• The Journal of the Acoustical Society of Korea
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• v.14 no.5
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• pp.83-88
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• 1995

The common practice for the identification of piezoelectric properties is based on the use of immittance of a resonator with a certain geometry and poling direction. In this paper, a new method is suggested to identify the complex-valued piezoelectric material constants. This method Is based on the minimization of differences between the analytical immittance and the experimental measurement of resonator. Non-linear minimization problems are formulated to find out the unknown properties relevant to the resonators. The immittance data used for identification are measured at a number of frequencies which cover the vicinity of resonance frequency and the low frequency region. To illustrate the proposed technique, the complex-valued coefficients are identified for a typical PZT4 ceramic composition.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.249-250
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• 2008

본 논문은 고창 전력품질 실증시험장에서 실 계통 연계를 위해 시험 중인 1.5M급 풍력발전 시뮬레이터의 선로정수를 PSCAD/EMTDC를 이용하여 모의하고 선로정수에 따른 풍력발전시스템이 계통에 미치는 영향을 분석하는데 중점을 두었다. 현재 고창에 설치되어있는 전력품질 실증시험장은 22.9kV 급전선에 SSTS(Synchronous Static Transfer Switch)의 한쪽 스위치로 직접 연결되어있으며 다른 한 쪽은 전력계통에서 발생되는 다양한 형태의 이벤트를 발생시키는 SSHG(Sag Swell Harmonics Generator)를 통하여 연결되어있다. 전력품질 향상기기중 하나인 DVR(Dynamic Voltage Restorer)는 SSTS의 부하쪽으로 직렬로 연결되어있으며 delta-wye 변압기를 통해 정류기 부하와 APF(Active Power Filter), 그리고 순저항부하와 유도성부하가 연결되어 있고 또한 SSHG를 통하여 연결된 배전선에는 DSTATCOM(Distribution Static Compensator)가 병렬로 연결되어있다. 본 논문에서는 고창에 있는 풍력발전 시뮬레이터와 동일하게 PSCAD/EMTDC로 구성하였으며 선로정수를 모델링 하기 위해 선로모델을 10Km, 20Km, 30Km, 40Km,로 설정하여 선로정수에 따른 계통영향을 분석하여 풍력발전 시뮬레이터에서 모의가능 한 선로정수 값을 제시한다.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.5
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• pp.469-476
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• 2010

The purpose of the study is to find ways to decrease turbidity and residual aluminum by improving the efficiency of coagulation process through controlling the pH of the source water with $CO_2$ when the pH increases by algal bloom or by the characteristics of the source water. Water quality parameters were monitored before and after $CO_2$ addition in February, March, April, and December, when the pH of the source water is over 8.0 and constant regardless of day and night. Water quality parameters closely related with evaluation of treated drinking water quality were monitored in detail, e.g. aluminum, turbidity, particle counts, TOC, THMs, 2-MIB, and geosmin. According to the results, inorganic water quality parameters such as turbidity, particle counts, and aluminum were decreased due to improved efficiency of the coagulation process. It was concluded that the pH of the water in the arrival basin must be controlled below 7.4 by adding $CO_2$ when the pH of the source water increasing. By controlling pH with $CO_2$, the water quality could be maintained within the drinking water quality goal of Seoul City (<30 particle/mL of particle count, <0.05 NTU of turbidity and <0.02 mg/L of aluminum). The change of the pH could not affect the concentrations of DBP's (e.g., THMs, CH, and HAAs) and taste/odor causing compounds (e.g., 2-MIB and geosmin). 2-MIB and geosmin were affected more by their initial concentrations in the source water.

• Journal of the Korea Society of Computer and Information
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• v.19 no.10
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• pp.13-21
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• 2014

The set covering problem (SCP) is one of representative combinatorial optimization problems, which is defined as the problem of covering the m-rows by a subset of the n-columns at minimal cost. This paper proposes a method utilizing Integer Programming-based Local Search (IPbLS) to solve the set covering problem. IPbLS is a kind of local search technique in which the current solution is improved by searching neighborhood solutions. Integer programming is used to generate neighborhood solution in IPbLS. The effectiveness of the proposed algorithm has been tested on OR-Library test instances. The experimental results showed that IPbLS could search for the best known solutions in all the test instances. Especially, I confirmed that IPbLS could search for better solutions than the best known solutions in four test instances.

