bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of short‐time Fourier transform for harmonic‐based protection of meshed VSC‐MTDC grids
Authors: Ashouri Mani , Silva Filipe F.D. , Bak Claus L.
Published: October 2018

This work studies the application of short‐time Fourier transform (STFT) to extract current harmonics of various fault types to design a protection method for meshed multi‐terminal voltage source converter‐high‐voltage direct current (VSC‐HVDC‐MTDC) grids. The frequency spectrum of fault current harmonics is used to detect internal and external faults, the faulty pole and fault type. The method does not need the implementation of series inductance on the sides of the DC lines and it is also effective for lines combining overhead lines and cables. The window function and hop size play the primary role in STFT, which are investigated in a sensitivity analysis. A modified version of CIGRE meshed DC grid system is simulated in PSCAD in order to show the robustness of the method, and further signal processing analysis is done in MATLAB. The results show the accurate detection and discrimination between faulty sections using the proposed harmonic‐based method and how important the STFT parameters are in order to have a robust protection algorithm.
Cooperated control strategy of generator re‐dispatching and multi‐HVDC modulation after ultra HVDC block
Authors: Wang Yuling , Shao Dejun , Xu Youping , Shen Xuhui , Duan Chengjin , Wang Yicong , Sun Haishun
Published: October 2018

With the increase of DC project voltage level and transmission capacity, the security and stability risk caused by DC blocking is gradually increasing. Aiming at reserve dispatch after ultra‐high voltage direct current (UHVDC) block, scenarios of DC power modulation participating in dispatching are presented. Mathematical models of generator re‐dispatching incorporated control of DC in AC/DC hybrid grid in three situations in terms of enough reserve capacity in the disturbed province, regional reserve capacity sufficient and insufficient to make up for the power deficiency are presented. Then, a decision‐aid system for optimal reserve dispatch after UHVDC block is proposed. Simulation results of Central China power grid indicate that the proposed scheduling scheme can reduce the operation risks of security and load loss if necessary.
Research on application of FDNE based on RTDS and comparison analysis of fault transient of Shanghai Sijing power grid
Authors: Xiaofeng Zou , Shihao Yang , Desheng Zhou , Jie Song
Published: October 2018

As a most widely applied real‐time digital simulation system, real time digital simulation (RTDS) is however quite limited on scale of simulation by the number of hardware purchased. Through frequency‐dependent network equivalent (FDNE), scale of simulation of RTDS could be largely increased by frequency equivalent on limited hardware. Based on basic principles of FDNE, function limitations and problem are analysed, taking the Shanghai Sijing district power grid as an example; detailed simulation model and FDNE equivalent module are built, transient characteristics under faults before and after FDNE equivalent are analysed. Furthermore, the fault characteristics of high‐voltage direct current (HVDC)‐Sijing power grid is also studied, which provides a realistic means for real‐time digital simulation of AC–HVDC hybrid power grid with limited hardware of RTDS.
Effect of PLL on transient performance of wind turbines generator under voltage phase jump
Authors: Liu Chao , Tian Xinshou , Chen Kai , Su Yuanyuan , Li Yan
Published: October 2018

With the increasing proportion of wind power installed capacity, the influences of transient characteristics of wind turbines generator on safety and stability of power grid is becoming more and more important. The rotor side of doubly fed induction generator (DFIG) is connected to the grid through a back‐to‐back inverter, and vector control based on phase‐locking synchronisation is used generally. Phase‐locked loop (PLL) drive internal potential phase changes to achieve synchronous operation with the grid. Therefore, PLL has great influence on transient characteristics of DFIG. A dynamic model of PLL is built in this study. Phase‐locking performance of PLL under voltage phase jump is studied by changing its parameters, and its impact mechanism on transient characteristics of DFIG is proposed. Simulation models are built with DIgSILENT/PowerFactory. The influence of parameters of PLL on phase‐locking performance of DFIG under voltage phase jump is simulated.
Alternate arm modular multilevel converter energy balancing via overlap onset control
Authors: Howell Steven , Wang Haiyue , Filizadeh Shaahin
Published: October 2018

This study introduces a novel method called overlap onset control (OOC) to balance and maintain alternate arm modular multilevel converter (AAC) submodule capacitor voltages at their desired value. OOC performs zero‐current switching and controls the timing of AAC commutation to regulate submodule voltages while retaining output voltage quality. The study uses steady‐state converter models to develop the mathematical foundations behind the proposed capacitor voltage regulation method and then presents electromagnetic transient simulation results in PSCAD/EMTDCto demonstrate OOC's ability to extend the AAC operating range.
Wavelet‐based EMTR method for fault location of VSC‐HVDC transmission lines
Authors: Zhang Xipeng , Tai Nengling , Zheng Xiaodong , Huang Wentao
Published: October 2018

A wavelet‐based electromagnetic time reversal method for locating faults in voltage source converter‐high‐voltage direct current (VSC‐HVDC) transmission lines is proposed in this study. This principle, firstly, is to use wavelet decomposition to filter the 1‐mode fault currents, which are recorded at ends of the transmission line. Secondly, the filtered currents are mirrored on time axes, which called time reversal. Thirdly, the time‐reversed currents are set as current sources at ends of the lossless mirror lines. Through assuming a fault at each point of line, the assumed fault currents are calculated, and the RMS of fault current at actual fault location is maximal according to a strict scientific proof. Theoretically, the Wavelet‐based Electromagnetic Time Reversal (WEMTR) method is robust against fault types and resistance. A multilevel converter‐HVDC system is established in Power Systems Computer‐Aided Design (PSCAD)/Electromagnetic Transients including DC (EMTDC) to verify the feasibility of the proposed method, and the transmission line is simulated by frequency independent phase model. The results show that, the fault location can be calculated exactly without high sampling rates.
New optical differential protection algorithm applied in bus protection
Authors: Sitong Zhu , Tongwei Yu , Yong Ying , Zhenyang Zhao , Dan Zhao
Published: October 2018

