Current Issue : January - March Volume : 2014 Issue Number : 1 Articles : 5 Articles
Extensive research has been devoted to economic production quantity (EPQ) problem. However, no attention has been paid to\r\nproblems where unit production and set-up costs must be considered as functions of production rate. In this paper, we address\r\nthe problem of determining the optimal production quantity and rate of production in which unit production and set-up costs are\r\nassumed to be continuous functions of production rate. Based on the traditional economic production quantity (EPQ) formula,\r\nthe cost function associated with this model is proved to be nonconvex and a procedure is proposed to solve this problem. Finally,\r\nutility of the model is presented using some numerical examples and the results are analyzed....
Most commonly used commercial engine simulation packages generate detailed estimation of the combustion and gas flow\r\nparameters. These parameters are required for advanced research on fluid flow and heat transfer and development of geometries\r\nof engine components. However, engine control involves different operating parameters. Various sensors are installed into the\r\nengine, the combustion performance is recorded, and data is sent to engine control unit (ECU). ECU computes the new set of\r\nparameters to make fine adjustments to actuators providing better engine performance. Such techniques include variable valve\r\ntiming, variable ignition timing, variable air to fuel ratio, and variable compression ratio. In the present study, two of the commercial\r\npackages, Ricardo Wave and Lotus Engine Simulation, have been tested on the capabilities for engine control purposes. These\r\npackages are compared with an in-house developed package and with reference results available from the literature. Different\r\nnumerical experiments have been carried out from which it can be concluded that all packages predict similar profiles of pressure\r\nand temperature in the engine cylinder. Moreover, those are in reasonable agreement with the reference results while in-house\r\ndeveloped package is possible to run simulations with changing speed for engine control purpose....
Contraflow on major evacuation routes is one scheme that has been adopted in many Gulf and eastern coastal states for hurricane\r\nevacuation. The idea is to reverse one direction of the roadway in order to accommodate the often substantially increased travel\r\ndemand moving away from the impact area. Efficient planning and operation is critical to a successful contraflow implementation.\r\nAlabama has an approximately 140-mile contraflow segment on I-65 between exit 31 and exit 167 and has carried out contraflow\r\noperations several times in past hurricane evacuations.Thetiming for the deployment of equipment and personnel and the initiation\r\nand termination of actual contraflow affects the effectiveness, safety, and cost of the operation. Researchers from the University of\r\nAlabama were tasked with the design of a decision support system for contraflow evacuation planning. The conceived decision\r\nsupport system consists of three main modules: the demand module, the network optimization module, and the incident and\r\ncharacterization module. This paper focuses on the design of the traffic incident generation and characterization module of the\r\nplanned decision support system....
This paper discusses an environment being developed to model a mission of the Space Launch System (SLS) and theMultipurpose\r\nCrew Vehicle (MPCV) being launched from Kennedy Space Center (KSC) to the International Space Station (ISS). Several\r\nmodels representing different phases of the mission such as the ground operations processes, engineered systems, and range\r\ncomponents such as failure tree, blast, gas dispersion, and debris modeling are explained. These models are built using different\r\nsimulation paradigms such as continuous, system dynamics, discrete-event, and agent-based simulation modeling. The High Level\r\nArchitecture (HLA) is the backbone of this distributed simulation.The different design decisions and the information fusion scheme\r\nof this unique environment are explained in detail for decision-making. This can also help in the development of exploration\r\nmissions beyond the International Space Station....
Empirical evidence created a commonly accepted understanding that synchronisation and stability of material flows impact its\r\nproductivity. This crucial link between synchronous and stable material flows by time and quantity to create a supply chain with the\r\nhighest throughput rates is at the heart of lean thinking. Although this supply chain triangle has generally been acknowledged over\r\nmany years, it is necessary to reach a finer understanding of these dynamics. Therefore, we will develop and study supply chains\r\nwith the help of fluid dynamics. Amultistage, continuous material flow ismodelled through a conservation law formaterial density.\r\nUnlike similar approaches, our model is not based on some quasi steady-state assumptions about the stochastic behaviour of the\r\ninvolved supply chain but rather on a simple deterministic rule formaterial flow density. Thesemodels allow us to take into account\r\nthe nonlinear, dynamical interactions of different supply chain echelons and to test synchronised and stable flow with respect to its\r\npotential impacts. Numerical simulations verify that the model is able to simulate transient supply chain phenomena. Moreover,\r\na quantification method relating to the fundamental link between synchronisation, stability, and productivity of supply chains has\r\nbeen found....
Loading....