scholarly journals Customer-Server Population Dynamics in Heavy Traffic

2021 ◽  
Author(s):  
Rami Atar ◽  
Prasenjit Karmakar ◽  
David Lipshutz
Keyword(s):  
Population Dynamics ◽  
Steady State ◽  
Closed Form ◽  
Population Size ◽  
Time Scales ◽  
Performance Measures ◽  
Heavy Traffic ◽  
The Other ◽  
Queueing Model ◽  
Server Vacations

We study a many-server queueing model with server vacations, where the population size dynamics of servers and customers are coupled: a server may leave for vacation only when no customers await, and the capacity available to customers is directly affected by the number of servers on vacation. We focus on scaling regimes in which server dynamics and queue dynamics fluctuate at matching time scales so that their limiting dynamics are coupled. Specifically, we argue that interesting coupled dynamics occur in (a) the Halfin–Whitt regime, (b) the nondegenerate slowdown regime, and (c) the intermediate near Halfin–Whitt regime, whereas the dynamics asymptotically decouple in the other heavy-traffic regimes. We characterize the limiting dynamics, which are different for each scaling regime. We consider relevant respective performance measures for regimes (a) and (b)—namely, the probability of wait and the slowdown. Although closed-form formulas for these performance measures have been derived for models that do not accommodate server vacations, it is difficult to obtain closed-form formulas for these performance measures in the setting with server vacations. Instead, we propose formulas that approximate these performance measures and depend on the steady-state mean number of available servers and previously derived formulas for models without server vacations. We test the accuracy of these formulas numerically.

scholarly journals Analysis of M/M/1 Queuing System with Customer Reneging During Server Vacations Subject To Server Breakdown and Delayed Repair

2018 ◽  
Vol 7 (4.10) ◽  
pp. 552
Author(s):  
Ch. Swathi ◽  
V. Vasanta Kumar
Keyword(s):  
Steady State ◽  
Closed Form ◽  
Detailed Analysis ◽  
Performance Measures ◽  
Queuing System ◽  
Multiple Vacation ◽  
Delayed Repair ◽  
Server Breakdown ◽  
Number Of Customers ◽  
Steady State Probabilities

In this paper, we consider an M/M/1 queuing system with customer reneging for an unreliable sever. Customer reneging is assumed to occur due to the absence of the server during vacations.  Detailed analysis for both single and multiple vacation models during different states of the server such as busy, breakdown and delayed repair periods is presented. Steady state probabilities for single and multiple vacation policies are obtained. Closed form expressions for various performance measures such as average number of customers in the system, proportion of customers served and reneged per unit time during single and multiple vacations are obtained.   

Polling systems with periodic server routeing in heavy traffic: distribution of the delay

2003 ◽  
Vol 40 (02) ◽  
pp. 305-326 ◽  
Author(s):  
Tava Lennon Olsen ◽  
R. D. van der Mei
Keyword(s):  
Steady State ◽  
Closed Form ◽  
Heavy Traffic ◽  
Linear Equations ◽  
Asymptotic Properties ◽  
Polling Systems ◽  
Parameter Setting ◽  
State Delay ◽  
Traffic Distribution ◽  
General Parameter

We consider polling systems with mixtures of exhaustive and gated service in which the server visits the queues periodically according to a general polling table. We derive exact expressions for the steady-state delay incurred at each of the queues under standard heavy-traffic scalings. The expressions require the solution of a set of only M—N linear equations, where M is the length of the polling table and N is the number of queues, but are otherwise explicit. The equations can even be expressed in closed form for several routeing schemes commonly used in practice, such as the star and elevator visit order, in a general parameter setting. The results reveal a number of asymptotic properties of the behavior of polling systems. In addition, the results lead to simple and fast approximations for the distributions and the moments of the delay in stable polling systems with periodic server routeing. Numerical results demonstrate that the approximations are highly accurate for medium and heavily loaded systems.

