• 한국응용과학기술학회지
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• 제35권4호
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• pp.1393-1406
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• 2018

본 연구는 3개의 운전변수(압력, 공기량, 운전시간)를 실험 설계하고 마이크로 버블의 종말부상속도(Terminal rise velocity)를 반응 값으로 하여 예측식 모델과 최적 조건을 수립하였다. 다항식 회귀분석을 통해 펌프의 압력($X_1$) 4.5bar, 공기량($X_2$) 3.3L/min 그리고 운전시간($X_3$)이 2.2min에서 종말상승속도(Terminal rise velocity)에 대한 최적값인 5.14 cm/min ($85.7{\mu}m/sec$)을 얻었다. 또한, 레이저 입자계수 측정장치를 이용하여 $2{\sim}5{\mu}m$ 및 $25{\sim}50{\mu}m$ 영역에서의 가장 높은 마이크로버블 직경크기 분포를 확인하였다.

• 전기전자학회논문지
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• 제23권2호
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• pp.594-598
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• 2019

HfZnO 박막 위 패턴 전사 기법을 이용하여 기존의 러빙법을 대체하는 배향 공정에 대하여 연구하였다. 정렬 패턴은 레이저 간섭 리소그래피를 이용하여 실리콘 웨이퍼 위에 제작하였다. 졸겔 공정을 이용하여 HfZnO 용액을 제작하였고, 유리기판 위에 스핀코팅하였다. 미리 제작한 정렬패턴을 스핀코팅된 HfZnO 위에 올려놓고, $100^{\circ}C$에서 30분간 소성하였다. HfZnO 박막에 평행한 그루브가 형성되었음을 atomic force microscopy 와 scanning electron microscopy로부터 확인할 수 있었다. HfZnO 박막을 이용하여 액정 셀을 제작하였으며, POM 분석으로부터 액정이 균일하게 정렬되었음을 확인할 수 있었다. 액정은 $0.25^{\circ}$의 프리틸트 각을 가졌으며, 수평배향 특성을 보여주었다. 액정 분자는 평행한 그루브에 의한 HfZnO 박막 표면 이방성에 의하여 균일하게 정렬되었음을 확인할 수 있었다.

• Journal of Periodontal and Implant Science
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• 제49권3호
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• pp.193-204
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• 2019

Purpose: The reaction of cells to a titanium implant depends on the surface characteristics of the implant which are affected by decontamination. The aim of this study was to evaluate the cytocompatibility of titanium disks treated with various decontamination methods, using salivary bacterial contamination with dental pellicle formation as an in vitro model. Methods: Sand-blasted and acid-etched (SA) titanium disks were used. Three control groups (pristine SA disks [SA group]; salivary pellicle-coated SA disks [pellicle group]; and biofilm-coated, untreated SA disks [NT group]) were not subjected to any decontamination treatments. Decontamination of the biofilm-coated disks was performed by 14 methods, including ultrasonic instruments, rotating instruments, an air-powder abrasive system, a laser, and chemical agents. MG63 cells were cultured in the presence of the treated disks. Cell proliferation assays were performed on days 2 and 5 of cell culture, and cell morphology was analyzed by immunofluorescence and scanning electron microscopy (SEM). A vascular endothelial growth factor (VEGF) assay was performed on day 5 of culture. Results: The cell proliferation assay revealed that all decontaminated disks, except for the 2 groups treated using a plastic tip, showed significantly less cell proliferation than the SA group. The immunofluorescence and SEM analyses revealed that most groups showed comparable cell density, with the exception of the NT group, in which the cell density was lower and bacterial residue was observed. Furthermore, the cells grown with tetracycline-treated titanium disks showed significantly lower VEGF production than those in the SA group. Conclusions: None of the decontamination methods resulted in cytocompatibility similar to that of pristine SA titanium. However, many methods caused improvement in the biocompatibility of the titanium disks in comparison with the biofilm-coated, untreated titanium disks. This suggests that decontamination is indispensable for the treatment of peri-implantitis, even if the original biocompatibility cannot be restored.

• 패션비즈니스
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• 제23권3호
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• pp.67-84
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• 2019

Since the early 2000s, various fashion design products that use 3D printing technology have constantly been introduced to the fashion industry. However, given the nature of 3D printing technology, the flexible characteristics of material of textile fabrics is yet to be achieved. The aim of this study is to develop the optimal design conditions for production of flexible and elastic 3D printing fabric structure based on plain weave, which is the basic structure in fabric weaving using SLS 3D printing technology. As a the result this study aims to utilize appropriate design conditions as basic data for future study of flexible fashion product design such as textile material. Weaving structural design using 3D printing is based on the basic plain weave, and the warp & weft thickness of 4mm, 3mm, 2mm, 1.5mm, 1mm, and 0.7mm as expressed in Rhino 6.0 CAD software program for making a 3D model of size $1800mm{\times}180mm$ each. The completed 3D digital design work was then applied to the EOS SLS Machine through Maker ware, a program for 3D printer output, using polyamide 12 material which has a rigid durability strength, and the final results obtained through bending flexibility tests. In conclusion, when designing the fabric structure design in 3D printing using SLS method through application of polyamide 12 material, the thickness of 1 mm presented the optimal condition in order to design a durable digital textile structure with flexibility and elasticity of the 3D printing result.

