航天GPS接收机设计   总被引：1，自引：0，他引：1  

杨春宝  张海云  邱宗德  尤政 《全球定位系统》2004,29(3):19-25

航天GPS接收机为航天器提供航迹、姿态、时问和相对距离等导航信息，提高航天嚣运行的自主性。文中介绍了清华宇航中。航天GPS接收的硬件和软件设计，给出测试结果和分析。  相似文献   

Energetic Particles Observed in the CUSP Region During a Storm Recovery Phase     

S. Y. Fu  Q. G. Zong  Z. Y. Pu  C. J. Xiao  A. Korth  P. Daly  H. Reme 《Surveys in Geophysics》2005,26(1-3):241-254

In this paper we report energetic ion behavior and its composition variations observed by the Cluster/RAPID instrument when the spacecraft was travelling in the high latitude magnetospheric boundary region on the day of the 31 March, 2001, strongest magnetic storm in the past 50 years. The Dst index reached −360 nT at about 09:00 UT. During its early recovery phase, large amounts of oxygen and helium ions were observed; the ratio of oxygen to hydrogen in the RAPID energy range reached as high as 250%, which suggests that the observed energetic particles might be of magnetospheric origin. The observations further show that enhanced energetic electron fluxes are confined in a very narrow region, while protons have occupied a larger region, and heavy ions have been observed in an even larger region. The flux of energetic electrons show a slight enhancement in a region where the magnetic field magnitude is around zero. These observed energetic ions could be quasi-trapped by the current sheet in the stagnation region of the cusp.  相似文献   

The Magnetospheric cusps: A Summary     

T. A. Fritz  Q. G. Zong 《Surveys in Geophysics》2005,26(1-3):409-414

The polar cusps of the magnetosphere are key regions for the transfer of mass, momentum, and energy from the solar wind into the magnetosphere. Understaning these key regions and the dynamical interactions that occur there are fundamentally important to determining the physical nature of the magnetosphere. In this paper we try to summarize many of the conclusions reached in the papers of this special issue emphasizing the present concepts and definition of the cusp, what variations could be temporal structures and what could be spatial structures. We address the need for further measurements and the role of present and planned projects to address these needs.  相似文献   

营养限制对三种浮游动物的影响   总被引：1，自引：0，他引：1  

陈蕾  李超伦  周孔霖  时永强  刘梦坛 《海洋学报(英文版)》2018,37(4):58-68

Nutrient imbalance—a mismatch in nutrient ratios between the available food supply and the demands of consumers—has the potential to be transported up food chains,exposing zooplankton to nutrient limitations.In this study,the response of Calanus sinicus(copepod),Moina mongolica(cladocera),and Brachionus plicatilis(rotifer) to nutrient-limited(no-limited,P-limited,and N-limited) food were evaluated from the perspective of growth,reproduction,and stoichiometric homoeostasis.The results indicated that the growth of three species was suppressed under nutrient-limited(especially P-limited) conditions.However,the effect of nutrient limitations on their reproduction was species-specific.For C.sinicus,the dietary UFA(unsaturated fatty acid) as a major phospholipid component affected their egg production and total FA supporting energy promoted the hatchability of eggs.Furthermore,excess carbon in the diet promoted egg production but reduced hatching success.For M.mongolica,nutritional(P and UFA) and energy(total FA) support affected their fecundity.B.plicatilis fecundity exhibited the same pattern of growth(no-limitedN-limitedP-limited).In terms of stoichiometric homeostasis,B.plicatilis' s elemental compositions were less likely to be affected by nutrient limitations than M.mongolica.We suggest that the effects of nutrient imbalances could potentially become an evolutionary force affecting ecosystem structure and stability in eutrophic waters.  相似文献   

Vortex-Induced Vibrations of A Long Flexible Cylinder in Linear and Exponential Shear Flows     

Gao  Yun  Yang  Bin  Zou  Li  Zong  Zhi  Zhang  Zhuang-zhuang 《中国海洋工程》2019,33(1):44-56

