bluuebunny/crossref_metadata_2025 huggingface dataset:
Short-Time Estimation of Fractionation in Atrial Fibrillation with Coarse-Grained Correlation Dimension for Mapping the Atrial Substrate
Authors: Vraka Aikaterini , Hornero Fernando , Bertomeu-González Vicente , Osca Joaquín , Alcaraz Raúl , Rieta José J.
Published: February 2020

Atrial fibrillation (AF) is currently the most common cardiac arrhythmia, with catheter ablation (CA) of the pulmonary veins (PV) being its first line therapy. Ablation of complex fractionated atrial electrograms (CFAEs) outside the PVs has demonstrated improved long-term results, but their identification requires a reliable electrogram (EGM) fractionation estimator. This study proposes a technique aimed to assist CA procedures under real-time settings. The method has been tested on three groups of recordings: Group 1 consisted of 24 highly representative EGMs, eight of each belonging to a different AF Type. Group 2 contained the entire dataset of 119 EGMs, whereas Group 3 contained 20 pseudo-real EGMs of the special Type IV AF. Coarse-grained correlation dimension (CGCD) was computed at epochs of 1 s duration, obtaining a classification accuracy of 100% in Group 1 and 84.0–85.7% in Group 2, using 10-fold cross-validation. The receiver operating characteristics (ROC) analysis for highly fractionated EGMs, showed 100% specificity and sensitivity in Group 1 and 87.5% specificity and 93.6% sensitivity in Group 2. In addition, 100% of the pseudo-real EGMs were correctly identified as Type IV AF. This method can consistently express the fractionation level of AF EGMs and provides better performance than previous works. Its ability to compute fractionation in short-time can agilely detect sudden changes of AF Types and could be used for mapping the atrial substrate, thus assisting CA procedures under real-time settings for atrial substrate modification.
A New Method for Peer-to-Peer Energy Exchange in Distribution Grids
Authors: Reihani Ehsan , Siano Pierluigi , Genova Michael
Published: February 2020

In this paper, distribution-level peer-to-peer energy exchange is proposed that allows increased matching between load and generation nodes. Contributions of the proposed improved matching system between the local load and generation nodes aim at making efficient use of unused power generation, reducing the cost of electrical energy for consumers, and assisting utility companies by reducing transmission line congestion. The proposed system for matching the load and generation nodes consists of a financial layer and technical layer. In the financial layer, nodes with an excess of energy provide a price to sell energy, while the nodes needing energy bid on a price to purchase energy. A market-clearing mechanism using pool clearing is applied to determine a final price for peer-to-peer exchange. The technical layer determines the connection of energy transfer between the generation and load nodes while considering the distance, power flow constraints, and specified time windows. The proposed approach is verified in a five-node system and the results are discussed.
Temporal Aspects in Emission Accounting—Case Study of Agriculture Sector
Authors: Timma Lelde , Dace Elina , Trydeman Knudsen Marie
Published: February 2020

Complex relations link climate change and agriculture. The vast majority of the studies that are looking into the quantification of the climate impacts use the Global Warming Potential (GWP) for a 100-year time horizon (GWP100) as the default metrics. The GWP, including the Bern Carbon Cycle Model (BCCM), was proposed as an alternative method to take into consideration the amount and time of emission, and the fraction of emissions that remained in the atmosphere from previous emission periods. Thus, this study aims to compare two methods for GHG emission accounting from the agriculture sector: the constant GWP100 and the time dynamic GWP100 horizon obtained by using the BCCM to find whether the obtained results will lead to similar or contradicting conclusions. Also, the effect of global temperature potential (GTP) of the studied system is summarized. The results show that the application of the BCCM would facilitate finding more efficient mitigation options for various pollutants and analyze various parts of the climate response system at a specific time in the future (amount of particular pollutants, temperature change potential). Moreover, analyze different solutions for reaching the emission mitigation targets at regional, national, or global levels.
Geographical Potential of Solar Thermochemical Jet Fuel Production
Authors: Falter Christoph , Scharfenberg Niklas , Habersetzer Antoine
Published: February 2020

