• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.4
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• pp.323-330
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• 2009

The objective of this research was to develop a practical integrated approach using extracted features from electrical resistance measurements and coupled electromechanical models of damage, for in-situ damage detection and sensing in carbon fiber reinforced plastic(CFRP) composites. To achieve this objective, we introduced specific known damage (in terms of type, size, and location) into CFRP laminates and established quantitative relationships with the electrical resistance measurements. For processing of numerous measurement data, an autonomous data acquisition system was devised. We also established a specimen preparation procedure and a method for electrode setup. Coupon and panel CFRP laminate specimens with several known damage were tested. Coupon specimens with various sizes of artificial delaminations obtained by inserting Teflon film were manufactured and the resistance was measured. The measurement results showed that increase of delamination size led to increase of resistance implying that it is possible to sense the existence and size of delamination. A quasi-isotropic panel was manufactured and electrical resistance was measured. Then three different sizes of holes were drilled at a chosen location. The panel was prepared using the established procedures with six electrode connections on each side making a total of twenty-four electrodes. Vertical, horizontal, and diagonal pairs of electrodes were chosen and the resistance was measured. The measurement results showed the possibility of the established measurement system for an in-situ damage detection method for CFRP composite structures.

• Journal of the Korean Association of Geographic Information Studies
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• v.5 no.2
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• pp.25-33
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• 2002

We were trying to understand indirectly the range of the discharge from the Nakdong with the dispersion of suspended solid(SS) related to the amount of discharge from river in this study. The range of dispersion of SS from the Nakdong was estimated using satellite remote sensing and numerical modeling. The stream field with two dimensional and numerical model using the condition of integrated depth was calculated. According to the results, the streamline flowed from Busan to the Jinhae Bay and Geojae Island. at the flood. The situation at the ebb was totally changed. The streamline flowed out Busan from the Bay. The velocity in offshore was faster than one at coastal water of the Nackdong. Residual current which was averaged during 12hours dominantly appeared the dominant direction from the southwestern part of the Nackdong to the northeastern part of it. The eastward current appeared at the eastern coast of Gaduck Is. Base on the results of the velocity field, the quantifying of the dispersion of SS was estimated by the method of numerical tracer related to the Lagrangian method. The significant range of the dispersion of the SS from the Nackdong was from the eastern coast of Gaduck Is, to the coastal areas of Busan, Korea. The estimated range of the dispersion of the SS using the SeaWiFS and Landsat satellite data was similar to the estimated results using the numerical model.

• Korean Journal of Remote Sensing
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• v.38 no.6_1
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• pp.1505-1514
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• 2022

Image matching is a crucial preprocessing step for effective utilization of multi-temporal and multi-sensor very high resolution (VHR) satellite images. Deep learning (DL) method which is attracting widespread interest has proven to be an efficient approach to measure the similarity between image pairs in quick and accurate manner by extracting complex and detailed features from satellite images. However, Image matching of VHR satellite images remains challenging due to limitations of DL models in which the results are depending on the quantity and quality of training dataset, as well as the difficulty of creating training dataset with VHR satellite images. Therefore, this study examines the feasibility of DL-based method in matching pair extraction which is the most time-consuming process during image registration. This paper also aims to analyze factors that affect the accuracy based on the configuration of training dataset, when developing training dataset from existing multi-sensor VHR image database with bias for DL-based image matching. For this purpose, the generated training dataset were composed of correct matching pairs and incorrect matching pairs by assigning true and false labels to image pairs extracted using a grid-based Scale Invariant Feature Transform (SIFT) algorithm for a total of 12 multi-temporal and multi-sensor VHR images. The Siamese convolutional neural network (SCNN), proposed for matching pair extraction on constructed training dataset, proceeds with model learning and measures similarities by passing two images in parallel to the two identical convolutional neural network structures. The results from this study confirm that data acquired from VHR satellite image database can be used as DL training dataset and indicate the potential to improve efficiency of the matching process by appropriate configuration of multi-sensor images. DL-based image matching techniques using multi-sensor VHR satellite images are expected to replace existing manual-based feature extraction methods based on its stable performance, thus further develop into an integrated DL-based image registration framework.

• Korean Journal of Agricultural and Forest Meteorology
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• v.21 no.4
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• pp.261-268
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• 2019

Climate change and drought stress are having profound impacts on crop growth and development by altering crop physiological processes including photosynthetic activity. But finding a rapid, efficient, and non-destructive method for estimating environmental stress responses in the leaf and canopy is still a difficult issue for remote sensing research. We compared the relationships between photochemical reflectance index(PRI) and various optical and experimental indices on soybean drought stress under climate change conditions. Canopy photosynthesis trait, biomass change, chlorophyll fluorescence(Fv/Fm), stomatal conductance showed significant correlations with midday PRI value across the drought stress period under various climate conditions. In high temperature treatment, PRI were more sensitive to enhanced drought stress, demonstrating the negative effect of the high temperature on the drought stress. But high CO₂ concentration alleviated the midday depression of both photosynthesis and PRI. Although air temperature and CO₂ concentration could affect PRI interpretation and assessment of canopy radiation use efficiency(RUE), PRI was significantly correlated with canopy RUE both under climate change and drought stress conditions, indicating the applicability of PRI for tracking the drought stress responses in soybean. However, it is necessary to develop an integrated model for stress diagnosis using PRI at canopy level by minimizing the influence of physical and physiological factors on PRI and incorporating the effects of other vegetation indices.

