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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

A Preliminary Examination of Data Envelopment Analysis for Prioritizing Improvements of a Set of Independent Four Way Signalized Intersections in a Region

Kumar, Manjunathan 28 January 2003 (has links)
Evaluation of critical transportation infrastructure and their operation is vital for continuous evolution to meet the growing needs of the society with time. The current practice of evaluating signalized intersections has two steps. The first is to determine the level of service at which the intersection is performing. Level of Service (LOS) is based on the average delay per vehicle that gets past the particular intersection under consideration. The second step is to do a capacity analysis. This considers the number of lanes and other infrastructure related factors and also includes the influence of the control strategies. The above-described procedure evaluates any one intersection at a time. It is necessary to compare and rank a given set of intersections for planning purposes such as choosing the sites for improvements. The research work presented in this thesis demonstrates how Data Envelopment Analysis (DEA) can be used as a tool to achieve the purpose of comparing and ranking a given set of comparable intersections. This study elaborates on various ways of representing different characteristics of an intersection. The demonstration has been restricted to four way signalized intersections. The intersections that were used for demonstration as part of this research were created in a controlled random fashion by simulation. / Master of Science
12

Simulation-based Optimisation of a Finished Goods Inventory : A qualitative and quantitative capacity analysis using discrete event simulation / Simuleringsbaserad optimering av ett färdigvarulager : En kvalitativ och kvantitativ kapacitetsanalys med hjälp av diskret händelsessimulering

Barnes, Patrik, Malmbom, Kevin January 2024 (has links)
In this thesis, we have conducted a holistic capacity analysis of Scania's Gearbox and Axle finished goods inventory, as they transition toward electrified mobility and have expectations of higher production volumes. Due to an increase in the volumes, the current capacity of the inventory is expected to not be enough. The purpose of this thesis is to analyse Scania's inventory, from a current and future perspective using a simulation approach and identify ways of managing the increased new production demands. Two objectives are answered in order to get a holistic capacity analysis. The first deals with an organisational perspective and how the organisation and way of working impact the capacity of the process. The goal is to identify barriers in the way of working in order to achieve more efficient production. By conducting semi-structured interviews with co-workers and managers, we gather insight into current problems and improvement areas in the production and IT systems in the inventory. We can also understand how communication flows between customers and suppliers in the internal supply chain and what effect communication has on the FVL process. The second objective deals with how storage time policies affect the production and inventory levels. With the help of discrete event simulation and both current and future production data, we find scenarios where inventory levels are within the limits of the inventory capacity by adjusting the time policies. Our results indicate that by adjusting storage time policies and having efficient production, the capacity of the finished goods inventory is sufficient for future demand scenarios. However, there is a strong connection between organisational aspects and capacity, and in order to handle higher volumes, factors such as communication, IT systems and ways of working need to be improved. Lastly, we provide recommendations for dealing with these issues, such as reducing lay time in inventory, changing the shift schedule for operators 2 and 3, including late order handling in the warehouse management systems, and consolidating the different IT systems into one. / I denna avhandling har vi genomfört en holistisk kapacitetsanalys av Scanias färdigvarulager för växellådor. Eftersom Scania aktivt arbetar med att introducera nya eldrivna produkter samtidigt som de fortsätter produktionen av fossildrivna produkter, förväntas produktionsvolymerna öka. Vid ökade volymer uppstår förväntningar om att kapaciteten i lagret inte kommer att räcka till. Syftet med denna avhandling är att analysera Scanias lager ur både ett nuvarande och ett framtida perspektiv. För att få en holistisk analys besvarar vi två frågeställningar. Det första handlar om ett organisationsperspektiv och hur organisationen och arbetssättet påverkar kapaciteten i processen. Målet är att identifiera hinder i arbetssättet för att uppnå en effektivare produktion. Genom att genomföra semistrukturerade intervjuer med medarbetare och chefer kan vi få insikt i nuvarande problem och förbättringsområden i produktionen, samt IT-system som används i lagret. Vi kan också förstå hur kommunikationen flyter mellan kunder och leverantörer i den interna leveranskedjan och vilken effekt kommunikationen har på FVL-processen. Det andra fokuset ligger på hur liggtiden av produkter påverkar lagernivån. Genom att använda diskret händelsesimulering så kan vi med hjälp av nuvarande och framtida produktionsdata, identifiera scenarier där lagernivå ligger inom gränserna för lagerkapaciteten genom att justera liggtiden. Från våra resultat finner vi att genom att minska liggtiden är kapaciteten av lagret tillräcklig för framtida volymökningar. Det finns dock en stark koppling mellan organisatoriska aspekter och kapacitet, och för att hantera högre volymer behöver faktorer som kommunikation, IT-system och arbetssätt förbättras. Slutligen ger vi rekommendationer för att hantera dessa frågor, såsom att minska liggande tid i lagret, ändra skiftschema för operatör 2 och 3, inkludera hantering av sena order i lagerhanteringssystemen, samt konsolidera de olika IT-systemen till ett enda.
13

