Effect of Compaction Scheme on Property Distribution for Cumulative Charge Facings Formed from a Heterogeneous Powder Composite

An experimental and numerical (finite element method) study is carried out for the effect of forming scheme on property distribution for cumulative charge facings made from composite heterogeneous powder material. An experimental procedure is developed for studying powder particle flow kinetics. It is shown that use of composite punches and partition of the moulded material into a number of sub-divisions with their successive compaction achieves a more uniform density distribution for an article. It is demonstrated how the direction of the force of friction on the die walls during compaction affects the compaction of articles with faces that are not perpendicular to the direction of the pressing. The results obtained make it possible to select the optimum compaction regime taking account of production features connected with powder material composition as well as service characteristics.     

Time-optimal velocity planning along predefined path for static formations of mobile robots

International Journal of Control, Automation and Systems - This paper is concerned with the problem of finding a time-optimal velocity profile along the predefined path for static formations of...     

Evolution,Generality and Robustness of Emerged Surrounding Behavior in Continuous Predators-Prey Pursuit Problem

We present the result of our work on the use of strongly typed genetic programming with exception handling capabilities for the evolution of surrounding behavior of agents situated in an inherently cooperative environment. The predators-prey pursuit problem is used to verify our hypothesis that relatively complex surrounding behavior may emerge from simple, implicit, locally defined, and therefore—scalable interactions between the predator agents. Proposing two different communication mechanisms ((i) simple, basic mechanism of implicit interaction, and (ii) explicit communications among the predator agents) we present a comparative analysis of the implications of these communication mechanisms on evolution, generality and robustness of the emerged surrounding behavior. We demonstrate that relatively complex-surrounding behavior emerges even from implicit, proximity-defined interactions among the agents. Although the basic model offers the benefits of simplicity and scalability, compared to the enhanced model of explicit communications among the agents, it features increased computational effort and inferior generality and robustness of agents' emergent surrounding behavior when the team of predator agents is evolved in noiseless environment and then tested in noisy and uncertain environment. Evolution in noisy environment virtually equalizes the robustness and generality characteristics of both models. For both models however the increase of noise levels during the evolution is associated with evolving solutions, which are more robust to noise but less general to new, unknown initial situations.     

Analysis of complexity indices for classification problems: Cancer gene expression data

Currently, cancer diagnosis at a molecular level has been made possible through the analysis of gene expression data. More specifically, one usually uses machine learning (ML) techniques to build, from cancer gene expression data, automatic diagnosis models (classifiers). Cancer gene expression data often present some characteristics that can have a negative impact in the generalization ability of the classifiers generated. Some of these properties are data sparsity and an unbalanced class distribution. We investigate the results of a set of indices able to extract the intrinsic complexity information from the data. Such measures can be used to analyze, among other things, which particular characteristics of cancer gene expression data mostly impact the prediction ability of support vector machine classifiers. In this context, we also show that, by applying a proper feature selection procedure to the data, one can reduce the influence of those characteristics in the error rates of the classifiers induced.     

Genetic programming incorporating biased mutation for evolution and adaptation of Snakebot

In this work we propose an approach for incorporating learning probabilistic context-sensitive grammar (LPCSG) in genetic programming (GP), employed for evolution and adaptation of locomotion gaits of a simulated snake-like robot (Snakebot). Our approach is derived from the original context-free grammar which usually expresses the syntax of genetic programs in canonical GP. Empirically obtained results verify that employing LPCSG contributes to the improvement of computational effort of both (i) the evolution of the fastest possible locomotion gaits for various fitness conditions and (ii) adaptation of these locomotion gaits to challenging environment and degraded mechanical abilities of the Snakebot.     

价廉通用马达相位角驱动系统设计

引言　　价廉相位角马达控制驱动系统的设计是在MC6 8HC0 5JJ6/MC68HC705JJ7微控制器(MCU)和MAC4DC无缓冲器双向可控硅的基础上的.　　……     

Toxicity bioassay of heavy metals in water using Tetrahymena pyriformis

The toxicities of five heavy metal compounds on the survival of the ciliated protozoan Tetrahymena pyriformis were determined. Three-day old cultured cells were exposed to five concentrations of each test compound in one or more of three water series; distilled, soft, and hard water. A culture of each sample was placed in a plastic petri dish and covered with mineral oil to prevent evaporation. The cells were counted initially, then again at 0·5 h, 1 h, 2 h, 1 day, 2 days, 3 days, and on the fourth day. Lethal threshold concentrations and tolerance limit medians were determined by graphic methods. On a weight bases cadmium was most toxic, followed in decreasing toxicity by mercury, cobalt, zinc, and lead. Compared to similar fish data, all heavy metals were more toxic to T. pyriformis except lead. The toxicity of lead in soft versus hard water exemplified an antagonistic effect with greater than seven times the amount of lead necessary in hard water to produce comparable mortality as lead in soft water. On the other hand, the toxicity of mercury is about twice as great in hard water as in soft water (a synergistic effect). T. pyriformis appears to be a more sensitive indicator than fish of heavy metal contamination of water. T. pyriformis bioassay should prove a good means of determining the existence of many water pollutants.