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1.
In the present paper, the effects of free convection currents and the viscous dissipation on the unsteady flow of an electrically conducting and viscous incompressible fluid around an uniformly accelerated vertical porous plate subjected to a suction or injection velocity inversely proportional to the square root of time, in presence of a transverse magnetic field, have been investigated. Analytical solutions for the velocity and the temperature distributions, the skin-friction and the rate of heat transfer are obtained for small magnetic parameterM. During the course of discussion the effects of the Grashof number Gr, the Eckert number Ec, the suction/injection parametera have been considered for unit value of the Prandtl number Pr.Nomenclature a suction/injection parameter - C p specific heat at constant pressure - B 0 magnetic induction - g acceleration due to gravity - Gr Grashof number (g(T w –T )/U 0 3 ) - K thermal conductivity - M magnetic field parameter (B 0 2 /U 0 2 ) - Pr Prandtl number (C p/K) - T temperature of the fluid near the plate - T w temperature of the plate - T temperature of the fluid at infinity - t time - t dimensionless time (tU 0 2 /) - u velocity of the fluid - u non-dimensional velocity (u/U 0) - U velocity of the plate - U dimensionless velocity of the plate (U/U 0) - U 0 reference velocity - v 0 suction velocity - v 0 non-dimensional suction velocity (v 0/U 0)=at –1/2 - Ec Eckert number ((U 0)2/3/C p(T w –T )) - T dimensionless temperature of the fluid near the plate ((T–T )/(T w –T )) - x, y coordinates along and normal to the plate - x, y dimensionless coordinates (y=yU 0/) - kinematic viscosity - coefficient of volume expansion - electric conductivity of the fluid - y/2t 1/2 - density of the fluid - skin-friction - dimensionless skin-friction - q rate of heat transfer - q non-dimensional rate of heat transfer - coefficient of viscosity - e magnetic permeability On leave of absence from Department of Mathematics, University of Dhaka, Bangladesh  相似文献   

2.
A search for low energy neutrinos of all flavours in correlation with 553 ray bursts detected by BATSE aboard the Compton Observatory has been performed by the LSD (Liquid Scintillator Detector) neutrino telescope. No excess ofe,, orv e,, candidate has been detected by LSD during the time interval in which BATSE detected the 90% of the photon flux for any of the GRBs analyzed. Upper limits on the neutrino fluxes are given in the paper.  相似文献   

3.
Calculations of the rotation parameters at initial stage of evolution on the basis of the model suggested by Jones and published observational data of NP 0532 were made. It is shown that the observed dependence of the angular velocity of NP 0532 and its first derivative with respect to time can be explained by an increase of the angle between the magnetic moment and the rotation axis. The time variation of rotation parameters essentially depends on the value and time variation of the viscosity of the star. In spite of the fact that the observational data are not extensive enough, it is possible to conclude that initial rotation frequency of NP 0532 did not exceed essentially 50 Hz.
, , NP 0532 . , . , . , , NP 0532 50 , .
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4.
, kT b mc 2 . . , , . E –5, - E 2, mc 2(kT /mc 2)1/7. , (>2.105 cm –3) . , -, , .  相似文献   

