• 대한정형도수물리치료학회지
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• 제19권1호
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• pp.49-54
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• 2013

Background: The purposed of this study is to examine the static and dynamic plantar foot pressure in chronic low back pain patients and normal adults. Methods: The subjects were divided into a group of 30 patients with chronic low back pain and a control group of 30 healthy persons. While static posture and dynamic posture at comfortable walking speeds, the low back pain group and the control group measured their plantar foot pressure and the trajectory of their center of pressure (COP) using the Matscan(R) system. Independent t-tests were measured to compare differences in plantar foot pressure characteristics between the left side and right side of the low back pain group and the control group. Results: In the comparison of differences in plantar foot pressure characteristics between the left side and right side of the low back pain group and the control group, the anteroposterior (AP) displacement of COP showed significant differences (p<.05). Although the low back pain group and the control group did not show any significant differences in leg length, weight distribution, mediolateral (ML) displacement of COP, static contract area, dynamic contract areas (p>.05), increases in the contract area values were shown in the hind foot in general. Conclusion: In this study, it was shown that patients with chronic low back pain were walking with short AP displacement of the COP as a compensatory action to avoid pain.

• 대한기계학회논문집
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• 제12권5호
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• pp.1150-1157
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• 1988

본 연구에서는 수치계산을 통해 진행하는 방향에 수직으로 일정한 압력구배를 받는 2차원 난류 자유제트의 발달을 고려해 보고자 한다.속도장을 구한 후에는 제 트의 온도가 주위온도 보다 높을 경우와 또 제트를 사이에 둔 양쪽 유체에 온도차가 있을때의 열확산 특성도 함께 알아보려는 것이다. 수직 방향으로 압력구배가 있는 유동장은 최근 활발히 연구가 진행되는 분야인 제트축에 수직방향으로 주위유동이 있 는 경우와 흡사하며 제트를 통한 열확산현상은 air curtain등 실제 응용도가 큼에도 불구하고 문헌에 보고된 것이 별로 없는 것으로 보여진다.

• 한국수소및신에너지학회논문집
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• 제16권1호
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• pp.1-8
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• 2005

Transition of momentum-controlling hydrogen jet to buoyant jet is experimentally investigated in order to develop a prediction model for the moving trajectory of hydrogen leaked from hydrogen devices. In the experiments, room-temperature helium, that has a similar density to the hydrogen leaked from high pressure tank, is horizontally injected through a 4mm tube and its moving trajectory is visualized by the shadowgraph method. The moving trajectories are found to be parabolic, thereby exhibiting increasing influence of the buoyancy. In analyzing the experimental results, the vertical movement is assumed to be controlled by the buoyancy while the horizontal movement is controlled by the air entrainment caused by the initial momentum. The resealing based on this assumption yields a single curve fitting to the all experimental results.

• 한국자동차공학회논문집
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• 제7권9호
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• pp.63-74
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• 1999

When a fuel was injected with opening the intake valve of a port fuel injection engine, the spray atomization and flow characteristics in the intake port have a strong influence on the mixture formation of a combustion chamber. Thus , this study was to clarify the spray flow characteristics of the air-assist gasoline spray with fine dropkets across the suction air stream in model intake port. For the simulated opening intake valve in port, suction air stream was varied to 10m/s ∼30m/s. And fuel pressur ewas fixed to 300kPa, but air assist pressure was varied to 0∼25kPa for a vairable spray conditions. Spray flow trajectory was investigated by means of laser sheet visualization and the measurements of droplet sizes and velocities were made by PDPA system. Measured droplets within the spray flow field were subdivided into five size groups and then, the flow characteristics of droplet size groups were investigated to the spray across a suction air stream.

• 한국지하수토양환경학회지:지하수토양환경
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• 제21권3호
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• pp.58-63
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• 2016

The study examined the level of heavy metal contamination by dividing military rifle shooting ranges into the three areas, i.e firing, trajectory, and target. The target area was found to be contaminated at a level higher (Cu 845 mg/kg, Pb 30,487 mg/kg) than the Worrisome Level of Soil Contamination (hereinafter referred to as the “Worrisome Level”) The trajectory area was predicted to be free from contamination, but it did indicate contamination although it was pretty much lower (Cu 23 mg/kg, Pb 99 mg/kg) than Worrisome Level. This is attributed to the contamination spread when rearranging the soil of the target area during the maintenance of the shooting range. The firing area was also predicted to be free from heavy metal contamination, but the results analyzed indicated a contamination higher (Cu 201 mg/kg, Pb 2,286 mg/kg) than Worrisome Level. This is attributed to the fragments of the broken bullet scattering due to the pressure generated as the bullet leaves the muzzle. An examination of heavy metal contamination in the discharge area as well as gutters to prevent the intrusion of rain water from perimeter revealed a high level of contamination (Cu 298 mg/kg, Pb 6,497 mg/kg), which makes it necessary to take measures.