A numerical study based on a wake oscillator model was conducted to determine the response performance of vortex-induced vibration(VIV) on a long flexible cylinder with pinned-pinned boundary conditions subjected to linear and exponential shear flows. The coupling equations of a structural vibration model and wake oscillator model were solved using a standard central finite difference method of the second order. The VIV response characteristics including the structural displacement, structural frequency, structural wavenumber, standing wave behavior,travelling wave behavior, structural velocity, lift force coefficient and transferred energy from the fluid to the structure with different flow profiles were compared. The numerical results show that the VIV displacement is a combination of standing waves and travelling waves. For linear shear flow, standing waves and travelling waves dominate the VIV response within the low-velocity and high-velocity zones, respectively. The negative values of the transferred energy only occur within the low-velocity zone. However, for exponential shear flow, travelling waves dominate the VIV response and the negative energy occurs along the entire length of the cylinder.  相似文献   

Study on biogenic amines in various dry salted fish consumed in China     

WU Yanyan  CHEN Yufeng  LI Laihao  YANG Xianqing  YANG Shaoling  LIN Wanling  ZHAO Yongqiang  DENG Jianchao 《中国海洋大学学报(英文版)》2016,15(4):681-689

This study was carried out to investigate the biogenic amines（BAs）, physicochemical property and microorganisms in dry salted fish, a traditional aquatic food consumed in China. Forty three samples of dry salted fish were gathered from retail and wholesale markets and manufacturers, which had been produced in various regions in China. Cadaverine（CAD） and putrescine（PUT） were quantitatively the most common biogenic amines. About 14% of the samples exceeded the histamine content standards established by the FDA and/or EU. The highest histamine content was found in Silver pomfret（Pampus argenteus）(347.79 mg kg^-1). Five of forty three samples exceeded the acceptable content of TYR(100 mg kg^-1), and 23.26% of dried-salted fish contained high contents of biogenic amines(above 600 mg kg^-1). In addition, species, regions, pickling processes and drying methods made the physicochemical property, microorganisms and biogenic amines in dry salted fish to be different to some extents. The total plate count（TPC） was much higher than that of total halophilic bacteria in all samples. The biogenic amines, physicochemical property and microbiological counts exhibited large variations among samples. Furthermore, no significant correlation between biogenic amines and physicochemical property and TPC was observed. This study indicated that dry salted fish may still present healthy risk for BAs, depending on the processing methods, storage conditions among others.  相似文献   

Ablation Characteristic of Ilmenite using UV Nanosecond and Femtosecond Lasers: Implications for Non‐Matrix‐Matched Quantification          下载免费PDF全文

Zhen Li  Zhaochu Hu  Detlef Günther  Keqing Zong  Yongsheng Liu  Tao Luo  Wen Zhang  Shan Gao  Shenghong Hu 《Geostandards and Geoanalytical Research》2016,40(4):477-491

Ilmenite (FeTiO₃) is a common accessory mineral and has been used as a powerful petrogenetic indicator in many geological settings. Elemental fractionation and matrix effects in ilmenite (CRN63E‐K) and silicate glass (NIST SRM 610) were investigated using 193 nm ArF excimer nanosecond (ns) laser and 257 nm femtosecond (fs) laser ablation systems coupled to an inductively coupled plasma‐mass spectrometer. The concentration‐normalised ⁵⁷Fe and ⁴⁹Ti responses in ilmenite were higher than those in NIST SRM 610 by a factor of 1.8 using fs‐LA. Compared with the 193 nm excimer laser, smaller elemental fractionation was observed using the 257 nm fs laser. When using 193 nm excimer laser ablation, the selected range of the laser energy density had a significant effect on the elemental fractionation in ilmenite. Scanning electron microscopy images of ablation craters and the morphologies of the deposited aerosol materials showed more melting effects and an enlarged particle deposition area around the ablation site of the ns‐LA‐generated crater when compared with those using fs‐LA. The ejected material around the ns crater predominantly consisted of large droplets of resolidified molten material; however, the ejected material around the fs crater consisted of agglomerates of fine particles with ‘rough' shapes. These observations are a result of the different ablation mechanisms for ns‐ and fs‐LAs. Non‐matrix‐matched calibration was applied for the analysis of ilmenite samples using NIST SRM 610 as a reference material for both 193 nm excimer LA‐ICP‐MS and fs‐LA‐ICP‐MS. Similar analytical results for most elements in ilmenite samples were obtained using both 193 nm excimer LA‐ICP‐MS at a high laser energy density of 12.7 J cm^?2 and fs‐LA‐ICP‐MS.  相似文献   

