• The Journal of Korean Academy of Prosthodontics
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• v.55 no.4
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• pp.381-388
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• 2017

Purpose: Unpredictable shrinkage of zirconia during sintering process causes discrepancy. Therefore, there have been attempts to reduce discrepancy by milling zirconia after sintering. However, due to the hardness of sintered zirconia, milling takes longer time, causes damage to the machine and causes chip formation. With customized zirconia block using the mean dimension of prepared natural dentition, it is expected to overcome these shortcomings. Materials and methods: The mean dimension of prepared natural dentition was analyzed as STL file after scanning of prepared teeth treated at SNUDH. The transverse, frontal and sagittal planes were set using Mimics and Photoshop. 3D volume was projected on each plane, and the outer line was measured through external tangent line, and the inner line was measured through inflection point of tangent line. Results: The mean height of prepared incisal (N = 57) is $6.60{\pm}1.05mm$, mesiodistal length is $2.98{\pm}0.73mm$, buccolingual length is $2.04{\pm}0.73mm$. The mean height of prepared premolar (N = 15) is $5.37{\pm}1.49mm$, mesiodistal length is $4.10{\pm}1.78mm$, buccolingual length is $5.86{\pm}1.55mm$. And the mean height of prepared molar (N = 13) is $5.11{\pm}1.29mm$, mesiodistal length is $6.80{\pm}1.18mm$, buccolingual length is $7.34{\pm}1.40mm$. Conclusion: Using the mean dimension of prepared natural dentition, it is expected to be able to fabricate customized zirconia block.

• The Journal of Korean Academy of Prosthodontics
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• v.57 no.3
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• pp.211-218
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• 2019

Purpose: The purpose of the present study was to compare the accuracy of four different metal copings fabricated by CAD/CAM technology and to evaluate clinical effectiveness. Materials and methods: Composite resin tooth of the maxillary central incisor was prepared for a metal ceramic crown and duplicated metal die was fabricated. Then scan the metal die for 12 times to obtain STL files using a confocal microscopy type oral scanner. Metal copings with a thickness of 0.5 mm and a cement space of $50{\mu}m$ were designed on a CAD program. The Co-Cr metal copings were fabricated by the following four methods: Wax pattern milling & Casting (WM), Resin pattern 3D Printing & casting (RP), Milling & Sintering (MS), Selective laser melting (SLM). Silicone replica technique was used to measure marginal and internal discrepancies. The data was statistically analyzed with One-way analysis of variance and appropriate post hoc test (Scheffe test) (${\alpha}=.05$). Results: Mean marginal discrepancy was significantly smaller in the Group WM ($27.66{\pm}9.85{\mu}m$) and Group MS ($28.88{\pm}10.13{\mu}m$) than in the Group RP ($38.09{\pm}11.14{\mu}m$). Mean cervical discrepancy was significantly smaller in the Group MS than in the Group RP. Mean axial discrepancy was significantly smaller in the Group WM and Group MS then in the Group RP and Group SLM. Mean incisal discrepancies was significantly smaller in the Group RP than in all other groups. Conclusion: The marginal and axial discrepancies of the Co-Cr coping fabricated by the Wax pattern milling and Milling/Sintering method were better than those of the other groups. The marginal, cervical and axial fit of Co-Cr copings in all groups are within a clinically acceptable range.

• The Journal of Korean Society for Radiation Therapy
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• v.27 no.1
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• pp.61-71
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• 2015

