Because of the complexities of tire-road interaction,the wheels of a multi-wheel distributed electricdrive vehicle can easily slip under certain working conditions.As wheel slip affects the dynamic per-formance and st...Because of the complexities of tire-road interaction,the wheels of a multi-wheel distributed electricdrive vehicle can easily slip under certain working conditions.As wheel slip affects the dynamic per-formance and stability of the vehicle,it is crucial to control it and coordinate the driving force.With this aim,this paper presents a driving force coordination control strategy with road identification for eight-wheeled electric vehicles equipped with an in-wheel motor for each wheel.In the proposed control strategy,the road identification module estimates tire-road forces using an unscented Kalman filter al-gorithm and recognizes the road adhesion coefficient by employing the recursive least-square method According to road identification,the optimal sip ratio under the current driving condition is obtainedand a controller based on sliding mode control with a conditional integrator uses this value for accel-eration slip regulation.The anti-slip controller obtains the adjusting torque,which is integrated with the driver-command-based feedforward control torque to implement driving force coordination control.The results of hardware-in-loop simulation show that this control strategy can accurately estimate tire-roadrces as well as the friction coefficient,and thus,can effectively fulfill the purpose of driving force coordinated control under different driving conditions.展开更多
How to allocate a resource efficiently and fairly attracts the attention of both researchers and practitioners. Data envelopment analysis（DEA） has been brought to bear on its solution. The existing literature applie...How to allocate a resource efficiently and fairly attracts the attention of both researchers and practitioners. Data envelopment analysis（DEA） has been brought to bear on its solution. The existing literature applies Gini coefficient to measure the fairness in the resource allocation process. However, the Gini coefficient is inapplicable in many applications. This paper proposes a novel centralized resource allocation model based on DEA that considers both the efficiency and the fairness. This paper adopts a notion of fairness, namely α-fairness that is well studied in welfare economics and is of practical significance. The new model integratesα-fairness with DEA to support resource allocation decisions. It aids decision makers in making a trade-off between the efficiency and the fairness. An illustrative application is used to validate the proposed approach.展开更多
Cooling in industrial production and refrigeration of perishable and</span><span style="font-size:10.0pt;font-family:""> non-</span><span style="font-size:10.0pt;font-family:&q...Cooling in industrial production and refrigeration of perishable and</span><span style="font-size:10.0pt;font-family:""> non-</span><span style="font-size:10.0pt;font-family:""> </span><span style="font-size:10.0pt;font-family:"">perishable products is common practice throughout the world. Research studies have been conducted both experimentally and numerically to simulate Vapor Compression Refrigeration System (VCRS) and its performance respectively, however, experimental procedure often seems to be expensive and time-consuming to carry out due to the function of many variables. This study was therefore designed to numerically simulate the performance assessment of a nanoparticle enhanced VCRS. A numerical model of a vapor compression refrigeration system was developed using standard refrigeration equations on each of the major components of the refrigeration system such as compressor, evaporator, condenser and expansion valve. The model