• 대한임베디드공학회논문지
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• 제15권3호
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• pp.149-157
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• 2020

Regarding previously-developed drone simulators, it was easy to check their flight stability or controlling functions based on the condition that their weight was fixed from the design. However, the drone is largely classified into two types that is the one with the fixed weight whose purpose is recording video with camera and racing and another is whole weight-variable during flight with loading the articles for delivery and spraying pesticide though the weight of airframe is fixed. The purpose of this thesis is to analyze the structure of drone and its flight principle, suggest dynamics-model-based simulator that is capable of simulating weight-variable drone and develop the simulator that can be used for designing main control board, motor and transmission along the application of weight-variable drone. Weight-variable simulator was developed by using various calculation to apply flying method of drone to the simulator. First, ground coordinate system and airframe-fixing coordinate system were established and switching matrix of those two coordinates were made. Then, dynamics model of drone was established using the law of Newton and moment balance principle. Dynamics model was established in Simulink platform and simulation experiment was carried out by changing the weight of drone. In order to evaluate the validity of developed weight-variable simulator, it was compared to the results of clean flight public simulator against existing weight-fixed drone. Lastly, simulation test was performed with the developed weight-variable simulation by changing the weight of drone. It was found out that dynamics model controlled various flying positions of drone well from simulation and the possibility of securing the optimum condition of weight-variable drone that has flying stability and easiness of controlling.

• Bulletin of the Korean Chemical Society
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• 제34권12호
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• pp.3553-3558
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• 2013

The three dimensional-quantitative structure activity relationship (3D-QSAR) studies on chemical features of pyridine-2-amines in the external region of c-Met active site (ER chemical features of pyridine-2-amines) were conducted by docking, comparative molecular field analysis (CoMFA), and topomer CoMFA methods. The CoMFA model obtained the partial least-squares (PLS) statistical results, cross-validated correlation coefficient ($q^2$) of 0.703, non cross-validated correlation coefficient ($r^2$) of 0.947 with standard error of estimate (SEE) of 0.23 and the topomer CoMFA obtained $q^2$ of 0.803, $r^2$ of 0.940, and SEE of 0.24. Further, the test set was applied to validate predictive abilities of models, where the predictive $r^2$ ($r{^2}_{pred}$) for CoMFA and topomer CoMFA models were 0.746 and 0.608, respectively. Each contribution of ER chemical features of pyridine-2-amines to the inhibitory potency showed correlation coefficients, $r^2$ of 0.670 and 0.913 for two core parts, 3-(benzo[d]oxazol-2-yl)pyridine-2-amine and 3-(1-(2,6-dichloro-3-fluorophenyl)ethoxy) pyridine-2-amine, respectively, with corresponding experimental $pIC_{50}$.

• 성인간호학회지
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• 제16권3호
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• pp.409-420
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• 2004

Purpose: This study aims to analyze the effectiveness of Tai chi exercise for improving balance and its tendency and helps to identify directions for future research. Method: 19 articles from Medline search of foreign journals(1981-2003) and 5 from Korean nursing journals (1981-2003) were surveyed. The contents analyses were focused on outcome measures and relative factors regarding balance. Result: Variable measures for balance were used in Tai Chi studies relating to balance. They included the functional measures such as 14 single-leg stance, 7 walking in physiological measures and 7 laboratory-based balance measures were done with platform stability test. The measure of effective Tai Chi exercise depended on the health status of subjects and the methods. Health status of subjects were only on physically inactive older adults in 17 articles and arthritis patients in 7 articles in the Tai Chi study. The significant effects of Tai Chi exercise on balance was revealed after 10weeks duration. Conclusion: Considering the results, Tai Chi exercise is more effective than any other studies for walking balance. But the reports on the outcome are inconsistent with wide variations in the choice of balance measures. It is suggested that future studies analyze systemic change through meta analysis and have a wide variety of subjects who need postural control and balance control. The methods of measures should be distinct from the balance state of subjects for the effectiveness of Tai chi exercise.