Lean e a melhoria de processos de Backoffice : implantação de ferramentas Lean no gerenciamento de um CSC

Sum, Fabiane Flores January 2016 (has links)
Processos de backoffice apresentam um grande impacto nos custos de uma empresa. Centros de Serviço Compartilhados têm sido implementados a fim de controlar e melhorar tais processos. O lean, por sua vez, tem em comum com os CSC o objetivo de trazer excelência a processos. Uma análise da literatura indica haver sinergia entre os métodos e que as ferramentas lean possam promover melhorias que a implantação exclusiva de um CSC não tenha atingido. O objetivo deste trabalho é implantar princípios e ferramentas lean visando a busca de excelência em processos de backoffice, que pertençam a um CSC maduro. Para analisar essa possibilidade foi realizado um estudo de caso em empresa do ramo metalúrgico que já dispõe de um CSC considerado maduro em pesquisas de benchmarking na área. Foram implementados: um estudo de estabilidade e capacidade, posteriormente a prática de gerenciamento diário para implementação de melhorias, ocorrendo coleta de dados qualitativa e quantitativa para avaliação dos seus impactos. Por fim, um questionário foi aplicado para detectar a percepção dos colaboradores a respeito das mudanças obtidas com as ferramentas. Os resultados indicaram que mesmo em um CSC já completamente implantado, havia instabilidade e incapacidade nos processos, detectadas através do estudo de capacidade e estabilidade que são usadas na metodologia Lean. Em relação à utilização de gerenciamento diário, agregado à gestão visual, observou-se ser a abordagem que possibilitaria melhores resultados Em uma pesquisa realizada com todos os níveis hierárquicos envolvidos, que comparava o cenário anterior às ferramentas, um mês após a implantação e a expectativa para o cenário em um ano, foi possível comprovar que 64% dos princípios Lean apresentados por Liker (2005) foram melhorados no primeiro mês e que existe uma expectativa de melhorar 95% dos princípios Lean e das funções da comunicação no próximo um ano com os estudos de capacidade/estabilidade e gerenciamento diário. Observou-se que, enquanto os estudos de capacidade e estabilidade detectam as falhas, o gerenciamento diário permite operacionalizar as mudanças, ao mesmo tempo em que reforça os princípios lean. Embora não possam ser generalizáveis os resultados obtidos, pode-se dizer que neste estudo foi possível atingir melhores níveis de desempenho dos processos de um CSC maduro utilizando ferramentas lean, confirmando a hipótese inicial. / Backoffice processes have a high impact on the costs of a company. Shared Service Centers (SSC) has been implemented in order to control and improve these processes. The lean methodology, in turn, has in common with the SSC the aim to bring excellence to processes. A literature review indicates that there is synergy between the methods and the lean tools can make improvements that exclusive implementation of a CSC has not reached. The aim of this study is to implement lean principles and tools aimed at the pursuit of excellence in backoffice processes, belonging to a mature SSC. To test the initial hypothesis it was conducted a case study in a metal industry that already has a mature SSC. It was implemented: stability and capacity analysis and the practice of daily management to implement improvements, occurring qualitative and quantitative data collection to assess its impact. Finally, a questionnaire was applied to detect the perception of employees about the changes obtained with the tools. The results indicated that even in a SSC already fully deployed, there is instability and failure in processes, detected by stability and capacity analysis that are used in lean methodology. Regarding the use of daily management, added to the visual management, was noted to be the approach would enable better results In a survey of all levels involved, which compared the previous scenario before the tools, one month after implantation and the expectation for the scenario in a year, it was possible to prove that 64% of the lean principles have been improved in the first month and it is expected to improve 95% of the lean principles and communication functions in one year with stability and capacity analysis and daily management. It was observed that, while the stability and capacity analysis detect faults, the daily management enables operational changes at the same time that increases lean principles perception. Although the results obtained may not be generalizable, it can be said that in this study it was possible to achieve better performance levels of processes of a mature CSC using lean tools, confirming the initial hypothesis.
14

