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1.
The white phosphor matrix 4SrO·7Al2O3 has been synthesized by firing the appropriate mixture of SrCO3, Al(OH)3 and H3BO3 in the molar ratios 1:3.5:0.135 at 1300°C for 4–7 h. The crystal structure of 4SrO·7Al2O3 has been determined as a orthorhombic Pmma space group with a=24.7451(2)Å, b=8.4735(6)Å, c=4.8808(1)Å, V=1023.41(3)Å3, Z=2, and D=3.66 g cm–3 by the Rietveld analysis. The refinement figures of merit are Rp=8.26, Rwp=11.60, Rbragg=4.44 and s=2.61 for 844 reflections with 2<119.94°. And the corresponding X-ray powder diffraction data are presented for search/match analysis. 相似文献
2.
Assistant Prof. M. E. Erguven 《Acta Mechanica》1986,61(1-4):165-174
Summary The problem of torsion of a transversely isotropic nonhomogeneous and elastic semiinfinite solid due to certain distributions of shearing forces prescribed on the plane boundary has been considered. The elastic properties of the material are continuous function of position. The shear moduli of the material are chosen asC
ii
(z) =
ii
cosh2
(kz), i=4, 6 where
ii
andk are constants. The aim of this paper is to determine the torsional deformation and shear stresses in the semi-infinite solid.With 1 Figure 相似文献
3.
The thermal conductivity, , and the heat capacity per unit volume, c
p
, have been measured for solid silver bromide (AgBr) using the transient hot-wire method. Measurements were made at temperatures in the range 100–400 K and at pressures up to 2 GPa. c
p
was found to be independent of temperature and pressure over these ranges. of AgBr was found to be similar to that of AgCl, which was measured previously. For AgBr, only acoustic phonons needed to be taken into account up to 340 K, but optic phonons probably carried some heat at higher temperatures. The Leibfried-Schlömann (LS) formula could describe the ratio (AgCl)/(AgBr), but not the ratio (1 GPa)/(0) for either substance. An empirical modification of the LS formula could describe the latter ratios but not the former. Further theoretical developments are required for understanding of (P) for even such relatively simple substances as AgCl and AgBr. 相似文献
4.
S. I. Moukhin 《Journal of Low Temperature Physics》1979,37(1-2):219-230
For a spin-glass with nonmagnetic defects (n
m
1/3l 1, where n
m is the magnetic impurity concentration and l is the mean free path) an absorption function () is derived. Three ranges of temperature and external magnetic field are considered. In the vicinity of the transition the value of () d is estimated as a function of temperature and field. 相似文献
5.
M. F. H. Schuurmans 《Journal of Engineering Mathematics》1971,5(3):195-205
Summary The validity of an approximation 0 of one of the solutions of a set of two linear coupled dispersive wave equations has been discussed. 0 is the solution of a linear Korteweg-de Vries equation and satisfies the same initial condition as . It is shown that for square integrable solutions having a spectral range not exceeding [–, ] the approximation is useful if 5
2t«1 in the sense that –0(t)« (t)(L
2
-norm). is a measure for the dispersion. The approximation fails in that sense ast . Some remarks to a similar nonlinear problem are made. 相似文献
6.
This paper attempts to further a better understanding of the piezoresistance coefficients by studying the piezoresistive effects in copper and copper-nickel alloys. The experimental evidence of isotropic piezoresistance coefficients (11=12) has been obtained for the annealed copper and copper-nickel alloys. The piezoresistance coefficients of the cold-worked copper and Cu60Ni40 alloy are of the tensor character (1112). A physical explanation has been given to the change of the (
ij
) tensor. 相似文献
7.
