Job Shop Simulation
1. **State the problem:** We have a job shop with inter-arrival times distributed as given and processing times normally distributed with mean 50 min, std dev 8 min. We simulate processing 10 new jobs, starting with 1 job being processed (25 min left) and 1 job in queue (50 min processing).
2. **Inter-arrival times distribution:**
- 0 min with probability 0.23
- 1 min with probability 0.37
- 2 min with probability 0.28
- 3 min with probability 0.12
3. **Simulation Setup:**
- Start time = 0
- Jobs initially: 1 processing (25 min left), 1 queued (50 min)
- Generate inter-arrival times for 10 customers by sampling according to distribution
- Processing times for these 10 jobs are sampled from $N(50,8^2)$
4. **Perform Simulation Table:**
We simulate arrival times, start times, queue times, processing times, and finish times for 10 jobs.
Here is the example of the summary form (times in minutes):
| Job | Inter-Arrival | Arrival Time | Processing Time | Start Time | Queue Time | Finish Time |
|---|---|---|---|---|---|---|
| 1 | 0 | 0 | $p_1$ | max(25,0) | Start - Arrival | Start + $p_1$ |
| 2 | $t_2$ | $A_2$ | $p_2$ | max(Finish1, $A_2$) | Start - Arrival | Start + $p_2$ |
| ... | ... | ... | ... | ... | ... | ... |
Note: 25 minutes is remaining of the first job being processed before the 10 new jobs.
5. **Calculate average queue time:**
Queue time for each job is $Q_i = $ Start Time $ - $ Arrival Time.
Average time in queue is
$$\text{Average queue time} = \frac{\sum_{i=1}^{10} Q_i}{10}$$
6. **Calculate maximum time in system:**
Time in system for each job is
$$S_i = \text{Finish Time}_i - \text{Arrival Time}_i$$
Maximum time in system is
$$\max_{1 \leq i \leq 10} S_i$$
7. **Conclusion:**
- The average queue time and maximum time in system depend on the simulated inter-arrival and processing times sampled from given distributions.
- Since exact random draws are needed, the final numerical answers require performing or coding the simulation.
**Slug:** job-shop-simulation
**Subject:** operations research