During the floral transition the shoot apical meristem changes its identity from a vegetative to an inflorescence state. This change in identity can be promoted by external signals, such as inductive photoperiod condi...During the floral transition the shoot apical meristem changes its identity from a vegetative to an inflorescence state. This change in identity can be promoted by external signals, such as inductive photoperiod conditions or vernalization, and is accompanied by changes in expression of key developmental genes. The change in meristem identity is usually not reversible, even if the inductive signal occurs only transiently. This implies that at least some of the key genes must possess an intrinsic memory of the newly acquired expression state that ensures irreversibility of the process. In this review, we discuss different molecular scenarios that may underlie a molecular memory of gene expression.展开更多
针对考虑安全约束的机组组合(security constrained unit commitment,SCUC)问题,在传统SCUC模型的基础上,建立考虑有功网损及其在电网中分布的SCUC模型,提出一种基于网损因子迭代的SCUC算法。此算法每次迭代先解固定网损因子的SCUC问题...针对考虑安全约束的机组组合(security constrained unit commitment,SCUC)问题,在传统SCUC模型的基础上,建立考虑有功网损及其在电网中分布的SCUC模型,提出一种基于网损因子迭代的SCUC算法。此算法每次迭代先解固定网损因子的SCUC问题,求得机组的运行状态,然后进行交流潮流计算,更新网损因子,进入下一次迭代。针对可能出现的网损因子振荡问题,提出SCUC和经济调度相结合的方法,选择对应发电成本较小的机组启停状态,进行经济调度优化和网损因子迭代计算,直至算法收敛。对IEEE 30和IEEE 118节点系统进行的仿真计算验证了所提算法的正确性和有效性。展开更多
This paper proposes a graph computing based mixed integer programming(MIP)framework for solving the security constrained unit commitment(SCUC)problem in hydro-thermal power systems incorporating pumped hydro storage(P...This paper proposes a graph computing based mixed integer programming(MIP)framework for solving the security constrained unit commitment(SCUC)problem in hydro-thermal power systems incorporating pumped hydro storage(PHS).The proposed graph computing-based MIP framework considers the economic operations of thermal units,cascade hydropower stations and PHS stations,as well as their technical impacts towards the network security.First,the hydro-thermal power system data and unit information are stored in a graph structure with nodes and edges,which enables nodal and hierarchical parallel computing for the unit commitment(UC)solution calculation and network security analysis.A MIP model is then formulated to solve the SCUC problem with the mathematical models of thermal units,cascade hydropower stations and PHS stations.In addition,two optimization approaches including convex hull reformulation(CHR)and special ordered set(SOS)methods are introduced for speeding up the MIP calculation procedure.To ensure the system stability under the derived UC solution,a parallelized graph power flow(PGPF)algorithm is proposed for the hydro-thermal power system network security analysis.Finally,case studies of the IEEE 118-bus system and a practical 2749-bus hydro-thermal power system are introduced to demonstrate the feasibility and validity of the proposed graph computing-based MIP framework.展开更多
We suggest that employees’ job satisfaction has relationship to friendship network other than professional commitment, and argue that friendship network in the same ward and across wards will have different effects o...We suggest that employees’ job satisfaction has relationship to friendship network other than professional commitment, and argue that friendship network in the same ward and across wards will have different effects on employees’ job satisfaction. A cross-sectional survey design utilizing questionnaires was selected to fulfill the research objectives. All of the 405 nurses in the En Chou Kong Hospital were surveyed. Three hundred and three nurses completed the questionnaire representing a response rate of 74.8%. The instruments included friendship network nomination, professional commitment scale, and nurses’ job satisfaction scale (NJSS). The regression model of job satisfaction was constructed, using friendship network variables in the ward and across wards and professional commitment as independent variables. R square for each model is 0.22-0.36 for the four dimensions of job satisfaction. Professional commitment is the robust predictor. The efficiency of friendship network in the ward is a good predictor, while it is negative related to satisfaction of work load. Further, the indegree in the ward is negative related to work load. Implication was discussed.展开更多
文摘During the floral transition the shoot apical meristem changes its identity from a vegetative to an inflorescence state. This change in identity can be promoted by external signals, such as inductive photoperiod conditions or vernalization, and is accompanied by changes in expression of key developmental genes. The change in meristem identity is usually not reversible, even if the inductive signal occurs only transiently. This implies that at least some of the key genes must possess an intrinsic memory of the newly acquired expression state that ensures irreversibility of the process. In this review, we discuss different molecular scenarios that may underlie a molecular memory of gene expression.
基金国家自然科学基金项目(51107060)国家教育部博士点新教师基金项目(200802481009)+1 种基金Project Supported by National Natural Science Foundation of China(51107060)Doctoral Fund for the New Teacher of Ministry of Education of China(200802481009)
文摘针对考虑安全约束的机组组合(security constrained unit commitment,SCUC)问题,在传统SCUC模型的基础上,建立考虑有功网损及其在电网中分布的SCUC模型,提出一种基于网损因子迭代的SCUC算法。此算法每次迭代先解固定网损因子的SCUC问题,求得机组的运行状态,然后进行交流潮流计算,更新网损因子,进入下一次迭代。针对可能出现的网损因子振荡问题,提出SCUC和经济调度相结合的方法,选择对应发电成本较小的机组启停状态,进行经济调度优化和网损因子迭代计算,直至算法收敛。对IEEE 30和IEEE 118节点系统进行的仿真计算验证了所提算法的正确性和有效性。
文摘This paper proposes a graph computing based mixed integer programming(MIP)framework for solving the security constrained unit commitment(SCUC)problem in hydro-thermal power systems incorporating pumped hydro storage(PHS).The proposed graph computing-based MIP framework considers the economic operations of thermal units,cascade hydropower stations and PHS stations,as well as their technical impacts towards the network security.First,the hydro-thermal power system data and unit information are stored in a graph structure with nodes and edges,which enables nodal and hierarchical parallel computing for the unit commitment(UC)solution calculation and network security analysis.A MIP model is then formulated to solve the SCUC problem with the mathematical models of thermal units,cascade hydropower stations and PHS stations.In addition,two optimization approaches including convex hull reformulation(CHR)and special ordered set(SOS)methods are introduced for speeding up the MIP calculation procedure.To ensure the system stability under the derived UC solution,a parallelized graph power flow(PGPF)algorithm is proposed for the hydro-thermal power system network security analysis.Finally,case studies of the IEEE 118-bus system and a practical 2749-bus hydro-thermal power system are introduced to demonstrate the feasibility and validity of the proposed graph computing-based MIP framework.
文摘We suggest that employees’ job satisfaction has relationship to friendship network other than professional commitment, and argue that friendship network in the same ward and across wards will have different effects on employees’ job satisfaction. A cross-sectional survey design utilizing questionnaires was selected to fulfill the research objectives. All of the 405 nurses in the En Chou Kong Hospital were surveyed. Three hundred and three nurses completed the questionnaire representing a response rate of 74.8%. The instruments included friendship network nomination, professional commitment scale, and nurses’ job satisfaction scale (NJSS). The regression model of job satisfaction was constructed, using friendship network variables in the ward and across wards and professional commitment as independent variables. R square for each model is 0.22-0.36 for the four dimensions of job satisfaction. Professional commitment is the robust predictor. The efficiency of friendship network in the ward is a good predictor, while it is negative related to satisfaction of work load. Further, the indegree in the ward is negative related to work load. Implication was discussed.
