• 한국가구학회지
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• 제23권3호
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• pp.298-304
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• 2012

Since 1990's, a flooring based on plywood has gotten customers' demand. Costs of raw material and production increased because of changed environment of industry. Tropical timber such as Red Meranti (Shorea acuminate) used for raw material of the floor has been depleting beside countries in South Eastern Asia changed species of afforestation. As a result, it gets hard to secure good quality of raw material for plywood. Moreover plywood price is increased suddenly after earthquake in Japan. Eucalyptus (Eucalyptus globulus) in china has been using for raw material as a countermeasure of changed environment of industry. In this study, possibility of using flooring consisted of Eucalyptus veneer as a core layer was checked by heat transfer experiments. Flooring consisted of Red Meranti was used for comparison. Two factors which impact on heat transfer are a type of density gradient and density difference between Long-grain veneer and Short-grain veneer. Red Meranti samples are 'M' type of density gradient on the other hand Eucalyptus samples are 'W' type of density gradient.

• Macromolecular Research
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• 제11권6호
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• pp.467-470
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• 2003

The dielectrophoretic technique was used to prepare density gradient polymers, polystyrene doped with a dipolar modifier, diphenyl sulfide. We have measured concentration gradients of the dopant by UV/Nis spectroscopy as a function of time in a nonuniform electric field. Measured concentration data at different positions of the sample confirmed that a concentration gradient arose after a nonuniform electric field was applied to the system, these data were used to compare the concentration profile with that predicted by the dielectrophoresis equation.

• 한국멀티미디어학회논문지
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• 제7권12호
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• pp.1639-1649
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• 2004

In this paper, a method for detection of forged signatures based on spectral analysis of directional gradient density function and a weighted fuzzy classifier is proposed. The well defined outline of an incoming signature image is extracted in a preprocessing stage which includes noise reduction, automatic thresholding, image restoration and erosion process. The directional gradient density function derived from extracted signature outline is highly related to the overall shape of signature image, and thus its frequency spectrum is used as a feature set. With this spectral feature set, having a property to be invariant in size, shift, and rotation, a weighted fuzzy classifier is evaluated for the verification of freehand and random forgeries. Experiments show that less than 5% averaged error rate can be achieved on a database of 500 signature samples.

• 천문학회지
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• 제29권1호
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• pp.63-73
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• 1996

The previous study of chemical evolution of the Galaxy is extended to the radial properties of the Galactic disk. The present model includes radial dependency of the time-dependent bimodal IMF, radial flow of material in the disk, and the change of type I supernova explosion rate with radial distance from the disk center as model parameters and observed gas and stellar density distributions and metallicity abundance gradient as observational constraints. The results of two models in this study explain the observed gas and stellar density distributions well, with the slope of the gas density gradient in the region of 4.5 kpc$Y_1$ and -0.123dex/kpc in model $Y_2$, respectively, which fit well the observed gradient of -0.l1dex/kpc. The abundance gradient reproduced in model $Y_1$ is getting flatter with decreasing radius, while that in model $Y_2$ is getting steeper, which fits better the observed abundance gradient. This result shows the necessity of exponentially increasing type I supernova explosion rate with decreasing radius in order to explain the observed abundance gradient in the disk. The fitness of observed density distribution and star formation rate distribution justifies the reliability of time-dependent bimodal IMF as a compound quantitative chemical evolution model of the Galaxy. The temporal variations of metallicity gradients for carbon, nitrogen and oxygen are also shown.

• 한국해양공학회지
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• 제33권1호
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• pp.92-97
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• 2019

The sea is stratified with water that has different densities because of pressure, temperature, and salinity. When conducting studies of internal waves in the ocean, the fluid is assumed to have layers that have discrete densities. This assumption is made because it is difficult to achieve layers that exhibit gradual changes in the density of the water. In this study, we used previous studies on ocean waves and their radiation issues in the density layer fluid to investigate the characteristics of internal waves in the ocean and their radiation patterns induced by a moving body in a stratified fluid. We also studied the difference in wave radiation between the density gradient layer and the discrete density layer. We found that the wave radiation patterns depended on the velocity of the moving body and the change in the density of the water. The crest apex shift phenomenon was observed in the density gradient in the layer of fluid.

• KSBB Journal
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• 제8권2호
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• pp.97-103
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• 1993

세포질 유전형질의 도입을 성공적으로 수행코자 세질 웅성 불임(eMS; cytoplasmic male sterili­t ty) 계통의 담배 MS(male sterility) Burley 21의 callus tissue에서 cytoplast를 분리시키고 이와 Ni­c cotiana tabacum Burley 64의 mesophyll protoplast 를 PEG방법에 의한 세포융합으로 cybrid cell올 유도할 수 있었다. cytoplast의 분라는 density gradient solution의 osmolarity를 일정하게 하는 것보다 gradient간의 차이가 더 효과적이였으며 분리된 cytoplast의 양은 재료로 이용된 protoplast의 20-30% 정도를 나타 내었다. 또한 cytoplast와 protoplast의 융합은 P PEG농도 50%에셔 효과적이었다.

