• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.478-482
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• 2002

Recently, the demand for the optical cable is rapidly glowing because the number of internet user increases and high speed internet data transmission is required. To meet this demand, it is necessary to have a sufficient manufacturing capability for mass and high-quality production. But the present optical cable winding system has some serious problems such that the optical cable of radius (6 mm -40 mm) is often piled up and collapsed usually at the edge of the bobbin in the process of the cable winding. It is often necessary to have an additional operator in order to adjust the cable, which causes the productivity decrease. In order to improve a performance of cable winding system which deals with relatively thick cable( radius : 6 mm -40 mm ), we developed a new guiding system for a high-speed self-align cable winding. First of all, the winding mechanism was analyzed. Synchronization logics for the motions of winding, traversing, and the guiding were created and implemented by using the PLC and guiding system controller in a prototype cable winding system manufactured in the CILS( Computer Integrated Large scale System ) lab. An experimental verification was carried out to validate the logic. Results showed that the winding system with the developed guiding system outperformed in reducing pile-up and collapse in the high-speed winding(up to 300 mm/s) compared with the system without the guiding system.

• 농업과학연구
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• 제47권1호
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• pp.43-58
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• 2020

Mulching plastic is used for the purpose of maintaining soil temperature, moisture, and weed and pest prevention in agriculture. Any remaining plastic after use may contaminate the soil and damage crop growth. To solve this problem, mulching plastic wrappers have been studied and developed, but the actual use rate is quite low due to their poor performance and frequent tearing of the plastic on the field. In this study, we developed a tractor attachable mulching plastic wrapper to minimize the tearing of the mulched plastic. The developed mulching plastic wrapper consists of hydraulic motors and pumps, valves, a microcontroller, and sensors. The collecting speed of the plastic mulch was calculated considering the tractor's travel speed and the radius of the collecting drum. A proportional controller was designed to control the rotating speed of the hydraulic motor as the plastic was wound around the collection drum and the radius increased. The performance of an indoor experiment was quite promising because the difference between the collecting speed predicted by the calculation and the actual collecting speed was 2.71 rpm. Based on a field verification test, the speed difference was max. 14.28 rpm; thus, the, proportional integral derivative (PID) controller needs to be considered to control the drum speed precisely. Another issue was found when the soil covered at the edge of the plastic was hardened or the road surface was uneven, the speed control was unstable, and the plastic was torn. In future research, vibrational plows will be equipped to break-up the harden soil for collecting the plastic smoothly.

• 한국제4기학회지
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• 제17권2호
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• pp.129-133
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• 2003

Water is critically important for Tricholoma matsutake(Tm) growth because it is the major component of the mushroom by over 90%. The mushroom absorbs water through the below ground hyphal colony. Therefore, the objectives of our study were to investigate spatio-temporal water changes in Tm colonies. This study was carried out at Tm fruiting sites in Sogni Mt National Park, where the below-ground mushroom colonies have been irrigated. To identify spatial water status within the Tm soil colony soil moisture and ergosterol content were measured at six positions including a mushroom fruiting position on the line of the colony radius. To investigate temporal soil moisture changes in the soil colony, Time Domain Reflectometry(TDR) sensors were established at the non-colony and colony front edge, and water data were recorded with CR10X data logger from late August to late October. Before irrigation, whereas it was 12.8% at non-colony, the soil water content within Tm colony was 8.0% at 0-5cm from the colony front edge, 6.2% at 10-15cm and 6.5-7.5% at 20-40cm. And the content was 12.1% at 80cm distance from the colony edge, which is similar to that at the non-colony. In contrast, ergosterol content which is proportional to the live hyphal biomass was only 0.4${\mu}g$/g fresh soil at the uncolonized soil, while 4.9 $\mu\textrm{g}$/g fresh soil at the front edge where the hyphae actively grow, and 3.8 ${\mu}g$/g fresh soil at the fruiting position, l.1${\mu}g$/g at 20cm distance and 0.4${\mu}g$/g in the 40cm rear area. Generally, in the Tm fungal colony the water content changes were reversed to the ergosterol content changes. While the site was watered during August to October, the soil water contents were 13.5∼23.0% within the fungal colony, whereas it was 14.5∼26.0% at the non-colony. That is, soil water content in the colony was lower by 1.0∼3.0% than that in the non-colonized soil. Our results show that Tm colony consumes more soil water than other parts. Especially the front 30cm within the hyphal colony parts is more critical for soil water absorption.

