• 한국연소학회지
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• 제14권3호
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• pp.37-44
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• 2009

An experimental study was conducted to reduce NOx emission in RT(radiant tube)burner by using oscillating combustion processes in RIST. A solenoid valve gives the various oscillating conditions, such as oscillation frequency, duty ratio of fuel flow. In this study, we used commercial software, CFD-ACE+ to predict combustion and NOx emission characteristics for various experimental oscillation conditions. The effect of oscillation frequency and duty ratio on NOx emission will be discussed in terms of flow field, temperature and equivalence ratio distributions in detail.

• 생태와환경
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• 제52권2호
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• pp.171-177
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• 2019

Smart farm is a breakthrough technology that can maximize crop productivity and economy through efficient utilization of space regardless of external environmental factors. This study was conducted to investigate the optimal growth and physiological conditions of Chinese matrimony vine (Lycium chinense) with LED light sources in a smart farm. The light source was composed of red+blue and red+blue+white mixed light using a LED system. In the red+blue mixed light, red and blue colored LEDs were mixed at ratios of 1:1, 2:1, 5:1, and 10:1, with duty ratios varied to 100%, 99%, and 97%. The experimental results showed that the photosynthetic rate according to the types of light sources did not show statistically significant differences. Meanwhile, the photosynthetic rate according to the mixed ratio of the red and the blue light was highest with the red light and blue LED ratio of 1:1 while the water use efficiency was highest with the red and blue LED ratio of 2:1. The photosynthetic rate according to duty ratio was highest with the duty ratio of 99% under the mixed light condition of red+blue+white whereas the water use efficiency was highest with the duty ratio of 97% under the mixed light of red+blue LED. The results indicate that the light source and light quality for the optimal growth of Lycium chinense in the smart farm using the LED system are the mixed light of red+blue (1:1) and the duty ratio of 97%.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 전력전자학술대회
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• pp.63-65
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• 2018

This paper presents a DTC-PWM(Direct Torque Control-Pluse Width Modulation) method of PMSM(Permanent Magnet Synchronous Motor) using the flux-torque hysteresis band. In order to keep the flux and torque error of the PMSM within the hysteresis band, the optimal PWM duty ratio is calculated by the error of the flux and torque with the flux and torque vector of the selected voltage vector. According to the flux duty ratios and the torque duty ratios, the optimized duty ratio to reduce the errors is selected by the calculated duty ratios. In the proposed method, the selected voltage vector is divided into d-q axis components with a simple method. And the flux duty ratios and torque duty ratios are estimated by the applied voltage vector. The proposed DTC-PWM for PMSM was verified by computer simulation.

• 한국기계가공학회지
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• 제6권2호
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• pp.59-66
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• 2007

Voice coil actuator is used linear motion system that requires precision positioning control. In order to control precision positioning of voice coil actuator, relation model between duty ratio and moving displacement of voice coil actuator is needed. This paper present a duty ratio - displacement model in PWM control of voice coil actuator. Transfer function of voice coil actuator is obtained by combining voice coil motor's equation of motion with the equation of circuit and characteristic of voice coil motor. Consider to initial condition of velocity and current, transfer function is transformed mathematical model. The induced model can predict output displacement, velocity and current according to duty ratio and amplitude. The model is verified by experimental tests such as velocity and displacement response of voice coil motor. Simulated results have tracking errors of less than 10 percent of experimental results.

• 전력전자학회논문지
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• 제19권2호
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• pp.124-132
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• 2014

In this paper, we implement a non-time-varying transfer function of the duty ratio to improve the control characteristics in a control system that Input voltage and the output voltage is varied, DC / DC converters for bi-directional charging. When control is performed with using controller gain of conventional design, characteristics of the control is varied to fluctuations of the input voltage. The proposed method is the equivalently removing method for duty ratio in entire control block, by voltage controller gain is changed for inverse of the duty ratio. The proposed non-time-varying duty ratio transfer function is applied to DC / DC converter for bi-directional charging. In this paper, feasibility and superiority is verified through PSIM simulations and experiments.

