矩形薄板的混沌运动研究

研究了气流和面外激励共同作用下四边完全简支的矩形薄板的混沌运动行为。考虑几何大变形理论,利用Hamilton变分原理,建立了气流作用下矩形薄板的非线性振动偏微分方程;并将偏微分方程离散为常微分方程。运用线性势理论,得到了气流的气动力。用梅尔尼科夫方法得到了混沌运动存在的必要条件;数值模拟给出了振动系统的分叉图、相图和庞加莱截面,验证了必要条件的正确性。研究结果表明,随着来流速度的增加,矩形薄板会发生不稳定振动,出现混沌运动。     

具有初挠度的受热双层金属圆板的混沌运动

考虑几何非线性和均匀静态温度的影响,研究了具有初挠度的双层金属薄板在周期时变横向载荷作用下的混沌运动。采用Galerkin法得到含二次和三次非线性项的动力学方程,利用Melnikov函数法,从理论上给出系统发生混沌运动的临界条件。借助于计算机代数系统Maple进行定量搜索与模拟,并利用Poincaré映射和相平面轨迹以及时程曲线加以判断。结果表明,受热双层板在强迫振动时存在复杂的混沌运动。     

Heat transfer in supersonic dusty-gas flow past a blunt body with inertial particle deposition effect

Heat transfer in a supersonic steady flow of a dilute dusty-gas past a sphere is considered at large and moderate Reynolds numbers. For the regime of inertial particle deposition on the frontal surface of the body, a parametric study of maximum increase in the particle-induced heat flux at the stagnation point is performed over a wide range of the Reynolds number, the particle inertia parameter, the ratio of the phase specific heats, and the body surface temperature.     

太阳系起源双螺旋星云复合成因说

银河系旋涡星云在旋转运动中，外旋带产生了次级原始太阳螺旋星云。原始太阳星云在旋转中产生物质分异，并有重物质向核部集中现象，当核部质量接近一个太阳质量时，遇超新星或类星体的强大压力或有物质参与而使原始太阳星云中核部收缩、集中、点火而具有核反应能发光的太阳。星云旋臂中的物质也成大小不等的原始星子。太阳产生了引力、磁力，又有太阳辐射，它们与旋臂扭动相反，二者呈双螺旋反向扭动复合，使星子集中并按轨道形成了各大行星。这一过程亦是星系的繁殖过程。     

Seismic evidence for convection-driven motion of the North American plate

Since the discovery of plate tectonics, the relative importance of driving forces of plate motion has been debated. Resolution of this issue has been hindered by uncertainties in estimates of basal traction, which controls the coupling between lithospheric plates and underlying mantle convection. Hotspot tracks preserve records of past plate motion and provide markers with which the relative motion between a plate's surface and underlying mantle regions may be examined. Here we show that the 115-140-Myr surface expression of the Great Meteor hotspot track in eastern North America is misaligned with respect to its location at 200 km depth, as inferred from plate-reconstruction models and seismic tomographic studies. The misalignment increases with age and is consistent with westward displacement of the base of the plate relative to its surface, at an average rate of 3.8 +/- 1.8 mm yr(-1). Here age-constrained 'piercing points' have enabled direct estimation of relative motion between the surface and underside of a plate. The relative displacement of the base is approximately parallel to seismic fast axes and calculated mantle flow, suggesting that asthenospheric flow may be deforming the lithospheric keel and exerting a driving force on this part of the North American plate.     

新型平板夯实机及其运载机构的设计研究

新型平板夯实机运动机构的运动力学模型，从中推导出最简单的工程计算模型。提出了一种方便实用的进行夯机移动转场的方法．     

Superconductivity in CaCuO2 as a result of field-effect doping.

Understanding the doping mechanisms in the simplest superconducting copper oxide-the infinite-layer compound ACuO2 (where A is an alkaline earth metal)-is an excellent way of investigating the pairing mechanism in high-transition-temperature (high-Tc) superconductors more generally. Gate-induced modulation of the carrier concentration to obtain superconductivity is a powerful means of achieving such understanding: it minimizes the effects of potential scattering by impurities, and of structural modifications arising from chemical dopants. Here we report the transport properties of thin films of the infinite-layer compound CaCuO2 using field-effect doping. At high hole- and electron-doping levels, superconductivity is induced in the nominally insulating material. Maximum values of Tc of 89 K and 34 K are observed respectively for hole- and electron-type doping of around 0.15 charge carriers per CuO2. We can explore the whole doping diagram of the CuO2 plane while changing only a single electric parameter, the gate voltage.     

