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Open AccessArticle
Study on Solidification Structure Evolution of Direct-Chill Casting High Purity Copper Billet Using Cellular Automaton-Finite Element Method
Metals 2020, 10(8), 1052; https://doi.org/10.3390/met10081052 (registering DOI) - 05 Aug 2020
Abstract
A heat transfer model and a cellular Automation-Finite Element (CAFE) coupling model were established to analyze the solid/liquid (S/L) interface and solidification structure evolution of high purity copper Direct-chill (DC) casting billet under different casting conditions. The simulation and actual experimental results of [...] Read more.
A heat transfer model and a cellular Automation-Finite Element (CAFE) coupling model were established to analyze the solid/liquid (S/L) interface and solidification structure evolution of high purity copper Direct-chill (DC) casting billet under different casting conditions. The simulation and actual experimental results of liquid sump shape and solidification structure were first compared to verify the accuracy of the model. It is proved that the model is effective for simulating the solidification structure of the actual DC casting high purity copper billet. After that, the model was used to predict the solidification structure under different casting temperatures, casting speeds, and heat transfer coefficients. It is shown that, with the increase of casting temperature, the grain size decreases first and then increases. There is a compromise between grain size and its uniformity, and the grain size is more uniform at higher casting temperature. With the increase of casting speed, the depth of liquid sump and the height of the S/L interface increase, but the total grain number of the billet cross-section decreases gradually. As the heat transfer coefficient increases, the depth of the casting liquid sump becomes shallow, but the height of the solid-liquid interface increases and the grain size increases gradually. For the preparation of high purity copper billets with large cross-sectional dimensions by DC casting, a fine solidified structure could be obtained by appropriately reducing the casting speed and cooling intensity. Full article
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Open AccessProceedings
The Analysis of Power Supply Topologies for Tethered Drone Applications
Proceedings 2020, 51(1), 25; https://doi.org/10.3390/proceedings2020051025 (registering DOI) - 05 Aug 2020
Abstract
This article presents three technical variants of a power supply system of a tethered multirotor drone. The proposed solutions can be applied as power sources for multirotor flying constructions used, among others, for surveillance systems or air quality measurements. The paper describes the [...] Read more.
This article presents three technical variants of a power supply system of a tethered multirotor drone. The proposed solutions can be applied as power sources for multirotor flying constructions used, among others, for surveillance systems or air quality measurements. The paper describes the topologies of the drones’ supply systems as well as their functional analysis. Full article
Open AccessArticle
The Effects of Co and W on Structural Stability and Mechanical Properties of Austenitic Heat-Resistant Steel Sanicro 25: A First-Principle Study
Metals 2020, 10(8), 1051; https://doi.org/10.3390/met10081051 (registering DOI) - 05 Aug 2020
Abstract
Sanicro 25 austenitic heat-resistant steel is expected to be used in superheaters and reheaters for ultra-supercritical power plants above 600 °C due to its excellent structural stability and high temperature mechanical properties. In this paper, the effects of Co and W on the [...] Read more.
Sanicro 25 austenitic heat-resistant steel is expected to be used in superheaters and reheaters for ultra-supercritical power plants above 600 °C due to its excellent structural stability and high temperature mechanical properties. In this paper, the effects of Co and W on the structural stability, thermodynamic stability and mechanical properties of Sanicro 25 steel are analyzed by calculating the formation energy, binding energy, Gibbs free energy, elastic constant, Peierls stress and generalized stacking fault energy (GSFE) with first-principles calculation method. By calculating the formation energy, binding energy and Gibbs free energy, it concludes that alloying elements Co and W in Sanicro 25 steel can improve the structural stability and thermodynamic stability. It indicates that W and a small amount of Co can improve the plasticity and ductility of Sanicro 25 steel by calculating the bulk modulus (B), shear modulus (G), Young’s modulus (E), the B/G ratio, Poisson’s ratio and Peierls stress. It is found that when Co and W are far from the stacking fault region, it will promote the formation of partial dislocations and twins in the system, thereby improving its plastic deformation ability and mechanical properties. Full article
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Open AccessFeature PaperReview
Proteomic Strategies to Evaluate the Impact of Farming Conditions on Food Quality and Safety in Aquaculture Products
Foods 2020, 9(8), 1050; https://doi.org/10.3390/foods9081050 - 04 Aug 2020
Abstract
This review presents the primary applications of various proteomic strategies to evaluate the impact of farming conditions on food quality and safety in aquaculture products. Aquaculture is a quickly growing sector that represents 47% of total fish production. Food quality, dietary management, fish [...] Read more.
