bluuebunny/crossref_metadata_2025_split huggingface dataset:
Z‐source inverter topologies with switched Z‐impedance networks: A review
Authors: Subhani Nafis , Kannan Ramani , Mahmud Apel , Blaabjerg Frede 
Published: January 2021

AbstractThe Z‐source inverter is one of the most interesting power electronic converters. Over the past decades, research and development have been in high demand to meet the challenges for improving the converter performance with reduced weight and cost while having high efficiency along with high gain or boost factor. Since the inception, tons of resolutions, customizations, and improvements have appeared to achieve these performance goals. To overcome the most common drawback, i.e. the low boost factor of classical Z‐source inverters, the switched inductor/capacitor and switched boost Z‐source inverter topologies have become predominant in the recent epoch. Furthermore, the higher component voltage stress, discontinuous input current, and high inrush start‐up current issues have also been addressed and solved in various literature as part of this topical advancement. In this study, a comprehensive review of various switched impedance network‐based Z‐source inverter topologies has been accomplished for providing a quick report to researchers and engineers so that they can consider this as a one‐stop solution for selecting inverters from this group. The overall study covers the methodology, features, and relevant important results of the latest switched Z‐source inverter models in order to demonstrate the coordination between pitfalls and improvements.
A non‐isolated single‐input dual‐output boost DC–DC converter
Authors: Farhadi‐Kangarlu Mohammad , Moallemi Khiavi Abdolhamid , Neyshabouri Yousef 
Published: January 2021

AbstractA new non‐isolated single‐input dual‐output boost DC–DC converter is introduced in this paper. The motivation of the work is that in various applications such as some multilevel converters, it is required to provide multiple dc sources that are not required to be isolated. In the proposed structure, the output ports of the converter can provide different values of power and still balance the output voltage. Even, if required, the output voltages can be set to different values. From practical point of view, the proposed topology uses minimum number of power‐electronic switches (two switches for two outputs) which have common ground making their drive circuit simple and easy to implement. The state‐space modelling of the proposed converter is presented, then, the model is used to design the passive elements. Moreover, the proposed converter is compared with the relevant converters. In order to verify the performance of the proposed DC–DC converter, a prototype of the converter has been implemented and the results are presented.
Decentralized stochastic programming for optimal vehicle‐to‐grid operation in smart grid with renewable generation
Authors: Wang Yue , Liang Hao , Dinavahi Venkata 
Published: January 2021

AbstractThis paper presents a decentralized stochastic programming operation scheme for a vehicle‐to‐grid system in a smart grid, which includes a series of equipment with random power generation and demands. For households with electric devices, renewable solar power generation, energy storage systems and electric vehicles, we consider utility operating expenses, including power loss and energy consumption cost as the objective function. For customers, we consider the cost of electricity, including battery degradation. To investigate the uncertainty of the devices, a bottom‐up approach is proposed to develop a random device usage model for analyzing customers' uncertain behaviour. Besides, a random renewable power generation model and an electric vehicle random driving model are implemented. The proposed approach is implemented with OpenMP to simulate the decentralized process on a multi‐core CPU while reducing the computational burden. A case study based on the IEEE 33‐bus distribution system with different scenarios is used to evaluate the performance of the proposed approach. The simulation results show that by introducing an optimal household operation schedule, the expense of distribution system utility company can be reduced in which both customers and operators can benefit from the optimization of the system schedules.
Impact of renewable energy sources on modelling of bidding strategy in a competitive electricity market using improved whale optimization algorithm
Authors: Sahoo Abhilipsa , Hota Prakash Kumar 
Published: January 2021

