广州地区的高温天气主要是受副热带高压和台风外围下沉气流的影响所致。文中采用BDA(Bogus Data Assimilation)方法,探讨BDA方案对广州地区台风背景条件下高温预报的改进能力。选取2005年7月中旬广州地区出现的高温天气进行研究。这是...广州地区的高温天气主要是受副热带高压和台风外围下沉气流的影响所致。文中采用BDA(Bogus Data Assimilation)方法,探讨BDA方案对广州地区台风背景条件下高温预报的改进能力。选取2005年7月中旬广州地区出现的高温天气进行研究。这是比较典型的受副热带高压和台风(海棠)共同影响造成高温的天气过程。分析有无采用BDA方案的模式初始场,结果表明:采用BDA方案同化Bogus模型可以调整台风中心位置和强度,使所得到的初始场中心位置与观测更为接近,台风强度(气压梯度力、风速)比未用Bogus的情况强,与观测值更为接近。数值模拟的结果表明,采用了BDA方案的敏感试验可以更好地预报台风路径和台风中心强度变化,从而更好地预报高温天气,对高温区分布、日平均温度大小等的预报都有改进。文中对引起这种预报差异的原因进行了讨论,并探讨高温预报改进的可能机制。大气下沉运动的增强是高温预报改进的主要原因。敏感试验由于广州中低层大气的水汽减少,大气的下沉增强,致使天空的云量减少,对太阳短波辐射的阻挡减小,从而地面吸收热量增多,温度升高,输送给大气的感热增加,大气温升高。采用BDA方案可以改进模式在台风"海棠"过程对广州高温的预报。展开更多
In recent years, great economic output of land has been achieved in economic-technological development areas in China, but the intensity of land use in some of these areas is very low. The degree of the low intensity ...In recent years, great economic output of land has been achieved in economic-technological development areas in China, but the intensity of land use in some of these areas is very low. The degree of the low intensity of land use needs to be evaluated. The current method of comprehensive evaluation and grading by one index system has the limitations due to the existence of differences between regions and industries. This paper evaluates industrial land use intensity by Total Factor Productivity (TFP) analysis, which not only measures the intensity but also illustrates the ef-ficiency of input factors. This method is applied to the Beijing Economic-technological Development Area (BDA). A comparison analysis on factor use efficiency and input structure of capital and labor between industries is also carried out in the absence of a labor-income ratio.展开更多
The development of microchannels with open flow for use in irrigation and rainy areas is challenged by electricity generation via hydrokinetic devices in shallow and low velocity flows.Conventional hydrokinetic turbin...The development of microchannels with open flow for use in irrigation and rainy areas is challenged by electricity generation via hydrokinetic devices in shallow and low velocity flows.Conventional hydrokinetic turbines are known to be highly dependent on current speed and water depth.Another drawback of conventional turbines is their low efficiency.These shortcomings lead to the need to accelerate the flow in the channel system to enhance the extracted power.The method of deploying a novel turbine configuration in irrigation channels can help overcome the low performance of conventional hydrokinetic turbines.Therefore,this study experimentally presents a bidirectional diffuser-augmented channel that includes dual cross flow/Banki turbines.Results show that the maximum efficiency of the overall system with two turbines is nearly 55.7%.The efficiency is low relative to that of hydraulic turbines.Nevertheless,the result can be considered satisfactory given the low head of the present system.The use of this system will contribute to a highly efficient utilization of flows in rivers and channels for electrical energy generation in rural areas.展开更多
摘要广州地区的高温天气主要是受副热带高压和台风外围下沉气流的影响所致。文中采用BDA(Bogus Data Assimilation)方法,探讨BDA方案对广州地区台风背景条件下高温预报的改进能力。选取2005年7月中旬广州地区出现的高温天气进行研究。这是比较典型的受副热带高压和台风(海棠)共同影响造成高温的天气过程。分析有无采用BDA方案的模式初始场,结果表明:采用BDA方案同化Bogus模型可以调整台风中心位置和强度,使所得到的初始场中心位置与观测更为接近,台风强度(气压梯度力、风速)比未用Bogus的情况强,与观测值更为接近。数值模拟的结果表明,采用了BDA方案的敏感试验可以更好地预报台风路径和台风中心强度变化,从而更好地预报高温天气,对高温区分布、日平均温度大小等的预报都有改进。文中对引起这种预报差异的原因进行了讨论,并探讨高温预报改进的可能机制。大气下沉运动的增强是高温预报改进的主要原因。敏感试验由于广州中低层大气的水汽减少,大气的下沉增强,致使天空的云量减少,对太阳短波辐射的阻挡减小,从而地面吸收热量增多,温度升高,输送给大气的感热增加,大气温升高。采用BDA方案可以改进模式在台风"海棠"过程对广州高温的预报。
基金Under the auspices of Fundamental Research Funds for the Central Universities (No. 2009SD-5)
摘要In recent years, great economic output of land has been achieved in economic-technological development areas in China, but the intensity of land use in some of these areas is very low. The degree of the low intensity of land use needs to be evaluated. The current method of comprehensive evaluation and grading by one index system has the limitations due to the existence of differences between regions and industries. This paper evaluates industrial land use intensity by Total Factor Productivity (TFP) analysis, which not only measures the intensity but also illustrates the ef-ficiency of input factors. This method is applied to the Beijing Economic-technological Development Area (BDA). A comparison analysis on factor use efficiency and input structure of capital and labor between industries is also carried out in the absence of a labor-income ratio.
基金This project is sponsored by the Ministry of Education Malaysia under ERGS Fund No.4 L.125.
摘要The development of microchannels with open flow for use in irrigation and rainy areas is challenged by electricity generation via hydrokinetic devices in shallow and low velocity flows.Conventional hydrokinetic turbines are known to be highly dependent on current speed and water depth.Another drawback of conventional turbines is their low efficiency.These shortcomings lead to the need to accelerate the flow in the channel system to enhance the extracted power.The method of deploying a novel turbine configuration in irrigation channels can help overcome the low performance of conventional hydrokinetic turbines.Therefore,this study experimentally presents a bidirectional diffuser-augmented channel that includes dual cross flow/Banki turbines.Results show that the maximum efficiency of the overall system with two turbines is nearly 55.7%.The efficiency is low relative to that of hydraulic turbines.Nevertheless,the result can be considered satisfactory given the low head of the present system.The use of this system will contribute to a highly efficient utilization of flows in rivers and channels for electrical energy generation in rural areas.