Operations Management
17th Edition
ISBN: 9781259142208
Author: CACHON, Gérard, Terwiesch, Christian
Publisher: Mcgraw-hill Education,
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Chapter 17, Problem 7CQ
Summary Introduction
To determine: Whether implied utilization is increased due to polling strategy in Erlang loss model is true or false?
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In general, pooling available safety capacity to serve all customers improves the performance of a service process, as inventory pooling also improved service level. However, if arrivals differ significantly in terms of processing requirements and waiting costs, it may be better to ________ and process them separately, because it will ________ variability in processing time within each class.
**segregate; increase
**segregate; reduce
**pool; reduce
**pool; increase
Reducing variability in interarrival and processing time is a key to the performance improvement in a process. Which one of the following is NOT an appropriate lever to reduce the variability?
**In manufacturing, choose more reliable supplier with consistent delivery time.
**In service operations, use reservation or appointments to reduce variability in interarrival times.
**Standardize work procedure, lower worker turnover rate to reduce the variability in processing times.
**Increase the level of customization to offer a…
A gradually growing queue of customers will form even if the (variable) arrival rate is equal to the process service rate, since matching capacity precisely to demand at all times is virtually impossible, as also recognizing that while demand can accrue to the next period(s), capacity is perishable. Assume customers are willing to wait.
Do you think the above statement is generally true, or false?
Each hour, 100 students want to ride a bus from the student union to Fraternity Row. The admiration places a value of $5/student/hour on each hour that a student is forced to wait for a bus. It costs university $ 10 per bus to send a bus from the student union to Fraternity Row. Assuming that demand occurs at a constant rate, how many buses should be sent each hour from the student union to Fraternity Row?
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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, operations-management and related others by exploring similar questions and additional content below.Similar questions
- Podunk University Operations Research Departmenthas two phone lines. An average of 30 people per hour tryto call the OR Department, and the average length of aphone call is 1 minute. If a person attempts to call whenboth lines are busy, he or she hangs up and is lost to thesystem. Assume that the time between people attempting tocall and service times is exponential.a What fraction of the time will both lines be free?What fraction of the time will both lines be busy? Whatfraction of the time will exactly one line be free?b On the average, how many lines will be busy?c On the average, how many callers will hang up eachhour?arrow_forwardSuppose that documents are transmitted by a facsimile machine. Assume that the documents arrive at random, 75% of which is of the fixed form with constant transmission (service) time 40 seconds, whereas the rest are exponentially distributed with the mean 2 minutes. 1. How many documents per hour can be transmitted with mean waiting time no greater than 30 seconds? 2. If the number of documents per hour is the same as (1), and if all documents are of the fixed form, how much is the mean waiting time? Please answer both 1 and 2 with a complete step and formula used.arrow_forwardThis is the time that it takes a unit to travel through theprocess from beginning to end. It includes time waitingin queues and buffers.arrow_forward
- Which of the following best reflects pooling capacity to reduce restroom queue lengths?a. Add more toilets to increase capacity.b. Install a flexible partition that can alter the size of the women’s and the men’srestrooms.c. Convert the separate men’s and women’s rooms into a single unisex restroom (thatboth men and women can use).d. Remove mirrors in the restroom to decrease the time users spend in the restroom.e. Add automatic flush capability to each toilet to decrease processing times.arrow_forwardA graphics reproduction i rm has four units of equipment that are automatic but occasionallybecome inoperative because of the need for supplies, maintenance, or repair. Eachunit requires service roughly twice each hour, or, more precisely, each unit of equipmentruns an average of 30 minutes before needing service. Service times vary widely, rangingfrom a simple service (such as pressing a restart switch or repositioning paper) to moreinvolved equipment disassembly. The average service time, however, is i ve minutes.Equipment downtime results in a loss of $20 per hour. The one equipment attendant ispaid $6 per hour.Using i nite queuing analysis, answer the following questions:a. What is the average number of units in line?b. What is the average number of units still in operation?c. What is the average number of units being serviced?d. The i rm is considering adding another attendant at the same $6 rate. Should the i rmdo it?arrow_forwardIn a large microelectronics plant, the assembly cell for circuit boards has a demand for 250 units an hour. Two feeder cells supply parts A and B to the assembly cell (one A and one B for each board). Standard containers that look like divided trays are used. A container will hold 24 As or 10 Bs. It takes 10 minutes to fill up a container with As and 24 minutes to fill up a container with Bs. Transit time to the assembly cell is 5 minutes for both A and B. No safety factor is used. Set up a kanban control system for the assembly process.arrow_forward
- A server operates with 70% utilization. The coefficient of variation for the service process is 0.6 and the coefficient of variation of the arrival process is 1. The average processing time is 3 minutes. What is the average time a customer spends in the system according to the single-server queue model? A. 9 minutes B. 6 minutes C. 3 minutes D. 7.5 minutes Consider an Erlang loss system. The average processing time is 6 minutes. The average interarrival time is 3 minutes. The number of servers is 9. What is the capacity of the system? A. 0.8 customers per minute B. 1.5 customers per minute C. 1.1 customers per minute D. 2.4 customers per minutearrow_forwardBased on the concepts of Production Modeling and Simulation, do the following:a) Given a model of a simple queue, describe, in a simplified way, what is a source of customers.arrow_forwardConsider two separate systems. One has an interarrival time of two hours andthe other an interarrival time of four hours. If the two systems are combined such that thecombined system’s demand is the sum of the demands from the two original systems,what is the interarrival time for the combined system?arrow_forward
- A copier store has four pieces of automatic equipment, but sometimes they are down because they need supplies, maintenance or repair. Each unit requires about two services every hour or, to be exact, each piece of equipment runs an average of 30 minutes before needing service. Service times vary greatly, from a simple service (such as pressing the reset switch or replenishing the paper) to disassembling the equipment in question. However, the average service time is five minutes. The time the equipment is down generates a loss of $60 per hour. The single employee who services the equipment earns $18 per hour. Using finite population analysis, answer the following questions: a. What is the average number of units idling? b. What is the average number of units still operating? c. What is the average number of units being serviced? d. The company is considering adding another manager at the same wage of $18 per hour. should it do so?arrow_forward(Requires the use of a spreadsheet or LINGO) USAirlines receives an average of 500 calls per hour fromcustomers who want to make a reservation (time betweencalls follows an exponential distribution). It takes an averageof 3 minutes to handle each call. Each customer who buys a ticket contributes $100 to US Airlines profit. It costs $15per hour to staff a telephone line. Any customer who receivesa busy signal will purchase a ticket on another airline. Howmany telephone lines should US Airlines have?arrow_forwardTrue or False? The average number of customers in queue plus the number of servers equals the average number of customers in the system. The main cause of delay at Logan Airport was overbooking, and building a new runway solved the delay problem. If a company hopes to increase the capacity of a process, the company needs to try to shorten the process’s cycle time. Little’s Law only applies to an M/M/1 queue, which is a special case of a G/G/C queue. If a queuing system has deterministic arrival rate λ and service rate μ, and λ < μ, then Lq = 0 in this queue.arrow_forward
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