• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.31 no.6_1
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• pp.471-481
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• 2013

Recently, the frequency of debris flow disaster has increased, which is one of the natural disasters during extremely heavy rainfall condition. This paper described the analysis method about deposition characteristics of debris flow using topographic characteristics of debris flow path. First, we observed topographic changes by differencing high- resolution LiDAR DEMs acquired before and after the occurrence of debris flow event. We assumed that deposition on outside of debris flow path was generated by movements due to the inertia of debris flows. Then, we analyzed three topographic characteristics of debris flow path: slope in flow direction, transition angle of flow path, and the net efficiency(L/H) of debris flows defined by the ratio of transport length(L) and elevation difference(H). We applied this method to Umyeon Mountain debris flow event in July 2011. The results showed that deposition on outside of debris flow path due to the inertia of debris flows was significantly related to the transition angle of debris flow path. Also, we figured out that there were more frequent such depositions in locations where the ratio of 'transition angle / (L/H)' is over 8.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.121-123
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• 2002

The design of an air seat cushion for preventing decubitus ulcer includes many design factors such as the even distribution of interface pressure, the minimization of mean and peak interface pressure values, and the reduction of interface shear force and pressure gradient. It involves the anatomic condition of plegia's buttock as well as air pressure in air cells of cushion. As a result, a suitable design of the cushion satisfying the all requirements is a difficult problem. Therefore, an appropriate and effective numerical tool to develop an air cushion orthosis is required. The purpose of the present study was to develop an air seat cushion orthosis having optimized air cells for evenly distributed interface pressure between the buttock and cushion surface. For the purpose, an advanced finite element (FE) model for the design of air cushion was developed. Since the interface pressure and shear force behavior, as well as stress analyses were primary concern, a FE air cell model was developed and verified by the experiments. Then, the interactions of two cells were checked. Also, the human part of the developed numerical model includes every material property and geometry related to buttock and femoral parts. For construction of dimension data of buttock and femoral parts, CT scans were performed. A commercial FE program was employed for the simulation representing the seating process on the orthosis. Then, sensitive analyses were performed with varying design parameters. A set of optimal design parameters was found satisfying the design criteria of the orthosis. The results were utilized to produce a prototype of the orthosis. Experimentally, the buttock interface pressure distributions from the optimized and previous ones were compared. The new seat orthosis showed a significantly improved interface pressure characteristics compared to the most popular one in the market. The new orthosis will be used for the development of the AI(artificial intelligent) controlled seat orthosis fur prevention of decubitus ulcer fur various plegic patients and the elderly.

• Journal of Korea Water Resources Association
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• v.33 no.2
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• pp.247-262
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• 2000

In this paper, the WSANN(Water Stage Analysis with Neural Network) model was presented so as to predict flood water stage at Jindong which has been the major stream gauging station in Nakdong river basin. The WSANN model used the improved backpropagation training algorithm which was complemented by the momentum method, improvement of initial condition and adaptive-learning rate and the data which were used for this study were classified into training and testing data sets. An empirical equation was derived to determine optimal hidden layer node between the hidden layer node and threshold iteration number. And, the calibration of the WSANN model was performed by the four training data sets. As a result of calibration, the WSANN22 and WSANN32 model were selected for the optimal models which would be used for model verification. The model verification was carried out so as to evaluate model fitness with the two-untrained testing data sets. And, flood water stages were reasonably predicted through the results of statistical analysis. As results of this study, further research activities are needed for the construction of a real-time warning of the impending flood and for the control of flood water stage with neural network method in river basin. basin.

• Journal of Korean Association for Spatial Structures
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• v.2 no.1 s.3
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• pp.85-92
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• 2002

Two way grid single-layer domes are of great advantage in fabrication and construction because of the simple fact that they have only four members at each junction. But, from a point of view of mechanics, the rectangular latticed pattern gives rise to a nonuniform rigidity-distribution in the circumferential direction. If the equivalent rigidity is considered in the axial direction of members, the in-plane equivalent shearing rigidity depends only on the in-plane bending rigidity of members and its value is very small in comparison to that of the in-plane equivalent stretching rigidity. It has a tendency to decrease buckling -strength of dome considerably by external force. But it is possible to increase buckling strength by the use of roofing covering materials connected to framework. In a case like this, shearing rigidity of roofing material increases buckling strength of the overall structure and can be designed economically from the viewpoint of practice. Therefore, the purpose of this paper, in Lamella dome and rectangular latticed dome that are a set of 2-way grid dome, is to clarify the effects of roofing covering materials for increasing of buckling strength of overall dome. Analysis method is based on FEM dealing with the geometrically nonlinear deflection problems. The conclusion were given as follows: 1. In case of Lamella domes which have nearly equal rigidity in the direction of circumference, the rigidity of roofing covering materials does not have a great influence on buckling-strength, but in rectangular latticed domes that has a clear periodicity of rigidity, the value of its buckling strength has a tendency to increase considerably with increasing rigidity of roofing covering materials 2. In case of rectangular latticed domes, as rise-span-ratio increases, models which is subjected to pressure -type-uniform loading than vertical-type-uniform loading are higher in the aspects of the increasing rate of buckling- strength according to the rate of shear reinforcement rigidity, but in case of Lamella dome, the condition of loading and rise-span-ratio do not have a great influence on the increasing rate of buckling strength according to the rate of shear reinforcement rigidity.

