bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of Liquid-based Cytology and Cell Block Combined Technique for an Accurate Diagnosis of Oral Diffuse Large B Cell Lymphoma: A Case Report
Authors: Yoshino Aya , Ishida Shintaro , Nakamura Shinsuke , Kita Ryosuke , Seto Mika , Matsumoto Shinji , Takeshita Morishige , Kondo Seiji
Published: October 2020

Primary oral diffuse large B cell lymphoma (DLBCL) is rare and the differential diagnosis is difficult due to its low incidence and nonspecific symptoms, which resemble those of common oral diseases in the initial clinical setting. We aimed to discuss the value of making an accurate diagnosis using liquid-based cytology (LBC) and cell block (CB) for not only the morphological interpretation but also cytohistological assessment of oral DLBCL. LBC and CBs made from oral brushing materials were prepared on the first medical examination and a morphological analysis and immunohistochemical analysis of specific biomarkers were performed. The analysis of LBC preparations showed the presence of large-size lymphocytes with large irregular nuclei and prominent nucleoli, suggesting the existence of large B-cell lymphoma. A more detailed histological subclassification of the CB specimen was performed, which was classified as the activated B-cell (ABC) phenotype of DLBCL, by confirming the immunohistochemical expression of CD10−/ B-cell lymphoma 6 (BCL6)+/ multiple myeloma oncogene 1(MUM1)+, which is a significant risk factor in DLBCL. Our findings suggest that the combination of LBC and CB is a useful and informative tool for making an accurate molecular diagnosis of oral DLBCL in cases in which lymphomas are clinically suspected.
Management of Young Athletes with Asymptomatic Preexcitation—A Review of the Literature
Authors: Książczyk Tomasz M. , Pietrzak Radosław , Werner Bożena
Published: October 2020

Introduction: The management of young athletes with asymptomatic preexcitation remains a challenge, regardless of the progress we have made in understanding the basis of condition and developing catheter ablation procedures. The risk of sudden death, however small, yet definite, being the first symptom is determining our approach. The aim of the study was to establish the current state of knowledge regarding the management of young athletes diagnosed with asymptomatic preexcitation, by conducting a literature review. Material and methods: A comprehensive literature review was completed in accordance to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The search was limited to English language publications using the following search terms: “asymptomatic” or “incidental” and “pre-excitation” or “Wolff–Parkinson–White” or “delta wave” and “athlete” or “sport”. The search was supplemented by hand review of the bibliographies of previous relevant systematic reviews. Results: The search resulted in 85 of abstracts, and the manual search of the bibliographies resulted in 24 additional papers. After careful analysis 10 publications were included in the review. In all but one of the presented papers, the authors used non-invasive methods and then either trans-esophageal or invasive EPS as a way to risk stratify asymptomatic patients. Evidence of rapid conduction through the accessory pathway was considered high risk and prompted sport disqualification. In the analysed reports there were combined: 142 episodes of the life-threatening events (LTE)/sudden death (SCD), of which 56 were reported to occur at rest, 61 during activity and no data were available for 25. Conclusions: athletic activity may impose an increased risk of life-threatening arrhythmias in patients with asymptomatic preexcitation; hence, a separate approach could be considered, especially in patients willing to engage in high-intensity, endurance and competitive sports.
Deep-Learning-Based Power Generation Forecasting of Thermal Energy Conversion
Authors: Lu Yu-Sin , Lai Kai-Yuan
Published: October 2020

ORC is a heat to power solution to convert low-grade thermal energy into electricity with relative low cost and adequate efficiency. The working of ORC relies on the liquid–vapor phase changes of certain organic fluid under different temperature and pressure. ORC is a well-established technology utilized in industry to recover industrial waste heat to electricity. However, the frequently varied temperature, pressure, and flow may raise difficulty to maintain a steady power generation from ORC. It is important to develop an effective prediction methodology for power generation in a stable grid system. This study proposes a methodology based on deep learning neural network to the predict power generation from ORC by 12 h in advance. The deep learning neural network is derived from long short-term memory network (LSTM), a type of recurrent neural network (RNN). A case study was conducted through analysis of ORC data from steel company. Different time series methodology including ARIMA and MLP were compared with LSTM in this study and shows the error rate decreased by 24% from LSTM. The proposed methodology can be used to effectively optimize the system warning threshold configuration for the early detection of abnormalities in power generators and a novel approach for early diagnosis in conventional industries.
Application of Positional Entropy to Fast Shannon Entropy Estimation for Samples of Digital Signals
Authors: Cholewa Marcin , Płaczek Bartłomiej
Published: October 2020

