• School Mathematics
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• v.9 no.1
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• pp.13-28
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• 2007

Division of fractions can be categorized as measurement division, partitive or sharing division, the inverse of multiplication, and the inverse of Cartesian product. Division algorithm for fractions has been interpreted with manipulative aids or models mainly in the contexts of measurement division and partitive division. On the contrary, there are few interpretations for the context of the inverse of a Cartesian product. In this paper the significance and the limits of existing interpretations of division of fractions in the context of the inverse of a Cartesian product were discussed. And some new easier interpretations of division algorithm in the context of a Cartesian product are developed. The problem to determine the length of a rectangle where the area and the width of it are known can be solved by various approaches: making the width of a rectangle be equal to one, making the width of a rectangle be equal to some natural number, making the area of a rectangle be equal to 1. These approaches may help students to understand the meaning of division of fractions and the meaning of the inverse of the divisor. These approaches make the inverse of a Cartesian product have many merits as an introductory context of division algorithm for fractions.

• Journal of Korea Water Resources Association
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• v.41 no.5
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• pp.491-501
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• 2008

In order to describe runoff characteristics of urban drainage area, outflow from subbasins divided by considering topography and flow path, is analyzed through stormwater system. In doing so, concentration time and time-area curve change significantly according to basin shape, and runoff characteristics are changed greatly by these attributes. Therefore, in this development study of FFC2Q model by MLTM, we aim to improve the accuracy in analyzing runoff by adding a module that considers basin shape, giving it an advantage over popular urban hydrology models, such as SWMM and ILLUDAS, that can not account for geometric shape of a basin due to their assumptions of unit subbasin as having a simple rectangular form. For subbasin shapes, symmetry types (rectangular, ellipse, lozenge), divergent types (triangle, trapezoid), and convergent types (inverted triangle, inverted trapezoid) have been analyzed in application of time-area curve for surface runoff analysis. As a result, we found that runoff characteristic can be quite different depending on basin shape. For example, when Gunja basin was represented by lozenge shape, the best results for peak flow discharge and overall shape of runoff hydrograph were achieved in comparison to observed data. Additionally, in case of considering subbasin shape, the number of division of drainage basin did not affect peak flow magnitude and gave stable results close to observed data. However, in case of representing the shape of subbasins by traditional rectangular approximation, the division number had sensitive effects on the analysis results.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.35T no.3
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• pp.46-52
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• 1998

In this paper, after inputting the computer with the attached number plate on the vehicle, using it, the color decomposition method and back propagation neural network proposed the extractable method of the vehicle number plate at high speed. This method separated R, G, B signal form input moving vehicle image to computer through video camera, then after transform this R, G, B signal into input image data of the computer by using color depth of vehicle number plate and store up binary value in the memory frame buffer. After adapting character's recognition algorithm, also improving this, by adapting back propagation neural network makes the vehicle number plate recognition system. Also minimalizing the similar color's confusion, adapting horizontal and vertical extracting algorithm by using the vehicle's rectangular architecture shows the extract and character's recognition of the vehicle number plate at high speed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.61-62
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• 2015

In this paper, a design method for a dual-band compact slot antenna using SRR(split-ring resonator) conductor is studied. The SRR conductor is loaded inside of a rectangular slot of the proposed antenna for dual-band operation. Final design parameters are obtained by analyzing the effects of the gap between the SRR conductor and slot, and the width of the SRR conductor on the input reflection coefficient and gain characteristics. A prototype of the proposed dual-band slot antenna operating at 2.45 GHz WLAN band and 3.40-5.35 GHz band is designed on an FR4 substrate with a dimension of 30 mm by 30 mm.

• Journal of the Korean Wood Science and Technology
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• v.42 no.6
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• pp.714-722
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• 2014

In the previous study, a variety of wood-based panels was thermally decomposed to manufacture carbonized boards that had been proved to be high abilities of insect and fungi repellence, corrosion and fire resistant, electronic shielding, and formaldehyde adsorption as well as sound absorption performance. Based on the previous study, carbonized medium density fiberboard (c-MDF) was chosen to improve sound absorption performance by holing and sanding process. Three different types of holes (cross shape, square shape, and line) with three different sanding thickness (1, 2, and 3 mm) were applied on c-MDF and then determined sound absorption coefficient (SAC). The control c-MDF without holes had 14% of SAC, however, those c-MDFs with holes had 16.01% (square shape), 15.68% (cross shape), and 14.25% (line) of SAC. Therefore, making holes on the c-MDF did not significantly affect on the SAC. As the degree of sanding increased, the SAC of c-MDF increased approximately 65% on sanding treated c-MDFs (21.5, 21.83, and 19.37%, respectively) compared to the control c-MDF (13%). Based on these results, composite sound absorbing panel was developed with c-MDF and MDF (11 mm). The noise reduction coefficient of composite sound absorbing panel was 0.45 which was high enough to certify as sound absorbing material.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.1
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• pp.81-88
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• 2022

In the NRC (New paradigm Reinforced Concrete) beam, steel forms, main angles used as main reinforcements, and shear angles used as basic shear reinforcements are welded and assembled in the form of vierendeel truss structures in a steel factory. After the NRC truss frame is installed at the site, additional main reinforcement and shear reinforcement are distributed. In this study, the shear performance evaluation of the NRC beam was conducted through shear tests in accordance with the type of shear reinforcement of the NRC beam (shear angle, inclined shear reinforcing bar, and U-type cover bar). As a result of the test, the initial stiffness was similar before the initial cracking of each specimen, and all specimens were shear fractured.The shear reinforcements of the specimens exhibited a yielding behavior at the time of the maximum sheat force, and the shear strengths of the specimens increased as the amount of reinforcement of the shear reinforcement increased. These results show that NRC shear reinforcements exhibit shear performance corresponding to their shear strength contribution. As a result of calculating the nominal shear strengths according to KDS 14 20 22, the experimental shear strengths of the NRC beam specimens with shear reinforcement was 37~146% larger than the nominal shear strengths, so It was evaluated as a safety side.

