A note on the algorithm of symplectic integrators

For a Hamiltonian that can be separated into N+1(N\geq 2) integrable parts, four algorithms can be built for a symplectic integrator. This research compares these algorithms for the first and second order integrators. We found that they have similar local truncation errors represented by error Hamiltonian but rather different numerical stability. When the computation of the main part of the Hamiltonian, H ₀, is not expensive, we recommend to use S ^* type algorithm, which cuts the calculation of the H ₀ system into several small time steps as Malhotra(1991) did. As to the order of the N+1 parts in one step calculation, we found that from the large to small would get a slower error accumulation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of Different Diets on the Dietary Attractability and Selectivity of Chinese Shrimp, Fenneropenaeus chinensis

Attractabilities of different diets and dietary selectivity of Chinese shrimp, Fenneropenaeus chinensis were studied through behavior observation and feeding experiment, respectively. The five diets used in the experiment are: Fish Flesh (FF), Shrimp Flesh (SF), Clam Foot (CF), Polychaete Worm (PW), and Formulated Diet (FD). No significant differences of attractability exist between any two different diets when every two natural diets or all five diets are provided simultaneously. On the other hand, significant differences of attractability exist between FD and every single natural diet when they are provided simultaneously. Results of behavioral observation indicate that natural diets are more attractive than FD. In feeding experiment, Chinese shrimp has distinct selectivity on different diets. It positively selects CF and PW, negatively selects FF and SF, and excludes FD absolutely. The results of the present studies indicate that the dietary selectivity of shrimp was based not only on the attractabilities of the diets, but also on the responses such as growth and food conversion.     

中国东部第四纪自然环境演化及庐山“冰碛层”堆积时期的自然环境研究

根据第四纪地层内孢粉组合和动物群等新资料恢复了我国东部各大区域第四纪各个时期的自然环境特征,其温暖期与干冷期的交替与深海沉积O~(18)温度变化趋势大致对应。庐山三次“冰期冰碛层”内孢粉组合表明均为温暖湿润针阔叶混交林景观,而不是寒冷的冰川环境。     

Numerical simulation of January 28 cold air outbreak during GALE Part I: The model and sensitivity tests of turbulence closures

A mesoscale planetary boundary layer (PBL) numerical model has been developed to study airflow over complex topography. Turbulence closures using the turbulent kinetic energy (TKE) and dissipation () equations are investigated in combination with the level 2.5 scheme of Mellor and Yamada (1982) to determine eddy diffusivities for momentum and heat. This modified E- closure is simpler than the level 3 one which requires more prognostic equations for moist turbulent transport.One-dimensional (1-D) model results show that the PBL mean flows under various stability conditions are not significantly sensitive to the modified Blackadar and Kolmogorov eddy mixing-length formulations used in this E- model, although the latter yields excessively large mixing lengths in the entrainment region of the upper PBL. Eddy mixing lengths in the Kolmogorov-type formulation can be better defined by introducing background dissipation. Using the same prognostic TKE equation, the 1-D model results are not significantly affected by different diagnostic formulations in the closures. The simulated results compare well with large-eddy simulations and those obtained using higher-order closure schemes including the level 3 one. The results are found to be insensitive to eddy Prandtl number, in contrast to the 2-D model results (see Part II).     

TL dating of loess in China

TL ages of 56 loess samples collected from Xinjiang and the middle reaches of the Yellow River were determined by using fine-grained quartz and man-made light source bleaching techniques.The results indicate that :1.The well-preserved loess sections in Xinjiang began depositing 400000 a ago.The loess/paleosol series may be comparable with that observed in the middle reaches of the Yellow River but the depositing time was probably delayed by 30000-50000a.2.The bottom boundary age of the Malan loess varies from one place to another.The TL dates can be divided into two group:70000-130000 a and 30000-50000 a.The TL data are con-sistent with the appearance of two warmer climate periods since the Pleistocene,indicating obvious regional differences in stratigraphic development of loess,i.e.,paleosol occurred in the warm climate period in the same location,but loess was deposited in other locations.The initial age of loess deposition tends to become older from west to east and from south to north .In contrast ,the cold cli-matic belt showed an opposite trend.The TL ages of loess provide strong evidence for the Quaternary stratigraphy throughout geological times and the shift tendency of climatic belt.3.The depositing rate of the Malan loess along the middle reaches of the Yellow River varies from place to place but the TL age shows a linear relationship with the depositing thickness.The de-positing rate of loess in the north is higher than that in the south,suggesting that loess materials are derived from desert areas of northern China.     

