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Appl. Sci., Volume 9, Issue 16 (August-2 2019)

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Open AccessFeature PaperArticle
Generation and Characterization of Mid-Infrared Supercontinuum in Bulk YAG Pumped by Femtosecond 1937 nm Pulses from a Regenerative Amplifier
Appl. Sci. 2019, 9(16), 3399; https://doi.org/10.3390/app9163399 (registering DOI)
Received: 23 July 2019 / Revised: 9 August 2019 / Accepted: 14 August 2019 / Published: 18 August 2019
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Abstract
We have demonstrated the generation of supercontinuum (SC) pulses in bulk, using femtosecond pulses directly derived from a Tm:YAP regenerative amplifier. The SC spans from 380 nm–4 μm. Such an SC combined with the applied 1937-nm pump pulse can be used in [...] Read more.
We have demonstrated the generation of supercontinuum (SC) pulses in bulk, using femtosecond pulses directly derived from a Tm:YAP regenerative amplifier. The SC spans from 380 nm–4 μ m. Such an SC combined with the applied 1937-nm pump pulse can be used in a mid-infrared optical parametric amplifier (MIR-OPA). A full characterization of the phase and stability of the SC provides important insight into the performance of such MIR-OPA systems. Using cross-correlation frequency-resolved optical gating (XFROG), we characterized the properties of the MIR section of the SC that can be used as a seed pulse in an MIR-OPA system. The pulse-to-pulse instability rooted in the intrinsic properties of the self-phase modulation process was observed in the retrieved trace and spectrum of the SC. In addition, the effect of the pump pulse quality was studied on the obtainable SC pulses. Full article
(This article belongs to the Special Issue Ultrafast Laser Pulses)
Open AccessArticle
Simulation of a Solar-Assisted Air-Conditioning System Applied to a Remote School
Appl. Sci. 2019, 9(16), 3398; https://doi.org/10.3390/app9163398 (registering DOI)
Received: 6 June 2019 / Revised: 11 July 2019 / Accepted: 15 August 2019 / Published: 18 August 2019
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Abstract
In this work, we present an absorption cooling system with 35 kW capacity driven by solar thermal energy, installed in the school of Puertecitos, Mexico, an off-grid community with a high level of social marginalization. The cooling system provides thermal comfort to the [...] Read more.
In this work, we present an absorption cooling system with 35 kW capacity driven by solar thermal energy, installed in the school of Puertecitos, Mexico, an off-grid community with a high level of social marginalization. The cooling system provides thermal comfort to the school’s classrooms through four 8.75-kW cooling coils, while a 110-m2 field of evacuated tube solar collectors delivers the thermal energy needed to activate the cooling machine. The characteristics of the equipment installed in the school were used for simulation and operative analysis of the system under the influence of typical factors of an isolated coastal community, such as the influence of climate, thermal load, and water consumption in the cooling tower, among others. The aim of this simulation study was to determine the best operating conditions prior to system start-up, to establish the requirements for external heating and cooling services, and to quantify the freshwater requirements for the proper functioning of the system. The results show that, with the simulated strategies implemented, with a maximum load operation, the system can maintain thermal comfort in the classrooms for five days of classes. This is feasible as long as weekends are dedicated to raising the water temperature in the thermal storage tank. As the total capacity of the system is distributed in the four cooling coils, it is possible to control the cooling demand in order to extend the operation periods. Utilizing 75% or less of the cooling capacity, the system can operate continuously, taking advantage of stored energy. The cooling tower requires about 750 kg of water per day, which becomes critical given the scarcity of this resource in the community. Full article
(This article belongs to the Special Issue Solar Energy Applications in Houses, Smart Cities and Microgrids)
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Open AccessArticle
A Systematic Experimental and Computational Analysis of Commercially Available Aliphatic Polyesters
Appl. Sci. 2019, 9(16), 3397; https://doi.org/10.3390/app9163397 (registering DOI)
Received: 4 July 2019 / Revised: 31 July 2019 / Accepted: 12 August 2019 / Published: 18 August 2019
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Abstract
Aliphatic polyesters, such as polylactic acid (PLA), polyglycolic acid (PGA), and their copolymer polylactic-co-glycolic acid (PLGA) have become an established choice in the biomedical field in a wide range of applications, from nanoparticles for local drug delivery to bone fixation screws, and, hence, [...] Read more.
Aliphatic polyesters, such as polylactic acid (PLA), polyglycolic acid (PGA), and their copolymer polylactic-co-glycolic acid (PLGA) have become an established choice in the biomedical field in a wide range of applications, from nanoparticles for local drug delivery to bone fixation screws, and, hence, in a huge spectrum of uses in different medical devices currently available on the market worldwide. The reason for their popularity lies in their combination of interesting peculiarities: in situ degradation, intrinsic biocompatibility (degradation products are recognized and metabolized), processability with standard industrial technologies, and tailorable properties. The knowledge of the degradation rate is an essential requirement for optimal device design when, e.g., fast adsorption time is required, or mechanical properties must be assured over a given time span. In this regard, experimental studies can be time- and money-consuming, due to the time scales (weeks–months) involved in the hydrolysis process. This work aims at providing to both industry and academia robust guidelines for optimal material choice through a systematic experimental and computational analysis of most commonly used PLGA formulations (selected from commercially available products), evaluating the degradation kinetics and its impact on polymer properties. Full article
(This article belongs to the Special Issue New Trends in Bioresorbable Polymers for Biomedical Applications)
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Open AccessArticle
Speech Enhancement Using Generative Adversarial Network by Distilling Knowledge from Statistical Method
Appl. Sci. 2019, 9(16), 3396; https://doi.org/10.3390/app9163396 (registering DOI)
Received: 6 July 2019 / Revised: 28 July 2019 / Accepted: 15 August 2019 / Published: 18 August 2019
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Abstract
This paper presents a new deep neural network (DNN)-based speech enhancement algorithm by integrating the distilled knowledge from the traditional statistical-based method. Unlike the other DNN-based methods, which usually train many different models on the same data and then average their predictions, or [...] Read more.