This review presents the primary applications of various proteomic strategies to evaluate the impact of farming conditions on food quality and safety in aquaculture products. Aquaculture is a quickly growing sector that represents 47% of total fish production. Food quality, dietary management, fish welfare, the stress response, food safety, and antibiotic resistance, which are covered by this review, are among the primary topics in which proteomic techniques and strategies are being successfully applied. The review concludes by outlining future directions and potential perspectives. Full article
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Open AccessFeature PaperArticle
Bounds on Relativistic Deformed Kinematics from the Physics of the Universe Transparency
Symmetry 2020, 12(8), 1298; https://doi.org/10.3390/sym12081298 - 04 Aug 2020
Abstract
We analyze the kinematics of electron-positron production in a photon-photon interaction when one has a modification of the special relativistic kinematics as a power expansion in the inverse of a new high-energy scale. We derive the equation for the threshold energy of this [...] Read more.
We analyze the kinematics of electron-positron production in a photon-photon interaction when one has a modification of the special relativistic kinematics as a power expansion in the inverse of a new high-energy scale. We derive the equation for the threshold energy of this reaction to first order in this expansion, including the effects due to a modification of the energy-momentum conservation equation. In contrast with the Lorentz invariance violation case, a scale of the order of a few TeV is found to be compatible with the observations of very high-energy cosmic gamma rays in the case of a modification compatible with the relativity principle. Full article
Open AccessFeature PaperArticle
The Use of Fuzzy Linear Regression and ANFIS Methods to Predict the Compressive Strength of Cement
Symmetry 2020, 12(8), 1295; https://doi.org/10.3390/sym12081295 - 04 Aug 2020
Abstract
In this paper, the prediction of compressive cement strength using the fuzzy linear regression (FLR) and adaptive neuro-fuzzy inference system (ANFIS) methods was studied. Specifically, an accurate prediction method is needed as the modeling of cement strength is a difficult task, which is [...] Read more.
In this paper, the prediction of compressive cement strength using the fuzzy linear regression (FLR) and adaptive neuro-fuzzy inference system (ANFIS) methods was studied. Specifically, an accurate prediction method is needed as the modeling of cement strength is a difficult task, which is based on its composite nature. However, many approaches are widely implemented in strength-predicting problems, such as the artificial neural network (ANN), Mamdani fuzzy rules in MATLAB, FLR and ANFIS models. Applying these methods and comparing the results with the corresponding observed ones, we concluded that the ANFIS method successfully decreased the level of uncertainty in predicting cement strength, as the average percentage error level was extremely low. Although the FLR method had the highest average percentage error level compared with the other methods, it provides a standard equation to estimate the output values by using symmetric triangular fuzzy numbers and determines the most important factor in increasing compressive strength, in contrast to ANFIS and ANN, which are black box models, and to the fuzzy method, which uses rules without providing the specific way by which the results come out. Thus, ANFIS and FLR are appropriate methods for dealing with engineering mathematical models by using fuzzy logic. Full article
(This article belongs to the Special Issue Recent Advances in Mathematical Modeling)
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Open AccessArticle
Distribution and Characterization of Deep Rhodolith Beds off the Campania coast (SW Italy, Mediterranean Sea)
Plants 2020, 9(8), 985; https://doi.org/10.3390/plants9080985 - 04 Aug 2020
Abstract
Rhodolith beds (RBs) are bioconstructions characterized by coralline algae, which provide habitat for several associated species. Mediterranean RBs are usually located in the mesophotic zone (below 40 m), and thus are frequently remote and unexplored. Recently, the importance and vulnerability of these habitats [...] Read more.
