• 한국산학기술학회논문지
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• 제14권10호
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• pp.5221-5229
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• 2013

본 연구의 목표는 한국형 피난 시뮬레이션 시스템을 개발하기 위한 한국형 피난부하모델을 구축하는 것이다. 이를 위해, 피난실험을 통해 도출된 한국인의 연령 및 장애유형별 피난속도와 선행연구에서 검증된 피난시간 계산 수식을 적용하였다. 그 결과, 건물 내부의 복도와 계단 및 출입구 정보를 바탕으로 각각의 유형(연령, 장애정도 등)에 따른 재실자의 피난시간을 도출할 수 있는 피난부하모델을 도출하였다. 피난부하모델의 검증을 위하여, 기존의 피난속도 계산 프로그램인 SIMULEX와 동일한 조건하에서 피난시간을 도출하여 비교평가하였다. 피난속도가 느릴수록 상호간의 계산결과가 비슷하였지만, 피난속도가 빨라지면 도출된 피난시간 결과값이 상이함을 알 수 있었다. 이는 한국형 피난부하모델과 SIMULEX의 피난속도 계산식 함수가 상이한 것에 기인한다.

• 대한토목학회논문집
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• 제14권5호
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• pp.1253-1263
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• 1994

수평흐름에 의한 제체내의 비정상침투류를 실험을 통하여 구명한 것으로 흐름의 속도와 수위의 변동에 따른 제체내에서의 침투류영향을 고려하므로써 하천제방의 안정성증대에 목적을 두었다. 실험은 투수계수가 서로 다른 3가지 모델($K_1=3.52{\times}10^{-1}cm/sec$, $K_2=1.94{\times}10^{-1}cm/sec$, $K_3=4.19{\times}10^{-2}cm/sec$)에 대하여, 각기 흐름의 속도를 60, 70, 80, 90 cm/sec로 변화시키고 동시에 수위를 상승 또는 하강시키는 방법으로 제체내에 발생하는 수위변화를 실험을 통하여 분석하였다. 분석결과 제체내의 침투현상은 제체의 투수계수가 크고, 흐름의 속도가 작을수록 유속의 변화에 따른 영향을 많이 받음을 알 수 있으며, 제외지 수위의 상승과 강하에 따른 배면부 및 표면부에서의 수위가 유속의 영향에 따라 변화함을 알 수 있다.

• Geomechanics and Engineering
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• 제15권4호
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• pp.987-995
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• 2018

In this study, a relationship between small-strain shear modulus ($G_{max}$) and overconsolidation ratio (OCR) based on shear wave velocity ($V_S$) measurement was established to identify the stress history of centrifuge model ground. A centrifuge test was conducted in various centrifugal acceleration levels including loading and unloading sequences to cause various stress histories on centrifuge model ground. The $V_S$ and vertical effective stress were measured at each level of acceleration. Then, a sensitivity analysis was conducted using testing data to ensure the suitability of OCR function for the tested cohesionless soils and found that OCR can be estimated based on $V_S$ measurements irrespective of normally-consolidated or overconsolidated loading conditions. Finally, the developed $G_{max}$-OCR relationship was applied to centrifuge models constructed and tested under various induced stress-history conditions. Through a series of tests, it was concluded that the induced stress history on centrifuge model by compaction, g-level variation, and past overburden load can be analysed quantitatively, and it is convinced that the OCR evaluation technique will contribute to better interpret the centrifuge test results.

• 대한조선학회논문집
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• 제38권1호
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• pp.108-115
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• 2001

선박의 주기관 및 발전기의 실린더내의 폭발소음은 배기관을 통하여 연돌 상부에서 전파되어 인접한 거주구 상층부 및 bridge wing 등의 소음을 증가시키는 주 요인이 되고 있다. 본 연구에서는 실제의 배기관인 400mm 및 600mm의 지름의 관에 대하여 0m/s 및 32m/s의 유속에 대하여 25dB 및 35dB silencer에 대하여 감음 성능을 실험하였다. 관내 유속은 축류 팬에 의하여 발생시켰고 실제 소음기(silencer)를 사용하여 감음 성능을 실측하였다.

