• 대한치과기공학회지
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• 제28권1호
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• pp.27-41
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• 2006

The physical property and phase transformation in a commercial dental casting high gold alloy was investigated as a function of ageing temperature and time using microvickers hardness tester, X-ray diffraction, optical and electron microscopy and EPMA analyser. 1. With increasing ageing time, the hardness of solution-treated gold alloys increased slowly at the initial stage of ageing treatment at an ageing temperature of $300{\sim}400^{\circ}C$, and it reached a maximum value of hardness at the medium stage. Finally, it decreased gradually during further ageing. The maximum value of hardness at was similar with that of the conventional materials and suitable for using as the crown & bridge. 2. During isothermal ageing at a temperature range of $300{\sim}400^{\circ}C$, three phases consisting of the Au-rich ${\alpha}_1$phase with a face-centered cubic structure, the Pt3Zn ${\alpha}_2$phase with an ordered AuCu3(L12) type(f.c.c.) and the Pt-rich ${\alpha}_3$phase with face-centered cubic structure in solution-treated gold alloys were transformed into different three phases consisting of the ${\alpha}_1$phase, the ${\alpha}_3$phase and the PtZn $\beta$phase with an ordered AuCu I(L10) type. 3. The hardening of gold alloys was attributed to the lattice strains of the matrix resulting from the transformation of the ${\alpha}_2$phase to the $\beta$phase. 4. The softening of gold alloys during over-ageing was attributed to the coarsening of the nodules consisting of the $\beta$phase and ${\alpha}_1$matrix.

• 환경생물
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• 제30권2호
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• pp.77-89
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• 2012

With the advent of the genomics era powered by DNA sequencing technologies, life science is being transformed significantly and biological research and development have been accelerated. Environmental biology concerns the relationships among living organisms and their natural environment, which constitute the global biogeochemical cycle. As sustainability of the ecosystems depends on biodiversity, examining the structure and dynamics of the biotic constituents and fully grasping their genetic and metabolic capabilities are pivotal. The high-speed high-throughput next-generation sequencing can be applied to barcoding organisms either thriving or endangered and to decoding the whole genome information. Furthermore, diversity and the full gene complement of a microbial community can be elucidated and monitored through metagenomic approaches. With regard to human welfare, microbiomes of various human habitats such as gut, skin, mouth, stomach, and vagina, have been and are being scrutinized. To keep pace with the rapid increase of the sequencing capacity, various bioinformatic algorithms and software tools that even utilize supercomputers and cloud computing are being developed for processing and storage of massive data sets. Environmental genomics will be the major force in understanding the structure and function of ecosystems in nature as well as preserving, remediating, and bioprospecting them.

• Molecules and Cells
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• 제21권3호
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• pp.428-435
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• 2006

Specific interaction of the epsin N-terminal homology(ENTH) domain with the plasma membrane appears to bridge other related proteins to the specific regions of the membrane that are invaginated to form endocytic vesicles. An additional $\alpha$-helix, referred to as helix 0 (H0), is formed in the presence of the soluble ligand inositol-1,4,5-trisphosphate [$Ins(1,4,5)P_3$] at the N terminus of the ENTH domain (amino acid residues 3-15). The ENTH domain alone and full-length epsin cause tubulation of liposomes made of brain lipids. Thus, it is believed that H0 is membrane-inserted when it is coordinated with the phospholipid phosphatidylinositol-4,5-bisphosphate [$PtdIns(4,5)P_2$], resulting in membrane deformation as well as recruitment of accessory factors to the membrane. However, formation of H0 in a real biological membrane has not been demonstrated. In the present study, the membrane structure of H0 was determined by measurement of electron paramagnetic resonance (EPR) nitroxide accessibility. H0 was located at the phosphate head-group region of the membrane. Moreover, EPR line-shape analysis indicated that no pre-formed H0-like structure were present on normal acidic membranes. $PtdIns(4,5)P_2$ was necessary and sufficient for interaction of the H0 region with the membrane. H0 was stable only in the membrane. In conclusion, the H0 region of the ENTH domain has an intrinsic ability to form H0 in a $PtdIns(4,5)P_2$-containing membrane, perhaps functioning as a sensor of membrane patches enriched with $PtdIns(4,5)P_2$ that will initiate curvature to form endocytic vesicles.