This paper introduces a new method of estimating Shannon entropy. The proposed method can be successfully used for large data samples and enables fast computations to rank the data samples according to their Shannon entropy. Original definitions of positional entropy and integer entropy are discussed in details to explain the theoretical concepts that underpin the proposed approach. Relations between positional entropy, integer entropy and Shannon entropy were demonstrated through computational experiments. The usefulness of the introduced method was experimentally verified for various data samples of different type and size. The experimental results clearly show that the proposed approach can be successfully used for fast entropy estimation. The analysis was also focused on quality of the entropy estimation. Several possible implementations of the proposed method were discussed. The presented algorithms were compared with the existing solutions. It was demonstrated that the algorithms presented in this paper estimate the Shannon entropy faster and more accurately than the state-of-the-art algorithms.
Digital Quantum Simulation of Nonadiabatic Geometric Gates via Shortcuts to Adiabaticity
Authors: Wang Yapeng , Ding Yongcheng , Wang Jianan , Chen Xi
Published: October 2020

Geometric phases are used to construct quantum gates since it naturally resists local noises, acting as the modularized units of geometric quantum computing. Meanwhile, fast nonadiabatic geometric gates are required for reducing the information loss induced by decoherence. Here, we propose a digital simulation of nonadiabatic geometric quantum gates in terms of shortcuts to adiabaticity (STA). More specifically, we combine the invariant-based inverse engineering with optimal control theory for designing the fast and robust Abelian geometric gates against systematic error, in the context of two-level qubit systems. We exemplify X and T gates, in which the fidelities and robustness are evaluated by simulations in ideal quantum circuits. Our results can also be extended to constructing two-qubit gates, for example, a controlled-PHASE gate, which shares the equivalent effective Hamiltonian with rotation around the Z-axis of a single qubit. These STA-inspired nonadiabatic geometric gates can realize quantum error correction physically, leading to fault-tolerant quantum computing in the Noisy Intermediate-Scale Quantum (NISQ) era.
On PTAs and Bilateral Trade: Is GVC Trade Sensitive to the Breadth of Trade Policy Cooperation?
Authors: Delera Michele , Foster-McGregor Neil
Published: October 2020

We study the relationship between the scope of trade policy cooperation and bilateral trade flows with a particular focus on global value chain (GVC) trade using data on the core and non-core provisions included in preferential trade agreements (PTAs). We find that broader PTAs have a larger impact on trade flows involving intermediates relative to flows involving all products, suggesting that GVC trade is particularly sensitive to the scope of trade policy cooperation. We also investigate different dimensions of heterogeneity in PTAs. We find that core provisions tend to drive the effect of PTAs on the level of GVC trade and that PTAs are particularly effective in raising the level of GVC trade between developing economies. We explore these issues using a sample of 189 countries over the period 1990–2015, with data obtained from the latest release of the EORA multi-regional input–output tables and UN-COMTRADE data.
Asynchronous Floating-Point Adders and Communication Protocols: A Survey
Authors: Srivastava Pallavi , Chung Edwin , Ozana Stepan
Published: October 2020

Addition is the key operation in digital systems, and floating-point adder (FPA) is frequently used for real number addition because floating-point representation provides a large dynamic range. Most of the existing FPA designs are synchronous and their activities are coordinated by clock signal(s). However, technology scaling has imposed several challenges like clock skew, clock distribution, etc., on synchronous design due to presence of clock signal(s). Asynchronous design is an alternate approach to eliminate these challenges imposed by the clock, as it replaces the global clock with handshaking signals and utilizes a communication protocol to indicate the completion of activities. Bundled data and dual-rail coding are the most common communication protocols used in asynchronous design. All existing asynchronous floating-point adder (AFPA) designs utilize dual-rail coding for completion detection, as it allows the circuit to acknowledge as soon as the computation is done; while bundled data and synchronous designs utilizing single-rail encoding will have to wait for the worst-case delay irrespective of the actual completion time. This paper reviews all the existing AFPA designs and examines the effects of the selected communication protocol on its performance. It also discusses the probable outcome of AFPA designed using protocols other than dual-rail coding.
Intra-Network Interference Robustness: An Empirical Evaluation of IEEE 802.15.4-2015 SUN-OFDM
Authors: Elsas Robbe , Hoebeke Jeroen , Van Leemput Dries , Shahid Adnan , Daneels Glenn , Famaey Jeroen , De Poorter Eli
Published: October 2020

While IEEE 802.15.4 and its Time Slotted Channel Hopping (TSCH) medium access mode were developed as a wireless substitute for reliable process monitoring in industrial environments, most deployments use a single/static physical layer (PHY) configuration. Instead of limiting all links to the throughput and reliability of a single Modulation and Coding Scheme (MCS), you can dynamically re-configure the PHY of link endpoints according to the context. However, such modulation diversity causes links to coincide in time/frequency space, resulting in poor reliability if left unchecked. Nonetheless, to some level, intentional spatial overlap improves resource efficiency while partially preserving the benefits of modulation diversity. Hence, we measured the mutual interference robustness of certain Smart Utility Network (SUN) Orthogonal Frequency Division Multiplexing (OFDM) configurations, as a first step towards combining spatial re-use and modulation diversity. This paper discusses the packet reception performance of those PHY configurations in terms of Signal to Interference Ratio (SIR) and time-overlap percentage between interference and targeted parts of useful transmissions. In summary, we found SUN-OFDM O3 MCS1 and O4 MCS2 performed best. Consequently, one should consider them when developing TSCH scheduling mechanisms in the search for resource efficient ubiquitous connectivity through modulation diversity and spatial re-use.
Dynamic Analysis of Shearer Traction Unit Considering the Longitudinal Swing
Authors: Ma Dejian , Zhang Xin , Wan Lirong , Zeng Qingliang , Ge Hongen
Published: October 2020

