• 토지주택연구
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• 제1권1호
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• pp.59-65
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• 2010

The paper presents a comparison between a semi-implicit time integration linear finite element implementation and fully-implicit nonlinear Newton-Raphson finite element implementation of a triphasic small strain mixture formulation of an elastic partially saturated porous medium. The pore air phase pressure pa is assumed atmospheric, i.e., $p_a$ = 0, although the formulation and implementation are general to handle increase in pore air pressure as a result of loading, if needed. The solid skeleton phase is assumed linear isotropic elastic and partially saturated 'consolidation' in the presence of surface infiltration and traction is simulated. The verification of the implementation against an analytical solution for partially saturated pore water flow (no deformation) and comparison between the two implementations is presented and the important of the porosity-dependent nature of the partially saturated permeability is assessed on comparison with a commercial code for the partially saturated flow with deformation. As a result, the response of partially saturated permeability subjected to the porosity influences on the saturation of a soil, and the different behaviors of the partially saturated soil between staggered and monolithic coupled programs is worth of attention because the negative pore water pressure in the partially saturated soil depends on the difference.

• 대한의용생체공학회:의공학회지
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• 제21권3호
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• pp.261-271
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• 2000

벽면운동(wall motion)과 임피던스 페이즈앵글(impedance phase angle; 압력파와 유랑파 기아의 위상차)을 고려하여 맥동유동하에 있는 복부대동맥 분기관모델에서 2차원 전산유체해석을 수행하였다. 해석결과 분기광 근처에서응 전단응력의 크기가 매우 급격한 변화를 보임을 관찰하였고 벽면운동은 전단응력의 진폭을 감소시키는 효과를 가져왔다. 임피던스 페이즈 앵글이 음의 값을 향해 갈수록 시간 평균된 벽면 전단응력(mean wall shear stress)의 값은 감소하였으나 진폭(amplitude of wall shear stress)은 오히려 증가하였다. 페이즈앵글의 영향은 평균 벽면전단응력이 영에 근접하는 외벽(outer wall or lateral wall)의 바같쪽으로 휘어지는 부분(curvature site)에서 상대적으로 크게 나타났는데 $-90^{\circ}$ 페이즈앵글(혈류파가 혈압파를 1/4주기 앞서는 경우)일 경우에 $0^{\circ}$의 경우에 비해 평균은 $50\%$정도 감소하였고 진폭은 $15\%$정도의 상승를 나타내었다. 그러므로 고혈압 환자와 같이 큰 음의 페이즈앵글을 갖는 경우, 벽면전단응력의 평균은 낮아지고 시간에 따라 변화량(진폭)은 증가하므로 low and oscillatory wall shear stress 이론에 의하면 동맥경화에 더 민감하게 된다. 비뉴턴유체로 모델링한 경우에는 뉴턴유체의 경우에 비해 벽면전단응력의 평균값이 증가하므로서 동맥경화에 덜 민감하게 된다.

• 한국운동역학회지
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• 제14권3호
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• pp.83-98
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• 2004

The purpose of this study was to investigate the test-retest of plantar pressures using the F-Scan system over speeds and plantar regions. 6 healthy female subjects in 20's were recruited for the study. Plantar pressure measurements during locomotor activities can provide information concerning foot function, particularly if the timing and magnitude of the loading profile can be related to the location of specific foot structures such as the metatarsal heads. The Tekscan F-Scan system consists of a flexible, 0.18mm thick sole-shape having 1260 pressure sensors, the sensor insole was trimmed to fit the subjects' right. left shoes - sneakers shoes & dress shoes. It was calibrated by the known weight of the test subject standing on one foot. The Tekscan measurements show the insole pressure distribution as a function of the time. This finding has important implications for the development of plantar pressure test protocols where the function of the forefoot is important. According to the result of analysis it is as follows 1) Center of force trajectory in women's dress shoes display direct movement, compare with center of force trajectory in Sneaker shoes displays a little bit curved slow pronation movement. Sneaker shoes in forefoot part display very quick supination movement, therefore, this shoes effects negative effectiveness for ankle's stability Considering center of force trajectory analyzing the more center of force close straight line, the more movement can be quick movement for locomotion. For foot pressure distribution, center of force trajectory in locomotion is better to curved trajectory with pronation movement. So sneaker shoes style is good shoes considering center of pressure distribution trajectory compare with women's dress shoes. 2) Women's dress shoes increased peak pressure in medial, this is effected by high hill's height. The more increased women's dress shoes's height, the more women's peak pressure will increase, pronation can increase compare with before. Supination movement increase, this focused pressure in lateral, also, supination increased more. If the supination movement increased, foot pressure focused in lateral, therefore, it is appeared force distribution in gait direction. This is bad movement in foot's stability. 3) Women's dress shoes in landing phase displayed a long time, this is when women's dress shoes wear, gait movement is unbalance, so, landing phase displayed a long time. For compensation in gait, swing phase quick movement. 4) Women's dress shoes displayed peak pressure distribution in lateral of rearfoot part, Sneakers shoes displayed peak pressure distribution in medial of forefoot part. Its results has good impact absorption compare with women's dress shoes. In forefoot part, sneakers shoes has good propulsive force compare with women's dress shoes.

