滑动摩擦力作用下弹簧振子的振动

对在粗糙水平面上作振动的弹簧振子进行研究,探讨该弹簧振子最后停止的位置,估算了弹簧振子的振动总次数,得出弹簧振子的相轨迹.     

基于Phyphox的气垫导轨上弹簧振子的阻尼系数研究

组装ESP32开发板和超声波测距传感器,让装有Phyphox软件的智能手机通过蓝牙接收传感器的信号,研究弹簧振子在气垫导轨上做阻尼运动中不同挡板面积对阻尼系数的影响。实验结果显示,阻尼系数与挡板面积呈线性关系。     

用“光具座”组装简易弹簧振子

"光具座"在高中用途太少,放着浪费.采用通用技术设计理念,拓宽光具座用途,用其组装的"单弹簧振子"和"双弹簧振子",能节省经费,满足教学要求,还能启发学生的创新意识,培养技术与学科结合能力,提高综合技术素养.     

弹簧振子实验研究

将焦利秤和转动惯量实验中的光电计时器相结合,增加一个新的实验项目———研究弹簧振子的周期变化规律,以求得弹簧的劲度系数和弹簧的有效质量.     

用计算机演示弹簧振子的简谐振动

本文介绍了一种用计算机演示弹簧振子简谐振动的简单方法。     

用振动旋转矢量和波动旋转矢量描述驻波波形

提出一种利用振动旋转矢量和波动旋转矢量来描绘驻波波形的方法,其特点是简单而直观．     

用计算机研究弹簧振子的运动规律

用计算机C语言程序建立一个弹簧振子模型 ,运用数值计算方法计算运动方程中的各个物理量 ,以研究弹簧振子的运动规律     

利用DISLab进行弹簧振子简谐运动实验条件的研究

利用DISLab研究弹簧振子简谐运动中力和位移随时间变化的关系,发现弹簧在振动过程中回复力存在滞后现象.本文通过设计实验,研究了弹簧的劲度系数、振子质量和振幅对回复力滞后的影响.     

浅谈平面振子的阻尼运动

从动力学方程出发并结合Mathcad数值计算,研究了平面振子的阻尼运动,并分析了阻尼系数对平面振子运动轨迹的影响.     

用Audition软件辅助测量弹簧振子的振动周期

介绍利用adobe audition 1.5软件测量弹簧振子的周期,研究周期与质量的关系.该方法能将测量值精确到0.001,从而提高实验精确度.     

弹簧振子在定常干摩擦阻尼作用下的振动

首先给出了弹簧振子在定常干摩擦阻尼作用下的振动微分方程,并通过分段求解,归纳出其在各个阶段的解的一般形式,然后分析了振动的基本规律,作出了振动的图象。     

Microstructural evolution of AZ31 magnesium alloy subjected to sliding friction treatment

Microstructural evolution and grain refinement mechanism in AZ31 magnesium alloy subjected to sliding friction treatment were investigated by means of transmission electron microscopy. The process of grain refinement was found to involve the following stages: (I) coarse grains were divided into fine twin plates through mechanical twinning; then the twin plates were transformed to lamellae with the accumulation of residual dislocations at the twin boundaries; (II) the lamellae were separated into subgrains with increasing grain boundary misorientation and evolution of high angle boundaries into random boundaries by continuous dynamic recrystallisation (cDRX); (III) the formation of nanograins. The mechanisms for the final stage, the formation of nanograins, can be classified into three types: (i) cDRX; (ii) discontinuous dynamic recrystallisation (dDRX); (iii) a combined mechanism of prior shear-band and subsequent dDRX. Stored strain energy plays an important role in determining deformation mechanisms during plastic deformation.     

弹簧振子实验方法的运用和改进

对弹簧振子振动周期经验公式的实验拟合中所用的实验方法进行了总结,对部分实验方法和实验装置进行了改进。     

Effects of non-flat contact and interference on self-assembled monolayers under sliding friction

