• Advances in nano research
• /
• 제5권4호
• /
• pp.281-301
• /
• 2017

In this disquisition, an exact solution method is developed for analyzing the vibration characteristics of magneto-electro-elastic functionally graded (MEE-FG) beams by considering porosity distribution and various boundary conditions via a four-variable shear deformation refined beam theory for the first time. Magneto-electroelastic properties of porous FG beam are supposed to vary through the thickness direction and are modeled via modified power-law rule which is formulated using the concept of even and uneven porosity distributions. Porosities possibly occurring inside functionally graded materials (FGMs) during fabrication because of technical problem that lead to creation micro-voids in FG materials. So, it is necessary to consider the effect of porosities on the vibration behavior of MEE-FG beam in the present study. The governing differential equations and related boundary conditions of porous MEE-FG beam subjected to physical field are derived by Hamilton's principle based on a four-variable tangential-exponential refined theory which avoids the use of shear correction factor. An analytical solution procedure is used to achieve the natural frequencies of porous-FG beam supposed to magneto-electrical field which satisfies various boundary conditions. A parametric study is led to carry out the effects of material graduation exponent, porosity parameter, external magnetic potential, external electric voltage, slenderness ratio and various boundary conditions on dimensionless frequencies of porous MEE-FG beam. It is concluded that these parameters play noticeable roles on the vibration behavior of MEE-FG beam with porosities. Presented numerical results can be applied as benchmarks for future design of MEE-FG structures with porosity phases.

• 한국지반환경공학회 논문집
• /
• 제19권12호
• /
• pp.5-14
• /
• 2018

최근 국내에 사용되고 있는 보강토옹벽 공법은 전면체의 재질, 보강재, 축조방법, 축조경사에 따라 수많은 종류가 제안되었으나 각 공법에 따른 설계방법이나 상세검토항목 등의 규정이 명확하지 않으며 집중호우에 따른 붕괴도 빈번하게 발생하고 있는 실정이다. 본 연구에서는 이러한 보강토옹벽의 설계에 있어서 좀 더 안정된 기술적 접근을 위해 설치높이별 단면을 가정하고 단일 강도의 보강재를 사용한 보강토옹벽의 인발파괴와 높이별 최적의 보강재 조합을 산정하고 산정된 각 단면에 대해서 보강길이비(L/H)에 따른 안전율 변화를 통하여 보강재의 최적 설계와 다단식 보강토옹벽의 최적 설계 그리고 보강재인 토목섬유의 재질에 따른 최적 길이비를 산정하여 제시하였다.

• 한국콘텐츠학회논문지
• /
• 제19권1호
• /
• pp.484-495
• /
• 2019

본 연구는 뷰티살롱 종사자의 셀프리더십이 조직시민행동과 이직의도에 미치는 영향을 파악하고 직무만족의 조절효과를 규명하고자 하였다. 이를 위해 뷰티살롱 종사자 330명을 대상으로 자료를 수집하였으며. SPSS v. 21.0을 활용하여 분석하였다. 연구 결과 셀프리더십은 조직시민행동과 이직의도에 긍정적인 영향을 미치는 것으로 나타났으며, 셀프리더십이 직무만족에 의해 조절되는지를 확인하기 위해 독립변수로 셀프리더십을 모델I에, 조절변수로 직무만족을 모델II에, 셀프리더십과 직무만족의 상호작용 변수를 모델III에 차례로 투입하여 위계적 회귀분석을 실시한 결과 모델I, II, III 모두 정(+)의 영향을 미치는 유의미한 관계가 있는 것으로 나타났다. 이와 같은 연구결과로 산업체 관계자는 구성원 스스로가 업무를 성공적으로 수행하기 위한 셀프리더쉽을 강화하기 위해 기술 교육 뿐만 아니라 자기계발 교육이 강화되어야 할 것이다.

• 한국인터넷방송통신학회논문지
• /
• 제18권6호
• /
• pp.187-193
• /
• 2018

국내에서의 전력에 대한 수요는 점진적으로 증가하고 있는 추세이다. 수요에 대응하기 위한 발전소는 기능이 다양해지고 효율이 점차 커져야 한다. 발전소 내의 전력 기기에서 사고가 발생하면 막대한 경제적 손실 및 장애를 초래하게 된다. 사고 발생의 원인 중의 하나로서 절연 성능이 저하 된 케이블이 있다. 케이블 사고를 미연에 방지하기 위하여 절연의 상태를 감시하고 확인하여야 한다. 케이블 사고는 연결 부위인 접속에서 발생하는 사고가 대부분을 차지한다. 본 연구와 관련하여 우리는 접속부 상태를 판별하기 위한 장비를 개발하였고, 한국서부발전(주)의 현장에 설치하여 운용 중이다. 본 논문에서는 현장에서 설치 운용 중인 장비에 대한 설명과 더불어 설치 운용된 결과를 통해 케이블의 수명을 예측할 수 있는 고전압 케이블 접속재의 안정적 사용을 위한 온라인 감시진단기법 중에서 사고가 가장 빈번하게 발생하는 접속부에 대해 안정적인 사용을 위한 진단의 정확성과 신뢰성을 향상시키기 위한 연구를 하였다. 이 논문에서 하드웨어 구성을 위주로 우리가 개발한 장비를 소개한다.

