철을 오염시킨 n-GaAs의Photoreflectance에 관한 연구

유재인,문영희,이동울,이정열,배인호,장광수 嶺南大學校 基礎科學硏究所 1998 基礎科學硏究 Vol.18 No.-

We investigated the variation of PR signals for n-GaAs surface treated with Fe as annealing method. The samples were annealed by isochronal(200∼600 ℃, 10 min) and isothermal(300 ℃, 10 ∼60 min) method. In PR signals measured from isochronal annealed samples, the rate of intensity decreasing for n-GaAs was 49%, and that for n-GaAs surface treated with Fe was 66%. We assumed that the large amount of decreasing intensity for Fe contaminated sample caused by decreasing carrier density due to increasing of ?? neutral acceptor at higher annealing temperature. In PR signals measured from isothermal annealed samples, the signals for annealed n-GaAs decreased with increasing annealing time, and the signals for n-GaAs surface treated with Fe continuously increased with increasing annealing time. It can be assumed that the increasing of PR intensity for Fe contaminated samples as annealing time caused by the diffusion of Fe atoms from the surface.

등척성 신전운동 시 요부근의 근 활성도

유원규,정영종,이재호,김창인 한국전문물리치료학회 2001 한국전문물리치료학회지 Vol.8 No.1

Back extension exercises have been used for rehabilitation of the injured low back, prevention of injury, and fitness training programs. However, excessive loading on low back can exacerbate existing structural weakness. The purpose of this study was to compare muscle activity of low back muscles during back extension exercises. Twenty healthy male subjects were evaluated, Electromyographic (EMG) activities of low back muscles at L1 and L5 level were recorded during seven different back extension exercises and two reference tasks by surface EMG and saved for data analysis. Reference tasks of lifting 20% and 40% of their body weight were included for comparison. The result were as follows: 1) Single-arm extension and single-leg extension exercises on quadruped position appeared to constitute a low-risk exercise for initial extensor strengthening. 2) When arm extension was combined with contralateral leg extension on quadruped position, EMG activities of low back muscles were increased, 3) EMG activity of low back muscles was highest during the trunk extension exercises on prone position. 4) EMG activities of low back muscles during arm and leg extension exercises on quadruped position were less than those of reference task of lifting 40% of their body weight. These results have important implications for progressive back extensor muscle

Pt계 촉매를 이용한 직접 개미산 연료전지의 특성 연구

유재근,이효송,김진용,김기호,이영우 충남대학교 공업교육연구소 2005 論文集 Vol.27 No.1

Direct Formic Acid Fuel Cells (DFAFCs) are potential alternative power sources for potable devices such as cellular phones, personal digital assistants (PDA) and laptop computers. In this study, we investigated the effect of the anode catalysts on the performance of direct formic acid fuel cell. We made the Pt-Pd catalysts using deposition method for the investigation of the fuel cell performance as a change of temperature and oxidant. Fuel cell with Pt-Pd anode catalyst showed the performance of 120 mW/㎠at room temperature. This result was much higher value than that of Pt-Ru catalyst which showed the best performance of commercial catalyst in our previous works. For this reason, we can conclude that the Pt-Pd catalyst is an excellent material for the oxidation of formic acid.

