관류형팬의 설계변수 특성에 관한 연구

박진욱 제주대학교 2005 국내석사

식품 중 폴리소르베이트 분석법 유효성 검증과 측정불확도 및 모니터링 연구

박진욱 서울과학기술대학교 2022 국내석사

본 연구에서는 식품첨가물 중 유화제로 사용되는 polysorbate류를 기기의 범용성을 고려하여 UV-spectrophotometer를 사용하여 정량 하고자 했으며 전처리법과 분석조건을 조사하였다. 이를 바탕으로 식품첨가물공전에 등재 되어있는 polysorbate 20, polysorbate 60, polysorbate 65, polysorbate 80에 대하여 국내 유통중인 제품의 함량을 구하였다. 사용된 분석법은 유효성 검증을 통해 신뢰성을 확인하였으며 측정불확도를 구하여 신뢰도를 수치화 하였다. 추가로 분석법의 적용성을 확인하기 위하여 시장조사를 통해 polysorbates가 많이 들어 있는 식품유형을 확인하였으며 그 결과 국내의 유통되는 피클, 떡, 빵, 식물성크림, 과채음료, 캔디류, 두부, 시럽, 소스류, 복합조미식품, 양념젓갈, 빙과류, 소시지, 과자류에 대하여 모니터링을 진행하였다. UV-spectrophotometer를 활용한 polysorbates의 분석법은 코발트용액을 사용한 비색법을 사용하였으며, 유효성 검증 결과 직선성은 r2 ≥ 0.9991, LOD 와 LOQ는 각각 2.3-4.9 mg/kg, 7.0-15.0 mg/kg, 정확성은 intra-day와 inter-day 각각 91.9–104.1%와 91.6-102.2%, 정밀성은 intra-day와 inter-day 각각 0.1-1.1 RSD%와 0.4-6.3 RSD%였다. 산출된 정확도와 정밀도 값은 모두 AOAC에서 준하는 범위 안에 들어왔음을 확인하였다. 측정불확도를 산출한 결과 상대불확도의 값은 0.9-11.2%로 나타났으며, CODEX에서 제시한 농도에 따른 상대불확도 범위(<16%)에 들어오는 것을 확인하였다. 모니터링 결과(n=230), 시판되고 있는 샘플에서 100% 검출율을 보였으며 polysorbate 20 중 피클(n=11)에서 29.10-198.00 mg/kg이 검출되었고, polysorbate 60 중 떡(n=19)에서 33.51-460.33 mg/kg, 식물성크림(n=20)에서 169.88-5148.05 mg/kg, 빵(n=12)에서 49.25-1,889.41 mg/kg, 과채음료(n=5)에서 58.05-1,158.64 mg/kg, 캔디류(n=5)에서 22.06-101.89 mg/kg 검출되었고, polysorbate 65 중 두부(n=29) 59.22-580.63 mg/kg, 시럽(n=11) 8.32-62.66 mg/kg이 검출되었고, polysorbate 80 중 소스류(n=29) 58.26-13,617.36 mg/kg, 떡(n=19) 18.34-164.82 mg/kg, 빙과류(n=15) 37.37-395.19 mg/kg, 소시지(n=15) 22.50-374.00 mg/kg, 양념젓갈(n=11) 35.37-1,115.56 mg/kg, 복합조미식품(n=13) 324.88-16,442.30 mg/kg, 피클(n=10) 50.15-129.41 mg/kg, 과자류(n=5) 58.33-325.43 mg/kg이 검출되었다. 본 연구는 샘플 모니터링 결과값을 통해 섭취량 평가에 필요한 데이터를 제공하며 국내 polysorbate의 섭취 안전성을 파악할 수 있을 것으로 기대된다. 또한 Polysorbate의 ADI 값과 비교하여 안전한 식품 섭취량 추정을 위한 기초자료로 기여할 것으로 기대된다. In this study, polysorbate used as an emulsifier among food additives was quantified using UV-spectrometer in consideration of the commonly available instrument, and pretreatment and analytical conditions were investigated. Based on this, the contents of product distributed in Korea were determined polysorbate 20, polysorbate 60, polysorbate 65, and polysorbate 80 registered in the Korean Food Additive Code. The analytical method confirmed the reliability through conducting the validation and estimating the measurement uncertainty. In addition, to confirm the applicability of