• Title/Summary/Keyword: structural boundaries

Search Result 278, Processing Time 0.022 seconds

Structural, optical, and electrical properties on Cu(In,Ga)$Se_2$ thin-films with Cu-defects and In/(In+Ga) ratio (Cu(In,Ga)$Se_2$ 박막의 Cu 결함 및 In, Ga 비율의 변화에 따른 구조적, 광학적, 전기적 특성 연구)

  • Jeong, A.R.;Kim, G.Y.;Jo, W.;Jo, H.J.;Kim, D.H.;Sung, S.J.;Kang, J.K.;Lee, D.H.;Nam, D.H.;Cheong, H.
    • 한국신재생에너지학회:학술대회논문집
    • /
    • 2011.11a
    • /
    • pp.47.1-47.1
    • /
    • 2011
  • We report on a direct measurement of two-dimensional chemical and electrical distribution on the surface of photovoltaic Cu(In,Ga)$Se_2$ thin-films using a nano-scale spectroscopic and electrical characterization, respectively. The Raman measurement reveals non-uniformed surface phonon vibration which comes from different compositional distribution and defects in the nature of polycrystalline thin-films. On the other hand, potential analysis by scanning Kelvin probe force microscopy shows a higher surface potential or a small work function on grain boundaries of the thin-films than on the grain surfaces. This demonstrates the grain boundary is positively charged and local built-in potential exist on grain boundary, which improve electron-hole separation on grain boundary. Local electrical transport measurements with scanning probe microscopy on the thin-films indicates that as external bias is increases, local current is started to flow from grain boundary and saturated over 0.3 V external bias. This accounts for carrier behavior in the vicinity of grain boundary with regard to defect states. We suggest that electron-hole separation at the grain boundary as well as chemical and electrical distribution of polycrystalline Cu(In,Ga)$Se_2$ thin-films.

  • PDF

A Study on Electrochemical Polarization Test for Embrittlement Damage Evaluation of Aged Cr-Mo Steel (Cr-Mo강 시효재의 취화손상 평가를 위한 전기화학적 분극시험에 관한 연구)

  • Yu, Hyo-Sun
    • Journal of the Korean Society for Nondestructive Testing
    • /
    • v.19 no.6
    • /
    • pp.411-419
    • /
    • 1999
  • It has been well recognized that a long term service at elevated temperature of $350^{\circ}C{\sim}550^{\circ}C$ induces embrittlement damage due to carbide precipitation and/or P, Sb and Sn segregation at grain boundaries and thereby deteriorates the grain boundary strength of heat resisting components in the energy-related plants. Therefore, it is very important to assess quantitatively the extent of embrittlement damage of heat resisting components to secure the reliable and efficient service condition and to prevent brittle failure in service. However, because fracture tests are limited in size and number of specimen obtained from the structural components, nondestructive test method is required. In this study, the optimum electrochemical parameters are investigated and discussed to evaluate nondestructive embrittlement damage for aged 2.25Cr-1Mo steels by means of electrochemical polarization test method (ECPTM) in proper corrosive environment. In addition, the electrochemical test results are compared with embrittlement degree evaluated by semi-nondestructive SP test.

  • PDF

Strongly Coupled Method for 2DOF Flutter Analysis (강성 결합 기법을 통한 2계 자유도 플러터 해석)

  • Ju, Wan-Don;Lee, Gwan-Jung;Lee, Dong-Ho;Lee, Gi-Hak
    • Journal of the Korean Society for Aeronautical & Space Sciences
    • /
    • v.34 no.1
    • /
    • pp.24-31
    • /
    • 2006
  • In the present study, a strongly coupled analysis code is developed for transonic flutter analysis. For aerodynamic analysis, two dimensional Reynolds-Averaged Navier-Stokes equation was used for governing equation, and ε-SST for turbulence model, DP-SGS(Data Parallel Symmetric Gauss Seidel) Algorithm for parallelization algorithm. 2 degree-of-freedom pitch and plunge model was used for structural analysis. To obtain flutter response in the time domain, dual time stepping method was applied to both flow and structure solver. Strongly coupled method was implemented by successive iteration of fluid-structure interaction in pseudo time step. Computed results show flutter speed boundaries and limit cycle oscillation phenomena in addition to typical flutter responses - damped, divergent and neutral responses. It is also found that the accuracy of transonic flutter analysis is strongly dependent on the methodology of fluid-structure interaction as well as on the choice of turbulence model.

