Summary of operations research knowledge points (7)

A full set of operations research knowledge points

Chapter 7 Network Planning Technology

1. Network planning technology

Network technology is a plan to organize production and scientific methods of program management, also known as the co-ordination method is the use of a comprehensive program assessment techniques and critical path method is more advanced management methods
to calculate technical assessment: Is the planned project Calculate, evaluate, and then select the most planned technique.
The Critical Route Method is a method of grasping the key routes to plan and arrange in the complicated work of the various faults of the planned project. Network planning technology is especially suitable for large-scale and complicated production projects or engineering projects.

Second, the network diagram

The network diagram is also called the arrow diagram or the overall planning diagram. It is a comprehensive reflection of the internal logical relationships of the various components of the planned project, the basis for planning and calculation, and the basis for network planning technology. Divided into arrows are network diagrams and nodes are network diagrams

Third, the composition of the arrow network diagram

The arrow network diagram is composed of three components: activity, node and line

1. Activities: Refers to operations or processes, indicated by arrows. For the direction of the button line, write the name of the activity on the left and the time occupied by the activity on the right.
   Virtual activity: does not consume resources and does not take up time.
   Virtual activities should be cited in the following two situations:
   (1) The work process between two nodes can only represent one activity. when the start and end points
   (2) in order to correctly represent the relationship between the various activities to undertake necessary to introduce a virtual event.
2. Node: Refers to the matter. The junction between two activities. Explain that the start or completion of an activity does not take up time or resources.
   A network should have only one start and end point. Except for the start point and the end point, all other nodes have duality, that is, the front is the end point, and the back is the start point
   . The numbering principle of the node is: the arrow end node is smaller than the arrow node, and non-continuous numbering is generally used.
   The numbering method is: go to the point and go to the line numbering method.
3. Route: Starting from the starting point of the network, following the direction of the arrow, passing through the interconnecting starting point and the arrow line, to a connecting line to the end point.
4. The line with the longest total operating time is the key line, or the main contradiction line. Determines the completion time of the entire network plan, and the total length of the line is called the road length. Key lines are marked with double or red lines on the map.

4. Editing and drawing of arrow-line network

Decomposition of tasks: Decompose the total tasks of a planned project into a certain number of sub-tasks, and determine that they have a mutual inheritance relationship.
The principle of decomposition: the division of labor must be clear, and the responsibilities must be clear. It is necessary to prevent the division of labor from being too detailed and the network diagram to be too complicated, but also to prevent the phenomenon of unclear division of labor and mutual wrangling. Specifically:
(1) The nature of the work or the work performed by different units should be separated
(2) The work performed by the same unit should be separated if the working hours are not consecutive.
(3) Anything that takes up time and does not consume resources, but affects the completion date of the project should be classified as a sub-task and included in the network diagram

Five, the calculation of network time

The calculation of the network time includes the calculation method on the graph, the table calculation method, and the matrix calculation method. The latter two are suitable for computer calculations.
Related symbols used in the calculation method on the graph:

Six, homework time

1. Single time estimation method: When estimating the operation time of each activity, only one time value is determined.
2. Three time estimation methods: when estimating the work time of each activity, first estimate the three time values, and then calculate the work time to complete the activity.
   

Seven, node time

1. The earliest start (completion) time of a node: Calculate from the start point and take the maximum value of the addition.
   The formula for calculating the earliest start time of a node is as follows:
2. The latest completion time of the node: Calculate from the end point and take the minimum value of the subtraction. The calculation formula for the
   
   latest completion time of a node is as follows: the node whose earliest start is Akin and the latest completion time is equal is called key point or key item, and the route through these points is the key route

8. Activity time

1. Earliest start time: the earliest start time of the arrow tail node
   

2. Earliest completion time: equal to its earliest time + operation time

3. The latest completion time: the latest completion time of the arrow node. It is also the latest start time of the activity + homework time.
   

4. The latest start time: the latest completion time of the arrow node-the work time, or the latest start time of the next activity.

Nine, nodal time difference

Node time difference = latest completion time-earliest start time
The point where the node time difference is 0 is the key point

1. Activity time difference (process time difference)
   
2. Line segment time difference
   Line segment: An activity between two key nodes, or a connection line where several activities between two key nodes are continuously connected is called a line segment.
   note:

• There is no third node between two key nodes as a line segment;
• There is a third node between the two key nodes, which counts as two line segments.
  The line segment time difference is equal to the longest of the total time difference of each activity in the line segment.

3. Line time difference
   Line: starting from the starting point, after the continuous connection activities, until the end of the line is called the line. The
   line time difference is equal to the sum of the time difference of each line.
   The line time difference of the key line is 0
4. Critical line
   (1) The line with the longest total operating time is the key line.
   (2) The line time difference of the key line is equal to 0.
   (3) The line that connects all the key nodes in series in order is called the key line.

Ten, the content of network plan optimization

Optimization is to work out the best plan, that is, the plan can make the most reasonable and effective use of manpower, material resources, and financial resources. And achieve the shortest cycle and lowest cost.

1. Time optimization: Seek the shortest engineering cycle under the basically guaranteed conditions such as human, material and financial resources.
2. Time and resource optimization: Under the condition of rational use of resources, seek the shortest project cycle.
   That is to say, it is necessary to comprehensively consider the two aspects of project progress and resource constraints to balance resources.
   The principle of balancing work is:
   (1) When allocating resources, give priority to ensuring the needs of key activities and activities with small time difference, which has achieved the shortest project cycle
   (2) Reasonable and even use of resources such as manpower and equipment , To avoid the sudden increase and decrease in the use of resources, thereby increasing the difficulty of transferring in and out.
3. Time and cost optimization
   (1) In the case of the shortest intelligent construction period, seek a lower cost solution
   (2) In the case of the lowest cost, seek a reasonable
   growth rate of the direct cost of the project cycle = (limit cost-normal cost) / ( Normal time-limit time)

11. The classification of expenses allocated to the project cost

The expenses allocated to the project cost can be divided into direct expenses and indirect expenses

1. Direct cost refers to the cost of the basic materials that constitute the product or engineering entity
2. Indirect costs refer to costs that cannot be directly calculated based on products or projects
3. Normal time is the use of normal process methods. The cost corresponding to the time that the activity can be completed and the normal time is called the normal cost.
4. The limit time is also called rush time, which refers to the time that the activity can be completed using the most advanced technological methods. The cost of the limit time is called the limit cost. The limit time is the shortest time to complete the activity. Even if the cost is increasing, the completion time cannot be shortened.