• Magazine of the Korea Concrete Institute
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• v.10 no.6
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• pp.149-159
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• 1998

The reasonable prediction of time-dependent deformation of prestressed concrete(PSC) box girder bridges is very important for accurate construction as well as good serviceability. The long-term behavior is mostly influenced by the probabilistic characteristic of creep and shrinkage. This paper presents a method of statistical analysis and sensitivity analysis of creep and shrinkage effects in PSC box been taken into account - model uncertainty, parameter variation and environmental condition. The statistical and sensitivity analyses are performed by using the numerical simulation of Latin Hypercube sampling. For each sample, the time-dependent structural analysis is performed to produce response data, which are then statistically analyzed. The probabilistic prediction of the confidence limits on long-term effects of creep and shrinkage is then expressed. Three measure are examined to quantify the sensitivity of the outputs of each of the input variables. These are rank correlation coefficient(RCC), partical rank correlation coefficient(PRCC) and standardiozed rank regression coefficient(SRRC) computed on the ranks of the observations. Three creep and shrinkage models - i. e., ACI model. CEB-FIP model and the model in Korea Highway Bridge Specification - are studied. The creep model uncertainy factor and the relative humidity appear to be the most dominant factors with regard to the model output uncertainty.

• Journal of the Korea Concrete Institute
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• v.19 no.5
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• pp.569-575
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• 2007

The repair of concrete surfaces does not normally take into account structural tolerance for longer service lift and better capabilities of concrete structures. In particular, the repair of surface spelling completes as mortar is applied, which does not display additional structural performances. The use of crimped wire mesh for better construction and fracture resistance, however, expects to have some reinforcement effects. Particularly, it is also expected that the repair of bottom part in structures built between bridges like irrigation structures results in the increase of flexural resistance. Therefore, this study is intended to perform the repair using crimp wire mesh and examine strength depending on the repair section and depth. For this, a slab with 150 mm in depth, 3,000 mm in length and 600 mm in width and total 8 objects to experiment such as upper part, upper whole, bottom part, bottom whole and crimp wire mesh reinforced are manufactured to perform flexural performance. The results of the analysis show that yield strength and failure load increase as the depth of repair materials in the experiment reinforced with crimp wire mesh get bigger. In the same condition, repair of bottom part is able to increase internal force of bending force. Besides, the results show that partial repair of structures under bending force cannot produce flexural performance. Consequently, the repair method with crimp wire mesh results in the increase of flexural resistance.

• Journal of the Korean earth science society
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• v.21 no.3
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• pp.208-218
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• 2000

The popularization and the common use of internet are realizing these days thanks to the development of web. Using the web as a teaching instrument is the Web Based Instruction(WBI). WBI, along with constructivism, has a great influence on the present educational society. However, many problems were found in learners' using the numerous WBI programs in cyber space. Above all, the interaction between teachers and learners is not enough, and searching for the materials on web is not easy. It's very difficult for a teacher to design and construct a WBI program in school teaching. But It is not so difficult to design and construct a WBI program based on interaction. Therefore, if a teacher familiar to students in school makes a web page and provides a cyberspace, the students will interact very easily them in the cyberspace. They can use the e-mail, bulletin board or discuss and chat. The cyberspace will make up for the insufficient interaction in school life. But because this program needs all students have proper material condition, there will be another kind of estranged learners. Thus, this problem can be solved by the cheap-popular PC offering movement backed by the government, and other types of projects systematically.

• Proceedings of the KIEE Conference
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• 2008.09a
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• pp.15-17
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• 2008

