Using WGM2012 to Compute Gravity Anomaly Corrections of Leveling Observations in China

Gravity Anomaly Correction(GAC)is a very important term in leveling data processing.In most cases,it is troublesome for field surveyors to measure gravity when leveling.In this paper,based on the complete Bouguer Gravity Anomaly(BGA)map of WGM2012,the feasibility of replacing in-situ gravity surveying in China is investigated.For leveling application,that is to evaluate the accuracy of WGM2012 in China.Because WGM2012 is organized with a standard rectangle grid,two interpolation methods,bilinear interpolating and Inverse Distance Weighted(IDW)interpolating,are proposed.Four sample areas in China,i.e.,Hanzhong,Chengdu,Linzhi and Shantou,are selected to evaluate the systems bias and precision of WGM2012.Numerical results show the average system bias of WGM2012 BGA in west China is about-100.1 mGal(1 mGal=10^(-5) m/s^(2))and the standard deviation is about 30.7 mGal.Tests in Shantou indicate the system bias in plain areas is about-130.4 mGal and standard deviation is about 6.8 mGal.All these experiments means the accuracy of WGM2012 is limited in high mountain areas of western China,but in plain areas,such as Shantou,WGM2012 BGA map is quite good for most leveling applications after calibrating the system bias.

Methodology for local correction of the heights of global geoid models to improve the accuracy of GNSS leveling

At present,one of the methods used to determine the height of points on the Earth’s surface is Global Navigation Satellite System(GNSS)leveling.It is possible to determine the orthometric or normal height by this method only if there is a geoid or quasi-geoid height model available.This paper proposes the methodology for local correction of the heights of high-order global geoid models such as EGM08,EIGEN-6C4,GECO,and XGM2019e_2159.This methodology was tested in different areas of the research field,covering various relief forms.The dependence of the change in corrected height accuracy on the input data was analyzed,and the correction was also conducted for model heights in three tidal systems:"tide free","mean tide",and"zero tide".The results show that the heights of EIGEN-6C4 model can be corrected with an accuracy of up to 1 cm for flat and foothill terrains with the dimensionality of 1°×1°,2°×2°,and 3°×3°.The EGM08 model presents an almost identical result.The EIGEN-6C4 model is best suited for mountainous relief and provides an accuracy of 1.5 cm on the 1°×1°area.The height correction accuracy of GECO and XGM2019e_2159 models is slightly poor,which has fuzziness in terms of numerical fluctuation.

On the Accuracy Assessment of the Latest Releases of GOCE Satellite-Based Geopotential Models with EGM2008 and Terrestrial GPS/Levelling and Gravity Data over Egypt

The Global Geopotential Models (GGMs) of GOCE (Gravity Recovery and steady- state Ocean Circulation Explorer) differ globally as well as regionally in their accuracy and resolution based on the maximum degree and order (d/o) of the fully normalized spherical harmonic (SH) coefficients, which express each GGM. The main idea of this study is to compare the free-air gravity anomalies and quasi geoid heights determined from several recent GOCE-based GGMs with the corresponding ones from the Earth Gravitational Model 2008 (EGM2008) over Egypt on the one hand and with ground-based measurements on the other hand. The results regarding to the comparison of GOCE-based GGMs with terrestrial gravity and GPS/levelling data provide better improvement with respect to EGM2008. The 4th release GOCE-based GGM developed with the use of space-wise solution strategy (SPW_R4) approximates the gravity field well over the Egyptian region. The SPW_R4 model is accordingly suggested as a reference model for recovering the long wavelength (up to SH d/o 200) components of quasi geoid heights when modelling the gravimetric quasi-geoid over the Egypt. Finally, three types of transformation models: Four-, Five- and Seven-parameter transformations have been applied to reduce the data biases and to provide a better fitting of quasi geoid heights obtained from the studied GOCE-based GGMs to those from GPS/levelling data. These models reveal that the standard deviation of vertical datum over Egypt is at the level of about 32 cm.

