• 천문학회지
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• 제49권4호
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• pp.123-126
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• 2016

Microlensing is generally thought to probe planetary systems only out to a few Einstein radii. Microlensing events generated by bound planets beyond about 10 Einstein radii generally do not yield any trace of their hosts, and so would be classified as free floating planets (FFPs). I show that it is already possible, using adaptive optics (AO), to constrain the presence of potential hosts to FFP candidates at separations comparable to the Oort Cloud. With next-generation telescopes, planets at Kuiper-Belt separations can be probed. Next generation telescopes will also permit routine vetting for all FFP candidates, simply by obtaining second epochs 4-8 years after the event. At present, the search for such hosts is restricted to within the "confusion limit" of θ_confus ∼ 0.25′′, but future WFIRST (Wide Field Infrared Survey Telescope) observations will allow one to probe beyond this confusion limit as well.

• Macromolecular Research
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• 제14권2호
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• pp.155-165
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• 2006

The present article describes the experimental and theoretical observations on the formation of holographic, polymer-dispersed, liquid crystals and electrically switchable, photonic crystals. A phase diagram of the starting mixture of nematic liquid crystal and photo-reactive triacrylate monomer was established by means of differential scanning calorimetry (DSC) and cloud point measurement. Photolithographic patterns were imprinted on the starting mixture of LC/triacrylate via multi-beam interference. A similar study was extended to a dendrimer/photocurative mixture as well as to a single component system (tetra-acrylate). Theoretical modeling and numerical simulation were carried out based on the combination of Flory-Huggins free energy of mixing and Maier-Saupe free energy of nematic ordering. The combined free energy densities were incorporated into the time-dependent Ginzburg-Landau (Model C) equations coupled with the photopolymerization rate equation to elucidate the spatio-temporal structure growth. The 2-D photonic structures thus simulated were consistent with the experimental observations. Furthermore, 3-D simulation was performed to guide the fabrication of assorted photonic crystals under various beam-geometries. Electro-optical performance such as diffraction efficiency was evaluated during the pattern photopolymerization process and also as a function of driving voltage.

• 대기
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• 제21권4호
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• pp.429-438
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• 2011

The climatology of surface UV radiation for Seoul, presented in Cho et al. (1998; 2001), has been updated using measurement of surface erythemal ultraviolet (EUV) and total ultraviolet (TUV) irradiance (wavelength 286.5~363.0 nm) by a Brewer Spectrophotometer (MK-IV) for the period 2004~2010. The analysis was also carried out together with the broadband total (global) solar irradiance (TR ; 305~2800 nm) and cloud amount to compare with the UV variations, measured by Seoul meteorological station of Korean Meteorological Agency located near the present study site. Under all-sky conditions, the day-to-day variability of EUV exhibits annual mean of 98% in increase and 31% in decrease. It has been also shown that the EUV variability is 17 times as high as the total ozone in positive change, whereas this is 6 times higher in negative change. Thus, the day to day variability is dominantly caused rather by the daily synoptic situations than by the ozone variability. Annual mean value of daily EUV and TUV shows $1.62kJm^{-2}$ and $0.63MJm^{-2}$ respectively, whereas mean value of TR is $12.4MJm^{-2}$ ($143.1Wm^{-2}$). The yearly maximum in noon-time UV Index (UVI) varies between 9 and 11 depending on time of year. The highest UVI shows 11 on 20 July, 2008 during the period 2004~2010, but for the period 1994~2000, the index of 12 was recorded on 13 July, 1994 (Cho et al., 2001). A 40% of daily maximum UVI belongs to "low (UVI < 2)", whereas the UVI less than 5% of the maximum show "very high (8 < UVI < 10)". On average, the maximum UVI exceeded 8 on 9 days per year. The values of Tropospheric Emission Monitoring Internet Service (TEMIS) EUV and UVI under cloud-free conditions are 1.8 times and 1.5 times, respectively, higher than the all-sky measurements by the Brewer. The trend analysis in fractional deviation of monthly UV from the reference value shows a decrease of -0.83% and -0.90% $decade^{-1}$ in the EUV and TUV, respectively, whereas the TR trend is near zero (+0.11% $decade^{-1}$). The trend is statistically significant except for TR trend (p = 0.279). It is possible that the recent UV decrease is mainly associated with increase in total ozone, but the trend in TR can be attributed to the other parameters such as clouds except the ozone. Certainly, the cloud effects suggest that the reason for the differences between UV and TR trends can be explained. In order to estimate cloud effects, the EUV, TUV and TR irradiances have been also evaluated for clear skies (cloud cover < 25%) and cloudy skies (cloud cover ${\geq}$ 75%). Annual mean values show that EUV, TUV and TR are $2.15kJm^{-2}$, $0.83MJm^{-2}$, and $17.9MJm^{-2}$ for clear skies, and $1.24kJm^{-2}$, $0.46MJm^{-2}$, and $7.2MJm^{-2}$ for cloudy skies, respectively. As results, the transmission of radiation through clouds under cloudy-sky conditions is observed to be 58%, 55% and 40% for EUV, TUV and TR, respectively. Consequently, it is clear that the cloud effects on EUV and TUV are 18% and 15%, respectively lower than the effects on TR under cloudy-sky conditions. Clouds under all-sky conditions (average of cloud cover is 5 tenths) reduced the EUV and TUV to about 25% of the clear-sky (cloud cover < 25%) values, whereas for TR, this was 31%. As a result, it is noted that the UV radiation is attenuated less than TR by clouds under all weather conditions.

