Diss. Nr. 7366 techn. Wiss. ETH Zürich.

The aim of the thesis was to gather information about magnetism, magnets and principles used in magnetic separation. The key point of this thesis was to assess the efficacy of an experimental magnetic separation operation. The first chapter is devoted to the introduction, which is a brief description of the problems of magnetic separation. The second chapter describes the current state of the problem, which explains the basic definitions and phenomena arising from the use of permanent magnets or electromagnets. Furthermore, this chapter describes in detail the magnetic separation. The third chapter is devoted to the work goals and methods of processing. The fourth chapter describes an experiment that was conducted to determine the effectiveness of a magnetic separator during the trial operation of transport technology to transport clinker. The last chapter is devoted to conclusions and contribution of this thesis.

This diploma thesis deals with design of the clothing storage. It is divided into two parts. In first, theoretical part was surveyed market and then produced recherche. Various materials were examined and it was decided which are most suitable for fabrication of the hanger. The hanger was designed to meet the requirements of modern times. The emphasis is mainly on simplicity and variability of use. The second part of this work is focused on the development of the clothing storage, its production on CNC, and resulting variants.

Polyimide is one of the most heat resistant polymers with high electric breakdown strength, good mechanical properties, and chemical resistance. Polyimide is used in severe environmental condition. Polyimide is commonly applied as electrical insulation in a fine gauge of invertered motor windings and in high voltage coils of encapsulated fly-back transformers. The wire insulation may be exposed to multi-stresses like ac, dc high voltages, temperatures etc. In this thesis, magnet wire insulation properties under multiple stresses are studied under ac, dc voltages and high temperatures. Accelerated degradation test is used to do study of Life -time characteristics of Magnetic wire MW 16-C, which has polyimide insulation. The results of accelerated aging test are evaluated with statistical tools Weibull and ALTA. The result shows that the time to failure can be represented by the inverse power law and the Arrhenius equation with respect to test voltage and temperature respectively.

Over the last three decades, the magnet school program has been employed as a desegregation tool to eliminate, reduce, or prevent minority group isolation in public schools in America. By definition, the magnet school program has three essential elements: a unified curriculum based on a special theme or method of instruction, enrollment of students beyond the geographic attendance zone, and student and parent choice. The impetus for magnet school programs emerged from debates covering busing, choice programs, educational quality, and racial balance. The early development of the magnet concept as a desegregation tool can be traced to judicial engagement of well-known court cases such as Brown v. Board of Education, 1954, where de jure segregation was ruled unconstitutional based on the equal protection clause of the 14th Amendment. In the late 1970s, the federal government began to provide financial support for magnet school programs through the Emergency School Aid Act (ESAA,1972) and established the Magnet Schools Assistance Program in 1984. Recent findings suggest that the magnet program may not be obtaining the desired results of eliminating, preventing, or reducing racial imbalances. Furthermore, it is believed that some districts receiving grants have little chance of reducing minority group isolation due to the limited pool of white students. This study was designed determine the extent of the reduction of minority group isolation in magnet school programs that received funding in the 1995 Magnet Schools Assistance Program. A survey instrument designed to gather enrollment information was mailed to the central office personnel who were responsible for the oversight of magnet school programs in sixty-four federally funded school districts. Findings of this study indicate that school districts with a significant population of minority students are unlikely to reduce minority group isolation using the Magnet Schools Assistance Program standard of at or no more than fifty percent minority enrollment in selected magnet programs even with financial assistance. Schools with high populations of minority students are unlikely to attract non-minority students. / Ed. D.

In this thesis I am presenting a detailed study to optimize the deposition of magnetic molecules and gold nanoparticles in atomically flat surfaces by self-assembling them from solution. Epitaxially grown and atomically flat gold surface on mica is used as substrate for this study. These surfaces have roughness of the order one tenth of a nanometer and are perfect to image molecules and nanoparticles in the 1-10 nanometers range. The purpose of these studies is to find the suitable parameters and conditions necessary to deposit a monolayer of nano-substance on chips containing gold nanowires which will eventually be used to form single electron transistors by electromigration breaking of the nanowire. Maximization of the covered surface area is crucial to optimize the yield of finding a molecule/nanoparticle near the gap formed in the nanowire after electromigration breaking. Coverage of the surface by molecules/nanoparticles mainly depends on the deposition time and concentration of the solution used for the self-assembly. Deposition of the samples under study was done for different solution concentrations and deposition times until a self-assembly monolayer covering most of the surface area is obtained. Imaging of the surfaces after deposition was done by tapping-mode AFM. Analysis of the AFM images was performed and deposition parameters (i.e. coverage or molecule/particle size distribution) were obtained. The subjects of this investigation were a molecular polyoxometalate, a single-molecule magnet and functionalized gold nanoparticles. The obtained results agree with the structure of each of the studied systems. Using the optimized deposition parameters found in this investigation, single-electron transport measurements have been carried out. Preliminary results indicate the right choice of the deposition parameters.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

No description available.

A range of lanthanide compounds incorporating soft bridging ligands or alkoxide ligands have been synthesised and their magnetic properties investigated. These two classes of compound have shown promise as single molecule magnets but have not been widely studied; this thesis aims to expand on this area of research. Softer bridging ligands are found to slightly increase superexchange interactions between metal centres compared to harder bridging ligands. The introduction to this thesis covers the basic properties of the lanthanides, paying special attention to their chemistry with soft donor ligands and alkoxide ligands. Also included is an introduction to the field of single-molecule magnetism and the role of lanthanide complexes in the study of this behaviour. In Chapter 2, four complexes are reported: the phosphine adducts [Cp'3Ln(H2PMes)] and the phosphide-bridged trimers [(Cp'2)Ln(μ-PHMes)]3 (Ln = Er, Gd). Their structures and magnetic properties are characterised. In Chapter 3, the novel dodecametallic thiolate-bridged lanthanide macrocycles [(Cp'2Ln)3({μ-SCH2}3CMe)]4 (Ln = Dy, Y, Gd) are reported and characterised by X-ray crystallography, NMR spectroscopy and magnetometry. [(Cp'2Dy)3({μ-SCH2}3CMe)]4 is shown to be a single-molecule magnet with Ueff = 69 cm-1. In Chapter 4, the novel thiolate-bridged lanthanide dimers [Cp'2Ln(μ-SCH2{C4H7S2})]2 (Ln = Dy, Y, Gd) are reported, showing sulfur-sulfur bonding leading to ring cyclisation of the bridging ligand [MeC(CH2S)3]3-. These complexes are characterised by X-ray crystallography, NMR spectroscopy and magnetometry. Extra NMR spectroscopic studies were performed to investigate the mechanism of ring closure on the bridging ligand. [Cp'2Dy(μ-SCH2{C4H7S2})]2 is shown to be a single-molecule magnet with Ueff = 87 cm-1. In Chapter 5, four new lanthanide siloxide clusters incorporating alkali metals are reported: the trigonal bipyramidal [Dy2K3(OSiMe3)9]; the octahedral [Dy2K4(OSiMe3)10]; the bi-capped cuboid [Y4K6O6(OSiMe3)12]6-; and the [Dy3K8O3(OSiMe3)12]- 'burger' cluster. All clusters are structurally characterised by X-ray crystallography and [Dy2K4(OSiMe3)10] is magnetically characterised. The synthetic rationalisation for formation of these diverse structures is investigated.