• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.4
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• pp.308-315
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• 2009

Because the attenuation of AE signal in composite materials is relatively higher than that of metallic materials, it is required to develop a damage assessment technique less affected by the attenuation property of composite materials in order to use AE sensing as a damage detection method. In the signal processing procedure, it is profitable to use the leading wave that arrives first because the leading wave is less influenced by the boundary conditions. Using wavelet transform, we investigated the frequency characteristics of impact induced AE signals focused on the leading wave in advance and chose the key factors to discriminate the damaged condition quantitatively. In this research, we established a damage assessment technique using the sharing percentage of the wavelet detail components of AE signal, and conducted a low-velocity impact test on composite laminates to confirm the feasibility of the proposed signal processing method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.1
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• pp.60-64
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• 2004

In this paper, we implemented a real-time remote home monitoring system which we have ported the Linux OS and HTTP(Hypertext Transfer Protocol) web server. The GoAhead web server was ported using by ARM cross compiler. And then we used the analog to digital converter ADC0809 for sensing the vii able input signal at widely separated home. We have implemented linux device driver for ADC(Analog to Digital Convertor) and CGI-C(Common Gateway Interface - C language) application program using Client pull method for monitoring real-time changing data. The factor of monitoring is temperature, intensity of illumination and gas's existence. And this system has ability which check the status of out door and gas valve. We have designed the embedded web server system for home emergency monitoring in low cost.

• The Korean Journal of Pesticide Science
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• v.17 no.1
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• pp.1-5
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• 2013

This study was conducted to the amount of pesticide residue in 21 different kinds of 100 commercial flowering teas. Multi-residue analyses of 203 pesticides was performed using the GC-ECD, GC-NPD, GC-MSD, and LC-MS/MS. Pesticide residues were detected in 4 samples (4%) of which 4 samples (4%) violated the maximum residue limits. 4 samples violating the limit were all imported teas. Pesticides detected were chlorpyrifos, flufenoxuron, lufenuron, pyrimethanil and methoxyfenozide. These results indicate the need of continuous monitoring of pesticide residue needs for safety of flowering teas.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.18 no.1
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• pp.32-39
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• 2013

Although space-borne satellites are useful in obtaining information all around the world, they cannot observe at a suitable time and place. In order to overcome these limitations, an airborne remote sensing system was developed in this study. It is composed of a SAR sensor and a thermal infrared sensor. Additionally GPS, IMU, and thermometer/hygrometer were attached to the plane for radiometric and geometric calibration. The brightness of SAR image varies depending on surface roughness, and capillary waves on the sea surface, which are easily generated by sea winds, induce the surface roughness. Thus, sea surface wind can be estimated using the relationship between quantified SAR backscattering coefficient and the sea surface wind. On the other hand, thermal infrared sensor is sensitive to measure object's temperature. Sea surface temperature is obtained from the thermal infrared sensor after correcting the atmospheric effects which are located between sea surface and the sensor. Using these two remote sensing sensors mounted on airplane, four test flights were carried out along the west coast of Korea. The obtained SAR and thermal infrared images have shown that these images were useful enough to monitor coastal environment and estimate marine meteorology data.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1865-1869
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• 2006

