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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.
381

A Model for Multiperiod Route Planning and a Tabu Search Method for Daily Log Truck Scheduling

Holm, Christer, Larsson, Andreas January 2004 (has links)
The transportation cost of logs from forest to customers is a large part of the overall cost for the Swedish forestry industry. Finding good routes from harvesting points to saw and pulp mills is a complex task, where the total number of feasible routes is extremely high. In this thesis we present two methods for log truck scheduling. The first is to, from a given set of routes, find the most valuable subset that fulfils the customers demand. We use a model that is similar to the set partitioning problem and a method that is referred to as a composite pricing coupled with Branch and Bound. The composite pricing based method prices the routes (columns) and chooses the most valuable ones that are then added to the LP relaxation. Once an LP optimum is found, the Branch and Bound method is used to find an integer optimum solution. We have tested this on a case of realistic size. The second method is a tabu search heuristic. Here, the purpose is to create efficient and qualitative routes from a given number of trips (referred to as predefined trips). From a start solution tabu search systematically generates new solutions. This method was tested on a small problem and on a five times larger problem to study how the size of the problem affected the result. It was also tested and compared on two cases in which the backhauling possibilities (i.e. instead of traveling empty the truck picks up another load on the return trip) had and had not been studied. The composite pricing based method and the tabu search method proved to be very useful for this kind of scheduling.
382

Hydrogen generation from dimethyl ether by autothermal reforming

Nilsson, Marita January 2007 (has links)
<p>Heavy-duty trucks are in idle operation during long periods of time, providing the vehicles with electricity via the alternator at standstill. Idling trucks contribute to large amounts of emissions and high fuel consumption as a result of the low efficiency from fuel to electricity. Truck manufacturers are working to develop equipment using auxiliary power units to supply the trucks with electricity, which operate independently of the main engine. Fuel cell-based auxiliary power units could offer high efficiencies and low noise and vibrations. The hydrogen required for the fuel cell can be generated in an onboard fuel reformer. This thesis is devoted to hydrogen generation from dimethyl ether, DME, by autothermal reforming focusing on the application of fuel cell auxiliary power units. In the search for alternative fuels, DME has lately been identified as a promising diesel substitute.</p><p>The first part of the thesis gives an introduction to the field of DME reforming with a literature survey of recent studies within the area. Included are also results from thermodynamic equilibrium calculations.</p><p>In the following parts of the thesis, experimental studies on autothermal reforming of DME are presented. A reformer constructed to generate hydrogen to feed a 5 kW<sub>e</sub> polymer electrolyte fuel cell is evaluated with emphasis on trying to work close to a practically viable process, i.e. without external heating and using gas mixtures resembling real conditions. Additional experiments have been conducted to investigate the use of catalytic oxidation of dimethyl ether as a heat source during startup. The results of these studies are presented in Paper I.</p><p>In the second experimental study of this thesis, which is presented in Paper II, Pd-based monolithic catalysts are evaluated at small scale for use in autothermal reforming of DME. A screening of various catalyst materials has been performed followed by a study of the influence on the product composition of varying operating parameters such as oxygen-to-DME ratio, steam-to-DME ratio, and temperature.</p>
383

Fuel Consumption and Emissions of Turnpike Doubles in the Canadian Prairie Region

Baumgartner, Thomas Peter 06 April 2011 (has links)
This research analyzes fuel consumption and emissions of Turnpike double trailer combinations (Turnpikes) on a regional network in the Canadian Prairies. The research: (1) establishes current benchmarks for fuel consumption of Turnpikes and five-axle tractor semitrailers (3-S2s) with van trailers; (2) develops fuel consumption models for these vehicle types; (3) establishes an understanding of current operating characteristics of Turnpikes in the region; and (4) estimates their system-wide effects in terms of fuel consumption and emissions in Manitoba by applying the developed models. Canadian Prairie region-based carriers revealed an increase in Turnpike travel (from 2007-2009) of 44 percent after the twinning of the Trans-Canada Highway between Winnipeg and Regina in 2007 was completed. Turnpikes can save one third of fuel consumed when compared to 3-S2s; have higher fuel consumption in the winter months; and their use in 2009 reduced fuel consumption and CO2 emissions by five percent compared to 3-S2s.
384

