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1.
Summary In the present note the problem of torsional vibration of a bar in which the moment of inertia and the torsional rigidity are proportional to 0 + 1s, wheres is the spanwise co-ordinate and 0 and 1 are real numbers, has been considered.  相似文献   

2.
The palaeo-intensities (F a) of the geomagnetic field in Egypt at some ages are determined by archaeomagnetic measurements and found to be:F a=36.2 T at 3100 B.C., Fa=46.8 T at 3000 B.C.,F a=36.5 T at 2780 B.C., 49.0 T at 2500 B.C., 36.4 T at 2200 B.C., 57.5 T at 1990 B.C., 62.1 T atca 1400 B.C., 61.5 T at 1400 B.C., 69.9 T at 600 B.C., 59.3 T at 550 B.C., 79.9 T at 460 B.C., 73.7 T at 450 B.C., 69.7 T at 320 B.C., 56.2 T at A.D. 50, 64.9 T, at A.D. 400, 54.4 T at A.D. 300, 57.5 T at A.D. 700 and 43.0 T at A.D. 1975.The palaeo-inclinations (I a) at some ages are found to be:I a=24.2° at 420 B.C., 44° at A.D. 50, 60.7° at A.D. 703 and 42° at A.D. 1795.The measured values ofF a are affected by the anisotropy of magnetic susceptibility of the samples by 13% to 20% of the expected correct value. The suitable correction of this effect is by multiplyingF by 1/((1+0.2(/90)) andF by 1/((1–0.13 (/90)), whereF andF are the resultant values ofF a if the laboratory field is perpendicular or parallel to the wall of the sample during the Thelliers' experiments, respectively, and is the angle between the direction of natural remnant magnetization of the sample and the direction of the laboratory field.The results of this paper, together with the previous results for Egypt and the neighbourhoods, lead to the production of the secular variation curve of the geomagnetic field in Egypt for the last 5000 years. The intensity of the field shows a periodicity of about 400 years with multiples.  相似文献   

3.
The amplitude response of a LCR gravimeter with the SRW-E feedback was determined on a vertical vibrating platform. The ink-pen recorder was connected parallel with the digital voltmeter input to obtain an analog response of the gravimeter to the harmonic motion of the base with a peak-to-peak amplitude of 10 m and periods excited in an interval of 4 - 10 s as by the ground motion of meteorological microseisms, and in the interval 10 -100 s as by surface waves of distant strong earthquakes. In the first interval, an unexpected maximum of the amplitude response was observed with the double amplitude of apparent 6,5 Gal (6.5 × 10 –8 m/s 2 ) at a period of 4.8 s, and a baseline shift with the amplitude of–64Gal was observed at the same period. The value of this direct component cannot be separated from the effect of the Earth's gravity field. In the second interval, the amplitude response of the gravimeter displayed one expected maximum at a period of 40 s with the double amplitude of 8.1Gal. At the usual level of microseisms with a peak-to-peak amplitude of up to 2 m the fluctuation of the gravimeter on the direct baseline shifted by –4.9 Gal was estimated at 1 Gal. With typical Rayleigh surface waves with periods of 20 s and double amplitudes of up to 100 m, the fluctuation reached 67 Gal.  相似文献   

4.
Summary Free vibration of a thick hollow cylinder of non-homogeneous elastic material having rigidity and density varying according to the laws: (i) =0(0+0 z) and Q=Q0(Q0+0 z) for finite and infinite length of the cylinder and (ii) 1/r = and Q = 1/r for finite length only are considered in this paper. Frequency equations are deduced and respective numerical solutions are obtained.  相似文献   

5.
Summary The coefficient of the gamma-ray absorption Cs 137 investigated in eclogites of the Bohemian Massif varies with fresh samples from0.2477 cm –1 to 0.2804 cm –1 . Symplectite is the main factor decreasing the value of down to0.242 cm –1 . On the contrary, the coefficient increases with the increasing content of clinopyroxene and especially of garnet. The linear dependence of the coefficient on the density may be expressed by the equation =0.0682+0.028.  相似文献   

6.
Summary Dispersion in Rayleigh waves is discussed for semi-infinite media with = 1(1 ± cos s z) and = 1(1 ± cosh s z), being the rigidity of the medium. A few workers tried with the above Fourier type of model but failed to find the dispersive nature. Because they neglected s due to the complexity of the calculation they arrived at a non dispersive frequency equation. This difficulty is removed in this paper and a dispersive frequency equation is obtained which shows both direct and inverse dispersion. The second model leads to non-convergent solution forz but shows many interesting results which are also discussed.  相似文献   

