• 소성∙가공
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• 제11권7호
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• pp.620-627
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• 2002

The purpose of this paper is the development of an automated measurement system for micro spring based on the digital image processing technique. This micro spring can be used in various engineering applications such as filament, load bearing springs, hard disk suspension and many others. Main functionality of the micro spring inspection system is to measure the representative pitch of the micro spring. The derivative operators are used for edge detection in gray level image. Measurement system developed in this paper consisted of new auto feeding mechanism to take advantage of air pressure. In the process of development of the micro spring inspection system based on the image processing and analysis, strong background technology and know-how have been accumulated to measure micro mechanical parts.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 추계학술대회 논문집(II)
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• pp.807-819
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• 2002

The air spring is used in secondary suspension system for railway vehicle to reduce and absorb the vibration and noise. In this paper, the characteristics and durability test was conducted in laboratory by using servo hydraulic fatigue testing system to evaluate the reliability. And to guarantee the adaptation of this air spring, the ride comfort and air pressure variation were measured in train test. The experimental results show that the characteristics and durability of domestic development productions are obtained the good results and the stiffness of the air spring which had become 6 year over increased. Also, the dynamic characteristics of domestic and existing product agree well the results obtained.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1470-1474
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• 2004

'Nanofluids' means suspension of common fluids with particles of the order of nanometers in size. The present research is an experimental study of critical heat flux (CHF) behavior in pool boiling of $water-TiO_2$ nanofluids under atmospheric pressure. CHF for pure water and $water-TiO_2$ nanofluids were respectively measured using disk-type copper block heater with 10mm diameter, and CHF of water with surfactant was also measured to consider the effect of surfactant used to disperse nanoparticle. The results show a large increase in CHF for $water-TiO_2$ nanofluids compared to pure water. After CHF occurred, heat flux in pool boiling for $water-TiO_2$ nanofluids was maintained in considerable value, but not for pure water.

• 제어로봇시스템학회논문지
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• 제8권2호
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• pp.158-166
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• 2002

A mathematical model and dynamic characteristics ova continuously variable damper for semi-active suspen- sion systems are investigated. After analyzing the geometry of a typical continuously variable damper, mathematical models fur individual components including piston, orifices, spring, and valves are first derived and then the flow equations for extension and compression strokes are investigated. To verify the developed mathematical model, the dynamic response of the model are simulated using MATLAB/SIMULINK and are compared with experimental results. The proposed model can be used not only for mechanical components design but also for control system design.

• Journal of Plant Biology
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• 제37권1호
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• pp.27-36
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• 1994

For establishing a transformation system of rice, an efficient introduction of foreign genes into embryogenic cell suspension by particle bombardment was conducted. The particle inflow gun based on the acceleration of DNA-coated tungsten particles using pressurized helium was constructed for delivery of DNA into rice cells. Several bombardment parameters were optimized using the transient expression of GUS gene. The conditions that gave the highest GUS gene expression of about 1000 blue spots per g fresh weight of bombarded cells include treatment of the cells with 0.5 M osmotic pressure, and use of the 410 kPa helium, 110 mm target distance, 13 mm syringe filter holder and 5 $\mu$L DNA/tungsten mixtures. It was also confirmed that rice actin promoter-intron construct gave the highest expression of all promoter-sequences studied. Eight weeks after the bombardment, stably transformed calluses were obtained on the selection medium containing 100 mg/L G418 and showed the strong activity in in situ GUS assay.

• International Journal of Automotive Technology
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• 제6권5호
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• pp.483-489
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• 2005

Based on a two-degree of freedom vehicle model, this paper investigates ride comfort for a heavy off-road vehicle mounted a nonlinear hydropneumatic spring, which is influenced by nonlinear stiffness and damping characteristics of the hydropneumatic spring. Especially, the damping force is derived by applying H. Blasius formula in modeling process according to the real physical structure of the hydropneumatic spring, and the established model of nonlinear stiffness characteristics have been validated by experiments. Furthermore, the effects of parameter variations of the hydropneumatic spring, such as initial charge pressure and damping coefficient, on body acceleration, suspension deflection and dynamic tire deflection are also investigated.

• 대한기계학회논문집B
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• 제35권3호
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• pp.293-299
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• 2011

본 연구에서는 다양한 형상의 나노입자를 분산시킨 알루미나 나노유체의 유동 특성을 실험적으로 조사하기 위하여 나노입자의 형상 변화에 따른 알루미나 나노유체의 압력강하를 층류영역에서 측정하였다. 이를 위해 Sphere, Rod, Platelet, 그리고 Brick 의 형태를 갖는 알루미나 나노입자를 물에 분산시켜 부피비 0.3%를 갖도록 Two-step 방법으로 제작하였다. 제작된 나노유체의 분산성을 파악하기 위하여 제타포텐셜을 조사하였으며, 나노입자의 형상을 파악하기 위하여 TEM 사진을 측정하였다. 다양한 형상의 나노입자를 분산시켜 0.3%의 부피비를 갖는 나노유체의 압력강하를 측정하였을 때, 입자 형상이 나노유체의 유동특성에 영향을 미치는 것을 확인하였다. 실험 결과를 바탕으로 나노입자의 단위질량당 표면적과 분산된 나노입자의 크기를 이용하여 나노유체의 압력강하 특성을 설명하였다.