Purpose : 3D Printers are used to create three-dimensional models based on blueprints. Based on this characteristic, it is feasible to develop a bolus that can minimize the air gap between skin and bolus in radiotherapy. This study aims to compare and analyze air gap and target dose at the branded 1 cm bolus with the developed customized bolus using 3D printers. Materials and Methods : RANDO phantom with a protruded tumor was used to procure images using CT simulator. CT DICOM file was transferred into the STL file, equivalent to 3D printers. Using this, customized bolus molding box (maintaining the 1 cm width) was created by processing 3D printers, and paraffin was melted to develop the customized bolus. The air gap of customized bolus and the branded 1 cm bolus was checked, and the differences in air gap was used to compare $D_{max}$, $D_{min}$, $D_{mean}$, $D_{95%}$ and $V_{95%}$ in treatment plan through Eclipse. Results : Customized bolus production period took about 3 days. The total volume of air gap was average $3.9cm^3$ at the customized bolus. And it was average $29.6cm^3$ at the branded 1 cm bolus. The customized bolus developed by the 3D printer was more useful in minimizing the air gap than the branded 1 cm bolus. In the 6 MV photon, at the customized bolus, $D_{max}$, $D_{min}$, $D_{mean}$, $D_{95%}$, $V_{95%}$ of GTV were 102.8%, 88.1%, 99.1%, 95.0%, 94.4% and the $D_{max}$, $D_{min}$, $D_{mean}$, $D_{95%}$, $V_{95%}$ of branded 1cm bolus were 101.4%, 92.0%, 98.2%, 95.2%, 95.7%, respectively. In the proton, at the customized bolus, $D_{max}$, $D_{min}$, $D_{mean}$, $D_{95%}$, $V_{95%}$ of GTV were 104.1%, 84.0%, 101.2%, 95.1%, 99.8% and the $D_{max}$, $D_{min}$, $D_{mean}$, $D_{95%}$, $V_{95%}$ of branded 1cm bolus were 104.8%, 87.9%, 101.5%, 94.9%, 99.9%, respectively. Thus, in treatment plan, there was no significant difference between the customized bolus and 1 cm bolus. However, the normal tissue nearby the GTV showed relatively lower radiation dose. Conclusion : The customized bolus developed by 3D printers was effective in minimizing the air gap, especially when it is used against the treatment area with irregular surface. However, the air gap between branded bolus and skin was not enough to cause a change in target dose. On the other hand, in the chest wall could confirm that dose decrease for small the air gap. Customized bolus production period took about 3 days and the development cost was quite expensive. Therefore, the commercialization of customized bolus developed by 3D printers requires low-cost 3D printer materials, adequate for the use of bolus.

• Journal of the Korea Convergence Society
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• v.8 no.11
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• pp.115-121
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• 2017

The present study aimed to obtain basic knowledge of a customized artificial joint based on the convergence research of Digital Imaging and Communications in Medicine(DICOM) and 5-axis machining technology. In the case of the research method, three-dimensional modeling was generated based on the medical image of the humerus bone, and the shape was machined using a chemical wood material. Then, the anatomical characteristics and the modeling machining computation times were compared. The results showed that the Stereolithography (STL) modeling required twice more time for semi-finishing and 10 times more time for finishing compared to the Initial Graphics Exchange Specification(IGES) modeling. For the 5-axis machining humerus bone, the anatomical structures of the anatomic neck, greater tubercle, lesser tubercle, and intertubercular groove were similar to those in the three-dimensional medical image. In the future, the convergence machining technology, where 5-axis machining of various structures(e.g., the surgical neck undercut of the humerus bone) is performed as described above, can be efficiently applied to the manufacture of a customized joint that pursues the precise model of a human body.

• Communications of Mathematical Education
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• v.28 no.3
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• pp.353-366
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• 2014

Recently, the widespread usage of 3D-Printing has grown rapidly in popularity and development of a high level technology for 3D-Printing has become more necessary. Given these circumstances, effectively using mathematical knowledge is required. So, we have developed free web tools for 3D-Printing with Sage, for mathematical 3D modeling and have utilized them in college education, and everybody may access and utilize online anywhere at any time. In this paper, we introduce the development of our innovative 3D-Printing environment based on Calculus, Linear Algebra, which form the basis for mathematical modeling, and various 3D objects representing mathematical concept. By this process, our tools show the potential of solving real world problems using what students learn in university mathematics courses.

• Journal of the Korean Society of Radiology
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• v.12 no.1
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• pp.115-122
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• 2018

The success of the total hip arthroplasty is revealed as initial stability, range of motion, and long term pain, etc. Depending upon choice of implantation options such as femoral neck offset, diameter of the femoral head, the lateral opening tilt. Especially the impingement between femoral head component and acetabular cup limits the range of motion of the hip. In this sense, estimation or evaluation of the range of motion before and after the total hip arthroplasty is important. This study provides the details of a computer simulation technique for the hip range of motion of intact hip as well as arthroplasty. The suggested method defines the hip rotation center and rotation axes for flexion and abduction, respectively. The simulation uses CT-based reconstructed 3D models and an STL treating software. The abduction angle of the hip is defined as the superolateral rotation angle from sagittal plane. The flexion angle of the hip is defined as the superoanterior angle from the coronal plane. The maximum abduction angle is found as the maximum rotation angle by which the femoral head can rotate superolaterally about the anterior-posterior axis without impingement. The maximum flexion angle is found as the maximum rotation angle by which the femoral head can rotate superoanteriorly about the medial-lateral axis without impingement. Compared to the normal hip, the total hip replacement hip showed decreased abduction by 60 degrees and decreased flexion by 4 degrees. This measured value implies that the proposed measurement technique can make surgeons find a modification of increase in the femoral neck offset or femoral head, to secure larger range of motion.

