Global ETD Search

1	Contributions to channel modelling and performance estimation of HAPS-based communication systems regarding IEEE Std 802.16TM Palma Lázgare, Israel Romualdo 24 October 2011 (has links) New and future telecommunication networks are and will be broadband type. The existing terrestrial and space radio communication infrastructures might be supplemented by new wireless networks that make and will make use of aeronautics-technology. Our study/contribution is referring to radio communications based on radio stations aboard a stratospheric platform named, by ITU-R, HAPS (High Altitude Platform Station). These new networks have been proposed as an alternative technology within the ITU framework to provide various narrow/broadband communication services. With the possibility of having a payload for Telecommunications in an aircraft or a balloon (HAPS), it can be carried out radio communications to provide backbone connections on ground and to access to broadband points for ground terminals. The latest implies a complex radio network planning. Therefore, the radio coverage analysis at outdoors and indoors becomes an important issue on the design of new radio systems. In this doctoral thesis, the contribution is related to the HAPS application for terrestrial fixed broadband communications. HAPS was hypothesised as a quasi-static platform with height above ground at the so-called stratospheric layer. Latter contribution was fulfilled by approaching via simulations the outdoor-indoor coverage with a simple efficient computational model at downlink mode. This work was assessing the ITU-R recommendations at bands recognised for the HAPS-based networks. It was contemplated the possibility of operating around 2 GHz (1820 MHz, specifically) because this band is recognised as an alternative for HAPS networks that can provide IMT-2000 and IMT-Advanced services. The global broadband radio communication model was composed of three parts: transmitter, channel, and receiver. The transmitter and receiver parts were based on the specifications of the IEEE Std 802.16TM-2009 (with its respective digital transmission techniques for a robust-reliable link), and the channel was subjected to the analysis of radio modelling at the level of HAPS and terrestrial (outdoors plus indoors) parts. For the channel modelling was used the two-state characterisation (physical situations associated with the transmitted/received signals), the state-oriented channel modelling. One of the channel-state contemplated the environmental transmission situation defined by a direct path between transmitter and receiver, and the remaining one regarded the conditions of shadowing. These states were dependent on the elevation angle related to the ray-tracing analysis: within the propagation environment, it was considered that a representative portion of the total energy of the signal was received by a direct or diffracted wave, and the remaining power signal was coming by a specular wave, to last-mentioned waves (rays) were added the scattered and random rays that constituted the diffuse wave. At indoors case, the variations of the transmitted signal were also considering the following matters additionally: the building penetration, construction material, angle of incidence, floor height, position of terminal in the room, and indoor fading; also, these indoors radiocommunications presented different type of paths to reach the receiver: obscured LOS, no LOS (NLOS), and hard NLOS. The evaluation of the feasible performance for the HAPS-to-ground terminal was accomplished by means of thorough simulations. The outcomes of the experiment were presented in terms of BER vs. Eb/N0 plotting, getting significant positive conclusions for these kind of system as access network technology based on HAPS. Broadband wireless communications Channel modelling High altitude platform station IEEE Std 802.16 State-oriented characterisation Performance evaluation Simulation approach Outdoor-indoor urban coverage 51 52 621.3
2	Open Pit Truck /shovel Haulage System Simulation Cetin, Necmettin 01 October 2004 (has links) (PDF) This thesis is aimed at studying the open pit truck- shovel haulage systems using computer simulation approach. The main goal of the study is to enhance the analysis and comparison of heuristic truck dispatching policies currently available and search for an adaptive rule applicable to open pit mines. For this purpose, a stochastic truck dispatching and production simulation program is developed for a medium size open pit mine consisting of several production faces and a single dump site using GPSS/H software. Eight basic rules are modeled in separate program files. The program considers all components of truck cycle and normal distribution is used to model all these variables. The program asks the user to enter the number of trucks initially assigned to each shovel site. Full-factorial simulation experiments are made to investigate the effects of several factors including the dispatching rules, the number of trucks operating, the number of shovels operating, the variability in truck loading, hauling and return times, the distance between shovels and dump site, and availability of shovel and truck resources. The breakdown of shovel and trucks are modeled using exponential distribution. Three performance measures are selected as truck production, overall shovel utilization and overall truck utilizations. Statistical analysis of the simulation experiments is done using ANOVA method with Minitab software. Regression analysis gives coefficient of determination values, R2, of 56.7 %, 84.1 %, and 79.6 % for the three performance measures, respectively. Also, Tukey&rsquo / s method of mean comparison test is carried out to compare the basic dispatching rules. From the results of statistical analysis, it is concluded that the effects of basic truck dispatching rules on the system performance are not significant. But, the main factors affecting the performances are the number of trucks, the number of shovels, the distance between the shovels and dump site, finally the availability of shovel and truck resources. Also, there are significant interaction effects between these main factors. Finally, an adaptive rule using the standardized utilization of shovels and trucks is developed. TN Mining Engineering, Metallurgy. 1-997
