The planning of mechanized tunneling projects requires the consideration of complex constraints and project objectives. Process simulation provides a tool to virtually evaluate different concepts in changing environme...
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ISBN:
(纸本)9781479939503;9781479920778
The planning of mechanized tunneling projects requires the consideration of complex constraints and project objectives. Process simulation provides a tool to virtually evaluate different concepts in changing environmental conditions. The consideration of uncertain influences is an essential task within the development of a holistic simulation model. Some aspects (e.g. technical disturbances) can be considered by application of a probability function. However, geotechnical constraints feature a fuzzy nature not well suited for a probabilistic approach. The authors present an approach based on Fuzzy Logic to integrate the performance related influence of wear of cutting tools on the advance rate. The approach is described in detail and demonstrated by an artificial example. simulation experiments were performed to illustrate the influence of wear on the advance rate in the context of disturbances. This innovative approach to consider such an essential performance factor is another step towards a holistic simulation model of mechanized tunneling projects.
A simulation model was built to represent the dynamics of a General Electric (GE) dishwasher wire rack production system associated with multiple types of racks and changeovers at the various work centers. A periodic-...
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ISBN:
(纸本)9781479939503;9781479920778
A simulation model was built to represent the dynamics of a General Electric (GE) dishwasher wire rack production system associated with multiple types of racks and changeovers at the various work centers. A periodic-review inventory policy was simulated for the wire rack production system using order-up-to safety stock SSi and a heuristic trigger variable P* as the control variables. A discrete optimization model was formulated and executed in order to find near optimal values for the control variables with respect to minimization of the total inventory levels while satisfying constraints on demand for the various types of racks. Three different scenarios involving optimization of the simulation model were conducted to help GE improve their production strategy.
The process of developing, verifying and validating models and simulations should be straightforward. Unfortunately, following conventional development approaches can render a model design that appeared complete and r...
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Seeking to enter new geographic markets where expected margins are relatively tight, a manufacturer of medical devices must reduce inventory and related costs in its finished goods supply chain. The manufacturer's...
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ISBN:
(纸本)9781479939503;9781479920778
Seeking to enter new geographic markets where expected margins are relatively tight, a manufacturer of medical devices must reduce inventory and related costs in its finished goods supply chain. The manufacturer's supply chain includes four echelons-factories, distribution centers, regional salespeople (also known as "vans"), and customers. The amount of inventory typically held and corresponding reorder policies near the customer end of this supply chain are not known. A simulation approach was selected to provide insight into those inventory levels based on assumed reorder policies. Analysis conducted using a simulation model implemented using SimPy point to significant potential savings, with the value of inventory-related savings over a four year period approaching $200 million.
Knowledge based methods have recently been applied to the control of material handling systems, specifically using simulation as a source of knowledge. Little research has been done however on ensuring a consistently ...
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ISBN:
(纸本)9781479939503;9781479920778
Knowledge based methods have recently been applied to the control of material handling systems, specifically using simulation as a source of knowledge. Little research has been done however on ensuring a consistently high quality of the data generated by the simulation, especially under changing circumstances such as differing load patterns in the system. We propose a self-adapting control that is able to automatically generate knowledge according to current circumstances using a parametrized simulation model, which uses observed system parameters as input. The control automatically triggers generation when necessary, detects changes in the system and also proactively anticipates them, resulting in consistently high performance. For the problem of knowledge generation (determining an optimal control action to a given situation), we present a look ahead simulation method that considers uncertainties. We validated our approach in a real world material handling system, developed by Lodige Industries GmbH.
In this paper, I shall propose an integrated model of worker skills and team motivation for a computer-based simulation game that can be used to provide experiential learning to students. They can act as project manag...
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ISBN:
(纸本)9781479939503;9781479920778
In this paper, I shall propose an integrated model of worker skills and team motivation for a computer-based simulation game that can be used to provide experiential learning to students. They can act as project managers here without being burdened by the costs and risks associated with unsuccessful projects. I shall present an approach of classifying skills into five different types (relevant to IT projects) and apply a five-point competency scale to each skill type. The Pearson Correlation will be applied to the scores of each skill type to generate an efficiency index that will characterize the effectiveness of a team working on a task. I shall also describe a model to represent the relationship between the social needs of team members and their motivation levels. The results of the actual simulation games will be presented here followed by a discussion on the practical implications and recommendations.
JaamSim is a free, open-source simulation package written in the Java programming language. A modern graphical user interface is provided that is comparable to commercial software, including drag-and-drop model buildi...
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ISBN:
(纸本)9781479939503;9781479920778
JaamSim is a free, open-source simulation package written in the Java programming language. A modern graphical user interface is provided that is comparable to commercial software, including drag-and-drop model building, an Input Editor, Output Viewer, and 3D graphics. Users are able to create their own palettes of high-level objects using standard Java and modern programming tools such as Eclipse. If you are writing hundreds or thousands of lines of code in the proprietary programming language provided with your commercial software, you would be far better off to write your code in Java and use JaamSim.
Conceptually, under restrictions, multiclass open queueing networks are positive Harris recurrent Markov processes, making them amenable to regenerative simulation for estimating the steady-state performance measures....
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ISBN:
(纸本)9781479939503;9781479920778
Conceptually, under restrictions, multiclass open queueing networks are positive Harris recurrent Markov processes, making them amenable to regenerative simulation for estimating the steady-state performance measures. However, regenerations in such networks are difficult to identify when the interarrival times are generally distributed. We assume that the interarrival times have exponential or heavier tails and show that such distributions can be decomposed into mixture of sums of independent random variables such that at least one of the components is exponentially distributed. This allows an implementable regenerative simulation for these networks. We show that the regenerative mean and standard deviation estimators are consistent and satisfy a joint central limit theorem. We also show that amongst all such interarrival decompositions, the one with largest mean exponential component minimizes the asymptotic variance of the standard deviation estimator. We also propose a regenerative simulation method that is applicable even when the interarrival times have superexponential tails.
A classic Kriging or Gaussian process (GP) metamodel estimates the variance of its predictor by plugging-in the estimated GP (hyper) parameters;namely, the mean, variance, and covariances. The problem is that this pre...
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ISBN:
(纸本)9781479939503;9781479920778
A classic Kriging or Gaussian process (GP) metamodel estimates the variance of its predictor by plugging-in the estimated GP (hyper) parameters;namely, the mean, variance, and covariances. The problem is that this predictor variance is biased. To solve this problem for deterministic simulations, we propose " conditional simulation" (CS), which gives predictions at an old point that in all bootstrap samples equal the observed value. CS accounts for the randomness of the estimated GP parameters. We use the CS predictor variance in the "expected improvement" criterion of " efficient global optimization" (EGO). To quantify the resulting small-sample performance, we experiment with multi-modal test functions. Our main conclusion is that EGO with classic Kriging seems quite robust;EGO with CS only tends to perform better in expensive simulation with small samples.
The complexity of simulation models has increased during the last years in semiconductor foundries. Manual and automated decisions have to be modeled in detail to make the right conclusions from them. We describe an a...
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ISBN:
(纸本)9781509044863
The complexity of simulation models has increased during the last years in semiconductor foundries. Manual and automated decisions have to be modeled in detail to make the right conclusions from them. We describe an approach that uses forward simulation to minimize modeling effort and mimics fab behavior to a high degree. The approach is applied to the problem of controlling time link chains. Results are presented and other applications are discussed.
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