bluuebunny/crossref_metadata_2025 huggingface dataset:
Recent advances in traffic optimisation: systematic literature review of modern models, methods and algorithms
Authors: Aleksander Rydzewski , Paweł Czarnul
Published: February 2021

Over the past few decades, the increasing number of vehicles and imperfect road traffic management have been sources of congestion in cities and reasons for deteriorating health of its inhabitants. With the help of computer simulations, transport engineers optimise and improve the capacity of city streets. However, with an enormous number of possible simulation types, it is difficult to grasp valuable, innovative solutions which are of the greatest value to city citizens. In this work, the authors expose various problems within this area having reviewed and analysed over 130 papers selected out of 1200 works in the field of urban simulations. The study describes the selection process of important papers and highlights characteristics of microsimulations, macrosimulations, computation optimisations and other approaches found in the literature which are especially useful and should be further built on in the future. They present and compare results provided in reviewed works in terms of throughput improvement, queue, waiting and travel time reduction, vehicle speed increase, speed‐ups as well as assumed simulation parameters. Finally, they focus on research gaps, such as a small number of works considering crisis simulations, few real‐world scale simulations as well as on software architectural changes and low‐level optimizations.
Real‐time estimation and prediction of lateral stability of coaches: a hybrid approach based on EKF, BPNN, and online autoregressive integrated moving average algorithm
Authors: Fu Rui , Zhang Hailun , Guo Yingshi , Yang Fei , Lu Yuping
Published: February 2021

This study aimed to develop a coach state estimation and prediction system to enhance driving safety. Different from existing vehicle stability estimation studies, the authors propose a hybrid method to estimate and predict the state of a coach in real time. First, the vehicle sideslip angle and yaw rate are estimated by a three‐degrees‐of‐freedom vehicle model combined with an extended Kalman filter (EKF) estimation algorithm. Then, a steering system is established that replaces the front‐wheel angle with the steering wheel input torque. Next, a seven‐degrees‐of‐freedom vehicle model analyses the effects of various driving influencing factors on the vehicle sideslip angle and the boundary of the stable region of the phase plane of the vehicle sideslip angle rate, and a boundary value parameter database is obtained. A back propagation neural network (BPNN) model is then established to obtain the boundary function parameter values under multifactor coupling conditions. Furthermore, an online prediction of the steering wheel input torque in a time series is done, and the prediction value is input to the steering system and neural network model. The effectiveness of the proposed method was evaluated via simulations based on MATLAB/Simulink and TruckSim software.
Directionality‐centric bus transit network segmentation for on‐demand public transit
Authors: Perera Thilina , Wijesundera Deshya , Wijerathna Lahiru , Srikanthan Thambipillai
Published: February 2021

The recent growth in real‐time, high‐capacity ride‐sharing has made on‐demand public transit (ODPT) a reality. ODPT systems serving passengers using a vehicle fleet that operates with flexible routes, strive to minimise fleet travel distance. Heuristic routing algorithms have been integrated in ODPT systems in order to improve responsiveness. However, route computation time in such algorithms depends on problem complexity and hence increases for large scale problems. Thus, network segmentation techniques that exploit parallel computing have been proposed in order to reduce route computation time. Even though computation time can be reduced using segmentation in existing techniques, it comes at the cost of degradation of route quality due to static demarcation of boundaries and disregarding real road network distances. Thus, this work proposes, a directionality‐centric bus transit network segmentation technique that exploits parallel computation capable of computing routes in near real‐time while providing high scalability. Additionally, a dynamic fleet allocation algorithm that exploits proximity and flexibility to minimise vehicle detours while maximising fleet utilisation is proposed. Experimental evaluations on a real road network confirm that the proposed method achieves notable speed‐up in flexible route computation without compromising route quality compared to a widely used unsupervised learning technique.
Multi‐task deep learning with optical flow features for self‐driving cars
Authors: Hu Yuan , Shum Hubert P. H. , Ho Edmond S. L.
Published: February 2021

The control of self‐driving cars has received growing attention recently. Although existing research shows promising results in the vehicle control using video from a monocular dash camera, there has been very limited work on directly learning vehicle control from motion‐based cues. Such cues are powerful features for visual representations, as they encode the per‐pixel movement between two consecutive images, allowing a system to effectively map the features into the control signal. The authors propose a new framework that exploits the use of a motion‐based feature known as optical flow extracted from the dash camera and demonstrates that such a feature is effective in significantly improving the accuracy of the control signals. The proposed framework involves two main components. The flow predictor, as a self‐supervised deep network, models the underlying scene structure from consecutive frames and generates the optical flow. The controller, as a supervised multi‐task deep network, predicts both steer angle and speed. The authors demonstrate that the proposed framework using the optical flow features can effectively predict control signals from a dash camera video. Using the Cityscapes data set, the authors validate that the system prediction has errors as low as 0.0130 rad/s on steer angle and 0.0615 m/s on speed, outperforming existing research.
High step‐up DC–DC converter composed of quadratic boost converter and switched capacitor
Authors: Rezaie Milad , Abbasi Vahid , Kerekes Tamas
Published: February 2021

