• EDISON SW 활용 경진대회 논문집
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• 제5회(2016년)
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• pp.183-189
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• 2016

In this paper, an optimization study on a helicopter rotor blade cross-section was made. Generalization was made to the baseline cross-section to simplify the analysis. To have better performance in aeroelastic response, with the aerodynamic center being the origin of the baseline, the distance between aerodynamic center and shear center, and the distance between mass center and shear center of the blade were minimized. For efficient searching of optimum solutions over the design space, grid search method, which is a method of graphical search was used. Two design variables, radius of balancing weight at leading edge, and offset of the spar from leading edge were selected for the study. Cubic spline interpolation method was used to accommodate searching of the optimum solution. 2-Leveled searching system was devised in accordance with the interpolation method. Optimum solution was found to show 6% decrease in both distance between aerodynamic center and shear center, and mass center and shear center to the baseline.

• 한국유체기계학회 논문집
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• 제17권5호
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• pp.67-71
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• 2014

Recently, the cross flow turbine attracts more and more attention for its good performance over a large operating regime at off design point. This study adopts a very low head cross flow turbine that has barely been studied before, and investigates the effect of air layer on the performance of the cross flow turbine. As open duct is applied in this study and free surface model is used between the air layer and water, an engineering definition of efficiency, instead of traditional definition of efficiency, is used. As torque at the runner fluctuates up and down at a reasonable limit, statistical method is used. Pressure and water volume fraction contours are shown to present the characteristics of air-water flow. With constant air suction in the runner chamber, the water level gradually drops below the runner and efficiency of the turbine can be raised by 10 percent. All considered, the effect of air layer on the performance of turbine is considerable.

• 대한예방한의학회지
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• 제18권3호
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• pp.23-39
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• 2014

Objective : This review aims at analyzing Complementary and Alternative Medicine (CAM) therapies, using for oral health to know current use of CAM in dental area by analyzing randomized controlled clinical trials (RCTs). Method : We searched the following 6 electronic databases until 1 July 2014. : Pubmed, Medline, Embase, Allied and Complementary Medicine Database(AMED), Cumulative Index to Nursing and Allied Health Literature(CINAHL), the Cochrane Library. We included parallel RCTs and cross-over RCTs that assessed the efficacy of CAM regardless of blinding and language. Results : A total of 154 RCT articles were included. There were 2-arm parallel study design(69.5%), 3-arm parallel study design(20.8%), 4-arm parallel study design(4.5%) and Cross-over design(5.2%). Complementary and alternative medicine RCTs in oral health tend to increase in the early-2000s and in the mid-2010s. In addition, 154 citations were classified according to diseases and interventions that categorized Natural Products studies(68.2%), Mind and Body Practices studies(31.8%). We classified in detail that vitamin and mineral therapies(29.9%), dietary supplements(24.7%), acupuncture(23.3%), Herbal medicine(13.6%), homeopathy (2.6%), energy therapies(2.6%), Massage(1.9%), biofeedback(0.6%), traditional medicine(0.6%). Conclusion : Increasing publications and diverse interventions regarding CAM for oral health is observed by analyzing RCTs from the literature review. Further studies are needed to be performed as systematic reviews to verify their effectiveness and the research to inquire into side effect.

• 한국구조물진단유지관리공학회 논문집
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• 제19권1호
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• pp.45-52
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• 2015

섬유복합체 (Fiber Reinforced Polymer, FRP)는 비강도가 높고, 비부식성 재료라는 특징을 가지고 있어서 건설 분야에서 철근을 대체할 수 있는 보강근 재료로 인식되고 있다. 몇몇 유리섬유 복합체 (Glass FRP, GFRP) 보강근이 상용화되어 있지만 GFRP는 철근에 비해 가격이 비싸고 상대적으로 낮은 탄성계수와 취성 파괴 특성 때문에 다소 경쟁력이 떨어진다. GFRP 보강근의 재료가격을 낮출 수 없다면 사용된 재료의 성능을 최대로 하여 보강근의 성능을 높이는 것이 상대적인 가격을 낮추는 방법이 될 수 있다. 일반적으로 FRP 보강근의 직경이 커질수록 인장강도는 감소하는 것으로 알려져 있다. 이의 원인 중 하나는 보강근이 인장을 받을 때 외력이 중앙에 위치한 섬유에 충분히 전달되지 못하여 외측에 위한 섬유들만이 인장에 저항하기 때문이다. 따라서 본연의 역할을 수행하지 못하는 섬유는 제거함으로써 보강근의 단가를 낮추면서 보강근이 소정의 성능을 발휘하도록 한다면 가격대비 성능이 최적화된 FRP 보강근을 제작할 수 있다. 본 연구에서는 직경 19 mm의 GFRP 보강근에 대해 단면 내에 중공이 존재하는 경우 중공비율에 따른 인장특성의 변화를 실험적으로 관찰하였다. 중공이 없는 GFRP 보강근 세 개, 네 가지 중공비율에 대해 각각 여섯 개의 GFRP 보강근 시편을 준비하여 인장실험을 실시하였으며 결과 분석을 통하여 인장특성 변화를 도출하였으며 이를 바탕으로 최적의 중공비율을 제안하였다.

