PERT

It has already been noted that PERT was developed to speed up the Polaris project. The Navy was dealing with hundreds of subcontractors, each constructing parts in a different location. These were then sent to an assembly point where the submarine was put together. Until the items arrived there, the activities were essentially independent. This is different from CPM, which was developed mainly for maintenance turnarounds at a given location. Under these conditions, everything was closely interrelated. 

From these three estimates a single value called the expected time (tc) is obtained from the following formula  

This estimate is used in much the same way the normal time estimate was used in constructing a CPM diagram and determining the critical path. Then an estimate is made of the probability of completing the total job in a certain time period. 

Time Estimates (Days) for the Installation of a Scrubber in an Existing Process 

80 100 Remove some existing piping and make changes in existing equipment (Q) 12 16 20 16.0 

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A DOT regulation covers both domestic and international shipping (9). For transportation safety, the DOT has information for first responders to incidents involving elemental phosphoms (10). In addition, the Chemtrec phone number 1-800-424-9300 accesses DOT emergency information and assistance in the United States. Also, the phosphoms producers in the United States have estabUshed a Phosphoms Emergency Response Team (PERT) to assist in handling P emergencies. 

Design and development plans need to identify the activities to be performed, who will perform them, and when they should commence and be complete. One good technique is to use a network chart (often called a PERT chart), which links all the activities together. Alternatively a bar chart may be adequate. In addition there does need to be some narrative, as charts rarely convey everything required. 

Arrow diagram - used to show steps necessary to implement a plan (e.g. PERT)... 

Method Structure Type e t R1 R2 R3 (02 Pert. Symm. Str. (O3 Pert. Asymm. Str. 

Unkenntnis, /. ignorance, un-klar, a. not clear indistinct turbid confused. -kondensierbar, a. uncondensable. -kontroUierbar, a. uncontrollable, -korri-pert, p.a. uncorrected, -korrodierbar, a. noncorrodible. 

For the more sophisticated requirements of complex one-off projects, techniques such as PERT, resource, leveling and precedence diagrams should be investigated. ... 

With time duration determined for each task of the project, the next step is to determine the earliest and latest starting times for each task. There are two commonly used methods for charting the project Gantt charts and PERT diagrams. The details of these two methods are discussed on the following pages. 

Gantt charts are limited in their ability to show the interdependencies of activities. In projects where the steps flow in a simple sequence of events, they can portray adequate information for project management. However, when several steps are under way at the same time and a high level of interdependency exists among the various steps, PERT diagrams are a better choice. 

PERT is an acronym for Program Evaluation and Review Technique. It is a more sophisticated form of planning than Gantt charts, and is appropriate for projects with many interactive steps. There are three components of a PERT diagram circles or other convenient, closed figures represent events arrows connecting the circles represent activities and non-activities connecting two events are shown as dotted-line arrows. (A non-activity represents a dependency between two events for which no work is required.)... 

PERT diagrams are most useful if they show the time scheduled for completing an activity on the activity line. Time is recorded in a unit appropriate for the project, with days being most common, and hours, weeks, or even months occasionally used. Some diagrams show two numbers for time estimates - a high estimate and a low estimate. 

The most sophisticated PERT diagrams are drawn on a time scale, with the horizontal projection of connecting arrows drawn to represent the amount of time required for their activity. In the process of diagramming to scale. 

M. Morita, T. Hanada, H. Tsutsumi, Y. Matsuda, in High Power. Ambient Temperature Lithium Batteries (Eds. W. D. Clark, G. Hal-pert), The Electrochemical Society, Pennington, NJ, 1992, PV 92-15, p. 101. 

Pert design should maintain a wall thickness as nearly constant es possible. Complete uniformity in this dimension is sometimes impossible to achieve. Walls of non-uniform thickness should be gradually blended from thick to thin. 

Pert wee RG (2006) Cannabinoid pharmacology the first 66 years. BrJ Pharmacol 147(Suppl 1 ) S 163—S171... 

Heckman, Behavior of Turbulent Scales in Hypersonic Sphere Wakes , Rept No DREV-R-696/73 Contract DAAH01-69-C-0921, ARPA Order — 133, Defence Res Est, Valcartier (Can) (1973) 42) Ya.L. Al pert, Waves and Satel-... 

Szell, A. Shelton, J.N. (1986). Sucrose dilution of glycerol from mouse embryos frozen rapidly in liquid nitrogen vapour. J. Reprod. Pert. 76,401-408. 

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