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排序方式: 共有293条查询结果,搜索用时 15 毫秒
141.
V. Yu. Davydov A. A. Klochikhin A. N. Smirnov I. Yu. Strashkova A. S. Krylov Hai Lu William J. Schaff H. -M. Lee Y. -L. Hong S. Gwo 《Semiconductors》2010,44(2):161-170
It is shown that a study of the dependence of impurity-related resonant first-order Raman scattering on the frequency of excitation light makes it possible to observe the dispersion of polar optical and acoustic branches of vibrational spectrum in hexagonal InN within a wide range of wave vectors. It is established that the wave vectors of excited phonons are uniquely related to the energy of excitation photon. Frequencies of longitudinal optical phonons E1(LO) and A1(LO) in hexagonal InN were measured in the range of excitation-photon energies from 2.81 to 1.17 eV and the frequencies of longitudinal acoustic phonons were measured in the range 2.81–1.83 eV of excitation-photon energies. The obtained dependences made it possible to extrapolate the dispersion of phonons A1(LO) and E1(LO) to as far as the point Γ in the Brillouin zone and estimate the center-band energies of these phonons (these energies have not been uniquely determined so far). 相似文献
142.
Po‐Chun Wang Gwo‐Long Li Shu‐Fen Huang Mei‐Juan Chen Shih‐Chien Lin 《ETRI Journal》2010,32(4):577-587
The layered coding structure of scalable video coding (SVC) with adaptive inter‐layer prediction causes noticeable computational complexity increments when compared to existing video coding standards. To lighten the computational complexity of SVC, we present a fast algorithm to speed up the inter‐mode decision process. The proposed algorithm terminates inter‐mode decision early in the enhancement layers by estimating the rate‐distortion (RD) cost from the macroblocks of the base layer and the enhancement layer in temporal, spatial, and inter‐layer directions. Moreover, a search range decision algorithm is also proposed in this paper to further increase the motion estimation speed by using the motion vector information from temporal, spatial, or inter‐layer domains. Simulation results show that the proposed algorithm can determine the best mode and provide more efficient total coding time saving with very slight RD performance degradation for spatial and quality scalabilities. 相似文献
143.
Bielański A. Małecka-Lubańska A. Micek-Ilnicka A. Poźniczek J. 《Topics in Catalysis》2000,11(1-4):43-53
Basing on the kinetic and sorption experiments a mechanism of catalytic formation of methyl-tert-butyl ether (MTBE) on H4SiW12O40 was proposed. A reaction intermediate, carbenium ion C4H 9 + , is forming at the catalyst surface from isobutene supplied from gas phase and protons supplied by the solid. Subsequently C4H 9 + reacts with methanol absorbed by the solid heteropolyacid. The model satisfactorily explains the anomalous reaction order with respect to methanol which under the applied conditions is positive at the initial stage of the catalytic process and becomes negative at its steady state. This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
144.
Kamila Sofińska Jakub Barbasz Tomasz Witko Jerzy Dryzek Katarzyna Haraźna Małgorzata Witko Joanna Kryściak-Czerwenka Maciej Guzik 《应用聚合物科学杂志》2019,136(4):47192
Insight into the topographic and mechanical properties of biomaterials allows for efficient selection of a material for a specific application. Here, atomic force microscopy (AFM) and force spectroscopy were exploited to reveal the topographic and mechanical characteristics of charcoal-purified, solvent-cast polyhydroxyoctanoate (PHO) film. The root mean square surface roughness of a PHO surface derived from ethyl acetate, acetone, or chloroform solution was 13.2, 11.5, or 30.9 nm, respectively, for 100 μm2 AFM images. The distribution of the local Young's modulus had a maximum of 25.4, 14.1, and 12.6 MPa for PHO films obtained from ethyl acetate, acetone, and chloroform solution, respectively. The positron annihilation spectroscopy measurements allowed us to determine the free volume in the polymer film structure (9.38%). Moreover, a number of additional techniques (X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, gel permeation chromatography, NMR, infrared spectroscopy, and polarized light microscopy) were used to reveal PHO features. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47192. 相似文献
145.
