• Journal of Biosystems Engineering
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• v.16 no.2
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• pp.133-141
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• 1991

This study was undertaken to investigate the structural and configurational characteristics of the tailings return-unit in the commercially available head-feed combines and to study the aero-dynamical behavior of the tailings in the units. The mathematical model of the motion of tailings in the thrower casing was developed and the simulated trajectories for different type of units was analyzed to compare with the measured ones. The air-stream velocity profile in various locations along the tailings returning duct was measured to find the effect of configurational characteristics and blade tip speed. The results of the study are summerized as follows. 1. The ejecting angle, which is the angle between the direction of the particle velocity ejecting from the blade and the horizontal axis, was found to be about $66^{\circ}$ in both the simulation and experiment. The angle was much greater than the setting angle of actual duct of the combines studied, which were $48{\sim}56^{\circ}$. By comparison of these results, it was suggested to change duct setting angle so as to reduce the frictional force, between the duct wall and tailings, by reducing the difference between the ejecting and setting angles. 2. The velocity of the air stream in the duct was in general higher in the upper bound of the duct compared to the lower and decreased as the stream went toward the end of duct. The comparison of the tailings units among the combines studied showed a superior performance with the tapered duct having small diameter in the outlet and with greater number of thrower blade.

• Journal of the Korean Society for Nondestructive Testing
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• v.17 no.4
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• pp.262-269
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• 1997

An eddy current probe ($8{\times}1$ multiple-element, surface scan) was successfully designed and fabricated at the KEPRI using the impedance equivalent circuit theory. The probe is intended for the detection of circumferential deformations (cross-section view) of the heat exchanger tubing that can occur due to corrosion, erosion, and denting. Optimum design parameters providing the highest sensitivity and signal-to-noise ratio, such as the coil dimensions, electrical characteristics, and test frequencies, were determined based on initial laboratory experiments conducted on the test specimen (SS304 tubing: OD : 9.68mm, wall-thickness : 0.47mm) containing artificial flaws (e.g., dents and corroded surface on tube OD) using the available Zetec-made probe. Using this parameters, a new probe was made and tested on an unknown specimen. The result indicated that the new probe is capable of detecting the circumferential deformation with the error of ${\pm}0.2%$ (0.022mm) of the tube O.D.

• Journal of the Korean Vacuum Society
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• v.20 no.4
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• pp.307-312
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• 2011

As a technique for removing cancerous tumors from normal tissue, radio-frequency electromagnetic waves were employed to heating target cells up to the critical temperature, which kills the cancerous cells. However, its use in treating tumors in soft organs is limited by inconvenient factors, which are use of high-currents and long time operation. In this work, the feasibility of the localized heating by inserting four conducting electrodes with tiny direct current is investigated. The heat source is resulting from the electric field as known as resistive heating. We have investigated the temperature distribution as a function of applying DC voltages ranging from 10 V to 30 V with 10 V step. From the simulation results, the mushroom-like lesion shape by applying 20 V is generated by four electrodes within a few minutes, that is proper to the clinical application.

• Progress in Medical Physics
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• v.11 no.2
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• pp.157-165
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• 2000

Purpose: For estimation of yields of l)NA damages induced by radiation and enhanced by oxygen, a mathematical model was used and tested. Materials and Methods: Reactions of the products of water radiolysis were modeled as an ordinary time dependant equations. These reactions include formation of radicals, DNA damage, damage repair, restitution, and damage fixation by oxygen and H-radical. Several rate constants were obtained from literature while others were calculated by fitting an experimental data. Sensitivity studies were performed changing the chemical rate constant at a constant oxygen number density and varying the oxygen concentration. The effects of oxygen concentration as well as the damage fixation mechanism by oxygen were investigated. Oxygen enhancement ratio(OER) was calculated to compare the simulated data with experimental data. Results: Sensitivity studies with oxygen showed that DNA survival was a function of both oxygen concentration and the magnitude of chemical rate constants. There were no change in survival fraction as a function of dose while the oxygen concentration change from 0 to 1.0 x 10$^{7}$ . When the oxygen concentration change from 1.0 $\times$ 107 to 1.0 $\times$ 101o, there was significant decrease in cell survival. The OER values obtained from the simulation study were 2.32 at 10% cell survival level and 1.9 at 45% cell survival level. Conclusion: Sensitivity studies with oxygen demonstrated that the experimental data were reproduced with the effects being enhanced for the cases where the oxygen rate constants are largest and the oxygen concentration is increased. OER values obtained from the simulation study showed good agreement for a low level of cell survival. This indicated that the use of the semi-empirical model could predict the effect of oxygen in cell killing.

• The Korean Journal of Applied Statistics
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• v.17 no.3
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• pp.573-594
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• 2004

Four statistics books, one translated by statisticians and three by non-statisticians, are reviewed. They are reviewed in terms of indices and bibliographies, statistical theory and terms, and the history of statistics. In addition, book review articles appeared in daily newspapers are considered. Unfortunately, we can find many(some of them trivial, and some others serious) problems in the translations. Many problems could have been got around if the books had been translated by statisticians. So, conclusion suggested in this article is very simple: Translation of statistics books, especially books for the laymen, is a job that Korean statisticians should not shift to others. Titles of the books reviewed in this article are as follows. 1. Rao, C. Radhakrishna(1997). Statistics and Truth : Putting Chance to Work, Second edition, World Scientific. 2. Best, Joel (2001). Damnel lies and Statistics : Understanding Numbers from the Media, Politicians, and Activists, University of California Press. 3. Bennett, Deborah J. (1998). Randomness, Harvard University Press; 4. Salsburg, David (2001). The Lady Tasting Tea : How Statistics Revolutionized Science in the Twentieth Century, W. H. Freeman.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.04a
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• pp.1086-1089
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• 2011