AbstractIn a competitive power market, generating utilities can be enhanced to achieve maximum profit by implementing a process of bidding strategy. Now‐a‐days renewable sources like solar and wind have become better alternatives significantly than other sources prior to power generation. These sources have extensive utilisation day‐by‐day in power sector and their impact in developing precise bidding strategies is getting more challenging aspect in the market. Since these renewable sources possess intermittent nature and undergo many uncertainties, the generating utilities encounter an unavoidable problem. Taking these aspects into consideration, attempts have been made using improved whale optimization algorithm to make the bidding strategy model for maximizing the power supplier's profit. Weibull and Beta distribution functions are used for modelling the stochastic characteristics of wind‐speed profile and solar‐irradiation, respectively. The proposed technique is tested and clarified with an IEEE‐30, IEEE‐57 and practical 75‐bus Indian system. The outcomes of this method were taken into comparison with other optimization techniques and found that it has an advantage upon other methods in solving bidding problems. Further, it is observed that the impact of renewable sources on bidding strategy reduces the market clearing price and the generation of thermal power while increases the total bidding power.
Enhanced modelling of doubly fed induction generator in load flow analysis of distribution systems
Authors: C.V.S. Anirudh , V Seshadri Sravan Kumar 
Published: January 2021

AbstractThis paper presents an accurate framework for incorporating the doubly fed induction generator based wind farms in load flow analysis of distribution systems. The proposed model for doubly fed induction generator is based on an accurate equivalent circuit and also takes into consideration the voltage dependent reactive power limits associated with the doubly fed induction generator. In addition, the developed approach is capable of handling a doubly fed induction generator operating in either maximum power point tracking or non‐maximum power point tracking modes. The proposed PQ model of doubly fed induction generator easily fits into the forward–backward technique that is typically employed for obtaining the load flow solution of distribution networks. Test results on 19‐bus and 133‐bus systems are reported to indicate the effectiveness of the proposed approach.
Sub‐Nyquist receiver using sampling frequency and instant offsets
Authors: Cheng Chi‐Hao , Dye Gregory , Pennington Jason 
Published: January 2021

AbstractWith rapid advance in analogue‐to‐digital converters, more analogue‐to‐digital converters in the market can cover multiple Nyquist zones. As a result, the implementation of a sub‐Nyquist receiver designed to cover a bandwidth wider than what is dictated by Nyquist theory has become more feasible than ever. This article presents a sub‐Nyquist receiver using both different sampling rates and an offset at sampling instant. Compared with other sub‐Nyquist receivers, the proposed design is straightforward to implement and can avoid issues conventional sub‐Nyquist receivers encounter at the presence of multiple signals.
ANFIS‐fuzzy logic based UPQC in interconnected microgrid distribution systems: Modeling, simulation and implementation
Authors: Renduchintala Udaya K. , Pang Chengzong , Tatikonda Krishna M. , Yang Lin 
Published: January 2021

AbstractThis study focuses on the improvement of the power quality in interconnected power distribution systems using connected microgrids. The power quality issues at the secondary distribution level are addressed using a unified power quality conditioner, which aids in controlling voltage imbalances and current harmonics. Further, a power control method, adaptive network‐based fuzzy inference system, is proposed as a global solution by installing independent compensating devices at the point of common coupling. The proposed strategy can improve the power quality in traditional installations because the proposed unified power quality conditioner method maximizes power utilization and improves the efficiency of the system. The microgrids integrate renewable energy sources, which generate green energy with low loss. Case studies, a prototype, and simulations via MATLAB/Simulink are used to validate the proposed method, and the results prove the enhancement in power quality control. The proposed control strategy had a response time of 0.3 s, reduced peak voltage distortions, and restored the voltage at the interconnecting point to a normal level. The total harmonic distortion of currents decreased from 21.13% to 14.74% when a PI technique was used to control the UPQC‐P, and the proposed adaptive network‐based fuzzy inference system‐based UPQC‐P reduced the harmonic content to 2.43% from 21.13%.
A novel path planning algorithm for mobile robot in dynamic environments using modified bat swarm optimization
Authors: Ajeil Fatin Hassan , Ibraheem Ibraheem Kasim , Humaidi Amjad J. , Khan Zeashan Hameed 
Published: January 2021

