• Transactions of the Korean Society of Machine Tool Engineers
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• v.18 no.2
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• pp.130-136
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• 2009

Semi-solid casting(SSC) of magnesium alloys is increasingly being used to produce high quality components. This process is similar to the injection molding of plastics and is called thixomolding. Using this process, higher strength, thinner wall sections and tighter tolerances without porosity are obtained. The high strength and low weight characteristics of magnesium alloys render the high-precision fabrication of thin-walled components with large surface areas. They are widely used for the IT, auto and consumer electronics industries. However, warpage of the thin-walled sections degrade quality of the parts produced in the SCC process. To produce thin-walled magnesium alloy parts, the geometry of gating system on the quality of the finished products should be clearly studied. In this paper, to minimize warpage of the thin-walled sections, Taguchi method is applied to the optimal design of the gate geometry in the thixomolding process. Width, height, length and angle of the gating system are selected for the robust design parameters. Effectiveness of the robust design is verified through the CAE software.

• Journal of Korean Neurosurgical Society
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• v.44 no.3
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• pp.178-181
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• 2008

Although endovascular intervention is the first-line treatment of intracranial aneurysm, intraprocedural rupture or extravasation is still an endangering event. We describe two interesting cases of extravasation during embolotherapy for ruptured peripheral cerebral pseudoaneurysms. Two male patients were admitted after development of sudden headache with presentation of intracerebral and subarachnoid hemorrhage, respectively. Initial angiographic assessment failed to uncover any aneurysmal dilatation in both patients. Two weeks afterwards, catheter angiography revealed aneurysms each in the peripheral middle cerebral artery and anterior inferior cerebellar artery. Under a general anesthesia, endovascular embolization was attempted without systemic heparinization. In each case, sudden extravasation was noted around the aneurysm during manual injection of contrast after microcatheter navigation. Immediate computed tomographic scan showed a large amount of contrast collection within the brain, but they tolerated and made an unremarkable recovery thereafter. Intraprocedural extravasation is an endangering event and needs prompt management, however proximal plugging with coil deployment can be sufficient alternative, if one confronts with peripheral pseudoaneurysm. Peculiar angiographic features are deemed attributable to extremely fragile, porous vascular wall of the pseudoaneurysm. Accordingly, it should be noted that extreme caution being needed to handle such a friable vascular lesion.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.899-905
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• 2000

The characteristics of air flow and engine performance with swirl ratio variance of intake port In a turbocharged DI diesel engine was studied in this paper. The intake port flow is important factor which have influence on the engine performance and exhaust emission because the properties in the injected fuel depend on the combustion characteristics. The swirl ratio for ports was modified by hand-working and measured by impulse swirl meter. For the effects on performance and emission, the brake torque and brake specific fuel consumption were measured by engine dynamometer and NOx, smoke were measured by gas analyzer and smoke meter. As a result of steady flow test, when the valve eccentricity ratio are closed to cylinder wall, the flow coefficient and swirl intensity are increased. And as the swirl ratio is increased, the mean flow coefficient is decreasing, whereas the gulf factor is increasing. Also, through engine test its can be expected to meet performance and emission by optimizing the main parameters; the swirl ratio of intake port, injection timing and compression ratio.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.502-507
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• 2003

Spiral jet is characterized by a wide region of the free vortex flow with a steep axial velocity gradient, while swirl jet is largely governed by the forced vortex flow and has a very low axial velocity at the jet axis. However, detailed generation mechanism of spiral flow components is not well understood, although the spiral jet is extensively applied in a variety of industrial field. In general, it is known that spiral jet is generated by the radial flow injection through an annular slit which is installed at the inlet of convergent nozzle. The objective of the present study is to understand the flow characteristics of the spiral jet, using a computational method. A finite volume scheme is used to solve 3-dimensional Navier-Stokes equations with RNG ${\kappa}-{\varepsilon}$ turbulent model. The computational results are validated by the previous experimental data. It is found that the spiral jet is generated by coanda effect at the inlet of the convergent nozzle and its fundamental features are dependent the pressure ratio of the radial flow through the annular slit and the coanda wall curvature.

• Archives of Pharmacal Research
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• v.23 no.5
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• pp.482-487
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• 2000

The antitumor activity of Bifidobacterium breve K-110, and K-I11, and B. infantis K-525 was investigated. These Bifidobacterial cells and their cell wail preparations (WPG) significantly increased the survival rate of mice who had been intraperitoneally implanted with sarcoma 180 cells. Solid tumor growth was inhibited even when the sarcoma 180 cells were implanted into the groins of the mice. However, the Bifidobacterial cells did not show in vitro cytotoxicity against tumor cell lines. Cell kinetic studies revealed that these WPGs induced neutrophils, which were followed by macrophages, at the site of peritoneal injection. The WPGs directly activated these cells to inhibit the growth of tumor cells in vitro assays. Our results suggest that Bifidobacterial WPGs induce and activate nonspecific phagocytes in situ to reject growing tumor cells in the mouse peritoneal cavity.

