1,157 research outputs found
Using patterned carbon nanotube films with optical anisotropy to tune the diffracted color from flexible substrates
No full textThe Demographic Modernization
No full textThe purpose of this paper is to describe the pattern of population growth during the period of socio-economic development, 1905~1976. This analysis looks at population trends for two broad periods: (1) the period of agriculture from 1905~1942, and (2) the period of development from 1946~1976. This latter phase is examined in terms of (a) the initial period of societal development (1949~1960), and (b) the most recent period of transition from 1961~1976. It was found that following the transformation from an agrarian to an urban-industrial society, the population has undergone a transition, but the transition of both fertility and mortality exhibited a different speed and pattern in the stages of socio-economic development. In the initial stage, a moderately high birth rate rose even higher while mortality decreased. If we look at the demographic transition in terms of declining mortality, it may be said that the population was in transition from about 1910 onward. But this mortality deceline was more in keeping with the Malthusian model rather than transition theory; and it was not until 1956, when socioeconomic development began to have an effect on social structure, that birth rate declines took place. As societal development went further, the birth rate decline accelerated while the deth rate decline slowed down, and the population seemed to be approaching a new demographic balance between low birth and death rates. The lag between the transitions of mortality and fertility decline was only about 50 years in Taiwan, as compared to 100-200 years in most modern European countries
Dynamics of changes in micronucleus frequencies in subjects post cessation of chronic low-dose radiation exposure
No full textUniversity Librarians’ Cognition of the Typical Messages for Library Building Programming
No full text業主與建築師在建築設計溝通過程中，常因雙方專業背景差異所產生之「資訊不對稱」現象，而導致雙方誤解對方的想法及企圖。本研究以問卷調查365位大學圖書館員，以確認性因素分析統計方法界定館員認知各類圖書館建築設計主題分類與屬於圖書館員或是建築師在意之範疇，對設計溝通資訊之分類方式，及建築需求書中呈現專業典型訊息之方法。上述典型訊息之合宜釐定，可協助圖書館員及建築師利用圖書館建築設計資訊進行合理的溝通，以及制定符合兩造需求之圖書館建築需求書。Misunderstanding of the partner’s ideas and intentions is quite a common condition in the design communication process between the client and architect, because of the “Asymmetric information” phenomena which come from different professional training for librarians and architects. Three hundred sixty five librarians are investigated with questionnaires. The statistic method – Confirmatory Factor Analysis method is applied for analyzing librarians’ categorization of the themes for library building design, as well as the themes, could be assigned to either the librarians’ or architects’ domains, and categorization of design communication information, and the presentation of professional typical messages into the architectural requirements for proposal. The appropriate defining of typical messages should form an effective communication base to help librarians and architects to set a good library programming to meet their needs
Tuning photonic bandgap of 3D opal structures by utilizing polymer and silica hybrid colloids
No full textProperties and Applications of Amorphous Gallium Arsenide Annealed to a Polycrystalline Form
No full textGaAs can be grown by Molecular Beam Epitaxy (MBE) in an amorphous form by lowering the growth temperature well below normal growth conditions. These growth conditions result in material that is very arsenic rich. When this material is annealed at moderate temperatures (400 to 500°C) it becomes polycrystalline and in some cases very conductive (rho = single digit mO-cm). Several aspects of the annealing were explored and annealing time, temperature, ambient, and ramp rate were all found to be important factors. Different conduction mechanisms were studied, and it was concluded that conduction is due to the formation of rhombohedral arsenic forming in between GaAs grains. These arsenic grains form a network around the GaAs grain structure, creating a conduction path through the material. Silicon doping of the amorphous GaAs lowers the amount of arsenic incorporation during growth. The silicon doped material has nearly the same resistivity as the undoped material when annealed but has a much better surface morphology. The phase change that this material goes through at a relatively low temperature makes it useful as an adhesion layer for wafer bonding. Using amorphous GaAs as an adhesion layer, GaAs substrates have been bonded to GaAs, InP, and glass at 400°C. MBE regrowths on bonded samples have shown moderate success.Made available in DSpace on 2015-09-25T20:08:23Z (GMT). No. of bitstreams: 2
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Previous issue date: 2003Embargo set by: Seth Robbins for item 82116
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Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDsRestricted to the U of I community idenfinitely during batch ingest of legacy ETDsU of I Only68 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2003
Wafer Bonding With Low-Temperature Grown Compound Semiconductor Materials for Optoelectronic Device Application
No full text75 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2003.Finally, I developed two methods to transfer a GaAs-based device layer on a transparent GaP substrate (for emission wavelength longer than 560 nm), which involve multiple processing techniques. One approach also includes the regrowth step, which further indicates the bonded sample can further be processed at high temperatures.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD
Growth and Characterization of Carbon-Doped Aluminum(x) Gallium(1-X) Arsenide and Aluminum(x) Gallium(1-X) Phosphide
