高耸闪蒸塔调谐质量阻尼减振技术的数值分析

针对高耸闪蒸塔在强风作用下振动响应过大的问题,将调谐质量阻尼器（TMD）减振技术应用到高耸闪蒸塔风振控制中,以保证设备运行安全并延长其使用寿命.通过Matlab数值模拟,研究了TMD安装后闪蒸塔顶端的风振能量减少率以及寻找最优参数.在此基础上,总结了能量减少率等值线图,可以通过协调二者的关系来解决TMD运行空间有限的难题.研究结果表明：TMD可以有效控制高耸闪蒸塔进行风振响应,在最优匹配参数下,TMD能够降低闪蒸塔的顶端振动能量约47.07％,为工程实际应用提供了一定参考.     

基于MTMD的某注塑机械手振动控制研究

针对某注塑机械手产生较大振动问题,采用多重调谐质量吸振器(MTMD)技术抑制机械手取件手指的振动;提出MTMD参数优化设计方法和参数选择技术路线;扫频分析表明,安装36个TMD后,机械手手指三个方向的振幅得到有效抑制.设计的动力吸振器减振效果良好.     

Nonstationary random analysis of structures with hybrid mass damper system

The building structure is modeled as a linear single-degree-of-freedom system, and an active mass damper (AMD) is also adopted as the control device in order to reduce the structural response due to the external random load. In addition, suppose that the input acceleration of earthquake can be modeled as the product of nonstationary envelope function and narrow-band stationary random process with Kanai-Tajimi spectrum. In order to obtain the nonstationary stochastic response of control system due to the narrow-band nonstationary random process, in consideration of exchanging the active control mode for the passive one, considerable efforts are generally required in the analytical formulation. This paper, therefore, proposes an analytical technique to acquire the response covariance matrix by utilizing the state transition matrix method in state space. The proposed technique is evaluated by comparing the analytical results with those from numerical simulations.     

Structural identification of a prototype pre-stressable leaf-spring based adaptive tuned mass damper: Nonlinear characterization and classification

The current paper focuses on a prototype adaptive TMD. Its design concept is based on pre-stressable leaf-springs that are controlled by piezoceramic (PZT) stack actuators. Experiments performed on the prototype showed that it is continuously tunable in a broad frequency range. Moreover, they revealed that the device exhibits structural nonlinearities. The current paper focuses on the structural identification of the prototype and attempts for the first time to characterize and classify the observed nonlinearities. Several experiments at different PZT voltage levels are performed. The results indicate PZT voltage dependent nonlinear softening and hardening stiffness. Based upon these observations, static experiments and proper data-pooling techniques, an effective “global” model for the nonlinear stiffness is derived. The estimated nonlinear model is finally validated upon static experiments as well as more realistic operational cases, that are vibrations of the prototype under typical ground excitation.     

汽车动力传动系双质量飞轮式扭振减振器特性分析

分析几种典型双质量飞轮式扭振减振器的结构,对其工作原理进行详细阐述,着重研究四种典型双质量飞轮式扭振减振器的弹性特性和扭转刚度,对汽车动力传动系双质量飞轮式扭振减振器的选型和设计具有一定的参考价值.     

Rapid dynamics prediction of tool point for bi-rotary head five-axis machine tool

Receptance Coupling Substructure Analysis (RCSA), an effective approach to rapidly predict the tool point frequency response function (FRF), generally requires the response of spindle-machine assembly by experiments. This method is feasible for three-axis machine tool because the spindle and its posture are normally unchangeable. But in terms of five-axis milling, the spindle-machine assembly changes continuously. The purpose of this study is to propose new techniques to solve the constantly-changing assembly response in order that RCSA can be used for bi-rotary head five-axis machine tools. Based on receptance matrix determination in coupling direction and single degree of freedom coupling simplification, the swivel model for holder tip receptances is established for swivel motion. According to the concept of oriented frequency response function, the rotational model is derived to calculate the holder tip receptances with rotary motion. By combining the swivel model and the rotational model, the holder tip receptance of arbitrary posture can be calculated by three orthogonal postures. A five-axis machine tool with bi-rotary head is used to conduct FRF tests on different postures. Experimental results show that the models proposed can accurately predict tool point frequency response of any posture and large difference in FRFs among those postures of bi-rotary head is detected.     

