• 소성∙가공
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• 제27권4호
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• pp.222-226
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• 2018

Severe plastic deformation (SPD) is a promising method for drastically enhancing the mechanical properties of the materials by grain refinement of metallic materials. However, inhomogeneous deformation during the SPD process results in the inhomogeneous microstructure of the SPD-processed material. We manufactured cylindrical copper specimens of 42 mm in diameter with ultrafine grains (UFG) using an equal channel angular pressing (ECAP) to figure out the relationship between homogeneous microstructure and the number of the processing passes. Two specimens, which are ECAP-processed 4 times (4pass) and 6 times (6pass) each with Route Bc, are prepared for comparison of mechanical properties and microstructure. The results show that the mechanical properties of the two specimens (4pass and 6pass) are similar. Moreover, both the specimens show highly enhanced mechanical properties. The 4pass specimen, however, shows inhomogeneity in hardness distribution, while the 6pass specimen shows a homogeneous distribution. Microstructure analysis reveals that the 4pass specimen has an inhomogeneous microstructure with incompletely refined grain structure. This inhomogeneity of the 4pass specimen could be explained by the circumferential rotation during ECAP process.

• 설비공학논문집
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• 제18권11호
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• pp.888-895
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• 2006

The present study has been conducted to investigate the effects of Reynolds number on heat/mass transfer and pressure drop characteristics in a rotating smooth two-pass duct. For stationary cases, the heat/mass transfer and pressure drop Is decreased on turning region of both leading and trailing surfaces as Reynolds number increases. For rotating cases, increment of Reynolds number affects differently the heat/mass transfer and pressure drop on the leading and trailing surfaces. In the first pass, for example, the heat/mass transfer on the leading surface is greatly increased, though the heat/mass transfer on the trailing surface is almost the same. The reason is that effect of the main flow is more dominant than effect of secondary flow. In particular, it gave decrement of the heat/mass transfer and the pressure drop at turning region and upstream region of second pass for both non-rotating and rotating cases.

• 산업경영시스템학회지
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• 제40권1호
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• pp.131-143
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• 2017

As the number of tourists visiting Seoul are continuously increasing, the demand of an integrative tour pass is also increasing. However, only a few tour passes are available for the tourists in Seoul. In this paper, we propose a new tour pass called "Seoul Landmark Pass" targeting foreign individual travelers and investigate the marketability of the proposed tour pass. For the configuration of the Seoul Landmark Pass we listed 17 candidate attractions charging entrance fee in Seoul, referring to e-guidebook on Visit Seoul web site. Among them we selected 6 attractions using the checklist with the attributes that foreign tourists would prefer. We also performed SWOT analyzes on existing tour passes to determine the benefits to be included in the proposed tour pass. To investigate the marketability of the proposed tour pass we have surveyed the foreign individual tourists in Seoul. Using the survey data, we have analyzed the intent of purchase by age, visiting period, visiting purpose, frequency of visit, and nationality to identify target customers. The results show that the intent of purchase is high among the Chinese tourists at the age of twenties who visited Seoul for the first time or second times. Also, the individual tourists prefer to bundle T-money card with the proposed tour pass. Finally, we have provided a brief review of the Price Sensitivity Measurement (PSM) method and applied PSM to determine the acceptable price range and the optimal price of the proposed tour pass. The optimal price of the proposed tour pass is determined at 53,000 won including T-money card.

• 동굴
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• 제88호
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• pp.45-50
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• 2008

It is rapidly increasing number using Hi-pass system passing through tollgate on the high way. However disabled people and man of merit have been excepted existing advantage of discount when they are using Hi-Pass. It is difficult to make a check an advantage when they are in a vehicle for using Hi-pass system technology in present. For solving this problem, we have fabricated virtual Hi-pass system combined fingerprint identification system (FIS) by AVR and fingerprint identification USB. We checked the chance of efficiency and utility in this system for getting a solution of conservative problem. And, it will be also used for entrance ticketing and transferring of cave tourism and so on.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.864-867
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• 2005

In this paper we introduce a design of parallel architecture for wavelet transformation on FPGA. We implement wavelet transforms though lifting scheme and apply Daubechies4 transform equations. This technique has an advantage that we can obtain perfect reconstruction of the data. We divide our process to high pass filter and low pass filter. With this division, we can find coefficients from low and high pass filters simultaneously using parallel processing properties of FPGA to reduce processing time. From the equations, we have to design real number computation module, referred to IEEE754 standard. We choose 32 bit computation that is fine enough to reconstruct data. After that we arrange the real number module according to Daubechies4 transform though lifting scheme.

