• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.5 s.122
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• pp.405-414
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• 2007

In recent years, experimental and theoretical studies show that turbulent flows looking disordered have a definite structure produced repetitively with visible order. As a core structure of turbulence, hairpin vertices are believed to play a major role in developing and sustaining the turbulence process in the near wall region of turbulent boundary layers and may be regarded as the simplest conceptual model that can account for the essential features of the wall pressure fluctuations. In this work, fully developed typical hairpin vortices are focused and the associated surface pressure distributions and their corresponding spectra are estimated. On the basis of the attached eddy model, the overall surface pressure spectra are represented in terms of the eddy size distribution. The model is validated by comparison of predicted wavenumber spectra with existing empirical models, the results of direct numerical simulation (DNS) and also spatial correlations with experimental measurements.

• Journal of the Korean Vacuum Society
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• v.21 no.1
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• pp.17-21
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• 2012

Ga-doped ZnO (GZO) thin films for application as transparent conducting oxide film were deposited on the glass substrate by using rf-magnetron sputtering system. The effects of working pressure on electrical and optical characteristics of GZO films were investigated. Regardless of the working pressure, all films were oriented along with the c-axis, perpendicular to the substrate. The electrical resistivity was about $8.68{\times}10^{-3}{\Omega}{\cdot}cm\sim2.18{\times}10^{-3}{\Omega}{\cdot}cm$ and the average transmittance of all films including substrates was over 90% in the visible range. The good transparents and conducting properties were obtained due to controle the working pressure. The obtained results have acceptable for application as transparent conductive electrodes in LCDs and solar cells.

• The Journal of the Petrological Society of Korea
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• v.21 no.2
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• pp.249-261
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• 2012

Olivine is a dominant mineral in the upper mantle and is elastically very anisotropic. When olivine is deformed under stress at high pressure and high temperature, lattice preferred orientation (LPO) is formed. It is known that the LPO of olivine is affected by water, stress, and pressure. In this paper, I reviewed the papers dealing with the effects of water, stress, and pressure on the LPO of olivine, summarized the papers on the LPOs of olivine in natural mantle rocks, and discussed its implications for seismic anisotropy in the upper mantle. In addition, I also described four types of LPOs of orthopyroxene recently found in natural spinel lherzolite.

• Membrane Journal
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• v.1 no.1
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• pp.34-43
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• 1991

The relationships between affinity of membranes and optimum operation conditions were investigated in the pervaporation of water(1)/ethanol(2) mixture through cellulose acetate(CA) membranes having more affinity to water and silicone rubber(SR) membranes having more affinity to ethanol. CA and SR membranes were prepared and amount of sorption, sorption selectivity, pervaporation separation factor and pervaporation rate in both of membranes were determined and compared. The effects of downstream pressure were analyzed using Thompson diagram and the sorption and pervaporation characteristics with composition of feed and operation temperature were examined in terms of affinity, activity coefficient, plasticizing effect and activation energy of individual species. In the separation of water through CA membranes, high performance of both pervaporation separation factor (water to ethanol, $[\alpha^2_1]_{PV}$) and pervaporation rate was obtained in the conditions of low downstream pressure, middle range of feed concentration and high temperature. In the separation of ethanol through SR membranes, pervaporation separation factor(ethanol to water, $[\alpha^2_1]_{PV}$) increased with downstream pressure and decreased with concentration of ethanol in feed and operation temperature, while pervaporation rate showed opposite trends to those of ($[\alpha^2_1]_{PV}$).

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1B
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• pp.61-70
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• 2010

This research presents a methodology to define and apply appropriate index that can measure the risk of regional flood damage. Pressure-State-Response structure has been used to develop the Flood Risk Index(FRI), which allows for a comparative analysis of flood risk assessment between different sub-basins. FRI is a rational assessment method available to improve disaster preparedness and the prevention of losses. The pressure and state index for flood at 117 sub-basins from the year 1980s until the t 10s showed proportional relations, but state index did not decrease even though response index increased. This shows that pressures for flood damage relatively exceed countermeasure for flood. Thus this means we need to strengthen design criteria for flood countermeasure in the future. The FRI is gradually going down in consequence of continuous flood control projects. Flood risk of Han River and Nakdong River area is relatively lower than that of Geum, Seumjin, and Youngsan River area.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.409-414
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• 2021

Tightness performance that blocks compartments is important for surface ships to achieve superior mission performance and survivability in combat environments. To meet the above requirements, airtightness of the structural elements and the appropriate strength to specific areas are checked during a test run after ship construction. In particular, air tests of compartments adjacent to the water surface are performed. In an air test, air is injected into the compartment up to the test pressure of the test memo. The pressure drop value is checked after 10 minutes to determine if the requirements of the corresponding area are satisfied. In summer, however, when the influence of the outside temperature is large, a phenomenon in which the internal pressure increases during the air test was identified. This phenomenon reduces the reliability of the test result. Therefore, a system was designed to compensate for temperature changes in the compartments through this study. The developed system calculates the amount of pressure change caused by a temperature change in the compartment and outputs a correction value. The pressure change was calculated using the ideal gas equation, reflecting the maintenance, increase, and decrease in temperature during the test process. A comparison of the calculated pressure correction value with the database of NIST REFPROP revealed a difference of 0.126% to a maximum of 0.253%.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.555-558
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• 2005

