A system for simulation, monitoring and diagnosis of controlled continuous processes with slow dynamics

This paper presents a modelling approach specifically designed to be used in a monitoring and diagnosis system based on the simulation of relevant process and control system variables. The model is based on semantically extended data flow diagrams with each computational process representing the incremental behaviour of a component of the plant to be modelled. Variable as well as delay time behaviour is associated with each component model to support an event-driven simulation which, in turn, reduces computation time. This plant model of independent but interacting computational processes is easily extendable, modifiable and adjustable according to changes in the plant.

The modelling approach is applied to a coal power plant process and is implemented in G2, an object-oriented, real-time expert system shell with built-in simulation and online external connection capabilities. Generic rules guiding the event-driven simulation and monitoring allow for modular adaptation of the model as the plant's structure and functionality change without requiring changes in the rule set.     

Platelet-activating factor type activity in plasma from patients with septicemia and other diseases

The purpose of the present study was to determine whether increased levels of platelet-activating factor (PAF) type activity can be detected in plasma from patients with septicemia and other diseases. A level of PAF below 0.5 ng/mL of plasma was considered normal. We found that plasma from a patient with adverse anaphylactoidic reaction to intravenous analgetics contained 2.1 ng PAF/mL. In seven patients with septicemia, including urosepsis, endocarditis and peritonitis, and with positive blood culture, increased plasma PAF levels (1–20 ng PAF/mL) were observed. Other patients with clinical indications of septicemia had negative blood cultures and/or increased levels of C-reactive protein (CRP). Yet, in the plasma from these patients, no increased PAF levels were detected under the assay conditions used. Two patients with allergic asthma, requiring treatment with steroids, had no measurable plasma PAF. In the plasma from a patient with idiopathic thrombocytopenic purpura (ITP) only an “endogenous” inhibitor of PAF induced platelet aggregation was initially observed. In spite of this, the patient responded to treatment with the PAF antagonist WEB 2086 with a dramatic increase in platelet count (Lohmannet al., Lancet ii, 1147, 1988). Thereafter, also increased PAF levels (3.3 ng PAF/mL) were detected in plasma, although some “endogenous” inhibitor of PAF was still present. In conclusion, increased PAF levels in plasma from patients support a role of PAF in certain human disease states, such as in anaphylactoid reaction, sepsis and septic shock. The type, relevance and specificity of endogenous inhibitors of PAF deserve further study. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Aspects of minimizing steel corrosion in liquid lead-alloys by addition of oxygen

Minimizing steel corrosion in liquid lead-alloys by addition of oxygen requires devices for efficient oxygen transfer and reliable oxygen sensors. The accuracy of electrochemical oxygen sensors is analyzed using theoretical considerations and results from experiments in stagnant lead–bismuth eutectic (LBE). Additionally, the feasibility of gas/liquid oxygen-transfer and the long-term performance of electrochemical sensors in flowing liquid metal are addressed on the basis of the operating experience of the CORRIDA loop, a facility for testing steels in flowing LBE.     

搅拌摩擦焊中工艺参数对扭矩的影响

通过在6056—T6的铝合金薄板上设计不同旋转频率、不同下压量的搅拌摩擦点焊试验,测量焊接过程中的搅拌头扭矩、下压作用力和试板温度曲线来研究焊接工艺参数对扭矩的影响.结果表明,在旋转频率相同而下压量不同的试验中,搅拌头扭矩随下压作用力增大而增大,而引起扭矩增大的最主要原因是下压作用力使搅拌区材料的力学性能发生了改变;在下压量相同而旋转频率不同的焊接试验中,搅拌头扭矩随旋转频率升高而减小,但扭矩和旋转频率的乘积(即焊接热输入功率)却随旋转频率升高而增大,分析认为旋转频率通过温度和材料的应变速率两个途径对搅拌头扭矩产生了影响,而温度的影响作用更显著.     

Powder Injection Molding of Ceramic Engine Components for Transportation

Silicon nitride has been the favored material for manufacturing high-efficiency engine components for transportation due to its high temperature stability, good wear resistance, excellent corrosion resistance, thermal shock resistance, and low density. The use of silicon nitride in engine components greatly depends on the ability to fabricate near net-shape components economically. The absence of a material database for design and simulation has further restricted the engineering community in developing parts from silicon nitride. In this paper, the design and manufacturability of silicon nitride engine rotors for unmanned aerial vehicles by the injection molding process are discussed. The feedstock material property data obtained from experiments were used to simulate the flow of the material during injection molding. The areas susceptible to the formation of defects during the injection molding process of the engine component were identified from the simulations. A test sample was successfully injection molded using the feedstock and sintered to 99% density without formation of significant observable defects.     

International cooperation and high-performance reduction in Siberia

In 1989, a cooperative agreement between German and Russian partners was signed, calling for the joint development and construction of a high performance 300 kA reduction cell. The original plan was to install six cells in an existing pilot potroom within the Sayansk Aluminium Smelter at Sayanogorsk, Russia. The cell design was based on detailed computer simulations, covering all important parameters that influence smooth and efficient pot operation. In January 1993, the new 300 kA cells were started up. Their technical performance has been excellent, with remarkable cell stability, productivity, and low energy consumption.     

轮胎工业用更安全的操作油

在欧洲，立法和公众压力正在使欧洲市场上的操作油性质发生变化。这引起欧洲橡胶行业对不使用有潜在致癌危险芳香油的新型轮胎和橡胶配方进行评述。本文对这一状况进行了研究，并探讨了美国市场上可能出现的动态，介绍了不同产品的需求量以及北美操作油和润滑油制造不断变化的局面。提供了轮胎配合用新一代操作的油制造方法及各种竞争油类性能的对比数据。     

State-preserving nonlinear model reduction procedure

Model reduction has proven to be a powerful tool to deal with challenges arising from large-scale models. This is also reflected in the large number of different reduction techniques that have been developed. Most of these methods focus on minimizing the approximation error; however, they usually result in a loss of physical interpretability of the reduced model. A new reduction technique, which preserves a non-prescribed subset of the original state variables in the reduced model, is presented in this work. The technique is derived from the Petrov–Galerkin projection by adding constraints on the projection matrix. This results in a combinatorial problem of which states need to be selected. A sequential algorithm has been developed based on the modified Gram–Schmidt orthogonalization procedure. The presented technique is applied to two examples where the reduction error is found to be comparable to the traditional POD method. At the same time, the technique has the advantage that the physical interpretation of the remaining states is retained.