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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.
261

Simulation based exploration of a loading strategy for a LHD-vehicle / Simuleringsbaserad utforskning av styrstrategier för frontlastare

Lindmark, Daniel January 2016 (has links)
Optimizing the loading process of a front loader vehicle is a challenging task. The design space is large and depends on the design of the vehicle, the strategy of the loading process, the nature of the material to load etcetera. Finding an optimal loading strategy, with respect to production and damage on equipment would greatly improve the production and environmental impacts in mining and construction. In this thesis, a method for exploring the design space of a loading strategy is presented. The loading strategy depends on four design variables that controls the shape of the trajectory relative to the shape of the pile. The responses investigated is the production, vehicle damage and work interruptions due to rock spill. Using multi-body dynamic simulations many different strategies can be tested with little cost. The result of these simulations are then used to build surrogate models of the original unknown function. The surrogate models are used to visualize and explore the design space and construct Pareto fronts for the competing responses. The surrogate models were able to predict the production function from the simulations well. The damage and rock spill surrogate models was moderately good in predicting the simulations but still good enough to explore how the design variables affect the response. The produced Pareto fronts makes it easy for the decision maker to compare sets of design variables and choose an optimal design for the loading strategy.
262

The effects of quasi-steady loading on a virtual spur gear model

Kelso, Michael Patrick 01 July 2011 (has links)
With the projected growth of wind energy in the United States expected to account for 20% of the energy portfolio by 2030, it can be expected that wind turbines will not only increase in number, but also in size. This increase in size implies that internal components, such as the gearbox, will also increase to handle the higher loads. And given the high failure rates for gearbox components already in existence, one could expect more failure if nothing is done to improve reliability. It is well known that wind loading is not constant, rather it is random and ultimately causes fatigue loading. This thesis is concerned with studying what the effects of dynamic loading are on a smaller gear system. It is assumed the findings of this study can be scaled to a larger wind turbine system. A simple spur gear pair is first simulated at constant loading to establish a baseline and then run with a sinusoidal input with differing amplitudes and frequencies. The hypothesis is that by varying the amplitude and frequency, the responses for gear contact force and input and output shaft torques will also vary. And if these variations are noted, then conclusions may be drawn as how the frequency and amplitude influence the system. After which, it may then be correlated to a wind turbine system. Knowing what affects the frequency and amplitude have on a smaller system may help to establish guidelines. For this model, mechanical simulation software is used to build a multibody dynamics model of a spur gear system with flexible shafts. Using known wind data obtained near Amarillo, TX, a matrix of possible frequencies and amplitudes for a sinusoidal input are implemented and the solutions compared to those at constant loading. It was found that the system responded similarly regardless of input, showing RMS values for accelerations of approximately 50 m/s2, gear contact forces of 520 N, input shaft torques of 42 Nm, and output shaft torques of 78 Nm. This behavior is not expected is most likely due to insufficiencies in the assumptions made to construct the model.
263

