• 대한인간공학회지
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• 제14권1호
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• pp.59-67
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• 1995

Depending upon the eye and head movement, the visual field is often classified into three categories ; stationary field, eye field and head and eye field. To investigate the effect of background condition on the size of the visual field, an experiment was conducted, in which the subject was instructed to search a target with distinct orientations. In each trial, a single target was presented on the perimeter modified to cover the range of 330 .deg. around the fixation point, with the visual angle subtended 1.4 .deg. vertically and horizontally. Nontarget density, meridian, size contrast and subject showed a significant effect on the visual field at .alpha. =0.01, where density was inversely proportional to the size of the visual field, and size contrast linearly proportional to the size of the visual field. The size of the visual field on horizontal axis was larger than that on vertical axis, and that on right and upper meridian was also larger than on left and lower meridian. The shape was found to be horizontally oriented oval and statistically asymmetric with respect to horizontal and vertical axes. In addition, the regression equations to predict the visual field on the given background condition were suggested. These results were expected to be used as a design guideline when arranging displays and controls on panels such as automobile display panels, cockpits, etc.

• 한국산업보건학회지
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• 제22권2호
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• pp.134-139
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• 2012

Objectives: This study was conducted to study the analytical variability of A & B counting rules in counting using a phase contrast microscope airborne fibers collected on filters in man-made mineral or vitreous fibers (MMMFs) industries. Methods: Fibers in filters were counted using A & B rules of NIOSH Method 7400. Intra-counter and inter-counter variations by fiber type and density were obtained. The types of MMMFs analyzed were glass wool fiber, rock wool fiber, slag wool fiber, and refractory ceramic fibers. The densities of fibers classified were <20 $fibers/mm^2,$ 20 - <50 $fibers/mm^2$, 50 - <100 $fibers/mm^2,$ and ${\geq}100$ $fibers/mm^2,$ respectively. Results: Intra-counter relative standard deviations by rule A were 0.084, 0.102, 0.071 for glass wool fibers, rock wool fibers and refractory ceramic fibers, and those by rule B were 0.139, 0.120 and 0.142, respectively. Inter-counter relative standard deviations by rule A were 0.281, 0.296, 0.180 for glass wool fibers, rock wool fibers and refractory ceramic fibers, and those by rule B were 0.396, 0.337 and 0.238, respectively. Conclusions: Intra-counter variation was not different significantly among fiber types (p>0.05), but B rule variation for ceramic fibers approximately 2 times greater than corresponding A rule estimates, and intra-counter and inter-counter variations were higher in the low fiber density.

• 대한방사선기술학회지:방사선기술과학
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• 제10권1호
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• pp.25-29
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• 1987

To compensate density of abnormal lung field for density of normal lung field, used each cellulose paper calculated sensitometry and contrast. As apply clinic part to the result: We are able to compensate density of abnormal lung that is pleural effusion atelectasis, etc for normal lung. We believe this method is good one because the method is simple to change exposure and the material is cheap enough to be accessible to every one and easily buyable and we need not be afraid of loss of image quality.

• 천문학회보
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• 제41권1호
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• pp.42.2-42.2
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• 2016

It is well known that theoretical models of Wolf-Rayet stars are not consistent with observational data in terms of temperature and stellar radius. Recent study in analytical and numerical simulations show the importance of density inhomogeneity in stellar envelope. Using 1-dimensional numerical simulations, we study how such clumpiness arisen over convective surface of Wolf-Rayet stars affect their evolutionary path. Starting from pure helium star models, we constructed 21 different initial conditions by varying stellar mass, metallicity, and the clumpiness of the sub-surface convection zone. We run the simulations until the oxygen-burning is reached and find that the influence of the clumpiness is sensitive to the initial metallicity. Our models with high metallicity including the effect of the density inhomogeneity can roughly explain the observed properties of Wolf-Rayet stars such as stellar radius and temperature. By contrast, despite a considerable amount of density inhomogeneity is given, low metallicity models could not fully explain observations. To understand the inconsistency in low metallicity models, detailed study with improved model is required, taking account of the error range of the observations.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 추계학술대회
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• pp.161-163
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• 2016

유기반도체는 무기반도체와 달리 가우시안 분포의 상태밀도를 가지며 전자밀도를 해석적으로 구하기 어려운 특성을 가지고 있다. 이런 특성 때문에 OLED 개발 과정에서 소자의 동작을 예측하기 어려워 적절한 소자의 전기적, 광학적 특성을 구하기 위해서는 시행착오를 반복하는 문제를 안고 있다. 본 논문에서는 유기반도체의 전자 밀도를 수치적으로 계산하는데 필요한 시간과 정확도의 최적화를 통하여 유기반도체 해석을 위한 기준을 제시하였다.

