Effects of the initiation position on the damage and fracture characteristics of linear-charge blasting in rock

To study the effects of the initiation position on the damage and fracture characteristics of linear-charge blasting, blasting model experiments were conducted in this study using computed tomography scanning and three-dimensional reconstruction methods. The fractal damage theory was used to quantify the crack distribution and damage degree of sandstone specimens after blasting. The results showed that regardless of an inverse or top initiation, due to compression deformation and sliding frictional resistance, the plugging medium of the borehole is effective. The energy of the explosive gas near the top of the borehole is consumed. This affects the effective crushing of rocks near the top of the borehole, where the extent of damage to Sections Ⅰ and Ⅱ is less than that of Sections Ⅲ and Ⅳ. In addition, the analysis revealed that under conditions of top initiation, the reflected tensile damage of the rock at the free face of the top of the borehole and the compression deformation of the plug and friction consume more blasting energy, resulting in lower blasting energy efficiency for top initiation. As a result, the overall damage degree of the specimens in the top-initiation group was significantly smaller than that in the inverse-initiation group. Under conditions of inverse initiation, the blasting energy efficiency is greater, causing the specimen to experience greater damage. Therefore, in the engineering practice of rock tunnel cut blasting, to utilize blasting energy effectively and enhance the effects of rock fragmentation, using the inverse-initiation method is recommended. In addition, in three-dimensional(3D) rock blasting, the bottom of the borehole has obvious end effects under the conditions of inverse initiation, and the crack distribution at the bottom of the borehole is trumpet-shaped. The occurrence of an end effect in the 3D linear-charge blasting model experiment is related to the initiation position and the blocking condition.

HY-PC:Enabling Consistent Positioning and Communication Using Visible Light

Visible light(VL)plays an important role in achieving high-precision positioning and low bit error radio(BER)data communication.However,most VL-based systems can not achieve positioning and communication,simultaneously.There are two problems:1)the hybrid systems are difficult to extract distinguishable positioning beacon features without affecting communication performance,2)in the hybrid systems,the lost data bits in the inter-frame gap(IFG)are hard to recover,which affects positioning and communication performance.Therefore,in this article,we propose a novel VL-based hybrid positioning and communication system,named HY-PC system,to solve the above problems.First,we propose the robust T-W mapping for recognizing specific Light Emitting Diodes(LEDs),which can provide stable LED recognition accuracy without adding extra beacon data and does not decrease the communication rate.Furthermore,we also propose the novel linear block coding and bit interleaving mechanism,which can recover the lost data bits in the IFG and improve data communication performance.Finally,we use commercial off-the-shelf devices to implement our HY-PC system,extensive experimental results show that our HY-PC system can achieve consistent high-precision positioning and low-BER data communication,simultaneously.

Novel Linear Piezoelectric Motor for Precision Position Stage

Conventional servomotor and stepping motor face challenges in nanometer positioning stages due to the complex structure, motion transformation mechanism, and slow dynamic response, especially directly driven by linear motor. A new butterfly-shaped linear piezoelectric motor for linear motion is presented. A two-degree precision position stage driven by the proposed linear ultrasonic motor possesses a simple and compact configuration, which makes the system obtain shorter driving chain. Firstly, the working principle of the linear ultrasonic motor is analyzed. The oscillation orbits of two driving feet on the stator are produced successively by using the anti-symmetric and symmetric vibration modes of the piezoelectric composite structure, and the slider pressed on the driving feet can be propelled twice in only one vibration cycle. Then with the derivation of the dynamic equation of the piezoelectric actuator and transient response model, start-upstart-up and settling state characteristics of the proposed linear actuator is investigated theoretically and experimentally, and is applicable to evaluate step resolution of the precision platform driven by the actuator. Moreover the structure of the two-degree position stage system is described and a special precision displacement measurement system is built. Finally, the characteristics of the two-degree position stage are studied. In the closed-loop condition the positioning accuracy of plus or minus 〈0.5 μm is experimentally obtained for the stage propelled by the piezoelectric motor. A precision position stage based the proposed butterfly-shaped linear piezoelectric is theoretically and experimentally investigated.

Stability and Robust Stability of Switched Positive Linear Systems With All Modes Unstable

This paper is concerned with the stability and robust stability of switched positive linear systems(SPLSs) whose subsystems are all unstable. By means of the mode-dependent dwell time approach and a class of discretized co-positive Lyapunov functions, some stability conditions of switched positive linear systems with all modes unstable are derived in both the continuous-time and the discrete-time cases, respectively. The copositive Lyapunov functions constructed in this paper are timevarying during the dwell time and time-invariant afterwards. In addition, the above approach is extended to the switched interval positive systems. A numerical example is proposed to illustrate our approach.

The linear position tracking servo systemusing a linear voice-coil motor

More and more linear servo systems have been used in servo applications. Direct drive technology can greatly increase the bandwidth and the tracking accuracy. A position servo-system based on linear voice-coil motor was designed for one linear oscillation movement application. Besides the conventional position, speed and current control loops, the speed and acceleration feed-forward control of command position signal were also used. The experimental test proved the correctness of the design, and the system can track the given periodic sinusoid position command signal of 15Hz with high accuracy. The linear voice-coil motor is very suitable for short stroke position tracking application with high dynamic response.

