聚集数据线性模型中广义岭估计相对效率问题

对于聚集数据的线性模型,给出了参数的广义岭估计及改进的广义岭估计的定义,并提出了广义岭估计及改进的广义岭估计在推广的欧氏模之比意义下及加权欧氏模之比意义下的二种相对效率。分别对广义岭估计及改进的广义岭估计,得到了两种相对效率的上界。     

切换线性系统的聚合优化

分析了切换线性系统的稳定性和优化问题,提出了一个Armijo步长优化的共轭梯度算法来寻找适当代价函数下的优化切换时间点集.为了确保优化切换路径是可压缩的,提出了代价函数需要满足的受限表达式.设计了几种优化分段状态反馈切换律来搜索聚合系统的最优切换路径,同时这些切换路径就是对应原始切换线性系统的次优化切换路径.最后,一个实例演示了不同切换律下的切换策略和优化代价.     

Prediction of mineral liberation characteristics of comminuted particles of high grade ores

In mineral processing, the liberation of valuable mineral is of key importance in achieving high recoveries from downstream separation processes such as froth flotation and gravity concentration. To quantify mineral liberation, information on ore texture of the parent rock as well as properties of comminuted particles is essential. These properties have been quantified by statistical measures such as the proximity function and covariance function, which were extracted from SEM images of parent rock and particle polished sections, using convenient and efficient image analysis techniques based on Labview™ software. To quantify fully liberated particles, a phase specific line segment function has been introduced and evaluated by placing random line segments on the image. It was also found that the ore texture assumptions made by Barbery are not valid for the high grade sulphide ore tested and the general applicability of these assumptions is therefore questionable. Using the measured information above, predictive liberation models to quantify volumetric grade distribution of particles in 1D and 3D have been developed based on Barbery’s work. Results show that the grade distributions of composite particles predicted from the proposed 1D model is closest to measured data than those of Barbery’s 1D model. The predictions using the proposed 3D model are similar to those predicted from Barbery’s model and are considered more realistic as the model does not rely on assumed ore texture but on measurements made on the parent rock and particle sections.     

QSPR Studies on Aqueous Solubilities of Drug-Like Compounds

A rapidly growing area of modern pharmaceutical research is the prediction of aqueous solubility of drug-sized compounds from their molecular structures. There exist many different reasons for considering this physico-chemical property as a key parameter: the design of novel entities with adequate aqueous solubility brings many advantages to preclinical and clinical research and development, allowing improvement of the Absorption, Distribution, Metabolization, and Elimination/Toxicity profile and “screenability” of drug candidates in High Throughput Screening techniques. This work compiles recent QSPR linear models established by our research group devoted to the quantification of aqueous solubilities and their comparison to previous research on the topic.     

考虑异质性的定频空调负荷聚合建模及功率跟踪策略

为便于建立空调负荷聚合模型,目前研究往往假设空调个体参数一致,忽略了空调受控群内部参数差异较大的实际情况,亦未计及空调最小停运时间与整数设定温度的影响,因此该文考虑空调负荷的异质性,提出一种改进型聚合建模方法。该方法根据空调额定制冷量分组,并通过模糊C-均值聚类算法提高受控群电功率的模拟精度。引入最小停运时间以及设定温度的整数约束,使仿真结果更接近实际定频空调运行工况。同时,在实际运算中采用坐标格式存储稀疏矩阵,提高运算速度和模型的实用性。基于该改进型聚合模型,进一步提出一种功率跟踪策略,该策略计算各聚类群每一时刻的需求响应能力,通过求解0—1整数规划问题实现调控对象最优组合。仿真算例验证所提策略对目标功率跟踪的良好效果。     

纳米三氧化二铝在水热条件下的聚集生长模式研究

通过对产物形貌及晶粒度测试,掌握水热温度、水热时间对水热产物影响的基本规律,运用临界成核理论及颗粒成长理论解释提高水热温度、延长水热时间导致的颗粒形态逆转的原因,结合晶体成长阶段性理论,揭示了提高水热温度或延长水热时间以及增大前躯体过饱和状态条件下诱发的两类聚集生长方式,阐述了第Ⅰ类聚集和第Ⅱ类聚集生长的根本原因,其中第Ⅰ类聚集生长是因为过饱和度的增大使得部分AlOOH颗粒在水热溶液中溶解形成的Al^3＋聚集体在另一些颗粒表面的叠合,而发生第Ⅱ类聚集生长的本质是由于pH酸碱环境使得多个AlOOH颗粒通过某些结构相容晶界间的键联而形成的具有特殊生长形态的颗粒。     

Hourly wind power variations in the Nordic countries

Studies of the effects that wind power production imposes on the power system involve assessing the variations of large‐scale wind power production over the whole power system area. Large geographical spreading of wind power will reduce variability, increase predictability and decrease the occasions with near zero or peak output. In this article the patterns and statistical properties of large‐scale wind power production data are studied using the data sets available for the Nordic countries. The existing data from Denmark give the basis against which the data collected from the other Nordic countries are benchmarked. The main goal is to determine the statistical parameters describing the reduction of variability in the time series for the different areas in question. The hourly variations of large‐scale wind power stay 91%–94% of the time within ±5% of installed capacity in one country, and for the whole of the Nordic area 98% of the time. For the Nordic time series studied, the best indicator of reduced variability in the time series was the standard deviation of the hourly variations. According to the Danish data, it is reduced to less than 3% from a single site value of 10% of capacity. Copyright © 2004 John Wiley & Sons, Ltd.