Improvement on the second-order solution of artificial satellite orbits

Three methods are proposed in this paper to lessen the complexity in the derivation and the resulting expressions of second-order analytical solutions of artificial satellite orbits while retaining the advantages of analytical solutions. Of the three, the one combining the theories of elliptical perturbation and of intermediate orbits is noteworthy for its simplicity. It can also be used with advantage in first-order and third- or higher order solutions.     

The solar particle event of July 16–19, 1966 and its possible association with a flare on the invisible solar hemisphere

An energetic solar proton and electron event was observed by particle detectors aboard Explorer 33 (AIMP-1) and OGO-3 during the period July 16–19, 1966. Optical and radio observations of the sun suggest that these particles were produced by a flare which may have occurred on July 16 near the central meridian of the invisible hemisphere. The active region to which the flare is assigned is known to have produced the energetic particle events of July 7 and 28, 1966. The propagation of the particles in the July 16–19 event over the 180° extent of solar longitude from the flare to the earth is discussed, and it is concluded that there must exist a means of rapidly distributing energetic particles over a large area of the sun. Several possible mechanisms are suggested.     

P-wave velocities in rocks at high pressure and temperature and the constitution of the central California crust

Summary. Velocities of compressional waves are determined for central California rocks at pressures up to 0.7 GPa (7 kb) and temperatures up to 450°C. These data are used to interpret the seismic velocity structure of the crust in the California Coast Ranges. The seismic data on both sides of the San Andreas fault are consistent with the following model; besides some patches of surface sediments the upper 10—15 km of the crust on the northeast side consists predominantly of sedimentary and metasedimentary rocks of the Franciscan assemblage; the lower crust, of a thickness of 15—20 km, may be composed of gabbroic or other mafic rocks. Across the fault on the south-west side, the entire crustal section is probably a granitic complex similar to that exposed on the surface. The proposed model is shown to be consistent with the observed gravity anomaly.     

面向Internet的农业气象产量动态预报

针对信息时代Internet网上用户对产量预报动态查询的需求 ,探讨了面向Inter net的农业气象产量预报的解决方案。试验结果表明 ,由于作物生长发育和产量形成是一个光、温、水、土条件长期、综合作用 ,生物量长期累积的过程 ,因此利用积分回归方法 ,考虑全生育期光、温、水气象因子的综合影响 ,根据已出现的天气实况 ,在假定后期天气条件正常的情况下 ,有可能预测出未来产量的趋势。随着天气实况的逐一出现 ,后期的预报结果可望逐步接近实际值。统计检验和试报结果误差均在允许范围内。     

RTK技术在高速公路土地登记测量中的应用

首先讨论RTK在高速公路土地登记测量中的优越性,根据两个实例,比较RTK与全站仪、不同的RTK结果之间的差异,RTK与全站仪的点位互差为3cm,不同方式的RTK结果的点位互差也为3cm。     

基于生态事件序列的时态关联规则挖掘

本文分析了时态关联规则挖掘的相关定义,介绍了强时态关联规则挖掘的步骤,设计并实现了基于时间约束的T-Apriori算法。提出了生态事件和生态时间序列的概念,以我国南海大亚湾海域的赤潮现象为例,研究了基于生态事件序列的时态关联规则挖掘问题。     

High Asia cryospheric observation: a proposed network under Global Cryosphere Watch (GCW)

In coordination with Global Cryosphere Watch (GCW) initiated by World Meteorology Administration (WMO), a regional observation network is proposed based on existing stations/sites over High Asia and cryospheric elements required by GCW. Thus, High Asian Cryosphere (HAC) network is preliminary designed, composing of seven "supersites", each containing several reference sites. The network covers major mountain ranges in High Asia, such as East Tianshan, Qilian, Tanggula, Nyainqentanglha, Himalayas as well as the central and eastern Qinghai-Xizang (Tibet) Plateau. Although multiple cryospheric elements were observed at the existing HAC network, many others, which are required by Integrated Global Observation System-Cryosphere Theme (IGOS-Cryosphere), are not yet included. More comprehensive observations are necessary to be included into "supersites" of HAC, so that the basic requirements for validation of satellite data, assimilation and coupled regional models can be met.     