• The Journal of the Acoustical Society of Korea
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• v.24 no.8
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• pp.498-504
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• 2005

We introduce a Korean speech recognition platform (ECHOS) developed for education and research Purposes. ECHOS lowers the entry barrier to speech recognition research and can be used as a reference engine by providing elementary speech recognition modules. It has an easy simple object-oriented architecture, implemented in the C++ language with the standard template library. The input of the ECHOS is digital speech data sampled at 8 or 16 kHz. Its output is the 1-best recognition result. N-best recognition results, and a word graph. The recognition engine is composed of MFCC/PLP feature extraction, HMM-based acoustic modeling, n-gram language modeling, finite state network (FSN)- and lexical tree-based search algorithms. It can handle various tasks from isolated word recognition to large vocabulary continuous speech recognition. We compare the performance of ECHOS and hidden Markov model toolkit (HTK) for validation. In an FSN-based task. ECHOS shows similar word accuracy while the recognition time is doubled because of object-oriented implementation. For a 8000-word continuous speech recognition task, using the lexical tree search algorithm different from the algorithm used in HTK, it increases the word error rate by $40\%$ relatively but reduces the recognition time to half.

• 대한공업교육학회지
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• v.41 no.2
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• pp.134-150
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• 2016

This study has analyzed the subjects of transportation technology problem solving activities at Energy and Transportation Technology unit in the 12 kinds of middle school Technology Home Economics textbooks of the 2009 national revised curriculum. An analysis frame was developed with systems and environmental mediums which are common elements of transportation and the subjects were analyzed. As a result of this study, first, 8 kinds of subjects among 20 subjects in analysis frame were suggested in the textbooks. Second, according to the environmental, there are 13 terrestrial activities, 2 atmospheric activities, and 1 marine activity in the textbooks. However, there is no space related activity. Third, according to the system, there are 13 activities for the structure, 12 activities for the propulsion and suspension system, 5 activities related to the control system, and 1 activity regarding guidance system. Fourth, there are 4 kinds of problem solving activities depending on categorizing result of the analysis of the activities.

• Journal of agriculture & life science
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• v.46 no.1
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• pp.71-81
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• 2012

This study was conducted to get basic information about making windbreak forest around Saemanguem reclaimed lands by analyzing the vegetation structure of 8 windbreak forests along the west coast of Korea and considering the methods of structural improvement. The total plants existing in the study areas were 25 families 40genus 43 species, and every tree layer consisted of only one tree species, Pinus thunbergii. There were 2 windbreak stands consisted of a species, and 2 consisted of multiple layer with a species. While, 4 windbreak stands consist of various species with several species. To make ecological system and functions of windbreak forests stabler, TL, STL and SL should be together in the vertical point, moreover, TL should be appeared at the in side and SL should be planted at the out side in the horizontal point. It is considered that mixed stand forest might be suitable for increasing the windbreak forest's functions and decreasing damage caused by disease and insects.

• Journal of Technologic Dentistry
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• v.40 no.4
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• pp.217-224
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• 2018

Purpose: The aim of this study was to evaluate accuracy of three type complete mandibular denture of before and after polymerization. Methods: Mandibular edentulous model was selected as the master model. 15 study models were made by Type IV stone. Wax complete mandibular dentures were produced by the denture base and artificial teeth. Before and after curing, STL files were obtained using a blue scanner. By superimposing the digitized complete mandibular denture data(after curing) with the CAD-reference(before curing) three-dimensionally, visual fit-discrepancies were drawn by calculating the root mean square (RMS) and visualized on a color-difference map. Each calculated RMS-value was statistically analyzed by 1-way analysis of variance(ANOVA) (${\alpha}=.05$). Results: Mean(SD) RMS-values was OM group $88.98(6.10){\mu}m$, BM group $82.35(13.46){\mu}m$, BDM group $77.83(9.46){\mu}m$. The results of the 1-way ANOVA showed no statistically significant differences in the RMS values of the Three groups for the material (P > .241). Conclusion : Deformation of artificial teeth position was observed in all groups after resin polymerization. But the values, all group were within the clinically acceptable range. The values of BDM group showed the least deformation than the other two groups.