Shearer traction failure occurs frequently, which seriously restricts the safe and efficient mining of coal. However, the influence of the shearer’s posture on traction has not been fully considered in the existing research. To improve traction reliability: the dynamic model of the traction unit is established considering longitudinal swing; the walking characteristics of the shearer and the dynamics of the traction unit are analyzed; and the influences of traction velocity, drum load cutting arm angle, and depression angle are discussed. The results show that the longitudinal swing is reciprocating and the positive swing is more serious. With the increase of the traction velocity, the walking stability of the shearer decreases while the contact force increases, especially the support slipper. The longitudinal swing increases with the increase of lateral load, but the supporting force of the support slipper decreases with the increase of cutting load. The forces of the walking wheel and the support slipper show an increasing trend with the increase of cutting arm angle. When the depression angle is 5–10°, the load distribution of the contact components of the traction unit is more balanced. The results provide a reference for the structure optimization of the shearer and the layout of coalface.
Image Characteristic Extraction of Ice-Covered Outdoor Insulator for Monitoring Icing Degree
Authors: Liu Yong , Li Qiran , Farzaneh Masoud , Du B. X.
Published: October 2020

Serious ice accretion will cause structural problems and ice flashover accidents, which result in outdoor insulator string operating problems in winter conditions. Previous investigations have revealed that the thicker and longer insulators are covered with ice, the icing degree becomes worse and icing accident probability increases. Therefore, an image processing method was proposed to extract the characteristics of the icicle length and Rg (ratio of the air gap length to the insulator length) of ice-covered insulators for monitoring the operation of iced outdoor insulator strings. The tests were conducted at the artificial climate room of CIGELE Laboratories recommended by IEEE Standard 1783/2009. The surface phenomena of the insulator during the ice accretion process were recorded by using a high-speed video camera. In the view of the ice in the background of the picture of fuzzy features and high image noise, a direct equalization algorithm is used to enhance the grayscale iced image contrast. The median filtering method is conducted for reducing image noise and sharpening the image edge. The maximum entropy threshold segmentation algorithm is put forward to extract the insulators and its surface ice from the background. Then, the modified Canny operator edge detection algorithm is selected to trace the boundaries of objects through the extraction of information about attributes of the endpoints of edges. After we obtained the improved Canny edge detection image for both of the ice-covered insulators and non-iced insulators, the icing thickness can be obtained by calculating the difference between the edge of the non-iced insulators image and the edge of the iced insulator image. Besides, in order to identify the icing degree of the insulators more accurately, this paper determines the location of icicles by using the region growth method. After that, the icicle length and Rg can be obtained to monitor the icing degree of the insulator. It will be helpful to improve the ability to judge the accident risk of insulators in power systems.
A Method to Improve Torque Density in a Flux-Switching Permanent Magnet Machine
Authors: Cao Junshuai , Guo Xinhua , Fu Weinong , Wang Rongkun , Liu Yulong , Lin Liaoyuan
Published: October 2020

With the continuous development of machines, various structures emerge endlessly. In this paper, a novel 6-stator-coils/17-rotor-teeth (6/17) E-shaped stator tooth flux switching permanent magnet (FSPM) machine is introduced, which has magnets added in the dummy slots of the stator teeth. This proposed machine is parametrically designed and then compared with the conventional 6/17 E-shaped stator tooth FSPM machine through finite element method (FEM) analysis. Then, combined with the results of FEM, the performance of two machines is evaluated, such as electromagnetic torque, efficiency, back electromotive force (back-EMF). The final results show that this novel 6/17 FSPM machine has greater output torque and smaller torque ripple.
Nearest Neighbors Time Series Forecaster Based on Phase Space Reconstruction for Short-Term Load Forecasting
Authors: Cedeño González Jose R. , Flores Juan J. , Fuerte-Esquivel Claudio R. , Moreno-Alcaide Boris A.
Published: October 2020