• Journal of the Korea Organic Resources Recycling Association
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• v.7 no.1
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• pp.1-12
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• 1999

The objective of this study is to improve the function of an artificial culture soil which was mixed mainly with alum sludge. The artificial culture soil was more efficient than the commercial culture soil for the growth of perennial ryegrass and bush clover. Artificial culture soil was prepared paper sludge(40%), alum sludge(30%), sewage sludge(20%), and compost (10%). This artificial culture soil had no adverse effect on phytotoxicity tests. The alum sludge gives some water holding capacity and cohesion strength to the soil enought to require no other addition of adhesive agents. The leaching of aluminum from the alum sludge was negligible even at very low pH(=2) due to the mixed compost.

• Journal of KIISE
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• v.43 no.6
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• pp.692-699
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• 2016

C compilers for 8-bit MCUs used in washing machines and refrigerators often do not follow the C standard to improve runtime performance. Developers who are unaware of the difference between C compilers following the C standard and the C compilers for 8-bit MCU can cause bugs that do not appear in the standard C environment but appear in the embedded systems using 8-bit MCUs. It is difficult for bug detectors that assume the standard C environment to detect such bugs. In this paper, we introduce integer promotion bugs caused by the different integer promotion rules of the C compilers for 8-bit MCU from the C standard and propose 5 bug patterns where the integer promotion bugs occur. We have developed an integer promotion bug detection tool and applied it to the washing machine control software developed by the LG electronics. The integer promotion bug detection tool successfully detected 27 integer promotion bugs in the washing machine control software.

• Composites Research
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• v.15 no.5
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• pp.14-18
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• 2002

In the present study, we investigated the effects or hydrostatic pressure and stacking sequence on the elastic work factor to determine compressive fracture toughness of graphite/epoxy laminated composites in the hydrostatic pressure environment. The stacking sequences used were unidirectional. $\textrm{[}0^{\circ}\textrm{]}_{88}$ and multi-directional, $\textrm{[}0^{\circ}/\pm/45^{\circ}/90^{\circ}\textrm{]}_{11s}$. The hydrostatic pressures applied for a $\textrm{[}0^{\circ}\textrm{]}_{88}$ case were 0.1 MPa, 70MPa, 140MPa. and 200MPa. The hydrostatic pressures applied for a $\textrm{[}0^{\circ}/\pm/45^{\circ}/90^{\circ}\textrm{]}_{11s}$ case were 0.1MPa, 100MPa, 200MPa, and 300MPa. It was found that the elastic work factor was not affected by the hydrostatic pressure and the stacking sequence. Also, it was found that the elastic work factor decreased in a linear fashion with delamination length.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.5
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• pp.863-869
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• 2017

In this study, the information breakdown structure of water purification plant has been made by classifying various the water purification methods and facilities. this can be utilized as a code system of computer for integrating information and analyzing quantitative of environmental impact and calculating cost of maintenance and energy consumption which was used during life cycle of water purification plant. Since the construction information contains many heterogeneous information, it is very important to have a code system for managing the integrated information. In addition, since water purification plant facilities are mainly composed of installation of facilities including many processes, a more detailed classification code is required. Therefore, in this study, the water purification breakdown structure which is not yet attempted in Korea was constructed by using facet classification system.

• Journal of the Korean GEO-environmental Society
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• v.13 no.8
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• pp.75-84
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• 2012

In this paper, strength and leaching characteristics of water sludge-added lightweight soils(WALS) considering reinforcing materials(waste fishing net, glue treated waste fishing net and geogrid) and layer(1 or 2 layer) were investigated using unconfined compression test and leaching test. Several specimens of water sludge-added lightweight soil consisted of water sludge, cement, and bottom ash were prepared according to flowability. Reinforcing material added into these specimens were waste fishing net and geogrid. A glue treated waste fishing net was also added in order to increase interlocking between soil mixture and waste fishing net. Strength increased in the order of WALS reinforced by waste fishing net, glue treated waste fishing net, and geogrid. Strength of specimen with double layer-reinforcing material was greater than that of specimen with single layer reinforcing material. Leaching result of WALS was also satisfied with standard of ministry of environment.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.12
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• pp.191-200
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• 2009

This paper, which consists of two parts, dealt with the parameter tuning of the power system stabilizer for a 612[MVA] thermal power plant in KEPCO system and its validation in field test. In Part 1 of the paper, the selection of parameters such as lead-lag time constants for phase compensation, system gain was optimized by using linear & eigenvalue analyses and they were verified through the time-domain transient stability analysis. In part 2, the performance of PSS was finally verified by the generator's on-line field test. Through the comparisons of simulation results and measured data before and after tuning of the PSS, the models of generator and its controllers including AVR, Governor and PSS used in the simulation are validated and confirmed.