scholarly journals Measuring the Cost for Some Single Channel Waiting Line Models

2018 ◽  
pp. 1-10
Author(s):  
Doaa A. Ali ◽  
Elham A. Ismail ◽  
Lobna E. AL-Tayeb
Keyword(s):  
Single Channel ◽  
Waiting Times ◽  
Arrival Rate ◽  
Service Rate ◽  
Rate Distribution ◽  
Study Results ◽  
Queue Lengths ◽  
The Cost ◽  
Waiting Line ◽  
The Ideal

Queuing models applications are centered on the question of finding the ideal level of services, waiting times and queue lengths. The aim of this study is to measure the cost for three models and compare the cost for the three single channel waiting line models instead of finding the ideal level of services, waiting times and queue lengths which calculated in many studies.  Each model depends on two important parameters arrival rate (λ) and service rate (μ) which followed different distributions.  The cost for the three single channel waiting line models is calculated when arrival rate (λ) is followed Poisson distribution and service rate (μ) is followed different distributions. The objective for the waiting line models is to minimize total expected costs by minimize the sum of service costs and waiting costs. Therefore, the study concerned with changing the distribution of the service rate (μ) and examining its impact on cost. This choice was made to emphasize the basic idea of the study (there is a relationship between the service rate distribution and the cost). The study results showed that there is a relationship between the service rate   distribution and the cost.  

Queues with time-dependent arrival rates. III — A mild rush hour

1968 ◽  
Vol 5 (3) ◽  
pp. 591-606 ◽  
Author(s):  
G. F. Newell
Keyword(s):  
Queueing Theory ◽  
Queue Length ◽  
Arrival Rate ◽  
Time Dependent ◽  
Service Rate ◽  
Diffusion Approximations ◽  
Dimensionless Form ◽  
Queue Lengths ◽  
The Mean ◽  
Mean Queue Length

The arrival rate of customers to a service facility is assumed to have the form λ(t) = λ(0) — βt2 for some constant β. Diffusion approximations show that for λ(0) sufficiently close to the service rate μ, the mean queue length at time 0 is proportional to β–1/5. A dimensionless form of the diffusion equation is evaluated numerically from which queue lengths can be evaluated as a function of time for all λ(0) and β. Particular attention is given to those situations in which neither deterministic queueing theory nor equilibrium stochastic queueing theory apply.

A generalization of little's law to moments of queue lengths and waiting times in closed, product-form queueing networks

1989 ◽  
Vol 26 (01) ◽  
pp. 121-133 ◽  
Author(s):  
James McKenna
Keyword(s):  
Sojourn Time ◽  
Queueing Networks ◽  
Waiting Times ◽  
Arrival Rate ◽  
Product Form ◽  
Single Server ◽  
Queue Lengths ◽  
The Mean ◽  
Expected Sojourn Time ◽  
Product Form Queueing Networks

Little's theorem states that under very general conditions L = λW, where L is the time average number in the system, W is the expected sojourn time in the system, and λ is the mean arrival rate to the system. For certain systems it is known that relations of the form E((L) l ) = λ lE((W) l ) are also true, where (L) l = L(L – 1)· ·· (L – l + 1). It is shown in this paper that closely analogous relations hold in closed, product-form queueing networks. Similar expressions relate Nji and Sji, where Nji is the total number of class j jobs at center i and Sji is the total sojourn time of a class j job at center i, when center i is a single-server, FCFS center. When center i is a c-server, FCFS center, Qji and Wji are related this way, where Qji is the number of class j jobs queued, but not in service at center i and Wji is the waiting time in queue of a class j job at center i. More remarkably, generalizations of these results to joint moments of queue lengths and sojourn times along overtake-free paths are shown to hold.

Queues with time-dependent arrival rates. III — A mild rush hour

1968 ◽  
Vol 5 (03) ◽  
pp. 591-606 ◽  
Author(s):  
G. F. Newell
Keyword(s):  
Queueing Theory ◽  
Queue Length ◽  
Arrival Rate ◽  
Time Dependent ◽  
Service Rate ◽  
Diffusion Approximations ◽  
Dimensionless Form ◽  
Queue Lengths ◽  
The Mean ◽  
Mean Queue Length

The arrival rate of customers to a service facility is assumed to have the formλ(t) =λ(0) —βt2for some constantβ.Diffusion approximations show that forλ(0) sufficiently close to the service rateμ, the mean queue length at time 0 is proportional toβ–1/5. A dimensionless form of the diffusion equation is evaluated numerically from which queue lengths can be evaluated as a function of time for allλ(0) andβ.Particular attention is given to those situations in which neither deterministic queueing theory nor equilibrium stochastic queueing theory apply.

scholarly journals Straight to colonoscopy: the ideal patient pathway for the 2-week suspected cancer referrals?

