Busy Period Research Articles

Instability of LRTF multiclass queueing networks

We provide an example of a strictly subcritical multiclass queueing network which is unstable under the longest remaining time first (LRTF) service discipline. It is a reentrant line with two servers and four customer classes, Poisson arrivals and deterministic service times. Our instability proof can be generalized to a class of light-tailed stochastic model primitives, including independent, identically distributed exponential service times. A similar example of an unstable deterministic, strictly subcritical LRTF network is also given. Our arguments work for any service discipline such that there are no departures from any network station during its busy period.

A Privacy-Preserving Ride Matching Scheme for Ride Sharing Services in a Hot Spot Area

Ride sharing is a service that enables users to share trips with others, conserving energy, decreasing emissions and reducing traffic congestion. Selecting a suitable partner for a user based on the their trip data is essential for the service, but it also leads to privacy disclosure, e.g., the user’s location and trajectory. Many privacy-preserving solutions for ride sharing services have been proposed, which are based on cryptographic technology and provide accurate matching services. However, these encryption-based algorithms are very complicated and difficult to calculate. In hot spots, such as stations, airports and sport gymnasiums, a large number of users may apply for a ride sharing service in short space of time, which will place huge pressure on the service provider. Using traditional matching methods increases the matching time and leads to a less favorable user experience. To solve these problems, we model them, aiming to maximize the vehicle’s carrying capacity and propose a lightweight privacy-preserving ride matching scheme for selecting feasible partners during busy periods with a large number of requests. To achieve this, we make use of the homomorphic encryption technique to hide location data and design a scheme to calculate the distances between users in road networks securely and efficiently. We employ a road network embedding technique to calculate the distance between users. Moreover, we use travel time instead of space distance, which makes matching more accurate. Further, with the encrypted itineraries of users, the service provider selects potential ride share partners according to the feasibility of time schedules. We use ciphertext packing to reduce overhead, improving the efficiency of ride matching. Finally, we evaluate our scheme with simulation and demonstrate that our scheme achieves an efficient and accurate matching service. It only takes a few seconds to complete the matching, and the matching accuracy is higher than 85 percent in most cases.

Friedrich Daniel Ernst Schleiermacher: Kritische Gesamtausgabe, V, 12: Briefwechsel 1811–1813 (Briefe 3561–3930). Edited by Simon Gerber and Sarah Schmidt

This further publication within the critical edition of Schleiermacher’s works offers us nearly 150 of his letters within a correspondence logging 370 letters sent and received in the two years from January 1811 through to June 1813, plus a few stray recent discoveries from 1808 to 1810 which top up material in earlier volumes (V, 10 and V, 11). This was an especially busy period in Schleiermacher’s life. His various responsibilities and roles alone take up half a page to list in the introduction (p. xxx-viii). These included being the first Professor of Theology in the University in Berlin, a year-long stint as Dean of the Theology Faculty, and member of the philosophy section of the Prussian Academy of Sciences from 1810, as well as having a role in the Education Department of the Prussian Government, not to mention his pastorate at Berlin’s Trinity Church, taken up in 1809. It is not surprising that he got by (or needed to get by) on four hours’ sleep a night and had regular periods of stomach cramp, including a seven-month bout during 1811, much commented on both by Schleiermacher himself and his correspondents.

Reliability modelling of a parallel-cold standby system with proviso of repair priority

Here, reliability modelling of a parallel cold standby system of four units has been done with the provision of priority to repair. Initially, the system has two operative units in parallel mode (called phase-I units) and the other two units are taken as spare in the cold standby (called phase-II units). The phase-I units (main units) are assumed as more efficient than that of the phase-II units (duplicate units). The units in phase-I and phase-II are non-identical but they are identical within the phases. The units in phase-II work simultaneously at the failure of units of phase-I. The priority to repair the units of phase-II has been given over the repair of the units of the phase-I. However, no priority is given for operation of the units of both phases. The repair activities are handled by a single server who attends the system immediately when required. The failure rate of the units follows negative exponential distribution while the distribution for repair time of the phase-I and phase-II units is assumed as arbitrary. Some significant reliability characteristics such as mean sojourn times (MST), transition probabilities, mean time to system failures (MTSF), availability, expected number of repairs (for both phase-I and phase-II units), busy period of the server, expected number of visits of the server and finally the profit function are obtained in steady state by making use of well-known semi-Markov process (SMP) and regenerative point technique (RPT). The graphical representation of these reliability characteristics has been made for arbitrary values of the rates associated with failure and repair times. The application of the present study can be seen in the power distribution system.

