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Study of an artificial boundary condition based on the damping-solvent extraction method

Qiang XU, Jianyun CHEN, Jing LI, Mingming WANG

《结构与土木工程前沿（英文）》 2012年第6卷第3期页码 281-287 doi: 10.1007/s11709-012-0167-5

摘要： A new artificial boundary condition for time domain analysis of a structure-unlimited-foundation system was proposed. The boundary condition was based on the damping-solvent extraction method. The principle of the damping-solvent extraction method was described. An artificial boundary condition was then established by setting two spring-damper systems and one artificial damping limited region. A test example was developed to verify that the proposed boundary condition and model had high precision. Compared with the damping-solvent extraction method, this boundary condition is easier to be applied to finite element method (FEM)-based numerical calculations.

关键词： damping-solvent extraction method structure-unlimited-foundation system spring-damper system artificial damping limited region finite element method

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Emergent limited perioperative transesophageal echocardiography: should new guidelines exist for limited

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《医学前沿（英文）》 2012年第6卷第3期页码 332-337 doi: 10.1007/s11684-012-0212-8

摘要：

Bedside limited echocardiography, or focused cardiac ultrasound, continues to gain popularity in many emergency rooms, intensive care units, and operating rooms as a rapid method of assessing unstable patients. Effective monitoring of cardiovascular function in conditions like cardiac arrest or near-arrest is the crucial step to guide successful resuscitative efforts. Transesophageal echocardiography (TEE) has emerged as one of the preferred cardiac diagnostic and monitoring modalities in the intraoperative setting due to the fact that it is less invasive than many other monitors, is immediately accessible, and allows for continuous real-time monitoring of cardiac function. However, the minimum training requirements needed for the anesthesia provider to obtain the competency, knowledge, and skills for basic certification in perioperative TEE far exceed those developed for other medical specialties. We believe there is an urgent need to develop (1) practical guidelines for emergent perioperative TEE use for anesthesiologists and (2) a requisite educational curriculum to teach the basic skills necessary to aid in the diagnosis and treatment of cardiac arrest or near-arrest scenarios. The measures elucidated in this report summarize the efforts of the Department of Anesthesiology at the University of Florida in establishing the necessary steps to make this process not only practical, but accessible to all trainees. We hope that these collective efforts will provide more trainees the confidence in utilizing TEE to aid in establishing a diagnosis in critical situations.

关键词： transesophageal echocardiography curriculum competency training hemodynamic instability

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Highlights of special issue on ‘Agriculture in Water-Limited Areas’

Pute WU

《农业科学与工程前沿（英文）》 2017年第4卷第2期页码 123-125 doi: 10.15302/J-FASE-2017147

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Development of rocking constraint device with vertical damping capacity for three-dimensional base-isolated

《结构与土木工程前沿（英文）》 2023年第17卷第3期页码 350-367 doi: 10.1007/s11709-022-0923-0

摘要： A new rocking constraint device (RCD) is developed for three-dimensional (3D) base-isolated frame structures by connecting a custom-designed cylinder pair to provide vertical damping with replaceable damping components installed outside the cylinders when the superstructure undergoes translational motion, and rocking constraint capacity when the superstructure is susceptible to rocking. Theoretical formulas for calculating the damping and rocking constraint stiffness of the RCD are proposed. Two series of sinusoidal loading tests are conducted at different loading frequencies and amplitudes to verify the damping and rocking constraint performance of the RCD. The test results show that the cylinder without orifices on its piston can provide the desired damping with a replaceable damping component, and that the RCD can effectively suppress rocking. Although the vertical stiffness of an individual cylinder is affected by the location of the replaceable damping component and loading frequency, the average vertical stiffness of the two cylinders, which determines the rocking constraint stiffness of the RCD, is independent of the two factors. Comparisons of the test and theoretical results indicate that the errors of the proposed formulas for calculating the damping and rocking constraint stiffness of the RCD do not exceed 12.9% and 11.0%, respectively.