다양한 교정용 브라켓 원재료에 부착하는 mutans streptococci 양의 비교분석

유진경,안석준,이신재,장영일 대한치과교정학회 2009 대한치과교정학회지 Vol.39 No.2

Objective: To estimate the effects of bracket material type on enamel decalcification during orthodontic treatment, this study analyzed the adhesion level of mutans streptococci (MS) to orthodontic bracket materials in vivo. Methods: Three different types of orthodontic bracket materials were used: stainless steel, monocrystalline sapphire, and polycrystalline alumina. A balanced complete block design was used to exclude the effect of positional variation of bracket materials in the oral cavity. Three types of plastic individual trays were made and one subject placed the tray in the mouth for 12 hours. Then, the attached bacteria were isolated and incubated on a mitis salivarius media containing bacitracin for 48 hours. Finally, the number of colony forming units of MS was counted. The experiments were independently performed 5 times with each of the 3 trays, resulting in a total of 15 times. Mixed model ANOVA was used to compare the adhesion amount of MS. Results: There was no difference in colony forming units among the bracket materials irrespective of jaw and tooth position. Conclusions: This study suggested that the result of quantitative analysis of MS adhesion to various orthodontic bracket materials in vivo may differ from that of the condition in vitro. 법랑질 탈회는 교정 치료 중에 발생하는 대표적인 부작용으로서 특히 교정용 브라켓에 대한 세균 부착이 그 원인이 될 수 있다. 본 연구의 목적은 서로 다른 표면 특성을 가진 세 종류의 브라켓을 구강 내 장착했을 때 각 재료의 표면에 대한 mutans streptococci 부착 정도를 측정하여 브라켓 재료에 따른 법랑질 탈회 및 치아 우식 발생 가능성을 분석하는 것이었다. 상하악 및 치아 부위별 mutans streptococci 부착 정도의 차이를 배제하고 브라켓 원재료에 따른 차이만을 검출하기 위하여 균형완전블록 실험계획을 설계하였다. 피실험자인 30세 여성의 구강 내에 장착할 수 있는 tooth positioner 형태로 3세트의 플라스틱 맞춤 트레이를 제작하였으며, 이 트레이에 직육면체의 형태(4 x 3 x 2 mm)로 제작한 stainless steel, monocrystalline sapphire, polycrystalline alumina 조각을 세트마다 서로 다른 순서로 전치부와 구치부 순면에 부착하였다. 이렇게 제작된 3종류의 실험장치를 12시간 동안 피실험자의 구강 내에 장착한 후, 각 브라켓 재료 표면에 형성된 치태를 채취하여 bacitracin이 포함된 mitis salivarius배지에서 48시간 배양 후 colony counting을 통해 그 표면에 부착된 mutans streptococci 양을 비교하였다. 이와 같은 방법으로 3세트의 실험장치에 대해서 각각 5회씩 총 15회의 실험을 시행하였다. 그 결과 상하악 및 치아 부위별 및 브라켓 재료별 세균 부착 정도는 모두 유의한 차이를 보이지 않았다. 결론적으로 본 연구의 결과 in vivo condition에서 브라켓 재료의 차이는 mutans streptococci 부착에 영향을 미치지 못하는 것으로 보였다.