도시화는 수문학적으로 산림이나 농경지와 같은 투수지역을 건물, 도로 등의 불투수지역으로 변화시키는 것이며, 이로 인하여 홍수파의 도달시간이 줄어들고 첨두유량이 증가하는 등의 수문변화를 수반하게 된다. 도로나 건물 등이 대부분을 차지하고 있는 도시지역에서는 지표면이나 식생으로부터 대기중으로 방출되는 증발산량이 농촌이나 산림지역보다 상대적으로 적으며, 강우시 토양중의 침투량과 지표면의 저류량도 도시지역에서는 매우 적게 나타난다. 본 연구에서는 도시화로 인하여 대규모의 토지이용 변화가 예상되는 신도시 개발예정지구인 판교 운중천 유역을 시험유역으로 선정하여 장기적인 수문/수질 모니터링을 수행하고 있으며, 향후 판교 시험유역에서 계측된 자료와 유역수문모형을 활용하여 개발 전후의 홍수 및 장기유출 특성을 분석하여 도시화가 하천의 수문 및 수질에 미치는 영향을 정량적으로 비교 분석하고자 한다. 이를 위해 2004년과 2005년에 시험유역내의 운중천과 금토천에 매송2교, 삼평교, 판교교, 운중저수지, 저수지 용수로, 내동교 등 총 6개의 수위관측소와, 매송2교와 내동교의 2개 우량관측소를 설치하여 실시간 계측을 수행하고 있으며, 인근의 기존에 운영되고 있던 탄천 본류의 성남과 궁내 수위관측소와 운중천의 낙생 우량관측소 자료를 활용하여 유역 수문자료를 수집하고 있다. 수집된 자료를 이용하여 장단기 유출분석을 수행한 결과, 택지개발공사가 시작되기 전인 현재로서는 택지개발 대상지구인 운중천 유역이나 비대상지구인 금토천 유역, 그리고 하류의 운중천 본류 유역 모두 강우시나 무강우시 비슷한 유출 특성을 가지고 있는 것으로 나타났다. 향후 도시화가 점차적으로 진행됨에 따라서 이러한 유출 특성의 변화 양상을 파악해 나간다면, 도시화에 따른 유출 특성의 변화는 물론 수질 변화에 대해서도 정성적, 정량적인 규명이 가능할 것으로 생각된다.TEX>의 범위이고, 2차 처리수의 유입수의 T-N, T-P 농도와 유사하였다.적인 방법론을 제시할 수 있을 것으로 사료된다.첨두홍수량을 저류하기 위해서 상대적으로 넓은 저류면적이 필요한 것으로 나타난다. 대등한 수위감소값의 홍수저감효과를 발휘하기 위해서 본 연구에서는 On-Line 저류지 면적은 Off-Line 저류지에 비 두배 이상이 필요한 것으로 보여졌다.들에 관한 정보는 종종 현장관측에서 조차 무시되는 경우가 많다. 이에 본 연구에서는 수질모형의 매개변수 중 특히 수리특성에 관련된 매개변수들이 수질에 미치는 영향을 파악하는 것을 목적으로 하고 있다. 이를 위해 적용된 수질모형은 QualKo를 사용하였으며, 대상 하천은 낙동강 본류 경남구간 시점 부근인 회천 합류 전부터 낙동강 본류 경남구간 종점 부근인 밀양강 합류 전까지의 경남 오염총량관리 기본계획 시 구축된 모형 매개변수를 바탕으로 분석을 수행하였다. 일차오차분석을 이용하여 수리매개변수와 수질매개변수의 수질항목별 상대적 기여도를 파악해 본 결과, 수리매개변수는 DO, BOD, 유기질소, 유기인 모든 항목에 일정 정도의 상대적 기여도를 가지고 있는 것을 알 수 있었다. 이로부터 수질 모형의 적용 시 수리 매개변수 또한 수질 매개변수의 추정 시와 같이 보다 세심한 주의를 기울여 추정할 필요가 있을 것으로 판단된다.변화와 기흉 발생과의 인과관계를 확인하고 좀 더 구체화하기 위한 연구가 필요할 것이다.게 이루어질 수 있을 것으로 기대된다.는 초과수익률이 상승하지만, 이후로는 감소하므로, 반전거래전략을 활용하는 경우 주식투자기간은 24개월이하의 중단기가 적합함을 발견하였다. 이상의 행태적 측면과 투자성과측면의 실증결과를 통하여 한국주식시장에 있어서 시장수익률을 평균적으로 초과할 수 있는 거래전략은 존재하므로 이러한 전략을 개발 및 활용할 수 있으며, 특히, 한국주식시장에

• Journal of Broadcast Engineering
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• v.10 no.4 s.29
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• pp.474-487
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• 2005

T-DMB (Terrestrial-Digital Multimedia Broadcasting) adopted MPEG-4 BIFS (Binary Format for Scene) Core2D scene description profile and graphics profile as the standard of video associated data service. By using BIFS, we can support to overlay objects, i.e. text, stationary image, circle, polygon, etc., on the main display of receiving end according to the properties designated in broadcasting side and to make clickable buttons and website links on desired objects. Therefore, a variety of interactive data services can be served by BIFS. In this paper, we implement real-time video associated data service system far T-DMB. Our developing system places emphasis on real-time data service by user operation and on inter-working and stability with our previously developed video encoder. Our system consists of BIFS Real-time System, Automatic Stream Control System and Receiving Monitoring System. Basic functions of our system are designed to reflect T-DMB programs and characteristics of program production environment as a top priority. Our developed system was used in BIFS trial service via KBS T-DMB, it is supposed to be used in T-DMB main service after improvement process such as intensifying system stability.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.3
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• pp.135-143
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• 2016

