• Journal of the Korean Society for Precision Engineering
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• 제24권12호
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• pp.50-56
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• 2007

Femtosecond laser ablation of the Invar alloy and hole drilling for a shadow mask are studied. We used a regenerative amplified Ti-sapphire laser with a 1kHz repetition rate, 184fs pulse duration and 785nm wavelength. Femtosecond laser pulse was irradiated on the Invar alloy with air blowing at the condition of various laser peak power. An ablation characteristic of the Invar alloy was appeared non-linear at $125J/cm^2$ of energy fluence. For the application to a shadow mask, the hole drilling of the Invar alloy with the cross section of a trapezoidal shape was investigated. The ablated micro-holes were characterized using an atomic force microscopy(AFM). The optimal condition of hole pattern f3r a shadow mask was $4\;{\mu}m$ z-axis feed rate, 0.2mm/s circular velocity, $26.4{\mu}J$ laser peak power. With the optimal processing condition, the fine circular hole shape without burr and thermal damage was achieved. Using the femtoseocond laser system, it demonstrates excellent tool for the Invar alloy micro-hole drilling without heat effects and poor edge.

• Journal of the Korea Safety Management & Science
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• 제16권3호
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• pp.165-173
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• 2014

This study is about determination of fire origin by using analysis of shadow that was recorded CCTV data at the fire scene. This analysis is based on straight and radiate nature of light. At fire experiment with about 1m flame, we conformed that 2-dimensional extension line is focused at the bottom of the fire. If the fire is burning at the same level with shadow, it indicate the point of origin exactly. In 3-dimensional analysis that connect extensional line between distinctive points the shadow and the objet, the line focused in the ${\emptyset}$ 50cm-circle. We estimate the reason of that is because of the character of combustion of gases. The line indicate not the point of origin but the flame that is over the point of origin. thus, you have to consider the line indicate the flame when you do 3-dimensional analysis.

• Journal of Korea Game Society
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• 제14권2호
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• pp.77-84
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• 2014

Presence of soft shadow effects from an area light makes virtual scenes look more realistic. However, since computation of soft shadow effects takes a long time, acceleration methods are required to apply it to real-time 3D applications. Many researches assumed that area lights are white rectangles. We suggest a new method which renders soft shadows under the area light source having arbitrary shape and color. In order to approximate visibility test, we use a shadow mapping result near a pixel. Complexity of shadow near a pixel is used to determine degree of precision of our visibility estimation. Finally, our method can present more realistic soft shadows for the area light that have more general shape and color in real-time.

• Journal of Korean Elementary Science Education
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• 제28권3호
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• pp.321-330
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• 2009

This study investigated the effects of teaching-learning lesson plan using cognitive acceleration instructional strategies applied to the unit, 'The Light and Shadow' in elementary school. Two classes of the second grade elementary students (N=63) in Chungcheongbukdo districts were assigned to control and treatment groups each, and were taught about 'The Light and Shadow' for 8 class hours. For the treatment group, teaching-learning lesson plan using cognitive acceleration instructional strategies developed by this research was applied. The traditional instruction by textbook and teacher's guides was used for the control group. All students were tested with the test for concept of the shadow and the test for academic achievement about the unit. As the result of the post-test, the scores of the treatment group were higher than those of the control group. However, it was not statistically meaningful difference. The scores of the treatment group were significantly higher than those of the control group in the delayed-post-test for concept of the shadow. No significant interaction was observed with respect to the students' gender, instruction and pre-level for the concept of the shadow. Data analysis indicated that the scores of the treatment group were significantly higher than those of the control group in the post-test and delayed- post-test for the concept of the shadow in the area of object permanence. Our research work shows the effectiveness of the teaching-learning lesson using cognitive acceleration instructional strategies for the development for concept of the shadow for elementary school students, and suggests the necessity for this kind of teaching-learning program in the fields.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• 제24권4호
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• pp.327-334
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• 2006

The aerial photos need in a simple object such as cartography and ground cover classification and also in a social objects such as the city plan, environment, disaster, transportation etc. However, the shadow, which includes when taking the aerial photos, makes a trouble to interpret the ground information, and also users, who need the photos in their field tasks, have a restriction. Generally the shadow occurs by the building and surface topography, and the detail cause is by changing of the illumination in an area. For removing the shadow this study uses the single image and processes the image without the source of image and taking situation. Also, applying the entropy minimization method it generates the 1-D gray-scale invariant image for creating the shadow edge mask and using the Canny edge detection creates the shadow edge mask, and finally by filtering in Fourier frequency domain creates the intrinsic image which recovers the 3-D color information and removes the shadow.