• Corrosion Science and Technology
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• 제20권2호
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• pp.45-51
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• 2021

In this work, we describe the effect of pulse anodizing duty ratio on the corrosion resistance of anodic films in magnesium AZ31B. The process involves the application of square pulse potential for a constant period with a duty ratio varying from 40, 60 and 80%. In several samples, a sealing treatment for 30 minutes was conducted after anodization in order to seal the pores available in the anodic layer. After anodizing, the surface morphology of the anodic layer was examined using a scanning electron microscope (SEM Hitachi SU3500). The corrosion characteristics of the sample were evaluated through an open circuit potential (OCP) and potentiodynamic polarization test using potentiogalvanostat. SEM observation shows that the increase of anodization duty ratio (α) results in a more uniform anodic layer, with fewer pores and cracks. The increase of duty ratio (α) decreases the OCP value from approximately -1.475 to about -1.6 Volt, and significantly improves the corrosion resistance of the anodic coating by 68%. The combination of anodization and sealing treatment produces an anodic coating with a very low corrosion rate of 4.4 mpy.

• 조명전기설비학회논문지
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• 제25권11호
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• pp.33-38
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• 2011

In this paper, the effect of pulse current and generated heat on characteristics of the LED is measured and evaluated. For experiments, the LED driving circuit and digital logic which determines period and duty ratio of lighting are designed. At rated current, the temperature and optical characteristics of the LED with change in duty ratio and period are compared, and those of the LED with change in duty ratio and existence of cooling fan are also compared at constant average current. As a result, frequency does not affect device temperature and optical characteristic of the LED but duty ratio does. Also, the cooling fan is less effective on those of the LED at rated current.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2008년도 추계학술대회 논문집
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• pp.16-18
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• 2008

A novel general direct duty ratio pulse width modulation strategy is proposed to modulate matrix converters. By using average concept over one switching period, the modulation algorithm and the required equations are derived to synthesize the desired output voltage and to achieve the controlled input power factor. The proposed method use continuous carrier and the predetermined duty ratio signal for directly generating gating signals an thus is named "direct duty ratio PWM(DDPWM)". The feasibility and validity of the proposed strategy are verified by experimental results.

• 생태와환경
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• 제53권3호
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• pp.304-310
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• 2020

Smart farm is a high-tech type of plant factory that artificially makes environmental conditions suitable for the growth of plants and manages them to automatically produce the desired plants regardless of seasons or space. This study was conducted by identifying the effects of Hertz and Duty ratio on the photosynthetic rate of ginseng, a medicinal crop, to find the optimal conditions for photosynthetic responses in smart farms. The light sources consisted of a total of 10 chambers using LED system, with 4 R+B(red+blue) mixed lights and 6 R+B+W (red+blue+white) mixed lights. In addition, the Hertz of the R+B mixed light was treated at 20, 60, 180, 540, 1620 and 4860 hz respectively. The R+B+W mixed light was treated with 60, 180, 540, and 1620 hz. Afterwards, experiments were conducted with the duty ratio of 30, 50, and 70%. As a result, the photosynthetic rate of ginseng according to duty ratio and Hertz was the highest at 60 hz when duty ratio was set to 50%. On the other hand, that was the lowest when the duty ratio was 30% at the same 60 hz. In addition, the photosynthetic rates were highest in the R+B mixed light and R+B+W mixed light at 60 hz. Therefore, the condition with the highest photosynthetic rate of ginseng in smart farms is 60 hz when the duty ratio in R+B mixed light is 50%.

• 한국통신학회논문지
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• 제23권8호
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• pp.2064-2071
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• 1998

휴대용 기기에서 자체 발진하여 클럭원으로 사용되는 TCXO의 출력과 같은 작은 진폭(400mV)의 정현파 입력을 내부 논리회로의 클럭원으로 사용하기 위한 파형정형 및 50%의 듀티 비(duty ratio)의 출력을 가지는 새로운 디지털 클럭레벨 변환기를 설계, 개발 하였다. 정, 부 두 개의 비교기, RS 래치, 차아지 펌프, 기준 전압 발생기로 구성된 새로운 신호 변환회로는 출력파형의 펄스 폭을 감지하고, 이 결과를 궤환루프로 구성하여 입력 비교기 기준 전압단자로 궤환시킴으로서 다지털 신호레벨의 정확한 50%의 듀티 비를 가진 출력을 생성할 수 있다. 개발한 레벨변환기는 ADC등의 샘플링 클럭원, PLL 또는 신호 합성기의 클럭원으로 사용할 수가 있다. 설계는 $0.8\mu\textrm{m}$ double metal double poly analog CMOS 공정을 사용하고, BSIM3 model을 사용하였으며, 실험결과 370mV의 정현파 입력율 50 + 3%의 듀티 비를 가진 안정된 논리레벨 출력 동작특성을 얻을 수 있었다.