基于腹地划分的中国城市群空间影响范围识别

城市群空间影响范围的界定是认清城市群内中心城市与腹地、城市与城市间相互关联的基础。采用主成分分析法计算中国287个地级及以上城市的结节性指数,利用累积耗费距离法和k阶数据场,综合测度了交通可达性与空间场能,根据场强"取大"原则对城市腹地进行了划分,依据城市腹地范围界定了城市群的空间影响范围。结果表明:①中国地级以上城市最大和最小结节性指数相差157.53倍,城市平均可达时间为193.43 min,场能平均值为5 412,最大和最小城市腹地相差3 751倍;②23个城市群中,空间影响范围最大的是北疆城市群,空间平均场强最大的是中原城市群;③城市群在空间上呈现为发育程度不同的"11+9+3"的分布格局和逆时针90°旋转的"β"型城市群连绵带发展格局;④基于腹地划分的城市群空间影响范围充分考虑了现实的交通网络和地形地貌特点,实现了对广域空间范围内城市腹地范围和城市群空间影响范围的定量测度。     

生态系统服务社会价值与生态价值的权衡与协同关系——以普达措国家公园为例

以香格里拉普达措国家公园为研究区,借助SolVES模型和InVEST模型,分别度量其社会价值（美学价值、文化价值、游憩价值）和生态价值（生境质量、碳储量、水源供给）的空间特征,并运用双变量空间自相关分析对二者空间权衡与协同关系进行研究。研究表明：① 社会价值的高值区呈“多核心,多条状”的空间格局,社会价值指数高达8.6（该指数介于1~10）,且距水体的距离越近对社会价值的贡献越大（贡献度为45.9%）;② 生态价值良好及优的空间范围占园区面积的1/2（49.91%）,主要位于原始森林保存良好的碧塔海片区和尼汝东北部扎诺一带;③ 社会价值与生态价值之间存在显著的空间依赖性,其中社会价值低,生态价值高的区域是园区最主要的空间聚集特征。该研究可为生态系统服务的可持续管理决策提供科学依据,以及有助于完善基于生态系统服务的社会?生态系统分析理论框架。     

测量监测技术在高层钢结构施工中的应用实践

本文结合大连期货大厦高层钢结构施工放样工程论述了高层钢结构主体施工控制和监测的工艺方法,具体介绍了首层控制网建立,内控点投测、轴线控制,标高控制、标高传递的步骤,以及钢柱扭转、错位、垂直度纠正的方法,对其它高层钢结构施工有参考价值。     

Meso‐scale particle modeling of concrete deterioration caused by alkali‐aggregate reaction

A meso‐scale particle model is presented to simulate the expansion of concrete subjected to alkali‐aggregate reaction (AAR) and to analyze the AAR‐induced degradation of the mechanical properties. It is the first attempt to evaluate the deterioration mechanism due to AAR using the discrete‐element method. A three‐phase meso‐scale model for concrete composed of aggregates, mortar and the interface is established with the combination of a pre‐processing approach and the particle flow code, PFC2D. A homogeneous aggregate expansion approach is applied to model the AAR expansion. Uniaxial compression tests are conducted for the AAR‐affected concrete to examine the effects on the mechanical properties. Two specimens with different aggregate sizes are analyzed to consider the effects of aggregate size on AAR. The results show that the meso‐scale particle model is valid to predict the expansion and the internal micro‐cracking patterns caused by AAR. The two different specimens exhibit similar behavior. The Young's modulus and compressive strength are significantly reduced with the increase of AAR expansion. The shape of the stress–strain curves obtained from the compression tests clearly reflects the influence of internal micro‐cracks: an increased nonlinearity before the peak loading and a more gradual softening for more severely affected specimens. Similar macroscopic failure patterns of the specimens under compression are observed in terms of diagonal macroscopic cracks splitting the specimen into several triangular pieces, whereas localized micro‐cracks forming in slightly affected specimens are different from branching and diffusing cracks in severely affected ones, demonstrating different failure mechanisms. Copyright © 2012 John Wiley & Sons, Ltd.     

水库重力测量检测非牛顿引力的实验数据分析新方法

本文提出水库重力测量检测非牛顿引力的实验数据分析新方法。利用近一天两重力仪的重力差值信号,基于同液面高度变化水体重力信号相等这一具有明显物理意义的准则,建立仪器零漂信号多项式系数矢量的矩阵方程,通过极大似然反演比较严格地计算漂移信号,并从中提取检测信号。实例计算结果表明:(1)当数据充分、漂移多项式阶数取值适当时,该方法完全有效;(2)在现有水库实验的设备和技术条件下,测定万有引力常数G对实验室值的偏离精度可达0.15％,优于矿井实验和先前水库实验的分析结果;若进一步改善水面高度测量,检测精度还可明显提高;(3)Hornberg水库实验重力仪G709在0.4％的精度范围内,未发现G对实验室值的偏离。     

