• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 2
  • 1
  • Tagged with
  • 4
  • 4
  • 4
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 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.
1

Methods for Utilizing Connected Vehicle Data in Support of Traffic Bottleneck Management

Khazraeian, Samaneh 27 October 2017 (has links)
The decision to select the best Intelligent Transportation System (ITS) technologies from available options has always been a challenging task. The availability of connected vehicle/automated vehicle (CV/AV) technologies in the near future is expected to add to the complexity of the ITS investment decision-making process. The goal of this research is to develop a multi-criteria decision-making analysis (MCDA) framework to support traffic agencies’ decision-making process with consideration of CV/AV technologies. The decision to select between technology alternatives is based on identified performance measures and criteria, and constraints associated with each technology. Methods inspired by the literature were developed for incident/bottleneck detection and back-of-queue (BOQ) estimation and warning based on connected vehicle (CV) technologies. The mobility benefits of incident/bottleneck detection with different technologies were assessed using microscopic simulation. The performance of technology alternatives was assessed using simulated CV and traffic detector data in a microscopic simulation environment to be used in the proposed MCDA method for the purpose of alternative selection. In addition to assessing performance measures, there are a number of constraints and risks that need to be assessed in the alternative selection process. Traditional alternative analyses based on deterministic return on investment analysis are unable to capture the risks and uncertainties associated with the investment problem. This research utilizes a combination of a stochastic return on investment and a multi-criteria decision analysis method referred to as the Analytical Hierarchy Process (AHP) to select between ITS deployment alternatives considering emerging technologies. The approach is applied to an ITS investment case study to support freeway bottleneck management. The results of this dissertation indicate that utilizing CV data for freeway segments is significantly more cost-effective than using point detectors in detecting incidents and providing travel time estimates one year after CV technology becomes mandatory for all new vehicles and for corridors with moderate to heavy traffic. However, for corridors with light, there is a probability of CV deployment not being effective in the first few years due to low measurement reliability of travel times and high latency of incident detection, associated with smaller sample sizes of the collected data.
2

Holistic Mine Management By Identification Of Real-Time And Historical Production Bottlenecks

Kahraman, Muhammet Mustafa January 2015 (has links)
Mining has a long history of production and operation management. Economies of scales have changed drastically and technology has transformed the mining industry significantly. One of the most important technological improvements is increased equipment, human, and plant tracking capabilities. This provided a continuous data stream to the decision makers, considering dynamic operational conditions. However, managerial approaches did not change in parallel. Even though many process improvement tools using equipment/human/plant tracking capabilities were developed (Fleet Management Systems, Plant Monitoring Systems, Workforce Management Systems etc.), to date there is no holistic approach or system to manage the entire value chain in mining. Mining operations are designed and managed around the already known system designated bottlenecks. However, contrary to common belief in mining, bottlenecks are not static. They can shift from one process or location to another. It is important for management to be aware of the new bottlenecks, since their decisions will be effected. Therefore, identification of true bottlenecks in real-time will help tactical level decisions (use of buffers, resource transfer), and identification of historical bottlenecks will help strategic-level decisions (investments, increasing capacity etc.). This thesis aims to address the managerial focus on the true bottlenecks. This is done by first identifying and ranking true bottlenecks in the system. The study proposes a methodology for creating Bottleneck Identification Model (BIM) that can identify true bottlenecks in a value chain in real-time or historically, depending on the available data. This approach consists of three phases to detect and rank the bottlenecks. In the first phase, the system is defined and variables are identified. In the second phase, the capacity, rates, and buffers are computed. In the third phase, considering particularities of the mine exceptions are added by taking mine characteristics into account, and bottlenecks are identified and ranked.
3

Lagerdimensionering vid bearbetningsproduktionen hos Volvo Powertrain i Skövde / Inventory Control in Machining Production at Volvo Powertrain in Skövde

