• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.300-305
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• 2001

The unsteady flow structure and the related noise generation, which are caused by the separation of a two-dimensional, incompressible, laminar boundary-layer on the flat plate under the influence of local adverse pressure gradient, are numerically examined. The characteristic lines of the wall pressure are examined to understand the unsteady behavior of vortex shedding near the reattachment point of the separation bubble. Also, the generation and propagation of the vortex-induced noise in the separated boundary-layer are calculated by the method of computational aero-acoustics (CAA), and the effects of Reynolds number, Mach number and the strength of the adverse pressure gradient on the unsteady flow and noise characteristics are examined.

• 한국조경학회지
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• 제29권1호
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• pp.140-151
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• 2001

This study based on the theoretical understanding of multi-layer planting which have engineering, ecological and landscape benefits, was conducted to find out the status of multi-layer planting in the apartment and neighborhood park in Seoul. This study was also aimed to seek for the problematic matters, and suggest a solution on the current multi-layer planting. The results of this study were as follows; 1) Since landscape woody plants have been classified just as tree and shrub in Korea, the classification for the multi-layer planting has been unreasonable, and landscape woody plants might have been classified as tree, sub-tree and shrub, or upper, middle, and lower-layer, It could be defined that upper layer is over eight meters in full growth, middle over 3-8 meters and lower under 3 meters. 2) In apartments, the upper layer consisted of eighteen species, the middle and lower layer seven species each. In neighborhood parks, the upper layer consisted of fifteen species, and the middle and lower layer five species each. 3) In terms of planting year of the surveyed areas, there were no differences in the number of species when planting year of the apartment was divided into two groups, the first half(1900-1995) and the second(1996-2000). But, in terms of individual occupation, the percentage was decreased in upper layer, while there was increasing in middle and lower layer. 4) As the result of survey of multi-layered area, it appeared that apartment was shown 0.65 percent and neighborhood park 0.61 percent of the planted area, which was less than 1 percentage of landscape architecturally planted area. 5) In apartment, the number of individual in middle layers has been increased in the first half and the second, but with respect to the correlation with multi-layered area, the apartments had the "$\rho$=0.208", saying that increasing middle layer was scattered planting instead of multi-layered planting. 6) In planting at the apartments in Korea, the planting density was limited, because the layer division was restricted to only tree and shrub. On the contrary, it was divided into upper, middle and lower tree in Japan. Therefore, in Korea, it should be classified as the planting density by dividing into tree, sub-tree, and shrubs, or upper, middle and lower tree by the law. And, it should be considered that the multi-layered planting has a proper organic relation as well as the planting density.g density.

• 한국가구학회지
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• 제21권5호
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• pp.347-353
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• 2010

This research examined the technical feasibility of composite that had 2- and 3- layers of fiberglass reinforcement to enhance the load carrying capacity of particleboard. Specimens were prepared from commercial particleboard. Results indicated that bending properties, hardness and impact bending energy increased as the number of layers of fiberglass reinforcement increased. The wood screw withdrawal load only decreased at the 3-layer of fiberglass reinforcement. The technique developed by this study may increase an opportunity to use particleboard for structural purposes.

• 대한산업공학회지
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• 제24권1호
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• pp.23-35
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• 1998

This article presents a network flow analysis to form flexible machine cells with minimum intercellular part moves and a neural network model to form part families. The operational sequences and production quantity of the part, and the number of cells and the cell size are taken into considerations for a 0-1 quadratic programming formulation and a network flow based solution procedure is developed. After designing the machine cells, a neural network approach for the integration of part families and the automatic assignment of new parts to the existing cells is proposed. A multi-layer backpropagation network with one hidden layer is used. Experimental results with varying number of neurons in hidden layer to evaluate the role of hidden neurons in the network learning performance are also presented. The comprehensive methodology developed in this article is appropriate for solving large-scale industrial applications without building the knowledge-based expert rule for the cellular manufacturing environment.

