• Journal of ILASS-Korea
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• 제1권3호
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• pp.51-59
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• 1996

An experiment was carried out on the structure of twin spray from pressurize-swirl nozzles, in order to investigate the effect of different size of spray nozzles on the characteristics of the overlap of two single sprays, for example, mean diameter, number density, and spatial distribution of flow rate. Using image processing method, the distributions of size and velocity of droplets of a single spray and twin spray were measured and compared to investigate the overlapping effect of two identical sprays. Comparing experimental results from a twin-spray with those from two-single sprays shows that the flow rate distribution of the twin-spray was concentrated around the midst of the overlapping region of two sprays. In this region, Sauter mean diameter (SMD) did not change much in the twin spray from 6032 nozzles, but it was smaller by 10 micrometers in the twin-spray than two-single sprays from 60063 nozzles. In spite of large difference in Weber numbers of the colliding sprays between the 60063 and 6032 nozzles, the phenomena did not have a big change in the overlapping region of twin spray. This shows that in the collision between droplets from two single spray in the overlapping region to cause the disruption of droplets, the size distribution of spray droplets was also important as well as Weber number.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제4권5호
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• pp.1157-1163
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• 2000

In this paper, we present a novel and practical stereo vision system that uses only one camera and four mirrors placed in front of the camera. The equivalent of a stereo pair of images are formed as left and right halves of a single CCD image by using four mirrors placed in front of the ten of a CCD camera. An object arbitrary point in 3D space is transformed into two virtual points by the four mirrors. As in the conventional stereo system, the displacement between the two conjugate image points of the two virtual points is directly related to the depth of the object point. This system has the following advantages over traditional two camera stereo that identical system parameters, easy calibration and easy acquisition of stereo data.

• Journal of Institute of Control, Robotics and Systems
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• 제19권6호
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• pp.547-554
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• 2013

This paper proposes a novel formation algorithm of identical robots based on object tracking method using omni-directional images obtained through fisheye lenses which are mounted on the robots. Conventional formation methods of multi-robots often use stereo vision system or vision system with reflector instead of general purpose camera which has small angle of view to enlarge view angle of camera. In addition, to make up the lack of image information on the environment, robots share the information on their positions through communication. The proposed system estimates the region of robots using SURF in fisheye images that have $360^{\circ}$ of image information without merging images. The whole system controls formation of robots based on moving directions and velocities of robots which can be obtained by applying Lucas-Kanade Optical Flow Estimation for the estimated region of robots. We confirmed the reliability of the proposed formation control strategy for multi-robots through both simulation and experiment.

• Journal of the Optical Society of Korea
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• 제20권3호
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• pp.358-362
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• 2016

We present a new scheme for optical encryption of a binary image. In our method, the original binary data page is first divided into two identical pages. In each data page, the “on” and “off” pixels are represented by two discrete phases that are 90° apart. The first page corresponds to the phase conjugation of the second page, and vice versa. In addition, the wavefront of the two data pages is changed simultaneously from planar to spherical, for better encryption. The wavefront modification is represented by an extra phase shift, which is a function of position on the wavefront. In this way the two separate pages are both encrypted, and therefore the pages cannot be distinguished in a CCD. If the first page is used as an encrypted data page, then the second page is used as the decryption key, and vice versa. The decryption can be done by simply combining the two encrypted data pages. It is shown in our experiment that encryption and decryption can be fully accomplished in the optical domain.

• Journal of the Institute of Electronics Engineers of Korea SP
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• 제48권1호
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• pp.23-32
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• 2011

In this paper, we develop a method for generating thumbnail images at hybrid domain combined the spatial domain and transform domain. The proposed method generates a pixel of a thumbnail image by adding a DC value of residual transform coefficients and an average value of an estimate block. For effectively calculating average values of estimate blocks, we propose a method for reconstructing the boundary pixels of a block. In comparison to the conventional method of decoding the bit stream then scaling down the decoded images, the developed method reduces the complexity by more than 60% while producing identical thumbnail images.

• Journal of the Korea Institute of Military Science and Technology
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• 제24권1호
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• pp.12-21
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• 2021

For successful automatic target recognition(ATR) with synthetic aperture radar(SAR) imagery, SAR target images of the database should have the identical or highly similar resolution with those collected from SAR sensors. However, it is time-consuming or infeasible to construct the multiple databases with different resolutions depending on the operating SAR system. In this paper, an approach for resolution conversion of SAR target images is proposed based on conditional generative adversarial network(cGAN). First, a number of pairs consisting of SAR target images with two different resolutions are obtained via SAR simulation and then used to train the cGAN model. Finally, the model generates the SAR target image whose resolution is converted from the original one. The similarity analysis is performed to validate reliability of the generated images. The cGAN model is further applied to measured MSTAR SAR target images in order to estimate its potential for real application.

