• Nuclear Engineering and Technology
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• v.18 no.2
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• pp.78-84
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• 1986

An equation of material number density sensitivity coefficient is derived using first-order perturbation theory. The beginning of cycle of Super-Phenix I is taken as the reference system for this study. Effective multiplication factor of the reference system is defined as system response function and fuel enrichment and fuel effective density are chosen for the variation of reference input data since they are described by material number density which is a component of Boltzmann operator. The nuclear computational code system (KAERI-26 group cross section library/1DX/2DB/PERT-V) is employed for this calculation. Sensitivity coefficient of fuel enrichment on effective multiplication factor is 4.576 and sensitivity coefficient of effective fuel density on effective multiplication factor is 0.0756. This work shows that sensitivity methodology is lesser timeconsuming and gives more informations on important design parameters in comparison with the direct iterative calulation through large computer codes.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.1
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• pp.11-22
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• 1987

A plane buoyant jet discharged vertically upward into a crossflow is analyzed by numerical solution of the governing equations of continuity, momentum and constituent transport. The turbulent transport is modelled by the Prandtl's mixing length theory. In the numerical solution procedure, the governing equations are transformed by stream function and vorticity transport, non-dimensionalyzed by discharge velocity, slot width, and parameters representing flow characteristics, and solved by Gauss-Seidel iteration method with successive underrelaxation. The numerical experiments were performed for the region of established flow of buoyant jet in the range of discharge densimetric Froude number of 4 to 32 and in the range of velocity ratio of 8 to 15, which is the ratio of discharge velocity to crossflow velocity. Variations of velocities and temperatures, flow patterns and vorticity patterns of receiving water due to buoyant jet were investigated. Also investigated are the effects of velocity ratio and discharge densimetric Froude number on the trajectories of buoyant jet. Computed are velocities, temperatures and local densimetric Froude numbers along the trajectory of the buoyant jet. Spreading rate and dispersion ratio were analyzed in terms of discharge densimetric Froude number, local densimetric Froude number and distance from the source along the jet trajectory. It was noted that the similarity law holds in both the profiles of velocity and temperatures across the jet trajectory and the integral type analysis of Gaussian distribution is applicable.

• Journal of the Korean Magnetics Society
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• v.5 no.6
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• pp.937-946
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• 1995

In this research, the processing control of NiCuZn Ferrite has been developed. The relationship between initial permeability and bulk density of NiCuZn Ferrite with processing factors was studied. NiCuZn Ferrite, which calcinated at $700^{\circ}C$ for 3 hours, was ball milled for about 60 hours to make a size of $0.5\mu\textrm{m}$ followed by granulation using spray dryer. The physical properties and the magnetic properties of NiCuZn Ferrite were investigated with the processing factor, such as (i) granule size and forming pressure, and (ii) sintering temperature. The green density of NiCuZn Ferrite was largely depended on the forming pressure rather than its granule size. The green density of NiCuZn Ferrite was increased from $2.484\;g/cm^{3}$ to $3.002\;g/cm^{3}$ with increase in forming pressure. The bulk density of NiCuZn Ferrite was increased from $3.470\;g/cm^{3}$ to $4.754\;g/cm^{3}$ linearly with increase in sintering temperature. The relationship between initial permeability and bulk density of NiCuZn Ferrite was expressed with the empirical equation,$\mu_{i}=a+b_{\rho}+c_{\rho}^2$ at forming pressure and sintering temperature.

• Journal of the Korean GEO-environmental Society
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• v.13 no.12
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• pp.17-25
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• 2012

In this study, dielectrical constant of the ground was measured using TDR method and correlated with water contents and density of ground. In order to evaluate the applicability as a cavity exploration, model experiments were carried out to analyze the effects of cavity size on the dielectrical constant. Test result indicated that dielectrical constant of the ground tended to linearly increase with the increase in water contents and density, which can be represented in a certain relational expression. Also, the dielectrical constant of ground varied sensitively with the cavity size of ground. The results conclude that the dielectrical constant, water contents and density of the ground proved to have a correlation among them, and the dielectrical constant is expected to be a basic data on cavity exploration.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.1
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• pp.34-39
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• 1994

The dilution and the shore attachment of buoyant effluent into a crossflow are investigated experimentally. The effluent is produced by discharging warm water through a side channel into an open channel crossflow with the same depth to the side channel flow. Buoyancy causes the effluent to lift off the bottom, spreads across the crossflow and stays as the surface layer. The geometry of the recirculating region and the dilution of the effluent depend mainly on the buoyancy. The condition of the shore attachment can be specified by the ratios of velocities and Froude numbers.

• Proceedings of the Korean Information Science Society Conference
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• 2008.06b
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• pp.261-264
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• 2008

본 논문에서는 영상의 중요한 특징을 강조하는 점의 분포를 가지는 자동화된 점묘화(stippling) 제작 방법을 제시한다. 예술가의 점묘화 일러스트 작품을 살펴보면 영상의 특징을 강조하는 방향성이 있는 점들을 사용해서 회화적인 느낌을 살림과 동시에 사물의 형태를 좀 더 명백히 파악할 수 있게 해준다. 하지만 컴퓨터 그래픽스 분야에서 연구된 기존 점묘화 기법 알고리즘은 입력 영상의 특징적인 형태를 고려하지 않고 색조에 따른 점의 밀도 변화만으로 사물을 표현하기 때문에 사물의 형태가 제대로 드러나지 않는 단점이 있다. 본 방법에서는 점의 분포가 대상의 형태를 반영하며 분포되게 하는 알고리즘을 적용하여 사물의 특징적인 형태를 강조한다. 이를 위해 영상의 특징선으로부터 추출한 특징 흐름(feature flow)을 따라 점을 배치시키는 방법을 사용한다. 그리고 입력 영상의 색조(tone)를 점묘화에 반영하기 위해 점의 크기가 입력 영상의 색조에 따라 자동으로 결정되도록 한다.