关键词： three-dimensional isolation rocking behavior rocking constraint device replaceable damping component sinusoidal test

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Bandwidth-limited active suspension controller for an off-road vehicle based on co-simulation technology

FENG Jinzhi, ZHENG Songlin, YU Fan

《机械工程前沿（英文）》 2008年第3卷第1期页码 111-117 doi: 10.1007/s11465-008-0020-7

摘要： This paper presents the design process of a controller for bandwidth-limited active hydro-pneumatic suspension employed by an off-road vehicle based on co-simulation technology. First, a detailed multi-body dynamic model of the vehicle is established by using the ADAMS/View software package, which is followed by validation using a vehicle field test. Second, a combined PID and fuzzy controller is designed for the bandwidth-limited active suspension system and then programmed by means of S-functions in Matlab/Simulink, to which a data exchange interface with ADAMS/View is also defined. Third, the proposed control algorithm is implemented on the multi-body dynamic vehicle model to enable the co-simulation to run repeatedly until a more practical controller is achieved. In the end, the proposed active suspension system is compared with a conventional passive system. Simulation results show that the proposed active suspension system considerably improves both the ride and handling performance of the vehicle and therefore increases the maximum traveling speeds even on rough roads.

关键词： co-simulation technology exchange interface conventional bandwidth-limited algorithm

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Approximation of structural damping and input excitation force

Mohammad SALAVATI

《结构与土木工程前沿（英文）》 2017年第11卷第2期页码 244-254 doi: 10.1007/s11709-016-0371-9

摘要： Structural dynamic characteristics are the most significant parameters that play a decisive role in structural damage assessment. The more sensitive parameter to the damage is the damping behavior of the structure. The complexity of structural damping mechanisms has made this parameter to be one of the ongoing research topics. Despite all the difficulties in the modeling of damping, there are some approaches like as linear and nonlinear models which are described as the energy dissipation throughout viscous, material or structural hysteretic and frictional damping mechanisms. In the presence of a mathematical model of the damping mechanisms, it is possible to estimate the damping ratio from the theoretical comparison of the damped and un-damped systems. On the other hand, solving the inverse problem of the input force estimation and its distribution to each SDOFs, from the measured structural responses plays an important role in structural identification process. In this paper model-based damping approximation method and a model-less structural input estimation are considered. The effectiveness of proposed methods has been carried out through analytical and numerical simulation of the lumped mass system and the results are compared with reference data. Consequently, high convergence of the comparison results illustrates the satisfactory of proposed approximation methods.

关键词： structural modal parameters damping identification method input excitation force identification Inverse problem

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Variable stiffness and damping magnetorheological isolator

Yang ZHOU, Xingyu WANG, Xianzhou ZHANG, Weihua LI

《机械工程前沿（英文）》 2009年第4卷第3期页码 310-315 doi: 10.1007/s11465-009-0039-4

摘要： This paper presents the development and characterization of a magnetorheological (MR) fluid-based variable stiffness and damping isolator. The prototype of the MR fluid isolator is fabricated, and its dynamic behavior is measured under various applied magnetic fields. The parameters of the model under various magnetic fields are identified, and the dynamic performance of the isolator is evaluated in simulation. Experimental results indicate that both the stiffness and damping capability of the developed MR isolator can be controlled by an external magnetic field.

关键词： magnetorheological (MR) fluid stiffness damping mathematical model dynamic performance parameter identification

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Two-stage scheduling on batch and single machines with limited waiting time constraint

Zhongshun SHI, Zewen HUANG, Leyuan SHI

《工程管理前沿（英文）》 2017年第4卷第3期页码 368-374 doi: 10.15302/J-FEM-2017034

摘要： This study addresses the problem of two-stage scheduling on batch and single machines with limited waiting time constraint; thus, the makespan is minimized. A mixed-integer linear programming model is proposed for this problem. Three tight lower bounds and a heuristic algorithm are developed. The worst-case performance of the proposed algorithm is discussed. A hybrid differential evolution algorithm is also developed to improve the solution quantity. Numerical results show that the hybrid algorithm is capable of obtaining high-quality solutions and exhibits a competitive performance

关键词： batch machine flow shop makespan limited waiting time

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Adaptation of Chinese and German maize-based food-feed-energy systems to limited phosphate resources—a

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《农业科学与工程前沿（英文）》 2019年第6卷第4期页码 313-320 doi: 10.15302/J-FASE-2019282

