国际以及国内土壤固化剂的研究现状和前景展望

将现有土壤固化剂分成四类，分析各类土壤固化剂的优缺点。总结现有的土壤固化机理．并对土壤固化剂的发展提出四点有意义的建议。     

多孔Fe-Mn合金表面微纳形貌调控及其生物相容性评价

铁基可降解金属因其良好的生物相容性和优异的机械性能,在骨科植入物领域具有广阔的应用前景,但必须突破其降解速率过慢的瓶颈问题。本研究通过电化学技术对3D打印多孔铁锰合金(Fe-30Mn)支架表面进行去合金化处理。通过扫描电镜观察发现,以盐酸和氯化钠分别作为去合金化处理介质溶液,可以在支架表面形成多微孔网络结构和片状纳米结构。接触角和粗糙度测试显示,2种微纳结构的构建均显著改善了Fe-30Mn支架表面亲水性,并提升了其表面粗糙度,多微孔网络结构更加粗糙并且亲水性更好。利用静态浸泡法和电化学耐腐蚀实验评估合金化处理前后支架的腐蚀速率,发现表面微纳结构的形成可加速Fe-30Mn支架的降解。建立体外成骨细胞培养模型,通过激光共聚焦观察及细胞增殖测试发现,经合金化处理的2种支架均能支撑细胞的贴附和增殖,具有良好的细胞相容性。结果表明,经电化学去合金化处理后,Fe-30Mn支架的降解速度得以增强,同时保持了良好的生物相容性,有望在骨修复领域得到较好应用。     

A Hermite‐Lobatto Pseudospectral Method for Optimal Control

A pseudospectral (PS) method based on Hermite interpolation and collocation at the Legendre‐Gauss‐Lobatto (LGL) points is presented for direct trajectory optimization and costate estimation of optimal control problems. A major characteristic of this method is that the state is approximated by the Hermite interpolation instead of the commonly used Lagrange interpolation. The derivatives of the state and its approximation at the terminal time are set to match up by using a Hermite interpolation. Since the terminal state derivative is determined from the dynamic, the state approximation can automatically satisfy the dynamic at the terminal time. When collocating the dynamic at the LGL points, the collocation equation for the terminal point can be omitted because it is constantly satisfied. By this approach, the proposed method avoids the issue of the Legendre PS method where the discrete state variables are over‐constrained by the collocation equations, hence achieving the same level of solution accuracy as the Gauss PS method and the Radau PS method, while retaining the ability to explicitly generate the control solution at the endpoints. A mapping relationship between the Karush‐Kuhn‐Tucker multipliers of the nonlinear programming problem and the costate of the optimal control problem is developed for this method. The numerical example illustrates that the use of the Hermite interpolation as described leads to the ability to produce both highly accurate primal and dual solutions for optimal control problems.     

GPS—RTK技术在土方测量中的应用

介绍了GPS—RTK技术在土方测量中的应用，分析了RTK应用于土方测量的诸多优势以及应该注意的问题。     

Analysis of effects of front and back surface dopants on silicon vertical multi-junction solar cell by 2D numerical simulation

The silicon vertical multi-junction(VMJ)solar cell has a good potential in high concentration,but it requires high quality front and back surface passivation layers to keep its high efficiency.We try to add dopants into the front and back surfaces of the VMJ cell to release this strict requirement in this work.The effects of recombination velocities,doping types and doping profiles of front and back surfaces on the performance of the P-type VMJ cell were calculated under 1 sun and 1000 suns.The 2D numerical simulation tool TCAD software was used.The performance of the VMJ cell without front and back surface dopants was also calculated for comparison.It was found that the requirement of high quality front and back surface passivation layers could be released remarkably by adding either N-type or P+-type front and back surface dopants.For the two types of front surface dopants,the highest efficiencies of the cells were got by light dopant;for the two types of back surface dopants,the doping type and profile affected little on the performance of the cell in our calculation range.It was also found that the series resistance of the VMJ cell with N-type front surface dopant was decreased by the 2D effect of front surface emitter.The VMJ cell with P+-type front surface dopant had the highest efficiency under 1000 suns and the VMJ cell with N-type front surface dopant had the highest efficiency under 1 sun in our calculation range.     

