Closed-form formulas for the optimal pole-based design of tuned mass dampers

This paper deals with the analysis and optimization of tuned mass dampers (TMDs). It provides design formulas for maximizing the exponential time-decay rate (ETDR) of the system transient response. A detailed analysis is presented for the classical TMD configuration, involving an auxiliary mass attached to the main structure by means of a spring and a dashpot. Analytic expressions of the optimal ETDR are obtained for any mass ratio and tuning condition. Then, a further optimization with respect to the latter is performed. The proposed method is applied also to other TMD configurations involving an auxiliary mass connected to both the main structure and the ground, as well as to a piezoelectric damping device. A justification to the well-known heuristic optimality condition based on the enforcement of coincident couples of complex conjugate poles is presented. That condition is shown, however, to fail in providing optimal solutions for some mass ratio values and/or TMD configurations, and the optimality conditions prevailing in those cases are derived. The present analysis, besides its theoretical interest, may be useful in practical applications, e.g., to assess the sensitivity of the optimal ETDR with respect to the design parameters or to promptly adjust some of those parameters during service, after any variation of the operative conditions.     

Regenerative amplification of the central component of the Rayleigh line in liquid

It is shown that the Rayleigh scattering signal excited in liquid during four-wave mixing of radiation of diode laser whose frequency difference is tuned in the vicinity of small detunings is amplified in the active element of the probe laser.     

Multi-layer evolution schemes for the finite-dimensional quantum systems in external fields

The operator-difference multi-layer (ODML) schemes for solving the time-dependent Schrödinger equation (TDSE) till six order accuracy by a time step are presented. The reduced schemes for solving a set of the coupled TDSE’s are devised by using a set of appropriate basis angular functions and a finite element method with respect to a hyper-radial variable. Convergence by a number of the basis functions and efficiency of the numerical schemes are demonstrated in the case of an exactly solvable model of the two-dimensional oscillator in time-depended electric fields.     

基于湍流模型的自适应光学系统响应矩阵测量方法

为了提高液晶自适应光学系统的校正精度,提出一种基于湍流模型的响应矩阵测量方法。该方法施加到液晶波前校正器上的波面是用来拟合待测像差的Karhunen-Loeve模式的线性组合,其模式系数分布服从Kolmogorov大气湍流模型。相比于传统的单模式和多模式响应矩阵测量方法,该方法具有更强的抗噪声干扰能力,能够显著提高响应矩阵测量精度。在信噪比为10的情况下,当重复率分别为1、5和10时,采用传统单模式法和多模式法获得的响应矩阵进行自适应校正后的斯特列耳比分别为0.06、0.02、0.49和0.23、0.40、0.67,而采用该方法可以达到0.34、0.56、0.68。     

位阻效应对受阻酚杂化体系阻尼机理的影响

针对尚未解决的受阻酚结构变化与杂化体系阻尼机理间关系的问题,本文采用分子动力学模拟方法构建了三种受阻程度不同的受阻酚/聚合物杂化体系,从理论上探讨了位阻效应对阻尼机理的影响.对体系氢键相互作用、结合能、相对自由体积及扩散系数进行模拟分析表明,位阻效应对受阻酚分子内氢键相互作用有显著的弱化效果,可减少小分子团聚倾向,有利于小分子与聚合物分子间氢键相互作用的形成.但是,过高的位阻对小分子运动有阻碍作用,不利于小分子与聚合物形成强烈的氢键键合,也即不利于杂化体系阻尼性能的提高.因此,如何选择受阻程度适中的受阻酚是制备高阻尼杂化材料的一关键要素.     

Data detection based on matrix decomposition for massive MIMO systems in realistic channel scenarios

Massive multiple-input multiple-output (MIMO) is a key technology for modern wireless communication systems. In massive MIMO receivers, data detection is a computationally expensive task. In this paper, we explore the performance and the computational complexity of matrix decomposition based detectors in realistic channel scenarios for different massive MIMO configurations. In addition, data detectors based on decomposition algorithms are compared to the approximate-inversion detection (AID) methods. It is shown that the alternating-direction-method-of-multipliers-based-Infinity-Norm (ADMIN) detection is promising in realistic channel environment and the performance is stable even when the ratio of the base-station (BS) antenna elements to the number of users is small. In addition, this paper studies the performance of several detectors in imperfect channel state information (CSI) and correlated channels. Our work provides valuable insights for massive MIMO systems and very large-scale integration (VLSI) designers to select the appropriate massive MIMO detector based on their specifications.     

Determination of binary systems based on light elements by the ratio of the Compton and Rayleigh scattering intensities

A generalization of the Compton method for determining elements with a low atomic number Z from 1 (H) to 9 (F) by the ratio of the intensities of incoherent (Compton) and coherent (Rayleigh) scattering is proposed. The generalization takes into account not only the dependence of this ratio on the effective atomic number of the scatterer material but also the momentum transfer variable x = . The new method is based on the application of calibration function of obtained by measuring scattering spectra at two values of x₁= 0.831 Å⁻¹ and x₂= 1.297 Å⁻¹ with a WDXRF spectrometer. The elemental atomic numbers and their concentrations of binary compounds with unknown compositions are determined by the solution of a system of linear equations. Coefficients of the equations are calculated from the measured ratios for the test sample and the regularization solution for the corresponding calibration. The experiments have been carried out for standard samples of single-component, binary and triple stoichiometric compounds based on H, Li, Be, B, C, O and F. The identification of these elements was found to be possible in the absence of a relationship between the positions of scattering peaks and the composition of the sample, and a qualitative and quantitative analysis of the composition of the material was carried out as part of the solution of a single inverse problem.     

