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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.
281

En social rörelse och finanspolitiska problem : En studie av två grupper inom Occupy-rörelsen

Cheng, Melanie January 2012 (has links)
I dagens värld har länder ett tätt sammanlänkat ekonomiskt samarbete. Detta innebär att ifall ett land drabbas av en finanskris, kommer även andra länder att falla likt dominobrickor, in i en väntande finanskris. Just detta skedde år 2008 och 2011, då ett flertal av världens länder drabbades av en stor finansiell kris. I skuggan av dessa kriser växte en social rörelse fram vars syfte var att uppmärksamma människor om vad som, enligt rörelsen, egentligen hade hänt. Rörelsen som växte fram är känd som Occupy-rörelsen. Denna studie har som mål att undersöka hur två grupper inom rörelsen skapar legitimitet för ett alternativt perspektiv på finansiella kriser men även hur de vill lösa pågående och framtida ekonomiska kriser. För att detta ska bli möjligt användes Snow & Benfords inramningsteorier. Enligt Snow & Benford ska en inramning ses som en strukturell bas av en persons perspektiv och värderingar inom ett policyområde. Genom att använda sig av olika inramningar kommer personer att skapa olika lösningar samt strategier för att lösa ett problem. Snow & Benford anser att detta perspektiv även går att använda på sociala rörelser. För att kunna göra denna studie studerade jag Occupy Wall Street samt Occupy Stockholms Internetsidor. Min studie visar ett tydligt resultat. Grupperna anser inte att finanskriserna är ett problem i sig, utan ett symptom. Finanskriserna är ett symptom av ett underskott. Ett demokratiskt underskott.
282

Dynamische Stoßsimulation eines flexiblen Schutzwandsystems für Prüfanlagen / Dynamic impact simulation of a protective wall system for test systems

Eisenbeiß, Jens 10 May 2012 (has links) (PDF)
flexibles Wandsystem mit Makrolonscheiben zum Schutz vor weggeschleuderten Bauteilen beim Probebetrieb von Prüfanlagen ; dynamische Simulation eines Aufpralls auf die Schutzwand ; Aufbau des Simulationsmodells, Modalanalysen, dynamische Analysen im Zeitbereich ; Ermittlung des zeitlichen Verlaufs von Spannungen, Verformungen, Schraubenbetriebskräften und Versagensindizes nach dem Aufprall
283

Derivatizations of Multi-Wall Carbon Nanotube for Doping of Conjugated Poly-(3-hexylthiophene) for Electric Conductivity and Photovoltaic Cells

Chen, Ying-ren 24 June 2010 (has links)
Due to entropy and Van der Waals¡¦ interaction, carbon nanotubes tend to aggregate degrading their excellent opto-electronic properties and limiting their applications. Chemical derivatizations were applied to the multi-wall carbon nanotube (MWCNT) by esterificating with different lengths of aliphatic pendants (COOC4H9, COOC10H21, and COOC18H37) to decrease the MWCNT aspect ratio to facilitate its dispersion, and to observe its percolation behavior. FTIR analysis revealed the more relevant absorption peaks of C-H at 2917 cm-1, 2846 cm-1 and C=O at 1733 cm-1 from the derivatization. H1-NMR showed that the aliphatic pendant functionalized MWCNT from the signals of OCH2 at £_ = 3.64 ppm, CH2 at £_ = 1.25 ppm, and CH3 at £_ = 0.88 ppm. Raman scattering indicated that esterification caused the ID/IG absorption peak area ratio to decrease. In applications, the electric conductivity was measured on thin-films of MWCNT:Poly-(3-hexylthiophene) (P3HT) as a function of nanotube content. Accompanied with nanotube doping concentration increased, the electric conductivity parallel to film surface (£m||) could range from an undoped value 1.4¡Ñ10-6 S/cm up to 1.2¡Ñ10-2 S/cm. The conductivity percolation threshold concentration decreased as the MWCNT aspect ratio increased due to the average distance between the nanotubes becoming sufficiently small for charges to hopping through P3HT. By incorporating [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM), bulk heterojunction photovoltaic (PV) cells of ITO/PEDOT:PSS/MWCNT:[PC61BM:P3HT]/LiF/Al were fabricated. By varying the ratio of MWCNT to the PC61BM:P3HT (0.8:1) mixtures, the PV cells showed the maximum power conversion efficiency (£bp) close to 4 % with MWCNT-COOC4H9 at a doping concentration of 0.01 wt. %.
284

Design of Roadside Barrier Systems Placed on Mechanically Stabilized Earth (MSE) Retaining Walls

