• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.448-453
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• 2001

A commercial CFD code is used to compute the 3-D viscous flow field within the inlet flow concentrator of the newly developed AHU(Air Handling Unit). To improve the performance of the AHU, the inlet air needs to be gradually accelerated to the fan's annular velocity without causing turbulence or flow separation. Three major geometric parameters were selected to specify the inlet shape of the AHU. Several numerical calculations are carried out to determine the influence of the geometric parameters on the performance of the AHU. The performance of the AHU could be measured by the inlet and outlet flow uniformity and the total pressure loss through the inlet flow concentrator. The optimized nondimensionalized velocity profile through the inlet flow concentrator were used for the design of the AHU with the various volume flow rates.

• Journal of the Chungcheong Mathematical Society
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• v.22 no.1
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• pp.89-99
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• 2009

Let $\mu$ be a finite positive Borel measure on the unit ball $B{\subset}\mathbb{C}^n$ and $\nu$ be the Euclidean volume measure such that ${\nu}(B)=1$. For the unit sphere $S=\{z:{\mid}z{\mid}=1\}$, $\sigma$ is the rotation-invariant measure on S such that ${\sigma}(S)=1$. Let $\mathcal{P}[f]$ be the invariant Poisson integral of f. We will show that there is a constant M > 0 such that $\int_B{\mid}{\mathcal{P}}[f](z){\mid}^{p}d{\mu}(z){\leq}M\;{\int}_B{\mid}{\mathcal{P}}[f](z)^pd{\nu}(z)$ for all $f{\in}L^p({\sigma})$ if and only if ${\parallel}{\mu}{\parallel_r}\;=\;sup_{z{\in}B}\;\frac{\mu(E(z,r))}{\nu(E(z,r))}\;<\;\infty$.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.218-219
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• 2018

This study analyzed the unit weight and compressive strength properties of lightweight concrete using high volume blast furnace slag powder by the mixing ratio of lightweight coarse aggregate to investigate the properties of lightweight concrete using domestic artificial lightweight aggregate.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.4
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• pp.483-490
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• 1998

The reflectivity of a grid ferrite electromagnetic wave absorber is analyzed using finite difference time domain (FDTD) method, which is usually used in anechoic chambers for EMI / EMS test. The frequency dispersive characteristics of ferrite medium and its boundary condition are modeled using magnetic flux in addition to E- and H-fields. By applying Floquets theorem, FDTD analysis of the grid ferrite absorber with periodic infinite array is simplified as a unit cell problem. The method of homogenization which is mainly utilized in the calculation of absorber reflectivity as a low frequency technique takes only into account volume fraction of the unit cell of the absorber except for the structure of medium geometry. However, the presented method in this paper can analyze the geometry effect of the unit cell with its medium characteristics up to high frequency region.

• Current Optics and Photonics
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• v.5 no.1
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• pp.32-39
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• 2021

We propose a three-dimensional (3D) streaming system based on a lamina display that can convey field information in real-time by creating floating 3D images that can satisfy the accommodation cue. The proposed system is mainly composed of three parts, namely: a 3D vision camera unit to obtain and provide RGB and depth data in real-time, a 3D image engine unit to realize the 3D volume with a fast response time by using the RGB and depth data, and an optical floating unit to bring the implemented 3D image out of the system and consequently increase the sense of presence. Furthermore, we devise the streaming method required for implementing augmented reality (AR) images by using a multilayered image, and the proposed method for implementing AR 3D video in real-time non-face-to-face communication has been experimentally verified.

• Journal of the Korea Institute of Building Construction
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• v.7 no.2 s.24
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• pp.77-83
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• 2007

This study investigated the fundamental properties of the lightweight foamed concrete depending on various admixtures, and the results were summarized as following. When 20% of cement kiln dust(CKD) and 0.002% of stabilizing agent were mixed to lightweight foamed concrete, it was necessary to use a superplasticizer because flowability was decreased. However, it could reduce sinking depth which were the extensive trouble of lightweight foamed concrete. Bulk density was divided into '0.4' and '0.5' grades on KS according to unit volume weight. The compressive strength was less than that of plain concrete when admixtures were applied, but the results exceeded the minimum strength of the each grades on KS. Totally, it is found that the combination of 20% of CKD and 0.002% of stabilizing agent makes it possible to reduce a sinking depth, recycle resources, and save cost when were mixed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.650-654
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• 1995