This study proposes a high step‐up DC–DC converter which is composed of a conventional quadratic boost converter, a switched capacitor and a coupled inductor. To reduce the number of components, the primary side of the coupled inductor is shared with the quadratic boost converter as one of its inductors. Furthermore, the output capacitor of the quadratic boost converter is divided into two capacitors and one of them is utilised in common with the switched capacitor. The converter is analysed and the obtained equations are used to compare the proposed converter with other converters which have similar structures. According to the comparisons, the proposed converter has advantages such as higher voltage gain, the lower voltage stress on the power switch and requiring a smaller inductor. In addition, the input source current is continuous and there is a common ground between the source and load. Increasing the turn ratio of the coupled inductor causes reduction of voltage stress on the power switch, diodes and capacitors. To investigate performance of the proposed converter, an 80 W prototype is built. The experiments show good accordance with the analysis and they demonstrate the high step‐up capability of the proposed converter.
First‐order integral switching surface sliding‐mode control method of active front end rectifier for fast charger applications
Authors: Nahavandi Ramin , Asadi Mehdi , Guerrero Josep M.
Published: February 2021

This study proposes a control technique based on integral switching surface sliding‐mode control for three‐phase pulse‐width modulation (PWM) rectifier. The proposed control system is based on the combination of a conventional proportional–integral (PI) controller and with two decoupled first‐order sliding‐mode (PI‐FOSM) current controller. A set of integral switching surfaces based on the state‐space equation are designed in the internal loop to force the grid currents to track their desired values. The proposed control approach improves the transient response and minimises the steady‐state error under uncertainty. In addition, a conventional PI controller is also employed for the voltage regulation loop and generating the current reference of inner loops. In the controller design, all parameters of the system are considered with bounded perturbations in the design of control law. The main advantage of the proposed controller is robustness property against variations of entertained PWM rectifier parameters and external disturbances. The proposed PI‐FOSM can improve transient performance and can decrease of the harmonic components under steady‐state condition. In order to validate the theoretical contributions of this study, the performance of the proposed controller has been investigated by using a prototype laboratory.
Analysis and implementation of a generalised switched‐capacitor multi‐level inverter having the lower total standing voltage
Authors: Majumdar Saikat , Mahato Bidyut , Jana Kartick Chandra
Published: February 2021

Most of the switched capacitor multi‐level inverters (SC‐MLIs) are designed with a single isolated voltage source and capacitors where voltage levels are obtained by the addition of these sources only. The common problems arise in SC‐MLIs are an unequal number of conducting paths, higher voltage drop across capacitors, sum of total inverter DC link voltages across the highest voltage rated switches and higher total standing voltage (TSV). The motivation of this work is to design a hybrid generalized SC‐MLI with reduced components aiming to maintain a constant voltage across the capacitors, to achieve higher voltage gain with minimum components used, minimum conducting paths, lower TSV, cost‐effective and an efficient inverter. A generalised SC‐MLI structure is also proposed, which can multiply the voltage across the capacitors in a binary asymmetrical manner. The design parameters of the proposed hybrid SC‐MLI topology are compared with the recently developed SC‐MLIs in terms of the number of switches, capacitors, TSV, conducting switches and industrial components cost to prove its superiority and effectiveness of the proposed inverter. The experimental prototype of a specimen 9‐level and 17‐level inverters are implemented using DS1103 and the corresponding results are presented.
Simplified hybrid space vector modulation for multilevel diode clamped converter
Authors: Bouzidi Mansour , Barkat Said , Krama Abdelbasset
Published: February 2021

This study proposes a new simplified hybrid space vector modulation (HSVM) algorithm for multilevel diode clamped converter (DCC). The main idea consists in combining the advantages of both space vector modulation (SVM) algorithms synthesised in abc and αβ coordinates to establish a new hybrid, simplified and generalised SVM algorithm. The HSVM algorithm offers a simple method to compute the duration time, automatic generation of all redundant states of the adjacent switching vectors without triangles identification stage and switching sequence definition for any DCC level. Moreover, all the computational processes are performed in one unique sector thanks to the proposed new reference voltage vector defined in abc‐coordinates. The proposed algorithm does not require any coordinates transformation or lookup tables. Also, it can be implemented with minimum computational burden using a low resources digital platform. The proposed HSVM is verified through MATLAB simulation and validated experimentally using three‐level DCC laboratory prototype. For high‐level DDC, the HSVM is tested in real time using hardware‐in‐the loop testing technology. Different case studies are performed to demonstrate the high performance of the proposed HSVM and its ability in lowering the computational resources requirement.
Single‐phase hybrid multilevel inverter topology with low switching frequency modulation techniques for lower order harmonic elimination
Authors: Siddique Marif Daula , Bhaskar Mahajan Sagar , Rawa Muhyaddin , Mekhilef Saad , Memon Mudasir Ahmed , Padmanaban Sanjeevikumar , Almakhles Dhafer J. , Subramaniam Umashankar
Published: February 2021