The solar thermochemical fuel pathway offers the possibility to defossilize the transportation sector by producing renewable fuels that emit significantly less greenhouse gases than conventional fuels over the whole life cycle. Especially for the aviation sector, the availability of renewable liquid hydrocarbon fuels enables climate impact goals to be reached. In this paper, both the geographical potential and life-cycle fuel production costs are analyzed. The assessment of the geographical potential of solar thermochemical fuels excludes areas based on sustainability criteria such as competing land use, protected areas, slope, or shifting sands. On the remaining suitable areas, the production potential surpasses the current global jet fuel demand by a factor of more than fifty, enabling all but one country to cover its own demand. In many cases, a single country can even supply the world demand for jet fuel. A dedicated economic model expresses the life-cycle fuel production costs as a function of the location, taking into account local financial conditions by estimating the national costs of capital. It is found that the lowest production costs are to be expected in Israel, Chile, Spain, and the USA, through a combination of high solar irradiation and low-level capital costs. The thermochemical energy conversion efficiency also has a strong influence on the costs, scaling the size of the solar concentrator. Increasing the efficiency from 15% to 25%, the production costs are reduced by about 20%. In the baseline case, the global jet fuel demand could be covered at costs between 1.58 and 1.83 €/L with production locations in South America, the United States, and the Mediterranean region. The flat progression of the cost-supply curves indicates that production costs remain relatively constant even at very high production volumes.
Possibility of Calcium Oxide from Natural Limestone Including Impurities for Chemical Heat Pump
Authors: Lai LanXin , Imai Toshio , Umezu Motohiro , Ishii Mamoru , Ogura Hironao
Published: February 2020

Improving energy recycle is an important way to save energy resources and preserve the global environment. Chemical heat pump (CHP) is a technology for saving energy, which utilizes chemical reactions to store thermal energy such as waste heat and solar heat, then release it to provide heat for heating/cooling/refrigeration. For a practical CHP, it is necessary to find cheaper and more stable supply materials. In order to evaluate the possibility of calcium oxide from natural Ofunato natural limestone including impurities, we compare Ofunato limestone with Kawara natural limestone and Garou natural limestone from Japan. These calcium oxides worked as a reactant for CaO/H2O/Ca(OH)2 CHP by repeated hydration/dehydration reaction cycle experiments in a thermogravimetric analyzer. As a result, Ofunato CaO exhibits a high hydration reaction rate after decarbonization at 1223 K for 5 h. The reactivity increased by the repeated hydration reaction although the first hydration rate was low. Furthermore, the sintering of impurities in Ofunato limestone occur easier than that in Kawara limestone with lower impurities. The impurities adhered to the surface of the CaO particle to make specific surface area of CaO particle smaller, which could inhibit hydration reaction of CaO particle. Even if Ofunato limestone contains some impurities, it can be utilized as a raw material for chemical heat pumps.
The Economic Feasibility of Floating Offshore Wave Energy Farms in the North of Spain
Authors: Castro-Santos Laura , Bento Ana , Guedes Soares Carlos
Published: February 2020

A technique to analyse the economic viability of offshore farms composed of wave energy converters is proposed. Firstly, the inputs, whose value will be considered afterwards in the economic step, was calculated using geographic information software. Secondly, the energy produced by each wave converter was calculated. Then the economic factors were computed. Finally, the restriction that considers the depth of the region (bathymetry) was put together with the economic outputs, whose value depends on the floating Wave Energy Converter (WEC). The method proposed was applied to the Cantabric and Atlantic coasts in the north of Spain, a region with a good offshore wave energy resource. In addition, three representative WECs were studied: Pelamis, AquaBuoy and Wave Dragon; and five options for electric tariffs were analysed. Results show the Wave Energy Converter that has the best results regarding its LCOE (Levelized Cost of Energy), IRR (Internal Rate of Return) and NPV (Net Present Value), and which area is best for the development of a wave farm.
Effect of Inlet Compound Angle of Backward Injection Film Cooling Hole
Authors: Jeong Yoon Seong , Park Jun Su
Published: February 2020

Backward injection film cooling holes were studied to improve film cooling effectiveness using simple cylindrical holes, and this principle was applied to an actual gas turbine. Although film cooling effectiveness was improved using a backward injection film cooling hole, the backward flow of combustion gas from the backward injection cooling hole was one of the major reasons for cracks in the hot components. To prevent cracks and backward flow in the backward injection film cooling hole, this study changed the inlet compound angle of the backward injection film cooling hole. Numerical analysis using CFX v. 17.0 was performed to calculate the flow characteristics and film cooling effectiveness of backward injection film cooling. Aa a result, the effect of the inlet compound angle of the backward injection film cooling hole was confirmed to prevent the backward flow, which increased upon increasing the inlet compound angle. This study shows that the backward flow and cracks in the backward injection film cooling hole can be prevented simply by changing the inlet compound angle.
Experimental Investigation on Time-Frequency Characteristics of Microseismic Signals in the Damage Evolution Process of Coal and Rock
Authors: Yang Wei , Li Chengwu , Xu Rui , Li Xunchang
Published: February 2020

