ON SYSTEMS' RELIABILITY AND REDUNDANCY

Abstract

A prime requirement of a system is that it be reliable and that the system designer has been able to estimate the reliability in numerical terms. Should it turn out that certain sections of the system arc too prone to fait the designer may consider duplicating such sections in some manner, i.e. the designer tries to enhance the overall reliability through use of redundancy. But how much—if anything—will be gained reliability wise by such a design change? A possible gain is hard to assess due to interaction between former and new components; however, it is frequently possible, by fairly simple means, to find upper and lower bounds for such gain in reliability

The purpose of this paper is twofold: first to introduce the readers to some fundamental concepts in the theory of system reliability, and second to present two new results valid for redundant system configurations (we ask the question: what arc the upper and lower bounds for the expected life or a parallel configuration, when the expected life for each of the blocks is parallel is known). (An expanded version of the paper is available from the authors upon request.)     

用于高速船舶的大功率柴油机

１ 摘要 ＰＡ６ Ｂ－ＳＴＣ柴油机是ＰＡ６柴油机的最新产品,至今已完成了１２、１６和 ２０缸机的开发,可满足高速渡轮和海军护卫舰推进动力市场对重量功率比、工作扭矩范围、总体尺寸、燃油消耗率和可靠性的要求。 该ＰＡ６改型机比其原型机功率增加了２５％,２０缸机的功率可达８１００ｋＷ。它的特点是采用相继涡轮增压（ＳＴＣ）,从而使其能够在中等转速时达到高的扭矩,能够在部分负荷时大大改善加速性能、降低燃油消耗率和排放。 旨在减轻重量、减小外形尺寸、降低船上安装费用和缩短安装周期的专门研究工作业已完成。２前言 Ｐ…     

Sausage Color Measured by Integrating Sphere Reflectance Spectrophotometry When Whole Blood or Blood Cured by Nitrite is Added to Sausages

Color changes of the cut surface were evaluated in sausages where small amounts of blood have been added. Whole blood or blood cured with nitrite and ascorbic acid was added in the range 0–7 kg/100 kg basic recipe. Changes were measured by reflectance spectrophotometry, using an integrating sphere. The results were evaluated using the CIE 1932 and CIE 1976 L*, a*, b* systems. Best evaluation of surfaces was gained by judging the spectra (380-760 nm), i.e. looking for the amount of nitrosoheme formed, and by calculating lightness as well as color, i.e. CIE 1932 AC or better CIE 1976 a* and b*.     

The dielectrically loaded ‘easitron’ circuit as a slow-wave structure for travelling-wave masers applications

Properties of the dielectrically loaded ?ensitron‘ slow-wave structure (SWS) for travelling-wave maser (TWM) applications are investigated in some detail. Approximating the parallel conductors by a sheath with an infinite conductivity along the conductors and zero conductivity perpendicular to them, the field components and dispersion characteristics of the SWS have been derived. The influence of the (isotropic) dielectric constant of the maser material on the group velocity, the phase-filling factor and the field polarization (essential for the calculation of the gain and. the isolation) has been studied. In particular, attention has been paid to these properties for the important frequency which yields the minimum Blowing factor. It is shown that the present SWS has favourable properties compared to other SWS^? _s (e.g. the comb-structure and the dielectrically filled waveguide). Also a high filling factor is obtained. Such an easitron may easily be fabricated using photo-etching techniques and is therefore quite useful for nun-wave frequencies, for example.     

LED illumination for video-enhanced DIC imaging of single microtubules

In many applications high‐resolution video‐enhanced differential interference contrast microscopy is used to visualize and track the ends of single microtubules. We show that single ultrabright light emitting diodes from Luxeon can be used to replace conventional light sources for these kinds of applications without loss of function. We measured the signal‐to‐noise ratio of microtubules imaged with three different light emitting diode colours (blue, red, green). The blue light emitting diode performed best, and the signal‐to‐noise ratios were high enough to automatically track the ends of dynamic microtubules. Light emitting diodes as light sources for video‐enhanced differential interference contrast microscopy are high performing, low‐cost and easy to align alternatives to existing illumination solutions.     

THE AROMA OF CANNED BEEF: PROCESSING AND FORMULATION ASPECTS

The influence of processing techniques and formulations on chemical and sensory aroma properties has been studied with the purpose of finding ways to improve the flavor of canned meat. HTST-sterilization, "aseptic" canning and sterilization in various packaging materials including flexible pouches have been investigated. It was found that "aseptic" canning and, especially, HTST-sterilization had a pronounced positive effect on aroma, in the latter case for samples packed in thin layers (flexible pouches). It was shown that addition of e.g., fumarate or maleate in small amounts (0.06–0.15%) before sterilization decreased the concentrations of hydrogen sulfide and mercaptans, and the additions of certain amino acids, e.g., arginine, decreased the concentrations of the aldehydes. Both types of ingredients resulted in an improved aroma. Storage changes have also been investigated. It was found that there was a tendency towards a more accelerated change in flexible pouches compared with rigid cans.     

Color of Black Salami Sausage: Dissociation of Heme from Myoglobin and Hemoglobin

Dissociation curves determined spectrophotometrically for myoglobin and hemoglobin in citric acid buffers showed that the heme groups dissociated from the proteins at pH-values comparable to those normally found in dry sausages. The extent of dissociation parallelled the degree of denaturation of the proteins as measured by differential scanning calorimetry. Extraction of newly prepared black salami sausage mince with phosphate buffer removed all pigments, which could not be extracted from ripened sausage with pH of about 4.5. This was in agreement with the solubility properties of the hydrophilic pigments myoglobin and hemoglobin, and the hydrophobic properties of the heme pigment. These experiments showed that the color of black salami sausage was due to heme.     

THE AROMA OF CANNED BEEF: APPLICATION OF REGRESSION MODELS RELATING SENSORY AND CHEMICAL DATA

The purpose of this investigation was to determine general relations between instrumental and sensory aroma data from a reference material consisting of a large set of different types of beef samples analyzed during several years. The relations obtained in this way have been tested on independent "unknown" samples. Different models have been used, basically derived from Stevens' law and formulated in analogy with models used in other psychophysical contexts. From the reference material a great number of highly significant relations-several with a correlation coefficient greater than 0.90–were obtained for the various odor notes used. Several of these seem to be examples of causative relations. When predicting sensory properties of unknown samples almost all the relations obtained with high correlation coefficient worked very well. These properties could be predicted by the gas chromatographic technique with the same accuracy as when the panel assessed the samples. Therefore, by applying the models in a proper way, the panel service in routine analyses may be supplemented or refined by using a gas chromatographic technique. These methods may, of course, also be used in product and process development work.