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排序方式: 共有496条查询结果,搜索用时 15 毫秒
41.
High Charge‐Carrier Mobility of 2.5 cm2 V−1 s−1 from a Water‐Borne Colloid of a Polymeric Semiconductor via Smart Surfactant Engineering 下载免费PDF全文
42.
Boundary element analysis of thermal stress intensity factors for interface griffith and cusp cracks
Kang Yong Lee
Woon Cheon Baik
《Engineering Fracture Mechanics》1994,47(6):909-918The thermal stress intensity factors for interface cracks of Griffith and symmetric lip cusp types under vertical uniform heat flow in a finite body are calculated by the boundary element method. The boundary conditions on the crack surfaces are insulated or fixed to constant temperature. The relationship between the stress intensity factors and the displacements on the nodal point of a crack-tip element is derived. The numerical values of the thermal stress intensity factors for an interface Griffith crack in an infinite body are compared with the previous solutions. The thermal stress intensity factors for a symmetric lip cusp interface crack in a finite body are calculated with respect to various effective crack lengths, configuration parameters, material property ratios and the thermal boundary conditions on the crack surfaces. Under the same outer boundary conditions, there are no appreciable differences in the distribution of thermal stress intensity factors with respect to each material property. However, the effect of crack surface thermal boundary conditions on the thermal stress intensity factors is considerable. 相似文献
43.
Spontaneous Current Oscillations during Hard Anodization of Aluminum under Potentiostatic Conditions
Nanoporous anodic aluminum oxide is prepared by hard anodization of aluminum under potentiostatic conditions using 0.3 M H2C2O4. Under unstirred electrolyte condition, spontaneous current oscillations are observed. The amplitude and period of these current oscillations are observed to increase with anodization time. As a consequence of the oscillatory behavior, the resulting anodic alumina exhibits modulated pore structures, in which the diameter contrast and the length of pore modulation increase with the amplitude and the period of current oscillations, respectively, and the current peak profile determines the internal geometry of oxide nanopores. The mechanism responsible for the oscillatory behavior is suggested to be a diffusion‐controlled anodic oxidation of aluminum. 相似文献
44.
Hahn YK Jin Z Kang JH Oh E Han MK Kim HS Jang JT Lee JH Cheon J Kim SH Park HS Park JK 《Analytical chemistry》2007,79(6):2214-2220
We demonstrate a novel magnetophoretic immunoassay of allergen-specific immunoglobulin E (IgE) based on the magnetophoretic deflection velocity of a microbead that is proportional to the associated magnetic nanoparticles under enhanced magnetic field gradient in a microchannel. In this detection scheme, two types of house dust mites, Dermatophagoides farinae (D. farinae) and Dermatophagoides pteronyssinus (D. pteronyssinus), were used as the model allergens. Polystyrene microbeads were conjugated with each of the mite extracts followed by incubation with serum samples. The resulting mixture was then reacted with magnetic nanoparticle-conjugated anti-human IgE for detection of allergen-specific IgE by using sandwich immuno-reactions. A ferromagnetic microstructure combined with a permanent magnet was employed to increase the magnetic field gradient ( approximately 10(4) T/m) in a microfluidic device. The magnetophoretic velocities of microbeads were measured in a microchannel under applied magnetic field, and the averaged velocity was well correlated with the concentration of allergen-specific IgE in serum. From the analysis of pooled sera obtained from 44 patients, the detection limits of the allergen-specific human IgEs for D. farinae and D. pteronyssinus were determined to be 565 (0.045 IU/mL) and 268 fM (0.021 IU/mL), respectively. These values are 1 order of magnitude lower than those by a conventional CAP system. For evaluation of reproducibility and accuracy, unknown sera were subjected to a blind test by using the developed assay system, and they were compared with the CAP system. As a result, coefficient of variance was less than 10%, and the developed method enabled a fast assay with a tiny amount of serum ( approximately 10 microL). 相似文献
45.
Dominance of Plasmonic Resonant Energy Transfer over Direct Electron Transfer in Substantially Enhanced Water Oxidation Activity of BiVO4 by Shape‐Controlled Au Nanoparticles 下载免费PDF全文
Mi Gyoung Lee Cheon Woo Moon Hoonkee Park Woonbae Sohn Sung Bum Kang Sanghan Lee Kyoung Jin Choi Ho Won Jang 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(37)
The performance of plasmonic Au nanostructure/metal oxide heterointerface shows great promise in enhancing photoactivity, due to its ability to confine light to the small volume inside the semiconductor and modify the interfacial electronic band structure. While the shape control of Au nanoparticles (NPs) is crucial for moderate bandgap semiconductors, because plasmonic resonance by interband excitations overlaps above the absorption edge of semiconductors, its critical role in water splitting is still not fully understood. Here, first, the plasmonic effects of shape‐controlled Au NPs on bismuth vanadate (BiVO4) are studied, and a largely enhanced photoactivity of BiVO4 is reported by introducing the octahedral Au NPs. The octahedral Au NP/BiVO4 achieves 2.4 mA cm?2 at the 1.23 V versus reversible hydrogen electrode, which is the threefold enhancement compared to BiVO4. It is the highest value among the previously reported plasmonic Au NPs/BiVO4. Improved photoactivity is attributed to the localized surface plasmon resonance; direct electron transfer (DET), plasmonic resonant energy transfer (PRET). The PRET can be stressed over DET when considering the moderate bandgap semiconductor. Enhanced water oxidation induced by the shape‐controlled Au NPs is applicable to moderate semiconductors, and shows a systematic study to explore new efficient plasmonic solar water splitting cells. 相似文献
46.
