• Journal of Advanced Marine Engineering and Technology
• /
• v.20 no.4
• /
• pp.412-412
• /
• 1996

To maintain high spacial accuracy and rapid CPU time in interpolating data from grid to random position or inversely in PIV, proposed many technuques are compared and discussed mainly in terms of interpolating error and computing time. And artificial PIV atmosphere data is furnished by CFD result. First, for interpolation from grid to random position, multiquadric method gives the highest accuracy with the longest CPU time and Taylor series expansion methods give reasonable accuracy with less calculating load. Secondly, the sub-pixel resolution analysis in estimating the coordinates of the maximum correlation coefficients essential in the grey level correlation PIV reveal that 8-neighbours 2nd-order least square interpolation gives utmost accuracy in terms of the real flow conditions.

• Journal of Ubiquitous Convergence Technology
• /
• v.2 no.1
• /
• pp.1-11
• /
• 2008

An effective solution to the problems caused by the explosive growth of World Wide Web is a web caching that employing an additional server, called proxy cache, between the clients and main server for caching the popular web objects near the clients. However, a single proxy cache can easily become the bottleneck. Deploying groups of cooperative caches provides scalability and robustness by eliminating the limitations caused by a single proxy cache. Two common architectures to implement the cooperative caching are hierarchical and distributed caching systems. Unfortunately, both architectures suffer from performance limitations. We propose an efficient hybrid caching architecture eliminating these limitations by using both the hierarchical and same level caches. Our performance evaluation with our investigated simulator shows that the proposed architecture offers the best of both existing architectures in terms of cache hit rate, the number of query messages from clients, and response time.

• Journal of Hydrospace Technology
• /
• v.2 no.1
• /
• pp.18-26
• /
• 1996

It is normal practice to consider bending wave modes only, when one applies SEA (Statistical Energy Analysis) to ship structures because of complexities in SEA modeling and evaluation of coupling loss factors for inplane modes. According to the result of Tratch[1], the inplane wave modes becomes important for the analysis of a foundation structure as the distance from the source and receiver increases. In this paper, the effect of inplane wave modes on structure-borne noise propagation in ship structures is presented. It is shown that the inplane wave could increase the noise level more than 10 dB compared with the results without inplane wave modes at high frequency bands for compartments far from the source location.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2013.05a
• /
• pp.278-280
• /
• 2013

To minimize construction quantity of nuclear facility, it is required to reduce reinforcing bar amount and solve reinforcing bar concentration and for this, it is necessary to develop application design technology and modular of high strength reinforcing bar. Hence, KHNP reduces excessive reinforcing bar amount which can cause possibility of poor construction of concrete through design standard development and modular of nuclear facility structure using high strength reinforcing bar to raise economics and has its purpose to maintain high-level safety and durability as they are.

• Annual Conference of KIPS
• /
• 2006.11a
• /
• pp.495-498
• /
• 2006

IT 서비스의 안정적인 공급과 IT 서비스의 품질 개선을 이루고자 하는 SLA(Service Level Agreement)에 대해 많은 연구와 시도가 지금까지 진행되어 왔다. SLA 시행에 있어서 측정 지표와 그 평가 기준 선정은 매우 중요하나, 대부분 SLA 측정 지표들은 기술관점의 항목들로 구성되어 있기 때문에, SLA 시행 결과가 사용자 중심이 아닌 서비스 제공자 중심으로 나타나고 있다. 이는 사용자의 불만족을 초래하고 서비스 제공자와의 의사 소통을 어렵게 만들고, 결국 SLA 도입 실패로 이어지는 원인이 되고 있다. 본 연구에서는 기존의 SLA 측정 지표들에서, 사용자 중심의 SLA 측정 지표로 활용할 수 있는 항목들을 BSC 의 인과관계모델을 통해 추출하고, AHP 기법을 통해 SLA 평가 기준들과 측정 지표들에 대한 가중치를 도출하였다. 이를 통하여 사용자 관점의 SLA 지표 선정 방법에 대한 명확한 기준을 제시하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 1998.05a
• /
• pp.177-186
• /
• 1998