Exact Results for the Distribution of the Partial Busy Period for a Multi-Server Queue

Exact Results for the Distribution of the Partial Busy Period for a Multi-Server Queue

Multi-server Markovian heterogeneous arrivals queue with two kinds of working vacations and impatient customers

This paper deals with multi-server queueing system with two kinds of Working Vacations (WVs) and impatient customers. A random timer is started whenever a customer comes into the system. The customer may abandon the system if the service is not completed before the impatience timer expires. Each time after serving all the customers, the system becomes empty and then the server begins 1st kind of vacation. On returning from 1st kind of WV, the server begins 2nd kind of WV whenever a system has no customers. When the server comes back from either 1st kind or 2nd kind of WV, if there is at least one customer in the system, the server switches to busy period. The steady state probabilities have been derived using the Probability Generating Functions (PGFs) method. Various measures of performance are presented and numerical illustrations are also provided.

1926. Risky businesses: Carbon dioxide monitoring to assess ventilation in grocery stores as an indicator of risk for respiratory virus transmission

Abstract Background Poorly ventilated indoor settings pose a risk for transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other respiratory viruses. Transmission often occurs in community, but limited information is available on the quality of ventilation in community settings. Methods We used carbon dioxide measurements to assess adequacy of ventilation in 6 grocery stores, including large warehouse stores, medium-sized stores, and small neighborhood groceries. Carbon dioxide levels were monitored continuously with values recorded once per minute using a handheld device during multiple shopping trips to each store during both busy (defined as long lines at checkout) and non-busy (defined as no lines at checkout) shopping times. Carbon dioxide readings above 800 parts per million (ppm) were considered an indicator of suboptimal ventilation for the number of people present. Results Carbon dioxide levels remained below 800 ppm in all 6 grocery stores during trips at non-busy shopping times, except for transient rises above 800 ppm (peak = 860 ppm) during check out in 2 stores. In 3 of the 6 stores (50%), carbon dioxide levels rose above 800 ppm for prolonged periods during busy shopping times, with considerable variability in levels in different store locations (ie, increased levels in crowded store locations). The figure shows carbon dioxide levels for 1 medium-sized grocery store during typical shopping trips during busy and non-busy shopping periods. Increase in carbon dioxide levels in parts per million (ppm) in a grocery store during busy and non-busy shopping trips. Peak levels of carbon dioxide above 800 ppm (dotted lines) were considered an indicator of suboptimal ventilation for the number of occupants present. Conclusion Ventilation in grocery stores may be sufficient to minimize the risk for airborne transmission of respiratory pathogens during non-busy shopping periods, but in some stores may be sub-optimal in crowded locations during busy shopping times. There is a need for additional studies to assess the quality of ventilation in a wide range of community settings. Disclosures All Authors: No reported disclosures.

The Markovian Bernoulli queues with operational server vacation, Bernoulli's weak and strong disasters, and linear impatient customers

This paper studies the stationary analysis of a Markovian queuing system with Bernoulli feedback, interruption vacation, linear impatient customers, strong and weak disaster with the server's repair during the server's operational vacation period. Each customer has its own impatience time and abandons the system as soon as that time ends. When the queue is not empty, the server's operational vacation can be interrupted if the service is completed and the server starts a busy period with a probability q or continues the operational vacation with a probability q. A strong disaster forces simultaneously all present customers (waiting and served) to abandon the system permanently with a probability p but a weak disaster is that all customers decide to be patient by staying in the system, and wait during the repair time with a probability p, where arrival of a new customer can occur. As soon as the repair process of the server is completed, the server remains providing service in the operational vacation period. We analyze this proposed model and derive the probabilities generating functions of the number of customers present in the system together with explicit expressions of some performance measures such as the mean and the variance of the number of customers in the different states, together with the mean sojourn time. Finally, numerical results are presented to show the influence of the system parameters on some studied performance measures.

