• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.4
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• pp.322-329
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• 2003

We have studied how surface pretilt angle affects generation of disclination line in liquid-crystal-on silicon cells for 45$^{\circ}$-twisted nematic (TN) and vertical alignment (VA) modes with pixel size of 15$\mu\textrm{m}$. Our studies show that when the pretilt angle is increased from 0$^{\circ}$to 3$^{\circ}$ in the 45$^{\circ}$-TN cell, the disclination line at left side of on-pixel becomes weak and is well suppressed with $\theta$$\_$p/=3$^{\circ}$ although the pixel size Is decreased. In the VA cell, when the pretilt angle is decreased from 89$^{\circ}$ to 86$^{\circ}$, the disclination line at right side of the on-pixel is suppressed well and even for a smaller pixel size, it does not exist when $\theta$$\_$p/=86$^{\circ}$. The results inform that the pretilt angle strongly affects the image quality of microdisplays.

• Journal of ILASS-Korea
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• v.4 no.4
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• pp.30-37
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• 1999

The breakup characteristics of liquid sheet formed by the liquid rocket injector has a close relation with the combustion efficiency. In this paper, basic characteristics of droplet size and velocity distribution were measured with PDPA for the Like Doublet Impinging Injector. Test variables were the angle of impact, the diameter of orifice and jet velocity. Water was used as test fluid. As a result, for impingement angle less than 90 degree, following correlations were obtained between drop size and design parameters : $D_{32}({\mu}m)=295.0{\times}V^{-0.09}\times(2\theta)^{-0.1}{\times}d^{0.072}$. For impingement angle greater than 100 degree, drop sizes were increased but eventually converged to a certain limiting value.

• Journal of the Ergonomics Society of Korea
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• v.23 no.2
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• pp.1-12
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• 2004

The purposes of this study were to investigate the relationship between anthropometric data of foot and other body sizes. to categorize the foot shape of elementary school boys and to find out determinant factors related the foot that enable us to deduce the foot shape and size for the design of more comfortable shoes. Subjects of this study were 249 elementary school boys of age ranged from 6 to 11 residing Seoul and lncheon area. Anthropometric sizes were measured with the direct measurement method using Martin scales and the indirect measurement method using digital photos. Pearson's correlation, factor analysis. cluster analysis. analysis of variance, post-hoc test, and cross tabs were performed for statistical analysis of the data by SPSS program. From the investigation on the relationship between foot-related items and body items, most items of foot measure were significantly related to body size items. However, angle of the foot did not related to other body sizes although other height items and mass items of the foot did have relationships with other body sizes. Results of ANOVA indicated there were significant differences in foot-related items except for items of foot angle and all body anthropometric items by subjects' age. This implicates big toe angle, little toe angle and foot ratio factors are required in sizing shoes besides foot length. On the basis of cluster analysis using factor scores. three different foot shapes were categorized. Type 1 was large and wide foot, Type 2 was small and narrow foot with large toe angle. and Type 3 was medium foot with no deformity on big toe. These three groups show significant differences in almost all measurement items. However, Rorher index and foot angle didn't show any significant differences among groups. This implicates the foot shape can be a determinant of shoe size.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.5
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• pp.974-982
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• 1992

The atomizations of CWM slurry and water are done by a wheel atomizer which is designed and manufactured for this experiment. The variables of the experiment are the angle of vane, aspect ratio, particle loading and the mean size of coal particle distribution. The main purposes of the experiment are to know how the angle of vane and aspect ratio of vane influence the size distribution of CWM droplets. The experimental results say there are no appreciable effects on the mean size of CWM droplets from the change of loading of coal prticles in slurry. The mean size of coal particle in slurry, however, influence quite strongly the mean size of CWM droplets. The mean size of CWM droplets is quite strongly affected by the angle of vane. The size distribution of CWM droplets is controllable by the change of aspect ratio.

• Journal of the Ergonomics Society of Korea
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• v.28 no.4
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• pp.71-76
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• 2009

Effects of dark adaptation have large safety implications. This study was aimed to investigate the effects of varying illuminance and the size of critical detail on visual performance (i.e., time-to-detect) in a dark room environment. While adapting to the dark environment, ten subjects were asked to detect and answer simple numerical expressions under 9 experimental conditions (3 illuminance level $\times$ 3 target size). The ANOVA results revealed that the time-to-detect was significantly affected by both of the illumination level and the size of critical detail. As illumination increased from 10 lux to 20 lux, the time-to-detect was significantly declined. For the size of critical detail, 0.5/min size (i.e., equal to 2 minutes of visual angle) resulted in a shorter time-to-detect, as compared to 0.7/min size (i.e., equal to 1.6 minutes of visual angle). Potential applications of this research include the development of design guidelines for illumination and warning signs in poorly illuminated viewing environments.