• 대한전자공학회논문지SP
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• 제39권1호
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• pp.70-76
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• 2002

본 논문에서는 홍채 영역 가운데 .개인의 특징을 가장 잘 나타내는 부분을 선택하여 특징을 추출함으로써 최소한의 홍채 영역을 사용하는 빠른 개인 식별 알고리즘을 제안하였다. 제안 알고리즘은 먼저 흑백 CCD 카메라를 통하여 눈 영상을 획득하고, 최소 탐색 영역을 갖는 개선된 원형 에지 검출기(circular edge detector)에 의해 결정된 동공 및 홍채의 중심과 반지름을 이용하여 홍채 영역을 추출하였다. 그 다음으로 동공 중심과 홍채 중심 축 사이에서 원의 중심과 반지름을 변화시켜가면서 홍채 영역을 여러 개의 원으로 나누고 원주 상에 나타나는 일차원 홍채 신호들 가운데 개인의 특징을 가장 잘 반영하는 부분을 선택한 후 그 영역에 일차원 Gator 필터를 적용하여 홍채 특징을 추출하였다. 개인 식별은 등록 과정을 통해 미리 저장되어 있는 홍채 신호와 개인 식별을 위하여 입력된 홍채 신호 사이의 상관도(correlation) 값을 기준으로 이루어졌다. 판단을 위한 상관도에 대한 임계치 설정은 실험을 통하여 얻은 확률 분포를 이용하여 Type Ⅰ에 러율과 Type Ⅱ 에러율의 평균이 최소가 되는 점으로 결정하였다. 그 결과로 제안 시스템의 성능은 평균 에러율이 약 5.2%로 나타났다.

• 한국농공학회지
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• 제34권1호
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• pp.78-86
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• 1992

This paper aims at investigating the effect of steel ratio and the magnitude of edge-ratio on the mechanical characteristics of reinforced concrete ring sector plate. The influence of steel bars was taken into account by coupling stiffness matrix of the steel bar element with that of the concrete plate element without dealing with separate element of steel bar and by establishing the composite stiffness matrix, which leads to the desirable result which does not increase th number of element could be obtained. Through case studies with 6 cases various steel ratios in ring sector plate supported at four edges and 4 cases with different open angles, the influence of the steel ratio was examined. A numerical analysis to find out the effect of the steel ratio d ue to above mentioned cases was carried out by 4 boundary conditions ; all edges clamped (B.C-1), all edges simply supported (B.C-2), curvilinear two edges clamped and other edges free (B.C-3) and curvilinear two edges simply supported and other edges free(B.C-4). The main results obtained are summarized as follows : 1. The effect of steel ratio on the magnitude of lateral deflection and x-directional bending moment at the center of sector plate and the midpoint of outer and inner curvilinear edges is almost the same up to $30^{\circ}$ of open angle. Beyond $30^{\circ}$ of the angle, the larger the angle, the greater the effect of ratio. 2. In design works using balanced steel ratio, the effect of steel bar can be ignored. But for larger open angles, especially greater than $90^{\circ}$, it proves desirable to consider the effect of steel bar. 3. The effect of the arc length of center circle/straight edge on lateral deflection and bending moment is remarkable in B.C-2. For larger open angle, the effect is also noted except for B.C-3 which turn out hardly affected. 4. The effect of the radius of curvature/straight side length on lateral deflection and x-directional bending moment is noted in B.C-2. As open angle increases, B.C-1 and B.C-3 almost agree and B.C-2 approaches B.C-4.

• 한국지반공학회논문집
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• 제36권11호
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• pp.149-156
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• 2020

약액 그라우팅은 지반의 강도 증진 및 차수 공법에 성공적으로 이용되어 왔으나, 그라우트의 유동은 지층의 투구계수 이방성에 크게 영향을 받는다. 따라서, 본 연구에서는 전산 유체 역학법을 이용하여 투수계수의 이방성이 수평 약액 그라우팅의 유효 반경에 미치는 영향을 알아보았다. 먼저 수평 방향 약액 주입 시뮬레이션을 위하여 공극 매질내 2상 점성 유체의 유동을 모델링하였고, 경화에 따른 확산과 점성 변화 또한 고려했다. 수치해석 결과, 투수계수의 이방성으로 인해 그라우트 구근의 형태가 타원체로 발달했고, 용해에 따른 확산 때문에 그라우트 구근의 모서리로 갈수록 공극내 그라우트 포화도가 점진적으로 감소했다. 이 결과를 바탕으로 10, 50, 90의 임계포화도를 설정하여 그에 따른 수평 방향 및 수직 방향 유효 반경을 산출하였다. 또한, 0.01 - 100의 수평·수직 방향 투수계수비에 따른 유효 반경을 산출하여 회귀식을 개발했다. 본 연구 결과는 투수계수 이방성을 가진 지층의 특성을 이용한 보다 효율적인 약액 그라우트 주입 전략 계획에 기여할 것으로 기대한다.

