Sangeeta Kalita

Bio: Sangeeta Kalita is an academic researcher. The author has contributed to research in topics: Bulk queue & M/G/1 queue. The author has an hindex of 2, co-authored 3 publications receiving 15 citations.

A two-phase queueing system with repeated attempts and Bernoulli vacation schedule

Abstract: This paper deals with the steady-state behaviour of an M/G/1 queue with repeated attempts in which the server provides two phases of heterogeneous service under Bernoulli vacation schedule. We carry out an extensive analysis of the system, including existence of stationary regime, embedded Markov chain, steady-state distribution of the server state and the number of customer in the orbit and some system performance measures. This model generalises both the classical M/G/1 retrial queue and the M/G/1 queue with two phases of service and Bernoulli vacation model.

Analysis of a Batch Arrival Poisson Queue Under Single Vacation Policy

Abstract: We consider a single server Markovian queueing system with compound Poisson arrivals of batches of random size under a single vacation policy, where the server takes exactly one vacation between two successive busy periods. We are concerned with the steady state distributions of the additional queue size, additional delay and queue waiting time distribution.

Investigation of N,N′‐Disulfopiperazinium Chlorometallates of Fe(III), Ni(II) and Co(II) as Hybrid Catalysts for the Synthesis of 1,2‐Dihydroquinazoline Derivatives

Abstract: Three organic salts of N,N′-disulfopiperazinium cation with complex metal chloride anions of Fe(III), Ni(II) and Co(II) cations were developed as Brønsted-Lewis acidic hybrid materials in solid state. Their structural compositions were established by FT-IR, UV-Visible, SEM, EDX, Powder XRD and Raman techniques. Thermogravimetric analyses showed removal of physisorbed water around 100 °C for Fe(III) salt in contrast to 150–170 °C for Ni(II) & Co(II) organic salts for strongly bound water molecules in highly crystalline state. Their Brønsted acidities were determined from comparative UV-visible spectra of 4-nitroaniline in water in presence of the halometallates while Lewis acidity strength was observed via FT-IR spectra of these salts in presence of pyridine as probe molecule. The catalytic activity of these acidic organic salts was investigated for three-component synthesis of 1,2-dihydroquinazolines as recyclable heterogeneous catalysts.

On a batch arrival Poisson queue under threshold policy with a grand vacation

Abstract: We consider an M x /M/1 queueing model under a threshold policy with grand vacation process, where the server takes a sequence of vacations, till he returns to find at least some prespecified number of customers (threshold) observed after each grand vacation. In this paper, an attempt has been made to derive the probability generating functions of the queue size distribution at a random point of time as well as at a departure point of time. The mean queue size of this model is also derived with some numerical examples.

Some New Results for Departure Process in the M X /G/1 Queueing System with a Single Vacation and Exhaustive Service

Abstract: A batch arrival queueing system with a single vacation between two successive busy periods and with exhaustive service is considered. The departure process h(t) is studied first on a single vacation cycle. The approach based on renewal theory is applied to obtain results in the general case. In particular, the explicit representation for the generating function of Laplace transform of the probability function of h(t) is derived. All formulae are written in terms of input parameters of the system and factors of a certain canonical factorization of Wiener–Hopf type. A numerical approach to results is discussed as well.

Unreliable MX/G/1 retrial queue with multi-optional services and impatient customers

Abstract: The present investigation deals with Mx/G/1 retrial queue with unreliable server and general retrial times. The server is subject to breakdowns and takes some setup time before starting the repair. The server renders first essential phase of service (FES) to all the arriving customers whereas second optional phase services (SOS) are provided after FES to only those customers who opt for it. The impatient customers are allowed to balk depending upon server’s status; they may also renege after waiting sometime in the queue. By incorporating the supplementary variables corresponding to service time, repair time, retrial time and setup time and then using generating function method, the queueing analysis has been done to obtain the queue size and orbit size distributions, and some other queueing as well as reliability measures. The effects of several parameters on the system performance are examined numerically by taking an illustration.

Analysis of m/g/1 queueing model with state dependent arrival and vacation

Abstract: This investigation deals with single server queueing system wherein the arrival of the units follow Poisson process with varying arrival rates in different states and the service time of the units is arbitrary (general) distributed. The server may take a vacation of a fixed duration or may continue to be available in the system for next service. Using the probability argument, we construct the set of steady state equations by introducing the supplementary variable corresponding to elapsed service time. Then, we obtain the probability generating function of the units present in the system. Various performance indices, such as expected number of units in the queue and in the system, average waiting time, etc., are obtained explicitly. Some special cases are also deduced by setting the appropriate parameter values. The numerical illustrations are provided to carry out the sensitivity analysis in order to explore the effect of different parameters on the system performance measures.

GI/G/1/∞ batch arrival queueing system with a single exponential vacation

Abstract: In the article the queueing system of GI/G/1 type with batch arrival of customers and a single exponentially distributed vacation period at the end of every busy period is considered. Basic characteristics of transient state of the system are investigated: the first busy period, the first vacation period and the number of customers served during the first busy period. New results for the Laplace transform of the joint distribution of these three variables are obtained in dependence on the initial conditions of the system.

Queueing model with state-dependent bulk arrival and second optional service

Abstract: This paper investigates a single server bulk queueing system with state-dependent rates and second optional service. The service time of the essential service is general-distributed whereas that of optional service follows the exponential distribution. By using supplementary variable technique, the probability-generating functions of the queue length distribution have been obtained. Further, the queue length distribution is established by using maximum entropy approach. The numerical illustrations are provided to verify the tractability of performance measures. The sensitivity analysis is also carried out to examine the effect of system descriptors.