Polling systems with periodic server routeing in heavy traffic: distribution of the delay

2003 ◽  
Vol 40 (2) ◽  
pp. 305-326 ◽  
Author(s):  
Tava Lennon Olsen ◽  
R. D. van der Mei
Keyword(s):  
Steady State ◽  
Closed Form ◽  
Heavy Traffic ◽  
Linear Equations ◽  
Asymptotic Properties ◽  
Polling Systems ◽  
Parameter Setting ◽  
State Delay ◽  
Traffic Distribution ◽  
General Parameter

We consider polling systems with mixtures of exhaustive and gated service in which the server visits the queues periodically according to a general polling table. We derive exact expressions for the steady-state delay incurred at each of the queues under standard heavy-traffic scalings. The expressions require the solution of a set of onlyM—Nlinear equations, whereMis the length of the polling table andNis the number of queues, but are otherwise explicit. The equations can even be expressed in closed form for several routeing schemes commonly used in practice, such as the star and elevator visit order, in a general parameter setting. The results reveal a number of asymptotic properties of the behavior of polling systems. In addition, the results lead to simple and fast approximations for the distributions and the moments of the delay in stable polling systems with periodic server routeing. Numerical results demonstrate that the approximations are highly accurate for medium and heavily loaded systems.

scholarly journals A Non-Markovian Multistage Batch Arrival Queue with Breakdown and Reneging

2014 ◽  
Vol 2014 ◽  
pp. 1-16 ◽  
Author(s):  
Sivagnanasundararam Maragathasundari ◽  
Santhanagopalan Srinivasan
Keyword(s):  
Steady State ◽  
Performance Measures ◽  
Large Scale ◽  
Graphical Representation ◽  
Computational Aspect ◽  
Queueing Model ◽  
Supplementary Variable ◽  
Industry Applications ◽  
System Breakdown ◽  
System Length

The present investigation deals with analysis of non-Markovian queueing model with multistage of services. When the server is unavailable during the system breakdown (or) vacation periods, we consider reneging to prevail. Supplementary variable techniques have been adopted to obtain steady state system length distributions. The numerical illustrations are provided to validate the tractability of performance measures as far as computational aspect is concerned. Numerical results in the form of graphical representation are also presented. Practical large scale industry applications are described to justify our model.

scholarly journals Population dynamics and performance of exotic versus indigenous chicken population in the selected districts of North Western Amhara, Ethiopia

2017 ◽  
Vol 1 (2) ◽  
pp. 90-99
Author(s):  
TILAHUN SISAY ◽  
KEFEYALEW ALEMAYEHU ◽  
ZEWDU WULETAW
Keyword(s):  
Population Dynamics ◽  
Population Size ◽  
Production System ◽  
Egg Production ◽  
The Other ◽  
Indigenous Chicken ◽  
Other Hand ◽  
Chicken Population ◽  
And Performance ◽  
North Western

Sisay T, Alemayehu K, Wuletaw Z. 2017. Population dynamics and performance of exotic versus indigenous chicken population in the selected districts of North Western Amhara, Ethiopia. Trop Drylands 1: 90-99. Chicken in Ethiopia contributes, respectively, 98.5% and 99.2% of the national egg and chicken meat production. The total chicken population is estimated to be 56.87 million of which 95.86, 2.79 and 1.35% are indigenous, crossbred and exotic breeds, respectively. The objective of this paper was to quantify the population dynamics and performance of exotic versus indigenous chicken population in the selected districts of northwestern Amhara, Ethiopia. Banja and Burie districts and six Kebeles (three/district) were purposively selected. A total 180 respondents were selected by systematic and simple random sampling techniques for the survey. On the other hand, a total of 90 exotic chicken owners were purposively selected for monitoring and evaluation. GLM procedure of SAS (2002) was used to quantify the fixed effects of agroecology and breeds on the egg production performance. The results revealed that the majorities (91.12%) of distributed exotic chickens were kept in traditional/backyard production system. The overall mean egg production for exotic chickens (141.58±11.5) was too low. Significantly, the mean number of clutch per year per hen of Bovans Brown chicken was higher (4.51±0.11 days) than Bovans white breeds (3.5±0.10 days). Shortage at first egg was attained from midland of Koekoek chicken breed (5.38±0.24 months) than from highland (6.54±0.10 months) in Bovans Brown chicken. A highly significant difference in mortality was observed between Bovans Brown (89%) and Koekoek breed (32.4%), respectively due to traditional farmers' management practice. Distribution of different exotic chicken genotypes in the region is increasing from time to time for the upgrading of local chicken ecotypes but, the survival, productivity and population size of exotic and their crosses were too low. On the other hand, the population size of the indigenous chicken and its productivity remains almost constant. Causes of chick mortality in the study area were disease and predator which need to be considered in the development plan of the districts. This is due to the inappropriate production system, genotype, and management. Therefore, production and productivity will be increased through the selection of indigenous chicken ecotypes and crossbreed or upgrading by introduction exotic cocks, pullets and or fertile eggs of high egg producing strains with an appropriate production system and management in respective production system.

