bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploring the Origin of Maximum Entropy States Relevant to Resonant Modes in Modern Chladni Plates
Authors: Shu Yu-Hsin , Tseng Yu-Chen , Lai Yu-Hsiang , Yu Yan-Ting , Huang Kai-Feng , Chen Yung-Fu
Published: January 2022

The resonant modes generated from the modern Chladni experiment are systematically confirmed to intimately correspond to the maximum entropy states obtained from the inhomogeneous Helmholtz equation for the square and equilateral triangle plates. To investigate the origin of maximum entropy states, the inhomogeneous Helmholtz equation is modified to consider the point interaction coming from the driving oscillator. The coupling strength associated with the point interaction is characterized by a dimensionless factor α. The δ potential of the point interaction is numerically modelled by a truncated basis with an upper index N. The asymptotic behavior for the upper index N is thoroughly explored to verify that the coupling strength of α = 1.0 can make the theoretical resonant modes agree excellently with the maximum entropy states as N→∞. It is further authenticated that nearly the same resonant modes can be obtained by using a larger coupling strength α when a smaller upper index N is exploited in the calculation.
Effects of Vaccination Efficacy on Wealth Distribution in Kinetic Epidemic Models
Authors: Bernardi Emanuele , Pareschi Lorenzo , Toscani Giuseppe , Zanella Mattia
Published: January 2022

The spread of the COVID-19 pandemic has highlighted the close link between economics and health in the context of emergency management. A widespread vaccination campaign is considered the main tool to contain the economic consequences. This paper will focus, at the level of wealth distribution modeling, on the economic improvements induced by the vaccination campaign in terms of its effectiveness rate. The economic trend during the pandemic is evaluated, resorting to a mathematical model joining a classical compartmental model including vaccinated individuals with a kinetic model of wealth distribution based on binary wealth exchanges. The interplay between wealth exchanges and the progress of the infectious disease is realized by assuming, on the one hand, that individuals in different compartments act differently in the economic process and, on the other hand, that the epidemic affects risk in economic transactions. Using the mathematical tools of kinetic theory, it is possible to identify the equilibrium states of the system and the formation of inequalities due to the pandemic in the wealth distribution of the population. Numerical experiments highlight the importance of the vaccination campaign and its positive effects in reducing economic inequalities in the multi-agent society.
Acknowledgment to Reviewers of Entropy in 2021
Authors:   Entropy Editorial Office
Published: January 2022

Rigorous peer-reviews are the basis of high-quality academic publishing [...]
Acknowledgment to Reviewers of Economies in 2021
Authors:   Economies Editorial Office
Published: January 2022

Rigorous peer-reviews are the basis of high-quality academic publishing [...]
Transition to Long-Term Baccalaureate School in Switzerland: Governance, Tensions, and Justifications
Authors: Hafner Sandra , Esposito Raffaella Simona , Leemann Regula Julia
Published: January 2022

In Switzerland, the baccalaureate school is an important pathway to university education, and the aspirations of families and students to enter baccalaureate school have grown. However, vocational education and training (VET) remains the predominant educational pathway and has a strong lobby. We investigate how in this context, the transition from primary education to baccalaureate school is governed and justified at the cantonal level. We study how two Swiss cantons try to meet the official or unofficial maximum baccalaureate quotas desired by educational policymakers through different selection procedures and admission criteria. Drawing on the Economics of Conventions, we conceptualize selection procedures as cantonal transition chains and show that the strategies, procedures, and instruments applied in governance are rooted in diverse principles of action. This causes tensions within cantons. Our analysis shows that agency and regulating effects in the governance of transitions must be understood as distributed among actors, technologies, and objects.
Declining Student Performance and Satisfaction following Back-to-Back Scheduling of Foundational Science Exams: Experience at a Large US Osteopathic Medical School
Authors: Schmidt Martin , Pinney Brian , Werning Sarah
Published: January 2022

Examinations are a significant source of academic stress, particularly in the demanding environment of medical education. In order to reduce the burden of anxiety, burnout and depression among students, medical schools aim at reducing academic stress by exploring alternatives to frequent, high-stakes assessment schedules. The bundling of examinations into integrated block assessments has emerged as a successful strategy to reach this goal, as the resulting reduction in examination days can provide uninterrupted periods of study time that allows for a deeper understanding of material as well as an opportunity for students to take wellness breaks between exams. The present study examines the outcomes of a natural experiment on back-to-back exam scheduling in two related medical school courses post hoc. The outcomes of the scheduling change on the academic performance and satisfaction of examinees were analyzed with a mixed-methods approach. The data show that the transition from a spaced-out to a back-to-back exam schedule was accompanied by a drop in academic performance and student satisfaction with the curricular schedule. The data presented suggest that without proper curricular integration, the block scheduling of exams has negative effects on learning outcomes and student satisfaction.
3-D Metamaterials: Trends on Applied Designs, Computational Methods and Fabrication Techniques
Authors: Alex-Amor Antonio , Palomares-Caballero Ángel , Molero Carlos
Published: January 2022

