• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1012
  • 177
  • 46
  • 37
  • 31
  • 17
  • 17
  • 15
  • 11
  • 8
  • 7
  • 4
  • 4
  • 4
  • 2
  • Tagged with
  • 1428
  • 774
  • 746
  • 736
  • 616
  • 561
  • 379
  • 300
  • 271
  • 269
  • 262
  • 252
  • 236
  • 229
  • 170
  • 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

Hokej a krize v ČR / Ice hockey and crisis in the CR

Záloha, Jiří January 2014 (has links)
Title: Ice hockey and crisis in the Czech Republic Objectives: Investigate the impact of the current economic crisis on ice hockey in the Czech Republic. Methods: Collect macroeconomic indexes of the Czech Republic and determine the impact of the economic crisis on its economy. Collecting and monitoring of economic indexes of ice hockey teams in the Czech republic before and during crisis. Results: The current global economic crisis affected the economy of the Czech Republic. This crisis affected the Czech ice hockey clubs as well and culminated in 2008 and 2009. The main cause was high dependence on income from sponsors, which constitutes about 70-80% of total income. During the crisis, many companies reduce their sponsorship activities. Currently, most clubs have already settled with the economic crisis and is expected to have as its end. Keywords: Ice hockey, crisis, the Czech republic
2

Investigation of the Cr solubility in the MC phase where M = Ti, Ta

Ehrenborg, Anna January 2016 (has links)
In this work the chromium solubility in MC, and M in Cr3C2 and Cr7C3 carbides in the Ti-Cr-C and Ta-Cr-C system have been examined experimentally. Special attention is given to the cubic MC phase due to its frequent use in industrial cemented carbides. A sample series was made where half of the samples were arc-melted and all samples were heat-treated at different temperatures. By arc-melting some of the samples it was possible to compare the arc-melted and non arc-melted samples to confirm equilibrium. Three phases were expected in each sample. The microstructure was examined by LOM and SEM. The phases were identified by XRD and the amount of Cr in each phase was measured by WDS in FEG-SEM or by microprobe analysis. A higher temperature for the heat-treatment allows more Cr to dissolve in the cubic carbide. Arc-melted samples allow more Cr to dissolve than the same system which has not been arc-melted. The Cr solubility in the cubic carbide in non arc-melted samples at 1400 degree Celcius is 8,1±0,4 at% in (Ti, Cr)C and 7,6±0,3 at% in (Ta, Cr)C. According to the samples the phase diagrams based on thermodynamic calculations are different to experimental data. Therefore, more experimental data should be made to update existing ternary diagrams.
3

Geometry and analysis of Cauchy-Riemann manifolds.

January 1998 (has links)
by Wong Wai Keung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 101-[102]). / Abstract also in Chinese. / Introduction --- p.1 / Chapter 1 --- CR Manifolds --- p.3 / Chapter 1.1 --- Abstract CR manifolds --- p.3 / Chapter 1.2 --- Embedded CR manifolds --- p.4 / Chapter 1.3 --- A normal form for generic embedded CR manifolds --- p.9 / Chapter 2 --- Differential Geometry of Strongly Pseudo-convex Manifolds --- p.18 / Chapter 2.1 --- Holomorphic vector bundles --- p.18 / Chapter 2.2 --- The cohomology groups Hq(M,E) --- p.20 / Chapter 2.3 --- "The spectral sequence {Erp,q(M)}" --- p.23 / Chapter 2.4 --- The Levi form --- p.31 / Chapter 2.5 --- Strongly pseudo-convex manifolds --- p.37 / Chapter 2.6 --- Strongly pseudo-convex real hypersurfaces --- p.40 / Chapter 2.7 --- Canonical affine connections --- p.44 / Chapter 2.8 --- Green's Theorem --- p.51 / Chapter 2.9 --- Canonical connections in holomorphic vector bundles --- p.53 / Chapter 3 --- The Harmonic Theory --- p.59 / Chapter 3.1 --- The fundamental operators --- p.59 / Chapter 3.2 --- The fundamental inequalities --- p.65 / Chapter 3.3 --- Kohn's harmonic theory --- p.67 / Chapter 3.4 --- The harmonic theory and the duality --- p.71 / Chapter 4 --- The Holomorphic Extension of CR Functions --- p.76 / Chapter 4.1 --- Approximation theorem --- p.76 / Chapter 4.2 --- The technique of analytic discs --- p.81 / Chapter 4.3 --- Holomorphic extension --- p.95 / Bibliography --- p.101
4

