bluuebunny/crossref_metadata_2025 huggingface dataset:
Impedance modelling of grid‐connected voltage‐source converters considering the saturation non‐linearity
Authors: Wu Tianhao , Xie Xiaorong , Jiang Qirong , Shen Zhuoxuan
Published: September 2020

The mainstream researches focus on the linearised impedance/admittance model and its related coupling effects or stability problems. However, since various non‐linear components exist in control loops, their non‐linear dynamics shall be described to improve the modelling accuracy. To fill in this gap, this study develops a large‐signal impedance/admittance model (LSIM/LSAM) to describe the dominant non‐linearity of modulation saturation in a grid‐connected voltage‐source converter (VSC). The LSAM represents the non‐linearity with the equivalent saturation gains based on the describing function theory and then incorporates the derived gains into conventional small‐signal AM (SSAM) to obtain a partially non‐linear admittance. The proposed LSAM distinguishes itself from SSAM by reflecting the improvement in the magnitude‐ and phase‐response of admittance during non‐linear oscillations. Case studies on a grid‐connected VSC containing saturation non‐linearity are conducted to validate the model's effectiveness in stability analysis. It is found that the frequency deviation and sustained oscillation caused by non‐linearity, which can hardly be assessed using SSAM, can be well captured by LSAM. The results of parameter analysis verify that the modulation saturation dominates the system non‐linearity.
Risk‐neutral and risk‐averse transmission switching for load shed recovery with uncertain renewable generation and demand
Authors: Zhang Yingqiu , Bansal Manish , Escobedo Adolfo R.
Published: September 2020

One of the main desired capabilities of the smart grid is ‘self‐healing’, which is the ability to quickly restore power after a disturbance. Due to critical outage events, customer demand or load is at times disconnected or shed temporarily. While deterministic optimisation models have been devised to help operators expedite load shed recovery by harnessing the flexibility of the grid's topology (i.e. transmission line switching), an important issue that remains unaddressed is how to cope with the uncertainty in generation and demand encountered during the recovery process. This study introduces two‐stage stochastic models to deal with these uncertain parameters, and one of them incorporates conditional value‐at‐risk to measure the risk level of unrecovered load shed. The models are implemented using a scenario‐based approach where the objective is to maximise load shed recovery in the bulk transmission network by switching transmission lines and performing other corrective actions (e.g. generator re‐dispatch) after the topology is modified. The benefits of the proposed stochastic models are compared with a deterministic mean‐value model, using the IEEE 118‐ and 14‐bus test cases. Experiments highlight how the proposed approach can serve as an offline contingency analysis tool, and how this method aids self‐healing by recovering more load shedding.
Near‐field uniformity analysis and compensation for finite‐sized beam combiner with the asymmetric layout
Authors: Hao Kaizi , Li Zhuo , Wang Xin , Zhou Lang , Wang Yiting
Published: September 2020

In a hardware‐in‐the‐loop simulation system, the insertion of an asymmetric layout beam combiner will seriously affect the near‐field uniformity. In this study, the effects of the aperture shape, transverse distance and size of the beam combiner on the near‐field uniformity were analysed. The square beam combiner with a transverse distance of 0.51 m and a size of 1.05 m × 1.05 m was regarded as the optimal design, but it still cannot meet the test requirements. In order to obtain excellent near‐field uniformity, an asymmetric Uniform + Linear taper compensation method was proposed. The maximum values of the amplitude fluctuation (Epv) and phase ripple (φpv) decreased dramatically from 2.62 dB and 16.79° to 0.78 dB and 7.42°, respectively. Asymmetric Uniform + Linear taper was achieved through serrating the edge of the beam combiner. When the number of serrations N was 22, Epv and φpv were <0.83 dB and 7.50°, respectively, which indicated that the near‐field uniformity can be significantly improved by asymmetric Uniform + Linear taper.
Dual‐output AC–DC converter with three‐port bridgeless PFC and non‐isolated DCX
Authors: Xu Xinyu , Jia Yihang , Wu Hongfei , Zhang Yanfeng
Published: September 2020

This study proposed a dual‐output AC–DC converter based on three‐port bridgeless power factor corrector (TPB‐PFC) and a non‐isolated resonant DC‐transformer (Ni‐DCX) for dual‐output DC voltage applications. A constant DC output voltage and a variable DC output voltage are provided simultaneously by the proposed AC–DC converter. Based on the TPB‐PFC converter, a stacked power conversion structure with reduced power conversion stage is presented. Therefore, lower power losses and higher efficiencies are achieved. Meanwhile, soft switching of all the power devices in the Ni‐DCX is achieved with open‐loop controlled and optimised operation of the Ni‐DCX, resulting in easy control and higher efficiency. In addition, switching losses of the TPB‐PFC are reduced thanks to the three‐level characteristic. Operation principles and characteristics of both TPB‐PFC and Ni‐DCX converter, and modulation and control strategies of the proposed AC–DC converter are analysed in detail. Feasibility and effectiveness of the proposed solutions are verified experimentally with a 2 kW dual‐output AC–DC prototype.
Broken rotor bar fault detection using Hilbert transform and neural networks applied to direct torque control of induction motor drive
Authors: Ramu Senthil Kumar , Irudayaraj Gerald Christopher Raj , Subramani Saravanan , Subramaniam Umashankar
Published: September 2020

