• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.495-498
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• 2004

In this paper, the arc and flame characteristics of wires were studied during a short-circuit. The short-circuit angle between wires was fixed as $90^{\circ}$ and the experiments were conducted on bare copper wires by varying the diameter of wires. The arc and flame patterns were taken by a high speed imaging system. The direction of arc and flame was explained with Lorentz force. After the short-circuit experiment, the shapes of molten wires were analyzed by a stereo microscope. In the results of experiment, the arc and flame of wires showed particular patterns. The flame characteristics by the diameter of wires were analyzed using a HSIS. We could find out the arc characteristics of wires which were different by the diameter.

• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.3044-3050
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• 2021

This study offers a Monte Carlo alternative for computing mass energy absorption coefficients of any material through calculation of photon energy deposited per mass of the sample and the energy flux obtained inside a sample volume. This approach is applied in this study to evaluate mass energy absorption coefficients of some amino acids found in human body at twenty-eight different photon energies between 10 keV and 20 MeV. The simulations involved a pencil beam source modeled to emit a parallel beam of mono-energetic photons toward a 1 mean free path thick sample of rectangular parallelepiped geometry. All the components in the problem geometry were surrounded by a 100 cm vacuum sphere to avoid any interactions in materials other than the absorber itself. The results computed using the Monte Carlo radiation transport packages MCNP6.2 and GAMOS5.1 were checked against the theoretical values available from the tables of XMUDAT database. These comparisons indicate very good agreement and support the conclusion that Monte Carlo technique utilized in this fashion may be used as a computational tool for determining the mass energy absorption coefficients of any material whose data are not available in the literature.

• Journal of Microbiology and Biotechnology
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• v.29 no.4
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• pp.617-624
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• 2019

Bacterial nanocellulose (BNC) which is generally synthesized by several species of bacteria has a wide variety of industrial uses, particularly in the food and material industries. However, the low levels of BNC production during the fermentation process should be overcome to reduce its production cost. Therefore, in this study, we screened and identified a new cellulose-producing bacterium, optimized production of the cellulose, and investigated the morphological properties of the cellulosic materials. Out of 147 bacterial isolates from ripened fruits and traditional vinegars, strain SFCB22-18 showed the highest capacity for BNC production and was identified as Komagataeibacter sp. based on 16S rRNA sequence analysis. During 6-week fermentation of the strain using an optimized medium containing 3.0% glucose, 2.5% yeast extract, 0.24% acetic acid, 0.27% $Na_2HPO_4$, and 0.5% ethanol at $30^{\circ}C$, about 5 g/l of cellulosic material was produced. Both imaging and IR analysis proved that the produced cellulose would be nanoscale bacterial cellulose.

• Implantology
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• v.22 no.4
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• pp.210-218
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• 2018

Purpose: The purpose of this study was to investigate the validity and reproducibility of a method based on cone-beam computed tomography (CBCT) technology for the visualization and measurement of gingival soft-tissue dimensions. Material and Methods: A total of 66 selected points in soft-tissue of the ex vivo head of an adult pig were investigated in this study. For the measurement of radiographic thickness (RT), wet soft-tissue surfaces were lightly covered with barium sulfate powder using a powder spray. CBCT was taken and DICOM files were assessed for soft-tissue thickness measurement at reference points. A periodontal probe and a rubber stop were used for the measurement of trans-gingival probing thickness (TPT). After flap elevation, actual thickness of soft-tissue (actual thickness, AT) was measured. Correlation analysis and intraclass correlation coefficients analysis (ICC) were performed for AT, TPT, and RT. Results: All variables were distributed normally. Strong significant correlations of AT with RT and TPT values were found. The two ICC values between TPT vs. AT and RT vs. AT differed significantly. Conclusion: Our results indicated that correlation of RT was stronger than that of TPT with AT. We concluded that soft tissue measurement with CBCT could be a reliable method, compared to the trans-gingival probing measurement method.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.38.3-38.3
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• 2021