M. C. Dökmeci 《Journal of Engineering Mathematics》1975,9(4):311-322
Summary To provide an isothermal, deterministic theory of anisotropic rods is the primary objective of this paper. Our starting point is the 3-D linear theory of micropolar elastodynamics. First, the governing equations of the theory are established by the use of a suitable averaging procedure together with a separation of variables solution for kinematic variables. Next, without making the usual definiteness assumption for the strain energy density, a dynamic uniqueness theorem is constructed for the solutions of the governing equations. Logarithmic convexity arguments are then used to enumerate a set of conditions sufficient for uniqueness. The theory includes the effects of warping and shearing deformations, and in fact, it incorporates as many higher order effects as deemed necessary in any special case. Also, the application of the theory is illustrated in a sample example.Nomenclature
Euclidean 3-space
- Xk, X1z, X
a system of right-handed Cartesian coordinates in, rod axis, lateral coordinates; k=1, (=2, 3)
-
, ,
a regular region of space in , its closure and boundary surface
-
L
d,L
complementary subsets of, on which deformations and stresses are prescribed, respectively;L
d L
=L,L
d L
= 0
- L
length of rod
-
A
area of cross-section of rod
-
C
a Jordan curve which boundsA
-
V, L
entire volume of rod and its boundary surface
-
L
1,L
t
lateral surface of rod, surface portion ofL
1 on which stresses are prescribed
-
A
r,L
1
right and left faces of rod
- dv, dA, ds
element of volume and area onA, and line element alongC
- ni,v
i
unit exterior normal vectors toL andC
- t
time
- tkl, mkl
components of stress and couple stress tensors
- fi, li
body force and body couple vectors per unit volume
-
, Jkl
mass density, components of microinertia tensor
- ui,
i
displacement and microrotation vectors
-
prescribed steady temperature increment
-
kl,
klm
components of Kronecker's delta and alternating tensor
- ti, mi
stress and couple stress vectors
-
kl, ekl
components of strain and infinitesimal strain tensors
- Cklmn, Dklmn
components of isothermal elastic stiffnesses
- Bkl
thermal coefficients of material
-
,
Lamé's elasticity constants
-
, , ,
elastic moduli of microisotropic continuum
- B
coefficient of linear thermal expansion
- di, dkl
ui or
i,
kl or ekl and/or
kl
- T
kl
(m,n)
, M
kl
(m,n)
components of stress and couple stress resultants of order (m, n)
- T
k
(m,n)
M
k
(m,n)
components of stress and couple stress vector resultants of order (m, n)
- d
k
(m,n)
, d
kl
(m,n)
components of deformation (u
k
(m,n)
,
k
(m,n)
) and strain (
kl
(m,n)
, e
kl
(m,n)
,
kl
(m,n)
) of order (m, n)
- F
i
(m,n)
, L
i
(m,n)
body force and body couple resultants of order (m, n)
- U
i
(m,n)
,
i
(m,n)
displacement and microrotation resultants of order (m, n)
- P
i
(m,n)
, Q
i
(m,n)
effective loads of order (m, n)
-
N , M, , P, Q, w,
T
11
(0,0)
,M
11
(0,0)
, P
1
(0,0)
, Q
1
(0,0)
, U
1
(0,0)
,
1
(0,0)
- v0
rod velocity, (E/)1/2
- K, W
kinetic and potential energy densities
- V, U
kinetic and potential energies per unit length of rod
-
total energy of rod
- C(m,n)
functions with derivatives of order up to and including (m) and (n) with respect to space coordinates and time, respectively
- G (t)
logarithmic convexity function
- ().
time differentiation, /t ()
- ()
partial differentiation with respect to the axial coordinate, /z ()
- E,v
Young's modulus, Poisson's ratio 相似文献
8.
A theoretical treatment is given of a superconducting reed clamped at one end and performing flexural vibrations in a homogeneous longitudinal magnetic fieldB
a. When the flux lines are rigidly pinned the reed behaves like an ideal diamagnet whose bending distorts the external field. This generates a magnetic restoring force (line tension) B
a
2
which is independent of the reed thicknessd, whereas the mechanical restoring force (stiffness) is d
3. Therefore, the resonance frequency /2 of a thin superconducting reed increases drastically when a fieldB
a is applied, or for a givenB
a, when the reed is cooled below its critical temperatureT
c. With decreasing pinning strength (characterized by Labusch's parameter ) the resonance frequency decreases, 22–
pin
2
where
pin
2
–1, and an attenuation
v
–2 occurs due to the viscous motion of flux lines. For larger vibration amplitudes an additional, amplitude-dependent damping
h
–3 occurs due to the hysteretic losses caused by elastic instabilities during flux motion.On leave from Centro Atómico, Bariloche, Argentina. 相似文献
9.