AbstractThis paper describes the path planning of an autonomous mobile robot using an advanced version of the swarm bat algorithm in a time‐varying situation. The foremost objective of this present contribution is to acquire the shortest path between the initial and end‐point avoiding dynamic obstacles. In this work, an adaptation of the frequency parameter of the standard bat algorithm to develop an improved version known as the modified frequency bat (MFB) algorithm is proposed. The modified frequency bat algorithm works in two steps, in the first step, the robot path is generated when there are no obstacles in the environment using the proposed method. As soon as an obstacle is detected near the robot, the second mode is initiated to avoid any obstacle. Extensive simulations are performed to validate the effectiveness of the proposed modified frequency bat algorithm by implementing it on standard benchmark functions and path planning problems and simultaneously matching its performance with the original bat algorithm. It has been concluded that the modified frequency bat algorithm shows superior performance as compared to the standard bat algorithm by drawing a shorter and collision‐free path for the mobile robot path‐planning problem.
Fast and robust motion averaging via angle constraints of multi‐view range scans
Authors: Zhang Xin , Zhang Yan , Qu Chengzhi , Tan Zhuangbin 
Published: January 2021

AbstractThe motion averaging problem arises when recovering the motions for a set of scans in three‐dimensional (3D) reconstruction. Motion averaging is taken as an optimisation problem, whose solution can be obtained via matrix decomposition in principal component analysis. The latest motion averaging methods utilize the Cauchy kernel function or overlap rate to construct the weighted matrix in the cost function, yielding weighted low‐rank sparse matrix decomposition solutions. Nevertheless, the over‐reliance on the initial value and high computational complexity remain two major problems. Here, we aim to improve the motion averaging performance via a fast and robust method based on the angle constraints of multiple scans. The additional term representing the angle constraint is added into the original cost function. By doing this, two benefits are facilitated: 1) the iteration times for the optimisation process are reduced; and 2) it effectively mitigates the over‐reliance on the initial value and thus caters for outliers and random noise of initial motions. Compared with state‐of‐the‐art motion averaging methods, it is indicated that the proposed method is more efficient and robust for numerical simulations of using both simulated motions and real 3D scanning data, given a large range of angle constraint values.
Outflows, envelopes, and disks as evolutionary indicators in Lupus young stellar objects
Authors: Vazzano M. M. , Fernández-López M. , Plunkett A. , de Gregorio-Monsalvo I. , Santamaría-Miranda A. , Takahashi S. , Lopez C. 
Published: January 2021

Context.The Lupus star-forming complex includes some of the closest low-mass star-forming regions, and together they house objects that span evolutionary stages from prestellar to premain sequence.Aims.By studying seven objects in the Lupus clouds from prestellar to protostellar stages, we aim to test if a coherence exists between commonly used evolutionary tracers.Methods.We present Atacama Large Millimeter Array (ALMA) observations of the 1.3 mm continuum and molecular line emission that probe the dense gas and dust of cores (continuum, C18O, N2D+) and their associated molecular outflows (12CO). Our selection of sources in a common environment, with an identical observing strategy, allows for a consistent comparison across different evolutionary stages. We complement our study with continuum and line emission from the ALMA archive in different bands.Results.The quality of the ALMA molecular data allows us to reveal the nature of the molecular outflows in the sample by studying their morphology and kinematics, through interferometric mosaics covering their full extent. The interferometric images in IRAS 15398-3359 appear to show that it drives a precessing episodic jet-driven outflow with at least four ejections separated by periods of time between 50 and 80 yr, while data in IRAS 16059-3857 show similarities with a wide-angle wind model also showing signs of being episodic. The outflow of J160115-41523 could be better explained with the wide-angle wind model as well, but new observations are needed to further explore its nature. We find that the most common evolutionary tracers in the literature are useful for broad evolutionary classifications, but they are not consistent with each other to provide enough granularity to disentangle a different evolutionary stage of sources that belong to the same Class (0, I, II, or III). The evolutionary classification revealed by our analysis coincides with those determined by previous studies for all of our sources except J160115-41523. Outflow properties used as protostellar age tracers, such as mass, momentum, energy, and opening angle, may suffer from differences in the nature of each outflow and, therefore, detailed observations are needed to refine evolutionary classifications. We found both AzTEC-lup1-2 and AzTEC-lup3-5 to be in the prestellar stage, with the possibility that the latter is a more evolved source. IRAS 15398-3359, IRAS 16059-3857, and J160115-41523, which have clearly detected outflows, are Class 0 sources, although, we are not able to determine which is younger and which is older. Finally Sz 102 and Merin 28 are the most evolved sources in our sample and show signs of having associated outflows, which are not as well traced by CO as for the younger sources.
The role of stochastic and smooth processes in regulating galaxy quenching
Authors: Kipper Rain , Tamm Antti , Tempel Elmo , de Propris Roberto , Ganeshaiah Veena Punyakoti 
Published: January 2021