Fidelity of J1269 and J24523

2007 ◽  
Vol 35 (2) ◽  
pp. 94-117 ◽  
Author(s):  
James A. Popio ◽  
John R. Luchini
Keyword(s):  
Steady State ◽  
Rolling Resistance ◽  
Test Methods ◽  
The Other ◽  
Reference Condition ◽  
Test Standards

Abstract This study compares data from the two Society of Automotive Engineers test methods for rolling resistance: J-2452 (Stepwise Coast-Down) and J-1269 (Equilibrium) steady state. The ability of the two methods to evaluate tires was examined by collecting data for 12 tires. The data were analyzed and the data showed that the two methods ranked the tires the same after the data were regressed and the rolling resistance magnitude was calculated at the Standard Reference Condition. In addition, analysis of the two methods using this matched set of testing provided an opportunity to evaluate each of these test standards against the other. It was observed that each test has merits absent from the other.

scholarly journals A Taylor Series Approach for Service-Coupled Queueing Systems with Intermediate Load

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Ekaterina Evdokimova ◽  
Sabine Wittevrongel ◽  
Dieter Fiems
Keyword(s):  
Performance Measures ◽  
Queueing Systems ◽  
Poisson Processes ◽  
Series Expansions ◽  
Service Rate ◽  
Single Server ◽  
Queueing Model ◽  
State Space Explosion ◽  
Finite Queues ◽  
Service Rates

This paper investigates the performance of a queueing model with multiple finite queues and a single server. Departures from the queues are synchronised or coupled which means that a service completion leads to a departure in every queue and that service is temporarily interrupted whenever any of the queues is empty. We focus on the numerical analysis of this queueing model in a Markovian setting: the arrivals in the different queues constitute Poisson processes and the service times are exponentially distributed. Taking into account the state space explosion problem associated with multidimensional Markov processes, we calculate the terms in the series expansion in the service rate of the stationary distribution of the Markov chain as well as various performance measures when the system is (i) overloaded and (ii) under intermediate load. Our numerical results reveal that, by calculating the series expansions of performance measures around a few service rates, we get accurate estimates of various performance measures once the load is above 40% to 50%.

scholarly journals The influence of two wildfires and biological control agents on the population dynamics of Melaleuca quinquenervia in a seasonally inundated wetland

2021 ◽  
Vol 14 (1) ◽  
pp. 3-8
Author(s):  
Philip W. Tipping ◽  
Melissa R. Martin ◽  
Jeremiah R. Foley ◽  
Ryan M. Pierce ◽  
Lyn A. Gettys
Keyword(s):  
Biological Control ◽  
Population Dynamics ◽  
Seedling Recruitment ◽  
Additional Treatment ◽  
Seed Rain ◽  
The Other ◽  
Melaleuca Quinquenervia ◽  
Biological Control Agents ◽  
Seedling Mortality ◽  
Sapling Growth

AbstractThe potential of Melaleuca quinquenervia (Cav.) S.T. Blake to reinvade cleared areas was evaluated over a 13-yr period that included two wildfires and the introduction of biological control agents. The first wildfire occurred in 1998 and was followed by a mean of 591.5 recruited seedlings m−2. Recruits from that fire were cleared 7 yr later in July 2005 for a second experiment to evaluate seedling recruitment into cleared areas. Seed rain, seedling recruitment and mortality, and sapling growth rates were measured in four plots located around individual large reproductive trees. A second natural wildfire in 2007 burned through those plots, leading to increases in seed rain followed by a pulse in recruitment of 21.04 seedlings m−2, 96.5% fewer than after the 1998 fire. Recruits in half of the plots around each tree were then treated with regular applications of an insecticide to restrict herbivory by biological control agents, while herbivory was not restricted in the other half. There was no difference in seedling mortality between treatments 1,083 d post-fire (2007) with 96.6% seedling mortality in the unrestricted herbivory treatment and 89.4% mortality in the restricted herbivory treatment. Recruits subjected to the restricted herbivory treatment grew taller than those in the unrestricted herbivory treatment, 101.3 cm versus 37.4 cm. Many of the recruits were attacked by the biological control agents, which slowed their growth. Although solitary M. quinquenervia trees retain some capacity to reinvade areas under specific circumstances, there was a downward trend in their overall invasiveness at this site, with progressively smaller recruitment cohorts due to biological control agents. Land managers should prioritize removing large reproductive trees over treating recently recruited populations, which can be left for many years for the biological control agents to suppress before any additional treatment would be needed.