Hydrodynamic change recorded by diatoms in sediments of Liuxihe Reservoir, southern China

Diatoms are used widely for paleolimnological studies in lakes, but their use for studying the environmental history of reservoirs has not been tested extensively. Reservoirs have hydrodynamic characteristics intermediate between those of rivers and lakes. This study assessed the utility of diatom assemblages as recorders of long-term changes in hydrodynamics and spatial gradients in Liuxihe Reservoir, an impoundment in southern China. Four sediment cores were collected in the reservoir, from the riverine, transition and lacustrine zones. Each core was sectioned at 2-cm intervals to investigate the stratigraphic distribution of accumulated diatoms. Varve counting was used to develop a chronology for one of the cores. The unique characteristics of Liuxihe Reservoir, including its large size, great depth, long narrow morphology and strong thermal stratification for 10 months of the year, limit secondary sedimentation processes and preserve the varves, enabling development of an accurate chronology. Damming profoundly altered the physical environment of the former river, especially in the lacustrine zone, where the change is clearly illustrated by diatoms in the sediment. Diatom abundance increased as a consequence of nutrient enrichment after construction of the dam in 1958, but later decreased as the new impoundment stabilized. After damming, relative abundance of Cyclotella increased along with a simultaneous decrease of Navicula and Achnanthes in the lacustrine zone, most significantly in 1963, when Cyclotella replaced Navicula as the dominant genus. This switch was indicative of a general shift from a lotic to a lentic habitat. A longitudinal gradient was apparent in the patterns of sedimentation and diatom accumulation at different sites in the reservoir, with diatom abundance highest in the transition zone. In the long term, water discharge from the reservoir showed a weak, but significant negative correlation with diatom abundance in the lacustrine zone (r = −0.320, P = 0.03). In summary, diatom assemblages in the Liuxihe Reservoir sediments recorded past changes in hydrodynamics, suggesting that paleolimnological study of some impoundments is feasible.     

Application of a simple binary mixing model to the reconstruction of lead pollution sources in two Mississippi River floodplain lakes

A simple binary mixing model is used to determine the isotopic ratios of lead (Pb) pollution sources to a lake located near a smelter closed because of excessive Pb aerosols (Horseshoe Lake Madison County, Illinois, USA). As a control, we also examine a relatively unpolluted lake in a rural area of Southern Illinois (Horseshoe Lake Alexander County). Sediment cores were taken from both lakes and analyzed for Pb and Pb isotopes by ICP-MS. The mixing model shows that Madison County Horseshoe Lake had 3 different sources of Pb in its history. The first source is sediment from the Mississippi River with an intermediate ²⁰⁶Pb/²⁰⁷Pb ratio (1.223 ± 0.009) which dominates inputs in pre-settlement times. From 1750 to 1933, the source of pollution Pb has the high ²⁰⁶Pb/²⁰⁷Pb ratio (1.256 ± 0.005) characteristic of ore from the southeast Missouri Pb mines. The most recently deposited pollution Pb comes from a source with a low ²⁰⁶Pb/²⁰⁷Pb ratio (1.202 ± 0.005). This source is similar in isotopic composition to pollution Pb found by several other investigators in the Eastern US and probably represents the mixture of ores used in modern industrial processes. It is unclear from the isotopic composition whether this source at Horseshoe Lake is the local Pb smelter or vehicle exhaust. The sediment core from Horseshoe Lake, Alexander County, shows a less variable isotopic composition. The binary mixing model showed a source composition of 1.225 ± 0.003 before 1850 and 1.231 ± 0.003 after this date. The change does not indicate a pollution source, but may be a shift in the sources of natural sediment with slightly different isotopic ratios to the lake. Our results show the value of simple binary mixing models to reconstruct the isotopic composition of Pb sources to lakes.     

Detection of trends in precipitation extremes in Zhejiang, east China

Extreme weather exerts a huge impact on human beings and it is of vital importance to study the regular pattern of meteorological and hydrological factors. In this paper, a selection of seven extreme indices is used to analyze the trend of precipitation extremes of 18 meteorological stations located in Zhejiang Province, east China using the Mann–Kendall test. Then the precipitation trends in the plum season (from May to July) and typhoon season (from August to October) are studied separately. The results show that the precipitation trend varies from east to west. There is a positive trend in the east and a negative one in the west. The largest part of Zhejiang Province shows a positive trend in heavy precipitation and the most significant upward trend is detected in Dinghai with 3.4?mm/year for precipitation on very wet days. Although the upward trend of extreme precipitation is not prevailing, the range of increase in specific areas is apparent, like Dinghai with 1.3?mm/year. Precipitation intensity exhibits an upward trend in most areas and a typical upward trend can be found in Dachendao, Tianmushan, and Yuhuan with 0.04, 0.02, and 0.05?mm/year respectively. Precipitation intensity in both plum and typhoon seasons has increased too, especially for the coastal stations.