Joint solution of leveling and gravity data in crustal deformation monitoring

Repeated leveling surveys can provide important geometric information of elevation change of points, due to the effect of the earth gravity field, the observed data of leveling also contains the information of gravity field. Repeated absolute gravity surveys or relative gravity surveys can provide rich information of gravity field, but since the gravity values at the points will change along with the variation of elevation, it also contains the information of elevation variation of points. In the classical adjustment method, the two kinds of observations will be solved respectively and the complementary information will be corrected as interference or processed as noises, as a result, not only the useful information will be lost, but also the accuracy of results will be effected. In the paper, the joint solution model for both observed data has been established in an integral geodetic frame, the calculation methods have been given, the fitting and forecasting of deformation field have been studied, the verification has been made by examples and certain of useful results have been obtained. The research indicates that the joint solution can give simultaneously the elevation of surface points and its rate of change, the parameters of local gravity field and its rate of change, which is advantageous to information extraction; The accuracy of joint solution is better than that of individual solution; The rank deficient robust solution and quasi stable robust solution are better than the corresponding non robust solution; The automatic selection of quasi stable points by using the method of quasi stable robust solution can effectively resist the interference of outliers and deformation anomaly to the initial datum; for the data with many resurveys, if the dynamic quasi stable robust estimation is made, not only the reliable quasi stable points can be found dynamically, but also the dynamic variation parameters will not or be less affected by the interference of observational outliers of each period, so the posterior accuracy of dynamic parameters can be improved obviously; when the points are abundant, establishing a deformation model to interpolate the deformation at the non surveyed points and estimating the crustal deformation of a certain time are also feasible.

Topology Optimization for Steady-State Navier-Stokes Flow Based on Parameterized Level Set Based Method

In this paper,we consider solving the topology optimization for steady-state incompressibleNavier-Stokes problems via a new topology optimization method called parameterized level set method,which can maintain a relatively smooth level set function with a local optimality condition.The objective of topology optimization is to􀀀nd an optimal con􀀀guration of theuid and solid materials that minimizes power dissipation under a prescribeduid volume fraction constraint.An arti􀀀cial friction force is added to the Navier-Stokes equations to apply the no-slip boundary condition.Although a great deal of work has been carried out for topology optimization ofuidow in recent years,there are few researches on the topology optimization ofuidow with physical body forces.To simulate theuidow in reality,the constant body force(e.g.,gravity)is considered in this paper.Several 2D numerical examples are presented to discuss the relationships between the proposed method with Reynolds number and initial design,and demonstrate the feasibility and superiority of the proposed method in dealing with unstructuredmesh problems.Three 3D numerical examples demonstrate the proposedmethod is feasible in three-dimensional.

Regional Evaluation of GOCE-Based GGMs with Ground-Based Gravity and GPS/Levelling Data over Egypt

The gravity field and steady-state ocean circulation explorer (GOCE) satellite mission has provided numerous Global Geopotential Models (GGMs) with different processing methodologies and model accuracies. In the current contribution, the latest releases of GOCE-based GGMs are evaluated on the regional scale using the available terrestrial GPS/Levelling and gravity data collected over Egypt. To overcome the spectral inconsistency between the GOCE-based GGMs and the ground-based data, the spectral enhancement method (SEM) is applied. Five of GOCE-based GGMs have been used, namely GOSG01S, IGGT_R1, IfE_GOCE05s_ GO_CONS_GCF_2_SPW_R5 (SPW_R5 in the following) and NULP-02. The evaluation process of GOCE-based GGMs with the available ground data over Egypt considering the SEM method shows remarkable improvements obtained from the SPW_R5 model. The model provides lower differences of the standard deviations with respect to the EGM2008 and the other applied geopotential gravity models as well as the applied ground-based gravity and GPS/Levelling data. The findings regarding the ground-based data show obvious reductions of about 15.16% and 32.22% achieved by the GOCE-based model in term of standard deviations differences of gravity anomalies and geoid heights, respectively. Therefore, the SPW_R5 model is recommended to be applied as a reference model for compensating the long-to-short wavelength (up to spherical harmonics degree/order 280) components when modelling the gravimetric geoid over Egypt.

