bluuebunny/crossref_metadata_2025 huggingface dataset:
Detailed quantitative comparison of half‐bridge modular multilevel converter modelling methods
Authors: Guo Deyang , Rahman Md H. , Ased Grain P. , Xu Lie , Emhemed Abdullah , Burt Graeme , Audichya Yash
Published: October 2018

This paper presents a detailed comparison of different modelling methods of the half‐bridge modular multilevel converter (HB‐MMC), namely, switching function, Thevenin equivalent, and averaged, considering both MMC implementations (large and reduced number of cells). The theoretical basis that underpins each modelling method are discussed. Offline PSCAD simulations are used to validate user‐defined switching function and averaged MMC models against the Thevenin equivalent model provided in PSCAD library for accuracy, considering steady‐state and DC fault conditions. Furthermore, the RTDS based real‐time simulation results of the user‐defined HB‐MMC switching function model are validated against the above mentioned offline models, considering steady‐state and DC short circuit fault operations. Simulation speed and efficiency of different offline HB‐MMC models being studied here are compared. From comprehensive corroboration of different HB‐MMC models presented here, it has been found that the averaged, switching function and Thevenin equivalent models produce practically identical results during steady‐state and DC faults. In detailed offline and real‐time simulation studies where fundamental and harmonic dynamics are of interest, switching function model is found to be faster and computational efficient compared to the Thevenin equivalent model.
Bipolar output direct‐coupled DC–DC converter applied to DC grids
Authors: Guo Lingyu , Yao Gang , Huang Chengjun , Zhou Lidan
Published: October 2018

The unipolar‐input bipolar‐output DC–DC converters with megawatt rating are the key equipment in the multi‐terminal HVDC and DC grids, especially in the DC wind farm. This paper presents a novel direct‐coupled transformerless DC–DC converter to interconnect unipolar DC system with bipolar DC transmission line based on cascaded sub‐modules. The sub‐modules can be achieved by active clamping (clamped diode), half bridge and full bridge. The proportional‐integral control strategy is employed to balance the capacitors' voltages in several sub‐modules and the energy between the upper and lower arms. Compared with other bipolar output DC–DC converters, the new direct‐coupled DC–DC converter offers several merits: (1) The volume and the cost can be reduced due to the absence of the transformer and the large‐scale sub‐module capacitance; (2) There is no extra AC–DC conversion process, so it can achieve higher efficiency; (3) The IGBTs only turn on or off once in a period, which results in lower power loss; (4) High step‐up ratio, redundancy, and fault tolerance can be achieved by changing the number of sub‐modules. Finally, the simulation of the proposed DC–DC converter based on MATLAB/Simulink platform is given to verify the feasibility of the topology and the accuracy of the theoretical analysis.
Principle of ultra‐high‐speed protection for DC transmission line based on inversion transformation of wavefront
Authors: Zhang Chenhao , Song Guobing , Han Wei , Shi Guang , Liu Chao
Published: October 2018

Ultra‐high‐voltage transmission raises high demand for ultra‐high‐speed operation of relay. In this study, the fault information contained in travelling wavefront is analysed on the basis of frequency‐dependent characteristic of transmission line parameters and broadband characteristic of the fault waveform. It can be concluded that the shape change of the fault mode current wavefront is related to the fault distance and the magnitude of the fault mode current wavefront is related to the transition resistance. Hence, a principle of ultra‐high‐speed protection for DC transmission line based on waveform inversion transformation is proposed. The simulation verifies the speediness and reliability of the principle.
Simulation and analysis of  ± 1100 kV UHVDC transmission system with hierarchical connection mode based on PSCAD/EMTDC
Authors: Ren Ziyuan , Li Jiangtao , Yu Fang , He Jiaxin , Liu Yuhao , Sun Yi
Published: October 2018

This study first introduces the structure and principle of the control system of ultra‐high‐voltage direct current (UHVDC) transmission system with hierarchical connection mode, mainly including the whole control logic, the voltage balance control module of high‐end and low‐end converter stations and the commutation failure prediction function. On this basis, this study sets up an electromagnetic transient equivalent model of UHV AC/DC interconnected system with hierarchical connection mode by simulation software electromagnetic transient design and control/power systems computer‐aided design (EMTDC/PSCAD) based on Zhundong–Huadong  ± 1100 kV UHVDC transmission project. The simulation analysis was first carried out in steady‐state operation. Comparing the electrical parameters of the model under the condition of bipolar total voltage with the actual project, the model is consistent with actual engineering parameters. Next, the simulation was undertaken when single‐phase grounding fault occurs on AC bus of rectifier side and inverter side. Finally, simulation waveforms and corresponding conclusion are summarised in this study. The results indicate that the DC control system established with hierarchical connection mode under the PSCAD/EMTDC environment has good adjustment effect and can provide a good reference for practise.
Efficiency‐optimised modulation technique of three‐level NPC inverter
Authors: Li Ning , Li Wanting , Zhang Hui , Yang Ping
Published: October 2018

