• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.5
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• pp.15-20
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• 2009

Hot-firing tests were performed on two 30 tonf-class regenerative cooling combustion chambers, with different injector distribution and wall cooling method. In the paper, the combustion stability test results were analyzed and presented. The pressure fluctuation and stability rating test(SRT) results of the combustion chambers were examined to evaluate combustion stability. The combustion chambers exhibited satisfactory results on combustion stability. The RMS values of the chamber pressure fluctuation were less than 3% of the chamber pressure and the decay time of artificial pressure peaks was measured to be around 10% of the reference decay time. It is interesting that the RMS values of pressure fluctuation in the combustion chamber with film cooling are smaller than those in the chamber with cooling injectors at the periphery row.

• Journal of Advanced Research in Ocean Engineering
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• v.4 no.4
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• pp.185-194
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• 2018

In this study, the extreme sloshing pressure was predicted using various statistical models: three-parameter Weibull distribution, generalized Pareto distribution, generalized extreme value distribution, and three-parameter log-logistic distribution. The estimation of sloshing impact pressure is important in design of liquid cargo tank in severe sea state. In order to get the extreme values of local impact pressures, a lot of model tests have been carried out and statistical analysis has been performed. Three-parameter Weibull distribution and generalized Pareto distribution are widely used as the statistical analysis method in sloshing phenomenon, but generalized extreme value distribution and three-parameter log-logistic distribution are added in this study. Additionally, statistical distributions are fitted to peak pressure data using three different parameter estimation methods. The data were obtained from a three-dimensional sloshing model text conducted at Seoul National University. The loading conditions were 20%, 50%, and 95% of tank height, and the analysis was performed based on the measured impact pressure on four significant panels with large sloshing impacts. These fittings were compared by observing probability of exceedance diagrams and probability plot correlation coefficient test for goodness-of-fit.

• Korean Journal of Applied Biomechanics
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• v.29 no.3
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• pp.197-204
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• 2019

Objective: The purpose of this study was to identify the effect of high-heels (HH) modification on metatarsal stress in female workers. Method: Seven females who work in clothing stores ($heights=160.4{\pm}3.9cm$; $weights=47.4{\pm}4.1kg$; $age=31.3{\pm}11.1yrs$; $HH\;wear\;career=8{\pm}6.5yrs$) wore two types of HH (original and modified). The modified HH had been grooved with 1.5 cm radius and 0.2 cm depth around the first metatarsal area inside of the shoes using the modified shoe-last. Participants were asked to walk for 15 minutes on a treadmill and to stand for 10 minutes with original and modified HH, respectively. Kinetics data were collected by the F-scan in-shoe system. After each test, participants were asked to rate their perceived exertion using the Borg's 15-grade RPE scale and interviewed about their feeling of HH. Nonparametric Wilcoxon signed-rank test and effect size (Cohen's d) were used to determine the difference of the variables of interest between the original and modified HH. Results: In the present study, modified HH of the peak contact pressure of 1st metatarsal (PCP) left, PCP right, pressure time integral (PTI) left, peak pressure gradient (PPG) left during standing and PPG right during walking are greater than original HH. And even it didn't show statistically significant, the average in all pressure values of modified HH showed bigger than original HH. It surmised to be related to awkward with modified HH. Even though they said to feel the comfortable cause of big space inside of HH in the interview, they seemed to be not enough time to adapt with new HH. So their walking and standing postures were unstable. Conclusion: Modified the fore-medial part of HH can reduce the stress in the first metatarsal head and big toe area during standing and walking.

• PNF and Movement
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• v.16 no.3
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• pp.461-473
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• 2018

Purpose: The purpose of this study was to evaluate and compare the effects of inspiratory muscle training with chest expansion exercises on pulmonary function, maximal inspiratory pressure, and gait in individuals with stroke. Methods: The participants in this study included 36 stroke patients. These patients were randomly divided into three groups: an inspiratory muscle training (IMT) with chest expansion (CE) group (n=12), an IMT group (n=12), and a control group (n=12). Participants in the IMT with CE group underwent IMT and CE exercises 5 times per week for 30 minutes over 4 weeks, whereas those in the CE group and the control group received IMT and conventional physical therapy, respectively, for the same duration. The investigator measured the patients' pulmonary function, maximal inspiratory pressure, and gait endurance. Results: After the intervention, the change values for the forced vital capacity (FVC), forced expiratory volume in one second (FEV1), peak expiratory flow (PEF), maximal inspiratory pressure (MIP), and six-minute walk test (6MWT) in the IMT with CE group and the control group were significantly greater than those of the control group (p<0.05). Similarly, after the intervention, the change values of the FVC, FEV1, PEF, MIP, and 6MWT in the IMT with CE group were significantly greater than those in the IMT group (p<0.05). Conclusion: These findings suggest that IMT with CE could be used to increase pulmonary function, maximal inspiratory pressure, and gait endurance in stroke patients.

