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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.
661

Optimierung des Flugzeugeinsatzes nach Brennstoffeffizienz

Lindner, Martin 01 August 2023 (has links)
Die Arbeit widmet sich der Einsatzplanung von Luftfahrzeugen (LFZ) und fokussiert dabei auf die herausfordernde Thematik des Verschleißes, der zu einer Heterogenität in der Brennstoffeffizienz innerhalb der Flotte führt. Dieser heterogene Effekt wird durch den sogenannten 'Performance Factor' (PF) quantifiziert, der den Verbrauch im Vergleich zu einem nicht verschleißbehafteten Referenz-LFZ adjustiert. Trotz der nachgewiesenen Auswirkungen auf die Effizienz wird der PF bisher in der Einsatzplanung weitgehend vernachlässigt. Das Ziel dieser Forschungsarbeit besteht in der systematischen Untersuchung des Potenzials zur Reduzierung des Brennstoffbedarfs und der damit verbundenen CO2-Emissionen durch eine effizienzorientierte Einsatzplanung mittels Berücksichtigung des PF. Zu diesem Zweck wird ein taktisches Modell, das sogenannte 'TARP-Modell,' entwickelt. Es ermöglicht eine integrierte Lösung der Phasen des Aircraft Routings und des Tail Assignments, wodurch individuelle Flugdurchführungskosten unter Berücksichtigung der Heterogenität der Flüge und der PF-Verteilung in der Flotte ermittelt werden können. Die erzielten Ergebnisse verdeutlichen, dass eine effizienzorientierte Einsatzplanung eine Senkung der Brennstoffkosten um etwa 0,25% bis 0,5% ermöglicht. Selbst bei unvorhergesehenen Flugplanstörungen und der vermehrten Nutzung von sogenannten Aircraft Swaps (TARP-R-Modell) bleibt das Potenzial weitestgehend erhalten, sofern der PF angemessen in die Entscheidungsfindung integriert wird. Es ist jedoch zu beachten, dass das Potenzial mit zunehmender Komplexität in der Flug- und LFZ-Zuordnung durch verstärkte Restriktionen abnehmen kann. Die vorliegende Arbeit leistet somit einen Beitrag zur Ressourcenschonung und zur Verringerung der Klimawirksamkeit des Luftverkehrs. Es ist anzunehmen, dass zukünftige technologische Fortschritte im Bereich des digitalen Zwillings die Berechnung des PF noch präziser gestalten werden, wodurch dessen Bedeutung sowohl wissenschaftlich als auch operationell weiter an Bedeutung gewinnen dürfte. / The thesis is dedicated to the aircraft rotation and assignment and focuses on the challenging issue of aircraft performance degradation, which leads to heterogeneity in fuel efficiency within the fleet. This heterogeneous effect is quantified by the so-called 'Performance Factor' (PF), which adjusts fuel consumption in comparison to a non-worn reference aircraft. Despite its proven impact on efficiency, the PF has largely been disregarded in aircraft planning practices. The main objective of this research is to systematically investigate the potential for reducing fuel consumption and associated CO2 emissions through an efficiency-oriented aircraft planning approach, incorporating consideration of the PF. To achieve this goal, a tactical model, referred to as the 'TARP model,' is developed. The model facilitates an integrated solution to the aircraft routing and tail assignment phases, enabling the determination of individual flight execution costs while accounting for the heterogeneity of flights and PF distribution in the fleet. The results obtained underscore that an efficiency-oriented aircraft planning approach can yield a reduction in fuel costs of approximately 0.25% to 0.5%. Even in the presence of unforeseen flight schedule disruptions and increased utilization of aircraft swaps (TARP-R model), the potential remains largely preserved, provided the PF is adequately integrated into the decision-making process. Nevertheless, it should be noted that the potential may diminish with growing complexity in flight and aircraft assignment, stemming from heightened restrictions. Consequently, this study contributes to resource conservation and the mitigation of the aviation industry's climate impact. Anticipated advancements in digital twin technologies are expected to further refine PF calculations, enhancing its significance both from a scientific and operational standpoint.
662

