Capability index - meaning

The critical characteristic on each component was analysed, calculated from the analysis and the value obtained was plotted against the process capability indices, Cpk and Cp, for the characteristic in question. See Appendix V for descriptions of the 21 components analysed, including the values of Cp and Cp from the SPC data supplied. Note that some components studied have a zero process capability index. This is a default value given if the process capability index calculated from the SPC data had a mean outside either one of the tolerance limits, which was the case for some of the components submitted. Although it is recognized that negative process capability indices are used for the aim of process improvement, they have little use in the analyses here. A correlation between positive values (or values which are at least within the tolerance limits) will yield a more deterministic relationship between design capability and estimated process capability. 

The process capability index is a means of quantifying a process to produce compo nents within the tolerances of the specification. Its formulation is shown below ... 

It should be noted that the Cp value could not indicate the proper process capability if the process is not centered since Cp does not account for where the process mean is with respect to the specifications. To alleviate this issue, another process capability index, Cpk, is used ... 

Suppose over a number of results the mean error is not zero. In SPC the mean error as a percentage of the tolerance half-range (which is T when the tolerance is T) is known as the index of accuracy, or capability index for setting ... 

There is one more index that is used, the overall quality index, or the corrected process capability index, Cpk. This is the distance of the mean of the measure to the nearest tolerance limit. 

Cp, Cpi, Process capability and the index of capability, respectively. Typically a process is considered capable when the capability or the capability index is 1.33 or greater. Cp = (upper — lower specification limit)/6s, where s = standard deviation of process output. Cpk (mean — nearer specification)/3s... 

A way of assessing a process to produce to a given total tolerance is to measure its Capability Index (Cp), where Cp = 2Tj 6a. For a process to be capable, Cp must be 1 or more. The Cp value compares the spread of 2T with the spread of 6cr, but unfortunately, does not take into account the actual location. Flowever, Cp values are used extensively, but the shortcomings can be overcome by using Cpt, which compares the spread between the upper tolerance and the process mean (x) with the actual spread from the process mean (3a), or the spread between the process mean (x) and the lower tolerance with the actual spread of the process from the process mean (3a). 

In Figs. 2.22 and 2.23 all the binary combinations are mapped as a function of the Mendeleev numbers of the two elements involved. The compound formation capability is represented in Fig. 2.22 by means of a few codes, whereas in Fig. 2.23 an indication is given of the thermal stability of the intermediate phases. To this end, values correlated to the so-called Raynor Index (Raynor 1972, 1974) are coded in this figure. 

Experimental Techniques. Chromatography was performed on a Varian model 5060 HPLC equipped with a RI-3 refractive index detector. A Vista Plus Gel Permeation Chromatography (GPC) data system was used consisting of a Vista 401 chromatography data system serially connected to an Apple II microcomputer. The Vista 401 performs data acquisition and allows data storage and automations capability while all SEC data processing is performed on the Apple II by means of user-interactive GPC software for automated, on-line calibration and polymer analysis. 

Therefore, it is possible to select, by means of the loading plot related to the PCA of all the available data (Fig. 19.3), a minimal number of variables (analytical indexes) capable of characterizing the cheeses. 

For measurement of intersex intensities, the mean intersex stage of all females is calculated to provide the intersex index (ISI). This index provides the best results for assessing the reproductive capability of a population (Bauer et al., 1995 Bauer et al., 1997). A value of 0 indicates that only normal females occur, and no restrictions of the reproductive capability are to be expected. ISI values above 0 show that intersex-affected females can be found and that reproductive success may be reduced. An ISI above 1 indicates the presence of some sterile females, and values above 2 indicate that most females in a population are sterilized due to intersex development. 

Melt index potential means the maximum MI that can be obtained with a catalyst activated at maximum temperature (871 °C), and making homopolymer at maximum reaction temperature (110 °C). Catalystshaving a high-MI potential need not be used to make high MI resins, but they have the capability. Low-MI polymers are typically manufactured more easily with catalysts having a high-MI potential. 

The integration of a DAE system can be performed by transformation in an ODE system. It is worthy to note that this operation might be confronted with the index problem. Index is the minimum number order of differentiation needed to transform a DAE system into a set of first-order ODEs. Problems of index one can be solved by means of standard differentiation methods. When the index is higher than one then the DAE system needs a special treatment. Modem codes have capabilities for automatic detection of index higher-than-one, diagnose the problem and suggest modifications. 

In order to describe rubber compounds from the point of view of their processing capabihty different methods are used [29]. In this respect full characterization is achieved by analyzing the flow curves of rubbers and rubber compounds. The flow curves can be obtained by different viscometers. In the rubber industry (over 100 years) a technological index has been widely used - the Mooney viscosity. It serves for a comparison and control. It is measured relatively quickly with the respective viscometer and in accordance with the International standard ISO 289-1 2002. The obtained Mooney viscosity gives information just for one point of the flow curve of the rubber or rubber compound and this is the reason that no full rheological characteristics of the elastomeric material are obtained [30]. In order to describe the processing capability of rubber compounds by means of Brabender Plasticorder, the measurements are usually performed at a relatively high... 

More specific and sophisticated methodology has been developed recently to elucidate how lipid oxidation products and other bioactive compounds act in the complex mechanism of LDL oxidation. A large amount of work has been published recently on the GC-MS or LC-MS analyses of cyclic oxidation products of arachidonate described as isoprostanes in biological samples as an index of oxidative status. Because the level of arachidonate in LDL and blood is relatively small (Table 13.2), much effort has been made to use instrumental means to improve the sensitivity required to analyse isoprostanes. This instrumental approach is still beyond the capability of many laboratories, however. LC-MS has the advantage of direct measurements of isoprostanes in contrast to GC-MS (see Chapter 6), which requires the use of two or three thermally stable derivatives. On the one hand, LC-MS still requires purification by reversed-phase solid-phase extraction, followed by TLC to remove impurities, but this step can also be avoided if one can invest in a highly selective MS/MS system. On the other hand, the well-established methodology to measure oxidation products of linoleate, which is present in LDL at levels about seven fold higher than that of arachidonate (Table 13.2), is much more within the capability of many laboratories than the more expensive LC-MS and GC-MS and MS/MS approaches required for isoprostanes. 

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