• Journal of Korean Society for Atmospheric Environment
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• 제22권E1호
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• pp.1-8
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• 2006

The purpose of this study was to evaluate the efficiency of a passive sampler in measuring atmospheric ammonia concentrations using chamber system. The ability of the passive sampler to quantitatively determine atmospheric ammonia gas was almost identical to that of the reference method (indophenol method). There was no significant difference between concentrations measured by the two methods. The detection and quantification limits of the ammonia passive sampler were 16.9 ppb and 25.3 ppb, respectively, for a 24-h sampling period. The average coefficient of variation between replicated samplers was $6.7{\pm}4.2%$. The concentrations measured by the two methods (passive sampler and indophenol method) were no significant difference with good a correlation (correlation coefficient=0.964).

• 조명전기설비학회논문지
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• 제27권11호
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• pp.27-36
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• 2013

Islanding in a gird connected inverter of wind power generation system may influence a bad effect on equipments or yield safety hazards on grid so it should be detected rapidly and exactly. A passive method to detect islanding is comparatively simpler than an active method but suffers from non detection zone (NDZ). On the other hand, the active method can significantly reduce NDZ by injecting a disturbance into inverter output. To improve the reliability of islanding detection, this paper proposes a hybrid anti-islanding detection method combining the conventional passive method as well as the active method based on novel harmonic injection method using fourier transform. The proposed scheme is fast to detect islanding when NDZ does not exist because it has the nature of passive method. Under NDZ, the active method can detect occurrence of islanding reliably. The effectiveness and validity of the proposed scheme is proved through comparative simulations.

• 한국산업보건학회지
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• 제16권4호
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• pp.346-355
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• 2006

The purpose of this study was conducted to ascertain the difference between impinger and passive sampling methods in the process of sampling and analyzing on airborne formaldehyde. Formaldehyde generating workplaces included in this study comprised four types of manufacturing industry such as two workplaces of products of wood, cork, straw and plaiting materials manufacturing industries, one casting metal manufacturing industry, and one parts and accessories for motor vehicles and it′s engines manufacturing industry. Workplaces contained in this study were located in some manufacturing area of Busan industrial complex and this study was carried out during a period from January 2003 to December 2004. Analytical accuracy, precision and detection limit of two methods was compared. Exposure level of its airborne concentration was evaluated in formaldehyde generating workplaces those were classified by types of industry, working process, and time. The results were as follows ; 1. A rate of recovery was 107.1% in impinger method and 101.8% in passive method, and precision was 7.79% in impinger method and 4.40% in passive method. There was no statistical significance in analytical accuracy and precision between two methods. A limitation of detection was 0.011 ppm in passive method which was lower than that of impinger method (0.020 ppm) by 1.8 times. 2. Airborne formaldehyde concentration of impinger method was different from passive method. It′s concentration by passive method was higher by 5.1 times than that by impinger method in the parts and accessories for motor vehicles and it′s engines manufacturing industry (P<0.05). Only in molding process among several types of processes, formaldehyde concentration in passive method was higher by 5.1 times than that in impinger method (P<0.05). Furthermore, formaldehyde concentration in passive method was higher by 1.7 times than that in impinger method (P<0.05) in the first half of year 2003. 3. The geometric mean of formaldehyde concentration in impinger method was lower than that in passive method, but there was no statistical significance of formaldehyde concentration by the difference of sampling method. In conclusion, it is difficult to conclude which is better between the two sampling methods because of no statistical significance for the difference of concentration. Because of lacks of certified passive sampling and analytical method, at present situation, studies on verification of accuracy and precision, obstructive reaction against validity on its exposure assessment, and research to develop domestically manufactured passive sampler in terms of cost-effectiveness should be continuously carried out.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.159-162
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• 2002

We introduce a simple optically passive detection scheme for Bragg grating sensors. This detection scheme is based on two cavity lengths in Fabry-Perot read-out interferometers to produce two quadrature phase shifted signals from the Bragg grating sensor. The passive detection technique is demonstrated by the use of Bragg grating sensors in measuring the dynamic vibrations of the composites.

• 대한전자공학회논문지SP
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• 제46권4호
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• pp.139-147
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• 2009

이 논문에서는 한 쌍의 수동 광대역 소나로 구성된 병렬구조 분산센서 망에 적용할 수 있는 에너지 인식 분산탐지 체계의 설계 및 성능분석에 대해 검토한다. 이 분산탐지기는 융합규칙으로 AND 규칙과 OR 규칙을 사용하였다. 이 경우 각 센서노드의 문턱값 규칙은 전체 분산센서망의 탐지확률을 최대로 하는 UMP(uniformly most powerful)임을 증명하였다. 그리고 소나 체계에서 오경보에 의해 발생하는 에너지 비용을 제한 조건으로 주었을 때, 탐지확률을 최대화하는 센서노드의 최적 문턱값이 갖는 특성을 이론적으로 검토하였다. 나아가 신호 강도, 에너지 비용에 대한 제한조건, 센서노드 사이의 간격등이 탐지성능에 미치는 영향을 수치실험을 통해 분석하였다.