Damping and added mass coefficients for a squeeze film damper using the full 3-D Navier-Stokes equation

Direct and cross-coupled damping coefficients are developed for the 2π-film, π-film (Gumbel cavitation condition) and homogeneous two-phase mixture films in a squeeze film damper. The numerical simulation uses the CFD-ACE+ commercial software, which employs a finite volume method for the discretization of the Navier-Stokes equations (NSE). In order to determine the dynamic coefficients, the NSE is combined with a finite perturbation method applied to the ‘equivalent journal’ of the damper. It was found that for the 2π-film and the Gumbel conditions, the damping coefficients exhibit linear characteristics, while the homogeneous cavitation model yields nonlinear coefficients. Using the CFD-ACE+, the inertia/added mass coefficients are derived for the limiting cases of the short and long dampers, respectively. The first set of forces is calculated by setting the fluid density to its actual value. The second set of forces is calculated when the density of the fluid is set close to zero (1E-10 kg/m³), thus practically eliminating the effects of the inertia terms. Subtracting the two sets of forces from each other, allows the determination of the inertia component contribution and the corresponding inertia coefficients. By varying the density, dynamic viscosity and whirling speed, it was found that the inertia coefficients follow a single curve represented by a function dependent on the modified Reynolds number, Re*. The inertia coefficients presented in this study are compared with the ones reported by other researchers that used the modified Reynolds equation. Some differences were found between the NSE based results and the Reynolds equation based outcomes. This is attributed to the three-dimensional effects introduced by the totality of the terms comprised in the full NSE.     

精铣削中抑制柔性工件颤振的阻尼器设计

针对精铣削过程中柔性工件的颤振抑制问题,提出了一种利用空气黏性的新型被动质量阻尼器。首先,该质量阻尼器由一个可在薄壁壳体内自由移动的圆柱形重物组成,通过重物和壳体之间的适当间隙提供了密集的能量耗散;其次,给出了该阻尼器的理论模型,并提出了一种合理的宽带调谐策略,使该阻尼器能够在较宽的工作范围内通过固定调谐来提供足够的阻尼效率。通过冲击实验和铣削实验对该阻尼器进行了有效性验证。结果表明:该阻尼器的临界轴向切削深度显著增加约100倍;与同等质量颗粒阻尼器相比,该阻尼器的阻尼效率明显提升,过度切削量减少了14倍;与传统调谐质量阻尼器相比,该阻尼器的峰值效率更小,但工作范围更大,因此适用于细长柔性工件的铣削加工。     

Transient suppression in FRF measurement: Comparison and analysis of four state-of-the-art methods

This paper compares four well selected methods for computing the non-parametric Frequency Response Function (FRF) of a periodically excited linear time invariant system. The suppression of the transient is mandatory when its influence in the data is large. Better suppression of the transient leads to a better non-parametric FRF estimate. A good non-parametric FRF estimate can be used to validate the parametric transfer function model in a second step. The suppression of the transient will be highlighted using the mean squared error of the non-parametric FRF estimate. Temperature transients caused by heat diffusion are used as example. The selected methods consist of two standard windowing methods and two methods based on the Local Polynomial Method (LPM). LPM was designed to find a non-parametric FRF estimate in the presence of nonlinearities. This paper will modify LPM to find a non-parametric FRF estimate for linear systems using a single experiment. The mean squared error of the four non-parametric FRF estimates will be compared and analyzed, based on a simulation and a measurement example.     

