检索结果-南通市图书馆

Comparison of three-dimensional fluorescence analysis methods for predicting formation of trihalomethanes and haloacetic acids

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2015年第1期27卷 159-167页

作者： Nicolás M.Peleato Robert C.Andrews department of civil Engineering University of Toronto

This work investigated the application of several fluorescence excitation–emission matrix analysis methods as natural organic matter（NOM） indicators for use in predicting the formation of trihalomethanes（THMs） and haloacetic acids（HAAs）. Waters from four different sources（two rivers and two lakes） were subjected to jar testing followed by 24 hr disinfection by-product formation tests using chlorine. NOM was quantified using three common measures： dissolved organic carbon, ultraviolet absorbance at 254 nm, and specific ultraviolet absorbance as well as by principal component analysis, peak picking,and parallel factor analysis of fluorescence spectra. Based on multi-linear modeling of THMs and HAAs, principle component（PC） scores resulted in the lowest mean squared prediction error of cross-folded test sets（THMs： 43.7（μg/L）^2, HAAs： 233.3（μg/L）^2）. Inclusion of principle components representative of protein-like material significantly decreased prediction error for both THMs and HAAs. Parallel factor analysis did not identify a protein-like component and resulted in prediction errors similar to traditional NOM surrogates as well as fluorescence peak picking. These results support the value of fluorescence excitation–emission matrix–principal component analysis as a suitable NOM indicator in predicting the formation of THMs and HAAs for the water sources studied.

关键词： Natural organic matter Fluorescence Principal component analysis PARAFAC Disinfection byproducts Drinking water

Dynamic anti-plane analysis for two symmetrically interfacial cracks near circular cavity in piezoelectric bi-materials

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2014年第10期35卷 1261-1270页

作者： A.HASSAN 宋天舒 department of civil Engineering Military Technical College College of Aerospace and civil Engineering Harbin Engineering University

The present paper is exposed theoretically to the influence on the dynamic stress intensity factor （DSIF） in the piezoelectric bi-materials model with two symmet- rically permeable interracial cracks near the edges of a circular cavity, subjected to the dynamic incident anti-plane shearing wave （SH-wave）. An available theoretical method to dynamic analysis in the related research field is provided. The formulations are based on Green＇s function method. The DSIFs at the inner and outer tips of the left crack are obtained by solving the boundary value problems with the conjunction and crack- simulation technique. The numerical results are obtained by the FORTRAN language program and plotted to show the influence of the variations of the physical parameters, the structural geometry, and the wave frequencies of incident wave on the dimensionless DSIFs. Comparisons with previous work and between the inner and outer tips are con- cluded.

关键词： symmetrically interfacial crack piezoelectric bi-material Green's function,dynamic stress intensity factor (DSIF) dynamic anti-plane shearing wave (SH-wave)

Multiplication factor for open ground storey buildings–a reliability based evaluation

在线全文

学校读者我要写书评

暂无评论

Earthquake Engineering and Engineering Vibration 2016年第2期15卷 283-295页

作者： Haran Pragalath D.C Avadhoot Bhosale Robin Davis P Pradip Sarkar department of civil Engineering NIT Rourkela

Open Ground Storey（OGS） framed buildings where the ground storey is kept open without infill walls, mainly to facilitate parking, is increasing commonly in urban areas. However, vulnerability of this type of buildings has been exposed in past earthquakes. OGS buildings are conventionally designed by a bare frame analysis that ignores the stiffness of the infill walls present in the upper storeys, but doing so underestimates the inter-storey drift（ISD） and thereby the force demand in the ground storey columns. Therefore, a multiplication factor（MF） is introduced in various international codes to estimate the design forces（bending moments and shear forces） in the ground storey columns. This study focuses on the seismic performance of typical OGS buildings designed by means of MFs. The probabilistic seismic demand models, fragility curves, reliability and cost indices for various frame models including bare frames and fully infilled frames are developed. It is found that the MF scheme suggested by the Israel code is better than other international codes in terms of reliability and cost.