영재반 중학생의 설계과정(Design Process) 기반 창의적 문제해결 질적 사례 연구

유재영,최준섭 부산대학교 과학교육연구소 2012 교사교육연구 Vol.51 No.3

The purpose of this study was to provide an empirical model of the design process that is used by gifted middle school students in problem solving. In order to achieve this purpose, research questions were in four areas: First, what is the design process that students use for problem solving? Second, is it possible for students to solve problems through ‘sketching’, ‘conceptual drawing’, and ‘part drawing’? Third, what are the difficulties faced by the students when at the construction stage of the design process? Fourth, what is the observed design process model used by the students during the problem solving? The following results were obtained from this study: First, it was possible for students to solve problems through the design process model and the process in each stage was iterative. The most difficult problem solving process observed in this research was during the brainstorming-sketching process. Conceptual drawing and sketching a process for solving the problem was performed repeatedly, requiring much time and effort from the students. Second, while students would engage in ‘sketching’, ‘conceptual drawing’, and ‘part and elements drawing’ in their problem solving, they perceived that ‘sketching’ was the most important process. Third, students had the most difficulty during the construction stage of the problem solving process as they were the lack of ability to use the tools necessary to build and construct their work. Fourth, the study concluded that the model identified in the students’ design process based problem solving was: 1)problem 2) brainstorming (idea creation) 3) sketching 4) conceptual drawing 5) part drawing 6) making 7) problem solving, feedback existed on some stage. 이 연구의 목적은 학생들이 어떤 설계과정을 통해 문제해결을 하는지에 관한 경험적 설계과정 모형을 제공하는 것이며, 이러한 연구의 목적을 달성하기 위해 첫째, 문제해결을 위해 학생들은 어떤 설계과정을 거쳐 왔고, 설계과정 이동경로의 특징은 무엇인가?, 둘째, 스케치, 구상도, 부품도를 통한 문제해결은 가능한가?, 셋째, 설계과정 중 제작을 통한 문제해결 사례에서 학생들이 어려워했던 점은 무엇인가?, 넷째, 설계과정 기반 문제해결을 통해 확인된 설계과정 모형은 무엇인가? 에 대한 연구 문제를 제시하여 다음과 같은 연구 결과를 얻을 수 있었다. 첫째, 설계과정을 통한 문제해결을 하는 동안 각 단계별로 반복적인 순환과정이 존재함을 확인할 수 있었고, 문제해결을 위해 JH팀과 SD팀 모두 문제해결을 위해 브레인스토밍-스케치 단계에서 가장 많은 그림을 그렸고, 또한 스케치-구상도, 제작-스케치 과정에서는 문제해결을 위한 반복 작업을 수행하여 가장 많은 시간과 노력을 투자하고 있음을 확인할 수 있었다. 둘째, 스케치, 구상도, 부품도를 통한 문제해결은 가능하며, JH, SD팀 모두 스케치를 설계과정에서 가장 중요한 단계로 인식하고 있었다. 셋째, 제작을 통한 문제해결 단계에서 학생들이 가장 어려워했던 것은 작품 제작 시에 사용되는 공구사용의 미숙으로 파악되었다. 넷째, 학생들의 설계과정 기반 문제해결을 통해 확인된 모형은 비선형(nonlinear) 모형으로 나타났으며, 모형에서 나타나는 단계는 문제-브레인스토밍(아이디어 생성)-스케치-구상도-부품도-제작-문제해결 과정을 거치는 것으로 파악되었다.

양방향 요소제거법을 이용한 신뢰성 기반 최적설계

유진식,박재용,황승민,임민규,오영규,한석영 한국공작기계학회 2008 한국공작기계학회 추계학술대회논문집 Vol.2008 No.-

This research presents a Reliability-Based Topology Optimization (RBTO) using Bi-directional Evolutionary Structural Optimization (BESO). An actual design involves uncertain conditions such as material property, operational load and dimensional variation. Deterministic Topology Optimization (DTO) is obtained without considering of uncertainties related to the uncertainty parameters. However, RBTO involves evaluation of probabilistic constraints, which can be done in two different ways, the reliability index approach (RIA) and the performance measure approach (PMA). The reliability index approach (RIA) and the performance measure approach (PMA) are adopted to evaluate the probabilistic constraints. In order to apply the BESO method to the RBTO, sensitivity number is defined as the change in the reliability index due to the addition or the removal of the ith element. In the BESO, a mesh-independency filter using nodal variables is used to remove the checkerboard patterns. The optimal topologies of RIA and PMA are obtained very similarly. It is shown that RBTO based on BESO can be effectively applied from the presented examples.

Al_(0.24)Ga_(0.76)As/GaAs HEMT 구조에서의 표면 광전압에 관한 연구

유재인,김종수,배인호,신영남,박성배 대구대학교 기초과학연구소 2000 基礎科學硏究 Vol.16 No.2

We report a surface photovoltage(SPV) study of Al_(0.24)Ga_(0.76)As/GaAs HEMT structure grown by molecular beam epitaxy. The energies of Eo transition for GaAs and Al_(0.24)Ga_(0.76)As were 1.41 and 1.71 eV, respectively. These values were in good agreement with photo reflectance(PR) measurement. As the frequency is increased from 25 to 55 Hz, the intensity of SPV signal is gradually reduced. Meanwhille, the intensity of SPV signal gradually increased as the temperature increased from 100 K to room temperature. From the former, the surface photovoltage of Al_(0.24)Ga_(0.76)As layer is 8.61 mV, which is about 1.4 times smaller than that of GaAs. This is due to influence of carrier mobility.