the analytical method, the food types containing a lot of polysorbates were identified through market survey, and as a result, monitoring was conducted on domestic distributed pickles, rice cakes, vegetable, bread, fruit/vegetable drink, candy, tofu, syrup, sauce, composite seasoning, ice cream, salted seafood, sausages, and confectionery. The analytical method for polysorbates with UV-spectrometer applied a colorimetric method using a cobalt solution, and as a result of validation, linearity (r2), LOD and LOQ are r2≥ 0.9991, 2.3-4.9 mg/kg, and 7.0-15.0 mg/kg, respectively. Accuracy is 91.9%-104.1% (intra-day) and 91.6%-102.2% (inter-day), respectively. Precision is 0.1 RSD%-1.1 RSD% (intra-day) and 0.4 RSD%-6.3 RSD% (inter-day), respectively. It was confirmed that both the calculated accuracy and precision values in compliance with the acceptable range of AOAC. As a result of calculating the measurement uncertainty, the values of the relative uncertainty were 0.9%-11.2% with acceptable range (<16%) according to the concentration represented by CODEX. Monitoring results (n=230), 100% detection rate was shown in commercially available samples. In the polysorbate 20, 29.10-198.00 mg/kg were detected in pickles (n=11). In the polysorbate 60, 33.51-460.33 mg/kg in rice cakes (n=19), 169.88-5148.05 mg/kg in vegetable cream (n=20), 49.25-1,889.41 mg/kg in bread (n=12), 58.05-1,158.64 mg/kg in fruit/vegetable drink (n=5), and 22.06-101.89 mg/kg in the candy (n=5) were detected. In the polysorbate 65, 8.32-62.66 mg/kg in the syrup and 59.22-580.63 mg/kg in the tofu were detected. In the polysorbate 80, 58.26-13,617.36 mg/kg in sauces (n=29), 18.34-164.82 mg/kg in the rice cakes (n=19), 37.37-395.19 mg/kg in the ice cream (n=15), 22.50-374.00 mg/kg in the sausages (n=15), 35.37-1,115.56 mg/kg in the seasoning salted fish (n=11), 324.88-16,442.30 mg/kg in the composite seasoning, 50.15-129.41 mg/kg in the pickled food(n=13), and 58.33-325.43 mg/kg in confectionery (n=5) mg/kg were detected. This study is expected to calculate EDI using the sample monitoring result value and find out the intake safety of polysorbate in Korea. In addition, it is expected to contribute to safe food intake by using it as basic data for comparing to ADI when establishing individual food standards for use of polysorbates.

