scholarly journals Analysis of a Discrete-Time Queueing Model with Disasters

Mathematics ◽  
2021 ◽  
Vol 9 (24) ◽  
pp. 3283
Author(s):  
Mustafa Demircioglu ◽  
Herwig Bruneel ◽  
Sabine Wittevrongel
Keyword(s):  
Discrete Time ◽  
Queueing System ◽  
Time Slot ◽  
Probability Distributions ◽  
Single Server ◽  
Bernoulli Process ◽  
Tail Probabilities ◽  
Mean Values ◽  
The Mean ◽  
The Impact

Queueing models with disasters can be used to evaluate the impact of a breakdown or a system reset in a service facility. In this paper, we consider a discrete-time single-server queueing system with general independent arrivals and general independent service times and we study the effect of the occurrence of disasters on the queueing behavior. Disasters occur independently from time slot to time slot according to a Bernoulli process and result in the simultaneous removal of all customers from the queueing system. General probability distributions are allowed for both the number of customer arrivals during a slot and the length of the service time of a customer (expressed in slots). Using a two-dimensional Markovian state description of the system, we obtain expressions for the probability, generating functions, the mean values, variances and tail probabilities of both the system content and the sojourn time of an arbitrary customer under a first-come-first-served policy. The customer loss probability due to a disaster occurrence is derived as well. Some numerical illustrations are given.

Asteroid and Comet Impact Speeds upon Mars: Significance for Panspermia and the Supply of Organics

1997 ◽  
Vol 161 ◽  
pp. 197-201 ◽  
Author(s):  
Duncan Steel
Keyword(s):  
Probability Distributions ◽  
Regions Of Interest ◽  
Significant Fraction ◽  
Organic Chemicals ◽  
Impact Speed ◽  
The Mean ◽  
The Impact

AbstractWhilst lithopanspermia depends upon massive impacts occurring at a speed above some limit, the intact delivery of organic chemicals or other volatiles to a planet requires the impact speed to be below some other limit such that a significant fraction of that material escapes destruction. Thus the two opposite ends of the impact speed distributions are the regions of interest in the bioastronomical context, whereas much modelling work on impacts delivers, or makes use of, only the mean speed. Here the probability distributions of impact speeds upon Mars are calculated for (i) the orbital distribution of known asteroids; and (ii) the expected distribution of near-parabolic cometary orbits. It is found that cometary impacts are far more likely to eject rocks from Mars (over 99 percent of the cometary impacts are at speeds above 20 km/sec, but at most 5 percent of the asteroidal impacts); paradoxically, the objects impacting at speeds low enough to make organic/volatile survival possible (the asteroids) are those which are depleted in such species.

scholarly journals Biases in CloudSat Falling Snow Estimates Resulting from Daylight-Only Operations

2021 ◽  
Vol 13 (11) ◽  
pp. 2041
Author(s):  
Lisa Milani ◽  
Norman B. Wood
Keyword(s):  
Water Cycle ◽  
Mean Values ◽  
The Mean ◽  
Satellite Missions ◽  
The Impact ◽  
Global Mean

Falling snow is a key component of the Earth’s water cycle, and space-based observations provide the best current capability to evaluate it globally. The Cloud Profiling Radar (CPR) on board CloudSat is sensitive to snowfall, and other satellite missions and climatological models have used snowfall properties measured by it for evaluating and comparing against their snowfall products. Since a battery anomaly in 2011, the CPR has operated in a Daylight-Only Operations (DO-Op) mode, in which it makes measurements primarily during only the daylit portion of its orbit. This work provides estimates of biases inherent in global snowfall amounts derived from CPR measurements due to this shift to DO-Op mode. We use CloudSat’s snowfall measurements during its Full Operations (Full-Op) period prior to the battery anomaly to evaluate the impact of the DO-Op mode sampling. For multi-year global mean values, the snowfall fraction during DO-Op changes by −10.16% and the mean snowfall rate changes by −8.21% compared with Full-Op. These changes are driven by the changes in sampling in DO-Op and are very little influenced by changes in meteorology between the Full-Op and DO-Op periods. The results highlight the need to sample consistently with the CloudSat observations or to adjust snowfall estimates derived from CloudSat when using DO-Op data to evaluate other precipitation products.

