• 대한치과교정학회지
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• 제17권1호
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• pp.93-106
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• 1987

The purpose of this study was to investigate the fittness of Golden relation items was advocated by Ricketts whether or not it is applicable to the young adult Korean dentitions and also to evaluate the several new Golden relation items conducted by the author. The material was consisted of 81 dental casts (34 male, 47 female) with ideal occlusion, which never undergone orthodontic, prosthodontic procedures. Measurements were made on the arch dimensions using sliding caliper (Mitutoyo. Co) and data were computerized and analyzed. The findings of this study were as follows, 1. The Golden proportion advocated by Ricketts dose not seem to directly applicable to the Korean normal dentition, however, the modification from the Ricketts' original shows the Golden proportion as follow: A first series of progressive Golden relations was found on the Golden ratio among the lower central incisors width, the inter mesioincisal width of the upper lateral incisors, and the upper first premolars width. A second series was found on the Golden ratio among the lower lateral incisors width, lower inter canine tips width and theupper first molar distal cusp tips width. A third series was found on the Golden ratio between the inter distal aspect width of e lower canine and the mesial cusp tips width of the lower second molars or inter cusp tips width of upper second premolars. 2. In addition to Ricketts' original, 4 new Golden proportions were found in young adult Korean dentition, these are as follows; The tips of lower canine width had Golden relation with the width of the upper first premolar buccal cusp tips or the width of the lower first molar central fossae. The distal aspect of the lower first premolars had Golden relation with the buccal surface widths of the lower or upper second molars. The width of upper lateral incisors had Golden relation with the upper second molar height. The width of the lower canine tips had Golden relation with the lower second molar height.

• 한국전산구조공학회논문집
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• 제25권3호
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• pp.219-226
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• 2012

기둥은 건물에서 하중을 지지하는 중요한 구성요소이므로 기둥의 손상 또는 파괴는 건물의 연쇄붕괴의 원인이 된다. 특히 폭발하중에 의한 기둥의 거동평가는 연쇄붕괴 방지에 있어 중요한 요소이다. 본 논문에서는 축하중을 받고 있는 기둥이 폭발하중을 받을 때의 거동과 폭발 저항성능을 평가하였다. 이를 위해 동일단면적과 비슷한 철근비를 가지는 기둥에서 주 철근의 개수를 달리하여 각 변수에 따른 폭발하중에 대한 폭발 저항성능을 평가하였다. 또한, 동일한 성능을 지니는 기둥에서 단면비를 달리하여 기둥의 폭발 저항성능을 비교하였다. 해석결과, 폭발 직후 충격량에 대한 수직 변형률은 철근의 개수 및 단면비에 영향을 받지 않는 것으로 나타났다. 그러나 수평변형의 경우 폭발압력을 받는 면의 철근 개수가 증가함에 따라 기둥의 저항성능이 증가하는 것으로 나타났다. 또한, 기둥 단면의 단면 2차모멘트가 클수록 폭발하중에 대한 저항 성능 및 복원력이 더 큰 것을 확인하였다.

• Steel and Composite Structures
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• 제37권6호
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• pp.711-731
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• 2020

This paper deals with free vibration of FG sandwich annular sector plates on Pasternak elastic foundation with different boundary conditions, based on the three-dimensional theory of elasticity. The plates with simply supported radial edges and arbitrary boundary conditions on their circular edges are considered. The influence of carbon nanotubes (CNTs) waviness, aspect ratio, internal pores and graphene platelets (GPLs) on the vibrational behavior of functionally graded nanocomposite sandwich plates is investigated in this research work. The distributions of CNTs are considered functionally graded (FG) or uniform along the thickness of upper and bottom layers of the sandwich sectorial plates and their mechanical properties are estimated by an extended rule of mixture. In this study, the classical theory concerning the mechanical efficiency of a matrix embedding finite length fibers has been modified by introducing the tube-to-tube random contact, which explicitly accounts for the progressive reduction of the tubes' effective aspect ratio as the filler content increases. The core of structure is porous and the internal pores and graphene platelets (GPLs) are distributed in the matrix of core either uniformly or non-uniformly according to three different patterns. The elastic properties of the nanocomposite are obtained by employing Halpin-Tsai micromechanics model. A semi-analytic approach composed of 2D-Generalized Differential Quadrature Method (2D-GDQM) and series solution is adopted to solve the equations of motion. The fast rate of convergence and accuracy of the method are investigated through the different solved examples. Some new results for the natural frequencies of the plate are prepared, which include the effects of elastic coefficients of foundation, boundary conditions, material and geometrical parameters. The new results can be used as benchmark solutions for future researches.