• 한국세라믹학회지
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• 제32권3호
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• pp.394-402
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• 1995

Electrical conductivity and thermoelectric power of the ferrous ferrite system of (Mg0.29-yMnyFe0.71)3-$\delta$O4 have been measured as function of the thermodynamic variables, cationic composition(y), temperature(T) and oxygen partial pressure(Po2) under thermodynamic equilibrium conditions at elevated temperatures. On the basis of the electrical properties-phase stability correlation, the stability regions of the ferrite spinel and its neighboring phases have been subsequently located in the log Po2 vs. y and log Po2 vs. 1/T planes in the ranges of 0 y 0.29, 1100 T/$^{\circ}C$ 1400 and 10-14 Po2/atm 1. The stability region, Δlog Po2(y, 1/T), of the ferrite spinel single phase widens with increasing Mn-content(y) and the boundaries of each region are linear against 1/T with negative slopes.

• 전기학회논문지
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• 제61권1호
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• pp.89-93
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• 2012

c-BN films were deposited on SKH-51 steels by electron assisted hot filament CVD method and microstructure development was studied processing parameters such as bias voltage, temperature, etching and phase transformation at boundary layer between BN compound and steel to develop a high performance wear resistance tools. A negative bias voltage higher than 200V at substrate temperature of $800^{\circ}C$ and gas pressure of 20 torr in B2H6-NH3-H2 gas system was one of optimum conditions to produce c-BN films on the SKH-51 steels. Thin layer of hexagonal boron nitride phase was observed at the interface between c-BN layer and substrate.

• 한국환경과학회지
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• 제24권11호
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• pp.1371-1384
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• 2015

This study analyzes the characteristics of Western North Pacific (WNP) tropical cyclone (TC) activity and large-scale environments according to the Western Pacific (WP) teleconnection pattern in summer. In the positive WP phase, an anomalous cyclone and an anomalous anticyclone develop in the low and middle latitudes of the East Asia, respectively. As a result, southeasterlies are reinforced in the northeast area of the East Asia including Korea and Japan which facilitates the movement of TC to this area, whereas northwesterlies are reinforced in the southwest area of the East Asia including South China and Indochina Peninsula which blocks the movement of TC to this area. Due to the spatial distribution of this reinforced pressure system, TCs develop, move, and turn more to the northeast of WNP than those in the negative WP phase. Consequently, the characteristics of this TC activity in the positive WP phase are associated with the location of upper tropospheric jet further to the northeast. Meanwhile, TCs in the negative WP phase mainly move to the west from Philippines toward south China and Indochina Peninsula. Furthermore, due to the terrain effect caused by the high passage frequency of TCs in the mainland China, the intensity of TCs are weaker than those in the positive WP phase.

• 대한물리의학회지
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• 제16권3호
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• pp.21-27
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• 2021

PURPOSE: This study examined the relationship between the severity of a hallux valgus (HV) deformity and the kinetic three-dimensional ground reaction force (GRF) through a motion analysis system with force platforms in individuals with a HV deformity during normal speed walking. METHODS: The participants were 36 adults with a HV deformity. The participants were asked to walk on a 6 m walkway with 40 infrared reflective markers attached to their pelvic and lower extremities. A camera capture system and two force platforms were used to collect kinetic data during gait. A Vicon Nexus and Visual3D motion analysis software were used to calculate the kinetic GRF data. RESULTS: This research showed that the anterior maximal force that occurred in the terminal stance phase during gait had a negative correlation with the HV angle (r = -.762, p < .01). In addition, the HV angle showed a low negative correlation with the second vertical maximal force (r = .346, p < .05) and a moderate positive correlation with the late medial maximal force (r = .641, p < .01). CONCLUSION: A more severe HV deformity results in greater abnormal translation of the plantar pressure and a significantly reduced pressure force under the first metatarsophalangeal joint.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1228-1229
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• 2008