A new single‐phase asymmetrical multilevel inverter (MLI) is presented in this study. The proposed topology generates a staircase output voltage waveform with a maximum number of levels using less number of components compared to several existing and recent topologies. The basic module consists of a combination of two isolated DC sources with ten switches that produce all the possible number of levels. Other advantages of the proposed MLI include improved output voltage performance and a low blocking voltage of the switches. The low switching frequency pulse width modulation (LSF‐PWM) technique has been used for the generation of gate pulses. In the LSF technique, selective harmonic elimination (SHE) and fundamental switching frequency PWM techniques have been discussed for the better output voltage waveform. The optimised switching angles with SHEPWM has been calculated using particle swarm optimisation considering the different combination of the elimination of lower order harmonics. Simulation work was carried out using MATLAB/SIMULINK, and a prototype was implemented to validate the proposed MLI module. Simulation and experimental results have been provided in the study to show the performance of the proposed topology with these modulation techniques.
Stability analysis and duty cycle limitation of grid‐connected current control strategy for multiple parallel three‐level T‐type grid‐connected inverters
Authors: Liu Jiang , Sun Xiangdong , Ren Biying , Zhang Qi
Published: February 2021

Multiple parallel three‐level T‐type inverters (3LT2Is) have become the trend in large‐power low‐voltage applications. In parallel operation of modular 3LT2Is, three aspects including current sharing control, circulating current suppression and neutral‐point potential (NPP) balance control should be considered. In this study, a grid‐connected current control strategy with the ability to independently adjust three control objectives is proposed for the multiple parallel three‐level T‐type grid‐connected inverters. The duty cycle limitation among current sharing, NPP balancing and circulating current and their influence are analysed in detail. The stability analysis of multi‐paralleled inverters on the basis of the single‐phase equivalent circuit is carried out considering the influence of circulating current. Experimental results prove the validity of the proposed control strategy.
Improvement of model predictive control for single‐phase inverters by using sinusoidal signal observers
Authors: Li Po , Li Ruiyu , Feng Haifeng , He Ying , Zhang Jingrui
Published: February 2021

Studies show that finite control set model predictive control (FCS MPC) is robust for single‐phase inverters in sinusoidal current tracking. That is, even if there are parameter uncertainties in inverter system, MPC can achieve accepted control performance. However, it is still necessary to reconstruct the unknown parameters. On the one hand, an accurate model is helpful to get better performance. On the other hand, accurate parameters can be used to determine the boundary of current reference. Relying on the strong robustness, under unknown offset free MPC (UOF MPC) frame, this study characterises the deviation of the parameters as an unknown sinusoidal signal, and designs two observers to reconstruct it. One is a linear observer for instantaneous value observation. The other is a time‐varying observer for the amplitude and phase identification. Its convergence is guaranteed by the Lyapunov function and the Laselle invariant set principle. All the proposed methods are validated by a rapid control prototype based on Labview FPGA platform. Moreover, experiments show that even if the reference exceeds the real maximum tracking current boundary, the proposed observers work well with accurate parameters identified and the reference can be adjusted online to avoid distorted current tracking.
Inductor‐based auxiliary circuit‐assisted ZVS in full‐bridge dc–dc converter for EV applications
Authors: Srivastava Manaswi , Tomar Pavan Singh , Verma Arun Kumar , Kanamarlapudi Venkata Ravi Kishore , Sandeep N.
Published: February 2021

This study proposes an efficient soft‐switched full‐bridge DC/DC converter (FBDC) topology operated with modified pulse width modulation (MPWM) for electric vehicle (EV) battery chargers, as the role of DC/DC converter is more prominent in on‐board charging. The proposed auxiliary circuit offers zero voltage switching (ZVS) turn‐on to all the active switches of the converter during full battery charging range. In consequence, the losses associated with the proposed FBDC are minimal and offer maximum efficiency as compared to available benchmark topologies operated with different gating schemes. The size of magnetic elements used in the proposed topology also reduced as to conventional FBDC operating with trailing edge pulse width modulation and phase shifted modulation gating techniques. A detailed designing and analysis of the MPWM operated ZVS FBDC is presented. Besides, the rationale behind the selection of switching frequency in order to ensure wide‐range ZVS is detailed. Further the proposed topology is compared with the other competent topologies for proving its significant merits. Simulation of the proposed configuration is performed at 3.3 kW. Following which, the experimental results obtained from a laboratory prototype of 500 W, 80 kHz validating the operability and feasibility of the proposed converter are presented.
Investigation of structure and performance of a permanent magnet vernier induction generator for use in double‐turbine wind systems in urban areas
Authors: Derakhshani Mohammad Mahdi , Ardebili Mohammad , Cheraghi Mohsen , Jafari Reza
Published: February 2021

In this study, a new double‐rotor permanent magnet vernier induction wind generator is proposed, which can be connected directly to a double‐turbine system used in urban areas. The proposed generator consists of a vernier machine and a squirrel‐cage induction machine, which includes a stator and two concentric rotors (a permanent magnet outer rotor and a squirrel‐cage inner one). Accordingly, first, the relationships governing the structures of each rotor are presented and investigated. Then, the performance of the generator connecting to a double‐turbine system is analysed. Optimisation of the presented generator is investigated by finite‐element analysis and also a laboratory prototype is constructed. Finally, both simulation and experimental results are compared, and the reliability of the proposed generator is validated.
Stability properties of non‐linear model predictive control of variable speed hydropower
Authors: Reigstad Tor Inge , Uhlen Kjetil
Published: February 2021