7.
We present new elasticity measurements on single-crystal fayalite and combine our results with other data from resonance, pulse superposition interferometry, and Brillouin scattering to provide a set of recommended values for the adiabatic elastic moduliC ij and their temperature variations. We use a resonance method (RPR) with specimens that were previously investigated by pulse superposition experiments. The nineC ij of fayalite are determined from three new sets of measurements. One set of our newC ij data is over the range 300–500 K. We believe that the relatively large discrep ncies found in someC ij are due in large part to specimen inhomogeneities (chemical and microstructural) coupled with differences in the way various techniques sample, rather than only systematic errors associated with experimental procedures or in the preparations of the specimens.Our recommendeaC ij's (GPa) and (C ij/T) p (GPa/K) are: The resulting values for the isotropic bulk and shear moduli,K s and , and their temperature derivatives are:K s=134(4) GPa; =50.7(0.3) GPa; (K s/T) p =–0.024(0.005) GPa/K; and (/T) p =–0.013(0.001) GPa/K. An important conclusion is thatK s increases as the Fe/(Fe+Mg) ratio in olivine is increased.  相似文献   

8.
Zusammenfassung Die atmosphärische Aerosolstreuung wird im Bereich 0.52.1 m und 4°40° experimentell untersucht. Sie scheint im Infraroten weitgehend durch die Verhältnisse im Sichtbaren charakterisierbar zu sein, wenn auch die Streudispersion ein unerwartet gegensätzliches Verhalten zeigt. BeiA-ähnlichen, visuellen Streutypen (oder Typen nahe 1) verschwindet diese ab etwa 1.1 m fast vollständig. DieB-ähnlichen, visuellen Streutypen (oder Typen nahe 2) tritt in einem Zwischenbereich (etwa 0.8 bis 1.3 m) starke Streudispersion auf. Für den Gesamtstreutyp wird eine Klassifizierung in Anlehnung an die im Sichtbaren gebräuchliche [11–14]2) vorgeschlagen.
Summary The scattering by the atmospheric aerosol of radiation in the region 0.52.1 m and 4°40° is investigated experimentally. The features in the infrared can be characterized by that in the visible, but the scattering dispersion is found to be different to that expected. At scattering types nearA (or 1) in the visible there is almost no scattering dispersion for 1.1 m. At types nearB (or 2) in the visible a high scattering dispersion in the region between 0.8 m and 1.3 m was observed. For the whole region of wavelength including the infrared a classification similar to that used in the visible [11–14]2) is suggested.

Mitteilungen des Astronomischen Instituts der Universität Tübingen Nr. 77  相似文献   

9.
Summary The principle of the sampling method of submicron aerosols with the Aerosol Spectrometer is briefly described and the analytic procedures for deriving the frequency-size distributionC d (d) from photo-micrographic particle counts and microphotometric light scattering measurementsS d (d) of identical areas of the particle deposit.After initial analysis the deposits were exposed to elevated temperature (80° C) for several hours and re-analyzed. Four representative aerosol types, originating from the high sea, the shore, vegetation, and metropolitan smog are analyzed in this manner for the range (0.2 d1.3 ). All show a very marked decrease, even disappearance of the smaller particles (d<0.5 ) and shrinkage of the larger particles (d<1 ). By far the largest effect is observed for the smog aerosols.This volatility appears to be caused by either evaporation of the particle substace or by the gradual oxidation of its organic components into more volatile products (CO2, H2O).  相似文献   

10.
Summary Rotatory vibrations of a thick spherical shell of isotropic non-homogeneous material with rigidity and density given by (i) = 0 r -2 withQ =Q 0 r -2 e 2mr and (ii) = 0 r m with =Q 0 r n have been discussed and the frequency equation is derived with numerical enumeration of frequency in each case.  相似文献   

11.
Summary We have discussed in the paper the disturbance produced in an infinite layer of nonhomogeneous elastic material characterised by = 0 Z and = 0 Z where and are the density and shear modulus respectively of the material due to periodic torsional force applied on the wall of a cylindrical hole in the layer. The variation of the displacement component with the depth of the layer is shown graphically and compared with the corresponding homogeneous case.  相似文献   

