• Structural Engineering and Mechanics
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• v.55 no.4
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• pp.857-869
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• 2015

The aluminum 7075-T6 is known as an alloy widely used in aircraft structural applications, which does not exhibit strain rate sensitivity during dynamic compressive tests. Despite mechanical importance of the material, there is not enough attention to determine appropriate sample dimensions such as a sample diameter relative to the device bar diameter and sample length to diameter (L/D) ratio for dynamic tests and how these two parameters can change mechanical behaviors of the sample under dynamic loading condition. In this study, various samples which have different diameters of 31.8, 25.4, 15.9, and 9.5 mm and sample L/D ratios of 2.0, 1.5, 1.0, 0.5, and 0.25 were tested using Split Hopkinson Pressure Bar (SHPB), as this testing device is proper to characterize mechanical behaviors of solid materials at high strain rates. The mechanical behavior of this alloy was examined under ${\sim}200-5,500s^{-1}$ dynamic strain rate. Aluminum samples of 2.0, 1.5 and 1.0 of L/D ratios were well fitted into the stress-strain curve, Madison and Green's diagram, regardless of the sample diameters. Also, the 0.5 and 0.25 L/D ratio samples having the diameter of 31.8 and 25.4 mm followed the stress-strain curve. As results, larger samples (31.8 and 25.4 mm) in diameters followed the stress-strain curve regardless of the L/D ratios, whereas the 0.5 and 0.25 L/D ratios of small diameter sample (15.9 and 9.5 mm) did not follow the stress-strain diagram but significantly deviate from the diagram. Our results indicate that the L/D ratio is important determinant in stress-strain responses under the SHPB test when the sample diameter is small relative to the test bar diameter (31.8 mm), but when sample diameter is close to the bar diameter, L/D ratio does not significantly affect the stress-strain responses. This suggests that the areal mismatch (non-contact area of the testing bar) between the sample and the bar can misrepresent mechanical behaviors of the aluminum 7075-T6 at the dynamic loading condition.

• Journal of the Korean Society of Industry Convergence
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• v.9 no.1
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• pp.21-27
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• 2006

The laminar burning velocity was measured using a spherical combustion bomb with central ignition. Mixtures with equivalence ratio between 0.6 and 1.2, were tested. The computation was carried out for the burning velocity using premix code of Chemkin program under the unburned gas pressure of 0.5bar-30bar and temperature of 300K-700K at ${\Phi}1.0$. The results showed little difference between these two methods. The burning velocity was decreased by increasing the pressure and increased by increasing the temperature. The burning velocity was predicted by using the following equations $$S_L(m/s) = S_{st}(T/300)^{1.85}(P)^{-0.45}$$ $$(0.5bar{\leq}P{\leq}30bar,\;300K{\leq}T{\leq}700K)$$).

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.523-528
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• 2003

AS City traffic means, the electric railway of the role is overwhelming with recognizing good merits of safety, no environment disruption and accurate destination time. Currently, Korea subway are running about 290km through eight subway lines. The latest constructed subway had been made by imperoved matherials which is going on improving. Therefore, we researched this project to keep up facilites easily, repress a leakge current and reduse install cost and repair time in changing facility at overhead Contact wire system because of arc by reforming construction plan about Expansion Joint and Air Section which is regarded as weak point when facilities are fixed and maintianed of Rigid Trolley bar System. as above we can contribute various part to making useful O.C.S(overhead contact wire system)

• Progress in Superconductivity and Cryogenics
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• v.9 no.4
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• pp.46-49
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• 2007

This paper describes the sensitive cooling performance change of J-T refrigerator for cryosurgical probe due to its working fluid. The analytical results of using 50 bar nitrous oxide are compared with the case of 300 bar argon. Bio-heat equation is numerically solved to investigate the effect of the probe temperature and the cooling power of the J-T refrigerator. The refrigerator using 50 bar nitrous oxide has larger cooling power above 185 K than the one with 300 bar argon, which enables fast cooling at early stage of cryosurgery, but the biological tissue away from the probe tends to be cooled slowly after the probe reaches its lowest operating temperature. When the repeated freeze-thaw cycle is employed for main tissue destruction mechanism, using high pressure nitrous oxide is more advantageous than argon if the freezing operation is within 2-3 minutes. The probe with high pressure argon is more suitable for the case of longer freeze-thaw cycle with fewer repetitions.

• The Journal of Dong Guk Oriental Medicine
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• v.7 no.1
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• pp.1-32
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• 1998

I found following idea, as a result of researching his Science idea, mainly, by translation of the "$Zh\bar{a}ng$ xi $ch\acute{u}n$ $Xu\acute{e}$ $Sh\acute{u}$ ssu $hsi\acute{a}ng$ "(張錫純 學術硏究). $Zh\bar{a}ng$ xi $ch\acute{u}n$ regarded $ch\tilde{u}ng$ $ch\bar{u}ng$ $ts'\bar{a}n$ $hs\bar{l}$' (衷中參西) as the core idea of The Chinese-Western medical combination. He didn't segregate philosophy of the West from One of the Orient. He persued to harmonize each other and thought that the Western medicint theory is included in the Chinese one in many parts. besides, He recognized that it is bad to reject each other, for the medical science's purpose is to save a life, and united The Chinese-Western medicine theory, by $ch\acute{u}ng$ $ch\tilde{u}ng$ $ch\bar{u}ng$ $ts'\bar{a}n$ $hs\bar{l}$'(衷中參西) idea which refers to consult the Western medicine on the basis of the Chinese one. Medical basic theory of $Zh\bar{a}ng$ xi $ch\acute{u}n$ brought up new views of the theory : Dae-gi(大氣), gi-Hwa(氣化) theory, Nongangubgan byung juing chi(論肝及肝病證治), Eum her chijung ja bi(陰虛治重滋脾). Lim Sangeung yong(臨床應用) of Hyul Her gub(血虛及)-Hwal Hyul Hwa $\breve{u}$ bub(活血化瘀法), on the basis of classics, such as, "$N\breve{e}i$ Ching"(內經), "Chin Kue $\breve{i}$ $y\bar{a}o$ $l\ddot{u}{\bar{e}}h$, "Shen $n\acute{u}ng$ $p\breve{e}n$ $t\acute{s}{\check{a}}o$ ching"(新農本草經) etc. I'll sum up $Zh\bar{a}ng$ xi $ch\acute{u}n's$ clinical idea now He unified Sang Han(像寒)-On Byung(溫病) with Yuk Kyung Byung Jung(六經辨證) and It was noticiable to utilize a kinds of Baek Ho Tang(白虎湯). He gave a detailed description about a method of grasp the symptoms of the cause of the internal medicine diseases and pathology and, he left abundant views of theory about using remedy and experience of clinic.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.6
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• pp.926-931
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• 2012

