硅微陀螺带通ΣΔ闭环检测环路设计

本文研究了SDM调制器在陀螺闭环检测中的应用,主要针对其闭环检测的结构设计和参数获取作了相应的研究和阐述。硅微机械陀螺敏感模态为二阶模态,基于SDM调制器的设计原理,结合DSToolbox来设计整个闭环检测电路,得到闭环检测电路的结构和参数。最终仿真得到的闭环检测系统的信噪比达到了106 dB。在量程为±200°/s,带宽为200 Hz时,分辨率可以达到0.001°/s。     

广东省珠江三角洲地区中小河流水生态现状及修复对策初探

珠三角中小河流水环境污染问题日益突出,水生态环境受到极大影响。结合珠三角地区河道水生态环境现状,对水生态修复对策进行了初探,包括加强源头控制、完善城镇污水收集及处理、面源污染治理、开展重点区域水生态系统修复、建设滨水区及加强系统管理等措施。最后简要介绍了茅洲河界河综合治理工程案例,该工程充分考虑了两岸排涝、堤防、道路交通、截污治污和岸线美化等内容,工程设计遵循自然、人水和谐的理念,可为中小河流水生态修复提供参考。     

废黄河口水流挟沙力公式探讨

利用废黄河口夏季和冬季实测水文泥沙资料,对多个典型的悬移质挟沙力公式进行应用计算,在此基础上,采用相关系数法、标准化最小距离法、集中系数法、偏离系数法4种检验方法对计算结果进行比较分析。结果表明:河口水流挟沙力公式能够较好地反映废黄河口水域的水流挟沙情况,并且具有较高的精度;对于各种检验方法,因为侧重点不同,所得到的检验结果会产生矛盾,所以建议采取多种检验方法对挟沙力公式进行综合评价。     

黄河三角洲湿地补水生态效益评价

借助景观模型强大的空间模拟功能和情景分析功能,运用生态经济学核算方法,以水和生态之间的关系为基础,对不同补水预案下的黄河三角洲湿地生态价值进行了评价。结果表明:实施生态补水后,湿地生态功能得到了有效恢复,湿地价值明显提高,湿地补水生态效益显著,若每年向湿地实施人工生态补水2.78亿~4.17亿m3,则黄河三角洲湿地每年能提供生态价值140亿~160亿元,湿地功能和价值基本恢复到1992年自然保护区建立时的水平;补水量与湿地价值并不具有良好的线性关系,当水量增加到一定程度时,补水生态效益增幅减小,表明黄河三角洲湿地需水存在一个适宜范围,并非水量越大越好。     

On the reproducibility of field-measured reflectance factors in the context of vegetation studies

This paper describes a study aimed at quantifying uncertainty in field measurements of vegetation canopy hemispherical conical reflectance factors (HCRF). The use of field spectroradiometers is common for this purpose, but the reliability of such measurements is still in question. In this paper we demonstrate the impact of various measurement uncertainties on vegetation canopy HCRF, using a combined laboratory and field experiment employing three spectroradiometers of the same broad specification (GER 1500). The results show that all three instruments performed similarly in the laboratory when a stable radiance source was measured (NEΔL < 1 mW m⁻² sr⁻¹ nm⁻¹ in the range of 400-1000 nm). In contrast, field-derived standard uncertainties (u = SD of 10 consecutive measurements of the same surface measured in ideal atmospheric conditions) significantly differed from the lab-based uncertainty characterisation for two targets: a control (75% Spectralon panel) and a cropped grassland surface. Results indicated that field measurements made by a single instrument of the vegetation surface were reproducible to within ± 0.015 HCRF and of the control surface to within ± 0.006 HCRF (400-1000 nm (± 1σ)). Field measurements made by all instruments of the vegetation surface were reproducible to within ± 0.019 HCRF and of the control surface to within ± 0.008 HCRF (400-1000 nm (± 1σ)). Statistical analysis revealed that even though the field conditions were carefully controlled and the absolute values of u were small, different instruments yielded significantly different reflectance values for the same target. The results also show that laboratory-derived uncertainty quantities do not present a useful means of quantifying all uncertainties in the field. The paper demonstrates a simple method for u characterisation, using internationally accepted terms, in field scenarios. This provides an experiment-specific measure of u that helps to put measurements in context and forms the basis for comparison with other studies.     

GSPress:一个GML流压缩器

GML已成为地理数据存储和交换的标准.在实际应用中,GML数据通常以数据流的形式在网络上传输.由于GML文档含有大量重复标签和高精度浮点数,使得GML文档通常比较大.因此如何有效地压缩GML数据流来减少网络传输的代价就显得越来越重要.本文提出一种GML数据流压缩算法,它只需扫描GML文档一次,将GML文档的结构和数据分离后分别进行压缩.对GML文档中的结构部分采用自适应方法进行压缩;对坐标数据则利用增量压缩的方法压缩.实验结果表明GSPress是一种高效的GML流压缩算法.     

Fabrication of bulk superconductors YBa2Cu3?xTexO7?δ with highly oriented layer structure using the melt-texture growth process

We report on the successful fabrication of bulk samples satisfying the nominal composition YBa₂Cu_3–x Te _x O_7– and containing highly single-crystal-like texture. While this type of crystal growing process is not new, our process requires only the existence of spatial temperature gradient in some parts of the common tube furnace. The samples with tellurium were found to be much more stable and better superconductors than the Y-123 specimen. Large layer textures with cross-section 50×500m² were observed to grow inside the usual bulk sample. The critical currents were measured by the d.c. magnetization method and found to be easily greater than 6000 A cm^–2 for the samples with Te.     

Environmental contamination of amorphous Bi-Sr-Ca-Cu-O fibers

A study of the environmental contamination of amorphous YBa₂Cu₃O₇- fibers has been undertaken in order to determine the best method to handle these materials during the fabrication of superconducting wire. The fibers often need to be handled in organic solvents as part of the cleaning and manipulating process. In organics that are free of water, the fibers retain their mechanical strength with little carbon contamination or other ill effects. Water, however, causes premature crystallization and destroys the mechanical strength of the fibers.     

赵凹油田安棚区中高渗油藏核三段Ⅰ油组沉积微相研究

以岩心相分析为基础,结合测井相分析,建立赵凹油田安棚区核三段I油组内各单层沉积微相的识别标志。研究沉积微相类型,查明研究区主要发育类型以及各单层沉积微相的空间展布与演化特征,总结出赵凹油田安棚区核三段I油组沉积模式。     

浅水三角洲沉积特征及布井方法——以铁边城地区延8储层为例

以铁边城地区侏罗系延安组延8储层为例,分析浅水三角洲的沉积特征。指出该类三角洲的骨架部分由分流河道砂体构成,是铁边城地区侏罗系延安组延8油藏主要储集层。该类砂体储层平面厚度变化大,垂向上相互叠加,开发时对布井要求较高。铁边城地区采用不规则正方形反九点布井方法,在储层变薄变差的砂体边部,适当缩小井距,可规避落空井的风险。