Reflection of Short Waves

—According to the energy equation,the relation between reflection and energy losses for shortwaves from mild beaches is established and analysed.A reflection coefficient varying with position and en-ergy losses is proposed.Different reflection tests are conducted to check the theoretical analysis.A modi-fied method to estimate the reflection coefficient at varied water depths is suggested based on the linearwave theory.The study indicates that the reflection coefficient from mild beaches has a changing trend forshort waves approaching shoreline.     

呼伦贝尔草原物候变化及其与气象因子的关系

草原物候是草原生态系统气候变化的敏感指示器,探索物候变化与气候变化的关系,对草原生态系统保护及全球气候变化研究具有重要意义。以呼伦贝尔草原为研究对象,基于2000—2015年MOD09Q1数据和气象数据,利用D-L拟合法对NDVI时间序列进行重构,采用动态阈值法提取草原物候期,利用相关分析法,分析了物候与气象因子之间的关系。研究表明:(1)返青期发生时间介于4月下旬～6月上旬(平均为第138 d),枯黄期发生时间介于9月～10月下旬(平均为第277 d),生长季长度主要在3. 5～6个月之间(平均为136 d)。空间上,西部和北部返青期较早,枯黄期较晚,生长季长度最长;中东部返青期较晚,枯黄期较早,生长季长度较短。(2)年际变化趋势上,返青期和枯黄期均以提前趋势为主,提前趋势的像元比例分别为61. 2%和63. 83%,生长季长度以延长趋势为主,延长趋势的像元占比为54. 95%。(3)冬季降水增加是返青期提前的主要原因,而春季降水增多和秋季温度升高是枯黄期提前的主要原因。研究结果有助于加深物候对气候变化响应的认识,以期更好地为草原物候研究和放牧优化管理提供参考。     

Multipath Mitigation of Continuous GPS Measurements Using an Adaptive Filter

Though state-of-the-art dual-frequency receivers are employed in the continuous Global Positioning System (CGPS) arrays, the CGPS coordinate time series are typically very noisy due to the effects of atmospheric biases, multipath, receiver noise, and so on, with multipath generally being considered the major noise contributor. An adaptive finite-duration impulse response filter, based on a least-mean-square algorithm, has been developed to derive a relatively noise-free time series from the CGPS results. Furthermore, this algorithm is suitable for real-time applications. Numerical simulation studies indicate that the adaptive filters is a powerful signal decomposer, which can significantly mitigate multipath effects. By applying the filter to both pseudorange and carrier phase multipath sequences derived from some experimental GPS data, multipath models have been reliably derived. It is found that the best multipath mitigation strategy is forward filtering using data on two adjacent days, which reduces the standard deviations of the pseudorange multipath time series to about one fourth its magnitude before correction and to about half in the case of carrier phase. The filter has been successfully applied to the pseudorange multipath sequences derived from CGPS data. The benefit of this techniques is that the affected observable sequences can be corrected, and then these corrected observables can be used to improve the quality of the GPS coordinate results. ? 2000 John Wiley & Sons, Inc.     

Improving BeiDou real-time precise point positioning with numerical weather models

Precise positioning with the current Chinese BeiDou Navigation Satellite System is proven to be of comparable accuracy to the Global Positioning System, which is at centimeter level for the horizontal components and sub-decimeter level for the vertical component. But the BeiDou precise point positioning (PPP) shows its limitation in requiring a relatively long convergence time. In this study, we develop a numerical weather model (NWM) augmented PPP processing algorithm to improve BeiDou precise positioning. Tropospheric delay parameters, i.e., zenith delays, mapping functions, and horizontal delay gradients, derived from short-range forecasts from the Global Forecast System of the National Centers for Environmental Prediction (NCEP) are applied into BeiDou real-time PPP. Observational data from stations that are capable of tracking the BeiDou constellation from the International GNSS Service (IGS) Multi-GNSS Experiments network are processed, with the introduced NWM-augmented PPP and the standard PPP processing. The accuracy of tropospheric delays derived from NCEP is assessed against with the IGS final tropospheric delay products. The positioning results show that an improvement in convergence time up to 60.0 and 66.7% for the east and vertical components, respectively, can be achieved with the NWM-augmented PPP solution compared to the standard PPP solutions, while only slight improvement in the solution convergence can be found for the north component. A positioning accuracy of 5.7 and 5.9 cm for the east component is achieved with the standard PPP that estimates gradients and the one that estimates no gradients, respectively, in comparison to 3.5 cm of the NWM-augmented PPP, showing an improvement of 38.6 and 40.1%. Compared to the accuracy of 3.7 and 4.1 cm for the north component derived from the two standard PPP solutions, the one of the NWM-augmented PPP solution is improved to 2.0 cm, by about 45.9 and 51.2%. The positioning accuracy for the up component improves from 11.4 and 13.2 cm with the two standard PPP solutions to 8.0 cm with the NWM-augmented PPP solution, an improvement of 29.8 and 39.4%, respectively.     

