• 천문학회지
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• 제49권5호
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• pp.193-198
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• 2016

Early-type galaxies (ETGs) are supposed to follow the virial relation $M=k_e{\sigma}^2R_e/G$, with M being the mass, σ_* being the stellar velocity dispersion, R_e being the effective radius, G being Newton's constant, and k_e being the virial factor, a geometry factor of order unity. Applying this relation to (a) the ATLAS^3D sample of Cappellari et al. (2013) and (b) the sample of Saglia et al. (2016) gives ensemble-averaged factors 〈k_e〉 = 5.15 ± 0.09 and 〈k_e〉 = 4.01 ± 0.18, respectively, with the difference arising from different definitions of effective velocity dispersions. The two datasets reveal a statistically significant tilt of the empirical relation relative to the theoretical virial relation such that $M{\propto}({\sigma}^2_*R_e)^{0.92}$. This tilt disappears when replacing R_e with the semi-major axis of the projected half-light ellipse, a. All best-fit scaling relations show zero intrinsic scatter, implying that the mass plane of ETGs is fully determined by the virial relation. Whenever a comparison is possible, my results are consistent with, and confirm, the results by Cappellari et al. (2013). The difference between the relations using either a or R_e arises from a known lack of highly elliptical high-mass galaxies; this leads to a scaling (1 - ϵ ) ∝ M^0.12, with ϵ being the ellipticity and $R_e=a\sqrt[]{1-{\epsilon}}$. Accordingly, a, not R_e, is the correct proxy for the scale radius of ETGs. By geometry, this implies that early-type galaxies are axisymmetric and oblate in general, in agreement with published results from modeling based on kinematics and light distributions.

• 대한전자공학회논문지SP
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• 제46권2호
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• pp.78-88
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• 2009

본 논문에서는 LDA를 이용한 얼굴 인식에서 발생하는 small sample size 문제를 해결하기 위한 효율적인 방법인 resampling 방법을 제안한다. 기존에는 regularization method를 사용하여 small sample size 문제를 해결하였는데, 이 방법을 사용하면 클래스내 분산행렬의 특이성을 없앨 수 있지만, 클래스내 분산행렬과 상수를 곱하는 과정에서 상수 값을 임의로 정해 주어야 하고, 이 상수 값에 따라 인식률이 개선되지 않을 수 있다는 문제점이 발생한다. 제안된 resampling 방법을 이용하여 학습 데이터의 수를 늘리면, regularization method보다 개선된 인식률을 얻을 수 있고, 또한 경험적으로 상수 값을 지정해 주는 과정을 거치지 않아도 되는 장점이 있다.

• Steel and Composite Structures
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• 제25권6호
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• pp.639-648
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• 2017

Fracture energy values KV have been measured on cast steel, used in the container manufacture, by instrumented Charpy impact testing. This material has a large ductility on the upper transition region at $+20^{\circ}C$ and a ductile tearing with an expended plasticity before a brittle fracture on the lower transition region at $-20^{\circ}C$. To assess the fracture toughness of this material we use, the $K_{IC}$-KV correlations to measure the critical stress intensity factor $K_{IC}$ on the lower transition region and the dynamic force - displacement curves to measure the critical fracture toughness $J{\rho}_C$, the essential work of fracture ${\Gamma}_e$ on the upper transition region. It is found, using the $K_{IC}$-KV correlations, that the critical stress intensity factor $K_{IC}$ remains significant, on the lower transition region, which indicating that our testing material preserves his ductility at low temperature and it is apt to be used as a container's material. It is, also, found that the $J_{\rho}-{\rho}$ energetic criterion, used on the upper transition region, gives a good evaluation of the fracture toughness closest to those found in the literature. Finally, we show, by using the ${\Gamma}_e-K_{IC}$ relation, on the lower transition region, that the essential work of fracture is not suitable for the toughness measurement because the strong scatter of the experimental data. To complete this study by a numerical approach we used the ANSYS code to determine the critical fracture toughness $J_{ANSYS}$ on the upper transition region.

• Nuclear Engineering and Technology
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• 제47권7호
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• pp.939-944
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• 2015

The calibration methods of neutron-measuring devices such as the neutron survey meter have advantages and disadvantages. To compare the calibration factors obtained by the shadow cone method and semi-empirical method, 10 neutron survey meters of five different types were used in this study. This experiment was performed at the Korea Atomic Energy Research Institute (KAERI; Daejeon, South Korea), and the calibration neutron fields were constructed using a $^{252}Californium$ ($^{252}Cf$) neutron source, which was positioned in the center of the neutron irradiation room. The neutron spectra of the calibration neutron fields were measured by a europium-activated lithium iodide scintillator in combination with KAERI's Bonner sphere system. When the shadow cone method was used, 10 single moderator-based survey meters exhibited a smaller calibration factor by as much as 3.1-9.3% than that of the semi-empirical method. This finding indicates that neutron survey meters underestimated the scattered neutrons and attenuated neutrons (i.e., the total scatter corrections). This underestimation of the calibration factor was attributed to the fact that single moderator-based survey meters have an under-ambient dose equivalent response in the thermal or thermal-dominant neutron field. As a result, when the shadow cone method is used for a single moderator-based survey meter, an additional correction and the International Organization for Standardization standard 8529-2 for room-scattered neutrons should be considered.

