• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 11
  • 10
  • 6
  • 6
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 40
  • 8
  • 6
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 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

Characterization of thermo-physical properties and forced convective heat transfer of poly-alpha-olefin (PAO) nanofluids.

Nelson, Ian Carl 15 May 2009 (has links)
Colloidal solvents, containing dispersed nanometer (~1-100 nm) sized particles, are categorized as nanofluids. With the growing heat loads in engineering systems that exceed the current technological limits, nanofluids are considered as an attractive option for more efficient heat removal for thermal management applications. Recent results reported in the literature show that the thermo-physical properties of coolants are enhanced considerably when seeded with very minute concentrations of nanoparticles. Hence, nanofluids research has provoked interest in thermal management applications. The convective heat transfer characteristics of nanofluids are reported in this study. Exfoliated graphite nanoparticles were dispersed in poly-alpha-olefin (PAO) at concentrations of 0.3% and 0.6% (by weight). The heat flux into a convective cooling apparatus was monitored and the results for nanofluid and the base fluid are presented. Thermo-physical properties of the nanofluid were measured and compared with the base fluid. The thermo-physical properties of the fluid are observed to increase with the addition of the nanoparticles. The specific heat of nanofluid was increased by ~50% compared to PAO. The thermal diffusivity was enhanced by ~400% compared to PAO. The viscosity of the nanofluid was enhanced by 10-1000 times compared to PAO. The viscosity of the nanofluid was observed to increase with temperature while the viscosity of PAO decreases with temperature. The convective heat flux was enhanced by the nanofluids by up to ~8 % for experiments performed at different heat inputs. The experimental results show that the convective heat transfer enhancement potentially results from the precipitation of nanoparticles on the heated surface and results in enhanced heat transfer surfaces (“nano-fins”).
2

Characterization of thermo-physical properties and forced convective heat transfer of poly-alpha-olefin (PAO) nanofluids.

Nelson, Ian Carl 15 May 2009 (has links)
Colloidal solvents, containing dispersed nanometer (~1-100 nm) sized particles, are categorized as nanofluids. With the growing heat loads in engineering systems that exceed the current technological limits, nanofluids are considered as an attractive option for more efficient heat removal for thermal management applications. Recent results reported in the literature show that the thermo-physical properties of coolants are enhanced considerably when seeded with very minute concentrations of nanoparticles. Hence, nanofluids research has provoked interest in thermal management applications. The convective heat transfer characteristics of nanofluids are reported in this study. Exfoliated graphite nanoparticles were dispersed in poly-alpha-olefin (PAO) at concentrations of 0.3% and 0.6% (by weight). The heat flux into a convective cooling apparatus was monitored and the results for nanofluid and the base fluid are presented. Thermo-physical properties of the nanofluid were measured and compared with the base fluid. The thermo-physical properties of the fluid are observed to increase with the addition of the nanoparticles. The specific heat of nanofluid was increased by ~50% compared to PAO. The thermal diffusivity was enhanced by ~400% compared to PAO. The viscosity of the nanofluid was enhanced by 10-1000 times compared to PAO. The viscosity of the nanofluid was observed to increase with temperature while the viscosity of PAO decreases with temperature. The convective heat flux was enhanced by the nanofluids by up to ~8 % for experiments performed at different heat inputs. The experimental results show that the convective heat transfer enhancement potentially results from the precipitation of nanoparticles on the heated surface and results in enhanced heat transfer surfaces (“nano-fins”).
3

Ts'ao Yü, playwright of discontent and disillusionment.

Hu, John Yaw-herng, January 1969 (has links)
Thesis--Indiana University. / Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.
4

Ts'ao Yü, playwright of discontent and disillusionment.

Hu, John Yaw-herng, January 1969 (has links)
Thesis--Indiana University. / Vita. Includes bibliographical references. Also issued in print.
5

Shanghai Su-pao sedition case, 1903-4.

