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981.
A series of polyacrylonitrile–dimethylsulfoxide–CuX2 (X=CF3SO3−, Cl−, Br−), films (foils) were prepared by means of the solution cast technique. The thickness of the foils was between 0.04 and 0.09 cm and they contained 70–80 wt.% of the solvent. Conductivities of the solid electrolytes were obtained from impedance measurements. The conductivity increases with the increase of the salt content up to 8 wt.%; at higher concentrations (>8 wt.%) the conductivity is more or less stable, and reaches, in the case of Cu(CF3SO3)2 and CuCl2, the level of ca. 10−3 Ω−1 cm−1 at room temperature. The foils based on the CuBr2 show even higher conductivity, close to 10−2 Ω−1 cm−1 at room temperature, a value comparable to that characteristic for liquid solutions. The temperature variation of the conductivity for all the systems studied is of the Arrhenius type. The activation energy, determined from linear plots lnσ=f(T−1), is of the order ca. 14 kJ mol−1 for the PAN/CuBr2/DMSO and of ca. 21 kJ mol−1 for the PAN/CuCl2/DMSO and the PAN/Cu(CF3SO3)2/DMSO systems. 相似文献
982.
A new solid-state NMR pulse sequence for recoupling 13C–1H dipolar interactions under magic-angle spinning is proposed, which works under a spinning speed of a few to several tens kilohertz. The sequence is composed of two different frequency switched Lee–Goldburg sequences, and the modulation of the spin part of the 13C–1H dipolar interaction is introduced by a virtual pulse sequence consisting of unitary operators connecting the rotating frame and the tilted rotating frame. When the cycle time of the spinning is equal to or twice the cycle time of the sequence, the 13C–1H dipolar interactions can be recoupled. The sequence is insensitive to experimental imperfections such as rf inhomogeneity or frequency offset, and the resulting lineshape can be represented by a simple analytical equation based on the zeroth-order average Hamiltonian. Experimental results for [2-13C]
-valine·HCl are reported. 相似文献
983.
This paper deals with the motion of viscous liquid column with finite length and two free surfaces in a vertical straight capillary tube. It is assumed that fluid is Newtonian. Linearizing the boundary conditions, analytic expressions in the form of infinite series have been obtained for velocity, piessure and free surface at low Reynolds number. The numerical calculation is carried out for a set of cylinder’s length of water and blood. It has been revealed that there are considerable circulating currents at the upper and lower meniscuses. Its maximum velocity is about 57% of the average velocity of the mainstream. Iner-tial effect is also studied in this paper. Using the time-dependent method in finite difference techniques, numerical solution of the corresponding nonlinear equation at Re<24.5 is computed. Comparing it with analytic exact solution at low Reynolds number shows that inertial effect is negligible provided Re<24.5. 相似文献
984.
Nonlinear bending of circular sandwich plates 总被引:2,自引:0,他引:2
刘人怀 《应用数学和力学(英文版)》1981,2(2):189-208
In this paper, fundamental equations and boundary conditions of nonlinear axisymmetrical bending theory for the circular sandwich plates with a soft core are derived by means of the method of calculus of variations. Especially in the case of very thin faces, the preceding fundamental epuations and boundary conditions simplity considerably. For example, a circular sandwich plate with edge clamped but free to siip under the action of uniform lateral load is considered. A more accurate solution of this problem has been obtained by means of the modified iteration method.Notation
r, ,z
system of cylindrical coordinates
-
a
radius of plate boundary
-
t
thickness of the face
-
h
thickness of the core
-
h
0
distance from middle of thickness of lower face to middle of thickness of upper face
-
E
Young's modulus of the face
-
Poisson's ratio of the face
-
G
2
shear modulus of the core
-
D
f
flexural rigidity of the face
-
D
flexural rigidity of the plate
-
C
shear rigidity of the plate
-
q
uniform lateral load
-
u
i
,v
i
,w
i(i=1, 2, 3)
radial, tangential and normal displacement of upper face, core and lower face, respectively
-
u
radial displacement of the middle plane of the plate
-
w
deflection of the middle plane of the plate
-
rotation of connecting line of corresponding points in middle planes of two faces
-
1i
,
i
,
zi
,
ri
,
zi
,
rzi (i=1,2,3)
strains at a point of upper face, core and lower face
-
ri
,
i
,
zi
,
ri
,
zi
,
rzi(i=1,2,3)
stresses at a point of upper face, core and lower face
-
r
,
0
radial and tangential stress of the middle plane of the plate, respectively
-
U
i(i
=1, 2, 3)
strain energy of upper face, core and lower face, respectively
-
V
work done by the external force
-
U
total potential energy of the plate
-
M
r
radial moment of the plate
-
Q
r
shearing force of the plate
-
m
radial moment of the face
-
stress function
-
dimensionless radial coordinate
-
k
dimensionless characteristic parameter
-
W
dimensionless deflection
-
W
0
dimensionless center deflection
-
S
r
,S
0
dimensionless radial and tangential stress, respectively
-
S
r
(0),S
0 (0)
dimensionless radial and tangential stress at center, respectively
-
S
0(1)
dimensionless tangential stress at edge
-
P
dimensionless uniform lateral load
-
A
2,A
3,B
2,B
3,a
1,.....,a
2,
1,
2,l
1,1,...l
1 1,3,m
1,...,m
33,n
0,2,...n
22,6,R
1,,...R
33
auxiliary quantity
-
L
differential operator 相似文献
985.