Context. Galaxies can be classified as passive ellipticals or star-forming discs. Ellipticals dominate at the high end of the mass range, and therefore there must be a mechanism responsible for the quenching of star-forming galaxies. This could either be due to the secular processes linked to the mass and star formation of galaxies or to external processes linked to the surrounding environment. However, the contribution from these smooth and stochastic processes to galaxy quenching has yet to be quantified.
Aims. In this paper, we analytically model the processes that govern galaxy evolution and quantify their contribution. The key advantage of our method is that we do not assume the strength of the contribution from any of these processes beforehand, but instead aim to find their efficiencies. We have specifically studied the effects of mass quenching, gas stripping, and mergers on galaxy quenching.
Methods. To achieve this, we first assumed a set of differential equations that describe the processes that shape galaxy evolution. We then modelled the parameters of these equations by maximising likelihood. These equations describe the evolution of galaxies individually, but the parameters of the equations are constrained by matching the extrapolated intermediate-redshift galaxies with the low-redshift galaxy population. In this study, we modelled the processes that change star formation and stellar mass in massive galaxies from the GAMA survey between z ≈ 0.4 and the present.
Results. We identified and quantified the contributions from mass quenching, gas stripping, and mergers to galaxy quenching. By modelling mass quenching, we found that quenching begins for galaxies above a mass of ≈1010.2 M⊙, but is dependent on the gas accretion rate before quenching. The quenching timescale is on average 1.2 Gyr and a closer look reveals support for the slow-then-rapid quenching scenario. The major merging rate of galaxies is about once per 10 Gyr, while the rate of ram pressure stripping is significantly higher. In galaxies with decreasing star formation, we show that star formation is lost to fast quenching mechanisms such as ram pressure stripping and is countered by mergers, at a rate of about 41% Gyr−1 and to mass quenching 49% Gyr−1. Therefore, slow quenching mechanisms have a greater influence on galaxies in group or cluster environments than fast quenching mechanisms.
Effects of erupting magnetic flux rope on running penumbral waves
Authors: Wang Wensi , Liu Rui 
Published: January 2021

Context. It is widely known that solar flares have a substantial impact on the low atmosphere but the matter of how they affect sunspot waves and oscillations is generally unknown. In addition, there are ongoing debates on whether the flare-induced photospheric changes are due to the momentum conservation with coronal mass ejections or to magnetic reconnection.
Aims. To shed light on the so-called “back reaction” of solar eruptions, we investigated how running penumbral waves (RPWs) at one foot of an erupting magnetic flux rope (MFR) respond to the rope buildup and subsequent erosion.
Methods. We used UV/EUV images from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory (SDO) to explore the changing behaviors of RPWs in response to the MFR evolution, as well as 135-s vector magnetograms from the SDO Helioseismic and Magnetic Imager to analyze the changes in photospheric magnetic field during the eruption.
Results. During the rope buildup stage, the western foot of the rope, which is completely enclosed by a hooked ribbon, expands rapidly and consequently ends up overlapping a sunspot penumbra. This converts the original penumbral field into the rope field, which is associated with a transient increase in electric currents flowing through the ribbon-swept penumbral region. During the rope erosion stage, the rope foot shrinks as the eastern section of the hooked ribbon slowly sweeps the same penumbral region, where the rope field is converted into flare loops. This conversion induces mixed effects on the photospheric field inclination but heats up the low atmosphere at the footpoints of these flare loops to transition-region temperatures, therefore resulting in the post-eruption RPWs with an enhanced contrast in the 1600 Å passband and an extended bandwidth to low frequencies at 3–5 mHz, compared with the pre-eruption RPWs that peak at 6 mHz.
Conclusions. This observation clearly demonstrates that it is the magnetic reconnection in the corona that impacts the low atmosphere and leads to the changing behaviors of RPWs, which, in turn, offer a new window onto diagnosing flare reconnections.
Constraining millisecond pulsar geometry using time-aligned radio and gamma-ray pulse profile
Authors: Benli Onur , Pétri Jérôme , Mitra Dipanjan 
Published: January 2021