Engström, Marcus, Gembäck, Johan January 2009 (has links)
<p>Volvo Powertrain tillverkar motorer och drivlinor till AB Volvos samtliga dotterbolag förutom Volvo Aero. Vid anläggningen i Skövde tillverkas motorer och delar till motorer och växellådor och vid anläggningen finns alla tre nödvändiga produktionsområden; gjuteri, bearbetning och montering. När rådande lågkonjunktur slog till stod bearbetningen med väldigt höga lagernivåer vilka företaget snabbt tvingades sänka då det blev huvudfokus från koncernledningen att minska det bundna kapitalet. Utan egentlig analys sattes nya gränsnivåer för lagren inom samtliga avdelningar på bearbetning och målet med examensarbetet har varit att ta fram en metod för att dimensionera säkerhetslagret på optimal nivå med bibehållen hög leveranssäkerhet. Därigenom skulle företagets lagernivåer kunna styrkas med hjälp av en teoretisk grund.</p><p>Som utgångspunkt har en lagernivådimensionering med servicenivåkonceptet SERV2 och där alla artiklar tillåts ha differentierade servicenivåer använts. Utifrån Volvo Powertrains förutsättningar har ett optimeringsproblem formulerats. Det visar sig vid närmare studie av detta problem att det är ett ickelinjärt heltalsproblem, vilket försvårar lösningsgången avsevärt. För att komma runt dessa beräkningsmässiga problem approximerades ett av bivillkoren för att ta fram en lösningsheuristik. Dock upptäcktes efter ett antal försök att denna inte uppfyllde samtliga bivillkor alla gånger varför det beslutades att låta heuristikens lösning fungera som startlösning till en sökmetod vid letandet efter lokalt optimum.</p><p>I rapporten beskrivs ingående vilka parametrar som behöver mätas och hur för att alla avdelningar ska använda samma mätmetod vid framtagande av nödvändiga indata. Metoden har implementerats i Excel där användaren får mata in värden på dessa parametrar vilka sedan används i de nödvändiga beräkningarna. De data som sedan presenteras som resultat är vilka batchstorlekar som ska produceras, vilken säkerhetslagernivå som ska gälla, vid vilken nivå en ny beställning ska genomföras samt uppnådd leveranssäkerhet.</p><p>Utöver denna del presenteras även ett nytt sätt att sköta lagerstyrningen i de fall där det finns en flaskhals tidigt i produktionsflödet och som därmed bestämmer produktionstakten i resten av flödet. Eftersom detta skapar en sugstyrning genom flödet där mellanlager är onödiga blir produktionen mer känslig för störningar, vilket leder till att tidigare dolda problem inom produktionen kommer upp till ytan.</p><p>Resultaten av genomförda simuleringar visar att metoden innebär minskade lagernivåer samtidigt som önskad leveranssäkerhet upprätthålls. Genom att implementera metoden kommer bearbetningen vid Volvo Powertrain i Skövde att få en metod att stödja sina beslut på vilken optimerar lagernivåerna samtidigt som en hög leveranssäkerhet garanteras.</p> / <p>Volvo Powertrain produces engines and drivelines to AB Volvo's subsidiaries except to Volvo Aero. At the plant in Skövde engines and parts for engines and transmissions are manufactured and the facility includes all three essential areas of production; casting, machining and assembly. When the current recession hit Volvo Powertrain were working with very high inventory levels, which the company was quickly forced to cut since it became the main focus of the group management to reduce the capital tied up. Without conducting any proper analysis were new stock limit levels set in all sections of the company. The aim of this master thesis was to develop a methodology for setting of safety stocks at optimum levels while maintaining high delivery reliability. This would allow the company's inventory levels to be defined using a theoretical basis.</p><p>As a starting point, a stock-level design with the service concept SERV2 together with allowing all articles to have differentiated levels of service was used. On the basis of Volvo Powertrain's conditions an optimization problem have been formulated. It turns out that this problem is a nonlinear integer problem, which makes solution very difficult. To overcome these computational problems one of the constraints were approximated in purpose to develop a heuristics. However, it was detected after several attempts, that the heuristics did not satisfy all the constraints at all times so it was decided to use the heuristic solution to act as a starting solution to a search method to search for a local optimum.</p><p>The report describes in detail the parameters that need to be measured and how to ensure that all departments are using the same method in the preparation of the necessary input data. The method has been implemented in Excel where the user may enter values for these parameters which are then used in the necessary calculations. The results that are presented includes what batch-sizes that are to be produced, the safety stock level to be applied, which re-order point  to be used and achieved service level.</p><p>In addition the report also presents a new way to manage stock control in cases where there is a bottleneck early in the production flow which therefore determines the rate of production in the rest of the flow. Since this creates a pull system through the process flow, the stock between the production steps is unnecessary. A drawback is that the production becomes more sensitive to disturbances but means that previously hidden problems in the production reach the surface.</p><p>The results of the simulations attempted show that the method involves reduction of inventory levels at the same time as the desired service level is maintained. By implementing the method Volvo Powertrain in Skövde will have a method to support their decisions which optimizes inventory levels at the same time as high service levels are guaranteed.</p>
4

Lagerdimensionering vid bearbetningsproduktionen hos Volvo Powertrain i Skövde / Inventory Control in Machining Production at Volvo Powertrain in Skövde

