深锥形槽体对细粒煤干扰沉降分级实验研究

本文重点研究了自制深锥形干扰沉降分级机在不同影响因素下对细粒煤的分级效率,结果表明:底部和中部同时给水形式的设计有利于细粒煤分级,底部与中部给水量比值对分级效率有一定影响但不明显;给料速度及浓度值越低,细粒煤分级效率越高。该装置的适宜分级条件为流量配比2∶1、给料速度0.50m/s、矿浆浓度40%时,粒级级配(0.25~0.125mm和1.0~0.5mm)分级效率接近65%,较常规分级旋流器分级效率50%~60%提高约5%~15%,实验结果表明深锥形干扰沉降分级机可有效实现细粒煤的分级。     

Quality assurance and quality control of subgrade compaction using the dynamic cone penetrometer

The Dynamic Cone Penetrometer (DCP) is a device that is used in the construction industry for the assessment of in situ soil compaction quality. Over the past few decades, numerous correlations have been developed between the DCP test results and soil strength and stiffness parameters. This paper proposes a comprehensive set of criteria and recommendations for quality control (QC) of compacted subgrade that take into account the inherent statistical variability of DCP test results. For the development of the QC criteria, a new statistical methodology is used to extract representative test values from the raw field DCP test data. In order to use the proposed QC criteria, soils are first classified into two broad categories (fine-grained and coarse-grained) depending on their fabric and response to compaction efforts. Test results indicate that (i) for fine-grained soils, the DCP test values have good correlation with the plasticity index (PI), which is indicative of the type and amount of clay content of the soil and (ii) for coarse-grained soils, the DCP test values have good correlation with the optimum water content of the soil, which is directly related to its in situ density. DCP blow count correlation equations are presented for both soil categories. Recommendations for field DCP testing and data analysis are also provided to highlight the significance of the statistical distribution of the DCP test results in QC testing of compacted subgrade.     

基于3DEC的结构面对采空区的影响机制

Ⅳ级结构面是构成岩块的边界面,影响着地下工程岩体的物理力学性质及应力分布状态。基于3DEC离散元软件,在特定的采空区应力场下,针对单组结构面以及多组结构面中可产生滑塌锥的情况分别开展了研究。结果表明:1)单组结构面对采空区的影响形式为滑移破坏,随着结构面倾角的增大,采空区顶板最大位移先增大后减小。2)多组结构面形成滑塌锥后并不一定意味着塌落,在黏聚力以及内摩擦角较大时滑塌锥仍然可以保持稳定;在黏聚力—内摩擦角—滑塌锥位移的三维曲面图中,形成稳定区、塌落区、滑移区三类。3)利用极限平衡理论对滑塌锥的稳定性进行力学分析,提出滑塌锥失稳的判定条件,具有一定的工程实用价值。     

海冰载荷作用下风力机抗冰锥体减载研究

提出了锥体抗冰结构来降低海冰对风力机结构的影响。以NREL 5 MW近海三叶片水平轴风力机为研究对象,基于Ralston算法建立冰载荷模型,采用开源多体动力学软件FAST计算塔架结构动力学响应,研究了不同锥角抗冰结构下塔顶位移和塔架载荷特性。结果表明:锥体结构能有效地缓解由海冰造成的危害,塔架剪切力、海冰载荷及塔顶位移随锥角的降低而减小,锥角由70°降至40°,海冰载荷降低55%~98%;安装锥体前后,塔架剪切力减小28.7%~58.9%,塔顶位移最多减小46%。     

A novel minimum weight formulation of topology optimization implemented with reanalysis approach

In this paper, we develop an efficient diagonal quadratic optimization formulation for minimum weight design problem subject to multiple constraints. A high-efficiency computational approach of topology optimization is implemented within the framework of approximate reanalysis. The key point of the formulation is the introduction of the reciprocal-type variables. The topology optimization seeking for minimum weight can be transformed as a sequence of quadratic program with separable and strictly positive definite Hessian matrix, thus can be solved by a sequential quadratic programming approach. A modified sensitivity filtering scheme is suggested to remove undesirable checkerboard patterns and mesh dependence. Several typical examples are provided to validate the presented approach. It is observed that the optimized structure can achieve lighter weight than those from the established method by the demonstrative numerical test. Considerable computational savings can be achieved without loss of accuracy of the final design for 3D structure. Moreover, the effects of multiple constraints and upper bound of the allowable compliance upon the optimized designs are investigated by numerical examples.     