3	A new framework considering uncertainty for facility layout problem Oheba, Jamal Bashir January 2012 (has links) In today’s dynamic environment, where product demands are highly volatile and unstable, the ability to design and operate manufacturing facilities that are robust with respect to uncertainty and variability is becoming increasingly important to the success of any manufacturing firm in order to operate effectively in such an environment. Hence manufacturing facilities must be able to exhibit high levels of robustness and stability in order to deal with changing market demands. In general, Facility Layout Problem (FLP) is concerned with the allocation of the departments or machines in a facility with an objective to minimize the total material handling cost (MHC) of moving the required materials between pairs of departments. Most FLP approaches assume the flow between departments is deterministic, certain and constant over the entire time planning horizon. Changes in product demand and product mix in a dynamic environment invalidate these assumptions. Therefore there is a need for stochastic FLP approaches that aim to assess the impact of uncertainty and accommodate any possible changes in future product demands.This research focuses on stochastic FLP with an objective to present a methodology in the form of a framework that allows the layout designer to incorporate uncertainty in product demands into the design of a facility. In order to accomplish this objective, a measure of impact of this uncertainty is required. Two solution methods for single and multi period stochastic FLPs are presented to quantify the impact of product demand uncertainty to facility layout designs in terms of robustness (MHC) and variability (standard deviation). In the first method, a hybrid (simulation) approach which considers the development of a simulation model and integration of this model with the VIPPLANOPT 2006 algorithm is presented. In the second method, mathematical formulations of analytic robust and stable indices are developed along with the use of VIPPLANOPT for solution procedure. Several case studies are developed along with numerical examples and case studies from the literature are used to demonstrate the proposed methodology and the application of the two methods to address different aspects of stochastic FLP both analytically and via the simulation method. Through experimentation, the proposed framework with solution approaches has proven to be effective in evaluating the robustness and stability of facility layout designs with practical assumptions such as deletion and expansion of departments in a stochastic environment and in applying the analysis results of the analytic and simulation indices to reduce the impact of errors and make better decisions 670
4	A FRAMEWORK TO INVESTIGATE KEY CHARACTERISTICS OF DIGITAL TWINS AND THEIR IMPACT ON PERFORMANCE Edwin S Kim (8974793) 29 April 2022 (has links) <p>The modern world of manufacturing is in the middle of an industrial revolution with the digital and physical worlds integrating through cyber-physical systems. Through a virtual model that is able to communicate with its physical system known as the Digital Twin, catered decisions can be made based on the current state of the system. The digital twin presents immense opportunities and challenges as there is a greater need to understand how these new technologies work together. </p> <p><br></p> <p>This thesis is an experimental investigation of the characteristics of the essential components of the Digital Twin. A Digital Twin Framework is developed to explore the impacts of model accuracy and update frequency on the system’s performance measure. A simple inventory management system and a more complex manufacturing plant is modeled through the framework providing a method to study the interactions of the physical and digital systems with empirical data.</p> <p><br></p> <p><br></p> <p>As the decision policies are affected by the state changes in the system, designing the Digital Twin must account for the direct and indirect impact of its components. </p> <p>Furthermore, we show the importance of communication and information exchange between the Digital Twin and its physical system. A key characteristic for developing and applying a digital twin is to monitor the update frequency and its impact on performance. Through the study there are implications of optimal combinations of the digital twin components and how the physical system responds. There are also limits to how effective the Digital Twin can be in certain instances and is an area of research that needs further investigation. </p> <p><br></p> <p>The goal of this work is to help practitioners and researchers implement and use the Digital Twin more effectively. Better understanding the interactions of the model components will help guide designing Digital Twins to be more effective as they become an integral part of the future of manufacturing.</p> Manufacturing Management Simulation and Modelling digital twin digital twin applications digital twin modelling simulation approach modeling analyses Systems Approach systems manufacturing Modern management strategies