This study presents a method for small‐signal analysis of an advanced, multi‐variable control system for variable speed hydropower (VSHP) plants. A model predictive controller (MPC) optimises the power plant performance. In parallel, a virtual synchronous generator‐type (VSG) converter control ensures that the VSHP contributes to virtual inertia and frequency control of the power system. The aim of the small‐signal analysis is to parametrise the cost function of the MPC to minimise oscillatory modes between the VSHP hydraulic system and the power system. A state‐space representation of the MPC is developed by assuming a stable steady‐state operating point equal to the reference values of the MPC cost function, and that no constraints are active. This state‐space representation allows for small‐signal analysis of the power system, including the MPC. The results show that the modes between the hydraulic system and the power system are well‐damped and negligible when the costs of deviations in the hydraulic system are low compared to the cost of deviations in the VSG power reference. Thus, these modes do not constrain the tuning of the VSG. The VSHP power output can, therefore, be optimised independently through the VSG controller to damp power oscillations and reduce frequency deviations.
Frequency excursion mitigation strategy using a novel COA optimised fuzzy controller in wind integrated power systems
Authors: Sharma Mandeep , Dhundhara Sandeep , Arya Yogendra , Prakash Surya
Published: February 2021

The uncertain demeanour from wind generators and loads adversely affect the grid operational stability. Various control approaches have been explored to remedy the system uncertainties while maintaining generation and load demand balance. This study proposes a fuzzy‐based proportional–fractional integral–derivative with filter controller to sustain frequency stability in wind integrated power systems having different configurations. The controller parameters have been tuned using a recently developed coyote optimisation algorithm (COA). The proposed control approach is executed and validated on three distinct configurations of two‐area power systems. All test models are integrated with a doubly fed induction generator (DFIG) type wind turbine units (WTUs). Different case scenarios have been considered to analyse the efficacy of the proposed control strategy in the presence of WTU. Furthermore, the impact of inertial support delivered by the DFIG‐WTU and higher penetration of wind energy in the power system has been studied. The analysis reveals that the control scheme in coordination with WTU support reduces the stress on a wind turbine during the inertial control scheme and maintains the grid frequency stability under unexpected load disturbances. Stability and robustness analysis are also conducted to verify the validity of the introduced control approach.
Design of a fuzzy current‐sensor less maximum power point tracking algorithm for photovoltaic systems
Authors: Saremi Mohammad , Pourfarzad Hamed , Nemati Milad
Published: February 2021

In this study, a fuzzy current‐sensor less maximum power point tracking (MPPT) algorithm is presented. The algorithm proposed to improve the performance and reduce the cost of photovoltaic systems. The proposed algorithm creates the variable step‐size/variable frequency specification in the drift‐free single input voltage sensor (SIVS) method designing a reliable and widely used fuzzy control algorithm. The proposed algorithm will improve the SIVS methods employing the advantages of the fuzzy controllers in the MPPT algorithms based on the real and false error areas analysis concept developed by Tousi et al. (2016). The proposed method will detect exact drift conditions and move to the optimal setpoint at the maximum speed. The method selects the correct direction, appropriate step‐size, and suitable control frequency to increase dynamic efficiency against the drift condition. Also, the steady‐state efficiency of the algorithm will increase because of high‐frequency and low‐power oscillation performances. The proposed method will be simulated and compared in Matlab/Simulink environment and tested in laboratory conditions on the designed solar charge controller.
Analysis and optimisation of a diesel‐PV‐wind‐electric storage system for a standalone power solution
Authors: Adefarati Temitope , Bansal Ramesh C. , Naidoo Raj , Potgieter S. , Rizzo R. , Sanjeevikumar Padmanaban
Published: February 2021

The universal power demand is increasing every day because of population growth, industrial revolution and high standards of living. The renewable energy technologies (RETs) are environmental and cost‐effective solutions to satisfy dynamic load profile based on the application of multiple components of a standalone microgrid system that encompasses photovoltaic (PV), diesel generator (DG), electric storage system and wind turbine generator (WTG). This study reveals more insight into various research questions that have not been completely addressed in past investigations. The contributions of the study are expressed: (i) analyse the effects of RETs on the total cost, (ii) test the total benefits, (iii) estimate the market benefit share of the unit that reflects the benefit of one generation unit in proportion to the whole power system, (iv) maximise and minimise the yearly average power generated by (PV and WTG) and DG. This research work presents the application of fmincon optimising tool to accomplish the objectives of the study owing to some significant characteristics. The outcomes of the work show the validity of the model and can assist the utilities to minimise the costs that are identified with the optimal operation of their power systems.
Hybrid spoof surface plasmon polariton and substrate integrated waveguide bandpass filter with high out‐of‐band rejection for X‐band applications
Authors: Sangam Ramanand Sagar , Kshetrimayum Rakhesh Singh
Published: February 2021