Rhodolith beds (RBs) are bioconstructions characterized by coralline algae, which provide habitat for several associated species. Mediterranean RBs are usually located in the mesophotic zone (below 40 m), and thus are frequently remote and unexplored. Recently, the importance and vulnerability of these habitats have been recognized by the European Community and more attention has been drawn to their investigation and conservation. This study reports the results of an extensive monitoring program, carried out within the Marine Strategy Framework Directive (2008/56/EC), in six sites off the Campania coast (Italy, Mediterranean Sea). New insights were given into the distribution, cover, vitality (i.e., live/dead rhodolith ratio), structural complexity, and coralline algae composition of RBs. Remotely operated vehicles (ROV) investigations allowed the description of several RBs, and the discovery of a RB with rhodolith cover >65% offshore the Capri Island. Only two sites (Secchitiello and Punta Campanella) showed a very low mean cover of live rhodoliths (<10%); hence, not being classifiable as RBs. The collected rhodoliths were mostly small pralines (~2 cm), spheroidal to ellipsoidal, with growth-forms ranging from encrusting/warty to fruticose/lumpy. Coralline algae identification revealed a high diversity within each bed, with a total of 13 identified taxa. The genus Lithothamnion dominated all sites, and Phymatolithon calcareum and Lithothamnion corallioides, protected by the Habitats Directive (92/43/EEC), were detected in all RBs. Full article
(This article belongs to the Special Issue Systematics and Ecology of Algae and Marine Plants )
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Open AccessArticle
Habitat Suitability Based Models for Ungulate Roadkill Prognosis
Animals 2020, 10(8), 1345; https://doi.org/10.3390/ani10081345 (registering DOI) - 04 Aug 2020
Abstract
Roads do not only have a detrimental effect on nature (fragmenting habitats, isolating populations and threatening biodiversity), but the increasing numbers of wildlife-vehicle collisions are also a direct threat to humans and property. Therefore, mitigation measures should be placed with respect to animal [...] Read more.
Roads do not only have a detrimental effect on nature (fragmenting habitats, isolating populations and threatening biodiversity), but the increasing numbers of wildlife-vehicle collisions are also a direct threat to humans and property. Therefore, mitigation measures should be placed with respect to animal distribution and movements across the roads. We simulated red deer, roe deer and wild boar movements in Lithuania, focusing on the two main highways A1 and A2. Using regional habitat suitability and linkage models, we calculated movement pathways and the most probable crossing zones in 2009. The prognostic value of these models was tested by comparing the pathway predictions to the real roadkill and roadkill cluster locations in 2002–2009 and 2010–2017. Across both periods and on both highways, the roe deer roadkill locations were significantly closer to the model-predicted pathways than to randomly selected points. The prediction of roadkill locations was also good for wild boar. The roe deer roadkill clusters and multi-species clusters were significantly better represented by the model than by random distribution. On both highways, the biggest differences in distance from the predicted locations were near big cities. We recommended wildlife movement models as an additional tool for planning wildlife-vehicle collision mitigation measures and we advise measures for increasing their predicting power. Full article
(This article belongs to the Section Wildlife)
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Open AccessArticle
A Design for a Manufacturing-Constrained Off-Axis Four-Mirror Reflective System
Appl. Sci. 2020, 10(15), 5387; https://doi.org/10.3390/app10155387 (registering DOI) - 04 Aug 2020
Abstract
Off-axis reflective optical systems find wide applications in various industries, but the related manufacturing issues have not been well considered in the design process. This paper proposed a design method for cylindrical reflective systems considering manufacturing constraints to facilitate ultra-precision raster milling. An [...] Read more.
Off-axis reflective optical systems find wide applications in various industries, but the related manufacturing issues have not been well considered in the design process. This paper proposed a design method for cylindrical reflective systems considering manufacturing constraints to facilitate ultra-precision raster milling. An appropriate index to evaluate manufacturing constraints is established. The optimization solution is implemented for the objective function composed of primary aberration coefficients with weights and constraint conditions of the structural configuration by introducing the genetic algorithm. The four-mirror initial structure with a good imaging quality and a special structural configuration is then obtained. The method’s feasibility is validated by designing an off-axis four-mirror afocal system with an entrance pupil diameter of 170 mm, a field of view of 3° × 3° and a compression ratio of five times. All mirrors in the system are designed to be distributed along a cylinder. Full article
(This article belongs to the Special Issue Optical Design and Engineering)
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Open AccessArticle
Effectiveness of Using Voice Assistants in Learning: A Study at the Time of COVID-19
Int. J. Environ. Res. Public Health 2020, 17(15), 5618; https://doi.org/10.3390/ijerph17155618 - 04 Aug 2020
Abstract
The use of advanced learning technologies in a learning management system (LMS) can greatly assist learning processes, especially when used in university environments, as they promote the development of Self-Regulated learning, which increases academic performance and student satisfaction towards personal learning. One of [...] Read more.