Load forecasting provides essential information for engineers and operators of an electric system. Using the forecast information, an electric utility company’s engineers make informed decisions in critical scenarios. The deregulation of energy industries makes load forecasting even more critical. In this article, the work we present, called Nearest Neighbors Load Forecasting (NNLF), was applied to very short-term load forecasting of electricity consumption at the national level in Mexico. The Energy Control National Center (CENACE—Spanish acronym) manages the National Interconnected System, working in a Real-Time Market system. The forecasting methodology we propose provides the information needed to solve the problem known as Economic Dispatch with Security Constraints for Multiple Intervals (MISCED). NNLF produces forecasts with a 15-min horizon to support decisions in the following four electric dispatch intervals. The hyperparameters used by Nearest Neighbors are tuned using Differential Evolution (DE), and the forecaster model inputs are determined using phase-space reconstruction. The developed models also use exogenous variables; we append a timestamp to each input (i.e., delay vector). The article presents a comparison between NNLF and other Machine Learning techniques: Artificial Neural Networks and Support Vector Regressors. NNLF outperformed those other techniques and the forecasting system they currently use.
An Adaptive Protection for Radial AC Microgrid Using IEC 61850 Communication Standard: Algorithm Proposal Using Offline Simulations
Authors: Memon Aushiq Ali , Kauhaniemi Kimmo
Published: October 2020

The IEC 61850 communication standard is getting popular for application in electric power substation automation. This paper focuses on the potential application of the IEC 61850 generic object-oriented substation event (GOOSE) protocol in the AC microgrid for adaptive protection. The focus of the paper is to utilize the existing low-voltage ride through characteristic of distributed generators (DGs) with a reactive power supply during faults and communication between intelligent electronic devices (IEDs) at different locations for adaptive overcurrent protection. The adaptive overcurrent IEDs detect the faults with two different preplanned settings groups: lower settings for the islanded mode and higher settings for the grid-connected mode considering limited fault contributions from the converter-based DGs. Setting groups are changed to lower values quickly using the circuit breaker status signal (XCBR) after loss-of-mains, loss-of-DG or islanding is detected. The methods of fault detection and isolation for two different kinds of communication-based IEDs (adaptive/nonadaptive) are explained for three-phase faults at two different locations. The communication-based IEDs take decisions in a decentralized manner, using information about the circuit breaker status, fault detection and current magnitude comparison signals obtained from other IEDs. However, the developed algorithm can also be implemented with the centralized system. An adaptive overcurrent protection algorithm was evaluated with PSCAD (Power Systems Computer Aided Design) simulations, and results were found to be effective for the considered fault cases.
Energy Performance of the European Union Countries in Terms of Reaching the European Energy Union Objectives
Authors: Vavrek Roman , Chovancová Jana
Published: October 2020

European energy policy, especially the project of the Energy Union, is one of the most rapidly developing areas of the EU, and one through which European institutions are obtaining gradually more extensive power over the performance of the national energy sectors. The paper focuses on an analysis of the energy performance of EU member states (MS) with regard to the priorities of the European Energy Union. For an assessment of the energy performance of EU countries, the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) was chosen, using the Coefficient of Variation method (CV) as an objective method for determining the weights of eight input indicators, including CO2 intensity, electricity and gas price, energy productivity, energy dependence, consumption of renewables and research and development. The analysis for the period from 2008 to 2016 showed significant changes in the input indicators, which directly influenced the results of both methods mentioned above. Long-term differences between the best- and worst-rated countries are seen mainly in CO2 emissions, energy imports and total consumption of renewable energy sources. It is these aspects of comprehensive energy performance and their convergence at the level of EU countries that we believe should be addressed in the near future.
The Impact of Implied Volatility Fluctuations on Vertical Spread Option Strategies: The Case of WTI Crude Oil Market
Authors: Łamasz Bartosz , Iwaszczuk Natalia
Published: October 2020

This paper aims to analyze the impact of implied volatility on the costs, break-even points (BEPs), and the final results of the vertical spread option strategies (vertical spreads). We considered two main groups of vertical spreads: with limited and unlimited profits. The strategy with limited profits was divided into net credit spread and net debit spread. The analysis takes into account West Texas Intermediate (WTI) crude oil options listed on New York Mercantile Exchange (NYMEX) from 17 November 2008 to 15 April 2020. Our findings suggest that the unlimited vertical spreads were executed with profits less frequently than the limited vertical spreads in each of the considered categories of implied volatility. Nonetheless, the advantage of unlimited strategies was observed for substantial oil price movements (above 10%) when the rates of return on these strategies were higher than for limited strategies. With small price movements (lower than 5%), the net credit spread strategies were by far the best choice and generated profits in the widest price ranges in each category of implied volatility. This study bridges the gap between option strategies trading, implied volatility and WTI crude oil market. The obtained results may be a source of information in hedging against oil price fluctuations.
Neutron Activation of Structural Materials of a Dry Storage System for Spent Nuclear Fuel and Implications for Radioactive Waste Management
Authors: Lee Se Geun , Cheong Jae Hak
Published: October 2020