• Steel and Composite Structures
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• 제48권3호
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• pp.275-291
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• 2023

This paper has focused on presenting vibration analysis of trapezoidal sandwich plates with 3D-graphene foam reinforced polymer matrix composites (GrF-PMC) core and FG wavy CNT-reinforced face sheets. The porous graphene foam possessing 3D scaffold structures has been introduced into polymers for enhancing the overall stiffness of the composite structure. Also, 3D graphene foams can distribute uniformly or non-uniformly in the plate thickness direction. The effective Young's modulus, mass density and Poisson's ratio are predicted by the rule of mixture. In this study, the classical theory concerning the mechanical efficiency of a matrix embedding finite length fibers has been modified by introducing the tube-to-tube random contact, which explicitly accounts for the progressive reduction of the tubes' effective aspect ratio as the filler content increases. The First-order shear deformation theory of plate is utilized to establish governing partial differential equations and boundary conditions for trapezoidal plate. The governing equations together with related boundary conditions are discretized using a mapping-generalized differential quadrature (GDQ) method in spatial domain. Then natural frequencies of the trapezoidal sandwich plates are obtained using GDQ method. Validity of the current study is evaluated by comparing its numerical results with those available in the literature. It is explicated that 3D-GrF skeleton type and weight fraction, carbon nanotubes (CNTs) waviness and CNT aspect ratio can significantly affect the vibrational behavior of the sandwich structure. The plate's normalized natural frequency decreased and the straight carbon nanotube (w=0) reached the highest frequency by increasing the values of the waviness index (w).

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2022년도 학술발표회
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• pp.516-516
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• 2022

Agricultural reservoirs are critical water resources structures to ensure continuous water supplies for rice cultivation in Korea. Climate change has increased the risk of reservoir failure by exacerbating discrepancies in upstream runoff generation, downstream irrigation water demands, and evaporation losses. In this study, the variations in water balance components of 400 major reservoirs during 1973-2017 were examined to identify the reservoirs with reliable storage capacities and resilience. A conceptual lumped hydrological model was used to transform the incident rainfall into the inflows entering the reservoirs and the paddy water balance model was used to estimate the irrigation water demand. Historical climate data analysis showed a sharp warming gradient during the last 45 years that was particularly evident in the central and southern regions of the country, which were also the main agricultural areas with high reservoir density. We noted a country-wide progressive increase in average annual cumulative rainfall, but the forcing mechanism of the rainfall increment and its spatial-temporal trends were not fully understood. Climate warming resulted in a significant increase in irrigation water demand, while heavy rains increased runoff generation in the reservoir watersheds. Most reservoirs had reliable storage capacities to meet the demands of a 10-year return frequency drought but the resilience of reservoirs gradually declined over time. This suggests that the recovery time of reservoirs from the failure state had increased which also signifies that the duration of the dry season has been prolonged while the wet season has become shorter and/or more intense. The watershed-irrigated area ratio (W-I_ratio) was critical and the results showed that a slight disruption in reservoir water balance under the influence of future climate change would seriously compromise the performance of reservoirs with W-I_ratio< 5.

• 한국산림과학회지
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• 제45권1호
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• pp.62-67
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• 1979

목재(木材)의 초박편시료(超薄片試料)에 자외선주사현미(紫外線走査顯微) 분광분석법(分光分析法)이 목재세포벽내(木材細胞壁內)의 리그닌 분포량(分布量) 변화측정(變化測定)에 우수(優秀)한 방법(方法)임이 판명(判明)되고 자작나무, 목질부(木質部)에서 복합세포간층(複合細胞間層)을 단리(單離)하여 분광분석법(分光分析法)과 정량분석(定量分析)을 수행(遂行), 도관(道管)의 이차막(二次膜)과 세포간층내(細胞間層內)의 리그닌은 주(主)로 Guajacylpropane으로 구성(構成)되었고, 목섬유(木纖維)와 방재세포(放財細胞)의 이차막내(二次膜內)의 리그닌은 대부분(大部分)이 Syringylpropane으로 구성(構成)되었고, 또 목섬유(木纖維) 및 방사세포(放射細胞)의 세포(細胞) 간층(間層)은 Guaiacyl- 및 Syringyl-propane으로 구성(構成)되었다는 연구보고(硏究報告)에 따라 본(本) 연구(硏究)는 너도밤나무 탈지(脫脂) 목분(木粉을 시료(試料)로 하여 마쇄단계별(磨碎段階別)로 Bjorkman리그닌(Milled Wood Lignin, MWL)을 추출(抽出)하여 MWL의 화학적(化學的) 구조(構造)와 특성(特性)을 분석(分析)하여 목재세포벽내(木材細胞壁內)의 리그닌의 구조적(構造的) 차이(差異)와 그 분포량(分布量), 그리고 MWL의 기원(基源)을 보다 명확(明確)히 구명(究明)하고j 수행(修行)하였다. 마쇄시간(磨碎時間)이 길어질수록 MWL의 pehnolic-OH기(基), 카보닐기(基) 그리고 메톡실기(基)의 함량(含量)이 높아지며 또한 단계별(段階別) MWL을 nitrobezene으로 산화(酸化)하여 얻은 vanillin량(量)은 감소(減少)하여 가고 반대로 syringaldehyde량(量)은 증가(增加)한다. 따라서 마쇄초기(磨碎初期)의 MWL은 세포간층(細胞間層) 부위(部位)로부터 온 것이고, 마쇄말기(磨碎末期)의 그것은 마쇄후기(磨碎后期)에 파괴(破壞)되는 목섬유(木纖維)의 세포벽(細胞壁) 이차막(二次膜)에서 유래(由來)된 것이라고 믿어진다. 그러므로 활엽수재목(闊葉樹材木)의 세포벽내(細胞壁內) 리그닌도 위치(位置)에 따라 화학적(化學的) 구조(構造)가 다르다는 것을 명화(明確)히 알 수 있다. 본(本) 연구(硏究)에서 마쇄단계별(磨碎段階別) 각(各) MWL을 젤 여과법(濾過法)에 의(依)한 분자량(分子量)을 분석(分析)한 바 마쇄초기(磨碎初期)MWL의 분자량(分子量)이 마쇄후기(磨碎后期) MWL의 그것보다 작았으나 세포벽내(細胞壁內) 리그닌의 분자량(分子量) 분포(分布)에 관(關)한 상세(詳細)한 것에 관(關)하여는 연구(硏究)가 필요(必要)함을 적시(摘示)한다.

