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991.
Thierry Woignier G. Pochet H. Doumenc P. Dieudonné L. Duffours 《Journal of Sol-Gel Science and Technology》2007,41(1):25-30
Volcanic (allophanic) soils are interesting in terms of the control of the greenhouse effect and the knowledge of the porous
features is of importance to understand the mechanism of C and N sequestration. These soils contain a peculiar clay: allophane
aggregates quite close to the synthetic mineral gels aggregates. These volcanic materials behave as gels during drying with
a large irreversible shrinkage that can modify the soil physical properties. Consequently, as for silica gels, we use the
CO2 supercritical drying procedure (SD) to control the drying step and to preserve the structural and textural properties of
the soils. The experimental results show that the N and C content in the soils is clearly dependent on the allophane content.
We also show that the textural properties, such as specific surface area, are higher for the supercritically dried samples,
compared to the classically dried samples, and SAXS results confirm the preserving effect of the SD. With these data, we propose
possible effects of the specific surface area on the C and N content of the allophanic soils. 相似文献
992.
Xu Zhang Dongfeng Xue Meinan Liu Henryk Ratajczak Dongli Xu 《Journal of Molecular Structure》2005,754(1-3):25-30
On the basis of the crystallographic characteristics of lithium niobate (LN) crystals, Law of Bravais and Pauling's third rule (i.e. Polyhedral Sharing Rule) are employed with the aim to find the relationship between the crystal structure and morphological faces of LN powders. In order to validate our analytical results, we have successfully synthesized LN powders and measured the corresponding X-ray powder diffraction. Our results show that the structural analysis is consistent with the experimental data and is helpful and effective for us to control the single-crystal growth and to design superstructures at the specific plane, starting from the viewpoint of the microscopic behaviors of constituent chemical bonds and polyhedra in the crystallographic frame. 相似文献
993.
We respond to criticisms of our paper “The Free Will Theorem”, and produce a new form of the theorem based on weaker assumptions. 相似文献
994.
Oleg I. Bogoyavlenskij 《Communications in Mathematical Physics》2007,269(2):545-556
The necessary and sufficient conditions for the decoupling of a quasi-linear system of partial differential equations into k non-interacting subsystems are derived. Several necessary conditions for the decoupling are found and applied to the Benney system. 相似文献
995.
We present a way of introducing joint distibution function and its marginal distribution functions for non-compatible observables.
Each such marginal distribution function has the property of commutativity. Models based on this approach can be used to better
explain some classical phenomena in stochastic processes. 相似文献
996.
Suoyuan Lian Lei Gao Zhenhui Kang Di Wu Yang Lan Lin Xu 《Solid State Communications》2004,132(6):375-378
Single-crystal magnetite nanowires with average diameter of ca. 20 nm and length of up to several micrometers were prepared by a simple alkaline surfactant-free hydrothermal process. The crystallinity, purity, morphology, and structural features of the as-prepared magnetite nanowires were investigated by powder X-ray diffraction, transmission electron microscopy (TEM) and selected area electron diffraction. The composition and length of nanowires depends on the pH, with higher pH favoring longer nanowires composed entirely of Fe3O4. A mechanism for nanowire growth is proposed. 相似文献
997.
998.
本文介绍利用景深短、高倍率、大口径的物镜,采用光学方法,对被测透镜上下表面调焦,从而测定其中心厚度的一种新方法,并对测量误差进行了探讨。 相似文献
999.
In this paper we report some of the important results of experimental investigations of the flicker noise near the metal-insulator
(MI) transition in doped silicon single crystals. This is the first comprehensive work to study low-frequency noise in heavily
doped Si over an extensive temperature range (2 K<T<500 K). The measurements of conductance fluctuations (flicker noise) were carried out in the frequency range 10−2<f<4 × 101 Hz in single crystalline Si across the MI transition by doping with phosphorous and boron. The magnitude of noise in heavily
doped Si is much larger than that seen in lightly doped Si over the whole temperature range. The extensive temperature range
covered allowed us to detect two distinct noise mechanisms. At low temperatures (T<100 K) universal conductance fluctuations (UCF) dominate and the spectral dependence of the noise is determined by dephasing
the electron from defects with two-levels (TLS). At higher temperatures (T>200 K) the noise arises from activated defect dynamics. As the MI transition is approached, the 1/f spectral power, typical of the metallic regime, gets modified by the presence of discrete Lorentzians which arise from generation-recombination
process which is the characteristic of a semiconductor. 相似文献
1000.