12.
Summary In this paper the quasi-static temperature and stress distributions set up in an elastic sphere by radiation from a point source at a finite distance from the centre of the sphere and out-side it, have been discussed. The temperature boundary condition has been taken in the general form involving an arbitrary function of time. The final solutions have been obtained in terms of series involving Legendre polynomials. Numerical calculations have been done on IBM 1620 Computer and a desk calculator. The results have been represented in graphs.Notation the del operator - u the displacement vector - T the excess of temperature over that at state of zero stress and strain - , Lamé's constants - /2(+) Poisson's ratio - coefficient of linear expansion - 2(1+) - a radius of the sphere - d distance of the point source from the centre of the sphere - d o a/d - K coefficient of thermal conductivity - h heat transfer coefficient of the surface  相似文献   

13.
Summary In this paper the generalized thermoelastic longitudinal waves and the temperature field set up due to coupling of the displacement and the temperature fields, with heat wave travelling with certain finite velocity, in an unbounded medium are studied. The thermoelastic displacement potential and the temperature field at any point are obtained in terms of the surface integrals involving the potential, the temperature and their normal derivatives.Notation x i the cartesian coordinate system,i=1,2,3 - n (u i) the displacement vector - (/x i) the del operator - t /t the derivative with respect to time - T o the temperature corresponding to the natural stat of zero stress and strain - T Absolute temperature - c e the specific heat - , Lamé's constants - 0 the density - coefficient of linear thermal expansion - K thermal conductivity coefficient - kk u - 0 the relaxation time  相似文献   

14.
Summary The frequency equation of Rayleigh waves propagating over the free surface of an isotropic, perfectly elastic, heterogeneous semi-infinite medium with material properties varying as = 0 e az , = 0 e az , = 0 e az (a>0) has been obtained. Solution of the frequency equation in closed form is obtained in two cases (i) =0, (ii) =, and the Rayleigh wave dispersion curves for phase and group velocities drawn. In both the cases the medium yields single Rayleigh modes which cannot propagate below certain cut-off frequencies. It is found that in case (i), <c<c 0 and 0.87500 <c g <c 0, and in case (ii), 1.03082 <c<c 1 and 0.90850 <c g <c 1, wherec andc g denote phase nad group velocities respectively, is the constant shear wave velocity of the mediumc 0 andc 1 are the corresponding Rayleigh wave velocities of the homogeneous medium of the same Poisson's ratio. The motion of the surface particles is found to be retrograde elliptical as in the homogeneous case, but the ratic of the major and minor axes now becomes frequency dependent and is plotted against frequency. In both the cases (i) and (ii), the ratio starts at a lower value at the cut-off frequency and approaches the corresponding value of the homogeneous medium at high frequencies.  相似文献   

15.
We estimate (/T) P of the lower mantle at seismic frequencies using two distinct approaches by combining ambient laboratory measurements on lower mantle minerals with seismic data. In the first approach, an upper bound is estimated for |(/T) P | by comparing the shear modulus () profile of PREM with laboratory room-temperature data of extrapolated to high pressures. The second approach employs a seismic tomography constraint ( lnV S / lnV P ) P =1.8–2, which directly relates (/T) P with (K S /T) P . An average (K S /T) P can be obtained by comparing the well-established room-temperature compression data for lower mantle minerals with theK S profile of PREM along several possible adiabats. Both (K S /T) and (/T) depend on silicon content [or (Mg+Fe)/Sil of the model. For various compositions, the two approaches predict rather distinct (/T) P vs. (K S /T) P curves, which intersect at a composition similar to pyrolite with (/T) P =–0.02 to –0.035 and (K S /T) P =–0.015 to –0.020 GPa/K. The pure perovskite model, on the other hand, yields grossly inconsistent results using the two approaches. We conclude that both vertical and lateral variations in seismic velocities are consistent with variation due to pressure, temperature, and phase transformations of a uniform composition. Additional physical properties of a pyrolite lower mantle are further predicted. Lateral temperature variations are predicted to be about 100–250 K, and the ratio of ( lnp/ lnV S ) P around 0.13 and 0.26. All of these parameters increase slightly with depth if the ratio of ( lnV S / lnV P ) P remains constant throughout the lower mantle. These predicted values are in excellent agreement with geodynamic analyses, in which the ratios ( ln / lnV S ) P and ( / lnV S ) P are free parameters arbitrarily adjusted to fit the tomography and geoid data.  相似文献   

