• 대한원격탐사학회지
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• 제21권5호
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• pp.405-415
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• 2005

It is difficult to classify tidal flat surface that is composed of a mixture of mud, sand, water and microphytobenthos. We used a Linear Spectral Unmixing (LSU) method for effectively classifying the tidal flat surface characteristics within a pixel. This study aims at 1) detecting algal mat using LSU in the Saemangeum tidal flats, 2) determining a suitable end-member selection method in tidal flats, and 3) find out a habitual characteristics of algal mat. Two types of end-member were built; one is a reference end-member derived from field spectrometer measurements and the other image end-member. A field spectrometer was used to measure spectral reflectance, and a spectral library was accomplished by shape difference of spectra, r.m.s. difference of spectra, continuum removal and Mann-Whitney U-test. Reference end-members were extracted from the spectral library. Image end-members were obtained by applying Principle Component Analysis (PCA) to an image. The LSU method was effective to detect microphytobenthos, and successfully classified the intertidal zone into algal mat, sediment, and water body components. The reference end-member was slightly more effective than the image end-member for the classification. Fine grained upper tidal flat is generally considered as a rich habitat for algal mat. We also identified unusual microphytobenthos that inhabited coarse grained lower tidal flats.

• Steel and Composite Structures
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• 제48권5호
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• pp.547-564
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• 2023

This study investigates the effect of bolt preloading on the rotational stiffness of stainless steel end-plate connections. An experimental programme incorporating 11 full-scale joint specimens are carried out comparing the behaviours of fully pre-tensioned (PT) and snug-tightened (ST) flush/extended end-plate connections, made of austenitic or lean duplex stainless steels. It is observed from the tests that the presence of bolt preloading leads to a significant increase in the rotational stiffness. A parallel finite element analysis (FEA) validated against the test results demonstrates that the geometric imperfection of end-plate has a strong influence on the moment-rotation response of preloaded end-plate connections, which is crucial to explain the observed "two-stage" behaviour of these connections. Based on the data obtained from the tests and FE parametric study, the performance of the Eurocode 3 predictive model is evaluated, which exhibits a significant deviation in predicting the rotational stiffness of stainless steel end-plate connections. A modified bi-linear model, which incorporates three key properties, is therefore proposed to enable a better prediction. Finally, the effect of bolt preloading is demonstrated at the system (structure) level considering the serviceability of semi-continuous stainless steel beams with end-plate connections.

• 한국압력기기공학회 논문집
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• 제17권2호
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• pp.75-82
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• 2021

The 3D printing technology is one of the fourth industrial revolution technology that drives innovation in the manufacturing process, and should be applied to nuclear industry for various purposes according to the manufacturing trend change. In nuclear industry, it can be applied to manufacture obsolete items and new designed parts in advanced reactors or small modular reactors (SMRs), replacing the traditional manufacturing technologies. A gate valve body was manufactured, which was obsolete in nuclear power plant, using DED(Directed Energy Deposition) metal 3D printing technology after restoring design characteristics including 3D design drawing by reverse engineering. The 3D printed valve body was assembled with commercial parts such as seat-ring, disk, stem, and actuator for performance test. For the valve assembly, including 3D printed valve body, several tests were performed, including pressure test, end-loading test, and seismic test according to KEPIC MGG and KEPIC MFC. In the pressure test, hydraulic pressure of 391kgf/cm² was applied to 3D printed valve body, and no leak was detected. Also the 3D printed valve assembly was performed well in end-loading and seismic tests.