​Impact of Extreme Hot Environmental Temperature Period on Marker Enzymes of Carbohydrate Metabolism in Non-descript Sheep from Arid Tracts of Rajasthan

2021 ◽  
Author(s):  
Anandita Srivastava ◽  
Nalini Kataria
Keyword(s):  
Carbohydrate Metabolism ◽  
Environmental Temperature ◽  
Age Groups ◽  
Extreme Temperature ◽  
Mean Value ◽  
Marker Enzymes ◽  
Mean Values ◽  
The Mean ◽  
The Impact ◽  
Enzymes Of Carbohydrate Metabolism

Background: The present investigation was envisaged to find out the impact of extreme hot environmental temperature period (ETP) on marker enzymes of carbohydrate metabolism in male and female non-descript sheep of various age groups i.e. 4 to 13 months from arid tracts of Rajasthan. Glucose-6-phosphate dehydrogenase (G-6-PDH) and malate dehydrogenase (MDH) marker enzymes of carbohydrate metabolism were considered for study. Methods: During the period October 2016-June 2017 blood samples were collected to harvest sera for spectrophotometric method from 240 healthy animals selected from private slaughter house during moderate and extreme hot environmental temperature periods (ETPs). The mean values of markers attained during moderate ETP were reckoned as the control. It was 10.00 ± 0.10 UL-1 and 42.00±1.00 respectively. Conclusion: The mean value of MDH was significantly (p≤0.05) higher while G-6-PDH significantly (p≤0.05) lowers during extreme hot temperature in comparison to moderate period. Therefore, it could be concluded that variations in enzyme markers were associated with changes in environmental temperatures. Probably ETP were able to produce a profound effect on carbohydrate metabolism in sheep. Therfore it can be suggested that during the period of extreme temperature balanced ration must be provided to the animal along with proper management to decrease the severity of temperature impact.

scholarly journals Records of performance and sanitary status from a dairy cattle herd in southern Brazil

2011 ◽  
Vol 31 (1) ◽  
pp. 01-09 ◽  
Author(s):  
Cláudio E. F. Cruz ◽  
Djeison L. Raymundo ◽  
Cristine Cerva ◽  
Saulo P. Pavarini ◽  
André G. C. Dalto ◽  
...  
Keyword(s):  
Dairy Cattle ◽  
Reproductive Performance ◽  
Cattle Herd ◽  
Lactation Period ◽  
Mean Values ◽  
Cattle Diseases ◽  
Dairy Cattle Herd ◽  
The Mean ◽  
The Impact ◽  
Voluntary Waiting Period

Over the last decades, the emphasis on the health of dairy cows has changed from an individual to a herd level. In this scenario, the role played by the recording system and its interpretation by veterinarians has gained primordial importance. The records of productive and reproductive performance and of sanitary status from a southern Brazilian dairy cattle herd have been presented and discussed. The period of study was 2000-2009. Mean values per lactation period were 349D 8436M 290F 275P 201SCS (D: days in lactation, M: kg of milk yield, F: kg of fat, P: kg of protein and SCS: somatic cell score in 1000 cells/ml of milk). Major indexes of reproductive efficiency included age at first calving (31 months), services per conception (2.1), intercalving interval (428 days), calving to conception interval (146 days), mean annual rates of parturitions (76.2%), fetal losses (9.8-19.0%), and stillbirths (3.6%), apart of voluntary waiting period (94 days). Main information on sanitary status of the herd was associated with the mean prevalence of common disorders of dairy cattle such as anaplasmosis (29.8%), mastitis (27.8%), digital diseases (26.3%), ovarian cysts (21.3%), placental retention (19.7%), postpartum uterine infections (10.6%), and calf diarrhea (23.7%) and pneumonia (16.8%), among others. In addition, culling reasons (low reproductive performance [56.3%] and udder/mastitis problems [33.6%]), causes of cattle deaths (anaplasmosis [16.4%] and leukosis [11.4]), and the impact of cattle diseases such as tuberculosis, leukosis, and neosporosis on the herd have also been presented and succinctly discussed. Numbers between brackets represent rates accumulated in the 10-year period.

scholarly journals Ultrasound-based examination of the medial ligament complex shows gender- and age-related differences in laxity

