Siyoul Jang

A ginsenoside-Rh1, a component of ginseng saponin, activates estrogen receptor in human breast carcinoma MCF-7 cells.

We have examined the possibility that a component of Panax ginseng, ginsenoside-Rh1, acts by binding to steroid hormone receptors such as receptors for estrogen, glucocorticoid, androgen, and retinoic acid. Ginsenoside-Rh1 activated the transcription of the estrogen-responsive luciferase reporter gene in MCF-7 breast cancer cells at a concentration of 50 microM. Activation was inhibited by the specific estrogen receptor antagonist ICI 182,780, indicating that the estrogenic effect of ginsenoside-Rh1 is estrogen receptor dependent. Ginsenoside-Rh1 induction of luciferase activity was dose-dependent in CV-1 cells transiently transfected with estrogen receptor and reporter plasmids. Next, we evaluated the ability of ginsenoside-Rh1 to induce the estrogen-responsive genes in MCF-7 cells. Ginsenoside-Rh1 increased c-fos and pS2 at the mRNA levels at 24h after treatment, although the effects were not as prominent as 17beta-estradiol. Western blot analysis showed that progesterone receptor protein was induced at 24h of treatment of ginsenoside-Rh1. However, ginsenoside-Rh1 failed to activate the glucocorticoid receptor, the androgen receptor, or the retinoic acid receptor in CV-1 cells transiently transfected with the corresponding steroid hormone receptors and hormone responsive reporter plasmids. These data support our hypothesis that ginsenoside-Rh1 acts as a weak phytoestrogen, presumably by binding and activating the estrogen receptor.

Ginsenoside-Rb1 acts as a weak phytoestrogen in MCF-7 human breast cancer cells

Ginseng has been recommended to alleviate the menopausal symptoms, which indicates that components of ginseng very likely contain estrogenic activity. We have examined the possibility that a component ofPanax ginseng, ginsenoside-Rb1, acts by binding to estrogen receptor. We have investigated the estrogenic activity of ginsenoside-Rb1, in a transient transfection system using estrogen-responsive luciferase plasmids in MCF-7 cells. Ginsenoside-Rbb1 activated the transcription of the estrogen-responsive luciferase reporter gene in MCF-7 breast cancer cells at a concentration of 50 μM. Activation was inhibited by the specific estrogen receptor antagonist ICI 182,780, indicating that the estrogenic effect of ginsenoside-Rbb1 is estrogen receptor dependent. Next, we evaluated the ability of ginsenoside-Rbb1, to induce the estrogen-responsive gene c-fos by semi-quantitative RT-PCR assays and Western analyses. Ginsenoside-Rbb1 increased c-fos both at mRNA and protein levels. However, ginsenoside-Rbb1 failed to activate the glucocorticoid receptor, the retinoic acid receptor, or the androgen receptor in CV-1 cells transiently transfected with the corresponding steroid hormone receptors and hormone responsive reporter plasmids. These data support our hypothesis that ginsenoside-Rbb1 acts a weak phytoestrogen, presumably by binding and activating the estrogen receptor.

Characteristic Dynamics Torque Vibration of Behavior in Wet Clutch Engagement for Dual Clutch Transmissions

Abstract : Engine torque is transferred to the transmission where drag torque is minimized improving fuel efficiency. This is particularly true in a wet clutch pack. This study measures slip friction when the wet clutch pack in a DCT (Dual-Clutch Transmission) is disengaged, and the friction pads are slipping. Shudder engagement velocity, and applied forces can be measured under various working conditions through these torque transfer experiments. Test results demonstrate that the design parameters, and engagement conditions of wet clutch packs can be optimized to reduce shudder and frictional vibration during engagement in a dual clutch transmission. Key words : Wet clutch(습식클러치), Dual clutch(듀얼클러치), Sliding friction(미끄럼마찰), Shudder(떨림), Frictional vibration(진동), Torque transfer(토크변화), DCT(듀얼클러치 변속기) Nomenclature 1)   : apply force  : separate plate inertia  : fly wheel inertia  : apply pressure on the piston  : friction plate of inner radius  : friction plate of outer radius 

Correlation between resin viscosity and imprinting pressure mode

The changes in the period of the imprinting process were studied by changing resin viscosities and imprinting pressure mode. If an imprinting process is required to achieve a proposed level of residual resin thickness or window open, an appropriate process period should be assigned with respect to the magnitude and rate of the imprinting pressure because the residual layer thickness (RLT) is significantly influenced by these factors. Furthermore, the impact of resin viscosity on RLT variation is as significant as that of the imprinting pressure mode. We performed a numerical simulation using a mold having repetitive elliptical protrusions with a pattern density of 12.03% to determine the influence of the considered process factors on the imprinting process period.

