• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.1029-1032
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• 2008

최근 각 분야에서 연구 및 개발하고 있는 IT 및 자동화 경향이 건설 유지관리에도 전파됨에 따라 유지관리 로봇의 개발과 함께 개발될 비파괴 시스템의 장착이 각광 받을 것으로 예상되고 있다. 토목 구조물의 경우, 이러한 첨단기술의 발전과 더불어 유지관리 측면에서 이러한 첨단기술을 사용하는 것이 적극적으로 고려되고 있다. 그 중 NDT 비파괴 검사방법이 토목구조물의 효율적인 유지관리를 해 적합한 방법으로 사료되고 있다. 본 연구에서는 콘크리트 구조물의 내부결함 탐상을 위해서 초음파 및 레이더 장비가 적용되었으며, 이를 활용하여 실험실 및 현장실험을 통하여 그 적용성을 실험적으로 분석하였다. 실험결과, 초음파 및 레이더 장비는 콘크리트 구조물의 내부결함을 탐상하는데 효과적임으로 분석되었다. 또한 본 연구에서는 실험결과를 바탕으로, 초음파 및 레이더 장비를 적용한 콘크리트 구조물의 유지관리를 위한 알고리즘을 개발 및 제안하였다.

• 한국멀티미디어학회논문지
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• 제18권6호
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• pp.701-709
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• 2015

Image stitching method is a technique for obtaining an high-resolution image by combining two or more images. In X-ray image for clinical diagnosis, the size of the imaging region taken by one shot is limited due to the field-of-view of the equipment. Therefore, in order to obtain a high-resolution image including large regions such as a whole body, the synthesis of multiple X-ray images is required. In this paper, we propose a rapid stitching method of digital X-ray images using template-based registration. The proposed algorithm use principal component analysis(PCA) and k-nearest neighborhood(k-NN) to determine the location of input images before performing a template-based matching. After detecting the overlapping position using template-based matching, we synthesize input images by alpha blending. To improve the computational efficiency, reduced images are used for PCA and k-NN analysis. Experimental results showed that our method was more accurate comparing with the previous method with the improvement of the registration speed. Our stitching method could be usefully applied into the stitching of 2D or 3D multiple images.

• 한국정밀공학회지
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• 제30권8호
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• pp.870-877
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• 2013

There has been much recent research interest in developing numerous kinds of human-machine interface. This field currently requires more accurate and reliable sensing systems to detect the intended human motion. Most conventional human-machine interface use electromyography (EMG) sensors to detect the intended motion. However, EMG sensors have a number of disadvantages and, as a consequence, the human-machine interface is difficult to use. This study describes a muscle volume sensor (MVS) that has been developed to measure variation in the outline of a muscle, for use as a human-machine interface. We developed an algorithm to calibrate the system, and the feasibility of using MVS for detecting muscular activity was demonstrated experimentally. We evaluated the performance of the MVS via isotonic contraction using the KIN-COM$^{(R)}$ equipment at torques of 5, 10, and 15 Nm.

• 조명전기설비학회논문지
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• 제12권3호
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• pp.45-50
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• 1998

본 논문은 기존의 지중배전케이블의 준공시험으로 사용되고 있는 DC시험을 대체 하기 위한 초저주파 전원의 적용결과로서, 실험실에서 제작한 5m 길이의 실제 케이블의 칼흠집 결함과 침결함에 대해 초저주파 전원의 결함검출 능력을 평가하였다. 이 시험에서 초저주파 시험은 케이블 절연체 내부에 존재하는 결함부위에서 전기트리 개시는 어렵지만, 일단 전기트리가 개시되면 트리의 진전이 매우 빠르고 내부결함이 검출되지 않는 경우, 시험으로 인한 새로운 결함이 형성되거나 결함이 더 확대되지 않는 것으로 나타났다. 따라서 초저주파전원은 지중배전선로의 현장시험용으로 적용되기보다는 제조업체의 품질검사 확인용으로 사용하는 것이 효과적이라 판단된다.

