ANTIPLANE CIRCULAR INCLUSION WITH A CURVED CRACK CROSSING THE BOUNDARY
Institute of Scientific and Technical Information of China (English)
Lu Jianfei; Wang Jianhua; Shen Weiping
2000-01-01
The weakly singular integral equation used to solve the problem of the curved crack crossing the boundary of the antiplane circular inclusion is presented. Using the principal part analysis method of the Cauchy type integral equation, the singular stress index at the intersection and the singular stress of angular regions near the intersection are obtained. By using the singular stress obtained, the stress intensity factor at the intersection is defined. After the numerical solution of the integral equation, the stress intensity factors at the end points of the crack and intersection are obtainable.
Line Crack Subject to Antiplane Shear.
1978-07-01
coh-e~eMre-i.ý- for brilýttle DD I JOANඑ 1473 EDITION Of INOV 95 16 ONSOLu materials . SERCUIRITY CLASSIFICATIONOTISPE(IA.Daauta) "PART 1 GOVERNMENT... materials . 1. INTRODUCTION In several previous papers 1i] - [4] we discussed the state of stress near the tip of a sharp line crack in an elastic...homo- geneous and isotropic solids there exist only two material moduli, X’(Ix’-xl) and 1i’(jx’-xj) which are functions of the distance I-xl. The
Crack Growth Mechanisms under Anti-Plane Shear in Composite Laminates
Horner, Allison Lynne
The research conducted for this dissertation focuses on determining the mechanisms associated with crack growth in polymer matrix composite laminates subjected to anti-plane shear (mode III) loading. For mode III split-beam test methods were proposed, and initial evaluations were conducted. A single test method was selected for further evaluation. Using this test method, it was determined that the apparent mode III delamination toughness, GIIIc , depended on geometry, which indicated a true material property was not being measured. Transverse sectioning and optical microscopy revealed an array of transverse matrix cracks, or echelon cracks, oriented at approximately 45° and intersecting the plane of the delamination. Subsequent investigations found the echelon array formed prior to the onset of planar delamination advance and that growth of the planar delamination is always coupled to echelon array formation in these specimens. The evolution of the fracture surfaces formed by the echelon array and planar delamination were studied, and it was found that the development was similar to crack growth in homogenous materials subjected to mode III or mixed mode I-III loading, although the composite laminate architecture constrained the fracture surface development differently than homogenous materials. It was also found that, for split-beam specimens such as those used herein, applying an anti-plane shear load results in twisting of the specimen's uncracked region which gives rise to a mixed-mode I-III load condition. This twisting has been related to the apparent mode III toughness as well as the orientation of the transverse matrix cracks. A finite element model was then developed to study the mechanisms of initial echelon array formation. From this, it is shown that an echelon array will develop, but will become self-limiting prior to the onset of planar delamination growth.
ELECTROELASTIC FIELD FOR AN IMPERMEABLE ANTI-PLANE SHEAR CRACK IN A PIEZOELECTRIC CERAMICS PLATE
Institute of Scientific and Technical Information of China (English)
李显方; 范天佑
2002-01-01
Electroelastic behavior of a cracked piezoelectric ceramics plate subjected to four cases of combined mechanical-electrical Ioads is analyzed. The integral transform method is applied to convert the problem involving an impermeable anti-plane crack to dual integral equations . Solving the resulting equations, the explicit analytic expressions for electroelastic field along the crack line and the intensity factors of relevant quantities near the crack tip and the mechanical strain energy release rate are obtained. The known results for an infinite piezoelectric ceramics plane containing an impermeable anti-plane crack are recoveredfrom the present results only if the thickness of the plate h → ∞.
Coupled fracture mode of a cracked disc under anti-plane loading
Directory of Open Access Journals (Sweden)
Pook Les P.
2014-06-01
Full Text Available The existence of three-dimensional effects at cracks has been known for many years, but understanding has been limited, and for some situations still is. Understanding improved when the existence of corner point singularities and their implications became known. Despite increased understanding, three-dimensional effects are sometimes ignored in situations where they may be important. The purpose of the present investigation is to study by means of accurate 3D finite element (FE models a coupled fracture mode generated by anti-plane loading of a straight through-the-thickness crack in linear elastic discs. The results obtained from the highly accurate finite element analyses have improved understanding of the behaviour of through cracked discs under anti-plane loading. The influence of plate bending is increasingly important as disc thickness decreases. It appears that a new field parameter, probably a singularity, is needed to describe the stresses at the disc surfaces. Calculation of the strain energy density (SED in a control volume at the crack tip shows that the position of the maximum SED is a function of disc thickness.
Stress Intensity of Antiplane Conjugate Cracks in Cubic Quasicrystal
Institute of Scientific and Technical Information of China (English)
ZHANG Lei
2008-01-01
Based on the theory of Muskhelishvili, the general solutions for stress and strain of conjugate cracks in cubic quasicrystal are obtained, with which the stress intensity factors of cubic quasicrystal at crack tips and the stress distribution functions of phonon and phason fields are given. The results show that though phason field is coupled with phonon field by constitutive equations, the stress intensity factors are not coupled with any other factors.
Antiplane contact problem for elastic half-space with cracks and stringers
Directory of Open Access Journals (Sweden)
Aghayan K.L
2016-03-01
Full Text Available The contact problem of load transfer of a thin elastic plate to the elastic half-space is considered. The half-space weakened by a system of finite length collinear tunnel cracks which are perpendicular to the half-space boundary. The border of half-space reinforced by stringers. By external forces applied to the plates and the banks of the cracks, the half-space - plate system deformed under antiplane strain. In the frame of well-known Melan model for stringer the solution of the problem is reduced to a system of singular integral equations, whose solution is built by numerically - analytical method of mechanical quadratures. The behavior of the contact stresses and stress intensity factors at the crack tip and the end points of stringers is investigated.
Three-dimensional effects on cracked components under anti-plane loading
Directory of Open Access Journals (Sweden)
F. Berto
2015-07-01
Full Text Available The existence of three-dimensional effects at cracks has been known for many years, but understanding has been limited, and for some situations still is. Understanding improved when the existence of corner point singularities and their implications became known. Increasingly powerful computers made it possible to investigate three-dimensional effects numerically in detail. Despite increased understanding, threedimensional effects are sometimes ignored in situations where they may be important. The purpose of the present investigation is to study by means of accurate 3D finite element (FE models a coupled fracture mode generated by anti-plane loading of a straight through-the-thickness crack in linear elastic plates. An extended version of the present work has recently been published in the literature. The results obtained from the highly accurate finite element analyses have improved understanding of the behaviour of through cracked components under anti-plane loading. The influence of plate bending is increasingly important as the thickness decreases. It appears that a new field parameter, probably a singularity, is needed to describe the stresses at the free surfaces. Discussion on whether KIII tends to zero or infinity as a corner point is approached is futile because KIII is meaningless at a corner point. The intensity of the local stress and strain state through the thickness of the cracked components has been evaluated by using the strain energy density (SED averaged over a control volume embracing the crack tip. The SED has been considered as a parameter able to control fracture in some previous contributions and can easily take into account also coupled three-dimensional effects. Calculation of the SED shows that the position of the maximum SED is independent of plate thickness. Both for thin plates and for thick ones the maximum SED is close to the lateral surface, where the maximum intensity of the coupled mode II takes place.
Institute of Scientific and Technical Information of China (English)
王成; 吴承平
2003-01-01
The improved near crack line analysis method was used to investigate aneccentric cracked plate loaded by two pairs of anti-plane point forces at the crack surface inan elastic-perfectly plastic solid. The analytical solutions of the elastic-plastic stress fieldsand displacements near the crack line have been found without the assumptions of the smallscale yielding. The law that the length of the plastic zone along the crack line is varied withan external loads and the bearing capacity of an eccentric cracked plate are obtained.
Institute of Scientific and Technical Information of China (English)
SUN Yu-guo; WU Lin-zhi
2005-01-01
The dynamic behavior of two collinear cracks in magneto-electro-elastic composites under harmonic anti-plane shear waves is studied using the Schmidt method for the permeable crack surface conditions. By using the Fourier transform, the problem can be solved with a set of triple integral equations in which the unknown variable is the jump of the displacements across the crack surfaces. In solving the triple integral equations, the jump of the displacements across the crack surface is expanded in a series of Jacobi polynomials. It can be obtained that the stress field is independent of the electric field and the magnetic flux.