调节阀多测点空化诱导振动敏感性分析

针对调节阀阀体不同测点处对流道内空化敏感性存在差异问题,开展了不同测点处空化诱导振动的差异性研究和空化发展状态敏感程度分析。搭建了调节阀空化振动加速度信号采集试验平台,同步采集了多测点处调节阀空化诱导振动的加速度信号。提出了加速度级比率和重心频率两个表征参数,并利用1/3倍频程谱对调节阀空化振动信号频谱进行划分,最终得到对空化发展最敏感的频带和测点位置。结果表明:调节阀阀体同一表面测点振动信号呈现相似性,不同表面测点信号差异性较大,即调节阀振动信号表现为各向异性;空化状态的发展主要引起中心频率10000 Hz以上的频带振动强度增大,适合作为监测调节阀空化状态的特征频带。

蓟县地震台gPhone、DZW和GS-15重力仪重力噪声水平对比

选取蓟县地震台同址观测的3台不同型号重力仪(gPhone、DZW和GS-15)2022年全年的连续观测数据,研究不同类型仪器对环境噪声的响应,计算3种重力仪的重力噪声水平,同时计算地震频段(200~600 s)的地震噪声等级,并与全国gPhone重力仪的地震噪声等级进行对比。结果表明:1)在频率低于10-3 Hz时,扣除固体潮和气压改正可以明显改进重力噪声水平;2)相同台站不同仪器重力噪声水平不同,gPhone型重力仪的背景噪声水平低于DZW型重力仪和GS-15型重力仪,其SNM值为3.355;3)2022年全国gPhone重力仪的地震频段噪声水平均值为5.418,蓟县台的噪声水平平均值为3.465,低于全国的噪声水平。研究结果可为3类重力仪观测数据的研究应用提供参考。

一次强下坡风爆发机制分析

应用地面观测站、ERA5再分析资料和高分辨率的WRF模式分析了一次美国博尔德(Boulder)的强下坡风事件,此次强下坡风暴爆发的机制是高空急流带断裂导致动量下传到背风坡山脚处。进一步分析表明,强下坡风的爆发与天气尺度系统高压脊过境及局地的背风坡重力波有关。在焚风的作用下,背风坡持续变暖导致重力波加强并转竖,侵蚀对流层顶的急流带,最终导致急流带断裂,高空动量下传至地面,强下坡风暴在背风坡爆发。

顾及服务质量影响下公园绿地服务水平差异分析

以福州市鼓楼区为例,基于交通出行数据,以住宅小区为需求点、公园出入口为供给点,采用改进引力模型对公园绿地可达性进行测度,探究在考虑服务质量前后公园绿地服务水平的差异及变化。研究发现:在考虑了公园的服务质量指标后能够更准确识别出公园服务水平高低不同的区域;通过对转移矩阵中公园可达性水平的变化差异与空间分布格局分析,可准确定位出城市中需新增公园数量或提高公园质量的区域,从而为城市的规划建设提供参考。

基于卫星重力和测高数据的格陵兰冰盖质量变化分析

格陵兰冰盖全部融化将导致全球海平面上升7m,因此准确估计格陵兰冰盖质量变化过程对理解其对全球气候变化响应和反馈作用具有重要意义。基于Gravity Recovery and Climate Experiment(GRACE)卫星及后继卫星GRACE-FollowOn(GRACE-FO)提供的近20年的月时变重力场数据,以及EuropeanRemote Sensing(ERS-2)、Envisat和CryoSat-2等卫星测高数据,本文对比分析了2002年4月-2020年12月格陵兰冰盖质量变化特征。研究结果表明:(1)卫星重力点质量模型与卫星测高产品估计的质量变化趋势空间分布较为一致,均表明格陵兰冰盖边缘低海拔区域质量亏损严重而内部高原存在质量累积。(2) 2002-2020年格陵兰质量损失对全球平均海平面变化贡献为0.73±0.01mm·a^(-1)。(3)格陵兰冰盖西南部和西北部对海平面变化的贡献占格陵兰总贡献量的43.69%,为主要的海平面上升贡献区。(4)格陵兰冰盖流域尺度的分析表明,Goddard Space Flight Center(GSFC)点质量模型与卫星测高估计的结果更为一致。