• 대한기계학회논문집B
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• 제21권11호
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• pp.1552-1561
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• 1997

In this numerical study, it is investigated for the ice-formation phenomena for water flow in a concentric tube. The freezing layers of ice in both the inner and outer wall of a concentric tube are simultaneously considered. In the solution strategy, the complete set of governing equations in both the solid and liquid regions are resolved. Numerical results are obtained by varying the inner/outer wall temperatures and Reynolds number. The results show that the inner/outer wall temperatures have the great effect on the thickness of the solidification layer thereof. The shapes of ice layer in both the inner and outer wall can be expressed as a function of inverse Graetz number. As the wall temperature in inner or outer tube decreases, the heat transfer coefficients in both inner and outer ice layer surfaces increase absolutely.

• Wind and Structures
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• 제30권2호
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• pp.133-140
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• 2020

In this paper, critical fluid velocity and frequency of laminated pipe conveying fluid are presented. Each layer of the pipe is reinforced by functionally graded carbon nanotubes (FG-CNTs). The internal fluid is assumed turbulent and the induced forces are calculated by momentum equations. The pipe is resting on viscoelastic foundation with spring, shear and damping constants. The motion equations are derived based on classical shell theory and energy method. Differential quadrature method (DQM) is used for solution and obtaining the critical fluid velocity. The effects of volume percent and distribution of CNT, boundary condition, lamina layer number, length to radius ration of pipe, viscoelastic medium and fluid velocity are shown on the critical fluid velocity. Results show that with increasing the lamina layer number, the critical fluid velocity increases.

• 대한기계학회논문집B
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• 제29권7호
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• pp.846-853
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• 2005

In this paper, mass transfer in turbulent flow around a rotating circular cylinder is investigated by Direct Numerical Simulation for Schmidt numbers Sc=1 and 1670. Correlation between Sherwood and Reynolds number predicted agrees well with other experimental results over both Sc. Reynolds analogy identified at Sc=1 definitely causes a strong correlation between concentration fluctuation and streamwise velocity. For Sc=1670, it is found that positive small values of concentration fluctuations are observed more frequently than the case of Sc=1 particularly out of the range of Nernst diffusion layer in the viscous sub-layer. This fact is fully confirmed by detailed statistical study using a probability density function of concentration fluctuations.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2007년도 춘계종합학술대회
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• pp.441-444
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• 2007

In this paper, the resonance characteristics of ZnO-based film bulk acoustic resonator (FBAR) devices with high-quality multi-layer reflectors are proposed. The ultrathin Cr film $(300\;\AA-thick)$ between $SiO_2$ film and W film is formed by a sputtering-deposition in order to enhance the adherence at their interfaces. The resonance frequency was observed to vary with the number of the reflectors. This seems to be attributed to the change in the effective thickness of the ZnO film. Also, increasing the number of layers has led to a significant improvement of the series/parallel quality factor.

• E2M - 전기 전자와 첨단 소재
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• 제9권2호
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• pp.138-145
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• 1996

A multilayer piezoelectric transformer (MPT) which generates a high voltage dc power with low driving voltage and high voltage setup ratio was made by the tape casting method. The measured electrical characteristics of the MPT agreed with the results simulated from the equivalent circuit of the MPT. With increasing the number of layer in the MPT, the resonance curve of the input cur-rent revealed an asymmetry due to the increasing input capacitance, while that of output dc voltages revealed symmetry. The MPT which has very thin layer was excellently characterized as low driving voltage and high voltage setup ratio. The output dc voltage is nonlinearly influenced by the number of layer in the MPT.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.85-86
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• 2008

We have developed charged particle type display using opposite-charged two particles. We fabricated the charged particle type display to be controlled the addressing layers by putting voltage. To get the effect of number of layers, we measured driving voltage, reflectivity, viewing angle, and color characteristics, for 1~2 layer. Reflectivity was different according to the number of layers and wavelength of yellow particles is alike to that.