• The Journal of Advanced Prosthodontics
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• 제8권5호
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• pp.388-395
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• 2016

PURPOSE. The purpose of this study was to evaluate the resistance to deformation under static overloading by measuring yield and fracture strength, and to analyze the failure characteristics of implant assemblies made of different titanium grades and connections. MATERIALS AND METHODS. Six groups of implant assemblies were fabricated according to ISO 14801 (n=10). These consisted of the combinations of 3 platform connections (external, internal, and morse tapered) and 2 materials (titanium grade 2 and titanium grade 4). Yield strength and fracture strength were evaluated with a computer-controlled Universal Testing Machine, and failed implant assemblies were classified and analyzed by optical microscopy. The data were analyzed using the One-way analysis of variance (ANOVA) and Student's t-test with the level of significance at P=.05. RESULTS. The group $IT4_S$ had the significantly highest values and group IT2 the lowest, for both yield strength and fracture strength. Groups $IT4_N$ and ET4 had similar yield and fracture strengths despite having different connection designs. Group MT2 and group IT2 had significant differences in yield and fracture strength although they were made by the same material as titanium grade 2. The implant system of the similar fixture-abutment interfaces and the same materials showed the similar characteristics of deformation. CONCLUSION. A longer internal connection and titanium grade 4 of the implant system is advantageous for static overloading condition. However, it is not only the connection design that affects the stability. The strength of the titanium grade as material is also important since it affects the implant stability. When using the implant system made of titanium grade 2, a larger diameter fixture should be selected in order to provide enough strength to withstand overloading.

• 한국컴퓨터그래픽스학회논문지
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• 제23권3호
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• pp.39-46
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• 2017

본 연구는 모바일 플랫폼의 가상현실 환경에 적합한 사용자 중심의 상호작용을 제공하기 위하여 시선기반 사용자 인터페이스를 제안한다. 이를 위해 제안하는 인터페이스가 모바일 가상 환경에서 사용자에게 상호작용의 만족도를 높이는지 여부를 실험하기 위하여 모바일 플랫폼 기반의 3차원 대화형 콘텐츠를 제작한다. 그리고 모바일 가상현실 콘텐츠의 입력 처리 방법으로 가장 일반적인 시선을 활용한 인터페이스를 시야 범위, 피드백 시스템의 2단계로 나누어 설계한다. 제안한 인터페이스 방법이 사용자에게 몰입감 향상의 효과, 기존과 차별화된 형식, 콘텐츠를 조작하는데 편리함을 제공하는 지 여부를 실험을 통해 분석한다.

• 한국전자파학회논문지
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• 제29권9호
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• pp.707-721
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• 2018

본 논문에는 30 cm 해상도를 갖는 소형 SAR(Synthetic Aperture Radar) 시스템 개발 결과를 소개하고, RAW 데이터 기반의 도플러 파라미터 추정 및 요동 보상 신호처리 알고리즘을 제시한다. 송수신 채널이 각각 2개이기 때문에 다중 편파 및 간섭계 영상 확보가 가능하며, 차량 탑재 시험을 통하여 다중 편파 SAR 데이터 획득 및 신호 처리 결과를 제시하였다. 플랫폼의 요동에 의한 잔여 위상 오차를 보상하는 알고리즘을 적용하였으며, 실제 차량 탑재 시험을 통하여 요동 보상에 따른 개선된 성능 결과를 제시하였다.

• Smart Structures and Systems
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• 제22권2호
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• pp.161-166
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• 2018

In the last decade, there has been an exponential increase of scientific interest in smart additive manufacturing (AM) technology. Among the different AM techniques, one of the most commonly applied processes is digital light processing (DLP). DLP uses a digital projector screen to flash an ultraviolet light which cures photopolymer resins. The resin is cured to form a solid to produce parts with precise high dimensional accuracy. During the curing process, there are several process parameters that need to be optimized. Among these, the exposure time affects the quality of the 3D printed specimen such as mechanical strength and dimensional accuracy. This study examines optimal exposure times and their impact on printed part. It was found that there is optimal exposure time for printed part to have appropriate mechanical strength and accurate dimensions. The gel fraction and TGA test results confirmed that the improvement of mechanical properties with the increasing UV exposure time was due to the increase of crosslinked network formation with UV exposure time in acrylic resins. In addition, gel fraction and thermogravimetric analysis were employed to microscopically investigate how this process parameter impacts mechanical performance.

