Correlation between continuous lobe reconnection in the mid magnetotail and substorm expansion onset

Data on plasma sheet crossing measured by Cluster/HIA and Cluster/FGM during the period from July to October in 2001 -2003 are analyzed. Based on previous work on the characteristic features of continuous lobe reconnection (CLR) described in reference, two case studies and a statistical analysis were carried out on correlation between CLR in the mid magnetotail and substorm expansion onset for the events occurring during this period. It is found that almost all CLR events are in close connection with substorms. The beginning of CLR is almost always a few minutes ahead of substorm activities seen in the near Earth magnetotail and on the ground-based stations. This provides a clear indication that CLR is the virtual cause of substorm expansion onset during the period of continuous southward interplanetary magnetic field.     

The effects of the guide field on the structures of electron density depletions in collisionless magnetic reconnection

Two-dimensional particle-in-cell simulations are performed to investigate the formation of electron density depletions in collisionless magnetic reconnection.In anti-parallel reconnection,the quadrupole structures of the out-of-plane magnetic field are formed,and four symmetric electron density depletion layers can be found along the separatrices due to the effects of magetic mirror.With the increase of the initial guide field,the symmetry of both the out-of-plane magnetic field and electron density depletion layers is distorted.When the initial guide field is sufficiently large,the electron density depletion layers along the lower left and upper right separatrices disappear.The parallel electric field in guide field reconnection is found to play an important role in forming such structures of the electron density depletion layers.The structures of the out-of-plane magnetic field By and electron depletion layers in anti-parallel and guide field reconnection are found to be related to electron flow or in-plane currents in the separatrix regions.In anti-parallel reconnection,electrons flow towards the X line along the separatrices,and are directed away from the X line along the magnetic field lines just inside the separatrices.In guide field reconnection,electrons can only flow towards the X line along the upper left and lower right separatrices due to the existence of the parallel electric field in these regions.     

混凝土结构新规范抗剪计算两个基本公式的对比分析

受剪是结构最基本的受力形式，受剪计算公式作为混凝土结构设计中最基本的公式在设计中经常使用．与旧规范相比，新规范对受剪计算公式作了一些调整，但由于旧规范习惯的影响，人们未能时这些变化引起足够的重视．本文通过比较新旧规范公式和使用范围的不同，结合常用混凝土强度等级和常见的配箍博况，对一般公式和集中荷载作用公式两个基本公式计算的结果进行了对比分析，分析表明抗剪计算两个基本公式的计算结果可能差距很大．本文对正确使用新规范受剪计算公式提出了建议．     

First-principles exploration of the stabilization mechanism of long-period stacking ordered structures in high performance Al alloys

Long-period stacking ordered(LPSO) structures, like 9 R, 12 R, 15 R and 18 R phases etc., play a key role in improving the mechanical properties of Al alloys. In the present study the Gaussian-Like distribution(GLD)model was utilized to investigate the effects of solute atoms(Cu, Fe, Ga, Ge, Li, Mg, Sc, Si, Sn, Sr, Ti, Y, Zn) on these phase stabilizations in Al alloys by first-principles calculations. The interaction energies between solute atoms and these phases were strictly calculated. The results suggested that the solute segregations showed different characteristics in these phase structures, and solute atoms(Ga, Ge, Si, Sn, Sr, Y) tended to segregate to the stacking fault(SF) planes of them, and Sr atom was the easiest to promote the stabilization of 15 R phase compared to other structures. High solute concentrations promoted the stabilizations of these phases, while high temperature inhibited their stabilizations. In the light of the degrees of reducing the intrinsic stacking fault energies(ISFEs), the solute atoms can be ranked by:(a) For 9 R and 12 R phases, Sr Y Sn Sc;(b) For15 R and 18 R phases, Sr Y Sc Sn. Thus, it may be concluded that Sr and Y atoms are hopeful to become the underlying candidates for exploring and exploiting high-performance Al alloys with LPSO structures.     

长岭断陷南部地区断陷层油气成藏机制及勘探潜力

利用天然气组成、轻烃指纹、碳同位素和生物标志化合物以及储层流体包裹体等地球化学特征,结合地质条件以及生烃史-热史模拟研究长岭断陷南部的龙凤山地区油气成因及成藏过程,揭示其油气成藏机制。结果表明:龙凤山地区断陷层天然气属于腐殖型和腐泥型的混合气,且为裂解气和干酪根热降解气组成的混合气,油气源主要为本地的沙河子组烃源岩,原油成熟度低于天然气,为同一油源不同热演化阶段的产物,属于次生凝析气藏,成藏表现为"近源多向供烃,复合输导,早期干酪根热降解成气与晚期原油裂解成气"的多期成藏模式;长岭南部地区发育优质烃源岩、营城组末期形成的反转构造提供了圈闭条件,具备较好油气输导条件、存在多期油气充注,油气勘探潜力大。     

钆基无机纳米粒子磁共振造影剂设计的研究进展

磁共振成像(MRI)技术是常见的临床医学影像学的检测手段之一.在临床诊断中使用最多的是纵向弛豫(T₁)造影剂：马根维显(Gd-DTPA).自其正式商用化后,人们对钆基造影剂进行了大量研究.文章介绍了钆基无机纳米粒子(Gd IONPs)造影剂的作用原理,阐述了无机纳米粒子的形貌、尺寸、表面修饰、氧空位等因素的影响,并对Gd IONPs造影剂的设计做了展望.     

