• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 108
  • 24
  • 24
  • 13
  • 13
  • 9
  • 3
  • 3
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 231
  • 96
  • 63
  • 37
  • 25
  • 25
  • 22
  • 21
  • 21
  • 20
  • 19
  • 19
  • 18
  • 16
  • 15
  • 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

Sail shape and sailing performance measurement : the Chinese lug sail

Chapman, Edward John Critchett January 2000 (has links)
No description available.
2

High pressure three-phase (gas/liquid/liquid) flow

Lei, Pan January 1996 (has links)
No description available.
3

Thermal Impact of a Calibrated Stereo Camera Rig

Andersson, Elin January 2016 (has links)
Measurements performed from stereo reconstruction can be obtained with a high accuracy with correct calibrated cameras. A stereo camera rig mounted in an outdoor environment is exposed to temperature changes, which has an impact of the calibration of the cameras. The aim of the master thesis was to investigate the thermal impact of a calibrated stereo camera rig. This was performed by placing a stereo rig in a temperature chamber and collect data of a calibration board at different temperatures. Data was collected with two different cameras and lensesand used for calibration of the stereo camera rig for different scenarios. The obtained parameters were plotted and analyzed. The result from the master thesis gives that the thermal variation has an impact of the accuracy of the calibrated stereo camera rig. A calibration obtained in one temperature can not be used for a different temperature without a degradation of the accuracy. The plotted parameters from the calibration had a high noise level due to problems with the calibration methods, and no visible trend from temperature changes could be seen.
4

Testing of different adhesives in electric drives for high pererrformance applications

Persson, Johan January 2010 (has links)
The task of this thesis is to test different adhesives uses in electrical drives for high performance applications. The purpose is to investigate possible replacements to the current used adhesive which will be obsolete in short term. This task is approached by first doing a literature search for typical testing methods for adhesives and which ones are appropriate for Moog. Then, a test rig is designed to accomplish the tests. Finally, the tests are evaluated and analysed to find out the best replacement adhesive.
5

The Feasibility of Natural Gas as a Fuel Source for Modern Land-Based Drilling Rigs

Nunn, Andrew Howard 2011 December 1900 (has links)
The purpose of this study is to determine the feasibility of replacing diesel with natural gas as a fuel source for modern drilling rigs. More specifically, this thesis (1) establishes a control baseline by examining operational characteristics (response, fuel usage, and cost) of an existing diesel-powered land rig during the drilling of a well in the Haynesville Shale; (2) estimates operational characteristics of a natural gas engine under identical conditions; and (3) draws a comparison between diesel and natural gas engines, determining the advantages and disadvantages of those fuel sources in drilling applications. Results suggest that diesel engines respond to transient loads very effectively because of their inherently higher torque, especially when compared with natural gas engines of a similar power rating. Regarding fuel consumption, the engines running on diesel for this study were more efficient than on natural gas. On a per-Btu basis, the natural gas engines consumed nearly twice as much energy in drilling the same well. However, because of the low price of natural gas, the total cost of fuel to drill the well was lowered by approximately 54%, or 37,000 USD. Based on the results, it is possible to infer that the use of natural gas engines in drilling environments is feasible, and in most cases, an economical and environmental advantage. First, when compared with diesel, natural gas is a cleaner fuel with less negative impact on the environment. Second, fuel cost can be reduced by approximately half with a natural gas engine. On the other hand, natural gas as a fuel becomes less practical because of challenges associated with transporting and storing a gas. In fact, this difficulty is the main obstacle for the use of natural gas in drilling environments. In conclusion, because of its minimal drawback on operations, it is recommended that in situations where natural gas is readily available near current market prices, natural gas engines should be utilized because of the cost savings and reduced environmental impact. In all other cases, particularly where transport and storage costs encroach on the cost benefit, it may still be advantageous to continue powering rigs with diesel because of its ease of use.
6