A. Pillay Narrainen L. R. Hutchings W. J. Feast R. L. Thompson I. A. Ansari N. Clarke 《Macromolecular Symposia》2005,231(1):103-109
Fréchet-type poly(arylether) first and second generation (G1 and G2 respectively) dendrons were prepared from 1-(bromomethyl)-3,5-bis(trifluoromethyl)benzene. The latter and the brominated versions of the two dendrons were successfully employed in the copper mediated living radical polymerization (LRP) of styrene-d8 giving polymers of predictable molecular weights and narrow polydispersities. Contact angle measurements and ion beam analysis were used to explore the adsorption of these materials to the air-polymer surface in blended films with unfunctionalized hydrogenous polystyrene. Although contact angle analysis indicated only modest changes in the hydrophobicity and lipophobicity of the surface, ion beam analysis clearly showed the formation of an excess layer of dendron functionalized polymer at the exposed surface that increased with increasing fluorine content. 相似文献
986.
Determination of titanium NMR parameters of ATiO3 compounds: correlations with structural distortion
Solid state 47,49Ti NMR spectra have been obtained for a number of perovskite and ilmenite ATiO3 compounds. The 49Ti quadrupole coupling constant varies from 2.75 MHz (CaTiO3) to 15.5 MHz (MgTiO3) and the electric field gradient at the titanium site was found to correlate well with the shear strain, independent of structure. The chemical shift in the perovskite structures varies by 160 ppm and correlates well with the mean Ti–O distance. The 25Mg and 113Cd NMR parameters are also reported for the relevant compounds. 相似文献
987.
Emil Polturak Amit Kanigel Nir Gov Tuvy Markovich Joan Adler 《Physica B: Condensed Matter》2000,280(1-4):142-145
We have recently observed that the resistance to shear of solid 4He decreases dramatically near the first-order BCC–HCP transition. In our view, the solid shears via a diffusive counter-flow of atoms and point defects. The mechanism of self diffusion couples point defects with one specific phonon which softens as the transition is approached. Since such a scenario can possibly lead to melting, it is important to understand (a) which type of point defect is associated with the reduction of shear resistance, and (b) can the presence of point defects lead to the softening of phonons. We report here the results of numerical simulations and analytic modeling. Our results indicate that split interstitials are much more effective than vacancies in lowering the resistance to shear. We suggest that these excitations can be generated as a result of a “local mode” excited in the crystal. 相似文献
988.
通过表面化学修饰,制备了超疏水CaCO3/SiO2复合粒子,并用接触角测量仪检测疏水性能,当CaCO3与纳米SiO2质量比小于10:1时,可以制得超疏水复合粒子.基于表面修饰的CaCO3/SiO2复合粒子,对亲水涂料进行改性,当CaCO3与纳米SiO2质量比小于6:1时,可以制得超疏水涂层,且涂层疏水性随复合粒子加入量的增加而增大.同时,采用扫描电镜、红外光谱和热重分析等对复合粒子进行结构表征,探讨了基于CaCO3/SiO2复合粒子制备超疏水表面的机理. 相似文献
989.
《Particuology》2023
Due to a higher operating temperature (≥800 °C), Solar Particle Receiver (SPR) which uses particles as the working medium is considered as one of best candidates to improve the thermoelectric conversion efficiency of concentrating solar power plants. In this paper, a quartz tube solid particle receiver model is fully developed by using the discretized lumped parameter method, in which the calculation process of particle temperature and thermal loss is clearly given. In order to improve the manipulation level of particle receiver during the operation, the dynamic characteristics of the quartz tube particle receiver are comprehensively studied by the disturbance test of selected input parameters. Besides, in order to grasp the influence rule of key parameters on the thermal performance of particle receiver, the key parameters’ sensitivity analysis is also deeply studied. The results show that the particle outlet temperature can reach as high as 810 °C under a relatively small value of solar flux 600 kW/m2, but the receiver efficiency is only about 75%; Besides, the receiver efficiency shows a variation tendency that it rises first falls afterwards with the increase of incident solar flux. The validity of proposed model is verified by a heating experimental system with a single quartz tube, and the relative error is not more than 7.9%. The research results are beneficial for understanding the dynamic characteristics and designing the particle receiver. 相似文献
990.