Two bandpass filters based on hybrid spoof surface plasmon polariton (SSPP) and substrate integrated waveguide (SIW) are presented for X‐band applications, herein. The dispersion and transmission characteristics of the proposed hybrid SSPP‐SIW structures are analysed, and the influence on the variation of their structural parameters is investigated. The proposed dumbbell‐shaped SSPP shows more slow‐wave effects than the rectangle‐shaped SSPP for the same height of grooves, and hence could be a good choice in the design of compact, low loss and highly integrated microwave and terahertz devices. The lower and upper cut‐off frequencies of hybrid SSPP‐SIW bandpass filters can be adjusted independently by varying the structural parameters of SIW and SSPP units, respectively. The proposed two filters exhibit excellent passband (8–13.15 GHz for filter I and 8–13.5 GHz for filter II) and wide upper‐band rejection (>42.5 dB from 14.1 to 20 GHz for filter I and >41 dB from 14.2 to 19.5 GHz for filter II) simultaneously. Their size is very compact, amounts to only about 1λg × 0.7λg, where λg is the guided wavelength in the SIW at the centre frequency.
Turning waste makeup cotton to a hollow structured carbon as anode for high‐performance lithium ions batteries
Authors: Cheng Yayi , Huang Jianfeng , Li Jiayin , Xie Hui , Wang Yongfeng , Yu Fangli , Shi Bingyao , Liu Boyang
Published: February 2021

A green and natural biomass carbon with hollow structure was first reported derived from waste makeup cotton, which was prepared by facile pyrolysis and carbonisation in the nitrogen‐filled vacuum tube furnace. Utilised as lithium‐ion batteries (LIBs) anode materials, the hollow structure exhibits superior cycling and rate performance. At the current density of 100 mA g−1, it demonstrates a reversible capacity of 340 mAh g−1 with the Coulombic efficiency of 58.8%, and the reversible capacity gradually increases to 450 mAh g−1 at 300 cycles, displaying long cycling stability. Even at a higher current density of 500 mA g−1, the capacity can be maintained around 245 mAh g−1 after 150 cycles. Moreover, the hollow carbon exhibits excellent rate capability (222 mAh g−1 at an ultrahigh rate of 2000 mA g−1). This enhanced property can be attributed to its special hollow structure, which could provide fast lithium ions and electrons transfer path to facilitate the electrochemical reaction. The authors believe this work could help to design new carbon materials with green and environmental protection as anode materials for LIBs.
Rapid and sensitive detection of neotame in instant grain beverages by paper‐based silver nanoparticles substrates
Authors: Han Mingming , Wei Weiwei , Lu Hongmei , Zhang Zhimin
Published: February 2021

Neotame is an artificial sweetener with increasing consumption in recent years, excessive intake of it may bring potential health risk. In this work, a rapid method was developed to detect neotame in instant grain beverages, which was based on surface‐enhanced Raman scattering (SERS) technique and filter paper‐based silver nanoparticles (AgNPs@FP) substrates. The designed substrate exhibits good SERS activity with an enhancement factor of 105 because of the synergistic effect of the concentrated silver nanoparticles and filter paper. Meanwhile, the stability and repeatability of this fabricated substrate have been investigated with the relative standard deviation of 6.1%. In addition, it shows an excellent linear relationship (R2 = 0.997) between the SERS signal and the logarithm concentration of neotame with a wide concentration range (0.05–5 g/kg) in the quantitative analysis. The limit of detection of neotame can be as low as 0.01 g/kg in instant grain beverages, which is below the maximum allowable addition level for neotame in instant grain beverages set in China (GB2760‐2014, 0.16 g/kg). The proposed method has great potential for the identification and quantification of neotame in food safety applications with high sensitivity.
Photospheric downflows observed with SDO/HMI, HINODE, and an MHD simulation
Authors: Roudier T. , Švanda M. , Malherbe J. M. , Ballot J. , Korda D. , Frank Z.
Published: February 2021

Downflows on the solar surface are suspected to play a major role in the dynamics of the convection zone, at least in its outer part. We investigate the existence of the long-lasting downflows whose effects influence the interior of the Sun but also the outer layers. We study the sets of Dopplergrams and magnetograms observed with Solar Dynamics Observatory and Hinode spacecrafts and an magnetohydrodynamic (MHD) simulation. All of the aligned sequences, which were corrected from the satellite motions and tracked with the differential rotation, were used to detect the long-lasting downflows in the quiet-Sun at the disc centre. To learn about the structure of the flows below the solar surface, the time-distance local helioseismology was used. The inspection of the 3D data cube (x, y, t) of the 24 h Doppler sequence allowed us to detect 13 persistent downflows. Their lifetimes lie in the range between 3.5 and 20 h with a sizes between 2″ and 3″ and speeds between −0.25 and −0.72 km s−1. These persistent downflows are always filled with the magnetic field with an amplitude of up to 600 Gauss. The helioseismic inversion allows us to describe the persistent downflows and compare them to the other (non-persistent) downflows in the field of view. The persistent downflows seem to penetrate much deeper and, in the case of a well-formed vortex, the vorticity keeps its integrity to the depth of about 5 Mm. In the MHD simulation, only sub-arcsecond downflows are detected with no evidence of a vortex comparable in size to observations at the surface of the Sun. The long temporal sequences from the space-borne allows us to show the existence of long-persistent downflows together with the magnetic field. They penetrate inside the Sun but are also connected with the anchoring of coronal loops in the photosphere, indicating a link between downflows and the coronal activity. A links suggests that EUV cyclones over the quiet Sun could be an effective way to heat the corona.
Dehnen: Sinn und Unsinn im Kontext evidenzbasierter Therapie
Authors: Riese Daniel , Kluge Marcel
Published: February 2021