Metamaterials are artificially engineered devices that go beyond the properties of conventional materials in nature. Metamaterials allow for the creation of negative refractive indexes; light trapping with epsilon-near-zero compounds; bandgap selection; superconductivity phenomena; non-Hermitian responses; and more generally, manipulation of the propagation of electromagnetic and acoustic waves. In the past, low computational resources and the lack of proper manufacturing techniques have limited attention towards 1-D and 2-D metamaterials. However, the true potential of metamaterials is ultimately reached in 3-D configurations, when the degrees of freedom associated with the propagating direction are fully exploited in design. This is expected to lead to a new era in the field of metamaterials, from which future high-speed and low-latency communication networks can benefit. Here, a comprehensive overview of the past, present, and future trends related to 3-D metamaterial devices is presented, focusing on efficient computational methods, innovative designs, and functional manufacturing techniques.
Run-Time Thermal Management for Lifetime Optimization in Low-Power Designs
Authors: Rossi Daniele , Tenentes Vasileios
Published: January 2022

In this paper, the magnitude of the temperature and stress variability of dynamic voltage and frequency scaling (DVFS) designs is analyzed, and their impact on the bias temperature instability (BTI) degradation and lifetime of DVFS designs is assessed. For this purpose, a design-time evaluation framework for BTI degradation was developed, which considered the statistical workload and die temperature profiles of DVFS operating modes. The performed analysis showed that, together with high stress variability, DVFS designs exhibited even higher temperature variability, depending on the workload and utilized operating modes, and the impact of temperature variability on lifetime could be up to 2× higher than that due to stress. In order to account for temperature variability on aging detrimental effects, a thermal management run-time system is proposed that honors the desired lifetime constraints by properly selecting temperature constraints that govern the utilized operating modes. The proposed run-time system was applied on the largest benchmark circuit from the IWLS 2005 suite, Ethernet circuit, synthesized with the 32 nm CMOS technology. The proposed system was verified to obtain lifetime and performance estimation and the trade-off with up to 35.8% and 26.3% higher accuracy, respectively, when compared to a system that ignores temperature variability and accounts for average temperature only. The proposed framework can be suitably utilized for tuning run-time throttling policies of low-power designs, thus allowing designers to optimize lifetime–performance trade-offs, depending on the requirements mandated by specific applications and operating environments.
Performance of 5G Trials for Industrial Automation
Authors: Ansari Junaid , Andersson Christian , de Bruin Peter , Farkas János , Grosjean Leefke , Sachs Joachim , Torsner Johan , Varga Balázs , Harutyunyan Davit , König Niels , Schmitt Robert H.
Published: January 2022

Wireless- and 5G-enabled industrial automation is expected to include a plethora of different applications with a wide variety of requirements. In this article, evaluations are undertaken for the deployment of 5G in realistic industrial production environments with realistic deployment settings. Both deployments using commercial 5G systems and a 5G prototype system including pre-commercial and standard compliant URLLC functionality have been investigated. Systematic latency and reliability measurements were performed, over the air and in live networks, for different packet sizes, different devices, and networks with different capabilities (at different sites) to characterize the expected performance. The results indicate that today’s 5G latency performance significantly depends on packet size, transmission direction (uplink or downlink), and network configuration as well as on the end device’s design and capabilities. Our over-the-air measurements also empirically show that 5G technology and future networks have the capability of providing one-way latency of around 1 ms in both uplink and downlink for the various packet sizes tested. It is concluded that the requirements for very low latencies can be achieved with high reliability guarantees, as required in some of the most stringent industrial IoT applications.
A Competency Framework for Teaching and Learning Innovation Centers for the 21st Century: Anticipating the Post-COVID-19 Age
Authors: Pérez-Sanagustín Mar , Kotorov Iouri , Teixeira António , Mansilla Fernanda , Broisin Julien , Alario-Hoyos Carlos , Jerez Óscar , Teixeira Pinto Maria do Carmo , García Boni , Delgado Kloos Carlos , Morales Miguel , Solarte Mario , Oliva-Córdova Luis Magdiel , Gonzalez Lopez Astrid Helena
Published: January 2022

