• 한국멀티미디어학회논문지
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• 제20권1호
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• pp.10-16
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• 2017

This paper proposes efficient schemes for image segmentation using the region-based active contour model. The developed methods can approach the boundaries of the desired objects by evolving the curves through minimization of the Mumford-Shah energy functionals, given arbitrary curves as initial conditions. Topological changes such as splitting or merging of curves should be handled for the methods to work properly without prior knowledge of the number of objects to be segmented. This paper introduces how to change topological structure of the curves and shows experimental results by applying the methods to the images.

• 융합신호처리학회 학술대회논문집
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• 한국신호처리시스템학회 2000년도 하계종합학술대회논문집
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• pp.225-228
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• 2000

본 논문에서는 물체의 경계나 형태 추출을 위하여 레벨 세트 이론을 바탕으로 한 새로운 곡선 전개 방법을 제안한다. 특히 전처리 과정에서 잡음의 효과적 처리를 위하여 기존의 필터 방식들이 가지는 단점인 경계 부분의 blurring 현상을 줄이고 정확한 에지 위치를 보존할 수 있는 비등방성 확산필터(anisotropic diffusion filter)를 사용한다. 기존의 레벨 세트 방식이 수축이나 팽창 중 단지 한가지의 방식만 적용되어지는 반면, 제안한 방법은 물체의 경계 추출시 팽창과 수축이 동시에 가능하므로 특히 초기 곡선이 여러 물체에 걸쳐져 있는 경우에도 정확한 형태 추출이 가능하였다. 아울러 초기 곡선의 설정이 위치나 형태에 거의 제한을 받지 않기 때문에 추출을 원하는 영역이 아주 조금만 포함되어 있어도 정확한 형태 추출이 가능하였다.

• 디지털산업정보학회논문지
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• 제17권4호
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• pp.43-52
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• 2021

IoT applications are quickly spread in many fields. Blockchain methods(BC), defined as a distributed sharing mechanism, offer excellent support for IoT evolution. The BC provides a secure way for communication between IoT devices. However, the IoT environments are threatened by hacker attacks and malicious intrusions. The IoT applications security are faced with three challenges: intrusions and attacks detection, secure communication, and compressed storage information. This paper proposed a system based on double-blockchain to improve the communication transactions' safety and enhance the information compression method for the stored data. Information security is enhanced by using an Ellipse Curve Cryptography(ECC) considered in a double-blockchain case. The data compression is ensured by the Compressed Sensing(CS) method. The conducted experimentation reveals that the proposed method is more accurate in security and storage performance than previous related works.

• International Journal of Computer Science & Network Security
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• 제21권6호
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• pp.119-126
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• 2021

The Internet of Things (IoT) applications are quickly spread in many fields. Blockchain methods (BC), defined as a distributed sharing mechanism, offer excellent support for IoT evolution. The BC provides a secure way for communication between IoT devices. However, the IoT environments are threatened by hacker attacks and malicious intrusions. The IoT applications security are faced with three challenges: intrusions and attacks detection, secure communication, and compressed storage information. This paper proposed a system based on double-blockchain to improve the communication transactions' safety and enhance the information compression method for the stored data. Information security is enhanced by using an Ellipse Curve Cryptography (ECC) considered in a double-blockchain case. The data compression is ensured by the Compressed Sensing (CS) method. The conducted experimentation reveals that the proposed method is more accurate in security and storage performance than previous related works.

• Nuclear Engineering and Technology
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• 제54권10호
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• pp.3595-3603
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• 2022

Nuclear safety-class DCS is used for nuclear reactor protection function, which is one of the key facilities to ensure nuclear power plant safety, the maintenance for DCS to keep system in a high reliability is significant. In this paper, Nuclear safety-class DCS system developed by the Nuclear Power Institute of China is investigated, the model of reliability estimation considering nuclear power plant emergency trip control process is carried out using Markov transfer process. According to the System-Subgroup-Module hierarchical iteration calculation, the evolution curve of failure probability is established, and the preventive maintenance optimization strategy is constructed combining reliability numerical calculation and periodic overhaul interval of nuclear power plant, which could provide a quantitative basis for the maintenance decision of DCS system.