was then simulated on a MATLAB platform with a CoolProp installed packages via Python under two different simulation cases. In the first case, the mass fractions were varied for CuO,</span><span style="font-size:10.0pt;font-family:""> </span><span style="font-size:10.0pt;font-family:"">TiO<sub>2</sub> and Al<sub>2</sub>O<sub>3</sub> nanoparticles while their densities remained constant and a reversed condition was investigated for the second case. The results showed that both the refrigerating effect and the Coefficient Of Performance (COP) of the system increase as both the mass fraction and density of all the nanoparticles increases. It also shows that the compressor work decreases as both the mass fraction and density of all the nanoparticles were increased. On comparing the computational and numerical analysis results, the study established no significant difference in terms of COP and the use of nanoparticles were found to have improved the COP of the system.展开更多
本研究利用Simrad EK60科学探鱼仪(38 k Hz)于2013年春季和2014年春季采集的南沙和中沙、西沙海域渔业声学数据,结合中层拖网取样,采用回声积分法研究了南海中南部中层鱼的资源量及其时空分布特征。结果显示,2014年春季中、西沙海域9次...本研究利用Simrad EK60科学探鱼仪(38 k Hz)于2013年春季和2014年春季采集的南沙和中沙、西沙海域渔业声学数据,结合中层拖网取样,采用回声积分法研究了南海中南部中层鱼的资源量及其时空分布特征。结果显示,2014年春季中、西沙海域9次中层拖网作业共捕获和鉴定鱼类和头足类79种,隶属于3纲16目37科60属,其中硬骨鱼纲的种类最多(65种),鞘亚纲次之(13种),软骨鱼纲1种,硬骨鱼纲中巨口鱼科、灯笼鱼科和钻光鱼科的种类最多,分别有20种、13种和6种;南沙海域中层鱼声学积分值(nautical area scattering coefficient,m^2/nmi^2)显著低于中沙、西沙及邻近海域,前者夜间向上迁移的强度高于后者;2013年春季南沙海域夜间10~200 m和白天200~1000 m声学积分值构成没有显著差异(P>0.05),而2014年春季中沙、西沙海域夜间10~200 m和白天200~1000 m声学积分值构成有极显著差异(P<0.01);南沙海域白天200~1000 m不同纬度组间中层鱼声学积分值构成有极显著差异(P<0.01),中沙、西沙海域声学积分值构成亦有极显著差异(P<0.01);南海中南部中层鱼声学积分值是(2387±601)m^2/nmi^2,基于现存公开发表的中层鱼的声学目标强度数据并取其均值,推算南海中南部中层鱼资源量是(8200±2100)万t。研究表明,南海中南部中层鱼声学积分值比全球平均值高约29.2%,可能是我国未来具有开发价值的大宗生物资源。展开更多
气体绝缘开关设备(GIS)中的隔离开关操作,会产生特快速瞬态过电压(VFTO)和壳体电位升高(TEV)等问题。该研究旨在通过试验方法研究TEV和VFTO之间的关系,并分析TEV在GIS回路中的形成原因和传播规律。研究中,首先利用自制的TEV和VFTO测量系...气体绝缘开关设备(GIS)中的隔离开关操作,会产生特快速瞬态过电压(VFTO)和壳体电位升高(TEV)等问题。该研究旨在通过试验方法研究TEV和VFTO之间的关系,并分析TEV在GIS回路中的形成原因和传播规律。研究中,首先利用自制的TEV和VFTO测量系统,在武汉特高压交流试验基地对GIS隔离开关操作时产生的TEV和VFTO波形进行了测量。从暂态波形时间对应角度分析,所有统计的时间偏差均在[-90μs,20μs]的区间内,证明了2者在时序上的对应关系;从幅值比例关系角度,使用Spearman相关系数分析,证明了TEV波形上的脉冲电压与隔离开关断口间的击穿电压满足正比单值函数关系。通过引入比例系数,分析了试验回路上不同位置处的TEV幅值,从试验角度验证了行波传输理论对TEV成因的解释。该研究还给出了通过少量现场试验确定某一位置最大TEV的方法,估算试验回路中可能出现的TEV最大值为51.37 k V,这一估算方法能够为TEV的理论分析和仿真计算提供支持。展开更多
基金This work was supported by the Weapons and Equipment Pre-Research Project of China(No.301051102).
文摘Because of the complexities of tire-road interaction,the wheels of a multi-wheel distributed electricdrive vehicle can easily slip under certain working conditions.As wheel slip affects the dynamic per-formance and stability of the vehicle,it is crucial to control it and coordinate the driving force.With this aim,this paper presents a driving force coordination control strategy with road identification for eight-wheeled electric vehicles equipped with an in-wheel motor for each wheel.In the proposed control strategy,the road identification module estimates tire-road forces using an unscented Kalman filter al-gorithm and recognizes the road adhesion coefficient by employing the recursive least-square method According to road identification,the optimal sip ratio under the current driving condition is obtainedand a controller based on sliding mode control with a conditional integrator uses this value for accel-eration slip regulation.The anti-slip controller obtains the adjusting torque,which is integrated with the driver-command-based feedforward control torque to implement driving force coordination control.The results of hardware-in-loop simulation show that this control strategy can accurately estimate tire-roadrces as well as the friction coefficient,and thus,can effectively fulfill the purpose of driving force coordinated control under different driving conditions.
