• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.39 no.2
• /
• pp.183-194
• /
• 2011

Synthetic aperture radar (SAR) is widely used because of high resolution imaging capability in all weather and day/night condition. In this paper development of Spotlight SAR simulator is proposed for image quality analysis. Proposed SAR simulator is based on the SAR system design parameters so that SAR image performance can be expected which is essential throughout the full system development procedure from the initial concept design stage to the final in-flight calibration and validation stage. The raw data of ideal point target is first generated by taking account of the flight and imaging geometry and the various SAR system design parameters, and the Spotlight image formation algorithm is implemented in order to obtain the point target response. Finally the image quality of the generated raw data is analyzed in terms of spatial resolution, peak to sidelobe ratio and integrated sidelobe ratio.

• The Journal of the Acoustical Society of Korea
• /
• v.38 no.2
• /
• pp.168-176
• /
• 2019

When an array receives a signal with a frequency higher than the design frequency, there is an ambiguity in beamforming due to spatial aliasing. In order to overcome this problem, Abadi proposed frequency-difference beamforming. However, there is a constraint that the minimum frequency bandwidth is required according to the value of the difference frequency. In this paper, we propose a method to find the direction of the target signal with spatial aliasing based on the frequency-wavenumber spectrum combined with Radon transform. The proposed method can estimate the direction of the target without ambiguities when the signal has nonnegligible bandwidth. We tested the algorithm by simulating a broadband signal and verified the results with the frequency-difference beamforming method using SAVEX15 (Shallow Water Acoustic Variability EXperiment 2015)'s shrimp noise data.

• Journal of the Korean Geotechnical Society
• /
• v.38 no.1
• /
• pp.5-15
• /
• 2022

Due to the Pohang earthquakes in 2017, concerns are increasing that Korea is no longer safe from liquefaction, and needs the research to take proper measures for liquefaction. Liquefaction is defined as the loss of shear strength of the ground. In order to solve this problem, many studies, such as composing a liquefaction hazard map using Liquefaction Potential Index (LPI), have been conducted. However, domestic researches on the comparative analysis of liquefaction prediction results are not sufficient. Therefore, in this study, liquefaction hazard maps were composed using the standard penetration test results, shear wave velocity values, and cone penetration test results. After that, the precision was determined by comparing the calculated LPI using the geotechnical information and predicted LPI via spatial interpolation target. Based on the analysis results, the predicted LPI value using geotechnical information is more precise than using calculated LPI value.

• International conference on construction engineering and project management
• /
• 2022.06a
• /
• pp.877-885
• /
• 2022

Vision-based activity recognition has been widely attempted at construction sites to estimate productivity and enhance workers' health and safety. Previous studies have focused on extracting an individual worker's postural information from sequential image frames for activity recognition. However, various trades of workers perform different tasks with similar postural patterns, which degrades the performance of activity recognition based on postural information. To this end, this research exploited a concept of human-object interaction, the interaction between a worker and their surrounding objects, considering the fact that trade workers interact with a specific object (e.g., working tools or construction materials) relevant to their trades. This research developed an approach to understand the context from sequential image frames based on four features: posture, object, spatial features, and temporal feature. Both posture and object features were used to analyze the interaction between the worker and the target object, and the other two features were used to detect movements from the entire region of image frames in both temporal and spatial domains. The developed approach used convolutional neural networks (CNN) for feature extractors and activity classifiers and long short-term memory (LSTM) was also used as an activity classifier. The developed approach provided an average accuracy of 85.96% for classifying 12 target construction tasks performed by two trades of workers, which was higher than two benchmark models. This experimental result indicated that integrating a concept of the human-object interaction offers great benefits in activity recognition when various trade workers coexist in a scene.

• The Journal of the Acoustical Society of Korea
• /
• v.29 no.8
• /
• pp.476-482
• /
• 2010

The ultrasonic transient fields and B-mode images of a point target which were simulated for a medical ultrasonic probe with a few defective piezo-elements were compared with those for a normal probe. The present study considered a 3.5 MHz linear array probe whose acoustic beam was formed by the 64 active elements of total 192 elements. The results showed that the maximum amplitude and -3 dB width of the acoustic fields by main-lobes decreased linearly as the defective element number increased from one to four. However, the depths of foci remained almost unchanged, and the pressure differences between main-lobes and side-lobes tended to decrease due to rise in pressures in side-lobes. Such changes in ultrasonic fields affected the B-mode images of point targets. So the artifacts were formed in the right and left side of the target, and the lateral spatial resolutions were decreased while the axial resolution was almost the same.

