Sherif I. Ammar
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View article: Cost optimization and analysis of retrial queues with hybrid vacation policies and fault correction: a metaheuristic approach
Cost optimization and analysis of retrial queues with hybrid vacation policies and fault correction: a metaheuristic approach Open
This study presents a comprehensive model for the steady state behavior of an M/G/ 1 retrial queue with fault correction and hybrid vacation policies, tackling real-world challenges such as system breakdowns, repair delays and cost optimiz…
View article: Analysis of Vacation Fluid M/M/1 Queue in Multi-Phase Random Environment
Analysis of Vacation Fluid M/M/1 Queue in Multi-Phase Random Environment Open
An M/M/1 fluid queue with various vacations is studied in the context of a multi-phase random environment. When the system is in operation (i = 1, 2, …, n), it behaves according to the M/M/1 fluid queue model. However, in any other situati…
View article: Analysis of Stationary Fluid Queue Driven by State-Dependent Birth-Death Process Subject to Catastrophes
Analysis of Stationary Fluid Queue Driven by State-Dependent Birth-Death Process Subject to Catastrophes Open
This paper investigates an infinite buffer capacity fluid queueing model driven by a state-dependent birth-death process prone to catastrophes. We employ the Laplace-Stieltjes transform and the continued fraction techniques to determine ex…
View article: Reliability and Optimization Measures of Retrial Queue with Different Classes of Customers under a Working Vacation Schedule
Reliability and Optimization Measures of Retrial Queue with Different Classes of Customers under a Working Vacation Schedule Open
A working vacation queueing model is described in this work, with three different classes of customers: regular, priority, and disaster. The regular server serves all arriving customers, whereas the optional reservice is only provided to t…
View article: Customer Behavior Analysis in Ticket Windows at Scenic Spots from Game-Theoretic Perspective
Customer Behavior Analysis in Ticket Windows at Scenic Spots from Game-Theoretic Perspective Open
In service industries, especially in some ticket windows at scenic spots, affected by congestion, some customers often find excuses or ask the acquaintances in the queue so as to jump the queue and complete their corresponding service as e…
View article: Ergodicity and perturbation bounds for<i>M<sub>t</sub></i>/<i>M<sub>t</sub></i>/1 queue with balking, catastrophes, server failures and repairs
Ergodicity and perturbation bounds for<i>M<sub>t</sub></i>/<i>M<sub>t</sub></i>/1 queue with balking, catastrophes, server failures and repairs Open
In this paper, we display methods for the computation of convergence and perturbation bounds for M t / M t /1 system with balking, catastrophes, server failures and repairs. Based on the logarithmic norm of linear operators, the bounds on …
View article: Accuracy of CBCT, Digital and Conventional Radiography in Evaluating the Shaping Performance of a Novel NiTi Rotary System ( An in Vitro Study)
Accuracy of CBCT, Digital and Conventional Radiography in Evaluating the Shaping Performance of a Novel NiTi Rotary System ( An in Vitro Study) Open
Aim: This study was designed to evaluate and compare the shaping abilities of ProTaper Gold and the ProTaper Universal systems using cone beam computed tomography (CBCT), digital and conventional radiography. Materials and Methods: Forty m…
View article: Fluid <i>M</i>/<i>M</i>/1 catastrophic queue in a random environment
Fluid <i>M</i>/<i>M</i>/1 catastrophic queue in a random environment Open
Our main objective in this study is to investigate the stationary behavior of a fluid catastrophic queue of M / M /1 in a random multi-phase environment. Occasionally, a queueing system experiences a catastrophic failure causing a loss of …
View article: Ergodicity and Perturbation Bounds for $M_t/M_t/1$ Queue with Balking, Catastrophes, Server Failures and Repairs
Ergodicity and Perturbation Bounds for $M_t/M_t/1$ Queue with Balking, Catastrophes, Server Failures and Repairs Open
In this paper, we display methods for the computation of convergence and perturbation bounds for $M_t/M_t/1$ system with balking, catastrophes, server failures and repairs. Based on the logarithmic norm of linear operators, the bounds on t…
View article: Ergodicity and Perturbation Bounds for $M_t/M_t/1$ Queue with Balking,\n Catastrophes, Server Failures and Repairs