FINITE TIME BLOW UP OF THE SOLUTIONS TO BOUSSINESQ EQUATION WITH LINEAR RESTORING FORCE AND ARBITRARY POSITIVE ENERGY

Finite time blow up of the solutions to Boussinesq equation with linear restoring force and combined power nonlinearities is studied. Sufficient conditions on the initial data for nonexistence of global solutions are derived. The results are valid for initial data with arbitrary high positive energy. The proofs are based on the concave method and new sign preserving functionals.

New Stability Tests of Positive Standard and Fractional Linear Systems

New tests for checking asymptotic stability of positive 1D continuous-time and discrete-time linear systems without and with delays and of positive 2D linear systems described by the general and the Roesser models are proposed. Checking of the asymptotic stability of positive 2D linear systems is reduced to checking of suitable corresponding 1D positive linear systems. It is shown that the stability tests can be also applied to checking the asymptotic stability of fractional discrete-time linear systems with delays. Effectiveness of the tests is shown on numerical examples.

Improved Study on Position Measurement System for Linear Motor Applied in Electromagnetic Launch System

The linear motor applied in electromagnetic emission system uses a closed loop position control strategy,which needs a set of position measurement system with high reliability,high resolution and integration to achieve real-time acquisition and analysis of position signals.The existing position controller is based on the simple logic chip design without memory function,and does not have the storage analysis and preprocessing function to position signals.Therefore,the system has insufficient scalability,low integration and reliability.Aiming at the improvement of the existing position measurement system,an intelligent position measurement system integrating the functions of position signals acquisition,processing and uploading,data storage and analysis is proposed in this paper,and its working principle and system composition are discussed in detail.The position,speed and acceleration obtained on the electromagnetic emission platform are in good agreement with the expected value of the system.As results,the feasibility and accuracy of the improved integrated intelligent position measurement system are verified,and the control performance of the system is also satisfied well,which can be good guidance and reference for subsequent engineering practice.

THE SYMMETRIC AND SYMMETRIC POSITIVE SEMIDEFINITE SOLUTIONS OF LINEAR MATRIX EQUATION——B^TXB = D ON LINEAR MANIFOLDS

This paper discusses the solutions of the linear matrix equation BT X B=Don some linear manifolds.Some necessary and sufficient conditions for the existenceof the solution and the expression of the general solution are given.And also someoptimal approximation solutions are discussed.

MULTIPLE POSITIVE SOLUTIONS FOR A CLASS OF QUASI-LINEAR ELLIPTIC EQUATIONS INVOLVING CRITICAL SOBOLEV EXPONENT

In this paper, we study the multiplicity results of positive solutions for a class of quasi-linear elliptic equations involving critical Sobolev exponent. With the help of Nehari manifold and a mini-max principle, we prove that problem admits at least two or three positive solutions under different conditions.

A PARALLEL IMAGINARY EBE METHOD FOR SOLVING POSITIVE DEFINITE LINEAR SYSTEMS

A parallel imaginary EBE (element-by-element )method for solving positive definite linear systems is presented. The EBE strategy is originally used as a sequential method[1.2], and later it is converted to a parallelmethod for solving finite element problem in solid mechanics[3]. The main contribution of this paper is to forma general parallel EBE method for the solution of anyPOsitive definite linear system through a so-called imaginary finite element technique. It is then POssible to use.finite elemental without finite element.

A New Class of Generalized Landau Linear Positive Operator Sequence and Its Properties of Approximation

In this paper two sequences of generalized Landau linear positive operators are introduced. They can be applied in approximating continuous functions with arbitrary growth order, defined on a finite interval or the whole real axis. The properties of approximation are studied and their asymptotic formulae are presented. These results show that their degrees of approximation are the best among existing operator sequences of Landau type, for example, their degrees of approximation for C 2[0, 1] are O(1/n 2) but corresponding degree of ordinary Landau operators are only O(1/n).

Decoupling Zeros of Positive Discrete-Time Linear Sys-tems

The notions of decoupling zeros of positive discrete-time linear systems are introduced. The relationships between the decoupling zeros of standard and positive discrete-time linear systems are analyzed. It is shown that: 1) if the positive system has decoupling zeros then the corresponding standard system has also decoupling zeros, 2) the positive system may not have decoupling zeros when the corresponding standard system has decoupling zeros, 3) the positive and standard systems have the same decoupling zeros if the rank of reachability (observability) matrix is equal to the number of linearly independent monomial columns (rows) and some additional assumptions are satisfied.

Control of magnetic levitation positioning stage with an eddy current damper

To enhance the system damping,a permanent magnet set which served as an eddy current damper was added to the magnetic levitation positioning stage which consists of a moving table,four Halbach permanent magnetic arrays,four stators and displacement sensors.The dynamics model of this stage was a complex nonlinear,strong coupling system which made the control strategy to be a focus research.The nonlinear controller of the system was proposed based on the theory of differential geometry.Both simulation and experimental results show that either the decoupling control of the movement can be realized in horizontal and vertical directions,and the control performance was improved by the damper,verifying the validity and efficiency of this method.

