• The Journal of Advanced Prosthodontics
• /
• v.5 no.4
• /
• pp.452-456
• /
• 2013

PURPOSE. The aim of this study was to evaluate the repeatability of the digitizing of silicon rubber impressions of abutment teeth by using a white light scanner and compare differences in repeatability between different abutment teeth types. MATERIALS AND METHODS. Silicon rubber impressions of a canine, premolar, and molar tooth were each digitized 8 times using a white light scanner, and 3D surface models were created using the point clouds. The size of any discrepancy between each model and the corresponding reference tooth were measured, and the distribution of these values was analyzed by an inspection software (PowerInspect 2012, Delcamplc., Birmingham, UK). Absolute values of discrepancies were analyzed by the Kruskal-Wallis test and multiple comparisons (${\alpha}$=.05). RESULTS. The discrepancy between the impressions for the canine, premolar, and molar teeth were $6.3{\mu}m$ (95% confidence interval [CI], 5.4-7.2), $6.4{\mu}m$ (95% CI, 5.3-7.6), and $8.9{\mu}m$ (95% CI, 8.2-9.5), respectively. The discrepancy of the molar tooth impression was significantly higher than that of other tooth types. The largest variation (as mean [SD]) in discrepancies was seen in the premolar tooth impression scans: $26.7{\mu}m$ (95% CI, 19.7-33.8); followed by canine and molar teeth impressions, $16.3{\mu}m$ (95% CI, 15.3- 17.3), and $14.0{\mu}m$ (95% CI, 12.3-15.7), respectively. CONCLUSION. The repeatability of the digitizing abutment teeth's silicon rubber impressions by using a white light scanner was improved compared to that with a laser scanner, showing only a low mean discrepancy between $6.3{\mu}m$ and $8.9{\mu}m$, which was in an clinically acceptable range. Premolar impression with a long and narrow shape showed a significantly larger discrepancy than canine and molar impressions. Further work is needed to increase the digitizing performance of the white light scanner for deep and slender impressions.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.45 no.9
• /
• pp.794-806
• /
• 2017

It is essential to protect the national space assets and space environment safely as a space development country from the continuously increasing space debris. And Active Debris Removal(ADR) is the most active way to solve this problem. In this paper, we studied the Artificial Neural Network(ANN) for a stable recognition model of vision-based space debris tracking system. We obtained the simulated image of the space environment by the KARICAT which is the ground-based space debris clearing satellite testbed developed by the Korea Aerospace Research Institute, and created the vector which encodes structure and color-based features of each object after image segmentation by depth discontinuity. The Feature Vector consists of 3D surface area, principle vector of point cloud, 2D shape and color information. We designed artificial neural network model based on the separated Feature Vector. In order to improve the performance of the artificial neural network, the model is divided according to the categories of the input feature vectors, and the ensemble technique is applied to each model. As a result, we confirmed the performance improvement of recognition model by ensemble technique.

• Journal of the Korean Magnetics Society
• /
• v.25 no.2
• /
• pp.52-57
• /
• 2015

The focal spot of electron beam depending on the anode angle in the structure and major parts of the X-ray tube was investigated by the OPERA-3D/SCALAR simulation program. The simulation worked on four spaces with with two spaces, including anode and cathode of X-ray tube, by applying the finite element method analysis. The analytical model and dimension for the emission orbit of thermal electrons made from one filament of the focused X-ray cathode is affected to the penumbra of detector for the X-ray depending on any real focal spot size. The model shape of focusing cap and focusing tube with an anode target angle and a cathode filament is analyzed by the current density distribution of thermal electrons. The focusing width of thermal electrons for the X-ray tube depended on the anode angle (${\theta}$). The focusing value of electron beams at a region of anode angle having $10^{\circ}{\sim}17^{\circ}$ maintained to below value of $70{\mu}m$. The minimum focal size of the electron beam was $40{\mu}m$ at an anode angle of $15^{\circ}$. The focused X-ray tube of many variables depended on the thermionic emission of hot electrons from the target trajectory. The focusing tube will contribute to the real design of X-ray for the development of future diagnosis medical device.