The deformation and failure of coal and rock materials is the primary cause of many engineering disasters. How to accurately and effectively monitor and forecast the damage evolution process of coal and rock mass, and form a set of prediction methods and prediction indicators is an urgent engineering problems to be solved in the field of rock mechanics and engineering. As a form of energy dissipation in the deformation process of coal and rock, microseismic (MS) can indirectly reflect the damage of coal and rock. In order to analyze the relationship between the damage degree of coal and rock and time-frequency characteristics of MS, the deformation and fracture process of coal and rock materials under different loading modes was tested. The time-frequency characteristics and generation mechanism of MS were analyzed under different loading stages. Meanwhile, the influences of properties of coal and rock materials on MS signals were studied. Results show that there is an evident mode cutoff point between high-frequency and low-frequency MS signals. The properties of coal and rock, such as the development degree of the original fracture, particle size and dense degree have a decisive influence on the amplitude, frequency, energy and other characteristic parameters of MS signals. The change of MS parameters is closely related to material damage, but has no strong relation with the loading rate. The richness of MS signals before the main fracture depends on the homogeneity of materials. With the increase of damage, the energy release rate increases, which can lead to the widening of MS signals spectrum. The stiffness and natural frequency of specimens decreases correspondingly. Meanwhile, the main reason that the dominant frequency of MS detected by sensors installed on the surface of coal and rock materials is mainly low-frequency is friction loss and the resonance effect. In addition, the spectrum and energy evolution of MS can be used as a characterization method of the damage degree of coal and rock materials. Furthermore, the results can provide important reference for prediction and early warning of some rock engineering disasters.
Development of a Bio-Solar House Model for Egyptian Conditions
Authors: Khater El-Sayed , Ashour Taha , Ali Samir , Saad Manar , Todic Jasna , Hollands Jutta , Korjenic Azra
Published: February 2020

The need for heating and cooling in traditional housing is becoming increasingly disadvantageous regarding high energy costs. But what is more concerning is the impact on our environment. The main goal of this paper is studying the prospects of using renewable energy for heating and cooling houses through an integrated bio-solar system in order to solve the energy scarcity problem. For this purpose, a simulation model for a bio-solar house made from different materials (walls made of bricks with straw bales and a roof made of concrete with straw bales) was developed successively in accordance with the energy balance and renewable energies such as biogas and solar energy were applied. This approach enabled an enhancement of the main factors affecting the performance of a building in terms of saving energy. The model was able to predict the energy requirements for heating and cooling of houses, the energy gained by a solar collector and by a biogas digester as well as the energy requirement for heating the biogas digester. Also, the purpose of this paper is to validate this developed simulation model by measuring energy requirements for heating of houses and solar radiation for solar collectors. The model is a simulation model for the bio-solar house with its three main parts—a straw house, a solar collector and a biogas digester. This paper demonstrates the values of the performed measurements and compares them to the theoretical, predicted values. The comparison indicates that the predicted energy requirements for the heating of buildings were a close approximation to the measured values. Another relevant deduction of the validation was the fact that the solar collector delivered the highest heat gain on 21st of June.
Benchmarking a Sustainable Energy Engineering Undergraduate Degree against Curriculum Frameworks and Pedagogy Standards from Industry and Academia
Authors: Durrans Bryn , Whale Jonathan , Calais Martina
Published: February 2020

There is an urgent need for educational institutions to produce graduates with appropriate skills to meet the growing global demand for professionals in the sustainable energy industry. For universities to stay at the forefront of meeting this global demand from industry, universities need to ensure their curricula and pedagogies stay relevant. The use of benchmarking is a key means of achieving this and ensuring any gap between university curricula and the practical needs of industry is minimized. The aim of this paper is to present an approach to benchmarking a sustainable energy engineering undergraduate degree with respect to curriculum frameworks recommended by industry and pedagogy standards required and recommended by academia and education research. The method uses the Murdoch University renewable energy engineering degree major as a case study. The results show that the learning outcomes of the renewable energy engineering units, in general, align well with the recommended learning outcomes for a complete sustainable energy degree, as prescribed by the Australian Government Office for Learning and Teaching. In addition, assessment task and marking criteria for the capstone unit of the major were at Australian Universities’ standard. A similar approach to benchmarking can be adopted by developers of new or existing sustainable energy engineering degrees in order to align with curriculum frameworks and pedagogy standards required by industry and academic peers.
Thermal Diffusion in Fibrous Aerogel Blankets
Authors: Lakatos Ákos , Trník Anton
Published: February 2020

Nowadays, the usage of thermal insulation materials is widespread not only in the building sector but also in the vehicle industry. The application of fibrous or loose-fill insulation materials like glass wool or mineral wool as well as aerogel is well known. Aerogel-based materials are among the best solid materials for thermal insulation available today; they are prepared through a sol–gel process. For building walls, the glass-fiber-enhanced types are the frequently used ones. They are prepared by adding the liquid–solid solution to the fibrous batting, which is called a sol–gel process. In the present paper, the changes in the most important building physical properties of aerogel blankets after thermal annealing are presented. The samples were subjected to isochronal heat treatments from 70 to 210 °C for 24 h. The changes in the thermal conductivity were followed by Holometrix Lambda heat flow meter, and differential scanning calorimetry results were also recorded. From the measured values, together with the densities, the most important thermal properties were calculated, such as thermal resistance, diffusivity, effusivity (heat absorption), and thermal inertia. In this paper, we attempt to clarify the role played by thermal annealing in the transient thermal properties of aerogel materials. Besides presenting the measurement results, a theoretical background is given. The investigations of not only the steady-state but also the transient thermal parameters of the materials are momentous at the design stage.
The Performance of the BTB-VSC for Active Power Balancing, Reactive Power Compensation and Current Harmonic Filtering in the Interconnected Systems
Authors: Alcalá Janeth , Cárdenas Víctor , Aganza Alejandro , Gudiño-Lau Jorge , Charre Saida
Published: February 2020