16.
— Starting with fundamental-mode Rayleigh-wave attenuation coefficient values (R) predicted by previously determined frequency-independent models of shear-wave Q (Q), we have obtained frequency-dependent Q models that explain measured values of R as well as of Lg coda Q and its frequency dependence at 1 Hz (Qo and , respectively) for China and some adjacent regions. The process combines trial-and-error selection of a model for the depth distribution of the frequency dependence parameter () for Q with a formal inversion for the depth distribution of Q at 1 Hz. Fifteen of the derived models have depth distributions of that are constant, or nearly constant, between the surface and a depth of 30 km. distributions that vary with depth in the upper 30 km are necessary to explain the remaining seven models. values for the depth-independent models vary between 0.4 and 0.7 everywhere except in the western portion of the Tibetan Plateau where they range between about 0.1 and 0.3 for three paths. These low values lie in a region where QLg and crustal Q are very low and suggest that they should also be low for high-frequency propagation. The models in which varies with depth all show a decrease in that value ranging between 0.55 and 0.8 in the upper 15 km of the crust and (with two exceptions where =0.0) between 0.3 and 0.55 in the depth range 15–30 km. The distribution of values between 0.6 and 0.8 (the higher part of the range) in the upper crust indicates that high-frequency waves will propagate most efficiently, relative to low-frequency waves, in a band that includes, and strikes north-northeastward from the path between event 212/97 and KMI to the path between event 180/95 and station HIA in the north.Acknowledgement. We thank Lianli Cong for providing his code for plotting crustal Q models and Robert Herrmann for writing the mode summation code for computing Lg synthetics used in this study. Our work benefited from helpful discussions with Jack Xie at Lamont-Doherty Earth Observatory of Columbia University. This research was sponsored by the Defense Threat Reduction Agency Contract No. DTRA-01-00-C-0213.  相似文献   

17.
Linear stacking procedures are used to retrieve the attenuation of 91 modes belonging to the 3rd, 4th and 5th Rayleigh overtones branches in the 80–160 s period range, and contributing to the so-called PhaseX wave group. Our data show in general slightly less attenuation than expected from available models. Data space inversion shows that, when combined with previously measured fundamental modeQ's, this new dataset improves resolution significantly in the 1000–2000 km depth range. Based on this remark, we carry out a number of parameter space inversions. Our results suggest a narrow (80–200 km) zone of high attenuation (Q =75–90), low attenuation in the intermediate mantle (670–1500 km); (Q 350), and lower values in the deeper mantle (Q 200).  相似文献   

18.
Summary Measuring, with the aid of two filters, the instantaneous intensity of the solar radiation in two wave lengths ( B = 0.44 , R = 0.64 ) by means of a sun photometer designed byVolz, we carried out determinations of the decadic turbidity coefficientB (=0.5 ) and the wave length exponent of the haze extinction for Mexico City. Observations were made for almost two and a half years (1960 to 1962 period). A seasonal size distribution in both parameters was found. Although the data thus obtained are provenient of a contaminated atmosphere, comparison of our data is made with those found for higher latitudes ofÅngström, Schüepp andVolz. The height of the homogeneous haze layerH D was calculated showing pronounced variations for a given wind direction. The maximum and minimum values ofB enable us to get, by the first approximation, the aerosol size distribution ofJunge for our latitudes. However, for exceptional very clear days having maximum actinometric intensity of the solar radiation the sensitivity of the microamperimeter in theVolz sun photometer fails.  相似文献   

19.
A theoretical model is presented which allows computing the efficiency with which aerosol particles of radius 0.1r10 m are collected by simple ice crystal plates of radius 50a c 640 m in air of various relative humidities, temperatures and pressures. Particle capture due to thermophoresis, diffusiophoresis and inertial impaction are considered. It is shown that the capture efficiency of an ice crystal in considerably affected by phoretic effects in the range 0.1r1 m. For aerosol particles ofr>1 m the efficiency is strongly controlled by the flow field around the crystal and the density of the aerosol material. Trajectory analysis also predicts that aerosol particles are preferentially captured by the ice crystal rim. Our theoretica results are found to agree satisfactorily with the laboratory studies presently available. Comparison shows that for the same pressure, temperature and relative humidity of the ambient air ice crystal plates are better aerosol particle scavengers than water drops.  相似文献   

20.
A theoretical model is presented which allows computing the efficiency with which aerosol particles of 0.001 r1 m are collected by columnar ice crystals in air of various relative humidities, temperatures, and pressures. Particle capture due to Brownian diffusion, thermo- and diffusiophoresis is considered. It is shown that phoretic effects importantly determine the particle capture process of 0.01r1 m. The various pressure-temperature levels studied are found to affect the collection efficiency only ifr>0.1 m. Comparison shows that water drops generally are better aerosol particle scavengers than columnar ice crystals.  相似文献   

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