In order to estimate the radiological characteristics of disused dry storage systems for spent nuclear fuel, a stepwise framework to calculate neutron sources (ORIGEN-ARP), incident neutron flux and reaction rate (MCNPX), effective cross-section (hand calculation), and residual activity (ORIGEN-2) was established. Applicability of the framework was demonstrated by comparing the residual activity of a commercialized storage system, HI-STORM 100, listed in the safety analysis report and calculated in this study. For a reference case assuming an impurity-free storage system, the modified effective cross-sections were theoretically interpreted and the need for managing disused components as a radioactive waste for at least four years was demonstrated. Sensitivity analyses showed that the higher burnup induces the higher residual radioactivity, and the impurity 59Co may extend the minimum decay-in-storage period up to 51 years within the reported range of 59Co content in stainless steel. The extended long-term storage over 100 years, however, caused no significant increase in residual radioactivity. Impurity control together with appropriate decay-in-storage was proposed as an effective approach to minimize the secondary radioactive waste arising from disused dry storage systems. The results of this study could be used to optimize the decommissioning and waste management plan regarding interim storage of spent fuel.
Predictive Trajectory Control with Online MTPA Calculation and Minimization of the Inner Torque Ripple for Permanent-Magnet Synchronous Machines
Authors: Decker Simon , Brodatzki Matthias , Bachowsky Benjamin , Schmitz-Rode Benedikt , Liske Andreas , Braun Michael , Hiller Marc
Published: October 2020

This paper presents an extended predictive trajectory control scheme combined with an inner torque ripple minimization considering the current-, flux-linkage-, and voltage-planes of permanent magnet synchronous machines. The extension of a fundamental machine model with flux-linkage harmonics allows the calculation of the inner torque ripple and enables its minimization. For this, the control is divided in two cases: (1) The dynamic operation or large signal behavior which uses the maximal torque gradient for the trajectory strategy during each control period for fastest dynamic operation, and (2) The stationary operation or small signal behavior, utilizing a real time capable polynomial approximation of the rotor position dependent torque hyperbolas (iso-torque curves) of permanent magnet synchronous machines for the ideal torque to current reference values. Since dynamic and steady-state operation is covered, torque to current look-up tables, such as maximum torque per ampere (MTPA)/maximum torque per volt/voltage (MTPV) look-up tables, are not required anymore. The introduced, new control approach is implemented in Matlab/Simulink based on finite element analysis and measured data. Furthermore, test-bench implementations based on measurement data are presented to show the real-time capability and precision.
Development of Changeover Operating Method Based on Performance Prediction of Hybrid Geothermal Heat Pump Systems through Field Test and Numerical Analysis
Authors: Shin Ji-Hyun , Seong Yoon-Bok , Kim Yong-In , Cho Young-Hum
Published: October 2020

The installation and operation of geothermal systems increased due to the expectation of good cooling and heating performance due to stable heat source temperatures. In actual geothermal system operations, heat source temperature rises or falls due to an imbalance of heating and cooling energy usage. Problems of source side temperature result in reduced geothermal system performance. The purpose of this study is to develop hybrid geothermal system operation technology to stabilize temperature and improve system performance by utilizing auxiliary heat source system. The auxiliary heat source system is operated by comparing the performance when operating the geothermal heat pump system alone and the performance when operating the hybrid geothermal heat pump system. The performance of a hybrid geothermal system is determined by the circulating water temperature of the geothermal system and the circulating water temperature of the auxiliary heat source system. Hybrid geothermal heat pump system performance is predicted through numerical analysis and collection of hybrid geothermal system performance data at various temperature ranges through field test. An operating method was developed using the predicted performance as the changeover operating point of the hybrid geothermal heat pump system. When applying the development and operation technology, it handled about 11% more load than the existing geothermal system operation. The addition of an auxiliary heat source increases the initial investment cost compared to the existing geothermal system, but decreases energy consumption, confirming that the initial investment cost of 15.3 years is recovered.
Safe and Efficient Polymer Electrolyte Membrane Fuel Cell Control Using Successive Linearization Based Model Predictive Control Validated on Real Vehicle Data
Authors: Vrlić Martin , Ritzberger Daniel , Jakubek Stefan
Published: October 2020

In this paper, a polymer electrolyte membrane fuel cell (PEMFC) stack control study is presented. The goal is to track the transient power demand of a real fuel cell (FC) vehicle while ensuring safe and efficient operation. Due to the dynamically changing power demand, fast transients occur in the internal states of the fuel cell (e.g., pressure, humidity, reactant mass) leading to degradation effects (e.g., high/low membrane overpressure, reactants starvation) which are avoided by imposing safety constraints. Efficiency is considered in terms of internal voltage losses minimization as well as minimization of the power of the compressor used to pressurize the cathode. For solving the optimization problem of power demand tracking, adhering to safety constraints, and maximizing efficiency, model predictive control (MPC) has been chosen. Due to the nonlinearity of the FC system, a successive linearization based MPC (SLMPC) is used to control the FC throughout its operating region. Simulation results show that the power demand can be fulfilled while at the same time ensuring safe operation in terms of adhering to constraints and that the minimization of internal voltage losses and compressor power lead to an approximate 9.5% less hydrogen consumption than in the actual reference vehicle.
Method for Determining the Probability of a Lack of Water Supply to Consumers
Authors: Szpak Dawid
Published: October 2020