Experiences of dysphagia trained nurses in the screening and early management of swallowing in acute stroke: A qualitative study

BACKGROUND: Nurses often carry out swallow screening when patients are admitted to hospital following a stroke, some receive further training to conduct more comprehensive tests. Little is known about how they perceive their role. The aim of this study was to understand the experiences of Dysphagia Trained Nurses (DTNs) in acute stroke who conduct the comprehensive tests. METHODS: Nine DTNs were recruited from one UK hospital. They were identified by maximum variation and convenience sampling ensuring a broad demographic. Semi-structured interviews were carried out during usual shift patterns, in a quiet room on the acute stroke unit by a research and clinical SLT. Thematic analysis was conducted by two researchers and a summary of themes was verified by the participants. RESULTS: Four main themes were identified relating to the role, screening tool, training and pathway. The role was highly regarded, bringing professional benefits such as job satisfaction and career development. Nurses also identified that it was an essential role in acute stroke for the health and wellbeing of patients. The tool was easy to use but needed adaptations at times and the pathway was difficult to adhere to during busy periods when the use of the test with certain patients was questioned. Training and support was deemed crucial for the role and confidence developed with experience. CONCLUSIONS: Dysphagia Trained Nurses who conduct comprehensive dysphagia screening tests in acute stroke value the role. Further research is needed to quantify the impact that the nurses have on patient outcomes and stroke pathways.

Reliability Modeling of a Food Industrial System with two Types of Repair Persons wherein Demand is Season Dependent

The present study pertains to developing a reliability model concerning a food industrial system that runs throughout the month except for Sundays. There are two types of repair persons engaged with the system, one known as operator while another is fitter. The operator is responsible for minor repairs, while the fitter is responsible for major repairs. It is also noticed that the operator is the first person who attends the failed unit in case of a major failure. If the operator is found incapable of repairing the unit within some patience time, then the fitter is called. While gathering the actual month-wise data of the plant, two types of seasons, namely normal and festival seasons, have been recorded. The festival season is from July to November, while the normal season is from December to June, based on consumer demand. During the months of the normal season, the system is shut down for a few days as the demand gets accomplished before the month ends. However, during the festival season, the system has to be kept operational throughout the month to fulfill the high demand for the product. The semi-Markov process and regenerative point technique are used to assess the reliability measures, namely mean time to system failure (MTSF), system availability in both seasons, expected busy period of the repair persons, and expected downtime of the system. The overall profitability of the system is also demonstrated by Graphical interpretation.

Analysis of Non-Steady Queue-Length Distribution in a Finite-Buffer Model with Group Arrivals and Power Saving Mechanism with Setups

In the manuscript, a probability distribution of the queue length is studied in a model with group Markov arrivals, arbitrarily distributed service times and finite waiting room. After the period of suspension of service due to lack of packets, each new busy period is preceded by a random setup time. Integral equations for time-dependent queue-length distribution are derived by identifying renewal moments in the operation of the system and by applying total probability law. The representation for the solution of the system is found in terms of Laplace transforms. Computational examples illustrating the impact of system parameters on the queue-length distribution are included.

Notes From the Editor

Gaming Law ReviewVol. 26, No. 9 Free AccessNotes From the EditorSteve RuddockSteve RuddockSearch for more papers by this authorPublished Online:3 Nov 2022https://doi.org/10.1089/glr2.2022.29064.strAboutSectionsPDF/EPUB Permissions & CitationsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail To say it's been a busy period in the gambling world would be an understatement. Post-COVID (or as post-COVID as we may ever be), all facets of the industry are picking up the pieces and placing them back together. Some are reassembling the pieces as they appeared in 2019, others are trying to assemble them in new, exciting ways, and still others, like Macau, are in a holding pattern, waiting for conditions to change for the better.COVID certainly threw a wrench in many companies' and jurisdictions' long-term goals, forcing several to scrap their plans and take a reactionary approach to a fast-evolving landscape. In most parts of the world, gambling appears to be entering a period of stability. However, a bleak economic outlook could serve as another disruptor that prolongs the reactionary period, preventing gaming companies from shifting back to a proactive business model.As I write this, the industry is preparing for Global Gaming Expo (G2E) in Las Vegas. When you read this, G2E will be over. Hopefully, companies will present their long-term plans and the paths they intend to blaze on many topics. The industry will have to address everything from responsible gaming to the onset of the cashless gaming era in the U.S. to cryptocurrencies and non-fungible tokens (NFTs) and their role in gaming to the legal and regulatory issues associated with social casinos to the increasingly inevitable collision of tribal gaming and online gaming.These are all topics that are on Gaming Law Review's radar for 2023. We would love to hear from you if you have something interesting to say on these topics or others.FiguresReferencesRelatedDetails Volume 26Issue 9Nov 2022 InformationCopyright 2022, Mary Ann Liebert, Inc., publishersTo cite this article:Steve Ruddock.Notes From the Editor.Gaming Law Review.Nov 2022.449-449.http://doi.org/10.1089/glr2.2022.29064.strPublished in Volume: 26 Issue 9: November 3, 2022Online Ahead of Print:October 18, 2022PDF download

