参数先验信息异常的影响与平差补偿     

曾安敏  张丽萍  崔吉春 《测绘科学》2008,33(2):35-37

若参数先验信息含有异常信息,必然造成序贯平差参数估值及其协方差的扭曲。本文首先分析了先验信息异常对参数结果的影响,然后通过对先验信息异常进行判断,再有针对性地引入部分附加参数,通过函数模型补偿法控制先验信息异常误差的影响。实测GPS算例表明,通过该方法能有效地抵制参数先验信息异常的影响。  相似文献   

Land expropriation in urbanizing China: an examination of negotiations and compensation     

Hui Wang  Xiao Chen  Sarah Swider 《Urban geography》2017,38(3):401-419

A driving force of urban development is “accumulation by dispossession” which occurs through expropriation, privatization, and commodification of land. While the macro theory is now well refined, there is still much we do not know about how the underlying processes occur and how they shape economic development and urbanization. In this study, we analyze 2009 survey data of land expropriation cases across 12 Chinese cities, and find that expropriation takes different forms leading to specific outcomes. In half the cases, local governments followed central government policies requiring them to pay standard rates of compensation, but in the other half, local governments negotiated with farmers over the terms of expropriation. In the latter scenario, farmers were more likely to receive compensation higher than the standard rate, particularly if they were embedded in local power structures, which we argue could be counteracted if all households in a rural collective negotiate one agreement rather than individual agreements. These findings move us closer to understanding why accumulation through dispossession sometimes contributes to economic growth and social development, and at other times undermines urban development leading to social instability.  相似文献   

华北地下水超采区冬小麦退耕的生态补偿问题探讨   总被引：10，自引：0，他引：10  

王学  李秀彬  辛良杰  谈明洪  李升发  王仁靖 《地理学报》2016,71(5):829-839

压减冬小麦种植面积是有效减少华北平原地下水用量最为有效的方法。近期,国家和地方政府均出台了土地休耕政策,拟在华北地下水超采区退耕冬小麦,实现“一季休耕、一季雨养”。然而,华北平原已经出现农户主动退耕冬小麦的现象。在此背景下,明确冬小麦退耕的瞄准目标、制订合理适度的补偿标准是土地休耕政策有效实施所面对的核心问题。本文利用农户问卷数据,构建多层次logit模型分析农户种植制度决策的影响因素,并计算冬小麦退耕的机会成本,旨在确定华北平原地下水超采区土地休耕政策的瞄准目标,并为农户补偿标准的制订提供建议。结果表明：① 地块层次的土地质量和灌溉条件是解释农户种植制度差异的关键因素,近70%的四等耕地和90%以上的旱地已退出冬小麦耕作,土地休耕政策应瞄准一、二、三等土地质量的水浇地;② 相似耕作条件的地块种植春、夏玉米的净收益大致相同,土地休耕的机会成本等于种植冬小麦的净收益;③ 仅考虑冬小麦对地下水资源的影响,土地休耕政策初期以地下水回升和地下水环境恢复为主要目标时,建议以350元/亩作为补偿标准参考值,后期目标转为维持地下水资源采补平衡时,可调整至280元/亩左右。  相似文献   

三电平逆变器驱动的IPMSM模型预测电流控制系统研究     

贾红云  李明阳 《南京气象学院学报》2021,13(3):363-368

三电平逆变器拓扑结构简单、所用器件较少且每个功率管所承受的电压应力小,适用于高电压、大容量的场合.相比于传统两电平逆变器,三电平逆变器输出电平的数量从2变成3,输出的电压电流谐波含量低,波形正弦度更好.本文提出内置式永磁同步电机模型预测电流控制算法,以提高控制系统电流动态响应速度,并针对该算法在控制系统中产生的时间延迟,引入二阶延迟补偿策略.对以上内容建立系统仿真模型,仿真结果表明：三电平逆变器相比两电平逆变器输出电流波形谐波含量更小、电机的动态及稳态性能更好.  相似文献   

火成岩覆盖区地震有效成像技术探讨及其在辽西金羊盆地油气调查中的应用          下载免费PDF全文

孙月成  李永飞  孙守亮  张涛  张伟  张宏 《中国地质》2021,48(5):1469-1484

辽西金羊盆地是下辽河盆地外围盆地群中面积最大的中生代盆地,盆地浅层火成岩广泛发育、其厚度大、期次较多,受火成岩对地震信号屏蔽以及该地区复杂的地震地质条件的影响,使得地震勘探采集的原始资料信噪比低、火成岩下伏地层反射能量弱,给地震资料的有效成像带来了极大挑战。本文根据原始地震资料特点,采用针对性的采集、处理技术,首先从采集方面以大能量激发、低频检波器接收,并且处理中应用反射能量补偿、静校正、叠前多域去噪等几项技术进一步提高资料的深层反射能量和信噪比,最后通过高精度速度场建模与地震偏移成像技术的多种方法对比,优选叠前时间偏移技术进行最终成像。与以往地震资料比较,采用这套有效成像技术重新处理的地震剖面信噪比、分辨率明显提高,更重要的深层反射能量得以有效恢复,火成岩的下伏地层反射信号清晰、地层接触关系明确,特别是大倾角地层及断层的成像得以明显改善,为后续的构造解释和勘探潜力区评价提供了高质量的地震资料。  相似文献   