This paper presents a new deep neural network (DNN)-based speech enhancement algorithm by integrating the distilled knowledge from the traditional statistical-based method. Unlike the other DNN-based methods, which usually train many different models on the same data and then average their predictions, or use a large number of noise types to enlarge the simulated noisy speech, the proposed method does not train a whole ensemble of models and does not require a mass of simulated noisy speech. It first trains a discriminator network and a generator network simultaneously using the adversarial learning method. Then, the discriminator network and generator network are re-trained by distilling knowledge from the statistical method, which is inspired by the knowledge distillation in a neural network. Finally, the generator network is fine-tuned using real noisy speech. Experiments on CHiME4 data sets demonstrate that the proposed method achieves a more robust performance than the compared DNN-based method in terms of perceptual speech quality. Full article
(This article belongs to the Section Computing and Artificial Intelligence)
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Open AccessArticle
Evaluation of High-Speed Handpiece Cutting Efficiency According to Bur Eccentricity: An In Vitro Study
Appl. Sci. 2019, 9(16), 3395; https://doi.org/10.3390/app9163395 (registering DOI)
Received: 21 July 2019 / Revised: 14 August 2019 / Accepted: 16 August 2019 / Published: 18 August 2019
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Abstract
This study aimed to evaluate the correlation between the cutting efficiency and bur eccentricity of high-speed handpieces. The prepared lithium disilicate samples were digitized using a 3D model scanner (reference model, RM) (n = 45), and the lithium disilicate samples were cut using [...] Read more.
This study aimed to evaluate the correlation between the cutting efficiency and bur eccentricity of high-speed handpieces. The prepared lithium disilicate samples were digitized using a 3D model scanner (reference model, RM) (n = 45), and the lithium disilicate samples were cut using three high-speed handpieces. To evaluate the cutting efficiency, the cut lithium disilicate sample was digitized (cutting model, CM), and the RM and CM were superimposed using a 3D analysis software. Bur eccentricity of the high-speed handpieces was measured using dedicated equipment. Statistical analyses were performed using an analysis software. The statistical differences in pairwise comparisons (α = 0.05) were analyzed using the Kruskal–Wallis and post hoc tests. The S-max M600 obtained a cutting efficiency of 6.13 mm3. TG-98 and TRAUS ATN-400 showed similar efficiencies of 2.914 and 3.05 mm3, respectively. There was a significant difference in the cutting efficiency of the S-max M600 compared with TG-98 and TRAUS ATN-400 (p < 0.001). S-max M600 had an eccentricity of 3.507 µm. TG-98 and TRAUS ATN-400 had eccentricities of 5.99 and 7.767 µm, respectively. There were statistically significant differences in the eccentricity among all the high-speed handpieces (p < 0.001). Full article
(This article belongs to the Special Issue Applied Sciences in Dentistry)
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Open AccessFeature PaperArticle
A Novel Combined Evolutionary Algorithm for Optimal Planning of Distributed Generators in Radial Distribution Systems
Appl. Sci. 2019, 9(16), 3394; https://doi.org/10.3390/app9163394 (registering DOI)
Received: 7 July 2019 / Revised: 3 August 2019 / Accepted: 15 August 2019 / Published: 17 August 2019
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Abstract
In this paper, a novel, combined evolutionary algorithm for solving the optimal planning of distributed generators (OPDG) problem in radial distribution systems (RDSs) is proposed. This algorithm is developed by uniquely combining the original differential evolution algorithm (DE) with the search mechanism of [...] Read more.
In this paper, a novel, combined evolutionary algorithm for solving the optimal planning of distributed generators (OPDG) problem in radial distribution systems (RDSs) is proposed. This algorithm is developed by uniquely combining the original differential evolution algorithm (DE) with the search mechanism of Lévy flights (LF). Furthermore, the quasi-opposition based learning concept (QOBL) is applied to generate the initial population of the combined DELF. As a result, the new algorithm called the quasi-oppositional differential evolution Lévy flights algorithm (QODELFA) is presented. The proposed technique is utilized to solve the OPDG problem in RDSs by taking three objective functions (OFs) under consideration. Those OFs are the active power loss minimization, the voltage profile improvement, and the voltage stability enhancement. Different combinations of those three OFs are considered while satisfying several operational constraints. The robustness of the proposed QODELFA is tested and verified on the IEEE 33-bus, 69-bus, and 118-bus systems and the results are compared to other existing methods in the literature. The conducted comparisons show that the proposed algorithm outperforms many previous available methods and it is highly recommended as a robust and efficient technique for solving the OPDG problem. Full article
(This article belongs to the Section Energy)
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Open AccessArticle
Modeling of the Snowdrift in Cold Regions: Introduction and Evaluation of a New Approach
Appl. Sci. 2019, 9(16), 3393; https://doi.org/10.3390/app9163393 (registering DOI)
Received: 17 July 2019 / Revised: 14 August 2019 / Accepted: 14 August 2019 / Published: 17 August 2019
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Abstract
Unbalanced, or non-uniform, snow loads caused by snow drifting or sliding in cold regions with heavy snowfalls, can be a serious problem for the building industry. However, the methods for predicting snow distribution still need to be improved. Field observation is the most [...] Read more.
Unbalanced, or non-uniform, snow loads caused by snow drifting or sliding in cold regions with heavy snowfalls, can be a serious problem for the building industry. However, the methods for predicting snow distribution still need to be improved. Field observation is the most direct and reliable method to study snow distribution, but because the natural environment is uncontrollable and varies dramatically, sometimes conclusions may be confused under the influence of the many variables in the investigation. This paper proposes a snowing experiment approach using an outdoor snow–wind combined experiment facility for the study of snow distribution. The facility can produce a stable and controllable wind field and snowfall environment. Experiments which focused on snowdrift around a building were conducted during the winter to make an evaluation of the repeatability and reliability of the new approach. Finally, from the analysis of results, it was demonstrated that the experimental facility was stable and that the similarity criterion adopted for the snowing pattern was reliable. Especially, the minimum value of the friction speed ratio was suggested to ensure the test accuracy. Full article
(This article belongs to the Special Issue Buildings and Structures under Extreme Loads)
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Open AccessArticle
Changes of Photovoltaic Performance as a Function of Positioning Relative to the Focus Points of a Concentrator PV Module: Case Study
Appl. Sci. 2019, 9(16), 3392; https://doi.org/10.3390/app9163392 (registering DOI)
Received: 15 July 2019 / Revised: 4 August 2019 / Accepted: 14 August 2019 / Published: 17 August 2019
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Abstract
This article examines the positioning features of polycrystalline, monocrystalline, and amorphous silicon modules relative to the focus points of concentrator photovoltaic modules under real meteorological conditions using a dual tracking system. The performance of the photovoltaic modules mounted on a dual-axis tracking system [...] Read more.