• 터널과지하공간
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• 제13권3호
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• pp.180-186
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• 2003

동적 인장강도를 평가하기 위해 수치해석기법을 이용하여 홉킨슨효과를 가정한 동적 인장시험의 암석 파쇄 과정을 해석하였다. 동적 인장 파쇄 과정과 정적 인장 파쇄 과정에 명확한 차이가 있음을 밝혔으며, 동적 인장강도와 정적 인장강도의 상위는 응력집중현상과 응력재분배에 의해 발생된다는 것을 지적하였다. 그러나 정적파쇄와 동적파쇄 과정에 큰 차이가 있음에도 불구하고 정적 인장강도와 동적 인장강도는 미시적 인장강도의 균질성 계수가 증가함에 따라 미시적 인장강도의 평균치에 근접하였다. 본 연구로부터 암석의 불균질성은 동적 인장강도에 영향을 미치는 요인이며, 동적 인장강도와 정적 인장강도의 상위를 발생시키는 중요한 요인임을 지적하였다.

• 천문학회보
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• 제41권2호
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• pp.34.1-34.1
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• 2016

The ultra hard X-ray band (14-195 keV) provides an important and unbiased way to understand black hole growth and relationship to the host galaxy. The Burst Alert Telescope (BAT) instrument on the Swift satellite has surveyed sky to unprecedented sensitivity, improving the number of known hard X-ray sources by more than a factor of 20 to 836 nearby AGN. The BAT AGN Spectroscopic Survey (BASS) is a study for the first large (N>600) and complete sample of ultra hard X-ray selected AGN with optical spectroscopy. In this talk, I present the observed relationship between black hole mass, bolometric luminosity, and Eddington ratio with optical emission line ratios. We show that [NII]/Ha ratio exhibits a significant correlation with Eddington ratio. We propose that the [NII]/Ha ratio is a useful indicator of Eddington ratio with 0.6 dex of scatter, and that it can be used to measure Eddington ratio and thus black hole mass from the measured bolometric luminosity, even for high redshift obscured AGN.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.237-244
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• 2002

Televiewer is a logging tool capable of scanning the borehole wall. The tool uses a rotating acoustic beam generator that acts as both a transmitter and receiver. The beams are sent toward the wall. The amplitude of a returning signal from the wall has nearly a linear relationship with the reflection coefficient R of the borehole wall, when the wall is smooth. As R depends only on rock impedance for fixed water impedance, the amplitude is directly associated with mass density and seismic velocity of rock. Meanwhile, the amplitude can be further reduced by wall roughness that may be caused by drilling procedures, differences in rock hardness, because the rough surface can easily scatter the acoustic energy and sometimes the hole becomes elongated in all directions according to the degree of weathering. In this sense, the amplitude is related to the hardness of rocks. For convenience of analysis, the measured amplitude image(2-D data(azimuth ${\times}$ depth)) is converted, with an appropriate algorithm, to the 1-D data(depth), where the amplitude image values along a predetermined fracture signature(sinusoid) are summed up and averaged. The resulting values are subsequently scaled simply by a scalar factor that is possibly consistent with a known strength. This scaled Televiewer reflectivity is named, as a matter of convenience,“Televiewer rock strength”. This paper shows, based on abundant representative case studies from about 8 years of Televiewer surveys, that Televiewer rock strength might be regarded, on a continuous basis with depth, as a quitely robust indicator of rock classification and in most cases as an approximate uniaxial strength that is comparable to the rebound value from Schmidt hammer test.

• 한국환경보건학회지
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• 제44권6호
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• pp.539-547
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• 2018

