• 한국항공우주학회지
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• 제44권5호
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• pp.431-438
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• 2016

본 논문은 자가발전형 쿼드콥터를 설계하고 제작한 내용을 다룬다. 본 논문에서 제안하는 자가발전형 쿼드콥터는 전자기유도원리를 이용해 설계된 두 가지 발전장치를 통해 추가 전력을 얻는다. 첫 번째 발전장치는 상용 BLDC모터와 프로펠러를 결합해 함께 회전시켜, BLDC모터를 발전기처럼 활용해 전력을 생산하는 장치이다. 두 번째 발전장치는 프로펠러의 회전축에 작은 자석들을 포함한 프레임을 결합해 함께 회전시켜 코일이 감긴 보호링에서 전력을 생산하는 장치이다. 본 발전장치들은 상용 쿼드콥터 프로펠러 하단에 장착되어 실용적인 발전을 할 수 있으리라 기대된다.

• 풍력에너지저널
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• 제15권2호
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• pp.23-36
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• 2024

In this study, a health monitoring system was developed for the two most vulnerable parts of a wind tower support structure: the connection between steel towers (L-Flange) and the concrete foundation-steel tower connection. To select assessment parameters for health monitoring, detailed FEM analysis was conducted using the ABAQUS program. Additionally, a testbed was established near the Jeju Woljeongri wind turbine farm to evaluate the applicability of measurement data by installing sensors. Through computational analysis and relevant criteria review, we defined limits for measurement parameters by vulnerable section. We categorized the structural safety evaluation into four stages: normal, caution, warning, and danger, and selected management criteria for each stage. From this, an algorithm to evaluate safety was developed, and a visualized monitoring platform based on the established critical parts monitoring system was developed.

• 한국결정성장학회지
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• 제15권5호
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• pp.175-181
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• 2005

스컬용융법에 의해 루틸 단결정들을 성장시켰으며, 서로 다른 융액의 유지시간에 따른 ingot의 특성을 비교하였다. 스컬용융법은 교류전자기장(RF)에 의해 전기가 흐르는 융액의 직접유도가열에 근거하며, 가열은 RF 에너지의 흡수로 실행된다. $TiO_2$는 상온에서는 부도체이지만 온도가 올라갈수록 전기 전도성이 증가한다. 따라서, 초기 RF 유도가열을 위해 티타늄 금속 링(외경 : 6cm, 내경 : 4cm, 두께 : 0.2cm)을 $TiO_2$ 분말(아나타제상, CERAC, 3N)내부에 묻었다. 스컬용융법에 의한 산화물 용융에서 매우 중요한 것은 융점에서의 전기 저항 값, RF generator의 주파수 그리고 냉각도가니 크기이다. 본 연구에서는, $TiO_2$의 융점에서의 전기저항$(10^{-2}\~10^{-1}\;{\Omega}{\cdot}m)$은 알루미나$(10^{-1}\;{\Omega}{\cdot}m)$의 지르코니아$(10^{-3}\;{\Omega}{\cdot}m)$의 전기저항 데이터를 바탕으로 추정하였다. 냉각도가니의 내부직경은 11cm, 높이는 14cm였으며, 이것은 침투깊이$(0.36\~1.13cm)$와 RF generator 주파수를 고려하여 결정하였다

• 전자공학회논문지
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• 제51권8호
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• pp.185-194
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• 2014

본 논문에서는 스마트 옷걸이를 이용한 의류 관리 시스템을 제안하였다. 제안하는 시스템은 스마트 옷걸이, 베이스 모듈, 서버 등으로 구성되며, 스마트 옷걸이는 MCU, LED, RFID 리더기, RF칩, 링센서, 밧데리 등으로 구성된다. 제안하는 시스템은 스마트 옷걸이가 의류에 부착된 RFID 태그를 읽어 무선으로 서버에 전송하면 서버와 연결된 베이스 모듈은 스마트 옷걸이와 통신을 하고 서버에 정보를 전송한다. 서버에서는 DB를 통해 의류를 관리하고 웹페이지 및 스마트폰을 통해 각종 정보를 표시할 수 있다. 제안한 시스템의 유용성을 확인하기 위하여 옷걸이를 많이 사용하는 의류 매장과 세탁소 관리시스템에 대하여 실험을 하였다. 스마트 옷걸이의 성능 실험으로 제안한 저전력 알고리즘을 적용하여 전류 소모량의 감소를 확인하고 배터리 수명을 예측할 수 있었다. 의류 매장 관리시스템은 소비자의 편리성과 판매량 증가를 증대 시킬 수 있다. 세탁소 관리 시스템은 대량의 세탁물 분류의 효율성과 소비자의 편리성을 증대 시킬 수 있다.

