Authigenic iron oxide formation in the estuarine mixing zone of the Yangtze River   总被引：2，自引：0，他引：2  

D. J. Fan  R. D. Neuser  X. G. Sun  Z. S. Yang  Z. G. Guo  S. K. Zhai 《Geo-Marine Letters》2008,28(1):7-14

Estuaries are elementary geochemical fronts where river water and seawater mix. Within this mixing zone, iron and other non-conservative elements can undergo complex reactions to form new solid phases. In order to understand authigenic iron oxide formation in the Yangtze River Estuary, two onsite water-mixing sets of experiments were conducted, one by mixing variable amounts of unfiltered Yangtze River water with filtered East China Sea water of different salinity (set 1), the other by mixing variable amounts of filtered Yangtze River water with filtered East China Sea water of different salinity (set 2). In set 2, the minerals newly formed in the course of mixing were investigated by means of a scanning electron microscope fitted with an energy-dispersive X-ray analytical system. It was found that ferrihydrite and lepidocrocite were formed in these mixing experiments, coexisting in nearly equal amounts. These iron oxides appear as aggregated particles with a large grain-size range of several microns to more than 100 μm. The electrolytic properties of seawater played an important role in the formation of these authigenic iron oxides. Kaolinite and organic aggregates were also found in the experimentally mixed pre-filtered waters. Amounts of newly formed suspended matter (set 2) were one to three orders of magnitude lower than those of total suspended matter (TSM) (set 1). This implies that newly formed minerals represent only a very small proportion of TSM in the estuarine mixing zone of the Yangtze River.  相似文献   

Estimation of the Roll Hydrodynamic Moment Model of a Ship by Using the System Identification Method and the Free Running Model Test     

Hyeon Kyu Yoon Nam Sun Son Gyeong Joong Lee 《Oceanic Engineering, IEEE Journal of》2007,32(4):798-806

When a fast container ship or a naval vessel turns, accompanying roll motions occur. This roll effect must be considered in the horizontal equations of the motion of the ship to predict the maneuverability of the ship properly. In this paper, a new method for determining a model structure of the hydrodynamic roll moment acting on a ship and for estimating the hydrodynamic coefficients is proposed. The method utilizes a system identification technique with the data from sea trial tests or from free running model (FRM) tests. To obtain motion data that is applied to the proposed algorithm, an FRM of a large container ship was developed. Using this model ship, standard maneuvering tests were carried out on a small body of water out of doors. A hydrodynamic roll moment model was constructed utilizing the data from turning circle tests and a 20-20 zig-zag test. This was then confirmed through a 10-10 zig-zag test. It was concluded that a model structure of the hydrodynamic roll moment model could be established without difficulty through a system identification method and FRM tests.  相似文献   

Describing neutron stars by the relativistic mean field theory     

Huan-yu Jia  Bao-xi Sun  Jie Meng  En-guang Zhao 《Chinese Astronomy and Astrophysics》2002,26(4):901-413

Neutron stars are studied in the framework of the relativistic mean field theory of interacting nucleons, hyperons, and mesons. Within the hadronic freedom, the cores of neutron stars are found to be dominated by hyperons when the density is sufficiently high. The influence of hyperon coupling constants on the transition from a neutron star to a hyperon-dominated strange neutron star is also investigated. It is found that the transition density gets its minimum value when the ratio of hyperon coupling constant to nucleon's takes the value of 0.65, and the calculated maximum mass of the neutron star is 1.4 M which lies within the range of the observational results.  相似文献   

A large Middle Pleistocene freshwater to oligohaline lake in the contemporary hyperarid Qaidam Basin （China）     

Steffen Mischke Ulrike Herzschuh Naida Sun Zizhen Qiao Zhencheng Sun 《《幕》》2006,29(1):34-38

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长江三峡库区地震地形变监测研究   总被引：8，自引：4，他引：4  

杜瑞林  邢灿飞  伍中华  李胜乐  乔学军  游新兆  王琪  孙少安  申重阳  凌模 《大地测量与地球动力学》2004,24(2):23-29

三峡地壳形变监测网络结合空间大地测量(GPS、InSAR)和传统大地测量的优点，在1998年以来的三峡工程建设期间和2003年水库首次蓄水中获取了大量监测成果。结果显示库区地壳运动的基本图像：垂直形变较为显著，主要来自因蓄水荷载而产生的形变，水平形变不明显．库区主要断层的活动性在蓄水期间有明显加强迹象。水准测量反映从1998年首期观测至2003年10月首次蓄水后的库区垂直位移．沉降范围较大；GPS给出了2003年蓄水前后库区的垂直位移，形变的范围主要集中在水库近岸区域。水准测量与GPS观测反应的垂直位移的量级基本一致，沉降的最大幅度在3～4cm左右。水准监测、GPS观测与重力监测结果有一定的对应性。从地壳形变监测与研究结果分析，近期负荷改变而诱发中强地震的可能性不大。  相似文献   

Mapping models for near-conservative systems with applications     

Ji-Lin Zhou  Yan-Ning Fu  Yi-Sui Sun 《Celestial Mechanics and Dynamical Astronomy》1994,60(4):471-487