Analysis of bonded anisotropic wedges with interface crack under anti-plane shear loading
Institute of Scientific and Technical Information of China (English)
M.GHADIRI; A.R.SHAHANI
2014-01-01
The antiplane stress analysis of two anisotropic finite wedges with arbitrary radii and apex angles that are bonded together along a common edge is investigated. The wedge radial boundaries can be subjected to displacement-displacement boundary condi-tions, and the circular boundary of the wedge is free from any traction. The new finite complex transforms are employed to solve the problem. These finite complex transforms have complex analogies to both kinds of standard finite Mellin transforms. The traction free condition on the crack faces is expressed as a singular integral equation by using the exact analytical method. The explicit terms for the strength of singularity are extracted, showing the dependence of the order of the stress singularity on the wedge angle, material constants, and boundary conditions. A numerical method is used for solving the resul-tant singular integral equations. The displacement boundary condition may be a general term of the Taylor series expansion for the displacement prescribed on the radial edge of the wedge. Thus, the analysis of every kind of displacement boundary conditions can be obtained by the achieved results from the foregoing general displacement boundary condition. The obtained stress intensity factors (SIFs) at the crack tips are plotted and compared with those obtained by the finite element analysis (FEA).
Institute of Scientific and Technical Information of China (English)
LI Lin; ZHOU Zhen-gong; WANG Biao
2006-01-01
The scattering problem of anti-plane shear waves in a functionally graded material strip with an off-center crack is investigated by use of Schmidt method. The crack is vertically to the edge of the strip. By using the Fourier transform, the problem can be solved with the help of a pair of dual integral equations that the unknown variable is the jump of the displacement across the crack surfaces. To solve the dual integral equations, the jump of the displacement across the crack surfaces was expanded in a series of Jacobi polynomials. Numerical examples were provided to show the effects of the parameter describing the functionally graded materials, the position of the crack and the frequency of the incident waves upon the stress intensity factors of the crack.
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The behavior of two parallel symmetry permeable cracks in functionally graded piezoelectric materials subjected to an anti-plane shear loading was investigated. To make the analysis tractable, it was assumed that the material properties varied exponentially with coordinate vertical to the crack. By using the Fourier transform, the problem could be solved with the help of two pairs of dual integral equations, in which the unknown variables were the jumps of the displacements across the crack surfaces. To solve the dual integral equations, the displacement on the crack surfaces expanded in a series of Jacobi polynomials. The normalized stress and electrical displacement intensity factors were determined for different geometric and property parameters for permeable electric boundary conditions. Numerical examples were provided to show the effect of the geometry of the interacting cracks and the functionally graded material parameter upon the stress intensity factors of cracks.
Institute of Scientific and Technical Information of China (English)
Sun Yuguo; Zhou Zhengong
2005-01-01
In this paper, the behavior of two collinear cracks in magneto-electro-elastic composite material under anti-plane shear stress loading is studied by the Schmidt method for permeable electric boundary conditions. By using the Fourier transform, the problem can be solved with a set of triple integral equations in which the unknown variable is the jump of displacements across the crack surfaces. In solving the triple integral equations, the unknown variable is expanded in a series of Jacobi polynomials. Numerical solutions are obtained. It is shown that the stress field is independent of the electric field and the magnetic flux.
Gherrous, M.; Ferdjani, H.
2016-11-01
The main objective of this work is the contribution to the study of the piezoelectric structures which contain preexisting defect (crack). For that, we consider a Griffith crack located at the interface of two piezoelectric materials in a semi-infinite plane structure. The structure is subjected to an anti-plane shearing combined with an in-plane electric displacement. Using integral Fourier transforms, the equations of piezoelectricity are converted analytically to a system of singular integral equations. The singular integral equations are further reduced to a system of algebraic equations and solved numerically by using Chebyshev polynomials. The stress intensity factor and the electric displacement intensity factor are calculated and used for the determination of the energy release rate which will be taken as fracture criterion. At the end, numerical results are presented for various parameters of the problem; they are also presented for an infinite plane structure.
Institute of Scientific and Technical Information of China (English)
周振功; 杜善义; 王彪
2003-01-01
In this paper, the non-local theory of elasticity is applied to obtain the behavior of a Griffith crack in the piezoelectric materials under anti-plane shear loading for permeable crack surface conditions. By means of the Fourier transform, the problem can be solved with the help of a pair of dual integral equations with the unknown variable being the jump of the displacement across the crack surfaces. These equations are solved by the Schmidt method. Numerical examples are provided.Unlike the classical elasticity solutions, it is found that no stress and electric displacement singularity is present at the crack tip. The non-local elastic solutions yield a finite hoop stress at the crack tip,thus allowing for a fracture criterion based on the maximum stress hypothesis. The finite hoop stress at the crack tip depends on the crack length and the lattice parameter of the materials, respectively.
Rajagopal, K. R.
2011-01-06
This paper is the first part of an extended program to develop a theory of fracture in the context of strain-limiting theories of elasticity. This program exploits a novel approach to modeling the mechanical response of elastic, that is non-dissipative, materials through implicit constitutive relations. The particular class of models studied here can also be viewed as arising from an explicit theory in which the displacement gradient is specified to be a nonlinear function of stress. This modeling construct generalizes the classical Cauchy and Green theories of elasticity which are included as special cases. It was conjectured that special forms of these implicit theories that limit strains to physically realistic maximum levels even for arbitrarily large stresses would be ideal for modeling fracture by offering a modeling paradigm that avoids the crack-tip strain singularities characteristic of classical fracture theories. The simplest fracture setting in which to explore this conjecture is anti-plane shear. It is demonstrated herein that for a specific choice of strain-limiting elasticity theory, crack-tip strains do indeed remain bounded. Moreover, the theory predicts a bounded stress field in the neighborhood of a crack-tip and a cusp-shaped opening displacement. The results confirm the conjecture that use of a strain limiting explicit theory in which the displacement gradient is given as a function of stress for modeling the bulk constitutive behavior obviates the necessity of introducing ad hoc modeling constructs such as crack-tip cohesive or process zones in order to correct the unphysical stress and strain singularities predicted by classical linear elastic fracture mechanics. © 2011 Springer Science+Business Media B.V.
Institute of Scientific and Technical Information of China (English)
周振功; 王彪
2003-01-01
The dynamic behavior of two collinear anti-plane shear cracks in a piezoelectriclayer bonded to two half spaces subjected to the harmonic waves is investigated by a newmethod. The cracks are parallel to the interfaces in the mid-plane of the piezoelectric layer.By using the Fourier transform, the problem can be solved with two pairs of triple integralequations. These equations are solved by using Schmidt's method. This process is quitedifferent from that adopted previously. Numerical examples are provided to show the effectof the geometry of cracks, the frequency of the incident wave, the thickness of thepiezoelectric layer and the constants of the materials upon the dynamic stress intensity factorof cracks.
Liu, Hai-Tao; Sang, Jian-Bing; Zhou, Zhen-Gong
2016-10-01
This paper investigates a functionally graded piezoelectric material (FGPM) containing two parallel cracks under harmonic anti-plane shear stress wave based on the non-local theory. The electric permeable boundary condition is considered. To overcome the mathematical difficulty, a one-dimensional non-local kernel is used instead of a two-dimensional one for the dynamic fracture problem to obtain the stress and the electric displacement fields near the crack tips. The problem is formulated through Fourier transform into two pairs of dual-integral equations, in which the unknown variables are jumps of displacements across the crack surfaces. Different from the classical solutions, that the present solution exhibits no stress and electric displacement singularities at the crack tips.
Institute of Scientific and Technical Information of China (English)
杜建科; 沈亚鹏; 高波
2004-01-01
A theoretical treatment of the scattering of anti-plane shear (SH) waves is provided by a single crack in an unbounded transversely isotropic electro-magneto-elastic medium. Based on the differential equations of equilibrium, electric displacement and magnetic induction intensity differential equations, the governing equations for SH waves were obtained. By means of a linear transform, the governing equations were reduced to one Helmholtz and two Laplace equations. The Cauchy singular integral equations were gained by making use of Fourier transform and adopting electro-magneto impermeable boundary conditions. The closed form expression for the resulting stress intensity factor at the crack was achieved by solving the appropriate singular integral equations using Chebyshev polynomial. Typical examples are provided to show the loading frequency upon the local stress fields around the crack tips. The study reveals the importance of the electromagneto-mechanical coupling terms upon the resulting dynamic stress intensity factor.
Institute of Scientific and Technical Information of China (English)
HuKeqiang; ZhongZheng; JinBo
2003-01-01
Following the theory of linear piezoelectricity, we consider the electro-elastic problems of a finite crack in a functionally gradient piezoelectric ceramic strip. By the use of Fourier transforms we reduce the problem to solving two pairs of dual integral equations. The solution to the dual integral equations is then expressed in terms ofa Fredholm integral equation of the second kind. Numerical calculations are carried out for piezoelectric ceramics. The electric field intensity factors and the energy release rate are shown graphically, and the electroelastic interactions are illustrated.
