A particle method with adjustable transport properties—the generalized consistent Boltzmann algorithm

The consistent Boltzmann algorithm (CBA) for dense, hard-sphere gases is generalized to obtain the van der Waals equation of state and the corresponding exact viscosity at all densities except at the highest temperatures. A general scheme for adjusting any transport coefficients to higher values is presented.     

An analytical particle damping model

Particle damping is a passive vibration control technique where multiple auxiliary masses are placed in a cavity attached to a vibrating structure. The behavior of the particle damper is highly non-linear and energy dissipation, or damping, is derived from a combination of loss mechanisms. These loss mechanisms involve complex physical processes and cannot be analyzed reliably using current models. As a result, previous particle damper designs have been based on trial-and-error experimentation. This paper presents a mathematical model that allows particle damper designs to be evaluated analytically. The model utilizes the particle dynamics method and captures the complex physics involved in particle damping, including frictional contact interactions and energy dissipation due to viscoelasticity of the particle material. Model predictions are shown to compare well with test data.     

Modeling and analysis of dual-chamber pneumatic spring with adjustable damping for precision vibration isolation

Dual-chamber pneumatic spring with adjustable damping (DCPS-AD) employs a variable orifice mechanism (VOM) to obtain the adjustable stiffness and damping characteristics. These adjustable characteristics are aimed at improving the performance of the pneumatic vibration isolation system (VIS). In order to understand thoroughly how the adjustable parameter of VOM affects the behavior of DCPS-AD, the model of DCPS-AD is derived analytically and validated experimentally. The influence of VOM on the performance of DCPS-AD is analyzed quantitatively. All the results demonstrate that VOM has the ability to vary complex stiffness distribution in frequency domain. Based on these results, the approach optimizing the performance of VIS is proposed, which is realized by adjusting VOM actively. Performance experimental measurements of VIS in frequency domain are carried out under different payload masses. The measurement results validate the proposed approach, which can optimize the performance of VIS when some application conditions varying.     

Soft hollow particle damping identification in honeycomb structures

The aim of this study is to provide a structural damping solution for space applications to enhance mission performance of honeycomb structures. Classical particle dampers are enclosures partially filled with small metallic or glass spheres, attached to a vibrating structure. The induced damping mechanism is mainly due to frictional losses and collision effects. This paper deals with replacing classical hard particles with soft hollow ones. This study is oriented toward experimental investigations and theoretical validation in order to distinguish dissipation phenomena. The experimental approach first relies on identifying the damping in small honeycomb samples filled with particles. Instead of dissipation by friction and impact, the elliptical shape of the measured hysteresis loops highlights that visco-elastic behavior is dominant with these specific soft particle dampers. Then, experimental and numerical validations are performed on aluminum honeycomb cantilever beams filled with particles. To take into account the effect of the particles, equivalent oscillators, based on the previous experimental damping identification, are added to a finite element model. These kinds of particle dampers are highly nonlinear as a function of excitation frequency and amplitude. It is shown that good damping efficiency is achieved across a large frequency range with low impact on structure stiffness. This paper suggests a convenient method to model the structural damping induced by soft hollow particles.     

灵敏度可调式压电薄膜水听器

本文介绍一种灵敏度可调式压电薄膜水听器，采用PVDF薄膜作为换能材料，聚碳酸脂作为背衬，薄膜粘贴在背衬的内壁，软性的背衬在声压的作用下形变。从而带动薄膜形变，产生电信号输出。水听器内装有前置放大器，调节放大器的负载电阻可调节水听器的灵敏度，灵敏度变化范围为出，水听器内装有前置放大器，100Hz-16kHz。     

A quantitative analysis on the energy dissipation mechanism of the non-obstructive particle damping technology

The non-obstructive particle damping (NOPD) technology has been recently developed from particle damping and impact damping technologies. In this paper, a quantitative analysis of the dissipation mechanism of NOPD based on a statistical theory is investigated for the first time to our knowledge. Under high-frequency vibrations, the dense granular motion of NOPD is very similar to turbulence. Thus, Kolmogorov's hypothesis in turbulence is adopted to describe the energy spectral density and velocity correlation function of the particles in the NOPD technology. It is shown that the NOPD's mean energy dissipation (per unit mass) increases with either the granular diameter or the volume ratio of the dense granular flow. The quantitative model for the NOPD technology presented in the paper should be useful in possible engineering applications of vibration reduction.     