A systematic method is presented to construct a mapping model for a near-conservative system, based on that of Hadjidemetriou for a Hamiltonian system [1]. The mapping we constructed preserves the basic features of the actual system. We apply this method to the forced oscillating system and to the 3 : 1 resonant grain motion in the presence of Poynting-Robertson drag.Supported by the National Natural Science Foundation of China.  相似文献   

Forced secondary resonances at the 3 : 1 commensurability     

Yi-Sui Sun  Ji-Lin Zhou  Tian-Ling Zhang  Chong-Qing Cheng 《Celestial Mechanics and Dynamical Astronomy》1994,59(4):313-325

For the 3 : 1 Jovian resonance problem, the time scales of the two degrees of freedom of the resonant Hamiltonian are well-separated [5]. With the adiabatic approximation, the solution for the fast oscillations can be found in terms of the slowly varying variables. Thus the rapidly oscillating terms in the slow oscillation equations can be treated as forced terms. We refer to the resonance between the forcing and intrinsic frequencies as a forced secondary one in this paper. We discuss the forced secondary resonances in asteroidal motion at the 3 : 1 commensurability by using Wisdom's method. The results show that the orbits situated originally near the resonance will leave the neighbourhood of resonance and tend to the separatrices and critical points for different energies, respectively. We have not found any stochastic web as expected in this case. Moreover, we study the problem of validity on the approximation of a system.The Project Supported by the National Natural Science Foundation of China.  相似文献   

Isolation,purification and characterization of the hydrogen evolution promoting factor of hydrogenase ofSpirulina platensis     

Gu Tian-qing  Zhang Hui-miao  Sun Shi-hua 《中国海洋湖沼学报》1996,14(1):27-30

A component (s-factor) with obvious promoting effect on hydrogen evolution of hydrogenase has been isolated and extracted from a cell-free preparation ofSpirulina platensis. The effect of the s-factor in the reaction system is similar to that of Na₂S₂O₄, but is coupled with light. The s-factor has the maximum absorption peak at 620 nm in the oxidized state, at 590 nm in the reduced state. The partially purified s-factor showed two bands by SDS-PAGE and is distinctly different from phycocyanin, which has no change of oxidized state and reduced state absorption spectra, and also has no promoting effect on hydrogenase ofSpirulina platensis under the light. The research supported by the NSFC.  相似文献   

关联指数误差和样本容量     

吴云  周硕愚  孙建中 《大地测量与地球动力学》1994,(1)

根据关联指数的定义，推导了ＧＰ法计算关联指数时的观测数据误差与关联指数误差的关系，导出了任意两个嵌入空间维上关联指数之差的表达式，并提出了一种确定样本容量限的方法。  相似文献   

温度和饵料对双刺纺锤水蚤产卵率和孵化率的影响     

孙晓红  孙松  李超伦  王世伟 《海洋科学集刊》2009,49(49):78-86

Acartia bifilosa (Copepoda: Calanoida) is a common species in offing of global waters and it often becomes dominant species in some estuaries. This species develops different strategy according to variation of environment. Despite its ecological role, Acartia bifilosa also has been concerned as live feeds in aquaculture, but study on egg production rate of this species in saturated diet in different temperature and different diet is so far not available. In order to interpret the importance of temperature and diet on natural population variation and also on aquaculture as foods of larval fish, the functional response of reproductive success of Acartia bifilosa was quantified in the laboratory using different temperatures and diets. Acartia bifilosa was captured in Jiaozhou Bay and acclimated to corresponding temperature for 3~4 days. In order to reduce the effect of large extent temperature range on organism, we captured Acartia bifilosa from March to June and acclimated them to temperature which is adjacent to natural temperature. Daily egg production rate (EPR, eggs female-1day-1) was detected for 11~15 days at 5 different temperatures ranged from 8.0 to 23 °C and all the females was feed on saturated diet all through the experiments. EPR on first day was not calculated in the mean EPR to eliminate the effect of different diets. This result showed that Acartia bifilosa spawned continuously during the experiment days and no obvious regulation was found. EPR was positively correlated with temperature from 8.0 to 23 °C. The highest mean EPR was observed at 23 °C (7.3 eggs female-1day-1), and the lowest value was found at 8 °C (3.8 eggs female-1day-1). The effect of diets on EPR was evaluated at two different temperatures (8.0 °C and 12.5 °C). Same trends were found at the two temperatures: mean EPR fed on Chaetoceros sp. was higher than that fed on Skeletonema costatum, and during the 14-day experiments, EPR was higher for females fed on Skeletonema costatum than chaetoceros sp. in the first few days (3~5 days), but it changed reversely in the subsequent days until the end of the experiments. Hatched eggs were observed in the two experiments at temperature 8°C and 12.5 °C and no diapause eggs were found. The hatching success rate was low at 8°C but reached 93.2% at 12.5 °C. According to the results in this paper, we detected the comfortable temperature range for EPR, and evaluated the effect of Skeletonema costatum which often brings out red tide in natural waters. These results are beneficial to ecological research for explaining population variation and population recruitment of this species, These data also can be used in Acartia bifilosa aquaculture.  相似文献