Lean e a melhoria de processos de Backoffice : implantação de ferramentas Lean no gerenciamento de um CSC

Sum, Fabiane Flores January 2016 (has links)
Processos de backoffice apresentam um grande impacto nos custos de uma empresa. Centros de Serviço Compartilhados têm sido implementados a fim de controlar e melhorar tais processos. O lean, por sua vez, tem em comum com os CSC o objetivo de trazer excelência a processos. Uma análise da literatura indica haver sinergia entre os métodos e que as ferramentas lean possam promover melhorias que a implantação exclusiva de um CSC não tenha atingido. O objetivo deste trabalho é implantar princípios e ferramentas lean visando a busca de excelência em processos de backoffice, que pertençam a um CSC maduro. Para analisar essa possibilidade foi realizado um estudo de caso em empresa do ramo metalúrgico que já dispõe de um CSC considerado maduro em pesquisas de benchmarking na área. Foram implementados: um estudo de estabilidade e capacidade, posteriormente a prática de gerenciamento diário para implementação de melhorias, ocorrendo coleta de dados qualitativa e quantitativa para avaliação dos seus impactos. Por fim, um questionário foi aplicado para detectar a percepção dos colaboradores a respeito das mudanças obtidas com as ferramentas. Os resultados indicaram que mesmo em um CSC já completamente implantado, havia instabilidade e incapacidade nos processos, detectadas através do estudo de capacidade e estabilidade que são usadas na metodologia Lean. Em relação à utilização de gerenciamento diário, agregado à gestão visual, observou-se ser a abordagem que possibilitaria melhores resultados Em uma pesquisa realizada com todos os níveis hierárquicos envolvidos, que comparava o cenário anterior às ferramentas, um mês após a implantação e a expectativa para o cenário em um ano, foi possível comprovar que 64% dos princípios Lean apresentados por Liker (2005) foram melhorados no primeiro mês e que existe uma expectativa de melhorar 95% dos princípios Lean e das funções da comunicação no próximo um ano com os estudos de capacidade/estabilidade e gerenciamento diário. Observou-se que, enquanto os estudos de capacidade e estabilidade detectam as falhas, o gerenciamento diário permite operacionalizar as mudanças, ao mesmo tempo em que reforça os princípios lean. Embora não possam ser generalizáveis os resultados obtidos, pode-se dizer que neste estudo foi possível atingir melhores níveis de desempenho dos processos de um CSC maduro utilizando ferramentas lean, confirmando a hipótese inicial. / Backoffice processes have a high impact on the costs of a company. Shared Service Centers (SSC) has been implemented in order to control and improve these processes. The lean methodology, in turn, has in common with the SSC the aim to bring excellence to processes. A literature review indicates that there is synergy between the methods and the lean tools can make improvements that exclusive implementation of a CSC has not reached. The aim of this study is to implement lean principles and tools aimed at the pursuit of excellence in backoffice processes, belonging to a mature SSC. To test the initial hypothesis it was conducted a case study in a metal industry that already has a mature SSC. It was implemented: stability and capacity analysis and the practice of daily management to implement improvements, occurring qualitative and quantitative data collection to assess its impact. Finally, a questionnaire was applied to detect the perception of employees about the changes obtained with the tools. The results indicated that even in a SSC already fully deployed, there is instability and failure in processes, detected by stability and capacity analysis that are used in lean methodology. Regarding the use of daily management, added to the visual management, was noted to be the approach would enable better results In a survey of all levels involved, which compared the previous scenario before the tools, one month after implantation and the expectation for the scenario in a year, it was possible to prove that 64% of the lean principles have been improved in the first month and it is expected to improve 95% of the lean principles and communication functions in one year with stability and capacity analysis and daily management. It was observed that, while the stability and capacity analysis detect faults, the daily management enables operational changes at the same time that increases lean principles perception. Although the results obtained may not be generalizable, it can be said that in this study it was possible to achieve better performance levels of processes of a mature CSC using lean tools, confirming the initial hypothesis.
15

