• BMB Reports
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• v.43 no.4
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• pp.257-262
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• 2010

The aim of work was to investigate changes of 7-ketocholesterol synthesis in alveolar macrophages in the dynamic of lung mechanical ventilation with injurious parameters. The goal of in vitro part of work was to observe influence of 7-ketocholesterol on iNOS and MIP1 $\beta$ production in bronchoalveolar lavage fluid (BALF) cells. We used 17 healthy domestic pigs randomly assigned into two treatment groups: group I with mechanical ventilation with physiological parameters; group II underwent injurious ventilation with high volume tidal (VT) and low positive end expiratory pressure (PEEP). Cells were analyzed for CYP27A1 protein and gene expression levels, 7-ketocholesterol production. In alveolar macrophages of group II, we obtained increase of production of CYP27A1 protein and 7-ketocholesterol, as well as the expression of the CYP27A1 gene at the 2nd hour of ventilation. In the in vitro experiments we show dose-dependent increase of MIP1 $\beta$ and decrease of CYP27A1, iNOS protein production after 7-ketocholesterol treatment.

• Journal of computational fluids engineering
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• v.20 no.3
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• pp.87-93
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• 2015

In this study, a numerical analysis was performed to simulate the thermal-hydraulic response of the secondary side of a steam generator(SG) model equipped with an orifice-type SG outlet flow restrictor to a main steam line break(MSLB) at a pressurized water reactor(PWR) plant. The SG analysis model includes the SG upper steam space and the part of the main steam pipe between the SG outlet and the broken pipe end. By comparing the numerical calculation results for the present SG model to those obtained for a simple SG model having no flow restrictor, the effects of the flow restrictor on the thermal-hydraulic response of SG to the MSLB were investigated.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1016-1021
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• 2004

The need for developing a mathematical model for pad-pivot friction in tilting pad proceeding bearings has been well-recognized, since previous experimental work about the performances of the bearings hypothesized that the friction in the bearings is closely related to their performances. Especially, the sliding friction between pad and pivot in the ball and socket type of the bearings can influence the performance of the bearing. We propose a mathematical model for pad-pivot friction in the ball and socket type, which considers the geometrics of the pad and pivot of the bearings, by assuming the sliding friction in the ball and socket bearing as Coulomb friction. By utilizing the proposed model for pad-pivot friction, we show the analysis of Reynolds equation and energy equation, which explain the thermo-hydrodynamic characteristics of tilting pad proceeding bearings, by taking into account the turbulence and inlet pressure building as well. The results of the study show that the performance of titling-pad proceeding bearings can be greatly influenced by the pad-pivot friction. In particular, we have shown that the analysis of the pad-pivot friction is useful to explain the static proceeding loci and the dynamic characteristics of the ball and socket type of the bearings. Furthermore, for a given operating condition, we can obtain various equilibrium states which satisfy the static equilibrium conditions, by considering the pad-pivot friction.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.6
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• pp.982-990
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• 1987

In previous modeling of Helmholtz-type pulse combustion water heater, muffler and the motion of the flapper valve were omitted. In present work, these have been included in modeling for providing more accurate information regarding the thermal and dynamic behavior of the water heater. In addition, a computer simulation based on the modeling was developed. The comparison of computer predictions with available experimental data shows that the simulation is satisfactory in predicting the nature of operating behavior, amplitudes of the pressure oscillations, and the magnitude of the frequency. But the predicted time-averaged axial temperature of the flue gas along the flue tube length is somewhat below the previous experimental results. The temperature pulsation of the combustion chamber and the velocity pulsation of the flue gas were predicted which have never been measured in previous studies. In particular, the latter is of importance for a valid determination of the heat transfer enhancement due to the gas flow pulsation. Heat transfer results in flue tube were presented and discussed. Also the effects on the installation of the muffler were investigated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.5 s.236
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• pp.655-662
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• 2005

This paper investigates the improvement of accuracy and fatigue life of the developed counter pressurized microcellular gears of polyacetal. It is shown that the fatigue life and operational characteristics of the counter pressurized microcellular gears are more improved than conventional injection molded plastic gears by the dynamic gear durability test. For the cases of test sea.5. conventional injection molded sea.5(SGea.) and counter pressurized microcellular gears(CGear) are manufactured. Durability test is performed on both conventional lnjection molded gears and counter pressurized microcellular gears. Accuracy variation and operational characteristics on fatigue life, wear and tooth surface temperature of CGear and Scear are compared and represented. Operational characteristics of the proposed counter pressurized microcellular gears show a good result in this research. The durability limit of counter pressurized microcellular gears is also obtained, and represented by a function of unit load as well as by a function off-factor.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.1
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• pp.33-41
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• 2011

