Memory in place

Geographers and psychologists both seek to understand people's behaviour and their cognitive and emotional lives so it is somewhat surprising that there has not been more theoretical cross‐fertilisation of the two disciplines. ‘On time, place and happiness’ is a rare but welcome exception, showing how research in social‐cognitive psychology might usefully clarify thinking about temporality, place and well‐being. This commentary examines several additional human memory phenomena that geographers might like to consider in their theorising about these matters.     

延津沙地间套复种四熟栽培模式研究

根据小麦、西瓜、花生、玉米的不同生育特性,合理选用不同熟期的品种,安排空间和生育期调控,提出了小麦西瓜花生玉米四熟的间套复种栽培模式,并对模式的基本原理、主要栽培技术和经济效益加以分析和总结。     

利用多频多系统GNSS OEM板卡实现高精度变形监测

针对近年来被广泛应用的多频多系统GNSS OEM板卡,设计并实现了一套基于多频多系统OEM板卡的低成本变形监测系统,包括数据解码、基线处理、网平差和坐标转换等,能够实时获取测站点高精度空间坐标。以某高层建筑形变监测为例,通过串口通信获取板卡多频多系统观测信息,并经过该系统解算,实现了监测点实时定位,且系统成本相比市场上测量型GNSS接收机系统下降了约40%。实验结果表明,该系统解码精度可达0.2 mm,静态模式定位精度可达到平面2 mm以内,高程5 mm以内,动态模式定位精度可达到平面5 mm以内,高程10 mm以内,验证了该系统的可靠性和适用性。     

复杂网络中多话题信息传播仿真研究

传统复杂网络话题传播研究,重点关注的是单个话题在网络中的传播,较少考虑多话题之间的相互影响因素。论文分析舆论传播过程中多个话题之间的竞争关系对话题传播的影响机制,建立基于复杂网络的多话题信息传播模型。通过对模型仿真实验及其结果分析表明,当引入个体信息环境影响因素后,一个话题的影响力大于舆论话题环境中其他话题的平均影响力,才会有较大概率影响到更多个体,否则只能在小范围内传播;个体对于话题记忆能力的变化在不同网络中会产生不同影响,在随机网络和BA网络中,人们对于话题的记忆越深,其传播的影响范围越大,而在规则网络和小世界网络中,较小的记忆长度能够让话题传播影响力更大;同时,在具有社群结构的网络中,度大的节点并非会一定会更多的参与某一话题的传播,因为度大的节点有更大概率获得更多的话题。     

Wind-driven, double-gyre, ocean circulation in a reduced-gravity, 2.5-layer, lattice boltzmann model

A coupled lattice Boltzmann （LB） model with second-order accuracy is applied to the reduced-gravity, shallow water, 2.5-layer model for wind-driven double-gyre ocean circulation. By introducing the secondorder integral approximation for the collision operator, the model becomes fully explicit. The Coriolis force and other external forces are included in the model with second-order accuracy, which is consistent with the discretization accuracy of the LB equation. The feature of the multiple equilibria solutions is found in the numerical experiments under different Reynolds numbers based on this LB scheme. With the Reynolds number increasing from 3000 to 4000, the solution of this model is destabilized from the anti-symmetric double-gyre solution to the subtropic gyre solution and then to the subpolar gyre solution. The transitions between these equilibria states are also found in some parameter ranges. The time-dependent variability of the circulation based on this LB simulation is also discussed for varying viscosity regimes. The flow of this model exhibits oscillations with different timescales varying from subannual to interannual. The corresponding statistical oscillation modes are obtained by spectral analysis. By analyzing the spatiotemporal structures of these modes, it is found that the subannual oscillation with a 9-month period originates from the barotropic Rossby basin mode, and the interarmual oscillations with periods ranging from 1.5 years to 4.6 years originate from the recirculation gyre modes, which include the barotropic and the baroclinic recirculation gyre modes.     