• Korean Journal of Optics and Photonics
• /
• v.20 no.2
• /
• pp.94-101
• /
• 2009

A novel method for the reconstruction of 3D shape and texture from elemental images has been proposed. Using this method, we can estimate a full 3D polygonal model of objects with seamless triangulation. But in the triangulation process, all the objects are stitched. This generates phantom surfaces that bridge depth discontinuities between different objects. To solve this problem we need to connect points only within a single object. We adopt a segmentation process to this end. The entire process of the proposed method is as follows. First, the central pixel of each elemental image is computed to extract spatial position of objects by correspondence analysis. Second, the object points of central pixels from neighboring elemental images are projected onto a specific elemental image. Then, the center sub-image is segmented and each object is labeled. We used the normalized cut algorithm for segmentation of the center sub-image. To enhance the speed of segmentation we applied the watershed algorithm before the normalized cut. Using the segmentation results, the subdivision process is applied to pixels only within the same objects. The refined grid is filtered with median and Gaussian filters to improve reconstruction quality. Finally, each vertex is connected and an object-based triangular mesh is formed. We conducted experiments using real objects and verified our proposed method.

• Korean Journal of Plant Taxonomy
• /
• v.42 no.2
• /
• pp.150-156
• /
• 2012

While preparing a floristic study of Korean hepatics, we discovered the six unrecorded species of Lejeuneaceae from Mt. Seolak, Mt. Gaya, Geojedo, Wando and Gageodo. Archilejeunea kiushiana, Drepanolejeunea angustifolia, Lejeunea aquatica, Lejeunea otiana, Leucolejeunea japonica, and Spruceanthus semirepandus, are reported here. A. kiushiana was characterized by unlobed underleaves, homogeneous oil-bodies, and four to six perianth-keels. D. angustifolia is similar to D. ternatensis, but it differs in the dorsal margin of the leaf-lobe, which is entire or denticulate, spines never present, and leaf cells smooth or with minute dorsal bulging. L. aquatica is similar to L. japonica in that it has a wider and similar shape (wider than long) of its underleaves and has homogeneous oil-bodies. The former, however, has minute leaf-lobules (5-15 cells), 1/10 to 1/5 the length of the leaf-lobe, versus leaf-lobules 1/4 to 1/3 the length of the leaf-lobe. L. otiana is similar to L. kodamae in that it has a large and acute first tooth of the leaf-lobule but differs in having plain leaf-lobules obliquely quadrate and an indistinct second tooth. Drepanolejeunea (Spruce) Schiffn. is widely distributed in tropical and subtropical regions (Mizutani, 1961). L. japonica is characterized by entire underleaves; one large, coarsely segmented oil-body per leaf cell; and a large second tooth of the leaf lobule, two to six cells long, and two to three cells wide at the base. S. semirepandus is widely distributed in tropical and subtropical regions in Asia. This species is characterized by small homogeneous and numerous oil-bodies, up to 10 smooth perianthkeels, and leaf-lobe acute at the apex.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.33 no.2
• /
• pp.95-101
• /
• 2020

The wind turbine blades should be designed to possess a high stiffness and should be fabricated with a light and high strength material because they serve under extreme combination of lift and drag forces, converting kinetic energy of wind into shaft work. The goal of this study is to understand the basic knowledge required to curtail the process time consumed during the construction of small wind turbine blades using carbon fiber reinforced polymer (CFRP) prepeg composites. The configuration of turbine rotor was determined using the QBlade freeware program. The fluid dynamics module simulated the loads exerted by the wind of a specific speed, and the stress analysis module predicted the distributions of equivalent von Mises stress for representing the blade structures. It was suggested to modify the shape of test specimen from ASTM D638 to decrease the variance in measured tensile strengths. Then, a series of experiments were performed to confirm that the bladder compression molded CFRP prepreg can provide sufficient strength to small wind turbine blades and decrease the cure time simultaneously.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.4
• /
• pp.653-659
• /
• 2017

In this study, the complex forging process of an outer support ring was developed and the prototype was manufactured. The current process, hot forging and MCT machining, has a disadvantage of excessive material removal rates and longer machining hours. To overcome this disadvantage, a general shape is given through hot forging and the precision is achieved through cold forging. The complex forging process was developed with the minimal machining process. Forging analysis was carried out to design a forging process using the commercial program, Deform-3D. The hot and cold forging processes were set up based on the analyzed result. The mold and prototype were manufactured. Hardness, surface roughness, internal defect, the grain low line of the prototype were evaluated. The results showed no particular problems, and there were no problems in mass production. Using complex forging, the material was reduced by approximately 27 % compared to the process using hot forging and MCT machining. In addition, the production speed was improved 2.15 fold compared to that of hot forging and MCT machining. Through this study, a cost-effective process and mold design technology were established, which is expected to have positive effects on other related automotive parts production.