Institute of Scientific and Technical Information of China (English)
2007-01-01
In this paper, the dynamic stress field near crack tips in the functionally graded materials subjected to the harmonic anti-plane shear stress waves was investi- gated by means of the non-local theory. The traditional concepts of the non-local theory were extended to solve the fracture problem of functionally graded materials. To make the analysis tractable, it was assumed that the material properties vary exponentially with coordinate parallel to the crack. By use of the Fourier transform, the problem can be solved with the help of a pair of dual integral equations, in which the unknown variable was the displacement on the crack surfaces. To solve the dual integral equations, the displacement on the crack surfaces was expanded in a series of Jacobi polynomials. Unlike the classical elasticity solutions, it is found that no stress singularities are present at crack tips. The non-local elastic solutions yield a finite hoop stress at crack tips, thus allowing us to use the maximum stress as a fracture criterion. The magnitude of the finite dynamic stress field depends on the crack length, the parameter describing the functionally graded materials, the circular frequency of the incident waves and the lattice parameter of materials.
Institute of Scientific and Technical Information of China (English)
ZHANG PeiWei; ZHOU ZhenGong; WU LinZhi
2007-01-01
In this paper, the dynamic stress field near crack tips in the functionally graded materials subjected to the harmonic anti-plane shear stress waves was investigated by means of the non-local theory. The traditional concepts of the non-local theory were extended to solve the fracture problem of functionally graded materials.To make the analysis tractable, it was assumed that the material properties vary exponentially with coordinate parallel to the crack. By use of the Fourier transform,the problem can be solved with the help of a pair of dual integral equations, in which the unknown variable was the displacement on the crack surfaces. To solve the dual integral equations, the displacement on the crack surfaces was expanded in a series of Jacobi polynomials. Unlike the classical elasticity solutions, it is found that no stress singularities are present at crack tips. The non-local elastic solutions yield a finite hoop stress at crack tips, thus allowing us to use the maximum stress as a fracture criterion. The magnitude of the finite dynamic stress field depends on the crack length, the parameter describing the functionally graded materials, the circular frequency of the incident waves and the lattice parameter of materials.
Institute of Scientific and Technical Information of China (English)
Jun Liang; Shiping Wu; Shanyi Du
2007-01-01
In this paper, the dynamic interaction of two parallel cracks in functionally graded materials (FGMs) is investigated by means of the non-local theory. To make the analysis tractable, the shear modulus and the material den-sity are assumed to vary exponentially with the coordinate vertical to the crack. To reduce mathematical difficulties, a one-dimensional non-local kemel is used instead of a two-dimensional one for the dynamic problem to obtain stress fields near the crack tips. By use of the Fourier transform,the problem can be solved with the help of two pairs of dual integral equations, in which the unknown variables are the jumps of displacements across the crack surfaces. To solve the dual integral equations, the jumps of displace-ments across the crack surfaces are expanded in a series of Jacobi polynomials. Unlike the classical elasticity solu-tions, it is found that no stress singularity is present at the crack tips. The non-local elastic solutions yield a finite hoop stress at the crack tips. The present result provides theoret-ical references helpful for evaluating relevant strength and preventing material failure of FGMs with initial cracks. The magnitude of the finite stress field depends on relevant param-eters, such as the crack length, the distance between two parallel cracks, the parameter describing the FGMs, the fre-quency of the incident waves and the lattice parameter of materials.
Institute of Scientific and Technical Information of China (English)
Liang Jun
2007-01-01
In this paper, the dynamic behavior of a permeable crack in functionally graded piezoelectric/piezomagnetic materials is investigated. To make the analysis tractable, it is assumed that the material properties vary exponentially with the coordinate parallel to the crack. By using the Fourier transform, the problem can be solved with the help of a pair of dual integral equations in which the unknown is the jump of displacements across the crack surfaces. These equations are solved to obtain the relations between the electric filed, the magnetic flux field and the dynamic stress field near the crack tips using the Schmidt method. Numerical examples are provided to show the effect pf the functionally graded parameter and the circular frequency of the incident waves upon the stress, the electric displacement and the magnetic flux intensity factors of the crack.
Directory of Open Access Journals (Sweden)
Bogdan Rogowski
2012-01-01
Full Text Available This paper investigated the fracture behaviour of a piezo-electro-magneto-elastic medium subjected to electro-magneto-mechanical loads. The bimaterial medium contains a crack which lies at interface and is parallel to their poling direction. Fourier transform technique is used to reduce the problem to three pairs of dual integral equations. These equations are solved exactly. The semipermeable crack-face magneto-electric boundary conditions are utilized. Field intensity factors of stress, electric displacement, magnetic induction, cracks displacement, electric and magnetic potentials, and the energy release rate are determined. The electric displacement and magnetic induction of crack interior are discussed. Obtained results indicate that the stress field and electric and magnetic fields near the crack tips exhibit square-root singularity.
Coupled fracture modes under anti-plane loading
Directory of Open Access Journals (Sweden)
Les P. Pook
2016-07-01
Full Text Available The linear elastic analysis of homogeneous, isotropic cracked bodies is a Twentieth Century development. It was recognised that the crack tip stress field is a singularity, but it was not until the introduction of the essentially two dimensional stress intensity factor concept in 1957 that widespread application to practical engineering problems became possible. The existence of three dimensional corner point effects in the vicinity of a corner point where a crack front intersects a free surface was investigated in the late 1970s: it was found that modes II and III cannot exist in isolation. The existence of one of these modes always induces the other. An approximate solution for corner point singularities by Bažant and Estenssoro explained some features of corner point effects but there were various paradoxes and inconsistencies. In an attempt to explain these a study was carried out on the coupled in-plane fracture mode induced by a nominal anti-plane (mode III loading applied to plates and discs weakened by a straight crack. The results derived from a large bulk of finite element models showed clearly that Bažant and Estenssoro’s analysis is incomplete. Some of the results of the study are summarised, together with some recent results for a disc under in-plane shear loading. On the basis of these results, and a mathematical argument, the results suggest that the stress field in the vicinity of a corner point is the sum of two singularities: one due to stress intensity factors and the other due to an as yet undetermined corner point singularity.
Institute of Scientific and Technical Information of China (English)
RayK.L.Su; FengWenjie; LiuJinxi; ZouZhenzhu
2003-01-01
The dynamic response of multiple coplanar interface cracks between two dissimilar piezoelectric strips subjected to mechanical and electrical impacts is investigated. Solutions to two kinds of electric boundary conditions on crack surfaces, i.e. electric impermeable and electric permeable, are obtained. Laplace and Fourier transforms and dislocation density functions are employed to reduce the mixed boundary value problem to Cauchy singular integral equations,which can be solved numerically. The effects of electrical load, geometry criterion of piezoelectric strips, relative location of cracks and material properties on the dynamic energy release rate are examined.
Institute of Scientific and Technical Information of China (English)
Yong-Dong Li; Wei Tan; Kang Yong Lee
2008-01-01
The problem considered iS a mode III crack lying parallel to the interface of an exponential-type functional graded material(FGM)strip bonded to a linear-type FGM substrate with infinite thickness.By applying the Fourier integral transform,the problem was reduced as a Cauchy singular integral equation with an unknown dislocation density function.The collocation method based on Chebyshev polynomials proposed by Erdogan and Gupta Was used to solve the singular integral equation numerically.With the numerical solution.the effects of the geometrical and physical parameters on the stress intensity factor(SIF)were analyzed and the following conclusions were drawn:(a)The region affected by the interface or free surface varies with the material rigidity,and higher material rigidity will lead to bigger affected region.(b)The SIF of the crack in the affected region and parallel to the micro-discontinuous interface is lower than those of the weak discontinuous cases.Reducing the weak-discontinuity of the interface will be beneficial to decrease the SIF ofthe interface-parallel crack in the region affected by the interface. (C)The effect of the free surface on SIF is more remarkable than that of the interface,and the latter is still more notable than that of the material rigiditV When the effects of the interface and free surface are fixed,increase of the material rigidity will enhance the value of SIF.
Corso, Francesco Dal; Bigoni, Davide
2016-01-01
An infinite class of nonuniform antiplane shear fields is considered for a linear elastic isotropic space and (non-intersecting) isotoxal star-shaped polygonal voids and rigid inclusions perturbing these fields are solved. Through the use of the complex potential technique together with the generalized binomial and the multinomial theorems, full-field closed-form solutions are obtained in the conformal plane. The particular (and important) cases of star-shaped cracks and rigid-line inclusions (stiffeners) are also derived. Except for special cases (addressed in Part II), the obtained solutions show singularities at the inclusion corners and at the crack and stiffener ends, where the stress blows-up to infinity, and is therefore detrimental to strength. It is for this reason that the closed-form determination of the stress field near a sharp inclusion or void is crucial for the design of ultra-resistant composites.
