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Totally found 187357 items.

  • [学位] Environmental earth science course development for preservice secondary school science teachers in the Republic of Korea
    The purposes of this study were: (1) evaluating the opinions of Korean professors, in departments of earth science education and departments of geology about the science concepts related to environmental issues that might be important for secondary, preservice earth science teachers in Korea, (2) ranking the environmental education topics to be included in a one-semester, sophomore-level, earth science courses for such teachers, and (3) designing environmental earth science lecture and laboratory course based on the topic rankings and educational theory. A researcher-developed opinionnaire contained 63 items relating to the 14 major environmental earth science topics found in suitable textbooks. The opinionnaire used a four-choice, Likert-type scale and was completed by 47 professors in summer, 1996: 17 from 10 earth science education departments and 30 from nine geology departments. These responses came from 51.1% of the sample population. At present, very few environment-oriented courses are offered in earth science, teacher education programs in Korea. Respondents considered the topics of "Waste Disposal" and "Fresh Water Resources and Pollution" as the most important to be included for prospective teachers. Other urgent environmental problems such as soil pollution by pesticides, air pollution caused by hydrocarbon fuels, landslides, flooding, typhoon, and droughts also were considered important. There was a high correlation (r =.87) in ranking of importance of topics by both groups of professors. This study shows that environmental earth science course should emphasize more on "the human impact on the environment" rather than "natural environmental hazards." On the other hand, natural hazards that commonly occur in Korea should be emphasized more than those that do not commonly occur in Korea. They also approved inclusion of some topics that had more relevance to non-Korean settings perhaps to make the course of greater worldwide relevance. Sample units of the proposed course are described for use in traditional- or constructivist-oriented approaches. By introducing the strengths of both constructivist and traditional teaching and learning, secondary school preservice teachers would experience various instructional strategies.
    关键词: Science education;Teacher education
  • [学位] In situ vibrational spectroscopic investigation of carbon(4) hydrocarbon selective oxidation over vanadium-phosphorus-oxide catalysts
    n-Butane selective oxidation over the VPO catalyst to maleic anhydride is the first and only commercialized process of light alkane selective oxidation. The mechanism of this reaction is still not well known despite over twenty years of extensive studies, which can be partially attributed to the extreme difficulties to characterize catalytic reactions real-time under typical reaction conditions. In situ spectroscopic characterization techniques such as infrared spectroscopy and laser Raman spectroscopy were used in the current mechanistic investigations of n-butane oxidation over VPO catalysts. To identify the reaction intermediates, oxidation of n-butane, 1,3-butadiene and related oxygenates on the VPO catalyst were monitored using FTIR spectroscopy under transient conditions. n-Butane was found to adsorb on the VPO catalyst to form olefinic species, which were further oxidized to unsaturated, noncyclic carbonyl species. The open chain dicarbonyl species then experienced cycloaddition to form maleic anhydride. VPO catalyst phase transformations were investigated using in situ laser Raman spectroscopy. During reduction-oxidation step changes, (VO)2P2O7 was readily converted to αII-, δ-VOPO4 and ultimately to β-VOPO 4 in O2/N2; these V5+ phases were eliminated in n-butane/N2. A “wet” nitrogen feed (5–10% H2O in N2) transformed (VO)2P2O 7 and αI-, αII-, β-, δ, γ-VOPO 4 to V2O5 at temperatures above 400°C. The presence of water vapor facilitated the loss of oxygen atoms involved in V-O-P bonding; separated vanadium oxide and phosphorus oxide species were formed. The isolated vanadium oxides than transformed to V2O5, and phosphorus species likely diffused from the catalyst lattice in the form of acid phosphates.