This article examines the positioning features of polycrystalline, monocrystalline, and amorphous silicon modules relative to the focus points of concentrator photovoltaic modules under real meteorological conditions using a dual tracking system. The performance of the photovoltaic modules mounted on a dual-axis tracking system was regarded as a function of module orientation where the modules were moved step by step up to a point where their inclination differed by 30° compared to the ideal focus point position of the reference concentrator photovoltaic module. The inclination difference relative to the ideal focus point position was determined by the perfect perpendicularity to the rays of the sun. Technology-specific results show the accuracy of a sun tracking photovoltaic system that is required to keep the loss in power yield below a defined level. The loss in power yield, determined as a function of the measurement results, also showed that the performance insensitivity thresholds of the monocrystalline, polycrystalline, and amorphous silicon modules depended on the direction of the alignment changes. The performance deviations showed clear azimuth dependence. Changing the tilt of the modules towards north and south showed little changes in results, but inclination changes towards northwest, southwest, southeast, and northeast produced results diverging more markedly from each other. These results may make the planning of solar tracking sensor investments easier and help with the estimate calculations of the total investment and operational costs and their return concerning monocrystalline, polycrystalline, and amorphous silicon photovoltaic systems. The results also provide guidance for the tracking error values of the solar tracking sensor. Full article
(This article belongs to the Special Issue Renewable Energy Systems 2019)
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Open AccessArticle
Exploring Efficient Neural Architectures for Linguistic–Acoustic Mapping in Text-To-Speech
Appl. Sci. 2019, 9(16), 3391; https://doi.org/10.3390/app9163391 (registering DOI)
Received: 4 July 2019 / Revised: 29 July 2019 / Accepted: 2 August 2019 / Published: 17 August 2019
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Abstract
Conversion from text to speech relies on the accurate mapping from linguistic to acoustic symbol sequences, for which current practice employs recurrent statistical models such as recurrent neural networks. Despite the good performance of such models (in terms of low distortion in the [...] Read more.
Conversion from text to speech relies on the accurate mapping from linguistic to acoustic symbol sequences, for which current practice employs recurrent statistical models such as recurrent neural networks. Despite the good performance of such models (in terms of low distortion in the generated speech), their recursive structure with intermediate affine transformations tends to make them slow to train and to sample from. In this work, we explore two different mechanisms that enhance the operational efficiency of recurrent neural networks, and study their performance–speed trade-off. The first mechanism is based on the quasi-recurrent neural network, where expensive affine transformations are removed from temporal connections and placed only on feed-forward computational directions. The second mechanism includes a module based on the transformer decoder network, designed without recurrent connections but emulating them with attention and positioning codes. Our results show that the proposed decoder networks are competitive in terms of distortion when compared to a recurrent baseline, whilst being significantly faster in terms of CPU and GPU inference time. The best performing model is the one based on the quasi-recurrent mechanism, reaching the same level of naturalness as the recurrent neural network based model with a speedup of 11.2 on CPU and 3.3 on GPU. Full article
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Open AccessArticle
Adsorption and Sensing Behaviors of Pd-Doped InN Monolayer upon CO and NO Molecules: A First-Principles Study
Appl. Sci. 2019, 9(16), 3390; https://doi.org/10.3390/app9163390 (registering DOI)
Received: 24 July 2019 / Revised: 8 August 2019 / Accepted: 12 August 2019 / Published: 17 August 2019
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Abstract
A transition metal (TM) doped InN monolayer has demonstrated with superior behavior for gas adsorption and sensing. For this paper, we studied the adsorption behavior of a Pd-doped InN (Pd-InN) monolayer upon CO and NO using the first-principles theory. Our results show that [...] Read more.
A transition metal (TM) doped InN monolayer has demonstrated with superior behavior for gas adsorption and sensing. For this paper, we studied the adsorption behavior of a Pd-doped InN (Pd-InN) monolayer upon CO and NO using the first-principles theory. Our results show that the Pd-InN monolayer has a stronger interaction with the CO molecule, compared with the NO molecule, with larger adsorption energy of 2.12 eV, compared to −1.65 eV. On the other hand, the Pd-InN monolayer undergoes more obvious deformation of the electronic behavior in the NO system, making the surface become semimetallic with a 0 eV band gap. Thus, the Pd-InN monolayer could be a promising candidate as a resistance-type sensor for NO detection and as a gas adsorbent for CO removal. We are hopeful that this work can offer the basic physicochemical properties and potential applications of the Pd-InN monolayer, which is beneficial for its further exploration in many fields. Full article
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Open AccessArticle
LCF: A Local Context Focus Mechanism for Aspect-Based Sentiment Classification
Appl. Sci. 2019, 9(16), 3389; https://doi.org/10.3390/app9163389 (registering DOI)
Received: 12 July 2019 / Revised: 10 August 2019 / Accepted: 15 August 2019 / Published: 17 August 2019
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Abstract
Aspect-based sentiment classification (ABSC) aims to predict sentiment polarities of different aspects within sentences or documents. Many previous studies have been conducted to solve this problem, but previous works fail to notice the correlation between the aspect’s sentiment polarity and the local context. [...] Read more.
Aspect-based sentiment classification (ABSC) aims to predict sentiment polarities of different aspects within sentences or documents. Many previous studies have been conducted to solve this problem, but previous works fail to notice the correlation between the aspect’s sentiment polarity and the local context. In this paper, a Local Context Focus (LCF) mechanism is proposed for aspect-based sentiment classification based on Multi-head Self-Attention (MHSA). This mechanism is called LCF design, and utilizes the Context features Dynamic Mask (CDM) and Context Features Dynamic Weighted (CDW) layers to pay more attention to the local context words. Moreover, a BERT-shared layer is adopted to LCF design to capture internal long-term dependencies of local context and global context. Experiments are conducted on three common ABSC datasets: the laptop and restaurant datasets of SemEval-2014 and the ACL twitter dataset. Experimental results demonstrate that the LCF baseline model achieves considerable performance. In addition, we conduct ablation experiments to prove the significance and effectiveness of LCF design. Especially, by incorporating with BERT-shared layer, the LCF-BERT model refreshes state-of-the-art performance on all three benchmark datasets. Full article
(This article belongs to the Section Computing and Artificial Intelligence)
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Open AccessArticle
Pricing Personal Data Based on Data Provenance
Appl. Sci. 2019, 9(16), 3388; https://doi.org/10.3390/app9163388 (registering DOI)
Received: 22 July 2019 / Revised: 14 August 2019 / Accepted: 14 August 2019 / Published: 17 August 2019
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Abstract
Data have become an important asset. Mining the value contained in personal data, making personal data an exchangeable commodity, has become a hot spot of industry research. Then, how to price personal data reasonably becomes a problem we have to face. Based on [...] Read more.