Nowadays, the use of power converters to control active and reactive power in AC–AC grid-connected systems has increased. With respect to indirect AC–AC converters, the tendency is to enable the back-to-back (BTB) voltage source converter (VSC) as an active power filter (APF) to compensate current harmonics. Most of the reported works use the BTB-VSC as an auxiliary topology that, combined with other topologies, is capable of active power regulation, reactive power compensation and current harmonic filtering. With the analysis presented in this work, the framework of the dynamics associated with the control loops is established and it is demonstrated that BTB-VSC can perform the three tasks for which, in the reviewed literature, at least two different topologies are reported. The proposed analysis works to support the performance criteria of the BTB-VSC when it executes the three control actions simultaneously and the total current harmonic distortion is reduced from 27.21% to 6.16% with the selected control strategy.
A Layered Bidirectional Active Equalization Method for Retired Power Lithium-Ion Batteries for Energy Storage Applications
Authors: Yang Yang , Zhu Wenchao , Xie Changjun , Shi Ying , Liu Furong , Li Weibo , Tang Zebo
Published: February 2020

The power from lithium-ion batteries can be retired from electric vehicles (EVs) and can be used for energy storage applications when the residual capacity is up to 70% of their initial capacity. The retired batteries have characteristics of serious inconsistency. In order to solve this problem, a layered bidirectional active equalization topology is proposed in this paper. Specifically, a bridge-type equalization topology based on an inductor is adopted in the bottom layer, and the distributed equalization topological structure based on the bidirectional BUCK-BOOST circuit is adopted in the top layer. State of charge (SOC) is used as the equalization target variable, and the bottom layer equalization algorithm based on a “partition” idea and route optimization is proposed. The static equalization experiments and charge equalization experiments are performed by the 12 retired batteries selected from an electric sanitation vehicle. The results show that the proposed equalization method can reduce the SOC difference between retired batteries and can effectively improve the inconsistency of the retired battery pack with a faster equalization speed.
Practical Considerations for Designing Reliable DC/DC Converters, Applied to a BIPV Case
Authors: Ravyts Simon , Van De Sande Wieland , Vecchia Mauricio Dalla , Broeck Giel Van den , Duraij Martijn , Martinez Wilmar , Daenen Michael , Driesen Johan
Published: February 2020

State-of-the-art reliability assessment typically starts from a given circuit topology, for which the most suitable components are selected using a Physics of Failure analysis. This paper, however, addresses the topology selection stage, which is the foundation in designing reliable converters. Based on an overview of the reliability performance of different components, a methodology is presented as a guideline for comparing topologies to one another. The focus is directed at practical consequences associated with certain designs. Furthermore, an overview is provided on the latest developments in component technology reliability improvements. The developed methodology is mainly intended for demanding applications, where long lifetimes are required or elevated ambient temperatures are present. After the topology selection, an overview of possibilities is given that allows further increasing converter availability. Finally, the methodology is applied to the design of module level converters for building integrated photovoltaics, which is a high temperature application with a high desired lifetime. A prototype and experimental results are presented.
Optimization and Extended Applicability of Simplified Slug Flow Model for Liquid-Gas Flow in Horizontal and Near Horizontal Pipes
Authors: Kim Tea-Woo , Woo Nam-Sub , Han Sang-Mok , Kim Young-Ju
Published: February 2020

The accurate prediction of pressure loss for two-phase slug flow in pipes with a simple and powerful methodology has been desired. The calculation of pressure loss has generally been performed by complicated mechanistic models, most of which require the iteration of many variables. The objective of this study is to optimize the previously proposed simplified slug flow model for horizontal pipes, extending the applicability to turbulent flow conditions, i.e., high mixture Reynolds number and near horizontal pipes. The velocity field previously measured by particle image velocimetry further supports the suggested slug flow model which neglects the pressure loss in the liquid film region. A suitable prediction of slug characteristics such as slug liquid holdup and translational velocity (or flow coefficient) is required to advance the accuracy of calculated pressure loss. Therefore, the proper correlations of slug liquid holdup, flow coefficient, and friction factor are identified and utilized to calculate the pressure gradient for horizontal and near horizontal pipes. The optimized model presents a fair agreement with 2191 existing experimental data (0.001 ≤ μL ≤ 0.995 Pa∙s, 7 ≤ ReM ≤ 227,007 and −9 ≤ θ ≤ 9), showing −3% and 0.991 as values of the average relative error and the coefficient of determination, respectively.
Exergy as Criteria for Efficient Energy Systems—A Spatially Resolved Comparison of the Current Exergy Consumption, the Current Useful Exergy Demand and Renewable Exergy Potential
Authors: Sejkora Christoph , Kühberger Lisa , Radner Fabian , Trattner Alexander , Kienberger Thomas
Published: February 2020

