Hydrothermal synthesis of kaolinite illustrated by X-ray diffractograms and scanning electron micrographs,part II

Summary The hydrothermal synthesis of kaolinite from various alumina and silica starting materials reacted at 200°C in aqueous solutions of oxalic acid and H₂SO₄ with the corresponding saturated water vapour pressure, in periods of time from 10 to 25 days, has been followed by X-ray diffraction measurements, scanning electron microscopy, and energy dispersive analysis of the products. The temperature and time periods of reactions were chosen on the basis of previously collected data on the effects of H₄EDTA, a complex-forming agent, and of H₂SO₄, an inorganic acid, on the rate of formation of kaolinite. Aluminium-complexing acids increase the rate of formation or decrease the temperature of formation of kaolinite as shown by evidence from X-ray diffraction patterns. The influence of the starting materials as sources of aluminum, amorphous aluminum hydroxides, pseudoboehmite, allophane or gibbsite, has also been examined by X-ray diffraction, scanning electron microscopy, and by energy dispersive analysis. Scanning electron micrographs indicated that silica is a more mobile phase than alumina, based on the progressive formation of a thin coating on gibbsite during early reaction, then by growth of clusters of platy crystals of kaolin, and finally by production of pellets of stacked crystal flakes. Where gibbsite was used in the reaction mixture, boehmite was commonly observed as an intermediate phase.With 16 Figures     

Possibilities of the utilization of micropetrographic parameters in the scientific classification of bituminous coals

Proposals for new scientific classifications of bituminous coals are based on micropetrographic parameters, i.e. vitrinite reflectance as a criterion of the coalification and maceral composition, presupposed to express the connection between the genetic peculiarities and physical, chemical, and technological properties of the coal mass. In the case of coals with high inertinite contents, however, the utilizability of these parameters meets with difficulties resulting from the subjectivity of determining the different transitional material and from insufficient knowledge of inertinite behaviour at higher temperatures. In the case of the maceral-variable bituminous coals produced in the Ostrava-Karviná Coal Basin, these insufficiencies are not important since it is especially the expression of the variability of the properties of isometamorphic vitrinites, which has decisive effects up-on the course of the thermo-chemical transformations, that is of principal importance to the scientific classification of these coals.In the first approximation, the properties of isometamorphic vitrinites may be expressed by the parameter (H/O)_at, closely connected with fluidity. While the micropetrographic parameters reflect in particular the peculiarities in the chemical structure of the aromatic parts of coal macromolecules, the parameter (H/O)_at expresses the properties of the non-aromatic structures of vitrinite, significantly affecting the course of its thermal degradation. The experimental results show that the value of the parameter (H/O)_at, fluidity and the course of degassing the coal of a lower coalification are independent of the maceral composition and vitrinite reflectance; also that the caking and coking properties of low-rank coals are especially dependent on the parameter (H/O)_at and partially on the micropetrographic parameters. All these facts should be taken into consideration in preparing new scientific classifications of bituminous coals.     

Velocities of seismic waves propagating through the Bohemian massif from foci in Poland

mam mm ua a na Pn, Pg, Sn u Sg nu¶rt;u u au -ma. aa, m ¶rt; amu 5° m numa ua¶rt;a ¶rt;am mu a na n au ma¶rt;amu u mu anmau , uu m n u ma¶rt;am¶rt;a. am nmau a uu m anmau mmu aua.     

Analysis and optimization of wide-band force-balance seismometer responses

¶rt; aau n¶rt;am uu, umu,au mummu u ¶rt;uau ¶rt;uanaa mu um. am n a nmua amm aamumuu um ¶rt; au uu nuu. ¶rt;ma ummuu m¶rt; nmuau mu um a a¶rt;a an¶rt;u n n¶rt;am uu n nmu.     

Transfer impedance of a probe in a drifting plasma

au un¶rt;a umu ¶rt;a na nu nauuu ¶rt;a uam mmu amm na aa. amau aa auum m mnam u mu ¶rt;a, m unam ¶rt; ¶rt;uamuu u na.     

Geomagnetic latitude aspects of the effect of the interplanetary parameters on geomagnetic storms

Summary In this work the previous author's results concerning the geomagnetic effect of the interplanetary parameters in dependence on geomagnetic latitude are verified, complemented and presented with better accuracy. Data of 7 intensive storms recorded in 1973–79 at 5 observatories with slight differences in local time and with the appropriate latitude distribution limited by real possibilities have been analysed. Even in these cases the derived values of the constants determining the dependence of storm-time variations of the geomagnetic field upon both the dynamic pressure of the solar wind(P) and the interplanetary electric field(E_y) vary relatively regularly with geomagnetic latitude. The anomaly of Dst and DR-variations from the Almeria Observatory (AE) evident in some intensive storms is pointed out here. Unlike the previous work the time characteristics () of the ring current decay have been studied from the standpoint of the main (_m) and recovery (_r) phases of the storm. This yields higher values of _r as compared to from the above mentioned work. On the other hand, a large decrease in the values of _r was observed in some cases at a latitude of about 40°, as in the earlier study. Actually this phenomenon does not occur in all intensive storms as could be expected. As to the investigated storms, _m seems to be independent of geomagnetic latitude and much lower in its magnitude than _r.     

Bilateral recursive restitution of true ground motion from near-field and far-field seismograms

Summary A two-sided recursive inverse filtering procedure, originally proposed by R. Vích, is used to restore the true ground motion from digital records of inertial electromagnetic seismographs. Numerical simulations of far-field and near-field P-wave seismograms are used to test the performance of the procedure and to derive criteria for recognizing successful restorations. The procedure is applied to seismograms of local microearthquakes as well as of teleseismic events, and the restored signals are compared with those obtained by causal (one-sided) inverse filtering. In all cases the two-sided approach proved to have fundamental advantages: a higher accuracy of the approximation of the true ground motion, a faster convergence to the best attainable approximation, a lower sensitivity to incoherent noise, and a more reliable discrimination between veracious and dubious results.     

Propagation velocity and radiation properties of induced tensile cracks

nua ¶rt;u a¶rt;am m aa ¶rt;uaaa . ¶rt;u aam ¶rt; ¶rt; uu umuo au uu m a u a u am mu ma. mu anmau mu ma n¶rt; auumu m a aa u anau nu au. num ma uu nu un u n mu ma n¶rt;mauu n¶rt;um uu m umua. mam ¶rt;umum mu u aua n au muna ma a umua uu un. ¶rt; aauua am na mu ma, m uam ua u.     

Laboratory measurements of electrical properties of rocks and minerals

In this paper all important results on laboratory measurements of electrical properties of rocks and minerals for the last four years are presented. Although basic results from all over world are reviewed, East European and U.S.S.R. works are described more extensively. Only D.C. conductivity results are considered, however all principal conclusions hold in similar form for both D.C. and A.C. conductivities. At the end the most important areas of further study and measurement are depicted and the main problems of the future are outlined.