During the COVID-19 pandemic, most Higher Education Institutions (HEIs) across the globe moved towards “emergency online education”, experiencing a metamorphosis that advanced their capacities and competencies as never before. Teaching and Learning Centers (TLCs), the internal units that promote sustainable transformations, can play a key role in making this metamorphosis last. Existing models for TLCs have defined the competencies that they could help develop, focusing on teachers’, students’, and managers’ development, but have mislead aspects such as leadership, organizational processes, and infrastructures. This paper evaluates the PROF-XXI framework, which offers a holistic perspective on the competencies that TLCs should develop for supporting deep and sustainable transformations of HEIs. The framework was evaluated with 83 participants from four Latin American institutions and used for analyzing the transformation of their teaching and learning practices during the pandemic lockdown. The result of the analysis shows that the PROF-XXI framework was useful for identifying the teaching and learning competencies addressed by the institutions, their deficiencies, and their strategic changes. Specifically, this study shows that most institutions counted with training plans for teachers before this period, mainly in the competencies of digital technologies and pedagogical quality, but that other initiatives were created to reinforce them, including students’ support actions.
Detection of DGA-Generated Domain Names with TF-IDF
Authors: Vranken Harald , Alizadeh Hassan
Published: January 2022

Botnets often apply domain name generation algorithms (DGAs) to evade detection by generating large numbers of pseudo-random domain names of which only few are registered by cybercriminals. In this paper, we address how DGA-generated domain names can be detected by means of machine learning and deep learning. We first present an extensive literature review on recent prior work in which machine learning and deep learning have been applied for detecting DGA-generated domain names. We observe that a common methodology is still missing, and the use of different datasets causes that experimental results can hardly be compared. We next propose the use of TF-IDF to measure frequencies of the most relevant n-grams in domain names, and use these as features in learning algorithms. We perform experiments with various machine-learning and deep-learning models using TF-IDF features, of which a deep MLP model yields the best results. For comparison, we also apply an LSTM model with embedding layer to convert domain names from a sequence of characters into a vector representation. The performance of our LSTM and MLP models is rather similar, achieving 0.994 and 0.995 AUC, and average F1-scores of 0.907 and 0.891 respectively.
Key Requirements for the Detection and Sharing of Behavioral Indicators of Compromise
Authors: Villalón-Huerta Antonio , Ripoll-Ripoll Ismael , Marco-Gisbert Hector
Published: January 2022

Cyber threat intelligence feeds the focus on atomic and computed indicators of compromise. These indicators are the main source of tactical cyber intelligence most organizations benefit from. They are expressed in machine-readable formats, and they are easily loaded into security devices in order to protect infrastructures. However, their usefulness is very limited, specially in terms of time of life. These indicators can be useful when dealing with non-advanced actors, but they are easily avoided by advanced ones. To detect advanced actor’s activities, an analyst must deal with behavioral indicators of compromise, which represent tactics, techniques and procedures that are not as common as the atomic and computed ones. In this paper, we analyze why these indicators are not widely used, and we identify key requirements for successful behavioral IOC detection, specification and sharing. We follow the intelligence cycle as the arranged sequence of steps for a defensive team to work, thereby providing a common reference for these teams to identify gaps in their capabilities.
A Comparative Analysis of S-S and LCCL-S Compensation for Wireless Power Transfer with a Wide Range Load Variation
Authors: Zhu Yuhao , Wu Hao , Li Fan , Zhu Yongsheng , Pei Yi , Liu Wen
Published: January 2022

Wireless power transmission (WPT) has great potential for charging electric vehicles. Constant voltage (CV) and constant current (CC) are two major types of battery charging modes. In this paper, we analyze the output characteristics of series-series (S-S) topology and double capacitances and inductances-series (LCCL-S) topology. Voltage gain variation is achieved in the LCCL-S compensation structure without additional components, and the system is still kept in resonant condition. A WPT experimental platform was also built and tested based on the theoretical analysis. When the load resistance is 300 Ω, a voltage gain of 0.7 or 2.22 is achieved for the LCCL-S with a compensating inductor of 100 μH or 33 μH, respectively. The experimental results fit the theoretical analysis. The CC/CV output characteristics and efficiencies of S-S and LCCL-S topologies in a wide load resistance range are also demonstrated. Moreover, zero voltage switch (ZVS) is also implemented in both two systems.
Analysis of Electricity and Natural Gas Security. A Case Study for Germany, France, Italy and Spain
Authors: Krikštolaitis Ričardas , Bianco Vincenzo , Martišauskas Linas , Urbonienė Sigita
Published: January 2022

This work aims to present an analysis of electricity and natural gas supply security in the four European Union countries with the highest level of consumption, namely Germany, France, Italy, and Spain. The goal of the study is to use and adapt a set of 22 indicators for estimating the level of energy security. The evaluation of an index called “Energy Security Level”, measuring the overall energy security, is performed for the period 2006–2018 in order to compare its evolution in each of the analyzed countries. The application of the proposed indicator system demonstrates which measures weakened or strengthened energy security in the past. The analysis of the energy security level demonstrates that Germany and France perform better than Italy and Spain in terms of energy security assurance. The main factors for these differences are the rich energy mix for Germany and the massive presence of nuclear power in France. These two elements make German and French energy systems more resilient than the Italian and Spanish ones. The results of sensitivity and uncertainty analysis demonstrate that the initial values of indicator weights have low impact on the uncertainty of energy security level estimations.
Performance Analysis of a Dynamic Line Rating System Based on Project Experiences
Authors: Rácz Levente , Németh Bálint , Göcsei Gábor , Zarchev Dimitar , Mladenov Valeri
Published: January 2022

