• Journal of the Korean Institute of Gas
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• v.13 no.1
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• pp.52-60
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• 2009

This study reflects the concept of risk-based design to present a systematic design means and a method to adjust regulations and standards towards a more reliable direction within the current law. In order to enhance the early design concentration and level in the part of safety design, a new Advanced Safety Analysis Table (ASAT) was developed to provide information on the systematized safety design element from the early design phase. Furthermore, a guideline was put forth about the selection of a safety device according to process trouble, on the basis of the ASAT. To apply the proposed ASAT and the selection method of a safety device according to process troubles, the ASAT was executed for the PGC (Process Gas Compressor) of the NCC (Naphtha Cracking Center), and the result of selecting the safety device was analyzed according to process trouble.

• Journal of the Korean Society of Safety
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• v.29 no.6
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• pp.68-75
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• 2014

It is very important to classify explosion hazardous area (EHA) suitably and to use proper explosion-proof electric installations for facilities using flammable gases and liquids. In the past, various examples in the Notification of Ministry of Employment and Labor were referred to in classifying EHA. But, at present, many companies use the hypothetical volume in Korean Standards (KS). This study reviews the validity of EHA classification based on the hypothetical volume by comparing the calculated radii of EHA with those obtained by a consequence analysis program called PHAST and a mathematical approach in British Standards (BS). The radii of EHA by the hypothetical volume were found to be slightly larger than those by the other two methods. This was attributed to rather conservative uses of a safety factor(k) and a correction factor(f) for availability of ventilation in calculating the hypothetical volume. Since the differences are not so conspicuous, however, it is concluded that the hypothetical volume in KS is a valid means for the classification of EHA. This study also presents a table of the radii of EHA for easy reference by small-scale companies using city gas, C3-LPG and flammable liquid(toluene), respectively. The table consists of 25 leakage scenarios corresponding to combinations of 5 pipe(nozzle) sizes and 5 operating conditions for each flammable gas and liquid.

• Earthquakes and Structures
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• v.26 no.3
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• pp.239-249
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• 2024

A new layered shear continuum model box was developed to address the dynamic response issues of buried oil and gas pipelines under multi-point excitation. Vibration table tests were conducted to investigate the seismic response of buried pipelines and the surrounding soil under longitudinal multi-point excitation. A nonlinear model of the pipeline-soil interaction was established using ABAQUS finite element software for simulation and analysis. The seismic response characteristics of the pipeline and soil under longitudinal multi-point excitation were clarified through vibration table tests and simulation. The results showed good consistency between the simulation and tests. The acceleration of the soil and pipeline exhibited amplification effects at loading levels of 0.1 g and 0.2 g, which significantly reduced at loading levels of 0.4 g and 0.62 g. The peak acceleration increased with increasing loading levels, and the peak frequency was in the low-frequency range of 0 Hz to 10 Hz. The amplitude in the frequency range of 10 Hz to 50 Hz showed a significant decreasing trend. The displacement peak curve of the soil increased with the loading level, and the nonlinearity of the soil resulted in a slower growth rate of displacement. The strain curve of the pipeline exhibited a parabolic shape, with the strain in the middle of the pipeline about 3 to 3.5 times larger than that on both sides. This study provides an effective theoretical basis and test basis for improving the seismic resistance of buried oil and gas pipelines.

• Journal of the Korean Institute of Intelligent Systems
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• v.17 no.1
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• pp.7-12
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• 2007

In this paper, we introduce an approach to design multi-fuzzy controllers for the superheat and the low pressure that have an influence on energy efficiency and stabilization of aft conditioning system. Air conditioning system is composed of compressor, condenser several evaporators and several expansion valves. It is quite difficult to control the air conditioning system because the change of the refrigerant condition give an impact on the overall air conditioning system. In order to solve the drawback, we design multi-fuzzy controllers which control simultaneously both three expansion valve and one compressor for the superheat and the low pressure of air conditioning system. The proposed multi fuzzy controllers are given as two kinds of controller types such as a continuous simplified fuzzy inference type and a discrete fuzzy lookup_table type. Here the scaling factors of each fuzzy controller ate efficiently adjusted by veal coding type Genetic Algorithms. The values of performance index of the conventional type are compared with the simulation results of discrete lookup_table type and continuous simplified inference type.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1995.10b
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• pp.125-130
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• 1995

Recently, the vehicle engine requried precision control of Air-Fuel rate and rigid restriction of exhaust gas. Therefore, we demanded excellent measuring equipment so as to improve of engine performance. Specially, throttle valve control is very important part in the engine control, because structure of engine dynamometer system is very important part in the engine control, because structure of engine dynamometer system is very complicate and it has nonlinear elements which is influenced of disturbance about vibration, a heat, a cooling, energy loss so on. In this study, we propose the method that the control technique using Fuzzy Look-up table and we obtained the satisfying result from realized the control system.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2002.11a
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• pp.315-320
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• 2002