This study proposes a new approach for the detection of broken rotor bar (BRB) fault in three phase induction motor drive using Hilbert transform (HT) and artificial neural networks (ANNs), where the machine is controlled by direct torque control (DTC). HT is preferred to develop the stator current envelope. The sideband frequency and its amplitude of the samples are the input for the ANN. By using fast Fourier transform, the amplitude and frequency components are extracted and the severity of fault is determined by comparing the magnitude of an average of sideband frequency with the fundamental frequency. High accuracy identification of fault is found by ANN, where the results are trained and tested to a minimum mean square error that will detect the number of BRB in the induction motor. DTC is adopted for a suitable control technique in the industrial drives system to maintain good performance in torque control. The performance of the proposed method is verified by using MATLAB/SIMULINK and experimental tests.
Voltage‐controlled power factor corrected CSC derived DC–DC converter for PMBLDC driven home appliances
Authors: Rathore Kuldeep Singh , Kalla Ujjwal Kumar , Palwalia Dheeraj Kumar , Singh Bhim , Mishra Anjanee Kumar
Published: September 2020

A voltage‐controlled canonical switching cell‐derived DC–DC converter with improved power quality feeding a variable speed permanent magnet brushless direct current (PMBLDC) motor‐drive system for home appliances, is presented in this study. The converter is operating in the continuous conduction mode (CCM). This converter has less stress on the converter devices due to CCM of operation. A single converter is used for both the power factor correction (PFC) and the speed control of the drive, thus reducing the number of elements in the system. The speed control, along with PFC in this system is achieved via a PI controller having speed reference as an input. This system is capable of providing the low speed to rated speed operation while maintaining a unity power factor. The Hall‐effect sensor‐based electronic commutation of a PMBLDC motor‐drive is implemented at the fundamental frequency. This significantly improves efficiency by reducing the switching losses of the voltage source inverter. A prototype of it is developed in the laboratory for implementation of the scheme. Simulated and real‐time experimental results of the scheme are presented here for performance validation at various dynamic and steady‐state operating conditions.
Non‐isolated DC–DC converter with cubic voltage gain and ripple‐free input current
Authors: Samuel Vijay Joseph , Keerthi Gna , Mahalingam Prabhakar
Published: September 2020

In this study, a non‐isolated high gain DC–DC converter is presented. The proposed converter yields a voltage conversion ratio value which is a cubic function of the voltage gain obtained from a boost converter. The proposed converter is synthesised by judiciously interfacing a two‐phase interleaved boost converter with voltage‐lift capacitor and a quadratic boost converter. Resultantly, the proposed converter yields a practical voltage gain of 21.11. Further, due to the use of interleaving technique, the input current is completely free from ripples. The proposed concept is validated by conducting experiments on 18/380 V, 160 W prototype converter. The experimental results clearly demonstrate that the proposed converter operates at a full‐load efficiency of 95.6%. Further, by practically implementing a simple closed‐loop control, the output voltage of the converter is quickly regulated against variations in input voltage and load current so as to provide the desired 380 V across the load terminals.
Development of grid‐interactive inverter utilising induction motor driven photovoltaic water pumping system
Authors: Vamja Rajan V. , Mulla Mahmadasraf A.
Published: September 2020

The stand‐alone solar photovoltaic water pumping system (SPVWPS) remains idle for a significant period of time, when irrigation is not required and when sun is not available. Due to this large idle period, the effective utilisation of SPVWPS assets, i.e. solar photovoltaic array, power electronics converter, and motor, is poor. This study presents an approach to increase the effective utilisation of SPVWPS under the aforementioned idle period. It is proposed to interface the grid with SPVWPS without adding extra power electronic interface. An innovative integrated photovoltaic inverter is constructed using existing SPVWPS components. The inverter enables the transfer of active power and exchange of reactive power with the grid during an idle period of SPVWPS. The three legs of the voltage source inverter (VSI) are interleaved with motor windings. The VSI switches are controlled with synchronous pulse width modulation to force a cophasal current in the motor windings. This accompanies a net motor torque to zero under grid‐interactive operation. Hence, the three‐phase VSI operates as a single‐phase grid synchronise converter, and the motor windings are used as filter inductance. The control system is presented to establish grid‐interactive functionality. A prototype is developed to verify system performance. The control system is implemented using the ARM Cortex‐M4 microcontroller.
Resilient multilevel inverter topology with improved reliability
Authors: Chappa Anilkumar , Gupta Shubhrata , Sahu Lalit Kumar , Gupta Krishna Kumar
Published: September 2020

Reliability is one of the significant worries of multilevel inverter (MLI) owing to the higher number of capacitors and switches. In this regard, fault‐tolerant single‐phase MLI topology with improved reliability is proposed in this work. Apart from the reduced device count, the proposed topology has fault‐tolerant characteristics without any extra switches or legs. Moreover, the voltage of the capacitor is balanced under pre and post‐fault operation without any external circuit. Less number of the turn‐on devices and power losses promise higher reliability of the proposed topology in comparison with recently proposed topologies. The reliability of the proposed topology, as well as recently proposed topologies, has been evaluated. A detailed quantitative comparison of the proposed inverter topology has been carried out with the recent literature. The robustness and effectiveness of the proposed topology are carried out under various operating conditions in the SIMULINK environment. Finally, an experimental test bench of the proposed topology is built and the obtained experimental results validate the simulation results.
Interleaved high step‐up ZVS DC–DC converter with coupled inductor and built‐in transformer for renewable energy systems applications
Authors: Nouri Tohid , Shaneh Mahdi , Ghorbani Alireza
Published: September 2020

