Influence of leaf water potential on diurnal changes in CO2 and water vapour fluxes

Mass and energy fluxes between the atmosphere and vegetation are driven by meteorological variables, and controlled by plant water status, which may change more markedly diurnally than soil water. We tested the hypothesis that integration of dynamic changes in leaf water potential may improve the simulation of CO₂ and water fluxes over a wheat canopy. Simulation of leaf water potential was integrated into a comprehensive model (the ChinaAgrosys) of heat, water and CO₂ fluxes and crop growth. Photosynthesis from individual leaves was integrated to the canopy by taking into consideration the attenuation of radiation when penetrating the canopy. Transpiration was calculated with the Shuttleworth-Wallace model in which canopy resistance was taken as a link between energy balance and physiological regulation. A revised version of the Ball-Woodrow-Berry stomatal model was applied to produce a new canopy resistance model, which was validated against measured CO₂ and water vapour fluxes over winter wheat fields in Yucheng (36°57′ N, 116°36′ E, 28 m above sea level) in the North China Plain during 1997, 2001 and 2004. Leaf water potential played an important role in causing stomatal conductance to fall at midday, which caused diurnal changes in photosynthesis and transpiration. Changes in soil water potential were less important. Inclusion of the dynamics of leaf water potential can improve the precision of the simulation of CO₂ and water vapour fluxes, especially in the afternoon under water stress conditions.     

面向服务的城乡规划辅助决策系统实现

城乡规划建设迫切需要信息化决策支持手段.文章从整体上详细地设计了城乡规划辅助决策系统的框架以及数据库:以GIS为核心,以ArcGIS Server为开发平台,采用Flex开发语言,设计并开发了城乡规划决策统一平台;基于面向服务的思想,在一体化集成框架的基础上,对城乡规划辅助决策系统数据库设计进行了论述,并对数据库设计中所涉及到的控制性详细规划的各类矢量地理空间数据进行了整合;初步实现了标准化的、统一的城乡规划辅助决策数据库.实验表明:该平台具有先进的网络服务特性、高度的集成性以及良好的移植性,为城市信息化管理辅助决策提供参考.     

哈尔滨市地下水中29种抗生素分布特征研究

当前对抗生素滥用监管及其研究正在加强,近年来中国主要水域中抗生素均有不同程度的检出,地表水及地下水中抗生素的污染状况持续受到关注。因进入环境中的抗生素种类繁多、结构复杂,一般实验室难以实现同时分析多种类抗生素。本文在哈尔滨市共采集地下水样品26组,采样范围包括人口密集、工业生产、农畜业等生活生产地区。利用超高效液相色谱-三重四极杆串联质谱联用技术分析了样品中的磺胺类、喹诺酮类、大环内酯类、β-内酰胺类、四环素类、林可酰胺类等6大类共29种典型抗生素含量,研究了哈尔滨市地下水中典型抗生素的检出及分布状况。结果表明：①哈尔滨市地下水中6大类典型抗生素均有不同程度检出,其中以磺胺类、喹诺酮类、大环内酯类、四环素类为主,检出率分别为61.5%、46.2%、42.3%、38.5%;②哈尔滨市地下水检出的抗生素含量范围在0.02~612ng/L之间,其中磺胺噻唑、磺胺嘧啶、林可霉素检出的最高浓度超过100ng/L,相比于国内外部分地区（如中国北京、天津,西班牙巴塞罗那）喹诺酮类整体含量偏低;③检出抗生素含量较高的采样点位主要分布在城市的中部、南部和东部地区,这些区域也是该市人口相对密集区,且附近普遍分布有制药厂、家禽牲畜养殖厂、城市排污口等。由此揭示了哈尔滨市城市地下水中抗生素分布特征受人类生产生活活动影响且具有明显的相关性。     

浅层结构不确定性对广角地震走时正演模拟结果的影响——以西沙地块OBS2011-1测线为例

海洋地球物理勘探中常使用多道地震数据建立浅部地层模型,结合海底地震仪广角地震数据进行射线追踪和走时反演求取地层速度特征.受采集环境和成本限制,部分海底地震仪测线缺少同步采集的多道地震数据,建立的初始模型其浅层结构有较大不确定性,可能会对正演模拟结果造成严重影响.本研究针对海底地震仪广角地震走时模拟中浅部结构的不确定性因素,使用RayInvr软件构建了理论模型和走时数据体,分析讨论了初始模型沉积层厚度与速度变化对正演模拟结果的影响.之后进行实测数据处理,在MCS2019-3测线数据的约束下建立初始模型,对OBS2011-1测线震相重新进行了走时拟合,将得到的模型结果与先前结果进行对比,得到以下结论：沉积层厚度及速度不确定性对走时模拟结果的浅部结构影响较大,深部结构影响较小;使用错误的速度与基底深度组合来拟合沉积层反射震相PsP,会使台站下方的地壳和地幔折射震相Pg和Pn,以及莫霍面反射震相PmP都出现走时小起伏,走时提前对应沉积层速度与厚度偏大,走时延后对应沉积层速度与厚度偏小;PsP震相缺失时,不同的速度-深度组合都可以很好地拟合震相,但会增加结果的不确定性.