Structural Basis of Viral RNA Recognition by RIG-I-Like Receptors

Lu, Cheng 2012 August 1900 (has links)
RIG-I-like receptors (RLRs), RIG-I, MDA5, and LGP2, are a family of innate immune receptors that recognize viral RNA in the cytoplasm and initiate antiviral responses including the induction of type I interferons and other pro-inflammatory cytokines. All three proteins have both an RNA helicase domain with ATPase activity and a C-terminal domain (CTD) which is responsible for RNA binding. RIG-I and MDA5 also have two tandem caspase activation and recruitment domains (CARDs) at the N-terminus which are involved in downstream signaling. To understand the structural basis of viral RNA recognition by the RLRs, especially RIG-I, we have performed extensive biochemical studies to determine the binding properties of RIG-I with different forms of RNA, including dsRNA with and without 5'-triphosphate (5'-ppp) groups, and 5'-ppp ssRNA. RIG-I CTD binds to these forms of RNA, and exhibits the highest affinity for 5'-ppp dsRNA. We also determined the crystal structures of RIG-I CTD in complex with dsRNA with and without 5'-ppp by X-ray crystallography. The structures showed that RIG-I recognizes the termini of the dsRNA and interacts with the two types of RNA in different orientations. By comparing these complex structures together with mutagenesis studies, we conclude that RIG-I CTD is a versatile binding module capable of recognizing different RNA ligands. Similar but partially differing sets of residues are involved in the recognition of dsRNA with and without 5'-ppp. Mutations of key residues at the RNA binding surface also abolished RIG-I signaling in cells. In order to compare the RIG-I/RNA interactions with other RLRs, we also determined the dsRNA binding surface of MDA5 CTD by NMR titration studies. MDA5 CTD has a similar binding surface to that of RIG-I CTD, however with slightly different surface electrostatic potentials which indicate different interactions with RNA. This may explain how MDA5 senses differing types of viruses compared to RIG-I. The current RIG-I activation model suggests that after stimulation by RNA binding, RIG-I undergoes an ATP-dependent conformational change, exposing the CARDs for downstream signaling. To understand the critical role that the helicase domain plays in RIG-I activation by structural approach, we also attempted to crystallize the dsRNA-bound helicase domain together with CTD.
7

Marine growth and the hydrodynamic loading of offshore structures

Theophanatos, Andreas January 1988 (has links)
This thesis presents the results of a study on the effects of marine growth on the hydrodynamic loading of offshore structures and proposes an approach that can be adopted by designers and operators to quantify these effects. The approach is based upon the realistic characterisation of marine growth and its temporal variations during the life span of template structures. Past research work and current design, inspection and maintenance practices are critically reviewed and their limitations with respect to marine growth are highlighted. The ecology of marine growth for a sample of North Sea platforms was examined to establish the variety and physical attributes of the fouling colonies. The traditional single-parameter characterisation of marine roughness was found to be inadequate. Appropriate parameters, verified by fluid loading experiments, are established. Details of the laboratory experiments undertaken with both real marine growth and artificial macro-roughness on circular cylinders are given. These tests were carried out at large scale (cylinders up to 521mm diameter) in a novel "buoyant cylinder" test rig (steady flow) and in a large wave flume (regular waves). A wide range of parametric variations were undertaken for the various types of marine growth in an attempt to establish a comprehensive database from which the loading effect of any likely, practically occuring, marine growth pattern can be estimated. The extent to which this is achieved and the requirements for further research are discussed in detail. It is concluded that the effects of marine growth are both substantial and diverse. Drag forces vary with type of fouling, overall thickness, surface cover, and distribution. Finally, detailed procedures are recommended for the design of new structures and the improved loading assessment of existing ones.
8

Studier och idrott : En jämförande studie mellan riksidrottsgymnasium och lokalt idrottsgymnasium i idrotterna fotboll och golf

Lennartsson, Tore, Söderström, Mikael January 2005 (has links)
<p>Syftet med studien har varit att undersöka faktorer som påverkar eleven vid val till lokalt idrottsgymnasium eller riksidrottsgymnasium inom idrotterna fotboll och golf samt undersöka hur eleverna upplever kombinationen skola/idrott och deras framtida målsättningar med sin idrott och sina studier.</p><p>Undersökningen bestod av en enkät, vilken besvarades av 48 elever som studerade i årskurs 3 läsåret 2004/2005 på det lokala idrottsgymnasiet Borgarskolan i Gävle, riksidrottsgymnasiet golf i Perstorp och riksidrottsgymnasierna fotboll i Västerås och Norrköping. Undersökningen kompletterades med sex intervjuer, en instruktör, en lärare och fyra elever.</p><p>Valet av idrottsgymnasium inom golf styrs, enligt denna undersökning, av bra träningsförhållanden samt en duktig instruktör. Att träningsgruppen håller hög kvalité har också betydelse. Föräldrarna har större påverkan vid val till riksidrottsgymnasium än vid val till lokalt idrottsgymnasium i både fotboll och golf. Vid val av idrottsgymnasium inom fotboll tycks valet främst påverkas av träningsförhållanden och kvalitén på träningsgruppen . Ekonomin är av mindre betydelse vid valet av gymnasium oavsett idrott.</p><p>Oavsett idrott och skola så upplever eleverna att satsningen på specialidrotten påverkats positivt genom att de gått i en idrottsklass. Eleverna på lokalt idrottsgymnasium fotboll är mindre nöjda med studieresultaten än eleverna på riksidrottsgymnasium fotboll. Eleverna på lokalt idrottsgymnasium golf är mer nöjda med studieresultaten än eleverna på riksidrottsgymnasium golf. Generellt är golfeleverna i stort sett nöjda, fotbollseleverna mindre nöjda med den personliga utvecklingen inom idrotten, eleverna på riksidrottsgymnasium fotboll något mer nöjda än eleverna på lokalt idrottsgymnasium fotboll.</p><p>Framtida målsättningen med idrotten är hög hos i stort sett samtliga elever, något högre hos de elever som går på riksidrottsgymnasierna än hos de elever som går på lokala gymnasiet. De flesta siktar på att nå nationell eller internationell nivå, samtliga elever på riksidrottsgymnasiet golf siktar på att nå internationell nivå. Målsättningen med studier är också hög, 33 av de 48 elever som svarade på enkäten hade för avsikt att studera på universitet eller högskola. Av dessa hade 22 elever som målsättning att kombinera en satsning på idrotten med studier.</p>
9

