• Journal of the Korean Society for Nondestructive Testing
• /
• v.21 no.3
• /
• pp.307-312
• /
• 2001

Ultrasonic signals from Charpy impact test specimen have been analyzed in order to evaluate the integrity of reactor pressure vessel. Base and weld metal that were extracted from reactor vessel doting plant outages according to the schedule of the surveillance test required by the related regulations have been used and the ultrasonic test parameters including velocity, attenuation, etc. showed a close correlations with the amount of neutron irradiation for base metal, relatively homogeneous materials. This result showed certain possibility where a nondestructive method could be used to predict the fluence of the Irradiation due to neutron in nuclear reactor vessel materials.

• Nuclear Engineering and Technology
• /
• v.13 no.3
• /
• pp.153-161
• /
• 1981

The dynamic behavior of the Ko-ri Unit 1 nuclear reactor following some credible and postulated accidents has been analyzed to a certain extent by means of neutronics and temperature equations formulated in terms of point reactor model. In general, the result of numerical calculation is harnessed to be incorporated in more elaborate models so as to predict transient behavior in a reliable mode as a part of accident analysis. It is shown in the case of power response upon an uncontrolled withdrawal of rod cluster control assembly at hot full power that the point reactor kinetics model proves to be good enough to reproduce the generic features described in the final safety analysis report of the Ko-ri Unit 1.

• Nuclear Engineering and Technology
• /
• v.18 no.2
• /
• pp.71-77
• /
• 1986

A one dimensional neutron kinetics program, BIK which is applicable to the safety analyses of PWR's is developed to analyze the reactor core in axial dimension. The BIK employs the finite difference technique in space and $\theta$-time integration method in time. Detailed models for the Doppler and moderator feedbacks and control rod motion are included. The benchmark of the nuclear model is carried out through the ANL benchmark problem and the time dependent nuclear power change in the rod ejection accident of KNU1 is calculated by BIK code. The results indicate that the BIK can predict the neutron dynamics with fair accuracy within the limits of one dimensional analysis and it is useful for the safety analyses of PWR's.

• Composites Research
• /
• v.21 no.1
• /
• pp.8-15
• /
• 2008

Single-walled carbon nanotube networks(SWNT-networks) were uniformly formed on a glass substrate by the dip-coating method. The changes of electrical and optical properties of SWNT-networks were investigated with respect to processing variables including number of dip, concentration of SWNT-colloidal solution, withdrawal velocity. Consequently, the sheet resistance and transmittance of the SWNTs-networks were sensitively controlled by the processing variables. The networks have highly uniform sheet resistance and optically excellent transmittance within the range of visible ray.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.05a
• /
• pp.431-433
• /
• 2007

The drawbeads, which is used for controlling the flow of the sheet by imposing the tension and for preventing the springback in the sheet metal forming process, affects a lot the formability because of the differences in the restraint and opening forces according to the drawbead shapes and dimensions. In this study, the experimental device enabling to measure the drawbead restraining and opening forces was manufactured and the drawing forces of circular, square, and step drawbeads are measured. The drawbead restraining and opening forces of a circular drawbead are increased as its drawbead height is increased. Similarly, those of a square drawbead are increased as its height is increased and shoulder radii decreased. Also, those of a step drawbead are increased as its height and difference in their heights are increased.

• Proceedings of the Korean Information Science Society Conference
• /
• 1998.10a
• /
• pp.538-585
• /
• 1998

이동 컴퓨팅 환경에서 이동 호스트는 무선망을 통해 서버와 연결된 후에서야 데이터를 획득 및 처리할 수 있다. 그러나, 이동 호스트는 낮은 대역폭과 이로 인한 지연, 네트워크 단절(disconnection)과 같은 무선망의 특성으로 인하여 사용상에 많은 불편함과 비효율성이 발생하고 있는 실정이다. 특히, 이동 호스트가 네트워크 단절로 인해 서버에 접근이 불가능하고 작업에 필요한 데이터가 캐쉬에 없을 경우에는 작업 처리가 불가능하다. 본 논문에서는 이와 같은 문제점을 해결하기 위하여 이동 호스트가 미래에 작업할 데이터를 미리 인출해서 캐쉬에 저장하는 선인출 메카니즘을 제안하였다. 본 논문의 선인출 메카니즘을 기록기, 분석기, 선인출 목록 생성기, 그리고 비교기로 구성된다. 기록기와 분석기는 이동 호스트의 파일 참조 패턴들을 기반으로 프로파일을 생성하며, 선인출로 인한 성능 감소를 최소화하기 위해 선인출과 캐쉬 교체 전략을 통합한 선인출 메카니즘을 제시하였다.

• Transactions of Materials Processing
• /
• v.8 no.4
• /
• pp.340-346
• /
• 1999

Circular drawbead forming and drawing characteristics of CO2 laser welded SPC1 blanks are investigated by experiments and numerical analysis. During the drawbead forming process, the distributions of major strain on upper and lower skins of the specimens are measured. During the drawing process, the drawing forces and the strain distributions are investigated. For the numerical analysis. DYNA3D and SGTAS, a developed rigid-plastic finite-element computer program are used. Numerical results predicted the deformation characteristics well in comparison with experiments. It is concluded that the strains and restraining forces during the forming and the drawing processes show different patterns according to the combination of welded blanks.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2003.10a
• /
• pp.140-143
• /
• 2003

The drawbead is an important part in sheet metal forming for automotive part and its effect is affected by various process parameters. Therefore in this study, drawbead friction test was performed at various process parameters - panels (cold rolled and galvanized sheet steel), lubricants (having three different viscosities), bead materials(steel, iron) and surface treatment of bead (Cr plating). Circular shape bead has been used for the test. The results show that friction and drawing characteristics were mainly influenced by the nature of zinc coating, viscosity of lubricants, surface treatment of a bead and hardness of coated layer.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.7 no.6
• /
• pp.51-59
• /
• 1993

In this paper, we study the effects that the variations of machine parameters and frequency of which affect the instability occured in induction motors when operated at low speed or light load, by obtaining the locus of dominant root for the characteristic equation.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1993.04b
• /
• pp.44-48
• /
• 1993

산업현장에서부터 실생활용품에 이르기까지 각종판재를 소재로하여 제작하는 가공품은 종류나 수가 매우 많다고 할수 있다. 이러한 제품들을 제작 하기 위해 여러단계의 성형 공정을 거치게 되며 원만한 성형공정 을 수행하기 위한 적절한 판재성형 제어방법으로써 다이곡률 반경의 변화나 블랭크홀딩가압정도의 부분적 변화로 드로잉률을 향상시키는 방법도 있으나 이보다 판재의 성형공정 제어방법에서 공구사이 상하에 비드 를 설치하여 판재를 성형할 경우 성형공정후 제품의 두께 분포가 비교적 균일해지고 드로잉의 마찰저항을 부분적으로 증가시키며 판재성형중 미끄럼 저항의 균형을 이루어 성형시킬 판소재가 절감도며 또한 성형중 주름을 억재하여 드로잉률을 향상시킨다. 다른 방법에 비해 비드는 설차가 간단해서 적절한 형상의 bead set을 선정하여 산업현장에서 실제 사용하고 있으며 또한 소재가 비드를 통과한후 탄성역에서 소성역으로 전환되기에 성형공정 이후 스프링백 현상으로인한 제품형상의 치수가 변하는 현상을 방지하는 효과도 기대할수 있다. 따라서 본 연구에서는 자동차용판재인 아연도금피막 강판으로 실험한 결과와 비드 이론식을 고찰해 보고자 한다.