Influence of silicate modified expansion agent on engineering performance of ultra-high-strength concrete

Wang, Yi-Sheng 강원대학교 대학원 2022 국내석사

At an early age, ultra-high-strength concrete (UHSC) exhibits a large autogenous shrinkage, which easily leads to matrix shrinkage and cracking. This poses a significant threat to the service life of a building structure. In this study, the effects of silicate modified expansive agents (SMEAs) on the engineering performance of UHSC were systematically investigated. The compressive strength, ultrasonic pulse velocity, and surface resistivity were determined. Moreover, Heat of hydration, TG, Fourier transform infrared spectroscopy (FTIR) and other microscopic analyses were used to characterize the chemical composition of the UHSC. It can be seen from the test results that the compressive strength of UHSC tends to decrease with the increase of SMEA addition. The results of TG, X-ray diffraction, and other microscopic analyses indicated that the main composition of the UHSC was a mixture of calcium (aluminate) silicate hydrate, calcium hydroxide, and ettringite.

Genetic Study of Non-reducing Polyketide Biosynthesis in Lichen-Forming Fungus Usnea Longissima

Wang Yi 순천대학교 2009 국내석사

Lichens produce many unique secondary metabolites with valuable biological activities, which mainly belong to polyketides. However, the slow growth and difficult culture of lichen and lichen forming-fungi limited research of lichen polyketides biosyntheses with traditional methods. Fungal polyketides synthase genes (PKSs) for a certain polyketide are usually organized in gene clusters. It implies that the complete PKSs genes for one polyketide can be cloned with special probe. This thesis applies modern bio-technique to clone directly polyketide synthase and discuss their function. To know the diversity of non-reducing PKSs in genera Usnea, a conserved primer targeting ketoacylsynthase (KS) domains of specific clades of PKS genes has been tested on various Usnea samples. Fifty KS fragments were obtained. Phylogenetic analysis showed that this non-reducing PKSs distribute widely in genera Usnea and cluster together according to their locality. The full sequence of U. longissima PKSI (UsPKS1) was cloned successfully through screening genomic library with the KS probe. The sequence characterization showed that a partial genes cluster of PKS was obtained. The gene cluster includes UsPKS1; zinc transcription factor of UsPKS1; 1,3,6,8-tetra-HN reductase; TGF beta-inducible nuclear protein; misfolded glycoproteins degradation protein. Sequence analysis of UsPKS1 suggests that it contains features of a non-reducing fungal type I PKS with ketosynthase; acyl carrier protein (ACP) transcaceylase; acyltransferase domain and thioesterase domain. Phylogenetic analysis suggests that it is similar with 1,3,6,8-tetrahydroxynaphthalene (T4HN) synthase.

The influence of social network on perceived social support and acculturation among Chinese international students in Korea

WANG, WEI YI 이화여자대학교 대학원 2014 국내석사

본 연구는 재한 중국인 유학생의 사회연결망을 감지된 사회적 지지 및 문화적응에 주는 영향에 관한 연구로 재한 중국인의 인구통계학적 속성 (나이, 성별, 체류기간, 전공, 한국어 능력), 현지의 사회연결망 실태가 한국에서 받는 지지와 문화적응에 어떤 영향을 주는지 밝히고자 하였다. 설문지를 이용하여 온라인과 오프라인 2가지 방법으로 서울에 위치한 중국인 유학생을 대상으로 실시하였다. 총 207 부의 유효 표본을 대상으로 SPSS을 이용해서 통계 분석을 하고 결과를 추출하였다. 결과는 나이가 어릴수록, 한국인과 상호작용 정도가 많을수록, 한국에 있는 강한 연결이 많을수록 감지된 사회적 지지를 더 잘 인식할 수 있었고, 한국어 능력이 뛰어날수록, 한국에 오기 전에 한국에 있는 친구를 많이 알수록 유학생의 심리적응에 더 좋은 영향을 줄 수 있다고 밝혀졌다. 그 중에 중국인과의 상호 작용을 유학생들의 감지된 사회적 지지나 심리적응에 영향을 주지 않았다. 이것은 중국인 유학생은 대부분 중국인들과만 상호 작용하는 것이 사실이지만 한국 사회 적응에 큰 도움이 되지 않는다는 것을 말한다. 주제어: 중국인 유학생, 사회연결망, 감지된 사회적 지지, 심리적 적응 With the increasing interests of Chinese international students study abroad, their acculturation overseas have become a highly interest in the disciplines like sociology, psychology, anthropology as well as mass media and communication. The current research tried to explore international students’ perceived instrumental social support and psychological acculturation under the influence of their local social network. This research used quantitative method through questionnaire research on a total number of 207 Chinese international students who study in universities located in Seoul currently. The analysis of the data was performed using IBM SPSS Statistics 18.0. Both correlation and multiple regressions were employed to prove the hypotheses. The results examined that students’ social network locally influenced greatly on their perceived instrumental social support and psychological acculturation. The younger, more interaction with locals and bigger off-line social network size in host country are more likely to get instrumental social support. While those who have higher level of language proficiency and knew friends in host country before arrival would have a better psychological acculturation. The study adds an example of international students’ social network literatures. The results provide some suggestions for Chinese international students in Korea to better adapt to the new environment. There is an urgent need to provide them more opportunities to connect with locals both in university and through social activities. Moreover, it is highly recommended that universities or language schools could build useful connections with students before their arrival, and Chinese students could also try to make friends no matter co-nationals or locals in local country through variable methods of SNSs. All in all, if students themselves do not attempt to figure out ways to integrate to the new culture, the social networks that they possessed would not benefit their sojourn acculturation, which, in return, will hinder their final purpose fulfilling in Korea.

