sizes, and significantly reduces training and generation times. Nonetheless, compared to modeling waveform directly, ways of effectively handling higher-dimensional outputs, multiple feature streams and regularization become more important with our approach. In this work, we extend our proposed system to include additional components for predicting F0 and phonetic timings from a musical score with lyrics. These expression-related features are learned together with timbrical features from a single set of natural songs. We compare our method to existing statistical parametric, concatenative, and neural network-based approaches using quantitative metrics as well as listening tests. Full article
(This article belongs to the Special Issue Sound and Music Computing) Printed Edition available
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Open AccessArticle Effect of Aggregate Mineralogy and Concrete Microstructure on Thermal Expansion and Strength Properties of Concrete
Appl. Sci. 2017, 7(12), 1307; https://doi.org/10.3390/app7121307
Received: 17 November 2017 / Revised: 4 December 2017 / Accepted: 13 December 2017 / Published: 18 December 2017
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Abstract
Aggregate type and mineralogy are critical factors that influence the engineering properties of concrete. Temperature variations result in internal volume changes could potentially cause a network of micro-cracks leading to a reduction in the concrete’s compressive strength. The study specifically studied the effect
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Aggregate type and mineralogy are critical factors that influence the engineering properties of concrete. Temperature variations result in internal volume changes could potentially cause a network of micro-cracks leading to a reduction in the concrete’s compressive strength. The study specifically studied the effect of the type and mineralogy of fine and coarse aggregates in the normal strength concrete properties. As performance measures, the coefficient of thermal expansion (CTE) and compressive strength were tested with concrete specimens containing different types of fine aggregates (manufactured and natural sands) and coarse aggregates (dolomite and granite). Petrographic examinations were then performed to determine the mineralogical characteristics of the aggregate and to examine the aggregate and concrete microstructure. The test results indicate the concrete CTE increases with the silicon (Si) volume content in the aggregate. For the concrete specimens with higher CTE, the micro-crack density in the interfacial transition zone (ITZ) tended to be higher. The width of ITZ in one of the concrete specimens with a high CTE displayed the widest core ITZ (approx. 11 µm) while the concrete specimens with a low CTE showed the narrowest core ITZ (approx. 3.5 µm). This was attributed to early-age thermal cracking. Specimens with higher CTE are more susceptible to thermal stress. Full article
(This article belongs to the Section Materials)
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Open AccessArticle Compensation for Group Velocity of Polychromatic Wave Measurement in Dispersive Medium
Appl. Sci. 2017, 7(12), 1306; https://doi.org/10.3390/app7121306
Received: 21 November 2017 / Revised: 13 December 2017 / Accepted: 15 December 2017 / Published: 18 December 2017
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Abstract
The estimation of instantaneous frequency (IF) method is introduced to compensate for the group velocity of electromagnetic wave in dispersive medium. The location of the reflected signal can be obtained by using the time-frequency cross correlation (TFCC), following which it is used to
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The estimation of instantaneous frequency (IF) method is introduced to compensate for the group velocity of electromagnetic wave in dispersive medium. The location of the reflected signal can be obtained by using the time-frequency cross correlation (TFCC), following which it is used to extract the transmitted signal from the total signal acquired. The signal propagated in the dispersive medium is attenuated and distorted by the attenuation characteristics, which depend on the frequency of the medium. By using the IF curve calculated for the transmitted signal, the changed center frequency and time terms can be obtained. The obtained terms are used to compensate for the group velocity error induced by signal distortion and attenuation. Through experiments and simulation, the accuracy of the proposed method is 2% higher than that of the conventional method when the signal propagates over a long distance. Full article
(This article belongs to the Special Issue Ultrasonic Guided Waves)
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Open AccessArticle Cognitive Routing in Software-Defined Underwater Acoustic Networks
Appl. Sci. 2017, 7(12), 1312; https://doi.org/10.3390/app7121312
Received: 17 November 2017 / Revised: 13 December 2017 / Accepted: 13 December 2017 / Published: 17 December 2017