A MILP Framework to Solve the Sustainable System Optimum with Link MFD Functions

Shakoori, Niloofar, De Nunzio, Giovanni, Leclercq, Ludovic 23 June 2023 (has links)
Given the increasing consciousness toward the environmental footprint of mobility, accommodating environmental objectives in existing transport planning strategies is imperative for research and practice. In this paper, we use the link macroscopic fundamental diagram (MFD) model to develop optimal routing strategies that minimize total system emissions (TSE) in multiple origin-destination (OD) networks. Piecewise linear (PWL) functions are used to approximate MFD for individual links, and to define link-level emissions. Dynamic network constraints, non-vehicle holding constraints, and convex formulations of the PWL functions are considered. Thus, the system-optimum dynamic traffic assignment (SO-DTA) problem with environmental objectives is formulated as a mixed integer linear program (MILP). Finally, on a synthetic network, numerical examples demonstrate the performance of the proposed framework.
663

Optimization Approach for Multimodal Sensory Feedback in Robot-assisted Tasks

Mandira S Marambe (11192937) 28 July 2021 (has links)
<div> <p><br></p> </div> Individuals with disabilities and persons operating in inaccessible environments can greatly benefit from the aid of robotic manipulators in performing activities of daily living (ADLs) and other remote tasks. Users relying on robotic manipulators to interact with their environment are restricted by the lack of sensory information available through traditional operator interfaces. These interfaces only allow visual task access and deprive users of somatosensory feedback that would be available through direct contact. Multimodal sensory feedback can bridge these perceptual gaps effectively. Given a set of object properties (e.g. temperature, weight) to be conveyed and sensory modalities (e.g. visual, haptic) available, it is necessary to determine which modality should be assigned to each property for an effective interface design. However, the effectiveness of assigning properties to modalities has varied with application and context. The goal of this study was to develop an effective multisensory interface for robot-assisted pouring tasks, which delivers nuanced sensory feedback while permitting high visual demand necessary for precise teleoperation. To that end, an optimization approach is employed to generate a combination of feedback properties to modality assignments that maximizes effective feedback perception and minimizes cognitive load. A set of screening experiments tested twelve possible individual assignments to form the combination. Resulting perceptual accuracy, load, and user preference measures were input into a cost function. Formulating and solving as a linear assignment problem, a minimum cost combination was generated. Results from experiments evaluating efficacy in practical use cases for pouring tasks indicate that the solution is significantly more effective than no feedback and has considerable advantage over an arbitrary design. <br>
664

Sjuksköterskans upplevelse av att invänta assistans med en kritiskt sjuk patient, inom ambulanssjukvård / The nurse's experience of waiting for assistance with a critically ill patient, in ambulance healthcare

