双足机器人行走稳定性研究

双足机器人行走的稳定性是双足行走最为重要的衡量指标之一.针对传统的基于零力矩点（ZMP）步态稳定性判据方法,分析了ZMP、COP的相互关系,表明在双足机器人与水平地面无粘性力和无吸附力作用下,其ZMP即为压力中心点COP.基于具有足趾关节的双足机器人足底支撑面多种变化,提出对多点接触时支撑多边形区域描述.结合ZMP/COP、COG的在支撑面内相对位置,提出了基于ZMP/COP、COG的综合稳定性判据.经仿真分析,与传统单一的ZMP稳定性判据相比,该综合稳定性判据能够更为准确地反映步态的稳定性.     

Orientation angle workspaces of planar serial three-link manipulators

This paper presents a classification on the workspaces of planar serial three-link manipulators, that is, position workspace and orientation angle workspace. Position workspace indicates the region reached by the reference point on the end-effector. Orientation angle workspace indicates a set of angle ranges by which the end-effector can reach with certain orientation for every point in the reachable position workspace. By introducing a virtual equivalent mechanism, reachable position workspace can be divided into several Grashof intervals and non-Grashof intervals. The calculation equations of orientation angle workspace are deduced in three situations according to the relationships among four link lengths in the virtual four-bar chain. Three examples are given for three kinds of relationship of link lengths. The orientation angle workspace of extended groups, that is, two of the three link lengths equal, and the orientation angle workspace when the reference point on the end-effector moves along a non-radial direction are also discussed. A program is developed to calculate orientation angle workspaces and output variation curves of orientation angle workspace and key data within the position workspace. The approach and program in this paper can be used for fast calculation and identification of the variation rule of the orientation angle workspace of any given planar serial three-link manipulator on the basis of its link parameters, and for the design of a highly dexterous serial manipulator with proposed link relations. Supported by the Natural Science Foundation of Shanxi Province (Grant No. 20041070)     

Construction of highly nonlinear resilient Boolean functions satisfying strict avalanche criterion

Boolean functions with high nonlinearity, high resiliency and strict avalanche criterion （SAC） play an important role in the designs of conventional cryptographic systems. In this paper, a method is proposed to construct resilient Boolean functions on n variables （n even） satisfying SAC with nonlinearity 〉 2n-1 -2n/2. A large class of cryptographic Boolean functions that were not known earlier were obtained.     

基于高斯滤波器组混合特征的录音回放攻击检测研究

录音回放是目前声纹识别技术应对各种仿冒语音攻击的主要手段。针对传统语音特征无法区分真实语音和回放语音的问题,提出一种基于高斯滤波器组的Fisher比混合倒谱特征提取算法。将高斯滤波器组代替传统三角滤波器组,分别采用线性频率和逆ERB频率替换MEL频率,形成高斯线性频率倒谱系数特征（G-LFCC）和高斯逆ERB频率倒谱系数特征（G-IEFCC）两个新的特征。通过Fisher准则将G-LFCC和G-IEFCC融合,生成新的混合特征参数,该特征提高了真实语音和回放语音在高频段的区分度,同时降低回放语音在低频段因不同录音及回放设备造成的干扰。在ASVSpoof2017评测数据上的实验结果表明,该算法混合特征具有较好的区分效果,与IMFCC、LFCC、CQCC和GSV等算法相比,等错误概率分别降低21.8%、38.8%、58.3%和43.7%。     

Extraction of locked-up coal by strengthening of rib pillars with FRP——A comparative study through numerical modelling

In some of the coalfields in India, coal seams are only developed but no extraction of pillars is possible due to the presence of surface or sub-surface structures and also non-availability of stowing materials which leads to huge amounts of coal being locked-up underground. Spontaneous heating and fire, accumulation of poisonous gases, severe stability issues leading to unsafe workings and environmental hazards are the major problems associated with the developed coal pillars. So, there is a pressing need for a technology for the mining industry to extract the huge amount of coal locked-up under different constraints. In this study, the locked-up coal is proposed to be extracted by artificially strengthening the rib pillars. The detailed comparative study is carried out to know the increase of extraction percentage of locked-up coal by strengthening the rib pillars with FRP. Extraction methodology is designed and studied through numerical modelling for its stability analysis to evaluate its suitability of application in underground.     