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Abstract
There are two different types of primary users (natural acoustic and artificial acoustic), and there is a long propagation delay for acoustic links in underwater cognitive acoustic networks (UCANs). Thus, the selection of a stable route is one of the key design factors
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There are two different types of primary users (natural acoustic and artificial acoustic), and there is a long propagation delay for acoustic links in underwater cognitive acoustic networks (UCANs). Thus, the selection of a stable route is one of the key design factors for improving overall network stability, thereby reducing end-to-end delay. Software-defined networking (SDN) is a novel approach that improves network intelligence. To this end, we propose a novel SDN-based routing protocol for UCANs in order to find a stable route between source and destination. A main controller is placed in a surface buoy that is responsible for the global view of the network, whereas local controllers are placed in different autonomous underwater vehicles (AUVs) that are responsible for a localized view of the network. The AUVs have fixed trajectories, and sensor nodes within transmission range of the AUVs serve as gateways to relay the gathered information to the controllers. This is an SDN-based underwater communications scheme whereby two nodes can only communicate when they have a consensus about a common idle channel. To evaluate our proposed scheme, we perform extensive simulations and improve network performance in terms of end-to-end delay, delivery ratio, and overhead. Full article
(This article belongs to the Special Issue Underwater Acoustics, Communications and Information Processing)
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Open AccessArticle Laterally Loaded Single Pile Response Considering the Influence of Suction and Non-Linear Behaviour of Reinforced Concrete Sections
Appl. Sci. 2017, 7(12), 1310; https://doi.org/10.3390/app7121310
Received: 10 November 2017 / Revised: 12 December 2017 / Accepted: 15 December 2017 / Published: 17 December 2017
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Abstract
A hybrid BEM-p-y curves approach was developed for the single pile analysis with free/fixed head restraint conditions. The method considers the soil non-linear behaviour by means of p-y curves in series to a multi-layered elastic half-space. The non-linearity of reinforced concrete pile sections,
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A hybrid BEM-p-y curves approach was developed for the single pile analysis with free/fixed head restraint conditions. The method considers the soil non-linear behaviour by means of p-y curves in series to a multi-layered elastic half-space. The non-linearity of reinforced concrete pile sections, also considering the influence of tension-stiffening, has been considered. The model reproduces the influence of suction by increasing the stress state and hence the stiffness of shallow soil-layers. Suction is modeled using the Modified-Kovacs model. The hybrid BEM-py curves method was validated by comparing results from data of 22 load tests on single piles. In addition, a detailed comparison is presented between measured and computed data on a large-diameter reinforced concrete bored single pile. Full article
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Open AccessArticle Fast Object Detection in Light Field Imaging by Integrating Deep Learning with Defocusing
Appl. Sci. 2017, 7(12), 1309; https://doi.org/10.3390/app7121309
Received: 12 October 2017 / Revised: 8 December 2017 / Accepted: 8 December 2017 / Published: 17 December 2017
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Abstract
Although four-dimensional (4D) light field imaging has many advantages over traditional two-dimensional (2D) imaging, its high computation cost often hinders the application of this technique in many fields, such as object detection and tracking. This paper presents a hybrid method to accelerate the
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Although four-dimensional (4D) light field imaging has many advantages over traditional two-dimensional (2D) imaging, its high computation cost often hinders the application of this technique in many fields, such as object detection and tracking. This paper presents a hybrid method to accelerate the object detection in light field imaging by integrating the deep learning with the depth estimation algorithm. The method takes full advantage of computation imaging of the light field to generate an all-in-focus image, a series of focal stacks, and multi-view images at the same time, and convolutional neural network and defocusing are consequently used to perform initial detection of the objects in three-dimensional (3D) space. The estimated depths of the detected objects are further optimized based on multi-baseline super-resolution stereo matching while efficiency is maintained, as well by compressing the searching space of the disparity. Experimental studies are conducted to demonstrate the effectiveness of the proposed method. Full article
