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991.
992.
We introduce the directed-edge-reinforced random walk and prove that the process is equivalent to a random walk in random
environment. Using Oseledec"s multiplicative ergodic theorem, we obtain recurrence and transience criteria for random walks
in random environment on graphs with a certain linear structure and apply them to directed-edge-reinforced random walks.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
993.
The experiment of this paper is the thermal test of the leakage current of silicon PIN detector.Raising temperature may cause the detector to increase leakage current,decrease depletion and increase noise.Three samples are used in the experiment.One (called △E) is the sample of 100 tan in thickness.The other two (called E1 and E2) are stacks of five detectors of 1000 μm in thickness.All of them are 12 mm in diameter.The experiment has been done for 21 hours and with power on continuously.The samples have undergone more than 60 ℃ for about one hour.They are not degenerated when back to the room temperature.The depletion rate is temperature and bias voltage related.With the circuit of the experiment and temperature at 35 ℃,△E is still depleted while E1 and E2 are 94.9% and 99.7% depleted respectively.The noises of the samples can be derived from the values at room temperature and the thermal dependence of the leakage currents.With the addition of the noise of the pre-amplifier,the noises of E1,E2 and AE at 24 ℃ are 16.4,16.3,and 10.5 keV (FWHM) respectively while at 35 ℃ are about 33.6,33.1,and 20.6 keV (FWHM) respectively. 相似文献
994.
A template free approach was adopted to explore the effect of polymerization environment on the synthesis of nanostructured
poly (1-naphthylamine) (PNA) using cupric chloride as oxidant and methyl alcohol as medium. The polymerization environment
was varied by carrying out the synthesis in the presence of nitrogen and oxygen. The morphology of the synthesized nanostructured
PNA was investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis and FT-IR spectroscopies.
PNA nanorods of sizes varying between 50–100 nm were obtained in presence of nitrogen while in presence of oxygen, it formed
aggregated globular particles of sizes varying between 80–100 nm. The results provide valuable information on controlling
the synthesis of one-dimensional nanostructured conducting polymers that exhibit superior processibility as compared to the
conventional conducting polymers. 相似文献
995.
Pierre Andreoletti 《Journal of statistical physics》2005,118(5-6):883-933
We give an alternative proof of the localization of Sinais random walk in random environment under weaker hypothesis than the ones used by Sinai. Moreover, we give estimates that are stronger than the one of Sinai on the localization neighborhood and on the probability for the random walk to stay inside this neighborhood. 相似文献
996.
C. Boldrighini G. Cosimi S. Frigio A. Pellegrinotti 《Journal of statistical physics》2005,121(3-4):361-372
We report some results of computer simulations for two models of random walks in random environment (rwre) on the one-dimensional
lattice
for fixed space–time configuration of the environment (“quenched rwre”): a “Markov model” with Markov dependence in time,
and a “quasi stationary” model with long range space–time correlations. We compare with the corresponding results for a model
with i.i.d. (in space time) environment. In the range of times available to us the quenched distributions of the random walk
displacement are far from gaussian, but as the behavior is similar for all three models one cannot exclude asymptotic gaussianity,
which is proved for the model with i.i.d. environment. We also report results on the random drift and on some time correlations
which show a clear power decay 相似文献
997.
对地气测量方法的发展历程作了系统的回顾,重点阐述了我国研究人员所作的贡献,并对目前该方法研究中的相关问题进行了讨论,指出在进行具体地质工作时,应多种测量方法同时使用,以求获得更准确的地质信息。 相似文献
998.
土壤环境生态对重金属元素迁移影响分析 总被引:7,自引:1,他引:7
程金沐 《广东微量元素科学》2005,12(6):12-15
作物中重金属元素主要来自土壤,其含量与作物种类和土壤环境有关。土壤中重金属元素含量、土壤pH值、Eh值、土壤化学组成、土壤质地等环境因素都影响作物中重金属元素含量。土壤pH值和Eh值影响重金属元素的活动性。重金属元素的水溶态容易被作物吸收,而难溶态和被土壤胶体固定的重金属元素,不能被作物吸收。同种作物重金属元素含量的差异主要取决于土壤环境。 相似文献
999.
Baker G.A. Pandey S. Maziarz E.P. Bright F.V. 《Journal of Sol-Gel Science and Technology》1999,15(1):37-48
We explore the potential of xerogel composites to tailor the behavior of active dopants that are sequestered within the xerogel. Toward this end, we report on the local dipolarity and dynamics of two fluorescent probes (pyrene and rhodamine 6G, R6G) each co-doped at low concentration directly into a series of binary xerogel composites. The composites that we have investigated are composed of tetraethylorthosilicate (Si(OCH2CH3)4,TEOS) plus one of several organically-modified silanes (ORMOSILs), organic oligomers, or a common surfactant. For convenience we divide these xerogel composites into two classes: (1) xerogels wherein the organic character arises from the addition of an ORMOSIL co-monomer, possessing a non-hydrolyzable organic functional group, that becomes covalently incorporated with in the xerogel and (2) xerogels wherein the organic content is adjusted by adding organic oligomers or a surfactant. Six organically-modified silylalkoxides of the form R
n
Si(OR)4–n
were investigated as ORMOSILs. Poly(ethylene glycol), Nafion, and Ionene 6,2 were tested as oligomers. Triton X-100 was used as the surfactant. To estimate the local dipolarity within these composites we used the static fluorescence from pyrene molecules that were sequestered within the composites. These experiments showed that the local dipolarity surrounding the average pyrene molecule can be tuned significantly, but this depends on the actual organic species that one uses to prepare the xerogel composite. Time-resolved fluorescence anisotropy measurements were used to quantify the R6G mobility within the same composites. These results demonstrate that certain organic additive scan be used to adjust the R6G mobility within the xerogel composite. 相似文献
1000.