Asymptotic Stability of 2-D Positive Linear Systems with Orthogonal Initial States

这份报纸处理 2-D 的 asymptotic 稳定性有直角的起始的状态的积极线性系统。与 1-D 系统不同，有直角的起始的状态 x 的 2-D 系统的 asymptotic 稳定性(我， 0 )， x ( 0 ， j )( Fornasini-Marchesini ( FM )模型)或 xv (我， 0 )， xh ( 0 ， j )( Roesser 模型)严格地依赖于合适的边界条件。第一，为 2-D 的一个 asymptotic 稳定性标准积极 FM 首先，模型被使起始的状态成为 x 介绍(我， 0 ) ， x (0， j ) 绝对会聚。然后，类似的结果也与任何绝对会聚的起始的状态 xv 为 2-D 被给积极 Roesser 模型(我， 0 ) ， xh (0， j ) 。最后，二个例子被给显示出这些标准的有效性并且由造成指数地会聚的起始的状态表明轨道的集中。

EXISTENCE OF POSITIVE SOLUTIONS TO QUASI-LINEAR EQUATION INVOLVING CRITICAL SOBOLEV-HARDY EXPONENT

This paper is concerned with the quasi-linear equation with critical Sobolev-Hardy exponent whereΩ(?)RN(N(?)3)is a smooth bounded domain,0∈Ω,0(?)s<p,1<p<N,p(s):=p(N-s)/N-p is the critical Sobolev-Hardy exponent,λ>0,p(?)r<p,p:=Np/N-p is the critical Sobolev exponent,μ>,0(?)t<p,p(?)q<p(t)=p(N-t)/N-p.The existence of a positive solution is proved by Sobolev-Hardy inequality and variational method.

强流脉冲束流位置探测器标定技术

电子直线感应加速器性能提升对束流探测器提出了高精度测量要求,由此不仅要求高精度的探测器设计装配技术,而且也要求探测器的准确标定。从强流脉冲束流位置探测器测量原理出发,从理论和实验两方面开展强流脉冲束流位置探测器标定技术研究。在理论上采用解析方法,分析了不同的计算处理方法和标定方法的标定效果,提出了特征平面标定,在建立的位置标定系统上,对用于多脉冲电子直线感应加速器的No.23电阻环进行了标定实验研究,实验结果验证了理论分析结果,根据理论和实验研究结果,确定了强流脉冲束流位置探测器标定方法。

位置标签增强的中文医学命名实体级联识别

针对一般领域的命名实体识别方法不能直接用于中文医学专业实体的识别,现有的相关研究只专注于英文文本和扁平结构的医学实体识别等问题,通过对专业领域实体识别方法的研究,结合中文医学实体的特点提出了一种面向中文医学实体的级联识别方法。将每个字符元素相对于实体的位置标签嵌入模型,并结合中文医学实体跨度内不同元素的重要程度进行实体的融合表示。通过序列标注方法检测字符的位置标签,利用字符的位置信息指导候选实体生成,并进行实体语义分类。模型在CMeEE和CCKS2018数据集以及中文糖尿病科研文献数据集上分别进行扁平实体、嵌套实体和不连续性长实体的识别实验。实验结果表明,该方法能够有效地识别中文医学文本中不同结构的实体。

具有执行器饱和的正线性系统的事件触发控制

尽管事件触发控制策略在提升通信效率方面效果显著,但在实际运用过程中,可能会因为触发次数的减少而导致系统稳定性下降.针对这一问题,本文提出了一种新的事件触发控制策略,实现了执行器饱和正线性系统在通信效率和系统稳定性之间的平衡.首先,引入权重因子构建了一种线性加权事件触发机制,并基于该机制和凸包技术设计了事件触发状态反馈饱和控制器;其次,利用线性余正Lyapunov函数方法,在事件触发机制下分别建立了一般吸引域估计和最大吸引域估计下闭环系统正性和稳定性的充分条件.这些条件可以退化为时间触发机制下的条件,从而实现通信效率和系统性能之间的平衡;再次,给出了事件间隔时间的严格正下界,从而避免了Zeno行为,即系统在有限时间内进行无限次触发;最后,通过一个仿真例子验证了所提出的事件触发控制策略的有效性和优越性.

基于反馈变换与积分反演PMSLM强鲁棒位置控制

为提高永磁同步直线电机位置控制系统的鲁棒性能,设计基于反馈线性化变换解耦系统的积分反演控制器。首先定义新的中间状态变量,通过状态反馈将永磁同步直线电机系统线性化解耦变换为带有非线性扰动状态的串联积分系统,避免常规反馈解耦时未知系数扰动状态无法补偿的问题;其次依据Lyapunov稳定条件设计反演控制器,在各级子系统的中间虚拟控制量的设计中加入积分环节,提高系统控制精度,并利用稳定条件设计扰动自适应律,估计并补偿系统扰动,提高永磁同步直线电机控制系统的鲁棒性能。最后搭建基于半实物仿真控制系统的试验平台,通过试验验证所提方法的正确性和有效性。