• Journal of the Korean Chemical Society
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• v.39 no.10
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• pp.769-775
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• 1995

The reaction between $CH_3$ radicals and $O_2$ was investigated in incident shock waves at temperatures between 1390 and 2250 K and densities from 1.5 to 5.3 mol/$m^{+30/3}$ using azomethane as a source of methyl radicals by following the consumption of CH3 radicals with time resolved UV absorption measurements at 213.9 nm. The rate constant expression $k_2=1.35{\times}10^{12}\;exp( - 5900 K/T)\;cm^3 mol^{-1}s^{-1}$ for the reaction of $CH_3 + O_2{\rightarrow}CH_2O + OH$ was derived.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.8-8
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• 2010

외부전하를 감지할 수 있는 EEPROM 구조를 기반으로 한 센서를 제안하였다. 부유게이트로부터 확장된 큰 면적의 접촉부위 (CCM)는 외부전하를 고정화하도록 설계되었으며, $0.13{\mu}m$ 단일-다결정 CMOS 공정에 적합한 적층의 금속-절연체-금속 (MIM) 제어케이트구조로 구성되었다. N-채널 EEPROM의 CCW 캐패시터 영역에 양의 전압이 인가되면 제어 게이트의 문턱전압이 음의 방향으로 변화하여 드레인 전류는 증가하는 특성을 보였다. 또한 이미 충전된 외부 캐패시터가 CCW의 부유게이트의 금속영역에 직접 연결되면, 외부 캐패시터로부터 유입된 양의 전하는 n-채널 EEPROM의 드레인 전류를 증가시키지만 반면에 음의 전하는 이를 감소시켰다. 외부 전압과 전하에 의해 PMOS의 특성은 NMOS에 비교하여 반대로 나타남이 확인되었다. EEPROM 인버터의 CCW 영역에 외부전하를 연결하면 인버터의 입-출력 특성이 기준 시료에 비해 외부전하의 극성에 따라 변화하였다. 그러므로, EEPROM 인버터는 외부전하를 감지하여 부유게이트에 고정된 전하의 밀도 크기에 따라 출력을 전압으로 표현할 수 있음을 확인하였다.

• Proceeding of EDISON Challenge
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• 2015.03a
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• pp.138-146
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• 2015

액체 상태의 물질이 매우 급속하게 냉각되면 일반적으로 과냉각액체(supercooled liquid) 상태에 도달한다. 과냉각액체는 더 낮은 온도에서 유리상(glass phase)으로 상전이를 일으킨다고 알려져 있는데, 이때 나타나는 동역학적 불균일성(dynamic heterogeneity)은 상전이를 기술하는데 중요한 역할을 한다. 그러나 일반적인 액체의 상전이를 연구할 때 주로 사용되던 상관함수(correlation function)으로는 이러한 불균일성을 정량적으로 표현하기 어렵기 때문에 동역학적 민감도(dynamic susceptibility)나 multi-time correlation function 등 동역학적 성질(dynamic property)로부터 특징적인 시간 개념 및 거리 개념을 도출하려는 연구가 많이 진행되어 왔다. 본 논문에서는 일반적으로 특징적인 거리 개념을 도출해 내는데 사용되는 4점 밀도 상관함수(four-point density correlation function)인 dynamic susceptibility(${\chi}^4$)가 입자 밀도의 요동(fluctuation)의 상관관계(correlation)가 지속되는 특징적인 시간 개념에 대한 정보 또한 포함하고 있다는 점에 주목하였다. 이에 따라 ${\chi}^4$의 시간에 대한 적분인 ${\tau}_4$를 새롭게 도입하였으며 그 결과로 ${\tau}_4$는 three-time density correlation function으로부터 도출한 ${\tau}_{Dh}$와 같은 축척(scaling)을 가지는 것을 확인하였다. 과냉각액체에 대한 장난감 모형(toy model)의 일종인 "Lennard-Jones potential 하에서 운동하는 서로 다른 두 종류의 입자들"을 연구에 사용하였다.

• Geotechnical Engineering
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• v.8 no.4
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• pp.17-30
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• 1992

Constitutive relations for lightly overconsolidated state of clayey soils. as well as normally consolidated state of those, play an important role in the analyses of geotechnical structures in clay deposits. For the practical point of view, a constitutive model applicable to lightly overconsolidated soils should be developed to easily evaluate the model parameters, and to precisely predict the various behavior of OC soils. For that purpose, a constitutive model for the lightly overconsolidated soil behavior has been proposed to rep- resent the undrained behavior which can be normalized using equivalent pressure, p. , Yielding within the initial yield surface is modeled exclusively using the given normally consolidated model parameters only. Furthermore, the proposed model can be applied to consider the effects of overconsolidation, secondary consolidation, and stress relaxation. The measured behavior in undrained triaxial tests has been Predicted easily and precisely in comparison with other models.