Input-output matching in linear mechanical systems

The steady state forced harmonic motion of a linear mechanical system is considered. It is shown that the output q of the system can be matched with its input p, in the sense that the condition p = λVq is satisfied, where V is a given weighting matrix. The quantities λ and q, satisfying the above matching equation, are called the matching coefficient and mode, respectively. The application of the matching method to the identification of unknown system matrices, and hence to shifting a system resonance frequency, is presented. Three practical methods of achieving input-output matching are proposed.     

Noether's theory of generalized linear nonholonomic mechanical systems

By introducing the quasi-symmetry of the infinitesimal transformation of the transformation group G_r, the Noether's theorem and the Noether's inverse theorem for generalized linear nonholonomic mechanical systems are obtained in a generalized compound derivative space. An example is given to illustrate the application of the result.     

广义线性非完整力学系统的Hojman守恒量

研究广义线性非完整力学系统的Lie对称性导致的Hojman守恒量,在时间不变的特殊Lie对称变换下,给出系统的Lie对称性确定方程、约束限制方程和附加限制方程,得到相应完整系统的Hojman守恒量以及广义线性非完整力学系统的弱Hojman守恒量和强Hojman守恒量,并举一算例说明结果的应用.     

On the negative point spectrum of quantum mechanical three-body systems

We consider quantum mechanical three-body systems interacting with two-body potentials that are sufficiently regular locally, decrease faster than r^?(2+?) at infinity, and are such that either one two-body subsystem (at least) has a negative energy bound state, or no two-body subsystem has a zero energy bound state or resonance. (This assumption excludes the possibility of the Efimov effect.) We then prove that (1) the discrete spectrum is finite, (2) the point spectrum has no negative accumulation points. (These results have been proved earlier by Sigal and Yafaev, respectively, by different methods and with slightly different assumptions.)     

Synthesis and characterisation of glycine sodium nitrite crystals having non linear optical behaviour

Glycine sodium nitrite (GSNi) having non linear optical efficiency more than KDP crystal has been obtained from solutions by slow cooling technique. The crystals are found to be chemically and thermally stable with orthorhombic unit cell. The presence of wide transparency window in UV–Visible region makes GSNi suitable for opto-electronic device applications. It has second harmonic generation efficiency of 1.273 times that of standard KDP crystal. GSNi crystal belongs to soft category of materials with work hardening index of 2.33. Crystals introduced in timer circuit gave a stable output with the capacitance value of 236 pF. I–V characteristic indicates a safe operating range of 300 V/cm. GSNi is seen to behave as a normal dielectric with applied frequency and crystals exposed to light exhibit negative LDR characteristic which is attributable to space charge formation.     

完整约束力学系统保Lie对称性差分格式

提出一种保完整约束力学系统Lie点对称性的差分格式.其具体做法是:首先求出完整约束力学系统的Lie点对称群,并将其延拓到离散的差分格点上;其次利用其特征方程找出独立的离散不变量;再应用独立的离散不变量来构造不变量的差分格式,且此差分格式在连续极限下应给出原系统的微分方程;最后给出一个例子,作为本文结果的说明.     

Energy content in linear mechanical systems with arbitrary time dependence

A novel complementary variables formulation, permits the obtainment of invariants of a mechanical system following the rationale of Abel's differential equation identity. This approach allows for the decomposition of the total energy of the system into the energy of the object and the dynamic energy of the field. The force acting on the object must be linear in the spatial variable but is arbitrary in the time variable. Several examples, such as the time dependent harmonic oscillator and a swing are described with this complementary variables formulation. The exact solution for the energy of a Lorentz pendulum with uniformly varying length is presented.     

A modeling concept of a mechanical system having a piecewise linear spring property for its diagnosis

Machine condition monitoring and fault diagnosis of rotating machinery are very important because of the wide use of rotating machinery in industry. Couplings and gears are used in many mechanical systems to connect elements and transmit power. The system is usually modeled as a single-degree-of-freedom system with a piecewise linear spring property, where the mass of main machine is only considered. In the present study, the dynamic behavior of a system with an unsymmetrical nonlinearity and a significant mass of the connecting part was investigated both experimentally and by numerical simulation. In the experiment, a 1/3 sub-harmonic oscillation was observed, but this oscillation was not found in the simulation using a single-degree-of-freedom system, in which the mass of the connecting part was ignored. However, when a two-degrees-of-freedom system was used that considered both the mass of the connecting part and the impact property, the 1/3 sub-harmonic oscillation was observed. Thus it is recognized that an adequate mathematical model for diagnosis in the early stage of abnormality must be selected on the basis of the mass ratio between the connecting part and the main body.     