• Geomechanics and Engineering
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• v.22 no.2
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• pp.165-171
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• 2020

Laboratory determination of strength and deformation behavior of clean sands and gravels has always been challenging due to the difficulty in obtaining their undisturbed samples. An alternative solution to this problem is to develop correlations between mechanical properties of cohesionless soils and their gradation characteristics. This study presents database of 3 natural sands with 11 varying particle size gradation curves to allow investigating relationships between mean particle size, maximum and minimum void ratio, relative density and shear strength of the test soils. Direct shear tests were performed at relative densities of 50, 75 and 95% to explore the effects of gradation and density on the angle of internal friction of the modeled sand samples. It is found that the mean grain size D₅₀ bears good correlations with void ratio range (e_max - e_min) and peak angle of internal friction 𝜙'_peak. The generated regression models are in good agreement with published literature and can be considered as reliable for natural sands in Pakistan. These empirical correlations can save considerable time and efforts involved in laboratory and field testing.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.29 no.1
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• pp.309-325
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• 1999

Purpose: To find out the effects that different tomographic angles have on the osteophytic lesion detectability of condyle head by comparison the individualized lateral tomographic image with the various tomographic angled images using SCANORA/sup (R)/. Materials & Methods: This study is performed to simulate osteophytic lesions by a series of dentin chips placed at six locations on condyle head. The control angle is 15° and from this angle. tomographic angle were varied with -10°, +10°, +20°. All the images with each sized dentin chip were scored by three dental radiologists with the use of confidence levels for presence or absence of the lesion, each examiner viewed one of the images twice. A rating scale from 0 to 2 (0, lesion definitely not present; 1. uncertain if lesion is present; 2, lesion definitely present). Responses were assessed by Tukey' s multiple comparison method and kappa value. Results: 1. The lesion size of 0.3 mm could not be detected in all the tomographic angles. As the size of the lesion increased the average value of lesion detectability also increased. 2. In the lesion sizes of 0.7 mm there was statistically significant difference between the 15° control angle and the altered tomographic angles (p<0.05). In 1.0 mm lesion there was no significant difference in the ±10° altered angles (p >0.05). but there was significant difference in the altered angle (p<0.05). In the lesion sizes of 0.3 mm and 2.0 mm there was no significant difference between the 15° control angle and all the altered angles (p >0.05). 3. In the anteromedial. anterosuperior, anterolateral area there was no significant difference between the 15° control angle and the ±10° altered angle (p >0.05), but in the comparison with the +20° altered angle there was significant difference (p<0.05). Conclusion: When imaging the lateral tomography of the temporomandibular joint used by SCANORA/sup (R)/, it can be considered that in the osteophytic lesion size of 2 mm and above, the tomographic angle difference within +20° to the horizontal angle of the condyle. has little effect on the lesion detectability. And in the lesion size of 1 mm, the altered angle within ±10° also has little effect on the lesion detectability.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.11
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• pp.1459-1466
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• 2004

The purpose of this study is to investigate the effect of swirler angle and the aspect ratio of swirl chamber of nozzle on the characteristics of single and twin spray. The characteristics of sprays have been investigated by measuring the spray angle, droplet size and velocity. Visualization of spray was conducted to obtain the spray angle and breakup process. The spray characteristics such as droplet size and velocity were measured by Phase Doppler Anemometry(PDA). It was found that the spray angle was increased with increasing the swirler angle. For both sprays, the axial velocity and SMD were decreased with increasing the swirler angle. It was also shown that the axial velocity and SMD were decreased with increasing the aspect ratio of swirl chamber, but for the twin spray, the axial velocity and SMD were not influenced significantly by the changing the aspect ratio of swirl chamber. The effect of swirler angle on the spray characteristics was greater than the aspect ratio of swirl chamber for single spray. The nozzle pitch was one of the important factors affecting the spray characteristics of twin spray.

• Journal of ILASS-Korea
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• v.10 no.4
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• pp.1-7
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• 2005

The purpose of this study is to investigate the effect of swirler vane angle and the aspect ratio of swirl chamber of nozzle on the characteristics of single spray. The characteristics of sprat's have been investigated by measuring the spray angle, droplet size and velocity Visualization of spray was conducted to obtain the spray angle and breakup process. The spray characteristics such as droplet size and velocity were measured by Phase Doppler Anemometry(PDA). It was found that the spray angle was increased with increasing the swirler angle. For both sprays, the axial velocity and SMD were decreased with increasing the swirler vane angle. It was also shown that the axial velocity and SMD were decreased with increasing the aspect ratio of swirl chamber The effect of vane angle un the spray characteristics was greater than the aspect ratio of swirl chamber for single spray.

• Communications of Mathematical Education
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• v.33 no.3
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• pp.295-317
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• 2019

Angle concept is widely used in all mathematics curriculums and is a basic concept in geometric domain. Since angle have a multifaceted and affect subsequent learning, it is necessary for students to understand various angle concepts. In this study, Singapore, U.K., Australia, and U.S. are selected as comparable countries to examine the angle-related contents and learning process that appear in the curriculum as a whole, and then look at the perspectives and the size aspects of angle in detail and give implications to the Korean curriculum based on them. According to the analysis, the four countries except Korea, supplement angle, complement angle, angles on a straight line, angles at a point, and finding angle were explicitly covered in the curriculum. And most countries gradually covered angle-related contents over several years, compared to Korea which intensively studied in a particular school year. In common, definition of angle was described as static, measurement of angle was described as dynamic. But in Korean curriculum, dynamic views on angles are described later and less compared to other countries, and range of angle size was narrower than in other countries'. From this comparison, this study suggest to discuss how to place and develop various contents of characteristics of angle in curriculum, address the angle using both static and dynamic perspectives, and introduce the angle size as the amount of rotation to learn the reflex angle, $180^{\circ}$, $360^{\circ}$ angle.