테니스장 서비스품질이 동호인의 만족도와 충성도에 미치는 영향

박진욱 조선대학교 교육대학원 2021 국내석사

The purpose of this study is to examine the service quality of a tennis court which is one of public sport facilities and analyze a difference in service quality and customer behavior according to demographic characteristics and the relationship between service quality and customer behavior of club members in a tennis court. This study developed a structured questionnaire. The questionnaire survey was conducted in three cities including Gwangju Metropolitan City for four weeks from March 1 to March 31, 2021. A convenience sampling method and a self administration method were applied for the survey and 250 questionnaires were used for statistical analysis. SPSS Ver. 22.0 and AMOS 22.0 were used for data processing to analyze study results. Using independent t-test analysis, one-way ANOVA, and structural equation model(SEM), the following conclusions were drawn. First, for a between-group difference in service quality in relation to age, there was a statistically significant between-group difference in tangibility(p<.001), reliability(p<.001), responsiveness(p<.001), assurance(p<.01), and empathy(p<.001). Satisfaction(p<.001) and royalty(p<.001) had also a statistically significant between-group difference. Moreover, for the service quality in relation to education, there was a statistically significant between-group difference in tangibility(p<.01), reliability(p<.01), responsiveness(p<.01), assurance(p<.001), and empathy(p<.001). Satisfaction(p<.01) and royalty(p<.01) in relation to education had also a statistically significant between-group difference. Second, tangibility( p<.001), reliability(p<.001), responsiveness(p<.001), and empathy(p<.001) of the service quality of a tennis court had an effect on satisfaction. Responsiveness(p<.05) and assurance(p<.001) of service quality had an effect on royalty. The satisfaction(p<.001) of a tennis court had an effect on royalty. In conclusion, this study suggests that the establishment of high service quality may satisfy consumer’s desire in the tennis court and service quality may ensure satisfaction and royalty. In particular, club members’ high satisfaction and royalty is an important strategy to improve management environment and maintain customers in the tennis court. Moreover, this study indicates that offering high level service quality to club members can be a differentiation strategy from other tennis courts.

