tailieunhanh - Project Planning and Control Part 3

Mạng lưới sản xuất theo cách này được gọi là theo cách khác nhau, "sơ đồ ưu tiên", "biểu đồ vòng tròn và liên kết" hoặc 'hoạt động trên sơ đồ nút' | 12 Precedence or activity on node AoN diagrams Some planners prefer to show the interrelationship of activities by using the node as the activity box and interlinking them by lines. Because the durations are written in the activity box dummy activities are eliminated. In a sense each connecting line is of course a dummy because it is timeless. The network produced in this manner is called variously a precedence diagram a circle and link diagram or an activity on node diagram . Precedence diagrams have a number of advantages over arrow diagrams in that 1 No dummies are necessary 2 They may be easier to understand by people familiar with flow sheets 3 Activities are identified by one number instead of two so that a new activity can be inserted between two existing activities without changing the identifying node numbers of the existing activities 4 Overlapping activities can be shown very easily without the need for the extra dummies shown in Figure . Project Planning and Control Analysis and float calculation see Chapter 15 is identical to the methods employed for arrow diagrams and if the box is large enough the earliest and latest start and finishing times can be written in. A typical precedence network is shown in Figure where the letters in the box represent the description or activity numbers. Durations are shown above-centre and the earliest and latest starting and finish times are given in Figure the corners of the box as explained in the key diagram. The top line of the activity box gives the earliest start ES duration D and earliest finish EF . Therefore EF ES D The bottom line gives the latest start and the latest finish. Therefore LS LF - D The centre box is used to show the total float. ES is of course the highest EF of the previous activities leading into it . the ES of activity E is 8 taken from the EF of activity B. LF is the lowest LS of the previous activity working backwards . the LF of A is 3 taken from the LS of activity B. .