• Restorative Dentistry and Endodontics
• /
• v.21 no.2
• /
• pp.619-627
• /
• 1996

There are increasing use of composite resin in the posterior teeth and the new indirect inlay technique was introduced for compensating much troubles faced in direct technique. Many researchers insisted that overall properties of restorative materials were enhanced by an additional curing but this technique still has a problems about using cement material. Resin inlay obtains retention force from friction and another adhesion to tooth structure. A shape of cavity preparation was noted but studies about cement thickness and bond strength with cavity divergency are rare. The purpose of this study is to assess the effect of cavity divergency on cement thickness and bond strength of resin inlay. Cavities, which divergency was $6^{\circ}$, $16^{\circ}$, and $26^{\circ}$ in each group, were prepared and their divergency was verified by Adobe Photoshop program through the image capture with stereo microscope and FlexCam. Inlays were fixed into the cavities with a resin cement, Superbond and were handled under chemical (in 75% ethanol for 24 hrs.) and thermal stress (500 cycles from $5^{\circ}$ to $55^{\circ}C$). MXT 70 (x400) was used for measuring the cement thickness and bond strength was evaluated with a universal testing machine. Following results were obtained : 1. The cement thickness in Mean (S.D.) were; 35.58 (10.31)${\mu}m$ in $6^{\circ}$ group, 35.97 (10.49)${\mu}m$ in $16^{\circ}$ group, and 41.43 (9.33)${\mu}m$ in $26^{\circ}$ group. But there was no significant difference between groups. 2. The bond strength in Mean (S.D.) were ; 33.18 (5.53)kg in $6^{\circ}$ group, 23.47 (13.40)kg in $16^{\circ}$ group, and 19.75 (10.48)kg in $26^{\circ}$ group. $6^{\circ}$ group showed significantly higher value compared to $16^{\circ}$ and $26^{\circ}$ groups (p<0.05). Although the results of this study indicate $6^{\circ}$ divergency will be good for resin inlay, cavity preparation with this type will have lots of difficulties in manufacturing, try-in, and cementation procedures, such as deformation. So it is concluded that $16^{\circ}$ divergent cavity preparation is recommended in resin inlay technique.

• Korean Journal of Breeding Science
• /
• v.42 no.3
• /
• pp.248-251
• /
• 2010

A lemon double freesia (Freesia hybrida Hort.), 'Shiny Lemon' was developed from a cross between the domestic breeding lines ('Golden Crown' and 'White Wings') and 'Yvonne' followed by seedling and line selections at the National Institute of Horticultural and Herbal Science, Rural Development Administration (RDA) in 2007. Growth and flowering characteristic tests were conducted from 2003 to 2006. 'Shiny Lemon' has large double type flower with lemon color (RHS Y13D). It has multiple florets, good flower shape, and upright leaves and stalks. The average cut flower yield of 'Shiny Lemon' was 7.1 cuttings per plant in the greenhouse from 2005 to 2007. Additionally, it has good production of cormlets and vigorous growth. 'Shiny Lemon' could be cultured under greenhouse conditions in Korea.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.1
• /
• pp.208-216
• /
• 2019

Rural houses are losing their original shape as they mimic the spatial composition of urban houses. Therefore, the purpose of this study was to extract the design elements needed for rural housing by applying Christopher Alexander's "A PATTERN LANGUAGE" to Standard Rural-House Design (SRHD). The scope and method of research was to compare and analyze the standard designs (SD) produced and distributed by the 'Korea Rural Community Corporation' from 2009 to 2014. The research result is summarized as follows. 1) The housing layout in the SD ignored the site conditions of various rural areas. 2) Most of the houses were not actively planned, considering that they contain various activities of rural life. 3) There was no room for children and the kitchen was planned to integrate the interior into a flexible space in the form of L.D.K. 4) There was no space plan that could be used as both a leasable annex and office space for the farming community. 5) Many small area plans were made because of the SD plan for couples only in 2014. Although the rural environment and living patterns were ignored in the SD, the diverse pattern language provided by the pattern language was developed as a SD element for rural houses, which is the most suitable housing plan for the farmers' livelihood pattern.