The energy transition from fossil-based energy sources to renewable energy sources of an industrialized country is a big challenge and needs major systemic changes to the energy supply. Such changes require a holistic view of the energy system, which includes both renewable potentials and consumption. Thereby exergy, which describes the quality of energy, must also be considered. In this work, the determination and analysis of such a holistic view of a country are presented, using Austria as an example. The methodology enables the calculation of the spatially resolved current exergy consumption, the spatially resolved current useful exergy demand and the spatially resolved technical potential of renewable energy sources (RES). Top-down and bottom-up approaches are combined in order to increase accuracy. We found that, currently, Austria cannot self-supply with exergy using only RES. Therefore, Austria should increase the efficiency of its energy system, since the overall exergy efficiency is only at 34%. The spatially resolved analysis shows that in Austria the exergy potential of RES is rather evenly distributed. In contrast, the exergy consumption is concentrated in urban and industrial areas. Therefore, the future energy infrastructure must compensate for these spatial discrepancies.
An Investigation of an Adaptive Neuro-Fuzzy Inference System to Predict the Relationship among Energy Intensity, Globalization, and Financial Development in Major ASEAN Economies
Authors: Hussain Hafezali , Slusarczyk Beata , Kamarudin Fakarudin , Thaker Hassanudin , Szczepańska-Woszczyna Katarzyna
Published: February 2020

The enhancement of the financial sector significantly drives a nation’s economy and thereby increase energy intensity. Considering this situation, the current study aims to examine the link between globalization and financial advancements with the energy intensity of the top 5 ASEAN (Association of Southeast Asian Nations) economies. The development structure of the ASEAN region is considered significant for having stable growth. The authors used the annual data from 1990 to 2018 for five of the largest ASEAN economies: Singapore, Malaysia, Thailand, Indonesia, and the Philippines. The present study used novel methodology, the Adaptive Neuro-Fuzzy Inference System (ANFIS), to examine the nonlinear behaviour among globalization, financial development, and energy intensity in the top 5 ASEAN countries. The study results using ANFIS confirm that globalization and financial development are positively correlated and have a significant impact on the energy intensity level in the top ASEAN countries. The results further suggest that globalization and financial development increase the level of energy intensity more in the countries that are developed relative to their peers in the top ASEAN countries. Moreover, the outcomes of ANFIS also suggest that those countries, which are more globalized and financially developed, have more potential to increase the level of energy intensity. Therefore, the government needs to focus more on projects that involve renewable energy and are environmentally friendly.
Voltage Stability Margin Index Estimation Using a Hybrid Kernel Extreme Learning Machine Approach
Authors: Villa-Acevedo Walter M. , López-Lezama Jesús M. , Colomé Delia G.
Published: February 2020

This paper presents a novel approach for Voltage Stability Margin (VSM) estimation that combines a Kernel Extreme Learning Machine (KELM) with a Mean-Variance Mapping Optimization (MVMO) algorithm. Since the performance of a KELM depends on a proper parameter selection, the MVMO is used to optimize such task. In the proposed MVMO-KELM model the inputs and output are the magnitudes of voltage phasors and the VSM index, respectively. A Monte Carlo simulation was implemented to build a data base for the training and validation of the model. The data base considers different operative scenarios for three type of customers (residential commercial and industrial) as well as N-1 contingencies. The proposed MVMO-KELM model was validated with the IEEE 39 bus power system comparing its performance with a support vector machine (SVM) and an Artificial Neural Network (ANN) approach. Results evidenced a better performance of the proposed MVMO-KELM model when compared to such techniques. Furthermore, the higher robustness of the MVMO-KELM was also evidenced when considering noise in the input data.
Optimal Price Based Demand Response of HVAC Systems in Commercial Buildings Considering Peak Load Reduction
Authors: Yoon Ah-Yun , Kang Hyun-Koo , Moon Seung-II
Published: February 2020