Studier och idrott : En jämförande studie mellan riksidrottsgymnasium och lokalt idrottsgymnasium i idrotterna fotboll och golf

Lennartsson, Tore, Söderström, Mikael January 2005 (has links)
Syftet med studien har varit att undersöka faktorer som påverkar eleven vid val till lokalt idrottsgymnasium eller riksidrottsgymnasium inom idrotterna fotboll och golf samt undersöka hur eleverna upplever kombinationen skola/idrott och deras framtida målsättningar med sin idrott och sina studier. Undersökningen bestod av en enkät, vilken besvarades av 48 elever som studerade i årskurs 3 läsåret 2004/2005 på det lokala idrottsgymnasiet Borgarskolan i Gävle, riksidrottsgymnasiet golf i Perstorp och riksidrottsgymnasierna fotboll i Västerås och Norrköping. Undersökningen kompletterades med sex intervjuer, en instruktör, en lärare och fyra elever. Valet av idrottsgymnasium inom golf styrs, enligt denna undersökning, av bra träningsförhållanden samt en duktig instruktör. Att träningsgruppen håller hög kvalité har också betydelse. Föräldrarna har större påverkan vid val till riksidrottsgymnasium än vid val till lokalt idrottsgymnasium i både fotboll och golf. Vid val av idrottsgymnasium inom fotboll tycks valet främst påverkas av träningsförhållanden och kvalitén på träningsgruppen . Ekonomin är av mindre betydelse vid valet av gymnasium oavsett idrott. Oavsett idrott och skola så upplever eleverna att satsningen på specialidrotten påverkats positivt genom att de gått i en idrottsklass. Eleverna på lokalt idrottsgymnasium fotboll är mindre nöjda med studieresultaten än eleverna på riksidrottsgymnasium fotboll. Eleverna på lokalt idrottsgymnasium golf är mer nöjda med studieresultaten än eleverna på riksidrottsgymnasium golf. Generellt är golfeleverna i stort sett nöjda, fotbollseleverna mindre nöjda med den personliga utvecklingen inom idrotten, eleverna på riksidrottsgymnasium fotboll något mer nöjda än eleverna på lokalt idrottsgymnasium fotboll. Framtida målsättningen med idrotten är hög hos i stort sett samtliga elever, något högre hos de elever som går på riksidrottsgymnasierna än hos de elever som går på lokala gymnasiet. De flesta siktar på att nå nationell eller internationell nivå, samtliga elever på riksidrottsgymnasiet golf siktar på att nå internationell nivå. Målsättningen med studier är också hög, 33 av de 48 elever som svarade på enkäten hade för avsikt att studera på universitet eller högskola. Av dessa hade 22 elever som målsättning att kombinera en satsning på idrotten med studier.
10

Group Based Rigging of Realistically Feathered Wings

Howard, Heather Vernette 2011 December 1900 (has links)
Digital birds are used in computer graphics to replace live animals both for the safety of the animal and to allow for more control over performance. The current treatment of avian wings in computer graphics is often over-simplified which results in a loss realism due to the incorrect form and motion of the feathers. This research attempts to address this problem by using the structure and motion of real bird anatomy to inform the creation of biologically accurate kinematic motion for wings. The hypothesis of this thesis is that a wing rig which follows biological accuracy will appear realistic in motion and facilitate efficient animation. This thesis describes the creation of a rig generation tool, called WingCreator, usable in 3D animation software to guide the construction of biologically accurate wings while maintaining a range of artistically-driven variability in form. The control system for the kinematic motion rig is designed to provide animators with intuitive control over wing behavior intended to result in efficient re-creation of realistic wing action including flapping and folding. WingCreator was tested by two riggers and one animator to gain feedback on the tools efficacy. The user feedback indicates that the resulting rig provides a control system that facilitates efficient animation while maintaining artistic control over the wing. Users reported that realism, however, could not be judged due to the numerous contributing outside factors, such as animation, lighting and texturing, that affect the perception of realism. WingCreator and its creation methodology is intended to be placed in the public domain for use by anyone and will add to the currently slim body of knowledge for creating realistic avian wings. Once placed in the public domain it is expected that this rig will be appropriated by animators who wish to create more accurate bird wing motion and by riggers who may use the biologically-driven methodology as a model for further exploration into depictions of other animals exhibiting complex form and structural motion behaviors.

Page generated in 0.0262 seconds