• Proceedings of the KIPE Conference
• /
• 2004.07a
• /
• pp.92-96
• /
• 2004

Islanding of PV systems can cause a variety of problems and must be prevented. However, if the real and active powers of RLC load and PV system are closely matched, islanding detection by passive methods becomes difficult. Active methods enables islanding detection by forcing the frequency of the voltage in the island to drift up/down. This paper shows the simulation and comparision by Matlab for the active methods.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2014.11a
• /
• pp.520-522
• /
• 2014

Due to the availability of easy-to-use and powerful image editing tools, the authentication of digital images cannot be taken for granted and it gives rise to non-intrusive forgery detection problem because all imaging devices do not embed watermark. Forgery detection plays an important role in this case. In this paper, an effective framework for passive-blind method for copy-move image forgery detection is proposed, based on Gabor filter which is robust to illumination, rotation invariant, robust to scale. For the detection, the suspicious image is selected and Gabor wavelet is applied from whole scale space and whole direction space. We will extract the mean and the standard deviation as the texture features and feature vectors. Finally, a distance is calculated between two textures feature vectors to determine the forgery, and the decision will be made based on that result.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.19 no.4
• /
• pp.443-452
• /
• 2016

Current low-altitude radar system often fails to detect small unmanned aerial vehicles (UAV) because of their small radar cross section (RCS) compared with larger targets. As a potential alternative, a passive bistatic radar system has been considered. We study an optimal deployment problem for the passive bistatic radar system. We model this problem as a covering problem, and develop an integer programming model. The objective of the model is to maximize coverage of a passive bistatic radar system. Our model takes into account factors specific to a bistatic radar system, including bistatic RCS and transmitter-receiver pair coverage. Considering bistatic RCS instead of constant RCS is important because the slight difference of RCS value for small UAVs could significantly influence the detection probability. The paired radar coverage is defined by using the concept of gradual coverage and cooperative coverage to represent a realistic environment.

• Journal of Conservation Science
• /
• v.29 no.1
• /
• pp.55-67
• /
• 2013

This study focused on analysis condition and application method of the passive infrared thermography according to the direction and time to nondestructively detect the blistering zone of stone cultural heritage. As a result, the passive thermographic images showed different temperature characteristics by time because it sensitively reacts to air temperature, insolation and sunshine direction. In particular, the insolation and sunshine direction, which are periodically changed from 6:00 to 17:00, irregularly made surface temperature. In addition, surface temperature differences were brought on fresh zones and blistering zones except specific time since blistering causes erratic thermal transfer. As a result of examining the detection characteristics of blistering by time, the blistering was well detected between 9:00 and 10:00 when there was rapid increase in air temperature and insolation in all direction except the north. However, this study isn't considered effects of four seasons because it is carried out in autumn, and the passive thermography has difficulty to analyze the quantitative area of blistering zone. Therefore, an additional study for synthetic consideration of the passive thermography analysis about four seasons and quantitative modeling of blistering zone using the active thermography are needed.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.6C
• /
• pp.349-354
• /
• 2011

Passive millimeter wave imaging has the capability of detecting concealed objects under clothing. Also, passive millimeter imaging can obtain interpretable images under low visibility conditions like rain, fog, smoke, and dust. However, the image quality is often degraded due to low spatial resolution, low signal level, and low temperature resolution. This paper addresses image registration and fusion between passive millimeter images and visual images. The goal of this study is to combine and visualize two different types of information together: human subject's identity and concealed objects. The image registration process is composed of body boundary detection and an affine transform maximizing cross-correlation coefficients of two edge images. The image fusion process comprises three stages: discrete wavelet transform for image decomposition, a fusion rule for merging the coefficients, and the inverse transform for image synthesis. In the experiments, various types of metallic and non-metallic objects such as a knife, gel or liquid type beauty aids and a phone are detected by passive millimeter wave imaging. The registration and fusion process can visualize the meaningful information from two different types of sensors.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.32 no.4
• /
• pp.359-370
• /
• 2022

Objective: This study is intended to design a commercially available passive sampler and conduct performance test on its use as a media for evaluating a working environment. Methods: This study was conducted to select adsorbents, design models, and evaluate storage stability and sampling rates for the development of new types of passive samplers. Results: The impurity detection, adsorbent capacity and breakthrough volume of five types of activated carbon were tested for selection of an adsorbent. One product was selected in consideration of the efficiency of purchase. A number of passive samplers were designed in a radial style and a badge style using plastic as a material. The final two prototypes were made using molds or 3D printing. For the storage stability evaluation, samples were stored at different temperature for 1~21 days and then analyzed. Most of the chemicals had excellent storage stability when refrigerated. However, some chemicals such as dichloromethane and methyl ethyl ketone need to be analyzed as soon as possible after sampling. Conclusion: In this study, new types of passive samplers for 66 chemical compounds were developed. The evaluation of storage stability and sampling rates showed different results depending on the properties of the chemical substance. For some chemicals such as methyl ethyl ketone and dimethylformamide, activated carbon is inappropriate as an absorbent. In future studies, additional experiments are required on chemicals that are difficult to collect with activated carbon.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2011.06a
• /
• pp.123-124
• /
• 2011

• ETRI Journal
• /
• v.35 no.1
• /
• pp.80-88
• /
• 2013

A passive infrared or pyroelectric infrared (PIR) sensor is mainly used to sense the existence of moving objects in an indoor environment. However, in an outdoor environment, there are often outbreaks of false alarms from environmental changes and other sources. Therefore, it is difficult to provide reliable detection outdoors. In this paper, two algorithms are proposed to reduce false alarms and provide trustworthy quality to surveillance systems. We gather PIR signals outdoors, analyze the collected data, and extract the target features defined as window energy and alarm duration. Using these features, we model target and false alarms, from which we propose two target decision algorithms: window energy detection and alarm duration detection. Simulation results using real PIR signals show the performance of the proposed algorithms.

• Journal of the Korean Society for Precision Engineering
• /
• v.25 no.2
• /
• pp.65-71
• /
• 2008

In this paper, we propose a new driving mode control algorithm for a mobile robot based on obstacle detection. The robot has a variable geometry single-tracked mechanism, so it can maximize a contact length with ground for the adaptability to off-road and puesue a stable system due to the lower center of gravity. However this robot system embodied passive type according to operator. In this reason, several problems are detected. So, this research presents a new method of obstacle detection using PSD infrared sensors and translates the variable tracks on the best suited driving mode actively. And experimental results about mentioned are presented.

• Convergence Security Journal
• /
• v.5 no.3
• /
• pp.33-41
• /
• 2005

Information can be leaked, changed, damaged and illegally used regardless of the intension of the information owner. Intrusion Detection Systems and Firewalls are used to protect the illegal accesses in the network. But these are the passive protection method, not the active protection method. They only react based on the predefined protection rules or only report to the administrator. In this paper, we develop the intrusion detection and protection system using Netfilter framework. The system makes the administrator's management easy and simple. Furthermore, it offers active protection mechanism against the intrusions.