• 천문학회지
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• 제29권spc1호
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• pp.63-64
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• 1996

The nature of distant faint blue field galaxies remains a mystery, despite the fact that much attention has been devoted to this subject in the last decade. Galaxy counts, particularly those in the optical and near ultraviolet bandpasses, have been demonstrated to be well in excess of those expected in the 'no-evolution' scenario. This has usually been taken to imply that galaxies were brighter in the past, presumably due to a higher rate of star formation. More recently, redshift surveys of galaxies as faint as B$\~$24 have shown that the mean redshift of faint blue galaxies is lower than that predicted by standard evolutionary models (de-signed to fit the galaxy counts). The galaxy number count data and redshift data suggest that evolutionary effects are most prominent at the faint end of the galaxy luminosity function. While these data constrain the form of evolution of the overall luminosity function, they do not constrain evolution in individual galaxies. We are carrying out a series of observations as part of a long-term program aimed at a better understanding of the nature and amount of luminosity evolution in individual galaxies. Our study uses the luminosity-linewidth relation (Tully-Fisher relation) for disk galaxies as a tool to study luminosity evolution. Several studies of a related nature are being carried out by other groups. A specific experiment to test a 'no-evolution' hypothesis is presented here. We have used the AUTOFIB multifibre spectro-graph on the 4-metre Anglo-Australian Telescope (AAT) and the Rutgers Fabry-Perot imager on the Cerro Tolalo lnteramerican Observatory (CTIO) 4-metre tele-scope to measure the internal kinematics of a representative sample of faint blue field galaxies in the red-shift range z = 0.15-0.4. The emission line profiles of [OII] and [OIII] in a typical sample galaxy are significantly broader than the instrumental resolution (100-120 km $s^{-l}$), and it is possible to make a reliable de-termination of the linewidth. Detailed and realistic simulations based on the properties of nearby, low-luminosity spirals are used to convert the measured linewidth into an estimate of the characteristic rotation speed, making statistical corrections for the effects of inclination, non-uniform distribution of ionized gas, rotation curve shape, finite fibre aperture, etc.. The (corrected) mean characteristic rotation speed for our distant galaxy sample is compared to the mean rotation speed of local galaxies of comparable blue luminosity and colour. The typical galaxy in our distant sample has a B-band luminosity of about 0.25 L$\ast$ and a colour that corresponds to the Sb-Sd/Im range of Hub-ble types. Details of the AUTOFIB fibre spectroscopic study are described by Rix et al. (1996). Follow-up deep near infrared imaging with the 10-metre Keck tele-scope+ NIRC combination and high angular resolution imaging with the Hubble Space Telescope's WFPC2 are being used to determine the structural and orientation parameters of galaxies on an individual basis. This information is being combined with the spatially resolved CTIO Fabry-Perot data to study the internal kinematics of distant galaxies (Ing et al. 1996). The two main questions addressed by these (preliminary studies) are: 1. Do galaxies of a given luminosity and colour have the same characteristic rotation speed in the distant and local Universe? The distant galaxies in our AUTOFIB sample have a mean characteristic rotation speed of $\~$70 km $s^{-l}$ after correction for measurement bias (Fig. 1); this is inconsistent with the characteristic rotation speed of local galaxies of comparable photometric proper-ties (105 km $s^{-l}$) at the > $99\%$ significance level (Fig. 2). A straightforward explanation for this discrepancy is that faint blue galaxies were about 1-1.5 mag brighter (in the B band) at z $\~$ 0.25 than their present-day counterparts. 2. What is the nature of the internal kinematics of faint field galaxies? The linewidths of these faint galaxies appear to be dominated by the global disk rotation. The larger galaxies in our sample are about 2"-.5" in diameter so one can get direct insight into the nature of their internal velocity field from the $\~$ I" seeing CTIO Fabry-Perot data. A montage of Fabry-Perot data is shown in Fig. 3. The linewidths are too large (by. $5\sigma$) to be caused by turbulence in giant HII regions.

• 한국광학회지
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• 제13권3호
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• pp.215-222
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• 2002

광기록매체용 Ge-Sb-Te다층박막 성장과정을 in-situ 타원계를 사용하여 실시간으로 모니터하여 각 층의 두께를 제어하고 성장된 Ge-Sb-Te 다층박막을 ex-site 분광타원법으로 확인하였다. 보호층인 ZnS-SiO$_2$와 기록층인 Ge$_2$Sb$_2$Te$_{5}$을 단결정실리콘 기층 위에 스퍼터링 방법으로 각각 성장시키면서 구한 타원상수 성장곡선을 분석하여 성장에 따르는 보호층의 균일성 및 기록 층의 밀도변화를 파악하고 이를 기초로 하여 Ge-Sb-Te광기록 다층박막의 두께를 정밀하게 제어하였다. Ge$_2$Sb$_2$Te$_{5}$ 단층박막 시료의 복소굴절율은 eX-Situ 분광타원분석을 통하여 구하였다. 제작된 다층구조는 설정된 다층구조인 ZnS-SiO$_2$(1400$\AA$)$\mid$ GST(200 $\AA$)$\mid$ZnS-SiO$_2$(200$\AA$)와 각 층의 두께 및 전체 두께에서 1.5% 이내에서 일치하는 정확도를 보여주었다.주었다.

