• The Korean Journal of Applied Statistics
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• v.29 no.7
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• pp.1385-1398
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• 2016

A pressurizer is a major equipment system in a nuclear power plant (NPP) and controls the reactor cooling system pressure within the allowable range. Faults in the pressurizer can be critical to the NPP; therefore, early fault detection in the pressurizer is significant for NPP safety. This study applies Mahalanobis Taguchi system (MTS), which is one of the promising pattern classification methods, based on the Mahalanobis distance concept and Taguchi quality engineering theory to the early fault detection problem of the pressurizer pressure control system. We conducted experiments using data from full scope NPP simulator based on a pressurizer pressure transmitter faults scenario to validate the faults detection performance of MTS. As a result, MTS can rapidly detect the faults compared to conventional faults detection based on single sensor monitoring.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.3
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• pp.479-486
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• 2002

In this study, the progressive inelastic deformation, so called, thermal ratchet phenomenon which can occur in high temperature structures of liquid metal reactor was simulated with thermal ratchet structural test facility and 316L stainless steel test cylinder. The thermal ratchet deformation at the reactor baffle cylinder of the liquid metal reactor can occur due to the moving temperature distribution along the axial direction as the sodium free surface moves up and down under the cyclic heat-up and cool-down transients. The ratchet deformation was measured with the laser displacement sensor and LVDTs after cooling the structural specimen which is heated up to 55$0^{\circ}C$ with steep temperature gradients along the axial direction. The temperature distribution of the test cylinder along the axial direction was measured with 28 channels of thermocouples and was used for the ratchet analysis. The thermal ratchet deformation was analyzed with the constitutive equation of nonlinear combined hardening model which was implemented as ABAQUS user subroutine and the analysis results were compared with those of the test. Thermal ratchet load was applied 9 times and the residual displacement after 9 cycles of thermal load was measured to be 1.79mm. The ratcheting deformation shapes obtained by the analysis with the combined hardening model were in reasonable agreement with those of the structural tests.

• Bulletin of the Korean Space Science Society
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• 2011.04a
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• pp.23.4-23.4
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• 2011

MIRIS is the main payload of the Science and Technology Satellite-3 (STSAT-3). which is being developed by KASI for infrared survey observation of the Galactic plane at Paschen alpha wavelength. Wideband filters in I and H band will also be used to observe cosmic infrared background. The MIRIS will perform astronomical observations in the near-infrared wavelengths of 0.9~2 ${\mu}m$ using a 256 ${\times}$ 256 Teledyne PICNIC FPA sensor providing a 3.67 ${\times}$ 3.67 degree field of view with a pixel scale of 51.6 arcsec. The flight model of the MIRIS has been recently developed, The system performance tests have been made in the laboratory, including opto-mechanics test, vibration test, thermal vacuum test and passive cooling test down to 200K, using a thermally controlled vacuum chamber. Several focus tests showed good agreements compared to initial design parameters. Recent efforts are being concentrated to improve the system performances, particularly to reduce readout noise level in electronics. After assembly and integration into the satellite bus, the MIRIS will be launched in 2012.

• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11B
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• pp.1394-1402
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• 2011

This paper describes solar light collecting system which employs parabolic reflector and Fresnel lens and its industrial application. We have introduced second-stage optical system so that it makes optical fiber overcome its numerical aperture limitation and also it makes focused light become collimated, which results in decreased light energy density. As result of these, light collecting efficiency become maximized and the system does not require separate cooling apparatus any more. The developed solar lighting system together with artificial light source like LED has been applied to plant factory as a hybrid lighting source. This makes us save electric energy for artificial lighting during day time. The intensity of LED light in the hybrid lighting system is controlled automatically according to ambient-light-sensor installed in the system so that the light intensity for a plant always keeps the same level no matter how the sun light changes. For a plant factory whose size is 330 square meters, when solar lighting system is applied, 28,080KWh electric energy can be saved per month.2 times.

• Radiation Oncology Journal
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• v.2 no.1
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• pp.11-20
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• 1984

The renewed interest in the use of hyperthermia in cancer therapy is bases on radiobiological and clinical evidence indicated that there may be a significant therapeutic advantage with the use of heat alone or combined with radiation or chemotherapy, There are many methods for generating heat for localized tumor as like radiofrequency, microwave, electromagnetic induction and ultrasound. But it is very difficult to be even thermal dose distribution and stable output of power and then the detection of temperature in tumor is difficult to be precise with thermocouples and semiconductor sensors. We designed the microwave heating generator, dipole antenna applicators and autometic temperature controlled thermocouples for localized hyperthermia on skin and in cavities. 1. The microwave generator with 120 W, 2,450MHz magnetron could be heating up to $40^{\circ}C\~50^{\circ}C\;for\;1\~2$ hours in living tissues. 2. The thermal dose distribution in tissue with microwave was described $42^{\circ}C\~44^{\circ}C$ with in 3 cm depth and $2\~6cm$ diameter area. 3. Skin surface heating applicator with spiral 3 times wave length antenna radiated high Power of microwave. 4, Intracavitary heating applicator with dipole antenna with autometic control temperature sensor kept up continuously constant temperature in tissue. 5. For constant thermal distribution, applied two steps power with 10W microwave after $17\~20W$ during first 10 minutes. 6. The cooling rate by blood flew in living tissue was rised as $10\%$ then meats.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.243-249
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• 2001