자일리톨과 불화나트륨을 함유한 저작성 정제가 교정환자의 구강위생에 미치는 영향에 관한 임상시험

유상훈,안석준,이신재,백승학,김태우,장영일,남동석 대한치과교정학회 2003 대한치과교정학회지 Vol.33 No.2

본 연구는 불화나트륨과 자일리톨 성분으로 구성된 구강 청정용 저작성 정제(덴포정, 하미즐, 부천, 경기)가 교정치료 중인 환자의 구강위생 상태에 미치는 영향을 알아보기 위해 시행되었다. 교정치료 중인 18세 이상의 성인 환자 30명을 대상으로 약제 상요 전, 2주 후, 4주 후에 피험자의 상악과 하악 전치 부위 및 구치 부위에서 각각 치은 지수, 치은 출혈 지수, 치태 지수를 측정하여 다음과 같은 결과를 얻었다. 1. 상하악 전치부와 구치부 모두에서 치태 지수가 약제 사용 전에 비해 사용 2주 후와 4주 후 유의성 있게 감소하였다(p<0.05). 또한, 적용 2주 후와 4주 후의 지수를 비교하였을 때 4주 후에 좀 더 개선된 경향을 보였으나, 통계적 유의성은 나타나지 않았다(p<0.05). 2. 치은 지수, 치은 출혈 지수도 상하악 전치부와 구치부 모두에서 적용 전에 비하여 2주 후와 4주 후 유의성 있게 감소하였다(p<0.05). 적용 2주 후와 4주 후의 지수의 비교 검증에서 통계학적으로 유의할 만한 차이가 보이지 않아 구강위생 상태의 개선이 계속 유지됨을 보였다. 본 연구의 결과는 치태 지수, 치은 지수, 치은 출혈 지수가 실험 정제 적용 후에 감소하여 구강위생 상태가 개선되었음을 보였다. 이러한 결과를 통해 덴포정을 교정치료 중인 환자에서 부가적으로 사용하였을 경우 치주조직의 건강을 증진시키는데 도움을 줄 수 있으리라고 생각된다. The aim of this study was to evaluate the effect a chewable tablet containing sodium fluoride and xylitol (DenPo, Hamizzle, Bucheon, Kyungki) on the oral hygiene state in the orthodontic patients. The subjects consisted of 30 adult orthodontic patients, who have worn the fixed orthodontic appliance at least 6 months. They were instructed to use the tablet forth a day. Gingival index (GI), plaque index (PI), and sulcus bleeding index (SBI) of upper and lower anterior and posterior regions were measured before using the tablet (TO), 2 weeks after using the tablet (T1), and 4 weeks after using the tablet (T2). The data were analyzed with Wilcoxon signed ranks tests. The results were as follows ; 1. PI was decreased significantly in the T1 and T2 stage compared with TO stage in the both anterior and posterior regions (p<0.05). Although PI was decreased in the T2 stage compared with T1, there was not statistical significance(p>0.05). 2. GI and SBI showed similar results compared with PL. In the T1 and T2 stage, there was statistically significant decrease in the GI and SBI (p<0.05). This study showed that the DenPo tablet could be used as an adjunct to improve oral hygiene in the orthodontic patients. The decrease of the indices may suggest that DenPo tablet could be effective in the plaque removal and prevention of gingival inflammation in the orthodontic patients.

