Determination of the original shape of pulsations from their spectra     

Jaroslav Střeštík 《Studia Geophysica et Geodaetica》1970,14(3):344-349

Zusammenfassung Es wird eine einfache auf der Symmetrie der Grundformeln der Fourierschen Transformation gegründete Methode, wie von den Spektralfunktionen zur ursprünglichen Pulsationsform zu gelangen, beschrieben. Mit dieser Methode wird die durchschnittliche Form der Pi2-Pulsationen konstruiert. Diese idealisierte Pulsation hat dieselben Eigenschaften wie ein statistisches Ensemble von Pulsationen. Der wirkliche Verlauf der Intensit?t des magnetischen Feldes bei Pi2-Pulsationen wird durch die Methode aus den Induktionsregistrierungen abgeleitet. Die berechnete Kurve zeigt starke Korrelation mit der direkten Registrierung der Intensit?t des magnetischen Feldes.

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Address: Boční II, Praha 4-Spořilov.  相似文献   

Core waves recorded in central Europe     

Libuše Ruprechtová  Vít Kárník  Reviewer K. Pěč 《Studia Geophysica et Geodaetica》1971,15(3-4):299-315

Summary The core waves recorded at four seismograph stations in Central Europe were investigated with the aim to find the most suitable set of travel-time curves and a fitting model of the core structure. Another travel-time curve was constructed by means of time differences between the core phases. The differences in the features of the travel-time curves were studied using records of shallow, intermediate and deep shocks from the same focal region (Tonga).  相似文献   

Effect of some co-dissolved inorganic groups on the photodecomposition of aqueous nitrates     

Enrico G. Gori  Henry M. Papée 《Pure and Applied Geophysics》1969,77(1):201-206

Summary The rate of nitrite formation, in UV-irradiated aqueous solutions of alkali metals, is found to depend on co-dissolved chemical compounds and on their reactivities. The effect of some common and simple components of the atmospheric aerosol is investigated in the laboratory.  相似文献   

Geomagnetic Pc3 Pulsations During the Total Solar Eclipse on Aug 11, 1999     

Střeštík  J.  Prikner  K. 《Studia Geophysica et Geodaetica》2003,47(3):565-578

The solar eclipse on August 11, 1999, observed in the region covered by many geomagnetic observatories, has offered a unique opportunity to look for an effect of the eclipse on geomagnetic pulsations. The pulsation activity digital data have been taken from Budkov Observatory in the Czech Republic (in the X component only), from observatories in Germany (Niemegk, Fürstenfeldbruck, Bad Bergzabern), in Hungary (Nagycenk), and for comparison in South Africa (Hermanus, conjugate-point station), and in Finland (Sodankylä, far from the eclipse zone). At all these stations the field in all three component has been recorded. The pulsation amplitudes in the X component exhibit a long-term minimum near the time of the eclipse. Spectral analysis of selected short intervals confirmed this decrease and also revealed a decrease of the average pulsation period during the eclipse. Such a change in the amplitude or in the period was not observed outside of the eclipse interval or in other days. Investigation in some narrower frequency bands showed that the maximal decrease occurred in the 15–20 s band. All these changes can be found in records from all the stations near the eclipse totality belt, also in records at the conjugate-point station, where no eclipse occurred. No signature has been found in records at the station situated far from the eclipse zone.  相似文献   

一次罕见冰雹天气的多普勒雷达回波分析   总被引：1，自引：0，他引：1  

田秀霞胡燕平  张敏李根娥  白红霞王颖 《河南气象》2006,(2):23-25

运用多普勒雷达的基本反射率(R)、风暴相对径向速度(SRM)、垂直积分液态含水量(VIL)等产品,分析了2004年6月20日华北南部罕见的冰雹大风天气过程。结果表明:这次冰雹大风天气过程主要是由超级单体回波中的中尺度气旋引起的;该过程持续时间比较长的原因是“指状”回波和超级单体回波的依次发生、发展。  相似文献   