Data have become an important asset. Mining the value contained in personal data, making personal data an exchangeable commodity, has become a hot spot of industry research. Then, how to price personal data reasonably becomes a problem we have to face. Based on previous research on data provenance, this paper proposes a novel minimum provenance pricing method, which is to price the minimum source tuple set that contributes to the query. Our pricing model first sets prices for source tuples according to their importance and then makes query pricing based on data provenance, which considers both the importance of the data itself and the relationships between the data. We design an exact algorithm that can calculate the exact price of a query in exponential complexity. Furthermore, we design an easy approximate algorithm, which can calculate the approximate price of the query in polynomial time. We instantiated our model with a select-joint query and a complex query and extensively evaluated its performances on two practical datasets. The experimental results show that our pricing model is feasible. Full article
(This article belongs to the Section Computing and Artificial Intelligence)
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Open AccessFeature PaperReview
Cucurbita Plants: From Farm to Industry
Appl. Sci. 2019, 9(16), 3387; https://doi.org/10.3390/app9163387 (registering DOI)
Received: 25 July 2019 / Revised: 13 August 2019 / Accepted: 14 August 2019 / Published: 16 August 2019
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Abstract
The Cucurbita genus, a member of Cucurbitaceae family, also known as cucurbits, is native to the Americas. Genus members, like Cucurbita pepo and Cucurbita maxima, have been used for centuries in folk medicine for treating gastrointestinal diseases and intestinal parasites. These pharmacological [...] Read more.
The Cucurbita genus, a member of Cucurbitaceae family, also known as cucurbits, is native to the Americas. Genus members, like Cucurbita pepo and Cucurbita maxima, have been used for centuries in folk medicine for treating gastrointestinal diseases and intestinal parasites. These pharmacological effects are mainly attributed to their phytochemical composition. Indeed, Cucurbita species are a natural source of carotenoids, tocopherols, phenols, terpenoids, saponins, sterols, fatty acids, functional carbohydrates, and polysaccharides, that beyond exerting remarkable biological effects, have also been increasingly exploited for biotechnological applications. In this article, we specifically cover the habitat, cultivation, phytochemical composition, and food preservative abilities of Cucurbita plants. Full article
(This article belongs to the Special Issue Functional Foods and Food Supplements)
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Open AccessArticle
Dimensional Stability of SBR-Modified Cementitious Mixtures for Use in 3D Additive Construction
Appl. Sci. 2019, 9(16), 3386; https://doi.org/10.3390/app9163386 (registering DOI)
Received: 24 July 2019 / Revised: 14 August 2019 / Accepted: 14 August 2019 / Published: 16 August 2019
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Abstract
This study experimentally investigated the dimensional stability of SBR (styrene butadiene rubber)-modified cementitious mixtures in order to determine whether their properties are sustainable as a 3D additive construction material. Dimensional stability refers to resistance to material deformation caused by changes in internal relative [...] Read more.
This study experimentally investigated the dimensional stability of SBR (styrene butadiene rubber)-modified cementitious mixtures in order to determine whether their properties are sustainable as a 3D additive construction material. Dimensional stability refers to resistance to material deformation caused by changes in internal relative humidity and temperature. Hence, drying and thermal shrinkage, which are the primary factors affecting dimensional stability, were tested. The mixing ratio of SBR-modified cementitious mixtures was determined based on a predetermined optimal flow of 70% ± 1% applicable for 3D additive construction applications. The results of this study showed that the elastic modulus, and drying shrinkage strain, excluding the coefficient of thermal expansion, all significantly improved as the SBR/cement ratio increased. In particular, drying shrinkage can be a disadvantage in 3D additive construction because drying in the printed mixtures is rapid due to the large specific exposure area of moldless construction. Consequently, mitigating drying shrinkage is very important. The elastic modulus, drying shrinkage, and coefficient of thermal expansion were all found to be associated with the dimensional stability obtained in this study. It was concluded that using SBR-modified cementitious mixtures was advantageous in terms of dimensional stability. Full article
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Open AccessFeature PaperArticle
The Hay Inclined Plane in Coalbrookdale (Shropshire, England): Analysis through Computer-Aided Engineering
Appl. Sci. 2019, 9(16), 3385; https://doi.org/10.3390/app9163385 (registering DOI)
Received: 10 June 2019 / Revised: 6 July 2019 / Accepted: 13 August 2019 / Published: 16 August 2019
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Abstract
This article analyzes the ‘Hay inclined plane’ designed by the English engineer and entrepreneur William Reynolds and put into operation in 1792 to facilitate the transport of vessels between channels at different levels using an inclined plane. To this end, a study [...] Read more.
This article analyzes the ‘Hay inclined plane’ designed by the English engineer and entrepreneur William Reynolds and put into operation in 1792 to facilitate the transport of vessels between channels at different levels using an inclined plane. To this end, a study of computer-aided engineering (CAE) was carried out using the parametric software Autodesk Inventor Professional, consisting of a static analysis using the finite-element method (FEM) of the 3D model of the invention under real operating conditions. The results obtained after subjecting the mechanism to the two most unfavorable situations (blockage situation of the inertia flywheel and emergency braking situation) indicate that, with the exception of the braking bar, the rest of the assembly is perfectly designed and dimensioned. In particular, for the blockage situation, the point with the greatest stress is at the junction between the inertia flywheel and the axle to which it is attached, the maximum value of von Mises stress being at that point (186.9 MPa) lower than the elastic limit of the cast iron. Also, at this point the deformation is very low (0.13% of its length), as well as the maximum displacement that takes place in the inertia flywheel itself (22.98 mm), and the lowest safety factor has a value of 3.51 (located on the wooden shaft support), which indicates that the mechanism is clearly oversized. On the other hand, the emergency braking situation, which is technically impossible with a manual operation, indicates that the braking bar supports a maximum von Mises stress of 1025 MPa, above the elastic limit of the material, so it would break. However, other than that element, the rest of the elements have lower stresses, with a maximum value of 390.7 MPa, and with safety factors higher than 1.7, which indicates that the mechanism was well dimensioned. Full article
Open AccessArticle
A Subjective Study on User Perception Aspects in Virtual Reality
Appl. Sci. 2019, 9(16), 3384; https://doi.org/10.3390/app9163384 (registering DOI)
Received: 30 June 2019 / Revised: 5 August 2019 / Accepted: 13 August 2019 / Published: 16 August 2019
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Abstract
Three hundred and sixty degree video is becoming more and more popular on the Internet. By using a Head-Mounted Display, 360-degree video can render a Virtual Reality (VR) environment. However, it is still a big challenge to understand Quality of Experience (QoE) of [...] Read more.
