海洋藻类--对付全球变暖的武器?     

江茹 《海洋信息》2002,(4):31-31

最近,由欧盟(则资助的研究项目(Parforce)研究人员发现了海洋藻类与气候变化之间的联系。项目研究人员发现,从海洋藻类及浮游生物释放的碘蒸汽,在海面上浓缩,形成对抗地球变暖的悬浮微粒。此悬浮微粒对地球气候变化及降  相似文献   

A comparison of Hα and soft X-ray characteristics of spotless and spot group flares     

V. Ruždjak  B. Vršnak  A. Schroll  R. Brajša 《Solar physics》1989,123(2):309-316

A comparative analysis of spotless and spot group flares recorded at Hvar and Kanzelhöhe Observatories during the 21st cycle of solar activity is presented. The rate of occurrence of two-ribbon flares was found to be significantly higher for the spotless flares. In comparison with spot group flares of corresponding H importance, the soft X-ray peak values have been systematically lower for the spotless flares. The highest peak values and the energy released in soft X-rays was found for flares with a H ribbon protruding over a major spot umbra. It was found that the effective plasma temperatures in spotless flares have been considerably lower than the temperatures in spot group flares.  相似文献   

The development, present significance and future prospects of socialist agricultural enterprises in Slovenia     

Igor Vrišer 《GeoJournal》1996,38(2):151-156

An important state sector developed in Slovenian agriculture under communism and although it accounted for a less than a tenth of the agricultural area it assumed a major role in supplying food to the urban markets; also in providing raw material to the food processing industry and for exporting. In the context of the transition to a market economy legislation has been enacted that provides for denationalisation and the restructuring of enterprises. This threatens the survival of the state sector and creates problems for the food market because the private farmers are not yet well-organised to provide an alternative supply. The government is committed by the legislation already passed but is anxious to avoid marketing problems.  相似文献   

Frequency modified fourier transform and its application to asteroids     

Miloš Šidlichovský  David Nesvorný 《Celestial Mechanics and Dynamical Astronomy》1996,65(1-2):137-148

Recently a method has been suggested to analyze the chaotic behaviour of a conservative dynamical system by numerical analysis of the fundamental frequencies. Frequencies and amplitudes are determined step by step. As the frequencies are not generally orthogonal, a Gramm-Schmidt orthogonalization is made and for each new frequency the old amplitudes of previously determined frequencies are corrected. For a chaotic trajectory variations of the frequencies and amplitudes determined over different time periods are expected. The change of frequencies in such a calculation is a measure of the chaoticity of the trajectory. While amplitudes are corrected, the frequencies (once determined) are constant. We suggest here simple linear corrections of frequencies for the effect of other close frequencies. The improvement of frequency determination is demonstrated on a model case. This method is applied to the first fifty numbered asteroids.  相似文献   

Dynamics of the plasmasphere in the dusk sector as observed in the outer ionosphere     

J. Bošková  F. Jiříček  J. Šmilauer  P. Tříska 《Studia Geophysica et Geodaetica》1994,38(1):82-92

Summary Direct measurements of the thermal plasma parameters in the topside ionosphere reveal variations of the plasmasphere boundary in the dusk sector. The ACTIVE satellite's near-polar orbits at altitudes of 500 – 1800 km around winter solstice 1989 were used to study the bulge region of the plasmasphere during intervals with different levels of geomagnetic agitation. The narrow, sharply defined trough in electron concentration corresponding to the plasmapause under quiet conditions situated at L = 6 – 7 moved to lower L-values with increasing geomagnetic activity. This narrow trough can be found in all main ion constituents. During periods of moderate geomagnetic activity, following the onset of a weak magnetic storm, a portion of the plasmaspheric bulge region was separated from the main plasmaspheric body. This can be seen in the outer ionosphere as an inner narrow trough at lower L-value. Troughs in light ions need no longer coincide with this in electron concentration. He⁺ is the most sensitive constituent reflecting the dusk sector plasmaspheric situation at this altitude.Dedicated to the Memory of Professor Karel P  相似文献   

