• 대한기계학회논문집
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• 제17권7호
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• pp.1751-1760
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• 1993

The squeeze casting process is considered as an attractive way to form the primary product of near net shape metal matrix composites for wide use in automobile industry. To understand for infiltration limit in squeeze casting processes, the SAFFIL short fiber preform of volume fraction $10%{\sim}23%$ were fabricated by vaccum pumping and speed control press, and the optimal condition for fiber preform fabrication had been experimentally obtained. The composite materials were fabricated by forced infiltration of molten metals such as Al6061, Al7075, pure Al, AC8A, and Al2024. The infiltration distance and deformation of fiber preform are observed, and tensile strength were measured from at the room temperature.

• 융합보안논문지
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• 제5권4호
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• pp.1-6
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• 2005

네트워크 시스템에 대한 악의적인 접근과 정보위협이 증가하고, 그 피해또한 기업에서 개인 사용자까지 확대되고 있다. 침입탐지 시스템, 침입차단 시스템 등 단위 보안 기능만을 제공하는 제품은 분산화, 지능화 되어가고 있는 복합적인 침입에 대한 대응에 한계가 있다. 여러 보안 제품을 연동하여 해커의 침입탐지, 대응 및 역 추적을 위한 통합 보안 관리의 필요성이 대두되고 있다. 그러나 통합보안 관리의 특성상 다양한 보안 제품에서 전송된 이벤트와 침입경보의 양이 많아 분석이 어려워 서버측의 부담이 되고 있다. 따라서 본 논문에서는 이러한 문제점을 해결하고자 침입경보 데이터를 축약하는 방법에 대하여 연구하고자 한다.

• 대한수학회지
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• 제58권5호
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• pp.1109-1129
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• 2021

This paper considers an anisotropic polytropic infiltration equation with a source term $$u_t={\sum\limits_{i=1}^{N}}{\frac{{\partial}}{{\partial}x_i}}\(a_1(x){\mid}u{\mid}^{{\alpha}_i}{\mid}u_{x_i}{\mid}^{p_i-2}u_{x_i}\)+f(x,t,u)$$, where p_i > 1, α_i > 0, a_i(x) ≥ 0. The existence of weak solution is proved by parabolically regularized method. Based on local integrability $u_{x_i}{\in}W_{loc}^{1,p_i}(\Omega)$, the stability of weak solutions is proved without boundary value condition by the weak characteristic function method. One of the essential characteristics of an anisotropic equation different from an isotropic equation is found originally.

• 한국지반환경공학회 논문집
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• 제20권12호
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• pp.49-55
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• 2019

사면 붕괴에 대한 해석은 지반특성과 여러 가지 복합적인 인자들로 인해 정확한 해석은 어려운 것이 사실이다. 지속적으로 발생하는 사면재해로 인하여 사면재해 발생 원인을 규명하기 위한 많은 연구가 이루어지고 있지만, 사면 붕괴의 가장 중요한 요소인 강우특성 및 강우로 인한 침투능에 따른 사면 안정성 평가는 미흡한 실정이다. 본 연구에서는 주문진표준사를 이용하여 단위중량별 정수위 투수시험을 통한 투수계수를 산정하였으며, 투수계수와 강우강도의 영향을 고려하여 침투능 및 침투량을 산정할 수 있는 강우강도별 일차원 침투실험을 실시하였다. 실험결과를 바탕으로 사질토지반에서의 기존 경험식의 적용성을 분석하였다.

• 한국농공학회지
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• 제31권2호
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• pp.104-115
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• 1989

