资源类型

期刊论文 1900

会议视频 33

会议信息 2

年份

2024 1

2023 89

2022 143

2021 135

2020 106

2019 123

2018 110

2017 120

2016 78

2015 100

2014 94

2013 84

2012 91

2011 85

2010 80

2009 65

2008 91

2007 105

2006 54

2005 30

展开 ︾

关键词

能源 11

风险分析 9

对策 5

影响因素 5

仿真 4

分析 4

制造业 4

可持续发展 4

数值模拟 4

隧道 4

2035年 3

ANSYS 3

农业科学 3

抗击疫情 3

数值分析 3

环境 3

营养健康 3

裂缝 3

预测 3

展开 ︾

检索范围：

排序： 展示方式：

Modal analysis of acoustic leak signal in pipelines using time-frequency analysis

JIAO Jing-pin, FEI Ren-yuan, HE Cun-fu, WU Bin

《机械工程前沿（英文）》 2006年 第1卷 第2期   页码 146-150 doi: 10.1007/s11465-006-0013-3

摘要： It is important to analyze the propagation characteristics of guided waves in acoustic leak location in pipelines. In this paper, the acoustic leak signal is analyzed in the time-frequency domain. Based on the relation of time-frequency distribution of the acoustic leak signal and the dispersion curves of guided waves, the mode components of acoustic leak signals were obtained. The research can provide a guideline for the mode selection in pipeline leak location, and help improve the accuracy of leak location.

关键词： dispersion     selection     guided     research     time-frequency    

HTML PDF 收藏

Short-term prediction of influent flow rate and ammonia concentration in municipal wastewater treatment plants

Shuai MA, Siyu ZENG, Xin DONG, Jining CHEN, Gustaf OLSSON

《环境科学与工程前沿（英文）》 2014年 第8卷 第1期   页码 128-136 doi: 10.1007/s11783-013-0598-9

摘要： The prediction of the influent load is of great importance for the improvement of the control system to a large wastewater treatment plant. A systematic data analysis method is presented in this paper in order to estimate and predict the periodicity of the influent flow rate and ammonia (NH ) concentrations: 1) data filtering using wavelet decomposition and reconstruction; 2) typical cycle identification using power spectrum density analysis; 3) fitting and prediction model establishment based on an autoregressive model. To give meaningful information for feedforward control systems, predictions in different time scales are tested to compare the corresponding predicting accuracy. Considering the influence of the rainfalls, a linear fitting model is derived to estimate the relationship between flow rate trend and rain events. Measurements used to support coefficient fitting and model testing are acquired from two municipal wastewater treatment plants in China. The results show that 1) for both of the two plants, the periodicity affects the flow rate and NH concentrations in different cycles (especially cycles longer than 1 day); 2) when the flow rate and NH concentrations present an obvious periodicity, the decreasing of prediction accuracy is not distinct with increasing of the prediction time scales; 3) the periodicity influence is larger than rainfalls; 4) the rainfalls will make the periodicity of flow rate less obvious in intensive rainy periods.

关键词： influent load prediction     wavelet de-noising     power spectrum density     autoregressive model     time-frequency analysis     wastewater treatment    

HTML PDF 收藏

Non-stationary signal analysis based on general parameterized time--frequency transform and its application

Peng ZHOU, Zhike PENG, Shiqian CHEN, Yang YANG, Wenming ZHANG

《机械工程前沿（英文）》 2018年 第13卷 第2期   页码 292-300 doi: 10.1007/s11465-017-0443-0

摘要：

With the development of large rotary machines for faster and more integrated performance, the condition monitoring and fault diagnosis for them are becoming more challenging. Since the time-frequency (TF) pattern of the vibration signal from the rotary machine often contains condition information and fault feature, the methods based on TF analysis have been widely-used to solve these two problems in the industrial community. This article introduces an effective non-stationary signal analysis method based on the general parameterized time–frequency transform (GPTFT). The GPTFT is achieved by inserting a rotation operator and a shift operator in the short-time Fourier transform. This method can produce a high-concentrated TF pattern with a general kernel. A multi-component instantaneous frequency (IF) extraction method is proposed based on it. The estimation for the IF of every component is accomplished by defining a spectrum concentration index (SCI). Moreover, such an IF estimation process is iteratively operated until all the components are extracted. The tests on three simulation examples and a real vibration signal demonstrate the effectiveness and superiority of our method.