• Informatization Policy
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• 제30권2호
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• pp.86-108
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• 2023

This study attempts to explain phenomenologically the shadow work that occurs among Kwangju·Jeonnam business support counselors as video consultation increases due to the counseling management systems used in business consulting for SMEs and digital transformation since COVID-19. Since digital shadow work is widespread, it has been considered basic and mandatory work, not recognized as shadow work itself, assuming that it is continuously used for a long time. We found that, in the case of the newly expanded video consulting systems, most of the users complain of burden and inconvenience and tend to choose face-to-face despite the time and cost savings associated with the former. These study results practically suggest that, in order to implement such digital systems successfully, a well-prepared system, an elaborate way of reducing the burden and inconvenience, and an adaptation period are considered critical as they can minimize the shadow work of users.

• The Journal of Information Systems
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• 제28권2호
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• pp.93-107
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• 2019

Purpose The purpose of this study is to explain the mechanism of user behaviors in password reset context based on descriptive data from conducting interviews. Specifically, this study attempted to describe the process of changing password from the shadow work perspective. Design/methodology/approach This study has interviewed 8 participants who can freely use numerous online web-sites. This study also employed the grounded theory methodology to analyze interview manuscripts. After conducting analyzing the manuscripts, this study has extracted 46 codes in the coding steps and ultimately presented 8 categories by combining similar concepts from those codes. Findings According to the results, this study provides new viewpoints to explain unique user behavior in the password reset context by capturing the shadow work based on the results. This study further offers practical implications to numerous practitioners by finding various codes, which related to users' reaction and behavior.

• Journal of Broadcast Engineering
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• 제21권1호
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• pp.24-35
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• 2016

By estimating environment light distribution, we can generate realistic shadow images in AR(augmented reality). When we estimate light distribution without sensing equipment, environment light model, geometry of virtual object, and surface reflection property are needed. Previous study using 3D marker builds surrounding light environment with a geodesic dome model and analyzes shadow images. Because this method employs candidate shadow maps in initial scene setup, however, it is difficult to estimate precise light information. This paper presents a novel light estimation method based on hierarchical light distribution model subdivision. By using an overlapping area ratio of the segmented shadow and candidate shadow map, we can make hierarchical subdivision of light geodesic dome.

• Journal of Korea Game Society
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• 제13권3호
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• pp.85-94
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• 2013

In this paper, we propose a scheme to reduce the number of shadow tests conducted during rendering of ray tracing. The shadow test is a very important process in ray tracing to generate photo-realistic images. In the rendering phase, the ray tracer determines whether to cull the shadow test based on information calculated from a shadow test conducted on the kd-tree in the preprocessing phase. In conventional rendering process, the proposed method can be used with little modification. The proposed method is suitable for a static scene, in which the geometry and light source does not change in the same manner as it does in the conventional method. The validity of the proposed scheme is verified and its performance is evaluated during cycle-accurate simulation. Through experiment results, we found that we could reduce up to 17% of the shadow test.

• Information Systems Review
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• 제23권4호
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• pp.165-182
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• 2021

In nowadays, Covid-19 has transformed patterns of consumers' behavior into a non-face-to-face mode. As the patterns of consumption have been digitalized, it has become a daily routine for consumers who perform so-called shadow work, which involves unpaid jobs that they have to do by themselves. In mobile grocery service context, consumers' shadow work could lead to shopping avoidance as well as switching toward other shopping channels. Thus, this study is to examine how consumers' perception of shadow work affect mobile shopping avoidance and switching intention toward other shopping channels. This study collected 283 survey data from online respondents who have experience on subscription services for ordering groceries in online. We also tested our research model by using partial least squares. Based on our results, this study has found that the perception of shadow work had a positive effect on mobile shopping avoidance as well as switching intention. We expect that our findings could contribute to relevant research on shadow work and suggest practical implications for digital platforms dealing with subscription business models