Lean e a melhoria de processos de Backoffice : implantação de ferramentas Lean no gerenciamento de um CSC

Sum, Fabiane Flores January 2016 (has links)
Processos de backoffice apresentam um grande impacto nos custos de uma empresa. Centros de Serviço Compartilhados têm sido implementados a fim de controlar e melhorar tais processos. O lean, por sua vez, tem em comum com os CSC o objetivo de trazer excelência a processos. Uma análise da literatura indica haver sinergia entre os métodos e que as ferramentas lean possam promover melhorias que a implantação exclusiva de um CSC não tenha atingido. O objetivo deste trabalho é implantar princípios e ferramentas lean visando a busca de excelência em processos de backoffice, que pertençam a um CSC maduro. Para analisar essa possibilidade foi realizado um estudo de caso em empresa do ramo metalúrgico que já dispõe de um CSC considerado maduro em pesquisas de benchmarking na área. Foram implementados: um estudo de estabilidade e capacidade, posteriormente a prática de gerenciamento diário para implementação de melhorias, ocorrendo coleta de dados qualitativa e quantitativa para avaliação dos seus impactos. Por fim, um questionário foi aplicado para detectar a percepção dos colaboradores a respeito das mudanças obtidas com as ferramentas. Os resultados indicaram que mesmo em um CSC já completamente implantado, havia instabilidade e incapacidade nos processos, detectadas através do estudo de capacidade e estabilidade que são usadas na metodologia Lean. Em relação à utilização de gerenciamento diário, agregado à gestão visual, observou-se ser a abordagem que possibilitaria melhores resultados Em uma pesquisa realizada com todos os níveis hierárquicos envolvidos, que comparava o cenário anterior às ferramentas, um mês após a implantação e a expectativa para o cenário em um ano, foi possível comprovar que 64% dos princípios Lean apresentados por Liker (2005) foram melhorados no primeiro mês e que existe uma expectativa de melhorar 95% dos princípios Lean e das funções da comunicação no próximo um ano com os estudos de capacidade/estabilidade e gerenciamento diário. Observou-se que, enquanto os estudos de capacidade e estabilidade detectam as falhas, o gerenciamento diário permite operacionalizar as mudanças, ao mesmo tempo em que reforça os princípios lean. Embora não possam ser generalizáveis os resultados obtidos, pode-se dizer que neste estudo foi possível atingir melhores níveis de desempenho dos processos de um CSC maduro utilizando ferramentas lean, confirmando a hipótese inicial. / Backoffice processes have a high impact on the costs of a company. Shared Service Centers (SSC) has been implemented in order to control and improve these processes. The lean methodology, in turn, has in common with the SSC the aim to bring excellence to processes. A literature review indicates that there is synergy between the methods and the lean tools can make improvements that exclusive implementation of a CSC has not reached. The aim of this study is to implement lean principles and tools aimed at the pursuit of excellence in backoffice processes, belonging to a mature SSC. To test the initial hypothesis it was conducted a case study in a metal industry that already has a mature SSC. It was implemented: stability and capacity analysis and the practice of daily management to implement improvements, occurring qualitative and quantitative data collection to assess its impact. Finally, a questionnaire was applied to detect the perception of employees about the changes obtained with the tools. The results indicated that even in a SSC already fully deployed, there is instability and failure in processes, detected by stability and capacity analysis that are used in lean methodology. Regarding the use of daily management, added to the visual management, was noted to be the approach would enable better results In a survey of all levels involved, which compared the previous scenario before the tools, one month after implantation and the expectation for the scenario in a year, it was possible to prove that 64% of the lean principles have been improved in the first month and it is expected to improve 95% of the lean principles and communication functions in one year with stability and capacity analysis and daily management. It was observed that, while the stability and capacity analysis detect faults, the daily management enables operational changes at the same time that increases lean principles perception. Although the results obtained may not be generalizable, it can be said that in this study it was possible to achieve better performance levels of processes of a mature CSC using lean tools, confirming the initial hypothesis.
16