基于重力原理的油水分离盒子在贯流泵站的应用探讨

研制一种用于贯流泵水导油腔油水分离的重力盒子,通过安装位置的优化设计,能实时测量油位并及时排出水导油腔的多余水分,消除了原液位变送器测量盲区。利用重力原理在盒子内实现油水分离,可有效解决困扰贯流泵安全运行的类似技术难题,进一步提升泵站自动化运行管理水平。

Global sea level variations from altimetry,GRACE and Argo data over 2005-2014

Total sea level variations（SLVs） are caused by two major components：steric variations due to thermal expansion of seawater,and mass-induced variations due to mass exchange between ocean and land.In this study,the global SLV and its steric and mass components were estimated by satellite altimetry,Argo float data and the Gravity Recovery and Climate Experiment（GRACE） data over 2005-2014.Space gravimetry observations from GRACE suggested that two-thirds of the global mean sea level rise rate observed by altimetry（i.e.,3.1 ± 0.3 mm/a from 2005 to 2014） could be explained by an increase in ocean mass.Furthermore,the global mean sea level was observed to drop significantly during the2010/2011 La Nina event,which may be attributed to the decline of ocean mass and steric SLV.Since early 2011,the global mean sea level began to rise rapidly,which was attributed to an increase in ocean mass.The findings in this study suggested that the global mean sea-level budget was closed from 2005 to 2014 based on altimetry,GRACE,and Argo data.

Using satellite altimetry leveling to assess the marine geoid

Based on the concept of Global Position System(GPS)/leveling,the satellite altimetry leveling(SAL) is first proposed to evaluate the marine geoid.SAL is derived by the difference among the mean sea surface(MSS),mean dynamic ocean topography(MDT),and leveling origin.In this study,(1) the original satellite altimetry data are processed to infer the vertical deflection and gravity anomaly,(2) the Chinese coastal marine geoids(CMG) are determined by using the differe nt methods(including Molodensky,least square collocation,Stokes formula,and two-dimensional fast Fourier transformation(FFT) with the vertical deflection and gravity anomaly data),(3) CMG are evaluated by using the results from above different methods,the Gravity field and steady-state Ocean Circulation Explorer(GOCE) gravity potential model(GGPM),and SAL.The results show that(1) CMG from the Molodensky method has the highest precision by using vertical de flection data,(2) the accuracy of CMG indicate good consistency between the SAL and GGPM,(3) SAL can be used as a new method for assessing marine geoid.

Addendum to: An Approach to Hierarchical Clustering via Level Surfaces and Convexity

This article is an addendum to the 2001 paper [1] which investigated an approach to hierarchical clustering based on the level sets of a density function induced on data points in a d-dimensional feature space. We refer to this as the “level-sets approach” to hierarchical clustering. The density functions considered in [1] were those formed as the sum of identical radial basis functions centered at the data points, each radial basis function assumed to be continuous, monotone decreasing, convex on every ray, and rising to positive infinity at its center point. Such a framework can be investigated with respect to both the Euclidean (L2) and Manhattan (L1) metrics. The addendum here puts forth some observations and questions about the level-sets approach that go beyond those in [1]. In particular, we detail and ask the following questions. How does the level-sets approach compare with other related approaches? How is the resulting hierarchical clustering affected by the choice of radial basis function? What are the structural properties of a function formed as the sum of radial basis functions? Can the levels-sets approach be theoretically validated? Is there an efficient algorithm to implement the level-sets approach?