• International Journal of Concrete Structures and Materials
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• 제8권2호
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• pp.129-139
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• 2014

In this study, the concrete fracture energy was obtained using the three point notched beam test method developed by Hillerborg et al. (Cem Concr Res 6(6):773-782, 1976). A total of 12 notched concrete beams were tested under two different loading conditions: constant stroke control and constant crack mouth opening displacement (CMOD) control. Despite individual fracture energies obtained from the two different loading conditions showing some variation, the average fracture energy from both loading conditions was very similar. Furthermore, the results obtained support the idea that a far tail constant "A" could change the true fracture energy by up to 11 %, if it is calculated using CMOD instead of LVDT. The far tail constant "A" is determined using a least squares fit onto a straight line according to Elices et al. (Mater Struct 25(148):212-218, 1992) and RILEM report (2007). It was also observed that the selection of the end point can produce variations of the true fracture energy. The end point indicates the point in the experiment at which to stop. An end point of 2 mm has been recommended, however, in this study other end points were also considered. The final form of the bilinear softening curve was determined based on Elices and Guinea's methods (1992, 1994) and RILEM report (2007). This paper proposes a bilinear stress-crack opening displacement curve according to test results as well as the CEB-FIP model code.

• 지역사회간호학회지
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• 제23권2호
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• pp.127-133
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• 2012

Purpose: This study was conducted to assess needs at each end-of-life care stage and to analyze importance and difficulty of care needs for home care nursing among non-cancer patients. Methods: We used a retrospective design. Total eligible patients were 117 at the ages of 40 and over, who continuously received home care nursing throughout beginning, stable, and near death stages, and finally died at home from January 1, 2006 to December 31, 2006. Descriptive statistics, Cochran's Q test, Friedman's test were used for data analysis. Results: In the area of physical care, the care need for 'assistance for activities in daily life' was significantly highest in the beginning stage. The care need for 'aggravation or adverse changes in physical symptoms' was significantly increased in the near death stage. In the area of psychospiritual care, 'family's psychological burden' was revealed as having the highest rate of care needs in the every stage. Conclusion: Future intervention should consider assessing care needs in end-of-life care for non-cancer patients who are provided with home care nursing.

• Journal of Mechanical Science and Technology
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• 제14권11호
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• pp.1232-1243
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• 2000

Motor vehicle accidents in rear impacts cause more than fifty percents of drivers to suffer from neck injuries. It is known that most neck injuries are associated with rear-end collisions at a speed lower than 32 km/h and between the Abbreviated Injury Scale (AIS) 1 and AIS 2. Two different types of low speed crash tests such as the frontal barrier and rear moving barrier crashes have been conducted by following the procedure of the Research Committee for Automobile Repairs (RCAR). The injury for the neck and the Head Injury Criteria (HIC) were measured by using the sensors mounted on dummies. We reviewed neck injures and the relationship between the neck and head injuries, and examined the deceleration of the body. Using the experimental test data at the neck, we investigated an improved neck injury criterion Nij. Also, the effects of the position of a head restraint on reducing the frequency and severity of the neck injury in rear-end collisions were investigated.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 A
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• pp.464-466
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• 2003

우리나라는 1980년대 이후 급격한 경제성장에 따라 년 10%대의 급격한 전력수요 증가를 보이고 있으며, 1인당 전력소비량 또한 매년 큰 폭의 증가세를 보이고 있다. 특히, 주요한 전력 수요 증가지대가 경인 지역에 집중되어 있으나, 이 지역은 인구 밀집지역으로 환경과 입지적인 관점에서 새로운 발전원을 개발하기가 곤란하다. 이에 따라 대용량 발전단이 있는 중서부권이나 영동권으로부터 수요지인 경인지역으로의 대규모 전력전송로가 필요하게 되었다. 이에 따라 1979년부터 765kV로의 전압격상을 준비하였으며, 1983년부터 765kV 연구개발을 시작하여 1997년 10월에 1차로 765kV 송전선로에 345kV 가압을 시작하여 2002년 5월 8일에 역사적인 765kV 송전을 개시하였다. 전력계통운용에서 765kV 송전선로의 중요도가 매우 커지게 됨으로써 국내 최초로 적용되는 765kV송전선로 보호시스템의 정동작 유무를 정확히 판단하여 전력계통의 보호 신뢰도를 향상시키는 문제가 중요하게 대두 되었다. 본 논문에서는 시각동기장치가 부착된 보호계전기 시험장치를 이용하여 양단 변전소에서 동시에 EMTP와 RTDS 둥으로 검토된 송전선로 고장상태를 인가하여 보호시스템의 정동작 여부를 종합적으로 판정하는 시험 기술을 개발하여 실적용한 사례와 향후 사용 계획에 대해서 기술하였다.