• Journal of the Korean Wood Science and Technology
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• 제32권3호
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• pp.42-51
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• 2004

Wood veneer-bamboo zephyr composite board (WBCB) was manufactured to evaluate the properties of bamboo as alternative raw materials for the manufacture of composite panels. Bamboo zephyr was prepared using Moso bamboo (Phyllostachys pubesens Mazel. et Z), Giant timber bamboo (Phyllostachys bambusoides Sieb. et Zucc), and Hachiku bamboo (Phyllostachys nigra var. henosos Stapf). The effect of age and species of bamboo on zephyr production was investigated in terms of the pass number of bamboo split through the rollers, and the width increasing rate of bamboo split. Five-ply WBCBs were produced with Keruing veneers as face and back layers, leading to three layers of bamboo zephyr sheets as core layer. Each layer was placed so that its grain direction was at right angles to that of the adjacent layer and the layers were bonded together with phenol-formaldehyde (PF) resin.The pass number of bamboo split was increased with an increase of the thickness of culm wall. At the same thickness, Moso bamboo showed no effect of the age of bamboo on the pass number. The pass number of split of Giant timber bamboo was lower than that of Moso bamboo. No significant effect of bamboo species and age on the width of zephyr produced was observed. The width of zephyr obtained could be expressed as a function of diameter multiplied by thickness of culm wall. The physical and mechanical properties of WBCB manufactured in all given conditions did not show any significant differences, and they were above the requirement of Korean Standard (KS).

• 한국해안해양공학회지
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• 제19권5호
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• pp.418-428
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• 2007

Boussinesq 방정식에 의한 파랑전파의 계산과정 중 파랑의 비선형 상호작용 및 쇄파발생에 의하여 수치잡음이 흔히 발생하며 이 잡음을 적절히 제어하지 않을 경우 해가 급속히 발산하게 된다. 본 연구에서는 계산 중간과정에 주기적으로 적용하여 수치잡음을 제거하기 위한 세가지 형태의 저파수통과 필터(FFT 필터, 가우스 필터, 그리고 Shapiro 필터)의 특성에 대하여 고찰하였다. 경사면 파동장에 대한 기존의 수리실험 결과와 본 수치해석 결과를 비교하고 각 필터의 잡음 제거효과, 주 시그널의 보존성, 그리고 계산 소요시간에 대하여 검토하였다. 그 결과, Shapiro 필터의 매개변수(필터 요소수와 통과수, 그리고 필터적용주기)를 적절히 설정함으로써 계산의 정확성과 효율성을 잘 달성할 수 있는 것으로 나타났다. 적정한 매개변수 선정을 위해서는 다소의 시행착오적 계산이 요구되나 대체적으로 필터 요소수 4에 대하여 50이내의 필터 통과수와 $100{\sim}200$ 시간스텝 정도의 적용주기가 타당한 것으로 판단된다.

• 대한기계학회논문집B
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• 제28권8호
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• pp.910-920
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• 2004

The heat/mass transfer characteristics in a rotating two-pass duct with and without rib turbulators are investigated in the present study. The square duct has a hydraulic diameter ($D_h$) of 26.7 mm, and $1.5\;mm{\times}1.5\;mm$ square $90^{\circ}$-rib turbulators are attached on the leading and trailing walls. The pitch-to-rib height ratio (p/e) is 10. The Reynolds number based on the hydraulic diameter is kept constant at 10,000 to exclude the Reynolds effect, and the rotation number is varied from 0.0 to 0.20. In the smooth duct, the curvature of the $180^{\circ}$-turn produces Dean vortices that enhance heat/mass transfer in the post-turn region. When rib turbulators are installed, heat/mass transfer is augmented 2.5 times higher than that of the smooth duct since the main flow is turbulated by reattaching and separating in the vicinity of the duct surfaces. The duct rotation results in heat/mass transfer discrepancy so that Sherwood number ratios are higher on the trailing surface in the first-pass and on the leading surface in the second-pass. In the turning region, Dean vortices shown in the stationary case transform into one large asymmetric vortex cell, and subsequent heat/mass transfer characteristics also change. As the rotation number increases, the heat/mass transfer discrepancy enlarges.

• 한국지열·수열에너지학회논문집
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• 제15권4호
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• pp.46-54
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• 2019

In this study, the performance of a shell and tube heat exchanger (STHE) and welded plate heat exchanger (WPHE) was measured experimentally. The pass numbers of the STHE was changed by 1, 2 and 4. As a result, the WPHE showed 2.1 times higher heat exchange capacity than that of the STHE. In case of pressure drop, the STHE with 1 and 2 pass number has a lower pressure drop than the WPHE, while the STHE with 4 pass presented higher pressure drop than the WPHE. The performance index considering the heat exchange capacity and pump consumption power, showed in oder of STHE_Pass1 > STHE_Pass2 > W PHE > STHE_Pass4 under the same flow rate. Therefore, when the WPHE was designed optimally under same operating condition with STHE, the maintenance fee and space can be reduced effectively by using the WPHE.

• 소성∙가공
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• 제24권4호
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• pp.234-240
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• 2015

Multi-pass shape drawing is very important to produce steel profiles in round samples. In the current study, a process design system is developed for a multi-pass shape drawing. In general, the number of passes for a multi-pass shape drawing is 2 to 3 when the reduction ratio, drawing stress, and productivity are considered. Therefore, calculating the drawing stress and designing the intermediated die shapes are very important. In order to calculate the drawing stress, a shape drawing load prediction method is proposed using a general axisymmetric drawing load prediction model. An intermediate die shape design method is proposed using the initial and the final product shapes. Based on this analysis, a process design system is developed for multi-pass shape drawing for steel profiles. The system works with AutoCAD. The system was applied to design a shape drawing of a spline.