Context. Since the launch of the Fermi Gamma-Ray Space Telescope, several hundred gamma-ray pulsars have been discovered, some being radio-loud and some radio-quiet with time-aligned radio and gamma-ray light curves. In the second Fermi Pulsar Catalogue, 117 new gamma-ray pulsars have been reported based on three years of data collected by the Large Area Telescope on the Fermi satellite, providing a wealth of information such as the peak separation Δ of the gamma-ray pulsations and the radio lag δ between the gamma-ray and radio pulses.
Aim. We selected several radio-loud millisecond gamma-ray pulsars with period P in the range 2–6 ms and showing a double peak in their gamma-ray profiles. We attempted to constrain the geometry of their magnetosphere, namely the magnetic axis and line-of-sight inclination angles for each of these systems.
Method. We applied a force-free dipole magnetosphere from the stellar surface up to the striped wind region – well outside the light cylinder – to fit the observed pulse profiles in gamma-rays, consistently with their phase alignment with the radio profile. In deciding whether a fitted curve is reasonable or not, we employed a least-square method to compare the observed gamma-ray intensity with that found from our model, emphasising the amplitude of the gamma-ray peaks, their separation, and the phase lag between radio and gamma-ray peaks.
Results. We obtained the best fits and reasonable parameters in agreement with observations for ten millisecond pulsars. Eventually, we constrained the geometry of each pulsar described by the magnetic inclination α and the light-of-sight inclination ζ. We found that both angles are larger than approximately 45°.
Successful Replantation of Tamai Zone I Amputation with Delayed Vein Repair
Authors: Özkan Burak , Uysal Ahmet Çagri , Markal Ertas Nilgün 
Published: January 2021

ZusammenfassungDie Rekonstruktion digitaler Venen ist eine der schwierigsten Phasen der Endgliedreplantation. Distal lokalisierte digitale Venen haben ein kleines Gefäßkaliber und kollabierte Lumina, so dass sie nur schwer zu identifizieren und zu versorgen sind. Digitale Venen sind gelegentlich auch in den ersten Minuten nach der arteriellen Anastomose nicht erkennbar. In dieser Situation kann der Patient einige Stunden nach der Revaskularisierung erneut in den Operationssaal gebracht werden, um die dann erweiterten Venen sekundär zu rekonstruieren. Die verzögerte Rekonstruktion digitaler Venen ist eine zuverlässige und alternative Methode zur Replantation ohne Venennaht. In diesem Bericht wird eine erfolgreiche Replantation mit verzögerter Rekonstruktion digitaler Venen in der Tamai Zone I vorgestellt.
Spinal Tuberculosis
Authors: Heyde Christoph Eckhard , Lübbert Christoph , Wendt Sebastian , Rodloff Arne , Völker Anna , von der Höh Nicolas H. 
Published: January 2021

AbstractTuberculosis is one of the most common infectious diseases worldwide. The
frequency in Germany is low, however, an increase has been observed in the past
few years. The incidence of extrapulmonary manifestation accounts for up to 10
to 20%. In 50% of these cases the spinal column is affected. Although literature
reveals worldwide experiences in the treatment, in Germany spinal tuberculosis
remains a rarity. Different pitfalls and specific characteristics regarding
diagnosis and therapy are to consider. Therefore, a presentation of these
specifics and their discussion based on the available literature will be
presented. The purpose is to achieve an increase in awareness regarding this, in
our latitudes, rare disease.