The use of advanced learning technologies in a learning management system (LMS) can greatly assist learning processes, especially when used in university environments, as they promote the development of Self-Regulated learning, which increases academic performance and student satisfaction towards personal learning. One of the most innovative resources that an LMS may have is an Intelligent Personal Assistant (IPA). We worked with a sample of 109 third-grade students following Health Sciences degrees. The aims were: (1) to verify whether there will be significant differences in student access to the LMS, depending on use versus non-use of an IPA. (2) To verify whether there will be significant differences in student learning outcomes depending on use versus non-use of an IPA. (3) To verify whether there will be significant differences for student satisfaction with teaching during the COVID-19 pandemic, depending on use versus non-use of an IPA. (4) To analyze student perceptions of the usefulness of an IPA in the LMS. We found greater functionality in access to the LMS and satisfaction with teaching, especially during the health crisis, in the group of students who had used an IPA. However, both the expansion of available information and the usability of the features embedded in an IPA are still challenging issues. Full article
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Open AccessArticle
A Lightweight Slice-based Quality of Service Manager for IoT
IoT 2020, 1(1), 49-75; https://doi.org/10.3390/iot1010004 - 04 Aug 2020
Abstract
Industry 4.0 and digital farming rely on modern communication and computation technologies such as the Internet of Things (IoT) to provide smart manufacturing and farming systems. Having in mind a scenario with a high number of heterogeneous connected devices, with varying technologies and [...] Read more.
Industry 4.0 and digital farming rely on modern communication and computation technologies such as the Internet of Things (IoT) to provide smart manufacturing and farming systems. Having in mind a scenario with a high number of heterogeneous connected devices, with varying technologies and characteristics, the deployment of Industry 4.0 and digital farming solutions faces innovative challenges in different domains (e.g., communications, security, quality of service). Concepts such as network slicing and Software-Defined Networking (SDN) provide the means for faster, simpler, scalable and flexible solutions in order to serve a wide range of applications with different Quality-of-Service (QoS) requirements. Hence, this paper proposes a lightweight slice-based QoS manager for non-3GPP IoT focusing on different use cases and their varying requirements and characteristics. Our focus in this work is on non-3GPP IoT unlicensed wireless technologies and not specifically the end-to-end network slice perspective as described in 5G standards. We implemented and evaluated different QoS models in distinct scenarios in a real experimental environment in order to illustrate the potential of the proposed solution. Full article
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Open AccessArticle
Using Digital Technology to Protect Health in Prolonged Poor Air Quality Episodes: A Case Study of the AirRater App during the Australian 2019–20 Fires
Fire 2020, 3(3), 40; https://doi.org/10.3390/fire3030040 (registering DOI) - 04 Aug 2020
Abstract
In the southern hemisphere summer of 2019–20, Australia experienced its most severe bushfire season on record. Smoke from fires affected 80% of the population, with large and prolonged exceedances of the Australian National Air Quality Standard for fine particulate matter (PM2.5) [...] Read more.
In the southern hemisphere summer of 2019–20, Australia experienced its most severe bushfire season on record. Smoke from fires affected 80% of the population, with large and prolonged exceedances of the Australian National Air Quality Standard for fine particulate matter (PM2.5) recorded in all major population centers. We examined if AirRater, a free smartphone app that reports air quality and tracks user symptoms in near real-time, assisted those populations to reduce their smoke exposure and protect their health. We distributed an online survey to over 13,000 AirRater users to assess how they used this information during the 2019–20 bushfire season, and why it was helpful to aid decision-making in reducing personal smoke exposure. We received responses from 1732 users (13.3%). Respondents reported the app was highly useful, supporting informed decision-making regarding daily activities during the smoke-affected period. Commonly reported activities supported by information provided through the app were staying inside (76%), rescheduling or planning outdoor activities (64%), changing locations to less affected areas (29%) and informing decisions on medication use (15%). Innovative and easy-to-use smartphone apps such as AirRater, that provide individual-level and location-specific data, can enable users to reduce their exposure to environmental hazards and therefore protect their health. Full article
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Open AccessArticle
A Simple Foot Plantar Pressure Measurement Platform System Using Force-Sensing Resistors
Appl. Syst. Innov. 2020, 3(3), 33; https://doi.org/10.3390/asi3030033 - 04 Aug 2020
Abstract
Generally, there are two types of working style, i.e., some people work in sitting conditions, and the remaining work mostly in a standing position. For people working in a standing position, they can spend hours in a day doing their work standing. These [...] Read more.
