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991.
从日地关系的角度出发,探讨太阳活动对人类流行性疾病的影响。根据云南地区自建国以来的15种流行性疾病每年人数的资料,对每种疾病人数的相对比率与太阳黑子相对数对应作图比较,并求其相关系数。考察结果为:猩红热、疟疾、炭疽、百日咳、白喉、流感、乙脑、痢疾、麻疹、脊髓灰质炎、姜片虫病、肝炎与太阳活动的关系不明确,伤寒、斑疹伤寒和流脑与太阳活动显著相关 相似文献
992.
布朗族使用傣历(祖葛历),以月份结合物候变化指导生产,生活中使用7d(天)为1轮的纪日制度,并将7个日名赋予不同寓意。这种状况可能距今只有200余年的历史,在此以前的历法,由于没有文字记录而被完全淡忘了,但从其先民的崖画和口头流传的传说中,有阴阳并重、同时崇拜太阳和月亮的内容看,是处于阴阳合历初期的“物候历”,其内容应与佤族(清朝时分化)的阴阳历相似。 相似文献
993.
994.
The first part of this article presents an analytic discussion of the linear properties of magnetohydrodynamic (MHD) wave propagation. Then, with a 2-dimensional, time-dependent, compressible MHD simulation subject to a self-consistent non-isothermal, non-uniform initial state, we study numerically the global propagation process following an initial pressure pulse applied at the base of the chromosphere. Our numerical results indicate that, if the pulse is applied near the pole, there are two modes, one fast, one slow of magnetoacoustic waves; whereas if the pressure pulse is applied near the equator, there is a fast mode and a standing disturbance located near the source. These results may help interpret the wave events observed by SOHO/EIT. 相似文献
995.
宁晰春 《地球科学与环境学报》1987,(1)
形成旋扭构造的动力可概括为五个方面:地块随着地球自转速率的变化,局部发生的旋扭;漂移在软流圈之上的地块遇到上拱的“热柱”受到局部牵制而旋扭;地幔熔融体物质对流循环产生蠕动式旋扭;岩石圈拖曳牵动引起旋扭;重力控制下密度分异所引起的水平漫流碰接于上升物质而旋转。欧亚大陆上分布着涡轮状、帚状、莲花状、连环状等各种旋扭构造。 相似文献
996.
Diagnosis is undertaken on the origin for the low-frequency component (LFC) of ENSOvariability in the context of 1979—1990 OLR and u-wind datasets.Evidence suggests that ① apower spectrum-yielded maximum,significant statistically,is derived from the OLR monthlyanomalies in a 3—5-year period range over the tropical central/western Pacific;②compositeanalysis of the signals of the monthly anomaly low frequency component (period>3 years)confirms further the dynamic features of the component as documented in Part Ⅰ:③serving asforcing on ENSO,the related monsoon region represents the source area of the component;④theone-point correlation maps of unfiltered OLR monthly anomalies with zonal wind on a lagged,asimultaneous and a leading basis show clearly the close relation between the u wind-associatedeastward travelling low-frequency wave and the low-frequency oscillation of low-latitude central/western Pacific large-scale convection and the east-moving mode is likely to be excited by theoscillation at a 3—5-year period range.It follows that the large-scale convection oscillation showsup as the origin of the eastward waves,i.e.,ENSO LFC. 相似文献
997.
过对鲁西东部中下寒武统研究表明:利用δ13C和δ18O以及Sr,Ni,V,Ba,B元素地球化学特征,不仅可以判断沉积古气候、古盐度、古水温、氧化-还原条件,而且还能提供海平面变化旋回及暴露-间断面确立的依据。研究证明此方法是非常有效的。 相似文献
998.
999.
Dual-spin or gyrostat satellites subject to gravitational torques can adopt an infinite number of possible equilibria obtained by adjusting the magnitude and direction of the rotor angular momentum within the satellite. This paper seeks to answer the question, which of these equilibria is best — and best is chosen here to mean most stable in the sense that the energy required to perturb the orientation by any prescribed amount is maximized, i.e. the smallest eigenvalue of the Hessian matrix of the dynamic potential energy is maximized. Using this criterion, it is shown that the conventional configuration for dual-spin satellites with the angular momentum of the rotor, the spacecraft principal axis of maximum moment of inertia, and the perpendicular to the orbital plane coincident is not always the best orientation. The optimal configuration is shown to have the minimum moment of inertia always aligned with the local vertical, but the principal axis of maximum moment of inertia, shifts from the perpendicular to the orbital plane to lying in-plane as the angular momentum of the rotor is increased from zero (corresponding to a rigid gravity gradient satellite) to some sufficiently large value which is determined as a function of parameters. For angular momentum greater than this value, global optimality is established analytically, and otherwise local optimality is proved analytically with global optimality demonstrated numerically. 相似文献
1000.
There are two explanations for the broadening mechanisms of the Caxix resonance line in the rising phase of a solar flare. One is due to the velocity dispersion of the chromospheric evaporation along the loop; the other is due to the non-thermal turbulence resulting from the flare energy release. In this paper we distinguish between these two possibilities by studying the influence of the loop orientation on the broadening of the Caxix resonance line, based on the data observed with SXT and BCS on Yohkoh. The results seem to support that the broadening of the Caxix resonance line is caused by non-thermal turbulence, rather than by the velocity dispersion. 相似文献