Determination Of The Phase Current Waveform For A Disc‐Type Axial‐Flux Wheel Motor

An optimal design of the driving current pattern for a disc‐type axial‐flux brushless DC wheel motor of an electric vehicle is proposed in this paper. The electro‐magnetic dynamic model of the motor is established with magnetic circuits, describing the relationship between the output torque and excitation current. The optimal current pattern, in terms of magnitude and phase angle, is then obtained by maximizing the output torque with respect to the rotor shift. Compared with the traditional three‐phase‐on current pattern of fixed 120–degree phase shift, both the average torque and efficiency with the driving current of an optimal advanced switching angle are seen to be improved under various loading conditions. The motor performance with the optimal driving waveform is simulated and verified by experiments.     

Scaling Gross Primary Production (GPP) over boreal and deciduous forest landscapes in support of MODIS GPP product validation

The Moderate Resolution Imaging Radiometer (MODIS) is the primary instrument in the NASA Earth Observing System for monitoring the seasonality of global terrestrial vegetation. Estimates of 8-day mean daily gross primary production (GPP) at the 1 km spatial resolution are now operationally produced by the MODIS Land Science Team for the global terrestrial surface using a production efficiency approach. In this study, the 2001 MODIS GPP product was compared with scaled GPP estimates (25 km²) based on ground measurements at two forested sites. The ground-based GPP scaling approach relied on a carbon cycle process model run in a spatially distributed mode. Land cover classification and maximum annual leaf area index, as derived from Landsat ETM+ imagery, were used in model initiation. The model was driven by daily meteorological observations from an eddy covariance flux tower situated at the center of each site. Model simulated GPPs were corroborated with daily GPP estimates from the flux tower. At the hardwood forest site, the MODIS GPP phenology started earlier than was indicated by the scaled GPP, and the summertime GPP from MODIS was generally lower than the scaled GPP values. The fall-off in production at the end of the growing season was similar to the validation data. At the boreal forest site, the GPP phenologies generally agreed because both responded to the strong signal associated with minimum temperature. The midsummer MODIS GPP there was generally higher than the ground-based GPP. The differences between the MODIS GPP products and the ground-based GPPs were driven by differences in the timing of FPAR and the magnitude of light use efficiency as well as by differences in other inputs to the MODIS GPP algorithm—daily incident PAR, minimum temperature, and vapor pressure deficit. Ground-based scaling of GPP has the potential to improve the parameterization of light use efficiency in satellite-based GPP monitoring algorithms.     

论《管理信息系统》思想理念及方法的重要意义

本文从中国信息系统现状分析入手 ,在对信息系统作简要介绍的基础上从企业和开发者两方面分层次论述了《管理信息系统》开发中对其思想理念和方法进行宣传培训的重要性     

5种指针分析算法的精度和效率比较

指针分析的研究已经有20多年的历史，也发表了很多相关的算法。对于研究者和工程人员来说，对不同的指针分析算法进行研究并用统一的标准进行精度及效率等内容的对比，是一件有意义的工作。考察了5种具有代表性的指针分析算法，并在固定外界影响因素的条件下对它们的精度和效率进行了测量和比较，最后分析了指针分析的结果如何影响一些客户分析的精度和效率。     

对MB形气态β+衰变源的效率刻度

利用医用回旋加速器产生的以^13N—NH3形式赋存的气态^13N核素,成功地实现了NaI探测系统对MB形探测容器内正电子衰变气体源的效率刻度，并与应用Monte Carlo计算的理论值取得较好符合，解决了反应堆一回路^13N监测仪难以进行效率因子刻度的难题。     

正极添加剂对MH/Ni电池高温充电行为的影响

为提高AA型MH/Ni电池在高温下的充电效率,筛选出CaF2、Y2O3、TiO2和Tm2O3作为正极添加剂,并通过正交实验确定了它们在混合添加时的合适用量。结果表明:在60℃以0 2C电流充电6h时,含复合添加剂电池的充电效率为78%,而空白电池只有48%;但加入添加剂后电池内阻增大11%,这可能是引起电池常温容量下降10%的原因之一。充电曲线表明:含上述复合添加剂的MH/Ni电池高温下充电后期电压明显升高,这可能是正极析氧过电位提高所致。     

软开关技术三相PWM逆变器及效率的分析研究

首先对一种软开关技术三相PWM逆变器电路的工作原理及实验验证结果进行了介绍和分析。然后用对比的方法对文中讨论的软开关逆变器电路的功率损耗及工作效率进行了详细的数学描述 ,给出了开关器件及由其构成的逆变器功率损耗的简化数学模型。最后在一个驱动三相电动机的逆变器实际电路中对相关的数学分析结论进行了实验验证 ,实验结果完全验证了文章中的理论分析结果     

新型高压放电灯的开发和应用

近年来，从节能和环保的观点出发开发成功许多具有高光效、高显色性、长寿命的新型高压气体放电灯。这些新型灯包括有大功率金卤灯、低功率陶瓷管金卤灯、高压钠灯、超高压汞灯和无电极金卤灯等。已被广泛应用于室外、室内照明、汽车照明和背光照明。本文主要介绍新HID灯的种类、特性和应用。     

电蓄热生活热水系统与燃煤锅炉的经济性分析

针对黑龙江省地处高寒地区采暖期的特点，分析了电采暖的方式、电加热锅炉的特点，通过绥化电业局电蓄热生活热水系统与燃煤锅炉的经济技术分析、投资比较，认为电锅炉效率大大高于燃煤锅炉效率，采用低谷用电和间歇运行可以降低电锅炉运行成本。     

用户投标情况下的电力市场失灵分析及决策模型研究

电力市场是电力系统改革所面临的新课题。由于电力市场的特殊性 ,电力市场不能完全象自由市场那样自发地调节供求关系 ,有效地配置资源 ,因此电力市场必须有强有力的管制机构———电力市场操作机构。电力市场操作人员应以电力市场效益最大化为目标 ,在满足电网安全性、完整性要求的前提下 ,正确引导参与者进行交易。在深入分析、研究了电力市场失灵发生的机理以后 ,提出了一种供电力市场操作人员使用的电力市场决策模型 ,并给出了经一个实验系统的检验结果。