말의 연골세포에서 아미드형 국소마취제의 연골 독성 평가

박진욱 충북대학교 2011 국내박사

연골세포는 관절연골을 구성하는 단일 유형의 세포로써, 초자연골은 연골세포와 세포외기질로 이뤄져 있다. 따라서, 연골세포는 연골에서 세포외기질의 합성과 유지를 단독으로 책임지고 있는 중요한 역할을 하고 있다. 연골세포 및 세포외기질은 관절의 병리적 측면에서 매우 중요한 요소이며, 일례로 뼈관절염은 사람과 동물 모두에서 통증 유발, 관절의 가동성 및 기능 소실을 동반하며, 환자의 삶의 질에 영향을 미치는 근골격계 주요 질환의 하나이다. 이러한 관절 질환은 관절연골의 소실과 퇴행으로 특징지어진다. 연골세포의 사멸 및 관절에서의 연골세포의 밀도 감소는 뼈관절염의 중증도와 연관되어 있으며, 세포 사멸은 기질의 퇴행을 야기하고, 또한 기질의 퇴행이 연골세포의 사멸을 유발시키는 문제점이 관절질환의 극복에 있어 중요한 측면으로 여겨지고 있다. 본 연구는 관절 내에 투여될 수 있는 다양한 약물 중에서도, 통증관리 목적으로 투여되는 약물의 하나인 국소마취제의 영향을 확인하는데 그 초점을 두고 있다. 말의 관절에 사용될 수 있는 국소마취제로는 부피바케인, 리도케인, 메피바케인 등이 있으며, 1 장의 연구에서는 관절연골에서 분리하여, 초대배양한 연골세포에서 앞서 기술한 약물간의 독성 비교를 실시하였다. 독성 평가를 위해 사용된 시험기법으로는 트리판 블루 배제 검사, 세포 생존율 검사, 헥스트 염색액과 프로피디움 요오드화물을 이용한 이중염색에 대한 형광현미경 검사 그리고 유세포 분석을 실시하였다. 시판되어 임상적으로 이용되는 0.5% 부피바케인이 가장 강한 독성을 발휘하였고, 그 독성의 기전은 세포괴사로 확인되었다. 2% 리도케인은 부피바케인에 비해 낮은 독성을 나타냈지만, 독성을 거의 나타내지 않은 2% 메피바케인에 비해 높은 독성을 보였다. 1 장의 연구에서는 상용 농도의 국소마취제를 배양 상태의 연골세포에 직접 처리하여 독성을 평가하였지만, 관절 내 투여와 같은 생체의 조건에서는 연골세포를 둘러싼 세포외기질과 관절액에 의해서 희석된 낮은 농도의 약물이 세포에 도달하게 된다. 그에 따라, 2 장의 연구에서는 상용 농도의 10배 이상 희석된 농도범위에서 부피바케인의 독성기전에 대한 실험을 실시하였다. 2 장의 연구에서는 아포토시스 (세포자멸사) 및 관련 기전을 확인하기 위하여 헥스트 염색액, 프로피디움 요오드화물 그리고 형광물질 이소치오시아네이트로 표지된 아넥신을 이용한 삼중염색에 대한 형광현미경 검사, 케스페이즈 활성 검사, 활성 산소종 검출 검사를 실시하였다. 또한 아포토시스의 조절과 관련된 유전자의 발현 정도의 변화를 확인하기 위한 역전사 중합효소연쇄반응 검사를 실시하였다. 상기의 검사법을 통해, 상대적으로 낮은 농도의 부피바케인은 말 연골세포에서 아포토시스를 유도함으로써 독성을 나타냄을 확인할 수 있었으며, 또한 이러한 독성이 산화적인 스트레스와 연관되어 나타남을 활성 산소종 검출을 통해 확인하였다. 연골세포에 대한 치유와 관련된 다양한 성장인자 및 관련 물질 중의 하나인 인슐린은 부피바케인의 연골독성을 감소시키는 효과를 갖고 있음이 본 실험을 통해서 입증되었다. 이것은 인슐린의 항아포토시스 효과에 의한 것이었다. 임상적 적용을 위해서는, 추가적인 연구를 통한 생체 내에서의 효과가 입증되어야 할 것이다. 그러나 본 연구는 실험관내 실험이라는 제한에도 불구하고, 국소마취제의 연골독성을 예방 또는 역전시킬 목적으로 인슐린의 적용 가능성을 시사한다고 판단된다. Intra-articular injections of local anesthetics are used for diagnostic and therapeutic purposes in equine practice. In general, these agents are known to have no adverse effect. Contrary to common belief, the cases of postoperative chondrolysis after arthroscopic procedures have been linked to intra-articular injection of bupivacaine in human, and it is considered that continuous infusion of this agent may be related to occasional but serious joint complications. Consequently, the objective of this study was to investigate the effects of local anesthetics on equine articular chondrocytes in vitro. This study especially focused on the chondrotoxic effect of local anesthetics and insulin’s antagonism of this toxicity. The aim of the study in the first chapter was to make a comparison of the toxicity of local anesthetics (bupivacaine, lidocaine, and mepivacaine) that are used in equine practice. Cell biological assays were conducted to evaluate toxicity of local anesthetics. These assays included cell viability assays, fluorescent microscopy, and flow cytometry. The purpose of the study in the second chapter was to investigate bupivacaine-induced chondrotoxicity using various detection methods and morphological and biochemical apoptotic markers. For this study, various examinations were conducted as follows; reactive oxygen species (ROS) detection, caspase-3 activity measurement, and fluorescent microscopy with triple staining. In addition, the insulin was examined to determine its effect on bupivacaine-induced toxicity. In the first chapter, bupivacaine was the most toxic among the three agents tested on equine chondrocytes. A relatively high concentration of bupivacaine, such as that in a commercially available solution, induced necrotic cell death. In the results of the second chapter, bupivacaine was also a potential inducer of apoptosis at a lower concentration with prolonged treatment time. Nuclear condensation, transposition of phosphatidylserine, and increased caspase activity corroborated the induction of apoptotic cell death after bupivacaine treatment. Bupivacaine also induced increase of ROS generation which related to oxidative stress and damage. Insulin is a peptide that can exert various physiological effects, one of which is the anti-apoptotic activity. In the present study, insulin suppressed the bupivacaine-induced chondrotoxicity by means of its anti-apoptotic property. Even though most pharmacological agents may not be absolutely free of side effects, if some agents result in chondrotoxic stimuli via apoptosis, they would be substituted with alternative agents with less risk. For this reason, veterinary clinicians should avoid using bupivacaine intra-articularly, if possible. The clinical value and limitations of the application of insulin cannot be determined by this in vitro study. However, insulin may be a possible candidate for use in the prevention or reduction of joint pathology.

