• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.1825-1830
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• 2014

Environmental emission of recent automobile is drastically enhanced that it is one of the obvious assignments of exhaust system. This study is a purpose to establish of influence distribution on maxima and minima through the location of pressure on exhaust variable valve. The experiment are checked with real angles using camera which exhaust variable valve is opened side of point. Data has extracted to opening angles with internal flow, pressure. Exhaust variable valve through the floating analysis was analyzed the characteristic of location point about pressure and velocity. The pressures indicated the reduced results internal pressure within muffler. The velocity indicated an opposite results and vibration state of valve was verified to be operated as high speed from lower section. The conclusion to obtain from this study was found out the result to make the optimum back pressure condition as more increasing pressure distribution on valve face if the velocity location attracted by bottom point in order to improve for engine performance.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.380-385
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• 2001

In the present study, flow characteristics of turbulent oscillatory flow in a square-sectional $180^{\circ}$ curved duct are investigated experimentally. In order to measure wall shear stress and pressure distributions, experimental studies for air flow are conducted in a square-sectional $180^{\circ}$ curved duct by using the LDV system with the data acquisition and the processing system. The wall shear stress measuring point bend angle of the $150^{\circ}$ and pressure distribution of the inlet (${\phi}=0^{\circ}$) to the outlet (${\phi}=180^{\circ}$) at $10^{\circ}$ intervals of the duct. The results obtained from the experimentation are summarized as follows: A wall shear stress value in an inner wall is larger than that in an outer wall, except for the phase angle (${\omega}t/{\pi}/6$) of 3, because of the intensity of secondary flow. The pressure distributions are the largest in accelerating and decelerating regions at the bend angle(${\phi}$) of $90^{\circ}$ and pressure difference of inner and outer walls is the largest before and after the ${\phi}=90^{\circ}$.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.5
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• pp.58-67
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• 1996

In the present study, the pressure distribution, wall shear stress distribution and friction factor of developing turbulent pulsating flows are investigated theoretically and experimentally in the entrance region of a square duct. The pressure distribution for turbulent pulsating flows are in good agreement with the theoretical values. The time-averaged pressure gradients of the turbulent pulsating flows show the same tendency as those of turbulent steady flows as the time-averged Reynolds number $(Re_{ta})$ increase. Mean shear stresses in the turbulent pulsating flow increase more in the inlet flow region than in the fully developed flow region and approach to almost constant value in the fully developed flow region. In the turbulent pulsating flow, the friction factor of the quasi-steady state flow $({\lambda}_{q, tu})$ follow friction factor's law in turbulent steady flow. The entrance length of the turbulent pulsating flow is not influenced by the time-averaged Reynolds number $(Re_{ta})$ and it is about 40 times as large as the hydraulic diameter.

• Journal of the Korean Geotechnical Society
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• v.20 no.4
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• pp.89-102
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• 2004

The generated blasting pressure wave initiated under decoupled-charge condition is a function of peak blasting pressure, rise time, and wave-shape function. The peak blasting pressure and the rise time are also the function of explosive and rock properties. The probabilistic distributions of explosive and rock properties are derived from the results of their property tests. Since the probabilistic distributions of explosive and rock properties displayed a normal distribution, the peak blasting pressure and the rise time can also be regarded as a normal distribution. Parameter analysis and uncertainty analysis were performed to identify the most influential parameter that affects the peak blasting pressure and the rise time. Even though the explosive properties were found to be the most influential parameters on the peak blasting pressure and the rise time from the parameter analyses, the result of uncertainty analysis showed that rock properties constituted major uncertainties in estimating the peak blasting pressure and the rise time rather than explosive properties. Damage and overbreak of the remaining rock around the excavation line induced by blasting were evaluated by dynamic numerical analysis. A user-subroutine to estimate the rock damage was coded based on the continuum damage mechanics. This subroutine was linked to a commercial program called 'ABAQUS/Explicit'. The results of dynamic numerical analysis showed that the rock damages generated by the initiation of stopping hole were larger than those from the initiation of contour hole. Several methods to minimize those damages were proposed such as relocation of stopping hole, detailed subdivision of rock classification, and so on. It was found that fracture probability criteria and fractured zones could be distinctively identified by applying fuzzy-random probability.

• Journal of Biomedical Engineering Research
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• v.24 no.4
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• pp.363-367
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• 2003

Contact area and pressure are important factors which directly influence a life of knee implants. Since implant's mechanical functions should be experimentally evaluated for clinical use, many studies using a knee simulator and a pressure sensor system have been conducted. However it has not been reported that the contact pressure's distribution of a knee implant motion was estimated in real-time during a gate cycle. Therefore. the objective of this study was to analyze the contact pressure distribution for the motion of a joint using the knee simulator and I-scan sensor system. For this purpose, we developed a force-controlled dynamic knee simulator to evaluate the mechanical performance of artificial knee joint. This simulator includes a function of a soft tissue and has a 4-degree-of-freedom to represent an axial compressive load and a flexion angle. As axial compressive force and a flexion angle of the femoral component can be controlled by PC program. The pressure is also measured from I-scan system and simulator to visualize the pressure distribution on the joint contact surfaces under loading condition during walking cycle. The compressive loading curve was the major cause for the contact pressure distribution and its center move in a cycle as to a flexion angie. In conclusion, this system can be used to evaluate to the geometric interaction of femoral and tibial design due to a measured mechanical function such as a contact pressure, contact area and a motion of a loading center.