• Steel and Composite Structures
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• 제27권5호
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• pp.577-598
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• 2018

The imperfect steel-concrete interface bonding is an important deficiency of the concrete-filled double skin tubular (CFDST) columns that led to separating concrete and steel surfaces under lateral loads and triggering buckling failure of the columns. To improve this issue, it is proposed in this study to use longitudinal and transverse steel stiffeners in CFDST columns. CFDST columns with different patterns of stiffeners embedded in the interior or exterior surfaces of the inner or outer tubes were analyzed under constant axial force and reversed cyclic loading. In the finite element modeling, the confinement effects of both inner and outer tubes on the compressive strength of concrete as well as the effect of discrete crack for concrete fracture were incorporated which give a realistic prediction of the seismic behavior of CFDST columns. Lateral strength, stiffness, ductility and energy absorption are evaluated based on the hysteresis loops. The results indicated that the stiffeners had determinant role on improving pinching behavior resulting from the outer tube's local buckling and opening/closing of the major tensile crack of concrete. The lateral strength, initial stiffness and energy absorption capacity of longitudinally stiffened columns with fixed-free end condition were increased by as much as 17%, 20% and 70%, respectively. The energy dissipation was accentuated up to 107% for fixed-guided end condition. The use of transverse stiffeners at the base of columns increased energy dissipation up to 35%. Axial load ratio, hollow ratio and concrete strength affecting the initial stiffness and lateral strength, had negligible effect of the energy dissipation of the columns. It was also found that the longitudinal stiffeners and transverse stiffeners have, respectively, negative and positive effects on ductility of CFDST columns. The conclusions, drawn from this study, can in turn, lead to the suggestion of some guidelines for the design of CFDST columns.

• 대한건축학회논문집:계획계
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• 제35권6호
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• pp.3-12
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• 2019

Current risk assessment methods typically determine accident risks embedded in construction projects by combining severity and frequency; however, they do not reflect the characteristics of construction projects. To solve the problem, this study aims to develop a novel risk assessment method that combines severity, frequency, and disaster influence factors (i.e., weather conditions and worker's characteristics) for assessing risks of activities occurring on a construction site actually. In this study, a severity was estimated by death against victims, and a frequency was estimated by the victim rate. The frequency was then converted to probability taking disaster influence factors into account. Thus, instead of considering severity and frequency for assessing the original risks (RO), the proposed method uses severity and probability to yield adjusted risks (RA) for each activity. A case study was conducted to determine if the proposed method works as intended in a real setting. The results show that RA is more sensitive to disaster influence factors than RO and, therefore, is able to assess the actual risks reflecting the working environment and conditions of a construction site. This study contributes to risk management of construction projects by offering a risk assessment method that measures a possibility of potential disasters from the probabilistic perspective. This method would help project managers assess accident risks in a more systematic and quantitative manner.

• 한국동물학회지
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• 제15권3호
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• pp.133-147
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• 1972

고추잠자리(Crocothemis servilia Drury)의 精子完成過程을 究明하기 爲하여, 本 硏究에 着手한 바, 다른 無脊椎動物의 精子完成過程에서 이미 밝혀진 構造들과 比較해 가면서 特殊한 分化相을 觀察한 結果, 첫째 核의 染色質이 漸次 濃縮되기 始作함에 따라서 核의 모양도 球形에서 楕圓形으로, 楕圓形에서 圓錐形으로 變하였으며 둘째로 核이 細胞의 一極端으로 移動하고 核의 尾部가 陷入되며 셋째 中心粒이 核 陷入 部位에 位置하여 여기에서부터 軸　가 形成된다. 넷째는 골지體에서 起因된 尖體顆粒은 核의 先端으로 移動되어 결국 尖體를 形成하게 된다.