Maximum Capacity Antenna Design for an Indoor MIMO UWB Communication System

Liu, Ran, Liu, Hao January 2012 (has links)
Ultra-wideband (UWB) offers a high data rate transmission, however it only can be used in short distance communication due to its low power restricted by regulations, therefore it is applicable for an indoor scenario. Within an enclosed (indoor) scenario, there exist many possible multipaths of electromagnetic waves which lead to an effect known as fading [Big07]. Since SISO systems suffer severely from it, in contrast, multiple-output-multiple-input (MIMO) systems take advantage of this multipath/diversity effect. Typical MIMO system utilizes antenna arrays to generate subchannels, but it has no guarantee of orthogonal channels or maximum capacity. Using a new antenna synthesis algorithm, optimal subchannels can be computed by decomposing the MIMO channel into parallel SISO subchannels through the employment of sampling antennas. Thereafter optimal real word antennas can be designed according to the synthesized antenna radiation pattern which result in the reduced hardware. The goal of this thesis will be expressed as follows: Firstly, a good strategy planning to reduce computing effort should be realized since all the design parameters to be analyzed are frequency dependent. Furthermore, a systematic framework of the synthesis must be designed for the UWB band. Lastly, the corresponding real world antenna should be designed and verified. In this thesis, a systematic synthesis framework has be developed and analyzed for the UWB spectrum. The channel matrix acquisition, the design of the ‘sampling antennas’ along with the algorithm to decompose the MIMO channel into parallel independent SISO subchannels are discussed in detail. Two realizations of the real world antennas as well as all the challenges in the design process are also presented. As consequences, an antenna system with optimal radiation pattern has been synthesized. This antenna system radiates orthogonal channels with sufficient power and has fixed beamforming (direction optimized according to the scenario and with averaging over various positions along with rotations) at the transmitter and receiver. The maximum capacity takes into account the scenario, frequency band, physical available space for the antenna array and polarization (added degree of freedom). This work also organizes the antenna synthesis algorithm for UWB in a systematic framework, meeting the objectives of the project. / In this thesis, a UWB antenna synthesis based on the averaging strategies for the predefined indoor communication scenarios has been proposed, which contains both the indoor communication theoretical analysis and real world realization. The algorithm can be applied in an arbitrary indoor scenario over ultra wideband frequency. All synthesized results demonstrated that the designed sampling antenna configuration is able to provide optimized solutions. The synthesis method is based on computing optimal antenna configurations for a MIMO ultrawideband system. In order to maximize the throughput, there exists a sampling volume for both transmit and receive antennas. As such, the face-centered and body-centered cubic antenna arrays are utilized. Given that the system operates in the UWB band with a cognitive feature, the type of antenna, orientation, placement and MIMO diversity scheme have been well investigated. The radiation patterns of the antenna array cover the sampling volume and the bandwidth cover the UWB band. The goal of this thesis work concentrates on the analysis of an indoor communication to find an optimum solution on the antenna configuration and placement. The final objective was to design and realize an optimal MIMO-UWB antenna system. / Add: Waldhornstrasse 19, Karlsruhe, 76131, Germany Tel: +49 176 34467663
17