裂纹起裂角预测方法研究

本文提出一个新的屈服准则,该屈服准则适用于岩石类材料的小范围屈服,旨在预测弹塑性材料的破坏行为,基于该屈服准则,推导出了I型,II型以及I-II混合型裂纹尖端塑性区半径并对在单轴拉伸和纯剪切等荷载作用下的裂纹尖端塑性区进行了分析。结果显示,荷载加载方式、裂纹倾斜角和材料内摩擦角对塑性区的形状与大小有显著影响。根据对裂纹尖端塑性区的分析,基于如下假设：裂纹沿塑性区最短路径扩展,本文在提出的屈服准则的基础上导出了新的断裂准则,该准则可预测裂纹开裂初始角。相较于其他断裂准则,文献实验结果与本文提出的准则吻合地更好,能更加精确的预测裂纹的起裂角。     

基于加权处罚的K-均值优化算法

在各种聚类算法中,基于目标函数的K-均值聚类算法应用最为广泛,然而,K-均值算法对初始聚类中心特别敏感,聚类结果易收敛于局部最优。为此,提出基于加权处罚的K-均值优化算法。每次迭代过程中,根据簇的平均误差的大小为簇分配权值,构造加权准则函数,把样本分给加权距离最小的簇中。限制簇集中出现平均误差较大的簇,提高聚类准确率。实验结果表明,该算法与K-均值算法、优化初始聚类中心的K-均值算法相比,在含有噪音的数据集中,表现出更好的抗噪性能,聚类效果更好。     

Study on influencing factors of adapters separating with the underwater missile

To analyze main factors affecting the separation reliability between a missile and adapters for the launching process, a six DOF underwater dynamic model for the missile and adapters is utilized to simulate the separation process, considering elastic forces of separating springs, hydrodynamic forces, gravity and buoyancy. Moreover, a criterion based on the maximum separating distance is put forward to determine whether adapters separate with the missile reliably. The results show that the magnitude and position of elastic force, the wedge angle and mass of the adapter significantly affect the separating process. The local sensitivity analysis for the reference status of design parameters demonstrates that the wedge angle of adapters has the maximum influence about 70.4% on the separating distance.     

多体量子态全可分的一个纠缠判据

研究了量子信息理论中多体量子态的纠缠探测问题.利用量子系统上的局域正交可观测量算子,以及多体复合系统的局域不确定关系和斜信息,讨论了有限维情形多体复合系统中全可分量子态与其关系.得到了多体量子态全可分的若干必要条件,推广了有限维两体量子系统的相应结果,获得了识别多体量子态纠缠性的一些方法.     

土的剪切动态空间滑动面及其强度准则分析

提出了多种动态空间滑动面及其相应的强度准则,分析了不同强度准则应力空间描述的强度破坏面,探讨了在多种动态空间滑动面下土强度准则的变化可能性及实用性。结果表明:对于方次动态空间滑动面,随着方次越高,其动态空间滑动面越垂直于小主应力坐标轴,平行于大主应力和中主应力平面,空间面上的正应力越来越接近于小主应力,而剪应力越来越退化;对于开方次空间滑动面,随着开方次越高,其空间滑动面越接近于正八面体面,空间面上的正应力和剪应力越来越平均化;对于方次空间滑动面强度准则,随着方次越高,其对应强度准则破坏面的规律性越来越差,强度准则随参数的变化也越来越敏感,只有在特定参数条件下其空间面才具有较好的规律性;对于开方次空间滑动面,随着开方次越高,越来越均化了三个主应力的贡献,开方次的次数和土的结构性强弱相关。