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排序方式: 共有116条查询结果,搜索用时 15 毫秒
1.
Marina Lulla Jelena Asari Jaan Aarik Kaupo Kukli Raul Rammula Unto Tapper Eero Kauppinen Väino Sammelselg 《Mikrochimica acta》2006,155(1-2):195-198
Quantitative electron probe microanalysis of highly insulating materials is a complicated problem, partially solved by coating
samples with grounded thin conductive layers or using novel scanning electron microscopy (SEM) techniques, such as low-voltage
and/or variable pressure SEM. In this work, some problems of quantitative X-ray microanalysis of thin HfO2 films, in particular the possibility to determine mass thickness correlated to the density of the layer material, are discussed.
For comparison, Al2O3, Ta2O5 and TiO2 films grown onto both semiconductive Si and insulating quartz substrates were also analysed. All the films studied were synthesized
by atomic layer deposition method. 相似文献
2.
Jaan A. Pesti Jill A. Downard Mark D. Lauritsen Goss S. Kauffman Walter M. Bryant George F. Huhn John F. Arnett Robert E. Yule James Segretario Kimberly A. Nelson Edward F. Gorko Gary O. Page Lisa M. Lloyd Richard E. Olson Christopher S. Bamum Joseph J. Mrowca 《Journal of heterocyclic chemistry》1998,35(1):249-255
The methanesulfonates of (α-(4-chlorophenyl)-α-[1-(2-chlorophenyl)ethenyl]-1H-1,2,4-triazole-1-ethanol and α-[1-(2-chlorophenyl)ethenyl]-α-(2,4-difluorophenyl)-1H-1,2,4-triazole-1-ethanol ( 1a, b ) are orally effective α-styryl carbinol derivatives developed for the treatment and prevention of systemic fungal infections. Practical new processes amenable for the large-scale production of these compounds are described. Of note is the selection of dichlorostyrene as a convenient precursor of the styryl portion, modification of a sensitive Grignard addition into a realistic preparative reaction and the use of 1,2,4-triazole simultaneously as a base transfer agent and nucleophile. 相似文献
3.
Ab initio calculations using the MP2/cc-pVTZ basis set do an excellent job of predicting the inversion barrier (247 vs. 232 cm−1) and dihedral angle (26°) of cyclopentene. DFT calculations also do an excellent job of predicting the vibrational frequencies of the d0, d1, d4, and d8 isotopomers. They have also allowed the reassignments of several of the vibrational frequencies. 相似文献
4.
Yang J Okuyama K Morris K Arp Z Laane J 《The journal of physical chemistry. A》2005,109(37):8290-8292
With the aid of a reported inversion splitting value, the far-infrared spectrum resulting from the ring-puckering vibration of coumaran has been reassigned and the one-dimensional potential energy function has been determined. The barrier to planarity is 155 +/- 4 cm(-1) and the dihedral angle is 25 degrees . These results agree well with the millimeter wave spectra values of 152 cm(-1) and 23 degrees , which utilized different data and a different type of potential function for the calculations. The MP2/cc-pvtz ab initio values of 238 cm(-1) and 26.5 degrees agree more poorly. If the benzene ring is assumed to remain rigid, the calculated barrier drops to 204 cm(-1). The puckering potential functions for the ring-flapping and ring-twisting vibrationally excited states were also determined and the barriers were found to be 149 and 156 cm(-1), respectively. 相似文献
5.
J. A. Aarik L. M. Dolginov L. V. Druzhinina P. G. Eliseev P. A. L
uk M. G. Milvidskij B. N. Sverdlov J. K. Friedenthal 《Crystal Research and Technology》1980,15(11):1311-1316
A possibility is shown of obtaining nearly perfect heterojunctions in the GaAlAsSb—GaAlSb system which do not contain any remarkable density of lattice mismatch defects at the heteroboundaries. Application to low threshold DH injection lasers for 1.4–1.8 μm spectral region for optical communications, moist-o-graphs etc. 相似文献
6.
7.
We present an equilibrium theory of diblock copolymers in which one of the blocks is crystallizable and the other is amorphous. The material is assumed to order in a lamellar structure of alternating semi-crystalline and amorphous layers with the chemical bonds which connect the copolymer blocks lying in the interfacial regions between the layers. The amorphous blocks are modelled as flexible chains, each with one end (the joint) anchored in an interface. Their contribution to the free energy is calculated via the self-consistent solution of the modified diffusion equations. The crystalline regions are modelled as folded chains, also with one end in an interfacial region (bonded to the corresponding end of an amorphous block). We find that the calculated amorphous block-free energies can be expressed as a single universal function depending on the total degree of polymerization of the amorphous block, its stretching, and a parameter proportional to the thickness of the interface. We have fitted an analytical form to this function, which can be used for any amorphous block, and we have combined it with our model of the crystallizable block to obtain scaling laws describing the equilibrium morphology. 相似文献
8.
V. Repän M. Laan P. Paris J. Aarik V. Sammelselg 《Czechoslovak Journal of Physics》1999,49(2):217-224
In the paper the results of experimental study of negative corona in a point – plane gap in a dust-free air flow at atmospheric pressure are presented. Both the low current mode (LCM) of the discharge and Trichel pulses are externally triggered by UV light. Close to the inception voltage of Trichel pulses short-duration current spikes appear besides the steady component of the LCM which indicates to the switch-on of Fowler-Nordheim type emission mechanism. At the inception voltage spike – Trichel pulse transition is recorded. The influence of dielectric layers at the cathode on the discharge parameters is discussed. 相似文献
9.
The gas-phase Raman spectra of 1,3-butadiene and its 2,3-d2, 1,1,4,4-d4, and d6 isotopologues have been recorded with high sensitivity and resolution of 0.7 cm−1. Hot band series of fundamentals and combinations involving the ν13 torsional vibration of the s-trans rotamer have been observed for each of the isotopologues. Modes studied were ν10 (CH wag), ν12 (CH2 twist), ν10 + ν12, ν15 (CH2 wag) + ν16 (CH2 twist), and ν23 (CH2 rock) + ν24 (CCC deformation). The spacings of the quantum states of the torsional contribution were found to decrease with additional excitation of this mode (ν13) in the upper vibrational states except for the ν23 + ν24 combination state. 相似文献
10.
Dmitri Neshumayev Arvo Ots Jaan Laid Toomas Tiikma 《Experimental Thermal and Fluid Science》2004,28(8):4343-886
This experimental research was focused on the investigation of the heat transfer augmentation by various turbulator inserts in gas-heated channels. The work was conducted directly in a convective part of a two fire-tube boiler. The flue ducts were positioned vertically and horizontally for various design applications. Twisted-tape insert (with the twist ratio y=4.12), the straight-tape insert, and the combined turbulator insert (the internal twisted tape with the twist ratio of 180° y=2.16 and an external tape, which spirally winded on an internal tape, with longitudinal pitch H360°=110 mm and the relative height of a tape (rib) e/D0=0.098;0.2) were investigated. The working fluids were the combustion products of light oil fuel and wood pellets. In addition, the experiments were conducted in the two fire-tube boiler without any inserts. Despite of relatively large data scattering obtained in these experiments some qualitative and quantitative conclusions were drawn. 相似文献