• 한국음향학회지
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• 제43권1호
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• pp.1-8
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• 2024

수동형 소나의 성능을 측정하기 위해 주어진 환경과 시스템 변수 하에서 보통 최대 탐지거리를 고려한다. 음파가 해표면 또는 해저면과 필연적으로 접촉하는 천해에서는 표적탐지가 최대 탐지거리까지 유지되는 게 일반적이다. 그러나 심해에서는 음파가 해표면 또는 해저면과 접촉하지 않을 수도 있으며, 이 경우 음파가 도달하지 않는 음영구역이 존재할 수도 있다. 이 경우 최대 탐지거리만으로 각 소나의 탐지성능을 완전하게 기술하기 어려울 수 있다. 보다 완전한 탐지성능 기술을 위해 '탐지견고성(Robustness Of Detection, ROD)' 개념을 도입하고자 한다. 동해 연안에서 수괴의 공간적 분포와 최대 탐지거리 및 탐지견고성은 밀접한 관계가 있으며, 최대 탐지거리와 탐지견고성은 서로 반대의 공간적 변동을 보인다. 경험직교함수(Empirical Orthogonal Function, EOF)를 도입하여 수온의 시공간적 분포를 분석한 결과 첫 번째 모드는 전형적인 계절 변화를 보이고, 두 번째 모드는 혼합층 등의 세기 변화를 반영하는 것으로 추정된다. 이 두 모드가 전체 변화의 약 92 %를 설명한다. 수심 5 m와 100 m 표적을 가정하여 수동형 소나의 최대 탐지거리와 두 모드의 계절 변화의 상관관계를 분석하면 첫 두 모드와 높은 음의 상관계수(약 -0.9)를 보인다. 수온의 계절적 변화는 표층 ~ 수심 200 m에서 발생하며, 이에 따라 수심 100 m에 표적이 존재한다고 가정하여 수동소나를 수심 100 m 이상에서 운용할 경우 계절변화가 미미한 탐지성능을 기대할 수 있다.

• 한국대기환경학회지
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• 제22권1호
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• pp.117-126
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• 2006

The purpose of this study is to develop a badge-type passive sampler for the measurement of short-term nitrogen dioxide and to evaluate its performance. The principle of the method is a colorimetric reaction of nitrogen dioxide with sulfanilic acid, N-1-naphthylethylendiamine, and phosphoric acid. First, it has been shown that the filter paper should be rinsed with ultrapure water and ultrasound, and then dried in a vacuumed desiccator. The concentration and volume of absorption reagent (triethanolamine) were $20\%$ and 100 ${\mu}L$, respectively. The extraction time was determined as 60 min. Second, duplicate measurements (n= 116) were carried out for evaluating the precision of the passive sampler. The relative error and the correlation coefficient between duplicates are $3.4\pm 3.0\%$ and 0.994, respectively. In addition, the $95\%$ confidence interval of intraclass correlation coefficient and the estimated value are 0.992$\sim$0.996 and 0.994, respectively. Third, a paired t-test was carried out for evaluating the accuracy of the passive sampler (n=40). In the result of the test, the $95\%$ confidence interval of the difference was -1.710 ppb <$\gamma$< 0.788 ppb. Finally, the average concentration of blanks, measurement detection limit, limit of detection, and limit of quantification are $2.4\pm 0.4$ ppb, 104 ppb, 3.8 ppb, and 7.0 ppb, respectively.

• 한국음향학회지
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• 제36권4호
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• pp.229-237
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• 2017

본 논문에서는 표적이 특정 탐지 빔 공간에 위치하는 동안 신호가 정상성을 유지하는 단기 정상성 개념을 활용한 자동 토널 탐지 기법을 제안 하였으며, 제안 기법의 연산량 감축 기법을 추가 제안하였다. 제안 기법은 신호의 정상성이 유지 되는 시간 동안 단일 빔 신호에서 추정된 문턱값과 입력신호의 기댓값을 비교함으로써 신호에 가변적이면서도 다수 표적에 의한 간섭 소음에 강인한 장점이 있다. 제안 기법의 성능 평가를 위하여 모사 신호 및 실제 해양 신호를 사용하였으며, 실험 결과 제안 기법이 기존 CFAR(Constant False Alarm Rate) 기법에 비하여 성능이 우수함을 확인하였다.

• 한국전자파학회논문지
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• 제27권4호
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• pp.403-406
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• 2016

본 논문에서는 인체 감지용 수동형 마이크로파 센서의 실용화를 위한 소형 수신기의 설계, 제작에 관해 기술한다. 먼저 기존의 5.1 GHz 센서에 의한 인체 감지 측정 실험 데이터를 이용하여 센서 수신기의 요구사항 및 설계 사양을 도출하였으며, 이를 토대로 소형 수신기를 설계, 제작하였다. 제작한 소형 수신기 센서로 실험실에서의 인체 감지 측정 실험 결과, 안테나로부터 4 m 거리에 있는 인체까지 감지가 확인되었다. 제작된 소형 수신기는 기존 수신기에 비해 크기는 약 60 %, 소비전력은 40 % 감소된 소형경량 저소비전력으로 구현함으로써 실용성을 높였다.

• Journal of Information Processing Systems
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• 제14권1호
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• pp.6-31
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• 2018

With the rapid development of the science and technology, it has been becoming more and more convenient to obtain abundant information via the diverse multimedia medium. However, the contents of the multimedia are easily altered with different editing software, and the authenticity and the integrity of multimedia content are under threat. Forensics technology is developed to solve this problem. We focus on reviewing the blind image forensics technologies for copy-move forgery in this survey. Copy-move forgery is one of the most common manners to manipulate images that usually obscure the objects by flat regions or append the objects within the same image. In this paper, two classical models of copy-move forgery are reviewed, and two frameworks of copy-move forgery detection (CMFD) methods are summarized. Then, massive CMFD methods are mainly divided into two types to retrospect the development process of CMFD technologies, including block-based and keypoint-based. Besides, the performance evaluation criterions and the datasets created for evaluating the performance of CMFD methods are also collected in this review. At last, future research directions and conclusions are given to provide beneficial advice for researchers in this field.