• Transactions of the Korean Society of Mechanical Engineers
• /
• v.11 no.5
• /
• pp.810-818
• /
• 1987

A new method is proposed to identify two-phase flow regimes in horizontal gas-liquid flow, based upon a statistical analysis of instantaneous pressure drop curves at an orifice. The probability density functions of the curves indicate distinct patterns depending upon the two-phase flow regime. The transition region also could be identified by the distribution shape of the probability density function. The statistical properties of the pressure drop are analyzed for various flow regimes and transitions. Finally, the data of flow patterns determined by the proposed method are compared with the flow pattern maps suggested by other investigators.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.11 no.5
• /
• pp.856-866
• /
• 1987

In the present paper a statistical method using probability density function has been applied to investigate experimentally the flow patterns and fluctuations of time-averaged local void fraction in air-water two-phase mixtures which flow vertically upwards in concentric annuli. This study was carried out using three vertical concentric annuli. The annular test section consists of a lucite outer tube whose inside diameter is 38mm and a stainless steel inner rod. The rod diameter is either 12mm, 16mm or 20mm. The two-phase flow patterns observed in the experiment were bubbly, slug, annular and each transition patterns. It was first demonstrated that the variance, coefficients of skewness and kurtosis calculated from probability density function on time-averaged local void fraction can be used to identify the flow patterns in the annular passage, and the fluctuation of time-averaged local void fraction varies with the radial position in annular gap and the flow pattern.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2003.09a
• /
• pp.426-430
• /
• 2003

Subsurface biobarrier technology has potential applications to contain contaminated groundwater and/or to degrade toxic pollutants in groundwater. Effective biobarrier formation is need to assess of hydrogeologic characteristics and to conduct practical operation strategies and design based on this prior to design biobarrier. Thus, in this study, we examined hydrogeologic characteristics in biobarrier construction site. Hydraulic conductivities which calculated from slug test data have shown difference with each well as 1.20$\times$10$^{-3}$ -6.00$\times$10$^{-5}$ cm/sec. Tracer test is a method in which concentration of tracer solution during withdrawal in each well by vacuum extraction system is measured with time. Tracer solution was continuously injected by constant head tank. Measured tracer concentration versus time data were fitted to analytical solution of convection dispersion equation (CDE). The fitting data of CDE to the measured data at each extraction well yielded were 0.61cm/min(pore velocity), 5.38$\textrm{cm}^2$/min(dispersion coefficient) for discharge rate of 0.47 1/min and 1.75cm/min(pore velocity), 36.34$\textrm{cm}^2$/min(dispersion coefficient) for discharge rate of 0.93 1/min. As a result, we acquired fundamental parameters which need to design biobarrier and operation strategies.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.23 no.5
• /
• pp.637-645
• /
• 1999

Horizontal two-phase flow pressure drop within rectangular channels with small gap heights have been examined experimentally. The gap heights range from 0.4mm to 4mm corresponding to aspect ratios(the channel height divided by the width) from 0.02 to 0.2. Water and air were used as the test fluids with the superficial velocity ranges being 0.03-2.39m/s and 0.05-18.7m/s, respectively. The experimental results In rectangular channels were compared with the Lockhart-Martinelli correlation, which are widely used for conventional round tube. The Lockhart-Martinelli correlation turned out to be Inappropriate to represent the present experimental data. In this respect, considering the aspect ratio and gap-height effects, an empirical correlation on two-phase flow pressure drop was proposed. The proposed correlation successfully covers the bubbly, plug, slug and annular flow regimes.

• Journal of the Korean Society for Precision Engineering
• /
• v.16 no.6
• /
• pp.45-51
• /
• 1999

The semi-solid forging is a new forging technology in which the billet is heated to the semi-solid state coexisting liquid and solid phase for making globular microstructure and subsequently formed. As the semi-solid forging is compared with conventional casting such as die casting and squeeze casting for the characteristics of its process, the product without inner defects such as gas porosity and segregation can be obtained and its microstructure is globular grain. Simutaneously, its mechanical properties are improved by globular microstructure and the lower temperature of the slug causes the cycle time of manufacturing to be shortened and the die life to be lengthened. As it is compared with conventional cold and hot forging, it is possible to minimize the equipment of production owing to a lower forming load and reduce the number of process by a followed treatment for complex shaped product. Therefore it is needed to confirm the quality of a semi-solid forged product by defining its characteristics quantitatively under these advantages. This paper investigates the formability of a master cylinder by its forming variables. And the microstructural characteristics and mechanical property of it is also studied.

