精密水准测量成果的折光改正

精密水准测量是研究地壳垂直运动及其它一些地球物理现象的一个重要手段,而大气折光则为精密水准测量成果中一项主要的系统误差,数值远比一般预期的为大。影响对资料的分析,有必要找到适当的计算方法将它消去。本文在比较几种不同方案之后,推荐一种以安格斯·李潘公式为基础的改进方案,可以用来处理历史上的水准测量成果及未来的水准成果,其适用范围有待于进一步外业试验加以鉴定。     

带COGO的实时GPS测量及其功能扩展

实时ＧＰＳ测量作用ＧＰＳ测量的一种新技术,它拥有许多传统ＧＰＳ所不具备的优势,已经得到越来越多用户的认可。带ＣＯＧＯ功能的实时ＧＰＳ测量尽管问世半年有余,但此项功能仍然鲜为人知。作者研究结果表明此项技术值得广泛推广应用,同时指出其潜力其大,在待深入开发。文中给出的种种案例和操作步骤可供实进作业用户参考。     

Trophic structure and functioning in a eutrophic and poorly flushed lagoon in southwestern Taiwan

Tapong Bay, a eutrophic and poorly flushed tropical lagoon, supports intensive oyster culture. Using the Ecopath approach and network analysis, a mass-balanced trophic model was constructed to analyze the structure and matter flows within the food web. The lagoon model is comprised of 18 compartments with the highest trophic level of 3.2 for piscivorous fish. The high pedigree index (0.82) reveals the model to be of high quality. The most-prominent living compartment in terms of matter flow and biomass in the lagoon is cultured oysters and bivalves, respectively. The mixed trophic impacts indicate that phytoplankton and periphyton are the most-influential living compartments in the lagoon. Comparative analyses with the eutrophic and well-flushed Chiku Lagoon and non-eutrophic tropical lagoons show that high nutrient loadings might stimulate the growth and accumulation of phytoplankton and periphyton and therefore support high fishery yields. However, net primary production, total biomass, fishery yields per unit area, and mean transfer efficiency of Tapong Bay were remarkably lower than those of Chiku Lagoon. The lower transfer efficiency likely results from the low mortality of cultured oysters and invasive bivalves from predation or the lower density of benthic feeders constrained by the hypoxic bottom water as a result of poor flushing. This might therefore result in a great proportion of flows to detritus. However, the hypoxic bottom water might further reduce the recycling of the entering detritus back into the food web. In contrast to many estuaries and tropical lagoons, poor flushing of this eutrophic tropical lagoon might induce a shift from detritivory to herbivory in the food web.     

Sonophotocatalysis of endocrine-disrupting chemicals

Sonolysis and photolysis often exhibit synergistic effects in the degradation of organic molecules. An assay of fish oocyte maturation provides an appropriate experimental system to investigate the hormonal activities of chemical agents. Oocyte maturation in fish is triggered by maturation-inducing hormone (MIH), which acts on receptors on the oocyte surface. A synthetic estrogen, diethylstilbestrol (DES), possesses inducing activity of fish oocyte maturation, and a widely used biocide, pentachlorophenol (PCP), exhibits a potent inhibitory effect on fish oocyte maturation. In this study, the effects of the combined treatment by sonolysis with photolysis (sonophotocatalysis) to diminish the hormonal activity of DES and the maturation preventing activity of PCP was examined. By sonophotocatalysis, hormonal activity of DES was completely lost within 30min and the inhibiting activity of PCP was lost within 120min. These results demonstrated that sonophotocatalysis is effective for diminishing the endocrine-disrupting activity of chemical agents.     