In order to improve the speed and reliability of bus protection, people put forward the optical current transformer (OCT) replaced the traditional electric–magnetic current transformer. As OCT has no magnetic saturation, no band limits, and can accurately and quickly transform the full‐waveform current signal in principle, the authors put forward a new optical differential protection algorithm which directly use the integral values of the operating current and the restraint current measured by OCT as the differential protection algorithm. The authors build 220 kV double bus protection model and simulate the actual fault current signal by Real Time Digital Simulator (RTDS). Then, the authors bring the fault current into the bus protection algorithm for verification, and analyse the simulation curves of restraint ratio. The simulation results prove the feasibility of the optical differential protection algorithm.
Study on the site selection for synchronous condenser responding to commutation failures of multi‐infeed HVDC system
Authors: Wang Qiang , Li Tianran , Tang Xiaobo , Liu Fusuo , Lei Jie
Published: October 2018

Power system shows increasingly prominent characteristic of ‘strong DC and weak AC’ at the primary construction stage of ultrahigh‐voltage AC/DC hybrid power grid. Faults occurring in the receiving‐end AC grid of the multi‐infeed high‐voltage DC (HVDC) system may result in simultaneous commutation failures (CFs) and short‐time huge power shortage, which are great threats to the stability of power grid. Owing to the strong support ability in reactive power, rotary inertia, and capacity of short circuit, synchronous condenser (SC) has received more and more attention in restraining CFs of multi‐infeed HVDC and speeding up transient recovery process after faults. From the angle of interplay between multi‐infeed HVDC systems, this study analyses SCs’ superiority in restraining CFs, and then determines the optimal dynamic reactive power compensation site layer by layer combining with multi‐infeed interaction factor, multi‐infeed effective short‐circuit ratio, and relative‐transient‐voltage‐drop‐area index. Finally, this study proposes a reliable and applicable site selection scheme for SCs to restrain CFs of the multi‐infeed HVDC system.
Quick recovery control strategy for zhou shan VSC‐MTDC
Authors: Qian Chen , Yi Lu , Peng Qiu , Zhuo Xuan Jia , Feng Xu , Hong Yu Hai , Yi Wu Jia
Published: October 2018

Zhou Shan voltage source converter multi‐terminal HVDC system (VSC‐MTDC) enhances the receptiveness of wind power and improves the reliability of power supply. Electrical energy transfers flexibly between the islands in Zhou Shan. Restricted by the half‐bridge sub module and disconnector, Zhou Shan VSC‐MTDC cannot realies fast DC fault recovery. In order to solve this problem, damping fast recovery system and DC breaker are added. Meanwhile, the corresponding control strategy is proposed. It is verified by experimental results that the control strategy will realise fast DC fault recovery and improve the reliability of Zhou Shan VSC‐MTDC dramatically.
Study on quick judgement of small signal stability using CNN
Authors: Shi Dongyu , Yan Jianfeng , Gao Bo , Xie Mei , Hou Jinxiu , Li Gang , Yu Zhihong , Lv Ying , Lu Guangming
Published: October 2018

Dynamic security assessment (DSA) is widely used in dispatching operation systems, and the small signal stability is one of the DSA's most time‐consuming calculation methods. In this article, a fast method is proposed aiming to predict the small signal stability metrics of designated oscillation mode, for example frequency or damping ratio. The method is much faster than the simulation and suitable for the online application. First, the t ‐distributed stochastic neighbour embedding (t ‐SNE) algorithm is performed which can create a mapping from the power system components to 2D coordinate depending on the electrical distance of each other; then, it will be transformed into a grid structure by meshing operation, on which the convolutional neural network (CNN) model can be run properly. Finally, with a large amount of simulation samples, the CNN model can be well trained using static quantities as its input and small signal stability metrics as its prediction target. While a new operation mode needs to be evaluated, the result will be obtained by CNN directly. The validity of proposed method is verified using online data of State Grid Corp of China. It is proved that the method meets the requirements for speed and accuracy of online analysis system.
Fractional modelling and simulation for single‐phase PWM rectifier
Authors: Zhu Pengfei , Wei Yanfang , Zheng Zheng , Wang Xiaowei , Ma Fangjun
Published: October 2018

Modelling and analysis of single‐phase PWM rectifier are usually based on integer order calculus theory, regardless of the fractional characteristics of inductors and capacitors, which will bring a deviation with the real system. Aiming at this problem, this paper first analyses the behaviours of the fractional order capacitors and fractional order inductors. Second, the fractional order model of single‐phase PWM rectifier is proposed. A new fractional order circuit for single‐phase PWM rectifier is presented. Based on the theory of instantaneous power, the value of DC component, the peak‐to‐peak value AC component, and the time of dynamic response of the DC‐side capacitor voltage are analysed. Third, the differences between integer model and fractional model for the rectifier are compared. Finally, the effectiveness of the proposed modelling method is validated simulation.
Economic optimisation of microgrid based on improved quantum genetic algorithm
Authors: Shan Huang , Hongjing Liu , Linlin Wu , Feng Zhou , Wang Miao , Yang Li , Jie Gao
Published: October 2018