• 영어어문교육
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• 제13권1호
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• pp.211-233
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• 2007

Caryl Churchill achieved spacial politics to resist dominant ideology in Cloud Nine. It is suggested that heterotopia is a counter-site to the places which are controlled by colonialism and sexuality. Churchill juxtaposes African colony of Victorian period in the first act and modern London in the second act. It implies that individuals are similarly oppressed by dominant ideology until now though several conditions for individuals are drastically improved. White heterosexual men in the play try to build their utopia to keep their privileges. If they find anything abnormal to their standard, they systematically classify people and organize them into the different ranks and levels to seclude them from their utopia. Actually, the ideal people in the ideal place are oppressed by patriarchal ideology, compulsory heterosexuality, and colonialism which are covertly associated with gender. Therefore, Churchill uses the cross-casting to challenge the artificiality of gender, sexuality, generation and race in the play. People realize that they need to find their own desires free from gender, compulsory heterosexuality, ethnic, and race and their subjectivity flowing in and out of space. It is the site that all the binary oppositions are deconstructed and creates new multiple nodes to expand the boundary of their communities to heterotopia in real places.

• 인터넷정보학회논문지
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• 제17권5호
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• pp.51-58
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• 2016

The unprecedented power of cloud computing (CC) that enables free sharing of confidential data records for further analysis and mining has prompted various security threats. Thus, supreme cyberspace security and mitigation against adversaries attack during data mining became inevitable. So, privacy preserving data mining is emerged as a precise and efficient solution, where various algorithms are developed to anonymize the data to be mined. Despite the wide use of generalized K-anonymizing approach its protection and truthfulness potency remains limited to tiny output space with unacceptable utility loss. By combining L-diversity and (${\alpha}$,k)-anonymity, we proposed a hybrid K-anonymity data relocation algorithm to surmount such limitation. The data relocation being a tradeoff between trustfulness and utility acted as a control input parameter. The performance of each K-anonymity's iteration is measured for data relocation. Data rows are changed into small groups of indistinguishable tuples to create anonymizations of finer granularity with assured privacy standard. Experimental results demonstrated considerable utility enhancement for relatively small number of group relocations.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.536-539
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• 2002

The reverse engineering (RE) technology can quickly generate 3D point cloud data of an object by capturing the surface of a model using a 3D scanner. In the rapid prototyping (RP) technology, prototypes are rapidly produced from 3D CAD models in a layer-by-layer additive basis. In this paper, a physical human head shape is duplicated using a new RP process, the Transfer-type Variable Lamination Manufacturing process using expandable polystyrene foam sheet (VLM-ST), after the point cloud data of a human head shape measured from 3D SNX scanner are converted to STL file. From the duplicated human head shape, it has been shown that the VLM-ST process in connection with the 3D scanner is a fast and efficient process in that shapes with free surface, such as the human head shape, can be duplicated with ease. Considering the measurement time and the shape duplication time, the use of 3D SNX scanner and the VLM-ST process is expected to reduce the lead-time fur the development of new products in comparison with the other existing RE-RP connected manufacturing systems.