Kim, Kang 16 January 2010 (has links)
Millions of square feet of mechanically stabilized earth retaining wall are constructed annually in the United States. When used in highway fill applications in conjunction with bridges, these MSE walls are typically constructed with a roadside barrier system supported on the edge of the wall. This barrier system generally consists of a traffic barrier or bridge rail placed on a continuous footing or structural slab. The footing is intended to reduce the influence of barrier impact loads on the retaining wall system by distributing the load over a wide area and to provide stability for the barrier against sliding or overturning. The proper design of the roadside barrier, the structural slab, and the MSE wall system requires a good understanding of relevant failure modes, how barrier impact loads are transferred into the wall system, and the magnitude and distribution of these loads. In this study, a procedure is developed that provides guidance for designing: 1. the barrier-moment slab, 2. the wall reinforcement, and 3. the wall panels. These design guidelines are developed in terms of AASHTO LRFD procedures. The research approach consisted of engineering analyses, finite element analyses, static load tests, full-scale dynamic impact tests, and a full-scale vehicle crash test. It was concluded that a 44.5 kN (10 kips) equivalent static load is appropriate for the stability design of the barrier-moment slab system. This will result in much more economical design than systems developed using the 240 kN (54 kips) load that some user agencies are using. Design loads for the wall reinforcement and wall panels are also presented.
285

Characterization of surfactant dispersed single wall nanotube - polystyrene matrix nanocomposite

Ayewah, Daniel Osagie, Oyinkuro 15 May 2009 (has links)
Carbon nanotubes (CNT) are a new form of carbon with exceptional electrical and mechanical properties. This makes them attractive as inclusions in nanocomposite materials with the potential to provide improvements in electrical and mechanical properties and allows for the creation of a new range of multifunctional materials. In this study single wall carbon nanotubes (SWCNT) were dispersed in polystyrene using a solution mixing method, with the aid of a surfactant. A good dispersion was achieved and the resulting nanocomposites were characterized for electrical conductivity and mechanical properties by 3 point flexural and fracture toughness tests. Results show a significant improvement in electrical properties with electrical percolation occurring between 0.1 and 0.2 wt%. A minor improvement was observed in the flexural modulus but the strength and fracture toughness values in the nanocomposites decreased relative to the neat material. Scanning electron microscopy (SEM) was performed to characterize the morphology and fracture surface of the specimens. The results of testing and microscopy show that the presence of the nanotubes has an adverse effect on the crazing mechanism in Polystyrene (PS) resulting in a deterioration of the mechanical properties that depend on this mechanism.
286

Effect of Collection Method and Archiving Conditions on the Survivability of Vegetative and Spore Forming Bacteria

Kassab, Asmaa S. 2009 August 1900 (has links)
To ensure effective detection of bio-particles, it is crucial to understand the effects of collection method and archiving conditions on the survivability of bioaerosols, consequently, the survivability of the spore-forming Bacillus globigii (BG) and MG1655 Escherichia coli (E. coli), was determined after collection. The survivability was defined as the culturable fraction of the archived bacteria/culturable fraction of the as-collected bacteria. The bacteria were aerosolized for up to four days at room temperature (RT, 25 degrees C) and at 4 degrees C and collected in a 100 L/min wetted wall cyclone (WWC) and a 12.5 L/min SKC BioSampler. Aqueous solutions of 0.01% Tween-20 and 30% Ethylene Glycol (EG), with or without 0.5% ovalbumin (OA), were used as the collection fluids. Antifoam B (A-F), at a concentration of 0.2% (V:V) was added to the BG samples containing OA. In general, samples archived at 4 degrees C showed higher survivability than at RT. The survivability were more stable in EG than in Tween-20 especially for BG, very likely due to the surfactant effect of the Tween-20, which would remove the spore coat and initiate germination. In the WWC, adding OA significantly increased the survivability of BG in EG and in Tween-20, especially at RT. Similar effect of OA was found for E. coli samples stored in EG, suggesting that OA might be beneficial in maintaining the survivability. Adding A-F increased the survivability of BG in EG. In the SKC, neither the addition of OA nor A-F seems to have a beneficial effect on the survivability of the spores in EG samples. The best collection fluid for maintaining survivability in the WWC is EG+A-F for BG, and EG+OA for E. coli. However, in the SKC, EG is the best for BG collection and Tween-20 for E. coli. Viability transfer ratios, VTR, (cells surviving collection at time zero/viable cells aerosolized) were calculated for both devices. A performance ratio was calculated as the VTR of the WWC/VTR of the SKC. The geometric mean of the performance ratio is 1.51+/-0.83 for BG and 2.60+/-0.16 for E. coli, indicating that viability transfer ratio of the WWC is typically higher than that of the SKC.
287