2011 ◽  
Vol 93 (2) ◽  
pp. 114-119 ◽  
Author(s):  
Andrew D Beggs ◽  
Ravinda D Bhate ◽  
Shashi Irukulla ◽  
Mayen Achiek ◽  
A Muti Abulafi
Keyword(s):  
Demographic Data ◽  
Waiting Times ◽  
Cost Savings ◽  
Cost Effective ◽  
Patient Pathway ◽  
Retrospective Audit ◽  
Cost Effective Method ◽  
The Uk ◽  
The Cost ◽  
The Ideal

INTRODUCTION The UK has a higher mortality for colon cancer than the European average. The UK Government introduced a 2-week referral target for patients with colorectal symptoms meeting certain criteria and 62-day target for the delivery of treatment from the date of referral for those patients diagnosed with cancer. Hospitals are expected to meet 100% and 95% of these targets, respectively; therefore, an efficient and effective patient pathway is required to deliver diagnosis and treatment within this period. It is suggested that ‘straight-to-test’ will help this process and we have examined our implementation of ‘straight-to-colonoscopy’ as a method of achieving this aim. PATIENTS AND METHODS We carried out a retrospective audit of 317 patients referred under the 2-week rule over a 1-year period between October 2004 and September 2005 and were eligible for ‘straight-to-colonoscopy'. Demographic data, appropriateness of referral and colonoscopy findings were obtained. The cost effectiveness and impact on waiting period were also analysed. RESULTS A total of 317 patients were seen within 2 weeks. Cancer was found in 23 patients and all were treated within 62 days. Forty-four patients were determined by the specialist to have been referred inappropriately because they did not meet NICE referral guidelines. No cancer was found in any of the inappropriate referrals. The use of straight-to-test colonoscopy lead to cost savings of £26,176 (£82.57/patient) in this group compared to standard practice. There was no increase in waiting times. CONCLUSIONS Straight-to-colonoscopy for urgent suspected cancer referrals is a safe, feasible and cost-effective method for delivery of the 62-day target and did not lead to increase in the endoscopy waiting list.

A generalization of little's law to moments of queue lengths and waiting times in closed, product-form queueing networks

1989 ◽  
Vol 26 (1) ◽  
pp. 121-133 ◽  
Author(s):  
James McKenna
Keyword(s):  
Sojourn Time ◽  
Queueing Networks ◽  
Waiting Times ◽  
Arrival Rate ◽  
Product Form ◽  
Single Server ◽  
Queue Lengths ◽  
The Mean ◽  
Expected Sojourn Time ◽  
Product Form Queueing Networks

Little's theorem states that under very general conditions L = λW, where L is the time average number in the system, W is the expected sojourn time in the system, and λ is the mean arrival rate to the system. For certain systems it is known that relations of the form E((L)l) = λ lE((W)l) are also true, where (L)l = L(L – 1)· ·· (L – l + 1). It is shown in this paper that closely analogous relations hold in closed, product-form queueing networks. Similar expressions relate Nji and Sji, where Nji is the total number of class j jobs at center i and Sji is the total sojourn time of a class j job at center i, when center i is a single-server, FCFS center. When center i is a c-server, FCFS center, Qji and Wji are related this way, where Qji is the number of class j jobs queued, but not in service at center i and Wji is the waiting time in queue of a class j job at center i. More remarkably, generalizations of these results to joint moments of queue lengths and sojourn times along overtake-free paths are shown to hold.

scholarly journals Analysis of Non-Idealities on CMOS Passive Mixers

Electronics ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 1105
Author(s):  
Antonio D. Martinez-Perez ◽  
Francisco Aznar ◽  
Guillermo Royo ◽  
Santiago Celma
Keyword(s):  
Final Section ◽  
Cmos Technology ◽  
Monte Carlo Analysis ◽  
Image Rejection ◽  
Structure Approach ◽  
Quadrature Scheme ◽  
Current State ◽  
The Cost ◽  
Image Rejection Ratio ◽  
The Ideal

