• KOREAN JOURNAL OF CROP SCIENCE
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• v.62 no.4
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• pp.361-366
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• 2017

This study was conducted to evaluate effects of seeding rate and depth during broadcast sowing on growth and yield of foxtail millet and proso millet over 2 years. The rate of sowing seeds was adjusted to 5, 7, 10 and 20 kg per ha on foxtail millet, and 5, 10, 15 and 30 kg per ha for proso millet. Sowing depth was 0.5, 1, 3, 5, 7, and 10 cm used tractor rotary attachment for shallow-tilling. The rate of seedlings standing when foxtail millet and proso millet were sowed to a depth of 0.5~5 cm was 72.0~78.0% and 73.0~80.5%, respectively. Plant height and weight at the three-leaf stage after emergence was highest for the treatment with 3 cm rotary depth. As the rate of broadcast seed sowing increased, plant length, diameter, seed length, and seeds on the panicle decreased. The grain yield of foxtail millet was highest with broadcast seed sowing of 10 kg per ha (3652, $3977kg\;ha^{-1}$) and proso millet was highest at broadcast seed sowing of 15 kg per ha (2226, $2052kg\;ha^{-1}$) in 2012 and 2013, respectively. Therefore, the optimum rate of sowed seeds under broadcast cultivation was $10kg\;ha^{-1}$ for foxtail millet and $15kg\;per\;ha^{-1}$ for proso millet. Optimum sowing depth for foxtail and proso millet under broadcast cultivation was 3 cm, using a rotary tractor attachment for shallow-tilling.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.3
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• pp.238-246
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• 2012

Once oil is spilled into marine environment, it experiences various weathering processes among which evaporation is the most dominant process in the initial stage of weathering. This study aimed to elucidate the effects of evaporation on the physicochemical properties of spilled oil using standardized laboratory experiments. Laboratory evaporation process was successfully reproduced using controlled rotary evaporation method. In case of Iranian Heavy crude (IHC), evaporation rate after 48 hours was $29.3{\pm}0.4%$ (n=40, p<0.001). Evaporation was simulated using ADIOS2 weathering model and the result was in agreement with laboratory experiment. Chemical composition changes of petroleum hydrocarbons including alkanes, polycyclic aromatic hydrocarbons (PAHs) and biomarkers by evaporation rate were also analyzed. As oil evaporated, low molecular weight alkanes and PAHs decreased, while biomakers showed conservative characteristics. Among biomarkers, $17{\alpha}(H)$, $21{\beta}(H)$-hopane was used for calculation of weathering rates, which matched with evaporative mass losses. Weathering rate calculation using hopane showed that stranded oils of weathering stage I (28.9%) and mesocosm oil weathering experiment till 5 days (26.5%) were mainly affected by evaporation process.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.3
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• pp.165-172
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• 1998

The electromechanical energy conversion conditioning and processing implementation in USM direct motion control system is generally divided into two power stages: the two-phase high-frequency ac power inversion stage for driving piezoelectric ceramic PZT transducer array off the USM stator and the mechanical thrust power conversion stage based on the frictional force between the piezo electric stator array and the rotary slider of the USM. However, the dynamic and steady-state mathematical modeling of the USM is extremely default from a theoretical point of view because it contains many complicated an nonlinear characteristics dependant on operation temperature. In +2$0^{\circ}C$~3$0^{\circ}C$, the operating characteristics of the USM has represented normal condition. But the other temperature, it has abnormal condition so that driving frequency, current and motor speed will be down. The recent USM has controller without temperature compensation. This study represents the fuzzy controller for speed compensation according to operating temperature by driving frequency.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.1953-1958
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• 2007

This paper presents the results of a series of performance tests for the integral Stirling cryocooler. Infrared sensor systems incorporating cryocoolers are required to be qualified to the appropriate environmental specification. Integral Stirling cryocooler for thermal imaging system have matured to the stage of undergoing formal qualification test program. The thermal environmental test of the Stirling cryocooler is presented in this paper. We performed that low and high temperature keeping test from $-40^{\circ}C$ to $+71^{\circ}C$ and operating test at high and low temperature cyclic range with acceptance tests performed at scheduled intervals. Cooldown time to 80K and steady state input power at 80K were determined as a function of cooler components temperatures at the compressor, hot end and cold tip. Tests performed on this cooler have been successful with a measured cooldown time to 80K of less than 5 minutes 24seconds for $71^{\circ}C$ ambient temperature with input power of 11W

• Proceedings of the KIEE Conference
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• 2001.11a
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• pp.65-68
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• 2001

