Nowadays, the economic grows fast and changes a lot. Meanwhile, the central city gets bigger and bigger. More and more buildings locate everywhere while people enjoy their modern life. The needs of electricity grow by the way. In order to provide more power, the Power Company has tried very hard to find new resources. However, there is another problem when transferring the power through crowded city. To avoid the geographic limitation, most of the overhead lines have been changed into under ground lines instead. Sooner or later, the under ground cable will become the main power transmission. This thesis focuses on the current rating distribution of Taiwan 161KV line with various PE underground cables that contain one circuit, two circuits, four circuits, and eight circuits. The current rating goes within various pipes. To find the best economic benefit with the lowest investment by rearranging the pipes to reach the most current rating and by matching the current rating from under ground cable with the over head cable is the main goal of this thesis. JCS NO.168 analyzes the set up map for all the pipes. In order to offer the best power supply, to maintain the longest cable life within the acceptable working days, the calculating scripts support to figure out the current rating in shortest time.

Univ., Diss.--Bayreuth, 2006. / Literaturverz. S . 241 - 248.

Thesis (M.S.)--University of Florida, 2006. / Title from title page of source document. Document formatted into pages; contains 61 pages. Includes vita. Includes bibliographical references.

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

Bimodal polyethylene resins are frequently used for pipe applications. In this work, blending was used to produce polyethylenes with comparable properties, particularly with respect to processing, stress crack resistance and tensile properties. Suitable blend components were identified, and their performance screened used ECHIP experimental design software. Blends were characterized using gel permeation chromatography (GPC), differential scanning calorimetry (DSC), tensile testing, stress crack resistance measurements, impact toughness testing, capillary rheometry and melt index measurements. GPC, DSC and melt index results reveal that the method of meltcompounding produced morphologically uniform blends, with different degrees of compatibility depending on the type and level of branching of blend components. Most of the blends produced showed higher crystallinity values compared to a reference bimodal resin. Binary high density polyethylene (HDPE) blends showed better stiffness and strength properties, whereas metallocene catalyzed linear low density polyethylene (mLLDPE) containing blends illustrated superior elongation and toughness properties compared to the reference polymer and other binary blends. The highest resistance to slow crack growth (SCG) was shown by low density polyethylene (LDPE) and mLLDPE containing blends due to their high branching content. The overall blend resistance to SCG or toughness can be enhanced with levels less than 20% by weight of LDPE or mLLDPE in the blend although the tensile properties are relatively unaffected at these low concentrations. The performance of blends was optimized by changing component polymers and their weight fractions, and a model to predict optimum blends was developed using the Maple code. Optimized blends showed higher branching content, comparable molecular weight, molecular weight distribution, tensile properties, viscosity and processing behaviour to the reference polymer. Optimized blend 3, in particular, encountered the same degree of shear thinning as the reference material. Better toughness and resistance to SCG were shown by the optimized blends when compared to the reference polymer.

Single-site catalysts revolutionized the polyolefin manufacturing industry and research with their ability to make polymers with uniform microstructural properties. Several of these catalysts are currently used commercially to produce commodity and differentiated-commodity resins. The key to their rapid success and industrial implementation resides in the fact that they can be used without major modifications in the polymerization reactors that previously used heterogeneous Ziegler-Natta and Phillips catalysts. Since most of these industrial processes use slurry or gas-phase reactors, soluble single-site catalysts must be supported on adequate carriers that ensure not only high activity, but also the formation of polymer particles with the proper morphology and bulk densities. Metallocene catalysts have been supported on a variety of carriers, but supporting late transition metal catalysts has not been investigated in detail, despite their very interesting properties such as tolerance to polar comonomers and impurities, activity in the absence of MAO, and the formation of short chain branches by the chain walking mechanism. The research work of this PhD thesis intends to fill this gap, by developing supported late transition metal catalysts with high catalyst activities towards ethylene polymerization and good polymer particle morphology. The effects of catalyst structure and polymerization conditions on silica-supported nickel diimine catalysts are discussed in Chapter 3. Compared with the equivalent homogeneous catalysts, the covalently-attached supported catalysts had high activities, produced spherical polyethylene particles with good morphologies, and polyethylene with higher melting temperatures, higher molecular weight averages, and broader molecular weight distributions. Borates used as internal activators during the synthesis of these supported catalysts successfully activated the nickel diimine complexes. In Chapter 4, MgCl2/alcohol adducts are recrystallized with alkylaluminum compounds and used as catalysts supports for nickel diimine complexes functionalized with amine groups. Polymerization results were compared with those of the equivalent SiO2-supported nickel diimine catalysts. MgCl2-based supported nickel diimine catalysts had high catalyst activity without the use of activators, and it was possible to control polymer molecular weight averages by changing the support composition. Although linear low density polyethylene made with metallocenes offers superior mechanical properties such as excellent toughness, impact strength and clarity, it suffers from poor processability. To overcome some of these disadvantages, Chapter 5 introduces methods to produce bimodal polyethylene resins using supported hybrid early and late transition metal catalyst systems. The presence of short chain branches in the higher molecular weight component is attributable to the incorporation of alpha-olefin molecules by the metallocene sites, while the nickel diimine catalyst sites produce chains with a distribution of short chain branch sizes through the chain walking mechanism. Finally, in Chapter 6 supporting a nickel diimine catalyst onto organo-modified montmorillonite (MMT) to prepare polyethylene/clay nanocomposites through in-situ polymerization is described. The thermal properties and crystallinity of the nanocomposites could be controlled by varying the fraction of MMT in the nanocomposite, and the dispersion of the MMT layers in the polymer matrix were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

Zugl.: Berlin, Humboldt-Univ., Diss., 2007

Universiẗat, Diss., 2007--Giessen.

Thesis (Ph. D.)--University of Hong Kong, 2008. / Also available in print.

Thesis (Ph D.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 225-231). Also available via the Internet.