OPSEARCH

This paper considers a discrete-time queue of packets awaiting movement according to the bulk service rule (L, K). Time is assumed to be divided into equal intervals called slots. The analysis has been carried out under the assumption that (i) service times of batches are independent of the number of packets in any batch, and (ii) there is no simultaneous arrival of packets and departure of batch in a single slot. The packets arrive one by one and their inter arrival times follow geometric distribution. The arriving packets are queued in FIFO order. One server transports packets in batches of minimum number L and maximum K and service times follow negative binomial NB(α, p1) distribution. The server accesses new arrivals even after service has started on any batch of initial number ‘j’ (L ≤ j < K). This operation continues till the random service time of the ongoing batch is completed or the maximum capacity of the batch being served attains “K’ whichever occurs first. The distribution of system occupancy just before and after the departure epochs is obtained using discrete-time analysis (DTA). The primary focus is on the various performance measures of the steady state distribution of the batch server at departure instants and also on numerical illustrations.

In this paper, we introduce new classes of higher order generalized strong invex functions under non-differentiable settings. The optimality results are derived for higher order strict global minimizers of non-differentiable multiobjective programming problems using these functions. Numerical examples and illustrations are provided in support of new classes of functions and the optimality conditions. We also study the mixed dual problem and establish weak, strong and converse duality results. Furthermore, as an application, we present a non-differentiable case of vector variational-like inequality problem and establish the equivalence between its solutions and higher order strict global minimizers of the non-differentiable multiobjective programming problem.

In this paper, the concept of neutrosophic soft ring is introduced and some basic properties related to it are established. Then the Cartesian product of neutrosophic soft ring, neutrosophic soft subring, neutrosophic normal soft ring, neutrosophic soft ideal are defined and illustrated by suitable examples. Several related properties and structural characteristics of these are studied here. Some theorems are also developed in each part.

In this paper, we consider the discrete-time Geo/G/1 retrial queue with preemptive resume and Bernoulli feedback. This model unifies the FCFS and LCFS preemptive resume disciplines. We analyze the Markov chain underlying the regarded queueing system and present some performance measures of the queueing system in steady-state. Besides, the stochastic decomposition property and the corresponding continuous-time queueing system are investigated. Finally, some numerical examples are provided to illustrate the effect of preemptive resume and feedback on some crucial performance characteristics of the system.

In a supply chain, the upper echelons plays a key role in tuning the chain performance. In the procurement cycle of the supply chain, the manufacturer outsources more parts and services to focus on their own core competencies. A situation may arise in which some suppliers may under perform in providing critical strategic supplies. This paper analyzes supplier performance using multi-criteria decision procedure along with Pareto analysis in identifying sub-optimal suppliers to be included in the supplier development to optimize the supply chain performance.

A previously developed method for evaluating the performance of zero order single input single output (SISO) processes using transfer function modeling assumed constant lags and zero or negligible noise. This work models the performance of SISO systems with variable lags and noise using transfer function modeling and fuzzy logic inference systems. Two single input single output processes exemplified by palm kernel crushing plants were used for the modeling. Plants 1 and 2 with the same system’s coefficient of performance (SCOP) of 0.4, which corresponds linguistic variable ‘Fair’, had the same performance. In comparison with queuing theory SCOP performed better as a performance assessment metric for the SISO processes. The results showed that fuzzy logic inference system could be effectively used to model zero order SISO systems with variable lags and noise. The results of the research could be extended to higher order SISO systems.

So far, many methods have been proposed to classify items based on ABC analysis, but the results of these methods have had relatively low compliance with the principles of ABC. More precisely, collective value and sometimes the number of items belonging to each category in the methods provided do not meet the basic requirements of ABC called Pareto’s principle. In this study, a number of hybrid methodologies including Shannon’s entropy, TOPSIS (the technique for order preference by similarity to ideal solution) and goal programming are respectively used for determining the weight of criteria which are effective in the inventory items classification, calculations of each item value and its classification based on Pareto’s principle. To this end, the value of each item as well as classification of inventory items is calculated based on Pareto’s principle. The performance of the proposed method is evaluated through (1) statistical analysis, (2) checking the percentage of similarity with other methods and (3) comparison with another method in terms of the number and value allocated to each class. The results confirm the capability of the listed method.