• Proceedings of the KWS Conference
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• 2009.11a
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• pp.121-121
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• 2009

자동차는 코너 주행 시 In-corner와 Out-corner 의 바퀴 궤적이 달라지므로, 특별한 장치가 없이 좌우 구동 측의 바퀴가 같은 속도로 회전을 하게 되면 정상적인 주행이 불가능하다. 따라서 정상적인 코너 주행이 가능 하려면, 코너 안쪽 바퀴보다 바깥쪽 바퀴가 더 빨리 회전해야 하며 이러한 회전 차를 보상받지 못할 경우 바깥쪽 바퀴가 끌리는 현상이 발생하는데 이를 방지하기 위해 디퍼렌셜 기어가 필요하다. 현재 디퍼렌셜 기어는 디퍼렌셜 케이스와 링기어를 볼트로 체결하는 조립 공법을 통해 생산되고 있다. 하지만 볼트 체결 공법은 조립을 위한 볼트와 볼트 체결을 위한 플랜지와 볼팅을 위한 홀을 가공하는 공정이 필요하기 때문에 재료비 절감 및 생산 효율 향상에 매우 불리하고 볼트체결을 위한 부분 때문에 불필요한 무게가 증가하게 된다. 따라서 본 연구에서는 이러한 기계적 체결 방식을 레이저 용접 방식으로 대체하여 재료비를 절감하고 무게 저감을 통해 주행성능을 향상시키고자 하였다. 링기어의 소재는 침탄처리강(SCM420H)이며 디퍼렌셜 케이스의 소재는 주철(GCD500)을 사용하고 있다. 주철은 용접시 용접부와 열영향부에서 마르텐사이트 조직과 레데브라이트, 시멘타이트 조직이 생성되며 고탄소 모재의 탄소 확산으로 인한 부분 혼합영역에서 탄소 합금이 생성되어 균열이 발생하는 등 용접성이 매우 좋지 않은 것으로 알려져 있다. 이러한 주철의 난용접성을 해결하는 방법으로는 고탄소 모재 용접시 발생하는 탄소의 확산을 억제하거나 예열이나 후열 처리를 통한 냉각 속도의 제어하는 방법과 오스테나이트 안정화 원소를 첨가한 필러와이어를 사용하여 용접시 마르텐사이트와 시멘타이트의 성장을 방해하는 방법 등이 이용되고 있다. 본 연구에서는 예열처리나 후열처리를 통한 주철의 용접법은 대량 생산을 통한 원가절감을 노리는 자동차 업계의 특성에 비추어 볼 때 비용이나 프로세스 구성 면에서 적용하는 것이 어려울 것이라 판단하여 Ni-base filler metal을 통한 주철의 용접법을 선택하였고 그 결과 실차에 적용하기 위한 비틀림 강성 테스트나 내구 테스트는 통과하였으나 NVH 테스트 결과 볼팅 체결 방식에 비하여 소음이 커지는 문제가 발생하고 링기어의 HAZ부가 고경화 되는 문제가 발생하였다. 때문에 용입깊이를 초기 시제품인 5mm에서 4mm로 변경시켜 입열량 감소 및 용접변형을 줄여 소음 문제를 해결하고자 하였으며 링기어의 침탄층을 1mm 절삭하여 링기어 HAZ부의 고경화 문제를 해결하고자 하였다. 이러한 용접 구조 변경이 용접변형 및 강성과 피로에 미치는 영향력을 알아보고자 용접 및 열처리 상용 소프트웨어인 SYSWELD, 구조해석 상용소프트웨어인 NX_NASTRAN, 피로 해석 상용 소프트웨어인 FEMFAT을 이용하여 시뮬레이션 하였고 실제 구조 변경한 용접 시제품과 비교, 분석하였다.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.30 no.3
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• pp.38-45
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• 1998