    关键词: Chemical engineering
  • [学位] Porous coordination networks based on trigonal ligand topologies and silver(I) trifluoromethanesulfonate
    This thesis details one supramolecular assembly approach to solid state construction whereby rigid, trigonal phenylacetylene nitrile ligands crystallized with trigonally coordinating silver trifluoromethanesulfonate predictably yields a porous, crystalline channels structure. Materials based on this combination of symmetries are shown to have the following properties: (1) The channel dimension can be controlled by ligand size variation. Hexagonal void spaces up to 27.3 A x 29.8 A (for 1,3,5-tris(4-(4-ethynylbenzonitrile)benzoethynyl)benzene $\cdot$AgOTf) are constructed by insertion of spacer groups in the ligand backbone. (2) The pore shape can be controlled by ligand modification. Substitution of pendant groups on the trigonally shaped backbone allows control of the cavity environment by introduction of such moieties as alcohols, alkenes, ethers, and chiral substituents without destruction of the hexagonal structure. (3) The cavities will function as a host to a variety of guest molecules. One examined channel dimension (for 1,3,5-tris(4-ethynylbenzonitrile)benzene$\cdot$AgOTf) allows for the after crystallization enclathration of various aliphatic and aromatic molecules (up to 1:3.5 host:guest). (4) The channels can be completely voided of guests without destruction of the host network. Rapid thermal evacuation produces an 'apohost' material retaining the original hexagonal channel motif. The apohost material selectively enclathrates only aromatic (1:3.5 host:guest) and no aliphatic molecules. (5) Solid state reaction between the host network with pendant alcohol and guest silyl triflates occur. A cross-linked host can be formed by the reaction with di-t-butylsilyl bis(trifluoromethanesulfonate) which does not destroy the channels.
    关键词: Chemistry
  • [学位] Liquid distribution and its effect on the organic removal in a trickle bed bioreactor
    Propylene glycol methyl ether was removed from wastewater in a trickling bed bioreactor under different liquid distribution conditions. A 0.3 m diameter column filled with two heights of 0.7 m and 1.4 m with 2 cm plastic spheres with were used. The wastewater flow rate varied from 0.184 to 0.918 kg/m 2.s. The effect of the initial liquid distribution was examined using two types of liquid distributors: a multipoint liquid distributor and a central single point liquid distributor. Over 96 hours of treatment period, the BOD 5 was reduced by 85% and 65% under the most uniform liquid distribution condition and the poor liquid distribution condition, respectively, achieved in this study. Increasing the liquid flow rate from 0.184 to 0.918 kg/m 2.s, it increased the dynamic liquid holdup by 53% and the apparent BOD5 removal rate constant by 23% at 1.4 m bed height using the multipoint liquid distributor. Moreover, with the use of the multipoint liquid distributor, the apparent reaction when the liquid flow rate was increased from 0.184 kg/m2.s to 0.918 kg/m2.s. In addition, it was found that the effect of an increase in the bed height on the percentage BOD5 removal was not significant when initial liquid distribution was uniform. Under the uniform initial condition, only 4% increase in the percentage BOD5 removal was observed when the bed height increased from 0.7 to 1.4 m whereas when the initial distribution was extremely non-uniform, the percentage of BOD5 removal was increased by 20% with increasing the bed height. The local distribution of the BOD5 removal was not uniform across the bed cross-section and it was affected by the liquid flow distribution across the bed cross-section.