The optimal dispatch of a microgrid is a complex issue with both important economic benefits and social benefits. To ensure the microgrid with distributed power to operate in a more economical, flexible and environmental way, and the advantages of distributed generation can be fully utilised, according to the problem of optimal scheduling of the microgrid, this study proposes a multi‐objective optimisation function model of the microgrid with an electric vehicle, which is used as a load and power generation unit at the same time, which aims to maximise the economic benefit and minimise the environmental cost of multi‐objective optimisation of the microgrid. In the process of optimisation, this study introduces the structure of a double chain and the adjustment strategy of the dynamical rotation angle, proposes a new modified quantum genetic algorithm, and compares with the traditional genetic algorithm and the fundamental quantum genetic algorithm. Finally, numerical examples are provided to verify the effectiveness and feasibility of the proposed model, strategy and algorithm.
Reactive power optimisation of distribution network with distributed generation based on genetic and immune algorithm
Authors: Hao Wenbo , Liu Boning , Yao Shujun , Guo Wanhua , Huang Wenerda
Published: October 2018

With the rapid development of new energy technologies, distributed power generation technology has attracted widely attention. The advantages of them are small investment, clean and environmental protection, reliable, and flexible power supply. They can output (or absorb) continuously adjustable reactive power and participate in the reactive power optimisation, which can keep the balance of reactive power and optimise the distribution of reactive power flow. In this study, firstly, the power flow model of typical distributed power supplies: wind power, solar power, and gas turbine power generation are researched. Then, the distributed power supply as a continuously adjustable reactive power device, combined with the traditional equipment, participate in reactive power optimisation. An objective function considering system loss is proposed to find optimal solution. Finally, the IEEE33 node system is used for verification. Results show that the distributed power supply can effectively reduce the system loss and improve the voltage stability. Meanwhile, the effectiveness and feasibility of the improved algorithm are verified. The optimisation of this study is the combination of genetic algorithm and immune algorithm. It can make up for the lack of local optimisation ability of genetic algorithm. Compared with the single algorithm, the global optimisation ability is greatly enhanced.
Error assessment method of electromechanical–electromagnetic hybrid simulation
Authors: Zheng Zewen , Zhang Hengxu , Zheng Weijie , Li Hao
Published: October 2018

With ultra high voltage direct current (UHVDC) and flexible alternating current transmission systems (FACTS) have been widely applied in power system, the AC/DC power grid is constantly extending which makes its composition more complicated. The independent electromechanical transient simulation and electromagnetic transient simulation cannot meet the need of rapidly developing modern power system in simulation technology. Electromechanical–electromagnetic hybrid simulation not only has the advantages of analysing large systems, but also accurate description of power electronic components. Analysing errors in hybrid simulations can help them to quantitatively analyse different hybrid simulation interface technologies to optimise simulation settings. Concerned fault types, fault location, and point fault cleaning time, an electromechanical–electromagnetic hybrid simulation scenarios probabilistic model based on Monte Carlo is put forward. Then adopt Prony method to quantitatively analyse the hybrid simulation errors. Through a typical example of UHVDC power grid in Shandong province, the error evaluation method of the hybrid simulation is demonstrated in detail. The research shows that this kind of assessment method can well analyse the numerical validity of hybrid simulation.
Novel reclosure scheme of MMC‐HVDC system based on characteristic signal injection
Authors: Wang Ting , Song Guobing , Wu Lei , Wei Han , Guang Shi , Chao Liu
Published: October 2018

Adaptive reclosing of AC line discriminates temporary faults and permanent faults by the coupling relationship between fault phase and the sound phase. While in the DC network, the electrical quantity of the DC system keeps constant after the DC line fault is cleared, and there is no coupling relationship between the sound and fault pole. This paper presents a fault identification method by injecting characteristic signals into a DC fault line. The electrode coupling characteristics of HVDC transmission lines, the injection method, and the selection of characteristic signal are given in detail. Then, the characteristic signals are injected into the sound pole through the additional control strategy of the converter station. As of electrode coupling characteristics of transmission lines, the fault line induces the coupling characteristic signal. This characteristic signal on the fault line is used to distinguish the fault property by the differences of the propagation feature between the two states, the fault existence and disappearance states. The simulation results verify the effectiveness of the method here.
Rapid modelling for flexible DC distribution network considering droop control
Authors: Chen Aikang , Yu Songtao , Xie Da
Published: October 2018

With the growth of DC electricity load, the difficulty to improve the power quality, and the increasing penetration of renewable power, flexible DC distribution network, which contains complex renewable energy generation equipment and a large number of power electronic converters, become an important research direction. The modelling of the DC distribution network is an essential step for the research on the coordination control. However, the traditional modelling will be a burden for simulation software. This article models all electrical devices as equivalent power sources based on the proportional–integral control and the power–voltage curve, ignoring the complex internal control processes. Based on the simplified models of power, load, DC/DC converters, and AC/DC converters considering droop control, a simplified model of a multi‐terminal flexible DC distribution network is derived. Taking the impact of droop control into account, the simulation of DC distribution power flow under the different distribution of generation and load is done. Results show that the simplified model of DC distribution network with droop control can accurately and rapidly simulate the transient process and steady states of the testing network.
Application of molecular simulation in transformer oil–paper insulation
Authors: Xiao Xia , Yang Wenyan , Li Linduo , Zhong Tingting , Zhang Xiaolin
Published: October 2018

