Durability physical factors

A wide range of techniques has been employed for the incorporation of a catalytically active species onto a support material. A summary of the most widely used techniques is given below as an introduction to later Sections in this Chapter, which describe the more important chemical and physical factors involved in the dispersion of metal salts onto supports and their influence on the activity, selectivity, and durability of the catalyst system. 

The type and number of materials to be stored and handled form the basis for warehouse planning. The physical characteristics of the material, to a great extent, determine materials-storage and -handling methods. Physical factors include dimensions, weight, shape, and durability. As a first step in warehouse planning, all materials to be stored must be identified and their physical characteristics listed. 

Uncertainties linked to the parameters - for various reasons, the available information on dependability is uncertain a small sample leading to a wide confidence interval, extrapolation of data from one installation to another, etc. Certain other parameters (delayed appearance of physical factors, time available after losing a system before undesirable effects ensue, etc.) connected with design or operation are also with uncertainties. Dependability is defined as the ability of an entity to perform one or several required functions under given conditions. This concept can encompass reliability, availability, maintainability, safety, durability, etc - or combinations of these abilities. Generally speaking, dependability is considered to be the science of failures and faults. 

The uncertainty of a measurement is always a very important consideration but it is especially so with durability tests. In addition to the basic physical test methods, there are the complications of exposure conditions, tests spanning long times and the process of extrapolating results to make predictions. The combination of these factors will inevitably lead to large uncertainties that can very easily be of such a magnitude that any conclusions are meaningless. Terms used to describe precision include repeatability, which refers to within laboratory variation and reproducibility, which refers to variation between laboratories. 

Chemists and statisticians use the term mixture in different ways. To a chemist, any combination of several substances is a mixture. In more formal statistical terms, however, a mixture involves a series of factors whose total is a constant sum this property is often called closure and will be discussed in completely different contexts in the area of scaling data prior to principal components analysis (Chapter 4, Section 4.3.6.5 and Chapter 6, Section 6.2.3.1). Hence in statistics (and chemometrics) a solvent system in HPLC or a blend of components in products such as paints, drugs or food is considered a mixture, as each component can be expressed as a proportion and the total adds up to 1 or 100%. The response could be a chromatographic separation, the taste of a foodstuff or physical properties of a manufactured material. Often the aim of experimentation is to find an optimum blend of components that tastes best, or provide die best chromatographic separation, or die material diat is most durable. 

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