Ystads kommun samlastning från outsourcing till insourcing

Fahim, Jonas, Vujevic, Marko, Paloma Gomez, Paolo January 2020 (has links)
Sveriges befolkning ökar ständigt men även leveranserna av varor ökar ständigt. Dettaresulterar att mer press sätts på kommunerna att forma väletablerade transportrutter. Däravhar vissa kommuner i Sverige lagt fokus på att forma dessa rutter och göra de mer effektivaför befolkningen och även öka vinsterna för företagen som står för leveranserna av godset.I denna studien har vi fokuserat på Ystads kommun och hur de har utvecklat sin strategi föratt uppnå dessa mål. En möjlig lösning för att effektivisera transportsystemet har varit attupprätta samlastning av gods. Huvudsyftet med denna studien är att se effekterna medsamlastningsprojekt inom Ystad kommun. För att kunna fullfölja vårt syfte har vi valt attintervjua olika individer som har en viktig roll inom transportsektorn i Ystad men äventidigare forskning som ger exempel av effekter som samlastningscentraler haft. En viktig delvar även samlandet av information från Ystad kommuns egna hemsida.Den teoretiska referensramen fick vi från vårt universitets egna sökmotor där vi hittade vårateorier med hjälp av nyckelord såsom “joint loading” och “co- loading”. Teorierna som vi harvalt har hjälpt oss genom vår undersökning och att besvara syftet. Eftersom denna studien ärav kvalitativ form har våra intervjuer utförts med tre individer som har en hög position inomtransportsektorn i Ystad. Den empiriska datan i kombination med våra teorier gav osstillräckligt med kunskap för att utföra en analys och presentera vårt resultat.Resultatet som vi presenterade indikerar att den miljömässiga aspekten fick en stor positivpåverkan där även företagen som hade implementerat en samlastningscentral fick en markantökning av sina vinster.Nyckelord: Samlastning, Samlastningscentral, effekt, miljöaspekt / As the population of Sweden rises, the demand for deliveries of goods grows significantly.This results in more pressure being put on the government to form a well establishedtransportation route. Therefore, some communities in Sweden have placed their focus ondeveloping the routes and making them more efficient for the population and to improve theprofits for the companies that deliver the goods.In this study we have focused on the community of Ystad and how they have resolved theirstrategy to achieve these goals. A possible solution in order to maximize the effectiveness hasbeen to establish joint loading of the goods. The main purpose of this study is to portray whatthe outcome of the joint loading project has had on the community of Ystad. To be able tofulfill our purpose we have conducted interviews of different people that have an importantrole in the transportation business but also searched for previous literature studies that giveexamples of earlier projects. An important part was also the gathering of information fromtransportation companies that was presented on their websites.The theoretical part was collected from our universities search engine where we found themthrough the keywords, joint loading and co-loading. The theories that we have mentionedhave helped us through the study and answer the question we brought out. Because this studyis of qualitative form, our interviews were conducted with three highly positioned individualsthat work in different transportation companies in Ystad. The empirical data together with ourtheories gave us a decent background in order to analyze our data and bring forward a result.The results that we present indicate that the environment was affected positively as well asthe profit of the companies that implemented the co loading project.Keywords: Joint loading, co- loading, effects, environmental aspect
264

Příspěvky k experimentálnímu zkoumání a numerickému popisu cyklického chování zemin / Contributions to the experimental investigation and numerical description of soil cyclic behavior

Duque Felfle, Jose Alejandro January 2021 (has links)
A wide range of geotechnical structures are subjected to episodes of cyclic loading. Among them, we can for example mention onshore and offshore foundations subjected to environmental loadings, pavements subjected to traffic loading, filling-emptying cycles on silos and water tanks, among many others. In order to develop constitutive models or numerical tools that accurately reproduce the soil behavior on the aforementioned geotechnical problems, a deep understanding on how soil behaves under cyclic loading is necessary. This behavior is, however, not trivial since non-linearity, small strain stiffness, stiffness degradation, cyclic hysteresis and recent stress history play a significant role. This dissertation presents some contributions to the experimental evidence and numerical description of soil cyclic behavior. It begins with comprehensive experimental databases on Malaysian kaolin and Zbraslav sand. In each database, several monotonic and cyclic tests were performed and analyzed considering a wide range of initial conditions and loading characteristics. In particular, the influence of the deviatoric stress amplitude, soil plasticity, initial stress ratio, drained cyclic preloading and sequence of packages of cycles with different deviatoric stress amplitudes was investigated on Malaysian...
265

Vliv vibrací na životnost vztlakových klapek letounu L 410 NG / Effect of vibrations on fatigue life of L 410 NG airplane flaps