Objectives: Ozone ($O_3$) advisories are issued by provincial/prefectural and city governments in Korea and Japan when oxidant concentrations exceed the criteria of the related country. Advisories issued only after exposure to high $O_3$ concentrations cannot be considered ideal measures. Forecasts of $O_3$ would be more beneficial to citizens' health and daily life than real-time advisories. The present study was undertaken to present a simplified forecasting model that can predict surface $O_3$ concentrations for the afternoon of the day of the forecast. Methods: For the construction of a simple and practical model, a multivariate regression model was applied. The monitored data on gases and climate variables from Japan's air quality networks that were recorded over nearly one year starting from April 2016 were applied as the subject for our model. Results: A well-known inverse correlation between $NO_2$ and $O_3$ was confirmed by the monitored data for Iksan, Korea and Fukuoka, Japan. Typical time fluctuations for $O_3$ and $NO_x$ were also found. Our model suggests that insolation is the most influential factor in determining the concentration of $O_3$. $CH_4$ also plays a major role in our model. It was possible to visually check for the fit of a theoretical distribution to the observed data by examining the probability-probability (P-P) scatter plot. The goodness of fit of the model in this study was also successfully validated through a comparison (r=0.8, p<0.05) of the measured and predicted $O_3$ concentrations. Conclusions: The advantage of our model is that it is capable of immediate forecasting of surface $O_3$ for the afternoon of the day from the routinely measured values of the precursor and meteorological parameters. Although a comparison to other approaches for $O_3$ forecasting was not carried out, the model suggested in this study would be very helpful for the citizens of Korea and Japan, especially during the $O_3$ season from May to June.

• 한국농림기상학회지
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• 제26권2호
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• pp.115-125
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• 2024

바람은 농업환경에 주요한 영향을 주는 기상요소이며, 강풍은 낙과, 시설물 파괴 등의 피해를 일으킨다. 본 연구는 LENS에 물리모델을 적용해서 농경지에 활용될 수 있는 저고도 풍속예측을 진행하였다. 물리모델은 LOG, POW가 사용되었고 지표 변수에 대해서는 환경부지표와 MODIS 지표를 따로 적용하였다. 농촌진흥청에서 운영하는 2022년도 3 m 고도의 바람 및 강풍 자료를 수집하고 검증을 진행하였고 결과를 산점도, 상관계수, RMSE, NRMSE, TS로 나타내었다. 풍속비교 4가지 방법의 결과에서 모델이 관측보다 더 크게 예측하고 있음을 확인할 수 있었다. 강풍 기준 값이 3 m s^-1 일 때, TS 가 약 0.65 정도로 나타났다. 결과는 RMSE와 NRMSE에서는 LOG_L, LOG_M, POW_L, POW_M 순으로 좋게 나타났고 상관계수와 TS에서는 역순으로 좋게 나타났다. 이러한 결과는 정해진 강풍 기준을 추가하여, 농경지 바람 및 강풍확률예측 연구에 도움이 될 것으로 기대된다.

• 방사선산업학회지
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• 제9권2호
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• pp.85-90
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• 2015

Purpose: Time of operation has been reduced and accuracy of operation has been improved since C-arm, which offer real-time image of patient, was introduced in operation room. However, because of the contamination of patient, C-arm could not be used more appropriately. Therefore, this study is to know factors of controlling exposure dose, image quality and the exposed dose of health professional in operation room. Materials and methods: Height of Wilson frame (bed for operation) was fixed at 130 cm. Then, Model 76-2 Phantom, which was set by assembling manual of Fluke Company, was set on the bed. Head/Spine Fluoroscopy AEC mode was set for exposure condition. According to detector size of C-arm, the absorbed dose per min was measured in the 7 steps OFD (cm) from 10 cm to 40 cm (10, 15, 20, 25, 30, 35, 40 cm). In each step of OFD, the absorbed dose per min of same diameter of collimation was measured. Moreover, using Nero MAX Model 8000, exposure dose per min was measured according to 3 step of distance from detector (20 cm, 60 cm, 100 cm). Finally, resolution was measured by CDRH Disc Phantom and magnification of each OFD was measured by aluminum stick bar. Result: According to detector size of C-arm, difference of absorbed dose shows that the dose of 20 cm OFD is 1.750 times higher than the dose of 40 cm OFD. It means that the C-arm, which has smaller size of detector, shows the bigger difference of absorbed dose per min (p<0.05). In the difference of absorbed dose in the same step of OFD (from 20 cm to 40 cm), the absorbed dose of 9 inch detect or C-arm was 1.370 times higher than 12 inch' s (p<0.05). When OFD was set to 20 cm OFD, the absorbed dose of non-collimation case was approximately 0.816 times lower than the absorbed dose of collimation cases (p<0.05). When the distance was 20 cm from detector, exposed does includes first-ray and scatter-ray. When the distance was 60 cm and 100 cm from detector, exposed does includes just scatter-ray. So, there was the 2.200 times difference of absorbed does. Finally, when OFD was increased, spatial resolution was 4 to 5 step was increased. However, low contrast resolution was not relative. Moreover, there was 1.363 times difference of magnification (p<0.05). Conclusion: When C-Arm is used, avoiding contamination of patient is more important factor than reducing exposed dose of health professional in operation room. Just controlling exposure time is just way to reduce the exposed does of workers. However, in the case, non-probability influence could be occurred. Therefore, this study proved that the exposed dose will be reduced if the factors such as using small detector size of C-arm, setting OFD from 20 cm to 25 cm and non-collimating. Moreover, dose management of C-arm in the non-interesting area will be considered additionally.