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981.
Two counterpropagating laser beams were used to significantly stretch soft dielectrics such as cells. The deforming forces act on the surface between the object and the surrounding medium and are considerably higher than the trapping forces on the object. Radiation damage is avoided since a double-beam trap does not require focusing for stable trapping. Ray optics was used to describe the stress profile on the surface of the trapped object. Measuring the total forces and deformations of well-defined elastic objects validated this approach. 相似文献
982.
Francis C. Moon 《Experimental Mechanics》1975,15(5):184-189
The passage of transient electric currents through a gas into a solid occurs in high-voltage switches and in lightning strikes. The experiments reported in this paper were designed to examine the vibration of a cantilevered conductor under electromagnetic forces of the arc and structural currents. Arcs are created at low pressures in a vacuum facility and the induced vibrations of the beam are measured. It is shown that the deflections are proportional to the square of the arc currents. Further, 5-μs photographs of the 2-ms arc, using a Kerr cell, show that the arc is distorted by the magnetic field of the beam currents. A simple analytical model is shown to reproduce the basic results of the experiments. 相似文献
983.
The final state for nonlinear systems with multiple attractors may become unpredictable as a result of homoclinic or heteroclinic bifurcations. The fractal basin boundaries due to such bifurcations for a four-well, two-degree-of-freedom, nonlinear oscillator under sinusoidal forcing have been studied, based on a theory of homoclinic bifurcation inn-dimensional vector space developed by Palmer. Numerical simulation is used as a means of demonstrating the consequences of the system dynamics when the bifurcations occur, and it is shown that the basin boundaries in the configuration space (x, y) become fractal near the critical value of the heteroclinic bifurcations. 相似文献
984.
985.
Jeffrey Luo Huibin Chang Amir A. Bakhtiary Davijani H. Clive Liu Po-Hsiang Wang Robert J. Moon Satish Kumar 《Cellulose (London, England)》2017,24(4):1745-1758
Polyacrylonitrile-co-methacrylic acid (PAN-co-MAA) and cellulose nanocrystal (CNC) composite films were produced with up to 40 wt% CNC loading through the solution casting method. The rheological properties of the solution/suspensions and the structural, optical, thermal, and mechanical properties of the resulting films were investigated. The viscosity of the composite suspensions increased with higher CNC loadings and with longer aging times. PAN-co-MAA/CNC films maintained a similar level of optical transparency even with up to 40 wt% CNC loading. The glass transition temperature (Tg) increased from 92 to 118 °C, and the composites had higher thermal stability below 350 °C compared to both neat PAN-co-MAA and neat CNC. The mechanical properties also increased with higher CNC loadings, elastic modulus increased from 2.2 to 3.7 GPa, tensile strength increased from 75 to 132 MPa, and the storage modulus increased from 3.9 to 10.5 GPa. Using the Kelly and Tyson model the interfacial shear strength between the PAN-co-MAA and CNC was calculated to be 27 MPa. 相似文献
986.
In this paper we establish asymptotic results and a generalized uniform law of the iterated logarithm (LIL) for the increments of a strictly stationary random process, whose results are proved by separating linearly positive quadrant dependent (LPQD) random process and linearly negative quadrant dependent (LNQD) one, respectively. 相似文献
987.
Designing a Highly Active Metal‐Free Oxygen Reduction Catalyst in Membrane Electrode Assemblies for Alkaline Fuel Cells: Effects of Pore Size and Doping‐Site Position 下载免费PDF全文
Seonggyu Lee Myounghoon Choun Youngjin Ye Prof. Dr. Jaeyoung Lee Yeongdong Mun Dr. Eunae Kang Jongkook Hwang Young‐Ho Lee Prof. Dr. Chae‐Ho Shin Prof. Dr. Seung‐Hyeon Moon Prof. Dr. Soo‐Kil Kim Prof. Dr. Eunsung Lee Prof. Dr. Jinwoo Lee 《Angewandte Chemie (International ed. in English)》2015,54(32):9230-9234
To promote the oxygen reduction reaction of metal‐free catalysts, the introduction of porous structure is considered as a desirable approach because the structure can enhance mass transport and host many catalytic active sites. However, most of the previous studies reported only half‐cell characterization; therefore, studies on membrane electrode assembly (MEA) are still insufficient. Furthermore, the effect of doping‐site position in the structure has not been investigated. Here, we report the synthesis of highly active metal‐free catalysts in MEAs by controlling pore size and doping‐site position. Both influence the accessibility of reactants to doping sites, which affects utilization of doping sites and mass‐transport properties. Finally, an N,P‐codoped ordered mesoporous carbon with a large pore size and precisely controlled doping‐site position showed a remarkable on‐set potential and produced 70 % of the maximum power density obtained using Pt/C. 相似文献
988.
Soonsang Hong Dr. Md. Rumum Rohman Dr. Jiangtao Jia Dr. Youngkook Kim Dr. Dohyun Moon Dr. Yonghwi Kim Dr. Young Ho Ko Prof. Dr. Eunsung Lee Prof. Dr. Kimoon Kim 《Angewandte Chemie (International ed. in English)》2015,54(45):13241-13244
The porphyrin boxes ( PB‐1 and PB‐2 ), which are rationally designed porous organic cages with a large cavity using well‐defined and rigid 3‐connected triangular and 4‐connected square shaped building units are reported. PB‐1 has a cavity as large as 1.95 nm in diameter and shows high chemical stability in a broad pH range (4.8 to 13) in aqueous media. The crystalline nature as well as cavity structure of the shape‐persistent organic cage crystals were intact even after complete removal of guest molecules, leading to one of the highest surface areas (1370 m2g?1) among the known porous organic molecular solids. The size of the cavities and windows of the porous organic cages can be modulated using different sized building units while maintaining the topology of the cages, as illustrated with PB‐2 . Interestingly, PB‐2 crystals showed unusual N2 sorption isotherms as well as high selectivity for CO2 over N2 and CH4 (201 and 47.9, respectively at 273 K at 1 bar). 相似文献
989.
Lee JS Moon SJ Yang BJ Yu J Schade U Yoshida Y Ikeda SI Noh TW 《Physical review letters》2007,98(9):097403
Optical spectra of a double-layered perovskite ruthenate Ca3Ru2O7 show a pseudogap opening around 200 cm(-1) below 50 K, which is attributable to the partial k-space gap opening due to the density wave instability. Unlike most other density wave materials, Ca3Ru2O7 has spectral weight redistributions, not near the energy gap region, but at a much higher energy region around 800 cm(-1). As a possible origin of these intriguing features, we discuss the orbital flip excitation in the density wave ground state. 相似文献
990.
A novel method of reconstructing wavefront aberrations by use of Zernike polynomials for radial shearing interferometers is discussed. This method uses matrix formalism to calculate the Zernike coefficients of a wavefront under test and shows the validity of reconstructing an arbitrary wavefront aberration from an interferogram taken by a radial shearing interferometer. We also propose a new interferometer setup to determine the shape and the direction (concave or convex) of wavefront aberration in a single measurement. 相似文献