Reliability analysis and selective maintenance for multistate queueing system

The reliability theory of the multi-state system (MSS) has received considerable attention in recent years, as it is able to characterize the multi-state property and complicated deterioration process of systems in a finer way than that of binary-state system. In general, the performance of the task processing type MSS is typically measured by an operation time (processing speed). Whereas, considering the queueing phenomenon caused by the random arrival and processing of tasks, some other criteria should be taken into account to evaluate the quality of service (QoS) and the profit of stakeholders, such as waiting time, service and abandon rate of tasks and consequent profit rate. In this article, we focus on the queueing process of tasks and analyse the performance and reliability of MSS in an M/M/2 queueing model, which is referred to as a multi-state queueing system (MSQS). Two kinds of deterioration are studied including the gradual degradation of servers and the sudden breakdown of the whole system. A performance assessment function is defined to obtain the profit rate of MSQS in different performance states. Based on the proposed performance function, the selective maintenance method is studied to optimize the accumulated profit under the constraint of maintenance resource and time.

Pendampingan Pengembangan Sistem Informasi Antrian Disabilitas Rumah Sakit Panti Waluyo Purworejo

Every patient has the right to receive healthcare service. However, not everyone has equal access to these services. This problem is especially apparent in patients with disabilities. Duta Wacana Christian University’s Faculty of Information Technology is working alongside Panti Waluyo Hospital in Purworejo to build a priority queueing system for disabled patients. This system is expected to improve patient admission and queueing process. The proposed system consists of a website and a mobile application which has undergo 6 months of continuous development and online mentorship, starting from January 2020 up until June 2020.

Eulerian polynomials and Quasi-Birth-Death processes with time-varying-periodic rates

A Quasi-Birth-Death (QBD) process is a stochastic process with a two dimensional state space, a level and a phase. An ergodic QBD with time-varying periodic transition rates will tend to an asymptotic periodic solution as time tends to infinity . Such QBDs are also asymptotically geometric. That is, as the level tends to infinity, the probability of the system being in state ( k , j ) (k,j) at time t t within the period tends to an expression of the form f j ( t ) α − k Π j ( k ) f_j(t)\alpha ^{-k}\Pi _j(k) where α \alpha is the smallest root of the determinant of a generating function related to the generating function for the unbounded (in the level) process, Π j ( k ) \Pi _j(k) is a polynomial in k k , the level, that may depend on j j , the phase of the process, and f j ( t ) f_j(t) is a periodic function of time within the period which may also depend on the phase. These solutions are analogous to steady state solutions for QBDs with constant transition rates. If the time within the period is considered to be part of the state of the process, then they are steady-state solutions. In this paper, we consider the example of a two-priority queueing process with finite buffer for class-2 customers. For this example, we provide explicit results up to an integral in terms of the idle probability of the queue. We also use this asymptotic approach to provide exact solutions (up to an integral equation involving the probability the system is in level zero) for some of the level probabilities.

Stationary Solution of a Fluid Queue Driven by a Queue with Chain Sequence Rates and Controlled Input

A fluid queueing system in which the fluid flow in to the buffer is regulated by the state of the background queueing process is considered. In this model, the arrival and service rates follow chain sequence rates and are controlled by an exponential timer. The buffer content distribution along with averages are found using continued fraction methodology. Numerical results are illustrated to analyze the trend of the average buffer content for the model under consideration. It is interesting to note that the stationary solution of a fluid queue driven by a queue with chain sequence rates does not exist in the absence of exponential timer.

A Stochastic Analysis of Queues with Customer Choice and Delayed Information

Many service systems provide queue length information to customers, thereby allowing customers to choose among many options of service. However, queue length information is often delayed, and it is often not provided in real time. Recent work by Dong et al. [Dong J, Yom-Tov E, Yom-Tov GB (2018) The impact of delay announcements on hospital network coordination and waiting times. Management Sci. 65(5):1969–1994.] explores the impact of these delays in an empirical study in U.S. hospitals. Work by Pender et al. [Pender J, Rand RH, Wesson E (2017) Queues with choice via delay differential equations. Internat. J. Bifurcation Chaos Appl. Sci. Engrg. 27(4):1730016-1–1730016-20.] uses a two-dimensional fluid model to study the impact of delayed information and determine the exact threshold under which delayed information can cause oscillations in the dynamics of the queue length. In this work, we confirm that the fluid model analyzed by Pender et al. [Pender J, Rand RH, Wesson E (2017) Queues with choice via delay differential equations. Internat. J. Bifurcation Chaos Appl. Sci. Engrg. 27(4):1730016-1–1730016-20.] can be rigorously obtained as a functional law of large numbers limit of a stochastic queueing process, and we generalize their threshold analysis to arbitrary dimensions. Moreover, we prove a functional central limit theorem for the queue length process and show that the scaled queue length converges to a stochastic delay differential equation. Thus, our analysis sheds new insight on how delayed information can produce unexpected system dynamics.

Performance Analysis and Optimal Allocation of Layered Defense M/M/N Queueing Systems

One important mission of strategic defense is to develop an integrated layered Ballistic Missile Defense System (BMDS). Motivated by the queueing theory, we presented a work for the representation, modeling, performance simulation, and channels optimal allocation of the layered BMDS M/M/N queueing systems. Firstly, in order to simulate the process of defense and to study the Defense Effectiveness (DE), we modeled and simulated the M/M/N queueing system of layered BMDS. Specifically, we proposed the M/M/N/N and M/M/N/C queueing model for short defense depth and long defense depth, respectively; single target channel and multiple target channels were distinguished in each model. Secondly, we considered the problem of assigning limited target channels to incoming targets, we illustrated how to allocate channels for achieving the best DE, and we also proposed a novel and robust search algorithm for obtaining the minimum channel requirements across a set of neighborhoods. Simultaneously, we presented examples of optimal allocation problems under different constraints. Thirdly, several simulation examples verified the effectiveness of the proposed queueing models. This work may help to understand the rules of queueing process and to provide optimal configuration suggestions for defense decision-making.

Exclusive queueing processes and their application to traffic systems

Pedestrian queues like those observed at ticket counters or supermarket checkouts are usually described by classical queueing theory. However, models like the M/M/1 queue neglect the internal structure (density profile) of the queue by focussing on the system length as the only dynamical variable. This is different in the Exclusive Queueing Process (EQP) in which the queue is considered on a microscopic level. It is equivalent to a Totally Asymmetric Exclusion Process (TASEP) of varying length. The EQP has a surprisingly rich phase diagram with respect to the arrival probability α and the service probability β. The behavior on the phase transition line is much more complex than for the TASEP with a fixed system length. It is nonuniversal and depends strongly on the update procedure used. In this paper, we review the main properties of the EQP and its applications to pedestrian dynamics, vehicular traffic and biological systems. We also mention extensions of the EQP and some related models.