一类振荡电路的微分方程分析法及其改进电路

通过微分方程稳定性的分析方法对单元振荡电路Colpitts振荡器进行了研究，得出电路的起振、稳定与其电路参数的密切关系，并对振荡规律进行了解释。根据振荡频率的表达式，给出一种改进后的电路，提出了振荡电路的另一类分析方法。     

The northern annular mode: More zonal symmetric than the southern annular mode

Fan （2007） recently documented the zonal asymmetry of the Antarctic oscillation （AAO） in the austral winter. In this research, the zonal asymmetry of the northern annular mode, or the Arctic oscillation （AO）, in the interannual variability is studied for the boreal winter. It is shown that there is zonal asymmetry of the AO as well, similar to the case of the Antarctic oscillation （AAO）. However, the zonal asymmetry of the AO is considerably weaker than that of the AAO. This is far beyond the speculation, since the zonal asymmetry of the geography is larger in the Northern Hemisphere than the Southern Hemisphere. The Western and Eastern Hemispheres portions of the AO are correlated at 0.54 for 1959-1998, comparing with 0.23 for the case of the AAO. The authors also discussed the physical reason for this inter-hemispheric difference, and partly attributed it to the El Ni~o and Southern Oscillation （ENSO） cycle which may be represented by the SO index. It is indicated that the SO associated sea-level pressure （SLP） patterns are more zonal symmetric in the high latitudes of the Northern Hemisphere than the Southern Hemisphere.     

Preliminary evidence indicating Dome A （Antarctica） satisfying preconditions for drilling the oldest ice core

Lowest temperature and snow accumulation rate are preconditions for retrieving the oldest ice core from the polar ice sheets. The 10-m depth firn temperature at Dome A, the summit of the Antarctic Ice Sheet, recorded by an automatic weather station （AWS） was -58.3℃ in 2005 and -58.2℃ in 2006, respectively. The 10-m firn temperature is an approximation of the annual mean air temperature （AMAT）, and this is the lowest AMAT that has been recorded on the surface of the Earth. The stable isotopic ratios （δ^18O and δD） of surface snow at Dome A are also lower than at other ice sheet domes along the East Antarctic Ice Divide such as Dome C, Dome F, Dome B and Vostok. These facts indicate that Dome A is the ＂pole of cold＂ on the Earth. The total amount of snow accumulation rate in 2005 and 2006 was only 0.16 cm, equaling 0.016 m water equivalent per year, the lowest precipitation ever recorded from Antarctica. Preliminary evidences indicate that Dome A is a candidate site for recovering the oldest ice core.     

基于振荡能量的失步振荡中心定位研究

失步解列在保护电力系统的稳定运行方面发挥着重要作用。然而,如果缺少失步振荡中心的位置信息,失步解列策略将无法得到有效实施。由于传统失步解列判据不能有效定位失步振荡中心,本文从振荡能量的角度阐释电力系统失步振荡过程,并创新性地提出了一个基于振荡能量的失步振荡中心定位方法。仿真算例验证了所提方法的有效性。     

21世纪的极地科学探索——面临的机遇和挑战

21世纪,极地系统的快速变化使人类面临着严峻的挑战,也给极地科学发展带来机遇。极地科学的发展将围绕全球气候变化和极地环境变化的研究和评估展开,更加强调多学科和全球化,注意时间和空间尺度上突破。突出研究极区在全球变化中的作用的同时,加强对南极的监测和保护,关注人类活动对南极地区的影响,合理利用南极的资源尤其是生物资源也是21世纪列入各国南极研究的任务之一。     

一类二阶非线性泛函微分方程的振动性

研究了一类二阶非线性泛函微分方程的振动性,建立了4个新的振动定理,并给出了其应用.推广了有关文献中的部分结果.     

高阶泛函微分方程的振动性质的判别

本文考虑形如x~(n)(t)+q(t)f(x(g,(t)),x(g_2(t)),…,x(g_n(f)))=0的泛函微分方程的振动性,利用一种新的技巧得到了上述方程振动性的一个判别准则。     

OSCILLATION OF THE SOLUTIONS OF IMPULSIVE HYPERBOLIC EQUATIONS WITH DELAY

Abstract. Oscillation properties of the solutions of impulsive hyperbolic equations with delay are investigated via the method of differential inequalities.     

中立型泛函微分方程的振动性质

本文给出了中立型泛函微分方程振动的两个新的充要条件.     

振动性的显式充要条件

本文给出了线性自治微分方程与差分方程所有解振动的显式充要条件。这个条件类似于判定稳定性的Ｒｏｕｔｈ－Ｈｕｒｗｉｔｚ判据。从而回答了Ｌａｄａｓ在１９９０年提出的一个公开问题。