半隐Euler法和隐中点法嵌入混合辛积分器的比较

当Hamilton函数分解为可积和不可积两部分时,前者能用分析方法给出解析解,而后者可借助一阶半隐Euler法或二阶隐中点法等数值求解,将这种解析和数值解法组合能构造二阶混合辛积分器.理论分析表明Euler嵌入法的稳定区要小于中点嵌入法的.再分别以圆形限制性三体问题和相对论自旋致密双星后牛顿Hamilton构型为例,详细比较了两嵌入法的性能特点.二者的数值精度、稳定性及计算效率与Hamilton的分解方式和轨道类型有关.就圆形限制性三体问题而言,当Hamilton采用势能和含坐标与动量混合项在内的动能分解 关键词： 辛积分器 后牛顿近似 自旋致密双星 混沌     

On mechanical motion damping of a magnetically trapped diamagnetic particle

We discuss eddy-current-induced limitations of the attenuation of mechanical motion of a diamagnetic particle trapped by an inhomogeneous magnetic field in the Earth's gravitational potential. We show that the mechanical frequency of the particle oscillation is independent on the particle properties and is proportional to the free fall acceleration constant, similarly to the classical mechanical pendulum. The frequency can be used to measure the gravity field. The eddy-current induced attenuation constant does not depend on the mass of the particle and reduces with the particle volume. The quality factor of the mechanical motion can be as high as 10⁹ and is comparable with the attenuation due to interaction of the particle with incompletely evacuated air. A possibility of usage of the particle as a quantum mechanical system is discussed.     

一种带可调光照部分的专用彩色图像处理系统

介绍了肺癌介入治疗模拟实验的专用彩色图像处理系统 ,硬件由可调光照部分、CCD摄像头、视频采集卡和微机四大部分构成。软件不仅可以进行一般的数字图像处理 ,而且针对肺癌介入治疗模拟实验中的特殊要求 ,设计了比例测量、导管口跟踪等专用功能。该系统除了用于肺癌介入治疗模拟实验 ,还可用做指导临床介入治疗 ,具有乐观的应用前景。     

A study on a micro mover driven by ultrasonic waves

In developing a mobile micro robot, it is important to realize an effective energy supply method. The existing general method is to supply energy from outside through a cable. However, supplying energy through a cable adds weight and restricts movement. Mounted energy sources, such as batteries, also add weight. We therefore propose a method of supplying energy to a robot externally without using a cable. Using the radiation of ultrasonic waves as a wave energy source, we devised a mover that can receive and use wave energy for propulsion. We investigated and clarified the movement this prototype mover through various experiments. Consequently, we proved the use of ultrasonic waves to be effective as a cable-free energy supply.     

颜色可调假彩色化新方法

本文提出一种颜色可调的密度假彩色编码的新光学方法.该方法是在光学相位调制密度假彩色编码方法的基础上,利用白光系统中双光栅的衍射效应和狭缝滤波技术,实现颜色可调的密度假彩色编码.给出了详细的理论分析,实验验证和实验结果.实践证明这是一种实用价值很高的方法.     

A derivation of the Christoffel equation with damping

This paper provides a derivation of the Christoffel eigenvalue equation for acoustic wave propagation in an acoustically damped piezoelectric medium. The damping tensor is shown to couple into both the stress and displacement constitutive equations. Application of the quasi-static approximation leads to an additional term in the Christoffel equation that generates a complex k-vector, due both to introduction of a complex term and to breaking of symmetry in the left-hand side of the eigenvalue equation, subsequently resulting in damping and a phase shift for a plane wave solution. Shown are the effects of damping on the eigenvalues of the piezoelectrically stiffened Christoffel equation for plane wave propagation in unconstrained quartz over a 1 MHz to 1 GHz frequency range.     

