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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.
31

Data Processing for NASA's TDRSS DAMA Channel

Long, Christopher C. 10 1900 (has links)
International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California / Presently, NASA's Space Network (SN) does not have the ability to receive random messages from satellites using the system. Scheduling of the service must be done by the owner of the spacecraft through Goddard Space Flight Center (GSFC). The goal of NASA is to improve the current system so that random messages, that are generated on board the satellite, can be received by the SN. The messages will be requests for service that the satellites control system deems necessary. These messages will then be sent to the owner of the spacecraft where appropriate action and scheduling can take place. This new service is known as the Demand Assignment Multiple Access system (DAMA).
32

Discovery, observations and theory of over luminous supernovae and peculiar transients

Chatzopoulos, Emmanouil 21 October 2010 (has links)
Modern wide-field imaging transient search projects led to the discovery of a new class of rare, over-luminous stellar explosions. Events like SN 2005ap (Quimby et al. 2007a), SN 2006gy (Quimby 2006; Smith et al. 2007), SN 2006tf (Quimby, Castro \& Mondol 2007; Quimby et al. 2007b; Smith et al. 2008), SN 2008am (Chatzopoulos et al. 2010), SN 2008es (Yuan et al. 2008; Gezari et al. 2008; Miller et al. 2008) SN 2008fz (Drake et al. 2009) and SN 2008iy (Miller et al. 2010) introduced us new evidence about stellar death, since traditional ideas about the mechanisms that can power these phenomena are found to be inadequate to explain the observed properties. The Texas Supernova Search Project (TSS; Quimby et al. 2005) and its successor, the ROTSE-Supernova Verification Project (RSVP; Yuan et al. 2007) discovered most of the above mentioned over-luminous supernovae (OLSNe) over the past five years of their operation. The advantage of this project is that it is essentially free of selection bias or the limits of a targeted search; the automated wide field (~3 square degrees) ROTSE-III telescopes (Akerlof et al. 2003), scan the whole sky blindly, looking for transients down to unfiltered magnitude ~19 mag and they do not focus on pre-selected galaxies. An estimated rate for these exceptionally luminous supernovae is ~ 2.6 10^{-7} events/Mpc^{3}/yr (Quimby et al. 2009a). Current and future transient search projects such as the SDSS-II Supernova Survey (Frieman et al. 2008),the Palomar Transient Factory (PTF; Law et al. 2009), SkyMapper (Schmidt et al. 2005), PanSTARRS (Chambers 2006) and Large Synoptic Survey Telescope (Tyson \& LSST collaboration 2002) are expected to increase the number of rare over-luminous (or, under-luminous) supernove and to discover new, unusual transients. / text
33

Fabrication of high energy density tin/carbon anode using reduction expansion synthesis and aerosol through plasma techniques

Lim, Tongli 03 1900 (has links)
Approved for public release; distribution is unlimited / The aim of this study was to fabricate tin/carbon (Sn/C) battery anodes using a novel approach, reduction expansion synthesis (RES), and test their performance as electrodes in lithium or sodium batteries. A second preparation route, the Aerosol-Through-Plasma (ATP) method, was also employed for comparison. The specimens generated were characterized, before and after cycling, using techniques such as X-ray diffraction, scanning, and transmission electron microscopy. The RES technique was successful in creating remarkably small (ca. <5 nm) nano-scale particles of tin dispersed on the carbon support. The use of the electrodes as part of coin cell batteries resulted in capacitance values of 320 mAh/g and 110 mAh/g for lithium-ion and sodium-ion batteries, respectively. Nano-sized Sn particles were found before and after cycling. It is believed that bonds between metal atoms and dangling carbon produced via the reduction of the carbon surface during RES were responsible for the materials' ability to withstand stresses during lithiation, avoid volumetric expansion, and prevent disintegration after hundreds of cycles. When tin loading in Sn/C was increased from 10% to 20%, an increase of capacitance from 280 mAh/g to 320mAh/g was observed; thus, increased tin loading is recommended for future studies. Tin/carbon produced using ATP presented morphology consistent with stable electrodes, although battery testing was not completed because of the difficulty of producing the material in sufficient quantity. / Military Expert 5, Republic of Singapore Navy
34