관상동맥 질환에서 SDF-1α의 농도

김보영,박용규,박형서,노상필,정승현,이유선,이정우,이재환,최시완,정진옥,성인환 충남대학교 의과대학 의학연구소 2003 충남의대잡지 Vol.30 No.1

Atherosclerosis is now viewed as an inflammatory disease of the vascular system. Expression of several chemokines, including monocyte chemoattractant protein(MCP)-1, MCP-4, RANTES(regulated on activation normal T-cell expressed and secreted), and interleukin-8(IL-8) are increased in human atherosclerotic plaques compared with normal vessels. They are involved in the pathogenesis of atherosclerosis and plaque rupture by activating and directing leukocytes into the atherosclerotic lesions. However, some are involved in homeostatic functions such as normal leukocyte traffic and growth regulation. SDF-la is a multi-functional cytokine that is involved in myelogenesis, hematopoiesis, angiogenesis and injured gastric mucosal regeneration in the gastric ulcer patient. SDF-la is recently shown to be highly expressed in atherosclerotic plaques and a potent platelet agonist. At least in high concentrations, SDF-la may mediate antiinflammatory and matrix stabilizing effects in unstable angina. Many studies are going on to know the function of SDF-la in coronary artery diseases. I investigated the difference of the plasma level of SDF-la between control group and coronary artery disease group. Total 75 subjects were enrolled. The diagnosis of coronary artery disease was confirmed in all patients by coronary angiography. Control subjects in this study were confirmed normal by coronary angiography. Clinical profile and risk factors were also reviewed. Control subjects in this study were 27 (M=10, F=17). Plasma for the study was collected before the angiography and centrifuged. SDF-la analysis was performed by ELISA. Plasma level of SDF-la is significantly increased in patients with stable angina(n=20) and unstable angina group(n=28) compared with healthy control group(n=27). the risk factors do not influence the plasma level of SDF-la in coronary artery diseases. In this study, plasma level of SDF-la is increased in patients with stable angina and unstable angina groups compared with healthy control group(P<0.05). the risk factors do not influence the plasma level of SDF-la in coronary artery diseases.

Bacillus lentimorbus WJ5의 감마선유도 돌연변이체들에서 공통으로 발현되는 방사선 관련 유전자의 microarray 분석

이영근,장화형,장유신,허재호,형석원,정혜영 한국환경생물학회 2004 환경생물 : 환경생물학회지 Vol.22 No.3

본 연구에서는 감마선으로 유도된 돌연변이체들에서 공통으로 발현되는 방사선 관련 유전자들의 발현을 연구하기 위하여, B. lentimorbus WJ5의 방사선 유도 돌연변이체에서 발현되는 유전자를 DNA microarray로 동시에 탐색하였다. DNA microarray는 B. lentimorbus WJ5 genome을 무작위로 절단하여 2,000단편으로 구성하였으며, 감마선 (^(60)Co)으로 유도된 7돌연변이체의 발현을 정량적으로 관찰하였다. 클러스터 분석결과 발현된 408 유전자 중 27개가 감마선 유도 돌연변이체 모두에서 유의하게 발현이 증가되었다. 특히, 복구(mutL, mutM)에너지 대사 (acsA, sdhB, p하, yhjB, citB), protease(npr), 산화자극에 대한 환원 (HMM)관련 유전자들이 동시에 증가되었다. 이는 감마선 유도 돌연변이체들에서 자발적인 직/간접 복구 관련 유전자의 발현 증가는 방사선 노출 직후 보이는 stress response와는 다른 현상임을 나타내는 것으로 생각된다. To study the radiation related gene expression in mutants of Bacillus lentimorbus WJ5 induced by gamm radiation, the simultaneous gene expression was analyzed by DNA microarray. We constructed DNA chips including two thousand randomly digested genome spots of B. lentimorbus WJ5 and compared its quantitative aspect with seven mutants induced by gamma radiation (^(60)Co). From the cluster analysis of gene expression pattern, totally 408 genes were expressed and 27 genes were significantly upregulated by the gamma radiation in all mutants. Especially, genes involved in repair (mutL, mutM), energy metabolism (acsA, sdhB, pgk, yhjB, citB), protease (npr), and reduction response to oxidative stress (HMM) were simultaneously upregulated. It seems that the induction of the direct and/or indirect repair related genes in mutants induced by gamma radiation could be remarkably different from the adaptive responses against acute exposure to radiation.