Ease-off拓扑修正的准双曲面齿轮齿面修形方法

为了提升驱动桥准双曲面齿轮传动的啮合性能，针对准双曲面齿轮刀倾半展成法(HFT)提出一种Ease-off拓扑修正方法。在建立齿面共轭啮合数学模型的基础上，推导出小轮基准齿面方程，通过计算小轮实际齿面与基准齿面之间的偏差，构建出Ease-off拓扑。借助二阶多项表达式对Ease-off拓扑分解，计算出齿面失配系数，通过调整齿面失配系数构建出修正Ease-off拓扑。通过比较当前Ease-off拓扑与修正Ease-off拓扑，消除小轮当前齿面与修正齿面之间的偏差，反求出小轮加工参数。最后以一对准双曲面齿轮为例进行齿面拓扑修形与磨齿加工，实际齿面印痕与仿真结果一致，验证了齿面拓扑修形方法的有效性。齿面加载接触分析结果表明，修形后齿面接触应力分布得到了改善，实际载荷下齿面接触重合度增加，从而验证了修形方案的合理性。     

高速率通信网络下时变系统的有限时域H∞控制

针对高速率通信网络和Round-Robin（RR）协议影响下网络化时变系统的有限时域[H∞]控制问题，考虑到系统中存在乘性噪声、随机时滞和量化效应，提出了一种基于观测器的有限时域[H∞]控制器的设计方法。利用李雅普诺夫稳定性理论和线性矩阵不等式（Linear Matrix Inequality，LMI）技术得到有限时域[H∞]控制器存在的充分条件。基于锥补线性化（Cone Complementarity Linearization，CCL）方法通过求解一组递归矩阵不等式得到观测器和控制器参数。所设计的控制器保证闭环网络化时变系统在给定的时域内稳定，且满足预定的[H∞]性能指标。数值仿真验证了所提方法的有效性。     

Numerical verification of the continuous calculation method for tip stress during the driving process of the dynamic penetration test

This paper presents a calculation method for obtaining the continuous variation in stress between the tip and the soil during dynamic penetration tests, particularly in the case of using the Panda 3® penetration testing device. The originality of the method is that the tip stress can be computed continuously throughout the driving process. For each impact of the hammer on the penetrometer, data are recorded by sensors located at the top of the apparatus. Then, the stress at the tip and the displacement of the apparatus are calculated with a method based on the propagation of waves in the device. A three-dimensional numerical model of the penetration test, based on the Panda 3® specifications and using the discrete element method (DEM), is proposed in this paper. The purpose of the simulations is to validate the calculation method by comparing the curves of the tip stress versus the penetration distance obtained in two different ways, the first being the distance directly observed at the tip and the second being the distance calculated from the data recorded at the top of the penetrometer, as with the experimental device. The entire apparatus is represented, including the hammer, the rod, and the tip, and is driven into the model soil. The calculation method is applied, and the results are compared to the actual response of the soil to the driving of the penetrometer directly at the tip, which can be obtained with the numerical model. The responses are found to be very similar, confirming the theoretical framework and its underlying assumptions. This method is applied to dynamic penetration tests and provides the opportunity to obtain mechanical parameters other than the tip resistance from the tests.     

大地电磁测深阶段式自适应正则化反演

如何合理确定正则化因子一直是地球物理反演的研究热点和难点。从提高反演稳定性的角度对正则化因子的选择进行考量，是确定正则化因子取值的新思路。此外，以往的正则化反演研究对非线性优化算法的随机性考虑不足。基于此，以Zhdanov提出的自适应算法为框架，提出了一种新的自适应正则化算法，即阶段式自适应算法，按照“阶段”自适应地调整正则化因子。将此方法分别应用于大地电磁测深（MT）的共轭梯度和差分进化算法（DE）反演。模型试验表明该算法可以提高反演的稳定性，在一定程度上降低衰减因子的影响，而且该算法具有同时适用于线性和非线性优化算法的特点。     

三维一阶速度-应力声波方程全波形反演

基于时间域三维一阶速度—应力声波方程，采用基于摄动理论的伴随状态法，推导出时间域三维一阶速度—应力声波方程的伴随方程及相应的纵波速度的梯度计算公式，并采用交错网格有限差分法计算正向传播波场及逆时外推的伴随波场，进而计算出纵波速度的梯度，在此基础上采用共轭梯度法更新纵波速度模型，实现了基于一阶速度—应力声波方程的三维全波形反演方法。由于基于一阶速度—应力声波方程，该方法能够方便地采用交错网格有限差分法求解。由于基于GPU在时间域实现，波场正向传播及逆时外推时较直接、快速。模型测试结果证明了方法的可行性和有效性。