Debonding of an elastic inhomogeneity of arbitrary shape in anti-plane shear
Wang, Xu; Yang, Moxuan; Schiavone, Peter
2016-08-01
We investigate the anti-plane shear problem of a curvilinear crack lying along the interface of an arbitrarily shaped elastic inhomogeneity embedded in an infinite matrix subjected to uniform stresses at infinity. Complex variable and conformal mapping techniques are used to derive an analytical solution in series form. The problem is first reduced to a non-homogeneous Riemann-Hilbert problem, the solution of which can be obtained by evaluating the associated Cauchy integral. A set of linear algebraic equations is obtained from the compatibility condition imposed on the resulting analytic function defined in the inhomogeneity and its Faber series expansion. Each of the unknown coefficients in the corresponding analytic functions can then be uniquely determined by solving the linear algebraic equations, which are written concisely in matrix form. The resulting analytical solution is then used to quantify the displacement jump across the debonded section of the interface as well as the traction distribution along the bonded section of the interface. In addition, our solution allows us to obtain mode-III stress intensity factors at the two crack tips. The solution to the anti-plane problem of a partially debonded elliptical inhomogeneity containing a confocal crack is also derived using a similar method.
Corso, Francesco Dal; Bigoni, Davide
2016-01-01
Notch stress intensity factors and stress intensity factors are obtained analytically for isotoxal star-shaped polygonal voids and rigid inclusions (and also for the corresponding limit cases of star-shaped cracks and stiffeners), when loaded through remote inhomogeneous (self-equilibrated, polynomial) antiplane shear stress in an infinite linear elastic matrix. Usually these solutions show stress singularities at the inclusion corners. It is shown that an infinite set of geometries and loading conditions exist for which not only the singularity is absent, but the stress vanishes ('annihilates') at the corners. Thus the material, which even without the inclusion corners would have a finite stress, remains unstressed at these points in spite of the applied remote load. Moreover, similar conditions are determined in which a star-shaped crack or stiffener leaves the ambient stress completely unperturbed, thus reaching a condition of 'quasi-static invisibility'. Stress annihilation and invisibility define optimal...
Antiplane response of isosceles triangular hill to incident SH waves
Institute of Scientific and Technical Information of China (English)
Qiu Faqiang; Liu Diankui
2005-01-01
In this paper, antiplane response of an isosceles triangular hill to incident SH waves is studied based on the method of complex function and by using moving coordinate system. The standing wave function, which can satisfy the governing equation and boundary condition, is provided. Furthermore, numerical examples are presented; the influences of wave number and angle of the incident waves and the angle of the hill's peak on ground motion are discussed.
A MOVING CRACK IN A NONHOMOGENEOUS MATERIAL STRIP
Institute of Scientific and Technical Information of China (English)
Wang Baolin; Han Jiecai
2006-01-01
This paper considers an anti-plane moving crack in a nonhomogencous material strip of finite thickness. The shear modulus and the mass density of the strip are considered for a class of functional forms for which the equilibrium equation has analytical solutions. The problem is solved by means of the singular integral equation technique. The stress field near the crack tip is obtained. The results are plotted to show the effect of the material non-homogeneity and crack moving velocity on the crack tip field. Crack bifurcation behaviour is also discussed. The paper points out that use of an appropriate fracture criterion is essential for studying the stability of a moving crack in nonhomogeneous materials. The prediction whether the unstable crack growth will be enhanced or retarded is strongly dependent on the type of the fracture criterion used. is a suitable failure criterion for moving cracks in nonhomogeneous materials.
Institute of Scientific and Technical Information of China (English)
GUO Jun-hong; LIU Guan-ting
2008-01-01
By means of the complex variable function method and the technique of conformal mapping,the anti-plane shear problem of an elliptic hole with two straight cracks in one-dimensional hexagonal quasicrystals is investigated.The solution of the stress intensity factor(SIF)for mode III problem has been found.Under the condition of limitation,both the known results and the SIF solution at the crack tip of a circular hole with two straight cracks and cross crack in one-dimensional hexagonal quasicrystals can be obtained.
A MIXED ELECTRIC BOUNDARY VALUE PROBLEM FOR AN ANTI－PLANE PIEZOELECTRIC CRACK
Institute of Scientific and Technical Information of China (English)
ttnAngZlaenyu; KuangZhenbang
2003-01-01
The analytical continuation method is adopted to solve a mixed electric boundary value problem for a piezoelectric medium under anti-plane deformation. The crack face is partly conductive and partly impermeable. The results show that the stress intensity factor is identical with the mode III stress intensity factor independent of the conducting length. But the electric field and the electric displacement are dependent on the electric boundary conditions on the crack faces and are singular not only at the crack tips but also at the junctures between the impermeable part and conducting portions.
DEFF Research Database (Denmark)
Marfelt, Mikkel Mouritz
2016-01-01
oriented but still emphasizes stable concepts. Moreover, it does not give primacy to oppression. Finally, it adopts a critical stance on the nature of the macro, meso, and micro levels as dominant analytical perspectives. As a result, this paper focusses on the importance of intersectionality...
Institute of Scientific and Technical Information of China (English)
Barbara Harbin Cobb
2009-01-01
<正>I’m a few years older than the People’s Re- public of China, but hardly an infant compared to China’s vast history and culture. China and I have intersected at many points, and I want to tell you about a few of them.
相贯线处含穿透裂纹接管的补强研究%Research on Reinforcement of Nozzle with Penetrated Crack at Intersecting Line
Institute of Scientific and Technical Information of China (English)
董硕; 喻健良
2009-01-01
由于含缺陷容器在补强下的安全评价对在役压力容器的使用有重要的意义,使用ANSYS软件,采用三维有限元方法,对带补强圈含肩部穿透裂纹接管在内压作用下结构的应力进行计算和分析.研究表明,在弹性范围内,此结构的最大Mises应力与内压呈线性关系,且结构最大Mises应力的位置为接管腹部下方容器和补强圈的焊接处.在内压一定的情况下,此结构的最大Mises应力比带补强圈无缺陷接管的应力大,比无补强圈无缺陷接管的应力小.此结论能够指导实际工程中对此类缺陷的补强和评定.%Safety evaluation on defective vessel with reinforcement is of great significance to serving pres-sure vessel. With ANSYS software and adopting three - dimensional finite element method (FEM), the study is performed on the maximum Mises stress of nozzle with reinforcement pad, which has penetrated cracks in its shoulder and effected by internal pressure. The research indicates the maximum Mises stress of the structure has the linear correlation with the internal pressure, and also states clearly the position of the stress is on the welded junction of vessel and reinforcement pad, which is fight under the nozzle abdo-men. With constant internal pressure, the value of maximum Mises stress of the structure is greater than that of nozzle with reinforcement pad but without defect, while it is less than that of nozzle with neither re-inforcement pad nor defect. The conclusion can be used in guiding the reinforcement and evaluation on such imperfections in engineering.
Institute of Scientific and Technical Information of China (English)
Zhengong Zhou; Peiwei Zhang; Linzhi Wu
2010-01-01
In this paper,the interactions of multiple parallel symmetric and permeable finite length cracks in a piezoelectric/piezomagnetic material plane subjected to anti-plane shear stress loading are studied by the Schmidt method.The problem is formulated through Fourier transform into dual integral equations,in which the unknown variables are the displacement jumps across the crack surfaces.To solve the dual integral equations,the displacement jumps across the crack surfaces are directly expanded as a series of Jacobi polynomials.Finally,the relation between the electric field,the magnetic flux field and the stress field near the crack tips is obtained.The results show that the stress,the electric displacement and the magnetic flux intensity factors at the crack tips depend on the length and spacing of the cracks.It is also revealed that the crack shielding effect presents in piezoelectric/piezomagnetic materials.
ANTI-PLANE ANALYSIS FOR ELLIPTICAL INCLUSION IN MAGNETOELECTROELASTIC MATERIALS
Institute of Scientific and Technical Information of China (English)
Gang Li; Baolin Wang; Jiecai Han; Shanyi Du
2009-01-01
This paper considers the multi-field coupling in magneroelectroelastic composite materials consisting of the inclusion and the matrix are magnetoelectroelastic materials. The mechanical, electric and magnetic fields around an elliptical cylinder inclusion are formulated by complex potentials. Inside the inclusion, the strain, electric and magnetic fields are found to be uniform and vary with the shape of the ellipse. When the inclusion is reduced to a crack, along the interface, the strain, electric field strength and magnetic field strength equal the corresponding remote ones, which can be used as the boundary condition. Special cases, such as a rigid and permeable inclusion, a soft and impermeable inclusion, a line inclusion and a crack problem are discussed in detail.
Ferrara, S; Morales, J F; Samtleben, H
2009-01-01
We apply the entropy formalism to the study of the near-horizon geometry of extremal black p-brane intersections in D>5 dimensional supergravities. The scalar flow towards the horizon is described in terms an effective potential given by the superposition of the kinetic energies of all the forms under which the brane is charged. At the horizon active scalars get fixed to the minima of the effective potential and the entropy function is given in terms of U-duality invariants built entirely out of the black p-brane charges. The resulting entropy function reproduces the central charges of the dual boundary CFT and gives rise to a Bekenstein-Hawking like area law. The results are illustrated in the case of black holes and black string intersections in D=6, 7, 8 supergravities where the effective potentials, attractor equations, moduli spaces and entropy/central charges are worked out in full detail.
