• Title/Summary/Keyword: detection technique

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Baseline-Free Crack Detection in Steel Structures using Lamb Waves and PZT Polarity (램파와 압전소자 극성을 사용한 강구조의 실시간 균열손상 감지기법 개발)

  • Sohn, Hoon;Kim, Seung-Bum
    • Journal of the Earthquake Engineering Society of Korea
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    • v.10 no.6 s.52
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    • pp.79-91
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    • 2006
  • A new methodology of guided wave based nondestructive testing (NDT) is developed to detect crack damage in civil infrastructures such as steel bridges without using prior baseline data. In conventional guided wave based techniques, damage is often identified by comparing the "current" data obtained from a potentially damaged condition of a structure with the "past" baseline data collected at the pristine condition of the structure. However, it has been reported that this type of pattern comparison with the baseline data can lead to increased false alarms due to its susceptibility to varying operational and environmental conditions of the structure. To develop a more robust damage diagnosis technique, a new concept of NDT is conceived so that cracks can be detected without direct comparison with previously obtained baseline data. The proposed NDT technique utilizes the polarization characteristics of the piezoelectric wafers attached on the both sides of the thin metal structure. Crack formation creates Lamb wave mode conversion due to a sudden change in the thickness of the structure. Then, the proposed technique instantly detects the appearance of the crack by extracting this mode conversion from the measured Lamb waves even at the presence of changing operational and environmental conditions. Numerical and experimental results are presented to demonstrate the applicability of the proposed technique to crack detection.

A Signal Detection Technique for OFDMA-based Wireless Mesh Networks with Different Time Delays (서로 다른 지연 시간을 갖는 OFDMA 기반의 Wireless Mesh Networks를 위한 신호 검출 기법)

  • Park, Chang-Hwan;Yoo, Hyun-Il;Kim, Yeong-Jun;Kwon, Dong-Seung;Cho, Yong-Soo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.6C
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    • pp.495-505
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    • 2010
  • In this paper, the effect of Near-Far Problem (NFP) among distributed nodes in OFDMA-based Wireless Mesh Networks (WMNs) is analyzed by investigating statistical characteristics of Time Difference of Arrival (TDoA) and Desired-to-Undesired power Ratio (DUR). In order to overcome the effects of Inter-Symbol Interference (ISI), Inter-Carrier Interference (ICI), and Inter Link Interference (ILI), caused by TDoA in WMNs, we derive effective SINR for each subcarrier, and then, propose the optimal starting point of FFT window which can minimize BER for each subcarrier. In addition, we propose a subcarrier-based Zero Forcing - 2 Dimensional Ordered Successive Interference Cancellation (ZF-2DOSIC) technique for signal detection in WMNs with TDoA. It is verified by simulation that the effective SINR and uncoded BER performances of the proposed signal detection technique for OFDMA-based WMNs are significantly improved, compared with those of conventional technique.

Design of Efficient Gradient Orientation Bin and Weight Calculation Circuit for HOG Feature Calculation (HOG 특징 연산에 적용하기 위한 효율적인 기울기 방향 bin 및 가중치 연산 회로 설계)

  • Kim, Soojin;Cho, Kyeongsoon
    • Journal of the Institute of Electronics and Information Engineers
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    • v.51 no.11
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    • pp.66-72
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    • 2014
  • Histogram of oriented gradient (HOG) feature is widely used in vision-based pedestrian detection. The interpolation is the most important technique in HOG feature calculation to provide high detection rate. In interpolation technique of HOG feature calculation, two nearest orientation bins to gradient orientation for each pixel and the corresponding weights are required. In this paper, therefore, an efficient gradient orientation bin and weight calculation circuit for HOG feature is proposed. In the proposed circuit, pre-calculated values are defined in tables to avoid the operations of tangent function and division, and the size of tables is minimized by utilizing the characteristics of tangent function and weights for each gradient orientation. Pipeline architecture is adopted to the proposed circuit to accelerate the processing speed, and orientation bins and the corresponding weights for each pixel are calculated in two clock cycles by applying efficient coarse and fine search schemes. Since the proposed circuit calculates gradient orientation for each pixel with the interval of $1^{\circ}$ and determines both orientation bins and weights required in interpolation technique, it can be utilized in HOG feature calculation to support interpolation technique to provide high detection rate.