The water distribution subsystem is the most failing subsystem included in the water supply system. One of the main consequences of water supply failures is the lack of water supply to consumers, which is always very onerous. The paper presents a method of determining the conditional probability that a break in the supply of water to consumers of a certain duration will be caused by a specific type of failure. The result of the work was to identify water supply network failures that result in the longest water supply suspension time. The method was presented on a real water supply system. In order to reduce the incidence of long-term interruptions in water supply, water supply companies should mainly continue replacing gray cast iron pipes with thermoplastic materials. Actions taken to increase the safety of drinking water supply meet the current standards for the safety of drinking water, developed by the World Health Organization and the European Union.
A Novel Data-Driven Method to Estimate Methane Adsorption Isotherm on Coals Using the Gradient Boosting Decision Tree: A Case Study in the Qinshui Basin, China
Authors: Zhang Jiyuan , Feng Qihong , Zhang Xianmin , Hu Qiujia , Yang Jiaosheng , Wang Ning
Published: October 2020

The accurate determination of methane adsorption isotherms in coals is crucial for both the evaluation of underground coalbed methane (CBM) reserves and design of development strategies for enhancing CBM recovery. However, the experimental measurement of high-pressure methane adsorption isotherms is extremely tedious and time-consuming. This paper proposed the use of an ensemble machine learning (ML) method, namely the gradient boosting decision tree (GBDT), in order to accurately estimate methane adsorption isotherms based on coal properties in the Qinshui basin, China. The GBDT method was trained to correlate the adsorption amount with coal properties (ash, fixed carbon, moisture, vitrinite, and vitrinite reflectance) and experimental conditions (pressure, equilibrium moisture, and temperature). The results show that the estimated adsorption amounts agree well with the experimental ones, which prove the accuracy and robustness of the GBDT method. A comparison of the GBDT with two commonly used ML methods, namely the artificial neural network (ANN) and support vector machine (SVM), confirms the superiority of GBDT in terms of generalization capability and robustness. Furthermore, relative importance scanning and univariate analysis based on the constructed GBDT model were conducted, which showed that the fixed carbon and ash contents are primary factors that significantly affect the adsorption isotherms for the coal samples in this study.
A Review of the Measures and Instruments to Promote Efficiency and Renewable Energy in Domestic Water Heating
Authors: Ortiz Dania , Leal Vítor , Azevedo Isabel
Published: October 2020

This paper identifies and characterizes the technical measures and policy instruments that can be used to promote energy efficiency and the use of renewable sources for domestic hot water (DHW). DHW presents a considerable potential for abatement of greenhouse gas emissions around the world. Measures were characterized in terms of level of transformation, impact and scope, among others. Policy instruments were characterized in terms of target groups, competences required for implementation, major challenges and nature of the instruments. A matrix showing the applicability of policy instruments per technical measure was derived, enabling policy makersto better choose articulated measures and policy instruments for their policy packs.
Impact of Lithium Salts on the Combustion Characteristics of Electrolyte under Diverse Pressures
Authors: Liu Changcheng , Huang Que , Zheng Kaihui , Qin Jiawen , Zhou Dechuang , Wang Jian
Published: October 2020

The electrolyte is one of the components that releases the most heat during the thermal runaway (TR) and combustion process of lithium-ion batteries (LIBs). Therefore, the thermal hazard of the electrolyte has a significant impact on the safety of LIBs. In this paper, the combustion characteristics of the electrolyte such as parameters of heat release rate (HRR), mass loss rate (MLR) and total heat release (THR) have been investigated and analyzed. In order to meet the current demand of plateau sections with low-pressure and low-oxygen areas on LIBs, an electrolyte with the most commonly used lithium salts, LiPF6, was chosen as the experimental sample. Due to the superior low-temperature performance, an electrolyte containing LiBF4 was also selected to be compared with the LiPF6 sample. Combustion experiments were conducted for electrolyte pool fire under various altitudes. According to the experimental results, both the average and peak values of MLR in the stable combustion stage of the electrolyte pool fire had positive exponential relations with the atmospheric pressure. At the relatively higher altitude, there was less THR, and the average and peak values of HRR decreased significantly, while the combustion duration increased remarkably when compared with that at the lower altitude. The average HRR of the electrolyte with LiBF4 was obviously lower than that of solution containing LiPF6 under low atmospheric pressure, which was slightly higher for LiBF4 electrolyte at standard atmospheric pressure. Because of the low molecular weight (MW) of LiBF4, the THR of the corresponding electrolyte was larger, so the addition of LiBF4 could not effectively improve the safety of the electrolyte. Moreover, the decrease of pressure tended to increase the production of harmful hydrogen fluoride (HF) gas.
A Comparative Analysis of Two Cable Yarder Technologies Performing Thinning Operations on a 33 Year Old Pine Plantation: A Potential Source of Wood for Energy
Authors: Picchio Rodolfo , Venanzi Rachele , Di Marzio Nicolò , Tocci Damiano , Tavankar Farzam
Published: October 2020