Waveform inversion of shallow seismic refraction data using hybrid heuristic search method (하이브리드 발견적 탐색기법을 이용한 천부 굴절법 자료의 파형역산)

  • Takekoshi, Mika;Yamanaka, Hiroaki
    • Geophysics and Geophysical Exploration
    • /
    • v.12 no.1
    • /
    • pp.99-104
    • /
    • 2009
  • We propose a waveform inversion method for SH-wave data obtained in a shallow seismic refraction survey, to determine a 2D inhomogeneous S-wave profile of shallow soils. In this method, a 2.5D equation is used to simulate SH-wave propagation in 2D media. The equation is solved with the staggered grid finite-difference approximation to the 4th-order in space and 2nd-order in time, to compute a synthetic wave. The misfit, defined using differences between calculated and observed waveforms, is minimised with a hybrid heuristic search method. We parameterise a 2D subsurface structural model with blocks with different depth boundaries, and S-wave velocities in each block. Numerical experiments were conducted using synthetic SH-wave data with white noise for a model having a blind layer and irregular interfaces. We could reconstruct a structure including a blind layer with reasonable computation time from surface seismic refraction data.

A Study on Contemporary Sports Star Fashion - Focusing on David Beckham and Tiger Woods - (현대 스포츠 스타 패션 연구 - 데이비드 베컴과 타이거 우즈를 중심으로 -)

  • Hahn, Soo-Yeon;Yang, Sook-Hi
    • The Research Journal of the Costume Culture
    • /
    • v.17 no.2
    • /
    • pp.296-308
    • /
    • 2009
  • The purpose of this study is to comprehend the contemporary sports star fashion and to contemplate aesthetic characteristics of sports star fashion, thereby to establish the styles of sports star fashion. For such purposes, this study first examines aesthetic characteristics of sports fashion and star fashion based on previous studies, in order to analyze aesthetic characteristics of sports star fashion, and conducts a case study by analyzing photographic materials of fashion styles of well-known male sports stars such as the English soccer player David Beckham and American golf player Tiger Woods. The result of this study is as follows: the aesthetic characteristics of the contemporary sports star fashion are virility, functionality, sensuality and deconstruction. (1) Virility emphasizes manly features by displaying trained and disciplined body. (2) Functionality is expressed through structural simplicity and temperance of decoration. High-tech textiles and fibers are favored in order to fit in comfortable bodily movement for the heavy exercises. (3) Sensuality, as an expression of indulgence of sexual pleasure, is expressed through bodily exposure. Lastly, (4) deconstruction, which means destroying existed boundaries of cultural categories, is shown as co-existence of design elements from different times and places, stereotypes and sensibilities. Virility and functionality are prominent characteristics expressed in sports uniforms and training costumes. Sensuality and deconstruction are shown in daily fashion and formal dress outside the sports field.

  • PDF

Numerical and Experimental Study of U-Bending of SUS304L Heat Transfer Tubes (SUS304L 튜브의 U-Bending 성형공정에 관한 해석적·실험적 연구)