关键词： rotary machines     condition monitoring     fault diagnosis     GPTFT     SCI    

HTML PDF 收藏

Time-domain and frequency-domain approaches to identification of bridge flutter derivatives

Zhengqing CHEN

《结构与土木工程前沿（英文）》 2009年 第3卷 第2期   页码 173-179 doi: 10.1007/s11709-009-0034-1

摘要： Flutter derivatives are essential for flutter analysis of long-span bridges, and they are generally identified from the vibration testing data of a sectional model suspended in a wind tunnel. Making use of the forced vibration testing data of three sectional models, namely, a thin-plate model, a nearly streamlined model, and a bluff-body model, a comparative study was made to identify the flutter derivatives of each model by using a time-domain method and a frequency-domain method. It was shown that all the flutter derivatives of the thin-plate model identified with the frequency-domain method and time-domain method, respectively, agree very well. Moreover, some of the flutter derivatives of each of the other two models identified with the two methods deviate to some extent. More precisely, the frequency-domain method usually results in smooth curves of the flutter derivatives. The formulation of time-domain method makes the identification results of flutter derivatives relatively sensitive to the signal phase lag between vibration state vector and aerodynamic forces and also prone to be disturbed by noise and nonlinearity.

关键词： long-span bridges     wind-induced vibration     flutter derivatives     forced vibration test     time-domain method     frequency-domain method    

HTML PDF 收藏

A frequency error estimation for isogeometric analysis of Kirchhoff–Love cylindrical shells

《结构与土木工程前沿（英文）》 doi: 10.1007/s11709-023-0006-x

摘要： A frequency error estimation is presented for the isogeometric free vibration analysis of Kirchhoff–Love cylindrical shells using both quadratic and cubic basis functions. By analyzing the discrete isogeometric equations with the aid of harmonic wave assumption, the frequency error measures are rationally derived for the quadratic and cubic formulations for Kirchhoff–Love cylindrical shells. In particular, the governing relationship of the continuum frequency for Kirchhoff–Love cylindrical shells is naturally embedded into the frequency error measures without the need of explicit frequency expressions, which usually are not trivial for the shell problems. In accordance with these theoretical findings, the 2nd and 4th orders of frequency accuracy are attained for the isogeometric schemes using quadratic and cubic basis functions, respectively. Numerical results not only thoroughly verify the theoretical convergence rates of frequency solutions, but also manifest an excellent magnitude match between numerical and theoretical frequency errors for the isogeometric free vibration analysis of Kirchhoff–Love cylindrical shells.

关键词： isogeometric analysis     Kirchhoff–Love cylindrical shell     free vibration     frequency error     convergence    

HTML PDF 收藏

Analysis of frequency characteristics of compliant mechanisms

WANG Wenjing, YU Yueqing

《机械工程前沿（英文）》 2007年 第2卷 第3期   页码 267-271 doi: 10.1007/s11465-007-0046-2

摘要： Much work is needed for a further study on the dynamic analysis of compliant mechanisms to improve their performance and operational accuracy. This paper uses the finite element method to develop a dynamic equation of the compliant mechanism. Natural frequencies and modes are derived. Using the differentials of a stiffness matrix to design parameters, a method for calculating the sensitivity of natural frequency is presented. The numerical simulation results indicate that the design parameters have an impact on the frequency characteristics of the compliant mechanisms and the proposed method is more accurate and convenient for analyzing frequency characteristics.