• 천문학회보
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• 제39권2호
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• pp.46-46
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• 2014

Interactions such as mergers and flybys play a fundamental role in shaping galaxy morphology. We used the Horizon Run 4 cosmological N-body simulations to study the frequency and the type of halo interactions as a function of the environment, the separation p, the mass ratio q, and the target halo mass. We defined targets as haloes more massive than 10^11 Msun/h, and a target is interacting if it is located within the virial radius of a neighbour halo more massive than 0.4 times the target mass. We find that the interaction rate as a function of time has a universal shape for different halo mass and large-scale density, with an increase and saturation. Larger density yield steeper slopes and larger final interaction rates, while larger masses saturate later. Most interactions happen at large-scale density contrast ${\delta}$ about 10^3, regardless of the redshift. We also report the existence of two modes of interactions in the (p,q) plane, reflecting the nature (satellite or main halo) of the target halo. These two trends strongly evolve with redshift, target mass, and large-scale density. Interacting pairs have similar spins parameters and aligned spins, with radial trajectories, and prograde encounters for non-radial trajectories. The satellite trajectories become less and less radial as time proceed. This effect is stronger for higher-mass target, but independent of the large-scale density.

• 한국분말재료학회지
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• 제24권2호
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• pp.147-152
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• 2017

Spherical-type zirconia granules are successfully fabricated by a spray-drying process using a water solvent slurry, and the change in the green density of the granule powder compacts is examined according to the organic polymers used. Two organic binders, polyvinyl alcohol (PVA) and 2-hydroxyethyl methacrylate (HEMA), which are dissolved in a water solvent and have different degrees of polymerization, are applied to the slurry with a plasticizer (polyethylene glycol). The granules employing a binder with a higher degree of polymerization (PVA) are not broken under a uniaxial press; consequently, they exhibit a poor green density of $2.4g/cm^3$. In contrast, the granule powder compacts employing a binder with a lower degree of polymerization (HEMA) show a higher density of $2.6g/cm^3$ with an increase in plasticizer content. The packing behavior of the granule powders for each organic polymer system is studied by examining the microstructure of the fracture surface at different applied pressures.

• Journal of Magnetics
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• 제22권2호
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• pp.227-233
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• 2017

The purpose of this study was to evaluate the effects of X-ray photon energy, tissue density, and the kernel essential for image reconstruction on the image quality by measuring HU and noise. Images were obtained by scanning the RMI density phantom within the CT device, and HU and noise were measured as follows: images were obtained by varying the tube voltages, the tube currents and eight different kernels. The greater the voltage-dependent change in the HU value but the noise was decreased. At all densities, changes in the tube current did not exert any significant influence on the HU value, whereas the noise value gradually decreased as the tube current increased. At all densities, changes in the kernel did not exert any significant influence on the HU value. The noise value gradually increased in the lower kernel range, but rapidly increased in the higher kernel range. HU is influenced by voltage and density, and noise is influenced by voltage, current, kernel, and density. This affects contrast resolution and spatial resolution.

• 한국지역지리학회지
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• 제15권6호
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• pp.689-706
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• 2009

주택입지에 영향을 미치는 공간변수의 우선순위를 평가하는 과정은 일부 전문가의 경험과 직관에 의존해 온 것이 사실이다. 산간 분지에서 주택(134채)의 밀도와 태양광도 관련 공간변수의 상관성을 파악하기 위해 다중공간 회귀분석 기법이 활용되었다. 전통적인 이론에서 주택 입지를 설명하는 전형적인 변수인 고도, 경사, 도로에 대한 접근성 등은 주택밀도에 대한 영향력에서 주요 변수로서 역할을 하지 못하였다 동지의 일사량과 일조시간이 산간분지에서 주택밀도를 설명할 수 있는 결정적인 변수였다. 산간분지에서 주택 입지가 전통적인 이론에서 제시하는 고도, 경사 등 이상적인 지형특성보다는 그림자로 인한 음지를 피하는 것을 최우선 순위로 고려하는 것이 확인되었다.

• Imaging Science in Dentistry
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• 제47권2호
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• pp.87-92
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• 2017

Purpose: The aim of this study was to determine whether the panoramic mandibular index (PMI) is useful for assessing bone mineral density. We also analyzed the potential correlations between PMI parameters and patient age. Materials and Methods: Four observers measured the PMI of both sides of the mental foramen using a picture archiving and communication system and images in the Digital Imaging and Communications in Medicine format. They studied 300 panoramic radiographic images of patients belonging to the following age groups: 40-49 years, 50-59 years, 60-69 years, 70-79 years, and 80-89 years. The observers were allowed to zoom in or out and to adjust the contrast of the images. Further, they were instructed to record the reasons for any measurements that could not be made. Then, we conducted a reliability analysis of the measured PMI and assessed the correlations between different patient age groups and the 3 parameters used for determining the PMI from the available data. Results: Among the 600 data items collected, 23 items were considered unmeasurable by at least 1 observer for the following 4 reasons: postoperative state, lesion, unidentified mental foramen, and alveolar bone loss. The intraobserver reproducibility of the measurable data was 0.611-0.752. The mandibular cortical width (MCW) decreased significantly as patient age increased. Conclusion: PMI had limited usability when the margin of the mental foramen was not clear. In contrast, MCW, a parameter used for determining the PMI, had fewer drawbacks than the PMI with respect to bone mineral density measurements and exhibited a significant correlation with patient age.