We are developing an optomechanical design of infrared telescope for the CubeSat and Unmanned Aerial Vehicle (UAV) which adapts the Linear Astigmatism Free- Three Mirror System in the confocal off-axis condition. The small entrance pupil (diameter of 40 mm) and the fast telescope (f-number of 1.9) can survey large areas. The telescope structure consists of three mirror modules and a sensor module, which are assembled on the base frame. The mirror structure has duplex layers to minimize a surface deformation and physical size of a mirror mount. All the optomechanical parts and three freeform mirrors are made from the same material, i.e., aluminum 6061-T6. The Coefficient of Thermal Expansion matching single material structure makes the imaging performance to be independent of the thermal expansion. We investigated structural characteristics against external loads through Finite Element Analysis. We confirmed the mirror surface distortion by the gravity and screw tightening, and the overall contraction/expansion following the external temperature environment change (from -30℃ to +30℃).

• Radiation Oncology Journal
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• v.14 no.1
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• pp.69-76
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• 1996

Purpose : The aim of this study is to investigate the random and systematic errors and tumor movement using electronic portal imaging device in lung cancer patients for the adequate margin in the treatment planning of 3-dimensional conformal therapy. Material and Methods : The electronic portal imaging device is matrix ion chamber type(Portal Vision, Varian). Ten patients of lung cancer treated with chest irradiation were selected for this study. Patients were treated in the supine position without immobilization device. All treatments were delivered by an 10 MV linear accelerator that had the portal imaging system mounted to its ganrty. AP or PA field Portal images were only analyzed. Radiation therapy field included the tumor, mediastinum and supraclavicular lymph nodes. A total of 103 portal images were analyzed for set-up deviation and 10 multiple images were analyzed for tumor movement because of respiration and cardiac motion. Result : The average values of setup displacements in the x, y direction was 1.41 mm, 1 78 mm, respectively. The standard deviation of systematic component was 4.63 mm, 4.11 mm along the x, y axis, respectively while the random component was 4.17 mm in the x direction and 3.31 mm in the y direction. The average displacement from respiratory movement was 12.2 mm with a standard deviation of 4.03 mm. Conclusion : The overall set-up displacement includes both random and systematic component and respiratory movement. About 10 mm, 25 mm margins along x, y axis which considered the set-up displacement and tumor movement were required for initial 3-dimensional conformal treatment planning in the lung cancer patients and portal images should be made and analyzed during first week of treatment, individually.

• The Korean Journal of Nuclear Medicine Technology
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• v.23 no.1
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• pp.29-34
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• 2019

Purpose An examination guide is a useful medium to provide the patient with an overview, pre- and post-test preparation, and precautions of nuclear testing. The design and arrangement of existing written texts and announcements were evaluated to elucidate the comprehension of patients undergoing testing. Materials and Methods Informational material describing bone scanning and $^{201}thallium$ myocardium perfusion single-photon emission computed tomography (SPECT), as a secondary examination, which accounts for the largest portion of gamma imaging at Asan Hospital (Seoul, South Korea), was selected as an improvement target in consultation with a national innovation center. Existing informational material was dispensed to patients scheduled for bone scans from November 2016 to February 2017 and the revised material was issued from March 2017 to May 2017. A survey was conducted of 200 patients who underwent $^{201}thallium$ myocardium perfusion SPECT before and after the revisions (n = 100 each time period) to assess the patients' understanding of the informational material. Results When comparing the use of the conventional vs. revised material, the number of patients who received treatment before bone scanning had decreased from 130 to 60, while the number of those who required additional imaging decreased from 53 to 14. Prior to the revision, 43% of patients underwent testing before preparation and 18% underwent additional testing. The decreased need for additional image acquisition after revision of the informational material resulted in a decrease in acquisition time of about 2 min, from 16.5 to 14.2 min. In the case of $^{201}thallium$ myocardium perfusion SPECT, patient comprehension of all five items surveyed had increased, while the number of patients who had repeatedly asked about various facets of the procedure pre- and post-testing had decreased from 36% to 16% and 31% to 14%, respectively. Conclusion Lower patient comprehension is accompanied by a decrease in image quality due to non-compliance during pre-testing and may lead to repetitive questions from the patient, which may also negatively affect the fatigue and work efficiency of the examiner. Improved readability and visibility of informational material through visualization was correlated with greater patient comprehension as well as improved image quality and acquisition time.