2020 ◽  
Author(s):  
Patricia M. Lutz ◽  
Matthias J. Feucht ◽  
Judith Wechselberger ◽  
Michael Rasper ◽  
Wolf Petersen ◽  
...  
Keyword(s):  
Knee Joint ◽  
Knee Flexion ◽  
Joint Space ◽  
Medial Knee ◽  
Mean Values ◽  
Age Related ◽  
Gender And Age ◽  
Joint Width ◽  
The Mean ◽  
The Impact

Abstract Purpose Ultrasound (US) examination of the medial joint space of the knee has played a subordinate diagnostic role up till now. The purpose of the present study was to describe mean values of medial joint width and to investigate the impact of gender, age, and body mass index (BMI) on medial joint laxity in healthy knees using modern, dynamic US in a standardized fashion in unloaded and standardized loaded conditions. Methods A total of 65 subjects with 79 healthy knees were enrolled in this study. All volunteers underwent clinical examination of the knee. The medial knee joint width was determined using US in a supine position at 0° and 30° of knee flexion in unloaded and standardized loaded (= 15 Dekanewton, daN) conditions using a specific device. Mean values were described and correlations between medial knee joint width and gender, age, and BMI were assessed. Results Thirty-two females and 33 males were enrolled in this study. The mean medial joint width in 0° unloaded was 5.7 ± 1.2 mm and 7.4 ± 1.4 mm loaded. In 30° of knee flexion, the mean medial joint width was 6.1 ± 1.1 mm unloaded and 7.8 ± 1.2 mm loaded. The average change between unloaded and loaded conditions in 0° was 1.7 ± 1.0 mm and in 30° 1.7 ± 0.9 mm. A significant difference between genders was evident for medial joint width in 0° and 30° of flexion in unloaded and loaded conditions (p < 0.05). With rising age, a significant increased change of medial joint space width between unloaded and loaded conditions could be demonstrated in 0° (p = 0.032). No significant correlation between BMI and medial joint width in US could be found. Conclusion Mean values of medial joint width in unloaded and standardized loaded conditions using a fixation device could be demonstrated. Based on the results of this study, medial knee joint width in US is gender- and age-related in healthy knees. These present data may be useful for evaluating patients with acute or chronic pathologies to the medial side of the knee. Level of evidence III.

Discordant GH and IGF-1 Results in Treated Acromegaly: Impact of GH Cutoffs and Mean Values Assessment

2020 ◽  
Author(s):  
Claudia Campana ◽  
Francesco Cocchiara ◽  
Giuliana Corica ◽  
Federica Nista ◽  
Marica Arvigo ◽  
...  
Keyword(s):  
Characteristic Curve ◽  
Area Under The Curve ◽  
Receiver Operator Characteristic Curve ◽  
Mean Values ◽  
Pituitary Diseases ◽  
Discordance Rate ◽  
Values Assessment ◽  
The Mean ◽  
The Impact

Abstract Context Discordant growth hormone (GH) and insulin-like growth factor-1 (IGF-1) values are frequent in acromegaly. Objective To evaluate the impact of different GH cutoffs on discordance rate. To investigate whether the mean of consecutive GH measurements impacts discordance rate when matched to the last available IGF-1 value. Design Retrospective study. Setting Referral center for pituitary diseases. Patients Ninety acromegaly patients with at least 3 consecutive evaluations for GH and IGF-1 using the same assay in the same laboratory (median follow-up 13 years). Interventions Multimodal treatment of acromegaly. Main Outcome Measures Single fasting GH (GHf) and IGF-1 (IGF-1f). Mean of 3 GH measurements (GHm), collected during consecutive routine patients’ evaluations. Results At last evaluation GHf values were 1.99 ± 2.79 µg/L and age-adjusted IGF-1f was 0.86 ± 0.44 × upper limit of normality (mean ± SD). The discordance rate using GHf was 52.2% (cutoff 1 µg/L) and 35.6% (cutoff 2.5 µg/L) (P = 0.025). “High GH” discordance was more common for GHf &lt;1.0 µg/L, while “high IGF-1” was predominant for GHf &lt;2.5 µg/L (P &lt; 0.0001). Using GHm mitigated the impact of GH cutoffs on discordance (GHm &lt;1.0 µg/L: 43.3%; GHm &lt;2.5 µg/L: 38.9%; P = 0.265). At receiver-operator characteristic curve (ROC) analysis, both GHf and GHm were poor predictors of IGF-1f normalization (area under the curve [AUC] = 0.611 and AUC = 0.645, respectively). The prevalence of disease-related comorbidities did not significantly differ between controlled, discordant, and active disease patients. Discussion GH/IGF-1 discordance strongly depends on GH cutoffs. The use of GHm lessen the impact of GH cutoffs. Measurement of fasting GH levels (both GHf and GHm) is a poor predictor of IGF-1f normalization in our cohort.