Telas de carbón como soporte de catalizadores bimetálicos Pt-Sn: efecto promotor del TiO2

Huidobro Pahissa, Ana 13 June 2003 (has links)
Este trabajo se centra en el estudio de las interacciones entre dos fases metálicas, el platino y el estaño, soportados sobre dos materiales que establecen distintas interacciones con las fases metálicas soportadas sobre ellos. Se eligió el Pt porque es un metal noble que se utiliza como catalizador en numerosas reacciones catalíticas. El estaño puede actuar como promotor del platino de manera que los sistemas bimetálicos basados en Pt-Sn han sido ampliamente investigados debido a sus buenas cualidades como catalizadores en procesos como el reformado de petróleo o reacciones de hidrogenación y deshidrogenación. Como soporte de estas fases activas se estudiaron dos materiales distintos: tela de carbón activo y óxido de titanio. Los carbones activados en forma de fibras y telas añaden a las ventajas de los carbones activos tradicionales otras como son mayor eficiencia de contacto y muy baja pérdida de carga, lo que abre un nuevo y muy interesante campo de investigación para la aplicación de estos materiales como soporte de catalizadores. Por otra parte, el estudio del óxido de titanio resulta interesante debido a que se produce entre este soporte y el platino una fuerte interacción metal-soporte. Este efecto, que no ha sido del todo clarificado aun, altera las características de los catalizadores y su influencia en la actividad catalítica final. / This work is related to the study of two metallic species interaction, platinum and tin, supported on different materials in such away that they establish separated kind of interaction. Platinum was chosen since is the one used in several catalytic reactions. Tin can act as a platinum promotor in such a way that Pt-Sn bimetallic systems have been widely investigated due to its good performance catalysts on reactions as fuel reforming o hydrogenation and dehydrogenation reactions. Two different materials were used as support for this catalyst: activated carbon cloth and titanium oxide. Activated carbon in the form of cloth adds to the well known characteristics of typical activated carbon, the improvement of a higher contact efficiency and adsorption rate and a low pressure drop on reaction conditions, which opens a new and very promising area of research to apply these materials as catalysts supports. On the other side, the study of titanium oxide is very interesting due to the effect of strong metal-support interaction produced between platinum and its support. This effect, no completely understood, changes the catalysts characteristics and affects to its final catalytic activity.
35