The three‐level NPC inverter has many advantages, such as the characteristics of high output power, low device stress, and low harmonic distortion of output waveform. It is widely used in the fields of high‐voltage conversion and reactive power compensation. As the most commonly used multi‐level inverter, three‐level NPC inverter has its own disadvantage which is the NP potential fluctuations. It may lead to poor output performance even damage to the devices. Therefore, the problem of NP potential fluctuation of three‐level NPC inverter has been the hotspot of its research. This paper presents an efficiency‐optimised dual modulation wave carrier‐based PWM (DMWPWM) strategy of three‐level NPC inverter. First, the basic principle of traditional DMWPWM is analysed, and the deficiency of traditional DMWPWM modulation technique is described. Then, the efficiency‐optimised DMWPWM strategy is deduced. Compared with traditional DMWPWM strategy, the new strategy inherits the advantage of traditional DMWPWM that the NP voltage balance can be maintained in any modulation index and power factor. Moreover, it can reduce the system switching loss which leads to efficiency improvement, and it is simple and easy to implement. Finally, the proposed modulation technique is verified by simulation.
Comparative research of harmonic suppression algorithm of the three‐level NPC converter
Authors: Ning Li , Tong Gao , Hui Zhang , Ping Yang
Published: October 2018

The three‐level NPC converter is an effective solution to medium‐voltage and high‐power electronic converters. Modulation strategy is one of research focus of the three‐level NPC converter. There are many modulation strategies of the three‐level NPC converter, among them, selective harmonic elimination PWM (SHEPWM) and selective harmonic mitigation PWM (SHMPWM) strategies are very useful technologies since they have the characteristics of low harmonics elimination or reduction. Nevertheless, the SHEPWM and the SHMPWM strategies have the disadvantages in solving non‐linear transcendental equations. Here, non‐linear transcendental equations solution of the SHEPWM and SHMPWM strategies are researched and compared. First, the homotopy algorithm is applied to the SHEPWM strategy. In the solution process, the initial value is obtained by the gravity centre coincidence method, and the numerical solution obtained by the homotopy algorithm is solved by the Newton iteration method to obtain the true solution. Second, the non‐linear transcendental equations of the SHMPWM technique are established and optimised. Finally, simulation models of the three‐level NPC converter using SPWM, SHEPWM, and SHMPWM strategies are built in MATLAB. The comparison and analysis of the three strategies are carried out to verify the effectiveness and superiority of SHEPWM and SHMPWM algorithms in harmonic suppression.
Online monitoring of high‐voltage switchgear installation
Authors: Wang Wei , Shi Hong‐jie , Yan Lin , Jin Tao , Wang Da‐wei , Niu Shu , Tao Wen‐biao
Published: October 2018

The high‐voltage distribution device is an important part of the power supply system which shoulders the dual tasks of control and protection. The function of the high‐voltage distribution device is closely related to the safe operation of the power supply system. The condition monitoring of high‐voltage distribution device can detect the specific parts of the fault in a timely and effective way which can improve the stability of the system. The mechanical vibration signal of circuit breaker body in mine high‐voltage distribution device is a rich information carrier which contains a large number of device operating status information. Using modern information processing technology, the special parameters of mechanical faults are extracted from vibration signals, which have very important practical significance. Based on the analysis of the common mechanical faults in the high‐voltage power distribution unit, a set of online vibration signal processing system with perfect function and reliable operation has been developed, which provides the technical guarantee for the reliable operation of the high‐voltage power distribution unit.
Analysis of the equivalent fault characteristics of DC system and its impact on distance protection based on power‐frequency variation
Authors: Cai Dongxiao , Li Haifeng , Zhu Xinchi
Published: October 2018

Here, the response characteristics of high‐voltage DC (HVDC) control system are studied in the case that fault occurs in the sending‐end AC system. Then the characteristics of DC system which is equivalent to power‐frequency variation impedance in the fault super‐imposed network are analysed by mathematical derivation and verified by simulations on PSCAD/EMTDC. The result shows that the equivalent power‐frequency variation impedance of HVDC system is affected by the rated capacity and the parameters of HVDC control system. The power‐frequency variation impedance becomes capacitive under certain fault conditions, which reduces the zone of distance protection based on power‐frequency variation and even leads to the operation failure.
Study on overvoltage characteristics and arrester configuration strategy for ±1 100 kV HVDC transmission lines
Authors: Zhu Xiaoguang , Liu Yichen , Deng Junbo , Yu Fang , Li Jiangtao , Guo Jie , Zhang Guanjun
Published: October 2018

Overvoltage caused by faults or switching is one of the decisive factors affecting the insulation level of equipment in UHVDC transmission systems. As for ±1 100 kV transmission projects, there has been no clear conclusion about the overvoltage distribution characteristics along transmission lines. This paper studies characteristics of the overvoltage distribution along ±1 100 kV transmission lines after building the simulation platform of ±1 100 kV UHVDC transmission systems with the use of PSCAD software. The typical fault conditions are simulated such as monopolar line‐to‐ground fault and line‐broken‐down fault of transmission lines. The distribution characteristics of overvoltage along the line under different faults are obtained. The simulation results show that the arresters installed along the lines can significantly reduce the switching voltage level of DC lines. The voltage‐current characteristics and the installation density of the arresters along the line have an important influence on the overvoltage suppression effect. Through the comparative analysis, a configuration scheme of arresters along the lines is proposed, which has a great effect for overvoltage suppression. The results are instructive for the design of insulation coordination in practical projects.
Integrated control strategy for smooth switching of the PV and battery‐storage micro‐grid based on operation state tracking
Authors: Yang Li , Song Gao , Wenhui Shi , Guoqing He , ZhengPing Wang
Published: October 2018