본 논문은 현행 전력기술 관리법에 의하여 시행되고 있는 전력시설물공사 감리제도의 제도개선에 관한 연구로서 연구자의 현장 실무경험과 감리제도의 일반사항, 감리업자와 감리원에 대한 사항, 감리업자 선정 및 입찰에 관한 사항을 조사하여 전력시설물공사 감리제도의 현황과 실태분석 및 개선방안을 제시한 내용으로 연구결과는 다음과 같다. 첫째, 법적 및 제도적 측면에서 시급히 개선될 사항이다. 정부는 1995년 12월 법률 제5,132호로 전력기술관리법을 제정하여 전력시설물에 대한 공사감리 업무를 별도 분리 발주하여 전문성을 높이도록 전기 분야 전문기술자에 의해 수행토록 하는 것을 골자로 하는 책임 감리제도를 도입하여 오늘에 이르고 있다. 그러나 공사 준골단계에서 전기사업법 제98조 2항에 의해 위탁업무를 하고 있는 전기 안전공사가 사용전 검사를 함으로서 책임 감리제도의 도입 취지를 무색케 한 정도로 심각한 국면에 접어들었다. 전력기술관리법이 제정되어 13년이 지난 오늘까지도 책임 감리제도가 성공적으로 정착되지 못한 근본적인 문제는 사용전 검사를 전기 안전공사에서 대행하고 있다는 것이다. 물론 그동안의 많은 노력으로 어느 정도의 개선은 있었지만 근본적인 문제가 해결되지 않고서는 전력시설물공사의 감리기술의 전문화를 기대하기 어려운 실정이다. 따라서 책임 감리계도의 성공적인 정착을 위해서는 전기사업법 제98조 2항에 의한 위탁 업무인 사용전 감사 제도를 감리업자에게 돌려줌으로서 책임과 권한을 실질적으로 부여하고 감리회사 자체의 기술력 및 기술자 확보와 기술개발에 필요한 운영자금 및 투자 확대를 유도해 나가야 하며, 무엇보다도 확실한 법적 제도적 뒤받침이 선행되어야 한다. 둘째, 제도적 측면에서 일반건축물은 사업주가 전력시설물공사 감리업자를 임의선정 및 수의계약에 의해 감리업자를 지정하고 해당 공사기간동안 전기 감리원을 투입토록 되어 있어 인건비에 미치지 못하는 저가수주와 다음계약을 위해 어쩔 수 없이 사업주에게 종속되는 경우가 많으며, 이로 인해 감리수행에 혼란이 야기되고 책임소재의 불분명 책임 감리원의 조정 및 통제기능이 약화되는 부작용이 나타나고 있다. 전력시설물공사의 감리는 전력시설물의 안전사고, 비효율 및 부실소지 둥을 방지하기 위해서 필수적이고 발주자 감리업자 시공업체에게 모두 도움을 주는 업무이며, 일정규모이상의 건축물은 자발적인 참여로 유도할 수 있도록 적격심사제도(PQ심사)도입이 적극 필요한 실정이다. 셋째, 운용측면에서 공동주택의 주택법에 의한 전력시설물공사 감리는 사업승인권자가 사업수행능력 평가기준(PQ 심사)에 따라 감리업자를 지정하고 해당 공사기간 동안에 전기 감리원을 투입토록 되어 있으나 평가기준이 세대수에 따라 정해져 있어 효율적, 기술적 측면에 미치지 못하는 경우가 많다. 수준 높은 감리를 수행하려면 그에 맞는 적정한 감리원의 투입이 필수적이다. 넷째, 운용 및 제도적 측면에서 공공발주 건축물(공동주택 포함)의 전력시설물공사는 사업수행능력 평가기준(PQ 심사)에 따라 감리업자를 지정하고 해당 공사기간 동안에 전기 감리원을 투입토록 되어 있으나 발주자 소속직원의 감리수행 근거에 의해 자체 감리를 함으로서 시장경쟁 및 민간경제 활성화의 제약, 부정부패 및 비효율 등 사회에 전반적으로 악영향을 끼쳐 하루 빨리 민간 감리업자에게로의 개선이 시급한 실정이다.

• Journal of the Korean Institute of Landscape Architecture
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• v.42 no.1
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• pp.123-132
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• 2014

This study aims to develop the diagnostic evaluation method of the riverine ecobelt for construction, conservation, and maintenance of the riverine ecobelt. The value indices in the proposed evaluation method are composed of total 5 fields and 19 elements. The 5 fields are flood control, environmental function, growth of plants, ecobelt function, and restoration potential. Flood control field is composed of total 3 elements such as length, width, and density of green area. Environmental function field is composed of 4 elements such as park use, landscape boundary and edge, microclimate control, non-point pollution control. Growth of plants field is composed of 6 elements such as species composition, forest height, stratum structure, vine plants, plant vitality, and succession of plants. Ecobelt function field is composed of 4 elements such as longitudinal connectivity, lateral connectivity, in-stream forest or habitat, roads on bank top. Restoration potential field is composed of 2 elements such as landform and land use of the immediate vicinity. The score system ranging 1~4 was adopted. The weighting parameters of elements were unified with each other. The final grade system ranging 1~5(1: very good~5: very bad) was adopted, and the final grade was evaluated by the mean values of each field. According to the test application of the diagnostic evaluation method of the riverine ecobelt, the final grades showed effectively the real condition of each site.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.9
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• pp.4277-4283
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• 2012

Slip coefficient, whose value is dependent on the condition of contact surface at the friction joint of high tension bolt, is determined by slip load. Because contact area affects slip load, contact area that varies with bolt hole size is also related to the slip coefficient. In this study, we manufactured 32 specimens and performed bending and tension tests in order to examine changes in slip coefficient and load with material type, bolt diameter, and size of bolt hole. Slip load of specimens with oversize bolt hole had strength that was more than 80% higher than the slip load of specimens with standard bolt hole, and it also exceeded the design slip strength. In addition, we observed significant correlation between net-section ratio and slip ratio of specimens with oversize and standard bolt hole. However, some differences between the specimens are thought to have been caused by reduction in initial axial force of high tension bolt, which is an important parameter of slip coefficient. It is self-evident that increased bolt hole size would lead to decrease in design strength as it reduces both slip coefficient and bolt axial force. Nevertheless, we suggest that some flexibility in regulation of bolt hole, as long as it does not threaten the structural stability, may be a positive factor in terms of workability and efficiency.