The Discovery of a Second Field Methane Brown Dwarf from Sloan Digital Sky Survey Commissioning Data

We report the discovery of a second field methane brown dwarf from the commissioning data of the Sloan Digital Sky Survey (SDSS). The object, SDSS J134646.45-003150.4 (hereafter SDSS 1346-00), was selected because of its very red color and stellar appearance. Its spectrum between 0.8 and 2.5 μm is dominated by strong absorption bands of H2O and CH4 and closely mimics those of Gliese 229B and SDSS 162414.37+002915.6 (hereafter SDSS 1624+00), two other known methane brown dwarfs. SDSS 1346-00 is approximately 1.5 mag fainter than Gliese 229B, suggesting that it lies about 11 pc from the Sun. The ratio of flux at 2.1 μm to that at 1.27 μm is larger for SDSS 1346-00 than for Gliese 229B and SDSS 1624+00, which suggests that SDSS 1346-00 has a slightly higher effective temperature than the others. Based on a search area of 130 deg2 and a detection limit of z*=19.8, we estimate a space density of 0.05 pc-3 for methane brown dwarfs with Teff approximately 1000 K in the 40 pc3 volume of our search. This estimate is based on small-sample statistics and should be treated with appropriate caution.     

Macrobenthos habitat mapping in a tidal flat using remotely sensed data and a GIS-based probabilistic model

This paper proposes and tests a method of producing macrofauna habitat potential maps based on a weights-of-evidence model (a probabilistic approach) for the Hwangdo tidal flat, Korea. Samples of macrobenthos were collected during field work, and we considered five mollusca species for habitat mapping. A weights-of-evidence model was used to calculate the relative weights of 10 control factors that affect the macrobenthos habitat. The control factors were compiled as a spatial database from remotely sensed data combined with GIS analysis. The relative weight of each factor was integrated as a species potential index (SPI), which produced habitat potential maps. The maps were compared with the surveyed habitat locations, revealing a strong correlation between the potential maps and species locations. The combination of a GIS-based weights-of-evidence model and remote sensing techniques is an effective method in determining areas of macrobenthos habitat potential in a tidal flat setting.     

大别山太湖—马庙断裂带两侧变质地体的增温变质作用

大别山榴辉岩地体以太湖 马庙断裂带为南界。该断裂带近东西走向, 向南倾斜。通过对石榴石中 Ｍｇ 含量由核部向边缘增高的生长环带构造的分析和详细的 Ｐ Ｔ 轨迹的计算表明, 断裂带北侧的榴辉岩和南侧的角闪岩及角闪片麻岩均经历了降压增温变质过程。热榴辉岩由地幔深处的折返和地温梯度的升高为可能的热源。     

GPS接收机天线装置定向标志线及平均相位中心参数的检测

本文讨论了GPS测量的重要误差来源之一——接收机天线相位中心漂移误差,研究了表征平均相位中心的基本参数及其检测和处理方法。如果用户设备进行了这种检测,并对观测成果作了相应的修正,目前大部分商品接收机在几十公里以内的短过测量中,精度可以提高到3 mm+2 ppm·d(d为边长,单位:km),同时解决了混合机组参加GPS网观测和处理的难题。     

GPS动力法定位的模型与估计问题

研究GPS在动力学环境下的网定位,对我国来说具有很大的吸引力。在GPS定位实践中,动力法及半动力法的轨道改进定位方式都具有广泛的应用,但前者概括了卫星定位中最一般的动力学问题。因此,本文归纳和建立了相应的动力法定位模型,包括轨道状态方程、地面测站的状态方程及观测方程。简要介绍了更能反映卫星定位问题统计和力学本质的最优滤波和最优控制的估计方法。最后给出了事后轨道估计的最佳平滑方程。     

切比雪夫多项式逼近在大地测量计算中的应用

本文根据切比雪夫多项式的定义和基本性质,导出求多项式函数最佳逼近的代数式,并运用这一结果解决了一些大地测量常用计算公式的最佳逼近问题。在同一电子计算机上利用这些数值逼近公式,其计算速度,以子午线孤长正反算为例可比相应的同精度的经典方法提高五倍至数十倍。