关键词： compliant mechanisms     convenient     sensitivity     work     analysis    

HTML PDF 收藏

Analysis of planetary gear transmission in non-stationary operations

Fakher CHAARI, Mohamed Slim ABBES, Fernando Viadero RUEDA, Alfonso Fernandez del RINCON, Mohamed HADDAR

《机械工程前沿（英文）》 2013年 第8卷 第1期   页码 88-94 doi: 10.1007/s11465-013-0361-8

摘要：

Planetary gearboxes operate usually in non-stationary conditions generated mainly by variable loads applied to these transmissions. In order to understand the dynamic behavior of planetary gearboxes in such conditions, a mathematic model is developed including driving unit, transmission and load. The variability of load induces a variable speed of the transmission which is taken into account when characterizing the main dynamic parameter of the transmission which is the mesh stiffness function. This function is not periodic following the variability of the transmission speed. The computation of the dynamic response shows an intimate relation between the vibration amplitude level and the load value. As the load increase the vibration level increase. A combined amplitude and frequency modulation is observed which is well characterized using Short Time Fourier transform more suited than the spectral analysis.

关键词： planetary gearbox     non-stationary conditions     variable load     dynamic response     time frequency analysis    

HTML PDF 收藏

Capacity limitation of nuclear units in grid based on analysis of frequency regulation

Yiping DAI, Pan JIANG, Lin GAO, Weimin KAN, Xiaoqing XIAO, Ge JIN

《能源前沿（英文）》 2012年 第6卷 第2期   页码 148-154 doi: 10.1007/s11708-012-0174-1

摘要： The increasing capacity of nuclear units in power grid poses threat to system stability and security. Load disturbance may cause overspeed of the units and trigger the overspeed protection controller (OPC). Repeating actions of valves have a strong impact on the security of the equipment and may result in a collapse of the power system. Based on the analysis of frequency regulation, mathematic models for nuclear units in the grid are established in this paper to simulate the dynamic process when load disturbance occurs. The critical action of the OPC is proposed as the constraint of safe operation for the units. The relationship between different styles of frequency regulation and the allowable capacity of the nuclear units in the grid is discussed. This research can help to estimate the capacity limitation of nuclear units in the grid.

关键词： nuclear units capacity     overspeed     primary frequency control (PFC)     second frequency control (SFC)    

HTML PDF 收藏

Meta-analysis of the diagnostic efficiency of frequency-doubling technology for primary glaucoma

LIU Ting, HE Xiangge

《医学前沿（英文）》 2007年 第1卷 第1期   页码 109-114 doi: 10.1007/s11684-007-0021-7

摘要： The overall diagnostic capabilities and utility of frequency-doubling technology (FDT) in patients with primary glaucoma, which was diagnosed by standard automated perimetry (SAP) and/or optic disc appearance as the gold standard, were assessed. A comprehensive electric retrieval in MEDLINE, EMBASE, Cochrane Library, BIOSIS, Previews, HMIC, IPA, OVID, CNKI, CBMdisc, VIP information, CMCC, CCPD, SSreader, 21dmedia and manual retrieval in related textbooks, journals, congress articles and their references at home and abroad were performed to identify relevant articles in English or Chinese. The corresponding references were retrieved by means of electric retrieval and manual retrieval from different databases or materials. Criteria for inclusion or exclusion were established according to validity criteria for diagnostic studies published by the Cochrane Methods Group on Screening and Diagnostic Tests. The quality of the included articles was then assessed and characteristics were extracted. Statistical analysis was performed with Meta Test version 0.6 software to test the heterogeneity of the included articles. The appropriate effects model was selected to calculate pooled weighted sensitivity and specificity. Summary receiver operating characteristic (SROC) curve was drawn and the area under the curve (AUC) was calculated. Finally, sensitivity analysis was performed. Twenty-one studies out of 206 retrieved articles were included, with a total of 3172 patients. The reported sensitivity of FDT ranged from 0.51 to 1.00, and specificity from 0.58 to 1.00. The pooled weighted sensitivity and specificity of FDT with 95% confidence intervals (95% CI) after correction for standard error were 0.86 (0.80 0.90) and 0.87 (0.81 0.91), respectively. The AUC of SROC was 93.01%. Sensitivity analysis demonstrated no disproportionate influences of individual studies. The included articles are of good quality and FDT can be a highly efficient diagnostic test for primary glaucoma based on Meta-analysis.

