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61.
钽酸盐Ba5YTi3Ta7O30的X射线衍射分析及其介电特性 总被引:1,自引:0,他引:1
在BaO -TiO2-Ta2O5 体系中通过掺Y3 +合成了钽酸盐Ba5YTi3Ta7O30,采用粉晶X射线衍射 (XRD)对其结构进行了分析 ,并测试了其陶瓷体的介电特性;结果表明 ,Ba5YTi3Ta7O30 在室温下属于填满型四方钨青铜结构顺电相,晶胞参数为a=1.24387(2)nm,c=0.39178(1)nm ,α= β=γ=90° ;频率为1MHz时Ba5YTi3Ta7O30 陶瓷的室温相对介电常数为155 ;而且介电损耗低至0.0009。 相似文献
62.
本文对古典风险模型中保险公司按单位时间常数率收到保险费的假设做了改进,将每次收到的保险费的次数看作是复合泊松过程,将每次收到的保费和每次的理陪额均看作是服从指数分布的随机变量,并引入带干扰风险的扰动项,从而对古典风险模型进行推广,且给出了相应的破产概率上界,分析了破产概率的上界与准备金,索赔额,净保费和扰动方差之间的关系. 相似文献
63.
M. Ferretti G. Cristoforetti S. Legnaioli V. Palleschi A. Salvetti E. Tognoni E. Console P. Palaia 《Spectrochimica Acta Part B: Atomic Spectroscopy》2007,62(12):1512-1518
This paper reports the results of a measurement campaign performed at the National Museum of Magna Grecia in Reggio Calabria (Italy). Portable X-Ray Fluorescence (XRF) and Laser-Induced Breakdown Spectroscopy (LIBS) instrumentation allowed in situ analysis of several bronze pieces belonging to the group of the so-called Porticello Bronzes. The find occurred at sea, off the village of Porticello (Reggio Calabria) in 1969 and consists of a number of fragments, including a bearded head, pertaining to at least two statues. The use of X-Ray Fluorescence and Laser-Induced Breakdown Spectroscopy techniques allowed for a classification of the fragments according to their elemental composition. The fragments appear to belong to at least two different statues; although, in general, the compositional classification agrees well with the stylistic analysis of the fragments, significant improvements with respect to previous achievements emerge from the joint results of the two techniques used. 相似文献
64.
Temperature dependences of thermoelectric power (TEP) and resistivity of a series of W-doped blue bronzes, K0.3Mo1−x WxO3 were presented. It was seen that the anomalous negative peak of the TEP near 60 K was greatly suppressed by the W-doping, while an anomaly of the resistivity near about 60 K appears and gradually strengthens with the doping. These results can be qualitatively explained by the change of the thermal excitation mechanism. 相似文献
65.
殷承元 《纯粹数学与应用数学》2013,(3):221-225
在轨迹二阶导数具有Hlder连续的条件下,利用高阶奇异积分思想和概率极限的理论,研究了在Brown运动下的随机奇异积分.得到了以Brown运动为积分元的随机奇异积分是存在性定理. 相似文献
66.
Recent developments in whole-cell spectroscopic methods allow rapid characterization of microorganisms of interest to human health, but have yet to be widely applied to marine microbiological studies. In this study of bacteria associated with the kelp Laminaria digitata, we have isolated 18 epiphytic bacterial strains from several thalli, sequenced their 16S rDNA, built corresponding phylogenetic trees, and characterized them using spectroscopic methods. Molecular taxonomy revealed Gram+Actinobacteria and Gram−Alphaproteobacteria, Gammaproteobacteria and Bacteroidetes. Twelve marine reference strains (Gram+Firmicutes, and Gram−Alphaproteobacteria, Gammaproteobacteria and Bacteroidetes) were treated accordingly. Whole-cell MALDI-TOF MS spectral profiles of 29 of the 30 strains were built into a database against which 16 replicate spectra of each strain were compared and categorized into groups. The proton HR-MAS NMR stack plots allowed visual delineation into taxonomic groups according to their most common peaks, in agreement with identifiable compounds from corresponding D2O solution spectra. With both methods, these groups corresponded to taxa identified by 16S rDNA sequences, MALDI-TOF MS being more discriminative than HR-MAS NMR. Culture age did not influence the spectral signatures in both approaches. Most cells grown under minimal conditions (VNSS medium) afforded HR-MAS NMR profiles markedly different to those grown in enriched conditions (ZoBell medium), indicating different adaptive metabolic responses between the two media. Spectral signatures obtained under strictly controlled conditions can be used as rapid and reliable tools for taxonomic purposes and as markers of physiological status. 相似文献
67.
Yaw-Shun Hong 《Journal of solid state chemistry》2010,183(8):1805-1810
The compounds KZnTiF6, KZnVF6, KVScF6, KCrScF6, and KMnScF6 are fluoride analogs of Tetragonal Tungsten Bronze. M2+-M3+ ionic ordering in these fluorides provided systems which contained linear trinuclear complexes of their respective paramagnetic ions. Magnetic coupling within these linear trimers occurred below 100 K in each of the five systems. Derived magnetic susceptibility equations were fitted to observed magnetic susceptibilities for each of the possible spin systems: KZnTiF6 (S=1/2), J/k=−114 K; KZnVF6 (S=1), J/k=−39 K; KVScF6 (S=3/2), J/k=−16 K; KCrScF6 (S=2), J/k=−4 K; and KMnScF6 (S=5/2), J/k=−7.5 K. 相似文献
68.
69.
FuHangSONG XiaoFAN XiuLiXU JieLuZHAO LiJunHAN JianGongSHI 《中国化学快报》2004,15(3):316-318
A new sesquiterpene-substituted benzoic acid has been isolated from the brown Alga Dictyopteris divaricata Okam.Its structure was elucidated as 3-[(2-hydroxy-2,5,5,8a-tetramethyldecahydro-1-naphthalenyl)methyl]-4-hydroxybenzoic acid, named dictyvaric acid on the basis of spectroscopic methods including IR, HRFABMS, 1D and 2D NMR techniques. 相似文献
70.
Potassium tungsten bronze KxLayWO3 (x>0.5 and y<0.01) was synthesized by rare earth co-permeation method using α-K7[SiMg3(OH2)3W9O37] as the precursor. Binding energies of La, W, O and C were determined by XPS. From the XPS data, a peak at 34.21 eV indicates that some
W6+ turned into W5+ by rare earth co-permeation. The binding energies La3d were the same in the surface and inner of the composite, showing that rare earth element La could diffuse into the body of the composite and the compound of
KxLayWO3 was formed at the same time. The binding energies of O1s in
KxLayWO3 surface were 531.4 eV and 532.0 eV, respectively, while peak at 531.4 eV disappeared through etching process. The result implies that the binding energy of 531.4 eV was due to the adsorbent O. In addition, the binding energies of C1s in the surface were 283.5 eV, 285.0 eV and 286.7 eV respectively, while the inner had only one peak at 285.0 eV due to standard C1s. This proves that there was no C in the core. 相似文献