共查询到20条相似文献，搜索用时 31 毫秒
1.
Top-down crack in asphalt pavements has been reported as a widespread mode of failure.A solid understanding of the mechanisms of crack growth is essential to predict pavement performance in the context of thickness design,as well as in the design and optimization of mixtures.Using the coupled element free Galerkin (EFG) and finite element (FE) method,top-down crack propagation in asphalt pavements is numerically simulated on the basis of fracture mechanics.A parametric study is conducted to isolate the effects of overlay thickness and stiffness,base thickness and stiffness on top-down crack propagation in asphalt pavements.The results show that longitudinal wheel loads are disadvantageous to top-down crack because it increases the compound stress intensity factor (SIF) at the tip of top-down crack and shortens the crack path,and thus the fatigue life descends.The SIF experiences a process "sharply ascending—slowly descending—slowly ascending—sharply ascending again" with the crack propagating.The thicker the overlay or the base,the lower the SIF; the greater the overlay stiffness,the higher the SIF.The crack path is hardly affected by stiffness of the overlay and base. 相似文献
2.
黄文金林本清魏梦伟尹秋雨朱志勇 《福建工程学院学报》2020,(1):29-34
为研究地铁车站建设对邻近道路的影响,采用数字化路面数据采集车(DHDV),对地铁1号线车站上方路面病害进行扫描,根据图形尺寸比例关系计算了站内与站外的路面高差、裂缝长度以及路面行驶质量指标,并利用电子地图技术对路面病害站内外分布情况进行统计,分析了路面病害与地铁车站的关联性。研究结果表明:地铁车站建设加剧了附近道路的路基沉陷和裂缝产生,道路维养措施应作相应调整;用DHDV和电子地图相结合的方法调查道路病害几何特征值及其分布,工作效率和计算精度高,可为道路维养决策和路面病害机理研究提供依据。 相似文献
3.
提出了基于人工神经网络（ＡｒｔｉｆｉｃｉａｌＮｅｕｒａｌＮｅｔｗｏｒｋｓ）对动力结构进行系统辨识的方法，即应用人工神经网络预测结构地震响应．采用ＢＰ算法的前馈网络（简称ＢＰ网络）对剪切模型结构进行系统辨识．首先用实际地震波及相应的模拟地震响应训练本文提出的ＢＰ网络，然后用“已学会”的ＢＰ网络预测其它地震波激励下的结构地震响应．还讨论了网络拓扑结构、输入单元数等对网络学习和预测的影响．通过本文可以发现，合适的人工神经网络结构能准确地辨识结构动力特性和预测结构动力响应 相似文献
4.
Kim-seng Chia Herlina Abdul Rahim Ruzairi Abdul Rahim 《Journal of Zhejiang University. Science. B》2012,13(2):145-151
Visible and near infrared spectroscopy is a non-destructive, green, and rapid technology that can be utilized to estimate
the components of interest without conditioning it, as compared with classical analytical methods. The objective of this paper
is to compare the performance of artificial neural network (ANN) (a nonlinear model) and principal component regression (PCR)
(a linear model) based on visible and shortwave near infrared (VIS-SWNIR) (400–1000 nm) spectra in the non-destructive soluble
solids content measurement of an apple. First, we used multiplicative scattering correction to pre-process the spectral data.
Second, PCR was applied to estimate the optimal number of input variables. Third, the input variables with an optimal amount
were used as the inputs of both multiple linear regression and ANN models. The initial weights and the number of hidden neurons
were adjusted to optimize the performance of ANN. Findings suggest that the predictive performance of ANN with two hidden
neurons outperforms that of PCR. 相似文献
5.
WANG Rui-min CAO Guang-yi ZHU Xin-jian 《浙江大学学报(A卷英文版)》2007,8(5):741-747
Model and simulation are good tools for design optimization of fuel cell systems. This paper proposes a new hybrid model of proton exchange membrane fuel cell (PEMFC). The hybrid model includes physical component and black-box com-ponent. The physical component represents the well-known part of PEMFC, while artificial neural network (ANN) component estimates the poorly known part of PEMFC. The ANN model can compensate the performance of the physical model. This hybrid model is implemented on Matlab/Simulink software. The hybrid model shows better accuracy than that of the physical model and ANN model. Simulation results suggest that the hybrid model can be used as a suitable and accurate model for PEMFC. 相似文献
6.
