• Korean Chemical Engineering Research
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• v.45 no.1
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• pp.67-72
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• 2007

An efficient method for identification of MIMO state space model has been developed by combining partial least squares (PLS) regression, balanced realization, and balanced truncation. In the developed method, a MIMO system is decomposed into multiple MISO systems each of which is represented by a high-order ARX model and the parameters of the ARX models are estimated by PLS. Then, MISO state space models for respective MISO ARX transfer function are found through realization and combined to a MIMO state space model. Finally, a minimal balanced MIMO state space model is obtained through balanced realization and truncation. The proposed method was applied to the design of model predictive control for temperature control of a high pressure $CO_2$ solubility measurement system.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.6
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• pp.1327-1335
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• 2012

TPMS (Tire Pressure Monitoring System) is a safety assistant system to prevent the serious accident due to the damaged tire by the abnormal tire pressure. It is designed to transmit the measured data for pressure and temperature of tires from the sensor unit installed in each tire to signal processing unit installed in a vehicle. Based on the received information, a driver monitors the condition of tires using a display device, to maintain the optimum travelling condition. Since TPMS should employ the wireless communication technique, it may suffer from various interferences from external electrical or electronics devices. In order to suppress them, the beamforming techniques such as switching, minimum-variance distortionless-response (MVDR), and generalized sidelobe canceler (GSC) have been considered for TPMS. In this paper, we calculate computational complexities of three beamformers and suggest mathematical basis to compare their performance of the complexity.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.3
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• pp.255-262
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• 2014

To investigate the effect of oil on evaporation heat transfer of plate heat exchanger, evaporation heat transfer experiment was carried out using experimental apparatus for micro gear pumped R134a-oil circulation. By varying oil circulation rate of POE oil from 0 to 5%, evaporation heat transfer performance of plate heat exchanger was investigated. As OCR(Oil Circulation Ratio) increases, the evaporation heat transfer coefficient of R134a decreases and pressure drop increases. When the evaporating temperature is $30^{\circ}C$ and the refrigerant mass flow rate is 80 g/s, evaporation heat transfer rate decreases by 10 % and pressure drop increases by 10% at 2% of OCR condition.

• Korean Chemical Engineering Research
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• v.56 no.2
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• pp.222-228
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• 2018

Benzene is one of the most widely used basic materials in the petrochemical industry. Generally, benzene exists as a mixture with alcohols rather than as a pure substance. Further, the alcohols-added mixtures usually exhibit an azeotropic composition. In this context, knowledge of the phase equilibrium behavior of the mixture is essential for its separation and purification. In this study, the vapor-liquid equilibrium data were measured in favor of a recirculating VLE apparatus under constant pressure for the 1 - propanol / benzene system. The measured vapor - liquid equilibrium data were also correlated by using the UNIQUAC and WILSON models and the thermodynamic consistency test based on the Gibbs/Duhem equation was followed. The results of the phase equilibrium experiment revealed RMSEs (Root Mean Square Error) and AADs (Average Absolute Deviation) of less than 0.05 for both models, indicating a good agreement between the experimental value and the calculated value. The results of the thermodynamic consistency test also confirmed through the residual term within ${\pm}0.2$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.10
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• pp.909-916
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• 2016

The beacon receiver is an equipment which detects and measures the signal strength of transmitting satellite beacon signal. Beacon signals transmitted by satellites are low power continuous wave(CW) signals without any modulation intended for antenna steering to satellite direction and power control purposes on the earth. The beacon signal detection method using a very narrow band analog filter and RSSI(Received Signal Strength Intensity) has been typically used. However, it requires the implementation to track the frequency at the beacon receiver, thus a beacon frequency variation of the satellite due to temperature changes and long-term operation. Therefore, in this paper, the beacon signal detection receiver is designed by using a very narrow band digital filter array for a faster acquisition and SNR(Signal to Noise Ratio) method detection. For this purpose, by calculating the satellite link budget with the rain attenuation between satellite and ground station, and then extracting the received $C/N_o$ of the beacon signal, this work derives the bandwidth and the array number of the configured digital filter that gives the required C/N.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.3
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• pp.589-597
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• 1992