    关键词: Chemical engineering
  • [学位] The role of major and minor stressors in moderating the transtheoretical model of exercise behavior among predominantly low -income patients attending primary care clinics
    A sedentary lifestyle is prevalent in the United States and is associated with poor health outcomes (Blair et al., 1989). While regular exercise has been shown to have numerous physical and mental health benefits, much of the population does not perform physical activity at a level necessary to achieve significant health benefits. Primary care settings have become increasingly targeted areas for physician-based exercise counseling. One popular theoretical model of exercise adoption is the transtheoretical model of exercise behavior (Prochaska & Marcus, 1994) which proposes that individuals progress through stages of exercise behavior. Researchers have explored constructs affecting movement through the stages of exercise behavior, such as decisional balance and self-efficacy (e.g. Marcus & Owen, 1992). However, connections between life events and the transtheoretical model for exercise behavior have not previously been examined in the literature. Recent research has shown the perception of stressful life events, particularly minor stressors, may mediate exercise behavior (Stetson et al., 1997). Minor stressors can lead to decreased ability to engage in exercise behavior in three ways: hindered performance of positive health behaviors such as exercise, increased perception of exercise as a stressor, and increased engagement in unhealthy coping behaviors (overeating, smoking, alcohol abuse, etc.). While minor life events may act as barriers to exercise behavior, no study has specifically examined their effect on exercise stage of change. In addition, the exercise stages of change model has not been validated among a low-income, primary care population. The current study examined cross-sectional and longitudinal relationships between major and minor life events and transtheoretical constructs for exercise behavior. This sample included predominantly low-income, primary care patients from across the state of Louisiana. Results provided some support for the use of the transtheoretical model among this population, as demonstrated by the replication of some of the relationship patterns between transtheoretical variables. While life events were positively correlated with some categories of physical activity, they failed to account for significant variance in stage movement across time. Shortcomings and strengths of the present study are discussed, and suggestions are made for future research.
    关键词: Psychotherapy;Behaviorial sciences;Sports medicine
  • [学位] Synthesis of photoresist materials for 193 nm exposure
    In the past decade, astonishing improvements had been made in the performance and cost of consumer electronic devices. The main driving force behind this progress has been the reduction of the feature size on the integrated circuits, made possible by the advancements in microlithographic imaging technology. One of the essential components in the microlithographic imaging is the photoresist, a radiation-sensitive polymeric imaging material that allows the realization of circuit patterns on silicon wafers. This dissertation presents the synthesis, characterization, and evaluation of new positive and negative tone photoresist materials designed for use in 193 nm lithographic application. These materials are based on polymers with alicyclic structures in their backbone and have emerged as excellent platforms from which to design photoresists for 193 nm exposure. New photoresist materials based on poly(tetracyclo[4.4.0.1 2,5.17,12]dodec-3-ene-5-carboxylate-alt-maleic anhydride) have demonstrated etch resistance superior to that of conventional deep UV APEX-E? photoresists while providing as small as 80 nm resolution at 193 nm. This class of polymers has also been adapted to the design of high performance negative tone photoresists for 193 nm microlithography. New systems based on a polarity switch mechanism for modulation of the dissolution rate have been designed. These systems are based on new polar, alicyclic polymer backbones that include a monomer bearing a glycol pendant group that undergoes the acid catalyzed pinacol rearrangement upon exposure and bake to produce the corresponding less polar ketone. This photo-induced, acid catalyzed change in polarity can be translated into a change in solubility and thereby provides a basis for imaging. This monomer was copolymerized with maleic anhydride and a bis-trifluoromethylcarbinol substituted norbornene and the copolymer ratio was optimized to provide optimum imaging properties. New photoresist materials based on these terpolymers have demonstrated the excellent lithographic performance and have produced negative tone images as small as 90 nm in width.
    关键词: Organic chemistry;Materials science;Electrical engineering
  • [学位] The political economy of oil in post -Soviet Kazakhstan
    This dissertation examines the way in which the Kazakhstani state redefined its role in managing oil and gas resources between 1992 and 1998. The governments of hydrocarbon-rich post-Soviet republics such as Russia, Kazakhstan, Azerbaijan, and Turkmenistan faced the common challenge of restructuring their petroleum industries to boost the export of oil and gas. This study argues that by 1998 three patterns have emerged, ranging from a more radical state retrenchment in Russia, to reinforced state monopoly in Azerbaijan and Turkmenistan, to a “mixed” pattern of state participation in Kazakhstan, consisting of both large-scale privatization of oil assets and the formation of a fully state-owned national oil company, Kazakhoil. This dissertation analyzes the process of restructuring Kazakhstan's oil sector through comparison with the Russian petroleum industry. In Russia, several private, vertically integrated oil companies (VICs) were formed on the basis of existing oil-producing units and soon emerged as essential players in the Russian oil sector. By contrast, Kazakhstan's marginalized status within the Soviet system of oil production resulted in the absence of organizationally strong sectoral interests capable of claiming control over the industry after the independence. Privatization of Kazakhstan's oil enterprises, conducted by the government in spite of the resistance from local oil managers, transferred controlling stakes to foreign investors and further weakened domestic oil interests. Unencumbered state autonomy allowed the increasingly authoritarian Kazakhstani government to adopt relatively modern and investor-friendly petroleum legislation by decree. In Russia, the government's efforts to reform oil-related legislation were blocked by the leftist-dominated Duma, the democratically elected lower chamber of the Russian parliament. On the basis of these findings, this dissertation concludes that the dynamics of state withdrawal from the oil sector in post-Soviet context are determined primarily by structural organization of domestic oil industry inherited from the Soviet era, resulting balance of power between the state and private sectoral actors, and general mode of state-society relations in each country.
