Carry-over time issues

Finally, an important characteristic identified in chemical production processes are time-consuming and costly setup operations. Thus, the representation of time is a critical issue in the modeling of chemical production processes. Three fundamental deficiencies of the representation result if continuous processes are modeled by standard bucket-oriented lot-sizing models. These are the carry-over of setup states... 

The first issue, a setup state carry-over between adjacent periods, is depicted in Figure 11.3. On a continuous time scale a sequence of five products (A to E) can be modeled straightforwardly. However, if the same is to be done in a bucket-oriented setting some difficulties arise. Production within a bucket is coupled with a corresponding setup operation which causes a lot of problems. 

Naive estimators associated with sequential tests may also be biased in the sense that the expectation of standard fixed trial estimators taken over all possible trials run to the same stopping rule may not be equal to the true treatment effect. Adjustments for estimators and associated intervals are possible but raise similar issues to those discussed under section 19.2.1. For example, suppose that we have a fixed parallel-group trial and calculate, as a conventional treatment estimate, the difference between the mean outcomes in each group. Suppose we then notice, however, on looking at the results for the patients ordered over time, that had we run this trial as a given sequential trial with three looks at equal intervals, then we would have stopped exactly at the point dictated by the fixed trial, which happens to correspond to the second look of the sequential trial. Had we carried out the sequential trial we should have adjusted the treatment estimator, but since we have carried out a fixed trial we shall not. 

The separation plant had been running smoothly for several weeks and the planned shutdown was some time away. On the day of the incident a number of unusual events occurred which contributed to its development. Shortly after the start of his day shift, the control room operator received a high vibration alarm from booster pump A in the crude fluid separation building. Following normal procedure, he switched over to the standby pump (pump B), switched off pump A, and told his supervisor of the alarm. The supervisor subsequently organized a work permit for work to be carried out on pump A by the day shift maintenance team. The permit was issued and repair work... 

Over the years, scientific research with human subjects has provided valuable information to help characterize and control risks to public health, but its use has also raised particular ethical concerns for the welfare of the human participants in such research as well as scientific issues related to the role of such research in assessing risks. Society has responded to these concerns by defining general standards for conducting human research. As an example, studies carried out for the authorization of a medical product, have to be conducted in line with the World Medical Association s Declaration of Helsinki, which describes the general ethical principles for medical research involving human subjects (World Medical Association 2004). The Helsinki Declaration was first issued by the World Medical Association in 1964 and has been revised several times since then. 

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