• Journal of Korean Neurosurgical Society
• /
• 제62권6호
• /
• pp.712-722
• /
• 2019

Objective : Although magnetic resonance guided focused ultrasound (MRgFUS) has been used as minimally invasive and effective neurosurgical treatment, it exhibits some limitations, mainly related to acoustic properties of the skull barrier. This study was undertaken to identify skull characteristics that contribute to optimal ultrasonic energy transmission for MRgFUS procedures. Methods : For ex vivo skull experiments, various acoustic fields were measured under different conditions, using five non-embalmed cadaver skulls. For clinical skull analyses, brain computed tomography data of 46 patients who underwent MRgFUS ablations (18 unilateral thalamotomy, nine unilateral pallidotomy, and 19 bilateral capsulotomy) were retrospectively reviewed. Patients' skull factors and sonication parameters were comparatively analyzed with respect to the cadaveric skulls. Results : Skull experiments identified three important factors related skull penetration of ultrasound, including skull density ratio (SDR), skull volume, and incidence angle of the acoustic rays against the skull surface. In clinical results, SDR and skull volume correlated with maximal temperature (Tmax) and energy requirement to achieve Tmax (p<0.05). In addition, considering the incidence angle determined by brain target location, less energy was required to reach Tmax in the central, rather than lateral targets particularly when compared between thalamotomy and capsulotomy (p<0.05). Conclusion : This study reconfirmed previously identified skull factors, including SDR and skull volume, for successful MRgFUS; it identified an additional factor, incidence angle of acoustic rays against the skull surface. To guarantee successful transcranial MRgFUS treatment without suffering these various skull issues, further technical improvements are required.

• 문화기술의 융합
• /
• 제5권2호
• /
• pp.345-353
• /
• 2019

비디오 씨쓰루 HMD(VSHMD)는 HMD 전면에 장착된 카메라를 통해 실세계 영상을 획득하여 이를 HMD의 디스플레이를 통해 실시간으로 출력하는 장치로서 혼합현실, 증강현실, 가상현실 구현 도구로 활용된다. 최근 카메라 및 디스플레이 기술이 급속히 발전하면서 VSHMD의 성능이 빠르게 향상되고 있으나 아직까지 VSHMD가 갖는 여러 기술적, 인간 요소적 문제들이 해결되지 못하고 있다. 본 논문은 지금까지 수행된 선행 연구 결과들을 시야각(FOV), 디스플레이 해상도, 영상지연, 시점차 등의 주요 설계 요소별로 정리하였다. 그리고 성공적인 VSHMD 개발을 위해 극복해야 할 인간요소 관점의 주요 연구주제들을 조사하였다. 이를 근거로 VSHMD의 설계, 개발 및 VSHMD 응용 서비스를 개발할 때 중요하게 다뤄야 하는 기술적 이슈들을 제시하였다.

• Journal of Microbiology and Biotechnology
• /
• 제31권8호
• /
• pp.1115-1122
• /
• 2021

Rotavirus (RV), as the main cause of diarrhea in children under 5 years, contributes to various childhood diseases. Valeriana jatamansi Jones is a traditional Chinese herb and possesses antiviral effects. In this study we investigated the potential mechanisms of V. jatamansi Jones in RV-induced diarrhea. MTT assay was performed to evaluate cell proliferation and the diarrhea mice model was constructed using SA11 infection. Mice were administered V. jatamansi Jones and ribavirin. Diarrhea score was used to evaluate the treatment effect. The enzyme-linked immunosorbent assay was performed to detect the level of cytokines. Western blot and quantitative reverse transcription-PCR were used to determine protein and mRNA levels, respectively. Hematoxylin-eosin staining was applied to detect the pathological change of the small intestine. TdT-mediated dUTP nick-end labeling was conducted to determine the apoptosis rate. The results showed V. jatamansi Jones promoted MA104 proliferation. V. jatamansi Jones downregulated phosphatidylinositol 3-kinase (PI3K) and protein kinase B (AKT) in protein level, which was consistent with the immunohistochemistry results. Moreover, V. jatamansi Jones combined with ribavirin regulated interleukin-1β (IL-1β), interferon γ, IL-6, tumor necrosis factor α, and IL-10, and suppressed secretory immunoglobulin A secretion to remove viruses and inhibit dehydration. V. jatamansi Jones + ribavirin facilitated the apoptosis of small intestine cells. In conclusion, V. jatamansi Jones may inhibit RV-induced diarrhea through PI3K/AKT signaling pathway, and could therefore be a potential therapy for diarrhea.