In central Italy, there are extensive European black pine (Pinus nigra Arn.) plantations which range from 30 to 60 years of age and where no thinning operations have been made. The main purpose of this study was to provide a comparative analysis of two cable yarder technologies (Maxwald, mobile pulley carriage and Savall, semi-automatic carriage), in terms of fuelwood production and cost, from the first thinning of a 33 year old plantation in slope areas of these plantations. The results showed that fuelwood production was cost-effective in both systems (Savall by 15.1 and Maxwald by 14.8 € m−3), although the productivity of the Savall system was higher than the Maxwald system (6.1 vs. 5.7 m3 h−1). The respect amounts of productivity have the potential to increase by 27% for the Savall yarder and 25% for the Maxwald yarder upon condition that the delay times are reduced to minimum level by proper training of workers, by a better organization, and planning of operations. The total effective CO2 emission by the Savall yarder was lower than the Maxwald yarder (1735 vs. 1772 g m−3). A sustainable production of fuelwood that is economically advantageous and environmentally sound in these plantations can be realized through an appropriate mechanization level and constant interaction with the silvicultural planning. This must be completed with adequate and efficient worker training.
Design Optimization of a Reluctance Lead Screw for Wave Energy Conversion
Authors: Tian Tian , Wu Weimin , Jiang Jiacheng , Zhu Lixun , Lu Kaiyuan , Blaabjerg Frede
Published: October 2020

A reluctance lead screw (RLS) is proposed in this paper which consists of a rotor and a translator, forming a magnetic device that is able to transfer low-speed linear motion into high-speed rotational motion. Permanent magnets (PMs) are only installed in the rotor, making it more suitable for long-stroke applications. The design aspects are assessed by finite element analysis (FEA) and the performance is evaluated. In addition, the thrust force per magnet volume is presented for evaluating the utilization rate of the PMs. The simulation results show that RLS has an advantage in terms of the PM utilization rate. A new method for realizing spiral magnets has also been developed which can not only reduce the manufacturing difficulties, but also ease the installation work. Finally, based on the simulations and analyses, two RLS prototypes designed for wave energy converters (WECs) are presented to show the potential applications of this novel topology.
An Inter-Comparison of Dynamic, Fully Coupled, Electro-Mechanical, Models of Tidal Turbines
Authors: Ortega Arturo , Tomy Joseph Praful , Shek Jonathan , Paboeuf Stephane , Ingram David
Published: October 2020

Production of electricity using hydrokinetic tidal turbines has many challenges that must be overcome to ensure reliable, economic and practical solutions. Kinetic energy from flowing water is converted to electricity by a system comprising diverse mechanical and electrical components from the rotor blades up to the electricity grid. To date these have often been modelled using simulations of independent systems, lacking bi-directional, real-time, coupling. This approach leads to critical effects being missed. Turbulence in the flow, results in large velocity fluctuations around the blades, causing rapid variation in the shaft torque and generator speed, and consequently in the voltage seen by the power electronics and so compromising the export power quality. Conversely, grid frequency and voltage changes can also cause the generator speed to change, resulting in changes to the shaft speed and torque and consequently changes to the hydrodynamics acting on the blades. Clearly, fully integrated, bi-directional, models are needed. Here we present two fully coupled models which use different approaches to model the hydrodynamics of rotor blades. The first model uses the Blade Element Momentum Theory (BEMT), resulting in an efficient tool for turbine designers. The second model also uses BEMT, combines this with an actuator line model of the blades coupled to an unsteady computational fluid dynamics simulation by OpenFOAM (CFD/BEMT). Each model is coupled to an OpenModelica model of the electro-mechanical system by an energy balance to compute the shaft speed. Each coupled system simulates the performance of a 1.2 m diameter, three-bladed horizontal axis tidal turbine tested in the University of Edinburgh FloWave Ocean Energy Research Facility. The turbulent flow around the blades and the mechanical-electrical variables during the stable period of operation are analysed. Time series and tabulated average values of thrust, torque, power, and rotational speed, as well as, electrical variables of generator power, electromagnetic torque, voltage and current are presented for the coupled system simulation. The relationship between the mechanical and electrical variables and the results from both tidal turbine approaches are discussed. Our comparison shows that while the BEMT model provides an effective design tool (leading to slightly more conservative designs), the CFD/BEMT simulations show the turbulence influence in the mechanical and electrical variables which can be especially important in assessing an additional source of stresses in the whole electro-mechanical system (though at an increased computational cost).
Test Grids for the Integration of RES—A Contribution for the European Context
Authors: Traupmann Anna , Kienberger Thomas
Published: October 2020