A zero voltage switching (ZVS) interleaved high step‐up converter with coupled inductor and built‐in transformer voltage multiplier cell is introduced in this study. A more flexible design is provided by increasing the voltage conversion ratio by utilising the turns ratios of the coupled inductor and built‐in transformer. The ZVS operation of the metal‐oxide‐semiconductor field‐effect transistors (MOSFETs) and absorption of the leakage current are realised through active clamp circuits. Furthermore, the voltage stress across the switching devices is minimised that give rises to implementation of low voltage rated MOSFETs and consequently low conduction losses. Meanwhile, the diode reverse current problem is alleviated by the leakage inductance of the coupled inductor and built‐in transformer. All of the abovementioned advantages make the proposed converter as a high efficiency candidate for high current and high step‐up applications. Finally, a 600 W, 48–700 V voltage conversion with the conversion efficiency of 97% is fabricated to probe the merits of the proposed converter.
Mutual inductance calculation of circular coils arbitrary positioned with magnetic tiles for wireless power transfer system
Authors: Li Zhongqi , Zhang Min
Published: September 2020

The mutual inductance between the primary and secondary coils is an important parameter in the wireless power transfer system, and the mutual inductance calculation of coils in many complicated circumstances has been studied. However, the mutual inductance calculation of two circular coils in arbitrary relative position with magnetic tiles have not been solved. In this study, an analytical formula of the mutual inductance with respect to the parameters of the system such as arbitrary relative position, geometry, and the properties of the magnetic tiles is proposed. The proposed formula is derived from the proposed parameter vector method, and the proposed parameter vector method can not only be used to explore the tendencies of the mutual inductance in arbitrary relative position, but also provide a fairly concise and general method for mutual inductance calculation. The finite‐element analysis and experimental results validated the reliability and accuracy of the proposed formula, and an accuracy of a few parts in a thousand can be readily attainable.
Improved convolutional neural network‐based quantile regression for regional photovoltaic generation probabilistic forecast
Authors: Yu Yixiao , Wang Mengxia , Yan Fangqing , Yang Ming , Yang Jiajun
Published: September 2020

Nowadays, an increasing number of photovoltaic (PV) plants are becoming integrated into one regional power grid. Under this circumstance, the probabilistic forecast of regional PV power generation is of significance for the regional power system operation and control. This study presents a novel probabilistic forecast method for regional PV generation that integrates the convolutional neural network (CNN) with non‐linear quantile regression (QR). In this method, the CNN structure is enhanced to extract the non‐linear features of the input data and generate the non‐linear QR function. As a result, the improved CNN can effectively process high‐dimensional and complex input data and the non‐linear QR model can provide quantile forecast information of regional PV power. The validity of the proposed method is verified by using it to forecast the regional PV generation from the clustered PV plants in the Weifang region of China.
Economic emission dispatch of hydro‐thermal‐wind using CMQLSPSN technique
Authors: Robert Leena Rose , Ravi Singh Lal Raja Singh
Published: September 2020

This study presents a multi‐objective based on a hybrid methodology to apply the problem of economic emission dispatch that is incorporated with hydro, thermal and wind power units. The hybrid method is the combination of both the modified quantum‐behaviour lightning search algorithm (MQLSA) and artificial intelligence technique with the help of PSNN. To determine the optimal amounts of the generated powers from the thermal, wind farms and hydro units, the proposed approach is introduced by minimising the cost of generation and the emission level simultaneously. MQLSA is utilised to generate the optimal combination of thermal power with the objective of the minimum error function to minimise the fuel and emission cost of the system with wind speed factor. To capture the optimised wind power with the objective of minimum speed factor, the PSO‐artificial neural network technique is utilised. The algorithm is integrated with the feasible solution constraint handling techniques. To validate the effectiveness of the proposed method, the six and ten generating thermal system with wind power is studied. The proposed hybrid technique is implemented in MATLAB/Simulink platform and the simulation result demonstrates the superiority of the proposed method compared to the various existing techniques.
Stochastic distributed microgrid energy management based on over‐relaxed alternative direction method of multipliers
Authors: Afrasiabi Mousa , Mohammadi Mohammad , Rastegar Mohammad , Afrasiabi Shahabodin
Published: September 2020

This study aims to design a stochastic distributed energy management framework taking into account the information privacy of autonomous agents. To develop this framework, first, the application of a scenario‐based method on the predicted probability density function (PDF) is suggested to deal with uncertainties of the low‐scale loads, renewable generations, i.e. wind and photovoltaic generations, and electricity market prices. Then, an alternative direction method of multipliers (ADMM) based method, namely over‐relaxed ADMM, is presented to optimise the operational set points considering each agent benefits and technical constraints. In this framework, the agents participate in scheduling programs without sharing influential information and corresponding historical data. The presented framework is tested on a realistic small‐scale microgrid (MG) system and real historical data. The performance and efficiency are verified by comparison of the proposed over‐relaxed ADMM method application with the application of standard ADMM and analytic targeting cascading in terms of accuracy and convergence speed. Furthermore, higher accuracy and lower computational complexity of predictive PDF‐based scenario generation techniques in distributed MG energy management are verified by comparison with distributed energy management based on predefined PDF and historical data.
Analytical three‐dimensional wind flow model for real‐time wind farm simulation
Authors: Kipke V. , Chhor J. , Sourkounis C.
Published: September 2020

