The Service Time Properties of an Unreliable Server Characterize the Exponential Distribution

1994 ◽  
Vol 26 (1) ◽  
pp. 172-182 ◽  
Author(s):  
Z. Khalil ◽  
B. Dimitrov
Keyword(s):  
Exponential Distribution ◽  
Service Time ◽  
Initial Conditions ◽  
Mean Values ◽  
Unreliable Server ◽  
Service Disciplines ◽  
The Mean ◽  
Server Reliability ◽  
Preemptive Repeat Different

Consider the total service time of a job on an unreliable server under preemptive-repeat-different and preemptive-resume service disciplines. With identical initial conditions, for both cases, we notice that the distributions of the total service time under these two disciplines coincide, when the original service time (without interruptions due to server failures) is exponential and independent of the server reliability. We show that this fact under varying server reliability is a characterization of the exponential distribution. Further we show, under the same initial conditions, that the coincidence of the mean values also leads to the same characterization.

The Service Time Properties of an Unreliable Server Characterize the Exponential Distribution

1994 ◽  
Vol 26 (01) ◽  
pp. 172-182 ◽  
Author(s):  
Z. Khalil ◽  
B. Dimitrov
Keyword(s):  
Exponential Distribution ◽  
Service Time ◽  
Initial Conditions ◽  
Mean Values ◽  
Unreliable Server ◽  
Service Disciplines ◽  
The Mean ◽  
Server Reliability ◽  
Preemptive Repeat Different

Consider the total service time of a job on an unreliable server under preemptive-repeat-different and preemptive-resume service disciplines. With identical initial conditions, for both cases, we notice that the distributions of the total service time under these two disciplines coincide, when the original service time (without interruptions due to server failures) is exponential and independent of the server reliability. We show that this fact under varying server reliability is a characterization of the exponential distribution. Further we show, under the same initial conditions, that the coincidence of the mean values also leads to the same characterization.

Characterizations of the Exponential Distribution via the Blocking Time in a Queueing System with an Unreliable Server

1998 ◽  
Vol 35 (1) ◽  
pp. 236-239 ◽  
Author(s):  
Jian-Lun Xu
Keyword(s):  
Exponential Distribution ◽  
Service Time ◽  
Coefficient Of Variation ◽  
Queueing System ◽  
Random Variables ◽  
Unreliable Server ◽  
Failure Times ◽  
Server Failure

The characterization of the exponential distribution via the coefficient of the variation of the blocking time in a queueing system with an unreliable server, as given by Lin (1993), is improved by substantially weakening the conditions. Based on the coefficient of variation of certain random variables, including the blocking time, the normal service time and the minimum of the normal service and the server failure times, two new characterizations of the exponential distribution are obtained.

An unreliable server characterization of the exponential distribution

1994 ◽  
Vol 31 (1) ◽  
pp. 274-279 ◽  
Author(s):  
Janos Galambos ◽  
Charles Hagwood
Keyword(s):  
Distribution Function ◽  
Exponential Distribution ◽  
Service Time ◽  
Unreliable Server ◽  
Memory Property ◽  
Lack Of Memory Property

Consider a workstation with one server, performing jobs with a service time, Y, having distribution function, G(t). Assume that the station is unreliable, in that it occasionally breaks down. The station is instantaneously repaired, and the server restarts the uncompleted job from the beginning. Let T denote the time it takes to complete each job. If G(t) is exponential with parameter A, then because of the lack-of-memory property of the exponential, P (T > t) = Ḡ(t) =exp(−γt), irrespective of when and how the failures occur. This property also characterizes the exponential distribution.

An unreliable server characterization of the exponential distribution

1994 ◽  
Vol 31 (01) ◽  
pp. 274-279 ◽  
Author(s):  
Janos Galambos ◽  
Charles Hagwood
Keyword(s):  
Distribution Function ◽  
Exponential Distribution ◽  
Service Time ◽  
Unreliable Server ◽  
Memory Property ◽  
Lack Of Memory Property

Consider a workstation with one server, performing jobs with a service time, Y, having distribution function, G(t). Assume that the station is unreliable, in that it occasionally breaks down. The station is instantaneously repaired, and the server restarts the uncompleted job from the beginning. Let T denote the time it takes to complete each job. If G(t) is exponential with parameter A, then because of the lack-of-memory property of the exponential, P (T > t) = Ḡ(t) =exp(−γt), irrespective of when and how the failures occur. This property also characterizes the exponential distribution.