Institute of Scientific and Technical Information of China (English)
Zhou Zhengong; Du Shanyi
2001-01-01
The behavior of two collinear anti-plane shear cracks in a piezoelectric layer bonded to two half spaces is investigated by the Schmidt method. The cracks are vertically to the imerfaces of the piezoelectric layer. By using the Fourier transform, the problem can be solved with two pairs of triple integral equations. These equations are solved using the Schmidt method. This process is quite different from that adopted previously. Numerical examples are provided to show the effect of the geometry of the interacting cracks and the piezoelectric constants of the material upon the stress intensity factor of the cracks.
Institute of Scientific and Technical Information of China (English)
ZHANG Pei-wei; ZHOU Zhen-gong; WANG Biao
2007-01-01
The dynamic interaction oftwo collinear interface cracks between two dislar.functionally graded piezoelectric/piezomagnetic material strips subjected to the anti-plane shear harmonic stress waves was investigated.By using the Fourier transform, unknown variable is jump of displacement across the crack surfaces.These equations are solved using the Schmidt method.Numerical examples are provided to show the effect of the functionally graded parameter,the circular frequency of the incident waves and the thickness of the strip upon stress,electric displacement and magnetic flux intensity factors of cracks.
BASIC SOLUTION FOR THE THREE-PHASE COMPOSITE CONSTITUTIVE MODEL IN ANTIPLANE PIEZOELECTRICITY
Institute of Scientific and Technical Information of China (English)
Wang Xu; Shen Yapeng
2000-01-01
A basic solution in series form for the three-phase composite cylindrical model in antiplane piezoelectricity subjected to the action of a singularity in the intermediate matrix region is presented. The so lution is obtained through the complex potential approach in conjunction with the techniques of analytical con tinuation, singularity analysis, Laurent series expansion in an annular region and Cauchy integral formulae, etc. Based on the complex potentials obtained, explicit expressions for the distribution of stress and electric displacement in the three regions are also derived.
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
Interaction between multiple curved rigid line and circular inclusion in antiplane loading condition was considered. Two kinds of elementary solutions corresponding to a concentrated force applying at inclusion and matrix material respectively were presented. Utilizing the elementary solutions and taking density function of traction difference along curved rigid line, a group of weakly singular integral equations with log kernels can be obtained. After the numerical solution of the integral equations, the discrete values of density functions of traction difference are obtainable. So stress singularity coefficients at rigid line tips can be calculated, and several numerical examples are given.
DYNAMIC ANTI-PLANE PROBLEMS OF PIEZOCERAMICS AND APPLICATIONS IN ULTRASONICS——A REVIEW
Institute of Scientific and Technical Information of China (English)
Jiashi Yang; Ji Wang
2008-01-01
We review theoretical results on anti-plane motions of polarized ceramics based on the linear theory of piezoelectricity.Solutions to dynamic problems of the propagation of bulk acoustic waves (BAW) and surface acoustic waves (SAW),vibrations of finite bodies,and applications to various piezoelectric devices including piezoelectric waveguides,resonators,mass sensors,fluid sensors,actuators,nondestructive evaluation,power harvesters (generators),transformers,and power transmission through an elastic wall by acoustic waves are discussed.Complications due to material inhomogeneity,initial stress,electromagnetic coupling,electric field gradient and semiconduction are also discussed. The paper cites 82 references.
TIME–HARMONIC BEHAVIOUR OF CRACKED PIEZOELECTRIC SOLID BY BOUNDARY INTEGRAL EQUATION METHOD
Directory of Open Access Journals (Sweden)
Rangelov Tsviatko
2014-03-01
Full Text Available Anti-plane cracked functionally graded finite piezoelectric solid under time-harmonic elecromechanical load is studied by a non-hypersingular traction boundary integral equation method (BIEM. Exponentially varying material properties are considered. Numerical solutions are obtained by using Mathematica. The dependance of the intensity factors (IF - mechanical stress intensity factor (SIF and electrical field intensity factor (FIF on the inhomogeneous material parameters, on the type and frequency of the dynamic load and on the crack position are analyzed by numerical illustrative examples
A MODE-Ⅱ GRIFFITH CRACK IN DECAGONAL QUASICRYSTALS
Institute of Scientific and Technical Information of China (English)
郭玉翠; 范天佑
2001-01-01
By using the method of stress functions, the problem of mode- Ⅱ Griffith crack in decagonal quasicrystals was solved. First, the crack problem of two-dimensional quasicrystals was decomposed into a plane strain state problem superposed on anti-plane state problem and secondly, by introducing stress functions, the 18 basic elasticity equations on coupling phonon-phason field of decagonal quasicrystals were reduced to a single higherorder partial differential equations. The solution of this equation under mixed boundary conditions of mode- Ⅱ Griffith crack was obtained in terms of Fourier transform and dual integral equations methods. All components of stresses and displacements can be expressed by elemental functions and the stress intensity factor and the strain energy release rate were determined.
Borel, Armand
1984-01-01
This book is a publication in Swiss Seminars, a subseries of Progress in Mathematics. It is an expanded version of the notes from a seminar on intersection cohomology theory, which met at the University of Bern, Switzerland, in the spring of 1983. This volume supplies an introduction to the piecewise linear and sheaf-theoretic versions of that theory as developed by M. Goresky and R. MacPherson in Topology 19 (1980), and in Inventiones Mathematicae 72 (1983). While some familiarity with algebraic topology and sheaf theory is assumed, the notes include a self-contained account of further material on constructibility, derived categories, Verdier duality, biduality, and on stratified spaces, which is used in the second paper but not found in standard texts. "The volume should be useful to someone interested in acquiring some basic knowledge about the field..." —Mathematical Reviews.
Institute of Scientific and Technical Information of China (English)
Guo Jun-Hong; Liu Guan-Ting
2008-01-01
Using the complex variable function method and the technique of conformal mapping, the anti-plane shear problem of an elliptic hole with asymmetric collinear cracks in a one-dimensional hexagonal quasi-crystal is solved, and the exact analytic solutions of the stress intensity factors (SIFs) for mode Ⅲ problem are obtained. Under the limiting conditions, the present results reduce to the Griffith crack and many new results obtained as well, such as the circular hole with asymmetric collinear cracks, the elliptic hole with a straight crack, the mode T crack, the cross crack and so on. As far as the phonon field is concerned, these results, which play an important role in many practical and theoretical applications, are shown to be in good agreement with the classical results.
Antiplane SH-deformations near a surface rigid foundation above a subsurface rigid circular tunnel
Lee, V. W.; Manoogian, M. E.; Chen, S.
2002-06-01
The problem on the dynamic response of a rigid embedded foundation in the presence of an underground rigid tunnel and subjected to excitation of incident anti-plane SH waves is analyzed. By using the exact analytical solution for the two-dimensional SH-wave propagation in and around both the surface rigid foundation and subsurface rigid tunnel, those aspects of the resulting ground motions that are of special interest and importance for seismic resistant design in earthquake analyses have been examined. The computed amplitudes of the resulting periodic ground motions display a very complicated wave-interference between the surface foundation and underground tunnel that lead to observed standing wave patterns, together with abrupt changes in the wave amplitudes and large amplification of the incident motions.
Antiplane SH-deformations near a surface rigid foundation above a subsurface rigid circular tunnel
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The problem on the dynamic response of a rigid embedded foundation in the presence of an underground rigidtunnel and subjected to excitation of incident anti-plane SH waves is analyzed. By using the exact analytical solution for thetwo-dimensional SH-wave propagation in and around both the surface rigid foundation and subsurface rigid tunnel, thoseaspects of the resulting ground motions that are of special interest and importance for seismic resistant design in earthquakeanalyses have been examined. The computed amplitudes of the resulting periodic ground motions display a very complicatedwave-interference between the surface foundation and underground tunnel that lead to observed standing wave patterns,together with abrupt changes in the wave amplitudes and large amplification of the incident motions.
Institute of Scientific and Technical Information of China (English)
SUN Jian-liang; ZHOU Zhen-gong; WANG Biao
2005-01-01
The dynamic behavior of two unequal parallel permeable interface cracks in a piezoelectric layer bonded to two half-piezoelectric material planes subjected to harmonic anti-plane shear waves is investigated. By using the Fourier transform, the problem can be solved with the help of two pairs of dual integral equations in which the unknown variables were the jumps of the displacements across the crack surfaces. Numerical results are presented graphically to show the effects of the geometric parameters, the frequency of the incident wave on the dynamic stress intensity factors and the electric displacement intensity factors. Especially, the present problem can be returned to static problem of two parallel permeable interface cracks. Compared with the solutions of impermeable crack surface condition, it is found that the electric displacement intensity factors for the permeable crack surface conditions are much smaller.