Micro‐grid which connects with the main grid can operate under the grid‐connected mode or the islands mode. During the switching process between the two operation modes, if the control strategy is not complete, there will be problems such as the AC bus voltage oscillation and current surge, which will result in the switchover failure. An improved energy storage inverter control method based on operation states tracking is adopted for the optical storage micro‐grid using master–slave control, which solves the problem of control variables mutation. Secondly, an improved software phase‐locked method based on grid phase state tracking is proposed in an energy storage inverter. The problem of instantaneous mutation of the phase angle is solved by cooperating with the micro‐grid operation state control signal during operation mode changes. Through the improvement of the two control strategies above, the transient shock phenomena of the micro‐grid voltage and current during the switching process is obviously improved, and the harmonic content of the AC voltage and current is obviously reduced. Finally, a detailed model of optical storage micro‐grid is established in MATLAB/Simulink, and the correctness and practicability of the improved control strategy are verified by simulation.
A bilayer interaction strategy for air‐conditioning load aggregators considering market‐based demand response
Authors: Zhu Yuchao , Wang Jianxue , Tian Dongmeng , Sun Chunxiao
Published: October 2018

With considerable portion of air‐conditioning load in total power consumption, air‐conditioning load aggregators are authorised to participate in power market by aggregating large amounts of air‐conditioning load with or without ice storage system. This paper studies on a bilayer interaction strategy for air‐conditioning load aggregators considering market‐based demand response, on the basis of a hierarchical deregulated day‐ahead market architecture. In the upper layer, load aggregators submit their bids to independent system operator (ISO), after evaluating their load regulation potential. With the aim of minimising load dispatch cost, ISO optimises the dispatch schedule and informs each LA of its bid‐winning capacity under a pay‐as‐bid pricing scheme. In the lower layer, air‐conditioning load aggregator adopts a flexible control strategy to optimise the control actions in an effort to maximise its own benefits, as well as keeping indoor temperature within the temperature range in the contract and achieving the desired aggregated demand response capacity allocated by ISO in the upper layer. Thermal dynamic characteristics and corresponding power consumption characteristics of air‐conditioning load control strategies are analysed. The resulting model is a mixed‐integer non‐linear optimisation problem. Finally, simulation verifies the feasibility and effectiveness of the proposed strategy.
Design, analysis, and testing of PP‐IGBT‐based submodule stack for the MMC VSC HVDC with 3000 A DC bus current
Authors: Chen Huifeng , Wakeman Frank , Pitman Julian , Li Gangru
Published: October 2018

Voltage sourced converter (VSC) high‐voltage direct current (HVDC) is moving to higher DC voltage and capacity, such as ±500 kV/3000 MW and ±800 kV/5000 MW for a single converter, which will bring tremendous challenges for converter submodule design. This work will focus on the design, analysis, and testing of press‐pack insulated‐gate bipolar transistor (IGBT) (PP‐IGBT)‐based modular multilevel converter (MMC) submodule stack that is suitable for such large converters. It starts with the introduction of internal structure and unique features of PP‐IGBT and diode, which make them good choices for such projects, then followed by study of submodule topological schemes and structural design of the stack. Moreover, it presents computational fluid dynamics (CFD) simulation results on coolers, and it also provides electrothermal simulation results, for the purpose of calculating losses and junction temperature of PP‐IGBT and diode. Furthermore, both device and stack level testing results will be reported, including reverse bias safe operating area, short‐circuit turn‐off, thermal cycling and short‐circuit‐failure‐mode tests for device, and double‐pulse commutation and frequency tests for the stack. In addition, trade‐off considerations for stray inductance between normal switching and shoot‐through fault will be discussed. Finally, by summarising these simulation and experimental studies, it is concluded that a PP‐IGBT‐based stack is proved to be a superb candidate for the coming gigawatt MMC converters.
Relationship between the engaging force of planetary gear train and the position‐correlated modal properties
Authors: Zhang Keming , Zhang Luke , Shao Yimin , Xiao Huifang , Xu Jin , He Rong , Li Liang , Li Hongwu
Published: October 2018

Planetary gear train (PGT) is widely used in a variety of fields such as helicopters and aircraft engines. The failure of meshing gear often happens in the PGT due to the working condition of high speed, variable load, high‐frequency excitation, assembly error etc. However, the causes of gear failure are still insufficiency, especially in the condition of high speed and high‐frequency excitation. In this work, the engaging force between gear meshing pair of the PGT under high‐frequency excitation is studied using the proposed position‐correlated modal properties calculation method, which is established by incorporating the effect of meshing position and meshing phase difference of each contact pair into the free vibration model to study the modal properties of the PGT at different meshing positions. The corresponding engaging force responses based on the position‐correlated modal properties are investigated. The simulation results show that the higher‐order natural frequencies of the system are greatly affected by the meshing position. The peaks of engaging force occur at meshing positions where the natural frequencies are equal to the excitation frequency, which can be the potential cause of the gear damage.
The CARMENES search for exoplanets around M dwarfs
Authors: Luque R. , Nowak G. , Pallé E. , Kossakowski D. , Trifonov T. , Zechmeister M. , Béjar V. J. S. , Cardona Guillén C. , Tal-Or L. , Hidalgo D. , Ribas I. , Reiners A. , Caballero J. A. , Amado P. J. , Quirrenbach A. , Aceituno J. , Cortés-Contreras M. , Díez-Alonso E. , Dreizler S. , Guenther E. W. , Henning T. , Jeffers S. V. , Kaminski A. , Kürster M. , Lafarga M. , Montes D. , Morales J. C. , Passegger V. M. , Schmitt J. H. M. M. , Schweitzer A.
Published: October 2018