• 한국분무공학회지
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• 제12권3호
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• pp.160-165
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• 2007

In this study, the breakup characteristics of mono disperse droplets were studied with various fuels, ethanol, diesel fuel, biodiesel fuel extracted from soybean oil, and pure water. In order to investigate the droplet behavior in air cross-flow conditions, the experimental equipment was composed of a droplet generator with an air nozzle, and a high-magnification photo detecting system. Droplets produced by the droplet generator were injected into the air stream flowing normal to a direction of liquid drop jet. Digital images of the droplet behavior in air flow field were recorded by controlling the air flow rate. From the inspections, droplet breakup mechanism is primarily classified into the two kinds of stage, first breakup stage and second breakup stage. At the first breakup stage, droplet deformation rate seems to be affected by the force induced by the surface tension and the viscosity. On the other hand, at the second breakup stage, droplet is broken up mainly induced by the surface tension, so the breakup transition can be divided by the regular Weber number.

• 지구물리와물리탐사
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• 제7권1호
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• pp.88-92
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• 2004

To improve the recovery rate of unlocated buried human remains in forensic investigations, there is scope to evaluate and develop techniques that are applicable to the Australian environment. I established controlled gravesites (comprising shallow buried kangaroos, pigs, and human cadavers) in South Australia, to allow the methodical testing of remote sensing equipment for the purpose of grave detection in forensic investigations. Eight-month-old pig graves are shown to provide more distinct identifying results using ground-penetrating radar when compared to four-year-old kangaroo graves. Two further aspects of this research are presented: information (obtained from a survey) relating to the police use of geophysical instruments for locating buried human remains, and the use of electrical resistivity for locating human remains buried in a coffin. The survey of Australian police jurisdictions, covering the period 1995-2000, showed that police searches for unlocated bodies have not successfully located human remains using any geophysical instruments (such as ground-penetrating radar, magnetometers, or electrical resistivity). Lower resistivity readings were found coincident with the 150-year-old single historical burial in a heavily excavated field, in a situation where its exact location was previously unknown.

• Journal of Electrical Engineering and Technology
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• 제7권3호
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• pp.389-395
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• 2012

In this paper, we analyzed the frequency spectrum of the electromagnetic waves radiated by an electric discharge as a basic study to develop an on-line diagnostic technique for power equipment installed inside closed-switchboards. In order to simulate local and series arc discharges caused by an electric field concentration and poor connections, three types of electrode systems were fabricated, consisting of needle and plane electrodes and an arc generator meeting the specifications of UL 1699. The experiment was carried out in an electromagnetic anechoic chamber, and the measurement system consisted of a PD free transformer, a loop antenna with a frequency bandwidth of 150 kHz-30 MHz, an ultra log periodic antenna with a frequency bandwidth of 30 MHz-2 GHz, and an EMI test receiver with a frequency bandwidth of 3 Hz-3 GHz. According to the experimental results, the frequency spectra of the electrical discharges were widely distributed across a range of 150 kHz-400 MHz, depending on the defects, while commonly found between 150 kHz and 10 MHz. Therefore, considering the ambient noise and antenna characteristics, the best frequency bandwidth for a measurement system to monitor abnormal conditions by detecting electromagnetic waves in closedswitchboards is 150 kHz-10 MHz.

• Smart Structures and Systems
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• 제30권4호
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• pp.385-395
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• 2022