No full textCarbon-doped GaAs and Al\sb{\rm x}Ga\sb{\rm 1-x}As with carbon concentrations ranging from 2 10\sp cm\sp{-3} to 3 10\sp{20} cm\sp{-3} have been characterized with Hall effect measurements, secondary ion mass spectrometry (SIMS), double crystal x-ray diffraction and nuclear reaction analysis in an ion channeling geometry. It was revealed that the surface morphology and elemental composition of p\sp+ Al\sb{\rm x}Ga\sb{\rm 1-x}As were critically dependent on the growth conditions due to the existence of a chemical reaction (etching) with the byproducts of the CCl\sb4 source. This "etching" effect was also observed during the growth of p-type Al\sb{\rm x}Ga\sb{\rm 1-x}P by MOCVD using CCl\sb4 as the dopant source. The hole concentration obtained from MOCVD grown Al\sb{\rm x}Ga\sb{\rm 1-x}P using CCl\sb4 is at least an order of magnitude lower than the reported concentrations in films grown by MOMBE.Carbon-doped epilayers grown by MOCVD yielded abrupt dopant profiles. However, the redistribution of carbon was observed during the growth of GaAs structures by MOMBE. This may result from defects generated due to the specific MOMBE growth conditions and was not observed in n-i-p+-i-n or HBT structures grown by MOCVD.The doping efficiency of carbon in Al\sb{\rm x}Ga\sb{\rm 1-x}As is shown to decrease when (C) 10\sp cm\sp{-3}. Two mechanisms are responsible: (1) the passivation of carbon acceptors by hydrogen and (2) the incorporation of electrically neutral carbon precipitates or interstitial clusters. For a single p\sp+ Al\sb{\rm x}Ga\sb{\rm 1-x}As layer, the hydrogenation of carbon acceptors can be reversed by a rapid thermal anneal step below 500\sp\circC. However, sample annealing at higher temperatures causes a reduction in hole concentration with a parallel drop in the lattice mismatch between the epitaxial layers and the GaAs substrate.The decrease in the lattice mismatch and the degradation of hole conduction upon high-temperature annealing are shown to result from the presence of interstitial carbon or carbon precipitates. These findings were confirmed by a direct measurement of the lattice site location of carbon atoms in GaAs and Al\sb{\rm x}Ga\sb{\rm 1-x}As both as-grown and annealed under rapid thermal annealing and arsenic rich conditions.Made available in DSpace on 2014-12-16T22:23:11Z (GMT). No. of bitstreams: 1
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Previous issue date: 1993Embargo set by: Seth Robbins for item 72168
Lift date: Forever
Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDsRestricted to the U of I community idenfinitely during batch ingest of legacy ETDsU of I Only140 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1993
Modeling the Evolution of the Wax Lake Delta in Atchafalaya Bay, Louisiana
Full text linkIn this study, a process-based, depth-averaged Delft3D hydrodynamic and morphologic model of the Wax Lake Delta in Atchafalaya Bay, Louisiana was developed to simulate a five year period of delta development. The purpose of this modeling effort was to test the ability of process-based modeling tools to successfully simulate typical delta-building processes and the resulting morphologic and stratigraphic characteristics of the delta. Recent developments in conceptual modeling of mouth bar formation and full delta development have confirmed the capability of process-based models to simulate the processes necessary for delta growth and the resulting long-term, geologic scale morphologic and stratigraphic features. In this attempt to model the actual development of a prototype delta using similar techniques to those employed in the conceptual delta models, the applicability of physics-based modeling to delta evolution simulation will be further validated. Morphology qualitatively reproduced typical river-dominant delta growth through the establishment of new depositional lobes while maintaining approximate radial symmetry. More specific stratigraphic features were also reproduced. The successive stacking of coarsening upwards sequences observed in Wax Lake Delta mouth bar deposits was evident in the stratigraphy of modeled incipient jet deposits, a result of the varying discharge regime. Though incipient jet deposits developed in the model at the distal ends of distributary channels, the prograding bars did not aggrade sufficiently to induce flow bifurcation and the development of a mature mouth bar depositional lobe. The overall coarsening-upwards, though sand dominant stratigraphic sequence of typical friction-dominant river mouth deposits is reproduced. Significant mud-dominant prodelta deposition is observed basinward of the original delta front location. In the prototype Wax Lake Delta, deposition of fine sediments in this area is hindered by waves and wind-induced transport, so the modeled mud depositional bodies do not reflect prototype development. Distributary channels are significantly incised and narrowed over the course of the simulation. The narrowing proceeds from significant sand-dominant subaqueous levee deposition on the channel banks. Though distributary channels in the real Wax Lake Delta do frequently incise through the full deltaic sedimentary sequence with channel extension, the modeled incision is persistent throughout the simulation. Upstream accretion of established delta lobes through sand-deposition, similar to the observed primary process of subaerial development in the neighboring Atchafalaya Delta, was also present in the modeled development. The Wax Lake Delta is clearly river-dominant according to traditional classification schemes; however, the deposition of fine sediments is influenced by basin processes that resuspend and export significant quantities from Atchafalaya Bay. The processes contributing to the coarse sediment depositional features that dominate the Wax Lake Delta are qualitatively simulated under purely riverine forcings, but the fine sediment dynamics cannot be accurately simulated in the present, process-limited model. Recommendations for improving morphological simulation include model redevelopment with an alternative, total load transport formulation and the inclusion of limited marine forcings that inhibit fine-sediment deposition.CoMEM - Coastal and Marine Engineering and ManagementSection Hydraulic EngineeringCivil Engineering and Geoscience
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