Molecular simulation technology is a new technology emerging with the rapid development of computer technology. It has the advantages of clear microscopic models, in‐depth and precise calculation etc., it has been widely used in the oil–paper insulation system of transformer in recent years. Based on the application of molecular simulation technology in the oil–paper insulation system of transformers in this study, the current research status and progress of molecular simulation in these area are elaborated in detail from the aspects of transformer insulating oil and insulating paper according to the domestic and foreign literature, and the application of molecular simulation technology in plant insulating oil and nano‐modified insulating oil is emphatically analysed. The complementing research method of molecular simulation and experiment is pointed out, which provides certain reference for solving many problems existing in the field of oil–paper insulation system of transformers.
Study of frequency domain dielectric properties of vegetable oil and mineral oil transformer
Authors: Li Linduo , Ren Qiaolin , Xiao Sa , Yang Wenyan , Xiong Wei , Fu Boqiao
Published: October 2018

To study the properties of vegetable oil transformer, the mineral and vegetable insulation oil two transformers with the same parameters are studied using the frequency domain spectroscopy (FDS) method. The complex capacitance and the dielectric loss factor are tested by the insulation diagnostic equipment IDAX300, these parameters can reflect the insulation properties of the transformer. The experimental results show that properties of vegetable oil transformer are different to the mineral. The complex capacitance and the dielectric loss factor tanδ of vegetable oil transformer are higher than those of mineral oil transformer, and the moisture content in vegetable oil is higher than that in mineral oil. The test results are also emphatically analysed, which ultimately laid a theoretical foundation for large‐scale operation of vegetable oil transformers.
Analysis of control interaction between D‐PMSGs‐based wind farm and SVC
Authors: Chen Yahao , Huang Biyue , Sun Haishun , Wang Long
Published: October 2018

According to an accident analysis report, with regard to sub‐synchronous oscillation (SSO) in Xinjiang, China, dynamic reactive compensation devices have great influence on the existence of sub‐synchronous harmonics. This paper based on the practical phenomenon for further study, focuses on the interaction between direct‐drive permanent synchronous generators (D‐PMSGs)‐based wind farm and static var compensator (SVC). Detailed electro‐magnetic transient simulation model, such as D‐PMSGs‐based wind farm compensated by SVC, is established in PSCAD/EMTDC. Time‐domain simulation results demonstrate that there is interaction between D‐PMSGs‐based wind farm and SVC, which is closely related with the control parameters of SVC and D‐PMSGs‐based wind farm. This type of control interaction will lead to sub‐synchronous oscillation. Therefore, the influence of above control parameters on the oscillation characteristics is further studied here. The practical significance of this paper is indicating the necessity of coordinating and optimising control parameters in large‐scale wind farm.
Feasible protection strategy for HVDC system by means of SFCL and passive resonance DC breaker
Authors: Lee Ho‐Yun , Asif Mansoor , Park Kyu‐Hoon , Lee Bang‐Wook
Published: October 2018

The key obstacle in implementing high‐voltage direct current (HVDC) grid, which is considered as the future of power grid, is the absence of effective DC circuit breaker (DCCB). At present, HVDC grid could be based on half‐bridge (HB) or full‐bridge (FB) voltage source converter (VSC). Among these two converter topologies, FB topology has an advantage of reverse current blocking at a much higher cost compared to HB technology and still requires a DCCB for isolating the faulty line. Therefore, HB technology is more realistic to implement HVDC grid economically if DC fault current could be controlled more effectively. In this respect, this article suggests feasible fault protection strategy based on superconducting fault current limiter (SFCL) and passive resonance circuit breaker (PRCB) which could be applied effectively to HB system. To evaluate the performance of suggested protection scheme, comparative study of full‐bridge modular multilevel converter (FB‐MMC) protection was performed. In addition, the process to determine the optimal range for quenching resistance of SFCL was also investigated. Consequently, the authors’ suggested protection scheme has shown remarkably improved fault current limiting and interruption performance compared to FB‐MMC protection scheme.
Magnetic fields in massive spirals: The role of feedback and initial conditions
Authors: Ntormousi Evangelia
Published: October 2018

Context.Magnetic fields play a very important role in the evolution of galaxies through their direct impact on star formation and stellar feedback-induced turbulence. However, their co-evolution with these processes has still not been thoroughly investigated, and the possible effect of the initial conditions is largely unknown.

Aims.This Letter presents the first results from a series of high-resolution numerical models, aimed at deciphering the effect of the initial conditions and of stellar feedback on the evolution of the galactic magnetic field in isolated Milky Way-like galaxies.

Methods.The models start with an ordered magnetic field of varying strength, either poloidal or toroidal, and are evolved with and without supernova feedback. They include a dark matter halo, a stellar and a gaseous disk, as well as the appropriate cooling and heating processes for the interstellar medium.

Results.Independently of the initial conditions, the galaxies develop a turbulent velocity field and a random magnetic field component in under 15 Myr. Supernova feedback is extremely efficient in building a random magnetic field component up to large galactic heights. However, a random magnetic field emerges even in runs without feedback, which points to an inherent instability of the ordered component.

