• 소성∙가공
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• 제13권1호
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• pp.15-20
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• 2004

본 연구에서는 자동차용 판재 성형시 발생하는 스프링백을 정확히 예측하기 위하여, 수정된Chaboche형에 기초한 혼합형 등방-이동경화규칙이 개발되었다. 또한 판재의 이방성을 위하여 최근 개발된 Barlat의 YId2000-24 비이차 비이방성 항복 함수가 이용되었다. 단순인장실험과 인장/압축(압축/인장) 실험에 의하여 Bauschinger 및 transient 거동과 비이방성이 측정되었으며, 유한요소해석에 의한 구성방정식의 검증을 위해 실제 자동차 부품을 부분 변형시킨 double S-rail이 제작되었다. 수정된 Chaboche 형 조성방정식과 비등방 항복함수를 적용한 유한요소에 의한 수치해석의 결과는 굽힘에 의한 스프링백과 비틀림에 있어서 실험과 잘 일치함을 알 수 있었다.

• 한국구조물진단유지관리공학회 논문집
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• 제6권1호
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• pp.213-221
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• 2002

This paper presents the experimental result of Reinforced Concrete column-steel beam joint connected by Band Plates(BP). Main parameters in the test are the shape of BP and thickness of plate. Ten interior and exterior RC column-steel beam joint specimens are designed. Cyclic loads are applied to the beam end of eight specimens (four interior specimens and four exterior specimens). To evaluate the cyclic effect, monotonic loads are acted for two specimens. All specimen showed similar failure pattern such as the plate of BP get torn after the large deformation. Even though the specimen with double cross type BP has lower strength than the specimen with single cross type BP, the energy dissipation capacity of the specimen turned out high. Thus, provided the strength of joint with double cross type to be designed to have suitable strength by increasing the thickness of plate, the joint system may show higher seismic capacity.

• 현장농수산연구지
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• 제25권4호
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• pp.90-102
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• 2024

Haploid/double haploid plants developed from isolated microspores can significantly accelerate plant breeding. Haploid plants can naturally double their chromosomes to create a pure homozygous line of diploid plants. We present a method for producing embryos from isolated microspores of hot peppers (Capsicum annuumL.). We analyzed the polyploidization levels of the regenerated plants. The donor plants produced the optimal stage of microspores following short-term growth under low-intensity light, which resulted in high rates of embryogenesis and cotyledonary embryogenesis. To find an efficient culture method, liquid, doubled-layer, and 2-step cultures were tested. Liquid culture yielded the highest number of embryos, whereas the highest efficiency for cotyledonary embryogenesis was afforded by the doubled-layer culture. When normal cotyledonary embryos were transplanted onto a regeneration medium, they developed into complete plants. From these, 208 plants were tested via flow cytometric analysis, and 35.6% and 72.7% of the chromosomes from the Milyang-jare and LV2319 genotypes, respectively, were found to be spontaneous double haploids. These results are the same as those obtained on analyzing horticultural characteristics, including the size of leaves and the size and shape of fruits. The present study provides information on the practical application of isolated microspore culture of hot peppers, factors that affect embryogenesis, and methods for polyploidy testing.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.149-153
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• 2008

Since magnesium alloy sheets have been employed in industrial field which requires the light weight and thin engineering components, most of researches have been focused on the formability of magnesium ahoy sheet. In warm press forming of magnesium alloy sheet, it is important to control the sheet temperature by heating the sheet in closed die. When forming a commercial AZ31 magnesium alloy sheets which are 0.5mm and 1.0mm thick, respectively, time arriving at target temperature and temperature variation in magnesium alloy sheet have been investigated. Sheet metals were mostly formed in simple shapes such as circular or rectangular. Few studies about forming of complex shapes were reported. Thus, the formability of magnesium alloy sheet for complex shapes is investigated. The process variable for a double sink shape deep drawing with circular and rectangular shape was investigated by varying temperature, velocities, and clearances. Accordingly, temperature, velocities, and clearances suitable for forming were suggested through investigating the thickness variation of the product.

• 한국육종학회지
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• 제42권5호
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• pp.431-438
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• 2010

Anthers of sweet pepper $F_1$ cultivar 'Special' were cultured on Dumas De Vaulx (C medium), supplemented with $0.1mgL^{-1}$ 2, 4-D and $0.1mg{\cdot}L^{-1}$ kinetin with 3% sucrose, and 0.32% phytagel. The calluses obtained were further sub-cultured on Murashige and Skoog (MS) medium without growth regulators for regeneration. Regenerated plantlets were grown in plastic pots under plastic house and characterized their cytological and morphological characters in spring, 2008. Twenty percent plantlets were identified as haploid plants after chromosome and ploidy analysis. Haploid plants contained 12 chromosomes, high stomatal density with small stomatal length as compared to diploid plants. Stomatal length in haploids was 23.3% smaller than diploids. Haploid plants were characterized as small leaf and petiole size, poor vigor, thin stem and short plant height, short internodes and small flower buds, fruit size and fruit weight as compared to diploid plants and most of the haploid fruits were seedless. SP55, SP62, SP68, SP72 and SP77 are found high yielding double haploids with high total soluble content (8.6, 8.7, 9.2, 9.1 and $9.8^{\circ}Brix$, respectively) and desirable fruit shape, and recommended them to exploit as inbred lines for heterosis breeding.

