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191.
Nadia T. Zakharova Michael I. Mishchenko 《Journal of Quantitative Spectroscopy & Radiative Transfer》2001,70(4-6):465-471
We use the T-matrix method to compute the scattering matrix for randomly oriented circular ice cylinders with diameter-to-length ratios 1 and 20 and surface-equivalent-sphere size parameters up to 12. We show that wavelength-sized, sharp-edged ice plates with extreme diameter-to-length ratios possess the same scattering properties as smooth platelike spheroids: their phase functions are similar to those of surface-equivalent compact particles, whereas all other elements of the scattering matrix are typical of Rayleigh scattering. 相似文献
192.
Han Hee-Siew Chen Da-Ren Pui David Y.H. Anderson Bruce E. 《Journal of nanoparticle research》2000,2(1):43-52
We have developed a fast-response nanometer aerosol size analyzer (nASA) that is capable of scanning 30 size channels between 3 and 100 nm in a total time of 3 s. The analyzer includes a bipolar charger (Po210), an extended-length nanometer differential mobility analyzer (Nano-DMA), and an electrometer (TSI 3068). This combination of components provides particle size spectra at a scan rate of 0.1 s per channel free of uncertainties caused by response-time-induced smearing. The nASA thus offers a fast response for aerosol size distribution measurements in high-concentration conditions and also eliminates the need for applying a de-smearing algorithm to resulting data. In addition, because of its thermodynamically stable means of particle detection, the nASA is useful for applications requiring measurements over a broad range of sample pressures and temperatures. Indeed, experimental transfer functions determined for the extended-length Nano-DMA using the tandem differential mobility analyzer (TDMA) technique indicate the nASA provides good size resolution at pressures as low as 200 Torr. Also, as was demonstrated in tests to characterize the soot emissions from the J85-GE engine of a T-38 aircraft, the broad dynamic concentration range of the nASA makes it particularly suitable for studies of combustion or particle formation processes. Further details of the nASA performance as well as results from calibrations, laboratory tests and field applications are presented below. 相似文献
193.
A. Milekhin N.P. Stepina A.I. Yakimov A.I. Nikiforov S. Schulze D.R.T. Zahn 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(2):355-359
Self-organised Ge dot superlattices grown by molecular beam epitaxy of Ge and Si layers utilizing Stranski-Krastanov growth
mode were investigated by Raman spectroscopy. An average size of Ge quantum dots was obtained from transmission electron microscopy
measurements. The strain and interdiffusion of Ge and Si atoms in Ge quantum dots were estimated from the analysis of frequency
positions of optical phonons observed in the Raman spectra. Raman scattering by folded longitudinal acoustic phonons in the
Ge dot superlattices was observed and explained using of elastic continuum theory.
Received 25 January 2000 相似文献
194.
Poly(ethylene terephthalate) (PET) has been mixed with fluorite (CaF2) particles to obtain micro- and nano-composites aiming to obtain a hybrid multifilament. In first term, the use of two montanic waxes and an amide wax as dispersing agents towards the compatibilization of the inorganic and organic components of the CaF2/PET composite were considered. To do this, non-isothermal crystallization studies by differential scanning calorimetry have been carried out. Moreover, the influence of the CaF2 particle size and concentration on the thermal properties of the system have been also studied by this technique. Finally, the extrapolation of the results has materialised as a novel PET/CaF2 hybrid multifilament. Thermal and mechanical properties and molecular weight of the multifilament have been as well evaluated. 相似文献
195.
《Journal of Saudi Chemical Society》2020,24(2):216-222
In this work, thiocarbohydrazide doped iron nanoparticles as a novel, green, heterogeneous, and inexpensive catalyst is reported. This catalyzed the three components reaction of dialkylacetylenedicarboxylate with aromatic aldehydes and aromatic amines to yield the corresponding furan derivatives EtOH. An indispensable part of green chemistry is to be able to recover and reuse catalysts without any notable drop in catalytic activity. The analysis of catalyst and application of that for the synthesis of title compounds in high yields reveal this property. The formation, size of the metal ions present in the material is confirmed by powdered X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). 相似文献
196.
Recent mathematical investigations have shown that under very general conditions, exponential mixing implies the Bernoulli property. As a concrete example of statistical mechanics that are exponentially mixing we consider the Bernoulli shift dynamics by Chebyshev maps of arbitrary order , which maximizes Tsallis entropy rather than the ordinary Boltzmann-Gibbs entropy. Such an information shift dynamics may be relevant in a pre-universe before ordinary space-time is created. We discuss symmetry properties of the coupled Chebyshev systems, which are different for even and odd N. We show that the value of the fine structure constant is distinguished as a coupling constant in this context, leading to uncorrelated behaviour in the spatial direction of the corresponding coupled map lattice for . 相似文献
197.
