Effects of mixing on the subduction of South Pacific waters identified by a simulated passive tracer and its adjoint

Effects of mixing on water mass subduction are analyzed in the South Pacific Ocean. Model simulations using a passive tracer and its adjoint are employed in conjunction with a particle tracking method to distinguish effects of mixing from those of advection. The results show that mixing processes can contribute to as much as 20% of the overall subduction rate in the South Pacific. Of this mixing contribution, about 30% can be attributed to meso-scale eddies, including their associated bolus transport, while the major part (70%) is due to other diabatic processes. The impact of mixing reaches its maximum near the Sub-Antarctic Front, accounting for nearly 30% of the total subduction rate. Consequently, estimates based on tracing particles or on advection alone may significantly underestimate the subduction rate in the South Pacific Ocean.     

Two methods for pore network of porous media

Two approaches of generating pore networks of porous media are presented to capture the pore fabric. The first methodology extracted pore structure from a computer simulated packing of spheres. The modified Delaunay tessellation was used to describe the porous media, and modified Nelder–Mead method in conjunction with three pore‐merging algorithms was used to generate the pore size and coordination number distributions of the randomly packed spheres. The Biconical Abscissa Asymmetric CONcentric bond was used to describe the connection between two adjacent voids. This algorithm was validated by predicting pore structure of a cubic array of spheres of equal radius with known pore sizes, throat sizes and coordination number distributions. The predicted distributions of pore structure agreed well with the measured. Then, the algorithm was used to predict pore structure and permeability of randomly packed spherical particles, and predicted permeability values were compared with published experimental data. The results showed that the predicted permeability values were in good agreement with those measured, confirming the proposed algorithm can capture the main flow paths of packed beds. The second methodology generated an equivalent pore network of porous media, of which the centers of voids were located in a regular lattice with constant pore center distance. However, this network allowed for matching both main geometrical and topological characteristics of the porous media. A comparison of the two approaches suggested that the second approach can also be used as a predictive tool to quantitatively study the microscopic properties of flow through porous media. Copyright © 2012 John Wiley & Sons, Ltd.     

Semi-empirical models of the white-light flare on October 24, 1991

On October 24, 1991, a white-light flare was observed both from space and from the ground. A multi-waveband spectral analysis shows that the peak time of the continuum emission coincides well with that of a radio burst at 2840 MHz and with the hard X-ray emission. Three semi-empirical models, corresponding to the pre-flare condition and to the peak time of continuum emission both with and without non-thermal excitation and ionization of hydrogen by an electron beam, have been obtained. The results indicate that there is fast heating both in the chromosphere and the photosphere. Some evidence is given that this WLF is very likely a result of bombardment by an electron beam. By taking into account non-thermal effects, the chromospheric temperature of the semi-empirical model is significantly reduced.     

Voids in a ΛCDM universe

We study the formation and evolution of voids in the dark matter distribution using various simulations of the popular Λ cold dark matter cosmogony. We identify voids by requiring them to be regions of space with a mean overdensity of −0.8 or less – roughly the equivalent of using a spherical overdensity group finder for haloes. Each of the simulations contains thousands of voids. The distribution of void sizes in the different simulations shows good agreement when differences in particle and grid resolution are accounted for. Voids very clearly correspond to minima in the smoothed initial density field. Apart from a very weak dependence on the mass resolution, the rescaled mass profiles of voids in the different simulations agree remarkably well. We find a universal void mass profile of the form  ρ(< r )/ρ( r _eff) ∝ exp[( r / r _eff)^α]  , where r _eff is the effective radius of a void and  α∼ 2  . The mass function of haloes in voids is steeper than that of haloes that populate denser regions. In addition, the abundances of void haloes seem to evolve somewhat more strongly between redshifts ∼1 and 0 than the global abundances of haloes.     

具有硅酸盐尘埃特征碳星的新的候选者

本文根据红外天文卫星的宽波段测光及低分辨率光谱资料，给出了两颗新的可能具有硅酸尘埃特征的碳星及４颗可能的候选者。     

板块构造图的制图理论与方法探讨

通过编制区域性1:300万“青藏高原板块构造图”和1:50万“柴达木北缘板块构造地质图”的体会,并结合国内学者对这两份图件的审查意见及建议,重点讨论有关区域性板块构造图编制的理论与方法,供区域地质工作者参考。     

ESR DATING OF FLUVIAL SEDIMENTS USING GE CENTER IN QUARTZ

Using the Ge centers of quartz sediments, the buried ages of fluvial sediments were determined by ESR technique. The ESR ages obtained from Ge centers are consistent with the TL ages, correspond with their horizons, accord with the geological background, and every ESR age is available. In this paper, determination of total dose of natural radiation (TD) and the reliability of ESR age using Ge center are also discussed.     

东风盐场卤水中可溶性糖的研究──Ⅰ、盐田卤水中可溶性糖的季节变化及其与海盐产量和质量之间的关系

对东风盐场9个站位卤水中由藻类植物产生的可溶性糖浓度的变化规律及其与海盐产量和质量之间的关系进行了研究。结果表明，各站位可溶性糖含量的变化范围为0．7－124．3mg／L，以6月份最高，2月份最低；卤水中可溶性糖在111mg／L－215mg／L范围内，结晶盐的产量随卤水中可溶性糖含量的增加而提高，但同时降低了NaCl的含量，并增加了可溶性杂质及水分的含量，从而降低了盐质。初始可溶性糖浓度为111mg／L、137mg／L、160mg／L、193mg／L和215mg／L的25．4°Be’的卤水，在日照下实验12天，其对应结晶盐的NaCl含量分别为91．66％、90．63％、90．48％、90．23％和88．46％，可溶性杂质的含量分别为3．05％、3．32％、3．33％和4．54％。     

香山绝对点周围的局部地壳变形及其对重力测量结果的影响

为了监视北京地区的地壳稳定性，北京测绘院对10多个基岩点和北京市区进行了多次沉降观测，结果表明香山点近10多年来高程变化只有几毫米，其重力效应可略而不计，但测点东北和东南方有两个较大的下沉区。用线积分法计算了两个局部沉降的重力效应，在沉降区中心其影响可达0.38μms^-2，但对香山点的重力效应非常小，完全可以忽略。因此得出如下结论：香山点观测到的重力变化不是地壳变形引起的。