Electric utility companies (EUCs) play an intermediary role of retailers between wholesale market and end-users, maximizing their profits. Retail pricing can be well deployed with the support of EUCs to promote demand response (DR) programs for heating, ventilating, and air-conditioning (HVAC) systems in commercial buildings. This paper proposes a pricing strategy to help EUCs and building operators achieve an optimal DR of price-elastic HVAC systems, considering peak load reduction. The proposed strategy is implemented by adopting a bi-level decision model. The nonlinear thermal response of an experimental building room is modeled using piecewise linear equations, which helps convert the bi-level model to the single-level model. The pricing strategy is implemented considering a time-of-use (TOU) pricing scheme, leading to low price volatility. Case studies are conducted for two types of load curves and the results demonstrate that the proposed strategy helps EUC promote the price-based DR of the commercial buildings for conventional load curves. However, EUC cannot reduce the peak load on duck curve caused by the large introduction of photovoltaic generators, even with price-sensitive HVAC systems in commercial building. This will be addressed in future studies by inducing DR participation of HVAC systems in residential buildings.
Full-Bridge Active-Clamp Forward-Flyback Converter with an Integrated Transformer for High-Performance and Low Cost Low-Voltage DC Converter of Vehicle Applications
Authors: Baek Jaeil , Youn Han-Shin
Published: February 2020

This paper presents a full-bridge active-clamp forward-flyback (FBACFF) converter with an integrated transformer sharing a single primary winding. Compared to the conventional active-clamp-forward (ACF) converter, the proposed converter has low voltage stress on the primary switches due to its full-bridge active-clamp structure, which can leverage high performance Silicon- metal–oxide–semiconductor field-effect transistor (Si-MOSFET) of low voltage rating and low channel resistance. Integrating forward and flyback operations allows the proposed converter to have much lower primary root mean square (RMS) current than the conventional phase-shifted-full-bridge (PSFB) converter, while covering wide input/output voltage range with duty ratio over 0.5. The proposed integrated transformer reduces the transformer conduction loss and simplify the secondary structure of the proposed converter. As a result, the proposed converter has several advantages: (1) high heavy load efficiency, (2) wide input voltage range operation, (3) high power density with the integrated transformer, and (4) low cost. The proposed converter is a very promising candidate for applications with wide input voltage range and high power, such as the low-voltage DC (LDC) converter for eco-friendly vehicles.
Wind Farm Yaw Optimization via Random Search Algorithm
Authors: Kuo Jim , Pan Kevin , Li Ni , Shen He
Published: February 2020

One direction in optimizing wind farm production is reducing wake interactions from upstream turbines. This can be done by optimizing turbine layout as well as optimizing turbine yaw and pitch angles. In particular, wake steering by optimizing yaw angles of wind turbines in farms has received significant attention in recent years. One of the challenges in yaw optimization is developing fast optimization algorithms which can find good solutions in real-time. In this work, we developed a random search algorithm to optimize yaw angles. Optimization was performed on a layout of 39 turbines in a 2 km by 2 km domain. Algorithm specific parameters were tuned for highest solution quality and lowest computational cost. Testing showed that this algorithm can find near-optimal (<1% of best known solutions) solutions consistently over multiple runs, and that quality solutions can be found under 200 iterations. Empirical results show that as wind farm density increases, the potential for yaw optimization increases significantly, and that quality solutions are likely to be plentiful and not unique.
Time Domain Particle Swarm Optimization of PI Controllers for Bidirectional VSC HVDC Light System
Authors: Faisal Syed F , Beig Abdul R , Thomas Sunil
Published: February 2020

This paper proposes a novel technique to tune the PI controllers of a bidirectional HVDC light system by embedding particle swarm optimization directly in the Simulink model in the design procedure. The HVDC light system comprises of a rectifier station, a DC link, and an inverter station. Each converter station requires four PI controllers to be tuned in the decoupled d-q vector control scheme, and with the bidirectional HVDC system, the required PI controllers are doubled. Tuning these many controllers using conventional methods is a challenging task, especially if the parameters of the converter stations are different. A novel approach to tune the PI controllers for a bidirectional HVDC system using the time-domain performance indices is presented in this paper. The time-domain performance indices are optimized using the particle swarm optimization (PSO) algorithm. The results of the proposed tuning method show that the proposed method not only gives superior results but also is less cumbersome to tune compared to conventional methods like modulus optimum (MO).
Strategic-Agent Equilibria in the Operation of Natural Gas and Power Markets
Authors: Chen Sheng , Conejo Antonio J.
Published: February 2020

We consider strategic gas/power producers and strategic gas/power consumers operating in both gas and power markets. We build a flexible multi-period complementarity model to characterize day-ahead equilibria in those markets. This model is an equilibrium program with equilibrium constraints that characterizes the market behavior of all market agents. Using a realistic case study, we analyze equilibria under perfect and oligopolistic competition. We also analyze equilibria under different levels of information disclosure regarding market outcomes. We study as well equilibria under different ownership schemes: no hybrid agent, some hybrid agents, and only hybrid agents. Finally, we derive policy recommendations for the regulators of both the gas and the power markets.
Indoor Temperature Improvement and Energy-Saving Renovations in Rural Houses of China’s Cold Region—A Case Study of Shandong Province
Authors: Cui Yanqiu , Sun Ninghan , Cai Hongbin , Li Simeng
Published: February 2020

