This paper investigates a control and protection strategy for a four-terminal modular multilevel converter(MMC)based high-voltage direct current(HVDC)system under a converter-side AC fault.Based on the system operatin...This paper investigates a control and protection strategy for a four-terminal modular multilevel converter(MMC)based high-voltage direct current(HVDC)system under a converter-side AC fault.Based on the system operating condition,a control and protection strategy against the fault with normal blocking of the converter is proposed.In practical,applications encountering such a fault,the MMC at the fault side may experience different conditions of blocking failure.The blocking failures may occur on:①the whole converter;②one converter arm;③one sub-module(SM)/several SMs of one converter arm;④other conditions.The phenomenon of the multi-terminal HVDC(MTDC)system following the fault is analyzed under the first three conditions with real-time simulations using the real-time digital simulator(RTDS).Based on the impact of different conditions on the MTDC system,the necessity of utilizing special control and protection is discussed.A special control and protection strategy is proposed for emergency conditions,and its effectiveness is verified by real-time simulation results.展开更多
With the increasing complexity of industrial application, an embedded control system (ECS) requires processing a number of hard real-time tasks and needs fault-tolerance to assure high reliability. Considering the cha...With the increasing complexity of industrial application, an embedded control system (ECS) requires processing a number of hard real-time tasks and needs fault-tolerance to assure high reliability. Considering the characteristics of real-time tasks in ECS, an integrated algorithm is proposed to schedule real-time tasks and to guarantee that all real-time tasks are completed before their deadlines even in the presence of faults. Based on the nonpreemptive critical-section protocol (NCSP), this paper analyzes the blocking time introduced by resource conflicts of relevancy tasks in fault-tolerant multiprocessor systems. An extended schedulability condition is presented to check the assignment feasibility of a given task to a processor. A primary/backup approach and on-line replacement of failed processors are used to tolerate processor failures. The analysis reveals that the integrated algorithm bounds the blocking time, requires limited overhead on the number of processors, and still assures good processor utilization. This is also demonstrated by simulation results. Both analysis and simulation show the effectiveness of the proposed algorithm in ECS.展开更多
A discrete artificial bee colony algorithm is proposed for solving the blocking flow shop scheduling problem with total flow time criterion. Firstly, the solution in the algorithm is represented as job permutation. Se...A discrete artificial bee colony algorithm is proposed for solving the blocking flow shop scheduling problem with total flow time criterion. Firstly, the solution in the algorithm is represented as job permutation. Secondly, an initialization scheme based on a variant of the NEH (Nawaz-Enscore-Ham) heuristic and a local search is designed to construct the initial population with both quality and diversity. Thirdly, based on the idea of iterated greedy algorithm, some newly designed schemes for employed bee, onlooker bee and scout bee are presented. The performance of the proposed algorithm is tested on the well-known Taillard benchmark set, and the computational results demonstrate the effectiveness of the discrete artificial bee colony algorithm. In addition, the best known solutions of the benchmark set are provided for the blocking flow shop scheduling problem with total flow time criterion.展开更多
Daily output from the hindcasts by the NCEP Climate Forecast System version 2 （CFSv2） is analyzed to understand CFSv2＇s skill in forecasting wintertime atmospheric blocking in the Northern Hemisphere. Prediction sk...Daily output from the hindcasts by the NCEP Climate Forecast System version 2 （CFSv2） is analyzed to understand CFSv2＇s skill in forecasting wintertime atmospheric blocking in the Northern Hemisphere. Prediction skills of sector blocking, sector-blocking episodes, and blocking onset/decay are assessed with a focus on the Euro-Atlantic sector （20°W-45°E） and the Pacific sector （160°E 135°W）. Features of associated circulation and climate patterns are also examined. The CFSv2 well captures the observed features of longitudinal distribution of blocking activity, but underestimates blocking frequency and intensity and shows a decreasing trend in blocking frequency with increasing forecast lead time. Within 14-day lead time, the Euro-Atlantic sector blocking receives a higher skill than the Pacific sector blocking. Skillful forecast （taking the hit rate of 50~ as a criterion） can be obtained up to 9 days in the Euro-Atlantic sector, which is slightly longer than that in the Pacific sector （7 days）. The forecast skill of sector-blocking episodes is slightly lower than that of sector blocking in both sectors, and it is slightly higher in the Euro-Atlantic sector than in the Pacific sector. Compared to block onset, the skill for block decay is lower in the Euro-Atlantic sector, slightly higher in the Pacific sector during the early three days but lower after three days in lead time. In both the Euro-Atlantic and the Pacific sectors, a local dipole pattern in 500-hPa geopotential height associated with blocking is well presented in the CFSv2 prediction, but the wave-train like pattern that is far away from the blocking sector can only maintain in the forecast of relative short lead time. The CFSv2 well reproduces the observed characteristics of local temperature and precipitation anomalies associated with blocking.展开更多
