A comparison of arithmetic operations of two dynamic process optimization approaches called quasi-sequential approach and reduced Sequential Quadratic Programming(rSQP)simultaneous approach with respect to equality co...A comparison of arithmetic operations of two dynamic process optimization approaches called quasi-sequential approach and reduced Sequential Quadratic Programming(rSQP)simultaneous approach with respect to equality constrained optimization problems is presented.Through the detail comparison of arithmetic operations,it is concluded that the average iteration number within differential algebraic equations(DAEs)integration of quasi-sequential approach could be regarded as a criterion.One formula is given to calculate the threshold value of average iteration number.If the average iteration number is less than the threshold value,quasi-sequential approach takes advantage of rSQP simultaneous approach which is more suitable contrarily.Two optimal control problems are given to demonstrate the usage of threshold value.For optimal control problems whose objective is to stay near desired operating point,the iteration number is usually small.Therefore,quasi-sequential approach seems more suitable for such problems.展开更多
The simulation of a high-temperature gas-cooled reactor pebble-bed module(HTR-PM) plant is discussed.This lumped parameter model has the form of a set differential algebraic equations(DAEs) that include stiff equation...The simulation of a high-temperature gas-cooled reactor pebble-bed module(HTR-PM) plant is discussed.This lumped parameter model has the form of a set differential algebraic equations(DAEs) that include stiff equations to model point neutron kinetics.The nested approach is the most common method to solve DAE,but this approach is very expensive and time-consuming due to inner iterations.This paper deals with an alternative approach in which a simultaneous solution method is used.The DAEs are discretized over a time horizon using collocation on finite elements,and Radau collocation points are applied.The resulting nonlinear algebraic equations can be solved by existing solvers.The discrete algorithm is discussed in detail;both accuracy and stability issues are considered.Finally,the simulation results are presented to validate the efficiency and accuracy of the simultaneous approach that takes much less time than the nested one.展开更多
AIM: To offer an up-to-date review of all availabletreatment strategies for patients with synchronous colorectal liver metastases(CLM).METHODS: A comprehensive literature search was performed to identify articles rela...AIM: To offer an up-to-date review of all availabletreatment strategies for patients with synchronous colorectal liver metastases(CLM).METHODS: A comprehensive literature search was performed to identify articles related to the management of patients with synchronous CLM. A search of the electronic databases PubMed, MEDLINE, and Google Scholar was conducted in September 2014.The following search terms were used: synchronous colorectal liver metastases, surgery, stage Ⅳ colorectal cancer, liver-first approach, and up-front hepatectomy.These terms were employed in various combinations to maximize the search. Only articles written in English were included. Particular attention was devoted to studies and review articles that were published within the last six years(2009-2014). Additional searches of the cited references from primary articles were performed to further improve the review. The full texts of all relevant articles were accessed by two independent reviewers.RESULTS: Poor long-term outcomes of patients with synchronous CLM managed by a traditional treatment strategy have led to questions about the timing and sequence of possible therapeutic interventions. Thus,alternative paradigms called reverse strategies have been proposed. Presently, there are four treatment strategies available:(1) primary first approach(or traditional approach) comprises resection of the primary colorectal tumor followed by chemotherapy;subsequent liver resection is performed 3-6 mo after colorectal resection(provided that CLM are still resectable);(2) simultaneous resection of the primary colorectal tumor and CLM during a single operation presents intriguing options for a highly select group of patients, which can be associated with significant postoperative morbidity;(3) liver-first(or chemotherapy-first) approach comprises preoperative chemotherapy(3-6 cycles) followed by liver resection,adjuvant chemotherapy, and resection of the primary colorectal tumor(it is best suited for patients withasymptomatic primary tumors and initiall展开更多
在机电暂态仿真计算中,常用的稀疏三角分解存在分解效率不高、并行度低等问题。基于隐式梯形积分法,首先根据雅克比矩阵的特点,将雅可比矩阵分裂,然后利用扩展的Sherrman-Morrison求逆公式递推求解,从而避免了稀疏三角分解,得到了一类...在机电暂态仿真计算中,常用的稀疏三角分解存在分解效率不高、并行度低等问题。基于隐式梯形积分法,首先根据雅克比矩阵的特点,将雅可比矩阵分裂,然后利用扩展的Sherrman-Morrison求逆公式递推求解,从而避免了稀疏三角分解,得到了一类新的机电暂态仿真算法。利用高性能的图形处理器(Graphics Processing Unit, GPU)对大规模合成系统进行仿真测试。结果分析表明,所提出的并行算法可以获得较好的加速比和良好的扩展性。展开更多
基金Supported by the National Natural Science Foundation of China（20676117） the National Creative Research Groups Science Foundation of China（60421002）
文摘A comparison of arithmetic operations of two dynamic process optimization approaches called quasi-sequential approach and reduced Sequential Quadratic Programming(rSQP)simultaneous approach with respect to equality constrained optimization problems is presented.Through the detail comparison of arithmetic operations,it is concluded that the average iteration number within differential algebraic equations(DAEs)integration of quasi-sequential approach could be regarded as a criterion.One formula is given to calculate the threshold value of average iteration number.If the average iteration number is less than the threshold value,quasi-sequential approach takes advantage of rSQP simultaneous approach which is more suitable contrarily.Two optimal control problems are given to demonstrate the usage of threshold value.For optimal control problems whose objective is to stay near desired operating point,the iteration number is usually small.Therefore,quasi-sequential approach seems more suitable for such problems.