Urban Air Mobility: Demand Estimation and Feasibility Analysis

Rimjha, Mihir 09 February 2022 (has links)
This dissertation comprises multiple studies surrounding demand estimation, feasibility and capacity analysis, and environmental impact of the Urban Air Mobility (UAM) or Advanced Air Mobility (AAM). UAM is a concept aerial transportation mode designed for intracity transport of passengers and cargo utilizing autonomous (or piloted) electric vehicles capable of Vertical Take-Off and Landing (VTOL) from dense and congested areas. While the industry is preparing to introduce this revolutionary mode in urban areas, realizing the scope and understanding the factors affecting the attractiveness of this mode is essential. The success of UAM depends on its operational efficiency and the relative utility it offers to current travelers. The studies presented in this dissertation primarily focus on analyzing urban travelers' current behavior using revealed preference data and estimating the potential UAM demand for different trip purposes in multiple U.S. urban areas. Chapter II presents a methodology to estimate commuter demand for UAM operations in the Northern California region. A mode-choice model is calibrated from the commuter mode-choice behavior observed in the survey data. An integrated demand estimation framework is developed utilizing the calibrated mode-choice model to estimate UAM demand and place vertiports. The feasibility of commuter UAM operations in Northern California is further analyzed through a series of sensitivity analyses. This study was published in Transportation Research Part A: Policy and Practice journal. In an effort to analyze the feasibility of UAM operations in different use cases, demand estimation frameworks are developed to estimate UAM demand in the airport access trips segment. Chapter III and Chapter IV focus on developing the UAM Concept of Operations (ConOps) and demand estimation methodology for airport access trips to Dallas-Fort Worth International Airport (DFW)/Dallas Love Field Airport (DAL) and Los Angeles International Airport (LAX), respectively. Both studies utilize the latest available originating passenger survey data to understand arriving passengers' mode-choice behavior at the airport. Mode-choice conditional logit models are calibrated from the survey data, further used to estimate UAM demand. The former study is published in the AIAA Aviation 2021 Conference proceeding, and the latter is published in ICNS 2021 Conference proceedings. UAM vertiport capacity may be a barrier to the scalability of UAM operations. A heavy concentration of UAM demand is observed in specific areas such as Central Business Districts (CBD) during the spatial analysis of estimated UAM demand. However, vertiport size could be limited due to land availability and high infrastructure costs in CBDs. Therefore, operational efficiency is critical for capturing maximum UAM demand with limited vertiport size. The study included in Chapter V focuses on analyzing factors impacting vertiport capacity. A discrete-event simulation model is developed to simulate a full day of commuter operations at the San Francisco Financial District's busiest vertiport. Besides calculating the capacity of different fundamental vertiport designs, sensitivity analyses are carried to understand the impact of several assumptions such as service time at landing pads, service time at parking stall, charging rate, etc. The study explores the importance of pre-positioning UAM vehicles during the time of imbalance between arrival and departure requests. This study is published in ICNS 2021 Conference proceedings. Community annoyance from aviation noise has often been a reason for limiting commercial operations at several major airports globally. Busy airports are located in urban areas with high population densities where noise levels in nearby communities could govern capacity constraints. Commercial aviation noise is only a concern during landing and take-offs. Hence, the impact is limited to communities close to the airport. However, UAM vehicles would be operated at much lower altitudes and have more frequent taking-off and landing operations. Since the UAM operations would mostly be over dense urban spaces, the noise potential is significantly high. Chapter VI includes a study on preliminary estimation of noise levels from commuter UAM operations in Northern California and the Dallas-Fort Worth region. This study is published in the AIAA Aviation 2021 Conference proceedings. The final chapter in this dissertation explores the impact of airspace restrictions on UAM demand potential in New York City. Integration of UAM operations in the current National Airspace System (NAS) has been recognized as critical in developing the UAM ecosystem. Several pieces of urban airspace are currently controlled by Air Traffic Control (ATC), where commercial operation density is high. Even though the initial operations are expected to be controlled by the current ATC, the extent to which UAM operations would be allowed in the controlled spaces is still unclear. As the UAM system matures and the ecosystem evolves, integrating UAM traffic with other airspace management might relax certain airspace restrictions. Relaxation of airspace restrictions could increase the attractiveness of UAM due to a decrease in travel time/cost and relatively more optimal placement of vertiports. Quantifying the impact of different levels of airspace restrictions requires an integrated framework that can capture utility changes for UAM under different operational ConOps. This analysis uses a calibrated mode-choice model, restriction-sensitive vertiport placement methodology, and demand estimation process. This study has been submitted for ICNS 2022 Conference. / Doctor of Philosophy / Urban Air Mobility (UAM) or Advanced Air Mobility (AAM) are concept transportation modes currently in development. It proposes transporting passengers and cargo in urban areas using all-electric Vertical Take-Off and Landing (eVTOL) vehicles. UAM is a multi-modal concept involving low-altitude aerial transport. The high capital costs involved in developing vehicles and infrastructure suggests the need for meticulous planning and strong strategy development in the rolling out of UAM. Moreover, urban travelers are relatively more sensitive to travel time savings and travel time reliability; therefore, the efficiency of UAM is critical for its success. This dissertation comprises multiple studies surrounding demand estimation, feasibility and capacity analysis, and the environmental impact of UAM. To estimate the potential for UAM, we need first to understand the mode-choice making behavior of urban travelers and then estimate the relative utility UAM could possibly offer. The studies presented in this dissertation primarily focus on analyzing urban travelers' current behavior and estimating the potential UAM demand for different trip purposes in multiple U.S. urban areas. The system planners would need to know the individual or combined effect of various parameters in the system, such as cost of UAM, network size of UAM, etc., on UAM potential. Therefore, sensitivity analyses with respect to UAM demand are performed against various framework parameters. Capacity constraints are not initially considered for potential demand estimation. However, like any other transportation mode, UAM could suffer from capacity issues that can cause operational delays. A simulation study is dedicated to model UAM operations at a vertiport and estimating factors affecting vertiport capacity. After observing the demand potential for certain optimistic scenarios, we realized the possibility of a large number of low-flying vehicles, which could cause annoyance and environmental impacts. Therefore, the following study focuses on developing a noise estimation framework from a full-day of UAM operations and estimating a highly annoyed population in the Bay Area and Dallas-Fort Worth Region. In our studies, modeling restricted airspaces (due to commercial operations at large airports) was always a critical part of the analysis. The urban airspaces are already quite congested in some urban areas, and we assumed that UAM would not operate in the restricted airspaces. The last study in this dissertation focuses on quantifying the impact of different levels of airspace restrictions on UAM demand potential in New York. It would help system planners gauge the level of integration required between the UAM and National Airspace System (NAS).
18

