基于指纹识别的室内定位中的隐私保护

基于指纹识别的定位是最流行的室内定位方法.在离线阶段,服务器测量指纹,比如来自特定空间已知位置的不同接入点（AP）的接收信号强度（RSS）,测量后服务器将测量结果保存在数据库中;在线上阶段,用户同时向服务器发送他当前指纹的测量结果以及位置查询请求,服务器将在数据库中查找与测量结果最接近的指纹.虽然这种方法已经被研究了很久,但现有的工作并没有考虑2个隐私要求：供应商希望保护他们花大代价收集的指纹,用户想要对服务器保留他们的指纹测量结果,以避免泄漏位置.为了实现隐私保护,本文提出一种使用加密技术的指纹匹配方案,这个方案在加密情况下计算由用户测量的指纹与服务器存储的指纹的距离,服务器存储的指纹在这一过程中仍处于密文空间.本文证明了这个方案在进行单点定位时能够很好地保证两者的隐私要求.为了减少高昂的时间开销,本文还提出了一个基于网格划分的改进方案,以及以有限的隐私损失为代价的扩展方案.为加强安全性,最后提出了有效对抗特定攻击的对策,在这种攻击中恶意用户可以通过重复定位获得服务器存储的指纹.使用公众 RSS指纹数据集的扩展实验结果显示本文方案足以在实现实时定位的同时保留定位精度.     

江西省新一代中短期预报业务流程介绍

按照中国气象局以数值预报产品为基础,以MICAPS预报人机交互系统为工作平台的思路．建立了包括气候背景、预报思路、天气会商、预报制作和管理5个模块的江西省新一代中短期预报业务流程,并重点介绍了数据转换、综合图定义、参数修改、网络改造等有关的本地化工作,以及包括天气形势描述、要素预报的人机交互修改、全省实况描述的预报制作和预报产品自动或半自动生成技术。     

城市环境下基于降维Kalman滤波的室内导航算法

提出了一种适用于室内超宽带定位的降维Kalman滤波算法,结合LSE算法与降维Kalman滤波算法进行定位求解,以数值仿真试验及物理试验验证了其有效性。     

Thermo-hydro-mechanical modeling of unsaturated soils using isogeometric analysis: Model development and application to strain localization simulation

This study presents a thermo-hydro-mechanical (THM) model of unsaturated soils using isogeometric analysis (IGA). The framework employs Bézier extraction to connect IGA to the conventional finite element analysis (FEA), featuring the current study as one of the first attempts to develop an IGA-FEA framework for solving THM problems in unsaturated soils. IGA offers higher levels of interelement continuity making it an attractive method for solving highly nonlinear problems. The governing equations of linear momentum, mass, and energy balance are coupled based on the averaging procedure within the hybrid mixture theory. The Drucker-Prager yield surface is used to limit the modified effective stress where the model follows small strain, quasi-static loading conditions. Temperature dependency of the surface tension is implemented in the soil-water retention curve. Nonuniform rational B-splines (NURBS) basis functions are used in the standard Galerkin method and weak formulations of the balance equations. Displacement, capillary pressure, gas pressure, and temperature are four independent quantities that are approximated by NURBS in spatial discretization. The framework is used to simulate strain localization in an undrained dense sand subjected to plane strain biaxial compression under different temperatures and displacement velocities. Results show that an increase in the displacement rate leads to reduction in the equivalent plastic strain while an increase in the temperature leads to an increase in the equivalent plastic strain. The findings suggest that the proposed IGA-based framework offers a viable alternative for solving THM problems in unsaturated soils.     

Instability of gradient dependent elasto-viscoplasticity for clay

A gradient-dependent viscoplastic constitutive model for water saturated clay is proposed to describe the strain localization phenomena and pattern formation during deformation. Second- and fourth-order gradients of volumetric viscoplastic strain are introduced into the constitutive equations to account for the non-local effects due to the motion of microstructures. A linear perturbation analysis is applied to this model. The instability of the government equations (i.e. the constitutive equations and the equations of motion for the clay skeleton and pore water) is discussed for both the one-dimensional and the two-dimensional situations. In addition, issues concerned with the formulation of boundary value problems by finite element analysis in relation to the formulation and the boundary conditions are presented. Copyright © 1999 John Wiley & Sons, Ltd.     