关键词： inclusion     sensitivity analysis     correction     specificity     appropriate    

HTML PDF 收藏

Conformal analysis of fundamental frequency of vibration of elastic clamped plates

QI Hongyuan, ZHU Hengjun

《机械工程前沿（英文）》 2007年 第2卷 第4期   页码 429-432 doi: 10.1007/s11465-007-0073-z

摘要： To calculate the fundamental frequency of vibration of special-shaped and elastic clamped plates, the conformal mapping theory is adopted to separate the interpolating points of a complicated boundary into odd and even sequences, both of which can be mutually iterated, so that the conformal mapping function between the complicated region and the unit dish region is established. Trigonometric interpolation and convergence along the normal direction methods are provided, and the complex coefficients of the conformal mapping function are calculated. Galerkin method is used to obtain the solution of fundamental frequency in the vibrating differential function of the complicated vibrating region. Finally, taking ellipse elastic clamped plates as an example, the effects on fundamental frequency coefficient caused by eccentric ratio and area size are analyzed.

关键词： direction     theory     vibration     odd     complicated boundary    

HTML PDF 收藏

基于钻头运动诱发套管头振动信号检测的井眼防碰监测方法

何保生,刘刚,王平双,文敏

《中国工程科学》 2011年 第13卷 第5期   页码 74-78

摘要：

针对海上加密调整井的井眼防碰问题，设计了一种井筒防碰地面监测预警系统，并进行了现场应用。系统利用加速度传感器监测通过套管传输到套管头上的钻头振动信号，利用数据采集、信号滤波放大和专门编制的监测软件记录分析传感器采集的振动信号，通过对信号的时域、频域分析，确定信号特征与井间相对距离的关系，识别钻头对风险井套管的趋近或碰撞。应用结果表明，该系统能有效感知通过地层、套管传输到套管头的钻头振动信号，并能识别出钻头对风险邻井的趋近，验证了系统在设计理论和方法上的可行性，为加密调整井的井眼防碰、保证钻井安全提供了一种有效的手段。

关键词： 调整井     防碰     风险井     振动信号     时域分析     频域分析    

HTML PDF 收藏

Design and analysis of a new high frequency double-servo direct drive rotary valve

Muzhi ZHU,Shengdun ZHAO,Jingxiang LI

《机械工程前沿（英文）》 2016年 第11卷 第4期   页码 344-350 doi: 10.1007/s11465-016-0406-x

摘要：

Researchers have investigated direct drive valve for many years to solve problems, such as fluid force imbalance and switching frequency. The structure of the rotary valve has received considerable research interest because of its favorable dynamic properties and simple structure. This paper studied the high frequency double-servo direct drive rotary valve (DDRV), and proposed a novel structure and drive method satisfying high reversing frequency and adequate quantity of flow. Servo motors are integrated into the valve by the innovative structure, which is designed to equilibrate the unbalanced radial fluid force with the symmetric distributed oil ports. Aside from the fast reversing function of the valve, the DDRV presented high performance in linearity of the flow quantity and valve opening as a result of the fan-shaped flow ports. In addition, a computational fluid dynamics (CFD) method based on Fluent was conducted to verify the flux regulation effect of the height change of the adjustable boss.

关键词： direct drive rotary valve     computational fluid dynamics (CFD)     flow regulation    

HTML PDF 收藏

General expression for linear and nonlinear time series models

Ren HUANG, Feiyun XU, Ruwen CHEN

《机械工程前沿（英文）》 2009年 第4卷 第1期   页码 15-24 doi: 10.1007/s11465-009-0015-z

摘要： The typical time series models such as ARMA, AR, and MA are founded on the normality and stationarity of a system and expressed by a linear difference equation; therefore, they are strictly limited to the linear system. However, some nonlinear factors are within the practical system; thus, it is difficult to fit the model for real systems with the above models. This paper proposes a general expression for linear and nonlinear auto-regressive time series models (GNAR). With the gradient optimization method and modified AIC information criteria integrated with the prediction error, the parameter estimation and order determination are achieved. The model simulation and experiments show that the GNAR model can accurately approximate to the dynamic characteristics of the most nonlinear models applied in academics and engineering. The modeling and prediction accuracy of the GNAR model is superior to the classical time series models. The proposed GNAR model is flexible and effective.