In the current state of the art, WiFi-alike standards require achieving a high Image Rejection Ratio (IRR) while having low power consumption. Thus, quadrature structures based on passive ring mixers offer an attractive and widely used solution, as they can achieve a high IRR while being a passive block. However, it is not easy for the designer to know when a simple quadrature scheme is enough and when they should aim for a double quadrature structure approach, as the latter can improve the performance at the cost of requiring more area and complexity. This study focuses on the IRR, which crucially depends on the symmetry between the I and Q branches. Non-idealities (component mismatches, parasitics, etc.) will degrade the ideal balance by affecting the mixer and/or following/previous stages. This paper analyses the effect of imbalances, providing the constraints for obtaining a 40 dB IRR in the case of a conversion from a one-hundred-megahertz signal to the five-gigahertz range (upconversion) and vice versa (downconversion) for simple and double quadrature schemes. All simulations were carried out with complete device models from 65 nm standard CMOS technology and also a post-layout Monte Carlo analysis was included for mismatch analysis. The final section includes guidelines to help designers choose the most adequate scheme for each case.

High-Efficiency Cut Blasting with Shell Radial Shaped Charge in Laboratory-Scale Blasting

2015 ◽  
Vol 1094 ◽  
pp. 445-450 ◽  
Author(s):  
Wei Chen ◽  
Hong Hao Ma ◽  
Zhao Wu Shen ◽  
De Bao Wang
Keyword(s):  
High Efficiency ◽  
Circular Tube ◽  
Rock Breaking ◽  
Shaped Charge ◽  
Axial Line ◽  
Rock Excavation ◽  
Crack Network ◽  
Utilization Ratio ◽  
The Cost ◽  
The Ideal

Due to the inefficiency problem of the cut blasting in rock excavation and rock breaking, a shell radial shaped charge device was proposed based of the ideal of ‘cutting to slotting’ and it was validated through experiments. For this device, the shell materials are used to be shaped materials and multiple shaped ring is designed on the circular tube. It can not only reduce charge quantity but also raise the utilization ratio of explosive energy. After explosion, multiple radial shaped charge jets can be formed along the axial line in sequence and then the surrounding rock mass would be cracked. The crack network will be formed along with the further extension of the fraction under the action of quasi static loading of detonation gas. The shell radial shaped charge device was tested through the cut blasting model experiment. Experimental results show that the utilization ratio of blasting hole nearly approaches 98% with this device. The blasting efficiency and cyclical footage can be improved effectively and the cost of drifting can also be reduced.

Agile framework for capital projects

2021 ◽  
Vol 61 (2) ◽  
pp. 422
Author(s):  
Polly Mahapatra ◽  
Paris Shahriari
Keyword(s):  
Oil And Gas ◽  
Hybrid Approach ◽  
Oil And Gas Industry ◽  
Quick Response ◽  
Capital Projects ◽  
Gas Industry ◽  
Response To Change ◽  
The Cost ◽  
Early Phases ◽  
The Ideal

Under the increased pressure of rapidly changing market conditions and disrupting technologies, continuous improvements in efficiency become indispensable for all oil and gas operators. Traditional project management principles in the oil and gas industry employ rigid methods of planning and execution that can sometimes hinder adaptability and a quick response to change. Considering the potential that Agile principles can offer as a solution, the challenge, therefore, is to identify the ideal, hybrid, approach that leverages Agile while incorporating the traditional linear workflow necessitated by the oil and gas industry. This paper seeks to assess pre-existing literature in the application of the Agile principles in the oil and gas industry with a focus on Major Capital Projects (MCPs), backed by the successes experienced as a result of specific pilot projects completed at Chevron’s Australian Business Unit. In particular, this paper will focus on how agility has resulted in improvements to the cost, schedule, teaming and cohesion of MCPs in the early phases as well as key learnings form the pilot agility projects.

Parents' Time Is Worth Money

PEDIATRICS ◽  
1983 ◽  
Vol 71 (3) ◽  
pp. 466-466
Author(s):  
DOUGLAS RICHARDSON
Keyword(s):  
Intensive Care ◽  
Cost Effectiveness ◽  
Economic Analysis ◽  
Bronchopulmonary Dysplasia ◽  
Neonatal Intensive Care ◽  
Waiting Times ◽  
Opportunity Costs ◽  
Home Management ◽  
Tacit Assumption ◽  
The Cost

To the Editor.— I was delighted to see Donn's letter about the cost effectiveness of home management of bronchopulmonary dysplasia.1 Such contributions are vital in helping to curb the rapidly rising costs of neonatal intensive care. However, his economic analysis is flawed. By tacit assumption, he omits any consideration of the opportunity costs to the parents. To omit this presumes that the parents' time is worth little or nothing, as we often seem to indicate by the long patient waiting times in our offices.

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