• Journal of Welding and Joining
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• 제26권6호
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• pp.59-66
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• 2008

Recently, automobile parts progress with modularization, which a great many allied products are modularized. Therefore, the purpose of this study is to develope modular housing for modularization of steering gear. Generally, steering gear housing is composed of valve housing and rack housing, it is important to combine two housings. However, housing having the pipe shape is very sensitive to welding distortion, and welding trajectory is very complicated. In order to solve this subject, cooperative control by using robots was constructed. Further, we developed the dedicated system to suit modular housing based on it, and applied laser welding to there. Moreover, welding speed was controlled in the rapid curve section so that the defect in trajectory of housing was reduced to obtain sound weldment. Accordingly, produced housing by this way is presented enough withstanding pressure to $100kg/cm^2$, and roundness and straightness are measured about 10/100 and 0.9/100 respectively.

• Archives of Plastic Surgery
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• 제46권4호
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• pp.386-389
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• 2019

The development of breast implant technology continues to evolve over time, but changes in breast shape after implantation have not been fully elucidated. Thus, we performed computerized finite element analysis in order to better understand the trajectory of changes and stress variation after breast implantation. The finite element analysis of changes in breast shape involved two components: a static analysis of the position where the implant is inserted, and a dynamic analysis of the downward pressure applied in the direction of gravity during physical activity. Through this finite element analysis, in terms of extrinsic changes, it was found that the dimensions of the breast implant and the position of the top-point did not directly correspond to the trajectory of changes in the breast after implantation. In addition, in terms of internal changes, static and dynamic analysis showed that implants with a lower top-point led to an increased amount of stress applied to the lower thorax. The maximum stress values were 1.6 to 2 times larger in the dynamic analysis than in the static analysis. This finding has important implications for plastic surgeons who are concerned with long-term changes or side effects, such as bottoming-out, after anatomic implant placement.

• Nuclear Engineering and Technology
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• 제55권6호
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• pp.2011-2017
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• 2023

Gas submerged jet is an outstanding thermohydraulic phenomenon in pool scrubbing of fission products during a severe nuclear accident. Experiments were performed on the hydraulic characteristics in the ranges of air mass flux 0.1-1400 kg/m²s and nozzle diameter 10-80 mm. The results showed that the dependence of inlet pressure on the mass flux follows a power law in subsonic jets and a linear law in sonic jets. The effect of nozzle submerged depth was negligible. The isolated bubbling regime, continuous bubbling regime, transition regime, and jetting regime were observed in turn, as the mass flux increased. In the bubbling regime and jetting regime, the air volume fraction distribution was approximately symmetric in space. Themelis model could capture the jet trajectory well. In the transition regime, the air volume fraction distribution loses symmetry due to the bifurcated secondary plume. The Li correlation and Themelis model showed sufficient accuracy for the prediction of jet penetration length.

• 대한기계학회논문집B
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• 제24권2호
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• pp.270-279
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• 2000

Recently, according to increase in the requirement of electric power, a thermoelectric power plant equipped with pulverized coal combustion system is highly valued, because coal has abundant deposits and a low price compared with others. For efficient use of coal fuel, most of plant makers are studying to improve combustion performance and flame stability, and reduce pollutants emission. One of these studies is how to control the profile of particle injection and velocity dependant on coal nozzle configuration. Basically, nozzle which has mixed flow of gas and particle is required to have the balanced coal concentration at exit, but it is very difficult to obtain that by itself without help of other device. In this study, coal distribution and pressure drop in gas-solid flow are calculated by numerical method in nozzle with various shapes of venturi diffuser as a means to get even coal particle distribution. The tentative correlations of pressure drop and exit coal distribution are deduced as function of the height, length and reducing angle of venturi from the calculated results. When coal hurner nozzle is designed, these equations are very useful to optimize the shape of venturi which minimize uneven particle distribution and pressure drop within coal nozzle.

• International journal of advanced smart convergence
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• 제9권1호
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• pp.202-208
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• 2020

Body balance necessary for ordinary daily activities can be undermined by diverse causes. In this study, as a way to control such a problem, we have produced smart insole as a wearable device in the form of insole and developed analysis software evaluating body balance, which measures ground reaction force applied to each area of sole and Center of Pressure (COP). The software visualized changes in COP positions while a user was moving and average COP positions, and it is also capable of measuring the COP values in the Anterior-Posterior (AP) and Medial-Lateral (ML) areas of feet. Through gait analysis, it can analyze the time of walking, strides, speed, COP trajectory while walking, etc. In addition, we have developed training contents for body balance improvement designed in consideration of Y-Balance Test and Timed Up and Go (TUG) Test. They were established in virtual reality similar to daily living environment so that people can expect more effective training results regardless of places.