Soil and water contamination caused by the abundant use of agricultural chemicals including herbicides and fertilizers draws public concerns since these chemicals may pollute the agricultural lands as well as the food products grown on these lands. As a method to reduce the use of agricultural chemicals mulching with thin plastic film has been commonly practised for many years. Although use of the plastic film for mulching is very effective in preventing the growth of weed, it is almost impossible to remove all of the plastic film from the agricultural land and the remaining film eventually contaminates the soils. Therefore, it is very imperative to develop a mulching material that decomposes completely to prevent soil pollution problems and to enhance the competitive edge of domestic agriculture. Mulch papers are believed to have many positive characteristics in preventing problems caused by the plastic mulch film since it decomposes completely after use. However, the basis weight of mulch papers needs to be reduced to improve its handling properties and to reduce the raw material costs of pulps. In this paper the possibilities of using domestic old corrugated containers in producing mulch papers were examined. Also use of unbleached softwood kraft pulps and dry strength additives were exploited along with two-layered sheet forming technology in decreasing the basis weight of the mulch paper. Results showed that reduction of 20g/$m^2$ of basis weight of mulch paper was possible by the appropriate raw material selection and application of strength resin. To use the mulch papers in paddy fields, however, further research to improve its durability should be pursued.

• Korean Journal of Remote Sensing
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• v.21 no.6
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• pp.457-468
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• 2005

Increasing of impervious surface resulting from urban development has negative impacts on urban environment. Therefore, it is absolutely necessary to estimate and quantify the temporal and spatial aspects of impervious area for study of urban environment. In many cases, conventional image classification methods have been used for analysis of impervious surface fraction. However, the conventional classification methods have shortcoming in estimating impervious surface. The DN value of the each pixel in imagery is mixed result of spectral character of various objects which exist in surface. But conventional image classification methods force each pixel to be allocated only one class. And also after land cover classification, it is requisite to additional work of calculating impervious percentage value in each class item. This study used the spectral mixture analysis to overcome this weakness of the conventional classification methods. Four endmembers, vegetation, soil, low albedo and high albedo were selected to compose pure land cover objects. Impervious surface fraction was estimated by adding low albedo and high albedo. The study area is the Tanchon watershed which has been rapidly changed by the intensive development of housing. Landsat imagery from 1988, 1994 to 2001 was used to estimate impervious surface fraction. The results of this study show that impervious surface fraction increased from $15.6\%$ in 1988, $20.1\%$ in 1994 to $24\%$ in 2001. Results indicate that impervious surface fraction can be estimated by spectral mixture analysis with promising accuracy.

• Journal of Korea Water Resources Association
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• v.52 no.spc2
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• pp.801-810
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• 2019

This study analyzes the impact on geomorphic changes downstream due to alternate bars developed weir upstream through laboratory experiments. The disturbance, such as a spur in the side wall, of the flow at the inlet of the channel triggers the development of alternate bar upstream at the beginning of the experiment, and gradually moved downstream with keeping their shapes over time. The bed in the downstream of weir in the mid of channel scoured due to the scarcity of sediment inflow because weir upstream traps it. Moreover, bar migration speed decreases as the bars approaches to the weir with time. However, as time increases, the alternate bars upstream migrate over the weir, and sediment in the eroded bed of the weir downstream are deposited. The phase of the bar upstream changes oppositely after passing through the weir. The phase of the bar downstream changes rapidly as the shape of alternate bar is clear upstream, which is affected by the strong disturbance. The phase of bar changes, and the bar migration speed decreases gradually with time, and finally stopped due to forcing effects on the bar by the disturbance. The faster the reaction of alternate bar with a long spur, the larger the bar height formed downstream and the shorter the bar length. This means that the larger the forcing effect of bar, the more it affects the bar migration. In addition, although the size of the alternate bar increases over time, the bar doesn't migrate downstream and a forced bar is generated.

• The Journal of the Convergence on Culture Technology
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• v.5 no.4
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• pp.329-337
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• 2019

It is true that many tales delivered in an 'Story-telling' auditorium or theater have not so much exquisite and refined forms as distorted and deteriorated ones. Furthermore, when false interpretations of tale-performers added into the category of the texts of tales, the problems can be made worse. In case of oral folk tales, there can be discordance between the standpoint of a tale-performer and the contents of a tale. This thesis is directly aimed at pointing out the 'Behavior Economics' problems concerned with the reading and interpretation of tales through investigating the missing parts of a text in reading tales. Man's rationality is meant to be confined to bounded rationality. Instead of making best choices, bounded rationality leads consumers to make a decision which they think suffices themselves to the point requiring no more consideration on the given item. It is the very Heuristic that does work in the process of this simplified decision making process. Heuristic utilizes established empirical notion and specific information, and that's why there can be cognitive 'Biases' sometimes leading to inaccurate judgment. As Oral Literature is basically based on heavy guesswork and perceptual biases of general public, it is imperative to contemplate oral literature in the framework of Heuristic of behavior economics. This thesis deals with thinking types and behavioral patterns of the general public in the perspective of heuristic by examining 'Story-tellings' on the basis of personal or public memory. In addition, heuristic involves how to deal with significant but intangible content such as the errors of oral story teller, the deviations of the story, and responses of the audience.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.257-257
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• 2019