• Journal of Korean Neurosurgical Society
• /
• 제64권1호
• /
• pp.23-29
• /
• 2021

Objective : Although stent-assisted coiling (SAC) has been reported to be safe and effective in treating wide-necked aneurysms, the technique has procedure-related complications. Thus, we reported our experiences of SAC using the Neuroform Atlas stent in treating wide-necked aneurysms and evaluated the incidence of and risk factors for procedure-related complications. Methods : From March 2018 to August 2019, we treated 130 unruptured wide-necked aneurysms in 123 patients with Neuroform Atlas stents. Angiographic results and clinical outcomes were reviewed retrospectively. Clinical and angiographic follow-up were performed in all cases (mean, 12.4 months) after the procedure. Results : There were eight cases (6.2%) of procedure-related complications (two dissections, five thromboembolisms, and one hemorrhage) and two (1.5%) of delayed complications (one ischemia and one hemorrhage). There was one case (0.8%) of failure of stent deployment and one (0.8%) of suboptimal positioning of the stent. Follow-up angiography showed complete obliteration in 103 (79.2%), residual neck in 16 (12.3%), and residual aneurysm in 11 cases (8.5%). Aneurysm locations in the middle cerebral artery (odds ratio [OR], 2.211; p=0.046) and the anterior communicating artery (OR, 2.850; p=0.039) were associated with procedure-related complications on univariate analysis. However, no independent risk factor for procedure-related complications was noted in multivariate analysis. Conclusion : The Neuroform Atlas showed a high rate of technical success. Good clinical and radiographic outcomes in early follow-up suggests that the device is feasible and safe. SAC of aneurysms on the middle cerebral artery or anterior communicating artery may require more attention to prevent possible procedure-related complications.

• 한국융합학회논문지
• /
• 제11권12호
• /
• pp.343-351
• /
• 2020

본 연구의 목적은 COVID-19 상황에 따른 스포츠 활동 실태를 파악하여 스포츠 활동 개선방안을 도출하는 것이다. 연구대상은 서울 및 경기도에 거주하고 있는 10대부터 60대의 남녀 총 697명을 편의표집법으로 선정하였다. 네이버 폼을 이용하여 설문지를 배포하였고 자료 분석은 SPSS 12.0 program을 이용하여 빈도분석을 하였으며 결과는 다음과 같다. 첫째, 현재 COVID-19 상황 속에서 61.4%가 스포츠 활동을 하고 있는 것으로 나타났다. 둘째, 스포츠 활동 참여자들은 유튜브 시청, 홈트레이닝/화상PT 등 비대면 스포츠를 즐기는 것으로 나타났다. 셋째, COVID-19 상황이 스포츠 활동에 가장 영향을 미치는 요인으로 확인되었다. 넷째, 향후 COVID-19와 같은 전염성 질병을 대비한 방안이 마련되었으면 좋겠다는 의견이 가장 많았다. 스포츠 활동 개선방안으로는 첫째, 다양한 온라인 콘텐츠 개발, 둘째, COVID-19 시대의 건강과 웰빙의 증진을 위한 국가정책 수립 및 이행, 셋째, 온라인 스포츠 활동을 위한 기술력 확보 등이 도출되었다.

• 대한건축학회논문집:구조계
• /
• 제35권8호
• /
• pp.157-168
• /
• 2019

Modular Construction is regarded as having enhanced safety compared to traditional construction since most of modular manufacturing process in plants. Unlike general consideration for safety in modular construction, several industrial accident data and studies have pointed out that the accident rate of modular construction is not enough less as much as the practitioners have expected. It means that there is a clear need for improvement of safety management in modular construction. To enhance safety, it is necessary to identify the type and cause of accident through accident cases in order to prevent safety accident in advance. In this consideration, this study analyzed the types and causes of accidents through root cause analysis procedure with accident cases of U.S. OSHA. The classification was carried out in the order of process type, accident type and cause of accident. By following the classification criteria in this study, the causal factor was derived and the root cause map was created. Based on the analysis results, cross-analysis was conducted and it is shown that activity characteristics of modular construction are related to safety accidents. In addition, prevention methods to reduce safety accident by major activity are presented in terms of organizational, educational and technical aspects. This study contributes that the result can be used as the basic safety management in the manufacturing and construction process of modular construction.