Gaze Interaction in Modern Trucks

Fjellström, Jonatan January 2014 (has links)
In this master thesis project carried out on Scania’s interaction design department in Södertälje an evaluation of the technology gaze interaction has been done. The aim was to see if the technology was suitable for implementation in a truck environment and what potential it had. The work started by doing a context analysis to get a deeper knowledge of the research done on within the area related to the subject. Following the context analysis a comprehensive need finding process was done. In this process, data from interviews, observations, ride along with truck drivers, benchmarking and more was analysed. The analysis of this was used to identify the user needs. Based on the user needs the concept development phase was conducted. The whole development phase was done in different stages and started off by an idea generation process. The work flow was made in small iterations with the idea to continuously improve the concepts. All concepts were evaluated in a concept scoring chart to see which of the concepts that best fulfilled the concept specifications. The concepts that best could highlight the techniques strengths and weaknesses were chosen and these are Head Up Display Interaction and Gaze Support System.. These concepts focused on the interaction part of the technique rather than a specific function. Test of the two concepts were conducted in a simulator to get data and see how they performed compared to today´s Scania trucks. The result overall was good and the test subjects were impressed with the systems. However there was no significance in most of the cases of driving except for some conditions where the concepts prove to be better than the systems used today. Gaze interaction is a technology that is suitable for a truck driving environment given that a few slight improvements are made. Implementation of the concepts have a good potential of reducing road accidents caused by human errors.
385

為尼加拉瓜馬拉瓜市El Carretón by El Morralito餐廳開發義大利三明治和義大利麵餐車服務 / El Carretón by El Morralito: Panini & Pasta Food truck in Managua, Nicaragua

羅來德, Lopez, Nester Unknown Date (has links)
為尼加拉瓜馬拉瓜市El Carretón by El Morralito餐廳開發義大利三明治和義大利麵餐車服務 / The mobile food industry in Nicaragua is as of the writing of this document, in a growth stage. The competition is low and the conditions are proper to quickly expand and settle as one of the leaders in the industry. Based on this, the owners of El Morralito, an Italian Panini & Pasta small eatery have decided to plan their expansion into the mobile food market by launching a Food Truck: El Carretón by El Morralito. Trained personnel, mobile sales point, customer relationships, focus on quality and profitability, and expertise in logistics are the key success factors that will ensure El Carretón successful in its initially target market, which comprehends mostly students and office employees around the center of Managua in a 2 Km radius that includes the biggest universities and the largest office compound in the capital. Launching the mobile brand as part of an existing company will allow the startup to initiate its operations with several sunk costs, that will reduce the initial investment required to launch the service. Synergies between the existing eatery and the mobile truck will allow each individual business to reduce its costs by sharing a central kitchen, storage space and to have additional procurement bargaining power by bulk purchasing, which will eventually reduce costs and increase profits. Based on these synergies, the expansion plan includes additional trucks of the same and new cuisines that could eventually be franchised. The financial analysis, which includes the expansion plan, proves the project to be profitable and desirable under its assumptions, based on the initial investment scheme.
386

Att ha en blick och en fallenhet för det. : En studie av yrkeskunnande inom lastbilsföraryrket.

