Design and analysis of micro-channel heat-exchanger embedded in Low Temperature Co-fire Ceramic (LTCC)

Increased device density, switching speeds of integrated circuits and decrease in package size is placing new demands for high power thermal-management. The convectional method of forced air cooling with passive heat sink can handle heat fluxes up-to 3-5W/cm2; however current microprocessors are operating at levels of 100W/cm2, This demands the usage of novel thermal-management systems. In this work, water-cooling systems with active heat sink are embedded in the substrate. The research involved fabricating LTCC substrates of various configurations - an open-duct substrate, the second with thermal vias and the third with thermal vias and free-standing metal columns and metal foil. Thermal testing was performed experimentally and these results are compared with CFD results. An overall thermal resistance for the base substrate is demonstrated to be 3.4oC/W-cm2. Addition of thermal vias reduces the effective resistance of the system by 7times and further addition of free standing columns reduced it by 20times.

Analysis of multiple cracking in metal/ceramic composites with lamellar microstructure

Financial support of this research by The Royal Society, UK (IE121116), The Carnegie Trust for the Universities of Scotland, UK (Trust Reference 31747) and DFG (PI 785/3-2, PI 785/1-2), Germany, is gratefully acknowledged. We thank Dr. S. Roy (KIT) for providing the microstructure images and Professor I. Tsukrov (University of New Hampshire, USA) for helpful discussions.

Re-modelling clay: ceramic practice and the museum in Britain (1970-2014)

This thesis analyses how the dialogue between ceramic practice and museum practice has contributed to the discourse on ceramics. Taking Mieke Bal’s theory of exposition as a starting point, it explores how ‘gestures of showing’ have been used to frame art‑oriented ceramic practice. Examining the gaps between the statements these gestures have made about and through ceramics, and the objects they seek to expose, it challenges the idea that ceramics as a category of artistic practice has ‘expanded.’ Instead, it forwards the idea that ceramics is an integrative practice, through which practitioners produce works that can be read within a range of artistic (and non-artistic) frameworks. Focusing on activity in British museums between 1970 and 2014, it takes a thematic and broadly chronological approach, interrogating the interrelationship of ceramic practice, museum practice and political and critical shifts at different points in time. Revealing an ambiguity at the core of the category ‘ceramics,’ it outlines numerous instances in which ‘gestures of showing’ have brought the logic of this categorisation into question, only to be returned to the discourse on ‘ceramics’ as a distinct category through acts of institutional recuperation. Suggesting that ceramics practitioners who wish to move beyond this category need to make their vitae as dialogic as their works, it indicates that many of those trying to raise the profile of ‘ceramics’ have also been complicit in separating it from broader artistic practice. Acknowledging that those working within institutions that sustain this distinction are likely to re-make, rather than reconsider ceramics, it leaves the ball in their court.

Rotary moulding of ceramic hollow wares

A novel processing method for the fast and economic production of hollow ceramic components has been developed by combining in situ coagulation moulding with a modified version of the technique of rotary moulding[Binner, J. G. P., Al-Dawery, I. A., Tari, G. and Yan, Y., Rotary casting technique. UK Patent application No. 0506349.0, March 2005], the latter being adapted from the polymer industry. The process was found to require a high solids content suspension, hence development work was performed in this direction though in the end a new, commercial suspension was utilised. Of the three forming routes of gel casting, direct coagulation casting and in situ coagulation moulding, the latter was found to be the most promising for the new process of rotary moulding of ceramics. Due to the low value of clay-based ceramics, a new low cost coagulant was identified and the effect of lactone concentration and temperature on setting time determined. Following substantial optimisation work, it was found that a two-speed approach to multi-axial rotation was the most successful; medium sized cream jugs could be produced in just 7 min. With respect to mould materials, the porous resin normally used for pressure casting of sanitary ware was found to be the best option, though since this is quite expensive conventional plaster-of-paris moulds were found to be a suitable material to enable companies, particularly SMEs, to become familiar with the technology whilst avoiding high costs for trials. The processed articles could be successfully fired and glazed using gas-fired kilns with no sign of any black cores. Major advantages of the process include the ability to precisely calculate the amount of ceramic slip required, eliminating either slip wastage or the need to pour used slip back into the virgin material as currently happens with slip casting. In addition, since the precursor suspension has a very high solids content, the time and energy required to dry the green product and associated moulds has been considerably reduced. © 2008 Elsevier Ltd. All rights reserved.