The effect of pressure on soot formation in premixed propane-air combustion is investigated at high pressures over the pressure range of 1 to 5 MPa by using a specially designed constant volume combustion bomb. The combustiom chamber of disk type with eight spark plugs located on the circumference at an interval of 45deg is 100mm in diameter by 14mm thick. The end gases are compressed to high pressures by the eight converging flames. The soot volume fraction in the chamber center during the final stage of combustion at the highest pressure is measured by the in-situ laser extinction technique, and the burnt gas temperature during the same period is measured by the two-color method. It is found that the soot yield rises with 50 to 100% for the respective equivalence ratio range of 1.9-2.2 at an interval of 0.1 when the combustion pressure is increased from 1 to 5 MPa, and that the turbulent flames decrease in the soot yield as compared with the laminar flames because the burnt gas temperatures increase with the drop of heat loss.

• Fire Science and Engineering
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• v.24 no.1
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• pp.95-102
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• 2010

The combustion characteristics of roof 'Jucsim' structure was analysed using real scale fire test on wooden structure heritage building. the fire test model was made to consider roof timberling internal structure for a Sunglemun. Structure of test body layed lime, soil, 'Jucsin' and ceiling board excepting roof tile to find heat propagation process by setting thermocouples. The first test to find fire growth and heat propagation process in the part of ceiling. The second test organized to find the efficiency of fire proof paint between ceiling board and inside of Jucsim structure. The third test try to get the performance level of fire proof fabric with the same manner. The result showed from the test proof the heavy smoke exposure with limited effect of fire proof paint however, reliable fire resistance effect showed in case of fire proof fabric.

• Journal of Advanced Navigation Technology
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• v.23 no.5
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• pp.460-465
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• 2019

In this study, we aim to derive a solution from the structural analysis for electrical failure of single board computers for computing navigation information. By analyzing the characteristic factor, we identify that crack occur on the central processing unit board due to a certain structural problem, and that the physical effect by the crack make communication function be impossible to perform, which it causes booting error. In order to find the location of excessive stress causing the crack, structural analysis for the single board computer is done. From the structural analysis, the areas where stress concentration occurs are identified, and improvement methods changing the structures are developed. As a result, we shows that stresses are reduced entirely on the stress distribution for the improved structure. In addition, heat analysis shows that changing the structure to reduce stresses is not affect to the heat radiation, and the thermal resistance of the actual equipment is verified by measuring the temperature of the heat sink applied with the improved structure.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.4
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• pp.70-79
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• 2012

For an aerodynamic test facility, it is very important to get the precise measurement data of pressure, temperature and mass flow rate at the upstream to the test article. Hence, a new measurement method using a bellmouth and rakes was studied for the large scale system of which the corrected mass flow is between 5 kg/s and 8 kg/s. The bellmouth was designed by ISO standard for 0.5% accuracy, and the rakes were designed by using the equal area method. From the results of 9 test trials, it is found that the Reynolds number of rakes and the mass flow rate ratio can be simply formulated by an one-dimensional equation. The mass flow rate of rakes was calibrated by this equation. By the result of calibration, The maximum error rate was -0.507%, and the average error rate was -0.000274%.

• Fire Science and Engineering
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• v.33 no.1
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• pp.23-29
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• 2019

Rechargeable battery such as lithium-ion battery has been noticed as a kinds of the energy storage system in the recent energy utilization and widely used actually in various small electronic equipment and electric vehicles. However, many thermal runaway caused battery accidents occurred recently, which still is obstacle for advanced application of lithium ion battery. One of the main differences to general fires is the existence of ionized electrolyte with electron during combustion. Therefore, we simply simulated the ion addition effects of battery fires by introducing an ionized fuel in jet diffusion flames. When the ionized methane through a corona discharge was used as fuel, the overall flame stability and shape such as flame length showed no significant difference from normal methane flame, but NOx and CO emissions measured at the post flame region decreased. The ion addition effect of methane oxidation was also numerically simulated with the modeling of hydrogen addition in the mixture. It was confirmed that the hydrogen addition at a fixed temperature had a similar effects on ionization of methane and hence could be modeled successfully.