摘要：

Phosphate is supplied to agriculture by mining and fertilizer production, followed by different steps of phosphate utilization, including primary production, feed and food consumption, and conversion of biomass, with accumulation in soils, but little recycling and severe environmental losses. Phosphate is a limited essential nutrient, however, with very uneven distribution worldwide. Closing the cycle and reducing primary phosphate consumption are fundamental future challenges. Maize has a relatively high phosphate requirement. China and Germany together cover the whole range of maize production systems. The new Sino-German international research training group “Adaptation of Chinese and German maize-based food-feed-energy systems to limited phosphate resources” (AMAIZE-P) was initiated in 2018 as a joint venture of the China Agricultural University (Beijing, China) and the University of Hohenheim (Stuttgart, Germany). The interdisciplinary and complementary research is driven by the hypothesis that under phosphate limited conditions, high productivity and high phosphate use efficiency can be achieved simultaneously by adapting phosphate cycling and availability (sources) to the multipurpose phosphate demands (sinks) in maize-based food-feed-energy systems. The educational program for doctoral researchers in China and Germany includes joint block seminars, thematic field trips, case studies, methodological courses, doctoral researchers’ conferences, intercultural training sessions and personal training.

关键词： international research training group limited resources maize phosphate

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Effects of green roof damping and configuration on structural seismic response

《结构与土木工程前沿（英文）》页码 1133-1144 doi: 10.1007/s11709-023-0959-9

摘要： Sustainable structures are critical for addressing global climate change. Hence, their structural resilience or ability to recover from natural events must be considered comprehensively. Green roofs are a widely used sustainable feature that improve the environment while providing excellent occupant amenity. To expand their usage, their inherent damping and layout sensitivity to seismic performance are investigated in this study. The soil of a green roof can serve as a damper to dissipate the energy generated by earthquakes or other dynamic events. Results of preliminary analysis show that a green roof soil can increase localized damping by 2.5% under both dry and saturated conditions. Based on these findings, nonlinear time-history analyses are conducted on a three-story building in SAP2000 to monitor the structural behavior with and without a green roof. The increased damping in the green roof soil is beneficial to the structural performance, i.e., it reduces the building displacement and acceleration by 10% and 12%, respectively. Additionally, certain configurations are more effective and beneficial to the structural response than others, which suggests the possibility of design optimization. Based on the findings of this study, new methods of modeling and considering green roofs in structural design are established.

关键词： green infrastructure green roof structural resilience seismic design

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Fluid damping clearance in a control valve of injector

ZHANG Jianming, ZHANG Weigang, YANG Bing, WANG Yawei

《机械工程前沿（英文）》 2007年第2卷第4期页码 439-441 doi: 10.1007/s11465-007-0075-x

摘要： A force model of a control valve of injector is set up, and the changes of the fluid damping clearance are investigated on the basis of the results of the computational fluid dynamics (CFD) and the experiments of control valve of injector. Results indicate that a damping clearance of 0.02–0.03 mm between the poppet and the valve guide is the most sufficient to dampen any excessive control valve poppet bouncing.

关键词： control computational bouncing CFD excessive control

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A method of analysis for modal aero-damping of vibrating blade in incompressible flow

Jun XING, Lin LI,

《能源前沿（英文）》 2009年第3卷第4期页码 465-471 doi: 10.1007/s11708-009-0037-6

摘要： By establishing a research model for aero-damping in a uniform incoming flow, the three-dimension analytical algorithm of the modal aero-damping based on the equivalent viscous damping principle was established. The algorithm, which is suited for low-speed flow, to compute aero-damping is based on classical lift line theory in aerodynamics, according to the analytical solution of unsteady aerodynamic force. According to the analytical equations, the modal aero-damping ratio for different nature frequencies of blades in various fluid field conditions can be solved, and the factors to affect the aero-damping can be determined.The first bend and the first torsion’s modal aero-damping ratios of a compressor blade are calculated by using the above algorithms. The results show that the aero-damping cannot be neglected comparing with the structure damping. It reflects the coupling degree between the flow field and the structure field, so the aero-damping is significant to compute the stress and life of blade.