• 대한기계학회논문집A
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• 제27권8호
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• pp.1303-1308
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• 2003

This research proposes an implementation method of linearized equations of motion for multibody systems with closed loops. The null space of the constraint Jacobian is first pre-multiplied to the equations of motion to eliminate the Lagrange multiplier and the equations of motion are reduced down to a minimum set of ordinary differential equations. The resulting differential equations are functions of ail relative coordinates, velocities, and accelerations. Since the coordinates, velocities, and accelerations are tightly coupled by the position, velocity, and acceleration level constraints, direct substitution of the relationships among these variables yields very complicated equations to be implemented. As a consequence, the reduced equations of motion are perturbed with respect to the variations of all coordinates, velocities, and accelerations, which are coupled by the constraints. The position, velocity and acceleration level constraints are also perturbed to obtain the relationships between the variations of all relative coordinates, velocities, and accelerations and variations of the independent ones. The perturbed constraint equations are then simultaneously solved for variations of all coordinates, velocities, and accelerations only in terms of the variations of the independent coordinates, velocities, and accelerations. Finally, the relationships between the variations of all coordinates, velocities, accelerations and these of the independent ones are substituted into the variational equations of motion to obtain the linearized equations of motion only in terms of the independent coordinate, velocity, and acceleration variations.

• Fisheries and Aquatic Sciences
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• 제1권2호
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• pp.276-282
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• 1998

As a part of the long-term ADCP mooring program to measure the mass flux through the Korea Strait, current velocity data were obtained for 39 days in the deepest point of the strait. Near-surface velocity of this observation was compared with Izuhara-Pusan sea level difference (SLD) to investigate the geostrophic relationship. Principal direction of the Tsushima Current at the mooring station is 44.6 degrees to the north from the east. Variability of the tidal current is greater than the nontidal current by a factor of two. Correlation coefficient of tidal current against SLD is 0.46 but the nontidal current is not correlated. The current velocity (U in cm/s) can be estimated from the demeaned SLD (in cm) by the relation U=23.63+0.64SLD where the maximum range of SLD is 52.9 cm. Current is coherent with SLD at semidiurnal, diurnal and 42.7-hour periods. A dominant nontidal variability with about 5-day period is not coherent with SLD.

• 대한조선학회논문집
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• 제46권3호
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• pp.219-231
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• 2009

Numerical simulations have been carried out for a 138K LNG Carrier (KLNG) model ship with free surface, using WAVIS 2.0 and Fluent 6.3.26 with various $y^+$ values and different grid densities. Level-set method for free surface capturing was adopted in WAVIS, while VOF has been used in Fluent. The calculated results were compared with the experiment data. Resistance coefficient, wave pattern, wave profile along the hull surface, axial velocity contours and transverse vectors had been analyzed. When the first $y^+$ value was fixed at 60, the simulation results from both WAVIS and Fluent were improved as the number of grids increased. The convergence time of WAVIS was much shorter than that of Fluent. Furthermore, WAVIS predicted the velocity field and the wave profile along the hull surface better than Fluent. However, Fluent gave better wave patterns.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.893-898
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• 2004

This research proposes an implementation method of linearized equations of motion for multibody systems with closed loops. The null space of the constraint Jacobian is first pre multiplied to the equations of motion to eliminate the Lagrange multiplier and the equations of motion are reduced down to a minimum set of ordinary differential equations. The resulting differential equations are functions of all relative coordinates, velocities, and accelerations. Since the coordinates, velocities, and accelerations are tightly coupled by the position, velocity, and acceleration level constraints, direct substitution of the relationships among these variables yields very complicated equations to be implemented. As a consequence, the reduced equations of motion are perturbed with respect to the variations of all coordinates, velocities, and accelerations, which are coupled by the constraints. The position, velocity and acceleration level constraints are also perturbed to obtain the relationships between the variations of all relative coordinates, velocities, and accelerations and variations of the independent ones. The perturbed constraint equations are then simultaneously solved for variations of all coordinates, velocities, and accelerations only in terms of the variations of the independent coordinates, velocities, and accelerations. Finally, the relationships between the variations of all coordinates, velocities, accelerations and these of the independent ones are substituted into the variational equations of motion to obtain the linearized equations of motion only in terms of the independent coordinate, velocity, and acceleration variations.