OBJECTIVE: To study the pharmacodynamics of vecuronium,atracurium, mivacurium and rocuronium in patients with end-stage renal failure. METHODS: Forty-six patients with end-stage renal failure scheduled for renal trans...OBJECTIVE: To study the pharmacodynamics of vecuronium,atracurium, mivacurium and rocuronium in patients with end-stage renal failure. METHODS: Forty-six patients with end-stage renal failure scheduled for renal transplantation and 53 patients with normal renal function were given either vecuronium, atracurium, mivacurium or rocuronium. The neuromuscular effects were monitored by the evoked response of the adductor pollicis to train-of-four stimulation of the ulnar nerve. RESULTS: Onset of vecuronium, atracurium and mivacurium occurred faster or tended to be faster in patients with end-stage renal failure, but there was no significant difference in onset by rocuronium between the control patients and renal failure patients. Furthermore, the no-response period, duration of action and recovery of atracurium did not differ between the two groups. There was no significant difference in duration of action or recovery of mivacurium between the two groups, whereas its no-response period was significantly prolonged in the patients with end-stage renal failure. There was no difference in no-response period or duration of action after the initial dose of vecuronium or rocuronium between the two groups. However, no-response period and duration of effect by vecuronium and rocuronium were prolonged with increasing incremental doses in patients with end-stage renal failure. CONCLUSIONS: All four muscle relaxants could be safely used in patients with end-stage renal failure. Onset of the relaxants were, in some cases, accelerated and no-response period of mivacurium was prolonged in patients with end-stage renal failure undergoing dialysis therapy. End-stage renal failure prolonged the no-response period and duration of action of vecuronium and rocuronium after repeated incremental doses, but did not alter those attributed to atracurium.展开更多
目的:评估两种不同冲封管频次(每24 h 1次与每12 h 1次)对1~3岁患儿外周静脉导管堵管率及留置时间的影响。方法:采用随机数字表法将2021年4月—6月3所医院1~3岁住院患儿分为观察组(n=115)和对照组(n=117),分别按照每24 h 1次与每12 h 1...目的:评估两种不同冲封管频次(每24 h 1次与每12 h 1次)对1~3岁患儿外周静脉导管堵管率及留置时间的影响。方法:采用随机数字表法将2021年4月—6月3所医院1~3岁住院患儿分为观察组(n=115)和对照组(n=117),分别按照每24 h 1次与每12 h 1次进行脉冲式冲管、正压封管,比较两组患儿留置针堵管发生率和留置时间。结果:意向性分析显示观察组和对照组留置针堵管率分别为10.4%、8.5%,两组比较,差异无统计学意义(P>0.05),差值为-1.9%(95%CI:-9.4%~5.6%),观察组冲封管频次非劣效于对照组。观察组和对照组留置针留置时间分别为(63.74±19.72)h、(68.43±19.52)h,两组比较,差异无统计学意义(P>0.05)。结论:每24 h生理盐水冲封管1次可维持1~3岁患儿外周静脉导管通畅,在不影响其留置时间的前提下节约成本、减轻护士工作量,为幼儿外周静脉导管的维护提供依据。展开更多
基金This work is supported by UK EPSRC and UK National Grid.
文摘This paper investigates a control and protection strategy for a four-terminal modular multilevel converter(MMC)based high-voltage direct current(HVDC)system under a converter-side AC fault.Based on the system operating condition,a control and protection strategy against the fault with normal blocking of the converter is proposed.In practical,applications encountering such a fault,the MMC at the fault side may experience different conditions of blocking failure.The blocking failures may occur on:①the whole converter;②one converter arm;③one sub-module(SM)/several SMs of one converter arm;④other conditions.The phenomenon of the multi-terminal HVDC(MTDC)system following the fault is analyzed under the first three conditions with real-time simulations using the real-time digital simulator(RTDS).Based on the impact of different conditions on the MTDC system,the necessity of utilizing special control and protection is discussed.A special control and protection strategy is proposed for emergency conditions,and its effectiveness is verified by real-time simulation results.
文摘With the increasing complexity of industrial application, an embedded control system (ECS) requires processing a number of hard real-time tasks and needs fault-tolerance to assure high reliability. Considering the characteristics of real-time tasks in ECS, an integrated algorithm is proposed to schedule real-time tasks and to guarantee that all real-time tasks are completed before their deadlines even in the presence of faults. Based on the nonpreemptive critical-section protocol (NCSP), this paper analyzes the blocking time introduced by resource conflicts of relevancy tasks in fault-tolerant multiprocessor systems. An extended schedulability condition is presented to check the assignment feasibility of a given task to a processor. A primary/backup approach and on-line replacement of failed processors are used to tolerate processor failures. The analysis reveals that the integrated algorithm bounds the blocking time, requires limited overhead on the number of processors, and still assures good processor utilization. This is also demonstrated by simulation results. Both analysis and simulation show the effectiveness of the proposed algorithm in ECS.