• Investigative Magnetic Resonance Imaging
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• 제17권4호
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• pp.267-274
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• 2013

목적: 뇌경색의 시기판단에 있어서 현성확산계수 지도의 부가적인 임상적 중요성을 다시 평가하기 위하여, 확산 강조영상과 현성확산계수 지도에서 뇌경색의 시간경과에 따른 변화 양상의 차이가 있는지 알고자 한다. 대상과 방법: 뇌경색 환자 127명의 199회 자기공명영상 검사를 대상으로 하였으며, 시간을 기준으로(117 검사), 날짜를 기준으로 (108 검사), 주수를 기준으로 (62 검사) 그룹을 나누었다. 확산 강조영상과 현성확산계수 지도에서 뇌경색의 중심부와 대측부위를 관심영역 0.3 $cm^2$ 이상으로 하여 신호 강도를 측정하여, 경색부위/대측정상부위의 비 (ratio)를 구하여 각 그룹에서 시간 경과에 따른 변화양상을 비교관찰하였다. 결과: 뇌경색은 발생 1시간 이내부터 영상에서 관찰되었으며, 확산강조영상에서 신호강도비는 12시간 이후에 2 이상으로 되어 6일까지 유지되다가 점차 감소하여 발생 30일경에 1로 감소 하였다. 현성확산계수비는 발생 24시간에 0.46 이었으며, 15일경에 1로 증가하였다. 뇌경색의 시간 경과에 따른 비의 곡선은 서로 역의 관계인 대칭적인 양상을 보였다. 결론: 확산강조영상과 현성확산계수 지도에서 뇌경색의 시간경과에 따른 변화양상은 역의 관계로서 현성확산계수 값은 확산강조영상으로부터 예측 가능하며, 현성확산계수 지도는 확산강조영상과 함께 판단하면 15-30일 사이의 아급성기 뇌경색의 진단에 도움이 될 수 있을 것이다.

• Geomechanics and Engineering
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• 제7권5호
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• pp.569-587
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• 2014

Triaxial compression creep tests were performed on salt rock samples using cyclic confining pressure with a static axial pressure. The test results show that, up to a certain time, changes in the confining pressure have little influence on creep properties of salt rock, and the axial creep curve is smooth. After this point, the axial creep curve clearly fluctuates with the confining pressure, and is approximately a straight line both when the confining pressure decreases and when it increases within one cycle period. The slope of these lines differs: it is greater when the confining pressure decreases than when it increases. In accordance with rheology model theory, axial creep equations were deduced for Maxwell and Kelvin models under cyclic loading. These were combined to establish an axial creep equation for the Burgers model. We supposed that damage evolution follows an exponential law during creep process and replaced the apparent stress in creep equation for the Burgers model with the effective stress, the axial creep damage equation for the Burgers model was obtained. The model suitability was verified using creep test results for salt rock. The fitting curves are in excellent agreement with the test curves, so the proposed model can well reflect the creep behavior of salt rock under low-frequency cyclic loading. In particular, it reflects the fluctuations in creep deformation and creep rate as the confining pressure increasing and decreasing under different cycle periods.

• 대한기계학회논문집B
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• 제27권3호
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• pp.275-285
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• 2003

A visualization study on the effect of forcing amplitude in tone-excited jet diffusion flames has been conducted. Visualization techniques are employed using optical schemes. which are a light scattering photography. Flame stability curve is attained according to Reynolds number and forcing amplitude at a fuel tube resonant frequency. Flame behavior is globally grouped into two from attached flame to blown-out flame according to forcing amplitude: one sticks the tradition flame behavior which has been observed in general jet diffusion flames and the other shows a variety of flame modes such as the flame of a feeble forcing amplitude where traditionally well-organized vortex motion evolves, a fat flame. an elongated flame. and an in-burning flame. Particular attention is focused on an elongation flame. which is associated with a turnabout phenomenon of vortex motion and on a reversal of the direction of vortex roll-up. It is found that the flame length with forcing amplitude is the direct outcome of the evolution process of the formed inner flow structure. Especially the negative part of the acoustic cycle under the influence of a strong negative pressure gradient causes the shapes of the fuel stem and fuel branch part and even the direction of vortex roll-up to dramatically change.