In this study, in order to measure energy-absorbing charactistics in collapse test of CFRP thin-walled laminates and interpretate the cause of decreasing age when collapse test is carried out under the environments of high temperatures and hygrothermals, the moisture absorbing behavior according to the variety of orientation angel is observed and collapse characteristics is compared with the influence of high temperatures and hygrothermals. Especially, we supposed to clearly understand reationship between collapse characteristics in proportion to the variety of orientation angel and moisture absorbing. The value of the maximum loading, mean loading,rate of energy absorption energy per unit volume and mass in CFRP thin-walled laminates on the high temperatures and hygrothermals is measured lower than under no moisture absorbing. The maximum collapse loading in dynamic impact test is taken measurement lower than in static collapse test regarding compared with collapse characteristics conformity with the variety of the CFRP circular laminates in high temperatures and hygrothermals. But the absorbed energy per unit mass and volume is almost same and the biggest amount of energy is shown in the CFRP circular laminates with orientation angel of 15 .deg.. Therefore, in the case of use to CFRP circular laminates with axisymmetric mode, CFRP thin-walled structal members with orientation angel of 10 .deg. , 15 . deg. are generally useful.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.9 no.3
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• pp.17-25
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• 2006

To increase freeze-thaw resistance of porous concrete, this study examined physical properties of polymer by replacing paste used as a binding material with polymer, using unsaturated polyester and epoxy resin, and changing the mixing ratio of polymer. According to the result of this study, when the mixing ratio of resin paste to aggregates was 11 to 16%, voids volume was 33 to 37% and unit weight was about 1620 to 1720kg/$m^3$. In comparison with previous studies using cement paste, voids volume increased by about 7 to 16%, while unit weight decreased by about 100 to 300kg/$m^3$. Compressive strength was 90 to 155kg/$cm^2$ at the age of 7 days, which was 5-40kg/$cm^2$ bigger than porous concrete using cement paste. From a viewpoint of freeze-thaw resistance, it was identified that pluse velocity fell by 0.23km/sec, about 7% of the original velocity, when the cycle of freeze-thaw was repeated 300 times. In spite of 300 repetitions of the cycle, relative dynamic modulus of elasticity was more than 60%, which suggested that its freeze-thaw resistance was more excellent compared with the result that relative dynamic modulus of elasticity of porous concrete using cement paste was 60 % or less under the condition of 80 repetitions of freeze-thaw cycle.

• Journal of the Korean Society of Safety
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• v.13 no.2
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• pp.30-38
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• 1998

In this study, in order to measure energy-absorbing characteristics in impact test of CFRP thin-walled laminates and interpret the cause of decreasing age when collapse test is carried out under the environments of high temperatures and hygrothermals, the moisture absorbing behavior according to the variety of orientation angle is observed and impact collapse characteristics of no moisture absorbing status is compared with that under the environments of high temperatures and hygrothermals. Especially, we try to obtain quantitative design data to develop CFRP thin-walled laminates with energy characteristics of optimum impact absorbing. The value of the maximum loading, mean loading, rate of energy absorption energy per unit volume and mass in CFRP thin-walled laminates on the high temperatures and hygrothermals is measured much lower than under no moisture absorbing. The maximum collapse loading in dynamic impact test is taken measurements lower than in static collapse test CFRP circular laminates in high temperatures and hygrothermals. But the absorbed energy per unit mass and volume is almost same each other and the biggest amount of energy is shown in CFRP circular laminates with orientation angle of $15^{\circ}$. Therefore, in the case of using CFRP circular laminates with axisymmetric mode, CFRP thin-walled structural members with orientation angle of $10^{\circ}$, $15^{\circ}$ has generally best condition.

• Journal of Nutrition and Health
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• v.36 no.3
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• pp.319-326
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• 2003

The purposes of this study were to : (a) analyze the menus of food service operations using the menu analysis techniques of Kasavana & Smith, Miller, Merricks & Jones, Pavesic and Uman, (b) closely examine the characteristics of the five analysis techniques. Calculations for the menu analysis were done by computer using the MS 2000 Excel spreadsheet program. Menu mix% and unit contribution margin were used as variables by Kasavana & Smith, sales volume and food cost% by Miller, sales volume and cash contribution by Merrick & Jones, weighted contribution margin and food cost% by Pavesic, and total cash contribution and unit contribution margin by Uman. In each case, a four-cell matrix was created, and menu items were located in each according they achieved high or low scores with respect to two variables. Items that scored favorably on both variables were rated in the top category (e.g., star, prime, signature, group A, winner) and those that scored below average on both were rated in the lowest category (e.g., dog, problem, loser, group D, loser). While the 3 methods of Kasavana & Smith, Miller, Merrick & Jones focus on customers' viewpoints, the others consider the managers' viewpoints. Therefore, it is more likely to be desirable for decision-making on menus if the menu analysis technique chosen is suited to its purpose.