湍流边界层中的相干结构是壁面摩擦阻力的主要来源。通过研究超疏水壁面对相干结构的影响,揭示其减阻机理。利用高时间分辨率粒子图像测速技术(TRPIV),分别对流速为0.165m/s的亲水壁面和超疏水壁面平板湍流边界层进行测量,得到了2种壁...湍流边界层中的相干结构是壁面摩擦阻力的主要来源。通过研究超疏水壁面对相干结构的影响,揭示其减阻机理。利用高时间分辨率粒子图像测速技术(TRPIV),分别对流速为0.165m/s的亲水壁面和超疏水壁面平板湍流边界层进行测量,得到了2种壁面瞬时速度矢量场的大样本时间序列。通过对比分析2种壁面的平均速度剖面和湍流度,得到了5.39%的减阻效果。通过二维空间两点相关函数的方法定义并提取相干结构,对比得到超疏水壁面能够有效减小相干结构流向尺度的结论。进一步采用λ ci 准则对发卡涡头进行识别,并以此为条件事件对其周围的脉动速度分布情况进行线性随机估计。结果表明:超疏水壁面能够有效削弱单个发卡涡头的强度,并且能够影响其周围发卡涡包结构的组织形式,整体减弱涡包下方近壁区低速流体质点的流向脉动,从而有效减小壁面摩擦阻力。展开更多
This paper presents a two-step procedure to enable residential Demand Response(DR)programs in Multi-Carrier Energy Systems(MCES),including combined heat and power generation,renewable resources,boiler,and energy stora...This paper presents a two-step procedure to enable residential Demand Response(DR)programs in Multi-Carrier Energy Systems(MCES),including combined heat and power generation,renewable resources,boiler,and energy storage systems.In the first step,an optimization problem is solved to determine the optimal energy cost for each customer.In the second step,the system operator(SO)minimizes the summation of the total loss cost of the electrical distribution system and a designed motivational payment,subject to various operational constraints of the MCES.The motivational payment is the function of deviation of the resulting energy cost of a home in the second step from the desired cost obtained in the first step.The main idea of the proposed procedure is to consider the concerns of customers and the operator,simultaneously.This paper also addresses the uncertainties in renewable resources generation.The proposed procedure is simulated on a test energy system for various cases.The results show that as the level of customer participation in the proposed program is increased,the technical aspects of the integrated energy system are improved.In addition,the customers’costs are decreased by participation in the proposed program.展开更多
The logarithmic moment estimations of parameters are proposed for two-parameter generalized Birnbaum-Saunders Logistic fatigue life distribution GBS-Logistic(α,β)under the full sample.The precisions of point estimat...The logarithmic moment estimations of parameters are proposed for two-parameter generalized Birnbaum-Saunders Logistic fatigue life distribution GBS-Logistic(α,β)under the full sample.The precisions of point estimations are investigated and compared with other point estimations by Monte-Carlo simulations.The approximate interval estimations of parameters are given by using Taylor expansion,and the precisions of approximate interval estimations are investigated by Monte-Carlo simulations.Finally,several examples show the feasibility of the methods.展开更多
In this paper, a-posteriori error estimators are proposed for the Legendre spectral Galerkin method for two-point boundary value problems. The key idea is to postprocess the Galerkin approximation, and the analysis sh...In this paper, a-posteriori error estimators are proposed for the Legendre spectral Galerkin method for two-point boundary value problems. The key idea is to postprocess the Galerkin approximation, and the analysis shows that the postproeess improves the order of convergence. Consequently, we obtain asymptotically exact aposteriori error estimators based on the postprocessing results. Numerical examples are included to illustrate the theoretical analysis.展开更多