Coronal index of solar activity VII,years 1988–1991     

M. Rybanský  V. Rušin  P. Gašpar  Richard C. Altrock 《Solar physics》1994,152(2):487-495

  相似文献   

Magnetic properties,self-reversal remanence and thermal alteration products of smythite     

Miroslav Krs  František Novák  Marta Krsová  Petr Pruner  Jiří Jansa 《Studia Geophysica et Geodaetica》1993,37(4):382-400

Summary This study is a follow up of the investigation of some magnetic properties and metastability of greigite in samples obtained from Miocene claystones in the Kruné hory (Erzgebirge) Piedmont basins (Bohemia). Three different methods of upgrading the smythite were applied; the magnetic properties of the concentrates are compared. The thermal conversion of smythite sets in at 200°C while greigite converts at 250°C. The first intermediate products to be formed are iron sulphides, marcasite clearly dominating over pyrite and pyrrhotite. Apart from a Fe³⁺ sulphate with a composition of Fe₂(SO₄)₃, oxidation of these sulphides gives rise to -Fe₂O₃. The result of the subsequent decomposition of the mentioned sulphate is the formation of -Fe₂O₃, which retains the sulphate structure. The final product of the thermal decomposition at 800°C is -Fe₂O₃. In the smythite concentrate the conversion to Fe³⁺ sulphate and -Fe₂O₃ is about twice as intensive as in greigite. No direct conversion to -Fe₂O₃ was found. During the thermal process self-reversals of remanence were observed, in various samples as many as four reversals in the temperature interval from 340 to 590°C. The occurrences of self-reversals of remanence were only observed at high degrees of thermal demagnetization, of the order of 10^–2 down to 10^–3 in the temperature interval of sulphide origin (below 400°C), and of the order of 10^–4 down to 10^–6 in the temperature interval of Fe-oxides origin (above 400°C).Presented at the 3rd Conference on New Trends in Geomagnetism, Castle of Smolenice, Czechoslovakia, June 22–29, 1992  相似文献   

An analysis of close binaries (CB) based on photometric measurements (VII)     

Gojko Djurašević 《Astrophysics and Space Science》1993,206(2):207-218

The paper is devoted to the actual problematics in the determination of orbital and physical parameters of active CB on the basis of the interpretation of photometric observations. One solves the problem in two stages: by obtaining a synthetic light curve in the case when the parameters of the corresponding CB model (Djuraevi, 1992a) are given a priori (direct problem) and by determining the parameters of the given model for which the best fit between the synthetic light curve and the observations is achieved (inverse problem) (Djuraevi, 1992b). In this paper, the above procedure is applied to a particular case of an interpretation of CB light curves AU Ser and RV Corvi.  相似文献   

An analysis of close binaries (CB) based on photometric measurements (V)     

Gojko Djurašević 《Astrophysics and Space Science》1993,206(1):129-144

The author considers the current problematics in the determination of the orbital and physical parameters for active close binaries (CB) of W Ser type based on the interpretation of photometric observations. In the particular case one analyses the light curves of CB RX Cas in the framework of the accretion-disc model explained in the second paper of this series (Djuraevi, 1992a). The change of the light curves with that of the system's physical-activity phase is analysed and the orbital and physical parameters of the system are determined for the maximum, minimum and the transition regime of the physical activity by applying the inverse-problem method described in the third paper of the series (Djuraevi, 1992b). In the paper a graphical illustration of the solutions obtained is also given.  相似文献   

激光扫描技术在中国古代建筑精细测绘中的应用 ——以西安钟楼三维建模及精细测绘项目为例     

李晓华  张茹 《北京测绘》2021,35(5):678-683

以西安钟楼的精细测绘与三维建模为工程实例,利用三维激光扫描技术对钟楼进行精细扫描测量,构建了准确翔实的钟楼三维模型,绘制了楼体详尽的纵横剖面、立面等二维图,为钟楼修缮和存档提供了准确的测量数据、图形、图像及模型.此外,通过该案例,详细分析了三维激光扫描技术在中国古建筑测绘应用中的技术优势与不足.  相似文献