• Journal of Yeungnam Medical Science
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• v.4 no.2
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• pp.83-88
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• 1987

An analytic expression for equivalent square fields and a table are derived using the empirical representations obtained from the measured field size dependence of output for square field in a phantom. The expression is applicable to radiation fields that consistent with the following two assumptions Imposed on these representations. 1) It is a linear function of the logarithm of the field area, and 2) It is approximately the same function for both square and circular field of similar areas. In this paper, the derived tables and BJR table were consulted.

• Journal of the Korean Solar Energy Society
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• v.32 no.spc3
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• pp.245-254
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• 2012

In photovoltaic system, the characteristics of photovoltaic module such as open circuit voltage and short circuit current will be changed because of cell temperature and solar radiation. Therefore, the boost converter of a PV system connects between the output of photovoltaic system and DC link capacitor of grid connected inverter as controlling duty ratio for maximum power point tracking(MPPT). This paper shows the dynamic characteristics of the boost converter by comparing single-loop and two-loop control algorithm using both analog and digital control. Both proposed compensation methods have been verified with computer simulation to demonstrate the validity of the proposed control schemes.

• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.3
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• pp.9-19
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• 2015

Internal air temperature of greenhouse is an important variable that can be influenced by the complex interaction between outside weather and greenhouse inside climate. This paper focuses on a data-based model approach to predict internal air temperature of the greenhouse. External air temperature, solar radiation, wind speed and wind direction were measured next to an experimental greenhouse supported by the Electronics and Telecommunications Research Institute and used as input variables for the model. Internal air temperature was measured at the center of three sections of the greenhouse and used as an output variable. The proposed model consisted of a transfer function including the four input variables and tested the prediction accuracy according to the sampling interval of the input variables, the orders of model polynomials and the time delay variable. As a result, a second-order model was suitable to predict the internal air temperature having the predictable time of 20-30 minutes and average errors of less than ${\pm}1K$. Afterwards mechanistic interpretation was conducted based on the energy balance equation, and it was found that the resulting model was considered physically acceptable and satisfied the physical reality of the heat transfer phenomena in a greenhouse. The proposed data-based model approach is applicable to any input variables and is expected to be useful for predicting complex greenhouse microclimate involving environmental control systems.

• Journal of IKEEE
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• v.3 no.1 s.4
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• pp.69-78
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• 1999

In this paper, direct conversion receiver was designed to even harmonic anti-paralled diode pair ring mixer. Using a second harmonic component of LO instead of LO signal and RF signal are mixed by SHP(Sub Harmonic Pumped) mixer with anti-parallel diode pair. Canceling the harmonics of LO signal in ring mixer, SHP mixer using anti-parallel diode pair could mostly reduce the radiation of LO signal through a input port the most, good isolation characteristic, and low spurious characteristic by LO signal was shown over broad band. The produced SHP mixer showed LO/IF, RF/IF and LO/RF isolation was 24.6dB,36.2dB and 22.5dB respectively. And conversion loss was measured 15.6dB, IF output -35.6dBm with -20dBm RF input and 5.5dBm LO signal. 1dB compression point of If signal, in respect to RF signal, was found at the 0dbm RF signal.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2003.09a
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• pp.69-69
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• 2003

Flat panel based digital radiography (DR) systems have recently become useful and important in the field of diagnostic radiology. For DRs with amorphous silicon photosensors, CsI(TI) is normally used as the scintillator, which produces visible light corresponding to the absorbed energy. The visible light photons are converted into an electric signal in the amorphous silicon photodiode. In order to produce good quality images, we need to understand the detailed behavior of DR detectors in radiation. We, therefore, investigated the relationship between DR outputs and X -ray in terms of absorbed energy, using the SPEC-78, X-ray energy spectrum model. We calculated the total filtration of X-ray equipment measuring air exposure and this value was used in the calculation of absorbed energy. The relationship between DR output and the absorbed energy of the X-ray was obtained by matching the absorbed energy with pixel values of real images under various conditions. It was found that the relationship between these two values was almost linear. The results were verified using phantoms made of water and aluminium. The pixel value of the phantom image was estimated and compared with previous results under various conditions. The estimated pixel value coincided with the results, although the effect of scattered photons introduced some errors.

