Thesis (M.Sc.)--University of Hong Kong, 2004. / Includes bibliographical references (p. 112-114)

City halls have long been regarded as the social, organizational, perceptual and physical centers of cities. A successful city can be recognized by the success of its city hall. As a city develops, so must its city hall. Over several decades of construction, urban sprawl in Michigan has resulted in an increasingly contiguous network of cities. Devoid of distinction, the boundaries of these cities meld with each other, disintegrating developed city centers. City halls have furthered this disintegration by relocating municipal service buildings along the periphery of downtowns reducing accessibility to the services and involvement with the vitality of the downtown. The city hall is then left to contend with mid-rise commercial buildings for prominence and distinction or to simply become isolated amidst residential neighbors. In downtown Ann Arbor the 1964 city hall stands, exemplary of an era concerned with accommodating the conveniences of driving, economy of construction and the modernist style. Building upkeep, working conditions, accessibility of services and expansion cause problems today. This thesis recognizes the city hall as an intrinsic part of the development of downtowns for midsized cities. It looks at how a city such as Ann Arbor could further that development by relocating and transforming the city hall into a new, central, responsive, informative and integrated hub for administrative and social functions, worthy of pride. Devised in response to numerous observations made across the State, related studies and discussion with city officials, the project identifies eight major criteria to consider when designing a new city hall. An integration of community and social programs with those of the administrative departments of the city, draw the citizens to use the building regularly and become more actively involved with political issues. Success of this project might assert the city as a leader in inspiring others to evaluate the role of architecture in smart growth planning and urban densification.

City halls have long been regarded as the social, organizational, perceptual and physical centers of cities. A successful city can be recognized by the success of its city hall. As a city develops, so must its city hall. Over several decades of construction, urban sprawl in Michigan has resulted in an increasingly contiguous network of cities. Devoid of distinction, the boundaries of these cities meld with each other, disintegrating developed city centers. City halls have furthered this disintegration by relocating municipal service buildings along the periphery of downtowns reducing accessibility to the services and involvement with the vitality of the downtown. The city hall is then left to contend with mid-rise commercial buildings for prominence and distinction or to simply become isolated amidst residential neighbors. In downtown Ann Arbor the 1964 city hall stands, exemplary of an era concerned with accommodating the conveniences of driving, economy of construction and the modernist style. Building upkeep, working conditions, accessibility of services and expansion cause problems today. This thesis recognizes the city hall as an intrinsic part of the development of downtowns for midsized cities. It looks at how a city such as Ann Arbor could further that development by relocating and transforming the city hall into a new, central, responsive, informative and integrated hub for administrative and social functions, worthy of pride. Devised in response to numerous observations made across the State, related studies and discussion with city officials, the project identifies eight major criteria to consider when designing a new city hall. An integration of community and social programs with those of the administrative departments of the city, draw the citizens to use the building regularly and become more actively involved with political issues. Success of this project might assert the city as a leader in inspiring others to evaluate the role of architecture in smart growth planning and urban densification.

High efficiency components are key elements of solid-state amplifiers for wireless application. We used HEMT (high-electron-mobility transistor) to obtain high mobility 2DEGs. AlGaN makes itself an attractive material for high frequency devices, and the system is particularly good for the investigation of quantum Hall effect. We studied the electronic properties of AlxGa1-xN/GaN heterostructures by using Shubnikov-de Haas (SdH) measurement. The T-dependent Hall measurement (from 4.2 K to 300K) was performed at the magnetic field 0.3T and the B-dependent Hall measurement (from 0.02T to 0.8 T) at constant temperature. From the field-dependent Hall measurements, we are able to calculate the individual mobility and carrier concentration for the two-subband-populated AlxGa1-xN/GaN heterostructures. Then, we can use T-dependent Hall effect measurement to calculate the binding energy of the deep-level trap Ed,which is a measure of the energy constant for the ionization of deep-level trap in thermal equilibrium.

This research proposes the architecture of motor driver IC for the application of small BLDC motors. Both analog and digital mixed-mode techniques are employed here to design BLDC fan motor driver IC. The controlling method of this motor driver IC mainly utilizes analog approach. Besides, in order to prevent any damages on motors due to abnormal operations, digital control circuit is also involved in this IC. This motor driver IC is used in heat-sinking fan on notebooks as well as on the motors with very small impedance, so the IC is designed to be able to work in low supply voltage, and has high driving capability at the output stage. Via the feedback signal generated by the Hall sensor, it controls the motor driver IC so that the IC can supply current accordingly to stator coil. Therefore, the purpose of controlling motors is then achieved.

We have studied the electronic properties of AlxGa1-xN/GaN heterostructures by using Shubnikov¡Vde Haas(SdH) measurement. Two SdH oscillations were detected on the sample of x=0.31, due to the population of the first two subbands with the energy separations of 94.2 meV. For the samples of x=0.22 and x=0.23, two SdH oscillations beat each other, probably due to a finite zero-field spin splitting. The spin-splitting energies are equal to 1.4~5.3 and 4.5 meV . The samples also showed a persistent photoconductivity effect after illuminating by blue light-emitting diode.

We discussed the electronic properties in AlxGa1-xN/GaN heterostructures. There are six different samples of AlxGa1-xN/GaN we prepared for this experiment, three of them are undoped AlxGa1-xN/GaN with different x values which is 0.17, 0.29 and 0.33, respectively. The others are Fe-doped AlxGa1-xN/GaN which the x value is 0.18, 0.19 and 0.21 for each sample. Comparing these two types¡¦ materials¡¦ results, we tried to confirm the impurity¡¦s characteristic in our samples. From the Hall measurement results, carrier concentration of Fe-doped AlxGa1-xN/GaN were pretty lower than undoped AlxGa1-xN/GaN, and the mobility at 4.2 K are almost two times to undoped AlxGa1-xN/GaN. At the same time, we performed Shubnikov-de Hass measurement, and two subbands of the 2DEG were populated on the samples for x value is 0.29 and 0.33. The energy separation for first two subbands is 109meV. We also observed obvious beat pattern in the SdH oscillations due to the spin splitting on the samples and the greatest spin-splitting energy is 5.96meV in our measurement. Furthermore, we observed evident PPC effect on the samples of Fe-doped AlxGa1-xN/GaN, the carrier concentrations increased at least 23% after illumination. Meanwhile the samples of undoped AlxGa1-xN/GaN can just produce 10.7% increment at most.

Thèse de doctorat : Science et ingénierie des matériaux : Vandoeuvre-les-Nancy, INPL : 2006. / Titre provenant de l'écran-titre. Bibliogr.

Zugl.: Braunschweig, Techn. Univ., Diss., 2006

Thèses (Ph.D.)--Université de Sherbrooke (Canada), 2002. / Titre de l'écran-titre (visionné le 30 août 2006). Publié aussi en version papier.