47.
Seong Kyu Cheon Min Ho Park Seong Su Jeong Ho Ik Jun Tae Hoon Kim 《Integrated ferroelectrics》2019,195(1):81-90
AbstractIn this paper, a piezoelectric small robot was proposed and experimented. The piezoelectric bender of the actuator was composed of trapezoid ceramics which were attached on both surfaces of the elastic body. And an X-shaped structure was composed of four piezoelectric ceramic benders. When AC voltages which have different duty ratio were applied to the four benders, the motion of straight line according to a stick slip of the bender tips was obtained. A FEA simulation was used to analyze the motion of straight line. The output characteristics of the prototype actuator which was fabricated based on the analysis data were measured. 相似文献
48.
Jae Hong Park Tae Yun Kwon Hyung Joon Kim Seung Rae Kim Dae Sung Yoon Chae-Il Cheon Hwan Kim Tae Song Kim 《Journal of Electroceramics》2006,17(2-4):565-572
The PZT thick film cantilever devices fabricated via MEMS process have much attraction because they are appropriate for biological
transducer or sensor, resulting from their large actuating force and relatively high sensitivity especially in liquid. By
means of resonance behavior, theoretical calculation and experimental verification of the PZT thick film cantilever devices
have not been studied before. Accordingly, we focused on the sensitivity analysis and interpretation of the PZT thick film
cantilevers in this study. Especially, the investigation for mass sensitivity of the PZT thick film cantilever is of importance
for physical, chemical and biological sensing application. The PZT thick film cantilever devices were constructed on Pt/TiO2/SiN
X
/Si substrates using screen printing method and MEMS process. The harmonic oscillation response (resonance frequency) was
measured using an optical laser interferometric vibrometer. The effect of cantilever geometry on the resonance frequency change
was investigated. Compared with the theoretical resonant frequency change by mass loading, the experimental resonant frequency
change of the PZT micromechanical thick film cantilever shows a variation of less than 2%. Mass sensitivities are estimated
to be 30.7, 57.1 and 152.0 pg/Hz for the 400 × 380 μm, 400 × 480 μm and 400 × 580 μm cantilever, respectively. 相似文献
49.
Tae Hoon Kim Seong Su Jeong Min Ho Park Ho Ik Jun Seong Kyu Cheon 《Integrated ferroelectrics》2019,195(1):91-99
AbstractT-shaped ambulatory piezoelectric actuator which can be used for various purposes such as lifesaving and environmental monitoring was proposed. The actuator consists of eight piezoelectric benders, t-shaped stator, and four legs, and it is very simple in structure and has the advantages of being easily manufactured and downsizing. It is also driven by four legs and can be moved forward and backward. The piezoelectric bender was composed of a carbon body and a ceramic plate. Vibration motions of the piezoelectric benders in x and z axes were transfer to the legs and the elliptical displacements at the ends of the legs were obtained by combination of the phase difference of 90 degrees. Characteristics of the actuators were simulated by finite element analysis, and the optimized prototype actuator was fabricated and experimented. 相似文献
50.
The non-transition metal spinel MgAl2O4 and the transition metal spinels (NiFe2O4, NiAlFeO4) have been prepared by standard ceramic processing method in the air. The effect of annealing atmosphere on the dielectric properties after sintering has been studied. The annealing atmospheres were N2, O2, and N2–H2 mixture. Dielectric constant ? r and tangent loss tanδ have been characterized by varying the measuring temperature and frequency (5 Hz–5 MHz) using the impedance analyzer. The ? r and tanδ of the non-transition metal spinel MgAl2O4 remained unchanged even with varying the annealing atmosphere. While the dielectric properties of the transition metal spinels, NiFe2O4 and NiAlFeO4 were critically dependent on the annealing atmosphere. Crystal structural models for the samples manufactured in air have been tested by the Rietveld refinement method for both the centrosymmetric Fd-3m and the noncentrosymmetric F-43m. The electron density distributions were determined by the whole pattern fitting based on the maximum entropy method (MEM). The dielectric properties of the samples have been also discussed in terms of the structure and electron distribution analysis results. 相似文献