Cost Optimization using Genetic Algorithm in Customers Intolerance Markovian Model with Working Vacation and Multiple Working Breakdowns

In this paper we consider a single server queueing model with working vacation and multiple working breakdowns. When on vacation, the server works at a different pace. Disturbances occur in the server due to multiple breakdowns. In working breakdowns server works at a different rate. During the time of interruption caused by working vacation and working breakdowns, the main server can find many implementations in operation. Both the server's lifespan and the time it takes to repair it are considered to be exponentially dispersed. Also, we have considered balking and reneging behaviours of customers. The stationary queue length distribution is computed using a matrix-analytic technique. Using Genetic Algorithm (GA) we optimize the cost function. The predicted length of a busy period, the expected length of a working vacation period, the expected length of a working breakdown period, the mean waiting time, and the average delay are all established. We compute numerical results to verify the analytical point of view. The effect of individual parameters is investigated using sensitivity analysis.

On busy periods of the critical GI/G/1 queue and BRAVO

We study critical GI/G/1 queues under finite second-moment assumptions. We show that the busy-period distribution is regularly varying with index half. We also review previously known M/G/1/ and M/M/1 derivations, yielding exact asymptotics as well as a similar derivation for GI/M/1. The busy-period asymptotics determine the growth rate of moments of the renewal process counting busy cycles. We further use this to demonstrate a Balancing Reduces Asymptotic Variance of Outputs (BRAVO) phenomenon for the work-output process (namely the busy time). This yields new insight on the BRAVO effect. A second contribution of the paper is in settling previous conjectured results about GI/G/1 and GI/G/s BRAVO. Previously, infinite buffer BRAVO was generally only settled under fourth-moment assumptions together with an assumption about the tail of the busy period. In the current paper, we strengthen the previous results by reducing to assumptions to existence of 2+epsilon moments.

The periodic steady-state solution for queues with Erlang arrivals and service and time-varying periodic transition rates

We study a queueing system with Erlang arrivals with k phases and Erlang service with m phases. Transition rates among phases vary periodically with time. For these systems, we derive an analytic solution for the asymptotic periodic distribution of the level and phase as a function of time within the period. The asymptotic periodic distribution is analogous to a steady-state distribution for a system with constant rates. If the time within the period is considered part of the state, then it is a steady-state distribution. We also obtain waiting time and busy period distributions. These solutions are expressed as infinite series. We provide bounds for the error of the estimate obtained by truncating the series. Examples are provided comparing the solution of the system of ordinary differential equation with a truncated state space to these asymptotic solutions involving remarkably few terms of the infinite series. The method can be generalized to other level independent quasi-birth-death processes if the singularities of the generating function are known.

A 5-Year Retrospective Analysis of the Risk Factors, Treatment, and Prognosis of Patients With Fungal Keratitis in Heilongjiang, China

To report the epidemiologic features, laboratory findings, and treatment outcomes of patients with fungal keratitis (FK) during a busy farming period (May, June, and September to November) in Heilongjiang Province, China. Retrospective, observational case series. In total, 251 patients diagnosed with FK at the Eye Hospital, First Affiliated Hospital of Harbin Medical University, from 2017 to 2021 were identified. Medical records were retrospectively analyzed, and demographic features, risk factors, monthly distributions, clinical characteristics, laboratory findings, treatment strategies, and prognostic data were collected. The number of FK cases in the busy farming period accounted for 74.1% (186/251) of the total. The mean patient age was 58.2±9.5 years. Males (66.7%) were more likely to develop FK than females (33.3%), and plant-related trauma was the main cause in 80.1% (149/186) of the cases. The most common causative fungal species was Fusarium (34.9%). In vivo confocal microscopy had the highest positivity rate for FK diagnosis (94.6%). The depth of hypopyon, depth of hyphae or spores, and infiltrate width were significantly positively correlated with delayed presentation. Patients with a longer time of presentation to the hospital were more likely to undergo surgery because of topical medical therapy failure. The most important measures for FK prevention are the use of eye protection during outdoor work and visiting the hospital for treatment as soon as possible after eye injury.