The nanotribology mechanism of alkanethiol self-assembled monolayers (SAM) chemisorbed on a gold surface under a non-flat contact by a tilt plane was studied using molecular dynamics (MD) simulations. The molecular trajectories, tilt angles, normal forces, shear forces, and frictional coefficient of the SAM were evaluated during the friction and relaxation processes for various parameters, including the tilt angle of the slider, interference magnitude, and SAM length. At the nanoscale, the magnitude of interface interactional forces is strongly dependent on the magnitude of the contact area, not on the surface geometry. The contact area and the exerted normal force of the SAM increase with decreasing the tilt angle of the slider at the same contact interference. In contrast, the periods in both normal force and shear force are gradually delayed as the tilt angle of the slider increases. Once the contact interference increases, the normal force and shear force increase together. During the sliding friction process with a smaller tilt slider angle, SAM molecules can maintain a better collective ordered structure. Short SAM molecules are more sensitive to a compressive loading and react to a larger normal force under the same contact interference due to the deformation of a larger tilt angle and decrease in chain length. The friction coefficient of SAM is significantly more dependent on the tilt angle of the slider than the contact interference.     

Dynamic polarization rotation and vector field steering based on phase change metasurface

Polarization rotation and vector field steering of electromagnetic wave are of great significance in modern optical applications. However, conventional polarization devices are bulky, monofunctional and lack of tunability, which pose great challenges to the miniaturized and multifunctional applications. Herein, we propose a meta-device that is capable of multi-state polarization rotation and vector field steering based on phase change metasurface. The supercell of the meta-device consists of four Ge₂Sb₂Te₅ (GST) elliptic cylinders located on a SiO₂ substrate. By independently controlling the phase state (amorphous or crystalline) of each GST elliptic cylinder, the meta-device can rotate the polarization plane of the linearly polarized incident light to different angles that cover from 19.8° to 154.9° at a wavelength of 1550 nm. Furthermore, by merely altering the phase transition state of GST elliptic cylinders, we successfully demonstrated a vector field steering by generating optical vortices carrying orbital angular momentums (OAMs) with topological charges of 0, 1 and −1, respectively. The proposed method provides a new platform for investigating dynamically tunable optical devices and has potential applications in many fields such as optical communications and information processing.     

Heat transfer and friction characteristics of solar air heater duct having protruded roughness geometry on absorber plate

Protruded roughness geometry is generally considered to be simple, an innovative and economic technique for improving thermal performance of solar air heater. Experimental investigation has been carried to study the effect of different shapes, position, and height of protrusions on heat transfer and friction characteristics of solar air heater duct for the range of parameters. Correlations for Nusselt number and friction factor have been brought out from the experimental data which can be further used for evaluating performance of solar air heater having the considered roughness geometry.     

Bound states of Klein—Gordon equation for double ring-shaped oscillator scalar and vector potentials

In spherical polar coordinates, double ring-shaped oscillator potentials have supersymmetry and shape invariance for θ and r coordinates. Exact bound state solutions of Klein—Gordon equation with equal double ring-shaped oscillator scalar and vector potentials are obtained. The normalized angular wavefunction expressed in terms of Jacobi polynomials and the normalized radial wavefunction expressed in terms of the Laguerre polynomials are presented. Energy spectrum equations are obtained.     

Heat transfer and friction factor correlation development for double-pass solar air heater having V-shaped ribs as roughness elements

In this present study, an experimental investigation has been carried out for a roughened double-pass solar air heater. The respective variation in other parameters, such as relative roughness pitch (p/e), relative roughness height (e/D_h), and angle of attack (α), were 5–20, 0.022–0.044, and 30°–75°, respectively. The effect of roughness and operating parameters on Nusselt number (Nu) and friction factor (f) has been determined, and the results are compared with those of a smooth absorber plate; considerable enhancement in both heat transfer and friction factor is noticed. Utilizing these experimental data, correlations for Nusselt number and friction factor correlations were also developed.     

Nonsingular terminal sliding mode approach applied to synchronize chaotic parameters and systems with unknown nonlinear inputs

This paper deals with the design of a novel nonsingular terminal sliding mode controller for finite-time synchro-nization of two different chaotic systems with fully unknown parameters and nonlinear inputs. We propose a novel nonsingular terminal sliding surface and prove its finite-time convergence to zero. We assume that both the master＇s and the slave＇s system parameters are unknown in advance. Proper adaptation laws are derived to tackle the unknown parameters. An adaptive sliding mode control law is designed to ensure the existence of the sliding mode in finite time. We prove that both reaching and sliding mode phases are stable in finite time. An estimation of convergence time is given. Two illustrative examples show the effectiveness and usefulness of the proposed technique. It is worthwhile noticing that the introduced nonsingular terminal sliding mode can be applied to a wide variety of nonlinear control problems.