We announce the discovery of two planetary companions orbiting around the low-mass stars Ross 1020 (GJ 3779, M4.0V) and LP 819-052 (GJ 1265, M4.5V). The discovery is based on the analysis of CARMENES radial velocity (RV) observations in the visual channel as part of its survey for exoplanets around M dwarfs. In the case of GJ 1265, CARMENES observations were complemented with publicly available Doppler measurements from HARPS. The datasets reveal two planetary companions, one for each star, that share very similar properties: minimum masses of 8.0 ± 0.5 M⊕ and 7.4 ± 0.5 M⊕ in low-eccentricity orbits with periods of 3.023 ± 0.001 d and 3.651 ± 0.001 d for GJ 3779 b and GJ 1265 b, respectively. The periodic signals around 3 d found in the RV data have no counterpart in any spectral activity indicator. Furthermore, we collected available photometric data for the two host stars, which confirm that the additional Doppler variations found at periods of approximately 95 d can be attributed to the rotation of the stars. The addition of these planets to a mass-period diagram of known planets around M dwarfs suggests a bimodal distribution with a lack of short-period low-mass planets in the range of 2–5 M⊕. It also indicates that super-Earths (>5 M⊕) currently detected by RV and transit techniques around M stars are usually found in systems dominated by a single planet.
Negative index and mode coupling in all-dielectric metamaterials at terahertz frequencies
Authors: Akmansoy Eric , Marcellin Simon
Published: October 2018

We elucidate the role of the mode coupling of the Mie resonances in all-dielectric metamaterials to ensure a negative effective index at terahertz frequencies. We perform a study as a function of the lattice period and of the frequency overlapping of the modes of resonance. We show that negative effective refractive index requires sufficiently strong mode coupling and that for even more strong mode coupling, the first two modes of Mie resonances are degenerate; the effective refractive index is then undetermined. We also show that it is possible to obtain near-zero, or even null, effective index with a judicious adjustment of the mode coupling. Further, we discuss the mode coupling effect with hybridization in metamaterials.
Hybrid Low Thrust Propulsion Trajectory Design and Optimization Using Virtual Gravity Method
Authors: Sun Chong , Yuan Jianping , Fang Qun , Cui Yao , Wang Mingxiao , Liu Yisi
Published: October 2018

a novel spacecraft trajectory design method using hybrid low thrust system is proposed in this paper. The hybrid system is constituted with a solar sail propulsion thruster and a solar electric propulsion thruster. In proposed method, the former one provides radical thrust and circumferential thrust to from a virtual gravity, while the later one provides a tangential thrust. In this way, the spacecraft is virtually motioned by constant tangential thrust in a virtual gravity field. Using proposed method, the thrusting trajectory can be parameterized, and a large number of feasible trajectories for circle to circle rendezvous problem can be obtained. To the end the steering law to minimize the fuel cost is found using Matlab optimization tools Fmicon function, and the result is compared with traditional pure solar electric propulsion method in terms of payload mass fraction. The simulation results show that the proposed method can reduced propellant consumption significantly compared with the pure SEP system.
Study on Active Fault Tolerant Flight Control Systems for Quadrotor UAV with Actuator Failures
Authors: Xing Xiaojun , Chen Xiaoran , Huang Longliang , Fan Dongsheng
Published: October 2018

The rotor blades' fatigue fracture of Quadrotor UAV easily causes the instability or even crash of the UAV due to high-load and long-endurance flight missions. Under this circumstances, an active fault-tolerant flight controller of Quadrotor UAV based on integral sliding mode is proposed to strengthen the fault-tolerant capability of UAV's attitude and position. First of all, nonlinear mathematical model of quadrotor UAV with actuator failures is derived by kinematics and dynamics analysis. Secondly, a fault observer is constructed to determine when the actuator failure will occur, subsequently the UAV's attitude and position flight controllers are compensated using integral sliding mode control. The digital simulation and flight test shows that the controller has powerful fault-tolerant capacity and preferable dynamic and static characteristics which can stabilize the attitude and position responses of UAV when partial failure of single blade occurs.
Research on Fault-Tolerant Flight Control Computer for High Altitude Long Endurance Unmanned Air Vehicle
Authors: Pan Jihui , Zhang Shengbing , Wang Danghui
Published: October 2018

With the development of high altitude long endurance UAV, Flight Control System in high altitude long endurance UAV must have so strong failure tolerance ability that it can improve the whole system reliability. Using redundancy technique can extremely improve failure tolerance and reliability of flight control system. Compared among civil and military aircraft and UAV, the architectures and redundancy management of fault-tolerant flight control computer (FCC)systems are introduced. Then, give a new architectures and redundancy management of fault-tolerant FCC systems for high altitude long endurance UAV. The experimental results show that the system meets the UAV's demand of high reliability, low cost and good expansibility, maximize the utilization of system resources and effectively improve the fault tolerant capability of airborne computer and the reliability of sensor subsystem. With fault injection test method, the results show that the fault tolerant methods improve fault detection rate and fault isolation rate.
A Strategy of Efficient and Accurate Cardinality Estimation Based on Query Result
Authors: Gao Jintao , Li Zhanhuai , Liu Wenjie
Published: October 2018