In an effort to clarify the wetted patterns of sandy loam soil under trickle irrigation conditions, the distance of wetted zone, infiltration capacity and soil wetted patterns, etc. were measured by gypsum block as soil moisture sensor located every 5 cm vertically and horizontaly in the soil bin under the such conditions as a). irrigation rates set to 2, 4, 6, 8 liters per hour b). total amount of water applied fixed to 14.62 liters per soil bin c) the hearing force of soil measured by plate penetrometer ranging from 1.04 to 1.22kg/cm$_2$ The results can be summarized as follows ; 1. The wetted distance in horizontal direction(H), the wetted distance in vertical direction(D), the horizontal infiltration capacity (iH) and the vertical infiltration capacity(in)could by explained as a function of time t. 2. The horizontal wetted distance (H) is explained by an exponetial function H= a$.$ t where b was found ranging from 021 to 026 under surface trickle irrigation, which was considered a lotlower than the classical value of 0.5 and these measurements were indifferent to the increasing irrigation rates. 3. As for the surface trickle irrigation where horizontal infiltration capacity(iH) is explained as iH = A $.$ t h, the coefficient A increases with respect to irrigation rates within the limits of 0.89~1.34. 4. In terms of surface trickle irrigation of the ratio of Dm Which is maximum vertical wetted distance to Hm, which is maximum horizontal wetted distance, found to be within range of 1.0 to 1.21. It was also noted that the value of Dm decreses when irrigation rates increases while the value of Hm changes the opposite direction. 5. The optimum location of sensors from emitter for surface trickle irrigation should he inside of hemisphere whose lateral radius is 28~30cm long and vertical radius is 10~12cm long. The distance between emitters should be within 60cm long. 6. In the study of vertical wetted distance( D) where D= a $.$ tb, the exponential coefficient b ranged from 0.61 to 0.75 in surface trickle irrigation, and from 0A9 to 0.68 for subsurface trickle irrigation. These measurements showed an increasing tendency to with respect to irrigation rates. 7. In case of vertical infiltration capacity( in), where iD= A $.$ t 1-h, the coefficient A for surface trickle irrigation found to be within range of 0.16 to 0.19 and did not show any relationships with varying degree of irrigation rates. However, the coefficient was varying from 0.09 to 0.22 and showed a tendency to increase vis-a-vis irrigation rates for subsurface trickle irrigation, in contrast. 8. In the observation of subsurface trickle irrigation, it was found that Dm/Hm ratio was within 1.52 to 1.91 and showed a decreasing tendency with respect to increasing rates of irrigation. 9. The location of sensors for subsurface trickle irrigation follows same pattern as above, with vertical distance from emitter being 10~17cm long and horizontal 22~25cm long. The location of emitter should be 50 cm. 10.The relationship between VS which is the volume of wetted soil and Q which is the total amount of water when soil is reached field capacity could be explained as VS= 2.914Q0.91and the irrigation rates showed no impacts on the above relationship.

• 한국물환경학회지
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• 제32권1호
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• pp.36-45
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• 2016

강우유출수 오염물 제거를 위한 침투시설에서 모래필터가 널리 적용된다. 공극폐색, 즉 필터 여재에 부유물이 침전되면 침투능이 저하되어 침투시설의 기능과 수명이 단축된다. 침투시설의 효과적인 설계 및 유지관리를 위해 모래필터 내의 물리적, 화학적, 생물학적 폐색 특성을 알아야 한다. 이 논문에서는 여재 깊이 변화에 따른 모래필터의 물리적 폐색 특성변화를 검토하였다. 연직방향, 변수위 침투조건에서 시행한 실험실 컬럼 침투실험으로부터 이들 특성변화를 관찰하였다. 실험결과, 폐색현상의 결과로서 필터의 여재 깊이가 증가할수록 부유물 제거효율이 증가하지만, 필터의 성능유지 기간은 감소하는 현상을 보였다. 모든 여재 깊이 조건에서 여재 깊이의 상부 15%에서 100~250 μm의 부유물이 침전되면서 폐색현상이 발현하는 조기폐색이 발생했다. 결과에 근거하여 침투시설의 첫번째 유지관리 시침투능 확보를 위해 여재깊이의 상부 15%를 긁어내는 방법을 제안할 수 있었다.

• Molecules and Cells
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• 제19권3호
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• pp.350-355
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• 2005

Selectins are carbohydrate-binding cell adhesion molecules that play a major role in the initiation of inflammatory responses. Heparin can bind to P-selectin, and its anti-inflammatory property is mainly due to inhibition of P-selectin. However, the strong anticoagulant activity of heparin limits its clinical use. We prepared periodate-oxidized, borohydride-reduced heparin (RO-heparin) by chemical modification and tested its anticoagulant and anti-inflammatory activities. Activated partial thromboplastin time (aPTT) assays showed that, compared with heparin, RO-heparin had greatly reduced anticoagulant activity. Intravenous administration of this compound led to reduction in the peritoneal infiltration of neutrophils in a mouse acute inflammation model. In vitro cell adhesion experiments demonstrated that the effect of RO-heparin on inflammatory responses was mainly due to inhibiting the interaction of P-selectin with its ligands. These results indicate that RO-heparin may be a safer treatment for inflammation than heparin, especially when selectin is targeted.