In this paper, due to the congestion the radio spectrum, frequency bands are shared among the satellite communication system. Therefore for satisfactory we have to design and predict with reasonable accuracy the level of interference that might exist among them, Interference among the satellite communication systems depends on many factors such as climate, radio frequency, time percentage of interest, distance and path topography, propagation delay time. This paper suggest design method of Low-Orbit satellite communication and calculates the field-of view of satellite, for the communication era using LEO. In addition, performs performance evaluation on the basis of link margine.

• Journal of radiological science and technology
• /
• v.16 no.2
• /
• pp.81-86
• /
• 1993

Proper evaluation about the penumbra is very important to improve the efficacy of radiation theraphy. There are two kinds of physical penumbra, geometric penumbra and transmission penumbra. In this study, we evaluated the variation of physical penumbra according to the varing energy level, changing the field size and depth. Physical penumbra width was decreased as the source size decreased, and as the SDD increased, but the consideration about the scatter radiation and mechanical stability is an important factor. For the two adjacent beams, upper collimator should be used and especially for Co-60 unit, it is efficient to use the extended collimator.

• Nuclear Engineering and Technology
• /
• v.43 no.6
• /
• pp.523-530
• /
• 2011

In a previous study, the stochastic space-dependent kinetics model (SSKM) based on the forward stochastic model in stochastic kinetics theory and the Ito stochastic differential equations was proposed for treating monoenergetic space-time nuclear reactor kinetics in one dimension. The SSKM was tested against analog Monte Carlo calculations, however, for exemplary cases of homogeneous slab reactors with only one delayed-neutron precursor group. In this paper, the SSKM is improved and evaluated with more realistic and complicated cases regarding several delayed-neutron precursor groups and heterogeneous slab reactors in which the extraneous source or reactivity can be introduced locally. Furthermore, the source level and the initial conditions will also be adjusted to investigate the trends in the variances of the neutron population and fission product levels across the reactor. The results indicate that the improved SSKM is in good agreement with the Monte Carlo method and show how the variances in population dynamics can be controlled.

• Journal of Mechanical Science and Technology
• /
• v.20 no.2
• /
• pp.197-204
• /
• 2006

The purpose of this study is to evaluate the AE characteristics for the basemetal, PWHT (post-weld heat treatment) and weldment specimens of SA-516 steel during fracture testing. Four-point bending and AE tests were conducted simultaneously. AE signals were emitted in the process of plastic deformation. AE signal strength and amplitude of the weldment was the strongest, followed by PWHT specimen and basemetal. More AE signals were emitted from the weldment samples because of the oxides, and discontinuous mechanical properties. AE signal strength and amplitude for the basemetal or PWHT specimen decreased remarkably compared to the weldment because of lower strength. Pre-cracked specimens emitted even lower event counts than the corresponding blunt notched specimens. Dimple fracture from void coalescence mechanism is associated with low-level AE signal strength for the basemetal or PWHT. Tearing mode and dimple formation were shown on the fracture surfaces of the weldment, but only a small fraction produced detectable AE.

• Earthquakes and Structures
• /
• v.10 no.3
• /
• pp.629-643
• /
• 2016

Among all the natural disasters, earthquakes are the most destructive calamities since they cause a plenty of injuries and economic losses leaving behind a series of signs of panic. The present study highlights the moment-curvature relationships for the structural elements such as beam and column elements and Non-Linear Static Pushover Analysis of RC frame structures since it is a very simplified procedure of non-linear static analysis. The highly popular model namely Mander's model and Kent and Park model are considered and then, seismic risk evaluation of RC building has been conducted using SAP 2000 version 17 treating uncertainty in strength as a parameter. From the obtained capacity and demand curves, the performance level of the structure has been defined. The seismic fragility curves were developed for the variations in the material strength and damage state threshold are calculated. Also the comparison of experimental and analytical results has been conducted.