• Journal of the Korean Chemical Society
• /
• v.26 no.3
• /
• pp.188-193
• /
• 1982

Four new thermotropic copolyesters were prepared and their liquid crystal properties were investigated by differential scanning calorimetry and on a hot-stage of a polarizing microscope. Three copolyesters had same mesogenic unit, triad aromatic ester structure, interconnected through a random combination of either odd-even, or odd-odd, or even-even number of methylene groups in the polymethylene flexible spacers. Another random copolyester consisted of mesogenic units of 1 : 1 mixture of central methyl-and bromohydroquinone moieties with two flanking p-oxybenzoate units connected by decamethylene spacer. All of the polyesters formed nematic liquid crystal phase upon melting. The transitions for melting and nematic ${\to}$ isotropic transformations could be reversibly observed by DSC as well as by microscopic study. The thermodynamic properties for their liquid crystal ${\to}$ isotropic phase transitions were discussed in relation to their chemical structures.

• Journal of Korean Society of Steel Construction
• /
• v.9 no.4 s.33
• /
• pp.501-513
• /
• 1997

The general behavior of curved girder including the warping effects is formulated by series of differential equations postulated by Vlasov. In order to determine the maximum shear force, the maximum bending moment, the maximum pure torsion, the maximum warping torsion, and the maximum bimoment for the curved girder grid bridges, it is important to find the location of live load applied to the curved girder grid bridges, so that the influence line can be estimated. In this paper, the influence line of shear force, bending moment, pure torsion, warping torsion, and bimoment due to unit vertical load and unit torsional moment for curved I-girder grid bridges are obtained by using the finite difference method.

• Korean Journal of Materials Research
• /
• v.3 no.4
• /
• pp.344-351
• /
• 1993

The crystal structunes of poly(ethylene terephthalate-eo-1, 4 cyciohexylene dimethylene terephthalate), P(ET CT), copolymers were studied by CPMAS solid state NMR spectroscopy. With the estimation of methylene resonance peaks, the bulkier CT component of the copolymer in the range of 0 20 mol% CT is excluded from the ET crystal lattice, whereas smaller ET component of the copolymer in the range of 66 100 mol% CT can be partially included into the CT crystal lattice. Those different crystallization behavior can be explained with the difference in chain bulkiness and crystal lattice dimension be tween two copolymer compurwnts.

• Journal of the Korean Applied Science and Technology
• /
• v.14 no.2
• /
• pp.87-91
• /
• 1997

서로 다른 씨클로펜타디엔 유도체가 ${\pi}$-결합된 최초의 비스무스 화합물인 ${\eta}^5-C_5(CH_3)_5Bi({\eta}^5-C_5H_5)_2$이 디펜타메틸씨클로펜타디에닐 비스무스디메틸아미드 $Cp{\ast}_2BiNMe_2[Cp{\ast}=C_5(CH_3)_5]$와 씨클로펜타디에닐 모노머와의 반응으로 합성되었다. 반응조건은 에테르 용매하에 -78$^{\circ}C$ 반응온도 조건하에서 얻어졌다. 합성된 반응물을 노르말 헥산 용매에서 재결정시킨 결과, 검은색 결정이 60% 수율로 얻어졌다. 그리고 재결정시킨 반응물을 190K에서 X-선 단결정 구조 분석 방법에 의해 그 구조를 밝혔다. 그 결과 결정계의 격자계는 I2/a, a=1756.00 picometer, b=906.00 picometer, c=2211.00 picometer, ${\beta}$=104.04, Z=8로 확인되었다. 여기서 a, b, c는 결정�Ю� 상수이고, ${\beta}$는 결정격자 상수인 b와 c간의 각도이며, Z는 단위 결정 격자당 분자의 갯수이다.

• Journal of Wetlands Research
• /
• v.14 no.3
• /
• pp.353-363
• /
• 2012

In order to operate the hydraulic structures efficiently for reducing flood damage after 4 Major River Restoration Project, it is essential to obtain enough hydraulic information with certain reliability. A coupled modeling system, providing spatial hydraulic information, for multi-dimensional hydraulic models was developed to complement 1-D hydraulic modeling. Developed system can offers spatial and grid unit information as well as line and section unit information from 1-D modeling. It is considered that the coupled modeling system can be used to provide various kinds of hydraulic information for river management and treatment.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2003.09a
• /
• pp.447-453
• /
• 2003