Deformation theory of compact complex manifolds and CR manifolds.

January 2006 (has links)
Ng Wai Man. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 87-88). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Infinitesimal Deformations for Compact Complex Manifolds --- p.4 / Chapter 2.1 --- Differentiable Family --- p.4 / Chapter 2.2 --- Local Triviality --- p.7 / Chapter 2.3 --- Complex Analytic Family and Deformations --- p.10 / Chapter 3 --- Existence Theorem --- p.15 / Chapter 3.1 --- Obstructions as a Necessary Condition --- p.15 / Chapter 3.2 --- The Existence Theorem --- p.16 / Chapter 3.3 --- Convergence Proof --- p.21 / Chapter 4 --- Completeness Theorem --- p.26 / Chapter 4.1 --- The Completeness Theorem --- p.26 / Chapter 4.2 --- Construction of Formal Power Series --- p.28 / Chapter 4.3 --- Convergence Proof --- p.32 / Chapter 4.4 --- Effective Parameters and Number of Moduli --- p.36 / Chapter 4.5 --- Examples --- p.40 / Chapter 5 --- CR Manifolds and Deformations --- p.42 / Chapter 5.1 --- CR Submanifolds and Tangential Complex --- p.42 / Chapter 5.2 --- Abstract CR Manifolds and its Cohomologies --- p.47 / Chapter 5.3 --- Strongly Pseudoconvex Manifolds --- p.51 / Chapter 5.4 --- Differentiable Family --- p.53 / Chapter 6 --- Stability Theorems --- p.55 / Chapter 6.1 --- Semi-continuity Theorem --- p.56 / Chapter 6.1.1 --- The Case of Compact Complex Manifolds --- p.56 / Chapter 6.1.2 --- The s.p.c. Compact CR Case --- p.63 / Chapter 6.2 --- Other Stability Theorems for Complex Manifolds --- p.66 / Chapter A --- The Complex Laplacian ´بa --- p.72 / Chapter B --- Hodge-Dolbeault Theorem --- p.77 / Chapter C --- Proof of Theorem 6.2 --- p.79 / Chapter D --- Subelliptic Estimates of --- p.82 / Bibliography --- p.87
5

Mortality Dependence of Cu Dual Damascene Interconnects on Adjacent Segments

Chang, Choon Wai, Gan, C.L., Thompson, Carl V., Pey, Kin Leong, Choi, Wee Kiong, Hwang, N. 01 1900 (has links)
Electromigration experiments have been carried out on straight interconnects that have single vias at each end, and are divided into two segments by a via in the center ("dotted-I" structures). For dotted-i structures in the second metal layer (M2) and with 25µm-long segments length, failures occurred even when the product of the current density and segment length (jL) was as low as 1250A/cm, even though via terminated 25µm-long lines are "immortal" when (jL)cr < 1500 A/cm. Moreover, we found the mortalities of the dotted-I segments to be dependent on the current density and current direction in the adjacent segment. These result suggest that there is not a definite value of jL product that defines true immortality in individual segments that are part of an interconnect tree, and that the critical value of jL for Cu dual damascene segments is dependent on the magnitude and direction of current flow in adjacent segments. Therefore, (jL)cr values determined in two-terminal via-terminated lines cannot be directly applied to interconnects with branched segments, but rather the magnitude as well as the direction of the current flow in the adjoining segments must be taken into consideration in determining the immortality of interconnect segments. / Singapore-MIT Alliance (SMA)
6