We investigated the effectiveness of natural zeolite (NZ) and sand (SD) as a capping material to block the release of heavy metals (Cd, Cr, Cu, and Zn) from heavily contaminated marine sediments and stabilize these heavy metals in the sediments. The efficiency of NZ and SD for blocking trace metals was evaluated in a flat flow tank attached with an impeller to generate wave. 0, 10, 30, and 50 mm depth of NZ or SD were capped on the contaminated marine sediments and the metal concentration in seawater was monitored. After completion of flow tank experiments, sequential extractions of the metals in the sediment below the capping material were performed. The difference of pH, EC, and DO concentration between uncapped and capped condition was not significant. The release of cations including Cd, Cu, and Zn were effectively blocked by NZ and SD capping but the interruption of Cr release was observed only in 50 mm depth of SD capped condition. However, the stabilization of Cr in 50 mm depth of SD capped condition was not achieved when compared to uncapped condition. NZ and SD capping were effective for stabilizing Cd, Cu, and Zn in marine sediments. It is concluded that the use of NZ with SD as a capping material is recommended for blocking Cd, Cr, Cu, and Zn release and stabilizing them in contaminated marine sediments.

• Journal of the Korean Geophysical Society
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• v.5 no.3
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• pp.199-209
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• 2002

We have carried out a nondestructive close examination for the purpose of the structural safety diagnosis of the Dabo Pagoda of Bulkuk temple located in Kyungju, Kyungbuk Korea. For estimating the mechanical properties of each rock block of the pagoda, ultrasonic measurements were conducted at 641 points of 255 blocks. The P-wave velocity ranges from 584m/sec through 5,169m/sec, and averages 2,901m/sec Based on this result, the uniaxial compressive strength was estimated to be $93{\sim}1,943kg/cm^2\;with\;396kg/cm^2$ of average, and the index of weathering is $0.07{\sim}0.88$ with 0.43 of average, which means the moderate degree of weathering. The comparison of the rock strength of each block with the overburden acting on the block reveals that the rock blocks related to the structure of the pagoda are relatively sound for uniform stress, but it is highly possible for a concentrated stress to lead to a partial failure. We suggest a monitoring of cracks due to the concentrated stress. The parapets of 1st and 2nd floors composed of small rock pieces are severely weathered. However, this is not directly related to the structural safety of the pagoda.

• Korean Journal of Optics and Photonics
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• v.28 no.6
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• pp.281-289
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• 2017

In the present research, the optical measurement error induced by vibration of the optical measurement tower for large mirrors at KRISS (Korea Research Institute of Standards and Science) is investigated. The vibrations of the tower structure, the interferometer, and the null lens are measured while the surface errors of the 600-mm-diameter on-axis aspheric mirror are measuring, under various environmental conditions. The increase of surface error induced by alignment error with respect to vibration is analyzed. As a result, the interferometer and the null lens, which are located on the top of the tower, are highly sensitive to vibration. Additionally, the surface error of the mirror is strongly increased when the vibration directions of the interferometer and the null lens are different. To reduce the alignment error and the surface error induced by vibration, the tower structure should be improved, to be insensitive to low-frequency vibration. Alternatively, optical measuring under stable conditions by vibration monitoring can improve the reliability of the surface error measurement.

• Korean Journal of Environmental Agriculture
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• v.37 no.1
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• pp.66-72
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• 2018

BACKGROUND: Constructed wetlands are low-cost alternatives for treating domestics sewage. However, previous study has reported that the removal of phosphorus in constructed wetlands was limited. Therefore, a new alternative was needed to extend the life of the constructed wetlands. The purpose of this study was to evaluate the effect of total phosphorus removal by oyster shell on longevity of constructed wetlands for treating domestic sewage. METHODS AND RESULTS: The changes of total phosphorus concentration and treatment efficiency in two constructed wetlands (CWs) classified as system A (coarse sand 100%) and system B (coarse sand 90%+oyster shell 10%) were investigated for 6 years. The actual saturation time of total phosphorus in the systems A and B was estimated to be longer than that of theoretical saturation by adsorption isotherm experiment. In particular, the saturation pattern of phosphorus in system A was maintained at a certain concentration level in the initial stage of operation, and finally saturation was reached as the saturation gradually progressed from the breaking point. In system B, the saturation period of phosphorus was prolonged as compared with system A due to the addition of oyster shells. CONCLUSION: Our results suggest that the longevity of the constructed wetlands can be extended due to the phosphorus saturation by adding the oyster shells to the coarse sands in constructed wetlands.