  • Kim, Y.B.;Kang, B.S.;Ku, T.W.
    • Transactions of Materials Processing
    • /
    • v.23 no.7
    • /
    • pp.405-412
    • /
    • 2014
  • As a major type of heat exchanger, the steam generator (SG) produces steam from heat energy of a nuclear power plant reactor. The steam produced by the steam generator flows into a turbine, and plays an important role in electric power generation. The heat transfer tubes in the steam generator consist of approximately 10,000 U-shaped tubes, which perform a structural role and act as thermal boundaries. The heat transfer tubes conduct the thermal energy between the primary coolant (about $320^{\circ}C$, $157kgf/cm^2$) obtained from the reactor and the secondary coolant (about $260^{\circ}C$, $60kgf/cm^2$) as part of the secondary system. Recently, the heat transfer tubes in the steam generator of the pressurized water reactor (PWR) are primarily produced from Alloy 600 and Alloy 690 seamless tubes. As a pilot study to find process parameters for the cold U-bending process using rotary draw bending, numerical and experimental investigations were conducted to produce U-shaped tubes from long straight SUS304L seamless tubes. 3D finite element simulations were run using ABAQUS Explicit with consideration of the elastic recovery. The process parameters studied were the angular speed, the operation period and the bending angle. Experimental verifications were conducted to insure the suitability of the final U-shaped configurations with respect to both ovality and wall thickness.

Japanism in modern fashion - From 2001 S/S to 2011 S/S - (현대패션에 나타난 재패니즘(Japanism)에 관한 연구 - 2001S/S에서 2011S/S를 중심으로 -)

  • Kim, Sun Young
    • The Research Journal of the Costume Culture
    • /
    • v.21 no.2
    • /
    • pp.151-166
    • /
    • 2013
  • This study aims to shed light on the diversity and complexity of design represented through modern fashion and to identify growth opportunities for globalizing and modernizing traditional clothing designs. To this end, formative trends and aesthetic characteristics of $21^{st}$ century fashion were analyzed, with an emphasis on Japanism reflected in the works of Western designers. The research methodology consisted of an analysis as well as a literature review. A total of 217 designs with Japanism characteristics were identified from the 2001 S/S collection to the 2011 S/S collection in Paris, Milano, New York, and London, and these were analyzed in terms of image, color details, pattern, and accessories. The research findings with regard to the characteristics of modern fashion designs that reflect Japanism were as follows. First, sensuality was projected by highlighting the erotic elements of Japanese clothing. Second, the underlying principles, styles, and elements of Japan's traditional clothing were embodied in a cross-cultural and eclectic manner that blurred the boundaries between styles by mix-and- matching the traditional and the contemporary, the East and the West, and different styles. Third, a variety of patterns, colors, accessories, and design techniques associated with Japanese traditional clothing played a critical role in creating flamboyant and decorative images in contemporary fashion. Fourth, the overlapping of the kimono style, the flat design that accentuates body curves, and the layered style has created a beautifully free-form fashion that demonstrates non-structural features.

Electrical Transport Properties and Magnetoresistance of (1-x)La0.7Sr0.3MnO3/xZnFe2O4 Composites

  • Seo, Yong-Jun;Kim, Geun-Woo;Sung, Chang-Hoon;Lee, Chan-Gyu;Koo, Bon-Heun
    • Korean Journal of Materials Research
    • /
    • v.20 no.3
    • /
    • pp.137-141
    • /
    • 2010
  • The $(1-x)La_{0.7}Sr_{0.3}MnO_3(LSMO)/xZnFe_2O_4$(ZFO) (x = 0, 0.01, 0.03, 0.06 and 0.09) composites were prepared by a conventional solid-state reaction method. We investigated the structural properties, magnetic properties and electrical transport properties of (1-x)LSMO/xZFO composites using X-ray diffraction (XRD), scanning electron microscopy (SEM), field-cooled dc magnetization and magnetoresistance (MR) measurements. The XRD and SEM results indicate that LSMO and ZFO coexist in the composites and the ZFO mostly segregates at the grain boundaries of LSMO, which agreed well with the results of the magnetic measurements. The resistivity of the samples increased by the increase of the ZFO doping level. A clear metal-to-insulator (M-I) transition was observed at 360K in pure LSMO. The introduction of ZFO further downshifted the transition temperature (350K-160K) while the transition disappeared in the sample (x = 0.09) and it presented insulating/semiconducting behavior in the measured temperature range (100K to 400K). The MR was measured in the presence of the 10kOe field. Compared with pure LSMO, the enhancement of low-field magnetoresistance (LFMR) was observed in the composites. It was clearly observed that the magnetoresistance effect of x = 0.03 was enhanced at room temperature range. These phenomena can be explained using the double-exchange (DE) mechanism, the grain boundary effect and the intrinsic transport properties together.