Cardinality estimation is an important component of query optimization. Its accuracy and efficiency directly decide effect of query optimization. Traditional cardinality estimation strategy is based on original table or sample to collect statistics, then inferring cardinality by collected statistics. It will be low-efficiency when handling big data; Statistics exist update latency and are gotten by inferring, which can not guarantee correctness; Some strategies can get the actual cardinality by executing some subqueries, but they do not keep the result, leading to low efficiency of fetching statistics. Against these problems, this paper proposes a novel cardinality estimation strategy, called cardinality estimation based on query result(CEQR). For keeping correctness of cardinality, CEQR directly gets statistics from query results, which is not related with data size; we build a cardinality table to store the statistics of basic tables and middle results under specific predicates. Cardinality table can provide cardinality services for subsequent queries, and we build a suit of rules to maintain cardinality table; To improve the efficiency of fetching statistics, we introduce the source aware strategy, which hashes cardinality item to appropriate cache. This paper gives the adaptability and deviation analytic of CEQR, and proves that CEQR is more efficient than traditional cardinality estimation strategy by experiments.
A Reputation Assessment Approach Based on Fuzzy Mathematics Mobile Application Crowdsourced Testers
Authors: Cheng Jing , Xue Feng , Zhang Yifei , Zhang Tao , Ma Chunyan
Published: October 2018

The anonymity and unsupervision of mobile application crowdsourced testing, makes the tester easy to slacken or cheat on test tasks, resulting in a drop in the quality of crowdsourced testing. To solve the problem, this paper proposes a method for assessing the reputation of a mobile application crowdsourced testers based on fuzzy mathematics. This method closely integrates crowdsourced testing features. By introducing a tester evaluation mechanism, building a reputation assessment model and studying the calculation and update of reputation in the crowdsourced testing, it achieves a reasonable assessment of the reputation of a crowdsourced tester and can effectively screen out high reputation testers, thus ensuring the quality of mobile application crowdsourced testing.
Performance of pulsed-electrochemical honing and pulsed-electrochemical finishing in improving quality of bevel gears
Authors: Pathak Sunil , Jain Neelesh Kumar
Published: October 2018

This article presents a comparative study concerning performance of pulsed-electrochemical honing (PECH) and pulsed-electrochemical finishing (PECF) in straight bevel gear finishing. Performance of these processes were compared in terms of average percentage difference in the considered parameters of surface features of bevel gear namely average percentage differences in average surface roughness ‘PDRa’, maximum surface roughness ‘PDRmax’ and depth of surface roughness ‘PDRz’, micro-geometry (i.e. average percentage differences in single pitch error ‘PDfp’, adjacent pitch error ‘PDfu’, cumulative pitch error ‘PDFp’, and percentage difference in runout ‘PDFr’) and finishing productivity (i.e. material removal rate ‘MRR’). Microstructure and microhardness were also considered as measure for performance assessment. Observed results show PECH is proficient in simultaneously improving all the considered responses of bevel gears by more than 50% as compared to PECF. The PECH-finished gear additionally displayed unrivalled microstructure and better microhardness when contrasted with PECF-finished gear. These changes will upgrade the working-life and operating performance of the finished gear.
Les pulsars radio : 50 ans de découvertes !
Authors: Cognard Ismaël
Published: October 2018

À la fin des années 1960, des impulsions radio régulières sont découvertes en provenance d'astres de notre galaxie. Analogue à celle d'un phare au bord de la mer, l'émission de ces « pulsars » est interprétée comme le passage d'un faisceau radio collimaté (peu divergent) sur la Terre. Parmi les milliers de pulsars connus aujourd'hui, certains sont dotés d'une stabilité de rotation hors du commun les rendant utilisables pour un grand nombre d'applications en physique fondamentale.

Un réseau de pulsars ultra-stables est actuellement utilisé pour chercher la signature des déformations de l'espacetemps induites par les ondes gravitationnelles prédites dans la foulée des travaux d'Albert Einstein. Ces ondes seraient émises par les couples de trous noirs de milliards de masses solaires situés aux centres des galaxies voisines.
Von ADAPTHERA zu Rheuma-VOR: Konzept der koordinierten Kooperation zur Verbesserung der rheumatologischen Versorgungsqualität
Authors: Schwarting Andreas
Published: October 2018

Rheumatologische Erkrankungsbilder nehmen in Ihrer Relevanz immer weiter zu. Die Kombination aus einem optimalen Behandlungsbeginn innerhalb von 12 Wochen nach Beschwerdebeginn und dem Mangel an Rheumatologen stellt eine große Herausforderung für alle Beteiligten dar. Ein möglicher Ansatzpunkt ist die koordinierte Kooperation von Patienten, Primärversorgern (Internisten, Orthopäden, Dermatologen) und den niedergelassenen Rheumatologen mithilfe einer zentralen Koordinationsstelle. Das erfolgreich etablierte rheinland-pfalzweite Netzwerk ADAPTHERA konnte zeigen, dass durch Risikostratifizierung eine zeitnahe Diagnose der Rheumatoiden Arthritis möglich ist und dabei die Ressource „Rheumatologe“ geschont wird. Die durch den Innovationsfonds des Gemeinsamen Bundesausschusses geförderte Proof-of-Concept Folgestudie Rheuma-VOR fußt auf dem gleichen Prinzip, jedoch stehen nun 3 entzündlich-rheumatische Erkrankungen (Rheumatoide Arthritis, Psoriasis Arthritis und Spondylarthritis) im Fokus. Zudem wurde das Projekt auf die Bundesländer Rheinland-Pfalz, Niedersachsen und dem Saarland ausgeweitet. Das Ziel ist die Steigerung der Versorgungsqualität in den 3 Bundesländern bei gleichzeitiger Reduktion der Wartezeiten.
Aktueller und künftiger Stellenwert der gefäßchirurgischen Expertise für Viszeralchirurgen – eine Expertenbefragung
Authors: Koscielny Arne , Schmidt Valeri , Branchi Vittorio , Verrel Frauke , Kalff Jörg , Matthaei Hanno
Published: October 2018

Hintergrund Aufgrund verfeinerter Techniken und optimierten perioperativen Managements werden immer ausgedehntere viszeralchirurgische und onkologische Operationen möglich. Hierbei sind zunehmend präoperativ planbare oder auch notfallmäßige gefäßchirurgische Eingriffe notwendig. Es ist unklar, ob derzeit Fachärzte für Viszeralchirurgie in der Bundesrepublik über ein erforderliches Maß an gefäßchirurgischer Expertise verfügen. Eine Einschätzung des aktuellen Stands und des zukünftigen Stellenwerts gefäßchirurgischer Expertise des Viszeralchirurgen ist daher Gegenstand der Expertenbefragung.