Axell, Mari, Aronsson Dekinnaird, Caroline January 2023 (has links)
Bakgrund: Sjuksköterskan inom ambulanssjukvården behöver hållas uppdaterad inom den medicinska och omvårdnadens utveckling. Detta då sjuksköterskans arbete inom ambulanssjukvården är ett omväxlande arbete, där varje dag är olik. Den komplexa vård och arbetsmiljön ställer därmed höga krav på både den enskilda sjuksköterskan, och på ambulansteamet. Detta då de ibland träffar på svårt sjuka patienter och ytterligare resurser behövs på plats för att lösa varierande situationer, något som även kan orsaka stress. Problemformulering: Att ställas inför en kritiskt sjuk patient och inse att ytterligare resurser krävs, är realitet för samtliga sjuksköterskor inom ambulanssjukvården. Att behöva vänta på assistans och samtidigt vårda en kritiskt sjuk patient är något som kan bygga på ytterligare stressfaktorer hos sjuksköterskorna. Då det är begränsat med forskning inom området, genomfördes denna studie. Syfte: Sjuksköterskans upplevelse av att invänta assistans med en kritiskt sjuk patient, inom ambulanssjukvården. Metod: Semistrukturerade intervjuer hölls med åtta sjuksköterskor. Deltagarna kom från tre olika ambulansområden inom Västra Götalandsregionen. Ambulansområdena var belagda i storstad, mindre stad och landsbygd. Intervjuerna analyserades med kvalitativ induktiv ansats. Resultat: Analys av upplevelsen att invänta assistans resulterade i tre kategorier, i form av “behov av kontroll”, “känna sig otillräcklig” och “känna sig otrygg”. Diskussion: Sjuksköterska inom ambulanssjukvården ställs inför känslomässiga utmaningar i väntan på assistans, med en kritisk sjukpatient. Känslan att vara otrygg och otillräcklig skapar en hög stress, som resulterar i att sjuksköterskan vill göra så mycket som möjligt för patienten, även om allt inte kan göras. Sjuksköterskan löper risk att drabbas av psykisk ohälsa, ångest och PTSD. / Background: Nurses in ambulance healthcare need to be kept up-to-date in medical and nursing developments. This is because the nurse's work in ambulance healthcare is varied work, where every day is different. The complex care and work environment therefore place high demands on both the individual nurse, but also on the ambulance team. This is because they sometimes encounter seriously ill patients and additional resources are needed on site to resolve varying situations, something that can also cause stress.  Problem formulation: Being faced with a critically ill patient and realizing that additional resources are required is a reality for all nurses in ambulance healthcare. Having to wait for assistance and at the same time care for a critically ill patient is something that can build on additional stress factors for the nurses. As there is limited research in the area, this study was conducted.  Purpose: The nurse's experience of waiting for assistance with a critically ill patient, within the ambulance service.  Method: Semi-structured interviews were held with eight nurses. The participants came from three different ambulance areas within the Västra Götaland region. The ambulance areas were covered in big cities, smaller cities, and rural areas. The interviews were analysed using a qualitative inductive approach.  Results: Analysis of the experience of waiting for assistance resulted in three categories, in the form of "need for control", "feeling inadequate" and "feeling insecure". Discussion: Nurses in the ambulance service face emotional challenges while waiting for assistance, with a critically ill patient. The feeling of being unsafe and inadequate creates a high stress, which results in the nurse wanting to do as much as possible for the patient, even if everything cannot be done. The nurse is at risk of mental illness, anxiety, and PTSD.
665

Using Commodity Flow Data for Predicting Truck Freight Flow on State Truck Routes

Jin, Goangsung 28 November 2011 (has links) (PDF)
The increase in truck traffic on highways has brought many problems and challenges to transportation planning and traffic operation, including traffic congestion, transportation system deficiency (insufficient truck parking, etc.), safety, infrastructure deterioration, environmental impacts (air quality and noise), economic development, and so forth. Along with the increase in truck traffic, the need for developing a statewide truck freight demand model has grown so that a state can estimate truck traffic at any point on its highways. The most significant hurdle to including freight transportation in the transportation modeling process is that most of the demand forecasting methodologies currently available were developed for passenger trips, not freight trips. This type of modeling methodology usually makes an assumption that freight trips follow the same behavioral mechanism as passenger trips. In order to overcome the weakness of using a typical four-step demand forecasting modeling process, the concept of commodity flow models (CFMs) can be used to develop a truck freight flow model. It is widely accepted that focusing on the freights enables CFMs to capture more accurately the fundamental economic mechanisms that drive freight movements. The type of commodity being carried is one of the most important characteristics of truck movements, and it is sometimes a challenge to obtain such information from the carriers. Thus, lately, the integration of the freight flow modeling and land use modeling has emerged as an alternate tool to estimate freight movements than the previously developed models. In this study, county-level multiple regression models relating land use to commodity flow were developed using a geographical information system and statistics. Then, a statistical/mathematical statewide commodity flow distribution model was developed by using a physical friction factor (physical distance), a statistical friction factor (Euclidean distance), and economic factors (differences of population and difference of employment among the counties). The commodity flow distributed among truck traffic analysis zones (TTAZs) by the statewide commodity flow distribution model were converted to truck trips and the resulting truck trips were assigned to Utah's truck routes using the all-or-nothing assignment procedure of TransCAD and a genetic algorithm. Truck freight data from the US Census Bureau's Commodity Flow Surveys, which have become available to the public for free via the Internet, enabled the development of a commodity flow based statewide truck freight demand model. It was found that the integration of the freight flow and land use data could be a practical method for modeling tuck traffic demand on state-wide truck routes although the current level of data availability on commodity flow and land use data still constrains the full capability of this type of modeling.
666