• 대한기계학회논문집B
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• 제27권1호
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• pp.105-116
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• 2003

The flow structure around the free end of a finite circular cylinder (FC) embedded in an atmospheric boundary layer (ABL) over open terrain was investigated experimentally with varying the free end shape. The experiments were carried out in a closed-return type subsonic wind tunnel. A finite cylinder with an aspect ratio (L/D) of 6 was mounted vertically on a long flat plate. The Reynolds number based on the cylinder diameter is about Re=7,500. The velocity fields near the FC free end were measured using the single-frame double-exposure PIV method. As a result, for the FC with a right-angled free end, there is a peculiar vortical structure, showing counter-rotating twin vortices near the FC free end. It is caused by the interaction between the entrained irrotational fluids from both sides of FC and the downwash flow from the FC free-end.

• 대한기계학회논문집A
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• 제34권8호
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• pp.1129-1136
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• 2010

체결클러치에 부착된 댐퍼스프링은 유체커플링에서 직결로 변환될 때 발생하는 엔진 토크의 진동을 흡수하는 역할을 한다. 본 연구에서는 체결클러치의 성능을 좌우하는 압축스프링 및 지지 판 구조물의 최적설계를 통해서 새로운 설계형상을 제안하였다. 체결클러치와 연결된 엔진, 변속기, 구동축 및 휠, 차체질량 등 주요 부품들을 다 포함하는 다물체 동역학모델을 구성하여 공진 회피에 필요한 스프링상수를 계산하였다. 또한 어닐링 모사법에 의한 스프링 최적설계코드를 개발한 후 스프링상수, 최대충격토크, 수축각도, 스프링개수, 피로강도 등을 입력하여 압축 스프링의 사양을 최적화하였다. 이들 스프링을 지지하는 3 가지의 판에 대해서 컴플라이언스를 최소화하고 체적비를 0.3 이하로 하는 위상최적화를 수행하여 새로운 형상을 제안하였다.

• 대한토목학회논문집
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• 제6권1호
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• pp.87-94
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• 1986

일반적으로 자연하천은 수심에 비해 하폭이 크고 완만한 곡률을 나타내므로 2차원 수치모형이 실용적인 것으로 알려져 있다. 본 연구에서는 만곡수로의 흐름특성을 분석하기 위하여 2차원 부정류의 운동방정식과 연속방정식을 차분화하고 Double Sweep 알고리즘에 의한 수치해석모형을 개발하였다. 본 모형의 적용성을 입증하기 위해 L.F.M 실험수로 및 I.I.H.R 실험수로의 실측치와 비교하여 비교적 잘 일치함을 확인할 수 있었다. 벽면마찰의 영향을 감소시키기 위하여 Chezy 계수의 적절한 조정으로 실측치에 더욱 접근된 결과치를 얻을 수 있었으며, 이류항의 영향을 분석하였다. 만곡수로내의 수면형태, 최대유속선이 이동경로 및 깊이방향 평균유속의 크기와 방향을 계산할 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 춘계학술대회 논문집
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• pp.33-36
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• 1998

This paper is a study on a linear ultrasonic motor with a first longitudinal$(L_1)$ and fourth bending $(B_4)$ double-mode rectangular plate. The stator vibrator is composed of an elastic material plate and of a piezo-ceramic element having a motion by electrical excitation. Each strain vector differs by $90^{\circ}$ generate travelling wave with the elliptical displacement motion of a point on the surface. To magnify displacement of longitudinal direction in elliptical displacement motion, the motor has a mechanism of the.displacement enlargement. In this paper, the vibration shape of the stator is simulated using the finite element method. A detailed model considered of the piezoelectric effect and of the exact geometry of the stator is used to calculate the displacement. The position of displacement mechanism is decided by the maximum displacement.

• Tribology and Lubricants
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• 제32권2호
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• pp.50-55
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• 2016

Recently, a double-side machining process has been adopted in fabricating a sapphire glass to enhance the manufacturability. Double-side lap grinding (DLG) is one of the emerging processes that can reduce process steps in the fabrication of sapphire glasses. The DLG process uses two-body abrasion with fixed abrasives including pallet. This process is designed to have a low pressure and high rotational speed in order to obtain the required material removal rate. Thus, the temperature is distributed on the DLG platen during the process. This distribution affects the shape of the substrate after the DLG process. The coolant that is supplied into the cooling channel carved in the base platen can help to control the temperature distribution of the DLG platen. This paper presents the results of computational fluid dynamics with regard to the heat transfer in a DLG platen, which can be used for fabricating a sapphire glass. The simulation conditions were 200 rpm of rotational speed, 50℃ of frictional temperature on the pallet, and 20℃ of coolant temperature. The five cases of the coolant flow rate (20~36 l/min) were simulated with a tetrahedral mesh and prism mesh. The simulation results show that the capacity of the generated cooling system can be used for newly developed DLG machines. Moreover, the simulation results may provide a process parameter influencing the uniformity of the sapphire glass in the DLG process.