The composites were fabricated 61[vol.%] ${\beta}$-SiC and 39[vol.%] $TiB_2$ powders with the liquid forming additives of 12[wt%] $Al_2O_3+Y_2O_3$ as a sintering aid by pressure or pressureless annealing at 1,650[$^{\circ}C$] for 4 hours. Reactions between SiC and transition metal $TiB_2$ were not observed in the microstructure and the phase analysis of the SiC-$TiB_2$ electroconductive ceramic composites. Phase analysis of SiC-$TiB_2$ composites by XRD revealed mostly of ${\alpha}$-SiC(6H), $TiB_2$, and In Situ $YAG(Al_5Y_3O_{12})$. The relative density, the flexural strength and the Young's modulus showed the highest value of 88.32[%], 136.43[MPa] and 52.82[GPa] for pressure annealed SiC-$TiB_2$ composites at room temperature. The electrical resistivity showed the lowest value of 0.0162[${\Omega}{\cdot}cm$] for pressure annealed SiC-$TiB_2$ composite at 25[$^{\circ}C$]. The electrical resistivity of the pressure annealed SiC-$TiB_2$ composite was positive temperature coefficient resistance (PTCR) but the electrical resistivity of the pressureless annealed SiC-$TiB_2$ composites was negative temperature coefficient resistance(NTCR) in the temperature ranges from 25[$^{\circ}C$] to 700[$^{\circ}C$].

• 한국전산구조공학회논문집
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• 제34권6호
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• pp.371-383
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• 2021

강-콘크리트 편개형 방폭문은 외피 구조로서의 강박스 내에 콘크리트 슬래브가 채워진 구조로서 힌지 및 렛치와 같은 지지부재에 의해 벽체에 고정되어 설치된다. 폭압이 작용하는 방향과 같은 정방향으로의 처짐 거동에 대해서는 많은 연구가 되어 왔으나, 부방향 처짐 거동에 대한 연구는 상대적으로 미흡한 수준이다. 본 연구에서는 폭압을 받는 편개형 방폭문의 부방향 처짐 단계에서 발생하는 반발 거동(rebound behavior)에 대해 유한요소해석으로 변수 분석을 하였다. 분석결과에 따르면 방폭문의 소성변형 내지는 파괴 정도, 반발작용 전후의 운동량 및 운동에너지 변화가 반발거동에 영향을 미치는 주요 요소로 분석되었다. 또한, 방폭문의 거동 특성이 준정적 영역에 속하는 경우에 비해 충격영역에 속하는 경우에서 더 큰 반발력이 발생하는 것으로 나타났는데, 이와 같은 결과는 변형에너지 보다 운동에너지가 상대적으로 더 크게 증가하는 충격영역에서의 거동 특성이 원인인 것으로 사료된다. 반발작용의 결과로 인해 지지부재에 과도한 변형이 발생할 수 있으므로 성능분석 및 설계 과정에서 이에 대한 고려가 필요하다. 또한, 부압이 미치는 영향을 검토한 결과에 따르면 강-콘크리트 방폭문의 경우에서도 반발에 의한 영향 및 부압 모두가 방폭문의 부방향 처짐에 기여할 때 반발력이 상대적으로 더 크게 증가하는 것으로 나타났다. 이와 같은 중첩 효과의 발생조건은 구조체 특성 및 폭발조건 등에 따라 다를 수 있으므로 이에 대해서는 더 많은 연구가 필요할 것으로 판단된다.

• 한국산학기술학회논문지
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• 제18권4호
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• pp.544-549
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• 2017

본 논문은 오존 방식 선박평형수 처리의 핵심 장치인 이젝터에 대하여 회전 운동하는 구동 유체가 기체-액체 이젝터의 효율에 미치는 영향에 관한 연구이다. 이젝터는 오존을 구동 노즐을 통해 분사되는 고압 액체(선박평형수)와 주변부의 저압 기체 간의 운동량 교환으로 발생되는 부압에 의해 기체(오존)를 흡입시키는 장치이다. 기존의 이젝터는 단순한 형태로 구동 유체가 분사되지만, 본 논문에서는 구동 노즐부에 회전 유도장치를 적용하여 구동 유체가 회전 운동하며 분사될 수 있도록 한다. 구동 유체의 회전 운동 유무에 따른 유동 특성을 파악하기 위하여 전산유체해석을 이용하였으며, 구동 유체의 압력과 유량, 흡입부에 발생하는 흡입 유체의 부압과 흡입 유량, 그리고 토출 압력이 예측되었다. 그 결과를 바탕으로 회전유도 장치가 적용된 이젝터의 효율은 22.25%로 산출되었으며, 구동 유체의 회전 운동이 없는 이젝터에 비해 약 1.7%의 효율이 향상되었다. 마지막으로 전산유체해석의 타당성을 검증하고자 실험 장치를 구축하여 회전 유도 장치가 적용된 이젝터에 대한 실험을 수행하였으며, 전산유체해석 결과와 비슷한 결과를 얻을 수 있었다.