Chao, Paul Chih-Chin, January 1971 (has links)
Thesis (M.A.)--University of Wisconsin--Madison, 1971. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.
6

Facing the challenge of digital information technology the case study of MingPao.com = Tou guo Ming bao gang zhan de fa zhan guan cha Xianggang bao ye mian dui zi xun ke ji hua de zhuan bian /

Liu, Yuen-hung, Jacqueline. January 2001 (has links)
Thesis (M.Journ.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 28-30). Also available in print.
7

Aplicación del Análisis del Ciclo de Vida en el estudio ambiental de diferentes Procesos Avanzados de Oxidación

Ruiz Fernández, Nilbia 13 July 2007 (has links)
La Química Verde es una disciplina reciente de la química cuyo objetivo es diseñar compuestos y procesos químicos que reduzcan o eliminen la generación de sustancias peligrosas para la salud humana y el medio ambiente, haciendo un uso sostenible de los recursos. Para cuantificar ambientalmente las mejoras introducidas en una reacción química de acuerdo con estrategias de Química Verde, o bien para comparar distintas alternativas, se requiere realizar balances de cargas ambientales y valorar éstas. En la presente tesis doctoral se presenta un modo de llevar a cabo esta valoración ambiental en el caso de la comparación de distintas alternativas.La tesis doctoral se centra en la evaluación ambiental de diferentes procesos avanzados de oxidación. Sobre la investigación de estos procesos se esta dedicando actualmente muchos recursos, estos son fundamentalmente de nuevas tecnologías para el tratamiento de efluentes contaminantes procedentes de diferentes tipos de actividades, particularmente agrícolas e industriales de los sectores químico, papelero, textil, etc.En particular, la tesis doctoral se ha centrado en la aplicación del Análisis del Ciclo de Vida (ACV) a los tratamientos de disoluciones acuosas de ácido salicílico y del tinte sintético Procion Red H-E7B mediante métodos de oxidación avanzada como son el proceso Fenton, foto-Fenton y la Fotocatálisis Heterogénea con posterior uso o no de un tratamiento biológico.En el primer capítulo de la tesis correspondiente a la introducción, se detalla de forma clara y concisa los principales fundamentos del ACV, incluyendo su metodología, así como los procesos de oxidación avanzada de Fenton, foto-Fenton y Fotocatálisis Heterogénea, conjuntamente con el acoplamiento con un tratamiento biológico. El ACV se centra en considerar el consumo de energía eléctrica, el costo de la producción de los compuestos químicos empleados en todo el proceso y los gastos originados en la depuración química y biológica de las aguas residuales resultantes. El cálculo del ACV se hace mediante programas estándares donde se tiene en cuenta hasta 10 factores que influyen en la salud humana, los recursos naturales, el medio ambiente, etc.El segundo capítulo de materiales y métodos explica en detalle los diferentes sistemas experimentales empleados y los métodos de cálculo del ACV. El tercer capítulo de resultados y discusión se presenta en dos partes bien diferenciadas. En la primera de ellas, se señalan los datos obtenidos en tratar el ácido salicílico y se realiza su ACV, como resultados más importantes se obtiene que el proceso de foto-Fenton es el menos impactante y que una especia inocua como el peróxido de hidrógeno da lugar a menos toxicidad. Por otro lado, la segunda parte estudia la determinación del ACV para el tratamiento del tinte Procion Red H-E7B estudiado previamente por el grupo de investigación. En las diferentes etapas se indica de forma clara los parámetros empleados para evaluar esta parte, las aproximaciones hechas, los datos obtenidos y las ideas que pueden dar lugar a su mejora, de esta parte se deduce que el acoplamiento foto-Fenton-biológico hace disminuir el impacto ambiental del proceso. Estos resultados son muy significativos cuando abren las puertas