Častulík, Lubomír January 2017 (has links)
Diplomová práce se zabývá návrhem metodiky pro stanovení vlivu vibrací na únavovou životnost a rychlost šíření trhlin u vztlakových klapek letounu L 410 NG. Úvodní část práce obsahuje potřebné informace o letounu a zatížení vztlakových klapek. Poté jsou popsány prostředky pro kvantitativní popis únavového procesu s využitím napěťového přístupu. Pro objasnění navrhované metodiky je uvedena definice obecného náhodného procesu a popis postupů aplikovaných na data získaná z letového měření. Hlavní část práce obsahuje podrobný popis navržené metodiky. Ta je zároveň aplikována na data získaná z měření na letounu L 410 UVP-E20.
266

Geodetic constraints on the present-day motions of the Arabian plate and the southern Red Sea region

Viltres, Renier 11 1900 (has links)
The present-day kinematics and deformation of the Arabian plate and the southern Red Sea region involves interaction of tectonic and non-tectonic processes including plate subduction, continental collision, seafloor spreading, intraplate magmatism, continental transform faulting, microplate rotation, hydrological loading cycles, and anthropogenic activity. Therefore, good constraints on the rates and directions of relative plate motion, plate boundary locations, and rheological properties in the area are essential to assess seismic and volcanic hazards in the region. In this thesis, I combine Global Navigation Satellite System (GNSS) measurements from over 200 stations with kinematic block modeling to provide updated estimates of the present-day motions of the Arabian plate and the southern Red Sea region. Using the non-rigid residual motions and changes in GNSS station baselines, I provide quantitative constraints on the internal deformation for the Arabian plate at different spatial scales. In addition, I use the GNSS station response to seasonal water exchange in the Red Sea to make inferences of the lithospheric elastic properties beneath Arabia. The GNSS-derived velocity field indicates coherent motion of both the Danakil block in the southern Red Sea and the Arabian plate at present. Current motions in the southern Red Sea region, however, are inconsistent with previous interpretations and require an additional plate boundary in the area. My updated fault slip rates improved earlier estimates limited by the number and spatial distribution of GNSS stations, particularly for the Arabian-Indian plate pair, for which slower right-lateral strike-slip motions are predicted. Non-rigid residual velocities within the Arabian plate interior indicate that large-scale internal deformations are compensated internally. However, at a smaller scale, I identify several localities accommodating significant strain, mostly related to anthropogenic activity. Ground response to surface mass loading associated with water transport in the Red Sea suggests that the Earth’s elastic structure beneath the Arabian plate is 20% to 30% less stiff than global averaged (i.e., AK135-F planetary model). Still, the lithosphere beneath both the Danakil block and the Arabian plate remains strong despite being affected by significant faulting and magmatism associated with the Nubian-Arabian-Eurasian plate interaction.
267

Seasonal Water Column Dynamics Exert Strong Control On The Chemical Partitioning Of Benthic Phosphorus Pools Of Shallow Eutrophic Freshwater Systems

Leduc, Meagan 01 January 2020 (has links)
In shallow lake systems, phosphorus (P) availability to cyanobacteria populations is often controlled by the release (internal loading) or sequestration of sediment P. This study provides novel insight into the feedbacks between the water column and benthic P pools across multiple time scales and explain how these dynamics influence chemical partitioning of P in lake sediment. Phosphorus partitioning in seasonal sediment core time series collected from a shallow eutrophic bay of Lake Champlain were quantified with SEDEX and enzyme hydrolysis selective extraction schemes. Time series extraction data were interpreted with concurrent water column physical and biogeochemical monitoring data to examine the relationship between water column dynamics and P partitioning of near-surface sediments in this intensively monitored system. Nonmetric multidimensional scaling analysis (NMDS) indicates that both sediment and water column time series cluster seasonally, linking water column variables such as pH, thermal stratification, and dissolved oxygen concentrations to the behavior of sediment P pools over the course of a year. Iron (FeP), exchangeable (Ex-P), calcium carbonate bound P (Ca-P) pools, and enzyme labile P were highly dynamic, especially in spring and summer. The SEDEX concentration data indicated that the sediment was mainly composed of inorganic bound P (De-P), but FeP and Ex-P pools proportionally varied most between sampling dates. Remarkably, while highly dynamic on an intra-annual timescale, the sediment ultimately returned to similar P concentration and chemical partitioning by late fall. The hysteretic nature of this interaction between water column dynamics and sediment P inventory/partitioning was clearly driven by systematic seasonal changes in water column physical, chemical, and ecological conditions governed by northern Vermont’s climate and the physical configuration of the bay and its watershed. This study provides novel insight into the unique challenges associated with improving water quality in lake systems impacted by internal loading of legacy P.
268