Conclusions.Supernova feedback greatly affects the velocity field of the galaxy up to large galactic heights, and helps restructure the magnetic field up to 10 kpc above the disk, independently of the initial magnetic field morphology. On the other hand, the initial morphology of the magnetic field can accelerate the development of a random component at large heights. These effects have important implications for the study of the magnetic field evolution in galaxy simulations.
Geomagnetic Gradient Bionic Navigation Based on Parallel Approach Method
Authors: Wang Qiong , Zhou Jun
Published: October 2018

Priori geomagnetic information is important to the geomagnetic navigation. However in practice, the precision of the geomagnetic information is a greatly constraint to the development of the geomagnetic navigation. In order to solve this problem, this paper present a geomagnetic gradient bionic navigation method based on parallel approach without any priori information. Inspired by the evidence that many creatures can navigate using the Earth magnetic field, the navigation process can be considered as a convergence of multi-objective problem, and develop the bionics navigation model. By introducing the parallel approach method to the navigation process, the heading angle can be estimated with the information of magnetic field gradient. The simulation results show the proposed method is able to navigation effectively without magnetic priori information, just rely on the actual geomagnetic measurement, which has implies potential application in the future.
Flight Performance Estimation of Bionic Flapping-Wing Micro Air Vehicle
Authors: Yang Wenqing , Song Bifeng , Gao Guanglin
Published: October 2018

Bionic flapping-wing micro air vehicle(MAV) has received worldwide attention.The flight performance calculation is an important step in the conceptual design.The differences in performance estimation methods between the flapping-wing and conventional fixed-wing aircraft are analyzed.Based on the results of the aerodynamic estimation and wind tunnel experimental measurement, the flight performance estimation method of flapping-wing micro air vehicle is proposed, and the performance of level flight, climbing, and duration are calculated and analyzed.The frequency represents the accelerator in a certain extent, while the frequency is coupled with lift and thrust.The results show that there may be two stable cruising states at certain frequencies, one is the small angle of attack with high speed, the other is the small speed with big angle of attack, and the two states have different power consumption.According to the parameters of the vehicle, climbing performance and duration performance can be obtained.The speed versus power characteristic curve is a U shape, minimum slope of the U curve can be obtained through the mapping method to calculate the farthest flight speed, and the minimum velocity of U-shaped curve is the speed for longest duration.The proposed flight performance calculation method can be used to evaluate the flight capability of bionic micro flapping-wing air vehicle.
A New Crack Propagation Model Based on the Notch Analysis Methodology
Authors: Zhao Kun , Wang Shengnan
Published: October 2018

In this paper, the fatigue crack propagation model of the metal structure is studied, and a new crack propagation rate model is proposed. Compared with the traditional method, only the nominal applied stress and the critical fracture stress are considered in the new method, and the new one is much easier and more efficient. By analyzing the 2024-T351 and 7075-T6 aluminum alloy materials test data, the new model is validated and the results are compared with the classical method of crack propagation. The result shows the new model has a similar trend with the existing crack propagation curve, and provides a better description for the low rate and high rate area, it also shows a strongly practicability.
Numerical and Experimental Study on TC4-DT Titanium Alloy Structure after Double Cold Expansion
Authors: Huo Lubin , Cao Zengqiang , Zhang Fan , Cao Yuejie
Published: October 2018

Cold Expansion and Interference Fit are two well-known techniques in hole strengthening, having been widely used in aviation industry. Double cold expansion is a new strengthening process which effectively combined with the two techniques. A modelling method based on ABAQUS finite element method is proposed in order to study the effect of double cold expansion, which will include cold expansion, reaming process, interference fit and springback after that, the influence of edge distance ratio (EDR) on the stress-strain distribution has been studied. Proto-LXRD device has been used to measure the residual stress distribution in the surface of the specimens. Simulation and experimental results show that the stress distribution of the simulation is in an higher level than that of experimental, but the trends of the stress distribution are in a good agreement.
An Airborne Multi-Sensor Task Allocation Method Based on Improved Particle Swarm Optimization Algorithm
Authors: Shi Guoqing , Wu Fan , Zhang Lin , Zhang Shuyang , Guo Cao
Published: October 2018

The characteristics of airborne multi-sensor task allocation problem are analyzed, and an airborne multi-sensor task allocation model is established. In order to solve the problems of local convergence and slow convergence of the traditional Particle Swarm Optimization (PSO) algorithm, the structure and parameters of the existing Particle Swarm Optimization algorithm are adjusted, and the direction coefficient and far away factor are introduced to control the velocity and direction of the particle far away from the worst solution, so that the particle moves away from the worst solution while moving to the optimal solution. Based on the improved Particle Swarm Optimization algorithm, an airborne multi-sensor task allocation method is proposed using maximum detection probability as objective function, and the algorithm is simulated. The simulation results show that this algorithm can effectively allocate tasks and improve allocation effects.
Supersonic Nozzle Optimization Design with Spline Curves Fitting the Nozzle Profiles
Authors: Wu Shenghao , Liao Daxiong , Chen Jiming , Chen Qin , Pei Haitao
Published: October 2018

Supersonic nozzle contour optimization design was applied to 0.6m×0.6m continuous transonic wind tunnel to improve flow quality in the test section. The Mach number root mean square deviation with the design value was chosen as optimization target. And the CFD results were verified with experimental results. Cubic spline curves with the optimal interpolating point distribution scheme were used to fit the nozzle contour. Efficient global optimization based on the Gaussian process surrogate model was used to reduce the times of evaluation. Results indicate that, the optimization framework can generate a supersonic nozzle contour with better flow quality and more accurate Mach number and that the optimal Mach number root mean square deviation is 0.001.
Management von Gefäßverletzungen bei militärischen Konflikten und Terroranschlägen
Authors: Engelhardt Michael , Elias Kristoffer , Debus Sebastian , Zischek Christoph
Published: October 2018