Multi-User Methods for FEA Pre-Processing

Weerakoon, Prasad 13 June 2012 (has links) (PDF)
Collaboration in engineering product development leads to shorter product development times and better products. In product development, considerable time is spent preparing the CAD model or assembly for Finite Element Analysis (FEA). In general Computer-Aided Applications (CAx) such as FEA deter collaboration because they allow only a single user to check out and make changes to the model at a given time. Though most of these software applications come with some collaborative tools, they are limited to simple tasks such as screen sharing and instant messaging. This thesis discusses methods to convert a current commercial FEA pre-processing program into a multi-user program, where multiple people are allowed to work on a single FEA model simultaneously. This thesis discusses a method for creating a multi-user FEA pre-processor and a robust, stable multi-user FEA program with full functionality has been developed using CUBIT. A generalized method for creating a networking architecture for a multi-user FEA pre-processor is discussed and the chosen client-server architecture is demonstrated. Furthermore, a method for decomposing a model/assembly using geometry identification tags is discussed. A working prototype which consists of workspace management Graphical User Interfaces (GUI) is demonstrated. A method for handling time-consuming tasks in an asynchronous multi-user environment is presented using Central Processing Unit (CPU) time as a time indicator. Due to architectural limitations of CUBIT, this is not demonstrated. Moreover, a method for handling undo sequences in a multi-user environment is discussed. Since commercial FEA pre-processors do not allow mesh related actions to be undone using an undo option, this undo handling method is not demonstrated.
667

Interval Matching and Control for Hexahedral Mesh Generation of Swept Volumes

Shepherd, Jason F. 01 April 1999 (has links) (PDF)
Surface meshing algorithms require certain relationships among the number of intervals on the curves that bound the surface. Assigning the number of intervals to all of the curves in the model such that all relationships are satisfied is called interval assignment. Volume meshing algorithms also require certain relationships among the numbers of intervals on each of the curves on the volume. These relationships are not always captured by surface meshing requirements. This thesis presents a news technique for automatically identifying volume constraints. In this technique, volume constraints are grouped with surface constraints and are solved simultaneously. A sweepable volume has source, target and linking surfaces. The technique described in this thesis uses graph algorithms to identify independent, parallel sets of linking surfaces, and determine if they correspond to through-holes or blind-holes. For blind-holes, the algorithm generates constraints that prevent the hole from being too deep in interval parameter space and, thus, penetrating opposite target surfaces. For each linking set, the adjoining source and target surfaces are partially ordered by the structure of the linking set. A small set of representative paths for each linking set is found, and the representative paths for all linking sets are gathered and distilled by Gaussian elimination into a small set of constraints.
668