关键词： frames probabilistic vulnerability facilitate details Probability codes multiplication drift columns

Evaluation of the remaining lateral torsional buckling capacity in corroded steel members

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2010年第11期11卷 887-897页

作者： Yasser SHARIFI Reza RAHGOZAR department of civil Engineering Kerman University

Corrosion is one of the main causes of deterioration in steel structures. Loss of thickness in flanges and web of corroded steel beams leads to reduction in section properties which can reduce the lateral torsional buckling capacity of the member. In this paper, thickness loss data were compiled from four samples of corrosion damaged I-beams removed from a petro-chemical plant. Visual examination of the four corroded beams showed that they were corroded uniformly. To improve the accuracy of the results, a large number of measurements for surface roughness were taken for each beam, totally 770 values to obtain the average thickness of flanges and web of each beam. The data was used to develop a corrosion decay model in order to calculate the percentage remaining lateral torsional buckling capacity of long and short span beams which are laterally unrestrained. To estimate the percentage of remaining lateral torsional buckling capacity in the corroded damaged I-beams, the readily available minimum curves for different types of universal beams in conjunction with information on the thickness loss were used. The results can be used by practicing engineers for better estimation on the service life of deteriorated steel structures.

关键词： Corrosion Steel structures Lateral torsional buckling Beams

Macroseismic intensity attenuation in Iran

在线全文

学校读者我要写书评

暂无评论

Earthquake Engineering and Engineering Vibration 2018年第1期17卷 139-148页

作者： Saman Yaghmaei-Sabegh department of civil Engineering University of Tabriz

Macroseismic intensity data plays an important role in the process of seismic hazard analysis as well in developing of reliable earthquake loss models. This paper presents a physical-based model to predict macroseismic intensity attenuation based on 560 intensity data obtained in Iran in the time period 1975-2013. The geometric spreading and energy absorption of seismic waves have been considered in the proposed model. The proposed easy to implement relation describes the intensity simply as a function of moment magnitude, source to site distance and focal depth. The prediction capability of the proposed model is assessed by means of residuals analysis. Prediction results have been compared with those of other intensity prediction models for Italy, Turkey, Iran and central Asia. The results indicate the higher attenuation rate for the study area in distances less than 70 km.

关键词： intensity prediction equations macroseismic attenuation model intensity data Iran

Seismic wave input method for three-dimensional soil-structure dynamic interaction analysis based on the substructure of artificial boundaries

在线全文

学校读者我要写书评

暂无评论

Earthquake Engineering and Engineering Vibration 2019年第4期18卷 747-758页

作者： Liu Jingbo Tan Hui Bao Xin Wang Dongyang Li Shutao department of civil Engineering Tsinghua University

The method of inputting the seismic wave determines the accuracy of the simulation of soil-structure dynamic interaction. The wave method is a commonly used approach for seismic wave input, which converts the incident wave into equivalent loads on the cutoff boundaries. The wave method has high precision, but the implementation is complicated, especially for three-dimensional models. By deducing another form of equivalent input seismic loads in the fi nite element model, a new seismic wave input method is proposed. In the new method, by imposing the displacements of the free wave fi eld on the nodes of the substructure composed of elements that contain artifi cial boundaries, the equivalent input seismic loads are obtained through dynamic analysis of the substructure. Subsequently, the equivalent input seismic loads are imposed on the artifi cial boundary nodes to complete the seismic wave input and perform seismic analysis of the soil-structure dynamic interaction model. Compared with the wave method, the new method is simplifi ed by avoiding the complex processes of calculating the equivalent input seismic loads. The validity of the new method is verifi ed by the dynamic analysis numerical examples of the homogeneous and layered half space under vertical and oblique incident seismic waves.

关键词： soil-structure dynamic interaction seismic wave input wave method equivalent input seismic loads substructure of artifi cial boundaries

CLASSICAL AND HOMOGENIZED EXPRESSIONS FOR BUCKLING SOLUTIONS OF FUNCTIONALLY GRADED MATERIAL LEVINSON BEAMS

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Solida Sinica 2015年第5期28卷 592-604页

作者： Shirong Li Xuan Wang Zeqing Wan department of civil Engineering Yangzhou University