Three hundred and sixty degree video is becoming more and more popular on the Internet. By using a Head-Mounted Display, 360-degree video can render a Virtual Reality (VR) environment. However, it is still a big challenge to understand Quality of Experience (QoE) of 360-degree video since user experience during watching 360-degree video is a very complex phenomenon. In this paper, we aim to investigate four QoE aspects of 360-degree video, namely, perceptual quality, presence, cybersickness, and acceptability. In addition, four key QoE-affecting factors of encoding parameters, content motion, rendering device, and rendering mode are considered in our study. To the best of our knowledge, this is the first work that covers a large number of factors and QoE aspects of 360-degree video. In this study, a subjective experiment is conducted using 60 video versions generated from three original 360-degree videos. Based on statistical analysis of the obtained results, various findings on the impacts of the factors on the QoE aspects are provided. In particular, regarding the impacts of encoding parameters, it is found that the difference of QoE is negligible between video versions encoded at 4 K and 2.5 K resolutions. Also, it is suggested that 360-degree video should not be encoded at HD resolution or lower when watching in VR mode using Head Mounted Display. In addition, the bitrate for good QoE varies widely across different video contents. With respect to the content motion factor, its impact is statistically significant on the perceptual quality, presence, and cybersickness. In a comparison of two rendering device sets used in this study, there is no statistically significant difference found for the acceptability and cybersickness. However, the differences of the perceptual quality and presence are indicated to be statistically significant. Regarding the rendering mode, a comparison between VR and non-VR modes is also conducted. Although the non-VR mode always achieves higher perceptual quality scores and higher acceptability rates, more than a half of the viewers prefer the VR mode to the non-VR mode when watching versions encoded at the resolutions of fHD or higher. By contrast, the non-VR mode is preferred at the HD resolution. Full article
(This article belongs to the Special Issue Augmented Reality: Current Trends, Challenges and Prospects)
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Open AccessArticle
Adaptive Backstepping Fractional Fuzzy Sliding Mode Control of Active Power Filter
Appl. Sci. 2019, 9(16), 3383; https://doi.org/10.3390/app9163383 (registering DOI)
Received: 23 July 2019 / Revised: 9 August 2019 / Accepted: 13 August 2019 / Published: 16 August 2019
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Abstract
An adaptive fractional-order fuzzy control method for a three-phase active power filter (APF) using a backstepping and sliding mode controller is developed for the purpose of compensating harmonic current and stabilizing the DC voltage quickly. The dynamic model of APF is changed to [...] Read more.
An adaptive fractional-order fuzzy control method for a three-phase active power filter (APF) using a backstepping and sliding mode controller is developed for the purpose of compensating harmonic current and stabilizing the DC voltage quickly. The dynamic model of APF is changed to an analogical cascade system for the convenience of the backstepping strategy. Then a fractional-order sliding mode surface is designed and a fuzzy controller is proposed to approximate the unknown term in the controller, where parameters can be adjusted online. The simulation experiments are conducted and investigated using MATLAB/SIMULINK software package to verify the advantage of the proposed controller. Furthermore, the comparison study between the fractional-order controller and integer-order one is also conducted in order to demonstrate the better performance of the proposed controller in total harmonic distortion (THD), a significant index to evaluate the current quality in the smart grid. Full article
(This article belongs to the Special Issue Control and Soft Computing)
Open AccessArticle
Reflections on the Limited Pervasiveness of Augmented Reality in Industrial Sectors
Appl. Sci. 2019, 9(16), 3382; https://doi.org/10.3390/app9163382 (registering DOI)
Received: 30 June 2019 / Revised: 12 August 2019 / Accepted: 13 August 2019 / Published: 16 August 2019
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Abstract
The paper aims to investigate the reasons why Augmented Reality (AR) has not fully broken the industrial market yet, or found a wider application in industries. The main research question the paper tries to answer is: what are the factors (and to what [...] Read more.
The paper aims to investigate the reasons why Augmented Reality (AR) has not fully broken the industrial market yet, or found a wider application in industries. The main research question the paper tries to answer is: what are the factors (and to what extent) that are limiting AR? Firstly, a reflection on the state of art of AR applications in industries is proposed, to discover the sectors more commonly chosen for deploying the technology so far. Later, based on a survey conducted after that, three AR applications have been tested on manufacturing, automotive, and railway sectors, and the paper pinpoints key aspects that are conditioning its embedding in the daily working life. In order to compare whether the perception of employees from railway, automotive, and manufacturing sectors differs significantly, a one-way analysis of variance (ANOVA) has been used. Later, suggestions are formulated in order to improve these aspects in the industry world. Finally, the paper indicates the main conclusions, highlighting possible future researches to start. Full article
(This article belongs to the Special Issue Augmented Reality: Current Trends, Challenges and Prospects)
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Open AccessFeature PaperArticle
Second-Harmonic Generation in Mie-Resonant GaAs Nanowires
Appl. Sci. 2019, 9(16), 3381; https://doi.org/10.3390/app9163381 (registering DOI)
Received: 15 July 2019 / Revised: 8 August 2019 / Accepted: 14 August 2019 / Published: 16 August 2019
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Abstract
We investigate the enhancement of second-harmonic generation in cylindrical GaAs nanowires. Although these nanostructures confine light in two dimensions, power conversion efficiencies on the order of 105 with a pump peak intensity of ~1 GW/cm2 are [...] Read more.