Data integration in characterizing a fracture-cavity reservoir,Tahe oilfield,Tarim basin,China     

Yongqiang Li  Jiagen Hou  Xiaoqiang Ma 《Arabian Journal of Geosciences》2016,9(8):532

Fracture-cavity reservoirs can be described in terms of storage space, filling materials and distribution, however, characterizing these variables remains a challenge. In this study, a method was developed to characterize complex reservoirs by integrating outcrop, core, well log, and seismic data from the Tahe oilfield. Outcrop analogs were used to identify and qualitatively analyze the genesis of different reservoir spaces. Cores, well logs, and seismic data were used to identify different types of reservoir space in the subsurface, to describe the spatial distribution, and to establish the distribution pattern of fracture-cavity reservoirs. Clastic sediments, collapse breccia, and chemical fillings were described from the cores and used to assess porosity and permeability. On the basis of the results, a three-dimensional geological model was constructed incorporating a structural model, a reservoir space model, and a property model. Caves and fractures were the main storage spaces and seepage passages. The cave model was built using multi-point geostatistical simulation, while the fracture model was established using deterministic modeling combined with manual interpretations and ant-tracking technology.  相似文献   

A New Ootype of Dinosaur Egg (Faveoloolithidae: Duovallumoolithus shangdanensis oogen. et oosp. nov.) from the Late Cretaceous in the Shangdan Basin,Shaanxi Province,China     

ZHENG Tingting  BAI Yi  WANG Qiang  ZHU Xufeng  FANG Kaiyong  YAO Yuan  ZHAO Yongqiang  WANG Xiaolin 《《地质学报》英文版》2018,92(3):897-903

A new ootype collected from the Upper Cretaceous Lijiacun Formation in the Shangdan Basin, Shaanxi Province is described in this paper. Based on general external shape, size, eggshell thickness and honeycomb‐like eggshell microstructure, eggs are referable to the oofamily Faveoloolithidae. Compared with other members of Faveoloolithidae, specimens described in this paper show special characteristics: adjacent pores are usually separated by two eggshell units between which often develop interspaces; columnar eggshell units are relatively closely arranged in radial view. According to these characteristics, we erect a new oogenus and a new oospecies: Duovallumoolithus shangdanensis oogen. et oosp. nov. The new discovery expands the diversity of Faveoloolithidae.  相似文献   

Effect of climate change on water resources in the Yuanshui River Basin: a SWAT model assessment     

Yingdong Yu  Jiahong Liu  Zhiyong Yang  Yongqiang Cao  Jing Chang  Chao Mei 《Arabian Journal of Geosciences》2018,11(11):270

The Yuanshui River Basin is one of the most important river basins ensuring food production and livelihoods in the Hunan and Guizhou Provinces of China. Based on digital elevation model, land use, soil, and meteorological data, the soil and water assessment tool was used to analyze the response of water resources in the basin to climate change. Specifically, the monthly runoff from the Yuanshui River Basin was simulated. Runoff measurements from the 1961–1990 series were used to calibrate model parameters, and measurements from the 1991–2010 series were used for model validation. The Nash–Sutcliffe efficiency coefficient, correlation coefficient, and water balance error were used to evaluate the simulation results; the values obtained for these parameters were 0.925, 0.929, and 2.0%, respectively, indicating that the established model can be applied successfully to runoff simulations. To evaluate the effects of climate change and human activities on runoff, 24 different climate scenarios were modeled. By comparing the model simulation results with the baseline scenario, the effects of climate change were analyzed by year, during the dry season, and during extremely dry conditions. The results showed that runoff decreased with increasing air temperature and decreasing precipitation, and that the effects of rainfall on runoff were greater than those of air temperature. Under the same baseline conditions, the effects of climate change on runoff were most pronounced during extremely dry months.  相似文献