Dahlström, Peter January 2014 (has links)
Syftet med denna studie var att få en insikt i och kunskaper om vad som gömmer sig bakom uttalanden som att man måste ha en blick och en fallenhet för det. I studien har två manliga lastbilsförare med lång erfarenhet av lastbilsföraryrket intervjuats om deras sätt att se på vilka kunskaper som behövs för att ses som en kompetent och yrkesskicklig lastbilsförare. Kunskaperna som lastbilsförarna lyfter fram är att ha en blick och en fallenhet för yrket. Studien visade att lastbilsförarna hade svårt att sätta ord på vad de menar med att ha en blick och en fallenhet för yrket. Resultatet i studien visade att det som lastbilsförarna pratar om när det gäller att ha en blick och en fallenhet för yrket bottnar i Aristoteles kunskapsbegrepp techne som ses som färdighetskunskap och fronesis som ses som förtrogenhetskunskap. Inom färdighetskunskapen ryms att ha en fallenhet för något, du har förmågan att utföra en handling. Denna förmåga utvecklas genom övning och erfarenhet, och det går inte att förutsäga hur långt en enskild förmåga kan utvecklas. Inom förtrogenhetskunskapen ryms att ha en blick för något, man kan se mönster eller beteenden som man kan tolka och se utgången av. Men, man kan inte ha en blick för något som man inte har upplevt innan. Båda kunskaperna bygger på att du har samlat på dig erfarenhet över tid. De samverkar med varandra i olika grad, beroende på personliga egenskaper, och den specifika situation de ställs inför. / The purpose of the study was to get an insight into what it is that hides behind the statement to have an eye for something and an aptitude for something. In this study i have been in contact with two male truck drivers who have a long experience from truck driving.In the study they told me what knowledge they see as needed to be seen as a competent and skilled truck driver. The knowledge that the truck drivers brings out is to have an eye and an aptitude for the profession. The study showed that truck drivers had a hard time putting into words what they mean by having an eye and an aptitude for the profession.   The results of the study showed that when it comes to having an eye and an aptitude for the profession that stems from Aristotle's concept of knowledge, techne seen as skill knowledge and phronesis seen as familiarity or intimate knowledge.Within skill knowledge fit to have an aptitude for something, you have the ability to perform an action. This ability develops with practice and experience, and it is not possible to predict how long an individual's ability can develop. Within familiarity knowledge fit to have an eye for something, you can see patterns or behaviors that can be interpreted.   But, you can´t have a look for something you have not experienced before. The knowledge is based upon what you have accumulated over time. The knowledge interacts with each other to different degrees depending on personal characteristics, and the specific situation they face.
387

Fuel Consumption and Emissions of Turnpike Doubles in the Canadian Prairie Region

Baumgartner, Thomas Peter 06 April 2011 (has links)
This research analyzes fuel consumption and emissions of Turnpike double trailer combinations (Turnpikes) on a regional network in the Canadian Prairies. The research: (1) establishes current benchmarks for fuel consumption of Turnpikes and five-axle tractor semitrailers (3-S2s) with van trailers; (2) develops fuel consumption models for these vehicle types; (3) establishes an understanding of current operating characteristics of Turnpikes in the region; and (4) estimates their system-wide effects in terms of fuel consumption and emissions in Manitoba by applying the developed models. Canadian Prairie region-based carriers revealed an increase in Turnpike travel (from 2007-2009) of 44 percent after the twinning of the Trans-Canada Highway between Winnipeg and Regina in 2007 was completed. Turnpikes can save one third of fuel consumed when compared to 3-S2s; have higher fuel consumption in the winter months; and their use in 2009 reduced fuel consumption and CO2 emissions by five percent compared to 3-S2s.
388

Linear Programming for Scheduling Waste Rock Dumping from Surface Mines

Nan Zhang Unknown Date (has links)
Abstract The removal of overlying waste rock in open pit mines to dumps is conventionally undertaken by draglines or by trucks and shovels, or by a combination of these. Waste rock dumps are the largest remnant structures of open cut mining operations and can absorb a large proportion of the mine operating costs. If the dumps are not properly developed they can be excessively expensive and can become a major safety risk and environmental hazard. There are many examples worldwide where poor design and construction of waste rock dumps have resulted in failures causing considerable loss of life and widespread damage, or have resulted in erosion and seepage that have led to severe environmental pollution. The proper design and scheduling of waste rock dumps and haul routes can significantly reduce costs, minimise the possibility of failures, and avoid harming the environment. This Thesis is limited to the consideration of trucks and shovels for waste rock haulage in open cut mining operations. It describes the development and application of a waste rock dump scheduling model using the Operations Research technique of Mixed-Integer Linear Programming, implemented in the mathematical modelling language AMPL. The model focuses on minimising the haulage cost for each block of waste rock taken from the open pit and placed in the dump. Allowance is made for the selective placement of benign and reactive waste rock, based on an open pit block model that delineates benign and reactive waste rock. The formulation requires input data including the xyz-coordinates of the block model for the open pit, information on whether the waste rock blocks are benign or reactive, the proposed time scheduling of waste rock haulage from the open pit, unit haulage costs, and the geometry of the waste rock dump, including the delineation of the zones that are benign and those that are reactive. The model was successfully tested by using both simple test data and actual mine site data. The application of the model to a simple case confirmed that it produces results that meet the Objective Function in producing an optimal haulage time and cost, and meets the various Constraints imposed. This model for scheduling the removal of waste rock from open cut mining operations with trucks and shovels will require further research and testing and, because the results are generated in a numerical format, there will also be a need to convert them to a graphical format to facilitate their interpretation. Ultimately, it will have the potential to provide a relatively low-cost scheduling tool that meets operators’ economic, safety and environmental goals.
389

