• Transactions of Materials Processing
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• v.31 no.3
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• pp.129-135
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• 2022

The purpose of this study was to quantitatively evaluate the influence of hardness of tool materials on wear resistance in the sheet metal forming process. Punches used in the wear test were made of STD-11 and K340 tool material, and the tempering temperature was set to 530℃ and 500℃, respectively, to control the hardness of the tool materials. The punches mimic the shape of stamping tool of automotive body component to reflect its plastic deformation, and are designed to concentrate wear on the curvature region of punches. Progressive die and coil sheet were used to save time, cost, and raw sheet materials. By quantitatively measuring the wear depth of the punches, the wear behavior and mechanism of the punches were investigated, and characteristics of hardness and wear resistance according to tool materials and tempering temperatures were evaluated. Testing results indicate that the punch made of K340 tool steel with higher hardness had better wear resistance than that of STD-11 tool steel, and the hardness and wear resistance of tool steel were significantly impacted by the tempering temperature.

• IE interfaces
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• v.12 no.4
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• pp.557-566
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• 1999

This paper considers a door-to-door service system in which pickups or deliveries are performed by a trip of a single vehicle. Each customer request specifies the quantity of the load transported, the location, and the time window within which it is to be picked up or delivered. Since the system is demand responsive, i.e., new or emergent requests become available in real-time, the current vehicle route has to be reconstructed to include these requests. In this case, only continuous vehicle tracking enables control over the requests and ensures that the requests are satisfied on time. This paper suggests a pilot pickup/delivery management system integrating a geographic information system(GIS) and a global position system(GPS) to efficiently deal with such a dynamic environment. The GIS offers a way of displaying the vehicle route on digital maps for the region under concerned. Also displayed is the current location of the vehicle obtained from the GPS. A heuristic algorithm is used to dynamically determine the vehicle route. A practical example is provided to show the feasibility of the system.

• Journal of the Korean Geographical Society
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• v.35 no.4
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• pp.529-547
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• 2000

과소지역 보은군의 목적별 통행이라는 교통수요와 이용 교통수단의 기능을 고찰한 결과 다음과 같은 점이 밝혀졌다. 먼저 보은군 주민은 의무적 통행보다 자유재량 통행의 공간적 범위가 넓고, 교통수단의 선택은 제한성, 편리성, 신속성에 의한다. 또 비벽지지역에서 근무.통근, 고급품 구매, 통원통행은 편리성 때문에 자가용 자동차의 이용이 많고, 통학은 제한성 때문에 비벼지지역이나, 벽지지역 모두 군내버스를 , 벽지지역에서의 고급품 구매는 편리성과 제한성 때문에 자가용 자동차와 시외버스를 많이 이용한다. 그리고 벽지지역의 통원은 공공 교통수단의 제한성에도 불구하고 병.의원이 집중한 상위 중심지를 방문한다.

• Nuclear Engineering and Technology
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• v.30 no.3
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• pp.222-234
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• 1998

The Westinghouse OT$\Delta$T DNB protection logic heavily restricts the operation region by applying the same logic for a full range of operating pressure in order to maintain its simplicity. In this work, a fuzzy neural network method is used to estimate the DNB protection limit using the measured average temperature and pressure of a reactor core. Fuzzy system parameters are optimized by a hybrid learning method. This algorithm uses a gradient descent algorithm to optimize the antecedent parameters and a least-squares algorithm to solve the consequent parameters. The proposed method is applied to Yonggwang 3&4 nuclear power plants and the proposed method has 5.99 percent larger thermal margin than the conventional OT$\Delta$T trip logic. This simple algorithm provides a good information for the nuclear power plant operation and diagnosis by estimating the DNB protection limit each time step.