数字基础设施水平对贸易增长空间的影响--基于RCEP国家面板数据的实证研究

使用扩展的引力模型分析数字基础设施水平对RCEP国家贸易规模及贸易增长空间的影响。数字基础设施水平主要体现在数量和质量两方面,贸易增长空间主要体现在贸易扩展边际和集约边际。研究结果显示,数字基础设施水平提升,对出口国贸易增长和贸易增长空间拓展具有促进作用。其中,数量增加能促进贸易量增长和扩展边际深化;质量提升对贸易扩展边际的深化作用要大于集约边际;RCEP各国间因数字基础设施水平差距形成的“数字鸿沟”对贸易量增长和贸易增长空间拓展产生了制约。因此,应鼓励中国企业加强与RCEP国家在数字基础设施方面的投资合作,缩小各国间的“数字鸿沟”,在着力培育RCEP国家数字贸易市场发展的同时,推动“一带一路”建设高质量发展。

强制湖退期湖底扇沉积构型的多样性与砂体分布特征——以渤海湾盆地东营凹陷沙三段中亚段为例

针对目前关于陆相湖盆不同体系域内部重力流沉积的差异性研究薄弱的情况,以渤海湾盆地东营凹陷史深100地区古近系沙河街组三段中亚段为例,综合利用岩心、测井和三维地震等资料,分析强制湖退期湖底扇沉积构型特征及四级基准面变化对其发育的影响。研究表明,四级基准面上升期湖底扇以异重流成因为主,下降晚期滑塌成因比例逐渐上升。四级基准面从上升到下降,异重流成因湖底扇内部水道延伸距离持续减小,导致湖底扇的平面形态从高度沟道化的扇形向裙带状的扇形转变;此外湖底扇内部的分支水道复合体构型样式由垂向加积转为侧向迁移,单一水道的横向规模逐渐减小;朵叶体复合体的构型样式从侧向摆动型补偿叠置演变为加积型叠置,单一朵叶体的横向规模逐渐增大。该研究深化了高频层序地层中重力流沉积规律的认识,并为湖底扇油气藏精细开发提供了地质依据。

安徽省绿色发展水平测度及空间联系分析

本研究采用熵权—TOPSIS、核密度估计、变异系数等方法测算并分析安徽省绿色发展水平与城市间发展差异,引入改进的引力模型计算各城市间绿色发展水平的相互作用力,分析其空间联系及演变规律。研究结果表明:安徽省绿色发展水平不断上升;2010—2020年安徽省绿色发展水平的核密度图由“单峰”向“双峰”演变,区域间差异先增大后减小;城市间绿色发展影响力呈现为“南高北低”的局面,形成合肥、蚌埠为中心的“双核”格局,芜湖成为第三个发展中心的趋势显著。

基于聚类-重心法和CFLP法的两级物流配送中心选址

为了确保物流配送中心选址的合理性,节约配送里程,降低配送的费用成本,将聚类-重心法和CFLP(Capacitated Fa⁃cility Location Problem)模型结合起来对城市的物流配送中心选址进行研究。首先,用最短距离聚类法进行配送区域划分;其次,通过CFLP模型结合聚类结果,以物流配送成本费用最小化原则选出二级物流配送中心;再次,分别对二级物流配送中心和城市中所有的区域物流配送中心使用重心法求出2个一级物流配送中心的坐标;最后,分别计算出2个一级配送中心的配送总距离和配送总费用,并进行对比分析。结果表明:选择通过对二级物流配送中心使用重心法求出的一级物流配送中心作为最终一级物流配送中心最为合理。该方法能应用到两级物流的配送中心选址过程中。

欧亚经济联盟数字贸易发展水平对中国出口贸易的影响研究

欧亚经济联盟是中国“一带一路”重要的贸易伙伴,双边贸易额逐年快速增长。数字贸易的发展为中国和欧亚经济联盟贸易合作注入了新动力,有力推动了双方贸易高质量发展。从信息网络基础建设、数字技术水平、数字产业水平、贸易潜力4个维度构建数字贸易发展水平指标评价体系,运用相对熵的TOPSIS法对2010—2020年欧亚经济联盟数字发展水平进行测度。进一步,采用扩展引力模型实证分析欧亚经济联盟数字贸易发展水平对中国出口贸易的影响。结果显示,欧亚经济联盟数字贸易水平发展速度较快,但总体水平偏低,各成员国间存在一定差距,同时数字贸易发展水平对中国出口贸易有显著促进作用。根据研究结论,提出了加快网络信息基础建设、完善数字贸易法律政策及治理能力、联合培养数字贸易专业人才、深化中国与欧亚经济联盟国家的数字贸易合作与往来等对策建议。