Canvas assignments (2021/22 Academic Year)
7ENT1127-0105 Operations Research and Logistics
Assignment Title: CW2: Simulation Modelling
| Submission deadline | 27-04-2022 23:59 | |||||
| Weighting %: | 60 | hours London UK | ||||
| (for students): | ||||||
| Time. | ||||||
| Authorship: | Individual | Target date for | 18-05-2022 23:59 | |||
| returning marked | hours London UK | |||||
| coursework: | Time. | |||||
| Tutor setting the | Number of hours you | |||||
| are expected to work | 40 | |||||
| work: | ||||||
| on this assignment: | ||||||
This Assignment assesses the following module Learning Outcomes (from Definitive Module Document):
- Evaluate quantitative modelling concepts for problem solving and decision making in a logistics context.
- Critique the logical process of modelling complex decision problems.
- Derive solution(s) using a suitable software package when required.
- Apply techniques and practice to model real world logistics problems.
- Critically analyse and report results individually and/or in a group.
Assignment Tasks:
Manufacturing simulation uses computers to make virtual models of manufacturing processes and systems, typically with the purpose of collecting important information for use in decision making. Operations researchers and managers uses a variety of simulation software in their practice, one of which is the Witness Simulation software.
In this assignment you are required to produce a report that addresses the following tasks.
- Explain the difference between a good decision and a bad decision. Briefly discuss how confirmation bias can affect the quality of decisions.
- With reference to Case Study A on Pages 4 and 5 below, you are required to use Witness Simulation software to evaluate decisions relating to due date specification in a job shop. You are required to use a trial-and-error method to determine good due date specification for the jobs arriving the case study’s job shop. Use delivery performance in terms of total late/early completion penalty costs to evaluate your due date specification. Start the simulation with an empty shop and run the simulation until 15,000 minutes. Data on the first 5,000 minutes should be discarded to allow for warm-up period and attainment of steady-state conditions. Clearly state any assumptions used in the simulation.
- Critically discuss the results of the simulation carried out in Question 2 above and the performance of the specified due date.
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Presentation
You must present your work as follows.
Your submission for this assignment must be a written report. The report must contain no more than 2500±10% words including any diagrams, calculations, figures and/or tables where appropriate. Reports shorter than the word count will not lose marks but will lead to the omission of material which can gain them. Any words over the suggested word count will not be marked. Do not use any mechanism, such as embedded jpeg images containing significant text, to circumvent the word count.
You are expected to provide a range of secondary sources to underpin your work. These must be cited and referenced according to the Harvard Referencing System. Include the word count in the header of your report.
Ensure that your report is well-structured and choose appropriate number and titles for the sections of the report please. There is no need to number the references section.
Your report must follow the guidance above and must include the specific instructions outlined below.
- Word-process the report on A4 paper.
- Use 1.15 line spacing.
- Font type must be Arial (font size11).
- Number all pages.
- Ensure that all diagrams / tables are labelled and numbered.
- Grammar, spelling and style, as well as clarity, contribute towards the assessment of the report.
- Use British Spelling i.e., ‘English (UK) Language’.
- Justify paragraphs – Align text to both left and right margins, using your word processor to add extra space between words as necessary.
You are expected to provide a significant range of secondary sources to underpin your work.
These should be cited and referenced according to the Harvard Referencing System.
Additional Note on Referencing
Mark is allocated for referencing in this assignment, and the mark is influenced by the thoroughness and integrity of the work as evidenced by your referencing. Marks are awarded not only for correct referencing practice, but also the extent to which the arguments have been supported by cited sources. As highlighted above, related work should be cited and referenced according to the Harvard Referencing System.
Submission Requirements:
The report must be submitted as a PDF file via the Assignment CW2 submission page on the module site. The report is intended to be marked anonymously. Hence, do not include any personal identifier in your submission.
Marks awarded for:
This assignment is worth 60% of the overall assessment for this module.
Marks out of 100% awarded for:
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| Main Tasks/Allocations | Marks | |||||||
| Available | ||||||||
| % | ||||||||
| Knowledge and understanding of the subject particularly in the context of the | 10 | |||||||
| topic covered in the assignment. | ||||||||
| 1. | Explanation of a Concept: | 10 | ||||||
| Explain the difference between a good decision and a bad decision. Briefly | ||||||||
| discuss how confirmation bias can affect the quality of decisions. | ||||||||
| 2. | Simulation Modelling | 45 | ||||||
| With reference to Case Study A on Pages 4 and 5 below, you are required | ||||||||
| to use Witness Simulation software to evaluate decisions relating to due date | ||||||||
| specification in a job shop. You are required to use a trial-and-error method | ||||||||
| to determine good due date specification for the jobs arriving the case study’s | ||||||||
| job shop. Use delivery performance in terms of total late/early completion | ||||||||
| penalty costs to evaluate your due date specification. Start the simulation with | ||||||||
| an empty shop and run the simulation until 15,000 minutes. Data on the first | ||||||||
| 5,000 minutes should be discarded to allow for warm-up period and | ||||||||
| attainment of steady-state conditions. Clearly state any assumptions used in | ||||||||
| the simulation. | ||||||||
| 25 | ||||||||
| (a) | Simulation Model Development. | |||||||
| 20 | ||||||||
| (b) | Results and Analysis | |||||||
| 3. | Critical Discussion: | 15 | ||||||
| Critically discuss the results of the simulation carried out in Question 2 above | ||||||||
| and the performance of the specified due date. | ||||||||
Overall presentation, report title and structure, effective communication, keeps to word limit.