An imperfectly B2 ordered Fe3Al aggregate was cast, thermomechanically hot rolled and finally annealed at 870 K. Subsequently, the specimen was rolled at 800–830 K to a strain of 80%. The microstructure and the crystallographic texture of the rolled polycrystalline sample was investigated within the range =20–80%. The microstructure consisted of flat, elongated grains. In numerous grains straight slip lines were detected. Even after =80% recrystallization was not observed. The rolling texture of Fe3Al considerably deviates from that of non-ordered body centered cubic (b.c.c.) alloys and pure b.c.c. metals. The {111}uvw texture fibre (7-fibre) was very pronounced, while the {hkl}110 fibre (-fibre) was very weak. The {112}110 orientation which represents the strongest texture component in non-ordered b.c.c. alloys did not occur at all. The textures are discussed in terms of the {110}111, {112}111, {112}111 and {123}111 slip systems. The contribution of crystallographic slip of the various types of potential slip systems was simulated by means of the Taylor theory. 相似文献
10.
Effect of crystalline phase, orientation and temperature on the dielectric properties of poly (vinylidene fluoride) (PVDF) 总被引:1,自引:0,他引:1
The effect of crystalline phase, uniaxial drawing and temperature on the real () and imaginary () parts of the relative complex permittivity of poly (vinylidene fluoride) (PVDF) was studied in the frequency range between 102 and 106 Hz. Samples containing predominantly and phases, or a mixture of these, were obtained by crystallization from a DMF solution at different temperatures. phase samples were also obtained from melt crystallization and from commercial films supplied by Bemberg Folien. Different molecular orientations were obtained by uniaxial drawing of and phase samples. The results showed that the crystalline phase exerts strong influence on the values of and , indicating that the a relaxation process, associated with the glass transition of PVDF, is not exclsively related to the amorphous region of the polymer. An interphase region, which maintains the conformational characteristics of the crystalline regions, should influence the process decisively. The molecular orientation increased the values of for both PVDF phases and modified its dependence with temperature over the whole frequency range studied. The influence of the crystallization and molecular orientation conditions on the dc electric conductivity (dc) were also verified. The value of dc was slightly higher for samples crystallized from solution at the lowest temperature and decreased with draw ratio. 相似文献
11.
V. Ya. Pupko 《Journal of Engineering Physics and Thermophysics》1966,11(2):136-139
An examination is made of the use of adjoint functions in heat conduction and convection theory. Formulas of perturbation theory are obtained for steady and unsteady cases, an interpretation of the physical meaning of adjoint temperature is given, and some applications of the theory are discussed.Notation (r,)
thermal conductivity
- t(r,)
temperature
- t *(r,)
adjoint temperature
- qV(r,)
density of heat release sources
- p(r,)
a parameter of adjoint equation
- r
generalized coordinate
-
time
- (rs, )
heat transfer coefficient
- I
linear functional of temperature
- (r,;r0,0) and *(r,; r0,0)
Green's function for t(r, ) and t *(r, )
- C(r,)
volume specific heat
- W(r, )
vector distribution of flow velocities
- V, S
volume and surface areas of body
- R
radius of HRE
- r,
radial and angular coordinates
- Fin, Fout
inlet and outlet flow areas of channel 相似文献
12.
The influences of stabilizers on - and -Al2O3 phase formations in Li2O(MgO)-Na2O-Al2O3 systems were investigated. When stabilized with 4MgCO3Mg(OH)25H2O, most of the -Al2O3 phase formed below 1200°C and further - to -Al2O3 transformation with an increase of temperature was not observed. On the other hand, when stabilized with Li2CO3,-Al2O3 formation occurred by two steps. First, -Al2O3 was partly formed below 1200°C, and, second, noticeable transformation from -Al2O3 to -Al2O3 occurred at higher temperature ranges. It was shown that transient eutectic liquid in the Li2O-Na2O-Al2O3 system promoted the - to -Al2O3 transformation at higher temperatures. Uniform distribution of both Mg2+ and Li+ stabilizing ions enhanced -Al2O3 formation at low temperatures. In the Li-stabilized systems, however, homogeneous distribution of Li+ ions hindered both the formation of transient eutectic liquid and the second - to -Al2O3 phase transformation at high temperatures. 相似文献
13.