• 한국결정성장학회지
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• 제33권6호
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• pp.216-225
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• 2023

본 연구에서는 냉간 헤딩 공정에서 성형하중과 펀치 금형의 마모 감소를 통한 펀치 수명 증대를 위해 헤딩용 펀치 형상 최적설계를 수행하였다. 기존 생산에 사용되는 냉간 헤딩 펀치와 성형공정에 대한 유한요소해석 시뮬레이션을 통해 성형하중과 유동 특성 분석, 펀치금형에 집중되는 유효응력 및 마모량에 대하여 분석하였으며, 이를 통해 금형 마모와 밀접한 주요 설계인자를 확인하였다. 펀치금형의 최적설계 변수로서는 펀치 금형 포인트각(Point angle), 에지 반경값(Corner radius), 펀치소재재종(die material type), 마찰계수(friction coefficient) 등의 4가지 변수를 대상으로 4인자 3수준 인자 및 변수 수준을 설정하고, 성형해석 시뮬레이션과 다구찌법을 활용하여 설계인자별 영향도를 분석하여 최적의 최적설계 인자를 결정하였다. 본 연구를 통해 얻어진 최적설계변수를 적용하여 냉간 헤딩용 펀치 최적설계 시뮬레이션 결과, 각 펀치에 발생하는 최대유효응력은 최대 8.9 % 감소 효과를, 최대 펀치 마모 깊이는 37 % 감소 효과를, 성형하중은 평균 20% 수준 의 감소효과를 얻을 수 있었다. 현재, 소성 성형제품군이 적용되는 자동차, 건설 플랜트사에서 요구되는 고품질에 대응하면서도 적정 제조원가 절감을 위한 성형성 개선을 위한 성형공정개발 및 금형설계의 최적화가 지속적으로 필요하며, 향후 연구 결과를 현업에 적용하여 제품 성형성 개선 및 금형수명 증대 관리를 위한 기술자료로 활용하고자 한다.

• Coupled systems mechanics
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• 제13권3호
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• pp.201-217
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• 2024

This study aims to develop a new model to obtain the minimum area in circular isolated footings with eccentric column taking into account that the surface in contact with the ground works partially in compression, i.e., a part of the contact area of the footing is subject to compression and the other there is no pressure (pressure zero). The new model is formulated from a mathematical approach based on a minimum area, and it is developed by integration to obtain the axial load "P", moment around the X axis "M_x" and moment around the Y axis "M_y" in function of σ_max (available allowable soil pressure) R (radius of the circular footing), α (angle of inclination where the resultant moment appears), y₀ (distance from the center of the footing to the neutral axis measured on the axis where the resultant moment appears). The normal practice in structural engineering is to use the trial and error procedure to obtain the radius and area of the circular footing, and other engineers determine the radius and area of circular footing under biaxial bending supported on elastic soils, but considering a concentric column and the contact area with the ground works completely in compression. Three numerical problems are given to determine the lowest area for circular footings under biaxial bending. Example 1: Column concentric. Example 2: Column eccentric in the direction of the X axis to 1.50 m. Example 3: Column eccentric in the direction of the X axis to 1.50 m and in the direction of the Y axis to 1.50 m. The new model shows a great saving compared to the current model of 44.27% in Example 1, 50.90% in Example 2, 65.04% in Example 3. In this way, the new minimum area model for circular footings will be of great help to engineers when the column is located on the center or edge of the footing.

• Structural Engineering and Mechanics
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• 제7권5호
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• pp.513-525
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• 1999

This paper presents exact close form solutions of plastic limit loads of a clamped circular plate under uniformly distributed load with different loading radii. A unified yield criterion, which includes a family of piecewise linear yield criteria and the commonly adopted yield criteria such as the Tresca criterion and the maximum principal deviatoric stress criterion or the twin shear stress criterion that are its special cases, and the Mises criterion can be approximated by it, is employed in the analysis. The plastic limit loads, moment fields and velocity fields of the clamped circular plate are calculated based on the unified yield criterion. The influences of the yield criteria, the edge effects and the loading radius on the plastic limits of the clamped circular plate are investigated. Analytical results are calculated and compared. The exact close form solutions presented in this paper provide efficient approaches for obtaining plastic limit loads and the corresponding moments and velocities of the clamped circular plates. The previously derived solutions based on the Tresca and the Mises criteria are its special cases.

• 대한기계학회논문집A
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• 제21권9호
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• pp.1520-1530
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• 1997

Machining pressed compacts of ceramic and WC-Co materials can be the most cost effective way of forming the bodies prior to sintering when the required number of pieces is small. In this study, in order to clarify the machinability for turning, the $Si_3N_4$ and the WC-Co green compacts unsintered were machined under different cutting conditions with various tools. Absorbing chips by vacuum hose decreases tool wear. The tool wear becomes larger in the order of the ceramic, CBN and cemented carbide tools in machining the $Si_3N_4$ green compacts. In machining the WC-Co green compacts, the tool wear becomes larger in the order of the ceramic, cemented carbide and CBN tools. The land of cutting edge does not affect tool wear. When machining with cemented carbide tool, the tool wear i equal cutting length is nearly identical in spite of the increase of cutting spee, and the roughness of machined surface was the best in the cutting speed of 90 m/min. The tool wear decreases with the increase of rake angle and relief angle and with the decrease of nose radius. The machined surfaces become worse with the increase of feed rate and depth of cut, and with the decrease of rake angle and relief angle. The tool wear is not affected by the feed and depth of cut.