INTERSECTIONAL DISCRIMINATION AGAINST CHILDREN
DEFF Research Database (Denmark)
Ravnbøl, Camilla Ida
This paper adds a perspective to existing research on child protection by engaging in a debate on intersectional discrimination and its relationship to child protection. The paper has a twofold objective, (1) to further establish intersectionality as a concept to address discrimination against ch...... children, and (2) to illustrate the importance of addressing intersectionality within rights-based programmes of child protection....
Deburring small intersecting holes
Energy Technology Data Exchange (ETDEWEB)
Gillespie, L.K.
1980-08-01
Deburring intersecting holes is one of the most difficult deburring tasks faced by many industries. Only 14 of the 37 major deburring processes are applicable to most intersecting hole applications. Only five of these are normally applicable to small or miniature holes. Basic process capabilities and techniques used as a function of hole sizes and intersection depths are summarized.
Institute of Scientific and Technical Information of China (English)
Zhanqi Cheng; Danying Gao; Zheng Zhong
2010-01-01
In this paper,a finite crack with constant length(Yoffe type crack)propagating in a functionally graded coating with spatially varying elastic properties bonded to a homoge-neous substrate of finite thickness under anti-plane loading was studied.A multi-layered model is employed to model arbitrary variations of material properties based on two linearly-distributed material compliance parameters.The mixed boundary problem is reduced to a system of singular integral equations that are solved numerically.Some numerical examples are given to demonstrate the accuracy,efficiency and versatility of the model.The numerical results show that the graded parameters,the thicknesses of the interracial layer and the two homogeneous layers,the crack size and speed have significant effects on the dynamic fracture behavior.
Mode III interfacial crack in the presence of couple stress elastic materials
Piccolroaz, Andrea; Radi, Enrico
2010-01-01
In this paper we are concerned with the problem of a crack lying at the interface between dissimilar materials with microstructure undergoing antiplane deformations. The micropolar behaviour of the materials is described by the theory of couple stress elasticity developed by Koiter (1964). This constitutive model includes the characteristic lengths in bending and torsion and thus it is able to account for the underlying microstructure of the two materials. We perform an asymptotic analysis to investigate the behaviour of the solution near the crack tip. It turns out that the stress singularity at the crack tip is strongly influenced by the microstructural parameters and it may or may not show oscillatory behaviour depending on the ratio between the characteristic lengths.
2D crack problems in functionally graded magnet-electro-elastic materials
Stoynov, Yonko
2016-12-01
Magneto-electro-elastic composite materials have extensive application in modern smart structures, because they possess good coupling between mechanical, electrical and magnetic fields. This new effect was reported for the first time by Van Suchtelen [1] in 1972. Due to their ceramic structure cracks inevitably exists in these materials. In this study we consider functionally graded magneto-electro-elastic materials subjected to anti-plane time harmonic load. We use Boundary integral equation method (BIEM) to evaluate the dependence of stress concentration near the crack tip on the frequency of the applied external load. For complex crack configurations numerical calculations are tedious and need too much time. Here we present a new analytical approach that will significantly improve the numerical procedure for calculation of stress intensity factors (SIF).
A finite crack with arbitrarily varied surface piezoelectricity
Xu, Yang; Wang, Xu
2017-01-01
We study the contribution of arbitrarily varied surface piezoelectricity to the anti-plane deformation and in-plane electric fields of a hexagonal piezoelectric material containing a finite crack. The varied surface piezoelectricity is incorporated by using an extended version of the continuum-based surface/interface model of Gurtin and Murdoch. In our discussion, the surface properties, including the surface elastic stiffness, the surface piezoelectric modulus and the surface dielectric permittivity, are assumed to be varied arbitrarily along the crack surfaces. By using the Green’s function method, the original boundary value problem is reduced to a system of two coupled first-order Cauchy singular integro-differential equations. Through a diagonalization strategy, the coupled system is transformed into two independent singular integro-differential equations, each of which can be numerically solved by using the collocation method. Our results indicate that the variation of the surface electroelastic moduli exerts a significant influence on the crack opening displacement, the electric potential jump across the crack faces and on the strengths of the logarithmic singularity in stresses and electric displacements at the crack tips.
Dynamic response of cylindrical cavity to anti-plane impact load by using analytical approach
Institute of Scientific and Technical Information of China (English)
翟朝娇; 夏唐代; 杜国庆; 丁智
2014-01-01
The transient response of an unlimited cylindrical cavity buried in the infinite elastic soil subjected to an anti-plane impact load along the cavern axis direction was studied. Using Laplace transform combining with contour integral of the Laplace inverse transform specifically, the general analytical expressions of the soil displacement and stress are obtained in the time domain, respectively. And the numerical solutions of the problem computed by analytical expressions are presented. In the time domain, the dynamic responses of the infinite elastic soil are analyzed, and the calculation results are compared with those from numerical inversion proposed by Durbin and the static results. One observes good agreement between analytical and numerical inversion results, lending the further support to the method presented. Finally, some valuable shear wave propagation laws are gained:the displacement of the soil remains zero before the wave arrival, and after the shear wave arrival, the stress and the displacement at this point increase abruptly, then reduce and tend to the static value gradually at last. The wave attenuates along the radial, therefore the farther the wave is from the source, the smaller the stress and the displacement are, and the stress and the displacement are just functions of the radial distance from the axis.
Surface effects in anti-plane deformations of a micropolar elastic solid: integral equation methods
Sigaeva, Taisiya; Schiavone, Peter
2016-03-01
The theory of linear micropolar elasticity is used in conjunction with a new representation of micropolar surface mechanics to develop a comprehensive model for the deformations of a linearly micropolar elastic solid subjected to anti-plane shear loading. The proposed model represents the surface effect as a thin micropolar film of separate elasticity, perfectly bonded to the bulk. This model captures not only the micro-mechanical behavior of the bulk which is known to be considerable in many real materials but also the contribution of the surface effect which has been experimentally well observed for bodies with significant size-dependency and large surface area to volume ratios. The contribution of the surface mechanics to the ensuing boundary-value problem gives rise to a highly nonstandard boundary condition not accommodated by classical studies in this area. Nevertheless, the corresponding interior and exterior mixed boundary-value problems are formulated and reduced to systems of singular integro-differential equations using a representation of solutions in the form of modified single-layer potentials. Analysis of these systems demonstrates that the classical Noether theorems reduce to Fredholms theorems leading to results on well-posedness of the corresponding mathematical model.
Institute of Scientific and Technical Information of China (English)
Wu Yang YU; Dong Hua WU; Gang Song LENG
2007-01-01
The purpose of this paper is to generalize the notion of intersection bodies to that of quasi Lp-intersection bodies. The Lp-analogs of the Busemann intersection inequality and the Brunn Minkowski inequality for the quasi Lp-intersection bodies are obtained. The Aleksandrov-Fenchel inequality for the mixed quasi Lp-intersection bodies is also established.
INTERSECTIONAL DISCRIMINATION AGAINST CHILDREN
DEFF Research Database (Denmark)
Ravnbøl, Camilla Ida
This paper adds a perspective to existing research on child protection by engaging in a debate on intersectional discrimination and its relationship to child protection. The paper has a twofold objective, (1) to further establish intersectionality as a concept to address discrimination against...
Three-dimensional effects on cracked discs and plates under nominal Mode III loading
Directory of Open Access Journals (Sweden)
A. Campagnolo
2015-10-01
Full Text Available The existence of three-dimensional effects at cracks has been known for many years, but understanding has been limited, and for some situations still is. Understanding improved when the existence of corner point singularities and their implications became known. Increasingly powerful computers made it possible to investigate three-dimensional effects numerically in detail. Despite increased understanding, threedimensional effects are sometimes ignored in situations where they may be important. The purpose of the present contribution is to review the study carried out by the same authors in some recent investigations, in which a coupled fracture mode generated by anti-plane loading of a straight through-the-thickness crack in linear elastic discs and plates has been analysed by means of accurate 3D finite element (FE models. The results obtained from the highly accurate finite element analyses have improved understanding of the behaviour of through cracked components under anti-plane loading. The influence of plate bending is increasingly important as the thickness decreases. It appears that a new field parameter, probably a singularity, is needed to describe the stresses at the free surfaces. Discussion on whether KIII tends to zero or infinity as a corner point is approached is futile because KIII is meaningless at a corner point. The intensity of the local stress and strain state through the thickness of the cracked components has been evaluated by using the strain energy density (SED averaged over a control volume embracing the crack tip. The SED has been considered as a parameter able to control fracture in some previous contributions and can easily take into account also coupled three-dimensional effects. Calculation of the SED shows that the position of the maximum SED in the discs case is a function of the thickness. In the plates case instead the position of the maximum SED is independent of plate thickness, contrary to disc results.
