• Nuclear Engineering and Technology
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• v.29 no.1
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• pp.45-57
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• 1997

The direct contact condensation phenomenon, which occurs when steam is injected into the subcooled water, has been experimentally investigated. Two plume shapes in the stable condensation regime are found to be conical and ellipsoidal shapes depending on the steam mass flux and the liquid subcooling. Divergent plumes, however, are found when the subcooling is relatively small. The measured expansion ratio of the maximum plume diameter to the injector inner diameter ranges from 1.0 to 2.3. By means of fitting a large amount of measured data, an empirical correlation is obtained to predict the steam plume length as a function of a dimensionless steam mass flux and a driving potential for the condensation process. The average heat transfer coefficient of direct contact condensation has been found to be in the range 1.0~3.5 ㎿/$m^2$.$^{\circ}C$. Present results show that the magnitude of the average condensation heat transfer coefficient depends mainly on the steam mass fin By using dynamic pressure measurements and visual observations, six regimes of direct contact condensation have been identified on a condensation regime map, which are chugging, transition region from chugging to condensation oscillation, condensation oscillation, bubbling condensation oscillation, stable condensation, and interfacial oscillation condensation. The regime boundaries are quite clearly distinguishable except the boundaries of bubbling condensation oscillation and interfacial oscillation condensation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.2
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• pp.771-789
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• 2019

Text detection has been a popular research topic in the field of computer vision. It is difficult for prevalent text detection algorithms to avoid the dependence on datasets. To overcome this problem, we proposed a novel unsupervised text detection algorithm inspired by bootstrap learning. Firstly, the text candidate in a novel form of superpixel is proposed to improve the text recall rate by image segmentation. Secondly, we propose a unique text sample selection model (TSSM) to extract text samples from the current image and eliminate database dependency. Specifically, to improve the precision of samples, we combine maximally stable extremal regions (MSERs) and the saliency map to generate sample reference maps with a double threshold scheme. Finally, a multiple kernel boosting method is developed to generate a strong text classifier by combining multiple single kernel SVMs based on the samples selected from TSSM. Experimental results on standard datasets demonstrate that our text detection method is robust to complex backgrounds and multilingual text and shows stable performance on different standard datasets.

• KIISE Transactions on Computing Practices
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• v.22 no.9
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• pp.419-425
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• 2016

In navigator systems, keeping map data up-to-date is an important task. Manual update involves a substantial cost and it is difficult to achieve immediate reflection of changes with manual updates. In this paper, we present a method for trajectory-center extraction, which is essential for automatic road map generation with GPS data. Though clustered trajectories are necessary to extract the center road, real trajectories are not clustered. To address this problem, this paper proposes a new method using the maximum overlapping interval and trajectory clustering. Finally, we apply the Virtual Running method to extract the center road from the clustered trajectories. We conducted experiments on real massive taxi GPS data sets collected throughout Gang-Nam-Gu, Sung-Nam city and all parts of Seoul city. Experimental results showed that our method is stable and efficient for extracting the center trajectory of real roads.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8C
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• pp.782-789
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• 2009

In this paper, we propose an algorithm for creating stereoscopic video from a monoscopic video. Parallel straight lines in a 3D space get narrower as they are farther from the perspective images on a 2D plane and finally meet at one point that is called a vanishing point. A viewer uses depth perception clues called a vanishing point which is the farthest from a viewer's viewpoint in order to perceive depth information from objects and surroundings thereof to the viewer. The viewer estimates the vanishing point with geometrical features in monoscopic images, and can perceive the depth information with the relationship between the position of the vanishing point and the viewer's viewpoint. In this paper, we propose a method to estimate a vanishing point with edge direction histogram in a general monoscopic image and to create a depth map depending on the position of the vanishing point. With the conversion method proposed through the experimental results, it is seen that stable stereoscopic conversion of a given monoscopic video is achieved.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.10
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• pp.1301-1308
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• 2016

