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伪距单点定位的精度分析及改进

GPS伪距单点定位速度快、不存在整周模糊度,因此具有很大的应用价值。分析了电离层延迟、对流层延迟、相对论效应、地球自转改正对伪距单点定位结果的影响,介绍了两种多历元求解时处理接收机钟差的方法,最后讨论了如何以大地坐标和高斯坐标为参数进行定位求解。     

港珠澳大桥隧道沉管安装定位及姿态监测技术

重点介绍了针对港珠澳大桥海底沉管对接过程中水下精密定位及姿态监测技术方法,采用了水上RTK定位与水下姿态监测技术相结合,并实时监测测量塔挠度,通过三维坐标转换实现了高精度的对接定位及姿态监测,开发可视化仿真模拟软件,指导沉管水下对接。简要介绍了安装定位过程的实施步骤、关键工序和定位精度分析。     

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潜水泵变频稳流抽水观测技术系统

潜水泵变频稳流抽水观测技术系统适用于不同观测条件,可以保证原有水文地球化学各测项的数字化和模拟观测,还可实施数字化水位与水温的同井观测,可以记录清晰的潮汐效应和同震效应,不低干天然自流状态下观测资料质量水平,是值得推广的新技术.     

经济欠发达地区农户对耕地非农转换的价值感知——西宁市郊区案例研究

针对耕地非农转化过程中产生的一系列社会问题,采用参与性农户调查方法,对西部欠发达地区西宁市郊区5个样本村190户农户进行了随机入户调查。根据城市开发进程、到市区距离和种植类型等条件,将调查样本村分为近郊城区化农村、近郊农村和远郊农村,就农户对耕地非农转换的基本认知及耕地非农转换的经济、社会和环境价值感知进行分析。结果表明:耕地征用后农户能理性感知和判别耕地非农转换价值,并普遍认为失去耕地后生活费用增加、生活保障降低、收入来源和就业机会少;感知主要受耕地数量、区位条件、耕地开发阶段等因素的影响;处于不同区位条件的农户对耕地非农转换的价值感知存在差异性,城区化农户已逐渐适应城市生活,近郊农户的非农转换经济和社会感知压力最大,远郊农民也感知经济和生活保障压力,但更希望能通过打工增加收入。     

Farmers＇ Perception to Farmland Conversion： A Questionnaire Survey in Xining City, Qinghai Province, China

China is experiencing a fast process of farmland conversion which is conducted mainly by local governments to fuel eco- nomic development. Social tension is aroused and policy makers take great concerns on coordinating interests among different stake- holders, especially for increasing farmers＇ interest. The purpose of this study is to get some insights related to land acquisition institution by exploring farmers＇ perception to farmland conversion. Participatory Rural Appraisal （PRA） was applied for the investigation in peri-urban area, of Xining City, Qinghai Province, China. The total of 519 householders from 15 villages completed valid questionnaire survey from July to November, 2012. The results indicate that farmland conversion has several impacts on farmers＇ life. Most farmers are gradually adapting to city life. Higher living expenses and more income are perceived by farmers with average score of 4.21 and 2.69, respectively. The average scores of 2.38 and 2.46 are for improvement of life security and more job opportunities. Farmers expect to get some stable ways of compensation in addition to lump-sum compensation in cash. Stable subsidies every year and obtaining same number of land received strong proposal. And these two options are cited by 49.6% and 43.9% of respondents. Farmland conversion brings about cleaner living condition and more amenities, but lower air visibility and drier air. Results reflect landless farmers＇ economic and life pressures and various demands. Local government should pay more attention to increase farmers＇ income and improve rural security system.     

软土三轴剪切蠕变试验研究及模型分析

将数字图像测量技术运用于三轴剪切蠕变试验,试验结果表明,土粒间水膜厚度对土的蠕变有很大的影响,不排水时,试样土颗粒间水膜保持不变,土的黏滞系数基本为一定值,土的流变变形较大;排水时,随着水的排出土体发生固结硬化,土颗粒间水膜变薄,土的密度增大,黏滞性增强,流变变形较小。在排水条件下,加载瞬间孔隙水压力会持续上升产生Manadei-Cryer效应,整个过程历时约10 min。随着偏应力水平的增加,试样发生鼓胀变形,进而形成剪切面发生剪切破坏;受排水路径的影响,剪切面通常位于试样偏下部位。对比数字图像测量方法和试样排水体积换算法在获得剪切应变时的试验结果,表明试验过程中试样变形的不均匀会导致排水体积换算法在计算剪切应变时产生较大误差;Singh-Mitchell模型很好地描述土的剪切流变特性,确定参数时两种方法得到的参数相差不大,偏应力水平较低时可采用排水量换算法进行确定。     

Hydrogen collisions in planetary atmospheres, ionospheres, and magnetospheres

Hydrogen is the most abundant element in the universe. Molecular hydrogen is the dominant chemical species in the atmospheres of the giant planets. Because of their low masses, neutral and ionized hydrogen atoms are the dominant species in the high atmospheres of many planets. Finally, protons are the principal heavy component of the solar wind.Here we present a critical evaluation of the current state of understanding of the chemical reaction rates and collision cross sections for several important hydrogen collision processes in planetary atmospheres, ionospheres, and magnetospheres. Accurate ab initio quantum theory will play an important role. The collision processes are grouped as follows:

(a)

H⁺+H charge transfer,

(b)

H⁺+H₂(v) charge transfer and vibrational relaxation, and

(c)

H₂(v,J)+H₂ vibrational, rotational, and ortho-para relaxation.

In each case we provide explicit representations as tabulations or compact formulas. Particularly important conclusions are that H⁺+H₂(v) collisions are more likely to result in vibrational relaxation than charge transfer and H₂ ortho-para conversion is at least an order-of-magnitude faster than previously assumed.