Evaluation of Two Ultrasonic Systems for Analysis of Porosity in Ceramic

The Ultrasound Laboratory of the Nuclear Engineering Institute (LABUS / IEN) has developed an ultrasonic technique to measure porosity in nuclear fuel pellets (UO2). By difficulties related to the handling of UO2 pellets, Alumina (Al2O3) pellets have been used in preliminary tests, until a methodology for tests with pellets of UO2 could be defined. In a previous work, in which a contact ultrasonic technique was used, good results were obtained to measure the porosity of Alumina pellets. In the current studies, it was found that the frequency spectrum of an ultrasonic pulse is very sensitive to the porosity of the medium in which it propagates. In order to define the most appropriate experimental apparatus for using immersion technique in future tests, two ultrasonic systems, available in LABUS, which permit to work with the ultrasonic pulse in the frequency domain were evaluated . One system was the Explorer II (Matec INSTRUMENTS) and the other the ultrasonic pulse generator Epoch 4 Plus (Panametrics) coupled with an oscilloscope TDS 3032B (Tektronix). For this evaluation, several frequency spectra were obtained with the two equipment, by the passage of the ultrasonic wave in the same pellet of Alumina. This procedure was performed on four different days, on each day 12 ultrasonic signals were acquired, one signal every 10 minutes, with each apparatus. The results were compared and analyzed as regard the repeatability of the frequency spectra obtained.

Aportaciones a la metodología de diseño basada en Síntesis de Alto Nivel. Aportaciones al diseño de IPs para procesado de eventos complejos y codificación de vídeo

Programa de doctorado: Ingeniería de Telecomunicación Avanzada. La fecha de publicación es la fecha de lectura

Relación de los estilos de liderazgo en el desempeño de la administración de las IPS hospitalarias de II y III nivel de complejidad de la ciudad de Manizales.

El liderazgo ha sido sujeto de varios estudios, confrontaciones y equivocaciones que lo han conllevado a múltiples y subjetivas interpretaciones y por consiguiente disparidad de actuaciones, siendo el sector salud no ajeno a esta situación. Sin embargo, no se discute la importancia que este conlleva en el actuar a nivel laboral y su influencia y/o relación con los resultados y objetivos organizacionales. Es por ello que esta investigación de corte cuantitativo se diseñó para identificar la relación de los estilos de liderazgo y el desempeño administrativo, siendo enfocado principalmente en los altos y medios directivos pues son estos los responsables de la obtención y mantenimiento de óptimos resultados para la sostenibilidad empresarial. Con el objetivo de identificar la relación específica de los estilos de liderazgo con el desempeño administrativo, el presente estudio se acogió a los indicadores de desempeño definidos por Bass y Avolio (Esfuerzo Extra, Satisfacción y Eficacia del Líder) aplicando por consiguiente el cuestionario Multifactorial de Liderazgo (MLQ) adaptado por Vega, Villa & Zavala, Villalón, siendo éste no solo uno de los instrumentos mas utilizados y estandarizados para el estudio del liderazgo, sino que también permite analizar la frecuencia de su uso, la primacía de cada estilo de liderazgo y especialmente y con objeto del presente estudio, la identificación subyacente del estilo de liderazgo de Rango Completo o Total. El presente cuestionario fue aplicada de forma presencial a los Gerentes Generales, Directores Médicos, Directores Científicos, Directores Administrativos y principales personas a cargo de las IPS hospitalarias de II y III nivel de complejidad de la ciudad de Manizales. En un principio se encontró que el estilo de liderazgo como variable principal mas utilizado por los altos y medios directivos de las IPS hospitalarias de II y III nivel de complejidad de la ciudad de Manizales es el Transformacional, seguido por el Pasivo Evasivo con su comportamiento Dirección por Excepción Activa y por último el Liderazgo Transaccional. Sin embargo no se encontró relación alguna entre los estilos de liderazgo como variables primarias con los indicadores de desempeño, comprobando por último que el Liderazgo de Rango Completo o Total es el estilo de liderazgo que tiene relación directa y positiva con los indicadores de desempeño Esfuerzo Extra, Satisfacción y Eficacia del Líder. Lo anterior permitió no solo apoyar la premisa relacionada con la importancia del liderazgo en toda organización, sino también considerar la importancia de ampliar el estudio incluyendo factores de causalidad que han determinado e influido en la aparición del los estilos de liderazgo.