Dielectric and Electrical Characteristics of Lead-Free Complex Electronic Material: Ba0.8Ca0.2(Ti0.8Zr0.1Ce0.1)O3

  • Sahu, Manisha;Hajra, Sugato;Choudhary, Ram Naresh Prasad
    • Korean Journal of Materials Research
    • /
    • v.29 no.8
    • /
    • pp.469-476
    • /
    • 2019
  • A lead-free bulk ceramic having a chemical formula $Ba_{0.8}Ca_{0.2}(Ti_{0.8}Zr_{0.1}Ce_{0.1})O_3$ (further termed as BCTZCO) is synthesized using mixed oxide route. The structural, dielectric, impedance, and conductivity properties, as well as the modulus of the synthesized sample are discussed in the present work. Analysis of X-ray diffraction data obtained at room temperature reveals the existence of some impurity phases. The natural surface morphology shows close packing of grains with few voids. Attempts have been made to study the (a) effect of microstructures containing grains, grain boundaries, and electrodes on impedance and capacitive characteristics, (b) relationship between properties and crystal structure, and (c) nature of the relaxation mechanism of the prepared samples. The relationship between the structure and physical properties is established. The frequency and temperature dependence of the dielectric properties reveal that this complex system has a high dielectric constant and low tangent loss. An analysis of impedance and related parameters illuminates the contributions of grains. The activation energy is determined for only the high temperature region in the temperature dependent AC conductivity graph. Deviation from the Debye behavior is seen in the Nyquist plot at different temperatures. The relaxation mechanism and the electrical transport properties in the sample are investigated with the help of various spectroscopic (i.e., dielectric, modulus, and impedance) techniques. This lead free sample will serve as a base for device engineering.

Assessment of Historical Earthquake Magnitudes and Epicenters Using Ground Motion Simulations (지진동 모사를 통한 역사지진 규모와 진앙 평가)

  • Kim, Seongryong;Lee, Sang-Jun
    • Journal of the Earthquake Engineering Society of Korea
    • /
    • v.25 no.2
    • /
    • pp.59-69
    • /
    • 2021
  • Historical records of earthquakes are generally used as a basis to extrapolate the instrumental earthquake catalog in time and space during the probabilistic seismic hazard analysis (PSHA). However, the historical catalogs' input parameters determined through historical descriptions rather than any quantitative measurements are accompanied by considerable uncertainty in PSHA. Therefore, quantitative assessment to verify the historical earthquake parameters is essential for refining the reliability of PSHA. This study presents an approach and its application to constrain reliable ranges of the magnitude and corresponding epicenter of historical earthquakes. First, ranges rather than specific values of ground motion intensities are estimated at multiple locations with distances between each other for selected historical earthquakes by reviewing observed co-seismic natural phenomena, structural damage levels, or felt areas described in their historical records. Based on specific objective criteria, this study selects only one earthquake (July 24, 1643), which is potentially one of the largest historical earthquakes. Then, ground motion simulations are performed for sufficiently broadly distributed epicenters, with a regular grid to prevent one from relying on strong assumptions. Calculated peak ground accelerations and velocities in areas with the historical descriptions on corresponding earthquakes are converted to intensities with an empirical ground motion-intensity conversion equation to compare them with historical descriptions. For the ground motion simulation, ground motion prediction equations and a frequency-wavenumber method are used to consider the effects of possible source mechanisms and stress drop. From these quantitative calculations, reliable ranges of epicenters and magnitudes and the trade-off between them are inferred for the earthquake that can conservatively match the upper and lower boundaries of intensity values from historical descriptions.