Trachytic Rock and Associated Fenitization in the Bayan Obo Ore Deposit, Inner Mongolia, China: Evidence for Magmatic-Hydrothermal Mineralization Related to a Carbonatitic Complex

Trachytic rock and its altered rock-fenite-in the Bayan Obo ore district, Inner Mongolia, China, were referred to as slate or feldspar rock before, and identified by the authors for the first time (in 1992). In the paper the mineral assemblages, structures and textures and petrochemical compositions of the rocks, as well as the electron microprobe analysis of feldspars in the rocks are described. The Sm-Nd isochron age of the trachytic rock is 1096±56 Ma, with INd=0.51100+4 (2σ) and εNd(t)= -4.4±0.7. Alterations of the trachytic rock, including microclinization, riebeckitization, aegirinization and biotitization, and accompanied rare element and REE mineralizations are discussed. Based on the occurrence of the trachytic rock and associated fenitization it is deduced that the Bayan Obo Fe-Nb-REE ore deposit is genetically related to magmatic-hydrothermal activity of an alkali carbonatite complex.     

火山碎屑岩对CO2的矿物捕获能力

CO2矿物捕获是指将大气中排放的CO2气注入到地下深部的含水层、油气田等渗透性储层中,通过一系列物理、化学反应,最终将CO2气以碳酸盐矿物的形式“固结”在岩石中。火山碎屑岩具有铁、镁离子含量高且容易释放及分布广泛等特点,是有前途的矿物捕获岩石类型。塔木察格盆地塔南凹陷铜钵庙组火山碎屑岩中发育大量的片钠铝石特征矿物,进一步证实了火山碎屑岩的矿物捕获能力。在火山碎屑岩中,CO2注入之后形成的矿物有片钠铝石、铁方解石、铁白云石等碳酸盐矿物,碳酸盐总量高达30%,说明CO2矿物捕获的能力较大。     

Distribution and migration of the common squidTodarodes pacificus in the Yellow Sea

Study of the distribution and migration of the common squid,Todarodes pacificus Steenstrup,basedon the index of important fishing ground(P) and fisheries statistics on the Yellow Sea and northern EastChina Sea during 1980—1991 showed that:1.Its catch in the fishing period(June to November) is 91.77% of the annual yield.The fishingground distributes over the northem and middle Yel1ow Sea and adjacent area of the Changjiang Estuary.2. It over-winters in the northem East China Sea and waters adjacent to Goto Island from De-cember to February and spawns in waters near Haijiao Is1and and west of Kyushu. The main stock mi-grates along 123°30′E to the ChangJiang Estuary, Haizhou Bay. offsea from Shidao to Qingdao,mideastern Yellow Sea, and offsea Weihai and Haiyang Island succesively for feeding after April. The sur-plus stock migrates again to the wintering ground in December.3.The favorable feeding temperature is 6-23℃(optimum of l3-20℃ in the Changjiang Estua-ry and 7-13℃ in the northern and middle Yel     

二十一世纪城市地质工作的思考

本文阐述了城市地质工作的历史发展,着重论述了城市地质工作的内容,进而对城市地质工作的思路、方法和组织管理提出了设想。     

正断层断距纵剖面图及其运动学:概念模型与地质实例

断距纵剖面图 （T H图）是指以断层的垂直断距为横轴、以地层或地质年龄为纵轴所绘制的随地层或地质年龄所变化的断距分布图。断距纵剖面图为确定正断层类型、断层形成时间和断层的纵向演化史提供了一个简单迅捷的工具。概念模型表明,断距纵剖面图可以明确无误地区分出简单后沉积型正断层、后沉积拱顶拉张型正断层、同沉积生长型正断层及其复合型正断层。简单后沉积型正断层的断距不随地层年龄的变化而变化, 其断距纵剖面图为一垂直线段。后沉积拱顶拉张型正断层的断距随地层年龄的增大而减小并趋向零值,同沉积生长型正断层的断距随地层年龄的增大而增大,复合型正断层则具其组合型断距纵剖面形态。除简单后沉积型正断层外,断距纵剖面图中的最大断距点代表了该断层的起始形成年代。     

CHARACTERISTICS OF SEDIMENT TRANSPORT AND CHANNEL FORMATION BY FLOODS AT HYPERCONCENTRATIONS OF SEDIMENT IN THE YELLOW RIVER

1. INTRODUCTIONThe Yellow River is a heavily sediment--laden river. Floods at Hyperconcentrationso f sediment (hereinafter simply referred to as hyperconcentrated flood) frequently occurring in the main river and its tributaries possess different characteristics of sedimenttransport. Sometimes they cause severe deposition whereas at other times they are capable of carrying substantial amount of sediment over long distances. The study on the lawof sediment transport is of significance to …