On the vibration of rotor-bearing system with squeeze film damper in an energy storage flywheel

The permanent magnetic bearing and the small-sized hydrodynamic spiral groove bearing are utilized as supports for the rotor of the energy storage flywheel system. The hydrodynamic bearing and the squeeze film damper do not need the oil cycle to remove the heat caused by friction because the friction loss is small. The linear dynamics model with four degrees of freedom is built to describe the vibration of the flywheel rotor-bearing system. The squeeze film dampers show good behavior in suppressing the vibration and improving the stability of the rotor-bearing system. The analytical solution of the dynamic characteristic coefficients of the squeeze film is achieved from Reynolds equation after some simplifications are taken. The numerical computation shows that the moment unbalance excites larger vibration of the rotor than the force unbalance. The upper damper plays an important role in helping the rotor pass its critical speed. The damping coefficient of the squeeze film dampers should be selected carefully. The flywheel arrived at the speed of 39,000 rpm and stored the energy of 308 Wh in the experiment. The calculated unbalance response is compared to the test response of the rotor storing quantities of kinetic energy. The comparison indicates that the dynamics model of the rotor-bearing-damper system is appropriate.     

Analytical study on effect of a circumferential feeding groove on unbalance response of a flexible rotor in squeeze film damper

Of recent years, a series of researches have shown that a circumferential feeding groove of squeeze film damper (SFD) has evident effect on fluid film forces in SFD. Therefore, the feeding groove also affects dynamic responses of a rotor in SFD. Present work studies the effect of the feeding groove on unbalance response of a flexible rotor in SFD based on new film force models that include effects of the feeding groove and fluid inertia on dynamic characteristics of the fluid film in SFD. Compared with the published work, unbalance responses predicated under considering effect of the feeding groove on the dynamic characteristics in SFD are small, and rotor speed region for unbalance responses with multiple solutions is different, affecting the stability of a rotor system. And the effect of the feeding groove on the unbalance response is related to action of fluid inertia.     

Experimental spectral damage prediction of a linear elastic system using acceleration response

The fatigue-related behavior of a linear elastic system (LES) can be efficiently identified using acceleration response if the frequency response function between the acceleration input and the stress response (FRFas) can be predetermined. In this paper, the spectral damage of an LES is predicted using energy isoclines, whose function consists of both FRFas and the fatigue material properties of the LES. The accuracy of the proposed method was verified through a uniaxial vibration test using flexible specimens and a comparison of the acceleration-based and strain-based spectral damage at the location of interest.     

Analytical study of the effect of a circumferential feeding groove on the unbalance response of a rigid rotor in a squeeze film damper

In recent years, a series of researchers have shown that a circumferential feeding groove of a squeeze film damper (SFD) has an evident effect on the forces of fluid film in SFD. Therefore, the feeding groove also affects the dynamic responses of a rotor in SFD. The present work studies the effect of the feeding groove on the unbalance response of a rigid rotor in a squeeze film damper based on the film force models that include effects of the feeding groove and fluid inertia on dynamic characteristics of the fluid film in SFD. Comparisons with the published work show that the feeding groove increases the orbit radius of rotor whirling and affects the unbalance response of a rotor system. The effect of the feeding groove on the unbalance response is also related to the action of fluid inertia.     

Development of dynamic response analysis algorithm for beam structures using transfer of mass coefficient