Material und Methoden Durch einen Fragebogen, versandt Mitte 2017 an die Lehrstuhlinhaber für Viszeralchirurgie der deutschen Universitätskliniken sowie an die leitenden Viszeralchirurgen anderer Kliniken, wurde die Rolle der gefäßchirurgischen Expertise in der Viszeralchirurgie erörtert. Es wurden personen-, klinik-, system- und eingriffsspezifische Fragen gestellt.

Ergebnisse An den Unikliniken werden im Vergleich zu nicht universitären Krankenhäusern signifikant häufiger gefäßchirurgische Eingriffe im Rahmen von viszeralchirurgischen Operationen durchgeführt (p < 0,001). Eine gefäßchirurgische Fachkompetenz ist jedoch sowohl universitär als auch außeruniversitär überwiegend vorhanden (72,8%), wohingegen fast ein Drittel aller Befragten den Wunsch nach mehr gefäßchirurgischer Expertise in der eigenen Klinik äußerte. Eine optionale Weiterbildungsrotation in die Gefäßchirurgie für 1 Jahr ist insbesondere an den Unikliniken möglich (92,9 vs. 73,8%; p = 0,031). Die knappe Mehrheit der viszeralchirurgischen Leiter geht davon aus, dass die Gefäßchirurgie in der Zukunft eine größere Rolle in der Viszeralchirurgie spielen wird (51,6%) und spricht sich für eine verpflichtende Rotation in die Gefäßchirurgie während der Weiterbildung zum Viszeralchirurgen von zumindest 6 Monaten aus (54,1%). Die zu vermittelnden gefäßchirurgischen Techniken sollten insbesondere die Thrombektomie und Embolektomie (95,6%), Gefäßnaht (98,6%), Patchplastik (89,1%) und ferner vaskuläre Bypassverfahren (45,5%) umfassen.

Schlussfolgerung Es existiert ein Expertenkonsens darüber, dass die gefäßchirurgische Expertise in der Viszeralchirurgie einen wichtigen und wachsenden Stellenwert innehat. Trotz meist vorhandener Weiterbildungsmöglichkeit scheint an einigen Kliniken noch Bedarf an gefäßchirurgischer Kompetenz zu bestehen. Die obligate Integration entsprechender Weiterbildungsinhalte in die Weiterbildungsordnungen der Landesärztekammern sollte daher diskutiert werden.
Synthesis of 1-Aza-6,7-dehydrotropanes via Copper(I)-Catalyzed Coupling of 5-Chloropentan-2-one with Hydrazines and Terminal Alkynes
Authors: Tehrani Kourosch , Van Beek Wim , Weemaes Karel , Herrebout Wouter , Vande Velde Christophe
Published: October 2018

A one-pot, three-component, Cu(I)-catalyzed coupling of primary hydrazines, 5-chloropentan-2-one, and terminal alkynes was developed. The resulting 1-aza-6,7-dehydrotropanes compose a new class of substances while related 1-azatropanes are scarcely described in literature and closely resemble tropane alkaloids. Hydrogenation of the double bond in 1-aza-6,7-dehydrotropanes triggered a rearrangement, involving a [1,3]-hydride shift, forming cyclic hydrazones.
Messenger RNA profiling of human platelets by microarray hybridization
Authors: Dugrillon Alex , Günaydin Ayse , Eichler Hermann , Klüter Harald , Bugert Peter
Published: October 2018

Platelets are generally believed to be inactive in terms of de novo protein synthesis. On the other hand, the presence of ribosomes and mRNA molecules is well established. Many studies have used reverse transcriptase (RT) -PCR for detection of gene transcripts in platelets. As RT-PCR is a very sensitive method, any leukocyte contamination of platelet preparations can lead to false results. We performed three filtration procedures to minimize leukocyte contamination of pooled buffy-coat platelet concentrates prior to RNA isolation. Furthermore, by applying a genomic PCR approach with 50 amplification cycles we demonstrated that nucleated cells were not detectable. Microarray hybridization was used to analyze 9,850 individual human genes in RNA from purified platelets. In total we identified 1,526 (15.5%) positive genes. The data were confirmed in six individual experiments each performed on a PC pooled from four individual blood donations. Genes specific for nucleated blood cells such as CD4, CD83 and others were negative and verified the purity of PC. Overrepresentation of positive genes was found in the functional categories of glycoproteins/integrins (22.6% vs. 15.5%, p=0.029) and receptors (20.7% vs. 15.5%, p<0.001). Gene transcripts encoding RANTES, GRO-α, MIP-1α, MIP-1β, and others were found at high levels of signal intensity and confirmed literature data. This work provides a mRNA profile of human platelets and a complete list of results can be downloaded from the website of our institute www.ma.uni-heidelberg.de/inst/iti/plt_array.xls. The knowledge about gene transcripts may have an impact on the characterization of novel proteins and their functions in platelets.
Pathophysiologie der Entzündung
Authors: Sahlmann C.-O. , Ströbel P.
Published: October 2018

