• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.183-190
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• 2002

In order to reduce NOx emissions in the 20kw class microturbines under development, the low NOx characteristics, as being an application to the lean premixed combustion technology, have been investigated. The study has been conducted at the conditions of high temperature and pressure. Air from a compressor with the temperature of 500K to 650K and the pressure of 0.3bar gauge to 0.7bar gauge, was supplied to the combustor through an air preheat-treatment. Sampling exhaust gases were measured at the immediate exit of the combustor. for the effect of temperature on NO and CO emissions. though NOx was increased, CO was decreased with increasing inlet air temperature. With increasing inlet air pressure, NOx and CO were increased also. NOx was decreased, but CO was increased with increasing inlet air mass flow rate. The test has been performed on the equivalent ratios of 0.10 to 0.25 in a lean region. NOx was increased with increasing equivalent ratios, but CO was decreased as an influence of flame temperature. In the very lean region of the equivalent ratio below 0.12, CO was increased suddenly, due to instability. As the results of this study, NOx and CO are found to be reduced to the similar level at the same time when operated at optimal conditions.

• Journal of Korean Association for Spatial Structures
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• v.6 no.1 s.19
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• pp.83-90
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• 2006

The GF(Gust Factor) method is usually used as a method to evaluate equivalent static wind loads for general structures. The GF method is performed on the assumption that the shape of the equivalent static wind load profile is typically similar to that of mean wind loads. The shape of fluctuating wind loads could be quite different with that of the mean wind loads in case of large-span structures. So, the effect of higher modes as well as first mode must be considered to evaluate the wind loads. In this study, the ACS (Advanced Conditional Sampling) method is suggested to evaluate of equivalent static wind loads after investigating about GF and LRC method. The An method ran derive effective static wind loads by combining wind pressures and inertia forces of a structure chosen at a maximum load effect. The maximum load effect is assessed with the time history analysis using pressure data measured in wind tunnel tests. Equivalent static wind loads evaluated using ACS, GF, and LRC methods are compared to verify the effectiveness of ACS method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.227-230
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• 2005

This paper describes the problems in measuring and evaluating the aviation noises and the differences on the noise characteristics between fighter and civil aircraft. From a standpoint of the duration time for aviation noise and the dynamic characteristics related with the sampling time, the measured values for landing and taking-off noises from the fighter are presented and explained in comparison with those from the civil aircraft. And also the aviation noises by the fighter and civil aircraft are evaluated by equivalent sound level and WECPNL, respectively. From the obtained results, it is recommended that the duration time and dynamic characteristics be deeply considered in evaluating and measuring the aviation noises, since they have a great influence on the final assessment results. As the number of flight is not sufficient and the noise source is strong impulse type, moreover, the aviation noise should be assessed by WECPNL.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.26 no.3
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• pp.301-306
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• 2016

Objectives: Direct-reading instrument(Photoionization detectors, PID) and quantitative analysis using active type air sampling (Gas chromatography-flame ionization detector, GC-FID) were tested to evaluate their ability to detect volatile organic compounds(VOCs) in a semiconductor manufacturing plant. Methods: The organic compounds used were acetone and ethanol which are normally used as cleaning solutions in the semiconductor manufacturing. The evaluation was based on the preparation of test solutions of known acetone and ethanol concentration in a chamber($600{\times}600{\times}1150mm$). Samples were prepared that would be equivalent to 5~100 ppm for acetone and 10~ 200 ppm ethanol. GC-FID and PID were evaluated simultaneously. Quantitative analysis was performed after sampling and the direct-reading instrument was checked using real-time data logging. Results: Positive correlations between PID and GC-FID were found for acetone and ethanol at 0.04~2.4% for acetone(TLV: 500 ppm) and 0.1~8.3% for ethanol(TLV: 1000 ppm). When the sampling time was 15 min, concentration of test solution was the most similar between measurement methods. However, the longer the sampling time, the less similar the results. PID and GC-FID had similar exposure patterns. Conclusions: The results indicate that PID and GC-FID have similar exposure pattern and positive correlation for detection of acetone and ethanol. Therefore, PID can be used for exposure monitoring for VOCs in the semiconductor manufacturing industry. This study has significance in that it validates measuring occupational exposure using a portable device.

• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.30-33
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• 2001

This paper discusses the system design of a synthetic aperture radar system based on a pulse-echo radar. The design consists of an ultra-wide bandwidth antenna, an amplitude modulation, timing stabilities, and high speed a/d conversions with an equivalent-time sampling. Experiment results show that GPR(Ground Penetrating Radar) can be used to explore buried electric facilities.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.12
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• pp.1213-1219
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• 2012

The purpose of this study is to present a guideline to design a short-term manual measurement of environmental noise level, which is more economical and flexible, but less representative than long-term automatic measurement. The proposed guideline can provide the number of measurement times and the length of measurement term required to secure the extent of the representativeness. The data was collected at 4 sites located in Seoul and at 4 sites located outside of Seoul. The probabilities for five-minute equivalent noise levels, Leq, 5min, to stay in an error range from the quarterly representative noise level were used to evaluate sampling techniques. The probability analysis of the daytime period showed that the noise levels measured between 10 am and 2 pm and between 9 pm and 10 pm have the probabilities higher than 60 %. On the other hand, even for the same length of total measurement time, increasing the number of random samplings results in higher probabilities than increasing the length of measurement term.

• Journal of Nutrition and Health
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• v.24 no.6
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• pp.547-559
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• 1991

The purposes of this study were to : a)determine the percentage of labor activities expen-ded in various work functionsof hospital foodservice b)estimate the labor time utilized in each work functions c)investigate the overall work patterns of hospital foodservice and d)provide the basic data for effective labor control This study was conducted in two hospitals with 1300 and 1200 ed capacities and every employees of the dietary department were included in 10days work measurement. Work sampling methodology developed by Donaldson and Ostenso was modified and used for observing overall activities of hospital dietary department. Consistency of data and observa-tion period were verified by 3$\delta$ control chart and control chart. Observed data were satisfied with confidence level of 95% and confidence interval of $\pm$0.05, The results of this study were as follows: 1) The direct work function indirect work function and delay were 74.8%, 9.2%, 16.0% respectively with A hospital and 82.2% 7.2%, 10.6% respectively with B hospital 2) The productivity indices of direct work indirect work and delay were 9.05 min/meal 1.12 min/meal 1.94 min/meal respectively and total 12.11 minutes were utilized per meal served in A hospital and 10.72 min/meal 0.94 min/meal 1.38 min/meal respectively and total 13.04 minutes were utilized per meal served in B hospital 3) Full time equivalent(FTE) utilized in daily work of irect work indirect work and delay were 62.24 men 7.69 men 13.35 men respectively in A hospital and 64.09 men 5.63 men 8.22 men respectively in B hospital. 4) The contents of work activities of each employee group showed that delay time of the service personnel group was more than any other employee groups in both A hospital and B hospital 5) Examination of daily work schedule by time intervals showed that transportation work function was carried out all day so it is necessary to improve this work.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2480-2482
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• 2005

This paper presents a complete solution to intelligent digital redesign problem (IDR) for sampled-data fuzzy systems. The IDR problem is the problem of designing a sampled-data state feedback controller such that the sampled-data fuzzy system is equivalent to the continuous-time fuzzy system in the sense of the state matching. Its solution is simply obtained by linear transformation. Under the proposed sampled-data controller, the states of the discrete-time model of the sampled-data fuzzy system completely matches the state of the discrete-time model of the closed-loop continuous-time fuzzy systems are completely matched at every sampling points.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.220-222
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• 2006

This paper presents intelligent digital redesign method of global approach for hybrid state space fuzzy-model-based controllers. For effectiveness and stabilization of continuous-time uncertain nonlinear systems under discrete-time controller, Takagi-Sugeno(TS) fuzzy model is used to represent the complex system. And global approach design problems viewed as a convex optimization problem that we minimize the error of the norm bounds between nonlinearly interpolated lineal operators to be matched. Also, by using the bilinear and inverse bilinear approximation method, we analyzed nonlinear system's uncertain parts more precisely. When a sampling period is sufficiently small, the conversion of a continuous-time structured uncertain nonlinear system to an equivalent discrete-time system have proper reason. Sufficiently conditions for the global state-matching of the digitally controlled system are formulated in terms of linear matrix inequalities (LMIs). Finally, a T-S fuzzy model for the chaotic Lorentz system is used as an example to guarantee the stability and effectiveness of the proposed method.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.496-498
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• 2005

This paper presents intelligent digital redesign method of global approach for hybrid state space fuzzy-model-based controllers. For effectiveness and stabilization of continuous-time uncertain nonlinear systems under discrete-time controller, Takagi-Sugeno(TS) fuzzy model is used to represent the complex system. And global approach design problems viewed as a convex optimization problem that we minimize the error of the norm bounds between nonlinearly interpolated linear operators to be matched. Also by using the power series, we analyzed nonlinear system's uncertain parts more precisely. When a sampling period is sufficiently small, the conversion of a continuous-time structured uncertain nonlinear system to an equivalent discrete-time system have proper reason. Sufficiently conditions for the global state-matching of the digitally controlled system are formulated in terms of linear matrix inequalities (LMIs).