This paper aims to demonstrate the performance and reliability analysis of a dynamic line rating (DLR) system at the Bulgarian demonstration site of the FLEXITRANSTORE project. As part of the project, various manufacturers’ different line monitoring DLR sensors and weather stations were installed on a 110 kV double-circuit overhead line (OHL). These devices provided input parameters to the DLR system based on objective measurements. This paper used statistical tools to examine the reliability and accuracy of installed devices, thus making products from different manufacturers comparable. In addition, two independent line monitoring and DLR models have been developed: the black-box and extended white-box models. The performances of the two models were analyzed for the same input parameters and compared to the field measurements. Based on the presented results, the reliability and accuracy of the applied weather stations of different companies were almost the same. This conclusion cannot be said for DLR line monitoring sensors, where the devices could be differentiated based on reliability and measurement accuracy results. In terms of models, the usability of the extended white-box model seemed to be limited in certain weather conditions, implicating a more significant role for soft-computing-based DLR models in the future. In addition to the results, root causes for the errors and future directions that may provide a framework for further research are also presented.
Wind Turbine Power Maximization Using Log-Power Proportional-Integral Extremum Seeking
Authors: Kumar Devesh , Rotea Mario A.
Published: January 2022

This paper proposes a Log-Power Proportional-Integral Extremum Seeking Control (LP-PIESC) framework for maximizing the power capture of a wind turbine operating at below-rated wind speeds, i.e., the so-called region-2 of a turbine’s power curve. Extremum seeking control (ESC) has emerged as a viable algorithm to maximize energy capture for a wind turbine operating in region-2. Despite the encouraging results of early ESC strategies, the basic algorithm suffers from slow and inconsistent convergence behavior under changing wind speed within region-2. It has been shown that replacing the power signal with its logarithm results in an algorithm that is robust and predictable even when the mean wind speed varies. In addition, new studies have suggested that replacing conventional ESC with proportional plus integral ESC (PIESC) results in faster convergence to optimal conditions. In the current paper, the idea of log-power feedback is merged with the PIESC scheme and is applied to tune the parameters of the region-2 torque controller for the NREL 5-MW turbine reference model. The results of this new algorithm are compared with the ESC with log-of-power feedback using NREL OpenFAST simulations. The log-power feedback PIESC is also implemented for the blade pitch set-point angle. Energy capture over the course of the simulations and damage equivalent loads calculated with MLife are used to assess the results. The simulations performed under different turbulent intensity cases demonstrate the rapid convergence of the log-power feedback PIESC.
Typical Damage Prediction and Reliability Analysis of Superheater Tubes in Power Station Boilers Based on Multisource Data Analysis
Authors: Liu Guangkui , Yang Xu , Yang Xisheng , Liang Kui , An Dong , Wu Di , Ren Xiaohan
Published: January 2022

The superheater and re-heater piping components in supercritical thermal power units are prone to creep and fatigue failure fracture after extensive use due to the high pressure and temperature environment. Therefore, safety assessment for superheaters and re-heaters in such an environment is critical. However, the actual service operation data is frequently insufficient, resulting in low accuracy of the safety assessment. Based on such problems, in order to address the issues of susceptibility of superheater and re-heater piping components to creep, inaccurate fatigue failure fracture, and creep–fatigue coupling rupture in a safety assessment, their remaining life prediction and reliability, as well as the lack of actual service operation data, multisource heterogeneous data generated from actual service of power plants combined with deep learning technology was used in this paper. As such, three real-time operating conditions’ data (temperature, pressure, and stress amplitude) during equipment operation are predicted by training a deep learning architecture long short-term memory (LSTM) neural network suitable for processing time-series data and a backpropagation through time (BPTT) algorithm is used to optimize the model and compared with the actual physical model. Damage assessment and life prediction of final superheater tubes of power station boilers are carried out. The Weibull distribution model is used to obtain the trend of cumulative failure risk change and assess and predict the safety condition of the overall system of pressurized components of power station boilers.
Evaluation of an Additional Generator on the Economic Effect Based on a Load Sharing Optimization of Medium-Speed/High-Speed Diesel Generators in a Microgrid
Authors: Yamano Shuhei , Akisawa Atsushi
Published: January 2022