Numerical Optimal Control of Hybrid Electric Trucks : Exhaust Temperature, NOx Emission and Fuel Consumption

Andersson, Fredrik, Andersson, Hampus January 2018 (has links)
The controls for a parallel hybrid electric truck are optimized using numerical optimal control. Trade-offs between catalyst light-off times, NOx emission and fuel consumption have been investigated for cold starts at two operating points, as well as temperature differences between conventional and hybrid powertrains during WHTC (World Harmonized Transient Cycle). A model describing the temperature dynamics of the aftertreatment system is implemented as well as temperature-based deNOx performance for both Cu-Zeolite and Fe-Zeolite catalysts. Control is performed in a piecewise linear fashion, resulting in a total of 23 states including control signals. It is shown that high temperatures can be a larger threat to catalyst performance when running the WHTC than low temperatures, for both conventional and hybrid powertrains. Furthermore, decreasing the light-off time of the catalyst does not always lead to decreased NOx emission, instead there is a trade-off between light-off time and NOx emission. It is found that there are controls that will realize decreased NOx emission for a hybrid truck during cold starts at the expense of increased fuel consumption.
390

Planification des opérations de cross-docking : prise en compte des incertitudes opérationelles et de la capacité des ressources internes / Scheduling cross-docking operations : Integration of operational uncertainties and resource capacities

Ladier, Anne-Laure 21 November 2014 (has links)
Dans une plateforme de cross-docking, les produits sont déchargés descamions entrants, triés puis directement rechargés dans les camions sortants– chaque produit passe moins de 24 heures sur la plateforme.L’analyse des écarts entre la littérature et les observations réalisées sur leterrain permet de dégager deux axes de recherche : la prise en compte desincertitudes opérationnelles d’une part, et de la capacité des ressourceshumaines de la plateforme d’autre part.Le problème de planification des camions entrants et sortants avec fenêtrede temps est modélisé par un programme linéaire et résolu par troisheuristiques différentes. La robustesse des plannings obtenus est ensuitetestée à l’aide d’un modèle de simulation à événements discrets, qui permetd’évaluer plusieurs reformulations robustes du modèle initial.Le problème de planification des employés sur la plateforme est traité àl’aide de trois programmes linéaires mixtes, résolus de façon séquentielle.La combinaison des deux modèles permet d’obtenir un modèle d’aide àla décision pour une plateforme de cross-docking. / In a cross-docking platform, goods are unloaded from inbound trucks,sorted and directly reloaded in outbound trucks – each product typicallystays less than 24 hours in the platform.By analyzing the gaps between the literature and on-field observations,we highlight two research directions: accounting for operational uncertainties,and for the human resource capacity in the platform.A truck scheduling problem with time windows for the inbound andoutbound trucks is modeled with an integer program and solved withthree different heuristics. The robustness of the schedules obtained is thentested with a discrete-event simulation model, which enables to evaluateseveral robust reformulations of the initial model.The employee timetabling and rostering problem in the platform is addressedwith three mixed integer linear problems solved sequentially. Thetwo models can be combined to serve as a decision-support tool for across-docking platform.

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