수학교육에서 인공지능 활용에 관한 수학교사들의 인식 분석

박진욱 한국교원대학교 대학원 2024 국내석사

본 연구는 수학교사의 개인 특성에 따른 인공지능을 활용한 수학교육에 대한 인식과 의견을 분석하고, 인공지능을 활용할 수 있는 방안과 Chat GPT의 출시 이후 변화될 수학교육의 모습에 대해 수학교사들이 어떤 생 각을 가지고 있는지 알아보고자 진행되었다. 본 연구에서 설정한 연구문제는 다음과 같다. 첫째, AI를 활용한 수학 교육에 대한 수학교사의 인식은 어떠한가? 둘째, Chat GPT의 출현이 교 육에 어떤 영향을 미치는지에 대한 수학교사의 인식은 어떠한가? 본 연구는 교수·학습 및 평가에서 인공지능을 활용하는 것에 대한 수학 교사들의 인식과 수학교사들의 인공지능 활용에 관한 의견과 생각을 연 구하고자 총 10문항의 설문지를 제작하여 사용하였다. 예비조사를 거친 후 2023년 9월 18일부터 28일까지 11일간 편의표집 방식으로 중고등학 교 수학교사 53명의 응답을 받아 분석하였다. 첫 번째 연구문제에 대해 살펴본 결과 인공지능을 활용한 수학교육에 대한 인식은 대체로 긍정적인 것으로 나타났다. 수학교사들은 수학교육 에서 교수 및 학습에선 긍정 60.4%, 보통 32.1%, 부정 7.5%로 응답하였 으며, 수학교육에서 평가에 관한 질문에선 긍정 37.8%, 보통 35.8%, 부 정 26.4%로 응답하였다. 수학교사들은 AI를 활용한 교수·학습에선 시대의 흐름과 변화가 계속되 고 있고, 개별화 학습에 효과적이고, 교사를 지원하는 도구로서 인공지 능이 사용될 수 있다는 점에서 필요하다고 인식하였다. 그리고, 현직 교 사들의 AI 활용 역량이 부족하고, 학교 환경 등 교육 환경이 인공지능을 도입하기에 어려움이 많고, 학생의 학습에 방해가 된다는 점에서 필요하 지 않다는 부정적인 인식도 확인되었다. 또한 교사들의 평가에 대한 인 식은, 성취 평가에서 객관성 및 공정성을 가지고, 교사의 업무 부담을 경감시키고, 즉각적 피드백이 가능하며, 학생의 학습에 도움이 되고, 개 별화 교육에 효과적이라고 인식하였다. 그리고, 인공지능 기술의 명확한 한계와, 인공지능을 활용한 평가의 필요성이 부재한다고 인식하고 부정 적인 반응을 보였다. 두 번째 연구문제에 대해 살펴본 결과 수학교사들은 Chat GPT를 비롯한 대화형·생성형 인공지능이 수학교육에 효과적이고, 학생들에게 도움이 될 것이라고 인지하고 있었다. 인공지능에 관해 부정적인 의견들도 있었 으나, 긍정적인 의견이 다수였으며 학생들의 개별화 교육에 도움이 되 고, 인공지능 이해 능력이 시대의 흐름에 따라 필수적인 역량이 되었으 며 교사의 업무 부담 또한 경감될 것으로 예상하였다. 교육부는 2025년부터 초등학교와 중학교에서 코딩 수업을 의무화하기로 결정하고 발표하였다. 이처럼 교육부에서 지속적으로 학생들과 교사들의 인공지능 리터러시 능력을 향상시킬 수 있는 노력이 필요할 것이고, Chat GPT를 비롯한 대화형·생성형 인공지능을 수학교육에서 적극적으로 사용할 방안을 모색해야 할 것이다.

(The) global spread of asbestos ban policy and it's impacts and implications on environmental health and safety