Engström, Marcus, Gembäck, Johan January 2009 (has links)
Volvo Powertrain tillverkar motorer och drivlinor till AB Volvos samtliga dotterbolag förutom Volvo Aero. Vid anläggningen i Skövde tillverkas motorer och delar till motorer och växellådor och vid anläggningen finns alla tre nödvändiga produktionsområden; gjuteri, bearbetning och montering. När rådande lågkonjunktur slog till stod bearbetningen med väldigt höga lagernivåer vilka företaget snabbt tvingades sänka då det blev huvudfokus från koncernledningen att minska det bundna kapitalet. Utan egentlig analys sattes nya gränsnivåer för lagren inom samtliga avdelningar på bearbetning och målet med examensarbetet har varit att ta fram en metod för att dimensionera säkerhetslagret på optimal nivå med bibehållen hög leveranssäkerhet. Därigenom skulle företagets lagernivåer kunna styrkas med hjälp av en teoretisk grund. Som utgångspunkt har en lagernivådimensionering med servicenivåkonceptet SERV2 och där alla artiklar tillåts ha differentierade servicenivåer använts. Utifrån Volvo Powertrains förutsättningar har ett optimeringsproblem formulerats. Det visar sig vid närmare studie av detta problem att det är ett ickelinjärt heltalsproblem, vilket försvårar lösningsgången avsevärt. För att komma runt dessa beräkningsmässiga problem approximerades ett av bivillkoren för att ta fram en lösningsheuristik. Dock upptäcktes efter ett antal försök att denna inte uppfyllde samtliga bivillkor alla gånger varför det beslutades att låta heuristikens lösning fungera som startlösning till en sökmetod vid letandet efter lokalt optimum. I rapporten beskrivs ingående vilka parametrar som behöver mätas och hur för att alla avdelningar ska använda samma mätmetod vid framtagande av nödvändiga indata. Metoden har implementerats i Excel där användaren får mata in värden på dessa parametrar vilka sedan används i de nödvändiga beräkningarna. De data som sedan presenteras som resultat är vilka batchstorlekar som ska produceras, vilken säkerhetslagernivå som ska gälla, vid vilken nivå en ny beställning ska genomföras samt uppnådd leveranssäkerhet. Utöver denna del presenteras även ett nytt sätt att sköta lagerstyrningen i de fall där det finns en flaskhals tidigt i produktionsflödet och som därmed bestämmer produktionstakten i resten av flödet. Eftersom detta skapar en sugstyrning genom flödet där mellanlager är onödiga blir produktionen mer känslig för störningar, vilket leder till att tidigare dolda problem inom produktionen kommer upp till ytan. Resultaten av genomförda simuleringar visar att metoden innebär minskade lagernivåer samtidigt som önskad leveranssäkerhet upprätthålls. Genom att implementera metoden kommer bearbetningen vid Volvo Powertrain i Skövde att få en metod att stödja sina beslut på vilken optimerar lagernivåerna samtidigt som en hög leveranssäkerhet garanteras. / Volvo Powertrain produces engines and drivelines to AB Volvo's subsidiaries except to Volvo Aero. At the plant in Skövde engines and parts for engines and transmissions are manufactured and the facility includes all three essential areas of production; casting, machining and assembly. When the current recession hit Volvo Powertrain were working with very high inventory levels, which the company was quickly forced to cut since it became the main focus of the group management to reduce the capital tied up. Without conducting any proper analysis were new stock limit levels set in all sections of the company. The aim of this master thesis was to develop a methodology for setting of safety stocks at optimum levels while maintaining high delivery reliability. This would allow the company's inventory levels to be defined using a theoretical basis. As a starting point, a stock-level design with the service concept SERV2 together with allowing all articles to have differentiated levels of service was used. On the basis of Volvo Powertrain's conditions an optimization problem have been formulated. It turns out that this problem is a nonlinear integer problem, which makes solution very difficult. To overcome these computational problems one of the constraints were approximated in purpose to develop a heuristics. However, it was detected after several attempts, that the heuristics did not satisfy all the constraints at all times so it was decided to use the heuristic solution to act as a starting solution to a search method to search for a local optimum. The report describes in detail the parameters that need to be measured and how to ensure that all departments are using the same method in the preparation of the necessary input data. The method has been implemented in Excel where the user may enter values for these parameters which are then used in the necessary calculations. The results that are presented includes what batch-sizes that are to be produced, the safety stock level to be applied, which re-order point  to be used and achieved service level. In addition the report also presents a new way to manage stock control in cases where there is a bottleneck early in the production flow which therefore determines the rate of production in the rest of the flow. Since this creates a pull system through the process flow, the stock between the production steps is unnecessary. A drawback is that the production becomes more sensitive to disturbances but means that previously hidden problems in the production reach the surface. The results of the simulations attempted show that the method involves reduction of inventory levels at the same time as the desired service level is maintained. By implementing the method Volvo Powertrain in Skövde will have a method to support their decisions which optimizes inventory levels at the same time as high service levels are guaranteed.

Page generated in 0.0855 seconds