ANALYSIS OF THE STRATIFICATION FEATURES OF THE YELLOW SEA AND THE LOCATION OF ITS GENERAL SHELF FRONT IN THE WARM HALF-YEAR

A stratification parameter ,defined as theamount of mechanical energy required to bring about vertical mixing, has been calculated for theYellow Sea using available data over the past ten years.T he monthly distributions of Log are obtained to explain the features of the Yellow Sea stratification.Fronts of the shallow shelf sea are often inseparably related with its stratifications. The front of the Yellow Sea in the warm half-year is generated in May and disappears in November. The shelf front moves shoreward and becomes strong in the heating season, but becomes weak in the cooling season upon return.     

三维曲面上的位场处理问题

通过理论分析和模型试算,进一步明确阐述了对实测重磁位场资料采用三维处理的合理性和用二维处理的不合理性。提出三维处理的必要性和其实用价值。并对目前的三维曲面位场数据处理方法做了评述。     

Initial results of centralized autonomous orbit determination of the new-generation BDS satellites with inter-satellite link measurements

Autonomous orbit determination is the ability of navigation satellites to estimate the orbit parameters on-board using inter-satellite link (ISL) measurements. This study mainly focuses on data processing of the ISL measurements as a new measurement type and its application on the centralized autonomous orbit determination of the new-generation Beidou navigation satellite system satellites for the first time. The ISL measurements are dual one-way measurements that follow a time division multiple access (TDMA) structure. The ranging error of the ISL measurements is less than 0.25 ns. This paper proposes a derivation approach to the satellite clock offsets and the geometric distances from TDMA dual one-way measurements without a loss of accuracy. The derived clock offsets are used for time synchronization, and the derived geometry distances are used for autonomous orbit determination. The clock offsets from the ISL measurements are consistent with the L-band two-way satellite, and time–frequency transfer clock measurements and the detrended residuals vary within 0.5 ns. The centralized autonomous orbit determination is conducted in a batch mode on a ground-capable server for the feasibility study. Constant hardware delays are present in the geometric distances and become the largest source of error in the autonomous orbit determination. Therefore, the hardware delays are estimated simultaneously with the satellite orbits. To avoid uncertainties in the constellation orientation, a ground anchor station that “observes” the satellites with on-board ISL payloads is introduced into the orbit determination. The root-mean-square values of orbit determination residuals are within 10.0 cm, and the standard deviation of the estimated ISL hardware delays is within 0.2 ns. The accuracy of the autonomous orbits is evaluated by analysis of overlap comparison and the satellite laser ranging (SLR) residuals and is compared with the accuracy of the L-band orbits. The results indicate that the radial overlap differences between the autonomous orbits are less than 15.0 cm for the inclined geosynchronous orbit (IGSO) satellites and less than 10.0 cm for the MEO satellites. The SLR residuals are approximately 15.0 cm for the IGSO satellites and approximately 10.0 cm for the MEO satellites, representing an improvement over the L-band orbits.     

Three-frequency BDS precise point positioning ambiguity resolution based on raw observables

All BeiDou navigation satellite system (BDS) satellites are transmitting signals on three frequencies, which brings new opportunity and challenges for high-accuracy precise point positioning (PPP) with ambiguity resolution (AR). This paper proposes an effective uncalibrated phase delay (UPD) estimation and AR strategy which is based on a raw PPP model. First, triple-frequency raw PPP models are developed. The observation model and stochastic model are designed and extended to accommodate the third frequency. Then, the UPD is parameterized in raw frequency form while estimating with the high-precision and low-noise integer linear combination of float ambiguity which are derived by ambiguity decorrelation. Third, with UPD corrected, the LAMBDA method is used for resolving full or partial ambiguities which can be fixed. This method can be easily and flexibly extended for dual-, triple- or even more frequency. To verify the effectiveness and performance of triple-frequency PPP AR, tests with real BDS data from 90 stations lasting for 21 days were performed in static mode. Data were processed with three strategies: BDS triple-frequency ambiguity-float PPP, BDS triple-frequency PPP with dual-frequency (B1/B2) and three-frequency AR, respectively. Numerous experiment results showed that compared with the ambiguity-float solution, the performance in terms of convergence time and positioning biases can be significantly improved by AR. Among three groups of solutions, the triple-frequency PPP AR achieved the best performance. Compared with dual-frequency AR, additional the third frequency could apparently improve the position estimations during the initialization phase and under constraint environments when the dual-frequency PPP AR is limited by few satellite numbers.     

Effects of molding water content and compaction degree on the microstructure and permeability of compacted loess

Acta Geotechnica - Molding water content and compaction degree are the major factors driving differences in the microstructure, which has a control on the permeability of compacted loess. Although...