     

四川九寨黄龙机场高填方地基变形三维动力分析

四川九寨黄龙机场具有高填方、高地震烈度、高海拔等三高的特点,高填方体地基在地震作用下的动力稳定与变形问题成为该机场需着重考虑的主要工程地质问题之一。在对目前各种动力分析方法研究的基础上,选用快速拉格郎日差分分析(FLAC)程序,对该机场元山子沟段高填方地基在地震作用下的变形规律进行了系统地研究,获得了一些有实际意义的认识。     

Complexity measurement of regional groundwater resources system using improved Lempel-Ziv complexity algorithm

In this paper, the self-adaptive artificial fish swarm algorithm (SAAFSA) is used to optimize the coarse graining of segment numbers, which are used in the Lempel-Ziv complexity algorithm. This approach improves the Lempel-Ziv complexity (LZC) algorithm of equal probability coarse graining. As a case study, the complexities of monthly series of groundwater depth were analyzed at seven farms in the Hongxinglong Administration. GIS technology was used to create spatial distributions of monthly groundwater depths. A projection pursuit model based on the SAAFSA was established and used for complexity attribution analysis at selected farms with different degrees of complexity. The three selected farms, Hongqiling, 852, and Youyi, each represent a certain degree of complexity. Further analysis shows that precipitation, evaporation, temperature, and human activities are the primary factors that cause complexity variations in local groundwater depth. The results reveal the evolution of the complexity characteristics of local groundwater depth and provide scientific evidence for the need to effectively allocate regional water resources. Additionally, the proposed method can be applied in complexity analyses of other hydrologic features, as well as in research regarding nonlinear time series in economic, engineering, medical, and signal analyses.     

Two-dimensional landslide dynamic simulation based on a velocity-weakening friction law

Surprisingly, hypermobility (high velocity and long run-out) is a remarkable feature of large landslides and is still poorly understood. In this paper, a velocity-weakening friction law is incorporated into a depth-averaged landslide model for explaining the higher mobility mechanism of landslides. In order to improve the precision of the calculation, a coupled numerical method based on the finite volume method is proposed to solve the model equations. Finally, several numerical tests are performed to verify the stability of the algorithm and reliability of the model. The comparison between numerical results and experimental data indicates that the presented model can predict the movement of landslide accurately. Considering the effect of velocity-weakening friction law, the presented model can better reflect the hypermobility of landslide than the conventional Mohr–Coulomb friction model. This work shows that the application of a universal velocity-weakening friction law is effective in describing the hypermobility of landslide and predicting the extent of landslides.     

A new multipath mitigation method based on adaptive thresholding wavelet denoising and double reference shift strategy

Multipath disturbance is one of the major error sources in high-accuracy positioning for global navigation satellite system (GNSS). Although various methods based on software and hardware strategies have been developed to mitigate this error, they are still limited by different kinds of factors and the effect is not ideal. After analyzing the existing methods, a new single-difference sidereal filtering method, based on adaptive thresholding wavelet denoising and double reference shift strategy (ATDR), is proposed to mitigate multipath effects for static short-baseline GNSS applications. The key idea of the proposed method is the use of both the adaptive thresholding wavelet denoising to extract an accurate multipath correction model from the reference Day and the double reference shift strategy to mitigate multipath for subsequent Day 2 more accurately and efficiently. By applying the introduced adaptive thresholding method, the average improvement rate of the RMS values of the single-difference residuals can reach about 15.82% compared with the constant thresholding method. Moreover, after applying the proposed ATDR method, the 3D positioning precision is improved by about 37.73% for the single epoch mode with 30 s data sampling rate and about 31.22% for the continuous mode with 1 s high sampling rate compared with the original results. Even compared with the constant thresholding single orbital reference (CTSR) method, the improvement percentage is about 33.94% in single epoch mode and about 25.40% in continuous mode for 3D positioning precision, respectively. In conclusion, the results of the two experiments indicate that the proposed ATDR method performs much better than the CTSR method in mitigating multipath for different sampling rates and different processing modes in the measurement domain for GNSS static short-baseline postprocessing applications.