With the continuous implementation of a plan for reconstruction of “Beautiful Countryside” in China, the rural environment and appearance of rural houses have been significantly improved. However, those houses in cold areas of China have great trouble with indoor temperature and heating-related energy consumption. After investigating the current situation of the layout, building envelope, indoor temperature, and energy consumption of the rural houses renovated by the plan of “Beautiful Countryside” in Shandong Province, this paper puts forward the improvement measures of raising indoor temperature and reducing energy consumption. On this basis, a typical rural house was selected, and DesignBuilder was utilized to simulate the effects before and after the application of different renovation measures for this house. The results show that the main way to raise indoor temperature and reduce energy consumption is to improve the thermal insulation performance of the building envelope, including renovation of the roof, exterior walls, doors and windows, and attached sunspace. In addition, combined with the achievements of “Beautiful Countryside” reconstruction, this paper shall propose specific renovation practices which are suitable for different rural houses. Based on the level of economic development in rural areas, it also puts forward some feasible renovation paths for different rural areas, and further provides references for other areas to carry out relevant work in the future.
Experimental Investigation on the High-frequency Pressure Oscillation Characteristics of a Combustion Process in a DI Diesel Engine
Authors: Zheng Xu , Zhou Nan , Zhou Quan , Qiu Yi , Liu Ruijun , Hao Zhiyong
Published: February 2020

It is difficult to decompose the in-cylinder pressure of combustion of the direct injection (DI) diesel engine, a transient process associated with complicated oscillation components, because of its steep property. An adaptive cyclic average method based on time varying filter based empirical mode decomposition (TVF-EMD) is proposed to decompose the in-cylinder pressure signal, and the cyclic number is determined adaptively with protruding ratio of high-frequency oscillation. The proposed method is used to compare with the ensemble empirical mode decomposition and original TVF-EMD. The results indicate that the proposed method can overcome the drawbacks of these methods and extract high-frequency oscillations accurately and effectively. Three evaluation indexes, center frequency, normalized energy, and average center frequency are defined to analyze the frequency and energy characteristics of high-frequency oscillation quantitatively. The influence of speed, load, rail pressure, main injection timing, pilot injection interval, and pilot injection quantity are investigated systematically. The energy of high-frequency oscillation reaches the peak at medium-high speed, and increase with engine load and rail pressure. However, the relationship of high-frequency oscillation with fuel injection parameters are non-monotonic.
Effects of Jet Induced by String-type Plasma Actuator on Flow Around Three-Dimensional Bluff Body and Drag Force
Authors: Matsubara Takatoshi , Shima Yoshiki , Aono Hikaru , Ishikawa Hitoshi , Segawa Takehiko
Published: February 2020

An experimental investigation of active flow control on a three-dimensional (3D) curved surface bluff body was conducted by using a string-type plasma actuator. The 3D bluff body model tested in this study was composed of a quarter sphere and a half cylinder, and the Reynolds number based on the diameter of half cylinder was set at 1.3 × 104. The modulation drive was adopted for flow control, and the control effects of variations in dimensionless burst frequency (fm+) normalized by the width of the model and freestream velocity were studied. Velocity distributions analyzed by particle image velocimetry showed that the recirculation region behind the model shrank due to the flow control. The static pressure distributions on the back surface of the model tended to decrease under any fm+ set in this study, especially in the ranges of 0.40 ≤ fm+ ≤ 0.64. The drag coefficient reached its maximum value under the similar ranges of fm+. Although the aerodynamic wake sharpening was observed due to the flow control, the entrainment of separated flow into the back surface of the model was enhanced. This scenario of wake manipulation was considered to be responsible for increasing drag acting on the model.
A Modified High Voltage Gain Quasi-Impedance Source Coupled Inductor Multilevel Inverter for Photovoltaic Application
Authors: Periyanayagam Madasamy , Kumar V Suresh , Chokkalingam Bharatiraja , Padmanaban Sanjeevikumar , Mihet-Popa Lucian , Adedayo Yusuff
Published: February 2020