• Journal of the Korean Institute of Gas
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• v.5 no.1
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• pp.7-14
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• 2001

In this work, the chemical composition of the exhaust gas from domestic gas boiler has been analysed in the point of thermodynamics and CO sensor has been characterized. We proposed that the combustion condition can be estimated by the exhaust gas composition, i.e., the excess air ratio and combustion temperature can be calculated simply by the measurement of the $O_{2}$ fraction and $H_{2}/CO$ in the exhaust gas. By analyse the on site situation domestic boiler, the excess air ratio is about $55\~110\%$. Therefore, the CO may be produced in domestic gas boiler by luminous(yellow) flames rapidly lose heat by radiation, turbulent flames may be partially quenched by the action of steep velocity gradients, and flames burning very close to a cold wall may be partial1y quenched by heat conductivity to the wall. The output voltage of CO sensor is lineally depend on the CO and $H_{2}$concentration. And the exhaust CO from boiler can be reduced by closed loop control with CO sensor

• Journal of Bio-Environment Control
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• v.23 no.3
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• pp.181-191
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• 2014

Modern commercial greenhouse requires the use of advanced climate control system to improve crop production and to reduce energy consumption. As an alternative to classical sensor-based control method, this paper introduces a model-based control method that consists of two models: the predictive model and the evaluation model. As a first step, this paper presents straightforward models to predict the effect of natural ventilation in a greenhouse according to meteorological factors, such as outdoor air temperature, soil temperature, solar radiation and mean wind speed, and structural factor, opening rate of roof ventilators. A multiple regression analysis was conducted to develop the predictive models on the basis of data obtained by computational fluid dynamics (CFD) simulations. The output of the models are air temperature drops due to ventilation at 9 sub-volumes in the greenhouse and individual volumetric ventilation rate through 6 roof ventilators, and showed a good agreement with the CFD-computed results. The resulting predictive models have an advantage of ensuring quick and reasonable predictions and thereby can be used as a part of a real-time model-based control system for a naturally ventilated greenhouse to predict the implications of alternative control operation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.10
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• pp.771-777
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• 2013

This paper dealt with the development of a LED floodlight for naval vessels to replace the conventional floodlight using an incandescent and a halogen lamp. We found a technical solution for current problems of conventional lights and also improved optical characteristics by developing a LED floodlight which has a typical long-lived light source with high efficiency. To satisfy the requirements specified in Korea Standard Vessels (KS V), the optical structure was designed with selected LED package and lens. A LED module was composed of 10 LEDs in series for stable luminous output, and an aluminium heat sink was adopted for effective heat-radiation design. The LED floodlight was fabricated as a module type so that it can easily replace the conventional light source. The power consumption of the prototype floodlight was only a tenth of a conventional one with the same optical performance. Also, a test showed the floodlight satisfied the electrical, optical and environmental requirements of the standards.

• Journal of the Korean Institute of Gas
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• v.3 no.2 s.7
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• pp.77-84
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• 1999

The XX company that is handling the class IV hazardous materials, located in Bu-Chon City and the LPG station in front of the XX company which is about 20 meters apart, was chosen as the standard model for this study In carrying out the consequence analysis, PHAST and Super-Chems were used for the study and utilizing the output of the simulation, we have evaluated the consequences throughout the probit analysis and explosion overpressure analysis. In case of Acetone, the effect distance of the damage on facilities-that is the result of radiation heat flux of $37.5kW/m^2$ by TNO model-is 68.51m by PHAST model and 40.93m by Super-Chem model. The risk assessment of the LPG station which is based on the explosion resulted as the analysis of the fire ball showed the diameter 125.2m, the height 206.2m and the duration 11.28sec and the effect distance for the radiant heat flux $37.5kW/m^2$ was 137.0m.

• Journal of Sensor Science and Technology
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• v.27 no.5
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• pp.335-339
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• 2018

The optical characteristics of a terahertz (THz) antenna-coupled bolometer (ACB) detector were evaluated using a pulsed quantum cascade laser (QCL) and radiation blackbody sources. We investigated a method for measuring the responsivity and noise-equivalent power (NEP) of the THz detector using two different types of light sources. When using a QCL source with a frequency of 3 THz, the average responsivity of 24 devices was $1.44{\times}10^3V/W$ and the average NEP of those devices was $3.33{\times}10^{-9}W/{\surd}Hz$. The average responsivity and NEP as measured by blackbody source were $1.79{\times}10^5V/W$ and $6.51{\times}10^{-11}W/{\surd}Hz$, respectively, with the measured values varying depending on the light source. This was because the output power of each light source was different, with the laser source being driven by a pulse type wave and the blackbody source being driven by a continuous wave. The power input to the THz sensor was also different. Futhermore, the responsivity and NEP values measured using band pass filter (BPF) were similar to those measured when using only THz windows. It was found that ACB sensor responds normally in the THz region to both the laser and the blackbody source, and the method was confirmed to effectively evaluate the characteristics of the THz sensor.