• ETRI Journal
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• v.39 no.1
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• pp.97-107
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• 2017

A fast and accurate building-level visual place recognition method built on an image-retrieval scheme using street-view images is proposed. Reference images generated from street-view images usually depict multiple buildings and confusing regions, such as roads, sky, and vehicles, which degrades retrieval accuracy and causes matching ambiguity. The proposed practical database refinement method uses informative reference image and keypoint selection. For database refinement, the method uses a spatial layout of the buildings in the reference image, specifically a building-identification mask image, which is obtained from a prebuilt three-dimensional model of the site. A global-positioning-system-aware retrieval structure is incorporated in it. To evaluate the method, we constructed a dataset over an area of $0.26km^2$. It was comprised of 38,700 reference images and corresponding building-identification mask images. The proposed method removed 25% of the database images using informative reference image selection. It achieved 85.6% recall of the top five candidates in 1.25 s of full processing. The method thus achieved high accuracy at a low computational complexity.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.2
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• pp.75-80
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• 2008

The fabrication of complex three-dimensional electrodes for micro electrical discharge machining (micro-EDM) is an important issue in the field of micromachining Localized electrochemical deposition (LECD) is a simple and inexpensive technique for fabricating micro-EDM electrodes. This study presents a new process for manufacturing electrodes with complex cross-sections using masks of different shapes, In this process, a non-conductive mask is placed between an anode and cathode that are immersed in a plating solution of acidified copper sulfate. The LECD is achieved by applying a pulsed voltage between the anode and cathode, which are separated by a small distance. In this setup, the cathode is placed above the anode and the mask, so that the deposited electrode can be used directly for EDM without changing the tool orientation. We found that the microstructure of the deposited electrode is influenced by the concentration of the plating solution and organic additives. Moreover, the values of the voltage, frequency, and duty cycle of the pulsed input have significant effects on the microstructure of the fabricated electrode. Finally, the optimum values of the voltage, frequency, and duty cycle were determined for the most effective fabrication of complex-shaped electrodes.

• The Research Journal of the Costume Culture
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• v.30 no.4
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• pp.495-512
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• 2022

This study aims to design a new sizing system for hygienic masks to protect against COVID-19-related respiratory disorders. The product sizes were collected from 70 commercially available hygienic masks, and 18 head measurements were obtained from the three-dimensional (3D) scan data of 2,048 men and women aged 20 to 69 years from the 6th Size Korea Survey. The statistical analysis was performed using the IBM Statistical Package for the Social Sciences (SPSS) 28.0 program. The "bitragion-subnasale arc" and "menton-sellion length" were chosen as the key body dimensions for the hygienic mask sizing system. The linear regressions with 18 3D head measurements were analyzed, and it was determined that the key body dimensions were useful for statistically predicting other 3D head measurements related to hygienic masks. A new sizing system was proposed for two types of masks, "masks with a tight fit" and "masks with a loose fit," taking into account the existing Korean Industrial Standards (KS) and the shortcomings of the sizes of hygienic masks on the market. The sizing system for tight-fitting masks consisted of the key body dimensions, with their sizes indicated by a pair of numbers. The sizing system for loose-fitting masks consisted solely of the bitragion-subnasale arc, with their sizes denoted by letters such as S, M, and L (denoting small, medium, and large, respectively). Future studies should consider this mask sizing system for different age groups, such as children and adolescents.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.27 no.4
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• pp.269-282
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• 2017

Objectives: Currently, masks against yellow dust and fine particulates are being certified with no consideration of facial dimensional variations among children and adults. The aims of this study were to develop masks against yellow dust and fine particulates for children in Korea and provide basic data to suggest new test methods for mask certification that consider the breathing capacity of children. Methods: A total of 730 study participants aged from six to 13 years old were recruited in the Seoul, Gyeonggi, and Incheon region. This study used a 3D scanning instrument to obtain 16 facial anthropometric data points. Literature reviews, a comparison of breathing capacity between adults and children, and analysis of children's pulmonary physiological data were conducted in order to suggest new test standards for certifying children's masks against yellow dust and fine particulates. In addition, types of children's masks, choice of wearing a mask or not, and reasons for not wearing masks were surveyed. Results: Based on a clustering analysis of participants' facial dimensions, facial shapes were classified into three groups: small, medium, and large. The sizes of children's masks were subtracted by using 3D sketch techniques(Large: $121.25mm{\times}89.46mm$, Medium: $111.92mm{\times}78.55mm$, Small: $102.13mm{\times}72.87mm$). In certifying children's mask, flow rates of $60{\ell}/m$ for the filtering efficiency test and $20{\ell}/m$ for the breathing resistance test were recommended, since children's pulmonary physiological capacity is about 60-70% of adults' pulmonary capacity. Conclusions: The results of this study suggest that three mask sizes for children would be sufficient and practical for providing protection against yellow dust and fine particulates. Revising current test methods for certifying respiratory protective devices for children is important, since children's pulmonary physiological capacity substantially differs from that of adults. Therefore, it is recommended that new test standards for certifying children's masks be promulgated in the near future.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.2
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• pp.171-181
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• 2009