• 한국생활과학회지
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• 제18권3호
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• pp.793-798
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• 2009

Hair cut is one of the best useful technical tool for hair styling. In this study using the rule of the layers of hair design, balanced for visual art, perceptual ability and form created by the principles of analysis and offer hair cuts and hair design of the representation of regions and even hair design as the basis of a student of Hair Beauty and all the people working in the field can create a variety of hair design puts the purpose to establish a basis. The result of this study can be outline as follows: First, the step line and the movement of the relationship between the law of the layers above and below the length of the same layer techniques, the same consists of a vertical cross-section of the overall round shape of the cut same layer is created and the appropriate volume and movement, the movement of low-layer round a little bit more feeling and expression is used when you want. High-layer used to want to move a lot of light and could see that. Second, the layer of the Law and over direction, lifting, section, the line control. weight control and analyzed by principle and the principle of the process of forming the written form was unknown. Third, hair design, the expansion of the expressive power of the law of the layers, and the section of the over direction depends on the presence of line control to express the length of the outline I had to, lifting the weight to adjust form controls, and the expression of Hair Design will be expanding the width. A hair designer, a layer style to create a zone he thought the law of the first layer formative area To further the reach will be a lot of research, leading up formative aspects of this research thesis do not have missing parts, or as a result of the Beauty of Hair Design and the width of a hair design education in the field can perform to help feed the reference materials that will be.

• 한국전자통신학회논문지
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• 제6권4호
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• pp.539-544
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• 2011

적당한 정수 $n({\geq}1)$에 대하여 2-valued 자기상관관계를 갖는 주기가 $2^n-1$인 균형 이진 수열(balanced binary sequences)은 대역확산 통신 시스템(spread-spectrum communication system)에서 많이 응용되고 있다. 본 논문에서는 르장드르 수열에 의해 구성되는 새로운 3-valued 비선형 이진 수열을 제안한다. 이 수열은 유한체 위에서 트레이스를 이용해 생성하는 가장 우수한 수열인 m-수열, GMW 수열, Kasami 수열, No 수열을 모두 포함한다. 제안된 수열은 Klapper에 의해 제안된 이차형식 수열보다 더 낮은 상호상관관계를 갖는다.

• 한국환경복원기술학회지
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• 제8권2호
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• pp.41-55
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• 2005

In an effort to preserve biodiversity in increasingly fragmented green patches, Korea has been installing eco-corridors over or under some arterial or expressways. In a survey of 43 such eco-corridors installed up until the year 2003, some problems and issues were identified. Some selected overseas eco-corridors were also investigated to find implications for the improvements of future installations in Korea. Major findings are; - For most existing eco-corridors, target species are not specified and locations of the eco-corridors are not well considered, and consequently it is questionable if wildlifes are crossing them - Most of existing eco-corridors lack supporting facilities such as fences that guide wildlife to cross them and prevent them from running into the road - Planting on the eco-corridors is not sufficient, not diverse enough in species, and not very considerate of wildlife but designed and planted in a similar manner as in urban parks - Where target species are not well specified, the location, width, cross section, and other aspects of the eco-corridors can not be optimized - It is suggested that eco-corridors are planned at early stages of road planning so that the number and locations of eco-corridor(s) decided as necessary and even the alignment and design of roads consider the installation of eco-corridors in advance - Monitoring of wildlife crossings is needed for improved eco-corridor planning and design - Nationwide green network plan is desirable to be made first and eco-corridors fit into it.

