The consequences of time-phased order releases on two M/M/1 queues in series.

A key characteristic of MRP applications includes the coordination of assembly and purchased component requirements by time-phased order releases. In the literature on order review and release strategies, time- phased order releases are described as a worthy alternative to load limited release mechanisms. This paper initializes the development of a stochastic model that quantifies the consequences of time-phased order releases on the stochastic system behavior. This is done by introducing them in an open queueing network composed of two M/M/1 stations. The core of the analysis is focused on the modified flow variability which is specified by the second-order stationary departure process at the first station in the routing. It is a process characterized by a negligible autocorrelation. Based on the stationary-interval method and the asymptotic method, we propose an approximating renewal process for the modified departure process. The modelling efforts provide interesting conclusions and practical insights on some coordination issues in stochastic multi-echelon systems.

Mathematical Models of Multiserver Queuing System for Dynamic Performance Evaluation in Port

We discuss dynamic system performance evaluation in the river port utilizing queuing models with batch arrivals. The general models of the system are developed. This system is modelled by M-X/M/n/m queue with finite waiting areas and identical and independent cargo-handling capacities. The models are considered with whole and part batch acceptance (or whole and part batch rejections) and the interarrival and service times are exponentially distributed. Results related to the batch blocking probability and the blocking probability of an arbitrary vessel in nonstationary and stationary states have been obtained. Numerical results and computational experiments are reported to evaluate the efficiency of the models for the real system

Mathematical Models of Multiserver Queuing System for Dynamic Performance Evaluation in Port

We discuss dynamic system performance evaluation in the river port utilizing queuing models with batch arrivals. The general models of the system are developed. This system is modelled by M-X/M/n/m queue with finite waiting areas and identical and independent cargo-handling capacities. The models are considered with whole and part batch acceptance (or whole and part batch rejections) and the interarrival and service times are exponentially distributed. Results related to the batch blocking probability and the blocking probability of an arbitrary vessel in nonstationary and stationary states have been obtained. Numerical results and computational experiments are reported to evaluate the efficiency of the models for the real system

Revisiting Street Intersections Using Slot-Based Systems

Since their appearance at the end of the 19th century, traffic lights have been the primary mode of granting access to road intersections. Today, this centuries-old technology is challenged by advances in intelligent transportation, which are opening the way to new solutions built upon slot-based systems similar to those commonly used in aerial traffic: what we call Slot-based Intersections (SIs). Despite simulation-based evidence of the potential benefits of SIs, a comprehensive, analytical framework to compare their relative performance with traffic lights is still lacking. Here, we develop such a framework. We approach the problem in a novel way, by generalizing classical queuing theory. Having defined safety conditions, we characterize capacity and delay of SIs. In the 2-road crossing configuration, we provide a capacity-optimal SI management system. For arbitrary intersection configurations, near-optimal solutions are developed. Results theoretically show that transitioning from a traffic light system to SI has the potential of doubling capacity and significantly reducing delays. This suggests a reduction of non-linear dynamics induced by intersection bottlenecks, with positive impact on the road network. Such findings can provide transportation engineers and planners with crucial insights as they prepare to manage the transition towards a more intelligent transportation infrastructure in cities

Automation considerations for a manufacturing system

This thesis examines the present manufacturing system of Apollo Valve Company, a solenoid control valves manufacturing. After analyzing the present system, the automation considerations and proposed new system were recommended. Chapter 1 presenti the background material of automation and manufacturing system. The development of the automated factory is also included. The plant layout, organization, and departments functions of the present system are briefly described in the Chapter 2. Analysis of the present manufacturing system by the production volume, by plant layout, and by the manufacturing operations, is discussed in Chapter 3. Proposed automation considerations and improvements, such as group technology (GT), computer-aided process planning (CAPP), computer-aided manufacturing (CAM), automatic assembly and testing, packing, and flexible manufacturing system (FMS), are presented in the Chapter 4. The last chapter, the conclusions are discussed and the new manufacturing system is recommended

Mathematical Models of Multiserver Queuing System for Dynamic Performance Evaluation in Port

We discuss dynamic system performance evaluation in the river port utilizing queuing models with batch arrivals. The general models of the system are developed. This system is modelled by MX/M/n/m queue with finite waiting areas and identical and independent cargo-handling capacities. The models are considered with whole and part batch acceptance (or whole and part batch rejections) and the interarrival and service times are exponentially distributed. Results related to the batch blocking probability and the blocking probability of an arbitrary vessel in nonstationary and stationary states have been obtained. Numerical results and computational experiments are reported to evaluate the efficiency of the models for the real system

Basics of inventory management (Part 5: The (R,b,Q)-model)

Inventory Models;management science

Configuration planning on an ICL computer utilizing a stochastic network analysis package

M.Sc (Computer Science.)This dissertation details the implementation of SNAP, a stochastic network analysis package, as the basis of an in-house computer configuration planning facility. The work was performed at Head Office, Gold Fields of South Africa Limited, Johannesburg, South Africa (GFSA) during the period April 1980 to December 1981. SNAP was developed by the Institute of Applied Computer Science at the University of Stellenbosch, Stellenbosch, South Africa. The implementation of SNAP at GFSA signalled the first in-house SNAP facility, and the first SNAP implementation on an ICL computer (although implementation had been in progress at another ICL site since 1979). Although this dissertation is very specific in nature, it is intended to provide an insight into the methodology employed in planning and implementing an in-house configuration planning facility. An overview of multiclass queueing network models and the SNAP package is provided, although no attempt is made to explain the stochastic theory of queueing networks in any detail. Attention is thereafter focussed on the various phases of the project. Problems were encountered in monitoring performance data, and these are looked at in some depth. The question of workload characterization and the difficulties of producing a satisfactory GFSA classification strategy are then presented. The model design, calibration and validation stages are explained using the GFSA model. Thereafter, use of the model for prediction purposes is illustrated by means of a number of examples. Finally, tne memory management model is discussed - main memory does not form part of the SNAP model and has to be dealt with as a separate issue