Using FEM to predict tree motion in a wind field 总被引：1，自引：0，他引：1
In this paper we propose a finite element （FE） simulation method to predict tree motion in a wind field, Two FE tree models were investigated： One model was generated based on a realistic nature-looking geometric tree model, and the other was a symmetric model to investigate the influence of asymmetric material properties on tree motion. The vortex-induced vibration （VIV） theory is introduced to estimate the fluctuating wind force being exerted on tree stems and the fluid-structure interaction （FSI） analysis is also included in the simulation. The results indicate that asymmetric material properties result in the crosswind displacement of the investigated node and the main swaying direction deviation. The simulation reveals that under wind loading, a tree with leaves has much larger swaying amplitude along the wind direction and longer swaying period than a tree without leaves. However, the crosswind swaying amplitude is mainly due to branch interaction. The numerical simulation proved that the interaction of tree branches can prevent dangerous swaying motion developing. 相似文献
7.
Calculation method of ship collision force on bridge using artificial neural network 总被引：1，自引：0，他引：1
Ship collision on bridge is a dynamic process featured by high nonlinearity and instantaneity. Calculating ship-bridge collision force typically involves either the use of design-specification-stipulated equivalent static load, or the use of finite element method （FEM） which is more time-consuming and requires supercomputing resources. In this paper, we proposed an alternative approach that combines FEM with artificial neural network （ANN）. The radial basis function neural network （RBFNN） employed for calculating the impact force in consideration of ship-bridge collision mechanics. With ship velocity and mass as the input vectors and ship collision force as the output vector, the neural networks for different network parameters are trained by the learning samples obtained from finite element simulation results. The error analyses of the learning and testing samples show that the proposed RBFNN is accurate enough to calculate ship-bridge collision force. The input-output relationship obtained by the RBFNN is essentially consistent with the typical empirical formulae. Finally, a special toolbox is developed for calculation effi- ciency in application using MATLAB software. 相似文献
8.
Transportation agencies spend millions of dollars annually to repair civil transportation infrastructure including pavements, earth structures and approach slabs distressed by soft compressible soils and expansive soils. Several research studies performed at the University of Texas at Arlington (UTA) focused on stabilizing these problematic soils so that they will provide better and more stable support to the transportation infrastructure. This paper focuses on a summary of two major distresses and mechanisms, and remedial measures for addressing these distress problems. A combined lime-cement stabilization method is fully evaluated in providing better support of pavement infrastructure, and these results are described here. Another major transportation infrastructure problem involving bridge approach slabs requires different treatment methods, and these results are briefly described. As a part of the recently completed research study assessments, both shallow and deep soil treatment methods for stabilizing soils are fully evaluated for their effectiveness in arresting the distress posed to the pavements and bridge approach slabs. These results along with a few future research needs are presented in this paper. 相似文献
9.
膨胀土的水分特征曲线通常是在实验室测得的, 在现场测量膨胀土的吸力不仅费时而且也非常困难. 本文采用人工神经网络技术用现场测得的含水量来预测土的吸力. 网络训练首先采用水分特征曲线相应的试验数据进行监督训练, 然后利用监督训练得到的网络单元的连接权值对现场测得含水量数据进行吸力预测, 预测结果与实测结果相近, 同时并对预测结果进行了分析讨论. 相似文献
10.
In this paper the residual stresses in a butt-welded plate of2.25Cr 1Mo has been analyzed using a 3D and transient finite element （FE） model. Also the effect of the welding-electrode speed has been studied using death and birth of FEs. For this purpose, a coupled thermo-mechanical FE solution has been used to obtain the temperature distribution and the resulting residual stresses. Also, the variations of the physical properties of the material with temperature have been taken into account. Results show that the residual stresses in the heat affected zone （HAZ） are maximum and change along the weld and also in the plate-thickness. It has been shown that use of the 3D and transient model will lead to more accurate and realistic results which are well compared with the experimental test data. 相似文献
11.