Generally, there are two types of working style, i.e., some people work in sitting conditions, and the remaining work mostly in a standing position. For people working in a standing position, they can spend hours in a day doing their work standing. These people do not realize that it can cause medical issues, especially for the feet, namely biometric problems. In addition, several doctors in Indonesia are already aware of this issue and state that the biometric problems faced by those kinds of people can be predicted from the load distribution on the foot. However, the tool used by the doctors in Indonesia to measure biometric problems is not a digital tool. Therefore it is very difficult to measure and predict the biometric problems quantitatively. This study aims to develop a low-cost static load measuring device using force-sensing resistor (FSR) sensors. The measuring instrument is designed in the form of a pressure plate platform which consist of 30 FSR 402 sensors. The sensors are placed right underneath the display area of the foot, 15 sensors on the soles of the left and right feet. Ten students from the Department of Mechanical Engineering, Diponegoro University (five men and five women) were asked to stand on the platform. Each subject also measured foot length (FL) to estimate shoe size, foot area contact (FAC) for validation between genders, and foot type using the digital footprint tools. From the results of measurements obtained for the left foot in the medial mid foot area, i.e., in sensors 5 and 7, not exposed to the load, on almost all subjects except subject number 3 with a load of 0.196 kg on sensor 7. The highest average load occurs in the heel area i.e., sensor 1 measured 0.713 kg and the smallest average load occurs in the five sensors, with 0 kg. A static load gauge that is designed to be used to measure each leg area for subjects with a shoe size of 40–42 with low price to be held in hospital-orthopedic hospitals and biomechanical research centers. Full article
(This article belongs to the Special Issue Feature Paper Collection in Applied System Innovation)
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Open AccessArticle
Flammability Characteristics of Surface Fuels in a Longleaf Pine (Pinus palustris Mill.) Woodland
Fire 2020, 3(3), 39; https://doi.org/10.3390/fire3030039 - 04 Aug 2020
Abstract
To investigate fuel flammability, we quantified burning characteristics of 21 fuel categories in a longleaf pine (Pinus palustris Mill.) woodland in central Alabama, USA. Litter was burned under controlled laboratory conditions. Flammability characteristics, including resistance to ignition, flaming duration, smoldering duration, maximum [...] Read more.
To investigate fuel flammability, we quantified burning characteristics of 21 fuel categories in a longleaf pine (Pinus palustris Mill.) woodland in central Alabama, USA. Litter was burned under controlled laboratory conditions. Flammability characteristics, including resistance to ignition, flaming duration, smoldering duration, maximum flame height, and percent consumption, were measured. The fuels were hierarchically clustered into five groups of similar flammability characteristics that explained 89% of the variance. Percent consumption and maximum flame height values ranged from 7% ± 1 standard errors (SE) and 12 cm ± 1 SE for the low flammability group (bark and charcoal), to 86% ± 1 SE and 62 cm ± 3 SE for the high flammability group (bracken fern (Pteridium latiusculum (Desv.) Hieron. ex R.E.Fr. = {syn: P. aquilinum}), grass, and fire-facilitating oak (Quercus spp.) leaves). Results support observed flammability differences between fuel types such as oak and pine (Pinus spp.) litter, and duff, and provide a previously unquantified comparison of surface fuels comprehensive of a longleaf pine community. Further, clustering analysis indicated that plant species that become abundant post-disturbance may help maintain fire-vegetation feedbacks in the absence of pine litter. Understanding flammability characteristics of surface fuels may further inform prescribed fire application in stands where fuels have been altered. Full article
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Open AccessArticle
Molecular Dynamics Simulation Study of the Mechanical Properties of Nanocrystalline Body-Centered Cubic Iron
Surfaces 2020, 3(3), 381-391; https://doi.org/10.3390/surfaces3030028 - 04 Aug 2020
Abstract
In the present work, the mechanical properties of nanocrystalline body-centered cubic (BCC) iron with an average grain size of 10 Å were investigated using molecular dynamics (MD) simulations. The structure has one layer of crystal grains, which means such a model could represent [...] Read more.
In the present work, the mechanical properties of nanocrystalline body-centered cubic (BCC) iron with an average grain size of 10 Å were investigated using molecular dynamics (MD) simulations. The structure has one layer of crystal grains, which means such a model could represent a structure with directional crystallization. A series of uniaxial tensile tests with different strain rates and temperatures was performed until the full rupture of the model. Moreover, tensile tests of the models with a void at the center and shear tests were carried out. In the tensile test simulations, peak stress and average values of flow stress increase with strain rate. However, the strain rate does not affect the elasticity modulus. Due to the presence of void, stress concentrations in structure have been observed, which leads to dislocation pile-up and grain boundary slips at lower strains. Furthermore, the model with the void reaches lower values of peak stresses as well as stress overshoot compared to the no void model. The study results provide a better understanding of the mechanical response of nanocrystalline BCC iron under various loadings. Full article
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Open AccessArticle
The Climate Fluctuation of the 8.2 ka BP Cooling Event and the Transition into Neolithic Lifeways in North China
Quaternary 2020, 3(3), 23; https://doi.org/10.3390/quat3030023 - 04 Aug 2020
Abstract
Early Neolithic lifeways in North China, which are marked by a low-level food production economy, population aggregation, and sedentism, thrived just after the period of a climatic cooling event at 8.2 ka. Instead of simply regarding this climate fluctuation as a cause for [...] Read more.