This study investigates the additional installation of a high-speed diesel generator to independent microgrids (MG) such as remote islands where relatively efficient medium-speed diesel generators (DGs) are mainly used. While small-sized and lightweight, high-speed DGs are not widely spread for continuous usage because their efficiency is lower than that of the medium-speed DGs. The objective of this study is to evaluate the performance of the new method of load sharing optimization to improve the economy by interconnecting a high-speed DG to an independent MG where the medium-speed DGs are operated. The study investigates the effect of operation cost reduction by installing the new load sharing method of operation following the load sharing pattern derived by the mixed-integer programming. As a result of this study, there was some effect to installing a high-speed DG operated by the conventional method. In addition, by adding the new method of load sharing with optimization, the economic effect became even higher.
Cost Optimized Building Energy Retrofit Measures and Primary Energy Savings under Different Retrofitting Materials, Economic Scenarios, and Energy Supply
Authors: Gustavsson Leif , Piccardo Chiara
Published: January 2022

We analyze conventional retrofit building materials, aluminum, rock, and glass wool materials and compared such materials with wood-based materials to understand the lifecycle primary energy implications of moving from non-renewable to wood-based materials. We calculate cost optimum retrofit measures for a multi-apartment building in a lifecycle perspective, and lifecycle primary energy savings of each optimized measure. The retrofit measures consist of the thermal improvement of windows with varied frame materials, as well as extra insulation of attic floor, basement walls, and external walls with varied insulation materials. The most renewable-based heat supply is from a bioenergy-based district heating (DH) system. We use the marginal cost difference method to calculate cost-optimized retrofit measures. The net present value of energy cost savings of each measure with a varied energy performance is calculated and then compared with the calculated retrofit cost to identify the cost optimum of each measure. In a sensitivity analysis, we analyze the cost optimum retrofit measures under different economic and DH supply scenarios. The retrofit costs and primary energy savings vary somewhat between non-renewable and wood-based retrofit measures but do not influence the cost optimum levels significantly, as the economic parameters do. The lifecycle primary use of wood fiber insulation is about 76% and 80% less than for glass wool and rock wool, respectively. A small-scale DH system gives higher primary energy and cost savings compared to larger DH systems. The optimum final energy savings, in one of the economic scenarios, are close to meeting the requirements in one of the Swedish passive house standards.
A New Decentralized Space Vector PWM Method for Multilevel Single-Phase Full Bridge Converters
Authors: Nguyen Phu Cong , Phan Quoc Dung , Nguyen Dinh Tuyen
Published: January 2022

This paper proposes a decentralized control structure and method for a multilevel single-phase power converter using space vector pulse width modulation (SVPWM). The focus of this paper is on the decentralized control structure for the power converter cells that will exchange information with neighboring cells in order to adjust the switching vector and switching time for each cell. In this study, the switching vectors and the corresponding switching times of each cell will be self-determined based on the phase angle of two neighboring cells. Normally, SVPWM applied to the multilevel power converters need complete information about the total cells and cell’s position to build a control algorithm. Meanwhile, a decentralized space vector pulse width modulation (DSVPWM) method is proposed that can be applied to power converters with any number of cells and can be considered as a multilevel SVPWM method. In addition, the decentralized multilevel single-phase power converter has high flexibility with which it is possible to easily adjust the number of active cells, so that the output voltage can be adjusted quickly; this provides the ability to dynamically reconfigure without interrupting the power energy supply process. The proposed control structure and method are effectively verified based on simulation and experimental results. Experimental results are evaluated based on a 9-level single-phase power converter, which has an RL load with rated parameters 220 V/500 W.
Fractal Characterization of Multimodal, Multiscale Images of Shale Rock Fracture Networks
Authors: Vega Bolivia , Kovscek Anthony R.
Published: January 2022

An array of multimodal and multiscale images of fractured shale rock samples and analogs was collected with the aim of improving the numerical representation of fracture networks. 2D and 3D reconstructions of fractures and matrices span from 10−6 to 100 m. The origin of the fracture networks ranged from natural to thermal maturation to hydraulically induced maturation. Images were segmented to improve fracture identification. Then, the fractal dimension and length distribution of the fracture networks were calculated for each image dataset. The resulting network connectivity and scaling associations are discussed at length on the basis of scale, sample and order of magnitude. Fracture network origin plays an important role in the resulting fracture systems and their scaling. Rock analogs are also evaluated using these descriptive tools and are found to be faithful depictions of maturation-induced fracture networks.
Efficient IoT-Based Formal Model for Vehicle-Life Interaction in VANETs Using VDM-SL
Authors: Iqbal Sidra , Zafar Nazir Ahmad , Ali Tariq , Alkhammash Eman H.
Published: January 2022