본 연구에서는 코움 드라이브에 비해 구동력은 크고 평행 판 구동 방식에 비해서는 선형 특성이 우수하며 안정된 구동거리가 증가하는 특성을 갖는 새로운 정전력(electrostatic force) 구동 방식을 제안한다. 운동 전극과 고정 전극을 기울어지게 배치하여 전극 면에 평행한 정전력 $F_x$와 전극 면에 수직인 정전력 $F_y$의 합력 $F_e$ 방향으로 전극을 운동시킴으로써 정전력의 방향과 전극의 운동 방향을 일치시킨다. 제안된 구동방식의 정전력 모델을 이용한 해석 결과 코움 드라이브에 비해서는 구동력이 50 % 이상 크며 평행 판 구동에 비해서는 안정된 구동 거리가 10 - 30 % 이상 증가하는 구동 특성을 얻을 수 있었다. 제안된 구동방식을 이용하여 HDD의 트랙 방향 저장 밀도를 증가시키기 위한 듀얼스테이지 서보(dual-stage servo)에 사용 될 마이크로 액츄에이터 (microactuator)를 설계하고 SoG(Silicon on Glass) 공정을 이용하여 제작하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.5
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• pp.9-17
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• 2005

In the early stage of helicopter design, an optimal configuration is usually determined after a numerous parametric study about the aerodynamic performance due to geometric variation. In order to improve the aerodynamic performance of a shrouded tail rotor, optimization of the tip clearance gap between blade and shroud, the blade planform shape, and the arrangement of blade spacing is required. In the present study, the aerodynamic performance characteristics of a shrouded tail rotor due to geometric variation was investigated by using an inviscid compressible unstructured mesh flow solver for rotary wings.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.1
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• pp.73-79
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• 2011

A portion of oil for lubrication of compressor flows together with refrigerant in the refrigeration system. If the oil discharge from a compressor is increased in the refrigeration system, not only pressure drop is increased in other components, such as evaporator and gas cooler, but also heat transfer coefficient in the heat exchangers is decreased. Oil discharge rate from a compressor may strongly depend on operating conditions of a compressor. In this study, one stage single rotary compressor is employed for measuring oil circulation ratio(OCR). Carbon dioxide and PAG oil are used as refrigerant and lubricant. Using a U-tube densimeter, mixture density is measured. Oil circulation ratio(OCR) can be estimated by measured mixture density. The results obtained indicate that the oil circulation ratio(OCR) is increased as the suction temperature or compressor operating frequency is increased. Oil circulation ratio(OCR) correlation of the compressor is also suggested.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.3
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• pp.93-101
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• 2018

FDM is one of the popular 3D printing technologies because of an inexpensive extrusion machine and multi-material printing. FDM can use thermoplastics such as ABS and PLA. The 3D-printed ABS parts fabricated by FDM are attractive in the automotive industry because of their weight. A 10% reduction in weight can increase the fuel economy by approximately 7%. To use 3D-printed ABS parts as automotive parts, we should evaluate the 3D-printed parts in terms of automotive reliability. In this study, 3D-printed ABS samples were evaluated using Ono's rotary bending fatigue test. We obtained an S-N curve for the 3D-printed ABS specimen from the finite-element analysis. The S-N curve can be useful in early-stage design decisions for 3D-printed ABS parts.

• Tribology and Lubricants
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• v.24 no.1
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• pp.1-6
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• 2008

An experimental study was conducted to evaluate the viscosity characteristics of multi-grade engine oils in which contain diesel fuels. Unused engine oils of SAE 5W40, 10W40 and 15W40 were blended with a diesel fuel ratio of 5%, 10%, and 15%. The viscosity of a diluted engine oil was measured with temperature variation ranging from $-20^{\circ}C$ to $120^{\circ}C$ using a rotary viscometer. The diluted engine oil in which is blended to a diesel fuel plays an important role for decreasing an engine oil viscosity, which may decrease the oil film thickness and a load-carrying capacity. Test results show that the viscosity tends to fall for the increased temperature when engine oil is mixed with a diesel fuel. Especially, the viscosity at a low temperature zone is radically decreased compared with a high temperature zone. Based on the experimental results, the empirical equation that can predict the viscosity of diluted engine oil is expressed in the exponential function with the variation of the temperature and a fuel ratio of diluted engine oil. This equation may be possible to predict the limitation of the oil-fuel dilution rate at the concept design stage of the CDPF system, which doesn't affect the influence of the tribological components.

• Journal of Power System Engineering
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• v.11 no.1
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• pp.98-106
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• 2007

This paper presents a statistical prediction procedure for the propeller racing of ships with twin screw propellers sailing in ocean waves. The propeller racing is one of the most important factors of seakeeping qualities in relation to the safety of main engine and shafting system. It is especially significant key word for designing the twin-screw-propeller-type ship in view of allowable maximum propeller diameter etc.. In former studies, the propeller racing generally means the situation (propeller exposed) in which the relative motion amplitude between ship hull and wave surface would exceed a depth of point in rotary disk propeller. Therefore, it seems that the magnitude of the amplitude and its exceeding frequency have been examined as a principal subject of study as usual. However, the time during which the amplitude exceeds a depth of point must be also one of most important factor affecting the trend of propeller racing. This paper proposes a simply practical method for estimating the time lasting of exposed propeller related to twin screw propeller racing in rough confused seas on the basis of the statistics. Then, it is confirmed that the practical method is useful and convenience for considering the propeller racing in the stage of the basic design.