국제통화기금(IMF ; International monetary Fund)관리시대를 겪으면서 우리나라는 모든분야에서 실적 및 성과지상주의를 도입하여 모든 것은 효율성과 유연성 위주로 제도를 바꾸었고, 동양의 전통사상인 충효와 신의는 실적과 평가라는 목적과 수단으로 대체되었다. 본 논문에서는 국민의 정부에서 시작되어 참여정부에 이르기까지 동 시기에 우리나라에서 주로 사용해 왔던 성과지상주의와 이에 편승하여 정부가 그동안 만들어 시행해 온 각종 평가 중에서 국가연구개발 평가에 대해 집중적으로 살펴보았다. 평가시스템들이 양산된 배경에는 외국계 상공인들의 요구와 우리나라 시장 확대를 통해 이익을 극대화 하려는 외교적 압력 외에도 평가시스템을 활용함으로써 얻게되는 특정정부부처 등 평가기관들의 권력상승작용에 대한 기대감등으로 경쟁적으로 평가시스템을 도입하였고, 평가시스템에 평가위원 등으로 참여하는 각 대학의 교수 등 평가자들 또한 평가자로서의 권한을 향유하는데 따른 평가집단으로서의 역할을 하면서 냉철한 검토와 준비없이 평가가 진행되고 있다. 따라서 피평가기관이 업무추진보다 평가준비에 더욱 많은 시간을 소비한다면 국가경제에 큰부담으로 작용할 것이므로 사업에 대한 각종평가는 년2회를 넘지 않도록 평가를 제한해야 한다.

• Journal of the Korean Institute of Gas
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• v.14 no.5
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• pp.13-18
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• 2010

This paper presents the development of an integrated control and safety management system for 9% nickel steel LNG storage tank. The new system added the measuring equipment of pressure, displacement and force compared to the conventional measurement and control system. The measured data has simultaneously been processed by integrating and analyzing with new control equipments and safety management systems. The integrated control and safety management system, which may increase a safety and efficiency of a super-large full containment LNG storage tank, added additional pressure gauges and new displacement/force sensors at the outer side wall and a welding zone of a stiffener and top girder of an inner tank, and the inner side wall of a corner protection tank. The displacement and force sensors may provide failure clues of 9% nickel steel structures such as an inner tank and a corner protection, and a LNG leakage from the inner tank. The conventional leak sensor may not provide proper information on 9% nickel steel tank fracture even though LNG is leaked until the leak detector, which is placed at the insulation area between an inner tank and a corner protection tank, sends a warning signal. Thus, the new integrated control and safety management system is to collect and analyze the temperature, pressure, displacement, force, and LNG density, which are related to the tank system safety and leakage control from the inner tank. The digital data are also measured from control systems such as displacement and force of 9% nickel steel tank safety, LNG level and density, cool-down process, leakage, and pressure controls.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1293-1300
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• 2011

The configurations of the evaporator and condenser of a water chiller can be determined from the trade-off between the heat transfer area, which is related to the capital cost and the pressure drop, which is associated with the operational cost. In this study, the design of the water chiller focused on minimizing the water pressure drop of both condenser and evaporator for given cooling capacity and requirements. Commercial enhanced tubes were employed to simulate real-life conditions. The results of the present analysis were compared with those obtained by HTRI software for verifying them. The results indicated that a reduction in the water pressure drop, which is associated with the short length of a tube, can be effected by decreasing the number of tube passes and increasing the number of tubes and the tube diameter. However, using a large number of tubes with smaller diameters can reduce the capital cost because the tubes are short. The reduction of the capital cost is due to the fact that a small-diameter tube has low internal thermal resistance and hence contributes to a decrease in the overall thermal resistance per unit length.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.2
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• pp.89-95
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• 2021

Pressure sores are an unresolved human challenge. In this study, a keyboard-type medical bed was developed and a body pressure sensor was installed to provide a method to control the keyboard so that the pressure sores do not reach the critical pressure. For this, a keyboard-type mattress using a 4bar link is developed, and a method of controlling the height adjustment of the keyboard within the critical pressure through a body pressure sensor is used. There is a feeling of discomfort in the body when the keyboard is raised and lowered from pressure sores, which is an important factor: pressure x time, and only time control is performed, but if the proposed method is used, pressure is controlled within the critical pressure, thereby preventing bedsores in a comfortable state. The effectiveness and validity of the developed medical bed system were verified through theories and experiments.