• Journal of computational fluids engineering
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• v.19 no.3
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• pp.8-13
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• 2014

In this study, wave characteristics coming with oblique incident angle to permeable trapezoidal submerged breakwater on the porous seabed are calculated by using boundary element method. This numerical analysis, based on the wave pressure function, is analyzing the continuity in the analytical region including fluid and structure. From the comparison of the reflection coefficients and damping coefficient, the results of this study are in good agreement with the existing results. The peak values of reflection coefficient obtained by permeable trapezoidal submerged breakwater on the porous seabed are smaller than those of permeable trapezoidal submerged breakwater on the non-porous seabed. The velocity vector in front of permeable trapezoidal submerged breakwater on the porous seabed is smaller than that in front of permeable trapezoidal submerged breakwater on the non-porous seabed with out the energy loss.

• Journal of Advanced Research in Ocean Engineering
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• v.3 no.4
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• pp.174-183
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• 2017

Numerical simulations were performed about the green water problem of a FPSO. Three regular waves in head sea were tested. A rectangular box-shaped FPSO was considered and it is assumed there is a vertical wall on the deck. For the numerical simulations, an open-source CFD code, OpenFOAM, was applied to solve the present problems. Focus is on wave fields around the FPSO, water flows and impact pressures on the deck. For the validation, the present calculation results were compared with the existing experimental of Lee et al. (2012) and Changwon university in KTTC Cooperative Study Report (2015). The statistical values and spatial distribution of the peak pressures are directly compared with the experimental data. Some discussions are made on the effects of the domain breadth on the Green water impact pressure.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.5
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• pp.594-601
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• 2016

Mass estimation analysis of loose-parts in pressure vessel is necessary for the structural integrity assessment of pressure boundary in nuclear power plants. Mass of loose-parts can be generally estimated from the peak values and the center frequency of impact signals. Magnitude of impact signals is, however, inevitably attenuated according to the traveling distance of the signals and depending on the frequencies. Attenuation rate must be therefore carefully compensated for the precise estimation of loose-part mass. This paper proposes a new compensation method for the attenuation rate based on Bessel function instead of Hankel function in conventional method which has a limitation of usage in near the impact location. It was verified that the suggested compensating equation based on the Bessel function can be applied to the attenuation rate calculation without any limitation.

• Wind and Structures
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• v.7 no.5
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• pp.333-344
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• 2004

This paper illustrates application of the proper orthogonal decomposition (POD) and the autoregressive (AR) model to simulate large wind pressures due to gusts on a low-rise building. In the POD analysis, the covariance of the ensemble of large wind pressures is employed to calculate the principal modes and coordinates. The POD principal coordinates are modeled using the AR process, and the fitted AR models are employed to generate the principal coordinates. The generated principal coordinates are then used to simulate large wind pressures. The results show that the structure characterizing large wind pressures is well represented by the dominant eigenmodes (up to the first fifteen eigenmodes). Also, wind pressures with large peak values are simulated very well using the dominant eigenmodes along with the principal coordinates generated by the AR models.

• Structural Engineering and Mechanics
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• v.32 no.2
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• pp.213-233
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• 2009

In this paper the study of a reinforced concrete wall used as protection against accidental explosions in the petrochemical industry is presented. Many alternatives of accidental scenarios and sizes of the wall are analyzed and discussed. Two main types of events are considered, both related to vessel bursts: Pressure vessel bursts and BLEVE. The liberated energy from the explosion was calculated following procedures firmly established in the practice and the effects over the structures and the reinforced concrete wall were calculated by using a CFD tool. The results obtained show that the designed wall reduces the values of the peak overpressure and impulse and, as a result, the damage levels to be expected. It was also proved that a reinforced concrete wall can withstand the blast load for the considered events and levels of pressure and impulse, with minor damage and protect the buildings.

• Journal of Biomedical Engineering Research
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• v.27 no.3
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• pp.83-88
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• 2006

A new method of measuring pulse arrival time (PAT), which is usually used for the estimation of systolic blood pressure, in an unconstrained manner using a chair, is proposed. The capacitive-coupled ECG (CC-ECG) measurement system and the air cushion with balancing tubes system were used for unconstrained PAT measurement. Firstly, the correlation between the standard PAT (S-PAT) from the photoplethysmography (PPG) and the PAT measured in an unconstrained manner (U-PAT) was evaluated. It was observed that U-PAT, which is the time delay from the R-peak of ECG to the steepest decent point of air cushion pressure wave, is significantly correlated with the S-PAT. Secondly, systolic blood pressure (SBP) measured by the radial tonometer is compared to the U-PAT. The ten-beat averaged U-PAT removed respiration effects and demonstrated a high intra-subject correlation with SBP in all participants. Finally, the tonometry SBP was estimated from these U-PAT values for one participant intermittently during half a day.