We investigate the enhancement of second-harmonic generation in cylindrical GaAs nanowires. Although these nanostructures confine light in two dimensions, power conversion efficiencies on the order of 10 5 with a pump peak intensity of ~ 1   GW / cm 2 are possible if the pump and the second-harmonic fields are coupled to the Mie-type resonances of the nanowire. We identify a large range of nanowire radii in which a double-resonance condition, i.e., both the pump and the second-harmonic fields excite normal modes of the nanowire, induces a high-quality-factor peak of conversion efficiency. We show that second-harmonic light can be scattered with large efficiency even if the second-harmonic photon energy is larger than 1.42 eV, i.e., the electronic bandgap of GaAs, above which the material is considered opaque. Finally, we evaluate the efficiency of one-photon absorption of second-harmonic light and find that resonant GaAs nanowires absorb second-harmonic light in the near-field region almost at the same rate at which they radiate second-harmonic light in the far-field region. Full article
(This article belongs to the Special Issue Recent Advances in Plasmonics and Nanophotonics)
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Open AccessArticle
Synthesis and Surface Modification of Nanostructured F-Doped ZnO: Toward a Transducer for Label-Free Optical Biosensing
Appl. Sci. 2019, 9(16), 3380; https://doi.org/10.3390/app9163380 (registering DOI)
Received: 9 July 2019 / Revised: 8 August 2019 / Accepted: 12 August 2019 / Published: 16 August 2019
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Abstract
In this work, the surface of nanostructured fluorine-doped ZnO (nZnO·F) is functionalized with protein A (PrA), and used as a model biomolecule. The chemical procedure is characterized by several analytical techniques such as Fourier Transform Infrared Spectroscopy, water contact angle analysis, and fluorescence [...] Read more.
In this work, the surface of nanostructured fluorine-doped ZnO (nZnO·F) is functionalized with protein A (PrA), and used as a model biomolecule. The chemical procedure is characterized by several analytical techniques such as Fourier Transform Infrared Spectroscopy, water contact angle analysis, and fluorescence microscopy. The surface modification of nZnO·F by binding increasing concentrations of PrA is also investigated by two label-free optical techniques, i.e., the spectroscopic reflectometry and the steady-state photoluminescence. The results are compared with those obtained using undoped nZnO substrates in order to highlight the better performances of nZnO·F due to the fluorine doping. The results of this study pave the way for the design and realization of a ZnO-based nanostructured platform for label-free optical sensing. Full article
(This article belongs to the Section Chemistry)
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Open AccessArticle
Optimizing Android Facial Expressions Using Genetic Algorithms
Appl. Sci. 2019, 9(16), 3379; https://doi.org/10.3390/app9163379 (registering DOI)
Received: 30 July 2019 / Accepted: 14 August 2019 / Published: 16 August 2019
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Abstract
Because the internal structure, degree of freedom, skin control position and range of the android face are different, it is very difficult to generate facial expressions by applying existing facial expression generation methods. In addition, facial expressions differ among robots because they are [...] Read more.
Because the internal structure, degree of freedom, skin control position and range of the android face are different, it is very difficult to generate facial expressions by applying existing facial expression generation methods. In addition, facial expressions differ among robots because they are designed subjectively. To address these problems, we developed a system that can automatically generate robot facial expressions by combining an android, a recognizer capable of classifying facial expressions and a genetic algorithm. We have developed two types (older men and young women) of android face robots that can simulate human skin movements. We selected 16 control positions to generate the facial expressions of these robots. The expressions were generated by combining the displacements of 16 motors. A chromosome comprising 16 genes (motor displacements) was generated by applying real-coded genetic algorithms; subsequently, it was used to generate robot facial expressions. To determine the fitness of the generated facial expressions, expression intensity was evaluated through a facial expression recognizer. The proposed system was used to generate six facial expressions (angry, disgust, fear, happy, sad, surprised); the results confirmed that they were more appropriate than manually generated facial expressions. Full article
(This article belongs to the Section Computing and Artificial Intelligence)
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Open AccessArticle
The Zerotrope, a Dynamic Holographic Display: Design and Implementation
Appl. Sci. 2019, 9(16), 3378; https://doi.org/10.3390/app9163378 (registering DOI)
Received: 18 July 2019 / Revised: 6 August 2019 / Accepted: 12 August 2019 / Published: 16 August 2019
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Abstract
This paper presents the Zerotrope, an improved version of the classic phenakistiscope and zoetrope devices. This device is used to create a new 360-degree dynamic 3D display by the inclusion of a single ultra-realistic full-color hologram. The Zerotrope is built with a zero-degree [...] Read more.
This paper presents the Zerotrope, an improved version of the classic phenakistiscope and zoetrope devices. This device is used to create a new 360-degree dynamic 3D display by the inclusion of a single ultra-realistic full-color hologram. The Zerotrope is built with a zero-degree transplane hologram mounted on a disk rotating at a constant speed. When a stroboscopic lamp synchronized with the rotation illuminates this hologram, the recorded characters, arranged radially around the center of the disk, are animated as in a stop-motion movie. The operation of the Zerotrope is successful and shows the effect of a 3D display without the need for special viewing aids. Full article
(This article belongs to the Section Applied Physics)
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Open AccessArticle
Feasibility of a Quasi-Static Approach in Assessing Side-Wind Hazards for Running Vehicles
Appl. Sci. 2019, 9(16), 3377; https://doi.org/10.3390/app9163377 (registering DOI)
Received: 18 July 2019 / Revised: 11 August 2019 / Accepted: 13 August 2019 / Published: 16 August 2019
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Abstract
This study is an examination into the feasibility of a quasi-static approach to evaluating the reaction forces that impact tires. This information could lend valuable insight into efforts to limit overturning and side-slip accidents of vehicles exposed to strong side winds. The performance [...] Read more.
This study is an examination into the feasibility of a quasi-static approach to evaluating the reaction forces that impact tires. This information could lend valuable insight into efforts to limit overturning and side-slip accidents of vehicles exposed to strong side winds. The performance of the quasi-static approach was evaluated by comparing the calculated tire forces with those created using TruckSim, which is a dynamic vehicle analysis software. Governing equations were formulated for two types of vehicles that are susceptible to the force of wind, vans, and trailers, by considering a force equilibrium, a compatibility condition, and several assumptions. The quasi-static approach for trailers is a novel expansion of the conventional approach to a two-axle vehicle. Proposed enhancements to the quasi-static approach reflect the additional rolling moment of a trailer. The curvature and the cant of a curved road were accounted for via centrifugal forces. Both uniform and turbulent wind conditions were considered in questioning the feasibility of this novel approach. Full article
(This article belongs to the Section Civil Engineering)
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Open AccessArticle
Modal Strain Energy-Based Structural Damage Detection Using Convolutional Neural Networks
Appl. Sci. 2019, 9(16), 3376; https://doi.org/10.3390/app9163376 (registering DOI)
Received: 24 July 2019 / Revised: 10 August 2019 / Accepted: 13 August 2019 / Published: 16 August 2019
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Abstract
In this paper, a convolutional neural network (CNN) was used to extract the damage features of a steel frame structure. As structural damage could induce changes of the modal parameters of the structure, the convolution operation was used to extract the features of [...] Read more.