The relationship between the critical buckling loads of functionally graded material （FGM） Levinson beams （LBs） and those of the corresponding homogeneous Euler-Bernoulli beams （HEBBs） is investigated. Properties of the beam are assumed to vary continuously in the depth direction. The governing equations of the FGM beam are derived based on the Levinson beam theory, in which a quadratic variation of the transverse shear strain through the depth is included. By eliminating the axial displacement as well as the rotational angle in the governing equations, an ordinary differential equation in terms of the deflection of the FGM LBs is derived, the form of which is the same as that of HEBBs except for the definition of the load parameter. By solving the eigenvalue problem of ordinary differential equations under different boundary conditions clamped （C）, simply-supported （S）, roller （R） and free （F） edges combined, a uniform analytical formulation of buckling loads of FGM LBs with S-S, C-C, C-F, C-R and S-R edges is presented for those of HEBBs with the same boundary conditions. For the C-S beam the above-mentioned equation does not hold. Instead, a transcendental equation is derived to find the critical buckling load for the FGM LB which is similar to that for HEBB with the same ends. The significance of this work lies in that the solution of the critical buckling load of a FGM LB can be reduced to that of the HEBB and calculation of three constants whose values only depend upon the through- the-depth gradient of the material properties and the geometry of the beam. So, a homogeneous and classical expression for the buckling solution of FGM LBs is accomplished.

关键词： FCM beam Levinson beam theory buckling critical load Euler-Bernoulli beam

Mechanical model of round window membrane under reverse excitation

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2016年第10期37卷 1341-1348页

作者： Yiqiang CHEN Wenjuan YAO department of civil Engineering Shanghai University

According to the vibration characteristics of the round window, a mechani- cal model of a round window membrane is established. The Euler equation of the round window and the complementary boundary conditions are derived by the variational prin- ciple. Combined with the Bessel function, an analytical solution of the round window displacement is obtained by MATHEMATICA. Combined with clinical characteristics of round window membrane lesion, the effect of sound transmission due to thickening of the round window membrane caused by the otitis media, shrinkage of the round window membrane area caused by otosclerosis, and hardening of the round window membrane itself is analyzed. The results show that with thickening of the round window membrane, the displacement of the round window membrane is decreased. In the meantime, with hardening of the round window membrane and shrinkage of the membrane area, the max- imum displacement Of the round window membrane is gradually reduced, leading to a decrease in sound transmission. Thus, the analyticM analysis can avoid interference of environment and the technical level of personnel, and it can evaluate transmission per- formance of the round window membrane efficiently, providing a theoretical basis for the reverse excitation of artificial prosthesis.

关键词： round window variational principle Euler equation complementary boundary condition Bessel function

Spectra of seismic force reduction factors of MDOF systems normalized by two characteristic periods

在线全文

学校读者我要写书评

暂无评论

Earthquake Engineering and Engineering Vibration 2020年第1期19卷 53-69页

作者： Li Xiao Tong Genshu Zhang Lei department of civil Engineering Zhejiang University

Seismic force reduction factor(SFRF) spectra of shear-type multi-degree-of-freedom(MDOF) structures are investigated. The modified Clough model, capable of considering the strength-degradation/hardening and stiffnessdegradation, is adopted. The SFRF mean spectra using 102 earthquake records on a typical site soil type(type C) are constructed with the period abscissa being divided into three period ranges to maintain the peak features at the two sitespecific characteristic periods. Based on a large number of results, it is found that the peak value of SFRF spectra may also exist for MDOF, induced by large high-mode contributions to elastic base shear, besides the mentioned two peak values. The variations of the stiffness ratio λk and the strength ratio λF of the top to bottom story are both considered. It is found that the SFRFs for λF ≤λk are smaller than those for λF > λk. A SFRF modification factor for MDOF systems is proposed with respect to SDOF. It is found that this factor is significantly affected by the story number and ductility. With a specific λF(= λk0.75), SFRF mean spectra are constructed and simple solutions are presented for MDOF systems. For frames satisfying the strong column/weak beam requirement, an approximate treatment in the MDOF shear-beam model is to assign a post-limit stiffness 15%-35% of the initial stiffness to the hysteretic curve. SFRF spectra for MDOF systems with 0.2 and 0.3 times the post-limit stiffness are remarkably larger than those without post-limit stiffness. Thus, the findings that frames with beam hinges have smaller ductility demand are explained through the large post-limit stiffness.

关键词： seismic force reduction factor multi-degree of freedom modifi ed Clough model characteristic period highmode eff ect post-limit stiff ness analysis