• Journal of Korean Society for Atmospheric Environment
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• v.22 no.E1
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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).

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.11
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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.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.16 no.4
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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.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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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.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.4
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• pp.139-147
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• 2009

In this paper, optimum design of energy-aware distributed detection is considered for a parallel sensor network system consisting of a fusion center and two passive sonar nodes. AND rule and OR rule are employed as the fusion rules of the sensor network. For the fusion rules, it is shown that a threshold rule of each sensor node has uniformly most powerful properties. Optimum threshold for each sensor is investigated that maximizes the probability of detection under a constraint on energy consumption due to false alarms. It is also investigated through numerical experiments how signal strength, an energy constraint, and the distance between two sensor nodes affect the system detection performances.

• The Journal of the Acoustical Society of Korea
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• v.43 no.1
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• pp.1-8
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• 2024

For measuring the performance of passive sonars, we usually consider the maximum Detection Range (DR) under the environment and system parameters in operation. In shallow water, where sound waves inevitably interacts with sea surface or bottom, detection generally maintains up to the maximum range. In deep water, however, sound waves may not interact with sea surface or/and bottom, and thus there may exist shadow zones where sound waves can hardly reach. In this situation, DR alone may not completely define the performance of each sonar. For complete description of sonar performance, we employ the concept 'Robustness Of Detection (ROD)'. In the coastal region of the East Sea, the spatial variations of water masses have close relations with DR and ROD, where the two parameters show reverse spatial variations in general. The spatial and temporal analysis of the temperature by employing the Empirical Orthogonal Function (EOF) shows that the 1-st mode represents typical pattern of seasonal variation and the 2-nd mode represents strength variations of mixed layers and currents. The two modes are estimated to explain about 92 % of the variations. Assuming two types of targets located at the depths of 5 m (shallow) and 100 m (deep), the passive sonar performance (DR) gives high negative correlations (about -0.9) with the first two modes. Most of temporal variations of temperature occur from the surface up to 200 m in the water column so that when we assume a target at 100 m, we can expect detection performance of little seasonal variations with passive sonars below 100 m.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.1
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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.

• The Journal of the Acoustical Society of Korea
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• v.36 no.4
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• pp.229-237
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• 2017

In this paper we propose an auto tonal detection method which exploits short term stationary when targets located in a detection beam area and then additional methods are proposed in order to reduce the computational complexity of the proposed method. The proposed method is adaptive to input signals and robust against interference caused by multiple targets because it compares an expected value of input signals with a threshold value which are estimated from a single beam while signals are keep stationary. The performances of the proposed methods are evaluated using by simulated data and acquired data from real ocean. The proposed method has shown better performance than conventional CFAR (Constant False Alarm Rate) methods.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.4
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• pp.403-406
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• 2016

This paper presents the design and implementation of the small size receiver to put a passive microwave sensor for human body detection to practical use. The requirements and specifications of the sensor receiver are drawn using the experimental data of human body detection by the existing sensor operated at 5.1 GHz. The small size sensor receiver to satisfy the drawn specifications is designed and implemented. The effectiveness of the fabricated sensor with small size receiver on human body detection is demonstrated experimentally in laboratory. The results show the sensor can detect human body to within 4 m distance from the antenna. The size and power consumption of the small size receiver are decreased to 60 % and 40 % compared to those of the existing receiver, respectively.

• Journal of Information Processing Systems
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• v.14 no.1
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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.