• Composites Research
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• v.16 no.6
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• pp.1-9
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• 2003

In this paper, probabilistic failure analysis based on Weibull distribution function is proposed to predict the fiber strength of composite pressure vessel. And, experimental tests were performed using fiber strand specimens, unidirectional laminate specimens and composite pressure vessels to confirm the volumetric size effect on the fiber strength. As an analytical method, the Weibull weakest link model and the sequential multi-step failure model are considered and mutually compared. The volumetric size effect shows the clearly observed tendency towards fiber strength degradation with increasing stressed volume. Good agreement of fiber strength distribution was shown between test data and predicted results for unidirectional laminate and hoop ply in pressure vessel. The site effect on fiber strength depends on material and processing factors, the reduction of fiber strength due to the stressed volume shows different values according to the variation of material and processing conditions.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.3
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• pp.10-18
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• 2001

In this paper, Supersonic jets impinging on a wedge were investigated in order to acquire fundamental design data for jet deflectors. Surface pressure distributions and pressure contours were obtained using a cold flow tester producing Mach 2 supersonic jets. Schlieren system was used to visualize the flow structure on the wedge surface. Numerical computations were performed and compared with the experimental results. Both results were in good agreement. The results showed that underexpansion ratio did not affect on the surface pressure distribution when the wedge is located at the nozzle exit. With increasing underexpansion ratio, pressure recovery decreased as the wedge is located farther from the nozzle exit. In the pressure contour, it was possible to locate the region where the peak pressure on the wedge surface was occurred.

• Journal of Biosystems Engineering
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• v.12 no.4
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• pp.22-30
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• 1987

실린더로부터 Prandtl수가 0.7인 주변공기로 전달되는 혼합대류 열전달현상을 Stream-Vorticity 함수로 표시된 재배방정식으로부터 유한차분법으로 분석하였다. Nusselt수와 실린더 주변의 온도분포가 조사된 제1편에 이어 Reynolds수와 Gradhof수가 실린더 주변의 공기속도분포, 경계층 박리지점(Separation point), 실린더 표면에서의 마찰계수 및 실린더 주변에서의 압력분포에 미치는 영향을 분석하였다.

• Korean Journal of Applied Biomechanics
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• v.19 no.1
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• pp.117-126
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• 2009

The purpose of this study was to investigate the effects of 12-week complex training program on foot pressure patterns of the elderly women. The training program consisted of aerobic exercise and muscular training for 12 weeks. Two stages of walking were given to the participants before and after treatment: (a) straight walking; and (b) turn at $45^{\circ}$ while walking. Data related to foot-pressure distribution(FPD) while walking were collected from each stage and analyzed. Results indicated that in both stage of walking, the mean of the foot pressure(FP) was significantly reduced after the participation in the program. Results also revealed that in all stages, the patterns of the FPD and the center of pressure(COP) were widely lower and more stable. Based on the results of this study, it was concluded that participating in a 12-week complex program bas impact on the gait patterns of the elderly women, reducing the foot pressure on their shoes.

• Journal of Energy Engineering
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• v.4 no.3
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• pp.354-363
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• 1995

차세대 연료전지인 용융탄산염 연료전지의 운전조건을 확립하기 위하여 운전변수와 단위전지 성능과의 관계를 살표보았다. 용융탄산염 연료전지에 산화제로 공기를 사용하는 경우 양극가스에 질소가 포함된다. 그리고 연료전지의 작동압력을 높이면 출력을 크게 할 수 있다. 그리하여 본 연구에서는 에너지 및 물질수지를 이용하여 양극가스내 질소 조성과 작동압력 변화에 따른 전지내의 온도분포 및 성능변화를 구하였다. 본 연구팀이 이미 발표한 용융탄산염 단위 연료전지의 전류밀도의 온도분포를 구하기 위한 수치모사가 이용되었다. 가스흐름의 형태는 십자류를 선택하였다. 양극가스내 질소의 영향은 냉각효과로 나타났다. 작동압력이 증가할수록 전지의 성능은 증가하였고, 기전력[mV]변화 대 압력[atm]의 상용대수값의 변화(즉, ΔV 대 Δ(log))의 1차함수 그래프 기울기는 79.9로 문헌상의 실험치와 유사하게 나타났다.