• Korean Journal of Remote Sensing
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• v.39 no.5_3
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• pp.997-1008
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• 2023

Ship detection at sea can be performed in various ways. In particular, satellites can provide wide-area surveillance, and Synthetic Aperture Radar (SAR) imagery can be utilized day and night and in all weather conditions. To propose an efficient ship detection method from SAR images, this study aimed to apply the You Only Look Once Version 5 (YOLOv5) model to Sentinel-1 images and to analyze the difference between individual vs. integrated models and the accuracy characteristics by polarization. YOLOv5s, which has fewer and lighter parameters, and YOLOv5x, which has more parameters but higher accuracy, were used for the performance tests (1) by dividing each polarization into HH, HV, VH, and VV, and (2) by using images from all polarizations. All four experiments showed very similar and high accuracy of 0.977 ≤ AP@0.5 ≤ 0.998. This result suggests that the polarization integration model using lightweight YOLO models can be the most effective in terms of real-time system deployment. 19,582 images were used in this experiment. However, if other SAR images,such as Capella and ICEYE, are included in addition to Sentinel-1 images, a more flexible and accurate model for ship detection can be built.

• Journal of Biomedical Engineering Research
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• v.25 no.6
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• pp.599-604
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• 2004

Implantable flexible sensor using polymer/metal multilayer processing technique for telemetrical real-time blood pressure monitoring is presented. The realized sensor is mechanically flexible, which can be less invasively implanted and attached on the outside of blood vessel to monitor the variation of blood pressure. Therefore, unlike conventional detecting methods which install sensor on the inside of vessel, the suggested monitoring method can monitor the relative blood pressure without injuring blood vessel. The major factor of sudden death of adults is a disease of artery like angina pectoris and myocardial infarction. A disease of circulatory system resulted from vessel occlusion by plaque can be preventable and treatable early through continuous blood pressure monitoring. The procedure of suggested new method for monitoring variation of blood pressure is as follows. First, integrated sensor is attached to the outer wall of blood vessel. Second, it detects mechanical contraction and expansion of blood vessel. And then, reader antenna recognizes it using telemetrical method as the relative variation of blood pressure. There are not any active devices in the sensor system; therefore, the transmission of energy and signal depends on the principle of mutual inductance between internal antenna of LC resonator and external antenna of reader. To confirm the feasibility of the sensing mechanism, in vitro experiment using silicone rubber tubing and blood is practiced. First of all, pressure is applied to the silicone tubing which is filled by blood. Then the shift of resonant frequency with the change of applied pressure is measured. The frequency of 2.4 MHz is varied while the applied pressure is changed from 0 to 213.3 kPa. Therefore, the sensitivity of implantable blood pressure is 11.25 kHz/kPa.

• Science of Emotion and Sensibility
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• v.21 no.4
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• pp.63-76
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• 2018

The purpose of this study was to investigate the effect of contact type textile electrode structure on heart activity signal acquisition for smart healthcare. In this study, we devised six contact type textile electrodes whose electrode size and configuration were manipulated for measuring heart activity signals using computerized embroidery. We detected heart activity signals using a modified lead II and by attaching each textile electrode to the chest band in four healthy male subjects in a standing static posture. We measured the signals four times repeatedly for all types of electrodes. The heart activity signals were sampled at 1 kHz using a BIOPAC ECG100, and the detected original signals were filtered through a band-pass filter. To compare the performance of heart activity signal acquisition among the different structures of the textile electrodes, we conducted a qualitative analysis using signal waveform and size as parameters. In addition, we performed a quantitative analysis by calculating signal power ratio (SPR) of the heart activity signals obtained through each electrode. We analyzed differences in the performance of heart activity signal acquisition of the six electrodes by performing difference and post-hoc tests using nonparametric statistic methods on the calculated SPR. The results showed a significant difference both in terms of qualitative and quantitative aspects of heart activity signals among the tested contact type textile electrodes. Regarding the configurations of the contact type textile electrodes, the three-dimensionally inflated electrode (3DIE) was found to obtain better quality signals than the flat electrode. However, regarding the electrode size, no significant difference was found in performance of heart signal acquisition for the three electrode sizes. These results suggest that the configuration method (flat/3DIE), which is one of the two requirements of a contact type textile electrode structure for heart activity signal acquisition, has a critical effect on the performance of heart activity signal acquisition for wearable healthcare. Based on the results of this study, we plan to develop a smart clothing technology that can monitor high-quality heart activity without time and space constraints by implementing a clothing platform integrated with the textile electrode and developing a performance improvement plan.