Efficient generation of polarized single photons or entangled photon pairs is crucial for the implementation of quantum key distribution (QKD) systems. Self organized semiconductor quantum dots (QDs) are capable of emitting on demand one polarized photon or an entangled photon pair upon current injection. Highly efficient single‐photon sources consist of a pin structure inserted into a microcavity where single electrons and holes are funneled into an InAs QD via a submicron AlOx aperture, leading to emission of single polarized photons with record purity of the spectrum and non‐classicality of the photons. A new QD site‐control technique is based on using the surface strain field of an AlOx current aperture below the QD. GaN/AlN QD based devices are promising to operate at room temperature and reveal a fine‐structure splitting (FSS) depending inversely on the QD size. Large GaN/AlN QDs show disappearance of the FSS. Theory also suggests QDs grown on (111)‐oriented GaAs substrates as source of entangled photon pairs. 相似文献
198.
When a colloidal suspension is exposed to a strong rotating electric field,
an aggregation of the suspended particles is induced to appear.
In such clusters, the separation between the suspended particles is so
close that one could not neglect the multiple image effect on the
electrorotation (ER) spectrum. Since so far the exact multiple image
method exists in two dimensions only, rather than in three dimensions,
we investigate the ER spectrum of the clustered colloidal particles in
two dimensions, in which many cylindrical particles
are randomly distributed in a sheet cluster. We report the dependence of
the ER spectrum on the material parameters.
It is shown that the multiple image method predicts two
characteristic frequencies, at which the rotation speed reaches
maximum. To this end, the multiple image method is numerically
demonstrated to be in good agreement with the known Maxwell-Garnett approximation. 相似文献
199.
Wei Zheng Wenxian Ye Pingan Yang Dashuang Wang Yuting Xiong Zhiyong Liu Jindong Qi Yuxin Zhang 《Molecules (Basel, Switzerland)》2022,27(13)
With the rapid development of communication technology in civil and military fields, the problem of electromagnetic radiation pollution caused by the electromagnetic wave becomes particularly prominent and brings great harm. It is urgent to explore efficient electromagnetic wave absorption materials to solve the problem of electromagnetic radiation pollution. Therefore, various absorbing materials have developed rapidly. Among them, iron (Fe) magnetic absorbent particle material with superior magnetic properties, high Snoek’s cut-off frequency, saturation magnetization and Curie temperature, which shows excellent electromagnetic wave loss ability, are kinds of promising absorbing material. However, ferromagnetic particles have the disadvantages of poor impedance matching, easy oxidation, high density, and strong skin effect. In general, the two strategies of morphological structure design and multi-component material composite are utilized to improve the microwave absorption performance of Fe-based magnetic absorbent. Therefore, Fe-based microwave absorbing materials have been widely studied in microwave absorption. In this review, through the summary of the reports on Fe-based electromagnetic absorbing materials in recent years, the research progress of Fe-based absorbing materials is reviewed, and the preparation methods, absorbing properties and absorbing mechanisms of iron-based absorbing materials are discussed in detail from the aspects of different morphologies of Fe and Fe-based composite absorbers. Meanwhile, the future development direction of Fe-based absorbing materials is also prospected, providing a reference for the research and development of efficient electromagnetic wave absorbing materials with strong absorption performance, frequency bandwidth, light weight and thin thickness. 相似文献
200.
S. Cordier F. Dorson F. Grasset Y. Molard B. Fabre H. Haneda T. Sasaki M. Mortier S. Ababou-Girard C. Perrin 《Journal of Cluster Science》2009,20(1):9-21
In this contribution, we present a review of our recent works about the design of phosphor nanoparticles and materials based
on [Mo6X14]2− cluster units (X = Cl, Br, I) as well as the functionalization of monocrystalline Si(111) surfaces by Mo6 clusters. Our purpose was to use the specific properties of cluster units found in inorganic solids for the design of new
nanomaterials with potential applications in nanotechnologies (e.g. phosphor dyes for bio labelling, light emitting diodes,
redox active molecular junctions…) using soft chemistry techniques. Phosphor Cs2Mo6X14@SiO2 nanoparticles emitting in 550–900 nm upon photo-excitation were synthesised using a ‘water in oil’ microemulsion technique.
They exhibit a regular shape (~45 nm) and are based on [Mo6X14]2− cluster units and Cs+ counter cations embedded in a silica matrix. ((n–C4H9)4N)2Mo6Br14@ZnO colloids and nanopowders are based on the association of ZnO crystalline nano-particles with Mo6 cluster units adsorbed on their surface. They exhibit a large emission window in the visible region that can be tuned by
modulation of the excitation wave length in order to selectively obtain the emission of either clusters units or ZnO nanocrystals
or of both entities. Functionalized surfaces were obtained by the attachment of cluster units on a Si(111) surface through
pyridine end capped organic chains using a multi-step procedure. Modified surfaces were characterized by X-ray photoemission
spectroscopy (XPS), atomic force microscopy (AFM), IR and electrochemical analysis. The surface coverage can be modulated
by the controlled introduction of inert organic chains among pyridine end-capped ones before the cluster anchoring step. 相似文献