多重压力对重点生态功能区农户生计资产可得性的影响——以甘南黄河水源补给区为例

重点生态功能区主要承担着提供持续、稳定生态服务的功能,农户作为维护其主体功能的最基础单元和该区最主要的经济活动主体,面临着自然、社会、政策等多重压力,其交互作用不仅加剧了农户的生计脆弱性,更影响到该区主体功能的发挥,当前急需辨明多重压力对农户生计的影响,以便寻求有效的生计脆弱性减缓对策。本文以甘南黄河水源补给区为例,运用入户调查数据与有序Logistic回归模型等方法在识别农户遭受关键压力的基础上,进一步探讨生计压力的交互作用对生计资产可得性的影响。结果显示：① 甘南黄河水源补给区大多数农户遭受自然+经济型多重压力,其中,重点保护区、恢复治理区及经济示范区农户遭受的多重压力分别以自然+经济型、自然+经济型、经济+社会型为主。② 在多重压力的冲击下,重点保护区与恢复治理区农户除了社会资产可得性变化处于稳定状态,其余各类资产可得性变化几乎处于降低态势,而经济示范区农户的金融资产与社会资产的可得性变化处于稳定状态,其余各类资产可得性变化均处于降低态势。③ 婚嫁支出高与农牧产品价格下降、牲畜患病与人畜饮用水困难、子女学费支出高+婚嫁支出高+农牧产品价格下降+养老无保障、建房开支高与生态政策、子女就业困难与农业病虫害等压力的交互作用分别对自然资产、物质资产、金融资产、社会资产、人力资产等的可得性变化影响最强烈。     

A partial susceptibility approach to analysing the magnetic properties of environmental materials: a case study

An approach to expressing the magnetic properties of environmental materials in terms of the contributions of the magnetic susceptibilities of specific magnetic components is reported. The approach links the partial susceptibilities of discrete particles, domains or mineral fractions with the concentration-dependent parameters by means of multiple linear regression methods. The case study, using the Liverpool street dust data set, demonstrates that the technique is able to model the contributions of the main magnetic components satisfactorily. Several factors may have a significant impact on the regression results. These include the validity of the linear proportional relationships between partial susceptibilities and the relevant concentration-dependent parameters, the adequacy of the variable selection procedure and the regression model, and the suitability of certain magnetic parameters.     

沿圆曲线的Radon变换数值解

研究具有紧支集且在支集内连续的二元函数沿上半圆曲线的Radon变换反演问题。基于对投影函数的Fourier变换,反演问题可以归结为具有弱奇性及震荡核的Abel积分方程的求解。我们证明了当圆曲线中心及半径在一定范围内变化时,在已知沿上半圆曲线的Radon变换情况下,这个积分方程的解具有唯一性,并给出了消除Abel积分方程弱奇性的数值方法。在考虑投影数据噪声的情况下,给出了多次加权改善系数矩阵条件数稳定的数值方法,并通过数值模拟验证所提出方法的有效性。     

Modelling the effects of temperature and food on individual growth and reproduction of Daphnia and their consequences on the population level

Individual based simulations of population dynamics require the availability of growth models with adequate complexity. For this purpose a simple-to-use model (non-linear multiple regression approach) is presented describing somatic growth and reproduction of Daphnia as a function of time, temperature and food quantity. The model showed a good agreement with published observations of somatic growth (r² = 0.954, n = 88) and egg production (r² = 0.898, n = 35). Temperature is the main determinant of initial somatic growth and food concentration is the main determinant of maximal body length and clutch size. An individual based simulation was used to demonstrate the simultaneous effects of food and temperature on the population level. Evidently, both temperature and food supply affected the population growth rate but at food concentrations above approximately 0.4 mg Cl⁻¹ Scenedesmus acutus temperature appeared as the main determinant of population growth.

Four simulation examples are given to show the wide applicability of the model: (1) analysis of the correlation between population birth rate and somatic growth rate, (2) contribution of egg development time and delayed somatic growth to temperature-effects on population growth, (3) comparison of population birth rate in simulations with constant vs. decreasing size at maturity with declining food concentrations and (4) costs of diel vertical migration. Due to its plausible behaviour over a broad range of temperature (2–20 °C) and food conditions (0.1–4 mg Cl⁻¹) the model can be used as a module for more detailed simulations of Daphnia population dynamics under realistic environmental conditions.     

基于波场外推压制水层多次波

重点讨论了基于克希霍夫积分的波场外推方法预测水层多次波的方法原理及具体的数值实现.自适应减法是波动方程方法压制多次波的另一个重要方面,考虑到Monk提出的带约束的互均衡化算法在复杂模型情况下压制效果不是很理想,本文对其算法进行了改进,提出了基于矩形窗和海宁(hanning)窗的分段匹配算法,模型算例的处理结果表明,改进后的算法具有一定的优越性.