• 한국가시화정보학회:학술대회논문집
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• 2002.11a
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• pp.7-10
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• 2002

A novel two-phase PIV algorithm using a single camera has been proposed, which introduces a method of image-separation into respective phase images, and is applied to freely rising single bubble. Gas bubble, tracer particle and background each have different gray intensity ranges on the same image frame when reflection and dispersion in the phase interface are intrinsically eliminated by optical filters and fluorescent material. Further, the signals of the two phases do not interfere with each other. Gas phase velocities are obtained from the separated bubble image by applying the two-frame PTV. On the other hand, liquid phase velocities are obtained from the tracer particle image by applying the cross-correlation algorithm. Moreover, in order to increase the SNR (signal-to-noise ratio) of the cross-correlation of tracer particle image, image enhancement is employed.

• The Journal of the Korea Contents Association
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• v.21 no.5
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• pp.1-10
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• 2021

This study empirically confirmed 'the political bias of the YouTube recommendation algorithm' and 'the selective exposure of user' to verify the Filter Bubble phenomenon of YouTube. For the experiment, two new YouTube accounts were opened and each account was trained simultaneously in a conservative and a liberal account for a week, and the "Recommended" videos were collected from each account every two days. Subsequently, through the text mining method, the goal of the research was to investigate whether conservative videos are more recommended in a righties account or lefties videos are more recommended in a lefties account. And then, this study examined if users who consumed political news videos via YouTube showed "selective exposure" received selected information according to their political orientation through a survey. As a result of the Text Mining, conservative videos are more recommended in the righties account, and liberal videos are more recommended in the lefties account. Additionally, most of the videos recommended in the righties/lefties account dealt with politically biased topics, and the topics covered in each account showed markedly definitive differences. And about 77% of the respondents showed selective exposure.

• KIPS Transactions on Software and Data Engineering
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• v.3 no.6
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• pp.231-236
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• 2014

The transit time of contrast agents and the parameters of time-intensity curves in ultrasonography are important factors to diagnose various diseases of a digestive organ. We have implemented an automatic parametric imaging method to overcome the difficulty of the diagnosis by naked eyes. However, the micro-bubble noise and the respiratory motions may degrade the reliability of the parameter images. In this paper, we introduce an optimization technique based on MRF(Markov Random Field) model to enhance the quality of the parameter images, and present an image tracking algorithm to compensate the image distortion by respiratory motions. A method to extract the respiration periods from the ultrasound image sequence has been developed. We have implemented the ROI(Region of Interest) tracking algorithm using the dynamic weights and a momentum factor based on these periods. An energy function is defined for the Gibbs sampler of the image enhancement method. Through the experiments using the data to diagnose liver lesions, we have shown that the proposed method improves the quality of the parametric images.

• Journal of the Korean Ceramic Society
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• v.47 no.3
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• pp.232-236
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• 2010

In recent years abrasive water jet (AWJ) has received significant attention as a technology used in the manufacturing industry for cutting materials. In this paper we report the development of a new preparation method of abrasives for water jet by using an air bubbling sedimentation rate control technique. The SiC abrasives prepared by an air bubbling sedimentation rate control technique using latex resin are found to be superior to the conventional abrasives not only in surface roughness uniformity but also in lifetime. The AWJ test results also show that the former has also better impact-resistance and wear-resistance than the latter.

• JOURNAL OF ELECTRICAL WORLD
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• s.262
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• pp.76-81
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• 1998

수배전설비의 발전은 각종 법령이 정비된 1950년대부터 시작하여 고도경제성장, 오일쇼크, 버블경기를 거쳐 오늘에 이르고 있다. ''90년대에 들어 계측$\cdot$감시$\cdot$제어분야는 하드웨어가 소형계산기와 데이터전송의 조합으로 바뀌면서 동시에 정보관리 기능이 부가된 형태로 발전되었으며, 이를 포괄하여 수배전 시스템이라 부르게 되었다. 수배전시스템은 각 시대마다 여러 가지 사회상황의 영향을 받으며 발전하여 왔다. 오늘날에 와서는 고조파억제, 내진설계, 온난화대책 등이 특히 클로즈업되어 앞으로의 방향에 대한 검토와 제품화가 진행되고 있다. 21세기를 앞둔 오늘날 수배전시스템에 요구되는 니즈는 ''전력공급의 신뢰성 향상'', ''자에너지'', 자인력'', ''자자원$\cdot$지구온난화 방지''로 대별되고 있다. 아울러 부하의 중요도나 경제성 등을 감안하여 다양해지고 있는 시스템에 대응하기 위해서는 보다 고도화된 범용성의 엔지니어링 기법과 설계에 의한 수배전시스템으로 더욱 진전될 것으로 기대되고 있다.