• 대한조선학회 특별논문집
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• 대한조선학회 2013년도 특별논문집
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• pp.30-34
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• 2013

Prevention of exhaust gas back flow becomes a great interest to shipyards and shipowners in large container carriers because exhaust gas pollutes cargoes, flows back into the deck house and the engine room area through fresh air intakes and fan rooms, gives harmful damages to the crew's health and also gives thermal damages to electric equipments on the navigation deck. The phenomena of exhaust gas back flow has been studied with the analysis of sea trial records and wind tunnel tests and the height of the exhaust gas pipe, the front area of the deck house, the inflow speed and the position of the radar mast platform has been confirmed as the principal factors of exhaust gas back flow phenomena. The simple empirical formula to estimate exhaust gas back flow phenomena and the design guidances of exhaust gas related structures on deck has been introduced. In future, parametric studies for the exhaust gas back flow factors will be carried out with the CFD analysis. The results of this study will be the guide for development of the prevention method of exhaust gas back flow phenomena for large container carriers.

• 약학회지
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• 제36권3호
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• pp.212-219
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• 1992

Although oral route is the most convenient route for drug administration, the short and variable transit of drug through GI tract restricts the sustained drug absorption after oral administration. Thus, for sustained absorption of drugs, it is desirable to prolong the GI transit time by retaining the dosage forms in the stomach. In this study, the enzyme-digestible swelling hydrogel was synthesized by heating the mixed solution of N-vinyl-2-pyrrolidone[monomer], acrylated albumin[crosslinking agent] and proxyphylline[drug] at $65^{\circ}C$ for 10 hours in the cylindrical test tube. The resultant hydrogel tablet (diameter; 0.77 cm, thickness; 0.47 cm) was designed to swell in the gastric fluid after oral administration to such a size that passing through the pylorus could be inhibited during the drug release. After releasing drug, the hydrogel was expected to be degraded by pepsin, an enzyme in the stomach, and eventually solubilized. Actually, the hydrogel synthesized in the study swelled to a size larger than the diameter of the pylorus ($1.3{\pm}0.7$ cm) and slowly digested in the presence of pepsin. Drug release from the hydrogel was prolonged up to about 12 hours. The swelling kinetics was dependent on albumin acrylation time, drug content and gel thickness. Particularly the gel thickness was the most important factor that influences on drug release. By adjusting these factors, the albumin-crosslinked hydrogel was expected to be retained in the stomach for up to 60 hours and used as a potential platform of drugs for long-term GI absorption.

• Journal of Ginseng Research
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• 제31권1호
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• pp.44-50
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• 2007

Ginseng powerfully tonifies the original Qi. Ginseng used for insomnia, palpitations with anxiety, restlessness from deficient Qi and blood and mental disorientation. In order to investigate whether Ginseng cerebral ischemia-induced neuronal and cognitive impairments, we examined the effect of Ginseng on ischemia-induced cell death in the hippocampus, and on the impaired learning and memory in the Morris water maze and passive avoidance in rats. Ginseng when administered to rat at a dose of 200 mg/kg i.p. water extracts to 0 minutes and 90 minutes after 4-VO, significantly neuroprotective effects by 86.4% in the hippocampus of treated rats. For behavior test, rats were administered Ginseng (200mg/kg p.o.) daily for two weeks, followed by their training to the tasks. Treatment with Ginseng produced a marked improvement in escape latency to find the platform in the Morris water maze. Ginseng reduced the ischemia-induced learning disability in the passive avoidance. Consistent with behavioral data, treatments with Ginseng reduced jschemia-induced cell death in the hippocampal CA1 area. Oxidative stress is a causal factor in the neuropathogenesis of ischemic-reperfusion injury. Oxidative stress was examined in a rat model of global brain ischemia. The effects of Ginseng on lipid peroxidation (inhibition of the production of malondialdehyde, MDA) in different regions of the rat brain were studied. Ferrous sulfate and ascorbic acid (FeAs) were used to induce lipid peroxidation. The antiperoxidative effect showed 48-72% protection from tissue damage as compared with untreated animals. These results showed that Ginseng have a protective effect against ischemia-induced neuronal loss and learning and memory damage.