박진욱 서울대학교 보건대학원 2013 국내박사

Out of 143 countries that consumed asbestos between 2003 and 2007, only 44 have banned asbestos. This study tried to explain how asbestos ban policy adopted and spread globally, how it impact world asbestos produce, trade, consumption, and mesothelioma mortality, historically and the future. Chapter I provide a rational explanation of why some countries have banned asbestos while others have not, based on a synthesis that asbestos ban policy of a country will rely on a process of cognition of threats and exploration of safer alternatives. As we hypothesized that increased social cost of mesothelioma, capacity of health-related infrastructures, and policy diffusion from adjacent countries were related to asbestos ban adoption, published databases of asbestos ban years, mesothelioma mortality, country rankings in health care and human rights standings, and distribution of banning countries over 14 regions were analysed accordingly. The average mesothelioma death rate was significantly higher for countries with asbestos bans than in those with no ban. No-ban countries had less well-developed health-related infrastructures. Among European countries, there was a tendency toward geographical diffusion of asbestos ban policy from Nordic to Western and then other European countries over the years. Even though aberrant cases were also noted where bans were instituted even without mesothelioma database, these were rather exceptions than rules. Risk cognition is a complex process, but the presence of well-functioning health infrastructures, as well as the increased social cost of mesothelioma, that can make the plight of asbestos victims visible to the eyes of public and policy makers, may have contributed to this process. Asbestos ban policy from adjacent countries might have facilitated the adoption of alternative solutions. Chapter II describes the world production and consumption of asbestos and the trade of asbestos-containing products. Data was obtained from the British Geological Survey, U.S. Geological Survey and United Nations Commodity Trade Statistics data, and described mainly the status of the income level and states which ban asbestos. World asbestos production increased until the late 1970s and then decreased for 15 years, finally plateauing in the last 15 years. Crude asbestos consumption in developed countries decreased; however, they plateaued or even increased in middle- and low-income countries. Most asbestos-containing products except crocidolite are still traded among countries which ban asbestos. The banning of asbestos is complete when there are no exports or imports of asbestos-containing end products. Even in countries which ban asbestos, the monitoring of the trade of asbestos-containing products is required. Chapter III attempts to build a prediction model of mesothelioma mortality according to the consumption of asbestos. A mesothelioma mortality prediction model was constructed based on cumulative asbestos consumption quantities as the exposure level. In each country, annual age-sex specific mortality rates were calculated by dividing the number of mesothelioma deaths by the corresponding age-group population. We use a negative binomial regression model to predict mesothelioma deaths by cumulative asbestos exposure. The model estimated that the latent period for mesothelioma was about 45 years. Predicted world future mesothelioma deaths among males during 2015-2070 ranged from 748,329 to 764,052 per million population, depending on the expected level of asbestos consumption. World mesothelioma deaths will peak in late 2039 according to the model and then decline.

Novel photoresponsive soft materials based on highly emissive cyanostilbene derivatives : studies on photophysical property, liquid crystalline behavior

박진욱 서울대학교 대학원 2013 국내석사

Photo-responsive materials are promising research areas for a wide range of applications such as optical device, and photo-actuator. Especially, azobenzene, and stilbene based soft materials are commonly known for implementing such applications due to their fast and reversible photo-induced isomerization behavior. Despite those remarkable properties, the molecules show low or non-fluorescence behavior in solid state. In order to solve such problem, fluorescent dyes are attached in azobenzene or stilbene unit via covalent, secondary bonding interactions, or host-guest mixed systems. Nevertheless, at the current stage, there are only a few reports to be successfully demonstrated. To date, we have reported a novel class of α-cyano-substituted stilbenic derivatives exhibiting a unique and peculiar fluorescence behavior, that is, aggregation-induced enhanced emission (AIEE): it is virtually non-fluorescent in the monomer state in solution but becomes highly fluorescent upon self-assembly into supramolecules. Furthermore, the cyanostilbene unit in typical AIEE molecules has a multiple function of enabling AIEE-type molecule to undergo a trans-cis photoisomerization, as commonly observed in stilbene and azobenzene materials. However, so far, there is no report on fluorescence property in combination with photoisomerization behavior by using such molecules. Herein, we report on a demonstration of fluorescence patterning technique via photo-induced isomerization behavior in soft state, LC or soft crystal, based on cyanostilbene derivatives for the first time. The molecules consist of rigid cyanostilbene/dicyanodistrylbenzene(DCS) backbone which shows AIEE behaivor and photo-responsive characters with different lengths of flexible alkoxy chains. In this respect, to clearly understand thermotropic LC and optical property in solid state, we study the following issues: i) the role of –CN group, ii) the role of length of alkyl chain, and iii) understanding of the differences in photoisomerization behavior between cyanostilbene and DCS beackbone. The photo-isomerization behavior is monitored by change of UV-vis abosrbance spectra and confirmed the conversition ratio of trans to cis isomer by 1H NMR data. Based on such characters, we demonstrated a fabrication of fluorescence patterning. Furthermore, we have synthesized a new cyanostilbene based material, GCS, which forms columnar hexagonal LC phase at room temperature. Thin film of GCS was prepared by spin-coated method. Initially, as-prepared film looks like amorphous state with a high transparency. However, a partial crystallization in the film occurs subsequently. During overnight under dark at near RT (25~30 °C), it was transformed into the perfectly uniform crystalline film that had same crystal arrangement to GCS bulk powder. In crystalline state, GCS exhibits intense blue fluorescence. Interestingly, such crystalline film shows a soft character. To understand such property, we have carried out GI-XRD measurement. In soft state, GCS shows phase transition behavior via photoisomerization process. Thus, we successfully demonstrate highly fluorescent micro patterns via unique property, so-called photo-tirrgered mass migration behavior, with phase transition by using soft crystalline material. In this work, we propose a new mechanism of ‘photo-triggered mass migration’ with phase transition, crystal to LC phase, for the first time.

