Southern high latitude climate variability in the Late Cretaceous greenhouse world

A palynological study of oil exploration wells in the Gippsland Basin southeastern Australia has provided a record of southern high latitude climate variability for the last 12 million years of the Cretaceous greenhouse world. During this time, the vegetation was dominated by a cool to temperate flora of Podocarpaceae, Proteaceae and Nothofagidites spp. at a latitude of 60°S. Milankovitch forced cyclic alternations from drier to wetter climatic periods caused vegetation variability from 72 to 77 Ma. This climate change was probably related to the waxing and waning of ephemeral (100 ky) small ice sheets in Antarctica during times of insolation minima and maxima. Drying and cooling after 72 Ma culminated from 68 to 66 Ma, mirroring trends in global δ¹⁸O data. Quantitative palynofloral analyses have the potential to provide realistic proxies for small-scale climate variability in the predominantly ice-free Late Cretaceous.     

Approximate analysis for relative motion of satellite formation flying in elliptical orbits

This paper studies the relative motion of satellite formation flying in arbitrary elliptical orbits with no perturbation. The trajectories of the leader and follower satellites are projected onto the celestial sphere. These two projections and celestial equator intersect each other to form a spherical triangle, in which the vertex angles and arc-distances are used to describe the relative motion equations. This method is entitled the reference orbital element approach. Here the dimensionless distance is defined as the ratio of the maximal distance between the leader and follower satellites to the semi-major axis of the leader satellite. In close formations, this dimensionless distance, as well as some vertex angles and arc-distances of this spherical triangle, and the orbital element differences are small quantities. A series of order-of-magnitude analyses about these quantities are conducted. Consequently, the relative motion equations are approximated by expansions truncated to the second order, i.e. square of the dimensionless distance. In order to study the problem of periodicity of relative motion, the semi-major axis of the follower is expanded as Taylor series around that of the leader, by regarding relative position and velocity as small quantities. Using this expansion, it is proved that the periodicity condition derived from Lawden’s equations is equivalent to the condition that the Taylor series of order one is zero. The first-order relative motion equations, simplified from the second-order ones, possess the same forms as the periodic solutions of Lawden’s equations. It is presented that the latter are further first-order approximations to the former; and moreover, compared with the latter more suitable to research spacecraft rendezvous and docking, the former are more suitable to research relative orbit configurations. The first-order relative motion equations are expanded as trigonometric series with eccentric anomaly as the angle variable. Except the terms of order one, the trigonometric series’ amplitudes are geometric series, and corresponding phases are constant both in the radial and in-track directions. When the trajectory of the in-plane relative motion is similar to an ellipse, a method to seek this ellipse is presented. The advantage of this method is shown by an example.     

Shock breakout in Type Ibc supernovae and application to GRB 060218/SN 2006aj

Recently, a soft blackbody component was observed in the early X-ray afterglow of GRB 060218, which was interpreted as shock breakout from the thick wind of the progenitor Wolf–Rayet (WR) star of the underlying Type Ic supernova 2006aj. In this paper, we present a simple model for computing the characteristic quantities (including energy, temperature and time duration) for the transient event from the shock breakout in Type Ibc supernovae produced by the core-collapse of WR stars surrounded by dense winds. In contrast to the case of a star without a strong wind, the shock breakout occurs in the wind region rather than inside the star, caused by the large optical depth in the wind. We find that, for the case of a WR star with a dense wind, the total energy of the radiation generated by the supernova shock breakout is larger than that in the case of the same star without a wind by a factor of >10. The temperature can be either hotter or colder, depending on the wind parameters. The time duration is larger caused by the increase in the effective radius of the star due to the presence of a thick wind. Then, we apply the model to GRB 060218/SN 2006aj. We show that, to explain both the temperature and the total energy of the blackbody component observed in GRB 060218 by the shock breakout, the progenitor WR star has to have an unrealistically large core radius (the radius at optical depth of 20), larger than 100 R_⊙. In spite of this disappointing result, our model is expected to have important applications to the observations on Type Ibc supernovae in which the detection of shock breakout will provide important clues to the progenitors of Type Ibc supernovae.     

天文底片保存和我国天文底片数字化的建议

阐述了国际上天文照相底片数字化工作的进展:底片的保存、底片数字化的意义和相关技术。扼要地介绍了国际虚拟天文台的情况及其与底片数字化的关系。分析了我国天文底片资料的保存现状,并提出了底片数字化建议:成立由各天文台专家组成的全国底片数字化协调小组,建立各单位保存底片的信息库、改进底片的保存条件、有步骤地对有价值底片上的全部目标进行扫描,以便将其与现代高精度的观测资料相结合,开展有意义的课题研究。     

九龙江口和厦门西港的盐度低频变化特征

本文根据厦门海洋站长序列盐度观测结果，分析九龙江口和厦门西港各种时间尺度的盐度低频波动特征，并探讨其机制。结果表明，九龙江径流量是影响厦门盐度的主要因素，但不是唯一因素。在亚潮频段。盐度对径流的响应可能有相当强的非线性。     

海坛岛风沙表层沉积物的粒度分布特征

本文对海坛岛风沙表层沉积物的粒度分布特征进行研究。结果表明：海坛岛风沙沉积物主要是由海岸带基岩和第四纪松散堆积物及闽江南下沿岸流所携带的泥沙，在海洋动力作用下堆积于海滩上，而后在强劲的ＮＮＥ向向岸盛行风作用下，海滩沙向陆搬运堆积而成的。风成沙的主要粒级为中沙，平均粒径为１．７３Ф；分选较好，标准差的平均值为０．６８，偏差多近于对称，偏态平均值为－０．０２；峰态窄，峰态平均值为１．２１。其搬运方式单     

南海东北部台风潮的数值后报及极值增水估计

本研究对近40年来影响南海东北部陆架海区的28次台风引起的风暴潮进行了数值后报,其中8个过程的沿岸后报增水值与实测值进行了比较,表明后报值与实测值符合良好,90%以上的最大增水值偏差在30厘米以下。为了得出本海区多年一遇的台风增水极值,在后报台风路径密集处选择了9个不同水深点,对每点取出各次台风下的最大增水值,然后用Weibull分布进行拟合,得出了各点的极值分布。     

辽宁菊花岛海域沉积物中某些化学要素分布特征研究

菊花岛周围海域38个站表层沉积物的铁、锰、铝、钛、磷、有机质、氮、铜、锌、铅、镉、镍和汞等化学要素含量的Q型因子分析计算表明,本区可划分为三个化学元素沉积区:1.海流悬浮沉积区;2.近岸波浪作用区;3.波浪海流作用区。柱状沉积物中铁等化学元素的迁移、富集受氧化——还原界面的控制。     

中华绒螯蟹人工半咸水工厂化育苗试验研究报告

在盐度为14—19‰的人工海水中,温度20—25℃条件下,189只平均体重100g的抱卵亲蟹产蚤状幼体4025万只。布苗密度为50—100万只/m~3为宜。必须经常换水,保持水质良好。人工饵料以单胞藻和丰年虫无节幼体为主,可适当加喂蛋黄。