• Journal of the Korean Society of Groundwater Environment
• /
• v.3 no.1
• /
• pp.1-8
• /
• 1996

Coastal waste dump in Pohang is composed of slags and sludge of POSCO. Hydraulic parameters in the coastal waste dump are very different from those in municipal landfills and general unconsolidated or fractured aquifers. In the waste dump pumping or slug tests are not adequate for the estimation of hydraulic parameters. Time-lag and amplitude of the tidal fluctuation of groundwater table are used to determine the hydraulic parameters. Groundwater table at the groundwater observation wells is about 40 cm higher than the sea level. The contributing factors of the groundwater-rise are estimated. Vertical profile of some chemical constituents in groundwater indicates the gradual transition of the fresh groundwater at the uppermost position to the sea water at the bottom.

• The Korean Journal of Malacology
• /
• v.11 no.2
• /
• pp.123-134
• /
• 1995

한국산 산민달팽이 (Incilaria fruhstorferi)의 자성 생식기관을 조직화학적 방법을 이용, 광학현미경으로 관찰한 결과는 다음과 같다. 알부민선(albumen gland)은 대자웅동체관 위에 있으며, 산성 점액다당류와 중성 점액다당류 그리고 단백질성 분비물을 형성하는 세포들로 구성되어 있었다. 수정실(fertilization chamber)을 구성하는 내강 상피는 불규칙한 단층섬모원주상피와 위중층섬모원주상피세포가 3대 1의 비율로 구성되어 있으며, 결합조직에서 형성된 산성점액다다류성 과립들이 상피세포를 거쳐 내강 속으로 분비되었다. 또한 수정실의 외측표면은 기능은 알 수 없으나 산성 점액다당류를 분비하는 대형 세포들로 둘러싸여 있었다 . 수란관(oviduct)의 내강은 크로 작은 돌기로 인해 별모양을 나타내었다. 내강은 위중층원주상피세포로 구성되었으며 그들 사이에서 분비세포의 존재는 확인되지 않았다.질(vagina)의내강은 덮은 세포는 해면조직 형태의 세포와 단층섬모원주상피세포 그리고 위중층섬모원주상피세포 등 다양한 종류로 구성되어 있었으며, 잘 발달된 두터운 근육층은 질의 신축성을 높여 주었다. 정자낭(spermatheca)은 그 형태와 크기, 색깔 등이 종에 따라 다양하고, 질과 연결되는 자성생식기관으로 알려져 있다.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.14 no.5
• /
• pp.1290-1299
• /
• 1990

Characteristics of flow patterns in horizontal gas-liquid two-phase flow for two different sizes of pipe were investigated based upon a statistical analysis of differential pressure fluctuations at an orifice. The probability density function and the power spectral density function of the traces indicate peculiar shapes depending upon the two-phase flow regime. Mixed and separated flows also could be identified by the autocorrelation function. The transition region from separated flow to mixed flow also could be identified by these statistical properties. The experimental data determined by this method were compared with the flow pattern maps suggested by other investigators. The result indicates that the statistical characteristics of differential pressure fluctuations at orifices may be a useful tool for identifying flow patterns of horizontal gas-liquid two-phase flow.

• Journal of Powder Materials
• /
• v.6 no.1
• /
• pp.69-74
• /
• 1999

The microstructure of the reagion of carters, created by Cu and W-Cu shaped charge jets, in a 1020 mild steel target has been intestiaged. The region ahead of the crater created by the Cu shaped charge jet, reveals dramatic grain refinement implying the occurrence of a dynamic recrystallization, while that of W-Cu one dose a martensitic transformation indicative of heating up to an austenitic region followed by rapid cooling.The impacting pressure calculated when the W-Cu shaped charge jet encounters the target is higher than that of the Cu one. The micro-hardness of the region ahead of the crater created by the W-Cu shaped charge jet is also higher than that of the Cu one. The microstructure of W-Cu slug remained in the inside of the craters depicts the occurrence of the remarkable elongation of W particles during the liner collaphse. From these results, the microstructural variation of the region ahead of the crater with Cu and W-Cu shaped charge jets is discussed in trems of the pressure dependency of the transformation region of ferrite and austenite phases.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.20 no.1
• /
• pp.384-398
• /
• 1996

An improved multi-channel Impedance Void Meter (IVM) is developed to measure an area-averaged void fraction. It consists of a main sensor, a reference sensor and a signal processor. The sensor was designed to be flush-mounted to the inner wall of the test section to avoid the flow disturbances. Guard electrodes are used to obtain evenly distributed electrical field in a measuring volume. A reference sensor is also installed to eliminate the drift in void signal caused by the changes in electrical properties of working fluid. The signal processor with three channels is specially designed so as to minimize the inherent error due to the phase difference between channels. As an example of applications, the mean and fluctuating components of void fraction are measured for bubbly and slug flow regime, and it is shown that IVM has good dynamic resolution which is required to investigate the structural developments of bubbly flow and the propagation of void waves in a flow channel.