• Journal of Acupuncture Research
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• v.23 no.5
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• pp.55-67
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• 2006

Purpose : This study was carried out to identified the effects of Cultivated Wild Ginseng Pharmacopuncture(CWG Pharmacopuncture) to the rats with surgically induced endometriosis. Methods : Endometrial tissue was implanted in the serosal wall of the small intestine in rats. The rats were divided randomly into an experimental and control group. The experimental group was treated with CWG Pharmacopuncture intravenous injection to the vein of tail and the control group was given same dose of normal saline for 4 weeks. And the size of the ectopic uterine tissue was estimated, and the serum progesterone, estradiol and cytokine($TNF-{\alpha}$, IL-2, IL-4, IL-6, IL-10) concentrations were analyzed. Results : 1. The size of the ectopic uterine implants in the experimental group was much smaller than that in the control group. 2. In analysis of serum hormone, the concentration of progesterone showed higher value than that of control group and estradiol showed lower value. 3. In analysis of cytokine, $TNF-{\alpha}$, IL-2 and IL-6 concentrations showed lower value than that of control group. 4. In analysis of cytokine, IL-4 concentration showed no significant difference and IL-10 concentrations showed higher value than that of control group. Conclusion : These results indicated that CWG Pharmacopuncture is useful treatment for endometriosis.

• YAKHAK HOEJI
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• v.51 no.6
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• pp.476-481
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• 2007

A polymorphic fungus, Candida albicans, causes various forms of infections such as disseminated candidiasis and vaginitis. Recent reports indicate that the fungus is a main etiological agent for the arthritis. In search of new sources for treatment of the fungal arthritis, we examined $18{\beta}$-glycyrrhetinic acid ($18{\beta}$-GA) against C. albicans-caused septic arthritis. The compound is isolated from Glycyrrhizae Radix that is known to have various immunomodulating activities and is one of the most popular herbal medicines. For induction of animal model of a septic arthritis, mice were given an emulsion form of C. albicans cell wall mixed with Complete Freund's Adjuvant (CFA) via footpad-injection. To determine prophylactic and therapeutic effects, the component was given to the animals before or after the induction of the arthritis, respectively. Data showed that intraperitoneal administration of $18{\beta}$-GA resulted in reduction of the inflammation, indicating the component had both prophylactic and therapeutic activities. For investigation of mechanism of the $18{\beta}$-GA, inhibitory effects on NO (nitiric oxide) and on T-lymphocyte proliferation were determined. Results demonstrated that $18{\beta}$-GA suppressed NO production from LPS (lipopolysaccharide)-treated macrophages and also inhibited proliferation of Con A (concanavalin A)activated T-cells. Taken together, $18{\beta}$-GA, a pentacyclic triterpene, has anti-arthritic activity against C. albicans-caused septic arthritis, possibly by blocking NO production and T-cell suppression.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.466-471
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• 2004

In gas turbines, excess air for combustion is available and therefore lean premixed combustion is the most promising approach to the significant reduction of thermal NOx emissions. At lean conditions, however, flame stability is inherently worse and hence combustion tends to be incomplete. Efforts have been devoted toward extending the operating range of complete combustion at leaner conditions. One of them is the lean-lean two-stage combustion where lean to ultra-lean secondary mixtures are mixed with the hot burned gas from the primary stage. Conventional flame combustion or flameless reaction are initiated depending on the conditions of the secondary zone. In the first part of the present study, the effects of fuel injection on the emissions and flame stability were investigated for a single tubular flame, In the second part, the emissions and flame stability were studied for a two-stage combustor with secondary mixture injected through the tangential slots on a cylindrical combustor wall. The effects of the ratio of air flow rates to the primary and secondary zones on the emissions and combustion characteristics were investigate.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.4
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• pp.637-643
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• 2002

The objective of this study is to provide a simple methodology to find optimum processing conditions to fabricate sub-micron structured DVD-RAM substrates with superb optical and geometrical properties. It was fecund that the birefringence, which is regarded as one of the most important optical properties for an optical disk, was very sensitive to the mold wall temperature history. Also, the integrity of the replication, represented by the land-groove structure and the radial tilt were influenced by the mold temperature and the compression pressure. A set of optimum conditions were obtained by applying Design of Experiment and the objective functions composed of three different objectives.

• Proceedings of the Korean Society of Laser Processing Conference
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• 2004.10a
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• pp.22-28
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• 2004

Pit and rim formation on the Acrylonitrile Butadiene Styrene(ABS) plastic surface was evaluated after it was irradiated by $CO_2$ and Nd:YAG laser beams. Our results show that thermal effect floor was well observed at the outer wall of pit with $CO_2$ laser irradiated while it was not the case with Nd:YAG laser irradiated. Also the volume and depth of pit formation increase proportionally with the energy intensities of two laser irradiations, but there are significant differences in the slope, width, and FWHM of the Pit formation with two types of laser irradiations. This result shows that $CO_2$ laser irradiation leads to better cooling contraction effect while Nd:YAG laser irradiation induces better recoil pressure effect during the interaction between ABS plastic and laser beam irradiation. The shape of the laser marking could vary significantly depending on the traveling path of molten plastic during injection molding of ABS plastic. Therefore, the selection of material and molding process can have a great impact on the performance of optical storage media.