M. M. Talianker 《Journal of Materials Science》1982,17(11):3097-3100
The athermal transformation in Zr-2 at.% Nb alloy has been investigated by transmission electron microscopy. Analysis of the selected-area diffraction pattern has shown that the orientation relationships between the omega and the parent-phase in quenched Zr-2 at.% Nb alloy are the same as have been previously observed for the reaction in pure zirconium. Thus it was deduced that the direct transition has taken place in the alloy during cooling. The-originated -particles were visualized using the dark-field technique. The formation of the athermal omega in the-region of-stabilized Zr-Nb alloy is discussed in terms of the relative positions of the free energy equilibrium curvesT
0
,T
0
,T
0
and the correspondingM
s
,M
s
andT
s
start curves. It is concluded that the omega phase can occur over a much wider range of alloy compositions than is usually recognized on the basis of transformation data. 相似文献
14.
Y. F. Nicolau M. Dupuy G. Rolland 《Journal of Materials Science: Materials in Electronics》1993,4(2):129-172
Extended structural defects in both -Hgl2 crystals grown in solution or from the vapour-phase were studied by optical microscopy, light scattering, SEM operated in cathodoluminescence and in secondary electron mode, X-ray topography, neutron, - and X-ray rocking curves and oscillating crystal X-ray diffraction. The observed dislocations were compared with theoretically calculated dislocations. Dislocation loops, having diameters ranging from 2 m to 500 m, are observed on all low index faces. Hohlstellen (lens-shaped voids) having axes along the [0 0 1] direction, less than 1 m in thickness, and diameters lying in the (001) planes, ranging from 2 m to 10 m are characteristic defects. Observed plastic deformations like glide sheets and bands, tilt and twist boundaries, kink and fatigue bands, ridges and rumplings were characterized. Growth rings, spherical void inclusions 10–30 m in diameter, orthogonal walls of forest screw dislocations parallel to 1 00 planes, and streaks (planar void sheets crossing the (001) planes) were only observed in crystals grown from the vapour-phase. Cross-penetration twins having (1 1 4) twin planes are described. The possible formation of stacking faults was analysed. The mosaicity of solution-grown crystals ranges from 1 to 6. A characteristic cellular structure, having a cell size ranging from 2 um to 10 m, was observed in all the crystals examined and correlated to local deviations from the stoichiometric composition. Solid lens-shaped inclusions, having diameters ranging from 3 m to 500 m and thicknesses ranging from 0.3 m to 50 m, respectively, are entrapped in many crystals and correlated to spiral hillocks observed on 001 growing faces. 相似文献
15.
Prof. H. F. Bauer 《Acta Mechanica》1989,77(3-4):153-170
Summary The response of a solidly rotating finite liquid column consisting of frictionless liquid is subjected to axial harmonic excitation. The response of the free liquid surface elevation and velocity distribution has been determined in the elliptic (>2
0) and hyperbolic frequency range (>2
0).Notation
a
radius of liquid bridge
-
h
length of liquid bridge
-
I
0,I
1
modified Besselfunctions
-
J
0,J
1
Besselfunctions
-
P
liquid pressure
-
r, ,z
cylindrical polar coordinates
-
t
time
-
u, v, w
velocity distribution in rotating liquid
-
axial excitation amplitude
-
elliptic case (>2
0)
-
hyperbolic case (>2
0)
-
liquid density
-
surface tension
-
liquid surface displacement
-
acceleration potential
-
0
rotational speed
-
axial forcing frequency
-
natural frequency of rotating system
-
02n
–1
natural frequency of harmonic axial response
With 8 Figures 相似文献
16.
V. A. Borodulya Yu. A. Buevich V. I. Dikalenko 《Journal of Engineering Physics and Thermophysics》1980,39(2):905-912
The transfer of a gas admixture through the boundary of a cloud of closed circulation of gas is examined with a view to both molecular and convective dispersion.Notation
a
particle radius
- c
concentration of the admixture
-
D, D
c
tensors of effective diffusion coefficients and of coefficients of convective dispersion, respectively
- D
parameter in (14)
- D0, Dm
coefficients of molecular diffusion, respectively not taking and taking compressibility into account
- F, f
functions in (17) and (18), respectively
- f
fraction of the volume of the sphere with radius RB occupied by the wake of the bubble
- g
acceleration of gravity
- K
mass-transfer coefficient determined in (22)
- k
coefficient in (7)
- L
coefficient in (22)
- p, s
functions determined in (13)
- Q, q
flow of admixture for the entire bubble and local flow, respectively
- rB, Rc
radii of bubble and of cloud of closed circulation, respectively
- r
radial coordinate
- U
lift velocity of the bubble
- u=v-w; u0=u*/u*
minimum velocity of fluidization
- V
volume of bubble
-
v, w
mean gas velocities in the gaps between particles and of the particles, respectively
-
parameter determined in (8)
-
,
parameters from (14)
-
porosity of the dense phase and of the cloud
-
polar angle
-
independent variable introduced in (12)
-
p = 1 -
flow function
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 2, pp. 323–333, August, 1980. 相似文献
17.