Internet traffic identification is an essential preliminary step for stable service provision and efficient network management. The payload signature-based-classification is considered as a reliable method for Internet traffic identification. But its performance is highly dependent on the number and the structure of signatures. If the numbers and structural complexity of signatures are not proper, the performance of payload signature-based-classification easily deteriorates. Therefore, in order to improve the performance of the identification system, it is necessary to regulate the numbers of the signature. In this paper, we propose a novel signature quality evaluation method to decide which signature is highly efficient for Internet traffic identification. We newly define the signature quality evaluation criteria and find the highly efficient signature through the method. Quality evaluation is performed in three different perspectives and the weight of each signature is computed through those perspectives values. And we construct the signature map(S-MAP) to find the highly efficient signature. The proposed method achieved an approximately fourfold increased efficiency in application traffic identification.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.25 no.4
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• pp.279-287
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• 2007

The increased availability of portable, low-cost, high resolution video equipments have resulted in a rapid growth of the applications for video sequences. These video devices can be mounted in handhold unit, mobile unit and airborne platforms like maned or unmaned helicopter, plane, airship, etc. This paper describes the feasibility fur generating image map from the experimental results we designed to track the interested points extracted by KLT operator in the neighboring frames and implement image matching for each frames taken from UAV (Unmaned Aerial Vehicle). In the image registration for neighbourhood frames of aerial video, the results demonstrate the successful rate of matching slightly decreases as the drift between frames increases, and also that the stable photographing is more important matching condition than the pixel shift.

• Korean Journal of Optics and Photonics
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• v.33 no.6
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• pp.287-294
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• 2022

This study presents a method for designing an athermal middle wavelength infrared (MWIR) zoom lens with the iterative selection of material compositions on an athermal glass map. The optical properties of glass for MWIR are generally very sensitive to temperature, compared with visible glass. To compensate for focus error due to temperature change, the non-athermalized zoom system requires a large amount of movement of a compensator, which results in an unstable zoom system. To solve this problem, the material compositions for an athermal zoom lens have effectively been obtained using the thermal aberration correction process analytically on an athermal glass map. An expander lens is used to enlarge the focal lengths of an original main zoom lens two times. Finally, while this expander is attached to an original athermal zoom system, the final zoom system equipped with this expander doubles the focal length ranges and has stable performance over a specified temperature range.

• The Journal of the Convergence on Culture Technology
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• v.6 no.4
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• pp.797-802
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• 2020

Over the past few years, smart devices, including smartphones, have been continuously required by users based on portability. The performance is improving. Ubiquitous computing environment and sensor network are also improved. Due to various network connection technologies, mobile terminals are widely used. Smart terminals need technology to make energy monitoring more detailed for more stable operation during use. The smart terminal which is light in small size generates the power shortage problem due to the various multimedia task among the terminal operation. Various estimation hardwares have been developed to prevent such situation in advance and to operate stable terminals. However, the method and performance of estimating the remaining amount are not relatively good. In this paper, we propose a method for estimating the remaining amount of smart terminals. The Capacity Estimation of lithium ion cells for stable operation was estimated based on machine learning. Learning the characteristics of lithium ion cells in use, not the existing hardware estimation method, through a map learning algorithm using machine learning technique The optimized results are estimated and applied.

• Proceedings of the IEEK Conference
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• 2001.06c
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• pp.145-148
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• 2001

This paper presents a phase-based stereo matching algorithm in order to efficiently extract 3-dimensional objects from two 2D images. Conventional phase-based methods, especially using windowed Fourier phases, inherit good properties in the cage of hierarchical approaches, because they basically use a multi-resolution phase map. On the contrary, their computational cost is too heavy. Therefore, a fast hierarchical approach, using multi-resolution phase-based strategy and reducing redundancies of phase calculations based on FFT concept is proposed in this paper. In addition, a structural matching algorithm on the phase domain is presented to improve the matching quality. In experimental results. it is shown that the computation loads are considerably reduced about 8 times and stable outputs are obtained from various images.

• Smart Media Journal
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• v.6 no.4
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• pp.32-40
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• 2017

In this paper, a robust text detection method based on edge enhanced contrasting extremal region (CER) is proposed using stroke width transform (SWT) and tensor voting. First, the edge enhanced CER extracts a number of covariant regions, which is a stable connected component from input images. Next, SWT is created by the distance map, which is used to eliminate non-text regions. Then, these candidate text regions are verified based on tensor voting, which uses the input center point in the previous step to compute curve salience values. Finally, the connected component grouping is applied to a cluster closed to characters. The proposed method is evaluated with the ICDAR2003 and ICDAR2013 text detection competition datasets and the experiment results show high accuracy compared to previous methods.