Wind energy conversion systems have gained an essential share of the electricity supply and are increasingly competitive with conventional power plants based on fossil fuel. Wind turbines are expected to continue their increase in rated power and size, exceeding 10 MW and more, imposing major challenges concerning not only the operation of future power grids but also mechanical stress on individual wind turbines, their aerodynamic interaction and holistic wind farm control strategies as well as simulation models being able to cover all these aspects. This study deals with requirements of a real‐time capable three‐dimensional wind flow model for wind farm simulation, covering key issues from wind modelling through wake interactions to prospects of advanced control strategies. Building upon this, a modular framework is proposed and implemented by integrating existing validated analytical models. Simulation results demonstrating the model capabilities are presented, discussed and evaluated concerning future research focus.
Modelling and design of wind‐solar hybrid generation projects in long‐term energy auctions: a multi‐objective optimisation approach
Authors: Aquila Giancarlo , de Queiroz Anderson R. , Lima Luana M.M. , Balestrassi Pedro Paulo , Lima J.W. Marangon , Pamplona Edson O.
Published: September 2020

This study proposes an approach to help the bidding processes of hiring wind‐photovoltaic farms in long‐term energy auctions. The proposed approach aims to define an optimal solution to configure wind‐photovoltaic farms based on mixture design of experiments and the Lp method, as well as an efficiency metric designed to achieve diversification and to identify the Pareto dominant optimal portfolio. The proposed method is simple and flexible for practical applications. Moreover, its associated goals of choosing the Pareto dominant optimal solutions are aligned with the goals of the electricity regulators responsible to manage the hiring process for a new generation. To validate the method, wind‐solar photovoltaic generation configurations in three Brazilian cities are analysed and the results are compared with other methods previously proposed in the literature. The results show that the proposed method has more intuitive criteria for the investor and regulator, without reducing the quality of the information provided to decision making.
Energy extraction characteristic of the flapping wing type vertical axis turbine
Authors: Hou Longfeng , Wang Bo , Zhu Bing
Published: September 2020

Flapping wings are known to be used not only for propulsion, but also for energy extraction from the surrounding fluid environment. In this work, the authors propose a vertical axis turbine based on flapping wings. Numerical experiments have been conducted. Results show (i) In a certain range of frequency, the vertical axis turbine equipped with flapping wings of circular or reversed‐D motion trajectory demonstrates better energy extraction performance when compared to the traditional vertical axis wind turbine. (ii) For the reversed‐D motion trajectory, as two airfoils begin to move apart from each other, the downstream flapping‐wing takes advantage of the trailing edge vortex of the upstream flapping‐wing to enhance its own energy extraction ability. However, for the circular motion trajectory, the two airfoils are usually located far away from each other. This leads to the result that the mutual influence between the two airfoils is very weak. Generally speaking, the application of flapping wings in the vertical axis turbine can improve the energy extraction efficiency in a certain range, which can provide another method for the design of a new type of vertical axis turbine in the research and industry.
Improved solutions to a TEAM problem for multi‐objective optimisation in magnetics
Authors: Di Barba Paolo , Mognaschi Maria Evelina , Lowther David A. , Sykulski Jan K.
Published: September 2020

New solutions to a recently proposed benchmark TEAM problem for Pareto optimisation are presented. In the benchmark, an air‐cored solenoid of small size, which can be used, for example, for magnetic fluid hyperthermia, is considered. Two shape optimisations of the solenoid are proposed in the benchmark: synthesising a uniform magnetic field in a control region, considering also a sensitivity function (Problem 1) or synthesising a uniform magnetic field, simultaneously minimising the power losses (Problem 2). The benchmark is solved by means of three different nature‐inspired algorithms and a genetic one, namely micro biogeography‐inspired algorithm, wind‐driven optimisation, and the cuckoo search, taking the genetic algorithm NSGA‐II as a reference, because all these methods have proven to be effective in solving multi‐objective optimisation problems.
Preparation of modified SrAl1.3Fe10.7O19 nanostructures and evaluation of size influence on its optical and magnetic properties
Authors: Peymanfar Reza , Javidan Abdollah , Selseleh‐Zakerin Elnaz
Published: September 2020

Modifying the morphology of nanostructures and its influence on the features of the tailored nanoparticles (NPs) has attracted a great deal of interest. In this research, the morphological effect on magnetic properties of the bare or modified NPs was investigated. Bare NPs were fabricated by the sol–gel route and modified NPs were prepared using hydrophilic absorbent cotton (HAC) to architect morphology of the NPs. X‐ray diffraction, field emission scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and Fourier transform infrared analyses confirmed that pure SrAl1.3Fe10.7O19 NPs were synthesised based on the modified sol–gel method. Results indicated that HAC as a novel and affordable template modified the shape of the NPs. The obtained results by the diffuse reflection spectroscopy suggest that the optical performance of the NPs can be tuned by modifying the size of them. Additionally, the hysteresis loops of the vibrating sample magnetometer attested that the saturation magnetisation (Ms) of the modified NPs was elevated.
Synthesis of flower‐like and hexagonal flake‐like ZnO using microwave method and their photocatalytic activity
Authors: Si Wei , Pei Liran
Published: September 2020