Marketing ventilation fan 3 kinds been using in kitchen of apartment house into compensation discharge performance of contaminant measure. When propane gas burns by gas table, did waste heat into measurement compensation with carbon dioxide that it happens. In measured all type of exhaust fan, discharge performance of carbon dioxide and waste heat was high there are been much displacement. Among A, B, C three types, performance of A type exhaust fan was most superior and performance of C type exhaust fan was most poor

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.367-369
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• 1997

The process of designing protective circuits for signal lines usually consists of a time-consuming trial-and-error procedure, which also requires expensive equipment. However, computer simulation can drastically reduce the costs and time of design procedures based on experimental validation. In this study a gas arrester Pspice-model considering the response time characteristics is presented. The effects of various waveforms on the transient behaviors and firing voltages of a gas arrester were modeled by controlled voltage source E and TABLE function of PSpice, respectively. To estimate the characteristics of the gas arrester model proposed, three different voltage waveforms were used in the simulation and the measurement. The results of the computer simulation are in Rood agreement with the results of the experimental analysis.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.2
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• pp.150-158
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• 1999

The process of designing protective circuits against damage by transient overvoltages requires much work and expensive equipment. However computer simulation using PSpice can overcome these problems. In this paper a gas tube and a ZnO varistor Pspice-model considering the steepness of the wave-front were presented. The effects of various waveforms on the transient behaviors and firing volt-ages of a gas tube were modeled by controlled voltage source E controlled current source G and TABLE function of PSpice. And the nonlinear characteristics of a ZnO varistor were modeled by controlled voltage source E and H. To estimate the characteristics of the models proposed various waveforms specified in IEC Std. 1000310-4-5 were used in the simulation and the actual tests. The simulation results were compared with test results and showed good agreement.

• Journal of Korean Society of Forest Science
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• v.112 no.4
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• pp.515-522
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• 2023

The aim of this study was to quantitatively evaluate a new stem volume table for estimating the growth, carbon storage, and greenhouse gas (GHG) absorption in Cryptomeria japonica and Chamaecyparis obtusa stands and to provide suggestions for improving the domestic GHG inventory. Carbon storage and GHG absorption were estimated using growing stock data obtained from invariable sub-sample plots between the 6^th and 7^th national forest inventories. We assessed changes in growing stock using the parameters employed by Kozak (1988) and Versions 1 and 2 of the stem volume table. Version 2 has new stem tables for 16 species, including Cryptomeria japonica, which were unavailable in Version 1. Version 2 also includes new data for trees with diameters at breast height equal to or greater than 30 cm. We found greater growing stock values using Version 2 than Version 1 for both stands, and the differences were statistically significant (p<0.001). Applying the new stem volume table increased GHG absorption by 22% for the Cryptomeria japonica stand and 13% for the Chamaecyparis obtusa stand. The growing stock estimation method used in this study should therefore be applied to re-estimate GHG absorptions in the forestry sector to produce accurate statistics for the IPCC guidelines.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.303-305
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• 2006

본 논문은 HVAC(heating, ventilating, and air conditioning) 시스템의 효율성과 안정성에 기초하여, 과열도와 저압을 제어하는 Multi Fuzzy 제어기 설계를 제안한다. HVAC 시스템은 Compressor(압축기), Condenser(응축기), Evaporator(증발기), Expansion Valve(확장 밸브) 로 구성되며, 각각의 기기에 대한 제어가 독립적으로 이루어져 있다. 기존의 제어가 한 제어기를 사용한 단일방식으로 이루어지다보니 HVAC 시스템의 특성인 냉매의 상태가 달라지면 시스템 전반적으로 그 영향이 파급되는 부분까지 고려를 해 주지 못하고, 제어기의 성능이 효율적이고 안정적이지 못했다. 본 논문에서는 HVAC 시스템의 효율과 안정도에 결정적인 영향을 미치는 파열도와 저압을 제어하기 위해, 비선형성이 강하고 불확실하며 복잡한 시스템을 쉽게 제어할 수 있는 Fuzzy 제어기를 구성하여, 3대의 Expansion Valve 와 1대의 Compressor 에서 동시에 제어하는 Multi 제어기를 설계한다. 제안된 Fuzzy 제어기는 이산형 lookup_table 방식과 연속형 간략추론 방식을 사용하여 제어기를 설계하고, 유전자 알고리즘(GAs)을 이용하여 최적의 Fuzzy 제어기의 환산계수를 구한다. 그리고 시뮬레이션 결과를 통해 이산형 lookup_table 방식과 연속형 간략추론 방식의 각각의 제어기를 사용한 결과를 비교한다.