Dem Dehnen geht ein guter Ruf voraus. Es soll Muskelkater und Verletzungen vorbeugen, beweglicher machen, Kontrakturen verhindern. Daniel Riese und Marcel Kluge machen den Evidenz-Faktencheck: Wird das Dehnen seinem Ruf gerecht?
Unterscheiden sich Patienten mit episodischer Migräne ohne Aura hinsichtlich der zervikalen muskuloskelettalen Funktion von einer symptomfreien Kontrollgruppe ohne Migräne?
Authors: Schneider Simon , Kubat Heike , Steinhoff Ute
Published: February 2021

Kopfschmerzen stellen für viele Menschen eine große Beeinträchtigung dar. Ziel der Arbeit war es, klinische Tests, die bereits bei Patienten mit Nackenschmerzen oder Whiplash Associated Disorders (WAD) angewandt werden, bei Migränepatienten ohne Aura im Vergleich mit einer symptomfreien Kontrollgruppe durchzuführen.

Im Rahmen einer Querschnittstudie wurden die Ergebnisse aus 2 Fragebögen und 6 klinischen Tests von Patienten mit episodischer Migräne (n = 23) mit den Ergebnissen einer symptomfreien Kontrollgruppe (n = 15) verglichen. Die Ergebnisse zeigten hoch signifikante Unterschiede (p < 0,001) zwischen den Gruppen für die Fragebögen und signifikante Unterschiede bei den Kopf-Auge-Bewegungskontrolltests, dem Joint-Position-Error-Test, Zervikalen Flexions-Rotations-Test, Fukuda-Stepping-Test (Merkmal > 45° Körperrotation) sowie dem Kraniozervikalen Flexionstest. Kein signifikanter Unterschied (p > 0,05) zeigte sich bei dem Fukuda-Stepping-Test (Merkmal > 1 m Vorwärtsgehen) sowie für den Single-Leg-Stance.

Verschiedene sensomotorische, okulomotorische und muskuloskelettale Auffälligkeiten konnten bei Patienten mit episodischer Migräne ohne Aura in dieser Studie aufgezeigt werden. Für therapeutische Prozesse sollten daher die Tests in Untersuchungsabläufe integriert werden. Es bedarf jedoch weiterer Studien, um die Effektivität von Therapien, die auf diese Dysfunktionen Einfluss nehmen, zu bewerten.
Functionalized Cyclopropanes as Versatile Intermediates for the Diversity-Oriented Synthesis of γ-Lactones, γ-Lactams and δ-Lactams
Authors: Sá Marcus M. , Maximiano Adrielle P. , Ramos Giovana S. , Marques Marcelo V.
Published: February 2021

A two-step procedure for the preparation of cyclopropanecarboxaldehyde-1,1-diester from a γ,δ-epoxyester and its synthetic versatility are described herein. The epoxide ring-opening/cyclopropanation process occurs in the presence of Mg(ClO4)2 under heating, resulting in cyclopropanemethanol-1,1-diester in 65% yield. A mild TEMPO-mediated oxidation of this substrate readily generated the corresponding aldehyde in 75% yield, which was applied in the one-pot synthesis of four cyclopropylidene-γ-lactams and three δ-lactams. In addition, vinylcyclopropanes were obtained through the Wittig reaction of the aldehyde with phosphonium salts and used as precursors for tetrahydrofurans.
A New “Denervation” Technique for Painful Arthritic Wrist
Authors: Rigoni Massimo , Raggi Massimiliano , Speri Luca
Published: February 2021

Wrist denervation is, by the way, one of the most performed and long-lasting surgical technique for wrist arthritis. Despite many progresses in upper extremity joint arthroplasty, wrist arthritis remains difficult to treat specially in young patients and heavy manual workers. The aim of this technical article is to describe a new outpatient's procedure in which applying pulsed radio frequency on nerve structure of the wrist could achieve similar clinical results of a wrist denervation without surgical incision.
Business groups and the study of international business: A Coasean synthesis and extension
Authors: Dau Luis Alfonso , Morck Randall , Yeung Bernard Yin
Published: February 2021

This paper harmonizes the business group literature in international business and across relevant fields within a unified theoretical framework. Business groups (firms under common control but with different, if overlapping, owners) are economically important in much of the world. Business groups’ economic significance co-evolves with their economies' institutions and market environments, patterns of particular interest to international business scholars. The vast literature on business groups raises discordant perspectives. This paper first proposes a unifying definition and provides a list of stylized historical observations on business groups across different parts of the world. It then develops a Coasean framework to harmonize seemingly disparate views from the literature by building on recent surveys and the stylized historical patterns of business groups. We enlist two concepts – fallacies of composition/decomposition and time inconsistency – to harmonize these perspectives. This yields a theoretical framework for understanding business groups that mobilizes concepts long-used to understand multinational enterprises: the economy's market and hierarchical transaction costs, openness, and their dynamic interactions. We then apply this framework to globalization and business group internationalization. This work leads to an overarching research agenda encompassing seemingly inconsistent prior work.
A bibliometric study of research topics, collaboration, and centrality in the iterated prisoner’s dilemma
Authors: Glynatsi Nikoleta E. , Knight Vincent A.
Published: February 2021