a un estudio profundo del ACV en la degradación de compuestos tóxicos por procesos inducidos por luz solar, lo cuál favorecería la disminución del impacto ambiental en evitar las actuales irradiaciones con una lámpara UV y el consecuente ahorro energético. Por otro lado, los resultados obtenidos permiten extender la investigación para realizar un estudio más riguroso de posteriores acoplamientos biológicos. / The Green Chemistry is a young chemical discipline, which aims at designing chemical compounds and processes that reduce or eliminate the production of substances dangerous for the human health and the environment by a sustainable use of the resources. In order to quantify environmentally the improvements introduced to a chemical reaction in compliance with the Green Chemistry strategies or in order to compare various possibilities it is required to carry out the balances of environmental charges and evaluate them. In the herein doctoral thesis the manner of carrying out this environmental evaluation is presented in the case of comparing various possibilities.The doctoral thesis is focused on the environmental evaluation of various advanced oxidation processes. Many resources are being nowadays applied to investigate these processes which are basically the new technologies for processing the polluting liquids coming from different kinds of activities, especially the agriculture and industrial from chemical, paper manufacture, textile and other sectors. The doctoral thesis is particularly focused on the application of Life Cycle Analyse (LCA) to the processing of watery solutions and salicylic acid and synthetic dye Procion Red H-E7B through advanced oxidation methods such as Fenton, photo-Fenton and a Heterogeneous Photocatalysis process, with, a subsequent use of biological processing included or not. In the first chapter of the thesis, following the introduction, the most important basis of LCA are clearly and concisely enumerated including their methodology as well as the advanced oxidation processes such as Fenton, photo-Fenton and a Heterogeneous Photocatalysis together with the biological processing. The LCA is mainly focused on considering the electrical energy consumption, chemical compound production cost throughout the whole processes and the costs incurred by chemical and biological purification of resulting residual waters. The LCA estimate is carried out by standard programs which take into consideration up to 10 factors affecting human health, natural resources, the environment etc.The second chapter focused on the materials and methods explains in details the different experimental systems applied and ways of estimating the LCA. The third chapter is about the results and the discussion, presented in two, well defined parts. In the first part the data achieved during the processing the salicylic acid are indicated and their LCA is carried out. The most important results are that photo - Fenton process is the least powerful and a watery substance such as hydrogen peroxide causes less toxicity. On the other hand, the second part analyses the importance of LCA for the Procion Red H-E7B dye processing, previously analysed by an investigation group. On different stages the parameters applied to evaluate this part are clearly indicated as well as the approach, the data obtained and the ideas how to improve them. This part allows to deduce that adding the biological photo-Fenton helps decrease the environmental impact of the process. These results are highly important if they launch a deep LCA study in degradation of toxic compounds by processes induced by solar light, which would help decrease environmental impact avoiding the present radiations of UV lamps and the consequent energetic savings. On the other hand the obtained results let extend the investigation in order to realise stricter analyses of subsequent biological processes.
8