Validation of a Public Transport Model / Validering av en kollektivtrafikmodell

Aho, Yousef, de Jong, Johannes January 2020 (has links)
During 2018, the Public Transport Administration (Trafikförvaltningen) in the Stockholm region spent approximately 2.2 billion SEK on new infrastructure investments related to the public transport system, many of which were based on their public transport models. The previously used method for validating these models has lacked scientific rigour, efficiency and a systematic approach, which has led to uncertainty in decision making. Furthermore, few scientific studies have been conducted to develop validation methodologies for large-scale models, such as public transport models. For these reasons, a scientific validation methodology for public transport models has been developed in this thesis. This validation methodology has been applied on the 2014 route assignment model used by Trafikförvaltningen, for the transport modes bus, commuter train and local tram. In the developed validation methodology, the selected validation metrics called MAPE, %RMSE and R^2 are used to compare link loads from a route assignment model with observed link loads from an Automatic Passenger Counting (APC) system. To obtain an overview of the performance of the route assignment model, eight different scenarios are set, based on whether the validation metrics meet acceptable thresholds or not. In the application of the developed validation methodology, the average link loads for the morning rush have been validated. To adjust the developed validation methodology to system-specific factors and to set acceptable metric thresholds, discussions with model practitioners have taken place. The validation has been performed on both lines and links, and for bus entire line number series have been validated as well. The validation results show that commuter train meets the set threshold values in a higher proportion than bus and local tram do. However, Trafikförvaltningen is recommended to further calibrate the route assignment model in order to achieve a better model performance. The developed validation methodology can be used for validation of public transport models, and can in combination with model calibration be used in an iterative process to fine-tune model parameters for optimising validation results. Finally, a number of recommendations are proposed for Trafikförvaltningen to increase the efficiency and quality of the validation process, such as synchronising model data with the observed data. / Under 2018 spenderade Trafikförvaltningen ungefär 2,2 miljarder kronor på nya infrastrukturinvesteringar för kollektivtrafiksystemet i Stockholm, varav många av dessa baserades på deras kollektivtrafikmodeller. Den tidigare metoden för att valideras dessa modeller har saknat gedigen vetenskaplig grund, effektivitet och ett systematiskt tillvägagångssätt, vilket lett till osäkerhet gällande investeringsbeslut. Dessutom har få vetenskapliga studier genomförts för att ta fram valideringsmetodologier för storskaliga modeller, såsom kollektivtrafikmodeller. Av dessa skäl har en vetenskaplig valideringsmetodologi för kollektivtrafikmodeller tagits fram i detta examensarbete. Denna valideringsmetodologi har tillämpats på Trafikförvaltningens 2014 års nätutläggningsmodell, för trafikslagen buss, pendeltåg och spårväg. I den framtagna valideringsmetodologin har de valda valideringsmåtten vid namn MAPE, %RMSE och R^2 använts för att jämföra länkbelastningar från en nätutläggningsmodell med observerade länkbelastningar från ett Automatisk Trafikanträkning-system (ATR). För att ge en översikt över modellens precision har åtta scenarios satts baserat på om valideringsmåtten godkänns eller inte enligt tröskelvärden. I tillämpningen av den framtagna valideringsmetodologin har de genomsnittliga länkbelastningarna för morgonens rusningstrafik validerats. För att justera den framtagna valideringsmetodologin efter systemspecifika faktorer och för att sätta godkända tröskelvärden för valideringsmåtten, har diskussioner med trafikanalytiker hållits. Valideringen har utförts både på linjer och länkar, och för buss har även hela linjeserier validerats. Valideringsresultaten för pendeltåg har en högre andel godkända mätningar än buss och spårväg. Trafikförvaltningen rekommenderas dock att kalibrera nätutläggningsmodellen ytterligare för att uppnå ett bättre resultat. Den framtagna valideringsmetodologin kan användas för valideringar av kollektivtrafikmodeller, och kan i kombination med modellkalibrering användas i en iterativ process för att finjustera modellparametrar och därmed optimera valideringsresultaten. Slutligen föreslås ett antal rekommendationer för Trafikförvaltningen för att öka effektiviteten och kvaliteten på valideringsprocessen, till exempel att synkronisera modelldata med observerad data.
669

Hardware-Efficient WDM/SDM Network : Smart Resource Allocation with SDN Controller / Maskinvarueffektivt WDM / SDM-nätverk : Smart resursallokering med SDN-controller