Characterizations of the Exponential Distribution via the Blocking Time in a Queueing System with an Unreliable Server

1998 ◽  
Vol 35 (01) ◽  
pp. 236-239
Author(s):  
Jian-Lun Xu
Keyword(s):  
Exponential Distribution ◽  
Service Time ◽  
Coefficient Of Variation ◽  
Queueing System ◽  
Random Variables ◽  
Unreliable Server ◽  
Failure Times ◽  
Server Failure

The characterization of the exponential distribution via the coefficient of the variation of the blocking time in a queueing system with an unreliable server, as given by Lin (1993), is improved by substantially weakening the conditions. Based on the coefficient of variation of certain random variables, including the blocking time, the normal service time and the minimum of the normal service and the server failure times, two new characterizations of the exponential distribution are obtained.

Prevalence and Molecular Characterization of Microbial Contaminants in Raw Cow Milk of Tangail District in Bangladesh

2021 ◽  
Vol 17 ◽  
Author(s):  
Shahin Mahmud ◽  
Md. Firoz Ali ◽  
Md. Omar Faruque ◽  
Muhammad Wasim ◽  
Fatematuz Zuhura Evamoni ◽  
...  
Keyword(s):  
Molecular Characterization ◽  
Raw Milk ◽  
Health Impact ◽  
Cow Milk ◽  
Milk Consumption ◽  
Salmonella Spp ◽  
Mean Values ◽  
The Mean ◽  
Quality Of Milk

Objectives: The aim of this study is to evaluate the microbial quality and associated health Methodology: An intensive study was carried out from January¬ to October 2019 at the Tangail district of Bangladesh to assess bacterial contamination of raw milk. A total of 60 samples were examined by following the standard bacteriological methods and the health impact was evaluated with the help of a semi-structured-based questionnaire. Molecular characterization of isolated bacteria was carried out by PCR. Results: Results revealed the mean values of TVC and TCC in raw milk, udder, oil, and utensil samples were 7.6×106, 8.8×106, 4.6×106, and 1.3×106 cfu/ml and 3.7×105, 1.4×106, 4.4×105, and 8.9×104 cfu/ml, respectively. The yeast and mold in raw milk, udder, and oil were 1.5×103, 1.8×103, and 1.3×102cfu/ml, respectively, and the mean values of E. coli in the above-mentioned samples were 1.9×103, 1.8×104, 2.1×103, and 1.6×103cfu/ml, respectively. On the other hand, the mean values of Salmonella spp. in raw milk, udder, oil, and utensil samples were 2.4×102, 7.9×102, 1.5×102, and 1.1×102cfu/ml, respectively. Some selected isolates confirmed by molecular identification were tested for their sensitivity against some common antibiotics used in Bangladesh. Escherichia coli showed 70% resistance to Amoxicillin and 90% sensitivity to Ciprofloxacin whereas Salmonella spp. And Staphylococcus aureus showed 90% resistance to Ampicillin and both were 80% and 90% sensitive to Ciprofloxacin, respectively. Conclusion, Significance, and Impact of Study: Milk producers should be appropriately trained to monitor the overall hygienic conditions surrounding the production and handling of milk until it reaches the consumer. Frequent monitoring of the milk production facility, occasional testing of raw milk, and minimal use of antibiotics will ensure the quality of milk. Consumption of quality milk and avoidance of raw milk consumption will reduce the health risk of the consumers.

scholarly journals Ampelographic and molecular diversity among grapevine (Vitis spp.) cultivars

2009 ◽  
Vol 45 (No. 4) ◽  
pp. 160-168 ◽  
Author(s):  
A. Sabir ◽  
S. Tangolar ◽  
S. Buyukalaca ◽  
S. Kafkas
Keyword(s):  
Molecular Characterization ◽  
Molecular Diversity ◽  
Genetic Distances ◽  
Mean Values ◽  
Issr Analysis ◽  
Geographic Origins ◽  
The Mean ◽  
Vitis Spp

This study presents the ampelographic and molecular characterization of 44 grapevine cultivars. Ampelographic data were obtained during two vegetation periods using the latest version of the descriptors. Based on the mean values transformed by the method indicated in IBPGR publications, a dendrogram was constructed. ISSR analysis was also employed to characterize the genotypes at the DNA level. Twenty primers, selected on the basis of their discriminating potential, generated a total of 157 bands, of which 140 were polymorphic. The dendrograms constructed by the two approaches were largely similar in both the clustering position and divergence of varietal groups. The least distance was observed between Yuvarlak Cekirdeksiz and Superior Seedless. The clustering position of cultivars throughout the dendrograms was basically related to the genetic distances and main uses, as well as to geographic origins.

scholarly journals A METHODOLOGICAL APPROACH TO THE CHARACTERIZATION OF BRAIN GLIOMAS, BY MEANS OF SEMI-AUTOMATIC MORPHOMETRIC ANALYSIS