基金Project supported by the National Basic Research Program of China (No. 2009CB320603)the National Natural Science Foundation of China (Nos. 60974007 and 60934007)
文摘The simulation of a high-temperature gas-cooled reactor pebble-bed module(HTR-PM) plant is discussed.This lumped parameter model has the form of a set differential algebraic equations(DAEs) that include stiff equations to model point neutron kinetics.The nested approach is the most common method to solve DAE,but this approach is very expensive and time-consuming due to inner iterations.This paper deals with an alternative approach in which a simultaneous solution method is used.The DAEs are discretized over a time horizon using collocation on finite elements,and Radau collocation points are applied.The resulting nonlinear algebraic equations can be solved by existing solvers.The discrete algorithm is discussed in detail;both accuracy and stability issues are considered.Finally,the simulation results are presented to validate the efficiency and accuracy of the simultaneous approach that takes much less time than the nested one.
文摘AIM: To offer an up-to-date review of all availabletreatment strategies for patients with synchronous colorectal liver metastases(CLM).METHODS: A comprehensive literature search was performed to identify articles related to the management of patients with synchronous CLM. A search of the electronic databases PubMed, MEDLINE, and Google Scholar was conducted in September 2014.The following search terms were used: synchronous colorectal liver metastases, surgery, stage Ⅳ colorectal cancer, liver-first approach, and up-front hepatectomy.These terms were employed in various combinations to maximize the search. Only articles written in English were included. Particular attention was devoted to studies and review articles that were published within the last six years(2009-2014). Additional searches of the cited references from primary articles were performed to further improve the review. The full texts of all relevant articles were accessed by two independent reviewers.RESULTS: Poor long-term outcomes of patients with synchronous CLM managed by a traditional treatment strategy have led to questions about the timing and sequence of possible therapeutic interventions. Thus,alternative paradigms called reverse strategies have been proposed. Presently, there are four treatment strategies available:(1) primary first approach(or traditional approach) comprises resection of the primary colorectal tumor followed by chemotherapy;subsequent liver resection is performed 3-6 mo after colorectal resection(provided that CLM are still resectable);(2) simultaneous resection of the primary colorectal tumor and CLM during a single operation presents intriguing options for a highly select group of patients, which can be associated with significant postoperative morbidity;(3) liver-first(or chemotherapy-first) approach comprises preoperative chemotherapy(3-6 cycles) followed by liver resection,adjuvant chemotherapy, and resection of the primary colorectal tumor(it is best suited for patients withasymptomatic primary tumors and initiall
文摘在机电暂态仿真计算中,常用的稀疏三角分解存在分解效率不高、并行度低等问题。基于隐式梯形积分法,首先根据雅克比矩阵的特点,将雅可比矩阵分裂,然后利用扩展的Sherrman-Morrison求逆公式递推求解,从而避免了稀疏三角分解,得到了一类新的机电暂态仿真算法。利用高性能的图形处理器(Graphics Processing Unit, GPU)对大规模合成系统进行仿真测试。结果分析表明,所提出的并行算法可以获得较好的加速比和良好的扩展性。
