Operations Research Fundamentals Chapter 7 Network Planning Technology

Chapter 7 Technical
 Test Points for Network Planning : Network Diagram; Key Routes; Calculation of Network Time and Time Difference, etc.
   -Network Diagram
  Planning and Leveling Technique: PERT for short, which is to calculate and evaluate planned items, and then select the most A technical
  key route method with planned plans : CPM for short, is a method of grasping the key route memory planning arrangement in the intricate work.
     1. The classification of network diagrams
   1. Wire-bonded network diagrams: arrows represent activities, and nodes represent the beginning or completion of activities.
   2. Node-type network diagram: nodes represent activities, and arrows indicate the spot undertaking relationship between activities. Rarely used
   two, the composition of the arrow network diagram
  1. Activity: refers to the operation or process, indicated by the arrow, and the direction of the arrow indicates the direction of advancement.
      Fictitious activity: A fictitious activity that does not consume resources or time.
   2. Node: starting or ending point, the junction of two activities, represented by a circle. There is only one starting point and one ending point.
   3. Route: Starting from the starting point, following the direction of the arrow line, passing through the interconnected nodes and the arrow line, it is a line to the end point.
   (1) Total operating time: On a line, adding up the operating time of each activity is the total operating time for changing the line, also called the road length.
   (2) Critical line: The line with the longest total operating time is the key line.
           All processes on the key route are called key processes.
      Note: Don’t mistake the shortest route for this case. The key route is actually confused with “the key route determines the shortest construction period”.
   3. Editing of arrow-line network diagrams
    1. When drawing, it is found that some logical relationships that are difficult to handle are that most of them need to add processes.
      (1) When two or more activities have the same start point and end point, virtual process needs to be introduced.
      (2) Before the activity has a succession relationship, virtual process
    2 needs to be introduced . After the sketch is revised, you need to check whether there are any additions. Excess virtual processes should be removed in time (so as not to increase the amount of calculation when calculating the time parameters)
    3. It is strongly recommended to check the logical relationship of the processes again in accordance with the process table after the network drawing is completed! This can avoid subsequent time parameter calculation errors caused by network drawing errors!
     Node label: It must be marked as the number of the node at the end of the arrow is less than the number of the arrow.
    Three calculation methods: calculation method on the graph, table calculation method (recommended), matrix calculation method
1, related symbols,
   node symbols: (a line in the middle of a circle is divided into two halves, and the semicircle is divided into two halves) The upper half is the knot Point mark: The left side of the lower half is the earliest start time, and the right side is the latest completion time.
   Rectangle: Symbol of the earliest start/complete time of the activity. The symbol is placed in the
   triangle above the arrow : the activity start/finish time symbol at the latest. The change symbol is placed below the arrow line.
  2) Homework time-the time to complete an activity. There are two methods:
    1. Single time estimation method: refer to the statistics of similar activities to determine a time value
    2. Three time estimation methods: first estimate three times (a- the most optimistic time, b- the most conservative time, m- Most likely time), and then find a time value (a+4m+b/6=1/6a+4/6m+1/6b)
   3) Node time (basically not included)
    4) Activity time (recommended table method )
     Earliest start time: ESi-j
     Earliest completion time: EFi-j
     Latest start time: LSi-j
     The latest completion time: LFi-j
four, the time difference and the key line
 only need to master the "total time difference"
network time difference-represents the maneuver time, you can use the time difference to support the key line
1) Node time difference: Sl=LFl-ESl, which is Click the difference between the right and left in the lower half. The node whose time difference is equal to 0 is called the key node.
2) Activity time difference
   1, total time difference: the difference between the worst start time and the earliest start time, or the difference between the latest completion time and the earliest completion time. The total time difference of key activities is equal to 0.
       TFi-j=LSi-j=LFi-j-EFi-j
   2, local time difference 1: the time difference of the starting node
   3, local time difference 2: the time difference of the completion node
   4, dedicated time difference: Total time difference-local time difference 1-local time difference 2
3) Line segment time difference: the largest total time difference among the activities of the line segment
4) Line time difference: The time difference of each line from the start point to the end point. The line time difference of the key line is equal to 0.