Detecting cracks on a concrete structure is crucial for structural maintenance, a crack being an indicator of possible damage. Conventional crack detection methods which include visual inspection and non-destructive equipment, are typically limited to a small region and require time-consuming processes. Recently, to reduce the human intervention in the inspections, various researchers have sought computer vision-based crack analyses: One class is filter-based methods, which effectively transforms the image to detect crack edges. The other class is using deep-learning algorithms. For example, convolutional neural networks have shown high precision in identifying cracks in an image. However, when the objective is to classify not only the existence of crack but also the types of cracks, only a few studies have been reported, limiting their practical use. Thus, the presented study develops an image processing procedure that detects cracks and classifies crack types; whether the image contains a crazing-type, single crack, or multiple cracks. The properties and steps in the algorithm have been developed using field-obtained images. Subsequently, the algorithm is validated from additional 227 images obtained from an open database. For test datasets, the proposed algorithm showed accuracy of 92.8% in average. In summary, the developed algorithm can precisely classify crazing-type images, while some single crack images may misclassify into multiple cracks, yielding conservative results. As a result, the successful results of the presented study show potentials of using vision-based technologies for providing crack information with reduced human intervention.

• 비파괴검사학회지
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• 제30권5호
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• pp.464-470
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• 2010

고온, 고압에서 운용되고 있는 설비의 안전성을 평가하기 위해서는 사용시간 동안 열화된 역학물성을 정기적으로 점검하여야 한다. 비파괴적으로 열화된 설비의 역학적 특성을 점검하기 위하여 표면형 프로브(surface type probe)를 사용한 가역투자율 측정방법이 제시된다. 가역투자율 측정방법은 가역투자율이 자기 이력곡선의 미분값임에 근거하고 있다. 가역투자율은 교류 섭동 자기장의 주파수에 동조된 록-인 증폭기로 측정된 탐지코일에 유도된 전압의 제 1 고조파이다 가역투자율의 첨두값은 보자력 영역에서 나타난다. 실험에 사용된 강재는 12Cr 페라이트 내열강으로 $700^{\circ}C$의 등온에서 열처리 시간을 달리한 11개의 시편을 제작하였다. 가역투자율 첨두값 사이의 간격 (peak interval of reversible permeability: PIRP), 비커스 경도 및 인장강도는 열화가 진행됨에 따라 초기에는 급격하게, 후반에는 완만하게 감소하였다. PIRP가 감소함에 따라 인장강도와 비커스 경도가 선형적으로 감소하였고 이 상관관계를 이용하면 측정한 가역투자율로 12Cr 페라이트 내열강의 열화된 역학적 물성을 비파괴적으로 평가할 수 있다.

• 한국물환경학회지
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• 제28권5호
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• pp.729-742
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• 2012

Recently, to using chemical coagulation process for T-P removal in STP effluent as tertiary treatment process is generalized in the country. The importance of analysis technique to save the treatment & maintenance cost during coagulation process is becoming more increased each day. Thus, it is necessary for the analysis technique during coagulation process to be presented well the characteristic of coagulation in field apply. There are a few analysis techniques such as Jar Test, zeta potential analysis and streaming current detecting techniques. But there are difficult to apply in field immediately due to long test time and difficult analysis techniques. And using PDA technique, it is reviewed applicability of the techniques as field index on pilot plant of P-CAP system The P-CAP system is composed of an in-line static mixer, a Flocculation Tank and the CAP reactor with 2 stage weir for effluent. Pre-test is performed to fix the mixing velocity in the Flocculation Tank using the PDA equipment and it fixed with 30RPM. Also, Jar Test is performed to select optimum dose of each coagulant for each T-P concentration level of influent. Result of continuous test on pilot plant of P-CAP system, the FSI in the Flocculation Tank is increased consistently by increasing each dosing concentration of coagulant such as LAS and PAC in the low level influent T-P concentration comparatively. It is considered that formed Al-hydroxide complexes for dosed coagulant are caused FSI variation. Furthermore, it seems that FSI value in the high level influent T-P concentration appeared lower than the opposite influent condition relatively because it is formed simultaneously Al-hydroxide complexes as solid type and Al-phosphorus complexes as soluble type. Thus, relation of FSI by PDA technique and T-P removal of final effluent on pilot plant of P-CAP system are very limited for the kind of coagulant and the characteristics of influent. And it though that FSI value by PDA technique with analyzing of turbidity in Flocculation Tank will be used restrictedly on field as the relative field-index.