Neutrino mass,luminosity variation,and spectrum of SN1987A

In this paper, the neutrino mass has been determined from SN1987a observation in a manner that the simultaneity of neutrino emission is not regarded as the starting point, but is itself defined through the analysis by Monte-Carlo simulation. The result is that the neutrino mass lies in 3–4 eV, possiblym _v 3.6 eV. Neutrino luminosity variation and neutrino spectrum are also obtained. Comparison with theories gives further support to the mass determination, and also predicts the mass of progenitor star of SN1987a to be in the range of 12–25M .The project supported by the National Natural Science Foundation of China.     

南海西部海域新生代构造古地理演化及其对油气勘探的意义

南海西部海域构造复杂,主要发育有北东—北东东向、北西向和近南北向3组深大断裂。其中,北西向断裂与板块汇聚、碰撞有关,多具走滑性质;北东—北东东向断裂具有与中国东部裂谷盆地相似的发育特点,呈张扭性质;近南北向断裂可能是南海在扩张活动期间于洋、陆壳过渡部位形成的走滑调节断裂,是洋盆扩张的西部边界。新生代里,南海经历了4次成盆事件与3期扩张活动,盆地经历了古新世—中始新世陆缘断陷、渐新世—早中新世扩展与中中新世以来的热沉降3个演化阶段。陆缘断陷阶段的充填系列主要是北东—北东东向与北西向的河流—冲积扇、湖泊沼泽等陆相沉积及火山岩等;盆地扩展阶段表现为中-小型断陷、断-坳陷逐渐复合与联合为大-中型坳陷,古地理格局逐渐由河流与湖沼陆相环境演变为滨海至浅海相的沉积环境;热沉降阶段的成盆活动逐渐减弱以至停止,地层表现超覆,盆地出现联合迹象。结合以往勘探与油气资源调查成果分析,认为南海西部海域陆架陆坡区发育的大-中型沉积盆地石油地质条件良好,蕴藏着丰富的油气资源,勘探潜力巨大。     

中国海监船舶导航与监控系统的研究

海监船舶在维护南海海洋权益、实施海域使用管理、海洋环境保护和海洋防灾救灾等方面起着重要的作用。文章从技术实现角度出发,结合海监船舶的航行方法、区域及受控监管特点,对海监船舶导航及监控的技术和信息需求做了深入研究,设计并基本实现了“海监船舶导航与监控管理信息系统”。     

南海大鹏湾夜光藻种群在其生态群落中的地位和功能

分析了１９９１年上半年南海大鹏湾盐田水域夜光菏和浮游动、植物之间的种群动态关系，结果表明，在春季高峰期３月至５月初，调查海域共出现１２个夜光藻和浮游动、植物高峰。其中，以发生４次赤潮的夜光藻种群占主导地位，其次是枝角类的鸟啄尖头蚤，其最高数量高达９６２３８ｉｎｄ／ｍ＾３。相比之下，在夜光藻和枝角类岛啄尖头捕食压力的影响下，浮游植物的春季高峰并不显著。调查结果表明夜光藻的过度繁殖，不但对产浮游性卵的     

在各类天气系统影响下石臼港沿岸波浪场的分布

本文查阅了从１９７３－１９８５，１３年的历史资料，对石臼港沿岸波浪场进行了详细的分类、统计分析和计算，提出了各类较强天气系统影响石（即指石臼港）的极端区域，同时获得了石港沿岸各类天气系统影响下的波浪分布特点以及波高计算式，为保障石港的生产及港口建设为石港的波了提供了有益的分析数据和预报手段。