Bifurcations in autonomous mechanical systems under the influence of joint damping

This contribution deals with the impact of joint damping on two classes of stability problems which are often found in engineering problems. In a first part, the principle structure of the equations of motion is derived when joints are modeled using Masing-, Prandtl- and Coulomb-elements. For these general formulations, some fundamental statements concerning stability and attractiveness of steady-state solutions may be given for large amplitudes and configurations which are not too close to the linear stability threshold. The second part focuses on analyzing the behavior at small amplitudes and in the vicinity of the linear stability threshold in more detail: to this end, a static stability problem (buckling) and two oscillatory self-excitation mechanisms (negative damping, non-conservative coupling) are discussed. For all considered problems, adding joint damping transforms the equilibrium points into sets of equilibria and bifurcations of the non-smooth problems occur near the linear stability threshold. Concerning the buckling problem adding joint damping does not alter the behavior fundamentally: still a local bifurcation occurs and attractiveness or instability of equilibrium solutions is preserved. In contrast, the oscillatory instability examples are strongly influenced by joint damping: here, global discontinuous bifurcations may occur. Besides the joint friction also the joint-stiffness may play a crucial role, since it determines whether attractive solutions in or about the equilibrium set exist. It is found that only in some cases a linear stability analysis of the corresponding system without joints may give correct indications on the behavior: consequently, neglecting joint-damping in stability analyses may lead to wrong results concerning self-excitation.     

Frequency matrix for the calculation of correlation functions in dipolar systems

The transverse correlation function of a truncated dipolar spin system in a high temperature approximation is calculated by means of a continuous set of variables and Mori's frequency matrix.     

Theory of cyclotron resonance lineshape for electron-phonon systems in two coupling schemes

A theory of cyclotron resonance lineshape due to electron-phonon interactions is presented on the basis of the projection operator method introduced by Argyres and Sigel. In addition to the extremely weak coupling scheme dealt with earlier, the moderately weak coupling scheme is included in the theory. The lineshape functions derived in the two schemes are similar to Lodder-Fujita's formula, and are reduced to Kawabata's formula in the elastic scattering approximation.     

关于电路量子电动力学系统中光子自由度的消除方案

基于超导传输线和超导量子比特相互耦合的电路量子电动力学(quantum Electrodynamics, QED)系统, 是目前固态量子信息领域的一个倍受关注的物理系统, 也是研究量子测量和量子控制的理想实验平台. 由于其中涉及的驱动场和超导传输线谐振腔支持的光子频率都在微波区, 在量子测量和量子控制研究中往往遇到 大量光子数引起的状态空间维数过大带来的数值模拟方面的困难. 为了避免这个困难, 往往采取"消除"光子自由度的办法, 建立一个只保留量子比特状态自由度的有效描述方案. 本文通过对单比特的量子测量动力学的数值模拟, 检验了 "绝热消除"和"极化子变换"两种方案的适用条件. 结果表明, 在量子非破坏(quantum non-demolition, QND) 测量情况下, 极化子变换精确适用于 任意驱动强度和任意(光子)泄漏速率微腔; 但在非QND测量情况下, 极化子变换相对通常的绝热消除方案, 并无优势. 在强泄漏微腔和弱耦合情况下, 两种消除光子自由度的方法都可以较好地描述 测量动力学; 但如果微腔光子泄漏速率不是很大或量子比特与微腔耦合较强, 则需要纳入光子自由度做完整模拟, 此时的量子测量属性是一个尚待研究的课题.     

Constraints on the squark mass matrix from CP-violation and SUSY predictions for theB^0 - \bar B^0 systems

The parametersc andA of the squark mass matrix, which control flavour violation and left-right maxing respectively, are constrained by fitting ∈ and ∈′. The predictions for mixing and CP-violation in the \(B^0 - \bar B^0 \) system are calculated and then compared with both the predictions of the standard model and the available experimental data.     

Improving the accuracy of the n-dB method for determining damping of non-lightly damped systems

Damping measurements using the spectral magnitude remain popular and are studied here for non-lightly damped systems using the variable bandwidth n-dB method, which is advantageous for non-lightly damped systems. The most commonly used estimator (based on normalised bandwidth) provides significant errors for non-lightly damped systems. An existing more accurate method (using the squares of the frequencies used in the former method) is exact for hysteretic damping, but still provides significant error for viscous damping. Improved estimators are developed in order to correct either exactly, or to insignificant errors, measurements taken with existing estimators. Neither further data nor the individual frequencies are required; the previously calculated damping values are corrected. The application of the improved estimators is dependent upon the existing estimator used and the damping type; however a strategy is suggested to reduce errors if the latter is unknown.