• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.231-238
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• 2010

Combustion stability rating tests under condition low pressure of a 75-$ton_f$ liquid rocket engine(LRE) thrust chamber were carried out. Mixing head with decreased number of injectors than that of the other but with the same mass flow rate to the combustion chamber showed self-oscillation instability in chamber pressure of 30 bar. The other combustion chamber with increased number of injectors showed that high frequency combustion stability was maintained under condition of same pressure, but self-oscillation instability was generated in chamber pressure of 20 bar which can be considered as stability boundary region of this mixing head.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.260-263
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• 2005

In this study, we analyzed the plantar shear stress and pressure of diabetic foot patients during walking by using in-shoe local shear force and plantar pressure measurement system. Twelve normal subjects and three diabetic foot patients with diabetic neuropathy in lateral heel were participated in this study. The center of pressure in diabetic foot patients moved more medially and directed toward 1st, 2nd metatarsal heads and hallux during late stance period, making pressure at the medial heel and 2nd metatarsal head significantly higher than in the normal. Shear stress at the heel were changed significantly in early stance and the magnitude of shear stresses in each metatarsal head were also changed. Further studies would be very helpful to design foot orthoses in patients with diabetic neuropathy or other diseases.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.2
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• pp.523-536
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• 1991

This dissertation analyzes the running mechanism of flexible and thin tape above rotating head through the numerical simulation and the experiment. The scope of analysis is confined to the phenomena of two dimensional elasto hydrodynamic lubrication between the protruded bump on a rotating cylinder and the running tape. This model is based on the elastic deformation equation of plate and shell and Reynolds equation. Finite difference method is employed as a numerical technique to calculate (1) the distribution of pressure between the running tape and rotating bump and (2) the vertical deformation of elastic thin tape over he rotating bump under hydrodynamic pressure. In numerical analyses, the effects of bump size on flying characteristics of the tape were evaluated and examined considering the influence of tension and stiffness of tape.

• Journal of Sensor Science and Technology
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• v.20 no.5
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• pp.322-328
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• 2011

There are many ways to detect the heart rate non-invasively such as ECG, PPG, strain gauge, and pressure sensor. In this paper, the pulse wave measurement system using bipolar biased head on mode of the Hall sensor is proposed for measuring the radial artery pulse. TMS320F2812 was used to implement the proposed system and a portable wireless network(zig-bee) was used to show the experimental result. It was confirmed from experiment that the performance of the implemented system was more stable and faster than PPG sensor or piezoelectric film pressure sensor.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.1
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• pp.107-112
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• 2009

This study was conducted for verification and systematization of estimation method about the headloss using CFD(Computational Fluid Dynamics). Head loss which happens between the inlet and outlet of in-line mixer can be a major factor for the design and construction. Also, this Case studies about the sensitivity related to the velocity in the piping system. As result, program's default calculation function was used to get each side's total pressure and the differential of each total pressure could be defined as head loss from in-line mixer. In the case of adopting pipe surface friction factor and geometry loss, Calculation residual can be much more reduced. It was found that residual of value between CFD method and field test ranged about 3 through 18 precent.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.4
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• pp.342-347
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• 2008

Bridge circuit was developed such that the pressure wave in the inkjet can be measured. In order to test the circuit, the microfab single ejector was used. For the experiment, the head was filled with nano silver ink (20wt%). In order to generate waveform voltage for jetting signal, the Agilent 33120 was used in order to generate arbitrary waveform. For the driver, PZD 350 from TREK was used in order to amplify the waveform. Experimental results show that the designed circuit can effectively detect the pressure wave in the inkjet head.

• Physical Therapy Rehabilitation Science
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• v.5 no.4
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• pp.178-184
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• 2016

Objective: Tension-type headache is caused by hormones, foods, irritants, stress, obesity, fatigue, and neck and head trigger points-prolonged abnormal posture. The purpose of this study was to evaluate the effects of relaxation approach on head posture, static postural stability, and headache in persons with tension-type headache. Design: Randomized controlled trial. Methods: Thirty-five persons with tension-type headache participated in this study. This study was a pretest-posttest with a control group design for a duration of 4 weeks (60 min/3 times/1 wk). The participants were randomly allocated to the relaxation approach group (n=18) and the control group with conventional rehabilitation including thermotherapy and transcutaneous electrical stimulation for the same period (n=17). Outcome measures involved forward head posture (FHP), foot pressure, neck disability index (NDI), and six-item headache impact test (HIT-6). Results: Relaxation approach and control groups improved significantly in the amount of forward head posture, neck disability index, and six-item headache impact test scores after training (p<0.05). The control group was found to be significantly different in the amount of FHP, backward foot pressure, NDI, and HIT-6 after training compared to before training (p<0.05). The relaxation approach group significantly improved in forward head posture, neck disability index, and six-item headache impact test compared with control group after training (p<0.05). Neck disability index and six-item headache impact test significantly improved after training compared with before training in the control group (p<0.05). However, the foot pressure was not significantly different between relaxation approach and control groups. Conclusions: This study suggests that treatment with relaxation approach combined with self-exercise would be effective in reducing the amount of forward head posture, neck disability and headache impacts.

• Journal of the Korean Institute of Gas
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• v.1 no.1
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• pp.101-105
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• 1997

When the water curtain system is employed to keep the liquefied gas in the underground storage cavern, clogging is observed in borehole. Since this phenomenon causes serious difficulties in managing LPG storage cavern, it needs to detect the degree of clogging accurately under various circumstances. Thus, in this study the active factors of clogging, that is, groundwater head, injection water flowrate, and seepage water flowrate, were investigated experimentally using a physical model. Experimental results show that groundwater head around storage cavern increases as cavern Pressure increases, while it decreases as clogging becomes severe. The pressure in storage cavern is required to reduce up to atmospheric pressure in order to detect and identify the degree of clogging more accurately. The decrease of uroundwater head due to clogging slows down as the pressure in borehole increases. As amounts of suspended matters in injected water increase, both injection water flowrate and seepage water flowrate decrease linearly with time, and the flowrate of injection water drops rapidly compared with seepage water flowrate.

• The Journal of the Korea Contents Association
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• v.8 no.6
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• pp.151-158
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• 2008

Poor posture of the neck and head has long been recognized as a factor contributing to the onset and perpetuation of pain in the head and neck region. This study were to evaluate the change of the neck pressure pain threshold in long term computer users. To elucidate change of the neck pressure pain threshold in long term computer users, the effect of computer using time(3, 6, 9, 12 and 15 hours) on neck pressure pain threshold were studied in 20 subjects. Neck pressure pain threshold were recorded 3, 6, 9, 12 and 15 hours group, and evaluated by pressure algometry to Trapezius muscle, Sternocleidomastoidius muscle, Suboccipitalis muscle and Temporalis muscle. Neck pressure pain threshold was significantly larger in 15 hours group(p<.05). But relation between neck pressure pain threshold in male group and female group were not significant differences(p>.05).

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.3
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• pp.28-38
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• 2003

Finite element analysis of cylinder heat/block compound under assembly, thermal and firing condition were performed. FE model including two cylinders with gasket, head bolts, liners and valve seats was used. FE modeling method and boundary conditions were introduced. Stress distribution and deformation of cylinder head and block under each loading condition were presented. Gasket pressure distribution and bore distortion level were predicted. Measured data of bore distortion was compared with the analysis results. The analysis result showed similar trends with the experimental data. High cycle fatigue analysis on the basis of this result has been performed in order to find the critical areas of the engine assembly.