• Journal of Korea Multimedia Society
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• v.8 no.10
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• pp.1369-1382
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• 2005

Vehicle segmentation, which extracts vehicle areas from road scenes, is one of the fundamental opera tions in lots of application areas including Intelligent Transportation Systems, and so on. We present a vehicle segmentation approach for still images captured from outdoor CCD cameras mounted on the supporting poles. We first divided the input image into a set of two-dimensional grids and then calculate the feature values of the edges for each grid. Through analyzing the feature values statistically, we can find the optimal rectangular grid area of the vehicle. Our preprocessing process calculates the statistics values for the feature values from background images captured under various circumstances. For a car image, we compare its feature values to the statistics values of the background images to finally decide whether the grid belongs to the vehicle area or not. We use dynamic programming technique to find the optimal rectangular gird area from these candidate grids. Based on the statistics analysis and global search techniques, our method is more systematic compared to the previous methods which usually rely on a kind of heuristics. Additionally, the statistics analysis achieves high reliability against noises and errors due to brightness changes, camera tremors, etc. Our prototype implementation performs the vehicle segmentation in average 0.150 second for each of $1280\times960$ car images. It shows $97.03\%$ of strictly successful cases from 270 images with various kinds of noises.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.8
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• pp.983-989
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• 2013

This study proposes a piezoelectric vibration energy harvester composed of two diagonally segmented energy harvesting units. An auxiliary structural unit is attached to the tip of a host structural unit cantilevered to a vibrating base, where the two components have beam axes in opposite directions from each other and matched short-circuit resonant frequencies. Contrary to the usual observations in two resonant frequency-matched structures, the proposed structure shows little eigenfrequency separation and yields a mode sequence change between the first two modes. These lead to maximum power generation around a specific frequency. By using commercial finite element software, it is shown that the magnitude of the output power from the proposed vibration energy harvester can be substantially improved in comparison with those from conventional cantilevered energy harvesters with the same footprint area and magnitude of a tip mass.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.222-222
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• 2003

나노크기 금속입자가 분산된 세라믹 나노복합재료는 향상된 기계적 특성과 함께 독특한 전기적, 자기적 특성을 보여주어 새로운 기능성 재료로의 응용가능성을 갖고 있다. 그러나 소결 중의 반응이나 입자성장 등으로 형성된 반응상 또는 조대한 입자상이 세라믹 기지의 입계 등에 존재한다면, 나노크기 금속상 분산에 의한 기계적 특성의 향상과 독특한 기능성 부여라는 장점들이 없어지게 된다. 따라서 요구되는 특성을 구현할 수 있는 금속분산 나노복합재료의 제조를 위해서는 미세조직 제어를 위한 최적의 제조공정 확립과 미세조직과 특성 등의 관계에 대한 연구가 요구된다. 본 연구에서는 기지상으로 A1$_2$O$_3$를, 분산상으로는 저융점 금속이며 일반적인 A1$_2$O$_3$의 가압소결시에 (약 140$0^{\circ}C$) 액상으로 존재하는 금속 Cu를 선택하여 조성이 5 vol% Cu가 되도록 복합재료를 제조하였다. $Al_2$O$_3$와 CuO 원료분말들은 습식 및 건식 볼 밀링을 통하여 균일한 분말혼합체로 제조되었다. 혼합분말은 열간가압소결기 내에 장입한 후 35$0^{\circ}C$에서 30분 동안 H$_2$가스를 흘려주며 CuO를 Cu로 환원 처리하였다. 계속해서 H$_2$분위기를 유지하며 승온한 후, 각각 1000-145$0^{\circ}C$에서 분위기를 Ar 으로 치환하였다. 소결은 145$0^{\circ}C$에서 30 ㎫의 압력으로 1시간동안 행하였다 소결한 시편들은 직사각형 형태로 가공하였으며 표면은 0.5$\mu\textrm{m}$의 다이아몬드 입자로 연마하였다. XRD, SEM 및 TEM을 이용하여 상분석 및 미세조직관찰을 행하였다. 파괴강도는 3중점 굽힘 법으로 (3-point bending test) 측정하였다. 이때 시편 하부의 지지 점간의 거리는 30mm, cross-head 속도는 0.5 mm/min으로 하였고 5개의 시편을 측정하여 평균값을 구하였다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.2
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• pp.167-172
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• 2011

In physical engineering, the turbulent flow on the surface roughness is very important. With the welding, design and paint, the hull surface roughness at each stage in the various aspects are important factors to be considered. In this study, the hull surface roughness geometry that was generalized to the PIV was applied to the tank test. The roughness of the surface changed the distance of the interval. Experimental velocity is Re = $1.1{\times}10^4$, Re = $2.0{\times}10^4$ and Re = $2.9{\times}10^4$. The turbulent intensity at the time-average were examined The roughness coefficient occurred with increasing turbulence intensities was stronger. The turbulence intensity away from the roughness in the shape was zero. The variation of turbulence intensity at the experimental flow conditions change was not affected.