5.
, v 0c (c — ). , , . 1919, . ( ) 0532. , .  相似文献   

6.
Since the average relation between the angular momentaP and the massesM of galaxies can be represented by a power lawPM , we can define a relative angular momentum =P/M (or a constant timeP/M ). For a random motion picture within protogalaxies, should follow a Maxwellian distribution and consequently the dispersion of log should be 0.210.For the reasonable range of ( to 2), the limited sample of galaxies with known dynamical parameters gives between and 1 times the Maxwellian value. For the plausible special case =2 the reciprocal of the maximum rotational velocityv m is already a measure of and the larger sample ofv m-values not only yields the Maxwellian but, moreover, shows the shape of the distribution.
PM , =constP/M . , (lg )=0.210. 7/42, . =2 v m- .
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7.
A numerical simulation of energetic particle motion in the interplanetary medium is carried out using HEOS-2 magnetometer data in order to computeD(), the pitch angle diffusion coefficient, where is cosine of pitch angle defined with respect to the local field. WhileD() exceeds that given by quasi-linear theory near 90° pitch angle, it is significantly less at higher values of , leading to a parallel transport coefficient in good accord with that given by experimental studies of solar proton propagation. In particular, =0.031 AU at a particle magnetic rigidity of 455 MV, while experimental results range from 0.05 to 0.07 AU (+100%, –50%) in this rigidity region. Furthermore, observed approximately -dependent solar proton pitch angle distributions are consistent with the computed findingD()/(1 – 2)2 ~ constant.The validity of various analytical corrections to quasi-linear theory as 0 are also investigated numerically.  相似文献   

8.
An approximate analytical method of solving the polytropic equilibrium equations, first developed by Seidov and Kuzakhmedov (1978), has been extended and generalized to equilibrium configurations of axisymmetric systems in rigid rotation, with polytropic index,n =n p + n , nearn p =0, 1, and 5. Though the details of the method depend on the value ofn p , acceptable results are obtained for | n | 0.5 to describe slowly rotating configurations in the range 0n1.5, 4.5n5. In the limit of rotational equilibrium configurations, when the distorsion may be large enough, a satisfactory approximation holds only in the range 0n, 1n1.5, 4.5n5.  相似文献   

9.
, . : , . , . . ( ) . . . HZ Her=Her X1, . . , . , ., hv 15–30 . , . Sco X1 .  相似文献   

10.
, , , , . , . , () (), , , . — .  相似文献   

11.
Orbital stability of quasiperiodic motions in the many dimensional autonomic hamiltonian systems is considered. Studied motions are supposed to be not far from equilibrium, the number of their basic frequencies may be not equal to the number of degrees of freedom, and the procedure of their construction is supposed to be converged. The stability problem is solved in the strict nonlinear mode.Obtained results are used in the stability investigation of small plane motions near the lagrangian solutions of the three-dimensional circular restricted three-body problem. The values of parameters for which the plane motions are unstable have been found.
. , , . . , . , .
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12.
. , . , , , . ) ) . , . 10 105 =10 , (300–1000 nc). 105 . . , , . . , .  相似文献   

13.
, , , , . , , . , , - - ( , ..). - .  相似文献   

14.
On the basis of the erenkov line emission theory in the optically thick case, a new interpretation of intensity ratios H/H and H/H in broad-line radio-galaxies (BLRGs) is reported. Calculation shows that if the theoretical ratio H/H is just taken to be the mean observed value 0.21, equivalently, the parameterX(H)=3.0, then the expected ratio H/H=6.70 is almost the same as the observations. By comparing these values with the previous investigations of QSOs (X(H)=20.9), we conclude that the number density of neutral hydrogen gas in BLRGs is almost one order-of-magnitude smaller than that in the QSOs.Preliminary verification of the erenkov line emission has been obtained by Xuet al. (1981) in the laboratory.  相似文献   