• Structural Engineering and Mechanics
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• 제77권1호
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• pp.75-87
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• 2021

The present study pertains to the introduction of two new types of grip adaptor for universal testing machines, namely Polyvinyl Chloride (PVC) and Polyoxymethylene (POM) grip adaptors, and their application to tension testing of FRP bars with different fiber and surface finish types. The tabs are connected to the FRP bar sample with the help of mechanical anchors, i.e. bolts. These new adaptors offer vital superiorities over the existing end tab designs (anchors with filling material or mechanical anchorage), including the reduction in the time and labor for production, reusability and the mild nature, i.e. low hardness of the tab material, which retards and even prevents peeling and crushing in the gripping regions of an FRP sample. The methods were successfully applied to FRP bars with different types of fiber (CFRP, GFRP and BFRP) and different types of surface texture (ribbed, wrapped, sand-coated and wound). The test results indicated that the both types of end caps prevented slip of the bar, crushing and peeling in the gripping zone. The mechanical properties from the material tests with the new caps were in perfect agreement with the ones from the material tests with steel tubular caps.

• Journal of Hospice and Palliative Care
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• 제24권1호
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• pp.13-25
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• 2021

Purpose: This descriptive study aimed to explore nursing workplace spirituality, end-of-life care stress, and resilience as factors influencing compassion fatigue among nurses working in hospice and palliative care units. Methods: Data were collected using a self-report questionnaire completed by 146 nurses at 14 hospice and palliative care institutions across South Korea who had worked in a hospice and palliative care institution for at least 6 months and had experience providing end-of-life care. Data were collected from February 25, 2019 to April 12, 2019, and analyzed using SPSS for Windows version 18.0. As appropriate, descriptive statistics, the t-test, analysis of variance, the Scheffé test, Pearson correlation coefficients, and stepwise multiple regression were used. Results: The survey results showed that factors influencing compassion fatigue were resilience, subjective health status, current satisfaction with the hospice ward, and end-of-life care stress. Higher levels of resilience, a subjective health status of "healthy", high levels of current satisfaction with the hospice ward, and lower levels of end-of-life care stress were associated with lower levels of compassion fatigue, explaining 42.9% of the total variance. Conclusion: The results of this study suggest that resilience is an important factor mitigating compassion fatigue among nurses at hospice and palliative care institutions. Therefore, intervention programs should be developed to reduce compassion fatigue.

• Geomechanics and Engineering
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• 제5권2호
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• pp.119-142
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• 2013

Pile load tests using Osterberg cells (O-cell) were conducted on cast-in-place concrete piles founded in oil sand fill and in situ oil sand at an industrial plant site in Fort McMurray, Alberta, Canada. Interpreted pile test results show that very high pile shaft resistance (with the Bjerrum-Burland or Beta coefficient of 2.5-4.5) against oil sand could be mobilized at small relative displacements of 2-3% of shaft diameter. Finite element simulations based on linear elastic and elasto-plastic models for oil sand materials were used to analyze the pile load test measurements. Two constitutive models yield comparable top-down load versus pile head displacement curves, but very different behaviour in mobilization of pile shaft and end bearing resistances. The elasto-plastic model produces more consistent matching in both pile shaft and end bearing resistances whereas the linear elastic under- and over-predicts the shaft and end bearing resistances, respectively. The mobilization of high shaft resistance in oil sand under pile load is attributed to the very dense and interlocked structure of oil sand which results in high matrix stiffness, high friction angle, and high shear dilation.