Entzündung ist das Resultat einer Aktivierung des Immunsystems aus unterschiedlichen Ursachen. Das Immunsystem ist ein hochkomplexes, evolutionär optimiertes Verteidigungssystem aus zellulären und humoralen Komponenten. Die Immunsituation des Wirtes, die Art und Virulenz des entzündlichen Agens und die (teilweise genetisch determinierte) Feinjustierung der Entzündungsreaktion entscheiden über den Ausgang einer Entzündungsreaktion. Probleme entstehen u. a. durch entzündungsbedingte Gewebedefekte (z.B. Fibrose) sowie durch ungenügende (Immundefizienz) oder überschießende Immunantworten (Autoimmunität). Das dynamische Gleichgewicht zwischen Immundefizienz und Autoimmunität wird durch stringente Selektionsmechanismen in Knochenmark und Thymus und durch Kontrollmechanismen (Checkpoints) in den peripheren lymphatischen Geweben sichergestellt. Viele Tumoren haben Eigenschaften, die zu einer Immunsuppression in ihrem Mikromilieu führen und umgehen dadurch ihre Zerstörung durch das Immunsystem.

In den vergangenen Jahren ist es gelungen, diese lokale Immunsuppression durch den Tumor teilweise zu durchbrechen. Erste klinische Studien haben sehr ermutigende Indizien dafür geliefert, dass die Nutzung des Immunsystems für therapeutische Zwecke eine sehr effektive Waffe bei der Bekämpfung von Tumorerkrankungen sein kann.
Peptidrezeptor-Radionuklidtherapie Somatostatinrezeptor- exprimierender Tumore
Authors: Boy C. , Bockisch A. , Kotzerke J. , Buchmann I. , Ezziddin S. , Scheidhauer K. , Krause B. J. , Schmidt D. , Amthauer H. , Rösch F. , Nagarajah J. , Führer D. , Lahner H. , Pöpperl G. , Hörsch D. , Walter M. A. , Baum R. P. , Poeppel T. D.
Published: October 2018

Diese Handlungsempfehlung soll eine Grundlage für die Qualitätssicherung der Peptid - rezeptor-Radionuklidtherapie (PRRT) von Patienten mit Somatostatinrezeptor-exprimierenden Tumoren schaffen, die zurzeit in Deutschland bei fehlenden gleichwertigen oder besseren Therapiealternativen im Rahmen eines individuellen Heilversuches erfolgt. Sie wurde interdisziplinär erarbeitet und enthält neben Definition, allgemeiner Zielsetzung und klinischen Hintergrundinformationen Angaben zu Indikationen und Kontraindikationen der PRRT. Im Mittelpunkt stehen die Anforderungen, die an das Behandlungszentrum gestellt werden, wie die enge Zusammenarbeit der an der Behandlung beteiligten Fachgebiete. Weiterhin wird spezifiziert, welche Untersuchungsbefunde vor der Therapie vorliegen müssen und wie die PRRT technisch und organisatorisch durchzuführen ist. Nach der Behandlung ist eine langfristige Nachsorge/Kontrolle der therapierten Patienten – u. a. zur Gewinnung onkologischer Qualitätsparameter – unabdingbar. Die gesamte Behandlung einschließlich der Nachsorge muss in enger Abstimmung und Zusammenarbeit der beteiligten Fachdisziplinen erfolgen, wobei in der Regel die Empfehlung zur PRRT durch ein multidisziplinäres Tumorboard erfolgen sollte.
Clinical Summarization Capabilities of Commercially-available and Internally-developed Electronic Health Records
Authors: McCoy A.B. , Wright A. , Sittig D.F. , Laxmisan A.
Published: October 2018

Objective: Clinical summarization, the process by which relevant patient information is electronically summarized and presented at the point of care, is of increasing importance given the increasing volume of clinical data in electronic health record systems (EHRs). There is a paucity of research on electronic clinical summarization, including the capabilities of currently available EHR systems.

Methods: We compared different aspects of general clinical summary screens used in twelve different EHR systems using a previously described conceptual model: AORTIS (Aggregation, Organization, Reduction, Interpretation and Synthesis).

Results: We found a wide variation in the EHRs’ summarization capabilities: all systems were capable of simple aggregation and organization of limited clinical content, but only one demonstrated an ability to synthesize information from the data.

Conclusion: Improvement of the clinical summary screen functionality for currently available EHRs is necessary. Further research should identify strategies and methods for creating easy to use, well-designed clinical summary screens that aggregate, organize and reduce all pertinent patient information as well as provide clinical interpretations and synthesis as required.
Determining Primary Care Physician Information Needs to Inform Ambulatory Visit Note Display
Authors: Clarke M.A. , Steege L.M. , Moore J.L. , Koopman R.J. , Belden J.L. , Kim M.S.
Published: October 2018

Background: With the increase in the adoption of electronic health records (EHR) across the US, primary care physicians are experiencing information overload. The purpose of this pilot study was to determine the information needs of primary care physicians (PCPs) as they review clinic visit notes to inform EHR display.

Method: Data collection was conducted with 15 primary care physicians during semi-structured interviews, including a third party observer to control bias. Physicians reviewed major sections of an artificial but typical acute and chronic care visit note to identify the note sections that were relevant to their information needs. Statistical methods used were McNemar-Mosteller’s and Cochran Q.