    关键词: Political science;Energy
  • [学位] Surfactant-enhanced nonaqueous -phase liquid contaminants removal from liquid -saturated media
    A combination of laboratory experiments were performed to improve our understanding on surfactant-enhanced removal of nonaqueous phase liquids (NAPLs) from liquid saturated media. The influence on surfactant type, surfactant concentration, ionic strength, pore velocity, alcohol amendments, and interfacial tension (IFT) in the removal of trichloroethylene (TCE) were characterized. The (solubilization) mass transfer rates were correlated to pore velocity, initial NAPL saturation, and surfactant concentration (manuscript 1). The kinetics of surfactant enhanced solubilization and the relative importance of processes at various scales on the nonequilibrium behavior were addressed (manuscript 2). Pore scale processes was monitored and their effects on surfactant-enhanced NAPL mass removal was evaluated (manuscript 3). Batch and column experiments were conducted to study the solubilization kinetics and the mass transfer relationships. In the batch experiments, completely mixed condition was applied while dissolved NAPL concentration in aqueous phase with time was monitored. Residual NAPL saturation was established in porous media and then solubilization was conducted while effluent NAPL concentration was recorded in the column experiments. A transport simulator was developed to estimate the parameters in the mass transfer correlation for the surfactant-NAPL systems. A physical transparent micromodel and a CCD-based digital image capture system were designed and for the pore scale visualization investigation. Mobilization and solubilization experiments were performed in the micromodel to address the influence of physical and chemical factors on the pore scale mass removal behaviors. Solubilization rates decreased with increasing in hydrocarbon tail length of the surfactant molecules and surfactant concentrations in the batch tests. For anionic surfactants the solubilization rate increased with electrolyte concentrations, while for the nonionic surfactant tested the rate exhibited negligible changes with salt concentration. Addition of alcohols to surfactant solutions increased or decreased the rate depending on the surfactant type and concentration. The solubilization rate was found to be a function of solubilization capacity. From the column experiments, mass transfer rate coefficients were determined as a function of aqueous phase pore velocity, NAPL volumetric fraction, and surfactant concentration. A correlation for predicting mass transfer rate coefficients for NAPL-surfactant system as a function of system properties was developed. Non-equilibrium conditions were found to be significant at relatively low NAPL volumetric fractions. The batch and column experiment results combined showed that the overall mass transfer rates measured in column experiments increased monotonically with the solubilization rates measured in batch tests, indicating processes at molecular/micellar scale played an important role in determining the mass transfer rate. The visualization studies showed that, at relative low capillary numbers (Nca) (<0.001) a mobilization flood under relatively lower IFT conditions resulted in a higher residual NAPL saturation than a flood under higher IFT conditions with a similar Nca. No significant differences were observed in the trapped NAPL blob size, shape, and distribution between these mobilization floods. This water-surfactant “path” dependent phenomenon was attributed to the larger number of trapped blobs resulted from lower IFT in the NAPL-surfactant systems. Dissolution fingers were observed and the fingering was found to decrease the mass removal rates. A small heterogeneity in the micromodel aperture size distribution controlled the distribution of trapped NAPL and the dissolution fingering.