Data Collection and Capacity Analysis in Large-scale Wireless Sensor Networks

Ji, Shouling 01 August 2013 (has links)
In this dissertation, we study data collection and its achievable network capacity in Wireless Sensor Networks (WSNs). Firstly, we investigate the data collection issue in dual-radio multi-channel WSNs under the protocol interference model. We propose a multi-path scheduling algorithm for snapshot data collection, which has a tighter capacity bound than the existing best result, and a novel continuous data collection algorithm with comprehensive capacity analysis. Secondly, considering most existing works for the capacity issue are based on the ideal deterministic network model, we study the data collection problem for practical probabilistic WSNs. We design a cell-based path scheduling algorithm and a zone-based pipeline scheduling algorithm for snapshot and continuous data collection in probabilistic WSNs, respectively. By analysis, we show that the proposed algorithms have competitive capacity performance compared with existing works. Thirdly, most of the existing works studying the data collection capacity issue are for centralized synchronous WSNs. However, wireless networks are more likely to be distributed asynchronous systems. Therefore, we investigate the achievable data collection capacity of realistic distributed asynchronous WSNs and propose a data collection algorithm with fairness consideration. Theoretical analysis of the proposed algorithm shows that its achievable network capacity is order-optimal as centralized and synchronized algorithms do and independent of network size. Finally, for completeness, we study the data aggregation issue for realistic probabilistic WSNs. We propose order-optimal scheduling algorithms for snapshot and continuous data aggregation under the physical interference model.
19

