• Journal of Life Science
• /
• v.7 no.4
• /
• pp.392-401
• /
• 1997

The poliovirus is a small, and non-enveloped virus. The RNA genome of poliovirus is continuous, linear, and has a single open reading frame. This polyprotein precursor is cleaved proteolytically to yield mature products. Most of the cleavages occur by viral protease. The mature proteins derived from the P1 polyprotein precursor are the structural components of the viral capsid. The initial cleavage by 2A protease is indirectly involved in the cleavage of a cellular protein p220, a subunit of the eukaryotic translation initiation factor 4F. This cleavage leads to the shut-off of cap-dependent host cell translation, and allows poliovirus to utilize the host cell machinery exclusively for translation its own RNA, which is initiated by internal ribosome entry via a cap-independent mechanism. The functional role of the 2B, 2C and 2BC proteins are not much known. 2B, 2C, 2BC and 3CD proteins are involved in the replication complex of virus induced vesicles. All newly synthesized viral RNAs are linked with VPg. VPg is a 22 amino acid polypeptide which is derived from 3AB. The 3C and 3CD are protease and process most of the cleavage sites of the polyprotein precursor. The 3C protein is also involved in inhibition of RNA polymerase II and III mediated transcription by converting host transcription factor to an inactive form. The 3D is the RNA dependent RNA polymerase. It is known that poliovirus replication follows the general pattern of positive strand RNA virus. Plus strand RNA is transcribed into complementary minus strand RNA that, in turn, is transcribed for the synthesis of plus strand RNA is transcribed into complementary minus strand RNA that, in turn, is transcribed for the synthesis of plus strand RNA strands. Poliovirus RNA synthesis occurs in a membranous environment but how the template RNA and proteins required for RNA replication assemble in the membrane is not much known. The RNA requirements for the encapsidation of the poliovirus genome (packaging signal) are totally unknown. The poliovirus infection cycle lasts approximately 6 hours.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2009.11a
• /
• pp.40.1-40.1
• /
• 2009

생체용 금속 임플란트의 표면개질은 생체활성화를위하여 오래 전 부터 관심을 가지고 연구해오고 있다. 최근에 표면개질을위하여 화학적 에칭, 샌드 블래스팅, 또는 나노튜브형성등 표면에 임의의 요철을 만들어서 사용하는방법이 가장 일반적으로 적용되어 상용화되고있다. 그러나 샌드블래스팅이나 화학적 에칭은 가공은 쉽지만 가공표면에 인체에 해로운 잔류물의존재로 생체적합성에 해로운 영향을 미칠 수 있다. 이러한 문제점들을 해결하기위하여 레이저를 사용하여 임플란트 표면을 개질한 예가 보고 되었다. 레이저를 사용한 표면처리 방법의큰 장점은 잔류물이 남지 않고 비교적 표면 거칠기의 제어가 용이하다. 금속합금의 표면개질에사용되는 레이저는 주로 Nd:YAG 레이저의 파장을 반으로 줄인 녹색레이저 ($\lambda$=532nm)를 사용하거나, 자외선파장영역의레이저를 사용하는 경우가 일반적으로 가장 보 편화된 가공방법으로 연구되었다. 표면의 거칠기는 수마이크로의크기와 수십나노의 크기를 갖는 표면을 생체적합적인 측면에서 요구하고 있다. 따라서 이러한 표면의 거칠기를조절할 수 있는 펨토레이저를 사용하여 표면에 균질한 표면의 텍스춰링을 통하여 그 특성을 개선할 수 있는지를 확인하는 것이 본 과제이다. 본 실험에서는 Ti합금을 진공 아크로를 이용하여 3원계합금을 제조하고 $1000^{\circ}C$에서 24시간 열처리 후 급냉(water quenching)하였다. 열처리 후 시편은 두께 2mm로 절단 하여 #2000까지 연마 후 하여 펨토 초(10-15 second) 펄스폭 대역을 갖는 레이저를 이용하여 수마이크로 크기의 미세 요철을 표면에 형성한 후, 표면의 특성을 조사해 보았다.(NRF-2009-0074672)

• Journal of the Korean Society for Nondestructive Testing
• /
• v.14 no.3
• /
• pp.177-184
• /
• 1994

The three dimensional measuring method with minimizing operational errors for the arbitrary shaped-internal cavity based on the information of the X-ray nondestructive test is presented. Two experimental tests using artificial cavities were considered in order to verify the availity of PEVACA. In these test, X-ray NDT was conducted for detecting cavities, and the comparion between the calculating values from PEVACA and the real values from measuring the cavities was performed. As a result of this study, three dimensional cavities information using PEVACA are in good agreement with the real measured values within ${\pm}0.5mm$. The computer code, "PEVACA", contributes not only to improvement of data accuracy but also to saving of the work time and data documentation.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.11 no.5
• /
• pp.218-223
• /
• 2001