Results: Physicians identified History of Present Illness (HPI), Assessment, and Plan (A&P) as the most important sections of a visit note. In contrast, they largely judged the Review of Systems (ROS) to be superfluous. There was also a statistical difference in physicians’ highlighting among all seven major note sections in acute (p = 0.00) and chronic (p = 0.00) care visit notes.

Conclusion: A&P and HPI sections were most frequently identified as important which suggests that physicians may have to identify a few key sections out of a long, unnecessarily verbose visit note. ROS is viewed by doctors as mostly “not needed,” but can have relevant information. The ROS can contain information needed for patient care when other sections of the Visit note, such as the HPI, lack the relevant information. Future studies should include producing a display that provides only relevant information to increase physician efficiency at the point of care. Also, research on moving A&P to the top of visit notes instead of having A&P at the bottom of the page is needed, since those are usually the first sections physicians refer to and reviewing from top to bottom may cause cognitive load.

Citation: Clarke MA, Steege LM, Moore JL, Koopman RJ, Belden JL, Kim MS. Determining primary care physician information needs to inform ambulatory visit note display. Appl Clin Inf 2014; 5: 169–190

http://dx.doi.org/10.4338/ACI-2013-08-RA-0064
A tannic extract for oral and topical treatment of CVI and haemorrhoids
Authors: Rohdewald P.
Published: October 2018

The present review summarizes investigations concerning the biological activity as well as the clinical actions of an extract from the bark of the French maritime pine, Pycnogenol®, on the signs and symptoms of the chronic venous insufficiency (CVI). Basis for the anti-oedema and anti-thrombotic action is the maintenance of endothelial health, the capillary sealing, the inhibition of platelet aggregation and the anti-inflammatory and anti-oxidative action of Pycnogenol® following oral and/or local administration. The improvement of microcirculation contributes to faster healing of ulcers and haemorrhoids. The inhibition of oedema formation of the lower limbs and deep vein thromboses was demonstrated after long haul flights. The comparison with some venotonics and elastic stockings demonstrated superior effects of Pycnogenol®. Mild unwanted effects were reported with a rate of about 1 %.
Who is who in der DGP?
Authors: Reich-Schupke Stefanie
Published: October 2018

Junge Ärzte mit Interesse an der Phlebologie werden früher oder später in ihrer phlebologischen Laufbahn Kontakt mit der Deutschen Gesellschaft für Phlebologie (DGP) bekommen – sei es im Rahmen von Fortbildungen, Jahrestagungen oder bei dem Wunsch nach finanzieller Förderung von wissenschaftlichen phlebologischen Projekten. Damit die DGP für sie keine große Unbekannte bleibt, möchten wir die Gesellschaft, ihre Aufgaben und die aktuelle Führungsriege einmal in der Serie „Junge Phlebologie“ vorstellen.
Primäre Varikose und venöse Malformation im Genitalbereich
Authors: Loose D. A. , Faerber G. , Weber J.
Published: October 2018

Die Pathogenese der primären Varikose und besonders auch der congenitalen vaskulären Malformationen im Genitalbereich ist bestimmt durch hämodynamische und hormonelle Faktoren. Sowohl eine primäre Varikose als auch eine sekundäre Varikose bei Gonadalveneninsuffizienz können zu ausgedehnten Vulvavarikositäten mit erheblichen Stauungsbeschwerden führen (Pelvines Stauungssyndrom).

Congenitale venöse Malformationen im Genitalbereich treten sowohl isoliert als auch in Verbindung mit venösen Malformationen der benachbarten Regionen auf und sollten so früh wie möglich behandelt werden. Entsprechend sind in den vergangenen Jahren unterschiedliche Behandlungstaktiken erarbeitet worden, wobei aktuell nach der interventionell radiologischen Okklusionsbehandlung der Gonadalveneninsuffizienz die Sklerotherapie der Vulvavarikositäten primär oder in Ergänzung mit der gefäßchirurgischen Extirpation der Venektasien zu empfehlen ist. Das betrifft auch die venösen Malformationen im Genitalbereich.
Sono-Quiz
Authors: Mendoza Erika
Published: October 2018

Nachdem nun über zwei Jahre Beiträge zu einzelnen Bereichen des Ultraschalls in der Phlebologieerschienen sind, möchten wir mit einem kleinen Quiz das erworbene Wissen abfragen.
Biomedical Data Mining
Authors: Combi C. , Tucker A. , Peek N.
Published: October 2018

Objective: To introduce the special topic of Methods of Information in Medicine on data mining in biomedicine, with selected papers from two workshops on Intelligent Data Analysis in bioMedicine (IDAMAP) held in Verona (2006) and Amsterdam (2007).

Methods: Defining the field of biomedical data mining. Characterizing current developments and challenges for researchers in the field. Reporting on current and future activities of IMIA’s working group on Intelligent Data Analysis and Data Mining. Describing the content of the selected papers in this special topic.

Results and Conclusions: In the biomedical field, data mining methods are used to develop clinical diagnostic and prognostic systems, to interpret biomedical signal and image data, to discover knowledge from biological and clinical databases, and in biosurveillance and anomaly detection applications. The main challenges for the field are i) dealing with very large search spaces in a both computationally efficient and statistically valid manner, ii) incorporating and utilizing medical and biological background knowledge in the data analysis process, iii) reasoning with time-oriented data and temporal abstraction, and iv) developing end-user tools for interactive presentation, interpretation, and analysis of large datasets.