Institute of Scientific and Technical Information of China (English)
Yang Xiaomeng; Hu Yuantai; Yang Jiashi
2005-01-01
We study electromechanical fields in the anti-plane deformation of an infinite medium of piezoelectric materials of 6 mm symmetry with a circular cylindrical hole. The theory of electroelastic dielectrics with electric field gradient in the constitutive relations is used. Special attention is paid to the fields near the surface of the hole.
Directory of Open Access Journals (Sweden)
A. Caserta
1998-06-01
Full Text Available This paper deals with the antiplane wave propagation in a 2D heterogeneous dissipative medium with complex layer interfaces and irregular topography. The initial boundary value problem which represents the viscoelastic dynamics driving 2D antiplane wave propagation is formulated. The discretization scheme is based on the finite-difference technique. Our approach presents some innovative features. First, the introduction of the forcing term into the equation of motion offers the advantage of an easier handling of different inputs such as general functions of spatial coordinates and time. Second, in the case of a straight-line source, the symmetry of the incident plane wave allows us to solve the problem of oblique incidence simply by rotating the 2D model. This artifice reduces the oblique incidence to the vertical one. Third, the conventional rheological model of the generalized Maxwell body has been extended to include the stress-free boundary condition. For this reason we solve explicitly the stress-free boundary condition, not following the most popular technique called vacuum formalism. Finally, our numerical code has been constructed to model the seismic response of complex geological structures: real geological interfaces are automatically digitized and easily introduced in the input model. Three numerical applications are discussed. To validate our numerical model, the first test compares the results of our code with others shown in the literature. The second application rotates the input model to simulate the oblique incidence. The third one deals with a real high-complexity 2D geological structure.
Institute of Scientific and Technical Information of China (English)
无
2005-01-01
The dynamic behavior of two collinear cracks in a piezoelectric layer bonded to two half spaces under harmonic anti-plane shear waves was investigated by means of Schmidt method. The cracks are vertically to the interfaces of the piezoelectric layer.The boundary conditions of the electrical field were assumed to be the permeable crack surface. By using the Fourier transform, the problem can be solved with the help of two pairs of triple integral equations. Numerical examples were presented to show the effect of the geometry of the interacting cracks, the piezoelectric constants of the materials and the frequency of the incident waves upon the stress intensity factors. The results show that the dynamic field will impede or enhance the propagation of the crack in a piezoelectric material at different stages of the frequency of the incident waves. It is found that the electric displacement intensity factors for the permeable crack surface conditions are much smaller than that for the impermeable crack surface conditions.
Aldazabal, G; Ibáñez, L E; Rabadan, Raul; Uranga, Angel M
2001-01-01
It is known that chiral fermions naturally appear at certain intersections of branes at angles. Motivated by this fact, we propose a string scenario in which different standard model gauge interactions propagate on different (intersecting) brane worlds, partially wrapped in the extra dimensions. Quarks and leptons live at brane intersections, and are thus located at different positions in the extra dimensions. Replication of families follows naturally from the fact that the branes generically intersect at several points. Gauge and Yukawa couplings can be computed in terms of the compactification radii. Hierarchical Yukawa couplings appear naturally, since amplitudes involving three different intersections are proportional to exp(-A_{ijk}), where A_{ijk} is the area of a string world-sheet extending among the intersections. The models are non-supersymmetric but the string scale may be lowered down to 1-10 TeV. The proton is however stable due to a set of discrete symmetries arising from world-sheet selection r...
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Existence of solutions for the anti-plane stress for a new class of “strain-limiting” elastic bodies
Bulíček, Miroslav
2015-04-21
© 2015, Springer-Verlag Berlin Heidelberg. The main purpose of this study is to establish the existence of a weak solution to the anti-plane stress problem on V-notch domains for a class of recently proposed new models that could describe elastic materials in which the stress can increase unboundedly while the strain yet remains small. We shall also investigate the qualitative properties of the solution that is established. Although the equations governing the deformation that are being considered share certain similarities with the minimal surface problem, the boundary conditions and the presence of an additional model parameter that appears in the equation and its specific range makes the problem, as well as the result, different from those associated with the minimal surface problem.
Fatigue crack shape prediction based on vertex singularity
Directory of Open Access Journals (Sweden)
Hutař P.
2008-11-01
Full Text Available Due to the existence of vertex singularity at the point where the crack intersects the free surface, stress distribution around the crack tip and the type of the singularity is changed. In the interior of the specimen the classical singular behaviour of the crack is dominant and can be described using analytic equations. Contrary to this, at the free surface or in the boundary layer close to free surface the vertex singularity is significant. The influence of vertex singularity on crack behaviour and a crack shape for a three-dimensional structure is described in this paper. The results presented make it possible to estimate fatigue crack growth rate and crack shape using the concept of the generalized stress intensity factor. The estimated fatigue crack shape can help to provide a more reliable estimation of the fatigue life of the structures considered.
CERN PhotoLab
1974-01-01
The experimental apparatus used at intersection 1 by the CERN-Bologna Collaboration (experiment R105). It consists of two almost identical magnetic spectrometers centered at 90 degrees on opposite sides of the intersection region. In each spectrometer one can see magnetostrictive wire spark chambers, a magnet, more chambers and various hodoscopes of scintillation counters. Gas Cerenkov counters (almost invisible in the picture) are located in the gap of each magnet. On the left hand side, a matrix of 119 lead glass Cerenkov counters is located behind some concrete and iron shielding.
CERN PhotoLab
1971-01-01
Intersection I-1 of the ISR in August 1971 showing the 90 degree large acceptance spectrometer of the Saclay-Strasbourg Collaboration which is studying the momentum spectra of electrons at large angles. On the left of the crossing region can be seen the track used by the CERN-Bucharest-Cracow-Tata Collaboration to bring nuclear emulsions into the ISR.
1971-01-01
Intersection I-2 of the ISR during the installation of experiments. On the left to the crossing region can be seen the massive iron plate structure of the muon detector being used by a British collaboration in a search for the intermediate vector boson. The magnet and hodoscopes on the right are part of the spectrometer arm of the Bristish-Scandinavian Collaration.
Intersectional embodiment and power
DEFF Research Database (Denmark)
Elg, Camilla; Jensen, Sune Qvotrup
Through almost two decades the term ‘intersectionality' has gained influence in post colonial studies, gender studies, feminist theory and other research fields occupied with how social differences are distributed and how individuals are socially constructed in stratified societies. The ‘interse...... differences and discuss the implications this has for our understanding of power relations....
Evolving fracture patterns: columnar joints, mud cracks, and polygonal terrain
Goehring, L.
2012-12-01
Contraction cracks can form captivating patterns, such as the artistic craquelure sometimes found in pottery glazes, to the cracks in dried mud, or the polygonal networks covering the polar regions of Earth and Mars. Two types are frequently encountered: those with irregular rectilinear patterns, such as that formed by an homogeneous slurry when dried (or cooled) uniformly, and more regular hexagonal patterns, such as those typified by columnar joints. Once cracks start to form in a thin contracting layer, they will sequentially break the layer into smaller and smaller pieces. A rectilinear crack pattern encodes information about the order of cracks, as later cracks tend to intersect with earlier cracks at right angles. In this manner they relieve the stresses perpendicular to the pre-existing crack. In a hexagonal pattern, in contrast, the angles between all cracks at a vertex are near 120°. In this presentation it will be shown how both types of pattern can arise from identical forces, and that a rectilinear, T-junction dominated pattern will develop into to a hexagonal pattern, with Y-junctions, if allowed to. Such an evolution can be explained as the result of three conditions: (1) if cracks advance through space, or heal and recur, that the previous positions of a crack tip acts as a line of weakness, guiding the next iteration of cracking; (2) that the order of opening of cracks can change in each iteration; and (3) that crack tips curve to maximise the local strain energy release rate. The ordering of crack patterns are seen in a number of systems: columnar joints in starch and lava; desiccation cracks in clays that are repeatedly wetted and dried; cracks in eroding gypsum-cemented sand layers; and the cracks in permafrost known as polygonal terrain. These patterns will each be briefly explored, in turn, and shown to obey the above principles of crack pattern evolution.
Institute of Scientific and Technical Information of China (English)
刘又文; 方棋洪
2004-01-01
A piezoelectric screw dislocation in the matrix interacting with a circular inhomogeneity with interfacial cracks under antiplane shear and in-plane electric loading at infinity was dealt with. Using complex variable method, a general solution to the problem was presented. For a typical case, the closed form expressions of complex potentials in the inhomogeneity and the matrix regions and the electroelastic field intensity factors were derived explicitly when the interface contains single crack. The image force acting on the piezoelectric screw dislocation was calculated by using the perturbation technique and the generalized Peach-Koehler formula. As a result, numerical analysis and discussion show that the perturbation influence of the interfacial crack on the interaction effects of the dislocation and the inhomogeneity is significant which indicates the presence of the interfacial crack will change the interaction mechanism when the length of the crack goes up to a critical value. It is also shown that soft inhomogeneity can repel the dislocation due to their intrinsic electromechanical coupling behavior.