The quasi-impedance source inverters/quasi-Z source inverters (Q-ZSIs) have shown improvement to overwhelmed shortcomings of regular voltage-source inverters (VSIs) and current-source inverters (CSIs) in terms of efficiency and buck-boost type operations. The Q-ZSIs encapsulated several significant merits against conventional ZSIs, i.e., realized buck/boost, inversion and power conditioning in a single power stage with improved reliability. The conventional inverters have two major problems; voltage harmonics and boosting capability, which make it impossible to prefer for renewable generation and general-purpose applications such as drive acceleration. This work has proposed a Q-ZSI with five-level six switches coupled inverter. The proposed Q-ZSI has the merits of operation, reduced passive components, higher voltage boosting capability and high efficiency. The modified space vector pulse width modulation (PWM) developed to achieve the desired control on the impedance network and inverter switching states. The proposed PWM integrates the boosting and regular inverter switching state within one sampling period. The PWM has merits such as reduction of coupled inductor size, total harmonic reduction with enhancing of the fundamental voltage profile. In comparison with other multilevel inverters (MLI), it utilizes only half of the power switch and a lower modulation index to attain higher voltage gain. The proposed inverter dealt with photovoltaic (PV) system for the stand-alone load. The proposed boost inverter topology, operating performance and control algorithm is theoretically investigated and validated through MATLAB/Simulink software and experimental upshots. The proposed topology is an attractive solution for the stand-alone and grid-connected system.
Practical and Ethical Considerations for Schools Using Social Media to Promote Physical Literacy in Youth
Authors: Bopp Trevor , Stellefson Michael
Published: February 2020

The rapid development of social media has led to its increased use by children and adolescents for health and well-being purposes. Accordingly, social interactions resulting from social media use can be further integrated into physical and health education pedagogy. Given the relationship between increased physical literacy and positive health outcomes, best practices and lessons learned from social media use in the healthcare industry should be adopted by health and physical educators practicing in schools. Thus, the purpose of this paper is to comment on several practical and ethical challenges and opportunities associated with using social media to improve physical literacy among youth. Specifically, two of the most prominent issues are discussed in depth: (1) integration of social media in physical education settings that educate children and adolescents about the biopsychosocial effects of physical activity, and (2) use of wearable technologies among youth to accrue experiences that enhance physical literacy competencies. In our opinion, health and physical educators who utilize the ALL-ENGAGE Playbook described in this commentary will successfully reach, engage, and impact students with popular social media that adequately promotes physical literacy, including through experiential use of wearable technologies.
Understanding the Resilience of Different Farming Strategies in Coping with Geo-Hazards: A Case Study in Chongqing, China
Authors: Peng Li , Tan Jing , Deng Wei , Liu Ying
Published: February 2020

Adjusting farming strategies are adaptive behaviors to cope with hazard risks. However, few studies have studied rural and remote mountain areas in China with little known about “farmers’ adaptation under the impact of geo-hazards”. Unlike traditional farmers’ behavioral adaptation studies, in this study, we focused on the resilience of farmers’ behavioral mechanisms to address local hazards such as geo-hazards. Our data were acquired through questionnaire responses (N = 516) in mountainous hazard-prone areas in Chongqing, China. The binary logit model and multinomial logit model were used to investigate the obstacles to different farming strategies and the determinants of adaptation strategy choice, focusing on the effects of disaster experience and social support on the adaptation strategy resilience. The results show that the most common adaptation strategy was adjusting crop varieties, and the largest adaptation obstacle was a lack of funds. Additionally, the age of the smallholder, farming acreage, agricultural income, social support, and disaster experience significantly increased the possibility of farmers adjusting their agricultural production. Of these, smallholder agricultural income, state disaster subsidy, the presence of disaster prevention construction, the smallholder’s property, and the presence of disaster-caused crop loss experience were the most important factors affecting a farmer’s adaptation strategy. In particular, farmers were more sensitive to disaster-caused property loss than to disaster-caused crop loss. This study can provide implications for the government to formulate disaster mitigation measures and for farming strategies at the smallholder level.
Horticultural Activity: Its Contribution to Stress Recovery and Wellbeing for Children
Authors: Shao Yuhan , Elsadek Mohamed , Liu Binyi
Published: February 2020

In recent years, children’s use of mobile phones has grown rapidly, which might lead to an increase in mental stress and negatively affect their health. Despite increasing evidence that horticultural activity can provide significant health benefits, few scientific evidence-based studies are currently available regarding these benefits to children’s health and wellbeing in schools. Therefore, this study aims to determine the potential benefits of horticultural activity for children from both psychological and physiological perspectives. Twenty-six elementary school students (mean age, 8.12 ± 0.21 years) were asked to perform a plant-related task and a mobile game task for 5 min. During both tasks, physiological sensors were used to measure the participants’ heart rate variability, skin conductance, and skin temperature. Additionally, the participants’ emotional responses were assessed using semantic differential and State–Trait Anxiety Inventory tests immediately after each task. Results revealed that, compared with the mobile game task, participants’ health statuses were positively correlated with the horticultural task, including a considerable decrease in skin conductance and sympathetic nervous activity, together with a marginal increase in parasympathetic nervous activity. Such responses suggested that horticultural activity increased relaxation and decreased feelings of stress. Furthermore, the horticultural activity was associated with a substantial increment in comfort, naturalness, relaxation, and cheerfulness feelings, as well as a significant reduction in depression and a reduction in total anxiety levels. Given these positive benefits, horticultural activity may provide a great contribution to children’s healthy life at school, prompt psychological relaxation and minimize mental stress relative to smartphone games.