• Applied Microscopy
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• 제50권
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• pp.23.1-23.9
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• 2020

We propose an effective deep learning model to denoise scanning transmission electron microscopy (STEM) image series, named Noise2Atom, to map images from a source domain 𝓢 to a target domain 𝓒, where 𝓢 is for our noisy experimental dataset, and 𝓒 is for the desired clear atomic images. Noise2Atom uses two external networks to apply additional constraints from the domain knowledge. This model requires no signal prior, no noise model estimation, and no paired training images. The only assumption is that the inputs are acquired with identical experimental configurations. To evaluate the restoration performance of our model, as it is impossible to obtain ground truth for our experimental dataset, we propose consecutive structural similarity (CSS) for image quality assessment, based on the fact that the structures remain much the same as the previous frame(s) within small scan intervals. We demonstrate the superiority of our model by providing evaluation in terms of CSS and visual quality on different experimental datasets.

• Spatial Information Research
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• 제19권5호
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• pp.1-11
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• 2011

This study mainly focused on the method of accurately extracting damage information in the im agery change detection process using the constructed high resolution aerial im agery. Bongwha-gun in Gyungsangbuk-do which had been severely damaged from a localized torrential downpour at the end of July, 2008 was selected as study area. This study utilized aerial im agery having photographing scale of 30cm gray image of pre-disaster and 40cm color image of post-disaster. In order to correct errors from the differences of the image resolution of pre-/post-disaster and time series, the prelim inary phase of image processing techniques such as normalizing, contrast enhancement and equalizing were applied to reduce errors. The extent of the damage was calculated using one to one comparison of the intensity of each pixel of pre-/post-disaster im aged. In this step, threshold values which facilitate to extract the extent that damage investigator wants were applied by setting difference values of the intensity of pixel of pre-/post-disaster. The accuracy of optimal image processing and the result of threshold values were verified using the error matrix. The results of the study enabled the early exaction of the extents of the damages using the aerial imagery with identical characteristics. It was also possible to apply to various damage items for imagery change detection in case of utilizing multi-band im agery. Furthermore, more quantitative estimation of the dam ages would be possible with the use of numerous GIS layers such as land cover and cadastral maps.

• Journal of Korean Society for Geospatial Information Science
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• 제21권2호
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• pp.93-98
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• 2013

Multi-temporal high resolution satellite images are essential data for efficient city analysis and monitoring. Yet even when acquired from the same location, identical sensors as well as different sensors, these multi-temporal images have a geometric inconsistency. Matching points between images, therefore, must be extracted to match the images. With images of an urban area, however, it is difficult to extract matching points accurately because buildings, trees, bridges, and other artificial objects cause shadows over a wide area, which have different intensities and directions in multi-temporal images. In this study, we analyze a shadow effect on image matching of high resolution satellite images in urban area using Scale-Invariant Feature Transform(SIFT), the representative matching points extraction method, and automatic shadow extraction method. The shadow segments are extracted using spatial and spectral attributes derived from the image segmentation. Also, we consider information of shadow adjacency with the building edge buffer. SIFT matching points extracted from shadow segments are eliminated from matching point pairs and then image matching is performed. Finally, we evaluate the quality of matching points and image matching results, visually and quantitatively, for the analysis of shadow effect on image matching of high resolution satellite image.

• Journal of Korean Neurosurgical Society
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• 제29권8호
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• pp.1098-1102
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• 2000

Pituitary abscess is a very rare disorder, since antibiotics therapy has become widely available. Clinically and radiologically, the preoperative diagnosis of pituitary abscess is difficult because of its features which may be identical to those of any space-occupying lesions of the sella turcica. A combination of clinical features, such as meningitis, paranasal sinusitis and panhypopituitarism with intrasellar cystic lesion with homogeneous ring enhancement on computed tomography or magnetic resonance image should raise the suspicion of a pituitary abscess. Drainage of the abscess through trans-sphenoidal approach, appropriate antibiotics therapy, endocrine assessment and hormonal replacement should bring complete recovery to the patient. The authors review the literature and report two cases of primary pituitary abscess.