基金Supported by the National Natural Science Foundation of China (61174040, 61104178)the Fundamental Research Funds for the Central Universities
文摘A discrete artificial bee colony algorithm is proposed for solving the blocking flow shop scheduling problem with total flow time criterion. Firstly, the solution in the algorithm is represented as job permutation. Secondly, an initialization scheme based on a variant of the NEH (Nawaz-Enscore-Ham) heuristic and a local search is designed to construct the initial population with both quality and diversity. Thirdly, based on the idea of iterated greedy algorithm, some newly designed schemes for employed bee, onlooker bee and scout bee are presented. The performance of the proposed algorithm is tested on the well-known Taillard benchmark set, and the computational results demonstrate the effectiveness of the discrete artificial bee colony algorithm. In addition, the best known solutions of the benchmark set are provided for the blocking flow shop scheduling problem with total flow time criterion.
基金Supported by the National(Key)Basic Research and Development(973)Program of China(2010CB428606 and 2014CB950900)China Meteorological Administration Special Public Welfare Research Fund(GYHY201206017)+1 种基金National Science and Technology Support Program of China(2009BAC51B05)LASW State Key Laboratory Special Fund(2013LASW-A05)
文摘Daily output from the hindcasts by the NCEP Climate Forecast System version 2 （CFSv2） is analyzed to understand CFSv2＇s skill in forecasting wintertime atmospheric blocking in the Northern Hemisphere. Prediction skills of sector blocking, sector-blocking episodes, and blocking onset/decay are assessed with a focus on the Euro-Atlantic sector （20°W-45°E） and the Pacific sector （160°E 135°W）. Features of associated circulation and climate patterns are also examined. The CFSv2 well captures the observed features of longitudinal distribution of blocking activity, but underestimates blocking frequency and intensity and shows a decreasing trend in blocking frequency with increasing forecast lead time. Within 14-day lead time, the Euro-Atlantic sector blocking receives a higher skill than the Pacific sector blocking. Skillful forecast （taking the hit rate of 50~ as a criterion） can be obtained up to 9 days in the Euro-Atlantic sector, which is slightly longer than that in the Pacific sector （7 days）. The forecast skill of sector-blocking episodes is slightly lower than that of sector blocking in both sectors, and it is slightly higher in the Euro-Atlantic sector than in the Pacific sector. Compared to block onset, the skill for block decay is lower in the Euro-Atlantic sector, slightly higher in the Pacific sector during the early three days but lower after three days in lead time. In both the Euro-Atlantic and the Pacific sectors, a local dipole pattern in 500-hPa geopotential height associated with blocking is well presented in the CFSv2 prediction, but the wave-train like pattern that is far away from the blocking sector can only maintain in the forecast of relative short lead time. The CFSv2 well reproduces the observed characteristics of local temperature and precipitation anomalies associated with blocking.
文摘OBJECTIVE: To study the pharmacodynamics of vecuronium,atracurium, mivacurium and rocuronium in patients with end-stage renal failure. METHODS: Forty-six patients with end-stage renal failure scheduled for renal transplantation and 53 patients with normal renal function were given either vecuronium, atracurium, mivacurium or rocuronium. The neuromuscular effects were monitored by the evoked response of the adductor pollicis to train-of-four stimulation of the ulnar nerve. RESULTS: Onset of vecuronium, atracurium and mivacurium occurred faster or tended to be faster in patients with end-stage renal failure, but there was no significant difference in onset by rocuronium between the control patients and renal failure patients. Furthermore, the no-response period, duration of action and recovery of atracurium did not differ between the two groups. There was no significant difference in duration of action or recovery of mivacurium between the two groups, whereas its no-response period was significantly prolonged in the patients with end-stage renal failure. There was no difference in no-response period or duration of action after the initial dose of vecuronium or rocuronium between the two groups. However, no-response period and duration of effect by vecuronium and rocuronium were prolonged with increasing incremental doses in patients with end-stage renal failure. CONCLUSIONS: All four muscle relaxants could be safely used in patients with end-stage renal failure. Onset of the relaxants were, in some cases, accelerated and no-response period of mivacurium was prolonged in patients with end-stage renal failure undergoing dialysis therapy. End-stage renal failure prolonged the no-response period and duration of action of vecuronium and rocuronium after repeated incremental doses, but did not alter those attributed to atracurium.
文摘目的:评估两种不同冲封管频次(每24 h 1次与每12 h 1次)对1~3岁患儿外周静脉导管堵管率及留置时间的影响。方法:采用随机数字表法将2021年4月—6月3所医院1~3岁住院患儿分为观察组(n=115)和对照组(n=117),分别按照每24 h 1次与每12 h 1次进行脉冲式冲管、正压封管,比较两组患儿留置针堵管发生率和留置时间。结果:意向性分析显示观察组和对照组留置针堵管率分别为10.4%、8.5%,两组比较,差异无统计学意义(P>0.05),差值为-1.9%(95%CI:-9.4%~5.6%),观察组冲封管频次非劣效于对照组。观察组和对照组留置针留置时间分别为(63.74±19.72)h、(68.43±19.52)h,两组比较,差异无统计学意义(P>0.05)。结论:每24 h生理盐水冲封管1次可维持1~3岁患儿外周静脉导管通畅,在不影响其留置时间的前提下节约成本、减轻护士工作量,为幼儿外周静脉导管的维护提供依据。