针对区域综合能源系统因多重不确定性因素导致的能量失衡问题,实现具有鲁棒性的区域综合能源优化调度,将信息间隙决策理论(information gap decision theory,IGDT)的鲁棒模型和模型预测控制(model predictive control,MPC)相结合,提出...针对区域综合能源系统因多重不确定性因素导致的能量失衡问题,实现具有鲁棒性的区域综合能源优化调度,将信息间隙决策理论(information gap decision theory,IGDT)的鲁棒模型和模型预测控制(model predictive control,MPC)相结合,提出了综合能源系统双层能量优化调度策略。上层利用IGDT对日前调度计划中的不确定因素进行建模,改善因源荷预测误差导致的日前调度计划与实际调度偏差较大问题,下层在日内采用MPC滚动优化,修正日前调度偏差,弥补IGDT开环控制的缺点。并针对IGDT难以处理多不确定性因素的问题,采用两点估计法(two point estimation method,2PEM)和Cornish-Fisher级数展开,将源荷多元不确定性转换为功率缺额的单一不确定性,提高了IGDT模型的求解效率。最后,通过算例验证了所提方法的有效性。展开更多
文摘湍流边界层中的相干结构是壁面摩擦阻力的主要来源。通过研究超疏水壁面对相干结构的影响,揭示其减阻机理。利用高时间分辨率粒子图像测速技术(TRPIV),分别对流速为0.165m/s的亲水壁面和超疏水壁面平板湍流边界层进行测量,得到了2种壁面瞬时速度矢量场的大样本时间序列。通过对比分析2种壁面的平均速度剖面和湍流度,得到了5.39%的减阻效果。通过二维空间两点相关函数的方法定义并提取相干结构,对比得到超疏水壁面能够有效减小相干结构流向尺度的结论。进一步采用λ ci 准则对发卡涡头进行识别,并以此为条件事件对其周围的脉动速度分布情况进行线性随机估计。结果表明:超疏水壁面能够有效削弱单个发卡涡头的强度,并且能够影响其周围发卡涡包结构的组织形式,整体减弱涡包下方近壁区低速流体质点的流向脉动,从而有效减小壁面摩擦阻力。
文摘This paper presents a two-step procedure to enable residential Demand Response(DR)programs in Multi-Carrier Energy Systems(MCES),including combined heat and power generation,renewable resources,boiler,and energy storage systems.In the first step,an optimization problem is solved to determine the optimal energy cost for each customer.In the second step,the system operator(SO)minimizes the summation of the total loss cost of the electrical distribution system and a designed motivational payment,subject to various operational constraints of the MCES.The motivational payment is the function of deviation of the resulting energy cost of a home in the second step from the desired cost obtained in the first step.The main idea of the proposed procedure is to consider the concerns of customers and the operator,simultaneously.This paper also addresses the uncertainties in renewable resources generation.The proposed procedure is simulated on a test energy system for various cases.The results show that as the level of customer participation in the proposed program is increased,the technical aspects of the integrated energy system are improved.In addition,the customers’costs are decreased by participation in the proposed program.
基金supported by the National Natural Science Foundation of China under Grant No.11671264
文摘The logarithmic moment estimations of parameters are proposed for two-parameter generalized Birnbaum-Saunders Logistic fatigue life distribution GBS-Logistic(α,β)under the full sample.The precisions of point estimations are investigated and compared with other point estimations by Monte-Carlo simulations.The approximate interval estimations of parameters are given by using Taylor expansion,and the precisions of approximate interval estimations are investigated by Monte-Carlo simulations.Finally,several examples show the feasibility of the methods.
基金supported partially by the innovation fund of Shanghai Normal Universitysupported partially by NSERC of Canada under Grant OGP0046726.
文摘In this paper, a-posteriori error estimators are proposed for the Legendre spectral Galerkin method for two-point boundary value problems. The key idea is to postprocess the Galerkin approximation, and the analysis shows that the postproeess improves the order of convergence. Consequently, we obtain asymptotically exact aposteriori error estimators based on the postprocessing results. Numerical examples are included to illustrate the theoretical analysis.
文摘针对区域综合能源系统因多重不确定性因素导致的能量失衡问题,实现具有鲁棒性的区域综合能源优化调度,将信息间隙决策理论(information gap decision theory,IGDT)的鲁棒模型和模型预测控制(model predictive control,MPC)相结合,提出了综合能源系统双层能量优化调度策略。上层利用IGDT对日前调度计划中的不确定因素进行建模,改善因源荷预测误差导致的日前调度计划与实际调度偏差较大问题,下层在日内采用MPC滚动优化,修正日前调度偏差,弥补IGDT开环控制的缺点。并针对IGDT难以处理多不确定性因素的问题,采用两点估计法(two point estimation method,2PEM)和Cornish-Fisher级数展开,将源荷多元不确定性转换为功率缺额的单一不确定性,提高了IGDT模型的求解效率。最后,通过算例验证了所提方法的有效性。