• 한국기계가공학회지
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• 제20권2호
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• pp.107-119
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• 2021

The cross-flow turbine is one of the most famous and widely used hydraulic power systems for a long time. The cross-flow turbine is especially popular in many countries and remote regions where off-grided because of its many benefits such as low cost, high efficiency at low head, simple structure, and easy maintenance. However, most modern turbines, including the cross-flow turbine, are unsuitable for the ultra-low head situation, known as less than 3m water head or zero head with over 0.5m/s flow velocity. In this study, we demonstrated a 20kW class inverted-type cross-flow turbine's performance. First, we reevaluated our previous studies and introduced how to design the inverted-type cross-flow turbine. Secondly, we fabricated the 20kW class inverted-type cross-flow turbine for the performance test. And then, we designed a testbed and installed the turbine system in the demonstration facility. In the end, we compare the demonstration with its previous CFD results. The comparing result shows that both CFD and real model fitted on guide vane angle at 10 degrees. At the demonstration, we achieved 42% turbine efficiency at runner speed 125 RPM.

• Journal of Oral Medicine and Pain
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• 제46권4호
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• pp.117-124
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• 2021

Purpose: Salivation is considered to be an important factor in the control of halitosis, and the amount of salivation has been shown to be closely related to the level of hydration. The purpose of our study was to evaluate the relationship between dehydration and halitosis. Methods: Twenty healthy young females with no dental problems were recruited. All participants were induced to become dehydrated and then over-hydrated. After inducing each hydration state, the severity of hydration and halitosis factor (organoleptic scores, amounts of resting and functional saliva, gas examinations, and tongue coatings) were measured. Hydration statuses were graded as dehydration, normal, or over-hydration according to urine osmolality. This was a cross sectional study with a cross over design. Results: The dehydrated status was associated with higher organoleptic scores than the normal or over-hydrated status (1.75±0.75 vs. 0.87±0.63, and 0.65±0.53, respectively. p<0.05). Mean values of CH₃SH, (CH₃)₂S in portable gas chromatography for the dehydrated, normal, and over-hydrated status were 11.70±37.00, 6.75±13.50, and 2.80±5.87 nmol/mol, 10.50±15.59, 7.25±10.87, and 1.50±2.55 nmol/mol, respectively. p>0.05). (CH₃)₂S (r=0.410, p=0.009) showed a moderate positive correlation with dehydration status. The resting salivation rates were relatively lower for the dehydrated status than for the normal or overhydrated status (p>0.05), and tongue coating results were also higher for the dehydrated status (p>0.05). Conclusions: Dehydration status appears to be positively correlated with a low resting salivation rate and high portable gas chromatography results. This shows that dehydration might be an etiologic factor of halitosis.

• 한국항공우주학회지
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• 제43권11호
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• pp.998-1007
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• 2015

방사형 인공위성 경우, 관성곱이 커서 단일 입 출력 가정이 불가능하기 때문에 고전적 제어기 설계방법을 사용하기 어렵다. 본 논문에서 현대 제어 이론인 $H_{\infty}$ 제어기 설계이론을 사용하여 방사형 인공위성의 자세 제어기 설계를 수행하였다. 설계 알고리즘으로 보다 안정적인 LMI 방법이 사용되었고, 설계 결과에 대한 안정성과 성능에 대한 강건성 해석을 위해 ${\mu}$-해석 방법이 적용되었다. 설계 결과, 일반적인 경우와 다르게 제어기가 포함되지 않은 개루프보다 제어기가 포함된 개루프의 cross-over frequency가 더 낮게 설계되는 것이 관측되었다. 즉 상대적으로 큰 관성곱 영향 때문에 단지 weighting 함수 조정으로 위성 기동성을 증가시키는데 한계가 있는 것으로 해석된다. ${\mu}$-해석을 위해 +/-5%의 관성모멘트 변화를 가정하였다. 안정성 및 성능에 대한 강건성 해석결과, +/-7% 관성모멘트 변화까지 시스템 안정성 및 성능이 보장됨이 확인되었고, 관성곱 변화보다 주관성모멘트 변화가 안정성 및 성능 저하에 더 영향을 주는 것으로 확인되었다.