In this paper, a convolutional neural network (CNN) was used to extract the damage features of a steel frame structure. As structural damage could induce changes of the modal parameters of the structure, the convolution operation was used to extract the features of modal parameters, and a classification algorithm was used to judge the damage state of the structure. The finite element method was applied to analyze the free vibration of the steel frame and obtain the first-order modal strain energy for various damage scenarios, which was used as the CNN training sample. Then vibration experiments were carried out, and modal parameters were obtained from the modal analysis of the vibration signals. The experimental data were inputted into the CNN to verify its damage detection capability. The result showed that the CNN was effective in detecting the intact structure, single damage, and multi damages with an accuracy of 100%. For comparison, the same samples were also applied to the traditional back propagation (BP) neural network, which failed to detect the intact structure and multiple-damage cases. It was found that: (1) The proposed CNN could be trained from finite element simulation data and used in real frame structure damage detection, and it performed better in structural damage detection than BP neural networks; (2) the measured data of a real structure could be supplemented by numerical simulation data, and satisfactory results have been demonstrated. Full article
(This article belongs to the Section Civil Engineering)
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Open AccessArticle
Zero Energy in the Built Environment: A Holistic Understanding
Appl. Sci. 2019, 9(16), 3375; https://doi.org/10.3390/app9163375 (registering DOI)
Received: 17 July 2019 / Revised: 8 August 2019 / Accepted: 13 August 2019 / Published: 16 August 2019
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Abstract
International pressures through global agreements such as the recent Paris agreement in 2015 have put stress on governments and industries to find lasting solutions for the built environment. The built environment was recognized as an important factor in reducing global emissions for the [...] Read more.
International pressures through global agreements such as the recent Paris agreement in 2015 have put stress on governments and industries to find lasting solutions for the built environment. The built environment was recognized as an important factor in reducing global emissions for the first time at the Conference of Parties (COP) 21 meeting in Paris through a dedicated ‘Buildings Day.’ The Global Alliance for Buildings and Construction (GlobalABC) was also launched at COP 21 as a network to globally support zero emission, efficient and resilient buildings and construction sector. The Paris Agreement brought all nations to collectively combat climate change with a view to limit temperature increases to no more than 2 degrees Celsius (°C). Nations agreed to report their efforts through the monitoring program. In most countries, residential and commercial buildings spend a large proportion of their energy in lighting, heating, ventilation, air conditioning and in various appliances requiring energy for operation. This paper takes a broad understanding of zero energy. Starting with buildings, the definitions also consider understanding zero energy and from a carbon perspective, considering going from beyond buildings to include precincts and cities. The paper brings an understanding of zero energy, its importance, and its urgency with respect to global commitments to reduce the impact of the building and construction sector and the role of governments and industries in supporting the lowering of emissions in the built environment now and in the future. Full article
(This article belongs to the Special Issue Zero-Energy Buildings)
Open AccessArticle
Improved Hierarchical Adaptive Deep Belief Network for Bearing Fault Diagnosis
Appl. Sci. 2019, 9(16), 3374; https://doi.org/10.3390/app9163374 (registering DOI)
Received: 9 July 2019 / Revised: 6 August 2019 / Accepted: 13 August 2019 / Published: 16 August 2019
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Abstract
Rotating machinery plays a vital role in modern mechanical systems. Effective state monitoring of a rotary machine is important to guarantee its safe operation and prevent accidents. Traditional bearing fault diagnosis techniques rely on manual feature extraction, which in turn relies on complex [...] Read more.
Rotating machinery plays a vital role in modern mechanical systems. Effective state monitoring of a rotary machine is important to guarantee its safe operation and prevent accidents. Traditional bearing fault diagnosis techniques rely on manual feature extraction, which in turn relies on complex signal processing and rich professional experience. The collected bearing signals are invariably complicated and unstable. Deep learning can voluntarily learn representative features without a large amount of prior knowledge, thus becoming a significant breakthrough in mechanical fault diagnosis. A new method for bearing fault diagnosis, called improved hierarchical adaptive deep belief network (DBN), which is optimized by Nesterov momentum (NM), is presented in this research. The frequency spectrum is used as inputs for feature learning. Then, a learning rate adjustment strategy is applied to adaptively select the descending step length during gradient updating, combined with NM. The developed method is validated by bearing vibration signals. In comparison to support vector machine and the conventional DBN, the raised approach exhibits a more satisfactory performance in bearing fault type and degree diagnosis. It can steadily and effectively improve convergence during model training and enhance the generalizability of DBN. Full article
(This article belongs to the Special Issue Machine Fault Diagnostics and Prognostics)
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Open AccessArticle
Digital Evaluation of the Accuracy of Computer-Guided Dental Implant Placement: An In Vitro Study
Appl. Sci. 2019, 9(16), 3373; https://doi.org/10.3390/app9163373 (registering DOI)
Received: 19 July 2019 / Revised: 8 August 2019 / Accepted: 13 August 2019 / Published: 16 August 2019
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Abstract
Compared to traditional implant surgical guides, computer-assisted implant surgical guides can be considered for positioning implants in the final prosthesis. These computer-assisted implant surgical guides can be easily fabricated with personal 3D printers after being designed with implant planning CAD software. Although the [...] Read more.