• 폴리머
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• 제30권3호
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• pp.196-201
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• 2006

온도감응성 고분자인 폴리 (에틸렌 글리콜)을 기본으로 하는 다이블록 및 트리블록 폴리에스테르 공중합체들은 비독성과 생체적합성 그리고 생분해성 특징 때문에 조직공학 분야 및 주사제형의 약물전달체에서 많은 응용이 이루어지고 있다. 본 연구에서는 다이블록 공중합체를 이용한 솔-젤 전이 현상을 갖는 고분자를 평균분자량 750 g/mole의 메톡시 폴리 (에틸렌 글리콜)과 카프로락톤을 실온에서 HCl $Et_2O$ 존재 하에서 개환중합을 통하여 합성하였다. 이 공중합체를 이용하여 in vivo상에서 골수간엽줄기세포와 골유도물질인 덱사메타손의 존재 여부에 따라 골분화의 가능성을 조사하였다. 조직을 파라핀으로 고정시켜 슬라이드를 제조한 후 hematoxylin & eosin, 본쿠사 및 오스테오칼신 염색을 통하여 골형성 정도를 확인하였다. 결론적으로 덱사메타손이 함유된 젤이 골형성에 도움을 주지만 젤만으로는 강한 골형성을 유도할 수 없으므로 줄기세포나 다른 골형성 유도재료를 사용하면 우수하게 골형성 효과를 가져올 것이라고 판단되었다.

• Restorative Dentistry and Endodontics
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• 제13권2호
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• pp.337-348
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• 1988

The purpose of this study was to examine the fracture strength and characteristics of teeth with MOD cavity preparation. Freshly extracted sound maxillary premolars were cleaned and stored in normal saline solution $37^{\circ}C$ for 72 hours before experiments. The roots of teeth were embedded in a self-curing resin, and the exposed crown were maintained in a vertical position by a modelling wax in a brass ring. The MOD cavities were prepared with No. 57 carbide bur under high speed to a depth of 2.0mm and a width of 2.0mm(Fig.1). All the prepared teeth specimens were divided into 7 groups according to the mode of cavity form and restorative materials (Table 1, 2): Group I, unpreapred, intact teeth as control Group II, prepared cavity without restoration Group III, prepared teeth restored with amalgam Group IV, prepared teeth restored with composite resin (P-10) Group V, prepared teeth with beveled enamel margins restored with composite resin (P-10) Group VI, prepared teeth restored with light-cured composite resin (P-30) Group VII, prepard teeth with beveled enamel margins restored with light-cured composite resin (P-30) After placement of restorations, all of the specimens were stored in water at $37^{\circ}C$ for 72 hours before testing. All of the specimens were tested on the Instron Universal Testing machine (No. 6025) in order to evaluate the strength of fracture. One metal ball 5.0mm in diameter contacting the specimens parallel to the occlusal surface was used to in this study (Fig. 1). The fracture characteristics of the specimens were examined with naked eye and in the scanning electron microscope (JSM-20). The results obtained from this study were as follows: 1. The mean fracture strength was the highest in group VI and that in group II was the lowest. 2. The progress of crack of teeth propagated into the pulp cavity. 3. In case of the group of the restored teeth, the crack occurred to be accompanied with cuspal fracture. 4. The crack of restored teeth was initiated along the pulpo-axial line angle of the cavity.

• Journal of Gastric Cancer
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• 제1권2호
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• pp.92-99
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• 2001

Purpose: E-cadherin is an adhesion molecule essential for tight connection between cells, forming the cadherin/catenin complex. Truncated $\beta$-catenin disrupts the interaction between E-cadherin and $\alpha$-catenin, leading to the loss of intercellular adhesion. Met protein, the hepatocyte growth factor receptor, plays important roles in signal transduction. We investigated the relationships between the expressions of E-cadherin, $\beta$-catenin, and c-met protein and the clinicopathological and prognostic parameters in gastric adenocarcinomas. Materials and Methods: The patterns of E-cadherin, $\beta$-catenin, and c-met protein expression were studied using immunohistochemistry in formalin-fixed, paraffin-embedded archival tissues from 76 surgically resected gastric adenocarcinomas. Results: Increased expressions of E-cadherin, $\beta$-catenin, and c-met were more significantly correlated in early gastric cancers (EGC) than in advanced gastric cancers (AGC) (P=0.002, P=0.003 and P=0.026). The positive immunoreactivities of all three markers were markedly lower in signet ring-cell type and poorly differentiated type lesions than in intestinal-type lesions. Decreased expression of the $\beta$-catenin protein correlated well with increased tumor invasion depth (P=0.039), and increased lymph node metastasis correlated well with reduced expression of c-met (P=0.046). Conclusion: In gastric cancers, reduced expressions of the E-cadherin, $\beta$-catenin, and c-met proteins may play some role in poorer tumor differentiation, deeper tumor invasion, and increased lymph node metastasis. Also, the c-met gene is thought to play a specific role in the mechanism of the yet unknown catenin action.