The flower‐like and hexagonal flake‐like ZnO microstructures were synthesised by a microwave method using ammonia water and sodium hydroxide as precipitant, respectively. The products were characterised by scanning electron microscopy, high‐resolution transmission electron microscopy, X‐ray diffraction and photoluminescence. The photocatalytic activity of the flower‐like and hexagonal flake‐like ZnO microstructures was evaluated by the degradation of methyl orange (MO) under ultraviolet (UV) light irradiation. The results indicated that the best flower‐like ZnO microstructure was obtained when the experimental conditions were [Zn2+] = 0.025 mol l−1, [Zn2+]:[NH3·H2O] = 1:1.5, microwave power = 231 W. Under the same reaction conditions, hexagonal flake‐like ZnO can be obtained by using sodium hydroxide as precipitant. The MO in aqueous solution was completely eliminated by flower‐like ZnO after 120 min of UV light irradiation. Under identical conditions, the degradation of MO in aqueous solution was completely finished within 150 min in the presence of hexagonal flake‐like ZnO. The flower‐like ZnO sample showed an enhanced photocatalytic activity compared with the hexagonal flake‐like ZnO for the MO degradation, which could be attributed to the presence of more active centres and hence can have more opportunities to contact with MO molecules.
The POLAR gamma-ray burst polarization catalog
Authors: Kole M. , De Angelis N. , Berlato F. , Burgess J. M. , Gauvin N. , Greiner J. , Hajdas W. , Li H. C. , Li Z. H. , Pollo A. , Produit N. , Rybka D. , Song L. M. , Sun J. C. , Szabelski J. , Tymieniecka T. , Wang Y. H. , Wu B. B. , Wu X. , Xiong S. L. , Zhang S. N. , Zhang Y. J.
Published: September 2020

Context.Despite over 50 years of research, many open questions remain about the origin and nature of gamma-ray bursts (GRBs). Linear polarization measurements of the prompt emission of these extreme phenomena have long been thought to be key to answering a range of these questions. The POLAR detector was designed to produce the first set of detailed and reliable linear polarization measurements in the 50 − 500 keV energy range. During late 2016 and early 2017, POLAR detected a total of 55 GRBs. The analysis results of 5 of these GRBs have been reported, and were found to be consistent with a low or unpolarized flux. However, previous reports by other collaborations found high levels of linear polarization, including some as high as 90%.

Aims.We study the linear polarization for the 14 GRBs observed by POLAR for which statistically robust inferences are possible. Additionally, time-resolved polarization studies are performed on GRBs with sufficient apparent flux.

Methods.A publicly available polarization analysis tool, developed within the Multi-Mission Maximum Likelihood framework (3ML), was used to produce statistically robust results. The method allows spectral and polarimetric data from POLAR to be combined with spectral data from theFermiGamma-ray Burst Monitor (Fermi-GBM) and theNeil Gehrels SwiftObservatory to jointly model the spectral and polarimetric parameters.

Results.The time-integrated analysis finds all results to be compatible with low or zero polarization with the caveat that, when time-resolved analysis is possible within individual pulses, we observe moderate linear polarization with a rapidly changing polarization angle. Therefore, time-integrated polarization results, while pointing to lower polarization, are potentially an artifact of summing over the changing polarization signal and thus washing out the true moderate polarization. We therefore caution against overinterpretation of any time-integrated results inferred herein and encourage the community to wait for more detailed polarization measurements from forthcoming missions such as POLAR-2 and LEAP.
A heuristic approach for green vehicle routing
Authors: Soysal Mehmet , Çimen Mustafa , Sel Çağrı , Belbağ Sedat
Published: September 2020

This paper addresses a green capacitated vehicle routing problem that accounts for transportation emissions. A Dynamic Programming approach has been used to formulate the problem. Although small-sized problems can be solved by Dynamic Programming, this approach is infeasible for larger problems due to the curse of dimensionality. Therefore, we propose a Dynamic Programming based solution approach that involves the ideas of restriction, simulation and online control of parameters to solve large-sized problems. The added values of the proposed decision support tool have been shown on a small-sized base case and relatively larger problems. Performance comparisons of the proposed heuristic against other existing Dynamic Programming based solution approaches reveal its effectiveness, as in most of the instance-setting pairs, the proposed heuristic outperforms the existing ones. Accordingly, the proposed heuristic can be used as an alternative decision support tool to tackle real routing problems confronted in sustainable logistics management.
Evaluation of the Hepatorenal B-Mode Ratio and the “Controlled Attenuation Parameter” for the Detection and Grading of Steatosis
Authors: Moret Antoine , Boursier Jérome , Houssel Debry Pauline , Riou Jérémie , Crouan Anne , Dubois Marine , Michalak Provost Sophie , Aubé Christophe , Paisant Anita
Published: September 2020

Purpose The aim of this study was to evaluate the hepatorenal index ratio of Supersonic Imagine (B-mode ratio) and the controlled attenuation parameter (CAP) of FibroScan for the noninvasive diagnosis and grading of steatosis.