• 한국패류학회지
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• 제27권4호
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• pp.283-289
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• 2011

염분변화에 따른 북방전복의 생리적 반응을 조사하기 위하여 고염분 및 저염분의 농도에 따라 생존율, 삼투질농도, 대사율 및 조직학적 반응을 분석하였다. 염분변화에 따른 북방전복의 생존율은 37 psu에서는 100%였다. 반면 19.8 psu에서 노출 6일째, 12.8 psu 이하에서는 노출 24시간 이내 모두 사망하여 북방전복의 7-days $LS_{50}$은 24.9 psu (20.1-28.2 psu)를 나타내었다. 염분변화에 따른 호흡률은 대조구에 비해 감소하였으며, 반면 암모니아질소 배설률은 증가하였다. 삼투질농도는 염분 26.8 psu이상에서는 1시간 이내 순치하였다. 북방전복 발근육의 조직학적 반응은 염분감소에 따라 혈림프동의 확장, 상피세포의 괴사 및 식세포 증가 등의 현상이 관찰되었다.

• Journal of Periodontal and Implant Science
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• 제40권2호
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• pp.49-55
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• 2010

Purpose: The purpose of this study was to preliminarily evaluate the influence of diabetes mellitus (DM) on periodontal tissue without establishment of periodontitis. Methods: Seven-week-old db/db mice were used for the diabetic experimental group and systematically healthy mice of the same age were used as controls. After 1 week of acclimatization, the animals were sacrificed for hard and soft tissue evaluation. The pattern of bone destruction was evaluated by stereomicroscope evaluation with alizarin red staining and radiographic evaluation by microscopic computerized tomography images. Histological evaluation was performed with hematoxylin and eosin stain for evaluation of soft tissue changes. Results: In both stereomicroscope evaluation and radiograph image analysis, aggressive form of bone destruction was observed in diabetic animals when compared to the systematically healthy controls. In histological evaluation, apical migration of junctional epithelium with slight inflammatory cell infiltration was observed with disarrangement of connective tissue fibers. Conclusions: Within the limits of this study, diabetic animals presented distortion in periodontal attachment and an aggressive bone loss pattern when compared to the healthy controls, suggesting that DM has an independent effect on periodontal tissue destruction irrespective of the presence or absence of periodontal disease.

• 한국연소학회지
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• 제20권4호
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• pp.34-41
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• 2015

Oxy-methane nonpremixed flames diluted with $CO_2$ were investigated to clarify impact of radiation heat loss and chemical effects of additional $CO_2$ to oxidizer stream on flame extinction. Flame stability maps were presented with functional dependencies of critical diluents mole fraction upon global strain rate at several oxidizer stream temperatures in $CH_4-O_2/N_2$, $CH_4-O_2/CO_2$, and $CH_4-O_2/CO_2/N_2$ counterflow flames. The effects of radiation heat loss on the critical diluent mole fractions for flame extinction are not significant even at low strain rate in nonpremixed $CH_4-O_2/N_2$ diffusion flame, whereas those are significant at low strain rate and are negligible at high strain rate (> $200s^{-1}$) in $CH_4-O_2/CO_2$ and $CH_4-O_2/CO_2/N_2$ counterflow flames. Chemical effects of additional $CO_2$ to oxidizer stream on the flame extinction curves were appreciable in both $CH_4-O_2/CO_2$ and $CH_4-O_2/CO_2/N_2$ flames. A scaling analysis based on asymptotic solution of stretched flame extinction was applied. A specific radical index, which could reflect the OH population in main reaction zone via controlling the mixture composition in the oxidizer stream, was identified to quantify the chemical kinetic contribution to flame extinction. A good correlation of predicted extinction limits to those calculated numerically were obtained via the ratio between radical indices and oxidizer Lewis numbers for the target and baseline flames. This offered an effective approach to estimate extinction strain rate of nonpremixed oxy-methane flames permitting air infiltration when the baseline flame was taken to nonpremixed $CH_4-O_2/N_2$ flame.