Hybrid Gates approach for R and D product portfolio management

Koh, Alex January 2012 (has links)
Companies today are aggressively finding ways to improve top-line growth by introducing innovative products faster to the market. To achieve both innovation and accelerated rollout, many are turning to techniques such as Stage Gate approaches to improve engineering and marketing collaborations to clarify short term resource allocations (day to day plan with employee assignment). While Stage Gate approaches have been shown to result in better project coordination and faster time to market by doing projects right, research also indicates the need to ensure alignment to company strategy by doing the right projects within the allocated annual budget through medium term (rough cut capacity plan with employee requirements) and long term resource allocations (business / strategic plan with funding requirements). Today, such medium to long term resource allocation methodologies tend to be broadly consolidated under Research and Development (R&D) product portfolio management. We argue that there is value in a philosophical change in viewing R&D product portfolio management from the context of (1.) long and medium term resource allocation phases separately, (2.) focusing on the overlapping regions between long and medium term and between medium and short term resource allocation phases and (3.) the evolving resource allocation perspective (monetary to headcount to skillset) through these phases. Cooper et al note that for R&D product portfolio management and the Stage Gate process to work together, one can expect one of two scenarios - a gates dominated approach (where the prioritization and resource decisions are made at short term focused Stage Gates) or a portfolio reviews dominated approach (where the prioritization and resource decisions are made at the long term focused portfolio reviews). We propose that with appropriate focus given to the medium term phase, a third approach that we call a Hybrid Gates approach can exist in a "gates dominated" environment. A case study on Freescale Semiconductor was used as an empirical inquiry to gain deeper understanding on the perceived value of this approach within a real-life context. Triangulating between structured surveys, unstructured surveys, and focused interviews; we were able to show perceived value to the organization in the following areas: (1.) Enhancing the understanding of decision maker's decision and solution spaces, (2.) Clarifying strategic expressions and "stress testing" new strategies, (3.) Improving horizontal and vertical communication within the organization and (4.) Aiding in objectivity in R&D investment allocation. Furthermore, we were able to conceptually show how this approach retains the advantages of the gates dominated and portfolio dominated approaches while minimizing their respective weaknesses. This research is novel and unique as we have not found any research literature that focuses on a Hybrid Gates approach perspective or studies where the implementation of MO-ZOLP is: (1.) this large in scale and (2.) designed specifically to support a Stage Gate dominated environment. We believe that this research contributes to the practising educator and researcher by providing them with an alternative approach on R&D project portfolio management in complex organizations that are using a Stage Gate process. We also believe that this research is valuable to the practitioner by providing them with a practical process and methodology in which change management for such activities can be achieved. In addition, we assessed the on-going value added to the organization, thus linking theory to practice and finally, to outcome.
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Kapcitetsanalys i Emballeringen : Emballeringslinjen: Kapacitetsanalys och flödesåtgärder inför potentiellproduktionsökning / Capacity Analysis in the Wrapping Line : Wrapping Line: An Analysis of Capacity and Arrangements in Flow for aPotential Increase in Production

Östlund, Hugo January 2021 (has links)
This project was implemented during spring 2021 as a bachelor thesis for the Bachelor Engineering Program in Mechanical Engineering at Karlstads University. The project wascarried out in collaboration with Stora Enso Skoghall Mill, which produces different types of cardboard material. In 2020, the overall production capacity was 875 000 tons of cardboard material. In November 2020 Skoghall Mill was authorized to precede an investigation regarding a possible production increase, which would result in a self-sufficient pulp production and an increase of 120 000 tons cardboard material per year.  The cardboard is winded into rolls before they are being transported to the customers. Before the transportation, the reels are given a protecting wrapping. This procedure occurs in a production segment called the Wrapping Line, which is a part of the Finishing Department. The Wrapping Line is one of the production areas that would be affected by a potential increase of production. Therefore, the responsible of the unit wanted to examine if the Wrapping Linehad enough capacity for a potential increase of this size.  The purpose of this paper was to carry out a capacity analysis for the line, identify bottlenecks in the flow and to present arrangements to make the production line more effective. Furthermore, an additional purpose was to identify how long the maintenance stops could beif the potential production increase is approved.  The capacity analysis was carried out using a simulation software called JaamSim. A model of the existing system was built in JaamSim, which afterwards was analyzed. The capacity analysis showed that Emballeringen has the needed capacity if the production increase isapproved. The capacity analysis also displayed the possible length of maintenance stops. Arrangements in flow was presented and prioritized so that the capacity in the Wrapping Linewould increase further.

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