Compared to traditional implant surgical guides, computer-assisted implant surgical guides can be considered for positioning implants in the final prosthesis. These computer-assisted implant surgical guides can be easily fabricated with personal 3D printers after being designed with implant planning CAD software. Although the accuracy of computer-assisted implant surgical guides fabricated using personal 3D printers is an important factor in their clinical use, there is still a lack of research examining their accuracy. Therefore, this study evaluated the accuracy of computer-assisted implant surgical guides, which were designed using two implant planning CAD software programs (Deltanine and R2gate software) and fabricated with personal 3D printers using a non-radiographic method. Amongst the patients who visited Kyungpook National University Dental Hospital, one patient scheduled to undergo surgery of the left mandibular second premolar was randomly selected. Twenty partially edentulous resin study models were produced using a 3D printer. Using the Deltanine and R2gate implant planning CAD software, 10 implant surgical guides per software were designed and produced using a personal 3D printer. The implants (SIII SA (Ø 4.0, L = 10 mm), Osstem, Busan, Korea) were placed by one skilled investigator using the computer-assisted implant surgical guides. To confirm the position of the actual implant fixture, the study models with the implant fixtures were scanned with a connected scan body to extract the STL files, and then overlapped with the scanned file by connecting the scan body-implant fixture complex. As a result, the mean apical deviation of the Deltanine and R2gate software was 0.603 ± 0.19 mm and 0.609 ± 0.18 mm, while the mean angular deviation was 1.97 ± 0.84° and 1.92 ± 0.52°, respectively. There was no significant difference between the two software programs (p > 0.05). Thus, the accuracy of the personal 3D printing implant surgical guides is in the average range allowed by the dental clinician. Full article
(This article belongs to the Special Issue Application of CAD/CAM and 3D Printing Technologies in Dentistry)
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Open AccessArticle
Reverse Engineering of Thermoregulatory Cold-Induced Vasoconstriction/Vasodilation during Localized Cooling
Appl. Sci. 2019, 9(16), 3372; https://doi.org/10.3390/app9163372 (registering DOI)
Received: 10 July 2019 / Revised: 2 August 2019 / Accepted: 8 August 2019 / Published: 16 August 2019
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Abstract
Biological systems, in general, represent a special type of control system. The physiological processes of homeostasis, which serve to maintain the organism’s internal equilibrium against external influences, are clear forms of biological control system. An example of the homeostasis is the control of [...] Read more.
Biological systems, in general, represent a special type of control system. The physiological processes of homeostasis, which serve to maintain the organism’s internal equilibrium against external influences, are clear forms of biological control system. An example of the homeostasis is the control of the organism thermal state or the thermoregulation. The thermoregulatory control of human skin blood flow, via vasoconstriction and vasodilation, is vital to maintaining normal body temperatures during challenges to thermal homeostasis such as localised cooling. The main objective of this paper is to reverse engineer the localised thermoregulatory cold-induced vasoconstriction/vasodilation (CIVC/CIVD) reactions using a data-based mechanistic approach. Two types of localised cooling were applied to the fingers of 33 healthy participants, namely, continuous and intermittent cooling. Modelling of the thermoregulatory cold-induced vasoconstriction/vasodilation reactions suggested two underlying processes, with one process being 10 times faster. A new term is suggested in this paper, namely, the latent heat of CIVD, which represents the amount of dissipated heat required to trigger the CIVD. Moreover, a new model for the thermoregulatory localised CIVC/CIVD reactions is proposed. The suggested new model states that, with an initial vasodilation state, the initial localised CIVC is triggered based on a certain threshold in the rate of heat dissipation from the skin to the surrounding environment. Full article
(This article belongs to the Special Issue Human Health Engineering)
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Open AccessArticle
In-Situ Approaches for the Preparation of Polythiophene-Derivative Cellulose Composites with High Flexibility and Conductivity
Appl. Sci. 2019, 9(16), 3371; https://doi.org/10.3390/app9163371
Received: 24 July 2019 / Revised: 10 August 2019 / Accepted: 12 August 2019 / Published: 15 August 2019
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Abstract
Composite materials of conjugated polymers/cellulose were fabricated by incorporating different polythiophene-derivative polymers: Poly(3,4-ethylenedioxythiophene) (PEDOT) and an alkylated derivative of poly(3,4-propylenedioxythiophene) (PProDOT). These conjugated polythiophenes were deposited by casting or spray coating methodologies onto three different cellulose substrates: Conventional filters papers as cellulose acetate, [...] Read more.
Composite materials of conjugated polymers/cellulose were fabricated by incorporating different polythiophene-derivative polymers: Poly(3,4-ethylenedioxythiophene) (PEDOT) and an alkylated derivative of poly(3,4-propylenedioxythiophene) (PProDOT). These conjugated polythiophenes were deposited by casting or spray coating methodologies onto three different cellulose substrates: Conventional filters papers as cellulose acetate, cellulose grade 40 Whatman® and cellulose membranes prepared from cellulose microfibers. The preparation of composite materials was carried out by two methodologies: (i) by employing in-situ polymerization of 3,4-ethylenedioxithiophene (EDOT) or (ii) by depositing solutions of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) or lab-synthetized PProDOT. Composite materials were studied in terms of electrical conductivity and surface morphology assessed by impedance spectroscopy, surface conductivity, SEM, and 3D optical profilometry. In-situ composite materials prepared by spray coating using iron trifluoromethane sulfonate as oxidizing agent can be handled and folded as the original cellulose membranes displaying a surface conductivity around 1 S∙cm−1. This versatile procedure to prepare conductive composite materials has the potential to be implemented in flexible electrodes for energy storage applications. Full article
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Open AccessArticle
Holographic Mixed Reality System for Air Traffic Control and Management
Appl. Sci. 2019, 9(16), 3370; https://doi.org/10.3390/app9163370
Received: 30 June 2019 / Revised: 8 August 2019 / Accepted: 13 August 2019 / Published: 15 August 2019
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Abstract
Based on a long-term prediction by the International Civil Aviation Organization indicating steady increases in air traffic demand throughout the world, the workloads of air traffic controllers are expected to continuously increase. Air traffic control and management (ATC/M) includes the processing of various [...] Read more.
Based on a long-term prediction by the International Civil Aviation Organization indicating steady increases in air traffic demand throughout the world, the workloads of air traffic controllers are expected to continuously increase. Air traffic control and management (ATC/M) includes the processing of various unstructured composite data along with the real-time visualization of aircraft data. To prepare for future air traffic, research and development intended to effectively present various complex navigation data to air traffic controllers is necessary. This paper presents a mixed reality-based air traffic control system for the improvement of and support for air traffic controllers’ workflow using mixed reality technology that is effective for the delivery of information such as complex navigation data. The existing control systems involve difficulties in information access and interpretation. Therefore, taking notice of the necessity for the integration of air traffic control systems, this study presents the mixed reality (MR) system, which is a new approach, that enables the control of air traffic in interactive environments. This system is provided in a form usable in actual operational environments with a head-mounted see-through display installed with a controller to enable more structured work support. In addition, since this system can be controlled first-hand by air traffic controllers, it provides a new experience through improved work efficiency and productivity. Full article
(This article belongs to the Special Issue Augmented Reality: Current Trends, Challenges and Prospects)
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