为了更加直观有效地描述路面平整度,提出了一种路面平整度的模拟方法,即随机正弦波法.该方法将路面平整度表示成大量具有随机相位的正弦或余弦之和,采用离散谱逼近目标随机过程,是一种离散化数值模拟路面平整度的方法.根据给定的路面功率谱系数,在时域路面随机位移输入的频率特征与给定的路面谱相一致的情况下,通过计算机模拟将路面平整度优化成为随机振动的等效信号,得到各等级下路面的平整度曲线.结果表明：随机正弦波法适用于实测道路谱的时域模拟,由于该方法数学推导严密,使用范围广泛,且模拟曲线直观,对于汽车平顺性研究具有十分重要的意义.最后,提出一个与路面功率谱系数相关的平整度指标——名义平整度指数. 相似文献
12.
In order to sufficiently exploit the advantages of different signal processing methods, such as wavelet transformation (WT), artificial neural networks (ANN) and expert rules (ER), a synthesized multi-method was introduced to detect and classify the epileptic waves in the EEG data. Using this method, at first, the epileptic waves were detected from pre-processed EEG data at different scales by WT, then the characteristic parameters of the chosen candidates of epileptic waves were extracted and sent into the well-trained ANN to identify and classify the true epileptic waves,and at last, the detected epileptic waves were certificated by ER. The statistic results of detection and classification show that, the synthesized multi-method has a good capacity to extract signal features and to shield the signals from the random noise. This method is especially fit for the analysis of the biomedical signals in biomedical engineering which are usually non-placid and nonlinear. 相似文献
13.
SINGH Bhupinder SINGH S.P KAUSHIK S.K. 《浙江大学学报(A卷英文版)》2007,8(2):257-263
INTRODUCTION Finite Element (FE) procedures are at present widely used in engineering modelling and analysis and employed extensively in the analysis of solids and structures and heat transfer and fluids (Bathe, 1996). The essence of FE solution of an engineering problem is that a set of governing algebraic equations is es-tablished which are then solved with the help of a digital computer. The first practical FE procedures were employed in linear analysis of solids and struc-tures (B… 相似文献
14.
官坤林建德 《福建工程学院学报》2020,(6):543-548
柔性基板材料种类多样并且存在各自的优缺点，筛选最优材料存在一定困难。为此，提出了层次分析法，对柔性基板材料进行评价。通过了解柔性基板材料的属性与性能，提取重要因素作为决策的准则，构建层次结构模型与判断矩阵，进行层次单排序与一致性检验及层次总排序。利用柔性基板材料的具体案例详细介绍了层次分析的运算过程，用MATLAB 软件编写程序，减少了层次分析法的计算量。评价结果，层次分析法只是筛选出备选方案中的最优者并不能为决策者提供新的思路，获得更优的方案得综合考量各种因素。 相似文献
15.
《Journal of Further & Higher Education》2012,36(5):694-714
In little over a decade, the observation of teaching and learning (OTL) has become the cornerstone of Further Education (FE) colleges’ quality systems for assuring and improving the professional skills and knowledge base of tutors. Yet OTL remains an under-researched area of inquiry with little known about the impact of its use on the professional identity, learning and development of FE tutors. This paper examines the specific practice of graded OTL and in so doing discusses findings from a mixed-methods study conducted in 10 colleges situated across the West Midlands region of England. Data from a questionnaire survey and semi-structured interviews were analysed within a theoretical framework that drew largely on aspects of Foucauldian theory as well as the twin phenomena of new managerialism and performativity. This analysis revealed how OTL has become normalised as a performative tool of managerialist systems designed to assure and improve standards, performance and accountability in teaching and learning. It is argued that FE has now outgrown graded OTL and it is time for a moratorium on its use. Colleges and tutors need to be given greater professional autonomy with regard to OTL and be allowed to develop their own systems that place professional learning and development at the forefront, rather than the requirements of performance management systems. 相似文献
16.
