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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.
1

SMALL-ANGLE X-RAY SCATTERING STUDIES OF NANOSTRUCTURED RESPIRATOR AND BATTERY MATERIALS

McDonald, Matthew 24 October 2013 (has links)
This work represents a small-angle X-ray scattering (SAXS) investigation into the structure of two rather different materials: chemically impregnated activated carbons (IACs) and the nanostructured alloy of tin-cobalt-carbon. Five impregnant species, namely sodium benzoate, potassium biphthalate, zinc chloride, potassium carbonate, and silver nitrate, were impregnated into activated carbon using the incipient wetness or imbibing method to various loadings and examined. Using a modified version of the Kalliat model and a suitable interpretation, two different impregnant behaviours arose: one marked by good chemical dispersion over all classes of carbon pores, the other characterized by a formation of large grains but little deposition in micropores or formation of small grains. A special apparatus was constructed to collect SAXS data of Li-ion coin cells with beryllium windows using a nanostructured SnCoC electrode. When one such cell was charged and discharged, the entry and exit of lithium atoms into the SnCoC material caused structural deformations, which were visible in SAXS data through the use of the modified Kalliat model. The size of the SnCo grains changed as lithium was inserted and removed from the SnCoC electrode. However, when the cell voltage was less than 0.2 V the SnCo grain size was constant, suggesting lithium insertion and removal below 0.2 V was occurring in the carbon matrix.
2

Spatial analysis of crop rotation practice in North-western Germany

Stein, Susanne 14 July 2020 (has links)
No description available.
3

Analyses of Two Ice Class Rules : for The Design Process of a Container Ship

Su, Yixiang January 2017 (has links)
During ice voyages, level ice and iceberg with huge inertia force can cause large deformation and even damage on the ship hull structure. Hence the hull structure for ice voyage requires higher strength than it for open water voyages. A container ship will be re-designed for ice voyages in the thesis. Generally, the ice strength is evaluated in ice class rules. IACS polar class and FSICR are adopted in this thesis. Ice class rules are based on experience and experiment data, but there has been no exact formula or parameters to described the ice properties so far. In other words, the results from ice class rules include uncertainties. In order to improve physical understanding, non-linear FE simulations will be processed after the re-design. In the simulations, the ship has a collision with different ice scenarios. The simulations are carried on ANSYS Workbench Explicit Dynamic using the solver of Auto-dyna. Afterwards, the results from the two designs schemes are compared and analysed.
4

Grain Refinement of Commercial EC Grade 1070 Aluminium Alloy for Electrical Application

Hassanabadi, Massoud January 2015 (has links)
The aluminium alloys for electrical conductivity applications are generally not grain refinedsince the addition of grain refiners drops the electrical conductivity by introducing impuritiesinto the melt. Non-grain refined aluminium may lead to bar fracture and cracks during themetalworking process. The present study focuses to find an optimum balance between the grain refiner addition andthe electrical conductivity of commercial EC grade 1070 aluminium alloy for electricalapplication. In order to reach this goal, the electrical conductivity and the macrostructure ofcommercial EC grade 1070 aluminium (commercial pure aluminium) have been studiedunder a series of controlled lab scale trails. Specific addition levels of different grain refiners(TiBloy, Al-5Ti-1B, Al-3Ti-0.15C, and Al-3Ti-1B) were added to the metal melt and sampleswere taken at specific time intervals. The collected samples were sectioned, ground andmacro-etched. Thereafter, the macrostructure was analysed by the use of a digital camera andthe electrical conductivity was measured at temperature. The obtained result was expressed asa percentage of the International Annealed Copper Standard (IACS %). The macro-structuralanalysis showed that TiBloy, Al-5Ti-1B, and Al-3Ti-1B, with the maximum addition level of0.1%, cannot grin refine commercial pure aluminium. However, at higher grain refiner levelsthe number of columnar grains increased and their size decreased. The Al-3Ti-0.15C master alloy, with the same addition level as the once chosen for the othergrain refiners (up to 0.1%), showed significantly better grain refining. By the addition of0.1% of this grain refiner the macrostructure became very equiaxed already after 30 minutesof grain refiner addition. The fading of the Al-3Ti-0.15 master alloy was, however, observedfor samples with a long holding time. Nevertheless, by maximum addition level (0.1%) and a90 minutes holding time the macrostructure remained as equiaxed grains. The electrical conductivity results showed that none of the applied grain refiners (TiBloy, Al-5Ti-1B, Al-3Ti-0.15C, and Al-3Ti-1B), with the maximum addition level of 0.1%, decreasedthe electrical conductivity of commercial pure aluminium.
5

Review of an industrially implemented model of zoning principles for electricity distribution and energy production

Åberg, Erik January 2011 (has links)
The interconnection of components of industrial automation and control systems (IACS) and enterprise systems involved in processes ranging from generation and transmission to billing within electric utilities poses challenges regarding cyber security as well as division of organisational responsibility. One means of organising these components and systems is to use a zone model in which they are segmented, offering layered defences as well as a logical grouping. One such zone model is the zone model under review, which was presented by Zerbst et al. in a CIRED paper from 2009. This master thesis reviews that zone model and compares it to other industry standard zone models which have been found to be able to be categorised into either functional based models or layered defence models. The outcome is a rough definition of what kind of content fits in the various zones of the reviewed model, as well as a normalised zone model to be used for comparison. A suggested method for dividing system components into zones is based on the 4R-method considering the response time, resolution, reliability and reparability of the system component, although its accuracy has not been empirically tested.

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