• Current Optics and Photonics
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• v.1 no.5
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• pp.529-537
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• 2017

We explored how changes in blood vessel compliance affected the systolic rise time (SRT) of the maximum blood pressure (BP) peak wave and the diastolic fall time (DFT) of the minimal BP peak wave, compared to photoplethysmograpic (PPG) parameters, using a two-compartment, second-order, arterial Windkessel model. We employed earlier two-compartment Windkessel models and the components thereof to construct equivalent blood vessel circuits, and reproduced BP waveforms using PSpice technology. The SRT and DFT values were obtained via circuit simulation, considering variations in compliance (the dominant influence on blood vessel parameters attributable to BP changes). And then performed regression analysis to identify how compliance affected the SRT and DFT. We compared the SRTs and DFTs of BP waves to the PPG values by reference to BP changes in each subject. We confirmed that the time-shift propensities of BP waves and the PPG data were highly consistent. However, the time shifts differed significantly among subjects. These simulation and experimental results allowed us to construct an initial trend curve of individual BP peak time (measured via wrist PPG evaluations at three arm positions) that facilitated accurate individual BP estimations.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.355-360
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• 2001

This study addresses a computational work of the impulsive wave which is discharged from the open end of a pipe. An initial compression wave inside the pipe is assumed to propagate toward atmosphere. The over pressure and wave-length of the initial compression wave are changed to investigate the characteristic values of the impulsive wave. The second order total variation diminishing (TVD) scheme is employed to solve the axisymmetric, compressible, unsteady Euler equations. The relationship between the initial compression wave form and impulsive wave is characterized in terms of the peak pressure of the impulsive wave and its directivity. The results obtained show that for the initial compression wave of a large wave-length the peak pressure of the impulsive wave does not depend on the over pressure of the initial compression wave, but for the initial compression wave of a very short wave-length, like a shock wave, the peak pressure of the impulsive wave is increased with an increase in the over pressure of the initial compression wave. The directivity of the impulsive wave to the pipe axis becomes significant with a decrease in the wave-length of the initial compression wave.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.6
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• pp.9-16
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• 2006

Variable valve timing is one of the attractive ways to control homogeneous charge compression ignition (HCCI) engine. Hot internal residual gas which can be controlled by variable valve timing(VVT) device, makes fuel evaporated easily, and ignition timing advanced. Regular gasoline was used as main fuel and di-methyl ether(DME) was used as ignition promoter in this research. HCCI engine operating range is limited by high combustion peak pressure and engine noise. High combustion pressure can damage the engine during operation. To avoid engine damage, the rich limits have to define using various methods. Peak combustion pressure, rate of cylinder pressure rise was considered to determine rich limit of engine operating range. Knock probability was correlated with the rate of cylinder pressure rise as well as the peak combustion pressure.

• Wind and Structures
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• v.5 no.2_3_4
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• pp.337-346
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• 2002

Wind tunnel pressure measurements and numerical simulations based on the Reynolds Stress Model (RSM) are compared with full and model scale data in the flow area of impingement, separation and wake for $60^{\circ}$ and $90^{\circ}$ wind azimuth angles. The phase averaged fluctuating pressures simulated by the RSM model are combined with modelling of the small scale, random pressure field to produce the total, instantaneous pressures. Time averaged, rsm and peak pressure coefficients are consequently calculated. This numerical approach predicts slightly better the pressure field on the roof of the TTU (Texas Tech University) building when compared to the wind tunnel experimental results. However, it shows a deviation from both experimental data sets in the impingement and wake regions. The limitations of the RSM model in resolving the intermittent flow field associated with the corner vortex formation are discussed. Also, correlations between the largest roof suctions and the corner vortex "switching phenomena" are observed. It is inferred that the intermittency and short duration of this vortex switching might be related to both the wind tunnel and numerical simulation under-prediction of the peak roof suctions for oblique wind directions.