物联网中移动Sensor节点漫游的组合安全认证协议

物联网包含感知子网和传输骨干网,其感知子网中节点能力受限,往往利用移动的传感器节点跨区域访问来获取信息;而其传输骨干网络需要依托现有Internet的基础设施,并利用其提供的强大服务.在这种情况下,移动节点的漫游带来了新的安全问题,一方面移动节点在感知子网间跨区域漫游,虽和MANET中一样需要保证移动节点漫游时高效安全地加入新的拜访域,但因传感节点资源极端受限而对轻量级有更高数量级的要求;另一方面资源受限的感知子网间移动节点漫游仅能提供轻量级安全,但是在接入骨干传输网时,不可因此降低骨干网络已有的安全性,即轻量级的安全协议和传统骨干网协议综合运用时,需具有组合安全性.本文针对这种基于骨干传输网的移动节点漫游问题,提出了一个新的随机漫游认证协议(RMRAP),兼顾安全性和实际应用的可行性,实现了漫游的轻量级身份认证,保护了漫游节点的隐私,同时实现了具有前向安全性,会话密钥对;并针对衔接骨干网和感知子网的基站进行了组合安全性的认证测试,验证了RMRAP的安全性;最后,从理论分析和实验仿真两个方面,分析了RMRAP协议的性能,并和相近工作进行了对比,对比表明,具有组合安全性的RMRAP在计算、通信开销方面,依然具有和同类协议可比较的相近性能.     

非概率模型中基本区间变量的重要性测度

针对区间变量情况下的非概率可靠性模型,提出一种基本区间变量对系统非概率可靠性指标影响的非概率重要性测度.所提非概率重要性测度可以直接全面地反映基本区间变量对结构安全影响的重要程度,从而指导工程设计.文中分析非概率重要性测度的基本性质,而后基于蒙特卡洛方法和区间模型非概率可靠性指标的一维优化算法,提出非概率重要性测度的求...     

随机不确定分布参数下随机可靠度的超限概率模型研究

针对分布参数具有随机不确定性时可靠度也有随机性的问题,建立给定约束可靠度情况下新的失效概率度量指标,该指标可以反映随机可靠度小于约束可靠度的可能性,从而可以更客观地反映随机不确定性分布参数下结构失效的可能性.基于三点估计建立新度量指标的求解方法,给出方法的原理及实现步骤.与通用数字模拟方法相比,所建立的新指标求解的三点...     

几何非线性问题的无网格法分析

用局部Petrov-Galerkin方法求解几何非线性问题,这是一种真正的无网格方法。这种方法采用移动最小二乘近似函数作为试函数;只包含巾心在所考虑点处的规则局部区域上以及局部边界上的积分;所得系统矩阵是一个带状稀疏矩阵。该方法可以容易推广到求解非线性问题以及非均匀介质力学问题。在涉及几何非线性问题的数值方法中,通常都采用增量和迭代分析的方法。本文从虚功原理出发,用移动最小二乘近似函数的权函数替代虚位移,并在整个分析过程中所有变量的表达格式都是采用全拉格朗日格式。数值算例表明,无网格局部Petrov-Galerkin方法在求解几何非线性问题时仍具有很好的精度。     

不确定性分布参数情况下可靠性特征值分析模型及其点估计求解方法

针对工程中普遍存在的基本变量分布参数具有不确定性的问题,建立分布参数为服从某种分布随机变量情况下的可靠性特征值分析模型,并采用点估计建立可靠性特征值模型的求解方法.当基本变量的分布参数为服从某种分布的随机变量时,传统上定义的失效概率亦变成随机变量,此时可以从失效概率随机变量的均值和标准差等特征值来重新认识和度量结构失效的可能性.在提出可靠性的特征值分析模型后,首先建立特征值分析模型的通用数字模拟法.并基于已有的三点估计建立失效概率均值和标准差的单重与双重矩估计方法.在给出所建模型求解方法的实现过程后,通过数值算例、工程算例来说明模型的合理性以及所提求解方法的精度和效率.相对于通用数字模拟方法,单重矩方法和双重矩方法在求解失效概率的一阶和二阶特征值时具有较高的效率,而且矩方法比较简单,计算过程中不需要迭代和求导,可以很方便地应用于分布参数具有不确定性的可靠性分析问题.