The authors developed the transfer mass coefficient method (TMCM) in order to compute effectively the dynamic response of a beam structure. In this paper, the algorithm for the dynamic response analysis of a three-dimensional beam structure is formulated. Through the computation results of numerical models, which are plane and space beam structures, obtained by the transfer mass coefficient method and the direct integration method, we verify that the transfer mass coefficient method can remarkably decrease the computation time of the direct integration method without the loss of accuracy in spite of using small computer storage. This paper was recommended for publication in revised form by Associate Editor Hong Hee Yoo Myung-Soo Choi received his B.S. and M.S. degrees from National Fisheries University of Pusan, Korea, in 1992 and 1994, respectively. He then received his Ph.D. degree from Pukyong National University in 1999. Dr. Choi is currently an Assistant Professor at the Department of Maritime Police Science at Chonnam National University in Yeosu, Korea. His research interests include mechanical vibration, structural dynamics, and optimum design. Jung-Joo Suh received his B.S., M.S. and Ph.D. degrees from National Fisheries Uni-versity of Pusan, Korea, in 1972, 1985 and 1995, respec-tively. Dr. Suh is currently a Professor at the Faculty of Marine Technology at Chonnam National University in Yeosu, Korea. His research interests include internal combustion engines and numerical analysis. Dong-Jun Yeo received his B.S., M.S. and Ph.D. degrees from National Fisheries University of Pusan, Korea, in 1981, 1985 and 1996, respectively. Dr. Yeo is currently a Professor at the Faculty of Marine Technology at Chonnam National University in Yeosu, Korea. He serves as an Academic Director of the Korean Society for Power System Engineering. His research interests include structural dynamics, vibration, and analytic techniques. Jung-Kyu Yang received his B.S. degree from Pusan Fisherise College, Korea, in 1973. He then received his M.S. and Ph.D. degrees from Chungnam National University in 1985 and 1996, respectively. Dr. Yang is currently a Professor at the Faculty of Marine Technology at Chonnam University in Yeosu, Korea. His research interests include combustion engineering, air flow characteristics, and numerical analysis. Jung-Hwan Byun received his B.S. and M.S. degrees from National Fisheries University of Pusan, Korea, in 1992 and 1995, respectively. He then received his Ph.D. degree from Pukyong National University in 1997. Dr. Byun is currently an Associate Professor at the Faculty of Marine Technology at Chonnam National University in Yeosu, Korea. His research interests include numerical analysis and synchronous control.     

Differentiation of isomeric amino acid residues in proteins and peptides using mass spectrometry

Characterization and differentiation of isomers in biological macromolecules using mass spectrometry is one of the most significant challenges facing scientists in the field. The capability of high‐resolution MS instruments along with the development of new fragmentation methods now provides the ability to indirectly differentiate between some isomers. This ability has enabled mass spectrometry to evolve into a multidisciplinary technique incorporating areas such as pharmaceutical research, proteomics, polymer science, medicine, environmental chemistry, and recently archeology. This article aims to review recent developments in mass spectrometry methodologies in the identification of structural and spatial isomers in biological macromolecules, such as aspartic acid and isoaspartic acid (Asp/IsoAsp), leucine and isoleucine (Leu/Ile), glutamic acid and γ‐glutamic acid, and D/L enantiomers. © 2012 Wiley Periodicals, Inc. Mass Spec Rev 31:609–625, 2012     

Measurements of volatile organic compounds in the earth's atmosphere using proton-transfer-reaction mass spectrometry

Proton-transfer-reaction mass spectrometry (PTR-MS) allows real-time measurements of volatile organic compounds (VOCs) in air with a high sensitivity and a fast time response. The use of PTR-MS in atmospheric research has expanded rapidly in recent years, and much has been learned about the instrument response and specificity of the technique in the analysis of air from different regions of the atmosphere. This paper aims to review the progress that has been made. The theory of operation is described and allows the response of the instrument to be described for different operating conditions. More accurate determinations of the instrument response involve calibrations using standard mixtures, and some results are shown. Much has been learned about the specificity of PTR-MS from inter-comparison studies as well the coupling of PTR-MS with a gas chromatographic interface. The literature on this issue is reviewed and summarized for many VOCs of atmospheric interest. Some highlights of airborne measurements by PTR-MS are presented, including the results obtained in fresh and aged forest-fire and urban plumes. Finally, the recent work that is focused on improving the technique is discussed.     

用SDRAM在高速数据采集和存储系统中实现海量缓存

SDRAM作为大容量存储器在高速数据处理系统中具有很大的应用价值.详细介绍了SDRAM的存储体结构、接口信号和操作方法,结合实际系统设计给出了使用大规模集成电路FPGA实现的硬件接口,并分析了操作SDRAM时的状态转移过程.     

