SCM Final Exam.txt

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SCM Final Exam.txt
2012-05-14 14:24:14

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  1. Scheduling
    establishing the timing of the use of equipment, facilities and human activities in an organization. effective scheduling can yield: ~cost savings, ~increases in productivity
  2. Key factors for scheduling in high-volume
    -process and product design, -preventive maintenance, -rapid repair when breakdown occurs, -optimal product mixes, -minimization of quality problems, -reliability of timing and supplies
  3. Key factors for scheduling in intermediate-volume
    -outputs are between standardized high -volume systems and made-to-order job shops, ~ run size, timing and sequence of jobs. -economic run size Q=(square root) 2DS/H * (square root) p/p-u
  4. Gantt chart
    used as a visual aid for loading and scheduling. powerpoint 16 slide 8
  5. Loading
    the assignment of jobs to processing centers
  6. Infinite loading
    jobs are assigned to work centers without regard for the capacity of the work center
  7. Finite loading
    jobs are assigned to work centers taking into account the work center capacity and job processing times
  8. Forward scheduling
    scheduling ahead from some point in time
  9. Bacward scheduling
    scheduling by working backwards in time from the due date
  10. Sequencing
    determine the order in which jobs at a work center will be processed
  11. Assumptions of priority rules
    • -the set of jobs is known; no new jobs arrive after processing begins; and no jobs are canceled,
    • -setup times is independent of processing sequence,
    • -setup time is deterministic, -processing times are deterministic rather than variable,
    • -there will be no interruptions in processing such as machine breakdowns, accidents, or worker illness
  12. Priority rules
    simple heuristics used to select the order in which jobs will be processed
  13. First come first served (local)
    jobs are processed in the order in which they arrive at a machine or work center
  14. Shorterest processing time (local)
    jobs are processed acording to processing time at a machine or work center, shortest job first
  15. Earliest due date (local)
    jobs are processed according to due date, earliest due date first
  16. Critical ratio (global)
    jobs are processed according to smaller ratio of time remaining until due date to processing time remaining
  17. Slack per operation (global)
    jobs are processed according to average slack time. compute by dividing slack time by number of remaining operations, including the current one
  18. Rush (local or global)
    emergency or preferred customers first
  19. Local
    particularly useful for bottleneck operations but not limited to those
  20. Global
    not all jobs require the same processing or even same order of processing as a result the set of jobs are different for different workstations
  21. Job flow time
    this is the length of time a job is at a particular workstation or work center
  22. Job lateness/Job tardiness
    this is the length of time the job completion date is expected to exceed the date the job was due or promised to a customer
  23. Makespan
    total time needed to complete a group of jobs from the beginning of the first job to the completion of the last job
  24. Average number of jobs
    jobs that are in a shop are considered to be work-in-process inventory: average number of jobs = total flow time / makespan
  25. Johnson's rule
    technique for minimizing completion time for a group of jobs to be processed on two machines or at two work centers. -minimizes the makespan, -minimizes total idle time, -several conditions must be satisfied
  26. Assumptions behind johnson's rule
    -job time must be known and constant, -job time must be independent of sequence, -jobs must follow same two-step sequence, -job priorities cannot be used, -all units must be completed at the first work center before moving to second
  27. Scheduling difficulties
    • -variability in: ~setup times, ~processing times, -setup times is dependent on the sequence, -interruptions,
    • -changes in the set of jobs, -no method for identifying optimal schedule: ~scheduling is not an exact science, ~ongoing task for a manager
  28. Solutions to scheduling difficulties
    • -setting realistic due dates,
    • -focusing on bottleneck operations: first, try to increase the capacity of the operations. If that is not possible, schedule the bottleneck operation first then schedule the non-bottleneck operations around the bottleneck operations, -considering lot splitting for large jobs. this probably works best when there are relatively large differences in job times
  29. Yield management
    the application of pricing strategies to allocate capacity among various categories of demand
  30. Challenges for scheduling in service systems
    • -scheduling services different from manufacturing: ~inability to store or inventory services, ~random nature of customer requests for service,
    • -point of customer contact: ~back-office and & front-office operations,
    • -scheduling service involves: ~customers, ~workforce, ~equipment
  31. Theory of constraints
    • -the theory of constraints goal is to maximize flow through the entire system:
    • -drum-buffer-rope, process batch and transfer batch,
    • -emphasizes balancing flow, -improve performance of bottleneck: ~determine what is constraining the operation, ~exploit the constraint, ~subordinate everything to the constraint, ~determine how to overcome the constraint, ~repeat the process for the next constraint
  32. Cyclical scheduling
    • -hospitals, police/fire departments, restaurants, supermarkets,
    • -rotating schedules: ~set a scheduling horizon, ~identify the work pattern, ~develop a basic employee schedule, ~assign employees to the schedule
  33. Project
    unique, one-time operations designed to accomplish a specific set of objectives in a limited time frame
  34. Roles of project manager
    work, human resources, communications, quality, time, costs
  35. project life cycle
    definition, planning, execution, delivery
  36. Definition
    1.goals, 2.specifications, 3.feasibility, 4.tasks, 5.responsibilities, 6.teams
  37. Planning
    1.schedules, 2.budgets, 3.resources, 4.risks, 5.staffing
  38. Execution (major)
    1.status reports, 2.changes, 3.quality
  39. Delivery
    1.train customer, 2.transfer documents, 3.release resources, 4.reassign staff, 5.lessons learned
  40. Work breakdown structure
    a hierarchical listing, may include several levels, lowest level detailed tasks
  41. Work breakdown structure
    level 1: project, level 2: major elements of the project, level 3:major supporting activities for each major element, level 4: list of activities
  42. Advantages and disadvantages of the Gannt chart
    A: is its simplicity, D: fail to reveal certain relationships among activities that can be curcial to effective project management
  43. Functions of PERT/CPM
    1.a graphical display of project activities, estimate of how long the project will take, indication of which activities are the most critical to timely project completion, indication of how long any activity can be delayed without delaying the project
  44. Precedence diagram
    diagram of project activities that shows sequential relationships by use of arrows and nodes
  45. AOA convention
    network diagram convention in which arrows designate activities
  46. AON convention
    network diagram convention in which nodes designate activities
  47. Activity
    project steps that consume resources and/or time
  48. Event
    the starting and finishing of activities, designated by nodes in the AOA convention
  49. Path
    a sequence of activities that lead from the starting node to the finishing node
  50. ES
    earliest time activity can start, assuming all preceding activities start as early as possible
  51. EF
    the ealriest time the activity can finish
  52. LS
    the latest time the activity can start and not delay the project
  53. LF
    the latest time the activity can finish and not delay the project
  54. Forward path algorithm
    • -for each path, start the left side of the diagram and work toward the right sides,
    • -for each beginning activity: ES=0,
    • -for each activity: EF=ES+activity time,
    • -for the following activity: ES=EF of preceding activity
  55. Backward path algorithm
    • -for each path, start the right side of the diagram and work toward the left sides,
    • -use the largest EF as the LF for all ending activities,
    • -for each activity: LS=LF-activity time,
    • -for the preceding activity: LF=LS of following activity
  56. Critical path
    the longest path; determines expected project duration
  57. Slack
    allowable slippage for a path; the difference between the length of a path and the length of the critical path
  58. Mean of probablistic times
  59. Variance of probablistic times
    S2act = (Tp-To)s2/36
  60. Mean of a particular path
    path mean = [SUM] of expected times of activities on the path
  61. Variance of a particular path
    Opath = (square root) [SUM] (variances of activities on path)
  62. Probability that a project will be finished within certain days
    z = specified time - path mean/ path standard deviation