Materials and Methods Two centers prospectively included patients who underwent liver biopsy, B-mode ratio and CAP evaluation all on the same day between June 2017 and July 2019. MRI and histological morphometry were also performed in center 1. Histology (classic semiquantitative score and morphometry) was used as the reference.

Results Concerning the B-mode ratio, the AUROCs for ≥ S1, ≥ S2 and ≥ S3 were respectively 0.896 ± 0.20, 0.775 ± 0.30 and 0.729 ± 0.39 with the best cut-off values being 1.22 for ≥ S1 (Se = 76.4 %, Sp = 93.2 %), 1.42 for ≥ S2 (Se = 70.2 %, Sp = 71.2 %) and 1.54 for ≥ S3 (Se = 68.4 %, Sp = 69.8 %). The correlation between the B-mode ratio and morphometry was moderate (Rs = 0.575, p < 0.001) and the correlation between the B-mode ratio and MRI was good (Rs = 0.613, p < 0.001). Concerning the CAP, the AUROCs for ≥  S1, ≥ S2 and ≥ S3 were 0.926 ± 0.18, 0.760 ± 0.30 and 0.701 ± 0.40, respectively, with the best cut-off values being 271 dB/m for ≥ S1 (Se = 84 %, Sp = 88.2 %), 331 dB/m for ≥ S2 (Se = 64.5 %, Sp = 74.7 %) and 355 dB/m for ≥ S3 (Se = 55.3 %, Sp = 75.1 %). The correlation between the CAP and morphometry and between the CAP and MRI was moderate in both cases (Rs = 0.526, p < 0.001 and Rs = 0.397, p < 0.001, respectively). The B-mode ratio was better at ruling in and the CAP was better at ruling out the disease.

Conclusion B-mode ratio and CAP show similar and good performance for the diagnosis of steatosis (≥ S1). However, both techniques are limited with respect to differentiating mild to moderate (≥ S2) or severe (≥ S3) steatosis.
COVID-19-Induced Cytokine Release Syndrome Associated with Pulmonary Vein Thromboses, Atrial Cardiomyopathy, and Arterial Intima Inflammation
Authors: Goette Andreas , Patscheke Markus , Henschke Frank , Hammwöhner Matthias
Published: September 2020

Coronavirus disease 2019 (COVID-19) is a viral disease induced by severe acute respiratory syndrome–coronavirus-2 (SARS-CoV-2), which may cause an acute respiratory distress syndrome (ARDS). First reports have shown that elevated levels of inflammatory cytokines might be involved in the development of organ dysfunction in COVID-19. Here, we can present a case of cytokine release syndrome induced by SARS–CoV-2 causing multiorgan failure and death. Of note, we can report on pulmonary vein thromboses as potential source of cerebrovascular embolic events. Furthermore, we present a specific form of an isolated inflammatory atrial cardiomyopathy encompassing atrial myocardium, perivascular matrix, as well as atrial autonomic nerve ganglia, causing atrial fibrillation, sinus node arrest, as well as atrial clot formation in the right atrial appendage. An associated acute glomerulonephritis caused acute kidney failure. Furthermore, all the described pathologies of organs and vessels were associated with increased local expression of interleukin-6 and monocyte chemoattractant protein-1 (MCP-1). This report provides new evidence about fatal pathologies and summarizes the current knowledge about organ manifestations observed in COVID-19.
Therapeutic Anticoagulation Delays Death in COVID-19 Patients: Cross-Sectional Analysis of a Prospective Cohort
Authors: Ionescu Filip , Grasso-Knight Giovi , Castillo Edward , Naeem Ehsun , Petrescu Ioana , Imam Zaid , Patel Vishal K. , Narasimhan Mangala , Nair Girish B.
Published: September 2020

A hypercoagulable state has been described in coronavirus disease 2019 (COVID-19) patients. Others have reported a survival advantage with prophylactic anticoagulation (pAC) and therapeutic anticoagulation (tAC), but these retrospective analyses have important limitations such as confounding by indication. We studied the impact of tAC and pAC compared with no anticoagulation (AC) on time to death in COVID-19. We performed a cross-sectional analysis of 127 deceased COVID-19 patients and compared time to death in those who received tAC (n = 67), pAC (n = 47), and no AC (n = 13). Median time to death was longer with higher doses of AC (11 days for tAC, 8 days for pAC, and 4 days for no AC, p < 0.001). In multivariate analysis, AC was associated with longer time to death, both at prophylactic (hazard ratio [HR] = 0.29; 95% confidence interval [CI]: 0.15 to 0.58; p < 0.001) and therapeutic doses (HR = 0.15; 95% CI: 0.07 to 0.32; p < 0.001) compared with no AC. Bleeding rates were similar among tAC and remaining patients (19 vs. 18%; p = 0.877). In deceased COVID-19 patients, AC was associated with a delay in death in a dose-dependent manner. Randomized trials are required to prospectively investigate the benefit and safety of higher doses of AC in this population.
A Randomised Interventional Study to Compare Autologous and Nonautologous Dural Substitutes Among Traumatic Brain Injury Patients
Authors: Pandit Vir Abhimanyu , Sharma Rajesh Kumar , Bhaskar Suryanarayanan , Kindra Amanjeet Singh , Choudhary Ajay , Gupta LN
Published: September 2020

Objectives To determine and compare the effectiveness and safety of galea-pericranium autologous dural graft with nonautologous polypropylene (G-patch) dural substitute among traumatic brain injury (TBI) patients.