The chemical-mechanical polishing process was carried out for 2"-dia. sapphire wafer grown by horizontalBridgman method on the urethane lapping pad with the silica sol. The polished wafer shows the full-width at halfmaximum of 200~400 arcsec in double-crystal X-ray diffraction, indicating that the slicing, grinding and lapping processes before the polishing process affected the crystalline structural property of the wafer surface by the mechanical residual stress. For the inclusion of surface treatments after chemical-mechanical polishing such as the thermal annealing at the temperature of $1,200^{\circ}C$for 4 hrs. and chemical etching, the crystalline quality was sigdicantly enhanced with the reduced full-width at half maximum up to 8.3 arcsec.arcsec.

• The Korean Journal of Applied Statistics
• /
• v.11 no.1
• /
• pp.163-175
• /
• 1998

The change of hazard rates at some unknown time point has been the interest of many statisticians. But it was restricted to the constant hazard rates which correspond to the exponential distribution. In this paper we generalize the change-point model in which any specific functional forms of hazard rates are net assumed. The assumed model includes various types of changes before and after the unknown time point. The Nelson estimator of cumulative hazard function is introduced. We estimate the change-point maximizing slope changes of Nelson estimator. Consistency and asymptotic distribution of bootstrap estimator are obtained using the martingale theory. Through a Monte Carlo study we check the performance of the proposed method. We also explain the proposed method using the Stanford Heart Transplant Data set.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.5 no.3
• /
• pp.209-214
• /
• 1995

Abstract 0.2 wt % $Fe_2O_3$ doped $SrTiO_3$ single crystals were grown by floating zone method in air and Nz atmosphere, respectively. The growth rate was fixed at 5 mm/hr and rotation speed was maintained at 30 rpm. As - grown crystals were cut perpendicular to its growth direction and then, annealed at 900, 1000 and $1100^{\circ}C$ for 2 hours in Nz atmosphere. Resistivities of each samples were measured and then converted into conductivities. By using these conductivity values, the activation energies were calculated and by means of the calculated activation energies, mechanism which contribute to increasing the electrical conductivity were investigated.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.3 no.4
• /
• pp.280-284
• /
• 2002

This paper presents computer simulations of the stacking and transferring system for the fast freeform fabrication system. The stacking and transferring system is essential for the fast freeform fabrication system and its stable motion is very important for consistent stacking of the cut slices. The stacking and transferring system can be modeled as a pneumatic system. The system consists of air compressor, the control valve, and the cylinder. The governing parameters have been changed and the simulation results are shown to predict the time response of the system. The results show some parameters should be correctly tuned to obtain stable system response.

• The Korean Journal of Applied Statistics
• /
• v.29 no.3
• /
• pp.513-523
• /
• 2016

Fitting a mixture of multivariate skew normal distribution (MSNMix) with multiple skewness parameter vectors via EM algorithm often requires a highly expensive computational cost to calculate the moments and probabilities of multivariate truncated normal distribution in E-step. Subsequently, it is common to fit an asymmetric data set with MSNMix with a simple skewness parameter vector since it allows us to compute them in E-step in an univariate manner that guarantees a cheap computational cost. However, the adaptation of a simple skewness parameter is unrealistic in many situations. This paper proposes an approximate estimation for the MSNMix with multiple skewness parameter vectors that also allows us to treat them in an univariate manner. We additionally provide some experiments to show its effectiveness.

• 전자공학회논문지 IE
• /
• v.46 no.3
• /
• pp.42-47
• /
• 2009

In CDMA system, the call admission control method using the variable effective bandwidth concept is employed in this paper. The bandwidth for a new call and a handoff call is allocated by considering the number of mobile station being served and dynamically assigned by taking account of the blocking rate of new calls and the dropping rate of handoff calls. There is reserved resource for handoff call. In the case radio resource is insufficient, a new call and a handoff call stand by in buffer for constant time. When radio resource come about, the waiting call is allocated the resource. I analyze the performance of system according to existence and nonexistence of buffer by a simulation study.

• Environmental Mutagens and Carcinogens
• /
• v.7 no.2
• /
• pp.59-64
• /
• 1987

Cytotoxic and genotoxic potential of monosodium glutamate (MSG) were evaluated in primary cultures of rat hepatocytes. When exposed to liver cell culture continuously for 24 hr, MSG did not show any cytotoxic effects up to 0.5% (w/v) level as determined by Tryphan Blue exclusion and lactic dehydrogenase release test. MSG also did not induce unscheduled DNA synthesis or DNA single-strand breaks in hepatocyte cultures up to 1% level. No synergistic effects of MSG were observed on aflatoxin B$_1$-induced DNA damage when 1% MSG was treated to liver cell culture along with aflatoxin B$_1$.