scholarly journals Receptor-operated Ca2+ channels in gastric parietal cells: gastrin and carbachol induce Ca2+ influx in depleting intracellular Ca2+ stores

1993 ◽  
Vol 289 (1) ◽  
pp. 117-124 ◽  
Author(s):  
S Roche ◽  
J P Bali ◽  
R Magous
Keyword(s):  
Steady State ◽  
Receptor Activation ◽  
Parietal Cells ◽  
The Other ◽  
Bivalent Cation ◽  
Gtp Binding ◽  
Gastric Parietal Cells ◽  
Type Receptor ◽  
Ca2 Channels ◽  
Stimulation Of

The mechanism whereby gastrin-type receptor and muscarinic M3-type receptor regulate free intracellular Ca2+ concentration ([Ca2+]i) was studied in rabbit gastric parietal cells stimulated by either gastrin or carbachol. Both agonists induced a biphasic [Ca2+]i response: a transient [Ca2+]i rise, followed by a sustained steady state depending on extracellular Ca2+. Gastrin and carbachol also caused a rapid and transient increase in Mn2+ influx (a tracer for bivalent-cation entry). Pre-stimulation of cells with one agonist drastically decreased both [Ca2+]i increase and Mn2+ influx induced by the other. Neither diltiazem nor pertussistoxin treatment had any effect on agonist-stimulated Mn2+ entry. Thapsigargin, a Ca(2+)-pump inhibitor, induced a biphasic [Ca2+]i increase, and enhanced the rate of Mn2+ entry. Preincubation of cells with thapsigargin inhibits the [Ca2+]i increase as well as Mn2+ entry stimulated by gastrin or by carbachol. Thapsigargin induced a weak but significant increase in Ins(1,4,5)P3 content, but this agent had no effect on the agonist-evoked Ins(1,4,5)P3 response. In permeabilized parietal cells, Ins(1,4,5)P3 and caffeine caused an immediate Ca2+ release from intracellular pools, followed by a reloading of Ca2+ pools which can be prevented in the presence of thapsigargin. We conclude that (i) gastrin and carbachol mobilize common Ca2+ intracellular stores, (ii) Ca2+ permeability secondary to receptor activation involves neither a voltage-sensitive Ca2+ channel nor a GTP-binding protein from the G1 family, and (iii) agonists regulate common Ca2+ channels in depleting intracellular Ca2+ stores.

scholarly journals Two Factors in Face Recognition: Whether You Know the Person’s Face and Whether You Share the Person’s Race

Perception ◽  
2021 ◽  
pp. 030100662110140
Author(s):  
Xingchen Zhou ◽  
A. M. Burton ◽  
Rob Jenkins
Keyword(s):  
Face Recognition ◽  
Factorial Design ◽  
Performance Measures ◽  
Recognition Accuracy ◽  
The Other ◽  
Familiarity Effect ◽  
Race Effect ◽  
Two Factors ◽  
Unfamiliar Face

One of the best-known phenomena in face recognition is the other-race effect, the observation that own-race faces are better remembered than other-race faces. However, previous studies have not put the magnitude of other-race effect in the context of other influences on face recognition. Here, we compared the effects of (a) a race manipulation (own-race/other-race face) and (b) a familiarity manipulation (familiar/unfamiliar face) in a 2 × 2 factorial design. We found that the familiarity effect was several times larger than the race effect in all performance measures. However, participants expected race to have a larger effect on others than it actually did. Face recognition accuracy depends much more on whether you know the person’s face than whether you share the same race.

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