최근 기후변화에 따른 대응을 위해 기존 수자원 활용의 고도화 및 배수능력 증대를 위해 다양한 방안이 추진되고 있으며, 그에 따라 기존 개수로에 신규 수로를 연결하여 합류와 분류를 시키는 사례가 증가하고 있다. 특히 신규 개수로 연결을 위한 분류부 형상은 관련 설계기준, 분류유량의 규모, 해당 지점의 하상변동 경향, 지형여건, 흐름 분류시설 및 구조물의 형태(양수펌프장, 스크린이나 수문, 암거설치)와 같은 구조적 요인 등에 의해 달라지지만, 이와 관련된 연구가 매우 부족한 실정이다. 따라서 본 연구에서는 2차원 수치모형을 이용하여 분류부 평면형상 변화에 따른 분류유량비와 흐름분리구역 분포 등에 대한 흐름특성을 분석하고 이수와 치수계획 수립 등에 활용하고자 한다. 본 연구에서는 TELEMAC-2D 모형을 이용하여 주수로 상류 유입흐름의 프루우드 수가 0.74, 0.52인 두 흐름에 대해 형상변화 폭을 주수로 폭(B)의 1B, 주수로 형상변화를 급확대, 점진적 확대 구간길이를 1B~3B로 변화시키며 분류유량비(분류수로 유입유량/상류 유입유량)와 흐름분리구역의 위치와 크기 등에 대한 분석을 수행하였다. 분류부 상류 유입흐름의 프루우드 수가 0.74, 분류유량비는 0.33인 흐름은 주수로 형상변화 구간길이가 1B 일 때 0.44~0.46, 3B일 때 0.54~0.60으로 점차 분류유량비가 증가한다. 반면 상류 유입흐름의 프루우드수가 0.52, 분류유량비가 0.52인 흐름은 주수로 형상변화 구간길이가 1B일 때 0.77~0.82에서 3B일 때 0.70~0.80으로 점차 분류유량비 증가율이 감소하는 경향을 나타내게 된다. 주수로 형상변화 폭을 0.5B, 1B로 달리하여 수로 형상변화를 시킨 경우 분류유량비 증가율은 각각 135~162%, 134~176%로 나타났으며, 이는 수로 형상변화 폭보다 변화구간 길이가 더 큰 분류유량비 변화에 영향을 미치는 것을 확인할 수 있다. 흐름분리구역은 상류 유입흐름의 프루우드 수가 0.74인 경우 수로형상 변화구간과 분류수로 입구에 형성되지만, 상류유입흐름의 프루우드 수가 0.52인 경우 수로형상변화 구간과 주수로 하류에도 형성된다. 수치실험 결과 동일수로 폭 직사각형 $90^{\circ}$ 분류수로에서 분류부 평면형상의 변화에 따라 주수로 하류방향흐름의 관성력은 감소하는 반면 분류수로로 향하는 횡압력경사와 흐름분리구역 발생위치 변화로 인해 분류 수로내 통수능이 증가하여 분류유량비가 급격하게 증가하게 된다. 또한 분류부 상류 유입흐름의 관성력이 작은 경우 분류부 평면형상 변화시 주수로 하류방향에서도 흐름분리구역이 형성되고 주수로 종방향 수위가 상승함에 따라 분류흐름 계획수립 시 세심한 주의가 필요하다.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.3
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• pp.209-218
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• 2011

The present study proposes a new estimation relationship for the transmission rate of the steel breakwater which is expected to make up for the weakness points in existing hard solution for shore protection. The steel breakwater consists of the wave dissipator of the dual horizontal plates, the supporting columns and their foundations, and thus its respective designs should also be conducted one by one. Furthermore, the breakwater has to ensure both functions of shore protection and structure stabilization. The study produced experimental data for the stability and safety investigation of the steel breakwater. The forces acting on the steel breakwater were classified into two categories, one is vertical up and down loads for the pile resistance and the other was maximum difference of the vertical load acting on horizontally different position for the torsion. The study applied the stability force produced by the summation of maximum pressure at each point and the safety force acting on each point simultaneously. The regular wave corresponding to the significant wave was utilized for measuring wave pressure and force. The study showed the method for the proper position of submerged upper plate by considering occurrence frequency of tide level. The design process finally determined by trial and error is proposed in the present study.