• Journal of Radiation Protection and Research
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• 제43권4호
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• pp.160-169
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• 2018

Background: This study aims to develop an integrated optical system that can simultaneously or selectively measure the signals obtained from radioluminescence (RL), thermoluminescence (TL), and optically stimulated luminescence (OSL), which are luminescence phenomena of materials stimulated by radioactivity, heat, and light, respectively. The luminescence mechanism of various materials could be investigated using the glow curves of the luminescence materials. Materials and Methods: RL/TL/OSL integrated measuring system was equipped with a X-ray tube (50 kV, $200{\mu}A$) as an ionizing radiation source to irradiate the sample. The sample substrate was used as a heating source and was also designed to optically stimulate the sample material using various light sources, such as high luminous blue light emitting diode (LED) or laser. The system measured the luminescence intensity versus the amount of irradiation/stimulation on the sample for the purpose of measuring RL, TL and OSL sequentially or by selectively combining them. Optical filters were combined to minimize the interference of the stimulation light in the OSL signal. A long-pass filter (420 nm) was used for 470 nm LED, an ultraviolet-pass filter (260-390 nm) was used for detecting the luminescence of the sample by PM tube. Results and Discussion: The reliability of the system was evaluated using the RL/OSL characteristics of $Al_2O_3:C$ and the RL/TL characteristics of LiF:Mg,Cu,Si, which were used as dosimetry materials. The RL/OSL characteristics of $Al_2O_3:C$ showed relatively linear dose-response characteristics. The glow curve of LiF:Mg,Cu,Si also showed typical RL/OSL characteristics. Conclusion: The reliability of the proposed system was verified by sequentially measuring the RL characteristics of radiation as well as the TL and OSL characteristics by concurrent thermal and optical stimulations. In this study, we developed an integrated measurement system that measures the glow curves of RL/TL/OSL using universal USB-DAQs and the control program.

• Laboraroty Animal Research
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• 제33권2호
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• pp.105-113
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• 2017

insenosides from Panax ginseng are well known for their diverse pharmacological effects including antithrombotic activity. Since adventitious roots of mountain ginseng (ARMG) also contain various ginsenosides, blood flow-improving effects of the dried powder and extract of ARMG were investigated. Rats were orally administered with dried powder (PARMG) or ethanol extract (EARMG) of ARMG (125, 250 or 500 mg/kg) or aspirin (30 mg/kg, a reference control) for 3 weeks. Forty min after the final administration, carotid arterial thrombosis was induced by applying a 70% $FeCl_3$-soaked filter paper outside the arterial wall for 5 min, and the blood flow was monitored with a laser Doppler probe. Both PARMG and EARMG delayed the $FeCl_3$-induced arterial occlusion in a dose-dependent manner, doubling the occlusion time at high doses. In mechanism studies, a high concentration of EARMG inhibited platelet aggregation induced by collagen in vitro. In addition, EARMG improved the blood lipid profiles, decreasing triglyceride and cholesterol levels. Although additional action mechanisms remain to be clarified, it is suggested that ARMG containing high amount of ginsenosides such as $Rg_3$ improves blood flow not only by inhibiting oxidative thrombosis, but also by modifying blood lipid profiles.

• Research in Vestibular Science
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• 제17권4호
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• pp.134-141
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• 2018

Objectives: We aimed to study the role of vestibular input on spatial memory performance in mice that had undergone bilateral surgical labyrinthectomy, semicircular canal (SCC) occlusion and 4G hypergravity exposure. Methods: Twelve to 16 weeks old ICR mice (n=30) were used for the experiment. The experimental group divided into 3 groups. One group had undergone bilateral chemical labyrinthectomy, and the other group had performed SCC occlusion surgery, and the last group was exposed to 4G hypergravity for 2 weeks. The movement of mice was recorded using camera in Y maze which had 3 radial arms (35 cm long, 7 cm high, 10 cm wide). We counted the number of visiting arms and analyzed the information of arm selection using program we developed before and after procedure. Results: The bilateral labyrinthectomy group which semicircular canal and otolithic function was impaired showed low behavioral performance and spacial memory. The semicircular canal occlusion with $CO_2$ laser group which only semicircular canal function was impaired showed no difference in performance activity and spatial memory. However the hypergravity exposure group in which only otolithic function impaired showed spatial memory function was affected but the behavioral performance was spared. The impairment of spatial memory recovered after a few days after exposure in hypergravity group. Conclusions: This spatial memory function was affected by bilateral vestibular loss. Space-related information processing seems to be determined by otolithic organ information rather than semicircular canals. Due to otolithic function impairment, spatial learning was impaired after exposure to gravity changes in animals and this impaired performance was compensated after normal gravity exposure.

