关于燃气小时计算流量公式的探讨

本文通过两种燃气小时计算流量公式的分析、比较,提出合理的方法,对最大负荷利用小时数（n）和燃具同时工作系数（K）进行修正,以使相同命题下的计算结果一致。     

Reactive power pricing structure for hydroelectric power station in condenser mode operation

Reactive power support is critical for system security and pricing of reactive power is a vital issue in restructured environment. Peaking units at hydroelectric power plant in condenser mode operation can provide major reactive power support. Therefore costing structure for hydroelectric power plant incorporating various cost components in condenser mode operation is presented in this paper. Major cost components include capital cost component, changeover cost component and a cost component related to number of service hours in condenser mode operation. A methodology is proposed based on these components. A case study of Koyna Hydro Electric Power Plant (KHEPP) is elaborated.     

福建太阳能资源分析

太阳能发电已成为世界各国实现可持续发展的能源战略决策。太阳能资源评价是太阳能开发利用的重要环节,是质量与效益的重要保证。本文对福建太阳能资源量及有关要素提出了一些初步的看法,供参考。     

郑州地区与国内其他资源带部分城市太阳能资源的比较

通过与其他资源带城市的太阳能辐射对比,发现郑州地区太阳能资源比较丰富,年总辐射变化比较平缓、稳定,太阳能资源比较优越。     

Solar radiation models—A review

Solar radiation models for predicting the average daily and hourly global radiation, beam radiation and diffuse radiation on horizontal surface are reviewed in this article. Estimations of monthly average hourly global radiation from daily summations are discussed. It was observed that Collares‐Pereira and Rabl model as modified by Gueymard (CPRG) yielded the best performance for estimating mean hourly global radiation incident on a horizontal surface for Indian regions. Estimations of monthly average hourly beam and diffuse radiation are discussed. It was observed that Singh‐Tiwari and Jamil‐Tiwari both models generally give better results for climatic conditions of Indian regions. Therefore, their use is recommended for composite climate of Indian regions. Empirical correlations developed to establish a relationship between the hourly diffuse fraction and the hourly clearness index using hourly global and diffuse irradiation measurements on a horizontal surface are discussed. Fifty models using the Angstrom–Prescott equation to predict the average daily global radiation with hours of sunshine are considered. It was reported that Ertekin and Yaldiz model showed the best performance against measured data of Konya, Turkey. Copyright © 2010 John Wiley & Sons, Ltd.     

Global,direct and diffuse solar radiation on horizontal and tilted surfaces in Jeddah,Saudi Arabia

The measured data of global and diffuse solar radiation on a horizontal surface, the number of bright sunshine hours, mean daily ambient temperature, maximum and minimum ambient temperatures, relative humidity and amount of cloud cover for Jeddah (lat. 21°42′37′′N, long. 39°11′12′′E), Saudi Arabia, during the period (1996–2007) are analyzed. The monthly averages of daily values for these meteorological variables have been calculated. The data are then divided into two sets. The sub-data set I (1996–2004) are employed to develop empirical correlations between the monthly average of daily global solar radiation fraction (H/H₀) and the various weather parameters. The sub-data set II (2005–2007) are then used to evaluate the derived correlations. Furthermore, the total solar radiation on horizontal surfaces is separated into the beam and diffuses components. Empirical correlations for estimating the diffuse solar radiation incident on horizontal surfaces have been proposed. The total solar radiation incident on a tilted surface facing south H_t with different tilt angles is then calculated using both Liu and Jordan isotropic model and Klucher’s anisotropic model. It is inferred that the isotropic model is able to estimate H_t more accurate than the anisotropic one. At the optimum tilt angle, the maximum value of H_t is obtained as ∼36 (MJ/m² day) during January. Comparisons with 22 years average data of NASA SSE Model showed that the proposed correlations are able to predict the total annual energy on horizontal and tilted surfaces in Jeddah with a reasonable accuracy. It is also found that at Jeddah, the solar energy devices have to be tilted to face south with a tilt angle equals the latitude of the place in order to achieve the best performance all year round.     

关于缩短大电流开关二极管反向恢复时间的研究

通过长期的工作实践，阐述了适当条件下的金扩散对缩短反向恢复时间，提高二极管2CK28开关速度，满足了反向恢复时间，改善了二极管的反向特性。     

Practicum training hours: Fact and fantasy.

Over the past five years, practicum experience has received increased attention as an important element in the sequence of training. Questions have arisen about the number of hours being counted and the activities occurring in practicum. This study examined the number of practicum hours accrued by comparing the actual number of direct service hours and total hours to an estimated length of time to complete those hours. Based on self-reports, it was estimated that graduate students spend between 2 and 7 years to accrue their practicum hours with 37.5 to 69.6% of that time in direct service. Implications for the profession, faculty, and students are provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

人工神经网络在相对湿度预测中的应用研究

相对湿度环境是农业生产监测与预测的重要内容,关系到植物的生长状况、多种病害的生态防治和灌溉措施的调节。针对相对湿度变化规律相当复杂,影响因素间非线性程度相当高,为了提高相对湿度预测精度,提出一种基于BP人工神经网络的相对湿度预测模型。该模型采用气象要素（日照时数、降水量、最小温度、平均温度和最大温度）实测数据作为神经网络的输入样本,并根据试验观测资料对模型进行了检验。结果表明：利用此模型分别对1987~1998年和1999~2000年陵水地区月平均相对湿度进行模拟和预测,相对湿度拟合值与实测值的相对误差为0.21%,相对湿度预测值与实测值的相对误差为0.28%。改进的BP人工神经网络能准确地捕捉相对湿度的变化趋势。运用BP人工神经网络方法进行相对湿度的研究,方法简洁,结果直观易懂,同时也为其他区域相对湿度研究提供借鉴。     

白云峡水电站增效扩容水能复核及技改方案研究

为准确掌握白云峡水电站增效扩容潜力,确保技改方案具有较高安全可靠性和节能经济性,采用参证站径流资料分析与发电量反算引用流量相互验证的设计思路,对电站扩容潜力进行了水能复核。考虑 “引红济石”调水流量和小水电技改技术要求,合理确定了与工程实际相匹配的最佳装机容量、方案和机组型号。研究表明：通过鹦鸽水文站径流资料及电站多年运行发电量统计数据的核算与反算,可获得反映电站水能指标的准确数据。进行机型优化比选与合理技术改造,可确保机组长期运行在高效工况区,增加出力和防止空蚀,在增效扩容的同时实现了节能降耗。