5-Why" technique

Many techniques are used to evaluate the root causes of accidenfs, buf one of fhe most useful is the "5-Why" technique, which is relatively easy to use and requires no advanced statistical analysis or data collection. The technique follows a sfrucfured ques-tion-and-answer sequence that contains a feedback loop fo fhe previous quesfion. By asking enough times why an event happened, the technique is supposed to "peel away... 

Why are coniparison.s of particle sizes between different instrumental techniques only qualitative ... 

Hydrotreating the LCO increases its cetane number to around 40 (Table 5.16), but this technique needs large amounts of hydrogen for rather mediocre results, the aromatics being converted into naphthenes which are still not easily auto-ignited. That is why LCO is sent to the domestic heating oil pool. 

The integral in Eq. (40) will be taken by the steepest descent method (SDM). The reason why we do not apply an analogous technique directly to the 5-function in Eq. (39) is not only because we want to get rid of the e integration, but also because the SDM proved more forgiving in terms of accuracy when used to approximate the 0-function, rather than the 5-function. 

The significant intrinsic limitation of SEC is the dependence of retention volumes of polymer species on their molecular sizes in solution and thus only indirectly on their molar masses. As known (Sections 16.2.2 and 16.3.2), the size of macromolecnles dissolved in certain solvent depends not only on their molar masses but also on their chemical structure and physical architecture. Consequently, the Vr values of polymer species directly reflect their molar masses only for linear homopolymers and this holds only in absence of side effects within SEC column (Sections 16.4.1 and 16.4.2). In other words, macromolecnles of different molar masses, compositions and architectures may co-elute and in that case the molar mass values directly calculated from the SEC chromatograms would be wrong. This is schematically depicted in Figure 16.10. The problem of simultaneous effects of two or more molecular characteristics on the retention volumes of complex polymer systems is further amplifled by the detection problems (Section 16.9.1) the detector response may not reflect the actual sample concentration. This is the reason why the molar masses of complex polymers directly determined by SEC are only semi-quantitative, reflecting the tendencies rather than the absolute values. To obtain the quantitative molar mass data of complex polymer systems, the coupled (Section 16.5) and two (or multi-) dimensional (Section 16.7) polymer HPLC techniques must be engaged. 

Why would we choose one ionization technique over another Well, each technique has a range of substrate (analyte) types and relative molecular masses for which it is best suited (as illustrated in Figure 5.1). 

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