Molecular Studies of Irradiation and SN-38 on Colorectal Cancer

Wallin, Åsa January 2008 (has links)
Colorectal cancer (CRC) is one of most common cancer diseases worldwide. In Swedenapproximately 5,000 new cases of CRC are generated each year, which makes it the thirdmost common cancer disease among both men and women. The past decades ofimproved treatment strategies have considerably increased the five-year survival for CRCpatients. However more could be achieved in this area, in particular for metastatic CRC,which is the cause of most CRC-related deaths. Therefore it is important to study thebiological response to certain treatments induced in CRC to find valuable predictiveand/or prognostic factors to select patients for better suited treatments. The aim of this thesis was to gain insight into the molecular changes that occurfollowing irradiation or treatment with SN-38 in rectal cancer patients or colon cancercell lines by studying the RNA expression, protein expression, DNA cell cycledistribution and apoptotic response. The expression of phosphatase of regenerating liver(PRL) proteins was investigated in rectal cancers from 125 patients included in arandomized clinical trial of preoperative radiotherapy (RT). Increased expression of PRLswas seen at the invasive margin of primary and metastatic cancers compared with theinner area of the tumors. Moreover, strong PRL staining at the invasive margin correlatedto distant recurrence and worse survival of patients in the RT group but not in non-RTgroup (Paper I). Radiosensitivity was studied by treating KM12C, KM12SM andKM12L4a colon cancer cell lines with radiation. KM12C is of low metastatic naturecompared with the highly metastatic KM12SM and KM12L4a. Upregulation of ΔNp73and PRL-3 might contribute to the radioresistant phenotype in KM12C. In contrast,KM12L4a shows a high frequency of apoptosis and lack of upregulation of ΔNp73, PRL-3 and survivin, which might explain its radiosensitive phenotype (Paper II). KM12C,KM12SM and KM12L4a were treated with SN-38 which inhibits topoisomerase 1 (topo-1). The results show that SN-38 induces G2/S arrest and possess the capacity to triggerapoptosis in the three cell lines (Paper III). To further elucidate SN-38 effect on these celllines, the gene expression profile following SN-38 treatment was studied. Oligonucleotidearrays consisting of ~27,000 spots were hybridized with sample and reference cDNA.Both unsupervised and supervised hierarchical clustering analysis, and functional analysiswere performed. Supervised hierarchical clustering gives a strong signal of 1453discriminated genes, the vast majority being upregulated. Both upregulated anddownregulated genes point toward a favorable impact of SN-38 regarding the apoptoticpathways. For example RhoB and Bax are upregulated together with downregulation ofKras and survivin, which promotes apoptosis (Paper IV). In conclusion, PRLs may be valuable biomarkers for RT resistance, predicting apoor prognosis in rectal cancer patients. Targeting radio-resistance factors, such asΔNp73 and survivin may contribute to an increased sensitivity to RT. SN-38 affects cellproliferation and apoptosis.
36

Catalizadores de Rh-soportado y su aplicación en la hidrogenación de crotonaldehído