(This article belongs to the Section Computer Science and Electrical Engineering)
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Open AccessArticle Wearable Plasma Pads for Biomedical Applications
Appl. Sci. 2017, 7(12), 1308; https://doi.org/10.3390/app7121308
Received: 20 November 2017 / Revised: 7 December 2017 / Accepted: 14 December 2017 / Published: 17 December 2017
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Abstract
A plasma pad that can be attached to human skin was developed for aesthetic and dermatological treatment. A polyimide film was used for the dielectric layer of the flexible pad, and high-voltage and ground electrodes were placed on the film surface. Medical gauze
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A plasma pad that can be attached to human skin was developed for aesthetic and dermatological treatment. A polyimide film was used for the dielectric layer of the flexible pad, and high-voltage and ground electrodes were placed on the film surface. Medical gauze covered the ground electrodes and was placed facing the skin to act as a spacer; thus, the plasma floated between the gauze and ground electrodes. In vitro and in vivo biocompatibility tests of the pad showed no cytotoxicity to normal cells and no irritation of mouse skin. Antibacterial activity was shown against Staphylococcus aureus and clinical isolates of methicillin-resistant S. aureus. Furthermore, skin wound healing with increased hair growth resulting from increased exogenous nitric oxide and capillary tube formation induced by the plasma pad was also confirmed in vivo. The present study suggests that this flexible and wearable plasma pad can be used for biomedical applications such as treatment of wounds and bacterial infections. Full article
(This article belongs to the Special Issue Smart Environment and Healthcare)
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Open AccessArticle Intensification of Organophosphorus Hydrolase Synthesis by Using Substances with Gas-Transport Function
Appl. Sci. 2017, 7(12), 1305; https://doi.org/10.3390/app7121305
Received: 3 November 2017 / Revised: 6 December 2017 / Accepted: 13 December 2017 / Published: 17 December 2017
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Abstract
We have performed studies and comparative analysis of the biosynthesis characteristics of intracellular recombinant enzyme, such as hexahistidine-containing organophosphorus hydrolase (His6-OPH) in Escherichia coli SG13009[pREP4] cells when various perfluorocarbon compounds (PFC) were introduced into the medium for cell cultivation. The PFC
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We have performed studies and comparative analysis of the biosynthesis characteristics of intracellular recombinant enzyme, such as hexahistidine-containing organophosphorus hydrolase (His6-OPH) in Escherichia coli SG13009[pREP4] cells when various perfluorocarbon compounds (PFC) were introduced into the medium for cell cultivation. The PFC were found to facilitate the biosynthesis of His6-OPH: increased levels of the total OPH-activity (up to 37%) were measured upon introduction of 1,1,1,2,2,3,3,4,4,5,5,6,6,6-tetradecafluorohexane (PFH) and 4,7,10,13,16,19,22,25,28,31-decaoxaperfluoro-5,8,11,14,17,18,21,24,27,30-decamethyl tetratriacontane (Polyether II) into culture medium. We have demonstrated the possibility of effective and multiple (at least five-fold) use of PFH for biosynthesis of intracellular recombinant protein His6-OPH, which catalyzes the hydrolysis of organophosphorus pesticides (OP), is widely used in agriculture and can be applied as new antidote for OP-detoxification in vivo. The multiple use of PFH was achieved through recycling of this substance: sediment of Escherichia coli SG13009[pREP4] cell biomass was collected at the end of each culture growing step and disintegrated with ultrasound, and obtained residue containing almost all of the initially introduced PFC was then added to the medium at the start of the following culture growing step. Full article
(This article belongs to the Section Chemistry)
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Open AccessArticle An NHPP Software Reliability Model with S-Shaped Growth Curve Subject to Random Operating Environments and Optimal Release Time
Appl. Sci. 2017, 7(12), 1304; https://doi.org/10.3390/app7121304
Received: 26 October 2017 / Revised: 8 December 2017 / Accepted: 12 December 2017 / Published: 16 December 2017
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Abstract
The failure of a computer system because of a software failure can lead to tremendous losses to society; therefore, software reliability is a critical issue in software development. As software has become more prevalent, software reliability has also become a major concern in