• 한국지반공학회논문집
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• 제31권6호
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• pp.27-44
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• 2015

일정수심상에서 임의반사율을 갖는 부분중복파와 흐름이 공존하는 경우 얕은 두께를 포함한 유한두께 및 무한두께의 해저지반내에서 동적응답을 나타내는 해석해를 유도한다. 해석해에서 반사율이 0인 경우는 진행파와 흐름과의 공존장으로, 반사율이 1인 경우는 완전중복파와 흐름과의 공존장으로 간단히 변환된다. Biot의 압밀이론에 기초하여 해저지반은 투과탄성매체로, 간극유체는 압축성으로, 그리고 지반내 간극수의 흐름은 Darcy법칙으로 각각 가정된다. 도출된 해석해는 기존의 해석결과와의 비교 검토로부터 검증되며, 실제 계산에서는 반사율, 흐름속도, 입사파의 주기 및 지반두께 등의 변화에 따른 지반변위, 간극수압, 유효응력 및 전단응력의 변동특성을 면밀히 검토한다. 이로부터 흐름이 존재하는 경우 흐름으로 인한 입사파와 반사파의 주기 및 파장의 변화로 인하여 흐름이 없는 경우의 지반내 동적응답과는 큰 차이를 나타내며, 또한 반사율의 크기에 따라 동적응답에서 큰 차이가 나타난다는 것을 확인할 수 있다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1919-1921
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• 1999

AlN thin films were fabricated by sputter for the application of MIS device with Al/AlN/Si structure. We controled that sub-temperature room-temperature. Sputtering pressure 5 mTorr, flow ratio Ar:$N_2$=1:1(4sccm:4sccm), and appended hydrogen gas $0{\sim}5%$. AlN thin films thickness fabricated to maintain $2700{\AA}$ time control. Before the experiment remove to the contaminated material use the Ultrasonic every 10 minute use the acetone and ethanol, then use the HF remove oxide-substance at 10 second. To analyze characteristic of the $H_2$ gas addition period, C-V and I-V characteristic make and experiment $H_2$ gas at addition period progressive capability of I-V and C-V characteristic.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(4)
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• pp.179-182
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• 2001

This paper has been studied a wavelet based still image transmission over the wireless channel. EZW(Embedded Zerotree Wavelet) is an efficient and scalable wavelet based image coding technique, which provides progressive transfer of signal resulted in multi-resolution representation. It reduces therefore the reduce cost of storage media. Although EZW has many advantages, it is very sensitive on error. Because coding are performed in subband by subband, and it uses arithmetic coding which is a kind of variable length coding. Therefore only 1∼2bit error may degrade quality of the entire image. So study of error localization and recovery are required. This paper investigates the use of reversible variable length codes(RVLC) and data partitioning. RVLC are known to have a superior error recovery property due to their two-way decoding capability and data partitioning is essential to applying RVLC. In this work, we show that appropriate data partitioning length for each SNR(Signal-to-Noise Power Ratio) and error localization in wireless channel.

• 한국터널지하공간학회 논문집
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• 제9권3호
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• pp.251-261
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• 2007

본 연구는 터널굴착 공사에 의한 지반거동을 평가하여, 구조물의 형상, 위치, 굴착공정 변화등의 다양한 조건과 지반/구조물의 상호작용이 고려된 모형실험을 기본으로 수행하였다. 굴착진행 단계에 따른 구조물의 손상 거동 평가시 인접 구조물이 밀집된 도심지 굴착에서는 보다 안전하고 보수적인 평가가 나타나는 각변위와 수평변형율에 의한 손상도표를 활용하는 것이 보다 안전할 것으로 판단된다. 모형실험시 구조물에 발생된 균열의 손상수준을 손상도표에서 평가해 본 결과, 균열손상 수준이 적용된 평가가 각변위와 수평변형율만 적용된 손상수준보다 안전측으로 평가되는 것을 확인할 수 있었다. 그러므로, 각변위와 수평변형율 뿐만 아니라 균열이 고려된 손상평가를 수행하는 것이 보다 바람직할 것으로 판단된다.