• Journal of Industrial Technology
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• v.14
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• pp.89-100
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• 1994

The effects of transient inrush currents on the dynamic characteristics of percentage differential relays are studied when the power transformers are reenergized. An algorithm of estimation the nonlinear magnetic property of power transformer and current trnasformer core are developed. Using this method, we can analyze the effect of inrush currents on the trip region of the percentage differential relays corresponding to the variation of the phase angle and the residual magnetism at the instant of switch closing. Test results are used to verify the availibility of the proposed algorithm. Finally a case study is performed to the 110 MVA main transformer in hydraulic power station.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.317-319
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• 2003

This paper describes an adaptive distance relay for double-circuit line protection with mutual impedance and fault resistance. Double-circuit lines have two operating condition; both lines of a double-circuit line are in operation and one line is switched-off and both ends of the line are grounded. For optimal distance protection, the trip region is calculated, which have respect to mutual impedance and fault resistance.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05a
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• pp.515-520
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• 1996

Since the conventional Westinghouse DNB (Departure from Nucleate Boiling) protection logic is implemented on analog circuits, the logic must be very simple. However, if the DNB protection logic is implemented in a digital processor, a little bit of complexity can be allowed to increase the thermal (or operation) margin. The Westinghouse OTΔT DNB protection logic heavily restricts the operation region by applying the same logic for a full range of pressure in order to maintain its simplicity. In this work, the different DNB protection logic is used for several regions of pressure. The proposed method is applied to Yonggwang 1&2 nuclear power plants and it is calculated that the improved OTΔT can have 5.07% percent more thermal margin than the conventional OTΔT trip logic.

• Journal of the Korean earth science society
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• v.34 no.3
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• pp.274-285
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• 2013

The purpose of this study was to develop geological field study sites for learning topography and geology of the area with igneous rocks, specifically in Duibaejae volcanic edifice and Seonang-bawi that were distributed in Goseong-gun, Gangwon-do area. As a follow up, we conducted a study to examine the effect of the study sites when applied to high school freshmen Earth science course. The study proceeded based on the Orion's model in the order of preparatory unit, field trip, and summary unit. The geological field study sites were developed based on the geological study elements presented in the Korean Earth science curriculum. Before the field trip, students simply memorized factual knowledge on minerals, rocks and etc., and showed very low level of understanding on the formation process of the region that was distributed with granite and basalt. Especially, their understanding showed that granite and basalt were formed from the same magma at the same time. After the field trip, they increased in-depth level of understanding about minerals, rocks, and geological structures, but were not able to explain the topographical characteristics of the two rocks because they did not recognize the times of the creation of granite and basalt. The reason is that they have learned the simple concept of the process of forming granite and basalt in their middle school, but that they have not learned the meaning of the difference between two the geological eras when each of the two rocks, granite and basalt, were formed.

• Atmosphere
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• v.23 no.4
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• pp.425-441
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• 2013

This study investigates the projections of water cycle, budget and river discharge over land in the world at the end of twenty-first century simulated by atmosphere-ocean climate model of Hadley Centre (HadGEM2-AO) and total runoff integrating pathways (TRIP) based on the RCP scenario. Firstly, to validate the HadGEM2-AO hydrology, the surface water states were evaluated for the present period using precipitation, evaporation, runoff and river discharge. Although this model underestimates the annual precipitation about 0.4 mm $mon^{-1}$, evaporation 3.7 mm $mon^{-1}$, total runoff 1.6 mm $mon^{-1}$ and river discharge 8.6% than observation and reanalysis data, it has good water balance in terms of inflow and outflow at surface. In other words, it indicates the -0.3 mm $mon^{-1}$ of water storage (P-E-R) compared with ERA40 showing -2.4 mm $mon^{-1}$ for the present hydrological climate. At the end of the twenty-first century, annual mean precipitation may decrease in heavy rainfall region, such as northern part of South America, central Africa and eastern of North America, but for increase over the Tropical Western Pacific and East Asian region. Also it can generally increase in high latitudes inland of the Northern Hemisphere. Spatial patterns of annual evaporation and runoff are similar to that of precipitation. And river discharge tends to increase over all continents except for South America including Amazon Basin, due to increased runoff. Overall, HadGEM2-AO prospects that water budget for the future will globally have negative signal (-8.0~-0.3% of change rate) in all RCP scenarios indicating drier phase than the present climate over land.

• The Journal of the Korea Contents Association
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• v.12 no.7
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• pp.437-444
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• 2012

This study features an analysis of the socio-economic factors of ten cities on the Honam-line that affect the number of train passengers. The 3 main factors based on the principal component analysis were the population, the distance between two regions, and the area size of each region while the number of automobiles has been conventionally used instead of the area size of each region. A formula to predict the train passengers by the regression analysis was developed and showed a good agreement to the number of real passengers. When Honam highspeed railway is opened, the traveling time between two regions as well as the area size of each regions should be more precisely considered.