Time-domain aeroelastic analysis of bridge using a truncated fourier series of the aerodynamic transfer function

박진욱 서울대학교 대학원 2013 국내석사

This study presents the exact relation between the real and imaginary parts of aerodynamic transfer functions for deriving impulse response functions that satisfy the causality condition. A truncated Fourier series is utilized to express the aerodynamic transfer functions, and the causality condition is defined in terms of the coefficients of a Fourier cosine and sine series, which represent the real and imaginary parts of the aerodynamic transfer functions, respectively. The impulse response functions that satisfy the causality condition are obtained through the inverse Fourier transform of the aerodynamic transfer functions that conform to the exact relation. The coefficients of the Fourier series are determined by minimizing the error between the transfer functions formed by measured flutter derivatives and by the Fourier series. Since the impulse response functions become a series of Dirac delta functions in the truncated Fourier series approximation method, the aerodynamic forces are easily evaluated as the sum of current and past displacements with the same number of the terms in the Fourier series. This study proposes these the truncated Fourier series approximation method. The validity of the truncated Fourier series approximation method is demonstrated for two types of bluff sections and one real bridge: a rectangular section with a width to depth ratio of 5, an H-type section and 2nd Jindo cable stayed bridge. Time-domain aeroelastic analyses are performed for an elastically supported system with each section. The applicability of the truncated Fourier series approximation method is also verified for a large-scale bridge, 2nd Jindo cable stayed bridge. The truncated Fourier series approximation method yields stable and accurate solutions for the examples efficiently.

Fabrication of Graphene/Conducting Polymer Nanohybrid Materials and Their Sensor Applications

박진욱 서울대학교 대학원 2016 국내박사

Graphene/conducting polymer (CP) nanohybrid materials have attracted considerable attention, due to their synergetic effects, including enhanced surface area, charge carrier mobility, thermal/electrical conductivity, and chemical/mechanical stability. To synthesize the graphene/CP nanohybrid materials for using in electronic device applications, covalent and non-covalent synthetic methods have been introduced. Contrary to non-covalent method, covalent functionalization requires time-consuming and harsh conditions, because it needs firstly to introduce functional group on the surface of graphene and CPs. On the other hand, non-covalent functionalization offers facile way to obtain graphene/CP nanohbyrid materials through secondary bonding interactions, such as π–π interactions. In-situ synthetic method, as one of the non-covalent synthetic method, is very promising and powerful tool to design graphene/CP nanohybrids owing to getting uniform nanohbyrid materials. Furthermore, the morphology and shape of the graphene/CP nanohybrids can be controlled by selectively designing the morphology of starting materials (graphene or CP materials). In this study, various graphene/CP nanohbyrid materials are introduced by using in-situ synthetic method. The synthesized nanohybrid materials exhibit excellent electrical/chemical properties, enabling to be applied in sensor applications. Synergetic effects of graphene/CP nanohbyrid mateirals provide rapid response/recovery time, when using as a transducer in the sensing device. Furthermore, the enlarged surface area from graphene/CP nanohybrids can provide the improved interactions with target analytes, leading to the ultrasensitive sensing performance.

노동조합 활동가의 정신건강 : 우울증과 직무스트레스

박진욱 서울대학교 대학원 2008 국내석사