• Journal of the Korean Society of Radiology
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• v.12 no.3
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• pp.335-341
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• 2018

With the improvement of medical state, patients' expectations for the most advanced medical equipment are increasing. Particularly, Magnetic Resonance Image (MRI) is used as one of the core image diagnosis methods in all clinical area. However, it has been reported that many of patients who go through the examination suffer from anxiety to the severe noise level during the examination. In this study, both the noise reduction evaluation of headsets with sound-blocking materials added to existing sound-absorbing materials and the existence of sound blocking materials as artifacts on the examination image are tested. An MRI test noise is recorded as a speaker by cross-ordination the sound material (sponge) and the sound material (acrylic plate, copper plate, and 3D copper plate) inside the headset made from 3D pring. A quantitative assessment of headsets showed that the average headset value was 81.8 dB. The average dB value of the most soundproof material combination(Copper, acrylic plate, sponge, sponge) headsets on headsets with added charactering material was measured at 70.4 dB, and MRI showed that the copper was diamagnetic substance and excluded. The second most soundproof headset(Sponge, acrylic plate, 3D copper plate, sponge) was measured at 70.6 dB and MRI showed no artifacts. The same simulation of the material printed with a 3D copper PLA containing approximately 40 % copper powder resulted in no artifacts, therefore, the material output as a 3D printing was better suited for use. For MRI related research, the mutual development of 3D printing is highly anticipated.

• Journal of Astronomy and Space Sciences
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• v.22 no.4
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• pp.441-450
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• 2005

The organic material is one of the most popular material for the satellites and the spacecrafts in order to perform the thermal management, and to protect direct exposure from the space environment. The present paper observes material property changes of organic material under the space environment by using ground facilities. One of the representative organic thermal management material of satellites, 2 mil ITO(Indium Tin Oxide) coated aluminized KAPTON was selected for experiments. In order to investigate the single parametric effect of protons in space environment, MC-50 cyclotron system in KIRAMS(Korea Institute of Radiological and Medical Science) was utilized for the ion beam irradiation of protons and ion beam dose was set to the Very Large August 1972 EVENT model, the highest protons occurrence near the earth orbit in history. The energy of ion beam is fixed to 30MeV(mesa electron volt), observed average energy, and the equivalent irradiance time conditions were set to 1-year, 3-year, 5-year and 10-year exposure in space. The procedure of analyses includes the measurement of the ultimate tensile strength for the assessment of quantitative degradation in material properties, and the imaging analyses of crystalline transformation and damages on the exposed surface by FE-SEM(Field Emission Scanning Electron Spectroscopy) etc.

• Imaging Science in Dentistry
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• v.30 no.2
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• pp.144-148
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• 2000

Sjogren's syndrome is a chronic inflammatory disease that predominantly affects salivary, lacrimal and other exocrine glands. We report a case of Sjogren's syndrome combined with MALT (mucose associated lymphoid tissue) lymphoma which occured in the parotid gland. A 57-year-old female with the complaint of painful swelling and lymph node enlargement was referred to our department. Sialograms of both parotid glands showed globular collections of contrast material uniformly distributed throughout the parotid gland. Salivary scintigraphy showed decreased uptake of the parotid gland. CT scan showed larger, slightly more dense parotid gland than normal and honeycomb glandular appearance. Also, It showed discrete, slightly more enhanced round mass in the left parotid gland. Histopathological finding showed replacement of salivary gland parenchyma with dense small lymphocytic infiltration having the feature of epimyoepithelial islands. Kappa light chain restriction of interglandular plasma cell could be seen.