Tribological behavior of Al₂O₃f/SiCp/Al hybrid metal matrix composites

Wang, YI-Qi 창원대학교 2009 국내박사

How to reduce perceived risk of medical tourism through message framing

Wang, Yi Fei Sungkyunkwan University 2015 국내석사

Carbon Fiber Reinforced Plastics (CFRPs) with Addition of Carbon Nanoparticles: Optimized Process and Characterization

YI-QI WANG 창원대학교 2012 국내박사

Carbon fiber reinforced plastic (CFRP) material is regarded as one kind of promising materials in many industry areas, especially for aerospace applications, due to their high ratios of strength and stiffness to weight, superior chemical and environmental resistance. The emergence of carbon nanotubes (CNTs) and vapor grown carbon nanofibers (VGCNFs) has also attracted great interest due to their high strength, electrical conductivity, physical and mechanical properties. In this dissertation, CNTs and VGCNFs have been added into CFRPs as the nano-reinforcements for improving electrical, mechanical, and wear properties using two different manufacturing methods. For the first method, CNTs and VGCNFs are deposited on carbon fabrics using electrophoretic deposition (EPD). Composites of the resulting hybrid material (CF-CNT or CF-VGCNF) in an epoxy matrix were fabricated by the vacuum-assisted resin transfer molding (VARTM) process. The electrical conductivities of the composites were significantly improved compared to those without the CNT and VGCNF reinforcement. The Taguchi method was used to optimize the EPD process conditions through the analysis of means and the analysis of variance (ANOVA) for achieving a highly uniform deposition of CNTs and VGCNFs. The parameters considered for optimization are: deposition time, applied voltage, concentration of CNTs or VGCNF in a distilled water suspension, and the distance between anode (a carbon fabric) and cathode (a copper plate). An orthogonal array of L9 (34) was created in the statistical design of experiments. In case of CNT EPD process, the through-thickness electrical conductivity of the composites produced using the optimum deposition conditions was about 35 times that of carbon fiber/epoxy composites. Moreover, in case of VGCNF EPD process, the through-thickness electrical conductivity of the composites produced using the optimum deposition conditions was more than 90 times that of carbon fiber/epoxy composites. When compared with the average electrical conductivity of the nine design experiments, the electrical conductivity of the CF-VGCNF/epoxy composite using a filler prepared under the optimum deposition conditions showed a 51% improvement. For the second method, CNTs are mixed with phenolic resin by a three roll milling machine following by film casting process. Three kinds of resin films were prepared, in which there are 1 wt%, 2 wt%, and 3 wt% CNTs. Then, the casted resin films were heated in oven at 120 ℃ for 9 min 30 s, which was called as B-stage process. After that, carbon fabrics and resin films were piled up in the molding for manufacturing composites by hot press process. Tensile tests were carried out for those composites. When compared with the composite manufactured by using the resin film containing 1 wt% CNTs, the tensile strength of the composite prepared by using the resin film containing 3 wt% CNTs showed an 8.8 % enhancement. From the fracture surface, it is confirmed that the CNTs were well dispersed in phenolic resin by the three roll mill process. Numerical simulation was performed to simulate the tensile behavior of the composite prepared by using the resin film containing 1 wt% CNTs. It is found that there is a very good agreement in Young’s modulus. Since the static analysis could not simulate the damage accumulation of the composite, the result of FEA increased linearly and it cannot predict the tensile behavior the after 0.8 % strain, from where failure behavior happened. Ball-on-disk wear tests were performed on the composites prepared by the second method. For the discrete wear test, the wear rate was measured after every 100 m wear test. The whole wear test process was divided into three stages according to the change of wear rate. From 0 m-100 m, the main weight loss was caused by the loss of matrix. And from 100 m-200 m, carbon fiber breakages and fibers removal played an important role in the wear mechanism, which is called as abrasive wear. After that, in the third stage, adhesive wear is the main wear mechanism. For the continuous wear tests, the wear rate was reduced with higher content of the additional CNTs. And the transient film could be partially generated only in the case of the composite prepared by resin films containing 3 wt% CNTs.

