1,721,031 research outputs found
Analytical studies on creep of sealed concrete under multiaxial stresses using a microplane model
No full textThe Poisson ratio resulting from multiaxial creep of concrete, which has been reported by some experimental works, is controversial. When calculated from measured strains, Poisson ratio is very sensitive to small experimental error. This sensitivity makes it difficult to determine whether the ratio varies with time or remains constant, and whether it has a different value with stress states. To understand precisely the properties of multiaxial creep of concrete, a new approach is needed. In this study, microplane model is applied to optimally fitting test data extracted from experimental studies on multiaxial creep of concrete. Double-power law is used as a model to represent volumetric and deviatoric creep evolutions on a microplane. Six parameters representing the volumetric and deviatoric compliance functions are determined from regression analysis, and the optimum fits accurately simulate the test data. Poisson ratio is calculated from the optimum fits and its value varies with time. Regression analysis is also performed on the assumption that multiaxial creep of concrete is isotropic. Four parameters are determined for this condition, and the error between the optimum fits and the test data is slightly larger than that for the six-parameter regression results. The constant Poisson ratio with time is obtained from the results of the four-parameter analysis, and the constant value can be used in practice without serious error
약물 복용 이력 없는 환자에서 발생한 간찰부 발진의 2예
No full textWe report a skin rash with a sharply demarcated erythema on the flexural area. The differential diagnoses included Baboon syndrome and symmetrical drug-related intertriginous and flexural exanthema. The diagnosis can be made based on the presence of previous cutaneous sensitization and causative agents. Our cases were consistent with a diagnosis of Baboon syndrome with no drug history. © 2022 Korean Dermatological Association. All rights reserved
Long-term behaviour of square concrete-filled steel tubular columns under axial service loads
No full textThis paper presents experimental and analytical studies on the long-term behaviour of rectangular concrete-filled steel tubular (CFT) columns under central axial loading. Four loading cases are considered in this study: ( a) a load applied simultaneously on both the inner concrete and steel tube (SCE); (b) a load applied only on the inner core concrete (CE); ( c) a load applied on the steel tube and three quarters of the inner concrete (SCQ); and (d) a load applied on the steel tube and half of the inner concrete (SCH). The last two loading cases ( SCQ and SCH) simulate a diaphragm installed in the steel tube. Specimens measuring 600 mm in length were tested for the first two loading cases ( SCE and CE), and specimens of three different lengths, 600, 900 and 1200 mm, were tested for the last two loading cases in order to investigate the effect of the diaphragm size and the length of the specimen on the long-term behaviour of rectangular CFT columns. In addition to the experimental study, three-dimensional finite element models for each specimen were established and verified from a comparison of the test data and the analysis results. From the test and analysis results, a number of conclusions can be drawn. The magnitude of long-term deformation of a CFT column with a diaphragm that covers more than a half of the cross-sectional area of the inner concrete is identical with that of a column under a load applied simultaneously on the entire section of the steel tube and the inner concrete. The diaphragm confines the lateral deformation of the end surface of the column, and its influence range is limited only to the end part of the column, meaning it is limited only from the surface to a depth as long as the width of the CFT column. The confinement effect and stress variation along the longitudinal axis do not occur except in the influence range of the diaphragm. In the case of loading only at the inner concrete, the inner concrete is confined at the corner by the steel tube, and the slip between the inner concrete and the steel tube increases over time
Small, low-loss heterogeneous photonic bandedge laser
Full text linkWe have demonstrated the operation of a new type of heterogeneous photonic crystal laser, a five-lattice-constant large photonic bandedge laser assisted by a photonic bandgap, in a triangular lattice at room temperature. When the air hole radius of the surrounding photonic crystal ( PC) is slightly smaller than that of the bandedge mode region, most in-plane losses of the first K point bandedge mode in the central region are suppressed and the quality factor of the mode is greatly enhanced to 50000. We identified the photonic bandgap-bandedge (PBG-BE) lasing modes through the spectral position, near-field pattern, and the state of polarization, which correspond well with the results of the three-dimensional (3D) finite-difference time-domain (FDTD) method computation. The two-dimensional (2D) feedback mechanism of the first K bandedge was verified through the Fourier analysis. Low threshold incident peak pump power of similar to 0.24 mW is achieved owing to the low optical loss of the PBG-BE mode. (C) 2004 Optical Society of America.This work was supported by the National R&D Project for Nano Science and Technology of
KISTEP, Korea
PEALD of a ruthenium adhesion layer for copper interconnects
No full textRuthenium thin films were produced by plasma-enhanced atomic layer deposition (PEALD) using an alternating supply of bis(ethylcyclopentadienyl)ruthenium [Ru(EtCp)(2)] and NH3 plasma at a deposition temperature of 270 degreesC. The film thickness per cycle was self-limited at 0.038 nm/cycle, which was thinner than the thickness obtained from the conventional ALD using oxygen instead of NH3 plasma. The ruthenium thin film prepared with PEALD had a preferential orientation toward (002), and it was progressively promoted with NH3 plasma power. The PEALD of ruthenium shows a merit in controlling ultrathin film thickness with less than 2 nm more precisely and more easily than the conventional ALD, due to the reduced transient period at the initial film growth stage. Also, ruthenium thin film improved the interfacial adhesion of metallorganic chemical vapor deposited copper to diffusion barrier metals by forming Cu-Ru chemical bonds at the interface without degrading the film resistivity of copper. (C) 2004 The Electrochemical Society.This work was supported by the project of National Research Laboratory (NRL).
The Korea Advanced Institute of Science and Technology assisted in meeting the publication costs of this article
Plasma-enhanced atomic layer deposition of ruthenium thin films
No full textPlasma-enhanced atomic layer deposition (PEALD) of ruthenium thin films was performed using an alternate supply of bis(ethylcyclopentadienyl)ruthenium [Ru(EtCp)(2)] and NH3 plasma. NH3 plasma acted as an effective reducing agent for Ru(EtCp)(2). The ruthenium film formed during one deposition cycle was saturated at 0.038 nm/cycle, and its resistivity was 12 muOmega cm. No carbon or nitrogen impurities were incorporated in the film as determined by elastic recoil detection time of flight. The film density was higher than that formed by a conventional ALD, in which oxygen was used. The root-mean-square surface roughness of a 50 nm thick PELAD ruthenium film was 0.7 nm. (C) 2004 The Electrochemical Society.This work was supported by the project of National Research Laboratory ~NRL!.
Korea Advanced Institute of Science and Technology assisted in meeting the publication costs of this article
Electrical properties of CuInSe2-films prepared by evaporation of Cu2Se and In2Se3 compounds
No full textWe prepared CuInSe2 films by evaporating In2Se3 and Cu2Se compounds instead of elemental sources, The resulting CuInSe2 film grown at 680 degrees C had a smooth and dense microstructure with the grain size of 2 similar to 3 mu m. But the CuInSe2 films were Cu-rich, with a low resistivity of about 0.1 Omega cm. So we conducted H-2 post annealing to control the electrical resistivity and composition of CuInSe2 films. In a H-2 atmosphere, the resistivity increased to about 100 Omega cm by annealing at 350 degrees C for 1 h. The resistivity decreased again when the annealing temperature was above 350 degrees C, This resistivity change might be related to the contents of Cu, In, Se atoms and the valency states of Cu and In ions in the films. We discussed the reason of resistivity change caused by H-2 post annealing in this paper
Highly directional vertical emission from heterogeneous photonic crystal cavity with elliptical air holes
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