Krstic, Vesna 19 July 2005 (has links)
Este trabajo ha sido realizado en el contexto de los proyectos de MAT 2002-03808 y MAT 2002-02158, financiados por la Dirección General de Investigación del Ministerio de Ciencia y Tecnología (MCyT). Se han sintetizado y caracterizado catalizadores Rh-soportado (sólo o promovido con Sn) utilizando diferentes tipos de soportes. Como soportes de catalizadores se utilizaron tanto materiales microporosos, silicatos laminares (bentonitas) de distinta procedencia y bentonitas modificadas mediante la introducción de pilares (PILC's) o transformadas en productos zeolíticos; como materiales mesoporosos, MCM-41, con una o dos fuentes de Silicio. Los mencionados catalizadores han sido aplicados en la hidrogenación de crotonaldehído, en fase gaseosa y condiciones suaves, de alto interés tanto académico como industrial en química fina, farmacéutica y alimentaria. Se han analizado y discutido la actividad/selectividad en relación con las diferentes características de los soportes y las distintas condiciones de trabajo como: temperatura de reducción del Rh, temperaturas de reacción, y presencia de estaño como promotor. Se han caracterizado los soportes y catalizadores mediante diferentes técnicas instrumentales UV-Vis, espectroscopia IR, ATG/DTG, DRX, isotermas de adsorción-desorción de N2, quimisorción de O2/H2, quimisorción de NH3, adsorción-desorción de piridina mediante espectroscopia IR-TF, XPS y se utilizó la Cromatografia de gases para la hidrogenación de crotonaldehído. Los resultados obtenidos ponen de manifiesto que tanto las arcillas de partida como las modificadas (con pilares o bien transformada en zeolitas) y materiales MCM-41, han resultado soportes idóneos para la formación de catalizadores heterogéneos de Rh y de Rh promovido con Sn, habiéndose generado, por tanto, nuevos materiales de alto valor añadido para el caso de las arcillas modificadas y nuevos retos de aplicación para los nuevos nanomateriales MCM-41. Así mismo se constata que la adición de Sn como promotor, modifica la conversión a todas las temperaturas de reacción, obteniéndose para todos los catalizadores, mayor selectividad hacia alcohol crotílico que en ausencia de Sn. En resumen, a lo largo de este trabajo se han logrado preparar catalizadores metal soportados utilizando unos nuevos soportes de catalizadores que muestran, generalmente, alta selectividad hacia alcohol crotílico en la hidrogenación de crotonaldehído, en condiciones suaves y a presión atmosférica, condiciones usuales de trabajo en la industria de química fina, farmacéutica y alimentaria, donde time mayor repercusión la aplicación de la reacción estudiada. / This work has been performed within the projects MAT 2002-03808 and MAT 2002-02158, financed by the DGESIC (Dirección General de Enseñanza Superior e Investigación y Ciencia) and CICYT (Comisión de Investigación Científica y Técnica), respectively.An Rh-supported catalyst (alone or promoted with Sn) has been synthesized and characterized using different types of supports. Aluminum silicate (clay) of different origins and clay modified by introduction of pillars (PILC's) or transformed into zeolytic products were used as microporous materials. MCM-41 (with one or two Silicon sources) was used as mesoporous materials. The catalyst has been applied in the hydrogenation of cortonaldehyde in gaseous phase and mild conditions. These have high academic and industrial interest. Activity and selectivity of catalysts have been analyzed at different conditions of work like: temperature of reduction of the Rh, temperatures of reaction and tin presence as promoter.These supports (micro and mesoporous materials) and catalysts have been characterized using different technical instruments: UV-Vis, spectroscopy IR, ATG/DTG, XRD, isotherms of adsorption-desorption of N2, chemisorptions of O2/H2, chemisorptions of NH3, adsorption-desorption of pyridine by DRIFTS, XPS and hydrogenation of crotonaldehyde by Gas Chromatography. The results obtained show that the natural clay material, as modified (with incorporation of pillars or transformed into zeolites), and materials MCM-41, have been good supports to the formation of heterogeneous catalysts of Rh and Rh promoted with Sn, having generated new materials of high value in the case of modified clays and raises new challenges of application for nanomaterials MCM-41. Also observed is that the addition of Sn as promoter was modifying the conversion at all temperatures of reaction, obtaining for all the catalysts greater selectivity to crotyl alcohol than without tin (Sn).In summary, throughout this work, we have been able to prepare and obtain metal supported catalysts using new supports of catalysts that show great selectivity towards crotyl alcohol in the hydrogenation of crotonaldehyde in mild conditions and atmospheric pressure. This is a very important reaction in the production of many pharmaceutical, agrochemical and fragrance compounds, having great repurcussion on the application of the studied reaction and attracting much interest in fundamental research in catalysis.
37

The Study of Creep and Shear Tests for Sn/3.0Ag/0.5Cu Solder Balls

Hsu, Chao-ming 05 July 2010 (has links)
The creep models of Sn/3.0Ag/0.5Cu solder material under tensile and shear loads are investigated in this study. The creep test results for Sn/3.0Ag/0.5Cu solder material with four operating temperatures, i.e. 120o, 135 o, 150 o and 165 oC are presented. The experimental results reveal that different creep equations are derived for the Sn/3.0Ag/0.5Cu solder material under tensile and shear loadings. The creep parameters, i.e. stress exponent, material constant and activation energy are curve fitted for the tensile and shear loading tests. The concept of failure toughness of solder ball joints is proposed and studied. The effects of high temperature aging and the thermal cycling loading on the failure toughness of different solder materials and ball sizes have also been explored. The difference between failure toughness values of traditional Sn/37Pb eutectic solder ball joints and the lead free Sn/3.0Ag/0.5Cu solder are compared and discussed. The results simulated from finite element method and experiment measurements under the ball shear test (BST) have been compared and studied. The variation stress, strain distributions and failure toughness during the ball shear testing are studied. The fracture behaviors of different ball joints under the high temperature aging and thermal cycles testing are examined and studied. The ball shear test results measured for the same size Sn/37Pb and Sn/3.0Ag/0.5Cu solder ball joints reveal different load-displacement variations. The relative ductility results are measured for the joint of Sn/37Pb solder ball. However, a high peak load and larger deformation are measured for Sn/3.0Ag/0.5Cu solder ball joints. Based on the definition of failure toughness proposed in this study, the higher failure toughness values are observed for the same size lead free Sn/3.0Ag/0.5Cu solder joints. The variation of failure toughness of different ball joints reveals that the high temperature aging and thermal cyclic loading reduce the failure toughness significantly. However, the measured failure toughness values indicate that the Sn/3.0Ag/0.5Cu solder joints have better ductility for the joints undergoing the high temperature aging and the thermal cycle loadings. Based on the measured results, the better reliability for the Sn/3.0Ag/0.5Cu ball joints is expected, due to the aging and cycling load testing.
38