The objective of this study was to analyse stress distribution of maxillary complex by use of face mask. The construction of the three-dimensional FEM model was based on the computed tomography(CT) scans of 13.5 years-old male subject. The CT image were digitized and converted to the finite element model by using the mimics program, with PATRAN. An anteriorly directed force of 500g was applied at the first premolar 45 degrees downwards to the FH plane and at the first molar 20 degrees downwards to the FH plane. When 45 degrees force was applied at maxillary first premolar, there were observed expansion at molar part and constriction at premolar part. The largest displacement was 0.00011mm in the x-axis. In the y-axis, anterior displacement observed generally 0.00030mm at maximum. In the z-axis, maxillary complex was displaced 0.00036 mm forward and downward. When 20 degrees force was applied at maxilla first molar, there were observed expansion at lateral nasal wall and constriction at molar part. The largest displacement was 0.001mm in the X-axis. In the Y-axis, anterior displacement observed generally 0.004mm at maximum. In the Z-axis, ANS was displaced upward and pterygoid complex was displaced downward. The largest displacement was 0.002mm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.27 no.1
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• pp.47-53
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• 2023

Devices such as X-Ray, CT, MRI, scanners, etc. can generate S&P noise from several sources during the image acquisition process. Since S&P noise appearing in the image degrades the image quality, it is essential to use noise reduction technology in the image processing process. Various methods have already been proposed in research on S&P noise removal, but all of them have a problem of generating residual noise in an environment with high noise density. Therefore, this paper proposes a filtering algorithm based on a three-dimensional plane equation by setting the grayscale value of the image as a new axis. The proposed algorithm subdivides the local mask to design the three closest non-noisy pixels as effective pixels, and applies cosine similarity to a region with a plurality of pixels. In addition, even when the input pixel cannot form a plane, it is classified as an exception pixel to achieve excellent restoration without residual noise.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.7
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• pp.7-16
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• 2000

This paper reports a methodology and its application for extracting cell capacitances and parasitic capacitances in a stacked DRAM cell structure by a numerical technique. To calculate the cell and parasitic capacitances, we employed finite element method (FEM), The three-dimensional DRAM cell structure is generated by solid modeling based on two-dimensional mask layout and transfer data. To obtain transfer data for generating three-dimensional simulation structure, topography simulation is performed. In this calculation, an exemplary structure comprising 4 cell capacitors with a dimension of $2.25{\times}1.75{\times}3.45{\mu}m^3$, 70,078 nodes with 395,064 tetrahedra were used in ULTRA SPARC 10 workstation. The total CPU time for the simulation was about 25 minutes, while the memory size of 201MB was required. The calculated cell capacitance is 24.34fF per cell, and the influential parasitic capacitances in a stacked DRAM cell are investigated.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.73-77
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• 1997

This paper describes the analysis of measuring error of on the machine measuring(OMM) system which can directly measure the three dimensional machined free surface dimension using scanning probe on milling machine. 21 inch TV shadow mask mould was measured using PTP(point to point)measurement algorithm at pallet clamped and unclamped state on OMM system, and using coordinate measuring machine(CMM) one after another. The OMM system was evaluated probe error, stylus contact error, center shift error, repeatability and so on. Consequencely, the conclusion derived that elastic displacement of pallet had effect on measuring error mainly, and pallet design and setup method would be important.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.1
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• pp.10-19
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• 1989

This paper proposes the object modeling algorithm using depth data. In order to extract the shape of the object, surface is classified by the magnitude and the direction of Z gradient within the 2x2 mask from input depth data. For the object combined with several primitives is separated by kernel points. Further, spatial relationship between surface regions is extracted for the recognition. Finally, the effectiveness of this algorithm is demonstrated by several experiments.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.616-619
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• 2003

Photochemical and photothermal effects have correlation with each other and depend on laser wavelength. Multi-scanning laser ablation process of polymer with DPSS(Diode Pumped Solid State) 3rd harmonic Nd:YVO$_4$ laser with wavelength of 355nm is applied to fabricate three-dimensional micro shape. The DPSSL photomachining system can rapidly and cheaply fabricate 2D pattern or 3D shape with high efficiency because we only use CAD/CAM software and precision stages instead of complex projection mask. Photomachinability of polymer is highly influenced by laser wavelength and its own chemical structure. So the optical characteristics of polymers for 355nm laser source is investigated by experimentally and theoretically.