Investigation of fluorescence of Cr ions germinate glass in submicron scale by SNOM

chen, victor 27 July 2010 (has links)
In recent years, the demand of the optical fiber communication bandwidth is increasing. Therefore, how to develop gain materials has become an important issue. The composition of a chromium-doped glass CaO-GeO2-Li2O-B2O3-Al2O3 is known to have good optical properties, the Cr-doped glass¡¦s radiation wavelength 1.2-1.5£gm covering entire communication band. The characteristics of a chromium-doped glass have potential to develop width band light source, optical amplifier and tunable wavelength laser. Our laboratory has successfully developed chromium-doped glass with infrared radiation characteristics. In order to improve it¡¦s optical properties. For example, increasing fluorescence intensity and less transmission loss. We shape the chromium-doped glass samples produced to high resolution transmission electron microscope sample, scanning its fluorescence intensity and Raman shift, two-dimensional graphics, comparing the difference between quench and heat treatment glass sample. The nanocrystal with infrared radiation characteristics appear when the heat treatment Raise up to appropriate temperature. To prove the nanocrystal distribution more uniform, higher fluorescence intensity, and smaller size of the nanocrystal to decreasing the transmission loss . We use different composition, or different nucleating agents and different heat treatment ways to analyze its transmission characteristics and internal structural changes. Near-field scanning optical microscope (SNOM) and high-resolution electron microscopy play a very important role in nano research. We also adjust the polarization film Polarizer use to reach the high resolution about 100nm. With this thesis we can analysis whether Cr3+ ion and Cr4+ ion exist in the same phase of nanocrystal and mapping high resolution fluorescence distribution picture to know how the nanocrystal appear by heat treatment, distinguish different nanocrystal by Ramen shift.
7

A Cooperative Prediction Based Approach to Spectrum Management in Cognitive Radio Networks

Barnes, Simon Daniel January 2016 (has links)
One of the problems facing wireless network planners is a perceived scarcity of spectrum. A technology that addresses this problem is cognitive radio (CR). A critical function of a CR network is spectrum sensing (SS). A secondary user (SU) in a CR network will perform SS to gather information about the radio environment within which it wishes to operate and then make decisions based on that information. While SS by individual SUs is very useful it has been found in the literature that a cooperative approach, where SUs share their individual results, may provide more accurate information about the radio environment. It has also been shown that it is beneficial for SUs to be able to make proactive decisions about spectrum resource allocation. To be able to make these proactive decisions, a SU will need to be able to make predictions about the future behaviour of other users of the same spectrum. This research project was divided into two parts. Firstly, a measurement campaign was performed to characterise spectrum scarcity in the South African context. Detailed information, about the occupancy of various commercially utilised South African frequency bands, was collected from spectrum measurement campaigns carried at the Hatfield campus of the University of Pretoria and at Pinmill Farm in Johannesburg. These bands included the television broadcast and mobile cellular bands. On average, the television broadcast bands were found to be underutilised highlighting the existence of a number of opportunities for television white space devices. However, the mobile cellular bands were found to be much more heavily occupied, particularly for the bands around 900 MHz, suggesting that mobile operators are currently in need of additional spectrum resources. The second part of this thesis followed a more theoretical approach and was based on the need for proactive decision making in CR networks. A single SU prediction method, of relatively cheap computational complexity, was proposed and tested under various traffic conditions. The premise that collaboration between SUs may improve the accuracy of single SU traffic predictions was then explored. Pre-fusion and post-fusion approaches to cooperative prediction were compared with the single SU prediction scenario. The prediction error for the cooperative approaches was found to be lower than for the single SU case, especially for the pre-fusion scenario. For example, for a signal-to-noise ratio of 8 dB and individual forecast probability of 0.9, the pre-fusion prediction error was found to be approximately 2% compared with 26% for single SU prediction error. The cost of this improvement, however, was added algorithm complexity. It was then demonstrated that primary user traffic prediction could be used to improve the energy consumption associated with cooperative SS in a CR network. Combined with an optimal scheduling algorithm, this approach was shown to prolong the lifetime of a group of twenty cooperating SUs by 21.2 time samples for a uniformly distributed group of SUs when predictions were made ten time samples into the future. / Thesis (PhD)--University of Pretoria, 2016. / The Sentech Chair in Broadband Wireless Multimedia Communication / The National Research Foundation / The Independent Communications Authority of South Africa / Electrical, Electronic and Computer Engineering / PhD / Unrestricted
8