Characterization of the system functions of ultrasonic linear phased array inspection systems

This work characterizes the electrical and electromechanical aspects of an ultrasonic linear phased array inspection system, using a matrix of system functions that are obtained from the measured response of individual array elements in a simple reference experiment. It is shown that for the arrays tested all these system functions are essentially identical, allowing one to use a single system function to characterize the entire array, as done for an ordinary single element transducer. The variation of this single system function with the number of elements firing in the array or with changes of the delay law used is examined. It is also demonstrated that once such a single system function is obtained for an array, it can be used in a complete ultrasonic measurement model to accurately predict the array response measured from a reference reflector in an immersion setup.     

Features of the oscillations of linear dynamic systems with dissipative coupling having two degrees of freedom

The natural frequencies of a system of this type lie between its partial frequencies. There are three characteristic regions of the mismatch between partial frequencies. In the central region (near the internal resonance point), the natural frequencies of the system practically coincide, and so do the oscillation amplitudes for these frequencies. In the left and right regions, the natural frequencies approach the partial frequencies. Generally, the motion consists in damped amplitude-phase-modulated oscillations. As time elapses, there occurs frequency tuning of the oscillators to one frequency at which damping goes more slowly, and the oscillations invariably go over to the in-phase mode. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 52–59, January, 2008.     

Synthesis of carbon planar structures with specified properties

A new method is proposed that allows an integrated technology to be used for the synthesis of carbon planar structures with predetermined properties. The method is based on the avalanche annealing of amorphous short-period superlattices. The synthesized samples are investigated by Raman spectroscopy and photoluminescence. The possibility of synthesizing carbon layers with diamond-like, graphite-like, graphene, or other structures is demonstrated experimentally using the example of a C/SiC superlattice.     

用单片机驱动线阵CCD的探讨

本文就弥补以往用单片机产生线阵 CCD驱动时序的不足进行了探讨 ;给出了使用 AVR单片机产生驱动TCD12 0 6线阵 CCD的具体实例及相应程序。其定时关系精确 ,驱动频率达到推荐的速率     

Optical properties of conjugated polymers having linear carbon moieties

Alternate conjugated copolymers consisting of phenylene or biphenylylene unit and linear carbons unit such as cumulene and polyyne were synthesized. The optical property of these polymers was investigated by UV–Vis and fluorescence spectroscopies. Among cumulene-type polymers, the polymer having allene moiety showed a unique hypsochromic shift and intense blue fluorescence in solution, while poly(phenylenebutadiynylene)s, typical of polyyne-type linear conjugated polymers, showed fluorescence in the region from blue-green to green in high efficiency besides thermotropic liquid crystalline property. Substituent effects of the polymers on optical property as well as the band structure were evaluated on the basis of Hammet parameters, which was utilized for designing of the polymers. The poly(arylenebutadiynylenes)s were applied in polymer LED. The devices consisting of ITO/PEDOT-PSS/emitting polymer/Ca/Al realized EL emissions in the region covering RGB colors.     

Moment analysis of focus-diverse point spread functions for modal wavefront sensing of uniformly illuminated circular-pupil systems

A new concept of using focus-diverse point spread functions (PSFs) for modal wavefront sensing (WFS) is explored. This concept is based on relatively straightforward image moment analysis of measured PSFs, which differentiates it from other focal-plane WFS techniques. The presented geometric analysis shows that the image moments are nonlinear functions of wave aberration coefficients but notes that focus diversity essentially decouples the coefficients of interest from others, resulting in a set of linear equations whose solution corresponds to modal coefficient estimates. The presented proof-of-concept simulations suggest the potential of the concept in WFS with strongly aberrated high signal-to-noise ratio objects in particular.     

Electrostatic potential of a point charge lattice having lamina geometry

The Coulomb potential energy of a lattice of point charges having infinite extension in two dimensions only is evaluated using an Ewald-like transformation. An exponential rather than a Gaüssian charge spreading function is used. The derived expansion is rapidly convergent.     

基于Verilog的线阵CCD驱动时序设计

针对东芝公司生产的TCD1209D芯片,介绍了一种基于Verilog语言的线阵CCD驱动方案,给出了关键部分的程序代码。采用Modelsim软件对设计方案进行了功能仿真,针对ALTERA公司的现场可编程门阵列EP2C8Q208C8N进行了适配。实验结果表明,该设计方案功耗小,抗干扰能力强,可移植性好,具有较高的开发效率。     

Semi-active damping control of suspension systems for specified operational response mode

A practical and effective semi-active on-off damping control law using semi-active actuators is developed for vibration attenuation of a natural, multi-degree-of-freedom suspension system, when its operational response mode is specified. It does not need the accurate system parameters and semi-active actuator dynamics. It reduces the total vibratory energy of the system including the work done by external disturbances and the maximum energy dissipation direction of the semi-active actuator is tuned to the operational response mode of the structure. The effectiveness of the control law using a single semi-active linear mount is illustrated with a three-degree-of-freedom excavator cabin suspension model.