Ergodicity and Perturbation Bounds for $M_t/M_t/1$ Queue with Balking,\n Catastrophes, Server Failures and Repairs Open
In this paper, we display methods for the computation of convergence and\nperturbation bounds for $M_t/M_t/1$ system with balking, catastrophes, server\nfailures and repairs. Based on the logarithmic norm of linear operators, the\nbounds o…
View article: On Probability Characteristics for a Class of Queueing Models with Impatient Customers
On Probability Characteristics for a Class of Queueing Models with Impatient Customers Open
In this paper, a class of queueing models with impatient customers is considered. It deals with the probability characteristics of an individual customer in a non-stationary Markovian queue with impatient customers, the stationary analogue…
View article: On limiting characteristics for a non-stationary two-processor heterogeneous system with catastrophes, server failures and repairs
On limiting characteristics for a non-stationary two-processor heterogeneous system with catastrophes, server failures and repairs Open
In this paper, we display a method for the computation of convergence bounds for a non-stationary two-processor heterogeneous system with catastrophes, server failures and repairs when all parameters varying with time. Based on the logarit…
View article: Disturbance solutions for the long–short-wave interaction system using bi-random Riccati–Bernoulli sub-ODE method
Disturbance solutions for the long–short-wave interaction system using bi-random Riccati–Bernoulli sub-ODE method Open
This article applied the Riccati–Bernoulli (RB) sub-ODE method in order to get new exact solutions for the long–short-wave interaction (LS) equations. Namely, we obtain deterministic and random solutions, since we consider the proposed met…
View article: New solutions for the unstable nonlinear Schrödinger equation arising in natural science
New solutions for the unstable nonlinear Schrödinger equation arising in natural science Open
In this work, three mathematical methods are applied, namely, the exp(-φ(ξ))-expansion method, the sine-cosine technique and the Riccati-Bernoulli sub-ODE method for constructing many new exact solutions of the unstable nonlinear Schröding…
View article: Role of routine hysteroscopy in previous failed ICSI: a continuous clinical dilemma
Role of routine hysteroscopy in previous failed ICSI: a continuous clinical dilemma Open
Background The benefit of hysteroscopy could extend beyond the treatment of intrauterine abnormalities. Irrigation of the cavity with saline may have a beneficial effect on implantation and pregnancy rates, since saline mechanically washes…
View article: \bf{M/G/1} fault-tolerant machining system with imperfection
\bf{M/G/1} fault-tolerant machining system with imperfection Open
The internet of things (IoT) is an emerging archetype of technology for the guaranteed quality of services (QoS). The availability of the uninterrupted power supply (UPS) is one of the most challenging criteria in the successful implementa…
View article: Performance Analysis of Preemptive Priority Retrial Queueing System with Disaster under Working Breakdown Services
Performance Analysis of Preemptive Priority Retrial Queueing System with Disaster under Working Breakdown Services Open
In this investigation, a novel sort of retrial queueing system with working breakdown services is introduced. Two distinct kinds of customers are considered, which are priority and ordinary customers. The normal busy server may become inad…
View article: Analysis of an N–Policy GI/M/1 Queue in a Multi–Phase Service Environmentwith Disasters
Analysis of an N–Policy GI/M/1 Queue in a Multi–Phase Service Environmentwith Disasters Open
This paper investigates an N-policy GI/M/1 queue in a multi-phase service environment with disasters, where the system tends to suffer from disastrous failures while it is in operative service environments, making all present customers lea…
View article: Transient solution of an M / M /1 vacation queue with a waiting server and impatient customers
Transient solution of an M / M /1 vacation queue with a waiting server and impatient customers Open
Recently, Ammar [1] has discussed the transient behavior of a multiple vacations queue with impatient customers. In this paper, a similar technique is used to derive a new elegant explicit solution for an M/M/1 vacation queue with impatien…