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991.
水库建成蓄水后,库底土壤中氮、磷的浸出会对库水水质会产生一定影响。本文以南水北调中线工程的调蓄水库———瀑河水库为例,在现场调查基础上,使用蒸馏水和模拟水分别进行模拟实验,分析研究了土壤中氮、磷浸出对库水中总氮、总磷浓度的影响。实验结果表明,总氮、总磷的浓度均发生一定程度的变化,且模拟水中的浓度变化小于蒸馏水中的变化;但从整体趋势看,源于土壤的含量较低,对库水水质未产生明显不良影响。 相似文献
992.
Punter Teade Kusters Rob Trienekens Jos Bemelmans Theo Brombacher Aarnout 《Software Quality Journal》2004,12(2):137-158
The importance of software product evaluations will grow with the awareness of the need for better software quality. The process to conduct such evaluations is crucial to get evaluation results that can be applied and meet customers' expectations. This paper reviews a well-known evaluation process: the ISO 14598 standard. The review focuses on the difficulties in selecting and evaluating the appropriate evaluation techniques. The review shows that the standard has problems in applying evaluation processes in practice due to insufficient attention to goal definition and to relationships between activities being implicit. Also, the standard ignores the trade-off between goals and resources and pays insufficient attention to feedback. To address these deficiencies, the W-process is proposed. It extends the standard through an improved process structure and additional guidelines. 相似文献
993.
In this paper, the problem of estimating uncertainty regions for identified models is considered. A typical approach in this context is to resort to the asymptotic theory of Prediction Error Methods for system identification, by means of which ellipsoidal uncertainty regions can be constructed for the uncertain parameters.We show that the uncertainty regions worked out through the asymptotic theory can be unreliable in certain situations, precisely characterized in the paper.Then, we critically analyze the theoretical conditions for the validity of the asymptotic theory, and prove that the asymptotic theory also applies under new assumptions which are less restrictive than the usually required ones. Thanks to this result, we single out the classes of models among standard ones (ARX, ARMAX, Box-Jenkins, etc.) where the asymptotic theory can be safely used in practical applications to assess the quality of the identified model.These results are of interest in many applications, including iterative controller design schemes. 相似文献
994.
Using recent papers on scanning electron microscopy (SEM) of chemical vapor deposition (CVD) diamond films, two analytical applications of the SEM are discussed: the morphologic investigations (secondary electron emission mode) and the recognition of impurities and defects [cathodoluminescence (CL) mode]. Studies of CVD diamond films by SEM demonstrate that the morphologies of these films are affected by synthesis conditions, especially by substrate temperature, methane concentration, and total pressure in the reactor. CL spectra and images are useful tools for clarifying the relationship between emission centers and different types of defects generated during the process of diamond crystal growth. The paper shows that the investigations of the morphology, crystallinity, local CL emission, as well as the surface distribution of CL spectra on CVD diamond films by SEM led to the correlative information for quality estimation of films in comparison with natural diamond. 相似文献
995.
The vision of mass customization has driven a movement toward low volume, high variety mass customization production (MCP)
at low price. However, defect identification and defect tracking in such systems are extremely difficult because of the frequent
reconfiguration needed by the number of different part types and the interruption of the information flow about quality with
each reconfiguration of the system. It is important to quickly rebuild quality information flow with MCP system’s reconfiguration
synchronously. This paper introduces a defect tracking method based on Quality Function Deployment for every MCP system module.
A defects tracking matrix (DTM) based on the House of Quality directly connects manufacturing technologies with quality defects
inside a MCP module. Each MCP reconfiguration requires the DTMs’ rearrangement and DTM-chain is proposed. A dynamic reconstructing
algorithm synchronizes the DTM-chain with each MCP reconfiguration. A case study demonstrates the usefulness of the DTM and
DTM-chain.
相似文献
Hua WangEmail: |
996.
997.
Quality evaluation model using loss function for multiple S-type quality characteristics 总被引:2,自引:2,他引:2
W.M. Chan R.N. Ibrahim P.B. Lochert 《The International Journal of Advanced Manufacturing Technology》2005,26(1-2):98-101
Most of the studies of quality system or product-quality assessment deal with a single quality characteristic to determine the quality loss. Products are often assessed on more than one quality characteristic. For this reason, different multivariate quality loss functions have been proposed. However, these loss functions only consider the nominal-the-best quality characteristics (N-type); they do not consider the condition when the quality characteristics are of the smaller-the-better (S-type). In this article, we present a quality evaluation model using loss function for multiple S-type quality characteristics. A numerical example is illustrated showing that using inappropriate loss functions will lead to inaccurate results that give either an underestimate or overestimate of the expected quality costs. 相似文献
998.
比较分析了当前国内所使用的几种易拉罐用铝板材与经高效熔体处理的试验铝板材的冶金质量和力学性能。结果表明:现用铝板中的夹杂物大多数为较粗大的复合夹杂物且含量较高;小块状第二相粒子大小相当,但均大于试验板材中的第二相尺寸,且分布不均匀性较明显;国产板材的常温拉伸性能低于国外板材,在三种板材中其各向异性最明显。经高效熔体处理的铝材中的夹杂物以细小Al2O3为主,夹杂物质量分数仅为0.273%;细小第二相均匀分布于基体,大多数为(Al,Fe,Mn,Mg,Si,RE)复合相;拉伸断口韧窝呈近等轴状,与国产板材相比,抗拉强度、屈服强度与伸长率分别提高9.1%、19.6%和12.8%,主要力学性能基本达到(有的甚至略优于)国外板材的性能水平。 相似文献
999.
1000.
针对经济型数控车床的使用中常遇到的实际问题,在加工轴、孔、球类零件时,使用G00、G92、G26、G27、G29及间隙补偿指令可用的技巧和注意事项;在提速的同时充分考虑指令使用与实际位移轨迹、累计误差、工序安排、运行速度、间补次数等多种因素,使编程简单化的同时提高加工精度,最大效益的发挥经济型数控车床的作用。 相似文献