Modeling of biological activity in expanded-bed, anaerobic activated carbon filters

Wang, Yi-Tin 1984 국내박사

Sample Size Calculation Based on the Semiparametric Analysis of Short-term and Long-term Hazard Ratios

Wang, Yi Columbia University 2013 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

We derive sample size formulae for survival data with non-proportional hazard functions under both fixed and contiguous alternatives. Sample size determination has been widely discussed in literature for studies with failure-time endpoints. Many researchers have developed methods with the assumption of proportional hazards under contiguous alternatives. Without covariate adjustment, the logrank test statistic is often used for the sample size and power calculation. With covariate adjustment, the approaches are often based on the score test statistic for the Cox proportional hazards model. Such methods, however, are inappropriate when the proportional hazards assumption is violated. We develop methods to calculate the sample size based on the semiparametric analysis of short-term and long-term hazard ratios. The methods are built on a semiparametric model by Yang and Prentice (2005). The model accommodates a wide range of patterns of hazard ratios, and includes the Cox proportional hazards model and the proportional odds model as its special cases. Therefore, the proposed methods can be used for survival data with proportional or non-proportional hazard functions. In particular, the sample size formula by Schoenfeld (1983) and Hsieh and Lavori (2000) can be obtained as a special case of our methods under contiguous alternatives.

Explaining the Strength of Legislative Committees: A Comparative Analysis

Wang, Yi-ting Duke University 2013 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

By what means can legislative committees exercise influence on policy outputs? How and why do committees in different countries differ in their abilities to do so? This dissertation argues that legislative committee power is a multidimensional concept. Committee procedures can be distinguished into three analytic dimensions: 1) committees' positive agenda power, their power to ensure the placement of legislative versions preferred by them on the floor; 2) committees' negative agenda power, their power to delay or block the progress of legislation; and 3) committees' information capacity, institutional incentives granted to them to gather and transmit information. These distinct dimensions benefit different legislative actors. Therefore, they reflect different features of a political system, and may not be consistently strong or week. Based on an original cross-national data set, the dissertation shows that committee procedures cluster empirically in these three distinct dimensions. Furthermore, the dissertation also demonstrates how legislators' electoral incentives, the composition of multiparty governments, preexisting authoritarian incumbents' uncertainty and bargaining power, and the changes in legislative memberships affect different dimensions of committee power.

On some geometric inequalities and applications

Wang, Yi Princeton University 2011 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

The thesis consists of two parts. In the first part, we investigate conformally flat manifolds with finite total Q-curvature and obtain the isoperimetric inequality on such manifolds. This is a higher dimensional analogue of Li and Tam's result [17] on surfaces with finite total Gaussian curvature. The main step in the proof is based on the construction of a quasiconformal map whose Jacobian is suitably bounded. The second part of the thesis is a joint work with my adviser Sun-Yung A. Chang, which is dedicated to the study of the Aleksandrov-Fenchel inequalities for quermass-integrals of a class of non-convex domains. The proof uses optimal transport maps as a tool to relate fully nonlinear curvature quantities of different orders defined on the boundary of the domain.