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新冠病毒肺炎 4

严格雪崩准则 3

Bent函数 2

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动力响应 2

动力学 2

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Identification of dynamic stiffness matrix of bearing joint region

Feng HU, Bo WU, Youmin HU, Tielin SHI

《机械工程前沿(英文)》 2009年 第4卷 第3期   页码 289-299 doi: 10.1007/s11465-009-0064-3

摘要: The paper proposes an identification method of the dynamic stiffness matrix of a bearing joint region on the basis of theoretical analysis and experiments. The author deduces an identification model of the dynamic stiffness matrix from the synthetic substructure method. The dynamic stiffness matrix of the bearing joint region can be identified by measuring the matrix of frequency response function (FRFs) of the substructure (axle) and whole structure (assembly of the axle, bearing, and bearing housing) in different positions. Considering difficulty in measuring angular displacement, applying moment, and directly measuring relevant FRFs of rotational degree of freedom, the author employs an accurately calibrated finite element model of the unconstrained structure for indirect estimation. With experiments and simulation analysis, FRFs related with translational degree of freedom, which is estimated through the finite element model, agrees with experimental results, and there is very high reliability in the identified dynamic stiffness matrix of the bearing joint region.

关键词: frequency response function (FRFs)     dynamic stiffness     finite element     synthetic substructure method     joint region    

Inverse identification of the mechanical parameters of a pipeline hoop and analysis of the effect of preload

Ye GAO, Wei SUN

《机械工程前沿(英文)》 2019年 第14卷 第3期   页码 358-368 doi: 10.1007/s11465-019-0539-9

摘要: To create a dynamic model of a pipeline system effectively and analyze its vibration characteristics, the mechanical characteristic parameters of the pipeline hoop, such as support stiffness and damping under dynamic load, must be obtained. In this study, an inverse method was developed by utilizing measured vibration data to identify the support stiffness and damping of a hoop. The procedure of identifying such parameters was described based on the measured natural frequencies and amplitudes of the frequency response functions (FRFs) of a pipeline system supported by two hoops. A dynamic model of the pipe-hoop system was built with the finite element method, and the formulas for solving the FRF of the pipeline system were provided. On the premise of selecting initial values reasonably, an inverse identification algorithm based on sensitivity analysis was proposed. A case study was performed, and the mechanical parameters of the hoop were identified using the proposed method. After introducing the identified values into the analysis model, the reliability of the identification results was validated by comparing the predicted and measured FRFs of the pipeline. Then, the developed method was used to identify the support stiffness and damping of the pipeline hoop under different preloads of the bolts. The influence of preload was also discussed. Results indicated that the support stiffness and damping of the hoop exhibited frequency-dependent characteristics. When the preloads of the bolts increased, the support stiffness increased, whereas the support damping decreased.

关键词: inverse identification     pipeline hoop     frequency response function     mechanical parameters     preload    

Calculation of collision frequency function for aerosol particles in free molecule regime in presence

Xiaowei LUO, Yannick BENICHOU, Suyuan YU

《能源前沿(英文)》 2013年 第7卷 第4期   页码 506-510 doi: 10.1007/s11708-013-0275-5

摘要: The collision frequency function for aerosol particles has already been calculated for the free molecule regime and for the continuum range. The present work, taking into account the influence of internal force fields such as magnetic force, electric force and molecular forces, created by particles themselves, recalculated the collision frequency in the case of particles much smaller than the mean free path of the gas (free molecule regime). Attractive forces increase naturally the collision frequency, while repulsive forces decrease it. The calculation was performed for all types of central forces deriving from a potential, including Coulomb forces and Van der Waals forces.

关键词: aerosol particles     collision frequency function     coagulation    

Effects of elastic support on the dynamic behaviors of the wind turbine drive train

Shuaishuai WANG, Caichao ZHU, Chaosheng SONG, Huali HAN

《机械工程前沿(英文)》 2017年 第12卷 第3期   页码 348-356 doi: 10.1007/s11465-017-0420-7

摘要:

The reliability and service life of wind turbines are influenced by the complex loading applied on the hub, especially amidst a poor external wind environment. A three-point elastic support, which includes the main bearing and two torque arms, was considered in this study. Based on the flexibilities of the planet carrier and the housing, a coupled dynamic model was developed for a wind turbine drive train. Then, the dynamic behaviors of the drive train for different elastic support parameters were computed and analyzed. Frequency response functions were used to examine how different elastic support parameters influence the dynamic behaviors of the drive train. Results showed that the elastic support parameters considerably influenced the dynamic behaviors of the wind turbine drive train. A large support stiffness of the torque arms decreased the dynamic response of the planet carrier and the main bearing, whereas a large support stiffness of the main bearing decreased the dynamic response of planet carrier while increasing that of the main bearing. The findings of this study provide the foundation for optimizing the elastic support stiffness of the wind turbine drive train.

