Zugl.: Berlin, Techn. Universiẗat, Diplomarbeit.

Mannheim, Univ., Diss., 2005.

Novel disc like molecules based on hexa-n-alkoxy benzoates of triphenylene were synthesised at Hull university. The compounds exhibited thermotropic liquid crystalline behaviour. The compounds differed chemically based upon the number and position of methyl additions to the ester benzoate linkage. Unsymmetrical compounds based on hexa-n-alkoxy triphenylenes were also examined. A number of techniques were employed to observe and measure the physical properties of these compounds. Polarising optical microscopy was used to observe and record the phase behaviour. Typical schlieren nematic textures were often observed in the liquid crystalline phase. The transition temperatures of the phase transitions were recorded to within +/-0.1 °C. Methyl additions to the ester benzoate linkage plays a major role in determining transition temperatures and also the ranges of liquid crystal phase. X-ray diffraction investigations allowed the molecular planar spacings to be measured, use of a heating stage enabled measurements to be taken in the liquid crystalline phase. All the samples produced a diffuse broad diffraction ring in the liquid crystalline phase, indicating that the samples are not highly ordered and that they are likely to have adopted a hexagonal packing arrangement. Planar spacings measured were in the range 22 - 30A, only one sample, DB26, showed a diffraction ring corresponding to a planar spacing of 4.1A, indicating that molecular columns or partial columns were able to form from molecules stacking one on top of another. Thus methyl groups on the ester benzoate linkage disrupt the formation of columns, in turn reducing transition temperatures. A number of methods of successfully aligning the discotic materials using surface treatments are presented. Rubbed PVA and HTAB layers aligned the samples hometropically, while SiO deposited layers aligned the samples homogeneously. (The SiO deposition used an evaporation angle of 45°, a deposition angle of 5° is commonly used to obtain homotropic alignment of calamitic materials.) Methods that produced homogeonous alignment of calamitic materials produced hometropically aligned discotic materials and vice-versa. FTIR allows conformational information about a molecule to be determined. The CH[2] wagging region was investigated to determine conformational information relating to the alkyl arms. Combination of FTIR and aligned samples allowed the alignment process to be investigated, it was determined that the alignment of the molecules occurs in a series of stages, the triphenylene cores align first on cooling, followed by the ester benzoate linkages and finally the alkyl arms. Computer modelling simulations allowed various molecular conformations to be observed, combination with X-ray diffraction data allowed molecular structures to be generated. The software allowed various molecular dimensions to be easily measured and the effect and extent of interdigitation of molecular arms to be observed. The molecular dynamics calculations were only able to calculate energy minimisations for crystalline structures, but the crystalline results offered valuable insights into the liquid crystalline structures and behaviour.

This thesis includes two topics. The first topic is a ZigBee transceiver used in 2.45 GHz band design. The second topic is a 2K/4K/8K multimode fast Fourier transformation ( FFT ) for DVB-H demodulators. The first topic includes simulations and hardware design. The chip is a physical layer design compliant with IEEE Std 802.15.4 standard, including a transmitter and a receiver for 2.45 GHz band. The measurement of the maximum power on silicon is about 731 £gW at 8 MHz. It is proved to be compliant with the low power consumption requirement specified by the standard. The second topic includes simulations and hardware design of an FFT for DVB-H demodulators. This processor is based on a pipeline architecture with radix-2, radix-22 and radix-23 computation element. We propose one sharing butterfly architecture to be used in the variable length FFT processor.

No description available.

No description available.

Aus dem Streubild der Kleinwinkelstreuung kann im Allgemeinen, die die Streuvertei-lung erzeugende Struktur nicht eindeutig rekonstruiert werden. Die Ursache dafür wird erörtert und die damit verbundenen Einschränkungen bei der rechnerischen Auswertung der Streukurven an Beispielen veranschaulicht. Dies geschieht an Streukurven, die mit bekannten Größenverteilungen berechnet wurden. Weiterhin wird untersucht, welche Fit- Ansätze sich zur Auswertung der Kleinwinkelstreuexperimente am besten eignen. Als Fit- Ansätze wurden Reihenentwicklungen nach Trigonometrischen- und Polynomfunkti-onen und eine theoretisch motivierte Funktion verwendet. Neben dem entscheidenden Vergleich mit der Streukurve der Ausgangsfunktion werden die Ergebnisse auch den Rechnungen gegenübergestellt, die mit der weit verbreiteten Glatter- Methode erzielt werden.

A new, high resolution, high precision and accuracy gravimetric geoid of Australia has been produced using updated data, theory and computational methodologies. The fast Fourier transform technique is applied to the computation of the geoid and terrain effects. The long, medium and short wavelength components of the geoid are determined from the OSU91A global geopotential model, 2'x2' (residual gravity anomalies in a 3 degrees cap and 1'x1' digital terrain model (DTM), respectively.Satellite altimeter gravity data have been combined with marine gravity data to improve the coverage of the gravity data, and thus the quality of the geoid. The best gridding procedure for gravity data has been studied and applied to the gravity data gridding. It is found that the gravity field of Australia behaves quite differently. None of the free-air, Bouguer or topographic-isostatic gravity anomalies are consistently the smoothest. The Bouguer anomaly is often rougher than the free-air anomaly and thus should be not used for gravity field gridding. It is also revealed that in some regions the topography often contains longer wavelength features than the gravity anomalies.It is demonstrated that the inclusion of terrain effects is crucial for the determination of an accurate gravimetric geoid. Both the direct and indirect terrain effects need to be taken into account in the precise geoid determination of Australia. The existing AUSGEOID93 could be in error up to 0.7m in terms of the terrain effect only. In addition, a series of formulas have been developed to evaluate the precision of the terrain effects. These formulas allow the effectiveness of the terrain correction and precision requirement for a given DTM to be studied. It is recommended that the newly released 9"x9" DTM could be more effectively used if it is based on 15"x15" grid.It is estimated from comparisons with Global ++ / Positioning System (GPS) and Australian Height Datum Data that the absolute accuracy of the new geoid is better than 33cm and the relative precision of the new geoid is better than 10~20cm. This new geoid can support Australian GPS heighting to third-order specifications.

Zugl.: Tübingen, Univ., Diss., 2007 u.d.T.: Bouziane, Markus: Pricing interest rate derivatives with fourier transform techniques / Lizenzpflichtig

Zugl.: Tübingen, Univ., Diss., 2007 u.d.T.: Bouziane, Markus: Pricing interest rate derivatives with fourier transform techniques