2014 ◽  
Vol 33 (3) ◽  
pp. 201 ◽  
Author(s):  
Artur Dawid Surowka ◽  
Dariusz Adamek ◽  
Edyta Radwanska ◽  
Marek Lankosz ◽  
Magdalena Szczerbowska-Boruchowska
Keyword(s):  
Aspect Ratio ◽  
Digital Image Analysis ◽  
Methodological Approach ◽  
Morphometric Parameters ◽  
Mean Values ◽  
The Mean ◽  
Analytical Tools ◽  
Brain Gliomas

The aims of this paper were to present a reliable morphometric procedure for glioma analysis for preliminary prognosis and to develop a semi-automatic procedure that is easy to use. The data presented are important to the extent that they verify the reliability of the results by showing that they are consistent with the findings from more complicated automatic analytical tools. The objects for analysis were digital images of haematoxylin-eosin stained glioma samples. The overall analysis consisted of digital image analysis and the determination of morphometric parameters. Interestingly, an increase in the mean values of aspect ratio with increasing malignancy grade was found. Moreover, the morphometric parameters in relation to the histological origin of gliomas were examined and it was found that, the cellular nuclei of glioblastoma multiforme reveal the biggest mean values of aspect ratio compared with other gliomas.

scholarly journals Biomechanical characterization of swimmers with physical disabilities

Motricidade ◽  
2018 ◽  
Vol 14 (4) ◽  
pp. 103-112 ◽  
Author(s):  
Valdir Junior ◽  
Alexandre Medeiros ◽  
Kelly Jesus ◽  
Nuno Domingos Garrido ◽  
Rui Corredeira ◽  
...  
Keyword(s):  
Swimming Performance ◽  
Velocity Variation ◽  
Swimming Velocity ◽  
Stroke Length ◽  
Stroke Frequency ◽  
Mean Values ◽  
Functional Classes ◽  
The Mean ◽  
Incremental Protocol

The evaluation of swimming technique is one of the main aspects to be considered in any training program, with biomechanics being an important source of knowledge. It was our objective to characterize the biomechanical parameters (SL and SF) relating them to the swimming velocity (v) at different intensities and to analyze within each swimming stroke cycle the intra-cyclic velocity variation (IVV) in a group of motor disabled swimmers. Eight disabled male swimmers (25.83 ± 2.93 years old, 72.45 ± 9.26 kg body mass and 1.79 ± 0.11 m of height) of the following functional classes: S6 (n = 1), S8 (n = 2) and S9 (n = 5) participated in this study. Swimmers were evaluated in the kinematic parameters v, stroke frequency (SF) and stroke length (SL) along with an incremental protocol of 6 x 200 m in the the crawl stroke. Data were registered in each step at the distances of 100 and 175 m. With increasing velocity, the mean values of SL decreased while the mean values of SF increased. To achieve higher swimming velocities, swimmers compensated the lack of the propulsive segment increasing SF to increase swimming speed. For the mean values of IVV at 100m distance, a decrease between the first and second levels, followed by a tendency to stabilize from the 2nd to the 6th level is presented. For the 175 m distance, there was a decrease in IVV with an increase in swimming velocity. Stroke frequency is directly related to the magnitude of IVV, which directly influences swimming performance.

scholarly journals EVALUATION OF RADIOACTIVITY IN THE PHOSPHOGYPSUM STOCKPILE OF “HIV” VELES, THE REPUBLIC OF NORTH MACEDONIA

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Mitko Janchev ◽  
Ivan Boev ◽  
Zdenka Stojanovska ◽  
Blazo Boev
Keyword(s):  
Natural Radionuclides ◽  
Radiation Risk ◽  
Waste Product ◽  
Gross Alpha ◽  
Mean Values ◽  
The Mean ◽  
Specific Activities ◽  
The Republic ◽  
High Concentrations

The production of phosphoric acid from natural phosphate ore generates an industrial waste product named phosphogypsum. Phosphogypsum contains considerable amounts of natural radionuclides from the 238U chain, originating from the ore but enriched during the technological process. In order to perform radiological characterization of the “HIV” (Chemical Industry Veles) phosphogypsum stockpile, five phosphogypsum samples were collected and analyzed. The mean values of gross alpha and beta specific activities ± standard deviation values were: (950±104) Bq/kg and (1694±220) Bq/kg, respectively. Further analysis showed increased gross activities of radionuclides of the 238U chain, while the radionuclides of the 232Th chain and 40K were below the detection limit. The mean values of the specific activities of 238U and 226Ra were (360±55) Bq/kg and (280±84) Bq/kg, respectively. The estimated annual outdoor effective dose, at 1m received by adults was 0.25 mSv/y, which is below a dose limit of 1 mSv/y for members of general public. The results obtained in this study show that radionuclides, although present in relatively high concentrations in the phosphogypsum pile, do not imply an increased external radiation risk for members of the population. The possible use of phosphogypsum in civil construction and agriculture may not be excluded if conditions of prior good planning taking into account the radionuclides activities exist.

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