关键词: wind turbine drive train     elastic support     dynamic behavior     frequency response function    

Topology optimization of transient problem with maximum dynamic response constraint using SOAR scheme

《机械工程前沿(英文)》 2021年 第16卷 第3期   页码 593-606 doi: 10.1007/s11465-021-0636-4

摘要: This paper proposes a novel method for the continuum topology optimization of transient vibration problem with maximum dynamic response constraint. An aggregated index in the form of an integral function is presented to cope with the maximum response constraint in the time domain. The density filter solid isotropic material with penalization method combined with threshold projection is developed. The sensitivities of the proposed index with respect to design variables are conducted. To reduce computational cost, the second-order Arnoldi reduction (SOAR) scheme is employed in transient analysis. Influences of aggregate parameter, duration of loading period, interval time, and number of basis vectors in the SOAR scheme on the final designs are discussed through typical examples while unambiguous configuration can be achieved. Through comparison with the corresponding static response from the final designs, the optimized results clearly demonstrate that the transient effects cannot be ignored in structural topology optimization.

关键词: topology optimization     solid isotropic material with penalization     transient response     aggregation function     second-order Arnoldi reduction    

基于频率响应函数的动力学模型修正方法研究

朱凼凼,冯咬齐,向树红

《中国工程科学》 2005年 第7卷 第8期   页码 89-94

摘要:

概述了国内外动力学模型修正技术的研究状况,研究了近些年发展起来的基于频响函数的动力学模型修正方法;利用航天器振动试验测量所得的频响函数,从理论上介绍了频响函数残差法、设计参数型频响函数法和摄动型频响函数法三种基于频响函数的动力学模型修正方法,为动力学模型修正技术的发展提供参考。

关键词: 航天器     动力学     频响函数     模型修正    

Comparison in executive function in Chinese preterm and full-term infants at eight months

null

《医学前沿(英文)》 2018年 第12卷 第2期   页码 164-173 doi: 10.1007/s11684-017-0540-9

摘要:

Executive function (EF) is increasingly recognized as being responsible for adverse developmental outcomes in preterm-born infants. Several perinatal factors may lead to poor EF development in infancy, and the deficits in EF can be identified in infants as young as eight months. A prospective cohort study was designed to study the EF in Chinese preterm infants and examine the relationship between EF in preterm infants and maternal factors during perinatal period. A total of 88 preterm infants and 88 full-term infants were followed from birth to eight months (corrected age). Cup Task and Planning Test was applied to assess the EF of infants, and the Bayley Scale of Infant Development (BSID-III) was used to evaluate cognitive (MDI) and motor abilities (PDI) of infants. In comparison with full-term infants, the preterm infants performed more poorly on all measures of EF including working memory, inhibition to prepotent responses, inhibition to distraction, and planning, and the differences remained after controlling the MDI and PDI. Anemia and selenium deficiency in mothers during pregnancy contributed to the differences in EF performance. However, maternal depression, hypertension, and diabetes during pregnancy were not related to the EF deficits in preterm infants. Future research should focus on the prevention of anemia and selenium deficiency during pregnancy and whether supplementing selenium in mothers during pregnancy can prevent further deterioration and the development of adverse outcomes of their offspring.

关键词: executive function (EF)     preterm infant     working memory     inhibition to prepotent response     inhibition to distraction     planning    

Microbial responses to the use of NaClO in sediment treatment

《环境科学与工程前沿(英文)》 2022年 第16卷 第2期 doi: 10.1007/s11783-021-1451-1

摘要:

• Chlorine addition enhanced the release of TOC, TN from the sediment.

关键词: Sediment chlorination     Substance mobility     Microbial response     Community composition     Function    

An efficient stochastic dynamic analysis of soil media using radial basis function artificial neural

P. ZAKIAN

《结构与土木工程前沿(英文)》 2017年 第11卷 第4期   页码 470-479 doi: 10.1007/s11709-017-0440-8

摘要: Since a lot of engineering problems are along with uncertain parameters, stochastic methods are of great importance for incorporating random nature of a system property or random nature of a system input. In this study, the stochastic dynamic analysis of soil mass is performed by finite element method in the frequency domain. Two methods are used for stochastic analysis of soil media which are spectral decomposition and Monte Carlo methods. Shear modulus of soil is considered as a random field and the seismic excitation is also imposed as a random process. In this research, artificial neural network is proposed and added to Monte Carlo method for sake of reducing computational effort of the random analysis. Then, the effects of the proposed artificial neural network are illustrated on decreasing computational time of Monte Carlo simulations in comparison with standard Monte Carlo and spectral decomposition methods. Numerical verifications are provided to indicate capabilities, accuracy and efficiency of the proposed strategy compared to the other techniques.