关键词： compressor different three-dimension analytical classical low-speed

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Dynamics of structural systems with various frequency-dependent damping models

Li LI,Yujin HU,Weiming DENG,Lei LÜ,Zhe DING

《机械工程前沿（英文）》 2015年第10卷第1期页码 48-63 doi: 10.1007/s11465-015-0330-5

摘要：

The aim of this paper is to present the dynamic analyses of the system involving various damping models. The assumed frequency-dependent damping forces depend on the past history of motion via convolution integrals over some damping kernel functions. By choosing suitable damping kernel functions of frequency-dependent damping model, it may be derived from the familiar viscoelastic materials. A brief review of literature on the choice of available damping models is presented. Both the mode superposition method and Fourier transform method are developed for calculating the dynamic response of the structural systems with various damping models. It is shown that in the case of non-deficient systems with various damping models, the modal analysis with repeated eigenvalues are very similar to the traditional modal analysis used in undamped or viscously damped systems. Also, based on the pseudo-force approach, we transform the original equations of motion with nonzero initial conditions into an equivalent one with zero initial conditions and therefore present a Fourier transform method for the dynamics of structural systems with various damping models. Finally, some case studies are used to show the application and effectiveness of the derived formulas.

关键词： damping viscoelasticity dynamic analysis mode superposition method Fourier transform method

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Development of a seismic design method based on response spectra for building structures

ZHOU Xiyuan, YU Ruifang

《结构与土木工程前沿（英文）》 2007年第1卷第2期页码 129-141 doi: 10.1007/s11709-007-0014-2

摘要： The assumption and problem of the mode-superposition response spectrum method in seismic design code is discussed based on a brief review of the development of the seismic design method for building structures. The scope of application for the classical damping theory is analyzed and the necessity of the research on mode-superposition method for non-classical damping is presented. The progresses on the mode superposition response spectrum theory are discussed. This includes: 1) the complex mode superposition method (in real form) for the non-classically damped linear system and the general calculation formula for the application of code; 2) the complex complete quadratic combination (CCQC) method for the non-classically damped linear system, which is based on the same assumptions as in deducing the complete quadratic combination (CQC) method which is popularly used in seismic design codes of many countries; 3) the complex complete quadratic combination with three components (CCQC3) method, which is a generalization of the CCQC method to the case of multi-components and multiple-support seismic excitations and deducing corresponding method; 4) the approach for calculation of seismic response of the non-classically damped system with overcritical damping and the calculation method of seismic response for the linear system with multiple eigenvalues; 5) the time-dependent CCQC (t) algorithm considering nonstationary earthquake ground motion; 6) an applied and effective method to solve the low order complex vector basis for the large linear non-classically damped system, which can be expediently used in practice to avoid the unknown errors coming from the forced uncoupling method; 7) bringing forward the concept of partial quadratic combination in order to reduce the calculation amount of CQC and CCQC methods, and studying the primary estimation-criterion. The reasonability and applicable scope of these methods are also briefly discussed in this paper.

关键词： generalization classical damping mode-superposition response calculation formula damping theory

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Dynamic characteristics analysis of active constrained layer damping plate with various boundary conditions

Jing LU, Yu XIANG, Qiao NI

《机械工程前沿（英文）》 2011年第6卷第4期页码 449-455 doi: 10.1007/s11465-011-0240-0

摘要：

Considering the direct and converse piezoelectric effect, expressions of piezoelectric membrane internal forces in the piezoelectric constrained layer were given. The control equations of the piezoelectric constrained layer and host plate were obtained in according with the thin plate theory. Based on the layer wised principle, the integrated first order differential equation of an active constrained layer damping (ACLD) plate was derived for the simply supported boundary condition. Then, this method was expanded to the ACLD plate with cantilever boundary condition by virtue of geometric analogy method. Employing the extended homogeneous capacity precision integration approach, a high precision semi-analytical method was proposed to analyze the dynamic characteristics of the ACLD plate with various boundary conditions. The comparison with the literature results has verified the accuracy and effectiveness of the present method.

关键词： active constrained layer damping (ACLD) plate dynamic characteristics semi-analytical method extended homogeneous capacity precision integration approach