Aggregate production: Fines generation during rock crushing     

M.S. Guimaraes  J.R. Valdes  A.M. Palomino  J.C. Santamarina 《International Journal of Mineral Processing》2007

The energy required to crush rocks is proportional to the amount of new surface area that is created; hence, a very important percentage of the energy consumed to produce construction aggregates is spent in producing non-commercial fines. Data gathered during visits to quarries, an extensive survey and laboratory experiments are used to explore the role of mineralogy and fracture mode in fines production during the crushing of single aggregates and aggregates within granular packs. Results show that particle-level loading conditions determine the failure mode, resulting particle shape and fines generation. Point loading (both single particles and grains in loose packings) produces clean fractures and a small percentage of fines. In choked operations, high inter-particle coordination controls particle-level loading conditions, causes micro-fractures on new aggregate faces and generates a large amount of fines. The generation of fines increases when shear is imposed during crushing. Aggregates produced in current crushing operations show the effects of multiple loading conditions and fracture modes. Results support the producers' empirical observations that the desired cubicity of aggregates is obtained at the expense of increased fines generation when standard equipment is used.  相似文献   

ESR dating of fluvial quartz: Estimate of the minimal distance transport required for getting a maximum optical bleaching     

Pierre Voinchet  Christophe Falgures  Hlne Tissoux  Jean-Jacques Bahain  Jackie Desprie  Florence Pirouelle 《Quaternary Geochronology》2007,2(1-4):363-366

An ESR experimental study of artificial optical bleaching of sedimentary quartz has shown that the aluminum center was maximally bleached after a 6-month illumination equivalent to natural light. This duration seems too long to apply in natural conditions. Nevertheless, the measurement of the ESR intensity of aluminum centers in quartz extracted from modern sediments and deposited in sandy bars shows that the maximum bleaching has effectively been reached.

In order to determine the relationship between the bleaching and the distance covered by a quartz grain in a river, samples were collected along the Creuse River (France) from its spring to about 170 km downstream, where maximum bleaching levels were observed in previous studies. The ESR intensities of the aluminum and titanium centers in quartz were measured, using X-band spectroscopy, before and after artificial bleaching. The difference measured between these sub-samples shows that the maximum bleaching level is obtained in the course of the first kilometer. Hence, the assumption that ESR dating of fluvial sediment is based on the optical bleaching was validated.  相似文献   

The Spatial and Temporal Characteristics of Pc3 Geomagnetic Activity over Canada in 2000, as a Guide to Planning the Times of Aeromagnetic Surveys     

Marc A. Vallée  Larry Newitt  Ian R. Mann  Mouhamed Moussaoui  Régis Dumont  Pierre Keating 《Pure and Applied Geophysics》2007,164(1):161-176

Geomagnetic activity affects aeromagnetic surveys. Geomagnetic variations are quite complex and can be quantified in different ways. A measure of geomagnetic activity that is useful for planning aeromagnetic surveys is the Pc3 pulsation index developed by the Australian Space Weather Agency. Purposeful to developing guidelines for planning aeromagnetic surveys in Canada, we study the variations in Pc3 index amplitude over Canada in 2000. This study shows distinct patterns associated with the sub-auroral zone, the auroral zone, and the polar cap. Average Pc3 index activity is higher during the months of February, July, September, and November in the auroral and sub-auroral zones. The station in the polar cap exhibits maximum activity near midday during the summer months. Detailed analysis of a magnetic storm shows that Pc3 index amplitude during the beginning of the solar storm is least important at the polar cap. The mean Pc3 index also relates to solar wind parameters such as the solar wind velocity and the vertical polarity of the interplanetary magnetic field. Analysis of the morning maximum of the Pc3 index observed in the auroral zone can be used to develop guidelines for planning aeromagnetic surveys in Canada and other areas of the world affected by auroral zones.  相似文献   