Daria Różycka Dr. Aleksandra Kowalczyk Dr. Marta Denel-Bobrowska Olga Kuźmycz Dr. Magdalena Gapińska Prof. Paweł Stączek Prof. Agnieszka B. Olejniczak 《ChemMedChem》2023,18(7):e202200666
Synthesis of acridine derivatives that act as DNA-targeting anticancer agents is an evolving field and has resulted in the introduction of several drugs into clinical trials. Carboranes can be of importance in designing biologically active compounds due to their specific properties. Therefore, a series of novel acridine analogs modified with carborane clusters were synthesized. The DNA-binding ability of these analogs was evaluated on calf thymus DNA (ct-DNA). Results of these analyses showed that 9-[(1,7-dicarba-closo-dodecaborane-1-yl)propylamino]acridine ( 30 ) interacted strongly with ct-DNA, indicating its ability to intercalate into DNA, whereas 9-[(1,7-dicarba-closo-dodecaborane-1-yl)propanamido]acridine ( 29 ) changed the B-form of ct-DNA to the Z form. Compound 30 demonstrated cytotoxicity, was able to inhibit cell proliferation, arrest the cell cycle in the S phase in the HeLa cancer cell line, and induced the production of reactive oxygen species (ROS). In addition, it was specifically localized in lysosomes and was a weak inhibitor of Topo IIα. 相似文献
146.
Kowal Marta Sorokowski Piotr Kulczycki Emanuel Żelaźniewicz Agnieszka 《Scientometrics》2022,127(1):265-273
Scientometrics - The beauty of science lies within its core assumption that it seeks to identify the truth, and as such, the truth stands alone and does not depend on the person who proclaims it.... 相似文献
147.
Influence of carrier concentration in membrane on citric acid transport rate through PIM was researched. Received dependence is not linear with evident percolation threshold. On the basis of the obtained results, the parameters of the percolation equation were calculated. The estimated value of the percolation threshold is XC = 0.13. On the basis of the received findings of the investigation, the transport mechanism of citric acid through PIM has been proposed. The presence of the percolation threshold and the absence of flux decreasing with the carrier’s molecule increasing prove that citric acid is transported in accordance with fixed-site jumping mechanism. 相似文献
148.
We show how a number of NP-complete as well as NP-hard problems can be reduced to the Sturm-Liouville eigenvalue problem in
the quantum setting with queries. We consider power queries which are derived from the propagator of a system evolving with
a Hamiltonian obtained from the discretization of the Sturm-Liouville operator. We use results of our earlier paper concering
the complexity of the Sturm-Liouville eigenvalue problem. We show that the number of power queries as well the number of qubits
needed to solve the problems studied in this paper is a low degree polynomial. The implementation of power queries by a polynomial
number of elementary quantum gates is an open issue. If this problem is solved positively for the power queries used for the
Sturm-Liouville eigenvalue problem then a quantum computer would be a very powerful computation device allowing us to solve
NP-complete problems in polynomial time.
相似文献
149.
Summary The aim of this contribution is twofold. First, a dispersive model of periodic composite solids made of an isotropic matrix
reinforced by a hexagonal system of slender fibres or by a honeycomb-like slender skeleton is formulated. Second, this model
is applied to the analysis of vibration and wave propagation problems in the above honeycomb based composites. Contrary to
the known homogenized models the main feature of the proposed model is that it describes the effect of cell size on the overall
dynamic behavior of a composite solid. It is shown that on the macro-level the response of honeycomb based composites is isotropic.
It is also proved that there exist dispersive dilatational-type and shear-type waves, which can propagate in these composites.
Simple formulae for lower and higher free vibration frequencies are derived, and the existence of certain restrictons imposed
on the physically allowable wave propagation speeds is shown. 相似文献
150.
Chih‐Yung Chang Chih‐Yu Lin Gwo‐Jong Yu Chin‐Hwa Kuo 《Wireless Communications and Mobile Computing》2013,13(4):377-392
In wireless sensor networks (WSNs), coverage of the monitoring area represents the surveillance quality. Since sensor nodes are battery powered and placed outdoor, there will be failures due to energy exhaustion or environmental influence, resulting in coverage‐loss. In literature, a number of studies developed robot repairing algorithms that aim at maintaining full coverage. However, they did not consider the time constraint for network maintenance. Furthermore, they did not consider the existence of obstacles and the constraint of limited energy of the robot. This paper presents a novel tracking mechanism and robot repairing algorithm for maintaining the coverage quality of the given WSN. Without support of location information, the tracking mechanism leaves robot's footmark on sensors so that they can learn better routes for sending repairing requests to the robot. Upon receiving several repairing request messages, the robot applies the proposed repairing algorithm to establish an efficient route that passes through all failure regions with low overhead in terms of the required time and the power consumption. In addition, the proposed repairing algorithm also considers the remaining energy of the robot so that the robot can move back to home for recharging energy and overcome the unpredicted obstacles. Performance results reveal that the developed protocol can efficiently maintain the coverage quality while the required time and energy consumption are significantly reduced. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献