VANETs have gained much attention from both industry and academia because of their characteristics, such as dynamic topology. There are various applications of VANETs that are classified on the basis of safety, efficiency, commercial usage, and productive areas. This paper presents an IoT-based formal model for vehicle-life integration enabling RSUs with the help of different approaches. We have developed a model that uses vehicle scenarios in smart transportation systems so that quick data transmission is provided between the source and destination vehicles. Further, fog-based RSUs provide a wide range to communicate with hospitals and emergency vehicles to deal with emergency situations. All the appropriate entities are connected to ensure a consistent traffic flow for the arrival of an emergency vehicle in emergency places. The UML, graph theory, and VDM-SL formal technique are used to represent this system. To model the network and discover appropriate paths for V2V communication, graph theory is applied. The system requirements are designed using a UML diagram. The VDM-SL, an object-oriented model-based formal technique, was utilized for this modeling procedure. This approach assures the safety and accuracy of systems by detecting flaws early in the design process. It also gives an exceptionally important answer to an issue and increases trust in the software’s quality.
The Modeling of Magnetic Fields in Electromagnetic Microgenerators Using the Finite Element Method
Authors: Gierczak Mirosław , Markowski Piotr Marek , Dziedzic Andrzej
Published: January 2022

The purpose of this paper is to analyze the magnetic field distribution over a disc with magnets. This disk is part of an electromagnetic microgenerator that allows the generation of electricity as a result of changes in the magnetic field. The other part of the microgenerator is the structure of the coils. In the previous work of the authors, a complete microgenerator system was presented where the coils were made using thick-film and low-temperature co-fired ceramic (LTCC) technology. Several studies related to the influence of the shape and number of coils on the generated power were carried out, as well as the realization of complete electromagnetic microgenerators with voltage rectifying circuits. Until now, a disc with 28 neodymium magnets of size 10 × 3 × 1.5 mm3 was used for testing. In order to optimize the structure of the microgenerator with respect to the disc with magnets and thus increase the generated power, it was decided to perform appropriate tests to analyze the magnetic field distribution for several configurations of the disc varying in the shape and the dimensions of the magnets. Simulations were performed in COMSOL Multiphysics using the finite element method.
The Technical State of Engineering Systems as an Important Factor of Heat Supply Organizations Management in Modern Conditions
Authors: Verstina Natalia , Evseev Evgeny , Tsuverkalova Olga , Kulachinskaya Anastasia
Published: January 2022

This article examines the features of the heat supply organizations (HSO) anti-crisis management, which has become relevant due to the pandemic in the spring of 2020. It is noted that the spread of coronavirus and the related economic problems had a negative impact on the sustainable development indicators of both countries and organizations. HSO, which are rarely considered in modern publications, are positioned in the study as the most important part of the economy of any country, on which the future stabilization of the economic situation among heat consumers depends. This study made it possible to draw a conclusion about the strengthening of the HSO engineering systems technical state role in the anti-crisis management of these organizations. The study summarizes and presents the main characteristics of the heating networks technical condition and systematizes all types of diagnostics that are encountered in practice. The characteristics of HSO management choices of the technical state monitoring methods is given. The authors propose a generalized model of the diagnostic methods choice, taking into account the sustainable development of a specific HSO. Perspective approaches to the improvement of the HSO heat supply systems state are determined, which will ensure the development and increasing reliability of urban infrastructure in the context of achieving sustainable development goals.
A Novel Strategy for Smart Building Convergence Based on the SmartLVGrid Metamodel
Authors: Fernandes Rubens A. , Gomes Raimundo C. S. , Dias Ozenir , Carvalho Celso
Published: January 2022

Smart buildings provide opportunities for technological transformations in building environments to improve resource management, comfort, and efficiency of the systems present in these facilities. For this, Internet of Things (IoT) solutions contribute, with monitoring and remote control features, to automate these environments. However, these solutions can promote the disposal or replacement of outdated but still-needed legacy systems. Thus, a reference model that uses retrofit techniques to update pre-existing systems would be an alternative to enable smart building convergence. The lack of models that advocate this type of strategy provides an opportunity for the emergence of methods capable of filling this gap. Thus, this work presents a strategy for implementing monitoring, control, and communication resources to achieve smart building convergence in legacy building systems. This strategy consists of the use of retrofit techniques based on the adaptation of the SmartLVGrid metamodel. To validate this proposal, we developed hardware platforms and, respectively, their firmware to implement the premises established in a legacy building lighting circuit. The results obtained present a new possibility of implementing smart buildings from the retrofit of legacy infrastructures, as the pre-existing building lighting circuit obtained new functionalities and was preserved as much as possible.
Design Optimization of Centralized–Decentralized Hybrid Solar Heating System Based on Building Clustering
Authors: Liu Yanfeng , Hu Deze , Luo Xi , Mu Ting
Published: January 2022