Intellectual curiosity (Quality of academic sources);Use and presentation of Harvard Referencing.
10
10
Total
100
Type of Feedback to be given for this assignment:
The presentation will have a percentage mark and generic feedback.
Additional information:
- Regulations governing assessment offences including Plagiarism and Collusion are available from https://www.herts.ac.uk/__data/assets/pdf_file/0007/237625/AS14-Apx3-Academic-Misconduct.pdf (UPR AS14).
- Guidance on avoiding plagiarism can be found here: https://herts.instructure.com/courses/61421/pages/referencing-avoiding-plagiarism?module_item_id=779436
- For undergraduate modules:
- a score of 40% or above represents a pass performance at honours level.
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- late submission of any item of coursework for each day or part thereof (or for hard copy submission only, working day or part thereof) for up to five days after the published deadline, coursework relating to modules at Levels 0, 4, 5, 6 submitted late (including deferred coursework, but with the exception of referred coursework), will have the numeric grade reduced by 10 grade points until or unless the numeric grade reaches or is 40. Where the numeric grade awarded for the assessment is less than 40, no lateness penalty will be applied.
- For postgraduate modules:
- a score of 50% or above represents a pass mark.
- late submission of any item of coursework for each day or part thereof (or for hard copy submission only, working day or part thereof) for up to five days after the published deadline, coursework relating to modules at Level 7 submitted late (including deferred coursework, but with the exception of referred coursework), will have the numeric grade reduced by 10 grade points until or unless the numeric grade reaches or is 50. Where the numeric grade awarded for the assessment is less than 50, no lateness penalty will be applied.
Case Study A
Consider a job shop scenario that consists of five machines and has capacity to process two job categories, CAT-1 and CAT-2. The first machine in the job shop is dedicated to pre-processing CAT-1 jobs only, whilst the second machine pre-processes CAT-2 jobs only. Machines 3 and 4 are dedicated to a variety of operations on both CAT-1 and CAT-2 jobs. Machine 5 is a quality assurance, inspection, machine. Jobs failing inspection are returned to Machine 4 for rework. A job fails inspection with probability of 0.25.
Jobs arrive the shop into buffers and are selected from the buffers on first-come first-served (FCFS) basis for processing on machines. Additional buffers may be used in the job shop as necessary and jobs arriving buffers are positioned at the end of the buffer queue. Table 1 below contains the characteristics of the job categories.
Table 1: Characteristics of Job Categories.
| Category | Job Inter-Arrival Time | Machine Visitation | Due Date from the start | |||||||||||
| Order | of processing | on first | ||||||||||||
| Machine. | ||||||||||||||
| CAT-1 | Negative | exponential | 1,3,4,5, (4 OR SHIP) | Time | job | starts | ||||||||
| distribution with rate parameter | processing on Machine 1 | |||||||||||||
| set to 80 minutes. | + X minutes. | |||||||||||||
| CAT-2 | Negative | exponential | 2,3,4,5, (4 OR SHIP) | Time | job | starts | ||||||||
| distribution with rate parameter | processing on Machine 2 | |||||||||||||
| set to 100 minutes. | + Y minutes. | |||||||||||||
The operation times follow uniform distribution, between 3 and 5 minutes on Machine 1, between 4 and 8 minutes on Machine 2, between 9 and 12 minutes on Machine 3, between 11 and 20 minutes on Machine 4, and between 2 and 6 minutes on Machine 5. The following common assumptions should be adopted in the study. Each machine has a constant capacity throughout, and the machines are always available. Set-up times are included in the operation processing times. Each of the machines can process only one job at a time. A job runs through all its operations sequence.
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Jobs failing inspection will need to be re-inspected on Machine 5 following rework on Machine 4. Variables X and Y must be determined to specify due date for the jobs. The job shop pays penalties shown in Table 2 for late/early job completion.
Table 2: Penalties for Late / Early Job Completion.
| Job Category | Penalty per late job completion | Penalty per early job completion | ||||||
| (Pence per minute) | (Pence per minute) | |||||||
| CAT-1 | 50 | 40 | ||||||
| CAT-2 | 80 | 30 | ||||||
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