Process control: An overview and personal perspective

This paper presents an overview and personnal perspective on recent developments and current practice in computer process model. The basic concepts behind conventional process control are reviewed to provide a starting point for the non-control specialist and process engineer. The ensuing sections on Internal Model Control (IMC), Model Predictive Control (MPC) and adaptive control illustrate the evolution of control technology from the traditional multiloop strategies to the modern, multivariable, model-based, computer control systems now being used in industry. The paper does not provide a complete, critical review of process control. However, the discussion and the recommended references should provide a good starting point for anyone wanting to become familiar with current practice and some of the new directions of process control.     

Analysis and tuning of adaptive generalized predictive control

The adaptive Generalized Predictive Controller (Clarke et al., 1987a, b) is capable of controlling plants with variable dead-time, unknown model orders and unstable poles and zeros. This paper shows how the GPC control law can be written in an equivalent general linear transfer function form which simplifies closed-loop (eg. root locus) analysis. Three recommended strategies for selecting the design parameters during the commissioning stage allow the user to adjust the closed-loop speed of response on-line using only a single active tuning parameter. Experimental runs confirm the ability of adaptive GPC to provide a consistent closed-loop response in spite of large process changes.     

Application of polymerase chain reaction for the correlation of Salmonella serovars recovered from greyhound feces with their diet

The polymerase chain reaction was employed to correlate Salmonella serovars isolated from fecal material of greyhounds suffering from gastroenteritis with those isolated from the diet fed to the greyhounds prior to onset of diarrhea. Kennels around the Abilene, Kansas, area were contacted and supplied with materials needed to collect a portion of the diet each day. With the onset of diarrhea, the kennels were instructed to ship the fecal material and diet from the previous 10 days to the laboratory for testing. Forty-one fecal samples and corresponding diets were screened for Salmonella, Clostridium perfringens, Campylobacter jejuni, Staphylococcus aureus, Staphylococcus intermedius, and pathogenic (piliated) Escherichia coli by direct culture using standard procedures. The fecal material was also screened for coronavirus and parvovirus using electron microscopy. Thirty-five "normal" fecal samples were screened for all of the above mentioned microorganisms as a control. In addition, the fecal material was screened for E. coli verotoxins I and II and clostridial enterotoxins. A total of 61 Salmonella isolates were recovered from the 41 samples of feces and diet submitted for testing; 31 were recovered from the feces and 30 from the diet. Four Salmonella isolates were recovered from the normal fecal samples. Results obtained by PCR, plasmid profiles, antigenic analysis, and antibiogram profiles indicated that 16 of the 31 isolates recovered from the fecal material were the same strain as that recovered from the diet.     

Model checking agent programming languages

In this paper we describe a verification system for multi-agent programs. This is the first comprehensive approach to the verification of programs developed using programming languages based on the BDI (belief-desire-intention) model of agency. In particular, we have developed a specific layer of abstraction, sitting between the underlying verification system and the agent programming language, that maps the semantics of agent programs into the relevant model-checking framework. Crucially, this abstraction layer is both flexible and extensible; not only can a variety of different agent programming languages be implemented and verified, but even heterogeneous multi-agent programs can be captured semantically. In addition to describing this layer, and the semantic mapping inherent within it, we describe how the underlying model-checker is driven and how agent properties are checked. We also present several examples showing how the system can be used. As this is the first system of its kind, it is relatively slow, so we also indicate further work that needs to be tackled to improve performance.     

Transmission microscopy of the corrosion scale formed on a stainless steel exposed to liquid sodium

The scale, formed on 304 stainless steel during exposure to sodium for 85 days, was removed electrolytically, examined in transmission in the Hitachi high voltage microscope and found to consist of hexagonal close packed crystallites, typically 0.3 to 1 m in diameter. Approximately 90% of the crystallites were of basal (0001) orientation and the others either of {4, ¯1, ¯3, 15} or {¯2110} orientations. Lattice parametersa=2.96 Å andc=13.89 Å were determined by analysing electron diffraction patterns derived from the scale. Confirmatory evidence was obtained by examining the scale formed after a shorter exposure of 29 days, in the Philips EM 200 microscope. Previous studies [1, 2] have indicated that the scale may be sodium chromite (with lattice parametersa=2.96 Å andc=15.95 Å). The results of the present study are in apparent conflict with this suggestion unless a contraction parallel to thec-axis 13% is assumed.     

智能虚化得到“专业范儿”

正我们告诉大家,如何综合运用Adobe Camera Raw与Photoshop的各项功能,打造一幅完美的具备专业效果的肖像照片。软件准备:Photoshop CS6学习目标:使用特殊模糊滤镜在保留细节的前提下美化皮肤,使用快速选择工具选择并美白牙齿和眼睛。操作耗时:15分钟     

Cytopathological Outcomes of Knocking down Expression of Mitochondrial Complex II Subunits in Dictyostelium discoideum

Mitochondrial Complex II is composed of four core subunits and mutations to any of the subunits result in lowered Complex II activity. Surprisingly, although mutations in any of the subunits can yield similar clinical outcomes, there are distinct differences in the patterns of clinical disease most commonly associated with mutations in different subunits. Thus, mutations to the SdhA subunit most often result in mitochondrial disease phenotypes, whilst mutations to the other subunits SdhB-D more commonly result in tumour formation. The reason the clinical outcomes are so different is unknown. Here, we individually antisense-inhibited three of the Complex II subunits, SdhA, SdhB or SdhC, in the simple model organism Dictyostelium discoideum. Whilst SdhB and SdhC knockdown resulted in growth defects on bacterial lawns, antisense inhibition of SdhA expression resulted in a different pattern of phenotypic defects, including impairments of growth in liquid medium, enhanced intracellular proliferation of the bacterial pathogen Legionella pneumophila and phagocytosis. Knockdown of the individual subunits also produced different abnormalities in mitochondrial function with only SdhA knockdown resulting in broad mitochondrial dysfunction. Furthermore, these defects were shown to be mediated by the chronic activation of the cellular energy sensor AMP-activated protein kinase. Our results are in agreement with a role for loss of function of SdhA but not the other Complex II subunits in impairing mitochondrial oxidative phosphorylation and they suggest a role for AMP-activated protein kinase in mediating the cytopathological outcomes.     

A 6.5-J flashlamp-pumped Ti:Al2O3 laser

A flashlamp-pumped Ti:A₂O₃ oscillator has delivered 6.5 J per pulse at 800 nm under long-pulse extraction conditions. The device was designed for efficient short-pulse (2-3 ns) amplification to the multijoule energy level. To date, a peak stored energy in excess of 5 J has been obtained and is available for short-pulse extraction studies. The design and resulting characterization of this laser are discussed. The results show that the energy available for short-pulse extraction is limited by the flashlamp pumping time