Clean heating has not been widely applied in rural Chinese areas. Considering the abundance of solar energy resources, harvesting solar energy for heating can be an effective solution to the problem of space heating in most rural areas. As the disperse building distribution in rural areas makes it difficult to implement centralized heating on a large scale, deploying centralized–decentralized hybrid solar heating system can achieve the best result from both the technical and economic perspectives. Taking a virtual village in Tibet as an example, this paper explores how to obtain optimal design of centralized–decentralized hybrid solar heating system based on building clustering. The results show that: (1) Compared with the fully centralized system and fully decentralized system, the centralized–decentralized hybrid solar heating system in the studied case could achieve a life cycle cost (LCC) saving of 4.8% and 2.3%, respectively; (2) The LCC of centralized–decentralized hybrid solar heating system basically decreases when the cost of the heating pipelines in the whole region decreases, but the emergence of single-household solar heating system may greatly increase the operating cost; (3) The necessity of designing a centralized–decentralized hybrid solar heating system can be determined by the pipeline price and building density, but the threshold values of pipeline price and building density are highly case-specific.
Investigation on Individual and Collective PV Self-Consumption for a Fifth Generation District Heating Network
Authors: Vivian Jacopo , Chinello Mattia , Zarrella Angelo , De Carli Michele
Published: January 2022

Renewable Energy Communities have been recently introduced in European legislation to promote distributed generation from renewable energy sources. In fact, they allow to produce and consume energy from shared local power plants. Low temperature district heating and cooling networks with distributed heat pumps have demonstrated their capability to exploit renewable and waste heat sources in the urban environment. Therefore, they are considered a promising infrastructure to help decarbonize the building sector. As their main operating cost is the electricity purchased by the utility for heat pumps and circulation pumps, this work investigates whether a Renewable Energy Community could help mitigate such cost by sharing electricity produced by local photovoltaic (PV) systems. The research relies on computer simulations performed with both physical and statistical models for the evaluation of electrical load profiles at the district level. Results show that due to the different seasonality between heating demand and PV production, the increase in self-consumption due to the distributed heat pumps is lower than 10%. The use of batteries does not seem convenient for the same reason. The environmental benefit of the proposed system is evident, with CO2 emissions reduced by 72–80% compared to the current situation depending on PV power installed. It also emerged that PV sharing significantly improves the self-consumption at the district level, in particular when the installed PV power is limited (+45%). In conclusion, results suggest that current incentives on PV-sharing make Renewable Energy Communities a viable option to improve the techno-economic performance of fifth-generation district heating and cooling networks.
Review of the Current Status of Ammonia-Blended Hydrogen Fuel Engine Development
Authors: Xu Xiaowei , Liu Enlong , Zhu Neng , Liu Fanfu , Qian Feng
Published: January 2022

As fossil fuels continue to be extracted and used, issues such as environmental pollution and energy scarcity are surfacing. For the transportation industry, the best way to achieve the goal of “carbon neutrality” is to research efficient power systems and develop new alternative fuels. As the world’s largest product of chemicals, ammonia is a new renewable fuel with good combustion energy. It can be used as an alternative fuel to reduce carbon emissions because of its proven production process, low production and transportation costs, safe storage, the absence of carbon-containing compounds in its emissions, and its future recyclability. This paper firstly introduces the characteristics of ammonia fuel engine and its problems; then it summarizes the effects of various ammonia-blended fuels on the combustion and emission characteristics of the engine from the combustion problem of ammonia-blended engine; then the fuel storage of ammonia-blended hydrogen is discussed, the feasibility of hydrogen production instead of hydrogen storage is introduced.
Stochastic versus Fuzzy Models—A Discussion Centered on the Reliability of an Electrical Power Supply System in a Large European Hospital
Authors: Pinto Constâncio António , Farinha José Torres , Raposo Hugo , Galar Diego
Published: January 2022

This paper discusses the Reliability, Availability, Maintainability, and Safety (RAMS) of an electrical power supply system in a large European hospital. The primary approach is based on fuzzy logic and Petri nets, using the CPNTools software to simulate and determine the most important modules of the system according to the Automatic Transfer Switch. Fuzzy Inference System is used to analyze and assess the reliability value. The stochastic versus fuzzy approach is also used to evaluate the reliability contribution of each system module. This case study aims to identify and analyze possible system failures and propose new solutions to improve the system reliability of the power supply system. The dynamic modeling is based on block diagrams and Petri nets and is evaluated via Markov chains, including a stochastic approach linked to the previous analysis. This holistic approach adds value to this type of research question. A new electrical power supply system design is proposed to increase the system’s reliability based on the results achieved.
Energy Performance Evaluation of Shallow Ground Source Heat Pumps for Residential Buildings
Authors: Shah Archan , Krarti Moncef , Huang Joe
Published: January 2022