基金supported by the National Natural Science Foundation of China(7117118171301155)+1 种基金the Fundamental Research Fundsfor the Central Universities(WK2040160008J2014HGBZ0172)
文摘How to allocate a resource efficiently and fairly attracts the attention of both researchers and practitioners. Data envelopment analysis（DEA） has been brought to bear on its solution. The existing literature applies Gini coefficient to measure the fairness in the resource allocation process. However, the Gini coefficient is inapplicable in many applications. This paper proposes a novel centralized resource allocation model based on DEA that considers both the efficiency and the fairness. This paper adopts a notion of fairness, namely α-fairness that is well studied in welfare economics and is of practical significance. The new model integratesα-fairness with DEA to support resource allocation decisions. It aids decision makers in making a trade-off between the efficiency and the fairness. An illustrative application is used to validate the proposed approach.
文摘Cooling in industrial production and refrigeration of perishable and</span><span style="font-size:10.0pt;font-family:""> non-</span><span style="font-size:10.0pt;font-family:""> </span><span style="font-size:10.0pt;font-family:"">perishable products is common practice throughout the world. Research studies have been conducted both experimentally and numerically to simulate Vapor Compression Refrigeration System (VCRS) and its performance respectively, however, experimental procedure often seems to be expensive and time-consuming to carry out due to the function of many variables. This study was therefore designed to numerically simulate the performance assessment of a nanoparticle enhanced VCRS. A numerical model of a vapor compression refrigeration system was developed using standard refrigeration equations on each of the major components of the refrigeration system such as compressor, evaporator, condenser and expansion valve. The model was then simulated on a MATLAB platform with a CoolProp installed packages via Python under two different simulation cases. In the first case, the mass fractions were varied for CuO,</span><span style="font-size:10.0pt;font-family:""> </span><span style="font-size:10.0pt;font-family:"">TiO<sub>2</sub> and Al<sub>2</sub>O<sub>3</sub> nanoparticles while their densities remained constant and a reversed condition was investigated for the second case. The results showed that both the refrigerating effect and the Coefficient Of Performance (COP) of the system increase as both the mass fraction and density of all the nanoparticles increases. It also shows that the compressor work decreases as both the mass fraction and density of all the nanoparticles were increased. On comparing the computational and numerical analysis results, the study established no significant difference in terms of COP and the use of nanoparticles were found to have improved the COP of the system.
文摘气体绝缘开关设备(GIS)中的隔离开关操作,会产生特快速瞬态过电压(VFTO)和壳体电位升高(TEV)等问题。该研究旨在通过试验方法研究TEV和VFTO之间的关系,并分析TEV在GIS回路中的形成原因和传播规律。研究中,首先利用自制的TEV和VFTO测量系统,在武汉特高压交流试验基地对GIS隔离开关操作时产生的TEV和VFTO波形进行了测量。从暂态波形时间对应角度分析,所有统计的时间偏差均在[-90μs,20μs]的区间内,证明了2者在时序上的对应关系;从幅值比例关系角度,使用Spearman相关系数分析,证明了TEV波形上的脉冲电压与隔离开关断口间的击穿电压满足正比单值函数关系。通过引入比例系数,分析了试验回路上不同位置处的TEV幅值,从试验角度验证了行波传输理论对TEV成因的解释。该研究还给出了通过少量现场试验确定某一位置最大TEV的方法,估算试验回路中可能出现的TEV最大值为51.37 k V,这一估算方法能够为TEV的理论分析和仿真计算提供支持。