In this study, the progressive inelastic deformation, so called, thermal ratchet phenomenon which can occur in high temperature liquid metal reactor was simulated with thermal ratchet structural test facility and 316L stainless steel test cylinder. The inelastic deformation of the reactor baffle cylinder can occur due to the moving temperature distribution along the axial direction as the hot free surface moves up and down under the cyclic heat-up and cool-down of reactor operations. The ratchet deformations were measured with the laser displacement sensor and LVDTs after cooling the structural specimen which experiences thermal load up to $550^{\circ}$ and the temperature differences of about $500^{\circ}C$. During structural thermal ratchet test, the temperature distribution of the test cylinder along the axial direction was measured from 28 channels of thermocouples and the temperatures were used for the ratchet analysis. The thermal ratchet deformation analysis was performed with the NONSTA code whose constitutive model is nonlinear combined kinematic and isotropic hardening model and the test results were compared with those of the analysis. Thermal ratchet test was carried out with respect to 9 cycles of thermal loading and the maximum residual displacements were measured to be 1.8mm. It was shown that thermal ratchet load can cause a progressive deformation to the reactor structure. The analysis results with the combined hardening model were in reasonable agreement with those of the tests.

• Analytical Science and Technology
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• v.13 no.2
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• pp.222-228
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• 2000

A detector for monitoring carbon monoxide (CO) in ambient air by nondispersive infrared (NDIR) spectroscopy has been developed and investigated its sensitivity and stability. The essential parts of the absorption cell are three spherical concave mirrors so as to improve the sensitivity by increasing the light path length in the cell. The radius and center of curvature of mirrors and position in the cell was calculated by computer simulation in order that the light path length may be 16m into the 50cm cell. The number of traversals and optical path properties were confirmed by laser beam alignment in transparent absorption cell. The photoconductive type lead selenide (PbSe) was used as CO sensing material, which was cooled to increase the responsibility by thermoelectric cooling method. The detection limit and span drift of the developed CO detector was 0.24ppm and 0.03ppm(v/v) respectively.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.64.1-64.1
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• 2011

MIRIS (Multipurpose Infra-Red Imaging System), is a small infrared space telescope which is being developed by KASI, as the main payload of Science and Technology Satellite 3 (STSAT-3). Two wideband filters (I and H) of the MIRIS enables us to study the cosmic infrared background by detecting the absolute background brightness. The narrow band filter for Paschen ${\alpha}$ emission line observation will be employed to survey the Galactic plane for the study of warm ionized medium and interstellar turbulence. The opto-mechanical design of the MIRIS is optimized to operate around 200K for the telescope, and the cryogenic temperature around 90K for the sensor in the orbit, by using passive and active cooling technique, respectively. The engineering and qualification model of the MIRIS has been fabricated and successfully passed various environmental tests, including thermal, vacuum, vibration and shock tests. The flight model was also assembled and is in the process of system optimization to be launched in 2012 by a Russian rocket. The mission operation scenario and the data reduction software is now being developed. After the successful mission of FIMS (the main payload of STSAT-1), MIRIS is the second Korean space telescope, and will be an important step towards the future of Korean space astronomy.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.9
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• pp.1-6
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• 2019

Preterm children require a controlled environment that is as close as possible to that inside the womb. Incubators are well equipped to fulfill this requirement; however, they are cumbersome and expensive, thereby restricting their portability and availability in less developed and rural areas. This research comprises the development and system validation of a portable incubator. The system consists of a collapsible baby enclosure that can be stowed inside the system base when not in use. The enclosure is made from acrylic such that it is easy to clean and allows unhindered visual observation of the occupant while being robust enough to withstand transit conditions. The system can be powered either by a mains supply or a 12-VDC automobile power supply. Additionally, it has an onboard battery to ensure a continuous supply during transit. A Peltier plate controlled using a microcontroller ensures the desired enclosure temperature irrespective of the ambient temperature. Built-in sensor probes can measure the skin temperature, pulse rate, blood oxygenation level, and ECG of the infant and display them on the system screen. The system function is validated by testing its peak power consumption and the heating and cooling performances of the environment control system.