Simulating coseismic deformation of quartz in the middle crust and fabric evolution during postseismic stress relaxation — An experimental study   总被引：3，自引：0，他引：3  

Claudia A. Trepmann  Bernhard Stckhert  Dorothe Dorner  Rasoul Hamidzadeh Moghadam  Martina Küster  Klaus Rller 《Tectonophysics》2007,442(1-4):83-104

Non-steady state deformation and annealing experiments on vein quartz are designed to simulate earthquake-driven episodic deformation in the middle crust. Three types of experiments were carried out using a modified Griggs-type solid medium deformation apparatus. All three start with high stress deformation at a temperature of 400 °C and a constant strain rate of 10^− 4 s^− 1 (type A), some are followed by annealing in the stability field of α-quartz for 14–15 h at zero nominal differential stress and temperatures of 800–1000 °C (type A + B), or by annealing for 15 h at 900 °C and at a residual stress (type A + C).The quartz samples reveal a very high strength > 2 GPa at a few percent of permanent strain. The microstructures after short-term high stress deformation (type A) record localized brittle and plastic deformation. Statisc annealing (type A + B) results in recrystallisation restricted to the highly damaged zones. The new grains aligned in strings and without crystallographic preferred orientation, indicate nucleation and growth. Annealing at non-hydrostatic conditions (type A + C) results in shear zones that also develop from deformation bands or cracks that formed during the preceding high stress deformation. In this case, however, the recrystallised zone is several grain diameters wide, the grains are elongate, and a marked crystallographic preferred orientation indicates flow by dislocation creep with dynamic recrystallisation. Quartz microstructures identical to those produced in type A + B experiments are observed in cores recovered from Long Valley Exploratory Well in the Quaternary Long Valley Caldera, California, with considerable seismic activity.The experiments demonstrate the behaviour of quartz at coseismic loading (type A) and subsequent static annealing (type A + B) or creep at decaying stress (type A + C) in the middle crust. The experimentally produced microfabrics allow to identify similar processes and conditions in exhumed rocks.  相似文献   

Southern Quebec (Canada) summer-season heat spells over the 1941–2000 period: an assessment of observed changes     

M. N. Khaliq  P. Gachon  A. St-Hilaire  T. B. M. J. Ouarda  B. Bobée 《Theoretical and Applied Climatology》2007,88(1-2):83-101

Summary Summer-season (May–September) daily maximum temperature (T _max) and daily minimum temperature (T _min) observations and three types of heat spells obtained from these temperature observations at seven weather stations located in southern Quebec (Canada) for the 60-year period from 1941 to 2000 are studied to assess temporal changes in their characteristics (i.e. frequency of occurrence, seasonal hot days and extremal durations of heat spells). Type-A and Type-B heat spells are obtained respectively from T _max and T _min observations and Type-C heat spells from simultaneous joint observations of T _max and T _min using suitable thresholds and spells of duration ≥1-day and ≥3-day. The results of this investigation show that the majority of the selected percentiles (i.e. 5P, 10P, 25P, 50P, 75P, 80P, 90P, 92P, 95P, and 98P) of T _max observations show a negative time-trend with statistically significant decreases (at 10% level) in some of the higher percentiles and in the maximal values at four out of seven stations. Almost all of the selected percentiles (same as for the T _max) and the maximal and minimal values of T _min observations show a positive trend, with statistically significant increases for all seven stations. Examination of frequencies of occurrence of heat spells, seasonal hot days and annual extremes of heat spell durations indicate that many of these characteristics of heat spells have undergone statistically significant changes over time at some of the stations for Type-A and Type-B heat spells as compared to Type-C heat spells. The Type-C heat spells are generally small in number and are found to be relatively temporally stable. More severe Type-C heat spells, i.e. the ones having T _max and T _min values simultaneously above very high thresholds and with duration ≥3-day have been rarely observed in southern Quebec.  相似文献