This manuscript explores the research topics and collaborative behaviour of authors in the field of the Prisoner’s Dilemma using topic modeling and a graph theoretic analysis of the co-authorship network. The analysis identified five research topics in the Prisoner’s Dilemma which have been relevant over the course of time. These are human subject research, biological studies, strategies, evolutionary dynamics on networks and modeling problems as a Prisoner’s Dilemma game. Moreover, the results demonstrated the Prisoner’s Dilemma is a field of continued interest, and that it is a collaborative field compared to other game theoretic fields. The co-authorship network suggests that authors are focused on their communities and that not many connections across the communities are made. The most central authors of the network are the authors connected to the main cluster. Through examining the networks of topics, it was uncovered that the main cluster is characterised by the collaboration of authors in a single topic. These findings add to the bibliometrics study in another field and present new questions and avenues of research to understand the reasons for the measured behaviours.
Passivation of III–V surfaces with crystalline oxidation
Authors: Laukkanen P. , Punkkinen M. P. J. , Kuzmin M. , Kokko K. , Lång J. , Wallace R. M.
Published: February 2021

Control of interfacial physicochemical properties associated with device materials to minimize the impact of point defects on device performance has been a dominant theme in the semiconductor industry. Control of the density of such defects for silicon has been well established for metal oxide-semiconductor field-effect device applications through deliberate reactions with chemically congruent species, such as hydrogen. In contrast, control of interfacial defects for technologically important III–V device materials is still an active area of research. Performance criteria for III–V devices are demanding in terms of energy efficiency, material consumption, sensitivity, and speed. The surface reactions of III–V crystals, including oxidation, are typically known to result in performance limitation for devices, causing significant degradation due to high defect-level densities at the surfaces/interfaces, in contrast to high quality bulk crystal regions. Here, we discuss the approach of utilizing atomically thin, ordered oxide interfacial layers of III–V compound semiconductors since they provide a unique opportunity for metal-oxide semiconductor applications, compared to the more common approach to avoid surface oxidation. Long-range ordered oxide interfaces have been obtained by oxidizing cleaned III–V surfaces intentionally in ultrahigh vacuum conditions. This can be combined with different passivation methods to decrease interfacial defect density in III–V devices. We present the current understanding of the physical and chemical properties of crystalline oxidized III–V materials, based on both experimental and computational models. The results are compared to those obtained by current state-of-the-art passivation methods.
Neutron total scattering investigation on the dissolution mechanism of trehalose in NaOH/urea aqueous solution
Authors: Qin Hong , Ma Changli , Gärtner Sabrina , Headen Thomas F. , Zuo Taisen , Jiao Guisheng , Han Zehua , Imberti Silvia , Han Charles C. , Cheng He
Published: February 2021

Trehalose is chosen as a model molecule to investigate the dissolution mechanism of cellulose in NaOH/urea aqueous solution. The combination of neutron total scattering and empirical potential structure refinement yields the most probable all-atom positions in the complex fluid and reveals the cooperative dynamic effects of NaOH, urea, and water molecules in the dissolution process. NaOH directly interacts with glucose rings by breaking the inter- and intra-molecular hydrogen bonding. Na+, thus, accumulates around electronegative oxygen atoms in the hydration shell of trehalose. Its local concentration is thereby 2–9 times higher than that in the bulk fluid. Urea molecules are too large to interpenetrate into trehalose and too complex to form hydrogen bonds with trehalose. They can only participate in the formation of the hydration shell around trehalose via Na+ bridging. As the main component in the complex fluid, water molecules have a disturbed tetrahedral structure in the presence of NaOH and urea. The structure of the mixed solvent does not change when it is cooled to −12 °C. This indicates that the dissolution may be a dynamic process, i.e., a competition between hydration shell formation and inter-molecule hydrogen bonding determines its dissolution. We, therefore, predict that alkali with smaller ions, such as LiOH, has better solubility for cellulose.
Non-equilibrium behavior of large-scale axial vortex cores
Authors: Ash Robert L. , Zardadkhan Irfan R.
Published: February 2021

A logical basis for incorporating pressure non-equilibrium and turbulent eddy viscosity in an incompressible vortex model is presented. The infrasonic acoustic source implied in our earlier work has been examined. Finally, this non-equilibrium turbulent vortex core is shown to dissipate mechanical energy more slowly than a Burgers vortex, helping us to explain the persistence of axial vortices in nature. Recent molecular dynamics simulations replicate aspects of this non-equilibrium pressure behavior.
An experimental investigation of the viscosity behavior of solutions of nanoparticles, surfactants, and electrolytes
Authors: Bollineni Praveen Kumar , Dordzie Gideon , Olayiwola Saheed Olawale , Dejam Morteza
Published: February 2021