• 제3의학
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• 제1권1호
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• pp.103-113
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• 1996

It is thought that the quantity and quality of the heat stimulation and the mechanism of heating process are important to understand the moxa-combustion. In order to get the basic data on the effective moxa-combustion method, combustion temperature changes (average temperature, peak temperature, average gradient temperature and maximum gradient temperature) of the heating period were measured respectively by the density of moxa material. For the experiment, samples of $300mg/0.26cm^3$ , $400mg/0.26cm^3$ and $500mg/0.26cm^3$ of moxa material were molded in a conical mold with each 10mm in diameter and height. 1. The average temperature and peak temperature of heating period on the moxa-combustion showed higher in the $400mg/0.26cm^3$ and $300mg/0.26cm^3$ than in the $500mg/0.26cm^3$ sample respectively. 2. The average gradient temperature of heating period on the moxa-combustion rose quickly in the $300mg/0.26cm^3$, $400mg/0.26cm^3$ and $500mg/0.26cm^3$ in that order and the maximum gradient temperature rose more quickly in the $300mg/0.26cm^3$ and $400mg/0.26cm^3$ than in the $500mg/0.26cm^3$ sample respectively. According to the above results, it is concluded that the density of moxa material is (the) more important (factor) than the weight or volume of moxa material on the combustion temperature changes of the heating period for the evaluation of the quality and quantity of moxa-combustion.

• KSBB Journal
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• 제16권5호
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• pp.523-525
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• 2001

커들란은 용액의 pH 7.0에서 salt 상태로 존재하기 때문에 커들란만이 액상에 녹아 있는 경우에는 분리공정은 원심분리를 함으로써 분리가 가능하다. 그러나, 세포외 다당류로 생산된 커들란읜 세포, 염 의 무기물이 섞여 있기 때문에 이러한 물질을 제거하는 것이 커들란 분리의 중요한 변수가 되었다. 커들란의 생산을 위한 분리에 관한 보고는 원심분리 방법을 이용한 것으로 알려져 있음 세포 및 불순물 등을 제거하여 순수한 커들란을 분리하기 위해 pH swing separation (pH가 높은 경우 커들란이 용액에 녹는 성질을 이용)을 이용하였으나 원심분리를 수 차례 반복해야 되기 때문에 소요되는 동력이 많이 필요하여 에너지 절감형 및 오염절감형의 새로운 공정의 개발이 필요하게 되었다. 온 연구에서는 pH swing separation 에서 동력비가 많은 드는 단점을 감소시키기위하여 커들란의 물리 화학적인 특성을 고려한 분리공정을 개발하였다. 향후 공정 개선을 위한 지속적인 연구가 필요하며 완성시 경제적이 공정을 개발하는 것이 가능할 것이다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제50권2호
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• pp.59-64
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• 2001

The distribution of current in the conductors influenced by the armature geometry and velocity is an important parameter for determining performance of an electromagnetic launcher(EML). the electric current in the early launching stage tends to flow on the outer surfaces of the conductors, resulting in very high local electric current density. However, the tendency for current to concentrate on the surface is driven by the velocity skin effect later in launching stage. The high current density produces high local heating and, consequently, increases armature wear which causes several defects on EML system. This paper investigates the effects of rail/armature geometry on current density distribution, launcher inductance gradient (L'), and contact force. Three geometrical parameters are used here to characterize the railgun system. These are the ratio of contact length to root length, relative position of contact leading edge to root trailing edge, and the ratio of rail overhang to the rail height. The distribution of current density, L', contact force between various configurations of the armature and the rail are analyzed and compared by using the EMAP3D program.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제26권2호
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• pp.108-120
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• 2022

We considered qualitative behaviour of the generalization of Einstein's model of Brownian motion when the key parameter of the time interval of free jump degenerates. Fluids will be characterised by number of particles per unit volume (density of fluid) at point of observation. Degeneration of the phenomenon manifests in two scenarios: a) flow of the fluid, which is highly dispersing like a non-dense gas and b) flow of fluid far away from the source of flow, when the velocity of the flow is incomparably smaller than the gradient of the density. First, we will show that both types of flows can be modeled using the Einstein paradigm. We will investigate the question: What features will particle flow exhibit if the time interval of the free jump is inverse proportional to the density and its gradient ? We will show that in this scenario, the flow exhibits localization property, namely: if at some moment of time t₀ in the region, the gradient of the density or density itself is equal to zero, then for some T during time interval [t₀, t₀ + T] there is no flow in the region. This directly links to Barenblatt's finite speed of propagation property for the degenerate equation. The method of the proof is very different from Barenblatt's method and based on the application of Ladyzhenskaya - De Giorgi iterative scheme and Vespri - Tedeev technique. From PDE point of view it assumed that solution exists in appropriate Sobolev type of space.