Evaluating the von Kármán Constant in Sediment-laden Air Flow

Li, Bailiang 2010 December 1900 (has links)
Shear velocity is a critical variable used in many hydrodynamic and aeolian applications. The Law of the Wall is commonly used to derive shear velocity as the product of the slope of a measured velocity profile and the von Kármán constant, κ = 0.4. However, a number of hydrodynamic experiments show that there is a substantial apparent decrease of κ in sediment-laden flow, which was explained by: 1) The energy loss to support the sediment particle suspension in the fluid and 2) The buoyancy effect due to stratification. The energy loss is associated with sediment concentration and grain size, and the stratification can be characterized by sedimentological flux Richardson number or gradient Richardson number. Since there is an apparent change of κ, the term “apparent von Kármán parameter”, or κa, was adopted from Wright and Parker to replace κ in sediment-laden flow. There has been no study to attempt to detect and to evaluate the variability of κa during aeolian saltation, which is the purpose of this dissertation research. Two “clear air” runs and fifteen “sediment-laden” runs were conducted at the northeast coast of Brazil. Wind profile data were collected by a stack of cup anemometers; “true” shear velocity was estimated by an ultrasonic anemometer; and sediment mass flux profile and grain size were estimated from the sand samples collected in a stack of vertical hose-style traps. With these estimates, κa, sediment concentration and sedimentlogical Richardson numbers were derived. Regression analysis indicates that there is a statistically insignificant relationship between κa and grain size, which may be caused by small range of grain size in the study site. However, there is strong statistical relationship between κa and bulk, volumetric concentration below 25 mm, S25, and between κa and sediment transport rate Q (kg/m/s) as: ka = -2088.4S25 0.3964 and ka = -3.134Q 0.4011 A strong relationship was also found between κa and sedimentological Richardson numbers in the lower saltation layer, which can be well explained by the stratification theory.
288

Development and Evaluation of a Virtual Haptic Environment

Lin, Chun-yu 13 July 2004 (has links)
As the progress of computer, virtual reality has become a more and more widespread technology and is applied extensively in entertainment, training, or medical science. To increase the interaction and reality of the virtual technology, the development of haptic feedback improves rapidly in recent years. This paper focuses on judgment existing collision detection algorithms, virtual wall models, and friction models from the view point of man-machine interface. A virtual environment interface with force feedback by using a joystick for computer game as a haptic device is established. A virtual environment is also built by employing the DirectX, a 3D computer graphic software developed by Microsoft Corp. Three virtual wall models are compared and four operational experiments are conducted to explore the influence of force feedback on operation task in virtual environment.
289

Experimental Study of Mean Water Level Variation on Platform

Wei, Wen-jun 13 October 2004 (has links)
According to the observational data in the northeast coast of Taiwan when the strong typhoon invaded, it was found that abnormal water variation happened several times, and all the abnormal water levels (storm surge) were higher than the normal engineering consideration. In this study, the variation of mean water level (wave set-up & wave set-down) due to progressive wave over a seabed with specific profile has been investigated. This specific seabed is simulated by the hydrodynamic physical models in the laboratory. Two kinds of experimental models are arranged; one is combined by three sections: slope, platform, and vertical wall, and another is combined by slope and vertical. Furthermore, two different slopes of 1/10 and 1/30 were considered. All experimental conditions were controlled such that incident waves break on slope and mean water levels were measured. In the first model arrangement, surf similarity parameter and dimensionless parameters form by incident and break wave condition are found to be functions of relative max mean water level, but when slope is steep(1/10), the relation between these dimensionless parameters is not obviously. In the second model arrangement, mean water level variation is compared with the theoretical value of single slope. When slope is mild(1/30), experimental results of mean water levels quit agree with theoretical value; when slope is steep(1/10), caused by the reflection of vertical wall, mean water levels in the break point and surf zone are different form theoretical value significantly.
290

Relationships Between Topography And Kerkenes (turkey), A Gis Analysis

Atalan Cayirezmez, Nurdan 01 October 2006 (has links) (PDF)
This study investigates the effect of topography in ancient city Kerkenes using Geographic Information Systems (GIS). Kerkenes, an Iron Age city located on a batholith in Yozgat province, Turkey, was chosen because of its exceptional size, short life and the availability of extensive data. Approximately seven kilometres of city wall in Kerkenes, including towers and seven gates, enclose 2.5 km&sup2 / . The research comprises topographic analysis and settlement data analysis. Elevation values collected by Global Positioning System (GPS) and 1:25000 scaled topographic maps are used to create and analyze elevation, slope and aspect maps. Basic statistics of the city wall, towers and gates are calculated and a procedure is then followed to examine the city wall, towers and gates to understand reasons for the line of the city wall, the uneven distribution of gates, the position of each individual gate, the positions and spacing of towers, and the water catchments. Advantages of the elevated site of Kerkenes for the foundation of a new capital within the region are demonstrated. The GPS data do not show statistically significant differences then the 1:25000 scaled topographic maps in regional scale, especially analyzing the elevation and slope data. Topographic analyses reveal that approximately 75% of the city wall coincides with the topographic divide which shows the city walls may serve both for urban water collection and for defence. City wall has divided into two as East section and West section by a north-south axis from the north end point of the city. There are 41 and 27 towers are detected on the West and East section, respectively. Towers on the West section are more closely spaced than the East section. There are also two and five gates in the West and East section, respectively. The East section of the city wall overlaps with the topographic divide only in the northeastern part. This situation can not be traced along the southeastern part of Kerkenes which may be the reason to include the strategically important two higher altitude areas (Kiremitlik and Kale) inside the city. The city wall in the West section, however, runs along the topographic divide which affects the number and the distribution of the towers.

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