The Characterization of Sn-doped SiO2 Thin Film Resistance Random Access Memory

Liao, Kuo-Hsiao 26 August 2011 (has links)
In this study, The bottom electrode¡]TiN¡^, middle insulator ¡]Sn¡GSiO2¡^, and top electrode ¡]Pt¡^ were deposited respectively by sputtering technique for fabricating the resistive random access memory with metal-insulator-metal structure. Experimental results were indicated that Sn-dopped SiO2 RRAM could be operated over 105 times and retention time was kept stable at thermal stress up to 85 ¢J over 104 s. In the previous researches, we had known that the supercritical carbon dioxide¡]SCCO2¡^ fluids could efficiently to passivate the traps in the devices. The leakage current of dielectric film would be reduced significantly after SCCO2 fluids treatment. To improve the dielectric properties of Sn-dopped SiO2 films, the SCCO2 fluids technology was introduced in this study. After SCCO2 fluids treatment, the leakage current of devices was reduced significantly, because the HRS conduction mechanism was transformed from Poole-Frenkel conduction to Schottky emission and the LRS conduction mechanism was transformed from Ohmic conduction to Hopping conduction. Addtionally, RTA treatment was introduced to improve the Sn-dopped SiO2 films. It could also reduce leakage current of devices after RTA treatment. At last, we used constant current forming to find the process of electrons hopping conduction.
39

Interfacial Reactions of Sn-Zn, Sn-Zn-Al, and Sn-Zn-Bi Solder Balls with Au/Ni Pad in BGA Package

Chang, Shih-Chang 16 June 2005 (has links)
The interfacial reactions of Sn-Zn and Sn-Zn-Al solder balls with Au/Ni surface finish under aging at 150¢J were investigated. With microstructure evolution, quantitative analysis, elemental distribution by X-ray color mapping from an electron probe microanalyzer (EPMA), the reaction procedure of phase transformation was proposed. During the reflow, Au dissolved into the solder balls and reacted with Zn to form £^-Au3Zn7. As aging time increased, £^-Au3Zn7 transformed to £^3-AuZn4. Finally, Zn precipitated near the Au-Zn intermetallic compound. On the other hand, Zn reacted with the Ni layer and formed Ni5Zn21. But the Al-Au-Zn IMC formed at the interface of Sn-Zn-Al solder balls, the reaction of Ni with Zn was inhibited. Even though the aging time increased to 50 days, no Ni5Zn21 was observed. The Joule effect was more apparent than the electromigration in the biased solder balls. First of all, the new phase (Au, Ni)Zn4 was proposed in the biased condition and in 175¢Jaging. Secondly, the thickness of the Ni5Zn21 IMC were the same between the anode and the cathode. Finally, We directly measure the temperature of the biased solder balls which was up to 173¢J.
40

Sn-Ag-Cu Solder Reliability and Ring Pattern Formation Mechanism

Lin, Sheng-Chih 20 August 2006 (has links)
none

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