何兴理黄诗浩林金阳 《福建工程学院学报》2020,(4):349-352
首先基于PEI基板磁控溅射ZnO薄膜,再在薄膜上的两端制备叉指电极,探讨了不同的叉指间距对这种柔性器件的影响。研究发现,当两个叉指式换能器(IDT)之间的距离增加时,谐振器的传输幅度会显著衰减。为了制造具有良好传输性能的器件,IDT之间的间距应小于声波波长的40倍。这些结果可以为柔性声波器件的发展提供参考。 相似文献
17.
BP人工神经网络-光度法同时测定VB1、VB2、VB6和VPP 总被引：1，自引：0，他引：1
用BP人工神经网络解析了VB1、VB2、VB6和VPP的紫外吸收光谱,提出同时测定这四种维生素的计算分析方法,并对复合维生素片中的VB1、VB2、VB6和VPP进行了同时测定,VB1、VB2、VB6和VPP平均相对误差分别为1.45%,1.57%,4.08%和1.87%.使用了改进的BP算法,避免了神经网络学习过程中可能产生的麻痹现象;提出了目标向量的简单变换方法. 相似文献
18.
针对智能汽车变道超车规划中轨迹模式和速度策略单一的问题,提出一种安全高效、多模式轨迹和车速自适应的变道超车规划方案。通过建立可调参数的三段式变道超车模型,利用五次多项式设计变道轨迹拟合算法,以安全性为要求设计侧翻约束和碰撞约束边缘条件。基于多目标优化函数进行多模式轨迹优化,得到不同模式变道轨迹的解集空间,并基于超车阶段的时间进行速度自适应规划。通过MATLAB/Simulink构建仿真测试试验,结果表明该方案在全速域,满足安全条件约束下,能输出3种模式(效率模式、舒适模式和综合模式)的变道超车轨迹,输出的轨迹特性稳定,在两车相对速度较小时自适应速度规划能够有效提升超车效率。 相似文献
19.
Habib M Hussain I Fang WH Rajput ZI Yang ZZ Irshad H 《Journal of Zhejiang University. Science. B》2006,7(4):320-323
In this experiment conducted to study the inactivation dynamics of infectious bursal disease virus （IBDV） by binary ethylenimine （BEI） in comparison with formalin, IBDV was isolated from the bursa of infected chickens and its confirmation was done by agar gel precipitation test. Viral suspensions were subjected to inactivation with BEI and formalin for pre-set time in- tervals. BEI was employed at concentrations of 0.001 and 0.002 mol/L while formalin was used at 0.1% and 0.2%. Sampling was done at 6, 12, 24, 36 and 48 h of incubation and samples were tested for their inactivation status in 9-day-old embryonated eggs and 3-week-old broiler chickens. IBDV was completely inactivated by 0.001 and 0.002 mol/L BEI after 36 h of incubation at 37℃, whereas formalin at 0. 1% and 0.2% concentrations inactivated IBDV in 24 h. 相似文献
20.
Domestic-minor sex trafficking (DMST) continues to affect youth in the United States; however, lack of empirical evidence for interventions and the complex sociopolitical discourses surrounding sex trafficking and the commercial sexual exploitation of children (CSEC) hamper delivery of effective services to this population. To explore perspectives on best practices with these young people, 20 in-depth interviews were conducted with key stakeholders whose work provides them with a unique vantage point on the needs and experiences of survivors of DMST in New Jersey. Notes from interviews were coded and analyzed for emergent themes. While key stakeholders generally agreed on best practices, there were several important areas of dispute that emerged regarding how best to serve youth involved in DMST, specifically with regard to youth running away from services, models of service provision, and the use of technology by these youth. Findings suggest that professionals from diverse backgrounds may disagree about the extent to which youth involved in DMST possess agency in their decision-making capacities as adolescents. This study explores these areas of dispute, and discusses the implications for the many different professionals and systems that must work together in providing services to this population. 相似文献