• Journal of Biosystems Engineering
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• 제9권2호
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• pp.37-47
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• 1984

Using the soil bin systems, this study was carried out to analyze the effects of the angular and tilling speed of the rotary shaft with the edge curves which were $30^{\circ}$ and $40^{\circ}$, and the edged blade which were single and double, on the torque requirement of rotary tillage. In the analyses, we developed the mathematical models for the torque requirments of rotary tillage, and analyzed the optimum conditions of each variable for the minimum tillage torque requriements. The results of the study were summarized as follows. 1. The required tilling torque by one rotary blade has the minimum value when the tilling speed of the rotary blade was low, and the revolution of the rotary blade was fast, in general. 2. The torque requirements of single edged blade was decreased to about 81% in comparing with that of double edged blade of which the edge curved angle was $40^{\circ}$ and the tilling speed was 29.40 cm/sec. But, for the mean values, the maximum torque requirements were decreased to 45%, and the mean torque requirements were decreased to 35%. 3. For the edge curved angle, the torque requirements of ${\theta}=40^{\circ}$ were 48% more than that of ${\theta}=30^{\circ}$ in the maximum tilling torque in case that the rotary blade were double edged blade. but, there was not a difference when the rotary blades were single edged blade. The mean tilling torques of ${\theta}=40^{\circ}$ were 6% more when the rotary blade was double edged blade, and were 11% less at single edged blade, than that of ${\theta}=30^{\circ}$. 4. In order to reduce the torque requirements for tilling, the optimum revolutions of the rotary shaft were analyzed as that 204-240 rpm for the double edged blade and 280-320 rpm for the single edged blade.

• 한국산업정보학회논문지
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• 제25권5호
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• pp.49-57
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• 2020

기존의 전기 모터는 큰 중량과 부피의 단점으로 항공기 적용에 적합하지 않다. 고온 초전도 (High-Temperature Superconducting: HTS) 모터는 전류 밀도와 자기장 밀도가 높으며 손실이 적어 일반 전기모터와 비교하여 크기와 무게를 크게 줄일 수 있다. 본 논문은 미래 항공기 전기 추진용 HTS 모터의 개념 설계 및 해석 결과를 제시한다. 회전속도가 7,200 RPM인 2.5 MW 용량의 HTS 모터를 설계하고 무게 대비 출력 비(kW/kg)를 분석하였다. HTS 모터 계자코일 (Field Coil)의 운전온도는 LH₂ (Liquid Hydrogen) 냉각을 고려하여 20K을 선정하였다. 고정자 권선 (Stator Winding)은 다상 구성 (Multi-Phase Configuration)으로 연결하였고 와전류 (Eddy Current) 손실을 최소화하기 위해 Litz 선을 사용하였다. 결과적으로 모터의 무게 대비 출력 비는 약 18.67 kW/kg으로 기존 모터보다 훨씬 높음을 확인하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 추계학술대회 논문집
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• pp.242-243
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• 2009

배기토출음은 공회전시 발생하는 소음에 큰 영향을 끼친다. 연비를 높이기 위하여 공회전시 RPM을 낮추면 엔진 점화 주파수가 낮아지며, 이 경우 배기계 위치에 따른 음향학적 공명 주파수와 일치하면 배기 토출음의 크기가 증가한다. 따라서 본 연구에서는 공회전시 배기토출음을 줄이기 위해 소음기의 위치와 각 배기관들의 길이를 최적화하였다. 최적화 결과로써 3 가지 배기계 위치를 얻을 수 있었고, 실제 실험과의 비교를 통하여 최적화된 배기계 위치가 그렇지 않은 배기계 위치에 비하여 소음 저감량이 높은 것을 확인하였다.

• Journal of Pharmaceutical Investigation
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• 제26권2호
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• pp.125-135
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• 1996

Solid lipid nanoparticles(SLN) are particulate systems for parenteral drug administration and suitable for controlled release. SLN were prepared by homogenization process. Dispersion at increased temperature (molten lipid) was performed to yield SLN loaded with lipophilic drugs. Tetracaine base, lidocaine base, prednisolone, methyltestosterone and ethinylestradiol were used as model drugs to access the loading capacity and to study the release behavior. To investigate production parameters(lipids, surfactant concentration, homogenizing rpm) in the formation of SLN, particle size was performed by laser diffraction analysis. The mean particle size of SLN with stearic acid or trilaurin was below 1 micron. By decreasing the particle size and increasing the surfactant concentration, the release rate was increased especially in the case of highly lipophilic drug loaded SLN. Methyltestosterone or ethinylestradiol loaded SLN showed a distinctly prolonged release over a few days.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.757-763
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• 2000

In vehicle exhaust systems the sound attenuation and the reduction of flow losses are often two competing demands. The present study considers a fully vehicle exhaust system and investigates experimentally both the sound attenuation and the flow performance of production configurations including the catalyst, the resonator, and the muffler. Dynamometer experiments have been This study is on the development of a new muffler composed of a valve system using an elasticity of spring. The valve system conducted with the daewoo 1500cc Lanos engine with speeds ranging from 1000 to 5000 rpm. Measurements include the flow rates, the temperatures and the absolute dynamic pressures of the hot exhaust gases at point locations. The present study describes the experimental aspects of an ongoing effort to validate and use the nonlinear fluid dynamic models in the time-domain for the prediction of the acoustic and power performance of firing internal combustion engines with full production exhaust systems.