• 한국강구조학회 논문집
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• 제16권5호통권72호
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• pp.555-564
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• 2004

강교량과 같은 구조물에 일반적으로 사용되는 강재는 부식에 약하며, 박판상 구조를 이룰 수 있다는 특징을 갖고 있다. 따라서, 이와 같은 강교량은 차량하중의 증가, 부식 등과 같은 외적요인에 의해 손상되어지기 쉬우며 그에 따른 보수 보강이 요구된다. 그리고, 강교량과 같은 강재 구조물의 보수 보강 방법들은 일반적으로 절단, 볼팅, 및 용접과정을 수반하게 된다. 그러나, 보수 보강 작업을 위해 행해지는 절단 및 용접에 의해 발생되는 응력 및 변형의 특징에 대해 아직 명확히 밝혀지고 있지 않다. 또한, 기존의 안전진단 방법으로는 용접에 의한 보수 보강 작업중 구조물의 안전을 평가하는 것은 문제가 있다. 따라서, 용접에 의한 보수 보강 작업에 따른 구조물의 안전에 대한 신뢰 및 기본적 자료를 확보하기 위해 절단 및 용접과 같은 입열에 의해 발생하는 응력을 일반화 하였다. 또한, 이와 같은 입열에 의해 발생하는 응력에 미치는 작용하중의 영향을 조사하였다.

• 한국농공학회지
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• 제40권5호
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• pp.68-79
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• 1998

In the years, the concern about high-strength concrete which is new material has been heightened as a result of active research and development. Recently, as the building structure has been being bigger, higher, longer and more specialized, the demand of material with high-strength concrete for building has been increasing. The demand of high -strength concrete is expected to increase with expansion of usage about the complex concrete structures such as bridge structure as well as nuclear plants, underground structures, hydraulic structures and arctic area sturctures. In this research, silica-fume was used as an admixture in order to get a high-strength concrete. Water/binder ration was limited no more than 18 percent and the amount of unit cement was increased. In this study, a number of trial in concrete mix was carried out to get optimal mix design, and the target slump with $10{\pm}2cm$ was set for in-situ construction. High-strength concrete with cylinder strength of 1,200kgf/$cm^2$ in the 28-days was produced and tested. The static test was carried out to measure the ultimate load, the initial load of flexural and diagonal cracking, crack patterns, fracture modes. The load versus strain and load versus deflection relations were obtained form the static test. The test results were compared with the shear strengths predicted by the equations of ACI code 318-89 and orther researchers. Based on the test results, shear strength equation of reinforced concrete beam using high strength concrete was proposed. Form an evaluation of the results of this experimental investigation, it was concluded that shear strength after diagonal tention cracking diminished with the increase in compressive strength for beams.

• 한국산학기술학회논문지
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• 제16권4호
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• pp.2911-2916
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• 2015

선하역사는 구조물 상부에 열차가 운행하는 구조로서 타 역사 구조물에 비하여 역사 내의 소음 진동에 취약한 구조이다. 선하역사의 진동 특성을 보다 정확히 파악하기 위해서는 접속교량에서 전달되는 진동에 대한 분석이 필요하다. 이 논문에서는 실험 및 해석을 통하여 접속교량에서 선하역사로 전달되는 진동의 특성을 분석하였다. 대상 구조물은 경춘선 금곡역으로 ABAQUS 3차원 수치해석 모델을 이용하여 해석을 수행하였다. 받침 변화에 따른 접속교량과 역사의 전달 특성 변화를 분석하기 위하여, 철도교량에 적용되어온 다양한 받침의 역학적 성질을 고려하여 해석을 수행하였다. 현장 진동 계측은 열차진행 방향에 따라 접속 교량 및 역사 구조물에 대하여 가속도계를 이용하여 수행하였다.

• 한국지반공학회지:지반
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• 제8권4호
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• pp.5-16
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• 1992

본 연구에서는 다짐 유발응력 (compaction induced stress)을 고려한 보강토 설계방법을 고안하였다. 현행 보강토 설계법은 다짐에 의해 유발되는 횡방향토압을 정량적으로 고려하지 라고 있으므로, 본 연구는 먼저 다짐 유발응력 산정방법을 검토하고 다음에 이를 보강토 설계에 통용 함으로써 새로운 설계방법을 제안하였다. 다짐 유발응력들 고려하면 벽체의 위쪽 부분에 토압이 산정되므로 이 부분에는 인장강도와 인발저항이 큰 보강재 사용이 바람직하다. 이를 위하여 새로이 개발한 보강재 GEOLOG를 소개하였다. 새로운 방법으로 보강토 옹벽을 설계하고 이를 종래의 방법과 비교 분석하여 보강토 공법에 관한 몇가지 결론을 제시하였다.

