基于Micro830的异步电动机控制系统设计

为解决异步电动机的控制问题,本文利用Micro830PLC控制器和PowerFlex 4M变频器,构建了异步电动机控制系统,结合RsLinx和FactoryTalk View Studio软件,实现了上位机对整套电机控制系统的实时监控。同时利用RsLinx建立OPC通讯,并在FactoryTalk View Studio上利用已建立的OPC数据服务器进行上位机操作。经过对控制系统进行调试及运行,结果表明,监控软件可以实现电动机启动、停止、正反转的自由切换,响应速度快,能够实现有效地控制,整个控制系统稳定性和精确度较高,操作方便,上位机监控软件能实现转速和方向的实时显示和有效控制。该系统实现了异步电动机方向和转速的准确控制,具有良好的应用前景。     

Experimental results concerning the role of Pt,Rh, Ba,Ce and Al2O3 on NO x -storage catalyst behaviour

NO _x -storage catalysts (NSC) with varied washcoat compositions have been investigated experimentally under lean and rich conditions. Besides the fact that Ba and Rh are essential for NO _x -storage and -reduction, it was observed that Ba accelerates the NO-reduction and decreases NO-oxidation kinetics. It also turned out to be the promoting species regarding water gas shift reaction. The results revealed kinetic inhibition effects by CO, C₃H₆ and NO, being less pronounced with Ba in the washcoat. It is further shown that the cyclic NO_x-conversion of the NSC is mainly determined by the processes in the regeneration phase.     

Deformation of nonfired refractories on phosphate binders. 4. Deformation due to heating and creep of cement composition

Results of a study of deformation due to heating and of creep of phosphate materials are presented. The range of necessary loads and the rate of temperature growth under nonisothermal conditions are determined. The role of the grain composition of the filler (α-Al₂O₃) of the model alumophosphate cement composition is shown. __________ Translated from Novye Ogneupory, No. 4, pp. 30–35, April, 2007.     

Mapping the structure of a liquid spray by means of neural networks

This paper presents the results of a study aimed at mapping the structure of a liquid spray system along the spray cone. Experimental results obtained by phase-Doppler anemometry (PDA) consisted of the number distributions of droplet size, velocity, and interparticle arrival time at different locations within the spray cone. The experimental data were analyzed by means of multivariate statistical techniques, in order to identify different regimes in the spray. Neural network models (NN) were fitted to the experimental data, resulting in good agreement between experimental and calculated results for most locations within the spray cone. However, in some parts of the cone the agreement was poor, and the general trends could not be well predicted by the NN models. The mismatch is due to unsteady spray conditions or incomplete atomization (e.g. existence of non-spherical particles). This fact was adopted as a criterion to identify the regions where the spray is fully established, corresponding to the regions of the spray where PDA measurements can be successfully performed. This criterion has been applied along the spray cone for different operating conditions, and can be used as a tool to map the fluid dynamic characteristics in liquid sprays.     

New insight into the interaction of sulfur with diesel NOx storage catalysts

A commercial NO_x-storage catalyst (NSC) has been subjected to different aging procedures on the engine bench simulating 100,000 km mileage. The aging consisted of cyclical sulfur exposure, subsequent sulfur removal and testing of the catalytic activity. More aggressive desulfation procedures result in more efficient sulfur removal and consequently good high temperature NO_x-conversion. However, low temperature NO_x-performance is lower than for agings employing more moderate desulfation conditions.

Sulfur post mortem analyses reveal a slight decrease of residual sulfur concentration over the length of all catalysts after completion of the aging. BET and CO-chemisorption data are in line with the increase of temperature from catalyst inlet to outlet during the desulfation. The conversion of BaCO₃ to BaSO₄ during the sulfur poisoning was followed by IR, TPD and TPR. A quantitative analysis of the data shows that at the end of the agings all residual sulfur is mainly located at barium sites as opposed to other oxide components like e.g. alumina or ceria. TPR data suggest that prolonged rich purges of the sulfated catalyst lead to an efficient decomposition of sulfates however some sulfur is being trapped in the form of BaS which seems difficult to remove under constant rich conditions.

XPS data suggest that the bulk sulfur amounts in the catalyst may be decoupled from the actual concentration at the catalyst surface. In that sense, the residual sulfur concentration might be limited in some cases as a criterion to assess the performance of a NSC. More reducing desulfation conditions cause the residual sulfur to be present in the form of more reduced sulfur species (sulfites, sulfides) on the catalyst.     

Abutilon indicum Seed Oil — Characterisation of HBr-Reactive Acids

The seed oil of Abutilon indicum (Malvaceae) contains three HBr-reactive fatty acids. These are shown to be cis-12,13-epoxyoleic (vernolic) acid, 1.6% 9,10-methylene-octadec-9-enoic (sterculic) acid, 0.9%; as well as 8,9-methylene-heptadec-8-enoic (malvalic) acid, 2.3%. Quantitative results are obtained by combining informations about the HBr-titration, the preparative thin layer separation of oxygenated and non-oxygenated acids, and gas liquid chromatographic analysis.     

Reaction of Hydrogen Bromide with Long Chain 1,2-Diols

The reactions of 1,2-hexadecanediol and 1,2-octadecanediol with hydrogen bromide in the presence of acetic anhydride have been investigated. The treatment of hydrogen bromide (48%) in acetic anhydride with 1,2-hexadecanediol gives mainly 1-bromo-2-acetoxy hexadecane (66%), 2-acetoxy hexadecanol (26%), and 1,3-hexadecanediol (8%). Similar products result from 1,2-octadecanediol. The structures of the products are based on combustion data, spectroscopic, and chemical evidences. The mechanism of the reaction has been discussed.     

What Role Does Ozone Play in Preventing Dental Caries? An Evidence-Based Review

Ozone, which is also referred to as triatomic oxygen or trioxygen, is a naturally occurring inorganic molecule that consists of three oxygen atoms. Ozone has proven microbiological properties and, for this reason, it is extensively used in modern medical practices. Ozone is a powerful oxidant that demonstrates bactericide, virucide, and fungicide effects. The strong oxidation effect it produces results in the formation of highly reactive free radicals that have the capability to destroy microorganisms. Ozone has been proposed as a means of preventing caries, and existing research confirms that this form of therapy does have promising potential. However, very few clinical studies have examined the impact that ozone treatment can have on the management of caries lesions. This article presents a detailed literature review of existing peer-reviewed sources that have examined the role ozone plays in preventing and treating caries.