현대 사회의 의학기술과 대체의학은 IT 기술과의 융합적 개발로 점차 발전하고 있다. 동양의학 이론을 통해 인체 중 손, 발, 얼굴 등이 오장육부와 관련이 있다는 학설이 널리 알려져 있다. 이 중 발은 '제2의 심장'이라고까지 불려지고 있다. 즉, 발이 건강해야 전신 건강을 유지할 수 있다는 의미도 있지만 실제로 혈액 순환에도 중요하다는 의미도 있다. 따라서, 본 논문에서는 심장과 관련된 발 영역인 왼쪽발바닥 네번째와 다섯 번째 발가락 사이에서 3cm정도 내려간 부위를 지압하여 심장 관련 얼굴 영역의 색상 변화를 측정하는 실험을 수행하였다. 지압에 쓰이는 지압봉은 일반 가정용으로 사용되는 150x10mm 크기의 지압봉이며 지압법으로는 뒤꿈치 방향에서 심장 지압점까지 누르면서하는 방법을 사용하였다. 이와 같은 발지압법을 수행한 후 심장과 관련된 얼굴 영역인 천정과 입술 부위의 붉은 정도를 Lab색체계로 측정하여 a*값 색상의 변화를 분석하였다.

• Progress in Superconductivity
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• v.12 no.2
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• pp.88-92
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• 2011

[ $MgB_2$ ]superconducting sheets have been fabricated using powder roll compaction method. Sheet-type $MgB_2$ bulk samples were successfully fabricated using the pre-reacted $MgB_2$ powders. In this work, $MgB_2$ powders were compacted by two rotating rolls and squeezed out as a form of $MgB_2$ sheets of ~1 mm thickness. The rolling speed of 0.3-0.7 rpm and the gap distance of 0.3-0.8 mm between the two rollers were carefully controlled to get a full compaction of the powders into bulk $MgB_2$ sheets. The densities of $MgB_2$ sheets were 1.98-2.05 g/$cm^3$, which is 75.44-77.99 % of the theoretical value of 2.63 g/$cm^3$. And the density comparison was made compared to those of typical $MgB_2$ bulks from uni-axial pressing and $MgB_2$ wires from Powder-In-Tube processing.

• Journal of the Korean Vacuum Society
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• v.15 no.1
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• pp.50-56
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• 2006

We investigated the adsorption of benzene and pyridine on $Si(5\;5\;12)-2\times1$ at 80 K by using variable-low temperature scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. The benzene molecule most strongly binds to two adatoms on the D3 and D2 units in a tilted butterfly configuration, which consists of $di-\sigma$ bonds between C atoms and Si adatoms and two C=C double bonds in the benzene molecule Pyridine molecules interact with adatom(s) on the D2 and D3 units through both Si-N dative bonding and $di-\sigma$ bonds. The dative bonding through the lone pair electrons of N atom produces a vertical configuration (pyridine-like), which is more stable than $di-\sigma$ bonds $Di-\sigma$ bonds can be formed either through Si-N1 and Si-C4 or Si-C2 and Si-C5.

• Journal of Biomedical Engineering Research
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• v.21 no.3 s.61
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• pp.261-271
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• 2000

The present study investigated flow dynamics of a two-dimensional abdominal aortic bifurcation model under sinusoidal flow conditions considering wall motion. impedance phase angle(time delay between pressure and flow waveforms), and non-Newtonian fluid using computational fluid dynamics. The wall shear stress showed large variations in the bifurcated region and the wall motion reduced amplitude of wall shear stress significantly. As the impedance phase angle was changed to more negative values, the mean wall shear stress (time-averaged) decreased while the amplitude (oscillatory) of wall shear stress increased. At the curvature site on the outer wall where the mean wall shear stress approached zero. influence of the phase angle was relatively large. The mean wall shear stress decreased by $50\%$ in the $-90^{\circ}$ phase angle (flow wave advanced pressure wave by a quarter period) compared to the $0^{\circ}$ phase angle while the amplitude of wall shear stress increased by $15\%$. Therefore, hypertensive patients who tend to have large negative phase angles become more vulnerable to atherosclerosis according to the low and oscillatory shear stress theory because of the reduced mean and the increased oscillatory wall shear stresses. Non-Newtonian characteristics of fluid substantially increased the mean wall shear stress resulting in a less vulnerable state to atherosclerosis.

• Applied Chemistry for Engineering
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• v.8 no.1
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• pp.132-139
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• 1997

This study was carried out to examine the kinetics and reaction mechanism of denitration with formic acid in the simulated radwaste solution containing 6 components such as Nd, Pd, Ru, Zr, Mo and Fe. All experiments were performed with the changes of initial nitric acid concentration, molar ratio of formic acid to nitric acid, and denitration time at $90^{\circ}C$ and a batch system. As results, destruction rate of nitric acid and formic acid was obtained as follows, respectively. $\frac{d[HNO_3]}{dt}=-4.842{\times}10^{-2}[HNO_3][HCOOH],\;\frac{d[HCOOH]}{dt}=-8.911{\times}10^{-2}[HNO_3][HCOOH]$ It was confirmed that denitration with formic acid was controlled by reaction mechanism suggested this study in the range of the initial nitric acid of 2~5M and $[HCOOH]/[HNO_3]$ of 1.5~2.0. In the 1M initial nitric acid, however, it was found that the nitric acid and the formic acid were decomposed by a different reaction mechanism.