5	Conduite orientée ordonnancement d'un simulateur dynamique hybride : application aux procédés discontinus / Control oriented scheduling of a dynamic hybrid simulator : application to batch processes Fabre, Florian 20 October 2009 (has links) Ce manuscrit présente des travaux visant à intégrer un module d'ordonnancement (ProSched) à l'environnement de modélisation et simulation dynamique hybride PrODHyS dans le but d'automatiser la génération de scénarii de simulation de procédés discontinus sur la base d'une recette et d'une liste d'ordres de fabrication (OF). La méthodologie développée repose sur une approche mixte optimisation/simulation. Dans ce cadre, trois points essentiels ont été développés dans ces travaux : - tout d'abord, concevoir et développer des composants réutilisables (classes de recette) permettant de modéliser de manière hiérarchisée et systématique le déroulement des opérations unitaires. Pour cela, les notions de jeton Task et de macro-place paramétrable ont été introduites dans les RdPDO et permettent de décrire les recettes à réaliser par assemblage de ces composants prédéfinis. - ensuite, définir un modèle mathématique générique d'ordonnancement basé sur un formalisme de représentation bien établi (le R.T.N.) qui permet de modéliser les principales caractéristiques d'un procédé discontinu et de fournir l'ensemble des données d'entrée nécessaires au modèle de simulation. Pour cela, un modèle PLNE basé sur la formulation Unit Specific Event a été mis en œuvre. - enfin, définir l'interface existant entre le modèle d'optimisation et le modèle de simulation, à travers la notion de place de pilotage et de centre de décision au niveau du simulateur. Dans ce cadre, différentes stratégies de couplage sont proposées. Les potentialités de cette approche sont illustrées par la simulation d'un procédé complet. / This thesis presents works which aim to incorporate a scheduling module (ProSched) to an environment for modeling and dynamic hybrid simulation PrODHyS in order to automate the generation of scenarios for simulation of batch processes based on a recipe and a list of production orders (OF). The methodology developed is based on a mixed optimization / simulation approach. In this context, three key points have been developed in this work: - First, design and develop reusable components (recipe classes) for the hierarchical and systematic modeling of the sequencing of unit operations. For this, the notions of Task token and macro-place have been introduced in the RdPDO formalism and allow the modeling of recipes by assembling these predefined components. - Secondly, define a generic mathematical model of scheduling based on a well defined graphical formalism (RTN) that models the main characteristics of batch processes and provide all input data necessary to the simulation model. For this, a MILP model based on the Unit Specific Event formulation has been implemented. - Finally, define the interface between the optimization model and the simulation model through the concept of control place and decision-making center at the simulator level. In this context, various strategies of mixing optimization and simulation are proposed. The potential of this approach is illustrated by the simulation of a complete manufacturing process Ordonnancement court terme Réseau de Petri Différentiel Objet Couplage Optimisation/simulation Control of dynamic hybrid simulation Short-term scheduling Mixed Integer Linear Programming Object Differential Petri nets Optimization / simulation approach
6	市場風險值管理之應用分析以某金融控股公司為例 / The analysis of Market Risk VaR management ：the case of financial holding company 周士偉, Chou, Jacky Unknown Date (has links) 2008年次貸風暴橫掃全球金融市場，Basel II制度歷經多年的實施，卻無法有效防阻金融風暴的發生。觀察2008已採用內部模型法之主要國際金融機構之年報，亦發現採用蒙地卡羅模擬法之代表銀行『德意志銀行』於該年度竟發生了35次穿透，市場風險管理到底出了什麼問題？這是被極度關心的現象，產官學界也對此現象提出了許多議題。2012年的現在，次貸的風暴尚未遠去，新的歐債危機也正在蔓延，若金融風暴再次來臨，市場風險管理是否能克服次貸風暴後所凸顯的缺失，市場風險管理的價值除被動管理外，是否還可以進階到主動預警，以作為經營決策的重要參考資訊？這些都是國內金融機構需積極面對的急迫的市場風險管理議題。個案金控的市場風險管理機制致力於解決次貸以來所凸顯的市場風險管理議題、提升市場風險衡量的精準度、擴大市場風險管理之應用範圍，並將市場風險管理的價值由被動管理角色進階到主動預警角色，以期作為經營決策的重要參考。經過多年的淬煉，其發展理念與經驗應具相當參考價值，故本論文以個案金融控股公司(以下簡稱個案金控)之實務經驗進行個案研究，除分析個案金控市場風險管理機制的基礎架構外，也將研究重心放在個案金控如何在此基礎架構下，開發多種進階市場風險量化管理功能。本論文除研究個案金控如何完善市場風險值量化機制外，也對各量化功能的實施結果進行分析，以期研究成果可更客觀的作為其他金融控股公司未來發展進階市場風險衡量機制之參考。市場風險風險值經濟價值信託基金操作風險風險因子一般風險值壓力風險值條件風險值增額風險值邊際風險值變異數-共變異數法歷史模擬法蒙地卡羅模擬法隱含波動度厚尾順景氣循環標準法內部模型法市場流動性風險外生性市場流動性風險內生性市場流動性風險流動性調整後風險值壓力測試回溯測試 Market Risk Value at Risk Economic Value Active Management VaR Tracking Error Risk Factor Common VaR Stressed VaR Conditional VaR Incremental VaR Marginal VaR Variance-Covariance Approach Historical Simulation Approach Monte Carlo Simulation Approach Fat Tail Time-Varying Volatility pro-cyclical Standardized Approach Internal Models Approach Implied Volatility Generalized Error Distribution Bernoulli trial test Likelihood ratio test Unconditional Coverage Test Conditional Coverage Test Backward Looking Model Forward Looking Model Forecasting VaR Pearson Correlation Cholesky decomposition Kendall Correlation Copula method Future Volatility Disconnection Market Liquidity Risk Exogenous Market Liquidity Risk Endogenous Market Liquidity Risk Liquidity-adjusted VaR Stress Test Backtesting Net Interest Income Re-pricing Model Maturity Model Duration Model

1

Page generated in 0.1257 seconds