• 천문학회지
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• 제40권4호
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• pp.157-160
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• 2007

I present a model to explain the mass segregation and shallow mass functions observed in the central parts of starburst stellar clusters. The model assumes that the initial pre-stellar cores mass function resulting from the turbulent fragmentation of the proto-cluster cloud is significantly altered by the cores coalescence before they collapse to form stars. With appropriate, yet realistic parameters, this model based on the competition between cores coalescence and collapse reproduces the mass spectra of the well studied Arches cluster. Namely, the slopes at the intermediate and high mass ends, as well as the peculiar bump observed at $6M_{\bigodot}$. This coalescence-collapse process occurs on a short timescale of the order of the free fall time of the proto-cluster cloud (i.e., a few $10^4$ years), suggesting that mass segregation in Arches and similar clusters is primordial. The best fitting model implies the total mass of the Arches cluster is $1.45{\times}10^5M_{\bigodot}$, which is slightly higher than the often quoted, but completeness affected, observational value of a few $10^4M_{\bigodot}$. The model implies a star formation efficiency of ${\sim}30$ percent which implies that the Arches cluster is likely to a gravitationally bound system.

• 한국IT서비스학회지
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• 제14권4호
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• pp.15-30
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• 2015

SMBA (Small and Medium Business Administration) and TIPA (Korea Technology and Information Promotion Agency for SMEs) have operated the Business Innovation Platform for SME Informatization based on cloud computing technology with the cooperation of seven industry cooperatives since 2013. This project will evolve into the open market platform where service providers and users voluntarily participate and transact. This research conducts the literature review about the concept of open market and the empirical analysis through survey for the software providers and the future users regarding the future operation methods. The policy about how the open market strategy for the business innovation platform needs to be designed and implemented are organized as the three differentiated government support strategies. The first is to provide free IT services including specialized core operation support S/W which is developed only for the small or home office group of firms which lack minimal informatization capability and budget. The second is to augment IT platform service through incorporating ERP supplier initiated commercial S/W sales window for those firms having medium level informatization capability. This includes to provide IT support for customization and system integration with existing government subsidized S/W. The third is to provide upgrading services of existing S/W functions to facilitate better system utilization. The results provide useful insight for government role to enhance SME competitiveness using IT.

• 정보과학회 논문지
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• 제44권8호
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• pp.767-773
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• 2017

클라우드 데이터베이스와 같은 분산 시스템 환경에서는 균일한 서비스 품질을 보장하기 위해 꼬리 응답시간을 짧게 유지하는 것이 중요하다. 본 논문에서는 카산드라 데이터베이스를 대상으로, 긴 꼬리 응답시간에 해당하는 지연이 메모리 공간 부족으로 인해 발생한다는 것을 보이며, 이러한 지연이 메모리 공간 확보를 위해 버퍼에 저장된 데이터를 저장장치에 완전히 내려쓸 때까지 카산드라가 사용자의 요청을 받지 않기 때문임을 밝힌다. 버퍼에 저장된 데이터를 내려쓰는데 걸리는 시간은 저장장치 성능에 따라 결정되므로 SSD의 가바지 컬렉션으로 인한 성능 저하가 꼬리 응답시간을 더 길게 만들고 있음을 관찰하였다. 우리는 자바가상기계에서의 가비지 컬렉션과 SSD에서의 가비지 컬렉션을 함께 수행하여 SSD의 가비지 컬렉션 비용을 숨기는, SyncGC 기법을 제안한다. 실험 결과, SyncGC 기법을 통해 꼬리 응답시간인 $99.9^{th}$와 $99.9^{th}-percentile$을 각각 31%, 36% 줄일 수 있었다.

• 방송공학회논문지
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• 제25권3호
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• pp.439-448
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• 2020

본 논문에서는 다시점 RGB-D 카메라의 포인트 클라우드 정합을 위한 수정된 최적화 알고리즘을 제안한다. 일반적으로 컴퓨터 비전 분야에서는 카메라의 위치를 정밀하게 추정하는 것은 매우 중요하다. 기존의 연구에서 제안된 3D 모델 생성 방식들은 많은 카메라 대수나 고가의 3차원 Camera를 필요로 한다. 또한 2차원 이미지를 통해 카메라 외부 파라미터를 얻는 방식들은 큰 오차를 가지고 있다. 본 논문에서는 저가의 RGB-D 카메라를 8개 사용하여 전방위 자유시점을 제공할 수 있는 3차원 포인트 클라우드 및 매쉬 모델을 생성하기 위한 정합 기법을 제안하고자 한다. RGB영상과 함께 깊이지도 기반의 함수 최적화 방식을 이용하고, 초기 파라미터를 구하지 않으면서 고품질의 3차원 모델을 생성할 수 있는 좌표 변환 파라미터를 구하는 방식을 제안한다.