埕岛地区中生代和新生代断层发育特征及其对沉积的控制作用

对穿过埕岛地区中生代和新生代主要断层的地震测线进行了详细的解释和分析，以了解该地区断层的发育演化特征及其对沉积的控制作用。结果表明，埕岛地区中生代以埕北断层、埕北20断层、埕北30北断层及其派生断层活动为主，主断层的发育演化普遍经历了由逆到正的构造负反转过程；新生代主断层中埕北20断层停止活动，其余两条断层均继承性活动，并开始发育以走滑性质为主的埕北30南断层以及其他次级北东向正断层。断层活动是埕岛地区中、新生代地层沉积的主要控制因素。埕岛地区中、新生代断层发育演化特征与济阳坳陷其他构造单元相似，但其平面组合特征具有一定的差异性，这与距离郯庐断裂带较近，受到更强烈的走滑作用有关。     

埕岛地区中生代和新生代断层发育特征及其对沉积的控制作用

对穿过埕岛地区中生代和新生代主要断层的地震测线进行了详细的解释和分析,以了解该地区断层的发育演化特征及其对沉积的控制作用.结果表明,埕岛地区中生代以埕北断层、埕北20断层、埕北30北断层及其派生断层活动为主,主断层的发育演化普遍经历了由逆到正的构造负反转过程;新生代主断层中埕北20断层停止活动,其余两条断层均继承性活动,并开始发育以走滑性质为主的埕北30南断层以及其他次级北东向正断层.断层活动是埕岛地区中、新生代地层沉积的主要控制因素.埕岛地区中、新生代断层发育演化特征与济阳坳陷其他构造单元相似,但其平面组合特征具有一定的差异性,这与距离郯庐断裂带较近,受到更强烈的走滑作用有关.     

Historical phenology: grape ripening as a past climate indicator

French records of grape-harvest dates in Burgundy were used to reconstruct spring-summer temperatures from 1370 to 2003 using a process-based phenology model developed for the Pinot Noir grape. Our results reveal that temperatures as high as those reached in the 1990s have occurred several times in Burgundy since 1370. However, the summer of 2003 appears to have been extraordinary, with temperatures that were probably higher than in any other year since 1370.     

Prediction of Emperor-Hawaii seamount locations from a revised model of global plate motion and mantle flow

The bend in the Hawaiian-Emperor seamount chain is a prominent feature usually attributed to a change in Pacific plate motion approximately 47 Myr ago. However, global plate motion reconstructions fail to predict the bend. Here we show how the geometry of the Hawaiian-Emperor chain and other hotspot tracks can be explained when we combine global plate motions with intraplate deformation and movement of hotspot plumes through distortion by global mantle flow. Global mantle flow models predict a southward motion of the Hawaiian hotspot. This, in combination with a plate motion reconstruction connecting Pacific and African plates through Antarctica, predicts the Hawaiian track correctly since the date of the bend, but predicts the chain to be too far west before it. But if a reconstruction through Australia and Lord Howe rise is used instead, the track is predicted correctly back to 65 Myr ago, including the bend. The difference between the two predictions indicates the effect of intraplate deformation not yet recognized or else not recorded on the ocean floor. The remaining misfit before 65 Myr ago can be attributed to additional intraplate deformation of similar magnitude.     

Deuterium in the Galactic Centre as a result of recent infall of low-metallicity gas

The Galactic Centre is the most active and heavily processed region of the Milky Way, so it can be used as a stringent test for the abundance of deuterium (a sensitive indicator of conditions in the first 1,000 seconds in the life of the Universe). As deuterium is destroyed in stellar interiors, chemical evolution models predict that its Galactic Centre abundance relative to hydrogen is D/H = 5 x 10(-12), unless there is a continuous source of deuterium from relatively primordial (low-metallicity) gas. Here we report the detection of deuterium (in the molecule DCN) in a molecular cloud only 10 parsecs from the Galactic Centre. Our data, when combined with a model of molecular abundances, indicate that D/H = (1.7 +/- 0.3) x 10(-6), five orders of magnitude larger than the predictions of evolutionary models with no continuous source of deuterium. The most probable explanation is recent infall of relatively unprocessed metal-poor gas into the Galactic Centre (at the rate inferred by Wakker). Our measured D/H is nine times less than the local interstellar value, and the lowest D/H observed in the Galaxy. We conclude that the observed Galactic Centre deuterium is cosmological, with an abundance reduced by stellar processing and mixing, and that there is no significant Galactic source of deuterium.     

A black phosphorus-graphite hybrid as a Li-ion regulator enabling stable lithium deposition

Lithium (Li) metal anodes have been regarded as the most promising candidates for high energy density secondary lithium batteries due to their high specific capacity and low redox potential. However, the issues of Li dendrites caused by nonuniform lithium deposition during battery cycling severely hinder the practical applications of Li metal anodes. Herein, a hybrid of black phosphorus-graphite (BP-G) is introduced to serve as an artificial protective layer for the Li metal anode. The two-dimensional few-layer BP, which is lithophilic, combined with the high electronic conductive graphite can act as a regulator to adjust the migration of Li ions, delivering a uniform and stable lithium deposition. As the growth of lithium dendrites is inhibited, the utilization of Li metal achieves > 98.5% for over 500 cycles in Li||Cu half cells, and the life span is maintained over 2000 h in Li||Li symmetric cells with a low voltage hysteresis of 50 mV. Moreover, the LiFePO₄||Li full cell with a BP-G Li-ion regulator presents significantly better specific capacity and cycling stability than that with the bare Li metal anode. Therefore, the introduction of the BP-G Li-ion regulator is demonstrated to be an effective approach to enable stable lithium deposition for rechargeable Li metal batteries.