深海近底三分量磁力仪设计   总被引：2，自引：0，他引：2  

章雪挺  唐勇  刘敬彪  黄孔耀 《热带海洋学报》2009,28(4):49-53

提出了一种新的深海海底三分量磁力仪设计思路，用于高灵敏度地磁测量调查海底矿体分布，其磁力测量探头基于各向异性磁阻传感器。详细分析了磁阻传感器的误差模型，提出用Broyden算法实现误差校正，并给出了在个人电脑上的实现结果。描述了水下系统中传感测量电路以及通信、存储功能的基本设计思路。最后给出目前的实验与测试数据，并提出了后续工作思路。  相似文献   

储层地震物理模拟的震源指向性及介质非均质性影响分析   总被引：1，自引：0，他引：1       下载免费PDF全文

司文朋  杨勤勇  邢廷栋  薛诗桂 《地球物理学报》2021,64(2):628-636

随着地震物理模拟的研究目标由地质构造发展为不同类型的油气储层,明确震源指向性及介质非均质性对实验结果的影响,对提高物理模拟数据的可信性及准确性具有重要意义.利用激光测振新方法对震源指向性进行了实验测试,得到了更加精确的指向性结果,形成了模拟数据振幅补偿方法.制作了具有不同尺度特征的非均质样品,在50 kHz至1000 kHz超声频段下对纵波速度及能量进行了测试,明确了不同的波长/介质尺度比(λ/a)范围内纵波速度及干扰波与有效波能量比的变化特征.结果表明,在地震物理模拟超声频段下射线速度向散射速度的转折点出现在λ/a≈2处;散射速度向等效介质速度的转折点出现在λ/a≈100处.当满足λ/a>200条件时,干扰波与有效波能量比小于5%时,可认为满足储层模拟的等效介质条件.  相似文献   

Growth and Physiological Response of Organs of Phragmites australis to Different Water Compensation in Degraded Wetlands     

LIXiaoyu  LIUXingtu  LIXiujun  LINJixiang  WENBolong 《湿地科学》2012,10(1):23-31

To study the effect of different water compensation on growth and physiology of reed in degraded wetlands,three water treatments in the field were conducted to test the height and photosynthesis of reed,the ions and soluble sugar contents of different organs.In the controls(without extra water compensation for 10 years),the height of reed was only 50 cm,the net photosynthetic rate,stomatal conductance,the intercellular CO2 concentration and transpiration rate were very low.The contents of Na + and Clin rhizome were higher than those in other organs.Discontinuous water compensation(continuous for 8 years,then stopped for 2 years)increased the height(2.1-fold),the net photosynthetic rate(41.8%),stomatal conductance(1.8-fold),transpiration rate(1.3-fold)of reed(Phragmites australis),and decreased the content of Na + (62.3%)and Cl- (71.1%)of rhizome significantly.Continuous water compensation(continuous for 10 years)increased the height(3.2-fold),the net photosynthetic rate(104%),stomatal conductance(2.4-fold),transpiration rate(1.5-fold)of reed,and decreased Na + (82.5%)and Cl - (64.7%)contents in rhizome, then accumulated the K+ ,H2PO4-,SO42- and soluble sugar contents significantly in rhizome.Interrupting water compensation led to the decrease of height(25.3%),the net photosynthetic rate(30.7%),stomatal conductance(17.3%) and increase of Na + (1.16-fold)in rhizome when comparing to the continuous water compensation.These results showed that recovering the degraded reed wetlands needed continuous water compensation yearly to promote reed growth.The organs of reed had corresponding physiological response characteristic to the different water compensation condition.Under long-time dry and waterlogging condition,the rhizomes both helped reed to adapt located environment,by enriching the ions such as Na+ ,Cl- ,and K+ ,H2PO4-,SO42- ,respectively.  相似文献   

一种时频信号相位补偿方法     

钟巍  龚大亮  龚航 《时间频率学报》2011,34(1)

为消除信号产生器内温度变化对信号相位的影响,提出了一种恒温控制和实时相位调整相结合的方法。在这种方法中,除恒温控制外,基于对信号产生器内部温度、相位测量值变化率、设备调相分辨率和相位波动指标等的分析研究,合理计算实时相位调整关键参数,进行实时相位调整,有效地减小信号产生器内部温度变化引起的相位波动,提高了输出端信号相位的一致性和稳定性。  相似文献   

生态补偿机制中的企业责任研究     

张平  胡明杰  张雪华  赵金锋 《河南气象》2009,(3):51-54

研究了企业在市场经济体制中的主体地位和企业承担的环境责任,通过对生态补偿的涵义和政策范围进行分析,明确了生态补偿与排污费、资源费之间的区别和联系,提出了完善企业履行生态补偿责任的政策框架、搭建企业履行生态补偿责任的职能体系及创新企业履行生态补偿责任执行形式的建议。  相似文献