Liu, Lida January 2019 (has links)
Optical networking has been developing for decades and wavelength-division multiplexing (WDM) is the main technology used to carry signals in fiber-optical communication systems. However, its development has slowed because it is approaching the Shannon limit of nonlinear fiber transmission. Researchers are looking for multi dimensional multiplexing. Space-division multiplexing (SDM) is an ideal way to scale network capacities. The capacity of WDM/SDM network could be expanded to several times the capacity of WDM network but the active hardware devices may also increase by several times. This project aims to answer a practical question: How to construct a WDM/SDM network with less hardware resource? There is no mature research about WDM/SDM network yet. Therefore, the problem can be divided into two parts: (1) how to build a WDM/SDM network and (2) how to allocate resource and compute routes in such a network to minimize hardware resources. First, this thesis proposes a WDM/SDM node which has bypass connections between different fibers and architecture on demand (AoD) to effectively decrease the number of active hardware devices within the node. Then, two types of networks were constructed: one with bypass connections in each node and another one without any bypass connections. These networks were under the control of a software defined network (SDN) controller. The controller knew the wavelength resources within the networks. Several algorithms were applied to these networks to evaluate the effect of a bypass network and to identify the desired characteristics (to find short length path and decrease the probability of spectrum fragmentation) of an algorithm suitable for a network with bypass connections. The results of applying the proposed algorithms in two networks proved that the bypass connections increased the blocking probability in small topology but did not affect the results in large topology. The results in a large-scale network with bypass network were almost the same as the results in a network without bypass connections. Thus, bypass connections are suitable for large-scale network. / Optiskt nätverk har utvecklats i årtionden och våglängdsdelningsmultiplexering (WDM) är den viktigaste tekniken som används för att bära signaler i fiberoptiska kommunikationssystem. Utvecklingen har dock minskat eftersom den närmar sig Shannon-gränsen för olinjär fiberöverföring. Forskare letar efter flerdimensionell multiplexering. Space-division multiplexing (SDM) är ett idealiskt sätt att skala nätverkskapacitet. Kapaciteten för WDM / SDM-nätverk kan utökas till flera gånger WDM-nätverkets kapacitet, men de aktiva hårdvaraenheterna kan också öka med flera gånger. Projektet syftar till att svara på en praktisk fråga: Hur konstruerar jag ett WDM / SDM-nätverk med mindre hårdvara? Det finns ingen mogen forskning om WDM / SDM-nätverk än. Därför kan problemet delas in i två delar: (1) hur man bygger ett WDM / SDM-nätverk och (2) hur man fördelar resurser och beräknar rutter i ett sådant nätverk för att minimera hårdvaruressurser. Först föreslår denna avhandling en WDM / SDM-nod som har förbikopplingsanslutningar mellan olika fibrer och arkitektur på begäran (AoD) för att effektivt minska antalet aktiva hårdvaraenheter inom noden. Sedan konstruerades två typer av nätverk: en med bypass-anslutningar i varje nod och en annan utan några bypass-anslutningar. Dessa nätverk kontrollerades av en mjukvarudefinierad nätverkskontroller (SDN). Styrenheten visste våglängdsresurserna i nätverket. Flera algoritmer applicerades på dessa nätverk för att utvärdera effekten av ett förbikopplingsnätverk och för att identifiera de önskade egenskaperna (för att hitta en kort längdväg och minska sannolikheten för spektrumfragmentering) av en algoritm som är lämplig för ett nätverk med bypass-anslutningar. Resultaten av att tillämpa de föreslagna algoritmerna i två nät visade att förbikopplingsförbindelserna ökade blockeringssannolikheten i liten topologi men inte påverkade resultaten i stor topologi. Resultaten i ett storskaligt nätverk med bypass-nätverk var nästan samma som resultaten i ett nätverk utan bypass-anslutningar. Bypassanslutningar är således lämpliga för storskaliga nätverk.
670

Visual Decision Support for Ensemble Clustering

Hahmann, Martin, Habich, Dirk, Lehner, Wolfgang 19 January 2023 (has links)
The continuing growth of data leads to major challenges for data clustering in scientific data management. Clustering algorithms must handle high data volumes/dimensionality, while users need assistance during their analyses. Ensemble clustering provides robust, high-quality results and eases the algorithm selection and parameterization. Drawbacks of available concepts are the lack of facilities for result adjustment and the missing support for result interpretation. To tackle these issues, we have already published an extended algorithm for ensemble clustering that uses soft clusterings. In this paper, we propose a novel visualization, tightly coupled to this algorithm, that provides assistance for result adjustments and allows the interpretation of clusterings for data sets of arbitrary size.

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