• 한국산업정보학회논문지
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• 제6권1호
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• pp.70-76
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• 2001

NdFeB로 만들어진 permanent magnet dc driver는 많은 분야에서 사용된다. 그중 소형 disk type servo driver는 컴퓨터의 hard disk driver나 floppy driver등과 같은 소형기기의 구동용으로 사용된다. 기존의 dc drive는 coil를 감아 winding으로 사용한다. 만들어진 driver에는 coper printed multilayer winding을 사용하였다. 이 논문에서는 thin film multilayer winding의 제조방법, 특성에 관하여 논한다. 또한 dc driver의 commutation를 위해 사용되는 hallsensor 대신에 비 선형 특성의 MR sensor를 선형화시켜 driver의 commutation에 사용하였으며 이렇게 만들어진 소형 driver의 rpm, torque등의 특성을 연구하였다.

• Smart Structures and Systems
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• 제2권1호
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• pp.47-60
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• 2006

Bi-spectrum is a tool in the signal processing for identification of non-linear dynamic behvaiour in systems, and well-known for stationary system where components are non-linearly interacting. Breathing of a crack during shaft rotation is also exhibits a non-linear behaviour. The crack is known to generate 2X (twice the machine RPM) and higher harmonics in addition to 1X component in the shaft response during its rotation. Misaligned shaft also shows similar such feature as a crack in a shaft. The bi-spectrum method has now been applied on a small rotating rig to observe its features. The bi-spectrum results are found to be encouraging to distinguish these faults based on few experiments conducted on a small rig. The results are presented here.

• 정보저장시스템학회논문집
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• 제2권2호
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• pp.144-149
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• 2006

Dynamic L/UL(Load/Unload) system has many merits. but it may happen an undesirable collision during the dynamic loading process. In this paper, the dynamics of negative pressure pico-slider was investigated through numerical simulation during the loading process. A simplified L/UL model for the suspension system has been presented and a simulation code has been developed to analyze the motion of the slider. A slider design has been simulated at various disk rotating speeds, skew angles of slider. We can decrease the possibility of collision and smoothen the loading process for a given slider-suspension design by selection an optimal rpm and pre-skew angle.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.85.6-85
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• 2001

This paper describes a 3-DOF attitude control of a small model helicopter in hover through explicit decoupling and adaptive control scheme. A model helicopter mounted on gimbal-stand is considered as a system that has 3 independent SISO systems representing motions about roll, pitch and yaw axis and these subsystems are identified from the test flight data. In this consideration, the contribution of others to yaw channel is neglected since it is relatively small. Two PID controllers based on Ziegler-Nichols method are designed for roll pitch channels independently. Also, adaptive fuzzy tuner is designed and applied to those PID controllers to cope with coupling effects between each channel and system uncertainties due to variation of engine RPM. The experimental results show that the attitude control ...

• Journal of Microbiology and Biotechnology
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• 제27권8호
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• pp.1428-1440
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• 2017

Phomopsis sp. XP-8 (an endophytic fungus) was previously found to produce pinoresinol diglucoside (PDG), a major antihypertensive compound of Tu-Chung (the bark of Eucommia ulmoides Oliv.), which is widely used in Chinese traditional medicines. In the present study, two bioconversion systems were developed for the production of PDG in Tris-HCl buffer containing glucose and Phomopsis sp. XP-8 cells (both resting and freeze-dried). When other factors remained unchanged, the bioconversion time, glucose concentration, cell ages, cell dosage, pH, temperature, and stirring speed influenced PDG production in a similar and decreasing manner after an initial increase with increasing levels for each factor. Considering the simultaneous change of various factors, the optimal conditions for PDG production were established as 70 g/l cells (8-day-old), 14 g/l glucose, $28^{\circ}C$, pH 7.5, and 180 rpm for systems employing resting cells, and 3.87 g/l cells, 14.67 g/l glucose, $28^{\circ}C$, pH 7.5, and 180 rpm for systems employing freeze-dried cells. The systems employing freeze-dried cells showed lower peak PDG production ($110.28{\mu}g/l$), but at a much shorter time (12.65 h) compared with resting cells (23.62 mg/l, 91.5 h). The specific PDG production levels were 1.92 and $24{\mu}g$ per gram cells per gram glucose for freeze-dried cells and resting cells, respectively. Both systems indicated a new and potentially efficient way to produce PDG independent of microbial cell growth.