A long-term sustainable energy transition can only be achieved by technological advancements and new approaches for efficiently integrating renewable energies into the overall energy system. Significantly increasing the share of renewable energy sources (RES) within the overall energy system requires appropriate network models of current transmission and distribution grids, which, as limiting factors of energy infrastructures, confine this share due to capacity constraints. However, especially regarding electrical network models, data (e.g., geographical data, load and generation profiles, etc.) is rarely available since it usually includes user-specific information and is, therefore, subject to data protection. Synthetically obtained electrical networks, on the other hand, may not be representative and may fail to replicate real grid structures due to the heterogeneous properties of currently operated networks. To account for this heterogeneity, this paper offers a contribution for the European electrical energy system and presents the development of four synthetic test networks at different voltage levels which are representative and include non-confidential time-series data. The test network development is based on an extensive literature research on a multitude of different network parameters for grids within the ENTSO-E (European Network of Transmission System Operators for Electricity) interconnected system in Europe. These parameters are then used to design the networks in NEPLAN®. Then, these networks are provided with load and generation profiles for enabling time-series calculations. To validate the representativeness of the test networks, a short-circuit analysis is conducted and the obtained results are compared to short-circuit parameters common for Austrian and German literature values as well as for value ranges for European ENTSO-E grids. The analysis shows that the presented test networks replicate European electrical network behavior accurately and can, therefore, be utilized for various application purposes to assess technological impacts on European ENTSO-E grids.
Longitudinal Modelling and Control of In-Wheel-Motor Electric Vehicles as Multi-Agent Systems
Authors: Nguyen Binh-Minh , Nguyen Hung Van , Ta-Cao Minh , Kawanishi Michihiro
Published: October 2020

This paper deals with longitudinal motion control of electric vehicles (EVs) driven by in-wheel-motors (IWMs). It shows that the IWM-EV is fundamentally a multi-agent system with physical interaction. Three ways to model the IWM-EV are proposed, and each is applicable to certain control objectives. Firstly, a nonlinear model with hierarchical structure is established, and it can be used for passivity-based motion control. Secondly, a linearized model with rank-1 interconnection matrix is presented for stability analysis. Thirdly, a time-varying state-space model is proposed for optimal control using linear quadratic regulator (LQR). The proposed modellings contribute the new understanding of IWM-EV dynamics from the view point of multi-agent-system theory. By choosing the suitable control theory for each model, the complexity level of system design is maintained constant, no matter what the number of IWMs installed to the vehicle body. The effectiveness of three models and their design approaches are discussed by several examples with Matlab/Carsim co-simulator.
Differential Equation Model of the LLC Resonant Converter in the Ideal Case
Authors: Li Fang , Lei Haodong , Hao Ruixiang , Liu Siwei , You Xiaojie , Gao Jingmin
Published: October 2020

The LLC resonant converter has been widely used in direct current (DC) power supply applications. However, fundamental harmonic approximation or other simplified analyses will introduce inevitable deviations. Therefore, the differential equation model with numerical solution of the LLC converter is proposed in this paper based on the operational principle of the ideal case. In order to solve the differential equation, initial values need to be substituted. The accurate LLC model based on time interval analysis is very complicated and cannot be used. In this paper, solution methods of the initial values corresponding to different switching frequencies are proposed. The initial values can be solved conveniently. Furthermore, the voltage gain curve is modified by the idealized analysis. Lastly, all the above research is verified by PSIM simulation. The work is helpful to understand the operational principle of the LLC resonant converter.
Simulation of Mixing Intensity Profile for Bioethanol Production via Two-Step Fermentation in an Unbaffled Agitator Reactor
Authors: Echaroj Snunkhaem , Ong Hwai Chyuan , Chen Xiuhan
Published: October 2020

Bioethanol synthesis techniques have been studied intensively due to the energy crisis and various environmental concerns. A two-step bioethanol production process was carried out multiple times in an unbaffled agitator tank. The parameters varied, including the fermentation temperature, the pH level, the amount of yeast, and the impeller type. Then, a simulation was used to obtain an image of the agitation behavior inside the agitator tank to compare the velocity profile of each type of impeller design. The impeller with eight blades was found to produce the highest flow velocity: 0.28 m/s. The highest concentration of bioethanol generated from the fermentation was 34 g/L, which was produced by using an eight-blade impeller at 30 °C, a pH level of 5, an agitation speed of 70 rpm, and 2 wt % yeast. The two-blade impeller produced the lowest bioethanol concentration, 18 g/L, under the same conditions. Ethanol concentration was found to peak at 40 °C and a pH level of 5. The geometry of the impeller, the fermentation temperature, and the pH level were each found to have a significant effect on the resulting bioethanol concentration according to the results of an ANOVA test. The amount of yeast had no effect on the fermentation reaction. Finally, the results demonstrated the possibility of using computational fluid dynamic modeling to determine the impeller’s behavior for the development of the bioethanol fermentation process. The simulation and experimental results from this research support the scaling up of a bioethanol production facility.