    关键词: Environmental engineering;Environmental science;Petroleum production
  • [学位] Stabilization mechanisms of calcium aluminate fibers made by the inviscid melt-spinning technique
    An eutectic composition (43.5:53.7 wt%) of calcium aluminate was analyzed for its reactivity towards carbon and its response to stress during solidification from the melt. Propane pyrolysis over calcium aluminate melts showed that aluminum carbides and carbide oxides were formed early in the reaction as a result of carbon interactions with the melt. Carbide oxides formed before carbides. Carbon monoxide formation was seen along with the carbide formation. It was not possible to observe calcium carbide formation. Accompanying aluminum carbide oxides and carbides formation, there was a significant increase in the population of tetrahedrally coordinated aluminum atoms. Depth profiling of calcium aluminate fibers formed by Inviscid Melt Spinning showed an excess of tetrahedrally-coordinated aluminum atoms as well as carbonates. It is proposed that this effect is what increases the surface viscosity and stabilizes calcium aluminate fibers. Ethers, ester and carboxylates were also seen at the surface propane stabilized calcia-alumina fibers which suggests that carbon monoxide may be reacting with carbon to form these species. It is postulated that polymerization rather than particle filler effects is responsible for the viscosity build-up in the formation of calcium aluminate fibers by IMS. Further, the fragility of calcia-alumina melt structures in the presence of stress, in particularly of different quenching methods, was demonstrated. Depending of the type of stress, deformed or undeformed tetrahedrally coordinated aluminum atoms can be increased and frozen in with simultaneous heat withdrawal. It was possible to delineate the melting behavior of (47.5:53.5) calcium aluminate samples. De-condensation of some tetrahedral aluminum atoms and the formation of pentahedrally coordinated aluminum atoms was seen with increasing temperature. Further, it was possible to make IR assignment of pentahedrally coordinated aluminum atoms at the 771 cm$\sp{-1}$ region for the calcium aluminate melt.
    关键词: Chemical engineering;Chemistry
  • [学位] Power and vulnerability: A study of the relationships between gender, caste and class inequalities and vulnerability to sexually transmitted diseases in rural south India
    This study examines women's vulnerability to sexually transmitted diseases (STDs) in Sringeri Taluk, a rural sub-district of Karnataka in South India. It consisted of a first phase of ethnographic research that examined how socio-political, economic and cultural factors and processes may increase women's vulnerability to STDs; and a second phase of epidemiological research that investigated specific questions arising from the first phase. Ethnographic research, conducted between July 1997 and September 1999, revealed three main sources of women's vulnerability to STDs: (1) the experience and embodiment of economic and socio-political disadvantage—based on caste, class and gender—through limitations on opportunity and choice, trafficking and prostitution, and violence against women within the home and without; (2) the State through the promotion of alcohol sales and the failure to prevent trafficking in women and prostitution; and (3) the health care system through which socio-political and economic inequalities are reinforced. A cross-sectional survey was conducted between April and July 1999. The study population, selected through a stratified, multistage cluster sampling procedure, consisted of 410 currently married women between the ages of 15 and 50 years and 303 men (including 249 spouses of interviewed women) between the ages of 15 and 60 years residing in villages within a 30 km radius of Sringeri town. The overall prevalence of bacterial STDs was low (2%) in contrast to the prevalence (10%) of markers of HBV infection (past and current). Approximately a third of women reported having experienced marital violence. In multivariate analyses, reports of violence were significantly associated with household-level (caste and class) and intra-household (women's economic autonomy and husband's alcohol consumption) factors. Lastly, the results highlighted the need for STD prevention education efforts to pay attention to the language that is used to convey ideas regarding risk and vulnerability and the need for condom promotion efforts to take into account issues of sexual pleasure and intimacy and to address repercussions that women may face as a result of suggesting condom use to their husband, particularly violence. Reducing women's vulnerability to STDs hinges on addressing inequalities experienced by women—as individuals and as members of households.
    关键词: Public health;Cultural anthropology;Womens studies
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