This paper evaluates the energy performance of shallow ground source heat pumps using the state-of-art whole building energy simulation tool. In particular, the paper presents a systematic and easy to implement approach to model the energy performance of shallow and helical ground heat exchangers and assess their energy efficiency benefits to heat and cool buildings. The modeling approach is based on the implementation of G-functions, generated using a validated numerical model, in a state-of-art whole building energy simulation tool. Both the numerical model and the simulation tool are applied to assess the energy performance of various shallow geothermal systems designed to meet heating and cooling needs for detached single-family homes in California. Specifically, a series of sensitivity analyses is conducted to determine the energy performance of the shallow geothermal systems in 16 locations representing all California climate zones. It is found that the suitability and the efficiency of the shallow geothermal systems vary widely and depend on several factors including their design specifications as well as the climate conditions. Compared with conventional air-to-air heat pumps, the shallow ground source heat pumps can be more energy efficient in most climate zones in California except those locations with extreme weather conditions resulting in either heating or cooling only operation. Moreover, configurations of shallow ground source heat pumps with 16 boreholes with 6.7 m (22 ft) depth are found to be cost-effective in several California climate zones.
An Analysis of the Performance Characteristics of Different Cylinder Temperatures for Ni-W and Ni-W-BN(h) Plated Piston Rings in an Air-Cooled Engine
Authors: Chou Chih-Cheng , Huang Pao-Chang , Dai Huang-Bin
Published: January 2022

An engine must operate at an appropriate working temperature, the wear resistance of the engine parts must be increased, and frictional loss of energy must be reduced to increase performance and reduce exhaust pollution. This study determines the effect of cylinder temperature and different coatings for piston rings on engine characteristics. Ni-W alloy and Ni-W-BN(h) composite coatings are applied to the compression ring, and the dynamometer test is performed over 50 h using different operating parameters. The experimental data are analyzed by curve fitting for engine performance with cylinder temperature (Tsc) and the concentration of exhaust pollution particles. The experimental results show that a Ni-W alloy plating increases the wear resistance of piston rings. A Ni-W-BN(h) composite coating contains self-lubricating particles, which increases the wear resistance and lubricating properties. In terms of engine performance, Ni-W-BN(h) coated piston rings give the best brake mean effective pressure (BMEP) and fuel conversion efficiency (ηf), and low fuel consumption reduces HC and CO emissions. Therefore, Ni-W-BN(h) is the best coating material for a piston ring.
An Empirical Analysis of Renewable Energy Contributions Considering Green Consumer Values—A Case Study of Poland
Authors: Bartoszczuk Paweł , Singh Uma , Rutkowska Małgorzata
Published: January 2022

This article examines the acceptance of renewable energy in the adoption of the climate package, taking into account the GREEN consumer values among consumers in Poland. The research problem addressed in this paper relates to the measurement of consumer values in terms of the GREEN concept; specifically, consumer acceptance of the available offerings provided by real businesses. In addition, consumer needs are important in terms of ensuring the acceptance of renewable energy, which will create opportunities for its production in the context of the Fit 55 climate package. The study formulates some research questions and hypotheses to justify the concept with empirical data by applying statistical tests. The study is presented in several sections with a detailed presentation of secondary and primary data. The main outcome of the research is based on the primary data using a structured survey questionnaire administered in Poland and 557 collected samples. Nowadays, the responsibility also lies with consumers, as green consumption will entail green production. The research concludes that Poland’s consumers have a good level of acceptance of RES, based on the current green energy situation of Poland, which may lead to sustainability and will benefit policy makers in government, corporations and end consumers.
Proposal of Wireless Charging Which Enables Magnetic Field Suppression at Foreign Object Location
Authors: Sato Shunta , Nakamura Sousuke
Published: January 2022

In the wireless power transmission (WPT) to electric vehicles (EVs) in parking lots, there is a risk of abnormal heat generation due to the absorption of the magnetic field in metallic foreign objects. Accordingly, currently available products are equipped with a function that automatically halts power transmission when a metallic foreign object is detected. However, if possible, continuing power transmission while suppressing the magnetic field absorption may be an another solution. Therefore, this paper proposes a novel function which enables wireless power transmission with high efficiency while suppressing the magnetic field absorption of metallic foreign objects. In this study, it was assumed that a metallic foreign body was present in an arbitrary point in a two-dimensional plane and the power transmission was conducted by the phased array WPT. An algorithm using particle swarm optimization (PSO) to search for the optimal combination of the phase and amplitude of the coil input voltages together with coil arrangements, in terms of both magnetic field suppression and transmission efficiency, is proposed. The simulation was performed with the lower efficiency boundary set as 85% and the load power set as 11 kW, in reference to the SAE J2954 standard. As a result, it was confirmed that the magnetic field suppression effect increased in accordance with the increase in the number of transmission (Tx) coils, thus indicating the effectiveness of the proposed algorithm.