Im Krieg und bei Terroranschlägen erleiden bis zu 12% aller Verwundeten schwere Gefäßverletzungen. Die Entwicklungen in der Gefäßtraumatologie sind daher eng mit den bewaffneten Konflikten des 20. und 21. Jahrhunderts verknüpft. In diesem Beitrag werden anhand der historischen Erfahrungen militärchirurgische Aspekte bei Gefäßverletzungen diskutiert und die aktuellen Standards der Militärchirurgie auf diesem Gebiet dargestellt. Während bis einschließlich zum Zweiten Weltkrieg verletzte Gefäße überwiegend ligiert werden mussten, konnte erstmals im Korea- und Vietnamkrieg ein hoher Anteil der Gefäßverletzungen erfolgreich rekonstruiert werden. Zusammen mit der verbesserten Evakuierung durch Einsatz von Hubschraubern führte dies zu einer Reduzierung der Amputationsrate von fast 50% auf unter 15%. Nach wie vor ist jedoch das Verbluten die Hauptursache vermeidbarer Todesfälle auf dem Schachtfeld. Die standardmäßige Einführung von Tourniquets, Hämostyptika und Ballonokklusion der Aorta haben die Überlebenschancen verbessert. Das Damage-Control-Prinzip ist insbesondere bei Forward Surgical Teams unverzichtbar und der temporäre intravasale Shunt hat sich frontnah als gefäßchirurgische Damage-Control-Maßnahme längst durchgesetzt. Aufwendige Ausbildungskonzepte vieler Streitkräfte sichern die gefäßchirurgische Notfallkompetenz der stationierten Militärchirurgen. Die Militärchirurgie verfügt aus Krisen- und Kriegsgebieten über reichlich Erfahrung in der Versorgung von massiven Blutungen und schweren Gefäßverletzungen. Zahlreiche hierbei gewonnene Erkenntnisse und Techniken wurden im Laufe der Zeit in die zivile Chirurgie übernommen und aktuelle militärische Entwicklungen beeinflussen auch heute noch die zivile Traumaversorgung.
Delayed Occluding Membrane (DOM) – ein neuer Ansatz zur Protektion der spinalen Ischämie bei endovaskulärem Aortenrepair
Authors: Gombert Alexander , Hussmann Larissa , Kotelis Drosos , Grommes Jochen , Löwen Alexander , Gesche Valentine , Thies Sabrina , Pich Andrij , Gries Thomas , Jockenhövel Stefan , Jacobs Michael , Greiner Andreas
Published: October 2018

Einleitung Sowohl die offene als auch die endovaskuläre Versorgung von thorakoabdominellen Aortenaneurysmen (TAAA) geht mit einem relevanten Risiko für eine Rückenmarksischämie mit einer folgenden Querschnittssymptomatik einher. Verschiedene existente Präventionskonzepte lassen zugleich keine definitive Versorgung des bestehenden TAAA zu. Im vorliegenden Artikel soll ein neuartiges Konzept auf der Basis einer langsam okkludierenden Hydrogel-Textil-Membran vorgestellt werden, das helfen könnte, das Risiko der spinalen Ischämie zu reduzieren.

Konzept Als variabel platzierbare Funktionseinheit von endovaskulären Prothesen wird eine Hydrogel-Textil-Membran entwickelt, die unter Einfluss von Blut bzw. dem im Blut enthaltenen Glutathion zur Quellung gebracht wird. Im weiteren Verlauf führt eine Degradation des Hydrogels zur abschließenden Stabilisierung, die nochmals durch zu erwartende, körpereigene Prozesse verstärkt wird. Dieses Hydrogel soll in den In-vitro-Versuchen einen abnehmenden, zeitlich festgelegten Fluss in den Aneurysmasack zulassen und sich letztendlich verschließen. Durch die Einbringung einer solchen Hydrogel-Textil-Membran in einer Stentprothese könnte somit ohne weitere Interventionen oder präoperative Maßnahmen die notwendige Kollateralbildung des spinalen Gefäßsystems ermöglicht werden. Das Risiko einer spinalen Ischämie könnte somit bei jeder endovaskulären Prozedur, unabhängig von allen weiteren Maßnahmen, auf ein Minimum reduziert werden. Es handelt sich beim vorgestellten Konzept um ein in der Entwicklung befindliches Produkt, daher können nur Zwischenergebnisse berichtet werden.