A mathematical model of slip-in booster separation dynamics is described. A longitudinal 3-DOF(degree of freedom) 2-body dynamic model is developed to simulate the separation dynamics. Aerodynamic models of the missile and the exposed area of booster are built. And, gas generator pushing the booster out and internal channel pressure drop are modelled. To simulate the model, it is assumed that the missile can maintain the 1g level-fight condition during the separation. With this assumption, the interaction forces between missile and booster through the separation phases: phase 0: initial, phase 1: linear translation, and phase 2: free flight motion are defined. Using the simulation, missile flight conditions for slip-in booster`s safe separation, which can be represented by Mach vs. height envelope, are suggested.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.5
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• pp.657-665
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• 2003

Several interesting results were obtained from the flow visualization experiment in the accompanying paper, Part I. in the present study, Part II, a numerical study has been carried out to explain the detailed flow phenomena in micro-channel filling process. Hele-Shaw flow approximation was applied to the micro-channel geometry based on the small characteristic length. And surface tension effect has been introduced on the flow front as the boundary condition with the help of a dynamic contact angle concept between the melt front and the wall. A dimensional analysis for numerical results was carried out and a strong relationship between dimensionless pressure and Capillary number is obtained. The numerical analysis results are compared with the flow visualization experimental observations. And the numerical system developed in the present study seems to be able to predict the interesting micro-channel filling flow characteristics observed from experiments.

• Journal of Power System Engineering
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• v.20 no.1
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• pp.50-56
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• 2016

This paper handled an investigation on the turbulent flow characteristics of three-dimensional small-size axial fan(SSAF) according to operating loads. Also, it was carried out by unsteady-state, incompressible and three-dimensional large eddy simulation(LES). The downstream flow type of SSAF is changed from axial flow to radial flow around the beginning of stall region at the aerodynamic performance curve. Axial mean velocity component largely grows around blade tip at the operating point of A to D, but transverse and vertical mean velocity components as well as Reynolds shear stresses highly develop around blade tip at the operating point of E to H. On the other hand, the peak value of turbulent kinetic energy developed around blade tip shows the highest at the operating point of E.

• International Journal of Quality Innovation
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• v.6 no.1
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• pp.24-34
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• 2005

This research topic evaluates the effectiveness and importance of environmental protection in the 21st century in light of the increasing demand on the earth's natural resources and the pressures on economic and industrial development to provide dynamic power. As the world and our fellow citizens become more conscious of environmental protection, companies are under greater pressure whilst pursuing economic growth. Therefore, domestic manufacturers have been devoting efforts to promote environmental management. This research conducts survey using questionnaires on the operational performance of the manufacturers who have ISO 14000 series accreditation and certification. The survey considers five dimensions/functions within a manufacturer, financial management, human resources management, production management, and marketing management. A total of 35 indices are used for analysis of the effects that the location, history, industry, number of employees, amount of capital, and revenue may have on the performance. This research targets the manufacturers approved of ISO 14000 series certification by Environment Administration Association. The statistical methods deployed are descriptive statistics, T-test, and single factor analysis of variance used for analysis. The conclusions reveal that a certain level of performance has been achieved in every dimension. After T-test, all the indices have reached a significant level. The indications are that ISO 14001 benefits all manufacturers the level of benefits however varies from company to company.

• International Journal of Highway Engineering
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• v.7 no.1 s.23
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• pp.39-47
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• 2005

Fiber reinforced soils have recently implemented to fills and base layers of highways and railroads, and deformation behaviors of reinforced soils in turn should be investigated. The paper evaluated deformation characteristics of fiber reinforced sands and their effectiveness of reinforcement using resonant column tests. The specimens were prepared by varying gradation and mixing polypropylene staple fibers of 0.3% fiber content. Maximum shear moduli of reinforced sands were increased by up to 30% with increasing uniformity coefficient. Shear moduli of well-graded reinforced sands were larger than those of poorly-graded ones regardless of confining pressure in the whole range of shearing strain and reinforcement was, in turn, more effective with higher uniformity coefficient.