• Metals and materials international
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• 제24권6호
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• pp.1256-1261
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• 2018

Both thermoplastic formability and electrical conductivity of Al-Ni-Y metallic glass with 12 different compositions have been investigated in the present study with an aim to apply as a functional material, i.e. as a binder of Ag powders in Ag paste for silicon solar cell. The thermoplastic formability is basically influenced by thermal stability and fragility of supercooled liquid which can be reflected by the temperature range for the supercooled liquid region (${\Delta}T_x$) and the difference in specific heat between the frozen glass state and the supercooled liquid state (${\Delta}C_p$). The measured ${\Delta}T_x$ and ${\Delta}C_p$ values show a strong composition dependence. However, the composition showing the highest ${\Delta}T_x$ and ${\Delta}C_p$ does not correspond to the composition with the highest amount of Ni and Y. It is considered that higher ${\Delta}T_x$ and ${\Delta}C_p$ may be related to enhancement of icosahedral SRO near $T_g$ during cooling. On the other hand, electrical resistivity varies with the change of Al contents as well as with the change of the volume fraction of each phase after crystallization. The composition range with the optimum combination of thermoplastic formability and electrical conductivity in Al-Ni-Y system located inside the composition triangle whose vertices compositions are $Al_{87}Ni_3Y_{10}$, $Al_{85}Ni_5Y_{10}$, and $Al_{86}Ni_5Y_9$.

• Metals and materials international
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• 제24권6호
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• pp.1193-1201
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• 2018

Dilatometry is a useful technique to obtain experimental data concerning transformation. In this paper, a dilation conversional model was established to calculate carbides fraction in AISI H13 hot-work tool steel based on the measured length changes. After carbides precipitation, the alloy contents in the matrix changed. In the usual models, the content of carbon atoms after precipitation is considered as the only element that affects the lattice constant and the content of the alloy elements such as Cr, Mo, Mn, V are often ignored. In the model introduced in this paper, the alloying elements (Cr, Mo, Mn, V) changes caused by carbides precipitation are incorporated. The carbides were identified using scanning electron microscope and transmission electron microscope. The relationship between lattice constant of carbides and temperature are measured by high-temperature X-ray diffraction. The results indicate that the carbides observed in all specimens cooled at different rates are V-rich MC and Cr-rich $M_{23}C_6$, and most of them are V-rich MC, only very few are Cr-rich $M_{23}C_6$. The model including the effects of substitutional alloying elements shows a good improvement on carbides fraction predictions. In addition, lower cooling rate advances the carbides precipitation for AISI H13 specimens. The results between experiments and mathematical model agree well.

• 대한의생명과학회지
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• 제25권1호
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• pp.40-53
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• 2019

Of the Acinetobacter spp., A. baumannii (genospecies 2) is the most clinically significant in terms of hospital-acquired infections worldwide. It is difficult to perform Acinetobacter-related taxonomy using phenotypic characteristics and routine laboratory methods owing to clusters of closely related species. The ability to accurately identify Acinetobacter spp. is clinically important because antimicrobial susceptibility and clinical relevance differs significantly among the different genospecies. Based on the medical importance of pathogenic Acinetobacter spp., the distribution and characterization of Acinetobacter spp. isolates from 123 clinical samples was determined in the current study using four typically applied bacterial identification methods; partial rpoB gene sequencing, amplified rRNA gene restriction analysis (ARDRA) of the intergenic transcribed spacer (ITS) region of the 16~23S rRNA, the $VITEK^{(R)}$ 2 system (an automated microbial identification system) and matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS). A. baumannii isolates (74.8%, 92/123) were the most common species, A. nosocomialis (10.6%, 13/123) and A. pittii isolates (7.5%, 9/123) were second and third most common strains of the A. calcoaceticus-A. baumannii (ACB) complex, respectively. A. soli (5.0%, 6/123) was the most common species of the non-ACB complex. RpoB gene sequencing and ARDRA of the ITS region were demonstrated to lead to more accurate species identification than the other methods of analysis used in this study. These results suggest that the use of rpoB genotyping and ARDRA of the ITS region is useful for the species-level identification of Acinetobacter isolates.