Methods A prospective interventional randomized comparative study was conducted at the Department of Neurosurgery from November 2013 to March 2015 after obtaining approval from the institutional ethicas committee. The study population included 50 cases of TBI which were divided into two groups of 25 each by the randomization technique and were treated either with autologous duraplasty (galea-pericranium) or nonautologous polypropylene (G-patch) dural substitute. The outcomes measured were time to duraplasty, blood loss, hospital stay, and the incidence of complications with the two techniques. The data were entered in a MS Excel spreadsheet and analysis was done using Statistical Package for Social Sciences (SPSS) version 21.0. A p value of < 0.05 was considered statistically significant.

Results The average time to harvest galea-pericranium was 5 minutes. Compared with the patients undergoing G-patch, the patients in group pericranium had comparable duraplasty time (minutes) (34.32 vs. 27.80, p = 0.44), significantly lower drain output (54.8 vs. 74.5, p = 0.017), comparable blood loss (322 vs. 308, p = 0.545), comparable blood transfusion (24% vs. 16%, p = 0.48), significantly lesser duration of hospital stay (8.6 vs. 10.44, p = 0.028), comparable wound infection (8% vs. 16%, p = 0.384), and comparable cerebrospinal fluid (CSF) leak (0% vs. 8%, p = 0.149).

Conclusion The study showed that galea-pericranium and polypropylene dural patch are equally effective and safe dural substitutes in providing a dural seal to minimize the CSF leaks and infections among posttraumatic brain injury patients.
Simplified model and performance analysis for radiant cooling panel with serpentine tube arrangement and thin insulation layer for moisture control in tropical climate
Authors: Ahmad N A , Lim C W
Published: September 2020

Radiant cooling panel (RCP) is widely known to improve thermal comfort and has the potential for energy saving. However, when applied the system in countries with a tropical climate, a major issue arises which is condensation on the surface panel. In this paper, a simplified model of top insulated RCP panel with serpentine tube arrangement integrated with thin insulation layer is developed to predict its performance. The numerical model is based on the principle of superposition of heat resistance and validated by using simulation software. The result produced by both models shows a good match in which the relative error calculated were 1.3% and 2.7% for cooling capacity and surface mean temperature respectively. Thus, the correctness of the numerical model to determine the cooling capacity and surface mean temperature of radiant cooling panel is validated. The thickness of the thin insulation layer plays a significant role as moisture control while maintaining the cooling capacity at 767W for surface mean temperature of 18.2ºC. When comparing various materials used as the thin insulation layer in RCP, it is also found that RCP with gypsum used as the thin insulation layer demonstrates better performance in maintaining the cooling capacity of RCP while controlling moisture condensation.
Research on robot arm control based on Unity3D machine learning
Authors: Lin Mu , Shan Lijun , Zhang Yongchun
Published: September 2020

Based on the Unity3D engine, the article uses deep reinforcement learning strategies to train the robotic arm through the reward function, and realizes machine learning and intelligent control of the robotic arm. After training and learning, the robotic arm can quickly and accurately find movement point in the environment and has high environmental adaptability. The application of powerful deep reinforcement learning strategies and virtual reality technology in engineering technology teaching has improved the teaching effect and teaching efficiency of mechanical structure cognition, curriculum design and other teaching links.
Fatigue life analysis of key equipment for high temperature reactor under variable working conditions
Authors: Chen Wen , Zhang Yanpeng , Qing Chen , Geng Jie
Published: September 2020

For the high temperature reactor with helium gas in the nuclear power plant, this paper has analysed the stress changes and temperature changes of the key equipment in the reactor under the changing conditions of the actual operation of the critical equipment [1-3]. Based on the threshold value that can satisfy the normal work, according to the expansion mechanism of fatigue crack in fracture mechanics, combined with the actual material parameters of the inner rod, this paper has prejudged the critical location or key products in the equipment, and the location and timing of their work tolerance limits. This paper has also calculated their residual fatigue life. It has certain guiding significance for the calculation of residual fatigue life of proprietary equipment in high temperature gas cooled reactor.
Echo signal simulation system
Authors: Gao Feng , Zhang Yang , Wang Zhenshan , Li Guijuan
Published: September 2020

In order to meet the demand of realistic simulation for complex target echo signal in water, the indirect method of frequency domain is employed to simulate the target echo signal in this paper. The plate element method is first used to forecast complex target echo characteristics in typical water. After generating frequency response function data, the data is imported into the echo signal simulation system. The system adopts FPGA real-time signal processing system based on PXIe bus. It receives hydrophone output signal by A/D sampling, extracts the incident acoustic signal and makes frequency domain transformation. After multiplying the transformed signal and frequency response function, scattering echo spectrum is obtained. And then the time domain transformation is made to get the time series of the echo signal. The series is loaded into the transmitting transducer by the power amplifier and the echo signal is simulated. The system has the high fidelity of the model, stable and reliable hardware system, and software system for easy operation.
Dynamic analysis of ISD suspension based on mechanical impedance
Authors: Xu Long , Chen Yijie , Du Fu , Zhang Zichao , Wang Le
Published: September 2020