关键词： linear and nonlinear     autoregressive model     system identification     time series analysis    

HTML PDF 收藏

Prediction of characteristic blast-induced vibration frequency during underground excavation by using

Tae Un PAK; Guk Rae JO; Un Chol HAN

《结构与土木工程前沿（英文）》 2022年 第16卷 第8期   页码 1029-1039 doi: 10.1007/s11709-022-0861-x

摘要： Blast-induced vibration produces a very complex signal, and it is very important to work out environmental problems induced by blasting. In this study, blasting vibration signals were measured during underground excavation in carbonaceous shale by using vibration pickup CB-30 and FFT analyzer AD-3523. Then, wavelet analysis on the measured results was carried out to identify frequency bands reflecting changes of blasting vibration parameters such as vibration velocity and energy in different frequency bands. Frequency characteristics are then discussed in view of blast source distance and charge weight per delay. From analysis of results, it can be found that peak velocity and energy of blasting vibration in frequency band of 62.5–125 Hz were larger than ones in other bands, indicating the similarity to characteristics in the distribution band (31–130 Hz) of main vibration frequency. Most frequency bands were affected by blasting source distance, and the frequency band of 0–62.5 Hz reflected the change of charge weight per delay. By presenting a simplified method to predict main vibration frequency, this research may provide significant reference for future blasting engineering.

关键词： wavelet analysis     blast-induced vibration     frequency characteristics     underground excavation    

HTML PDF 收藏

标题 作者 时间 类型 操作

Modal analysis of acoustic leak signal in pipelines using time-frequency analysis

JIAO Jing-pin, FEI Ren-yuan, HE Cun-fu, WU Bin

期刊论文

Short-term prediction of influent flow rate and ammonia concentration in municipal wastewater treatment plants

Shuai MA, Siyu ZENG, Xin DONG, Jining CHEN, Gustaf OLSSON

期刊论文

Non-stationary signal analysis based on general parameterized time--frequency transform and its application

Peng ZHOU, Zhike PENG, Shiqian CHEN, Yang YANG, Wenming ZHANG

期刊论文

Time-domain and frequency-domain approaches to identification of bridge flutter derivatives

Zhengqing CHEN

期刊论文

A frequency error estimation for isogeometric analysis of Kirchhoff–Love cylindrical shells

期刊论文

Analysis of frequency characteristics of compliant mechanisms

WANG Wenjing, YU Yueqing

期刊论文

Analysis of planetary gear transmission in non-stationary operations

Fakher CHAARI, Mohamed Slim ABBES, Fernando Viadero RUEDA, Alfonso Fernandez del RINCON, Mohamed HADDAR

期刊论文

Capacity limitation of nuclear units in grid based on analysis of frequency regulation

Yiping DAI, Pan JIANG, Lin GAO, Weimin KAN, Xiaoqing XIAO, Ge JIN

期刊论文

Meta-analysis of the diagnostic efficiency of frequency-doubling technology for primary glaucoma

LIU Ting, HE Xiangge

期刊论文

Conformal analysis of fundamental frequency of vibration of elastic clamped plates

QI Hongyuan, ZHU Hengjun

期刊论文

基于钻头运动诱发套管头振动信号检测的井眼防碰监测方法

何保生,刘刚,王平双,文敏

期刊论文

Design and analysis of a new high frequency double-servo direct drive rotary valve

Muzhi ZHU,Shengdun ZHAO,Jingxiang LI

期刊论文

General expression for linear and nonlinear time series models

Ren HUANG, Feiyun XU, Ruwen CHEN

期刊论文

Prediction of characteristic blast-induced vibration frequency during underground excavation by using

Tae Un PAK; Guk Rae JO; Un Chol HAN

期刊论文

司景舰：基于压缩感知的能源金融高频时间序列数据重构（2020年7月12日）

2022年06月10日

会议视频