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The failure of a computer system because of a software failure can lead to tremendous losses to society; therefore, software reliability is a critical issue in software development. As software has become more prevalent, software reliability has also become a major concern in software development. We need to predict the fluctuations in software reliability and reduce the cost of software testing: therefore, a software development process that considers the release time, cost, reliability, and risk is indispensable. We thus need to develop a model to accurately predict the defects in new software products. In this paper, we propose a new non-homogeneous Poisson process (NHPP) software reliability model, with S-shaped growth curve for use during the software development process, and relate it to a fault detection rate function when considering random operating environments. An explicit mean value function solution for the proposed model is presented. Examples are provided to illustrate the goodness-of-fit of the proposed model, along with several existing NHPP models that are based on two sets of failure data collected from software applications. The results show that the proposed model fits the data more closely than other existing NHPP models to a significant extent. Finally, we propose a model to determine optimal release policies, in which the total software system cost is minimized depending on the given environment. Full article
(This article belongs to the Section Computer Science and Electrical Engineering)
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Open AccessArticle The Use of Heat-Resistant Concrete Made with Ceramic Sanitary Ware Waste for a Thermal Energy Storage
Appl. Sci. 2017, 7(12), 1303; https://doi.org/10.3390/app7121303
Received: 17 November 2017 / Revised: 9 December 2017 / Accepted: 14 December 2017 / Published: 16 December 2017
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Abstract
The paper presents the results obtained in the course of a study on the concrete made of aggregate obtained from wastes of sanitary ceramics. Previous examinations proved high in strength and durability of concrete of this type, and it showed a resistance to
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The paper presents the results obtained in the course of a study on the concrete made of aggregate obtained from wastes of sanitary ceramics. Previous examinations proved high in strength and durability of concrete of this type, and it showed a resistance to high temperatures. The material was classified as a fireproof concrete. While searching for the optimal applications of such concrete, a series of examinations and analyses on its thermal energy storage (TES) properties were performed. This paper describes the two-stage experiment on the thermal behavior of the concrete made with sanitary ceramic wastes during cooling processes in comparison to different building materials subjected to the same thermal conditions. On the basis of the thermal, infrared analysis, and suitable calculations, the thermal power and the ability of the composite to store thermal energy was estimated. Finally, it was stated that the concrete made of sanitary ceramic waste aggregate and alumina cement can be recommended as a heat-accumulating material, and in combination with high durability can be used, e.g., for the construction of fireplace bodies. Full article
(This article belongs to the Section Materials)
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Open AccessArticle Printing Speed and Quality Enhancement by Controlling the Surface Energy of Cliché in Reverse Offset Printing
Appl. Sci. 2017, 7(12), 1302; https://doi.org/10.3390/app7121302
Received: 28 October 2017 / Revised: 21 November 2017 / Accepted: 30 November 2017 / Published: 15 December 2017
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Abstract
Printed electronics is one of the emerging technologies owing to its low cost and productivity. Recently, many researchers tried to adapt printing technology to the fabrication of fine electronic patterns on flexible substrates, including the gate line of thin film transistors. In this
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Printed electronics is one of the emerging technologies owing to its low cost and productivity. Recently, many researchers tried to adapt printing technology to the fabrication of fine electronic patterns on flexible substrates, including the gate line of thin film transistors. In this study, we fabricated a flexible cliché using the nanoimprint process and used it in reverse offset printing. Then, we analyzed the effect of the surface energy of the imprinted cliché on process parameters, such as printing speed and rolling direction. We showed that the productivity of the process and quality of printed pattern can be considerably enhanced by controlling the surface energy of the cliché. When a flexible cliché is manufactured using a resin with a surface energy considerably different from that of the blanket, the ink can be detached easily and fine patterns can be engraved successfully regardless of the pattern shape. Full article
(This article belongs to the Special Issue Thin-Film Transistors)
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