Schlussfolgerung Die erfolgreiche Entwicklung einer langsam und gezielt okkludierenden Hydrogel-Textil-Membran als Komponente von endovaskulären Aortenprothesen könnte das klinisch bedeutsame Risiko spinaler Ischämie reduzieren helfen.
Modification of Oligopeptides on Aspartic Acid or Lysine Residues by Solid-Phase Synthesis through On-Resin Side-Chain Conjugation
Authors: Shen Hongyan , Ning Xibo , Liu Di , Liu Shimiao , Zhang Mingjie
Published: October 2018

On-resin side-chain conjugations of various moieties to oligo­peptides were performed through an orthogonal protecting protocol using side-chain-protecting groups for aspartic acid or lysine that could be selectively removed on-resin. Various types of modification, such as PEGylation, biotinylation, glycosylation, or fluorophore-labeling of peptides, were realized by using this strategy. The formation of ester, amide, hydrazide, and thiourea bonds was accomplished through the on-resin conjugation. Our work provides an improved and convenient solid-phase synthetic protocol for the modification of oligopeptides on their aspartic acid or lysine residues. This is a universal and practical method that is expected to increase the potential application of peptide-related drugs.
Murine thrombosis models
Authors: Day Sharlene , Reeve Jennifer , Myers Daniel , Fay William
Published: October 2018

Due to exciting advances in molecular biology, the laboratory mouse has become an important and frequently used model for studying thrombosis. This article reviews several experimental approaches that have been used to study arterial, venous, and microvascular thrombosis in mice. The advantages and limitations of different models are examined. Related topics of mouse anesthesia, phlebotomy, and in vitro hemostasis testing are also reviewed.
D-dimer and factor VIIa in atrial fibrillation – prognostic values for cardiovascular events and effects of anticoagulation therapy
Authors: Oldgren Jonas , Andersson Ulrika , Ezekowitz Michael D. , Reilly Paul A. , Connolly Stuart J. , Yusuf Salim , Wallentin Lars , Eikelboom John W. , Siegbahn Agneta
Published: October 2018

Coagulation markers may improve monitoring the risk of stroke and bleeding in patients with atrial fibrillation (AF) during anticoagulant treatment. We examined baseline levels of D-dimer and their association with stroke, cardiovascular death and major bleeding in 6,202 AF patients randomised to dabigatran or warfarin in the RE-LY trial. The effects of treatment on serial levels of D-dimer and coagulation factor (F) VIIa in 2,567 patients were also analysed. Baseline D-dimer levels were related to the rate of stroke/systemic embolism (SEE) with 0.64 % in the lowest quartile (Q1, as reference) (D-dimer < 298 μg/l), 1.38 % Q2 (D-dimer 298–473 μg/l), 1.71 % Q3 (D-dimer 474–822 μg/l) and 2.00 % in Q4 (D-dimer > 822 μg/l) (p=0.0007). Similar associations were shown for cardiovascular death and major bleeding. Addition of baseline D-dimer to established clinical risk factors improved prediction of stroke/SEE, cardiovascular death and major bleeding (C-index increased from 0.66 to 0.68, 0.71 to 0.73 and 0.66 to 0.67, respectively). Dabigatran provided a greater reduction of D-dimer levels than warfarin regardless of baseline anticoagulant treatment. Ontreatment levels of FVIIa were markedly reduced by warfarin (median 12.1–13.8 mU/ml) but significantly higher with dabigatran (median 39.4–49.0 mU/ml) at all-time points. Dabigatran is associated with greater reduction in D-dimer without the pronounced reduction of FVIIa seen with warfarin. These different effects on the coagulation system might explain the better efficacy and less intracranial bleeding observed with dabigatran compared with warfarin.

Clinical Trial Registration: NCT00262600 (www.clinicaltrials.gov).

Supplementary Material to this article is available online at www.thrombosis-online.com.
Therapie mit 177Lu-PSMA-617, Dosimetrie und Nachsorge beim metastasierten kastrationsresistenten Prostatakarzinom
Authors: Fendler Wolfgang , Kratochwil Clemens , Ahmadzadehfar Hojjat , Rahbar Kambiz , Baum Richard , Schmidt Matthias , Pfestroff Andreas , Lützen Ulf , Prasad Vikas , Heinzel Alexander , Heuschkel Martin , Ruf Juri , Bartenstein Peter , Krause Bernd
Published: October 2018

Eine Radioligandentherapie (RLT) mit Lutetium-177 markierten Inhibitoren des Prostataspezifischen Membranantigens (177Lu-PSMA) erfolgt bei Patienten mit metastasiertem kastrationsrefraktären Prostatakarzinom (mCRPC) und fehlender Therapiealternative. Die RLT wird an deutschen Universitätsklinika seit 2013 im Rahmen der Ausübung der ärztlichen Heilkunde angeboten. Diese Konsensusempfehlung gibt Orientierung für die Durchführung einer RLT mit 177Lu-PSMA-617. Sie wurde im Rahmen einer Expertenrunde der Deutschen Gesellschaft für Nuklearmedizin (DGN) im Dezember 2015 erarbeitet und enthält Empfehlungen zu Indikationsstellung, Voruntersuchung, Therapieablauf, Begleittherapie, Dosimetrie und Nachsorge. Die Konsensusempfehlung dient der Information des beteiligten medizinischen Personals und zielt auf eine Harmonisierung der Therapieabläufe sowie eine Verbesserung der Qualität der medizinischen Versorgung des einzelnen Patienten.
Die Bedeutung von Schilddrü senhormontransportern
Authors: Braun D.
Published: October 2018

William Allan, Nash Herndon und Florence Dudley publizierten 1944 Beobachtungen zu einem vererbbaren Syndrom, das sich durch Muskelschwä che, mentale Retardierung (Intelligenzquotient < 30) und Entwicklungsverzö gerungen auszeichnete. Die mä nnlichen Patienten waren unfä hig, ihren Kopf zu halten, hatten Sprachdefizite und konnten meist weder sitzen noch gehen. Inzwischen ist bekannt, dass das Allan-Herndon-Dudley- Syndrom (AHDS) nach dem fragilen X-Syndrom die zweite beschriebene X-chromosomal vererbte Krankheit ist.

