Bus Route Assignment Problem in Logistics and Transportation Systems
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Questions and Answers

What is the goal of the formulation described in the text?

  • Minimize the flow on each arc
  • Maximize the flow on each arc
  • Minimize the cost of satisfying demand (correct)
  • Maximize the cost of satisfying demand
  • In the context of the formulation, what do the constraints (7b) represent?

  • Maximum flow on each arc
  • Minimum flow on each arc
  • Flow balance equations (correct)
  • Cost of each arc
  • What does the notation ∑𝑗∶(𝑖,𝑗)∈𝐴 represent in the text?

  • Summing over all arcs entering node 𝑖
  • Summing over all nodes 𝑗 such that the arc (𝑖, 𝑗) belongs to 𝐴 (correct)
  • Summing over all arcs in the graph
  • Summing over all arcs leaving node 𝑗
  • What is the role of 𝑙𝑖𝑗 and 𝑢𝑖𝑗 in the formulation?

    <p>They represent lower and upper bounds for flow on each arc</p> Signup and view all the answers

    What is the significance of the notation ⎧> 0, { 𝑏𝑖 is ⎨< 0, {= 0, ⎩ if supply node, if demand node, if transshipment node?

    <p>It indicates whether a node is a supply, demand, or transshipment node</p> Signup and view all the answers

    What does the objective function (7a) aim to minimize in the formulation?

    <p>Cost of satisfying demand</p> Signup and view all the answers

    In the context of the formulation, what does 𝑐𝑖𝑗 represent?

    <p>Cost of each arc</p> Signup and view all the answers

    Which term is used to collectively refer to the constraints (7b) in the context of the formulation?

    <p>&quot;Flow balance equations/constraints&quot;</p> Signup and view all the answers

    What does the notation ∑ 𝑥𝑖𝑗 − ∑ 𝑥𝑗𝑖 = 𝑏𝑖 , ∀𝑖 ∈ 𝑉 in constraint (7b) represent?

    <p>Flow balance equations</p> Signup and view all the answers

    What problem type does the above formulation represent?

    <p>Minimum Cost Network Flow (MCNF) problem</p> Signup and view all the answers

    Which type of problems can be solved as LPs and will produce integer optimal solutions?

    <p>Shortest path and max flow problems</p> Signup and view all the answers

    What happens to the MCNF structure if additional constraints or variables are added that break the structure?

    <p>It no longer has the special LP property</p> Signup and view all the answers

    In which type of problems is it obvious that they can be written with a source node 𝑠 and sink nodes 𝑡?

    <p>Shortest path and max flow problems</p> Signup and view all the answers

    What is the main idea behind the illustration in Figure 23?

    <p>To demonstrate how to convert the transportation problem to have a source and sink</p> Signup and view all the answers

    What do all red arcs with cost 𝑐𝑖𝑗 = 0 represent in the context of the text?

    <p>Main transportation routes</p> Signup and view all the answers

    What does it mean for a supply node if 𝑏𝑖 is ⎧> 0?

    <p>It means the supply node has excess inventory</p> Signup and view all the answers

    What type of problems are covered in MCNF problems?

    <p>Network flow problems</p> Signup and view all the answers

    What do the constraints (7b) represent in the context of the formulation?

    <p>Capacity constraints</p> Signup and view all the answers

    What is the role of the 'capacity' attribute in the function maximum_flow?

    <p>To identify the attribute representing the capacity of the graph's arcs</p> Signup and view all the answers

    What is the main goal of solving the shortest path problem?

    <p>To minimize the distance between the source and target vertex</p> Signup and view all the answers

    In the context of the formulation, what does 𝑐𝑖𝑗 represent?

    <p>The cost associated with arc (i, j)</p> Signup and view all the answers

    What type of problems are covered in MCNF problems?

    <p>Minimum Cost Network Flow problems</p> Signup and view all the answers

    What happens to the MCNF structure if additional constraints or variables are added that break the structure?

    <p>It becomes infeasible to solve</p> Signup and view all the answers

    What does it mean for a supply node if 𝑏𝑖 is ⎧> 0?

    <p>The node has excess supply that needs to be distributed</p> Signup and view all the answers

    Which term is used to collectively refer to the constraints (7b) in the context of the formulation?

    <p>Flow conservation constraints</p> Signup and view all the answers

    What do all red arcs with cost 𝑐𝑖𝑗 = 0 represent in the context of the text?

    <p>Optimal paths with no cost associated</p> Signup and view all the answers

    What is the significance of the notation ⎧> 0, { 𝑏𝑖 is ⎨< 0, {= 0, ⎩ if supply node, if demand node, if transshipment node?

    <p>It determines whether nodes are source, sink, or transshipment points</p> Signup and view all the answers

    What does the notation ∑𝑗∶(𝑖,𝑗)∈𝐴 represent in the text?

    <p>The sum of costs for all arcs connected to node i</p> Signup and view all the answers

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