Estudo da união adesiva entre cimentos resinosos e ligas a base de níquel-cromo, em funçao da aplicação de primers adesivos metálicos / Bonding strength between resin cements and niquel-chromium alloys related to the use of adhesive metal primers

Lisboa, Marcio Vieira 04 July 2005 (has links)
A força de adesão entre resinas e ligas de metais básicos resulta do embricamento mecânico entre a superfície do metal e a resina e da interação química entre óxidos presentes na superfície dos metais e monômeros adesivos das resinas compostas. A literatura, entretanto, mostra que ainda persistem algumas dúvidas sobre a interação entre os diversos tipos de sistemas adesivos e metais básicos, por isso, essa pesquisa visa: verificar se a presença do Be na composição de ligas a base de Ni-Cr influencia a união metal básico/resina; comparar dois cimentos resinosos adesivos nessa função e verificar a influência da utilização de condicionadores (primers) adesivos metálicos para ligas nobres sobre essa união. Após 2500 termociclos, foram realizados testes de resistência à tração em 160 corpos-de-prova, que consistiam de dois discos de Ni-Cr-Be (Verabond – Aalba Dental Inc., Cordelia, CA-USA) com 6 mm de diâmetro e 2 mm de espessura cimentados entre si, e dois discos de Ni-Cr (Durabond - Odonto Comercial Importadora Ltda, São Paulo, SP), com as mesmas dimensões, cimentados entre si. Foram utilizadas diferentes marcas comerciais de sistemas adesivos: os cimentos resinosos adesivos, Panavia F (Kuraray Co. Ltd.), Bistite II DC (Tokuyama Corp.) e os agente de união (primers adesivos metálicos), Alloy Primer (Kuraray Co. Ltd. ), Metaltite (Tokuyama Corp.) e Cesead Opaque Primer (Kuraray Co. Ltd.). Discos cimentados sem primers serviram como grupo controle. Os resultados mostraram que houve diferença estatisticamente significante entre as duas ligas (Ni-Cr-Be –24,82 ± 7,6 MPa e Ni-Cr - 22,32 ± 7,9 MPa). Já para os cimentos houve superioridade adesiva do cimento Panavia F, que obteve média de resitência adesiva de 27,49 ± 4,8 MPa, sobre o cimento Bistite II, que obteve média de resistência adesiva de 19,63 ± 8,4 MPa. Os primers utilizados não apresentaram influência positiva sobre o Panavia F já que os grupos sem primer para esse cimento obtiveram média de 28,18 ± 5,6 MPa que é equivalente a média dos outros grupos com Panavia. Entretanto, para o cimento Bistite II DC os primers Alloy Primer e Metaltite obtiveram as menores médias, 12,7 ± 7,6 MPa e 15,71 ± 4,8 MPa respectivamente, enquanto sem primer, ou com o Cesead Opaque Primer, as médias foram significantemente superiores, 24.47 ± 6 MPa e 25.70 ± 6,8 Mpa respectivamente. Diante dos resultados conclui-se que os primers adesivos metálicos não potencializaram a adesão de cimentos resinosos adesivos sobre ligas de Ni-Cr. / The bond strength for resin and basic metals comes from the interaction between oxides in the metal surface and adhesive monomers in the composite resins composition. The literature shows that still are some questions about this interaction so this research intends to: verify if the presence of Be at Ni-Cr alloy plays some influence for this union, compare two resin luting cements at this function and study the influence the use of metal primers for noble metals in this mecanism of adhesion. After 2500 thermocycles, tensile bond strength tests were loaded at 160 specimens, which consisted of two metals discs with 6 mm in diameter and 2 mm thick from a Ni-Cr-Be alloy (Verabond – Aalba Dental Inc., Cordelia, CA-USA) bonded togheter and two metal discs from a Ni-Cr alloy (Durabond - Odonto Comercial Importadora Ltda, São Paulo, SP) bonded togheter. Diferent brand adhesive systems were used: the resin cements, Panavia F (Kuraray Co. Ltd.) and Bistite II DC (Tokuyama Corp.) and the metal primers, Alloy Primer (Kuraray Co. Ltd.), Metaltite (Tokuyama Corp.) and Cesead Opaque Primer (Kuraray Co. Ltd.). Nonprimed specimens served as control group. The results indicated that there is statiscal diferences beetwen the two alloys (Ni-Cr-Be –24,82 ± 7,6 MPa e Ni-Cr - 22,32 ± 7,9 MPa). Panavia F had founded greater bond strength (27,49 ± 4,8 MPa) than Bistite DC (19,63 ± 8,4 MPa). The metal primers did not show any positive influence for the Panavia bond strength when we considere that the no primer group had 28,18 ± 5,6 MPa bond strength media which were equivalente to the others Panavia´s groups. However for the Bistite cement, the bond strength for Alloy primer and Metaltite were the lower medias, 12,7 ± 7,6 MPa and 15,71 ± 4,8 MPa respectivally, while the no primer or the Cesead Opaque Primer groups showed superior medias 24,47 ± 6 MPa and 25,70 ± 6,8 MPa respectivally. The outcome of this research shows that the metal primers used did not incresead the bond strength between resin cements and Ni-Cr alloys.
9