• Nuclear Engineering and Technology
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• v.29 no.3
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• pp.229-239
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• 1997

To investigate the realistic behavior of mass and energy release and resultant containment response during large break Loss of Coolant accident (LOCA), analyses are performed for Yonggwang (YGN) 3&4 nuclear power plants by using a merged version of RELAP5/CONTEMPT4 computer code. Comparative analyses by using conservative design computer codes are also peformed. The break types analyzed are the double-ended guillotine breaks at the cold leg and hot leg. The design analysis resulted in containment peak pressure during post-blowdown phase for the cold leg break. However, the RELAP5/CONTEMPT4 analyses show that the containment pressure has a peak during blowdown phase, thereafter it decreases monotonously without the second port-blowdown peak. For the hot leg break, revised design analysis shows much lower pressure than that reported in YGN 3&4 final safety analysis report. The RELAP5/CONTEMPT4 analysis shoos similar trend and confirmed that the bypass flow through the broken loop steam generator during post-blowdown is negligibly small compared to that of cold leg break. The low pressure and temperature predicted tv realistic analysis presented in this paper suggest that the design analysis methodology contains substantial margin and it can be improved to provide benefit in investment protection, such as, relaxing plant technical specifications and reducing containment design pressure.

• Journal of Korean Society of Steel Construction
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• v.21 no.3
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• pp.245-255
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• 2009

The low-rise buildings with gable roofs are commonly used in a number of industries. In order to study the characteristics of peak external pressure coefficient on low-rise buildings with gable roofs, wind-tunnel test have been carried out. Wind-induced pressures were measured simultaneously at many points on wind-pressure models, typical of simple low-rise buildings with gable roofs, which have seven different roof slope with constant width(D), height(H), and length(D). The pressure measurements were made in one kind of turbulent boundary layer, which simulated the natural winds over typical suburban terrains at a geometric scale of 1/150. The results indicate that peak external pressure coefficient on the roof and wall edges were increased. The results compared with wind standard of KBC-2005 and standards of various nations. The comparative resultant, experimental result appeared very similar at AIJ-2004. But the results were somewhat larger then wind standard of KBC-2005.

• Korean Journal of Applied Biomechanics
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• v.22 no.1
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• pp.113-121
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• 2012

The purpose of this study was to evaluate the effects of forefoot rocker shoes equipped with a metatarsal bar on lower extremity muscle activity and plantar pressure distribution. Ten healthy women in the age of twenties were participated in this study as the subjects. All subjects walked on a treadmill(Gait Trainer, BIODEX, USA) wearing normal shoes and metatarsal bar shoes, during which the plantar pressure distribution and muscle activity were measured. Using Pedar-X system(Novel Gmbh, Germany), the plantar pressure was measured for six regions of the foot: forefoot, midfoot, rearfoot, 1st metatarsal, 2-3th metatarsal, and 4-5th metatarsal, and for each sub-region, 4 features such as maximum force, contact area, peak pressure, and mean pressure were analyzed based on the plantar pressure. EMG(Electromyography) activity was measured by attaching surface electrodes to the rectus femoris, biceps femoris, tibialis anterior, and gastrocnemius medial head, and magnitude of muscle contraction was analyzed in IEMG(Integrated EMG) value. The results show that the maximum force, contact area, peak pressure, and mean pressure in the midfoot all increased while maximum force, peak pressure, contact area, mean pressure in the 1st metatarsal and 2-3th metatarsal all decreased when wearing functional shoes. Also, muscle activities in the four muscles were all decreased when wearing the functional shoes. This paper suggests that forfoot rocker shoes equipped with a metatarsal bar can help disperse the high pressure and absorb the shock to the foot as well as give positive influence on gait pattern and postural stability by reducing muscle fatigue during walking.