Rotary bar was cutting tool being in use for deburring scale after welding metal and for eliminating sharp edges. It was necessary to develop exclusive 6-axis machine being possible to process machining continuously for making an cutting edge of rotary bar and to revise easily machining program. This study aimed at the structural analysis of strength according to the configuration of new made 6-axis machine and at the machining accuracy and durability of rotary bar. As a result of test, the runout of new rotary bar manufactured out of 6-axis machine was decreased from 0.385 mm to 0.027mm extensively than old one. And good cutting ability and durability was obtained equal quality compared with imported products.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.7
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• pp.587-594
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• 2016

The Split Hopkinson pressure bar (SHPB) test method, which is composed of three cylindrical bars, measuring devices and frames, is known for its reliable technique of acquiring the mechanical properties of specimens under a high strain rate. This paper demonstrates the processing of design and fabrication of SHPB. First of all, numerical analysis is applied in order to determine the design parameters of SHPB apparatus and verify the validity of design for a SHPB facility. Following this, SHPB apparatus were fabricated in accordance with acquired design parameters by simulation. In order to verify the validity of SHPB apparatus, experimental results using Al6061-T6 were compared with numerical data obtained from a corresponding simulation. The result of this comparative study demonstrates the applicability and validity of the fabricated apparatus.

• Journal of Korean Medicine Rehabilitation
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• v.18 no.2
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• pp.81-96
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• 2008

Objectives : This study was performed to investigate inhibitory effects of Gamipalmul-tang($jiaweibawu-t{\bar{a}}ng$) on the hematological and histological changes of obese mice. Methods : C57BL/6 mice were divided into four groups (normal group, high fat diet with normal saline, high fat diet with reductil, high fat diet with Gamipalmul-tang($jiaweibawu-t{\bar{a}}ng$) and fed for 8 weeks. Body weight change, final increase of body weight, ALT, AST, creatinine, total cholesterol, LDL-cholesterol, HDL-cholesterol, triglyceride, glucose, cell viability by cytotoxicity, the expression of ${\beta}3AR$ in 3T3-L1 cell, the expression of leptin, ${\beta}3AR$ and serotonin in adipocyte tissue and size of adipocyte were observed in 8 weeks. Results : 1. In 3T3-L1 cell. the expression of ${\beta}3AR$ was increased significantly. 2. The final increase of body weight in obese-mouse were decreased significantly. 3. The level of AST, ALT were decreased significantly. 4. The level of LDL-cholesterol was decreased significantly and HDL-cholesterol was increased significantly. 5. The levels of triglyceride was decreased and leptin and glucose were decreased significantly. 6. In adipocyte tissue, the expression of ${\beta}3AR$ were increased significantly. 7. In adipocyte tissue, the expression of leptin and serotonin were decreased significantly. 8. The size of Adipocyte was decreased. Conclusions : On the basis of these results, we concluded that Gamipalmul-tang($jiaweibawu-t{\bar{a}}ng$) has inhibitory effects in rat.

• Journal of Plant Biotechnology
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• v.31 no.4
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• pp.261-266
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• 2004

This experiment was carried out to confirm the stability of bar gene introduced into petunia plant through Agrobacterium-mediated transformation, in successive generation, or after crossing or back-crossing. Some of different 25 transgenic plants were used in crossing and back-crossing to wild type, or repeated-selfing to T$_4$ generation. On the processing of experiment, it was found that some lines lost their resistant ability to herbicide basta, or showed non-Mendelian segregation mode: produced much more susceptible segregants than resistant plants. Even though there are exceptional cases, which was off from expected, the genetic stability of bar gene introduced could be confirmed strongly, because in almost case, the segregation of resistant and susceptible plants to basta was done under Mendelian-law according to single gene dominant model.

• Journal of the Korean Statistical Society
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• v.5 no.2
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• pp.91-100
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• 1976

The use of the statistic $t = \sqrt{n} (x-\mu)/S$, where $\bar{X) = \sum X_i/n, \mu = E(X_i), S^2 = \sum(X_i-\bar{X})^2/(n-1)$ in statistical inference is usually done under the assumption of normality of the population. If the population is not normally distributed the tabulated values of student t are no longer valid. The moments of t are obtained as a power series in $1/\sqar{n}$ whose coefficients are functions of the cumulants of X. The cumulants are obtained from the moments in the usual manner. The first eight cumulants of t are given up to terms of order $1/n^3$. The first eight cumulants of t are given up to terms of order $1/n^3$. These results extend those of Geary who gave the first six cumulants of t to order $1/n^2$.