关键词: stochastic analysis     random seismic excitation     finite element method     artificial neural network     frequency domain analysis     Monte Carlo simulation    

Demand response based congestion management in a mix of pool and bilateral electricity market model

Ashwani KUMAR, Charan SEKHAR

《能源前沿(英文)》 2012年 第6卷 第2期   页码 164-178 doi: 10.1007/s11708-012-0187-9

摘要: The independent system operator (ISO) is a key element in the deregulated structure with one of the responsibilities of transmission congestion management (CM). The ISO opts market based solutions to manage congestion receiving bids from generation companies (GENCOs) as well as distribution companies (DISCOMs) to reschedule their generation and relocate demand. The nodal prices increases during the congestion hours and the demand response to nodal prices will be an effective tool for the control of congestion. In this paper, demand response-based CM has been proposed for a mix of pool and bilateral electricity market model. The linear bid curves have been considered for demand bids to respond to the congestion in the network. The bilateral demand has been obtained with minimum deviations in their preferred schedule. The impact of flexible alternating current transmission system (FACTS) devices viz static var compensator (SVC) and thyristor controlled series compensator (TCSC) has also been considered for demand management during congestion. Multi-line congestion cases have been considered to study the impact on demand response without and with FACTS devices. The proposed approach has been tested on the IEEE 24 bus test system.

关键词: bid function     congestion management (CM)     demand response     pool+bilateral electricity market     static var compensator (SVC)     thyristor controlled series compensator (TCSC)    

复杂机械结构中高频动响应能量有限元方法研究

祝丹晖,解妙霞,孔祥杰,张文博,陈花玲

《中国工程科学》 2013年 第15卷 第1期   页码 106-112

摘要:

从理论研究和应用研究两个方面追踪了国内外关于能量有限元的发展现状,并指出能量有限元已趋向于预示越来越复杂的结构动响应;接下来介绍本课题组近年来利用能量有限元方法针对实际复杂结构及复杂载荷环境中的高频动响应问题所做的研究工作,主要包括3个部分:一是在考虑多种传递波功率流耦合的情况下,发展了圆柱壳、截锥壳等复杂结构的高频响应能量有限元方法,从而得到了此类结构的中高频局部动响应特性;二是考虑在脉动载荷、混响室等复杂环境中,利用能量有限元方法并结合能量边界元方法预示了结构的高频振动特性和声振耦合特性;三是开发了能量有限元的计算软件,为其大规模应用奠定了基础。最后指出了能量有限元方法目前存在的问题和进一步研究的方向。

关键词: 中高频响应     能量有限元方法     声振响应预示     机械结构     动力学    

深水钻井隔水导管挠曲方程和固有频率的计算及其研究

姜伟

《中国工程科学》 2011年 第13卷 第5期   页码 66-73

摘要:

从深水钻井应用的隔水导管的使用实际情况出发,应用弹塑性力学中的位移复分原理的Ritz法,考虑了隔水导管所受到的轴向张力T和隔水导管受力产生的倾角α以及由于自重q所产生的自重横向分力qsin α和轴向分力qcos α,建立了较为合理的挠曲方程,并且由此得到隔水导管的固有振动频率的简易计算求解方法。由于该挠曲方程结合了钻具的实际情况,其挠曲方程的约束条件采用的是一端铰支、一端自由的形式,因此其研究更接近实际情况,研究旨在为深水钻井隔水导管的合理使用设计和选择,提供一种更快捷实用的方法,对深水钻井作业有一定的指导意义。

关键词: 深水钻井     隔水导管     挠曲方程     固有频率     形状函数    

Load shedding scheme for an interconnected hydro-thermal hybrid system with SMES

D. TYAGI, Ashwani KUMAR, Saurabh CHANANA

《能源前沿(英文)》 2012年 第6卷 第3期   页码 227-236 doi: 10.1007/s11708-012-0198-6

摘要: The frequency of the power system varies based on the load pattern of the consumers. With continuous increase in the load, the frequency of the system keeps decreasing and may reach its minimum allowable limits. Further increase in the load will result in more frequency drop leading to the need of load shedding, if excess generation is not available to cater the need. This paper proposed a methodology in a hybrid thermal-hydro system for finding the required amount of load to be shed for setting the frequency of the system within its minimum allowable limits. The load shedding steps were obtained based on the rate of change of frequency with the increase in the load in both areas. The impact of superconducting magnetic energy storage (SMES) was obtained on load shedding scheme. The comparison of the results was presented on the two-area system.