Als diagnostisches Kriterium ist inzwischen eine bestimmte Schilddrü senhormonkonstellation hinzugekommen. Die Krankheit ist mit Mutationen im X-chromosomal lokalisierten SLC16A2 Gens assoziiert. SLC16A2 kodiert für einen spezifischen Plasmamembran- Schilddrü senhormon-Transporter, den Monocarboxylattransporter 8 (MCT8)
Graves'-Basedow disease in pregnancy
Authors: Andersen S. L. , Laurberg P.
Published: October 2018

Thyroid hormones are essential development factors and maternal thyroid dysfunction may cause pregnancy complications and diseases in the fetus/child. In the present review we discuss new data on the incidence of Graves'-Basedow disease (GBD) in and around pregnancy, and how hyperthyroidism may affect the risk of spontaneous abortion and stillbirth.

A special concern in pregnant women is the potential side effects from the use of antithyroid drugs (ATDs). One type of side effects is the allergic/toxic reactions to the drugs, which seem to be similar in and outside pregnancy, and another is that ATDs tend to over treat the fetus when the mother with GBD is made euthyroid. To avoid fetal hypothyroidism, the lowest possible ATD dose should be used to keep maternal thyroid function at the upper limit of normality with low serum TSH. Birth defects after the use of methimazole (MMI) (or its prodrug carbimazole) have been considered to be very rare, and no risk has previously been associated with the use of propylthiouracil (PTU). However, a recent Danish national study found that 1/30 of children exposed to MMI in early pregnancy had birth defects associated with this, and many defects were severe. PTU exposure was associated with defects in 1/40, and these defects were less severe. Proposals are given on how to reduce the risk of ATD associated birth defects.
VKCFD2 – from clinical phenotype to molecular mechanism
Authors: Czogalla K. J. , Watzka M. , Oldenburg J.
Published: October 2018

Vitamin K 2,3-epoxide reductase complex, subunit 1 (VKORC1) is an enzyme essential for the vitamin K cycle. VKORC1 catalyses the reduction of vitamin K 2,3-epoxide to the quinone form of vitamin K and further to vitamin K hydroquinone. The generated vitamin K hydroquinone serves as substrate for the enzyme γ-glutamyl-carboxylase which modifies all vitamin K-dependent proteins, allowing them to bind calcium ions necessary for physiological activity. Vitamin K-dependent proteins include the coagulation factors FII, FVII, FIX, FX, and proteins C, S und Z. Insufficient VKORC1 enzyme activity results in deficiency of the vitamin K-dependent clotting factors leading to haemorrhagic disorders. This phenotype is known as vitamin K clotting factor deficiency type 2 (VKCFD2). Worldwide, only four families of independent origin have been reported with this rare bleeding disorder. Affected family members carry the mutation VKORC1:p.Arg98Trp in homozygous form, the only mutation found so far to be associated with VKCFD2. Now, ten years after the identification of the VKORC1 gene, the molecular pathomechanism of VKCFD2 has been clarified. The Arg98Trp mutation disrupts an ER retention motif of VKORC1 leading to mislocalisation of the protein to outside the endoplasmatic reticulum. In this review, we summarize the clinical data, diagnosis, therapy and molecular patho -mechanism of VKCFD2.
The history of canine cruciate ligament surgery from 1952 – 2005
Authors: Vaughan L. C.
Published: October 2018

This article is reprinted by kind permission of Veterinary History where it first appeared in Vol. 14, No. 2 (2008), pgs. 119–136. The paper is the text of an invited lecture that was given by the late Professor Leslie Vaughan. It has not been peer-reviewed, but is reprinted for readers of VCOT. An obituary to Professor Vaughan was published in VCOT 2009 22(3): IX-X.
Matching Clinicians to Operative Cases
Authors: Wanderer J. , Was A.
Published: October 2018

Background: Patient and surgical case complexity are important considerations in creating appropriate clinical assignments for trainees in the operating room (OR). The American Society of Anesthesiologists (ASA) Physical Status Classification System is the most commonly used tool to classify patient illness severity, but it requires manual evaluation by a clinician and is highly variable. A Risk Stratification System for surgical patients was recently published which uses administrative billing codes to calculate four Risk Stratification Indices (RSIs) and provides an objective surrogate for patient complexity that does not require clinical evaluation. This risk score could be helpful when assigning operating room cases.

Objective: This is a technical feasibility study to evaluate the process and potential utility of incorporating an automatic risk score calculation into a web-based tool for assigning OR cases.

Methods: We created a web service implementation of the RSI model for one-year mortality and automatically calculated the RSI values for patients scheduled to undergo an operation the following day. An analysis was conducted on data availability for the RSI model and the correlation between RSI values and ASA physical status.

Results: In a retrospective analysis of 46,740 patients who received surgery in the year preceding the web tool implementation, RSI values were generated for 20,638 patients (44%). The Spear-man’s rank correlation coefficient between ASA physical status classification and one-year mortality RSI values was 0.404.

Conclusions: We have shown that it is possible to create a web-based tool that uses existing billing data to automatically calculate risk scores for patients scheduled to undergo surgery. Such a risk scoring system could be used to match patient acuity to physician experience, and to provide improved patient and clinician experiences. The web tool could be improved by expanding the input database or utilizing procedure booking codes rather than billing data.