High‐precision mass spectrometric analysis using stable isotopes in studies of children

The use of stable isotopes combined with mass spectrometry (MS) provides insight into metabolic processes within the body. Herein, an overview on the relevance of stable isotope methodology in pediatric research is presented. Applications for the use of stable isotopes with MS cover carbohydrate, fat, and amino acid metabolism as well as body composition, energy expenditure, and the synthesis of specific peptides and proteins, such as glutathione and albumin. The main focus of these studies is on the interactions between nutrients and the endogenous metabolism within the body and how these factors affect the health of a growing infant. Considering that the early imprinting of metabolic processes hugely impacts metabolism (and thus functional outcome) later in life, research in this area is important and is advancing rapidly. The major fluxes on a metabolic level are the synthesis and breakdown rates. They can be quantified using kinetic tracer analysis and mathematical modeling. Organic MS and isotope ratio mass spectrometry (IRMS) are the two most mature techniques for the isotopic analysis of compounds. Introduction of the samples is usually done by coupling gas chromatography (GC) to either IRMS or MS because it is the most robust technique for specific isotopic analysis of volatile compounds. In addition, liquid chromatography (LC) is now being used more often as a tool for sample introduction of both volatile and non‐volatile compounds into IRMS or MS for ¹³C isotopic analyses at natural abundances and for ¹³C‐labeled enriched compounds. The availability of samples is often limited in pediatric patients. Therefore, sample size restriction is important when developing new methods. Also, the availability of stable isotope‐labeled substrates is necessary for measurements of the kinetics and concentrations in metabolic studies, which can be a limiting factor. During the last decade, the availability of these substrates has increased. Furthermore, improvements in the accuracy, precision, and sensitivity of existing techniques (such as GC/IRMS) and the development of new techniques (such as LC/IRMS) have opened up new avenues for tackling these limitations. © 2011 Wiley Periodicals, Inc. Mass Spec Rev 31:312–330, 2012     

Natural frequencies of a beam–mass system in transverse vibration: Rayleigh estimation versus eigenanalysis solutions

A frequency analysis of a beam carrying multiple point masses at various locations are presented by using an eigenanalysis and the Rayleigh's estimation. In the eigenanalysis, the frequency equation is generated by satisfying all boundary and mass-loading conditions. As for Rayleigh's method, the frequency is obtained by solving an algebraic expression involving a specified shape function. As compared with the general expression derived by virtue of Rayleigh method, the eigenfrequency equation is lengthy with products of transcendental functions. The Rayleigh's results with each respective shape function are compared with the eigenfrequencies to verify the effectiveness of Rayleigh's method with assumed shape functions. It is found that the Rayleigh method with the simple shape functions can provide good approximation and can thus replace the solving of complicated eigenfrequency equations. The time saving by using Rayleigh's method becomes more significant as the number of masses carried by the beam increases.     

基于多岛遗传算法的漂浮式风力机稳定性多重调谐质量阻尼器优化控制

将多重调谐质量阻尼器（MTMD）引入漂浮式风力机控制领域以提高漂浮式风力机的稳定性。以NREL 5MW风力机及ITI Barge平台为研究对象,提出在漂浮式风力机机舱和塔架中配置2个参数不同的调谐质量阻尼器（TMD）,并基于多岛遗传算法,算出MTMD系统最优参数。通过对3种典型工况下、有无配置MTMD的漂浮式风力机进行模拟计算,研究了最优MTMD的控制效果。结果表明：多岛遗传算法能够有效优化MTMD参数;MTMD控制优于单一TMD控制;经参数优化后,MTMD对漂浮式风力机振动的控制效果更好,塔顶纵向位移和平台横摇角标准差抑制率分别提升了80.4%和83.8%;MTMD对漂浮式风力机不同部位的控制效果不同,控制效果最好的为塔顶纵向位移、塔根横向弯矩及平台横摇角;不同环境工况下,MTMD对漂浮式风力机都有着明显的控制效果,其中纵向载荷和位移的标准差抑制率分别为10.3%~12.1%和76.1%~78.3%,横向载荷和位移的标准差抑制率分别为75%~77.7%和8.9%~10.8%。