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301.
Barón-González AJ Frontera C García-Mu?oz JL Rivas-Murias B Blasco J 《J Phys Condens Matter》2011,23(49):496003
The origin of dielectric anomalies and magnetodielectric response of La(2)MnCoO(6) has been investigated by means of ultra-high resolution synchrotron x-ray powder diffraction, neutron powder diffraction, resistivity, magnetization and dielectric measurements. The study has been performed on two different bulk samples presenting different degrees of Mn/Co order: 95 and 74%. Beside the well-known influence on magnetic properties, our results show that the main effect of disorder lies on the electrical resistivity. Bond distances clearly show Mn(4+)/Co(2+) valence states in the well-ordered sample, while for the disordered one this picture still holds. AC resistivity data show dielectric anomalies and a small magnetodielectric effect, but impedance complex plane analyses prove that these phenomena appear at the frequency-temperature region where extrinsic effects dominate the dielectric response. 相似文献
302.
Harekrishna Bar Dipak Kr. Bhui Gobinda P. Sahoo Priyanka Sarkar Santanu Pyne Ajay Misra 《Colloids and surfaces. A, Physicochemical and engineering aspects》2009,348(1-3):212-216
An eco-friendly process for rapid synthesis of silver nanoparticles has been reported using aqueous seed extract of Jatropha curcas. Formation of stable silver nanoparticles at different concentration of AgNO3 gives mostly spherical particles with diameter ranging from 15 to 50 nm. The resulting silver particles are characterized using HRTEM, XRD and UV–vis spectroscopic techniques. XRD study shows that the particles are crystalline in nature with face centered cubic geometry. 相似文献
303.
Christian von Lücken Benjamín Barán Carlos Brizuela 《Computational Optimization and Applications》2014,58(3):707-756
Multi-objective evolutionary algorithms (MOEAs) are well-suited for solving several complex multi-objective problems with two or three objectives. However, as the number of conflicting objectives increases, the performance of most MOEAs is severely deteriorated. How to improve MOEAs’ performance when solving many-objective problems, i.e. problems with four or more conflicting objectives, is an important issue since a large number of this type of problems exists in science and engineering; thus, several researchers have proposed different alternatives. This paper presents a review of the use of MOEAs in many-objective problems describing the evolution of the field, the methods that were developed, as well as the main findings and open questions that need to be answered in order to continue shaping the field. 相似文献
304.
305.
This paper studies a queuing model where two customer classes compete for a given resource and each customer is dynamically quoted a menu of price and leadtime pairs upon arrival. Customers select their preferred pairs from the menu and the server is obligated to meet the quoted leadtime. Customers have convex–concave delay costs. The firm does not have information on a given customer’s type, so the offered menus must be incentive compatible. A menu quotation policy is given and proven to be asymptotically optimal under traditional large-capacity heavy-traffic scaling. 相似文献
306.
P. Maák G. Kurdi A. Barócsi K. Osvay A.P. Kovács L. Jakab P. Richter 《Applied physics. B, Lasers and optics》2006,82(2):283-287
Our paper deals with temporal shaping of ultrashort pulses by direct spectral filtering performed with bulk acousto-optic
filters using noncollinear geometry. This geometry allows arbitrary optical pulse repetition rate and high diffraction efficiency
at relatively large optical apertures. A theoretical model of the pulse shaper is presented, emphasizing the degrees of freedom
in this shaping technique. Phase and angular dispersion effects are analyzed, and experimental results on generating controllable
pulse trains are presented.
PACS 42.65.Re; 42.79.J 相似文献
307.
Liang Di Chapman David C. Li Youli Oakley Douglas C. Napoleone Tony Juodawlkis Paul W. Brubaker Chad Mann Carl Bar Hanan Raday Omri Bowers John E. 《Applied Physics A: Materials Science & Processing》2011,102(1):213-217
β-SiC nanowires were synthesized by a simple carbothermal reduction of carbonaceous silica xerogel. The morphology and structure
of the nanowires were investigated by X-ray diffraction, scanning electron microscope and transmission electron microscopy.
The results showed that the nanowires were hexagonal prism-shaped hierarchical nanostructures. The typical stacking faults
and twin defects of SiC nanowires were also observed. Band-gap characterization and photoluminescence properties of SiC nanowires
were investigated by UV-vis absorption spectroscopy and fluorescence photometry, respectively. The results showed the SiC
nanowire was an indirect transition semiconductor and the band gap energy for the SiC nanowires was 2.85 eV. The photoluminescence
peak value at 470 nm (2.64 eV) originating from the SiC nanowires was a little higher than the value of band-gap energy. 相似文献
308.
The structure of trans-1,4-dibromo-1,4-dicarboxymethylcyclohexane (I) has been determined by single crystal x-ray diffraction. The molecules, located on symmetry centers, are in the rigid chair conformation with the Br and COOCH3 axial and equatorial, respectively. The molecular geometry observed in the crystal is similar to that calculated for the isolated molecule using ab initio calculations performed at the HF/6-31(d) level. A peculiar arrangement of the carboxymethyl substituents, along with short contacts involving the Br atoms, seem to play a role in the stabilization of the crystalline structure. 相似文献
309.
310.
M. D. Baró N. Clavaguera S. Bordas M. T. Clavaguera-Mora J. Casas-Vázquez 《Journal of Thermal Analysis and Calorimetry》1977,11(2):271-276
The kinetics of bulk crystallization of Se61.5Ge15 4Sb23.1 glasses was investigated from their thermal behaviour. In the thermal characterization of a glass the recrystallization temperature is highly dependent on both the rate of heating and the thermal history of the glass. Vitreous samples were prepared by quenching. From ratedependent curves it was found that the recrystallization process obeys first-order kinetics with an apparent activation enthalpy of 48±5 kcal/mole. Further analysis allows determination of both the activation enthalpy,H=90±4 kcal/mole, and the kinetic exponent of the Avrami equation,n=1.9±0.3.
Zusammenfassung Die Kinetik der Massenkristallisation von Glas-Arten der Zusammensetzung Se61.5Ge15.4Sb23.1 wurde an Hand ihres thermischen Verhaltens studiert. Bei der thermischen Charakterisireung von Glas hängt die Rekristallisationstemperatur stark sowohl von der Aufheizgeschwindigkeit als auch von der Wärmevorgeschichte des Glases ab. Glasige Proben wurden durch rasches Abkühlen hergestellt. Aus den geschwindigkeitsabhängigen Thermogrammen geht hervor, dass der Rekristallisierungsprozess der Kinetik erster Ordnung gehorcht, mit einer scheinbaren Aktivierungsenthalpie von 48±5 kcal/mol. Die weitere Analyse ermöglicht die Bestimmung sowohl der AktivierungsenthalpieH=90±4 kcal/mol als auch des kinetischen Exponentenn=1.9±0.3 der Avrami-Gleichung.
Résumé Etude de la cinétique de la cristallisation dans la masse de verres Se61.5Ge15.4Sb23.1 à partir de leur comportement thermique. La température de recristallisation dépend fortement tant de la vitesse de chauffage que de l'histoire thermique du verre. Des échantillons vitreux ont été préparés par refroidissement rapide. La recristallisation obéit à une cinétique du premier ordre, avec une enthalpie d'activation apparente de 48±5 kcal·mol–1. Une analyse ultérieure permet de déterminer l'enthalpie d'activationH=90±4 kcal-mol–1 ainis que l'exposant cinétiquen=1.9±0.3 de l'équation d'Avrami.
Se61.5Ge15.4Sb23.1 . , , . . , 48±5 /. H=90±4/ , n=1.9±0.3 .相似文献