We have calculated the attenuation of longitudinal ultrasound due to real order parameter fluctuations in impure polar and planarp-wave superconductors. The quasiparticle self-energy and the corresponding vertex corrections have been included in thet-matrix approximation for arbitrary scattering rate =1/2N and all scattering phase shifts
N (0
N/2). We obtain sound attenuation peaks belowT
c whose heights, positions, and shapes depend on 0 (sound frequency), (0),
N, and (coupling strength due to particle-hole asymmetry). The peaks become much more distinct and sharper for
N
=/2 (resonant scattering by impurities) than for
N=0 (Born approximation). By choosing ,
N, and suitably, qualitative agreement between calculated and observed peaks in UBe13 and UPt3 can be achieved. 相似文献
18.
The problems involved in automating the processing of experimental data are considered. Primary-processing algorithms based on methods of analyzing nonstationary random processes are described.Notation {x()}
a nonstationary random process
- {y()}
an unknown random process (in a special case, a stationary random process)
- A()
a deterministic process
-
time
- M[y()]
mean value of the random process {y()}
- d[y()] =2
variance of the random process {y()}
- Ri
difference between the recorded and predicted values
- c
relative accuracy
-
estimate of the mean value of the random process
- Cs
a weighting coefficient
- and T
observation period
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 2, pp. 220–224, August, 1980. 相似文献
19.
Contrary to previous statements in the literature, large deviations from Matthiessen's rule in fine wiresare to be expected on the basis of a straight-forward solution of the ordinary transport equation, assuming the relaxation-time approximation and imposing the idealized condition of diffuse scattering of electrons at the boundaries. Using Chambers' path-integral method to evaluate the current density in a wire of arbitrary cross-sectional shape, the effects of boundary scattering on the resistivity in the regimed 0.1 have been calculated for two model Fermi surface geometries. For the temperature-dependent part of the resistivity,
d
(T)
d
(T)–
d
(0), two distinct types of behavior are found in the alternative cases: (1) for a spherical Fermi surface,
d(T)
increases logarithmically with
d(0); (2) for a cylindrical Fermi surface,
d
(T) increases essentially linearly with
d
(0). [In each case the qualitative dependence of
d(0) on /d is, for practical purposes, linear. However, the correct value of the product in the cylindrical case is not simply given in the ordinary way by the slope of an empirical plot of
d
(0) vs.d
–1.] A comparison of theoretical results for the two simple models with the published data for indium and gallium shows that the actual temperature-dependent size effects are consistent, both qualitatively and, by a rough estimation, quantitatively, with the expected behavior. 相似文献
20.
Hydrodynamically developing flow of Oldroyd B fluid in the planar die entrance region has been investigated numerically using SIMPLER algorithm in a non-uniform staggered grid system. It has been shown that for constant values of the Reynolds number, the entrance length increases as the Weissenberg number increases. For small Reynolds number flows the center line velocity distribution exhibit overshoot near the inlet, which seems to be related to the occurrence of numerical breakdown at small values of the limiting Weissenberg number than those for large Reynolds number flows. The distributions of the first normal stress difference display clearly the development of the flow characteristics from extensional flow to shear flow.List of symbols D
rate of strain tensor
-
L
slit halfheight
-
P
pressure, indeterminate part of the Cauchy stress tensor
- R
the Reynolds number
-
t
time
-
U
average velocity in the slit
- u
velocity vector
-
u,v
velocity components
-
W
the Weissenberg number based on the difference between stress relaxation time and retardation time
-
W
1
the Weissenberg number based on stress relaxation time
-
x,y
rectangular Cartesian coordinates
-
ratio of retardation time to stress relaxation time
-
zero-shear-rate viscosity, 1 + 2
- 1
non-Newtonian contribution to
- 2
Newtonian contribution to
- 1
stress relaxation time
- 2
retardation time
-
density
- (, , )
xx, yy and xy components of 1, respectively
-
determinate part of the Cauchy stress tensor
- 1
non-Newtonian contribution to
- 2
Newtonian contribution to 相似文献