• Animal Systematics, Evolution and Diversity
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• no.nspc5
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• pp.29-46
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• 2005

As a commemorative joint survey for the 20th anniversary of the Korean Society of Systematic Zoology, molluscan fauna of Jindo Island was investigated from the materials collected from 3 localities of Jindo Island from 29th to 30th of June, 2004. A total of 77 species of 37 families were identified. Among them, 26 species of 18 families are reported for the first time in this area, including Onchidella kurodai (Taki, 1935) that is new to Korean fauna. For O. kurodai, external morphologies were described in detail with illustrations. Combining the present data with those of the previous works revealed that a total of 115 species from 43 families have been recorded in Jindo Island and its adjacent areas thus far. From a biogeographic point of view, some gastropod species (Bittium craticulatum, Mocroschisma dilatatum, Cantharidus japonicus, C. callichroa, Homalopoma sangarense, and Crepidula onyx) encountered from Jindo Island were the species previously recorded in the southern and/or eastern offshores of Korean peninsula, including Jeju Island (Choe, 1992). Along with the fact that Jindo Island contains a large number of molluscan species ranging over the Yellow Sea coast, this finding is another line of evidence supporting the Kim and Kwon (1983)'s idea that this area is an overtopping zone of marine organisms which dwell in both the Yellow sea and southern part of Korean sea waters. No comprehensive faunistic survey was not made in the present study. We expect that further supplementary study would generate more biogeographic and faunistic knowledges than what we understand through the present study.

• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.790-803
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• 2019

The dioctyl terephthalic acid (DOTP) process produces plastic plasticizers by esterification of terephthalic acid with powder in the form of octanol. In this study, the dust explosion characteristics of terephthalic acid directly injected into the manhole in the form of powder in the presence of flammable solvent or vapor in the reactor of this process were investigated. Dust particle size and particle size distribution dust characteristics were investigated, and pyrolysis characteristics of dust were investigated to estimate fire and explosion characteristics and ignition temperature. Also, the minimum ignition energy experiment was performed to evaluate the explosion sensitivity. As a result, the average particle size of terephthalic acid powder was $143.433{\mu}m$. From the thermal analysis carried out under these particle size and particle size distribution conditions, the ignition temperature of the dust was about $253^{\circ}C$. The lower explosive limit (LEL) of the terephthalic acid was determined to be $50g/m^3$. The minimum ignition energy (MIE) for explosion sensitivity is (10 < MIE < 300) mJ, and the estimated minimum ignition energy (Es) based on the ignition probability is 210 mJ. The maximum explosion pressure ($P_{max}$) and the maximum explosion pressure rise rate $({\frac{dP}{dt}})_{max}$ of terephthalic acid dust were 7.1 bar and 511 bar/s, respectively. The dust explosion index (Kst) was 139 mbar/s, corresponding to the dust explosion grade St 1.

• Ecology and Resilient Infrastructure
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• v.8 no.4
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• pp.165-178
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• 2021

We studied driftwood behaviors including generation and deposition in a tsunami using a numerical simulation. We used an integrated two-dimensional numerical model, which included a driftwood dynamics model. The study area was Sendai, Japan. Observation data collected by Inagaki et al. (2012) were used to verify the simulation results by comparing them with driftwood deposition patterns. A simplified model was developed to consider the threshold of driftwood generation by the drag force of water flows. To consider the volume of driftwood generated, we estimated the total wood number in the study area using Google Earth. Therefore, we simulated more than 13,000 pieces of driftwood that were generated and transported inland from approximately 300,000 trees that were growing in the forest. The final distribution of the driftwood was similar to the observation data. The reproducibility of the generation and deposition patterns of driftwood showed good agreement in terms of longitudinal deposition pattern. In the future, a sensitivity analysis on driftwood parameters, such as the size of the wood, boundary conditions, and grid size, will be implemented to predict the travel patterns of driftwood. Such modeling will be a useful methodology for disaster prediction based on water flow and driftwood.