Efficacy of gapseal® in preventing microleakage at the dental implant abutment interface

Badi Mohamed, Hadeel Mohamed January 2021 (has links)
Magister Chirurgiae Dentium (MChD) / Dental implants have proven to be a success in the past decades, however the inevitable presence of microgaps at the implant abutment interface leading to microleakage is still a distressing concern. Microbial leakage can lead to peri-implant disease and bone loss and reduces implants' success rates. Measures to decrease the effect of the microgap were introduced; amongst them is the application of silicone sealing gels, such as GapSeal®.
269

Analýza zatížení hráčů fotbalu v zápase z hlediska hráčského postu / Analysis of soccer match loading according to player position.

Bujnovský, David January 2014 (has links)
Title: Analysis of load football players in a match in terms of gaming post. Objectives: The aim of this essay is to determine the size of the musculoskeletal load of players during friendly football matches. At the same time the aim is to determine the differences in the size of the musculoskeletal load between the different players' positions measured in the file. Methods: This essay deals with the indirect (mediated) observations, due to the fact that data was recorded by devices from which this data was then processed to obtain the result. To evaluate the size of the musculoskeletal load sport testers "Polar Team 2" were used. For the statistical evaluation the processed material significance using the so-called "size effect" was used. Results: Regarding the size of the musculoskeletal load, no substantively significant difference was found between the defenders and midfielders in the zone above the ANP. Significant material differences were observed between defenders and attackers, materially significant differences were also found between the midfielders and attackers in the zone above the ANP. However, based on the conditions under which measurements were carried out, it is clear that definite conclusions cannot be drawn. Keywords: Football, physical load, heart rate, player's positions
270

Assessment of nutrient loading in lake Ringsjön from the catchment of Hörbyån Creek in Southern Sweden.

Singh, Durgesh Kumar January 2013 (has links)
Lake Ringsjön, located in south of Sweden, has been subject of eutrophication since 1950s and received several restoration efforts. Latest restoration effort, “Project Ringsjön”, was proposed in 2003 to improve lake condition against eutrophication by reducing nutrient concentration. This study was done to assess the nutrient loading into the lake from the catchment of Hörbyån Creek, which is discharging into the lake from southeast. Study addresses the nutrient loading conditions from Hörbyån Creek before and after the implementation of “Project Ringsjön” in 1998 and 2010 respectively. Thus a water quality analysis was performed to observe the changes in total nitrogen and total phosphorus concentration in Hörbyån Creek between these years. Effort was also made to investigate nutrients contribution of different watersheds in the catchment. This study also addresses the effect of seasonal variability and land use on nutrient loading. In order to achieve objectives, annual and monthly water quality modelling was performed on the river. HEC-RAS software was used to simulate water quality variables loading from catchment into the lake, such as nitrates, nitrite, ammonium, organic nitrogen, inorganic phosphorus and orthophosphate. Results indicated increase in average annual total nitrogen concentration from 4.18 mg/l to 4.56 mg/l and reduction in average annual total phosphorus concentration from 0.165 mg/l to 0.083 mg/l in the water discharging into the lake from catchment. The watershed occupying mostly agriculture area was observed to have maximum nutrients contribution, which might be due to high fertilizer leakage. It was also observed that maximum nutrient loading was taking place in November and March; probably due to high runoff generated from precipitation and snow melting that carried additional nutrients to the water bodies. Results also indicated that the studied catchment area was contributing high nutrient concentration for eutrophication in both years; however, there was small decrease in total phosphorus concentration in 2010 compare to 1998.

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