Stimulated second-order processes in the interaction of a spinless quantum particle beam with a self-consistent electromagnetic field

A nonlinear theory of interaction of two electromagnetic waves with a beam or a gas of spinless charged particles is developed. The effects of stimulated Compton scattering of electromagnetic waves and stimulated particle pair production (annihilation) during a collision of two electromagnetic quanta are investigated. Other stimulated processes that can occur only in a medium and decelerate electromagnetic waves are also considered. The relation between stimulated processes and various types of instabilities considered in classical electrodynamics of plasmas and plasmalike media is demonstrated.     

四温区温度可调制冷装置的制冷系统

在深冷区、冷冻区、冰温区及冷藏区蒸发器两端并联单向电磁阀实现三级分流以控制和分配制冷量,实现四温区温度可调,形成多种组合节能运行模式或延伸功能,同时减少主机开停机次数达到节能目的。     

脉冲间隔可调的双脉冲TEA CO2激光器

本文介绍一种新颖的TEACO_2激光器.它是采用共腔式结构,在一次激励下可获得脉冲时间间隔τ从0～15μs的连续可变的双脉冲、而无需气体循环的系统.本文还给出了该器件的结构、控制电路的设计特点,实验结果及结论.     

V-splitter with adjustable power splitting ratio

A novel graded-index silica-glass V-shape optical splitter is numerically demonstrated. The compact-size 1 × 2 V-splitter design and performance evaluation are performed using finite-difference-time-domain method. The power splitting-ratio can be adjusted during design by simply shifting the splitter input core laterally with respect to its V-shape apex location. The splitter shows good performance when tested over the S, C, L, U wideband wavelength range. It shows small excess-loss and reasonable return-loss with a polarization insensitive operation over the entire wideband range. The V-splitter is suitable for photonic integrated circuits and planer lightwave circuits aimed to applications in optical communications.     

A comment on quantum-mechanical damping

The question of introducing damping into quantum mechanics has come into prominence again. It is argued, from previous experience with the damping of a harmonic oscillator, that it is easy to violate the uncertainty principle, particularly if it is overlooked that absorbers are also emitters. The usual classical equations for a damped system are those for a smoothed variable, with the noise fluctuations subtracted. In the case of a damped harmonic oscillator the process of subtracting the noise and so defining a smoothed variable was examined many years ago, and to some extent can be used to justify present practice.     

Harmonic entanglement with second-order nonlinearity

We investigate the second-order nonlinear interaction as a means to generate entanglement between fields of differing wavelengths and show that perfect entanglement can, in principle, be produced between the fundamental and second-harmonic fields in these processes. Neither pure second-harmonic generation nor parametric oscillation optimally produce entanglement; such optimal entanglement is rather produced by an intermediate process.     

A novel micro accelerometer with adjustable sensitivity based on resonant tunneling diodes

Resonant tunnelling diodes (RTDs) have negative differential resistance effect, and the current--voltage characteristics change as a function of external stress, which is regarded as meso-piezoresistance effect of RTDs. In this paper, a novel micro-accelerometer based on AlAs/GaAs/In_0.1Ga_0.9As/GaAs/AlAs RTDs is designed and fabricated to be a four-beam-mass structure, and an RTD-Wheatstone bridge measurement system is established to test the basic properties of this novel accelerometer. According to the experimental results, the sensitivity of the RTD based micro-accelerometer is adjustable within a range of 3 orders when the bias voltage of the sensor changes. The largest sensitivity of this RTD based micro-accelerometer is 560.2025 mV/g which is about 10 times larger than that of silicon based micro piezoresistive accelerometer, while the smallest one is 1.49135 mV/g.