연구지역은 경남 양산시 상북면 삼삼리 일원으로 양산단층과 인접하며 급한 경사의 자연사면으로 이루어져 있다. 수치지형자료를 이용하여 고도값을 갖는 자료층을 추출한 후 10m$\times$10m 크기의 격자별로 DEM으로 변환하고, 이로부터 단위 격자의 경사도, 경사방향도, 음영도를 작성하고 흐름분배 알고리즘을 이용하여 설정된 격자별로 상부사면의 기여면적과 습윤지수를 산정하였다. 높은 습윤지수를 보이는 지역은 북서-남동 방향의 선형구조로 나타나며, 국소지역의 전단단열 특성과 일치한다. 한편 연구지역에서 전기비저항 탐사를 실시하여 높은 습윤지수를 나타내는 지역과 저비저항 이상대의 분포를 비교한 결과 습윤지수가 높은 지역은 모두 낮은 전기비저항 이상대로 관찰된다. 즉 습윤지수는 암석의 화학적 풍화를 수반하는 파쇄대의 분포와 일치하며 이를 토대로 국소지역에서 파쇄대의 예측과 암석의 안정성을 예측하는 방법으로 이용될 수 있다.

• Korean Journal of Crystallography
• /
• v.7 no.2
• /
• pp.156-164
• /
• 1996

The atomic configurations of GaAs ∑19, {331}/{331} [110] and ∑3 {111}/{111} [110] tilt grain boundaries were investigated by HRTEM (High-resolution Transmission Electron Microscopy). The boundary planes lie parallel to the crystallographic planes with high number density of coincident lattice sites for given misorientations, exhibiting particular atomic structural units. Secondary boundary dislocations with a core diameter of about 2nm were observed at boundary steps when a slight deviation from exact ∑-related misorientations occurs in the bicrystal system. The relation between the secondary boundary dislocation and the boundary step was discussed based on a DSC lattice model.

• Composites Research
• /
• v.18 no.1
• /
• pp.16-22
• /
• 2005

Application fields on structural health monitoring of fiber Bragg gratings (FBGs) are gradually expanded even to a primary structure as well as a secondary structure and a specimen. For the reason, verification for the reliability of FBGs such as signal characteristics and mechanical strength becomes much more important. In this study, mechanical strength characteristics of FBGs with their fabrication process and reflectivity are investigated with various grating lengths. From the results of tension tests, it is shown that the mechanical strength of optical fibers decreases about $50\%$ just by jacket stripping and the amount of decrease is dependent on stripping methods. About $55\%$ of mechanical strength of stripped optical fibers decreases if gratings are formed in the core and it is regardless of grating lengths and reflectivity. However, the width of strength distribution increases relative to increases in reflectivity.

• KIPS Transactions on Computer and Communication Systems
• /
• v.6 no.5
• /
• pp.239-246
• /
• 2017

Communications for mobile sink groups such as rescue teams or platoons bring about a new challenging issue for handling group mobility in wireless sensor networks. Recently, a group region-based approach has been proposed to send data to a mobile sink group. However, it uses excessive flooding for 3 steps (group region discovery, region information notification, and data dissemination) to support mobile sink group. Thus, it causes high energy consumption and data delivery failure. Moreover, its per-sink mobility supporting scheme makes energy consumption and data delivery failure more serious. Thus, this paper proposes an Energy-efficient and Reliable Mobile Group communication protocol (ERMG) to support a mobile sink group, which exploits a virtual grid structure. For the group region discover and notification and the data dissemination, ERMG uses communications with only cell heads of grid cells that manages group sinks. ERMG also uses a per-grid based scheme to support sink mobility. Simulation results show that ERMG has 30% less energy consumption and 6% more desired delivery deadline success ratio than the existing protocols.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1998.05a
• /
• pp.40-45
• /
• 1998

Th-232를 Fertile 핵연료로 사용한 압력관형 고전환 경수로심을 설계하였다. 토륨 Blanket은 10년 정도 노내에 위치시키고, 농축 우라늄 Driver는 매년 재장전하도록 설계하였다. Driver로는 $UO_2$핵연료와 U-10%Zr 금속 핵연료를 사용하였고, Blanket으로 이중 탄소 피막 핵원료를 ThO$_2$에 적용한 핵연료를 사용하였다. 핵연료봉의 구조는 울진 3/4호기 핵연료와 같은 재원으로 하였으며 육각형 격자 배열로 집합체를 구성하였다. Seed Bundle을 1년 단위로 교체하고 Blanket Bundled을 5년-10년간 노내에 위치시키는 경우 경수로보다는 높은 전환율 갖는 원자로를 설계할 수 있다.