Study of mold elastic rigidity during UV imprinting process

AbstractThe duration and magnitude of imprinting pressure are very influential in the imprinting process, especially in window-open imprinting process. Resin flows spread over the imprinting area according to both the squeeze motion of the mold and the pressure gradient of the mold cavity-protrusion structure, which causes relatively large contact pressure concentrated in certain locations on the imprinting area. The concentrated contact pressure distorts the mold shape, which then results in pattern distortion. When the pattern density of the mold is unevenly distributed, especially across a large imprinting area, pattern distortion is easily influenced by the rigidity of the mold. To avoid pattern distortions, the imprinting period, and the magnitude and rate of the imprinting pressure must be optimized. In this study, variations in resin layer thickness and elastic deformation of mold materials are analyzed using elastohydrodynamic lubrication (EHL) theory. The film thicknesses of the resin layer are computed down to ∼nm and compared with the consideration of the elastic rigidity of the mold materials and without.

Analysis of residual layer thickness of resin in an imprinting process using a soft mold

The selection of proper mold material for an imprinting process is important with respect to the manufacturing cost of the mold as well as the interfacial material mechanics between the resin and the mold. Among the various material characteristics of the mold, its rigidity is an influential factor for the distribution shape of the residual layer thickness (RLT) of the resin, and is therefore an important consideration for subsequent etching processes (window open processes) that remove the residual resin layer. In this work, variations in the RLT for a rectangular mold structure are simulated using thin film lubrication theory and compared with experimental results from an imprinting process.

Monochromatic Image Analysis of Elastohydrodynamic Lubrication Film Thickness by Fringe Intensity Computation

Point contact film thickness in elastohydrodynamic lubrication (EHL) is analyzed by image processing method for the images from an optical interferometer with monochromatic incident light. Interference between the reflected lights both on half mirrorCr coating of glass disk and on super finished ball makes circular fringes depending on the contact conditions such as sliding velocity, applied load, viscosity-pressure characteristics and viscosity of lubricant under ambient pressure. In this situation the film thickness is regarded as the difference of optical paths between those reflected lights, which make dark and bright fringes with monochromatic incident light. The film thickness is computed by numbering the dark and bright fringe orders and the intensity (gray scale image) in each fringe regime is mapped to the corresponding film thickness. In this work, we developed a measuring technique for EHL film thickness by dividing the image patterns into two typical types under the condition of monochromatic incident light. During the image processing, the captured image is converted into digitally formatted data over the contact area without any loss of the image information of interferogram and it is also interpreted with consistency regardless of the observer’ s experimental experience. It is expected that the developed image processing method will provide a valuable basis to develop the image processing technique for color fringes, which is generally used for the measurement of relatively thin films in higher resolution.

Frictional Torque Transfer Behaviors of Friction Pads in Wet Clutch Engagement

For stable frictional torque transfer, wet clutch pads have the functional requirements of a high traction and a low wear rate with positive μ-V frictional characteristics. However, because of the intrinsic negative μ-V frictional characteristics of a friction material that has a static friction coefficient greater than its kinetic friction coefficient, the frictional torque transfer has unstable vibrations during the clutch-pad engagement.To reduce the vibration mode during the engagement of wet clutch pads, the kinetic friction coefficient should be made greater than the static friction coefficient through modifications in the design parameters as well as in the characteristics of the friction materials. To obtain positive μ-V frictional characteristics, it is important to manipulate the static-friction coefficient, which largely develops in the boundary lubrication stage during the clutch-pad engagement. The formation of the boundary film is described by slip boundary conditions and hydrodynamic lubrication films. It also includes the elastic deformation of the wet pad material due to the contact pressure. The wet clutch pad material is made of a porous structure through which the lubricant can easily spread when the applied load and sliding speed are imposed. The lubrication and the direct contact of the surfaces are simultaneously considered for a frictional torque transfer that lasts for less than one second, depending on the working conditions.In this study, some of the computational results with a measured μ-V friction coefficient covering both the static and kinetic friction during the wet-clutch engagement are obtained for the lubrication and the direct-contact pressures.Copyright

A Study on Numerical Solution Method for Efficient Dynamic Analysis of Constrained Multibody Systems

An efficient computational method for the constrained multibody systems is proposed. In the proposed method, local parametrization method is employed to apply the same solution method for position, velocity, and acceleration analyses since the coefficient matrices for each analysis have an identical matrix pattern. The skyline solution method is used to overcome numerical inefficiency when solving large scaled equations. Subsystem partitioning method is derived systematically to perform parallel processing for the real time simulation. To show the numerical accuracy and efficiency of the proposed method, three numerical problems are solved.Copyright