• Journal of Chest Surgery
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• v.20 no.1
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• pp.30-38
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• 1987

Sixty-eight consecutive patients have been subjected to total corrective surgery of tetralogy of Fallot at the Hanyang University Hospital between August 1975 and December 1984. Of these, the pressure of chambers and great arteries were measured, before and immediately following an operation in 39 of the survived group and 11 of the expired group. The values of postoperative peak pressure were correlated with the outcome of the operation. The result are as followings; 1] Compared to the average peak pressure of right atrium in the survived group, 14.46*4.16 mmHg, that in the expired group, 19.36*8.19 mmHg, was significantly lower, 2] Compared to the average systolic pressure of right ventricle in the survived group, 56.72z16.37 mmHg, that in the expired group, 70.45*15.26 mmHg, was significantly lower. 3] Compared to the average systolic pressure of pulmonary artery in the survived group, 33.26*12.95 mmHg, that in the expired group, 37.55*11.63 mmHg, was higher. But the difference was not significant. 4] Compared to the average peak pressure of left atrium in the survived group, 17.41*6.90 mmHg, that in the expired group, 31.18*12.47 mmHg, was significantly higher. 5] Compared to the average systolic pressure of left ventricle in the survived group, 103.82~12.83 mmHg, that in the expired group, 90.55*20.02 mmHg, was significantly lower. 6] Compared to the average value of the right ventricle-pulmonary artery systolic pressure gradient [RV-PA] in the survived group, 24.95a15.44 mmHg, that in the expired group, 35.09*17.01 mmHg, was significantly higher. 7] Compared to the average value of the right ventricle to left ventricle systolic pressure ratio [RV/LV] in the survived group, 0.55*0.15, that in the expired group, 0.80a0.20, was significantly higher. 8] Compared to the average value of the pulmonary artery-left atrium peak pressure gradient [PA-LA] in 15.85x12.29 mmHg that in the expired group, 4.18x6.00 mmHg, was significantly lower. It is, therefore, suggested that in the operating room, PA-LA is as valuable as RV - PA, RV/LV in making important surgical decision and predicting the prognosis.

• 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 Korean Foot and Ankle Society
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• v.26 no.3
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• pp.130-135
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• 2022

Purpose: Smart insoles are wearable devices that are inserted into shoes. Smart insoles with built-in pressure and acceleration sensors can measure the plantar pressure, stride length, and walking speed. This study evaluated the validity and reliability of the plantar pressure measurements of smart insoles during walking on flat ground. Materials and Methods: Twenty one subjects were included in this study. After wearing smart insoles, I-SOL^® (Gilon, Seongnam, Korea), the subjects walked a 10 m corridor six times at a rate of 100 steps/min, and the middle three steps, free from direction changes, were chosen for data analysis. The same protocol was repeated after wearing Pedar-X (Novel Corporation, Munich, Germany), an insoletype plantar pressure measurement equipment with proven validity. The average maximum pressure (P_peak, kPa) and the time at which P_peak appeared (P_time, %stride) were calculated for each device. The validity of smart insoles was evaluated by using the interclass correlation coefficient (ICC) of P_peak and P_time between the two instruments, and Cronbach's alpha was obtained from the P_peak values to evaluate the reliability. Results: The ICC of P_peak was 0.651 (good) in the hallux, 0.744 (good) in the medial forefoot, 0.839 (excellent) in the lateral forefoot, and 0.854 (excellent) in the hindfoot. The ICC of P_time showed 0.868 (excellent) in the hallux, 0.892 (excellent) in the medial forefoot, 0.721 (good) in the lateral forefoot, and 0.832 (excellent) in the hindfoot. All ICC values showed good or excellent results. The Cronbach's alpha of P_peak measured in the smart insoles was 0.990 in the hallux, 0.961 in the medial forefoot, 0.973 in the lateral forefoot, and 0.995 in the hindfoot; all indicated excellent reliability in all areas. Conclusion: The plantar pressure measurements of smart insoles during walking on a flat ground showed validity compared to Pedar-X, and high reliability after repeated measurements.