• Proceedings of the KSME Conference
• /
• 2000.11b
• /
• pp.377-380
• /
• 2000

The collapsible phenomena of the circular tubes due to the excessive transmural pressure are investigated experimentally. Collapsible tubes are installed in the test section where the external pressure is applied to the test tubes by applying the hydrostatic head. The collapsible circular tubes are made of rubber, whose diameters are 6 and 4.2 mm, respectively. The hydrostatic water head of the upper reservoir is applied to the test section. Pressures at the upstream and downstream sides are measured by the pressure transducers. The collapsible phenomena are observed as the transmural pressure Increases, and also the flutter phenomenon occurs due to the critical transmural pressure.

• Journal of the Korean Society for Railway
• /
• v.7 no.3
• /
• pp.200-207
• /
• 2004

Theoretical study has been conducted to clarify pressure characteristics of KTX (Korea Train eXpress) in tunnel. The severe pressure change in tunnel may give rise to the ear-discomfort for passenger and fatigue for car body. Critical tunnel lengths which are induced by x-t diagram analysis can be applied to the experimental results measured by using the running test with atmospheric pressure sensors and portable data acquisition system in previous study. In this study, the tunnels from 200m to 4000m in length have been chosen for the investigation of tunnel length effects. We found that there are similar patterns of external pressure change for each critical tunnel length. The critical tunnel lengths are governed by train speed, train length and sonic velocity. And, the patterns of pressure wave in tunnel are classified into eight groups.

• Current Applied Physics
• /
• v.18 no.11
• /
• pp.1375-1380
• /
• 2018

Atmospheric-pressure plasma has a great potential in many applications due to its simplicity rather than low pressure plasmas. In material processing, biomedical applications, and many other applications, the input power, gas flow rate, and the geometry of electrode have been mainly considered and studied as important external parameters of atmospheric-pressure plasma control. Besides, since the atmospheric-pressure plasmas are typically generated in an open air, the relative humidity is difficult to control and can change day by day. Therefore, the relative humidity cannot be ignored for plasmas. Thus, in this work, the atmospheric-pressure plasma jet was characterized by changing relative humidity, and it was found that the increase in electron density and OH radicals are due to Penning ionization between helium metastable and water vapors at higher humidity condition.

• The Korean Journal of Health Service Management
• /
• v.6 no.1
• /
• pp.53-63
• /
• 2012

The purpose of this study is to examine the influence of external image and self perfectionism on the depression. The survey collected 240 subjects from 3 university students in Seoul, Korea. The research period was from May to June of 2011 and the collected data were analyzed using the SPSS 15.0. As a result of this research, those with lower self image level, those with higher self perfectionism increased the depression level. It is necessary to develop programs for university students considering the fact that external image and self perfectionism influence on the depression. Moreover, it should be developed that solutions can decrease psychological pressure and overcome overwhelming expectation.

• Proceedings of the KSME Conference
• /
• 2000.04a
• /
• pp.661-665
• /
• 2000

A method of considering the fluid induced external force in structural dynamic analysis is presented in this study. The fluid induced pressure distribution around a structure in discrete number of orientation. and velocity is calculated by using a CFD code and tabulated as resultant forces and moments in a database. These forces and moments are interpolated and employed as external forces during the dynamic analysis of structure. The reliability and usefulness of the present method is validated by using a simple discrete system example through transient analysis. The flutter speed is obtained and compared to the analytical solution. Comparing to the method in which structural dynamic and fluid flow analyses are performed simultaneously, the present method is very efficient to save computational effort.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2004.04a
• /
• pp.349-355
• /
• 2004

The material such as steel or concrete has used to civil structures such as drainage pipes , but many problems such as corrosion in using steel and concrete pipes have happened. So, Necessity of developing new materials with high strength and anti-corrosion has been topic recently. One of this topics is study about ERP pipe. The strength of orthotropic FRP tends to be higher than it of isotropic FRP, the buckling problems can be significant in materials with high strength. thus, the study about bucking of orthotropic FRP-pipe is needed. In this study, buckling analysis of laminated cylindrical composite structures subjected In ply angle change under external uniform pressure was performed.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.43 no.2
• /
• pp.105-111
• /
• 2001

This study is performed to develop an agricultural hydraulic structure for collecting and draining pipe using polymer concrete. The water permeability of collecting and draining pipe shows an 5.917$\ell$/$\textrm{cm}^2$/h, it is more 190 times as large as in the world maximum rainfall. The external pressure on the collecting and draining pipe is in the range of 1.85~5.25tf/m under 2-edge test, 2.6~6.2tf/m under sand mat and the vertical displacement is in the range of 0.48~1.06mm, 1.01~1.89mm, respectively. Also, an increasing rate of external pressure on the developed pipe is higher than that of PVC pipe to the variation of t/D. Accordingly, the pipe developed in this study will be used widely in agricultural hydraulic structures such as collecting and draining structure.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2000.11a
• /
• pp.689-694
• /
• 2000

The traditional concept after Terzaghi was that consolidation was the dissipation process of pore water pressure compatible to external loading which was generated immediately after the loading. However, a theory of one-dimensional consolidation based on elasto-viscous liquid model proposed by Yoshikuni(1994) explained that the process of primary and secondary consolidation was considered to be not a simple process of dissipation of pore water pressure but a simultaneous process of dissipation and generation by external loading. This study attempts to demonstrate general consolidation behaviour of clayey soils including effects of consolidation history, load increment and thickness of cohesive layer by one-dimensional Finite Difference Method(F.D.M) analysis from the viewpoint of elasto-viscous consolidation theory.

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.291-294
• /
• 2002

This study describes the external spray characteristics of deflector nozzle such as the breakup procedures of liquid sheet, spray angle, discharge coefficient and bubble behaviors of spray and SMD at deflector nozzle. In order to visualize the spray behaviors shadow graphy technique were used. According to the increase of injection pressure, development of the spray passes through the dribbling, distoted jet, closed bubble due to the contraction by surface tension forces, the bubble opens into hollow tulip shape, and the curved surface straightened to form a conical sheet like as the simplex swirl atomizer. Spray cone angle was nearly 90 deg. Variations of SMD were examined in order to describe the dependency of SMD on the injection pressure and orifice diameter. The shape of deflector and oriffice diameter had an effect on the discharge coefficient.

• Journal of Energy Engineering
• /
• v.23 no.4
• /
• pp.183-188
• /
• 2014

Solenoid operated electromagnetic control valve (ECV) using in an external variable displacement swash plate type compressor is widely used for air conditioning control system because of its low energy consumption and high efficient characteristics. ECV controls the entire vehicle air conditioning system by means of a pulse width modulation (PWM) system that supplied from an external controller. Different pressure ports located within ECV has important functions to control the air/refrigerant flow through its internal passages. The flow paths are preciously maintained with acceptable ranges of leakage (gap) between the parts inside it which is followed by effective design and critical dimensioning of its internal features. Therefore, it saves energy losses from the solenoid operation as well as ensures the balance of forces within it. The research paper highlights analysis of the leakages (at different pressure ports) and dimensioning tolerance factors that affects the ECV performance.