15.
The problem of stability of the equilibrium points in the problem of motion of a mass point in the neighbourhood of a rotating triaxial ellipsoid in a degenerate case (the Gaussian of the Hamiltonian is equal to zero) is investigated.It is proved that the equilibrium points in the degenerate case are stable in the strict sence.
Résumé On étudie le problème de la stabilité des positions d'équilibre relatif dans le problème du mouvement du point matériel au voisinage de l'ellipsoid à trois axes tournant dans un cas dégénéré (le gaussian du Hamiltonian égal zéro).On a démontré que des positions d'équilibre relatif dans le dégénéré sont stables dans le sens rigoureux.
( )., .
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16.
The period of very high energy (E>2×1012 eV) gamma-ray emission of Cyg X-3 by using the data of observations of the source made during 6 years, 1972–1977, was specified. The value of the period is equal to 0.199 683±1×10–6 days. Phase histogram reveals two peaks, one lagging the other by 0.6 of the period. The averaged 6 year data amounts to 1.8×10–10 quanta cm–2 s–1 (peak intensity). It corresponds to luminosity of about 1.2×1037 erg s–1 if one assumes that an emission is isotropical and the distance is equal to 10 kpc.
- E>2×1012 Cyg X-3 . 1972–1977 . - T=0,199 683 ±10–6 . , 0,6 . 1,8×10–10 –2 –1 ( ), 1,2×1037 / 10 .
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17.
Using the flux-transport equation in the absence of sources, we study the relation between a highly peaked polar magnetic field and the poleward meridional flow that concentrates it. If the maximum flow speed m greatly exceeds the effective diffusion speed /R, then the field has a quasi-equilibrium configuration in which the poleward convection of flux via meridional flow approximately balances the equatorward spreading via supergranular diffusion. In this case, the flow speed () and the magnetic field B() are related by the steady-state approximation () (/R)B()/B() over a wide range of colatitudes from the poles to midlatitudes. In particular, a general flow profile of the form sin p cos q which peaks near the equator (q p) will correspond to a cos n magnetic field at high latitudes only if p = 1 and m = n /R. Recent measurements of n 8 and 600 km2 s–1 would then give m 7 m s–1.  相似文献   

18.
The contact binary system CC Com (=12h09m33s.8, =+22°4339, (1950);V max=11.31, (B-V)max=1.24) is a W UMa-type system with the shortest known period. The photometric solution of CC Com is presented using the Wilson and Devinney method. The results show that the CC Com belongs to the late-type eclipsing binary with the spectral type K5V and K6V, low temperatureT 1=4300 K,T 2=4265 K, the mass ratioq=0.5873±0.0021, and the inclinationi=87°.719±1°.44. The best regions of the gravity darkening exponents , the bolomotric albedov, and the limb-darkening coefficients are tested. It is found that 0.1250.065, 0.1v0.5, =0.5 are better regions for CC Com. The third body ofl 3 is not found to be significant. The results are combined with the spectroscopic results of Rucinski to provide an estimate of the absolute parameters.  相似文献   

19.
, , . . ( I), ( II). I , () . -, . , , (R/R i)2/3, R/R i- . ( II) . , . , , , . , . , , . , , - , , . , , , , . , . . . 1969 .  相似文献   

20.
Tian  Lirong  Liu  Yang  Wang  Huaning 《Solar physics》2003,215(2):281-293
Magnetogram data of 517 bipolar active regions are analyzed to study latitude, magnetic flux, polarity separation dependence of tilt angle of the active regions with well-defined bipolar magnetic configurations. The data were obtained at Huairou Solar Observing Station in Beijing during 1988 to October 2001. By statistical analysis, it is found: (1) The tilt angle () is a function of the latitude (). Our observed result, sin=0.5 sin, is in good agreement with that obtained by Wang and Sheeley (1991). (2) The tilt angle is a function of the magnetic flux. The tilt angle increases (decreases) with flux increasing when the flux is smaller (larger) than 5×1021 Mx. (3) The tilt angle is a function of the magnetic polarity separation. The tilt angle increases (decreases) with the separation increasing when the separation is smaller (larger) than 8×109 cm. (4) The magnetic flux ( in 1020 Mx) is correlated to the magnetic polarity separation (d in Mm), following 20d 1.15. The result is close to the observed result of Wang and Sheeley (1989), 20d 1.3. (5) The tilt fluctuations are independent of the latitude, but depend slightly on the separation, which is similar to the result obtained by Fisher, Fan, and Howard (1995). (6) The distribution function of the ratio of net magnetic flux to total magnetic flux is almost centered around zero net flux. The imbalance of magnetic flux is lower than 10% for 47% of our samples; 31% of active regions are in imbalance of the magnetic flux between 10% and 20%.  相似文献   

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