Reliability analysis of captive power plant system where the working of standby unit depends on connecting unit

Captive power plants usually operate parallel to the gridline to overcome the losses associated with power failures. While the connectivity of the power plant and gridline highly depends on the functioning of the electrical breaker. This study reveals the importance of connecting device breakers in a captive power plant to operate the system at full or reduced capacity and safer it from reverse feeding. Using semi-Markov processes reliability model is developed for steam turbine generators interconnected with gridline by an electric breaker. The expressions are formed for reliability measures like mean time to system failure, availability, busy period, and profit using regenerative point techniques. Also, these measures are evaluated numerically using an actual dataset belonging to a captive power plant. Graphical plotting shows a decline in profit with increasing the failure rates of turbine generators, gridline, and working probability of breaker. The revenue per unit uptime of the system is forecasted to get productive profit with different failure rates of the power generator.

Performance analysis for Bernoulli feedback queues subject to disasters: a system with batch Poisson arrivals under a multiple vacation policy

ABSTRACT We analyze an M/G/1 system with batch Poisson arrivals and instantaneous Bernoulli feedback, operating under a Multiple Vacation Policy. The system is subject to disasters that occur according to an independent Poisson process and are followed by (random) repair periods with general distribution. The analysis is carried out using the supplementary variable method. The Laplace transform of the time between two consecutive disasters is obtained and the existence of the stationary regime for the system is shown. Besides obtaining the stationary distribution for the number of customers in the system, we use the information regarding the rates of occurrence of various events provided by the supplementary variable solution to obtain a great variety of additional results. These include the Laplace transform of the busy period distribution and the probability that a customer completes service. We indicate areas of application of our model to real-life systems, in particular in Vehicle ad hoc Networks (VANETs), and we use the analytic results obtained to optimize such a system under a Quality of Service constraint. Finally, we analyze a variant of the system subject to disasters even when the server is not busy.

Estimating waiting times, patient flow, and waiting room occupancy density as part of tuberculosis infection prevention and control research in South African primary health care clinics.

Transmission of respiratory pathogens, such as Mycobacterium tuberculosis and severe acute respiratory syndrome coronavirus 2, is more likely during close, prolonged contact and when sharing a poorly ventilated space. Reducing overcrowding of health facilities is a recognised infection prevention and control (IPC) strategy; reliable estimates of waiting times and 'patient flow' would help guide implementation. As part of the Umoya omuhle study, we aimed to estimate clinic visit duration, time spent indoors versus outdoors, and occupancy density of waiting rooms in clinics in KwaZulu-Natal (KZN) and Western Cape (WC), South Africa. We used unique barcodes to track attendees' movements in 11 clinics, multiple imputation to estimate missing arrival and departure times, and mixed-effects linear regression to examine associations with visit duration. 2,903 attendees were included. Median visit duration was 2 hours 36 minutes (interquartile range [IQR] 01:36-3:43). Longer mean visit times were associated with being female (13.5 minutes longer than males; p<0.001) and attending with a baby (18.8 minutes longer than those without; p<0.01), and shorter mean times with later arrival (14.9 minutes shorter per hour after 0700; p<0.001). Overall, attendees spent more of their time indoors (median 95.6% [IQR 46-100]) than outdoors (2.5% [IQR 0-35]). Attendees at clinics with outdoor waiting areas spent a greater proportion (median 13.7% [IQR 1-75]) of their time outdoors. In two clinics in KZN (no appointment system), occupancy densities of ~2.0 persons/m2 were observed in smaller waiting rooms during busy periods. In one clinic in WC (appointment system, larger waiting areas), occupancy density did not exceed 1.0 persons/m2 despite higher overall attendance. In this study, longer waiting times were associated with early arrival, being female, and attending with a young child. Occupancy of waiting rooms varied substantially between rooms and over the clinic day. Light-touch estimation of occupancy density may help guide interventions to improve patient flow.

Kazahskaya nacional'naya intelligenciya i sibirskie deyateli: istoriya vzaimodejstviya (vtoraya polovina XIX — nachalo XX v.)

The article shows the history of the relationship of individual representatives of the Kazakh national intelligentsia with Siberian public and political figures in the middle of the 19th century to the end of 1917. The first stage of relations includes the 1850s - 1890s. During this period, the main aspects of cooperation in the fields of science, education, ethnography are formed, joint meetings of the Kazakh and Siberian intelligentsia are held. The second stage covers the end of the 19th - beginning of the 20th century. At this time, the Kazakh elite, who studied and worked in educational and scientific institutions and institutions of Siberia, came into contact with such Siberian figures as G.N. Potanin, A.M. Yarmosh, P. S. Vologodskiy. The third stage of mutual contacts includes the activation of ties throughout 1917. During this short but busy period, the leaders of the Kazakh national movement Alash take an active part in the work of the Siberian Congresses.