• Nuclear Engineering and Technology
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• 제44권4호
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• pp.429-436
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• 2012

Critical heat flux (CHF) is the thermal limit of a phenomenon in which a phase change occurs during heating (such as bubbles forming on a metal surface used to heat water), which suddenly decreases the heat transfer efficiency, thus causing localized overheating of the heating surface. The enhancement of CHF can increase the safety margins and allow operation at higher heat fluxes; thus, it can increase the economy. A very interesting characteristic of nanofluids is their ability to significantly enhance the CHF. Nanofluids are nanotechnology-based colloidal dispersions engineered through the stable suspension of nanoparticles. All experiments were performed in round tubes with an inner diameter of 0.01041 m and a length of 0.5 m under low pressure and low flow (LPLF) conditions at a fixed inlet temperature using water, 0.01 vol.% $Al_2O_3$/water nanofluid, and SiC/water nanofluid. It was found that the CHF of the nanofluids was enhanced and the CHF of the SiC/water nanofluid was more enhanced than that of the $Al_2O_3$/water nanofluid.

• 자원리싸이클링
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• 제5권3호
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• pp.56-64
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• 1996

탄산칼슘의 다형 제어를 목적으로 합성 음료, 의약품 등으로서도 폭넓게 이용되고 있는 ${C_2}{H_4}{OH}$계에서 수산화칼슘을 현탁시키고 감미제, 의약품 등의 용도로서도 이용되고 있는 에틸렌글리콜을 첨가하면서 탄산칼슘 생성 및 탄산칼슘 다형결정화 특성에 대해 연구하였다. 세라믹 bubble plate를 부착 제작한 반응기를 사용하여 $CO_2$gas와 반응 진행시 전기전도도의 연속 측정을 통해 변화시점에서 일부 현탁액을 분리 분말화하여 X선 회절 및 전자현미경을 통해 중가 생성물과 이들이 각각 Vaterite, Aragonite, Calcite로 전이됨을 확인하였다. ${C_2}{H_4}{OH}$에 대한 에틸렌글리콜 첨가를 10 vol%로 하여 500ml의 반응 현탁액에 10~50g의 수산화칼슘 첨가 변화에 따른 생성물을 조사하였다. 결정화단계에서 수산화칼슘 10g 첨가시를 제외하고는 모든 조건에서 겔화(gelation)가 일어나며 그 생성 유지시간은 수산화칼슘 양이 많아질수록 짧아짐을 관찰할 수 있었다. 상온 상압하에서 생성되기 어려웠던 Vaterite가 $Ca(OH)_2$의 30g 첨가반응계에서 구형으로 생성됨을 확인할 수 있었다. 이는 칼슘계, 흡착제 등의 가능성을 부여한 복합재료로서의 Vaterite 합성을 상온 상압화에서${C_2}{H_4}{OH}$ 계에서 다형제어 할 수 있음을 보여주었다. 탄산칼슘의 동질이상중 Vaterite는 준안정상이고 분말화 과정에서 이미 Calcite로 전이되기 쉬우나 G5 glass filter와 vacuum drier를 사용하여 안정적인 구형의 Vaterite을 확인할 수 있었다.

• The Plant Pathology Journal
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• 제36권4호
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• pp.335-345
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• 2020

Tomato grey mould has been one of the destructive fungal diseases during tomato production. Ten mM of menadione sodium bisulfite (MSB) was applied to tomato plants for eco-friendly control of the grey mould. MSB-reduced tomato grey mould in the 3rd true leaves was prolonged at least 7 days prior to the fungal inoculation of two inoculum densities (2 × 10⁴ and 2 × 10⁵ conidia/ml) of Botrytis cinerea. Protection efficacy was significantly higher in the leaves inoculated with the lower disease pressure of conidial suspension compared to the higher one. MSB-pretreatment was not effective to arrest oxalic acid-triggered necrosis on tomato leaves. Plant cell death and hydrogen peroxide accumulation were restricted in necrotic lesions of the B. cinereainoculated leaves by the MSB-pretreatment. Decreased conidia number and germ-tube elongation of B. cinerea were found at 10 h, and mycelial growth was also impeded at 24 h on the MSB-pretreated leaves. MSB-mediated disease suppressions were found in cotyledons and different positions (1st to 5th) of true leaves inoculated with the lower conidial suspension, but only 1st to 3rd true leaves showed decreases in lesion sizes by the higher inoculum density. Increasing MSB-pretreatment times more efficiently decreased the lesion size by the higher disease pressure. MSB led to inducible expressions of defence-related genes SlPR1a, SlPR1b, SlPIN2, SlACO1, SlChi3, and SlChi9 in tomato leaves prior to B. cinerea infection. These results suggest that MSB pretreatment can be a promising alternative to chemical fungicides for environment-friendly management of tomato grey mould.