Multi-Time Window Feature Extraction Technique for Anger Detection in Gait Data

  • Beom Kwon;Taegeun Oh
    • Journal of the Korea Society of Computer and Information
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    • v.28 no.4
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    • pp.41-51
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    • 2023
  • In this paper, we propose a technique of multi-time window feature extraction for anger detection in gait data. In the previous gait-based emotion recognition methods, the pedestrian's stride, time taken for one stride, walking speed, and forward tilt angles of the neck and thorax are calculated. Then, minimum, mean, and maximum values are calculated for the entire interval to use them as features. However, each feature does not always change uniformly over the entire interval but sometimes changes locally. Therefore, we propose a multi-time window feature extraction technique that can extract both global and local features, from long-term to short-term. In addition, we also propose an ensemble model that consists of multiple classifiers. Each classifier is trained with features extracted from different multi-time windows. To verify the effectiveness of the proposed feature extraction technique and ensemble model, a public three-dimensional gait dataset was used. The simulation results demonstrate that the proposed ensemble model achieves the best performance compared to machine learning models trained with existing feature extraction techniques for four performance evaluation metrics.

Comparison of Change Detection Accuracy based on VHR images Corresponding to the Fusion Estimation Indexes (융합평가 지수에 따른 고해상도 위성영상 기반 변화탐지 정확도의 비교평가)

  • Wang, Biao;Choi, Seok Geun;Choi, Jae Wan;Yang, Sung Chul;Byun, Young Gi;Park, Kyeong Sik
    • Journal of Korean Society for Geospatial Information Science
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    • v.21 no.2
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    • pp.63-69
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    • 2013
  • Change detection technique is essential to various applications of Very High-Resolution(VHR) satellite imagery and land monitoring. However, change detection accuracy of VHR satellite imagery can be decreased due to various geometrical dissimilarity. In this paper, the existing fusion evaluation indexes were revised and applied to improve VHR imagery based change detection accuracy between multi-temporal images. In addition, appropriate change detection methodology of VHR images are proposed through comparison of general change detection algorithm with cross-sharpened image based change detection algorithm. For these purpose, ERGAS, UIQI and SAM, which were representative fusion evaluation index, were applied to unsupervised change detection, and then, these were compared with CVA based change detection result. Methodologies for minimizing the geometrical error of change detection algorithm are analyzed through evaluation of change detection accuracy corresponding to image fusion method, also. The experimental results are shown that change detection accuracy based on ERGAS index by using cross-sharpened images is higher than these based on other estimation index by using general fused image.

A Review of Change Detection Techniques using Multi-temporal Synthetic Aperture Radar Images (다중시기 위성 레이더 영상을 활용한 변화탐지 기술 리뷰)

  • Baek, Won-Kyung;Jung, Hyung-Sup
    • Korean Journal of Remote Sensing
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    • v.35 no.5_1
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    • pp.737-750
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    • 2019
  • Information of target changes in inaccessible areas is very important in terms of national security. Fast and accurate change detection of targets is very important to respond quickly. Spaceborne synthetic aperture radar can acquire images with high accuracy regardless of weather conditions and solar altitude. With the recent increase in the number of SAR satellites, it is possible to acquire images with less than one day temporal resolution for the same area. This advantage greatly increases the availability of change detection for inaccessible areas. Commonly available information in satellite SAR is amplitude and phase information, and change detection techniques have been developed based on each technology. Those are amplitude Change Detection (ACD), Coherence Change Detection (CCD). Each algorithm differs in the preprocessing process for accurate automatic classification technique according to the difference of information characteristics and the final detection result of each algorithm. Therefore, by analyzing the academic research trends for ACD and CCD, each technologies can be complemented. The goal of this paper is identifying current issues of SAR change detection techniques by collecting research papers. This study would help to find the prerequisites for SAR change detection and use it to conduct periodic detection research on inaccessible areas.