• 한국가시화정보학회:학술대회논문집
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• 2002.11a
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• pp.31-34
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• 2002

Imaging techniques using x-ray beam at high energies (>6KeV) such as contact radiography, projection microscopy, and tomography have been used to nondestructively discern internal structure of objects in material science, biology, and medicine. This paper introduces the x-ray micro-imaging method using 1B2 micro-probe line of PAL (Pohang Accelerator Laboratory). Cross-sectional information on low electron density materials can be obtained by probing a sample with coherent synchrotron x-ray beam in an in-line holography setup. Living organism such as plants, insects are practically transparent to high energy x-rays and create phase shift images of x-ray wave front. X-ray micro-images of micro-bubbles of $20\~120\;{\mu}m$ diameter in an opaque tube were recorded. Clear phase contrast images were obtained at Interfaces between bubbles and surrounding liquid due to different decrements of refractive index.

• Journal of KIISE
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• v.42 no.7
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• pp.910-918
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• 2015

This paper presents a parameter visualization technique to overcome the limitation of the naked eye in contrast-enhanced ultrasonography. A method is also proposed to compensate for the distortion and noise in ultrasound image sequences. Meaningful parameters for diagnosing liver disease can be extracted from the dynamic patterns of the contrast enhancement in ultrasound images. The visualization technique can provide more accurate information by generating a parametric image from the dynamic data. Respiratory motions and noise from micro-bubble in ultrasound data may cause a degradation of the reliability of the diagnostic parameters. A multi-stage algorithm for respiratory motion tracking and an image enhancement technique based on the Markov Random Field are proposed. The usefulness of the proposed methods is empirically discussed through experiments by using a set of clinical data.

• Geophysics and Geophysical Exploration
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• v.13 no.4
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• pp.336-348
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• 2010

The Single-channel seismic survey with the source of bubble pulser and drilling survey was carried out in 2008 and 2009 for the site survey of Daecheon-Wonsando area, which was a proposed area of Korea-China subsea tunnel. The goal of this study is to analyze the depth and characteristics of acoustic basement for the stability assessment and tunnel design in this proposed area through combining drilling data with this single-channel seismic data after detailed processing. For this purpose, among the data processing schemes which are usually applied to multi-channel seismic data, we applied the F-K filtering to eliminate the AC(alternating current) noise and the post-stack depth migration to produce depth section. As a result, we verified that the improved depth section could be obtained from single-channel seismic data, and the distribution and characteristics of basement could be analyzed in survey area through the combined analysis with drilling data. However, we could not interpret the detailed structures, fault and fracture zone, due to the quality of bubble pulser source and single-channel data. We expect that those detailed structures can be analyzed when higher resolution seismic data is provided. Therefore, we recommend some items for future seismic survey of subsea tunnel to obtain the high resolution seismic data.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.4
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• pp.85-94
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• 2003

The asynchronous design methods proved to have the higher performance in power consumption and execution speed than synchronous ones because it just needs to activate the required module without feeding clock in the system. Despite the advantage of CISC machine providing the variable addressing modes and instructions, its execution scheme is hardly suited for a synchronous Pipeline architecture and incurs a lot of overhead. This paper proposes a novel asynchronous pipeline architecture, A80sl, whose instruction set is fully compatible with that of Intel 80C51, an embedded micro controller. We classify the instructions into the group keeping the same execution scheme for the asynchronous pipeline and optimize it eliminating the bubble stage that comes from the overhead of the multi-cycle execution. The new methodologies for branch and various instruction lengths are suggested to minimize the number of states required for instructions execution and to increase its parallelism. The proposed A80C51 architecture is synthesized with 0.35${\mu}{\textrm}{m}$ CMOS standard cell library. The simulation results show higher speed than that of Intel 80C51 with 36 MHz and other asynchronous counterparts by 24 times.

• KIPS Transactions on Software and Data Engineering
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• v.4 no.7
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• pp.297-300
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• 2015

In medical ultrasonography, transit time and contrast enhancement patterns are considered as important parameters to analyze liver diseases. In many recent researches, time-intensity curves(TIC) have been used for calculating the transit time of the contrast agents. However, the intensity curve may include the variations which are caused by the micro-bubble effect of contrast agents. In this paper, we propose a complementary approach to diagnostic parameter extraction which utilizes a density information as well as the intensity data. The proposed technique improves the accuracy in extraction of the transit time and velocity of contrast agents for detection and characterization of focal liver lesions. Through the experiments using a set of clinical data, we show that the proposed methods can improve the reliability of the parametric image data.