Schedule situation

During the project duration, the project management is required to prepare a monthly order report for the company management illustrating the state of execution, the schedule situation as well as the current cost situation. Mostly such an order report contains a forecast in which the looming technical, commercial or schedule problems are to be identified. 

Breakeven charts present a snapshot of the present situation by means of graphs which are generally drawn in the manner shown in Figs. 9-2, 9-3, and 9-4. Since the lines are straight, this implies that Cs, Cy , and Aee will remain constant over the range of variation of R, which is of interest. The values would be based on the production rate currently achieved (or scheduled), since all the data are available from... 

In Table 1, drawn up by the author, of abbreviations in common use those in bold type are in the main schedule of BS 3502. In this list the names given for the materials aie the commonly used scientific names. This situation is further complicated by the adoption of a nomenclature by the International Union of Pure and Applied Chemistry for systematic names and a yet further nomenclature by the Association for Science Education which is widely used in British schools but not in industry. Some examples of these are given in Table 2. Because many rubbery materials have been referred to in this book. Tables 3 and 4 list abbreviations for these materials. 

The number of experiments that can be done satisfactorily in a one-semester course varies widely with the physical situation and the individual skills of the student. Therefore, no attempt is made to suggest a schedule. I recommend, however, that a common core of about five experiments be assigned. The remainder of the preparations can then be chosen by individual students as dictated by their interests as well as by the availability of chemicals and special equipment. The common experiments, representing frequently used and important techniques, might be chosen from Chapter 1, Sections I and IV Chapter 2, Section I Chapter 3, Section I Chapter 4, Section I Chapter 5, Section I Chapter 6, Sections III and IV Chapter 7, Sections II and VI Chapter 8, Section II Chapter 9, Sections I and II Chapter 11, Sections I and III or Chapter 13, Section II, Since many of the other experiments draw on the products of this suggested list, the possibility of multistep syntheses also presents itself, and several such sequences are outlined in Appendix 1. Also included, in Appendix 2, are the commercial suppliers of the chemicals required when these chemicals are not routinely available. 

The most common schedule in use is 40, and it is useful for a wide range of pressures defined by ANSI Std. B 36.1 (American National Standards). Lighter wall thickness pipe would be designated Schedules 10, 20, or 30 whereas, heavier wall pipe would be Schedules 60, 80, 100, 120, 140, 160 (see Appendix Table). Not all schedules are in common use, because after Schedule 40, the Schedule 80 is usually sufficient to handle most pressure situations. The process engineer must check this schedule for both pressure and corrosion to be certain there is sufficient metal wall thickness. 

After administering penicillin to a patient in an outpatient setting, you request that the patient unit about 30 minutes before leaving. The patient is reluctant to stay, saying that die has a busy schedule. Discuss how you would handle this situation. 

A more compact alphabet for this situation is one for which we create a unique symbol for each batch type, and allow the multiple occurrence of this symbol to stand for scheduling the batch type more than once. The feasibility predicate would be suitably modified to check to see when enough of the type had been added to a given branch. This gives the... 

All of the schedules considered so far involved transferring material from one step to another, from a step to storage or from storage to a step without any time delay. This is known as zero-wait transfer. An alternative is to exploit the equipment in which a production step has taken place to provide hold-up. In this situation, material is held in the equipment until it is required by the production schedule. A schedule using equipment hold-up is shown in Figure 14.17c. This reduces the cycle time to 15 h. 

Suppose the CPM diagram for a job is given in Figure 13-3, and the men required for each task are given in Table 13-4. If each activity is scheduled at the earliest possible time it could begin, and it is desired to complete the job in the shortest possible time, number of men employed changes from 5 to 37 and fluctuates widely. (See figure 13-4) This is obviously an intolerable situation. 

The use of computers for equipment design and for planning schedules (CPM, PERT) has already been discussed. A number of other situations where computers are useful follow. No attempt will be made to indicate how computer programs should be written. However, I shall attempt to show what must be considered both by the person who writes and the one who uses the program. 

In a situation where the plant schedule already exists, the problem addressed in this chapter can be stated as follows. For each water using operation, given ... 

In a situation where scheduling is not given beforehand, time is treated as an optimisation variable to provide a truly optimal schedule for freshwater demand and wastewater generation. The problem, in this particular case, can be stated as follows. Given the aforementioned (i)-(v ) conditions for each water using operation as well as ... 

The constraints derived above complete the zero effluent scheduling formulation for both the situation where the contaminant mass is negligible and where it is not negligible. 

Other established attempts on heat integration of batch plants are based on the concept of pinch analysis (Linnhoff et al., 1979 Umeda et al., 1979), which was initially developed for continuous processes at steady-state. As such, these methods assume a pseudo-continuous behaviour in batch operations either by averaging time over a fixed time horizon of interest (Linnhoff et al., 1988) or assuming fixed production schedule within which opportunities for heat integration are explored (Kemp and MacDonald, 1987, 1988 Obeng and Ashton, 1988 Kemp and Deakin, 1989). These methods cannot be applied in situations where the optimum schedule has to be determined simultaneously with the heat exchanger network that minimises external energy use. 

Constraints (10.1), (10.2), (10.8)-(10.14), in conjunction with the overall plant scheduling constraints, constitute a complete MILP formulation for direct heat integration in batch processes in a situation where the batch size is allowed to vary at different instances along the time horizon of interest. 

The crane simulation is also performed within a few seconds. The size and the complexity depend on the problem instance. Since the number of batches is always fixed, the main factor affecting the number of binary variables is the number of maintenance jobs. It should be mentioned that each schedule optimization run also considers two previous batches that are already in production from a resource availability perspective. The initial situation based on the previous batches, defines the complexity. If the production is far from the ideal production cycle, the flexibility may be very low and the main task of the optimization is to increase the total throughput as fast as possible. At this point, the schedule is very sensitive to additional disturbances, which may directly affect the throughput. However, when an optimal production cycle has been reached, a rescheduling optimization may use the existing flexibility (for instance time buffers between the most critical steps) to minimize or to eliminate the throughput decrease caused by disturbances. 

If a schedule is computed based on a model that does not consider uncertainties, this schedule can become suboptimal or even infeasible when the situation has changed. For example, a schedule can become suboptimal if a batch is unexpectedly of inferior quality and the revenues are a function of its quality. A schedule can become infeasible if there is an unexpected plant failure that reduces the plant capacity a batch has to be immediately transferred to another unit, but no unit is available. Then it is impossible to modify the infeasible schedule to a feasible one. 

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