• Smart Structures and Systems
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• 제6권3호
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• pp.197-209
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• 2010

The structural state of a bridge is currently examined by visual inspection or by wired sensor techniques, which are relatively expensive, vulnerable to inclement conditions, and time consuming to undertake. In contrast, wireless sensor networks are easy to deploy and flexible in application so that the network can adjust to the individual structure. Different sensing techniques have been used with such networks, but the acoustic emission technique has rarely been utilized. With the use of acoustic emission (AE) techniques it is possible to detect internal structural damage, from cracks propagating during the routine use of a structure, e.g. breakage of prestressing wires. To date, AE data analysis techniques are not appropriate for the requirements of a wireless network due to the very exact time synchronization needed between multiple sensors, and power consumption issues. To unleash the power of the acoustic emission technique on large, extended structures, recording and local analysis techniques need better algorithms to handle and reduce the immense amount of data generated. Preliminary results from utilizing a new concept called Acoustic Emission Array Processing to locally reduce data to information are presented. Results show that the azimuthal location of a seismic source can be successfully identified, using an array of six to eight poor-quality AE sensors arranged in a circular array approximately 200 mm in diameter. AE beamforming only requires very fine time synchronization of the sensors within a single array, relative timing between sensors of $1{\mu}s$ can easily be performed by a single Mote servicing the array. The method concentrates the essence of six to eight extended waveforms into a single value to be sent through the wireless network, resulting in power savings by avoiding extended radio transmission.

• 한국구조물진단유지관리공학회 논문집
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• 제11권2호
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• pp.134-144
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• 2007

본 연구에서는 구조물의 모니터링 시스템을 위하여 최근에 급속하게 발전하는 스마트 센서 기술을 이용하여 스마트 센서 장치를 개발하였고 다양한 실험을 통하여 개발한 스마트 센서의 기본적 성능 평가와 모형 구조물을 이용한 손상 검출 실험을 실시하였다. 본 논문은 Part 1로써 스마트 센서의 개발과 성능 평가에 관한 것이고 Part 2에서는 스마트 센서를 이용한 손상 검출 결과를 유선 계측 시스템을 이용한 실험결과와 비교하였다. 스마트 센서는 고 출력의 무선 모뎀과 고 성능 MEMS 센서, AVR 마이크로컨트롤러를 이용하여 개발하였으며 센서의 제어와 운영을 위한 임베디드 프로그램을 개발하였다. 스마트 센서의 성능을 검증하기 위하여 민감도와 분해능 분석 실험과 캔틸레버 보와 가진기를 이용한 데이터 획득 실험, 실 구조물을 이용한 현장 적용 실험을 실시하였다. 실험 결과, 개발한 스마트 센서의 성능에 대한 만족스런 결과를 얻었다.

• Bulletin of the Korean Chemical Society
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• 제31권6호
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• pp.1704-1710
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• 2010

The structure of a 2D grid-like copper(II) complex [Cu$(NCO)_2$(pyz)](pyz=pyrazine) (1) consists of 1D chains of Cu-pyz units connected by double end-on (EO) cyanato bridges. Each Cu(II) ion has a distorted octahedral coordination, completed by the four EO cyanato and two pyrazine ligands. Magnetic interactions through EO cyanato and pyrazine bridges in 1 are discussed on the basis of DFT broken-symmetry calculations at the B3LYP level. For model dicopper(II) complexes I (bridged by cyanato) and II (bridged by pyrazine), electronic structure calculations reproduce very well the experimental couplings for the S = 1/2 ferromagnetic and antiferromagnetic exchange-coupled 2D system: the calculated exchange parameters J are +1.25 $cm^{-1}$ and -3.07 $cm^{-1}$ for I and II, respectively. The $\sigma$ orbital interactions between the Cu $x^2-y^2$ magnetic orbitals and the nitrogen lone-pair orbitals of pyrazine are analyzed from the viewpoint of through-bond interaction. The energy splitting of 0.106 eV between two SOMOs indicates that the superexchange interaction should be antiferromagnetic in II. On the other hand, there are no bridging orbitals that efficiently connect the two copper(II) magnetic orbitals in I because the HOMOs of the basal-apical NCO bridge do not play a role in the formation of overlap interaction pathway. The energy separation in the pair of SOMOs of I is calculated to be very small (0.054 eV). This result is consistent with the occurrence of weakly ferromagnetic properties in I.