Improvement of Passivity of Fe - xCr Alloys (x < 10%) by Cycling Through the Reactivation Potential

Ulaganathan, Jaganathan 26 February 2009 (has links)
Classically 13% Cr is required for stable passivity of steel in acidic and neutral solutions. Some authors (Mansfeld, Fujimoto) have published potential cycling procedures that generate thick Cr-rich films. Fujimoto cycles right to the transpassivity potential and back in H2SO4 solution. Our idea is to work close to the reactivation potential where the passive film (Fe2O3) is reductively dissolved to Fe2+. While using an equimolar acetate buffer (pH 4.7), we have obtained new insights into the reactivation process. It is under a kind of thermodynamic control, in that the film cannot be reduced, and the metal cannot be dissolved, faster than would exceed the equilibrium concentration of Fe2+ at the electrode surface. Reductive dissolution leads to gel-like Cr-rich film, but Fe dissolution occurs through it, if formed in a single step. However alternating formation and reductive dissolution of a Fe-rich film assist the formation of a more robust Cr-rich film
10

Improvement of Passivity of Fe - xCr Alloys (x < 10%) by Cycling Through the Reactivation Potential

Ulaganathan, Jaganathan 26 February 2009 (has links)
Classically 13% Cr is required for stable passivity of steel in acidic and neutral solutions. Some authors (Mansfeld, Fujimoto) have published potential cycling procedures that generate thick Cr-rich films. Fujimoto cycles right to the transpassivity potential and back in H2SO4 solution. Our idea is to work close to the reactivation potential where the passive film (Fe2O3) is reductively dissolved to Fe2+. While using an equimolar acetate buffer (pH 4.7), we have obtained new insights into the reactivation process. It is under a kind of thermodynamic control, in that the film cannot be reduced, and the metal cannot be dissolved, faster than would exceed the equilibrium concentration of Fe2+ at the electrode surface. Reductive dissolution leads to gel-like Cr-rich film, but Fe dissolution occurs through it, if formed in a single step. However alternating formation and reductive dissolution of a Fe-rich film assist the formation of a more robust Cr-rich film

Page generated in 0.0363 seconds