BACKGROUND:?The incidence of hepaticojejunostomy stricture is 4%-10% in experienced centres. Many access loops have been designed and used to facilitate endoscopic intervention for this complication of hepaticojejunos...BACKGROUND:?The incidence of hepaticojejunostomy stricture is 4%-10% in experienced centres. Many access loops have been designed and used to facilitate endoscopic intervention for this complication of hepaticojejunostomy. In this study, we investigated the effectiveness and safety of gastric access loop. METHODS:A retrospective analysis was conducted on 13 patients who had undergone hepaticojejunostomy with gastric access loop between June 1999 and September 2003. Eleven patients were followed up for a mean period of 51 months (range 20-81 months). Two patients were lost to follow up. RESULTS:?On follow-up, 8 patients had patent jejuno- gastrostomy (end to side anastomosis between Roux loop of jejunum and stomach) and hepaticojejunostomy. Three patients developed stricture of jejunogastrostomy at 41 months, 63 months and 81 months of follow-up. Among these 3 patients, one also had hepaticojejunostomy stricture. In the patient with hepaticojejunostomy stricture, dilatation of jejunogastrostomy stricture was attempted but failed. None of the patients had any evidence of bile gastritis/cholangitis. There was no procedure related morbidity/mortality. CONCLUSIONS:Further studies involving large numbers of patients are required before wide application of gastric access loop in hepaticojejunostomy though it is a safer option than percutaneous transhepatic manipulations or revision surgery.展开更多
分子动力学(MD)模拟是研究硅纳米薄膜热力学性质的主要方法,但存在数据处理量大、计算密集、原子间作用模型复杂等问题,限制了MD模拟的深入应用。针对晶硅分子动力学模拟算法中数据访问不连续和大量分支判断造成并行资源浪费、线程等待...分子动力学(MD)模拟是研究硅纳米薄膜热力学性质的主要方法,但存在数据处理量大、计算密集、原子间作用模型复杂等问题,限制了MD模拟的深入应用。针对晶硅分子动力学模拟算法中数据访问不连续和大量分支判断造成并行资源浪费、线程等待等问题,结合Nvidia Tesla V100 GPU硬件体系结构特点,对晶硅MD模拟算法进行设计。通过全局内存的合并访存、循环展开、原子操作等优化方法,利用GPU强大并行计算和浮点运算能力,减少显存访问及算法执行过程中的分支冲突和判断指令,提升算法整体计算性能。测试结果表明,优化后的晶硅MD模拟算法的计算速度相比于优化前提升了1.69~1.97倍,相比于国际上主流的GPU加速MD模拟软件HOOMDblue和LAMMPS分别提升了3.20~3.47倍和17.40~38.04倍,具有较好的模拟加速效果。展开更多
In this paper, the closed loop transmit diversity technology for the Wideband Code Division Multiple Access(WCDMA) systems is investigated in a multipath Rayleigh fading channel. The RAKE receiver model and the weighi...In this paper, the closed loop transmit diversity technology for the Wideband Code Division Multiple Access(WCDMA) systems is investigated in a multipath Rayleigh fading channel. The RAKE receiver model and the weighing vector algorithm are presented. The performance is theoretically analyzed in terms of the average maximal Signal-to-Noise Ratio(SNR) gain available over the Space-Time block coding based Transmit Diversity(STTD) technology. Theoretic analysis and simulation results show that the closed loop transmit diversity can provide a 3dB performance gain over the open loop scheme in a single path fading channel, while the performance gain decreases dramatically with the increasing inherent multipath diversity of the wireless channel.展开更多
文摘BACKGROUND:?The incidence of hepaticojejunostomy stricture is 4%-10% in experienced centres. Many access loops have been designed and used to facilitate endoscopic intervention for this complication of hepaticojejunostomy. In this study, we investigated the effectiveness and safety of gastric access loop. METHODS:A retrospective analysis was conducted on 13 patients who had undergone hepaticojejunostomy with gastric access loop between June 1999 and September 2003. Eleven patients were followed up for a mean period of 51 months (range 20-81 months). Two patients were lost to follow up. RESULTS:?On follow-up, 8 patients had patent jejuno- gastrostomy (end to side anastomosis between Roux loop of jejunum and stomach) and hepaticojejunostomy. Three patients developed stricture of jejunogastrostomy at 41 months, 63 months and 81 months of follow-up. Among these 3 patients, one also had hepaticojejunostomy stricture. In the patient with hepaticojejunostomy stricture, dilatation of jejunogastrostomy stricture was attempted but failed. None of the patients had any evidence of bile gastritis/cholangitis. There was no procedure related morbidity/mortality. CONCLUSIONS:Further studies involving large numbers of patients are required before wide application of gastric access loop in hepaticojejunostomy though it is a safer option than percutaneous transhepatic manipulations or revision surgery.
文摘分子动力学(MD)模拟是研究硅纳米薄膜热力学性质的主要方法,但存在数据处理量大、计算密集、原子间作用模型复杂等问题,限制了MD模拟的深入应用。针对晶硅分子动力学模拟算法中数据访问不连续和大量分支判断造成并行资源浪费、线程等待等问题,结合Nvidia Tesla V100 GPU硬件体系结构特点,对晶硅MD模拟算法进行设计。通过全局内存的合并访存、循环展开、原子操作等优化方法,利用GPU强大并行计算和浮点运算能力,减少显存访问及算法执行过程中的分支冲突和判断指令,提升算法整体计算性能。测试结果表明,优化后的晶硅MD模拟算法的计算速度相比于优化前提升了1.69~1.97倍,相比于国际上主流的GPU加速MD模拟软件HOOMDblue和LAMMPS分别提升了3.20~3.47倍和17.40~38.04倍,具有较好的模拟加速效果。
基金Supported by the National Natural Science Foundation of China (No. 60496311)
文摘In this paper, the closed loop transmit diversity technology for the Wideband Code Division Multiple Access(WCDMA) systems is investigated in a multipath Rayleigh fading channel. The RAKE receiver model and the weighing vector algorithm are presented. The performance is theoretically analyzed in terms of the average maximal Signal-to-Noise Ratio(SNR) gain available over the Space-Time block coding based Transmit Diversity(STTD) technology. Theoretic analysis and simulation results show that the closed loop transmit diversity can provide a 3dB performance gain over the open loop scheme in a single path fading channel, while the performance gain decreases dramatically with the increasing inherent multipath diversity of the wireless channel.