• 상하수도학회지
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• 제20권3호
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• pp.431-441
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• 2006

This study investigated the physiological characteristics of biofilm microorganisms formed onto the different drinking water distribution pipe surfaces. The simulated drinking water distribution pipe system which had several PVC, STS 304, and GS coupons was operated at flow velocity of 0.08 m/sec (Re 1,950) and 0.28 m/sec (Re 7,300), respectively. At velocity of 0.08 m/sec, the number of viable heterotrophic bacteria in the biofilm over the 3 months of operation averaged $3.3{\times}10^4$, $8.7{\times}10^4$, and $7.2{\times}10^3CFU/cm^2$ for PVC, STS, and GS surfaces, respectively. The number of attached heterotrophic bacteria averaged $1.4{\times}10^3$, $5.6{\times}10^2$, and $6.5{\times}10^2CFU/cm^2$ on PVC, STS, and GS surfaces at the system with relatively high flow velocity of 0.28m/sec. The changes of physiological profile of biofilm-forming microorganisms were characterized by community-level assay that utilized the Biolog GN microplates. Biofilms that formed on different pipe surfaces displayed distinctive patterns of community-level physiological profile (CLPP), which reflected the metabolic preference for different carbon sources and/or the utilization of these carbon sources to varying degrees. The CLPP patterns have shown that the metabolic potential of a biofilm community was different depending on the pipe material. The effect of the pipe material was also characterized differently by operation condition such as flow rate. At flow velocity of 0.08 m/sec, the metabolic potential of biofilm microorganisms on GS surface showed lower levels than PVC and STS biofilms. For biofilms on pipe material surfaces exposed to water flowing at 0.28 m/sec, the metabolic potential was in order of PVC>GS>STS. Generally, the levels of the bacterial biofilm's metabolic potentials were shown to be notably higher on pipe surfaces exposed to water at 0.08 m/sec when compared to those on pipe surfaces exposed to water at 0.28 m/sec.

• Clinical and Experimental Pediatrics
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• 제53권1호
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• pp.41-47
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• 2010

목 적 : 아디포넥틴은 혈관벽의 염증 반응을 억제시켜 혈관의 remodeling을 조절하는 내인적 조절 인자이다. 그러나 가와사키병에서 아디포넥틴의 역할은 알려져 있지 않다. 이 연구의 목적은 혈중 아디포넥틴 농도와 IL-6, $TNF-{\alpha}$, lipid profile, C 반응 단백 등 몇몇 parameter들의 상관 관계를 알아보고, 아디포넥틴과 심기능의 연관성을 밝히는 것이다. 방 법 : 실험군은 가와사키병으로 진단받은 총 22명의 환아(급성기 22명, 아급성기 환아 20명)를 대상으로 하였고, 대조군은 총 31명(열성 질환이 있는 환아 13명, 건강아 18명)을 대상으로 하였다. 두 군 모두에서 혈액 검사와 TDI를 실시하였다. 결 과 : C 반응 단백은 대조군에 비해 가와사키 군에서 유의하게 증가되었다. 아디포넥틴, IL-6, $TNF-{\alpha}$ 치는 두 군 간에 유의한 차이가 없었다. 하지만 아디포넥틴과 C 반응 단백, 혈소판 수치 사이에 유의한 음의 상관 관계가 있었다. TDI로 측정한 수축기 심근 속도와 A 심근 속도가 급성기에서 아급성기, 대조군에 비해 유의하게 심근 속도가 감소됨이 확인되었고, 아디포넥틴과는 양의 상관 관계를 보였다. 결 론 : 급성 가와사키 환아에서 혈중 아디포넥틴 농도가 낮을수록 염증 반응이 심하며 좌심실의 기능이 떨어짐을 확인할 수 있었다.