关键词: critical load     frequency response     load shedding     multi-area system     rate of change of frequency     superconducting magnetic energy storage (SMES) device    

Load shedding scheme for the two-area system with linear quadratic regulator

D. TYAGI, Ashwani KUMAR, Saurabh CHANANA

《能源前沿(英文)》 2013年 第7卷 第1期   页码 90-102 doi: 10.1007/s11708-012-0224-8

摘要: The power system is prone to many emergency conditions which may lead to emergency state of operation with decay in the system frequency. The dramatic change in the frequency can result in cascaded failure of the system. In order to avoid power system collapse, load shedding (LS) schemes are adopted with the optimal amount of load shed. This paper proposed a methodology in a two-area thermal-thermal system for finding the required amount of load to be shed for setting the frequency of the system within minimum allowable limits. The LS steps have been obtained based on the rate of change of frequency with the increase in load in steps. A systematic study has been conducted for three scenarios: the scheme with a conventional integral controller; the scheme with a linear quadratic regulator (LQR); and the scheme with an LQR and superconducting magnetic energy storage devices (SMES). A comparison of the results has been presented on the two-area system.

关键词: critical load     frequency response     load shedding (LS)     multi-area system     rate of change of frequency     linear quadratic regulator (LQR)     superconducting magnetic energy storage devices (SMES)    

Soil seismic analysis for 2D oblique incident waves using exact free-field responses by frequency-based

《结构与土木工程前沿(英文)》 2022年 第16卷 第12期   页码 1530-1551 doi: 10.1007/s11709-022-0900-7

摘要: The seismic analysis of a viscoelastic half-space under two-dimensional (2D) oblique incident waves is carried out by the finite/infinite element method (FIEM). First, the frequency-domain exact solutions for the displacements and stresses of the free field are derived in general form for arbitrary incident P and SV waves. With the present formulation, no distinction needs to be made for SV waves with over-critical incident angles that make the reflected P waves disappear, while no critical angle exists for P waves. Next, the equivalent seismic forces of the earthquake (Taft Earthquake 1952) imposed on the near-field boundary are generated by combining the solutions for unit ground accelerations with the earthquake spectrum. Based on the asymmetric finite/infinite element model, the frequency-domain motion equations for seismic analysis are presented with the key parameters selected. The results obtained in frequency and time domain are verified against those of Wolf’s, Luco and de Barros’ and for inversely computed ground motions. The parametric study indicated that distinct phase difference exists between the horizontal and vertical responses for SV waves with over-critical incident angles, but not for under-critical incident angles. Other observations were also made for the numerical results inside the text.

关键词: oblique incident waves     critical angle     half-space     finite/infinite element approach     seismic response analysis    

标题 作者 时间 类型 操作

Identification of dynamic stiffness matrix of bearing joint region

Feng HU, Bo WU, Youmin HU, Tielin SHI

期刊论文

Inverse identification of the mechanical parameters of a pipeline hoop and analysis of the effect of preload

Ye GAO, Wei SUN

期刊论文

Calculation of collision frequency function for aerosol particles in free molecule regime in presence

Xiaowei LUO, Yannick BENICHOU, Suyuan YU

期刊论文

Effects of elastic support on the dynamic behaviors of the wind turbine drive train

Shuaishuai WANG, Caichao ZHU, Chaosheng SONG, Huali HAN

期刊论文

Topology optimization of transient problem with maximum dynamic response constraint using SOAR scheme

期刊论文

基于频率响应函数的动力学模型修正方法研究

朱凼凼,冯咬齐,向树红

期刊论文

Comparison in executive function in Chinese preterm and full-term infants at eight months

null

期刊论文

Microbial responses to the use of NaClO in sediment treatment

期刊论文

An efficient stochastic dynamic analysis of soil media using radial basis function artificial neural

P. ZAKIAN

期刊论文

Demand response based congestion management in a mix of pool and bilateral electricity market model

Ashwani KUMAR, Charan SEKHAR

期刊论文

复杂机械结构中高频动响应能量有限元方法研究

祝丹晖,解妙霞,孔祥杰,张文博,陈花玲

期刊论文

深水钻井隔水导管挠曲方程和固有频率的计算及其研究

姜伟

期刊论文

Load shedding scheme for an interconnected hydro-thermal hybrid system with SMES

D. TYAGI, Ashwani KUMAR, Saurabh CHANANA

期刊论文

Load shedding scheme for the two-area system with linear quadratic regulator

D. TYAGI, Ashwani KUMAR, Saurabh CHANANA

期刊论文

Soil seismic analysis for 2D oblique incident waves using exact free-field responses by frequency-based

期刊论文