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ABSTRACT

To avoid particle contamination in clean process production, unidirectional air flow with HEPA-filtered air is used, either in the entire room or partly in the critical process region (clean air zones), the purpose of this presentation is to describe a number of observations in unidirectional air flow and to discuss the interaction between air movements and the dispersion of airborne contaminants, it has been shown, by using smoke photography technique, that wake regions and vortex streets can easily be formed behind the working operator and objects. If a contaminant is emitted in the region of a vortex an accumulation can occur. It is important for the user to investigate that such vortices do not occur in the clean working zone.  相似文献   
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From some basic relations in estimation theory, a comprehensive set of formulae are obtained for the periodic solution of Riccati equations. To obtain numerically stable algorithms, square root formulations are introduced. Both the discrete-time and continuous-time cases are considered. Closed-loop properties for periodic systems are also investigated. The results are applied to multirate measurement sampling. The control of a continuous stirred tank reactor serves as an illustrative example. The temperature measurements are then complemented by concentration analysis available at a slower rate than the basic sampling and control rate. The results give some guidelines about the benefits of multirate sampling.  相似文献   
3.
The combined effects of freezing rate, frozen storage and reconstitution method on meat quality and yield were studied in multifactorial experiments using pan-fried 1.5 cm slices of longissimus muscles and deep-fat fried meat patties. On the whole, a slight improvement in sensory quality and yield was seen with increasing freezing rate, except that liquid nitrogen immersion freezing influenced flavor negatively. In contrast with earlier results of ours with raw beef, an advantage was now seen for reconstitution after previous thawing over reheating directly from the frozen state, and pan frying gave better sensory quality but lower yield than continuous microwave reheating. Tenderness of sliced, cooked beef tended to increase during frozen storage, while the opposite was earlier observed for frozen raw beef. Otherwise, a general trend was seen towards decreasing yield and sensory quality during frozen storage. A number of significant interactions between variables was obtained, suggesting that their influence on quality and yield is interrelated in a rather complex manner.  相似文献   
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Financing of Investment in Eastern Europe: A Theoretical Perspective   总被引:1,自引:0,他引:1  
Eastern Europe suffers from a worsening capital shortage problem.This paper studies ways to find the needed funds. It is arguedthat firms need funds in order to transform illiquid ideas intoliquid claims, possibly through a chain of intermediaries. Itshows that collateral (proven assets) plays the central rolein increasing liquidity of liabilities and determining the firm'scapacity to fund investments. A model is offered to illustratehow firm growth is limited by the net worth of its marketableassets. The analysis is extended to specialized assets for whichthe liquidation value is less than the ongoing value. The importantsecond variation of intermediation is also examined. A key featureof the intermediation model is that intermediaries themselvesare constrained by their net worth. Some lessons are then drawnregarding the status and future of financing in Eastern Europe.The intermediation model suggests that granted the scarcityof capital, financing of investments will have to be more information-intensive:intermediaries will have to take a more active role in monitoringfirms. Capital formation is likely to be a slow process, sincethe capital base is so small. Private investments will be gearedtowards smaller, safer and shorter-term projects. The logicof liquidity-constrained growth argues for letting small firmscarry the brunt of the responsibility for future prosperityin Eastern Europe.  相似文献   
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Five polymer films commonly used in food packages were stored in an aqueous solution of 10 apple aroma compounds. Substances absorbed by the polymers were determined by a supercritical fluid extraction/gas chromatography method. Polypropylene absorbed most aromas, more than 2× amounts absorbed by low density polyethylene. Polyamide and polyester absorbed very small amounts of the aromas. Esters and aldehydes were absorbed much more than alcohols. Molecular size also affected absorption, larger molecules being absorbed to a greater extent than smaller ones. For most materials the absorption equilibrium was reached within a week.  相似文献   
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The combined effects of aging, freezing rate, frozen storage and cooking method on beef quality and yield were studied in a multifactorial experiment, using 1.5 cm slices of LD muscles from young steers. Aging for 2 wk resulted in significantly more tender, but slightly less juicy frozen meat than aging for 4 days. Prolonged frozen storage gave tougher meat and a larger tenderness difference between aging times. Freezing rates of 13, 2.0 and 0.04 cm/h differed but little in their effect on sensory quality, but slightly lower yield and redness value were noted for the lowest rate. Pan frying directly from the frozen state resulted in slightly higher juiciness and cooking yield, with larger differences in yield between freezing rates, than cooking after previous thawing. Significant interactions were noted for cooking method × freezing rate and for aging time × frozen storage time  相似文献   
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The effects of sampled-data control on continuous-time linear stochastic systems are considered. For such systems the state covariance will vary during the sampling periods. Algorithms to compute this time-varying matrix are given. Due to this time variation, an averaged value of the covariance mairix is also introduced. Plants including an arbitrary time delay are accepted. Reasons for the intersample variance alterations are finally illustrated by two examples.  相似文献   
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