Face Detection based on Pupil Color Distribution Maps with the Frequency under the Illumination Variance (빈도수를 고려한 눈동자색 분포맵에 기반한 조명 변화에 강건한 얼굴 검출 방법)

  • Cho, Han-Soo
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.9 no.5
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    • pp.225-232
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    • 2009
  • In this paper, a new face detection method based on pupil color distribution maps with the frequency under the illumination variance is proposed. Face-like regions are first extracted by applying skin color distribution maps to a color image and then, they are reduced by using the standard deviation of chrominance components. In order to search for eye candidates effectively, the proposed method extracts eye-like regions from face-like regions by using pupil color distribution maps. Furthermore, the proposed method is able to detect eyes very well by segmenting the eye-like regions, based on a lighting compensation technique and a segmentation algorithm even though face regions are changed into dark-tone due to varying illumination conditions. Eye candidates are then detected by means of template matching method. Finally, face regions are detected by using the evaluation values of two eye candidates and a mouth. Experimental results show that the proposed method can achieve a high performance.

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The Real-Time Detection of the Malicious JavaScript (실시간으로 악성 스크립트를 탐지하는 기술)

  • Choo, Hyun-Lock;Jung, Jong-Hun;Kim, Hwan-Kuk
    • Journal of Internet Computing and Services
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    • v.16 no.4
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    • pp.51-59
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    • 2015
  • JavaScript is a popular technique for activating static HTML. JavaScript has drawn more attention following the introduction of HTML5 Standard. In proportion to JavaScript's growing importance, attacks (ex. DDos, Information leak using its function) become more dangerous. Since these attacks do not create a trail, whether the JavaScript code is malicious or not must be decided. The real attack action is completed while the browser runs the JavaScript code. For these reasons, there is a need for a real-time classification and determination technique for malicious JavaScript. This paper proposes the Analysis Engine for detecting malicious JavaScript by adopting the requirements above. The analysis engine performs static analysis using signature-based detection and dynamic analysis using behavior-based detection. Static analysis can detect malicious JavaScript code, whereas dynamic analysis can detect the action of the JavaScript code.

A Tunable Band-Pass Filter for Multi Bio-Signal Detection (대역폭 조정 가능한 다중 생체 신호 처리용 대역 통과 필터 설계)

  • Jeong, Byeong-Ho;Lim, Shin-Il;Woo, Deok-Ha
    • Journal of IKEEE
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    • v.15 no.1
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    • pp.57-63
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    • 2011
  • This paper presents a tunable band pass filter (BPF) for multi bio-signal detection. The bandwidth can be controlled by the bias current of transconductance (gm), while conventional BPF exploited switchable capacitor array for band selection. With this design technique, the die area of proposed BPF reduced to at least one tenth the area of conventional design. The simulation results show the high cut-off frequency tuning range of from 100Hz to 1Khz. The circuit was implemented with a 0.18um CMOS standard technology. Total current consumption is 1uA at the supply voltage of 1V with sub-threshold design technique.

Analysis of Detection Ability Impact of Clang Static Analysis Tool by Source Code Obfuscation Technique (소스 코드 난독화 기법에 의한 Clang 정적 분석 도구의 성능 영향 분석)

  • Jin, Hongjoo;Park, Moon Chan;Lee, Dong Hoon
    • Journal of the Korea Institute of Information Security & Cryptology
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    • v.28 no.3
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    • pp.605-615
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    • 2018
  • Due to the rapid growth of the Internet of Things market, the use of the C/C++ language, which is the most widely used language in embedded systems, is also increasing. To improve the quality of code in the C/C++ language and reduce development costs, it is better to use static analysis, a software verification technique that can be performed in the first half of the software development life cycle. Many programs use static analysis to verify software safety and many static analysis tools are being used and studied. In this paper, we use Clang static analysis tool to check security weakness detection performance of verified test code. In addition, we compared the static analysis results of the test codes applied with the source obfuscation techniques, layout obfuscation, data obfuscation, and control flow obfuscation techniques, and the static analysis results of the original test codes, Analyze the detection ability impact of the Clang static analysis tool.