scholarly journals Imprecise Imputation as a Tool for Solving Classification Problems with Mean Values of Unobserved Features

2013 ◽  
Vol 2013 ◽  
pp. 1-12
Author(s):  
Lev V. Utkin ◽  
Yulia A. Zhuk
Keyword(s):  
Partial Information ◽  
Probability Distributions ◽  
Classification Problem ◽  
Support Vector ◽  
Classification Problems ◽  
Mean Values ◽  
Numerical Examples ◽  
The Standard Model ◽  
The Mean ◽  
Available Information

A method for solving a classification problem when there is only partial information about some features is proposed. This partial information comprises the mean values of features for every class and the bounds of the features. In order to maximally exploit the available information, a set of probability distributions is constructed such that two distributions are selected from the set which define the minimax and minimin strategies. Random values of features are generated in accordance with the selected distributions by using the Monte Carlo technique. As a result, the classification problem is reduced to the standard model which is solved by means of the support vector machine. Numerical examples illustrate the proposed method.

The stationary tail asymptotics in the GI/G/1-type queue with countably many background states

2004 ◽  
Vol 36 (4) ◽  
pp. 1231-1251 ◽  
Author(s):  
Masakiyo Miyazawa ◽  
Yiqiang Q. Zhao
Keyword(s):  
State Space ◽  
Discrete Time ◽  
Priority Queue ◽  
Decay Rates ◽  
Single Server ◽  
Renewal Theorem ◽  
Tail Probabilities ◽  
Markov Renewal Equation ◽  
Geometric Decay ◽  
Background State

We consider the asymptotic behaviour of the stationary tail probabilities in the discrete-time GI/G/1-type queue with countable background state space. These probabilities are presented in matrix form with respect to the background state space, and shown to be the solution of a Markov renewal equation. Using this fact, we consider their decay rates. Applying the Markov renewal theorem, it is shown that certain reasonable conditions lead to the geometric decay of the tail probabilities as the level goes to infinity. We exemplify this result using a discrete-time priority queue with a single server and two types of customer.

scholarly journals Comparative statistical analysis of simulated ice management effectiveness

2019 ◽  
Vol 2 (1) ◽  
pp. 79-91
Author(s):  
Amy Price ◽  
Maria Yulmetova ◽  
Sarah Khalil
Keyword(s):  
Confidence Intervals ◽  
Probability Distributions ◽  
Management Effectiveness ◽  
Distribution Fitting ◽  
Management Performance ◽  
Distance Ratio ◽  
The Mean ◽  
Comparative Statistical Analysis ◽  
Level Of Experience ◽  
The Impact

AbstractIce management is critical for safe and efficient operations in ice-covered waters; thus, it is important to understand the impact of the operator’s experience in effective ice management performance. This study evaluated the confidence intervals of the mean and probability distributions of two different sample groups, novice cadets and experienced seafarers, to evaluate if there was a difference in effective ice management depending on the operator’s level of experience. The ice management effectiveness, in this study, is represented by the “clearing-to-distance ratio” that is the ratio between the area of cleared ice (km2) and the distance travelled by an ice management vessel (km) to maintain that cleared area. The data analysed in this study was obtained from a recent study conducted by Memorial University’s “Safety at Sea” research group. With the distribution fitting analysis providing inconclusive results regarding the normality of the data, the confidence intervals of the dataset means were obtained using both parametric approaches, such as t-test, Cox’s method, and Johnson t-approach, and non-parametric methods, namely Jackknife and Bootstrap methods, to examine if the assumption of normality was valid. The comparison of the obtained confidence interval results demonstrates that the mean efficiency of the cadets is more consistent, while it is more varied among seafarers. The noticeable difference in ice management performance between the cadet and seafarer sample groups is revealed, thus, proving that crew experience positively influences ice management effectiveness.

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