The development of inerter has brought rapid development of vehicle suspension’s configuration design. More and more inerter vibration isolation networks have been proposed by scholars. As vibration isolation networks became more complex, traditional dynamic model calculations became difficult. So, a mechanical impedance dynamic model was proposed in this paper, which can be applied to the suspension of different vibration isolation networks. At the same time, the influence of the inerter on the frequency of the three-element parallel ISD suspension was studied, which provides a basis for the selection of suspension parameters.
Kinematic analysis and simulation of human upper limb rehabilitation training mechanism
Authors: Mei Ying , Yin Jiaojiao , Shen Zuo
Published: September 2020

A rehabilitation training mechanism of human upper limb is proposed, it consists of the 3-RRS parallel mechanism and the crank-rocker mechanism. First, their degrees of freedom are analyzed. Then, their kinematics are analyzed by analytical method. Finally, the 3-RRS parallel mechanism and the crank-rocker mechanism are simulated with the software UG and SolidWorks respectively, the results of simulation show that the movement path of the handle on the moving platform of the 3-RRS parallel mechanism coincides with the trajectory of the human arm, it can be used for the rehabilitation training of the human shoulder joint. For the crank-rocker mechanism, the center angles of movement path of the rocker and the handle on the connecting-rod are within the range of motion angles of human elbow joint and wrist joint, it can be used for the rehabilitation training of the elbow and wrist joints. They will all produce soft impulses at the beginning and end points, and the soft impulses will increase as the rotating speed of the driving links increases, so their driving links must rotate at a lower speed.
Model research on NOX emission of an ultra-supercritical circulating fluidized bed boiler
Authors: Zhang Peng , Wang Hu , Xin Shengwei , Hu Changhua , Cao Peiqing , Du Jiajun
Published: September 2020

It requires that coal-fired generator units to meet ultra-low emission standards by 2020 in policy of environmental protection in China. Compared with pulverized coal boiler, circulating fluidized bed (CFB) boiler technology has the natural advantage of low NOX emission, which has the ability to directly realize ultra-low NOX emission inside the furnace. To accurately obtain NOX emission characteristics in an ultra-supercritical CFB boiler under construction, model research and experimental verification of NOX emission prediction were carried out in this paper. The results indicate that three models could all predict NOX emission in the CFB boiler, and the deviation among the predicted values calculated by these models can be controlled within 15%. When an ultra-supercritical CFB boiler burns existing engineering coal, NOX emission would be higher than 50 mg/Nm3, which requires structural improvement and operation parameters optimization to ensure that NOX emission inside the furnace of the CFB boiler could directly reach the ultra-low emission standard.
Co-simulation analysis of the single stage screw feedback digital hydraulic cylinder
Authors: Ma Changlin , Hao Lin , Gao Yunguang , Han Yangyang
Published: September 2020

Taking the single-stage spiral feedback digital hydraulic cylinder as the research object, on the basis of analyzing its composition and mechanical feedback mechanism, we explored the idea of collaborative simulation based on AMESim and Simulink software, and finally realized the collaborative simulation of digital hydraulic cylinder. In this simulation, we use AMESim software to build the mechanical and hydraulic models, Simulink software to build the step-in motor model, and integrate the hydraulic model into the Simulink platform environment through the software interface. We can easily change the parameters to analyze its performance, and provide a convenient way for digital hydraulic cylinder performance optimization research.
Submodelling method for modelling and simulation of high-density electronic assemblies
Authors: Kong Lingsong , Yao Quanbin , Lv Xiaorui , Zhao Wenzhong
Published: September 2020

In order to enable the computation of fatigue life prediction of high-density electronic assemblies (solder joints > 4000), a modified submodelling approach was developed to integrate the detailed interconnections into equivalent layers with consistent mechanical parameters and thus reduce the complexity of modeling and simulation. The approach incorporates the uniform equivalent interconnect layers into the global model and simulate the general system response to thermo-mechanical loads. Displacements calculated from this first simulation are fed into a local model with more details of worst-case solder joints, in order to obtain local indicator of fatigue life. In this paper, referred to mechanical experimental methodology, a FEA process was used to extract the mechanical parameters of the equivalent layer. The validity of the modified submodelling approach was verified on fatigue life prediction of a high-density flip-chip package under thermal cycling.
Development and application of online load measurement system for hanger and support
Authors: Wan Yu , Liu Xubi , Jin Chuanling , Yin Jiyang
Published: September 2020

It was difficult to monitor the load and evaluate the performance of the hanger and support of power plant. The online load measurement system for hanger and support was developed and some experiments had been carried out. Compared with the offline bench performance testing machine, the experimental results showed that the average measurement error of the online measurement system was less than 1%. It can effectively measure the performance parameters of the hanger, conveniently and reliably monitor the real-time load of the hanger, which is important for the safe operation of the hanger and the steam/water pipeline in the power plant.