水口山矿田矿床定位模式及找矿远景区评价

文章从水口山矿田所处大地构造背景及矿田构造岩浆作用分析入手,阐明了矿田内两大成岩成矿系列:Ⅰ与燕山中期中酸性侵入类有关的中温热液接触交代(夕卡岩)型铅锌铜银硫矿床,Ⅱ与燕山晚期英安质次火山-火山岩有关的浅成低温热液铅锌金银矿床.讨论了两者间的时空关系,分析了控矿因素,总结了矿床定位模式,并结合地物化遥资料进行了矿田内找矿远景区的评价.     

基于WiFi信号室内定位技术的研究

主要对基于WiFi信号的室内定位技术中的三角形定位法进行了研究。鉴于现有的三角形定位模型受信号强度和环境干扰的约束影响,定位精度不高,提出了一种结合室内影响因素约束的权重改正定位模型,更加切合复杂的室内定位环境。通过试验测试和数据分析,经过加权去噪模型改正后的定位精度更高,适用性更广。     

Influence of the intermediate principal stress and principal stress direction on the mechanical behavior of cohesionless soils using the discrete element method

In this paper, the Discrete Element Method (DEM) is employed to numerically explore the response of hollow cylinder specimens of granular soils under complex stress paths. Two series of numerical tests are conducted to clarify the effects of the principal stress direction α and the intermediate principal stress through the b-value on the mechanical response of granular materials. The effects of α and b-value on the non-coaxiality of the principal stress and the principal plastic strain increment directions are investigated. It is observed that b-value and α significantly affect the non-coaxial behavior of granular materials. Finally, the results are discussed and compared with those obtained from physical laboratory tests.     

基于摩尔-库仑模型的非线性本构模型的开发及其在应变局部化中的应用

以FLAC中的Mohr-Coulomb（M-C）本构模型为基础,在C++环境下实现了考虑拉伸截断的非线性本构模型的二次开发。针对应力及位移的分布规律,将理想弹塑性的Hoek-Brown（H-B）本构模型、M-C本构模型及自定义本构模型的数值解及H-B本构模型的理论解进行了比较,验证了自定义本构模型的正确性。采用弹-脆-塑性的自定义本构模型,以先加载,后挖洞的方式模拟了圆形巷道围岩的应变局部化过程,在计算模型的边界条件对称及均质本构参数的条件下,模拟出了4个对称的V型坑,模拟结果与静水压力条件下岩爆的现场观测及试验结果吻合,而采用接近脆性的H-B应变软化模型所得结果的对称性较差     

基于无网格法的含缺陷岩石变形局部化数值模拟研究

利用自主开发的基于无网格法的岩石力学计算分析程序,采用Mohr-Coulomb破坏准则,考虑材料塑性屈服后的软化特性,研究单轴压缩条件下含一个缺陷的岩石试样的变形特性,探讨含缺陷材料的岩石变形局部化的演化规律。计算结果表明,岩石试件的破坏是一个渐进破坏的过程;加载过程中试件中的缺陷弱粒子首先出现粒子破坏并产生声发射,随加载进行试件产生微裂隙并扩张形成一个变形局部化带,局部化带扩张、发展,最终形成一个明显的剪切破坏带,缺陷粒子对试件的破坏起到了控制作用。岩石的声发射记录了岩石材料的塑性破坏过程,岩石试件的剪切破坏带与塑性区的发展具有非常类似的规律,但塑性区面积要大于剪切破坏带,从所处位置来看剪切破坏带位于塑性区之内,通过研究声发射特征信息发现变形局部化发生在应力-加载步（应变）达到峰值强度前。