基于聚类的差分进化算法的两阶段最优潮流方法

差分进化算法是一种广泛应用于求解非线性优化问题的全局最优解的元启发式方法,但存在容易找到次优解或近似局部最优解的问题.为此,提出了一种求解高质量局部最优解甚至全局最优解的基于聚类的差分进化算法的两阶段方法,并将该方法应用于电力系统最优潮流问题.所提方法由基于聚类的差分进化算法和局部优化算法组成.第Ⅰ阶段是基于聚类的差分进化算法利用强大的全局搜索能力快速确定包含局部最优解的区域;第Ⅱ阶段是局部优化算法利用局部寻优能力为非线性优化问题高效寻找高质量的局部最优解甚至全局最优解.在一组基准函数上测试了该两阶段优化方法的求解性能,并通过对IEEE 118节点电力系统最优潮流的计算,验证了所提两阶段优化方法的有效性和实用性.     

Characterization of Grain-Boundary Segregation in MgO

Using Auger electron spectroscopy, segregation of Ca and Si corresponding to the adsorption of a partial monolayer adjacent the boundary in polycrystalline MgO was observed. Segregation of Sc is different in nature; the distribution consists of a 3.0-nm wide region corresponding to a positive space charge layer balancing a negative boundary charge. Various segregation models are applied to the observed behavior.     

On a reliable data communication broadcast system

This paper describes the design and implementation of a 3 KHz band HF data broadcast communication system, using a quantized frequency modulation, adaptive lattice equalizer together with forward error correcting code (FEC) to obtain a high link reliability and low error rate. A frequency diversity approach is also used in the selection of the timely best carrier frequency, and a microcomputer is implemented into the system for automatic best carrier acquisition, data transmission and clock synchronization, with minimum operator's attention. Extensive field experiments were conducted and experimental results indicate that the system can achieve, for daytime operation, a link reliability of 87–98%, with a probability of error between 10^?4 to 10^?5, depending upon data rate (50, 75bps) and FECs used. For night time operation, the link reliability reduces to from 65–93% with a probability of error down in the order of 10^?3.     

潮流计算中PV-PQ节点转换逻辑的研究

详细地研究了潮流计算中的PV-PQ节点转换逻辑，指出潮流计算中因为节点类型识别错误引起的发散是系统失去电压稳定性的一种表现形式，它对应于约束诱导型电压崩溃现象。几种补逻辑的使用会导致潮流计算收敛于一个不稳定解。文中通过对一个实际系统算例和IEEE 118节点标准算例的数值试验说明了这一情况。并给出了潮流计算中要获得稳定解必须满足的稳定性条件的数学列式，说明了它与PV-PQ转换逻辑的等价关系。最后指出了在基于连续潮流的电压稳定性评估中如果采用不合理的PV-PQ补转换逻辑将得到错误的结果。     

一种在线电力系统静态稳定增强控制算法

提出了一种在线应用的电力系统静态稳定增强控制算法。这一算法基于连续线性规划技术，将增强控制问题分解为稳定临界点及其控制灵敏度的计算问题和基于灵敏度的优化控制问题。在前一个子问题中，运用基于连续潮流的间接方法分别计算得到每个故障的稳定临界点。在后一个子问题中，采用了参与控制集和部分变量的可控区间限制等策略来提高线性规划问题的计算有效性。一个3000节点的实际系统的应用表明，文中所提算法是有效实用的。     

Manoeuvring multitarget tracking method in cluttered environment

A method for tracking a manoeuvring multitarget in a cluttered environment is presented. The clutter or false alarms are assumed to occur uniformly and to be independently distributed. The algorithm is performed by taking a sliding window of length uT (T is the sampling time) at time K. Instead of solving a large problem, the entire set of targets and measurements is divided into clusters so that a number of smaller problems are solved independently. When a set of measurements is received, we form a new data-association hypothesis for the set of measurements lying in the validation gales; with each cluster from time K — u + 1 to K the probability of each track history is computed, and ihen by choosing the largest of these histories we perform the target measurement updated with the adaptive state esiimator. Meanwhile, the covariance-matching technique is adopted so that the accuracy of the adaptive state estimator will be improved. Simulation has shown the effectiveness of the tracking algorithm.     

Decentralized variable-structure adaptive controller synthesis of large-scale systems subjected to bounded disturbances

The regulation control problem is considered for a large-scale system in the presence of interconnected terms, system parameter variations and external disturbances. Based on the technique of parameter estimations and the theory of variable-structure systems, this paper presents a new and feasible design algorithm for the synthesis of a decentralized variable-structure adaptive controller which can easily tackle the control problem of large-scale systems subjected to interconnected terms, system parameter variations and bounded disturbances. In contrast to previous results, the restrictive condition that the exact value of the parameter describing the input gain must be known can be relaxed. A series of computer simulations are also included to illustrate the proposed design algorithm.     

Fouling and Flux Restoration of Ultrafiltration of Passion Fruit Juice

Fouling phenomena of passion fruit juice in tubular ultrafiltration (UF) system were studied. The membrane deposit was found to be composed of pectin, sugars, citric acid, hemicellulose, and cellulose. Rinsing behaviour of the fouled membrane indicated that the deposit might be in the form of gel. Scanning electron microscopic examinations showed slime-like deposit on the fouled membrane. Intermittent on-off operation was able to restore the flux effectively. Rebounding of the gel layer at sudden release of pressure may explain the effect of on-off operation on flux restoration.     

OCCURRENCE OF TRANSGLUTAMINASE IN GREY MULLET (MUGIL CEPHALUS) MUSCLE AND IT'S EFFECT ON MINCED FISH PRODUCT

The gel strength of the minced fish product made from the unwashed mullet mince was found higher than that of the washed product. Transglutaminase (TGase) was found in the water soluble fraction of mullet muscle. It's optimal temperature was at 30C to 35C and the optimal pH was 7.5 to 7.7. Increased setting time at 30C, increased the gel strength of the minced fish product produced from the unwashed mullet mince. p-Chloromercuribenzoate (PCMB), an inhibitor to TGase was added to the mullet mince up to 2.0 mM, the mince was set at 35C and then heated to 85C. The gel strength of the product was inversely correlated to the PCMB concentration, Y₁= - 0.45X + 1.66 (r = 0.95). Studies of setting of the mullet mince at temperatures ranging 20 to 60C indicated that maximal gel strength was obtained at 35C, coinciding with the optimal temperature of TGase. Meat from 21.5 monthold grey mullet produced a minced product of higher gel strength than those produced from younger fish, although the muscle TGase activities were not significantly different.     

Egg White Lysozyme Purification by Ultrafiltration and Affinity Chromatography

Isolation and purification of lysozyme from hen egg white was studied using a two-step procedure. The egg white was diluted 5- to 9-fold with sodium phosphate buffer, and then processed by sequential dilution diafiltration using a UF membrane (molecular weight cut-off 300,000 dalton). The membrane process increased the specific activity of lysozyme 6-fold, and recovered 96% of lysozyme activity. The permeate from diafiltration was further purified by affinity chromatography using chitin as adsorbent. The second step of the process yielded a product of specific activity of 70,400 units/mg protein. The overall lysozyme recovery was 79%.