• Journal of KIISE:Software and Applications
• /
• v.27 no.5
• /
• pp.551-562
• /
• 2000

Content-based image retrieval system retrieves an image from a database using visual features. Among approaches to express visual aspects in queries, 'query by sketch' is most convenient and expressive. However, every 'query by sketch' system has the query imperfectness problem. GContent-based image retrieval system retrieves an image from a database using visual features. Among approaches to express visual aspects in queries, 'query by sketch' is most convenient and expressive. However, every 'query by sketch' system has the query imperfectness problem. Generally, the query image produced by a user is different from the intended target image. To overcome this problem, many image retrieval systems use the spatial relationships of the objects, instead of pixel coordinates of the objects. In this paper, a query-converting algorithm for an image retrieval system, which uses the spatial relationship of every two objects as an image feature, is proposed. The proposed algorithm converts the query image into a graph that has the minimum number of edges, by eliminating every transitive edge. Since each edge in the graph represents the spatial relationship of two objects, the elimination of unnecessary edges makes the retrieval process more efficient. Experimental results show that the proposed algorithm leads the smaller number of comparison in searching process as compared with other algorithms that do not guarantee the minimum number of edges.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.49 no.9
• /
• pp.347-352
• /
• 2012

In this paper, an 2D spatial-map construction for workers identification and avoidance of AGV using the detection scheme of the spatial coordinates based on stereo camera is proposed. In the proposed system, face area of a moving person is detected from a left image among the stereo image pairs by using the YCbCr color model and its center coordinates are computed by using the centroid method and then using these data, the stereo camera embedded on the mobile robot can be controlled for tracking the moving target in real-time. Moreover, using the disparity map obtained from the left and right images captured by the tracking-controlled stereo camera system and the perspective transformation between a 3-D scene and an image plane, depth map can be detected. From some experiments on AGV driving with 240 frames of the stereo images, it is analyzed that error ratio between the calculated and measured values of the worker's width is found to be very low value of 2.19% and 1.52% on average.

• Progress in Medical Physics
• /
• v.8 no.2
• /
• pp.19-26
• /
• 1997

3-dimensional Neuronavigator, Viewing Wand(ISG Technologies, Toronto, Cannda) is the surgery aid equipment for real time image (CT or MRI) guided surgery. The assurance of spatial accuracy of this system is important for clinical application. In this study, we have designed the acrylic brain phantom and measured the spatial error with that phantom. The phantom has designed to have capability to simulate image guided surgery. The phantom has 22 vertical rods whose diameters are 5mm and each rods has different length. CT scans were performed by 2.0mm slice and reconstructed for 3-Dimensional analysis. End point of rods can be obtained using reconstructed 3- Dimensional images and they are compared to actual position data. Average deviation was less than 2mm for various situations. Spatial error of Viewing Wand is acceptable in the clinical points of view, while cosmetics of the software needs to be modified to more user friend. Better accuracy can be expected when we apply the mixed fiducial fit registration and surface fit registration method. And even better results can be obtained if registration points distributed even and symetric around the target.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.16 no.1
• /
• pp.171-180
• /
• 2013

As the second-largest 1st degree of ecological zone in Kangwon Province, Pyeongchang County is expected to play an important role in expanding the protected areas of the Republic of Korea. However, Pyoungchang County is expected to experience an increase in demand for development due to the 2018 Winter Olympics. Problems related to various stakeholders and limited budget will arise regarding the issue of expanding the protected areas. In this study, in order to effectively control these problems, we designed expansion plans for the 1st degree ecological zoning map areas and the observed data of threatened species I and II in Pyoungchang County by using the MARXAN Software. As for the methods, we first set the planning units(PUs) for the spatial analysis. The PUs include boundary length, land cost, land status, etc. Then, we made the input data by controlling the conservation features, BLM(Boundary Length Modifier) and iteration numbers. There are two measures for the establishment of the protected areas, one of which only concerns with the ecological priority, and the other with combining the land cost on forest. The one illustrated shows that the larger patches that include the conservation feature was selected as a candidate of the protected areas. The other one presented shows that inexpensive land cost areas were selected. As this study produces visual results and enables an efficient application of various values in selecting protected areas, we believe that it will be useful to various stakeholders in spatial decision-making process.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.31 no.2D
• /
• pp.335-342
• /
• 2011

Geotechnical Information which had been constructing and offering by Minister of Land, Transport and Maritime Affairs (MLTM) has been target on the whole of country. Today, the 100,000 number of geotechnical data has been managed as 2d GIS database. But, it is difficult to apply this database for analyzing and designing geotechnical works. In this paper, we have developed Geotechnical Information Application System (GIAS) based 3d geo-spatial information technique for the effective uses. First, GIAS based on GIS framework was implemented to effectively find out spatial geologic structure of study area. Second, we invited some experts from each field and listened their opinions. According to the surveying on the applicability-ratio, the experts showed higher interest in this system. In this study, it was verified that the 3d GIS-based system was very useful for the usability-ratio.