Early Neolithic lifeways in North China, which are marked by a low-level food production economy, population aggregation, and sedentism, thrived just after the period of a climatic cooling event at 8.2 ka. Instead of simply regarding this climate fluctuation as a cause for the significant socio-economic transition, this paper attempts to explore the interplay between people’s choices of coping strategies with climate change as a perspective to learn how people respond to this climate fluctuation and how such responses generated the interlocked socio-economic transitions. This analysis indicates that pre-existing changes in human adaptive behaviors prior to the cooling events were sufficient to enable people in certain areas to apply the intensification of food procurement in circumscribed territories as a strategy to cope with the climate fluctuations of the 8.2 ka BP cooling event. The application of such a coping strategy facilitated the economic and sociopolitical transition into Neolithic lifeways and led to the flourishing development of Neolithic cultures after 8 ka BP in North China. Full article
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Open AccessArticle
New Concept for Studying the Classical and Quantum Three-Body Problem: Fundamental Irreversibility and Time’s Arrow of Dynamical Systems
Particles 2020, 3(3), 576-620; https://doi.org/10.3390/particles3030039 (registering DOI) - 04 Aug 2020
Abstract
The article formulates the classical three-body problem in conformal-Euclidean space (Riemannian manifold), and its equivalence to the Newton three-body problem is mathematically rigorously proved. It is shown that a curved space with a local coordinate system allows us to detect new hidden symmetries [...] Read more.
The article formulates the classical three-body problem in conformal-Euclidean space (Riemannian manifold), and its equivalence to the Newton three-body problem is mathematically rigorously proved. It is shown that a curved space with a local coordinate system allows us to detect new hidden symmetries of the internal motion of a dynamical system, which allows us to reduce the three-body problem to the 6th order system. A new approach makes the system of geodesic equations with respect to the evolution parameter of a dynamical system (internal time) fundamentally irreversible. To describe the motion of three-body system in different random environments, the corresponding stochastic differential equations (SDEs) are obtained. Using these SDEs, Fokker-Planck-type equations are obtained that describe the joint probability distributions of geodesic flows in phase and configuration spaces. The paper also formulates the quantum three-body problem in conformal-Euclidean space. In particular, the corresponding wave equations have been obtained for studying the three-body bound states, as well as for investigating multichannel quantum scattering in the framework of the concept of internal time. This allows us to solve the extremely important quantum-classical correspondence problem for dynamical Poincaré systems. Full article
Open AccessFeature PaperArticle
Differential Evolution in Waveform Design for Wireless Power Transfer
Telecom 2020, 1(2), 96-113; https://doi.org/10.3390/telecom1020008 - 04 Aug 2020
Abstract
The technique of transmitting multi-tone signals in a radiative Wireless Power Transfer (WPT) system can significantly increase its end-to-end power efficiency. The optimization problem in this system is to tune the transmission according to the receiver rectenna’s nonlinear behavior and the Channel State [...] Read more.
The technique of transmitting multi-tone signals in a radiative Wireless Power Transfer (WPT) system can significantly increase its end-to-end power efficiency. The optimization problem in this system is to tune the transmission according to the receiver rectenna’s nonlinear behavior and the Channel State Information (CSI). This is a non-convex problem that has been previously addressed by Sequential Convex Programming (SCP) algorithms. Nonetheless, SCP algorithms do not always attain globally optimal solutions. To this end, in this paper, we evaluate a set of Evolutionary Algorithms (EAs) with several characteristics. The performance of the optimized multi-tone transmission signals in a WPT system is assessed by means of numerical simulations, utilizing a simplified Single Input Single Output (SISO) model. From the model evaluation, we can deduce that EAs can be successfully applied to the waveform design optimization problem. Moreover, from the presented results, we can derive that EAs can obtain the optimal solutions in the tested cases. Full article

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