挥发性油藏酸气回注的最小混相压力与组分优化

高含H_2S和CO_2酸性气体的低渗透挥发性油藏在开发过程中,H_2S和CO_2会以溶解气的形式被采出,并占有较高的摩尔分数。分离器条件下的气态轻烃通过回注地层,在油藏压力高于最小混相压力(MMP)时达到混相驱动,一方面可以显著提高驱油效率,另一方面可以起到减缓压力衰竭的目的。H_2S和CO_2作为污染气体,分离和回收成本较高;而与烃气一同回注地层势必会对MMP产生影响。因此,需要研究酸性气体对溶解气回注MMP的影响规律并且合理地优化回注气组分。在对目标区块原油组分拟合重组的基础上,通过混合单元格法预测MMP,研究了溶解气主要组分的混相能力以及H_2S和CO_2对烃气驱MMP的影响规律,通过正交试验方法优化了注入气比例。结果表明:作为酸性杂质气体H_2S和CO_2具有较强的混相能力,可以降低注气MMP;最优注气形式为溶解气直接回注地层。     

断裂带盖层油气封盖断接厚度下限的预测方法及其应用

在含油气盆地盖层未被断裂完全错开的条件下,采用断层岩石封闭能力与下伏储层岩石封闭能力比较的研究方法,建立一套盖层封闭油气所需断接厚度下限的预测方法,并将其应用于南堡凹陷南堡1号构造,研究馆三段火山岩盖层封闭下伏东一段油气所需断接厚度下限。结果表明:馆三段火山岩盖层在f1、f2、f3、f4断裂处封闭油气所需断接厚度均小于实际盖层的断接厚度,因此对下伏东一段储层中的油气均是封闭的,这与目前东一段油气分布有着较好的吻合关系;该方法用于研究盖层封闭油气所需断接厚度下限是可行的。     

基于有效检测准则的fMRI源信号数目的估计方法

独立成分分析方法已经成功地运用于分析功能磁共振成像数据.尽管独立成分分析方法是一个很有前景的数据驱动分析方法,但是在执行独立成分分析之前,需要确定好独立成分的数目.准确地估计出功能磁共振成像数据中独立成分数目对减少过估计或者低估计能起重要作用,目前有许多信息理论准则方法已经广泛运用于独立成分数目估计中,但通常容易出现过估计现象.该文提出一种基于有效检测准则的fMRI源信号数目的估计方法.模拟数据实验结果表明,该方法对不同平滑数据具有很好的鲁棒性.将该方法用于真实的功能磁共振成像数据中,可以减少色噪声下真实数据的过估计,对功能磁共振成像源信号数目的估计表现出了较好的综合性能.     

Leaf cuticular characters of Ginkgo and implications for paleoatmospheric CO2 in the Jurassic

A combination of carbon isotope composition and stomatal characters of fossil leaves provides information about paleoatmospheric CO₂ levels and the physiology of fossil plants. Plant anatomy, physiology, and geochemistry have been employed to reconstruct the paleoatmospheric CO2 concentrations throughout Jurassic time and to investigate the physiological response of fossil Ginkgo to an atmosphere of much higher CO₂ than usual. Our results show that fossil Ginkgo in China lived in an atmosphere with a CO₂ concentration 3—5 times higher than that of today. It used a carbon isotopic discrimination similar to that of the living plant, but had much higher water use efficiency (3—5 times that of the extant). The physiological traits of Ginkgo in different atmospheres suggest that CO₂ might have played a contributory role in the rise and fall of maidenhair trees.     

具有介孔结构的锐钛矿型C,Co-MTiO2抗菌性能研究

为了开发不需要人造光源激发,只需要微弱室内光线且改性离子不易泄漏的新型无机抗菌材料,以钛酸异丙酯为钛源,表面活性剂十二胺为模板剂,通过水热合成和超声波联用技术,合成了非金属元素C和金属元素Co共掺杂的具有介孔结构的锐钛矿型二氧化钛(C,Co-MTiO2).用N2等温吸附-解吸附、X-射线衍射(XRD)、高分辨透射电镜(HRTEM)、紫外可见吸收光谱(UV-Vis)和X-射线光电子能谱(XPS)对材料进行了表征,结果表明,该材料为热稳定性好,比表面积高,具有较大介孔孔径的锐钛矿型TiO2.在无人造光源激发的室内环境中,进行了材料的抗菌性能以及细菌吸附研究,结果表明这种材料在该环境中对大肠杆菌(E.colli)有很好的抑制作用和吸附作用,比Co-MTiO2的抑菌活性提高了20%,具有很好的应用前景.     

对宇观天体和微观粒子质量-半径统一计算的注记

 以宇观天体、“多成分宇宙”中稳定粒子质量和半径的统一计算结果为基础,进而对Dirac大数D;中微子“反常荷”和“反常磁矩”;最重的玻色子与最轻的费米子相互关联;混沌理论的菲根鲍姆常数δ以及哈勃常数H作了分析计算,所得结果与实验数据或惯用值很好相符.说明由宇宙演化的两类自由流阻尼标度导出的宇观天体、微观粒子的质量和半径统一计算公式是正确的.