Several studies have reported that the viscosity profile of nanofluids has a similar trend to electrolytes. This behavior is attributed to the complex interactions of the ions of nanoparticles (NPs) with the ions of aqueous solutions. Recently, laboratory experiments have shown that nanofluids are suitable candidates for enhanced oil recovery in different reservoirs. The improvement in oil recovery during nanofluid injection is attributed to the wettability alteration, interfacial tension reduction, and viscosity modification. Low salinity water and surfactants are used to stabilize and prevent the aggregation of NPs, which are injected into the reservoir. However, the interactions between the reservoir/injected fluids with NPs alter the properties of the fluid. The complex interactions among the ions present in the solutions of NPs, surfactants, and electrolytes (NSE) that result in the viscosity modification are not completely understood. Therefore, this work presents a detailed study on the complex interactions existing between the ions of NPs and other ions of aqueous solution present in the reservoir fluid using the dynamic light scattering, transmission electron microscopy, and Fourier transform infrared spectroscopy techniques to understand the viscosity behavior of NSE solutions. The viscosity profile of NSE solutions with increasing concentration of NPs has the same trend as aqueous solutions, while that with increasing concentration of the sodium dodecyl sulfate surfactant behaves like spherical particles. The explained mechanisms behind the viscosity behavior of NSE solutions in this study can improve the optimization design for nanofluid injection into the reservoir.
The measurement of anisotropic thermal transport using time-resolved magneto-optical Kerr effect
Authors: Pham Ngoc Luu Ly , Kang Kyuhwe , Choi Gyung-Min
Published: February 2021

Owing to the increasing demand for the improved management of thermal transport in devices, it is necessary to develop an optimal method for the measurement of anisotropic heat conduction. Although several techniques have been used to measure the heat transport in anisotropic materials, the accurate determination of anisotropic thermal conductivity remains a major challenge. In this study, we present time-resolved magneto-optical Kerr effect measurement using a pump–probe technique to investigate the thermal characterization of various materials. A substrate/ferromagnetic metal (FM) structure is prepared, where FM acts as a transducer to detect the thermal transport in substrates of silicon, sapphire, and highly ordered pyrolytic graphite. By performing experiments under various modulation frequencies and laser spot sizes, we determine both in-plane and through-plane thermal conductivities. We also discuss the limitations of measurement and provide useful guidelines to determine the thermal properties of different materials with high accuracy.
Energetics and magnetism of topological graphene nanoribbons
Authors: Ohfuchi Mari , Sato Shintaro
Published: February 2021

The topological properties of graphene nanoribbons (GNRs) have received a significant amount of attention in emerging fields such as spintronics and quantum computing. This study is focused on the energetics and magnetism of symmetry-protected junction state arrays, which are realized in the alternating periodic structures of two topologically different armchair GNRs. We found that the antiferromagnetic states require at least eight unit cells for each segment of the periodic armchair GNRs, where the armchair GNRs whose numbers of carbon atoms in a row are seven and nine are connected with a junction structure. We also found the junction structure that provides more stable antiferromagnetic states. Furthermore, we propose an end (armchair GNRs/vacuum interface) structure to avoid disturbing the global topological properties of the junction state array. This means that if the topological end states (non-trivial phases of the Su, Schrieffer, and Heeger model or Majorana fermions) exist, they are properly formed at the endmost junctions without the requirement for extra effort such as long end extension. We believe that this study can add new guidelines and challenges for realizing graphene-based quantum computing.
Monotonic rising and oscillating of capillary-driven flow in circular cylindrical tubes
Authors: Sun Bohua
Published: February 2021

Capillary rise is one of the best-known capillarity phenomena, and some capillary flows rise monotonically, whereas others oscillate, but no criteria have been formulated for this scenario. In this paper, the critical radius of the capillary tube is predicted numerically by Levine’s model. To the best of our knowledge, the phase–space diagram of capillary velocity vs height is obtained for the first time, which shows that the phase transition from oscillating to monotonically rising occurs when the phase trajectory decreases exponentially to somewhere other than the “attractor.” Two general Maple codes are provided as an essential part of this paper.
In the eye of the STORM: Tracking the myosin-binding protein C N terminus in heart muscle
Authors: Colson Brett A.
Published: February 2021

Colson discusses a recent investigation of the localization of N-terminal myosin-binding protein C in cardiac muscle.
A spinorial proof of the rigidity of the Riemannian Schwarzschild manifold
Authors: Raulot Simon
Published: February 2021

We revisit and generalize a recent result of Cederbaum (Cederbaum in preparation; Cederbaum 2017 Oberwolfach Report) concerning the rigidity of the Schwarzschild manifold for spin manifolds. This includes the classical black hole uniqueness theorems (Bunting and Masood-ul-Alam 1987 Gen. Relativ. Gravit.
19 147; Gibbons, Ida and Shiromizu 2002 Phys. Rev. Lett.
89 041101; Hwang 1998 Geom. Dedicata
71 5) as well as the more recent uniqueness theorems for photon spheres (Cederbaum 2015 Contemp. Math.
667 86; Cederbaum and Galloway 2017 Commun. Anal. Geom.
25 303; Cederbaum and Fehrenbach personal communication).