Utmaningarna inom Human Resources : att lyckas möta förväntningarna

Bodén, Sofie January 2013 (has links)
Personalarbetet har förändrats mycket de senaste åren, det har orsakat att delar av organisationerna inte följt med i denna förändring. Yrkesrollen var förr mer omsorgsinriktad och fokuserade mer på medarbetarna men idag innehåller yrkesrollen mer ett affärstänk samt har ett arbetsgivarfokus. Syftet med studien var att få en ökad förståelse för vilka utmaningar HR-arbetare möter i sin yrkesroll när de ska tillgodose ledningens direktiv och medarbetarnas behov. Om det finns några utmaningar, vad de i så fall innebär och hur HR-arbetare lyckas hantera dessa utmaningar. Sex personer från olika privata företag i Stockholms län intervjuades, materialet transkriberades och analyserades tematiskt. Resultatet visade att en utmaning var att det fanns olika förväntningar på HR. En annan utmaning gällde att ledningen och medarbetarna hade olika maktpositioner, vilket påverkade HR:s prioriteringar. Dessa utmaningar hanterade intervjupersonerna genom kommunikation, tydlighet samt genom att klargöra representantfokus vilket tolkades motverka en rollkonflikt.
9

Thermal Performance of Poly Alpha Olefin Nanofluid with Spherical and Non-spherical Nanoparticles

Park, Chan Hyun 2011 May 1900 (has links)
Research on nanofluids has been undertaken for several years because of the reported enhancements of thermal properties such as thermal conductivity and enhanced heat transfer performance in laminar flow. Nanofluid is the fluid where nanoparticles are dispersed in a base fluid. Thermal conductivity and viscosity are considered to be the most prominent factors in the efficient use of nanofluids. A change in thermal conductivity and viscosity also changes the convective heat transfer coefficient. Nanoparticles can be metallic or non-metallic and also can have different shapes. In this study, Poly-Alpha-Olefin (PAO) has been used as a base fluid with Alumina (Al2O3) nanoparticles. Poly-Alpha-Olefin is commonly used for engine lubrication in military applications and cooling in electronic and industrial devices. Several nanofluid samples were made by METSS Corp. in Ohio, USA using different dispersants, different base fluids and different morphology of alumina nanoparticles. The mass fraction of nanoparticles is from 2.5 to 20 percent. The thermal properties of each sample such as thermal conductivity and viscosity have been measured. Thermal conductivity of nanofluids and pure base fluids were both measured and the thermal conductivity enhancement has been calculated. Also, the heat transfer coefficient has been determined for laminar flow under constant heat flux conditions. Results indicate that all the tested nanofluids and base fluid samples show a Newtonian behavior. Among the nanofluid samples, NF-048, which contains non-spherical Alumina nanoparticles exhibits the greatest thermal conductivity enhancement when compared to pure PAO. Heat transfer tests were conducted with pure PAO and NF-048, and an enhancement in convective heat transfer coefficient was observed. The thermal conductivity of NF-048 increases with temperature, which is consistent with heat transfer results. Furthermore, the percentage enhancement in convective heat transfer coefficient was shown to increase non-linearly with the axial distance in the heat transfer section. NF-048 exhibits a lower Re (Reynolds number)*Ra (Rayleigh number) than pure PAO under laminar flow constant heat flux conditions indicating that nanoparticle morphology and composition are the two main factors responsible for convective heat transfer enhancement at low Reynolds number.
10

On Shen Pao-Chen¡¦s Thought Applied in the Model of Glolocalization for Taiwan ¡V The Responses of the Late Qing Dynasty¡¦s ¡§Westernization Movement¡¨ to the Globalization within the Process of the Capitalism

Lee, Tung-shun 11 September 2007 (has links)
As the late period of Qing Dynasty, there was a great event of ¡§ Botan Village Issue¡¨ Which happened in Taiwan, Shen Pao-Chen, the Imperial Commissioner who had been sent to take charge of Taiwan in 1874 & manage the defense to prevent the occupation of Taiwan by Japan, was impressed With the necessity of managing great reforms and infrastructures, including establishing new counties, civilizing the savage aborigines, moving governor to Taiwan, abolishing prohibition, reinforcing military administration, building shrines for Cheng Chen-Kung, and improving morale. In view of all Shen Pao-Ching¡¦s life, he was really a Pioneer ahead of his time for Taiwan¡¦s modernization. Aleader of nation must be with a certain spirit of adventure when his nation encounters heavy risk. Therefore, the spirit is what we can learn form him; he had established so mush infrastructure and reforms for Taiwan. All of things done by late Qing dynasty (Self-strengthening movement ) on Taiwan in process of globalization, social changes, the responses of the localization, and the transformation of ¡§ Glolocalization¡¨, which were rather mature and successful and it is able a key turning point in late Qing¡¦s policy for Taiwan.

Page generated in 0.0213 seconds