Lengliné, Olivier; Schmittbuhl, Jean; Elkhoury, Jean; Toussaint, Renaud; Daniel, Guillaume; Maloy, Knut Jurgen
2010-05-01
Observations of aseismic transients in several tectonic context suggest that they might be linked to seismicity. However a clear observation and description of these phenomena and their interaction is lacking. This owes to the difficulty of characterizing with a sufficient resolution processes taking place at depth. Here we aim to study these interactions between aseismic and seismic slip taking advantage of an unique experimental setup. We conducted a series of mode I crack propagation experiments on transparent materials (PMMA). The crack advance is trapped in a weakness plane which is the interface between two previously sandblasted and annealed plexiglass plates. A fast video camera taking up to 500 frames per second ensures the tracking of the front rupture. The acoustic system is composed of a maximum of 44 channels continuously recording at 5 MHz for a few tens of seconds. Piezo-electric sensors are composed of a 32 elements linear array and individual sensors surrounding the crack front. An automatic detection and localization procedure allows us to obtain the position of acoustic emission (A.E.) that occurred during the crack advance. Crack front image processing reveals an intermittent opening which might be linked to the time and space clustering of the AE. An analogy between the mode I (opening) and the mode III (antiplane slip) allows us to interpret our results in term of slip on faults. Our experiment thus helps to reveal the interplay between seismic and aseismic slip on faults.
Steady-state propagation of a Mode III crack in couple stress elastic materials
Mishuris, G; Radi, E
2012-01-01
This paper is concerned with the problem of a semi-infinite crack steadily propagating in an elastic solid with microstructures subject to antiplane loading applied on the crack surfaces. The loading is moving with the same constant velocity as that of the crack tip. We assume subsonic regime, that is the crack velocity is smaller than the shear wave velocity. The material behaviour is described by the indeterminate theory of couple stress elasticity developed by Koiter. This constitutive model includes the characteristic lengths in bending and torsion and thus it is able to account for the underlying microstructure of the material as well as for the strong size effects arising at small scales and observed when the representative scale of the deformation field becomes comparable with the length scale of the microstructure, such as the grain size in a polycrystalline or granular aggregate. The present analysis confirms and extends earlier results on the static case by including the effects of crack velocity an...
Crash patterns at signalized intersections
Polders, Evelien; Daniels, Stijn; HERMANS, Elke; Brijs, Tom; Wets, Geert
2015-01-01
Traffic signals are often implemented to provide for efficient movement and to improve traffic safety. Nevertheless, severe crashes still occur at signalized intersections. This study aims to improve the understanding of signalized intersection safety by identifying crash types, locations and factors associated with signalized intersections. For this purpose, 1295 police-reported crashes at 87 signalized intersections are analyzed based on detailed crash descriptions, i.e. crash data and c...
Intersectional embodiment and power
DEFF Research Database (Denmark)
Elg, Camilla; Jensen, Sune Qvotrup
. The ‘intersectional' perspective creates a focus on the coexistence and mutual formation of different kinds of social difference in the construction of the individual social position. The concept of habitus as it was coined by Pierre Bourdieu has been an inspiration for some of this research. However, the focus...... on the embodiment of social dispositions and the social formation of the individual as body inherent in Bourdieu's work have not yet gained weight in this development within ‘difference research'. It might not come to much surprise as the radical sociology of embodiment implicit in the theory of habitus does...... not seem to gain much attention in social stratification research in general. In our paper we will present our work on an embodied approach to intersectionality, which is inspired by Pierre Bourdieu and other thinkers of embodiment. We will argue for the importance of a focus on the embodiment of social...
Chen, C M; Sharakin, S A; Chen, Chiang-Mei; Gal'tsov, Dmitri V.; Sharakin, Sergei A.
1999-01-01
New solution to the six-dimensional vacuum Einstein's equations is constructed as a non-linear superposition of two five-dimensional solutions representing the Melvin-Gibbons-Maeda Universe and its S-dual. Then using duality between D=8 vacuum and a certain class of D=11 supergravity configurations we generate M2 and M5 fluxbranes as well as some of their intersections also including waves and KK-monopoles.
Evolving fracture patterns: columnar joints, mud cracks, and polygonal terrain
Goehring, Lucas
2012-01-01
When cracks form in a thin contracting layer, they sequentially break the layer into smaller and smaller pieces. A rectilinear crack pattern encodes information about the order of crack formation, as later cracks tend to intersect with earlier cracks at right angles. In a hexagonal pattern, in contrast, the angles between all cracks at a vertex are near 120$^\\circ$. However, hexagonal crack patterns are typically only seen when a crack network opens and heals repeatedly, in a thin layer, or advances by many intermittent steps into a thick layer. Here it is shown how both types of pattern can arise from identical forces, and how a rectilinear crack pattern evolves towards a hexagonal one. Such an evolution is expected when cracks undergo many opening cycles, where the cracks in any cycle are guided by the positions of cracks in the previous cycle, but when they can slightly vary their position, and order of opening. The general features of this evolution are outlined, and compared to a review of the specific p...
Hopkins, Deborah; Datuin, Marvin; Aldrin, John; Warchol, Mark; Warchol, Lyudmila; Forsyth, David
2017-02-01
Results are presented from laboratory experiments and simulations that demonstrate the ability to localize fatigue cracks around fastener holes using spherically focused ultrasonic probes for shear-wave inspections. For the experiments, fatigue cracks were created in aluminum plates in a testing frame under cyclic loading. With the exceptions of one specimen with a mid-bore crack and another with a "through" crack, the remaining specimens contain surface-breaking cracks. All of the specimens were inspected for the cracks intersecting the back wall, and some were flipped over and re-inspected with the crack intersecting the front surface. Parameter and variable sensitivity studies were performed using CIVA Simulation Software. In contrast to C-scans where detection and localization of small cracks can be very difficult, modeling and initial experimental results demonstrate that cracks can be accurately located in "True" B-scans (B-scans projected in the part along the beam path). Initial results show that small-amplitude diffracted/scattered signals from the crack tips and edges are essential in obtaining clear crack traces in the True B-scans. It is important therefore that experimental data be acquired with sufficient gain to capture the diffracted/scattered signals. In all of the cases studied here, saturating the high-amplitude specular reflections from the fastener hole and crack enhanced the crack trace in the True B-scans.
Effects of friction and high torque on fatigue crack propagation in Mode III
Nayeb-Hashemi, H.; McClintock, F. A.; Ritchie, R. O.
1982-12-01
Turbo-generator and automotive shafts are often subjected to complex histories of high torques. To provide a basis for fatigue life estimation in such components, a study of fatigue crack propagation in Mode III (anti-plane shear) for a mill-annealed AISI 4140 steel (RB88, 590 MN/m2 tensile strength) has been undertaken, using torsionally-loaded, circumferentially-notched cylindrical specimens. As demonstrated previously for higher strength AISI 4340 steel, Mode III cyclic crack growth rates (dc/dN) IIIcan be related to the alternating stress intensity factor ΔKIII for conditions of small-scale yielding. However, to describe crack propagation behavior over an extended range of crack growth rates (˜10-6 to 10-2 mm per cycle), where crack growth proceeds under elastic-plastic and full plastic conditions, no correlation between (dc/dN) III and ΔKIII is possible. Accordingly, a new parameter for torsional crack growth, termed the plastic strain intensity Γ III, is introduced and is shown to provide a unique description of Mode III crack growth behavior for a wide range of testing conditions, provided a mean load reduces friction, abrasion, and interlocking between mating fracture surfaces. The latter effect is found to be dependent upon the mode of applied loading (i.e., the presence of superimposed axial loads) and the crack length and torque level. Mechanistically, high-torque surfaces were transverse, macroscopically flat, and smeared. Lower torques showed additional axial cracks (longitudinal shear cracking) perpendicular to the main transverse surface. A micro-mechanical model for the main radi l Mode III growth, based on the premise that crack advance results from Mode II coalescence of microcracks initiated at inclusions ahead of the main crack front, is extended to high nominal stress levels, and predicts that Mode III fatigue crack propagation rates should be proportional to the range of plastic strain intensity (ΔΓIII if local Mode II growth rates are
Institute of Scientific and Technical Information of China (English)
LIU Diankui; LIN Hong
2004-01-01
An analytical method is developed for scattering of SH-waves and dynamic stress concentration by an interacting interface crack and a circular cavity near bimaterial interface. A suitable Green's function is contructed, which is the fundamental solution of the displacement field for an elastic half space with a circular cavity impacted by an out-plane harmonic line source loading at the horizontal surface. First, the bimaterial media is divided into two parts along the horizontal interface, one is an elastic half space with a circular cavity and the other is a complete half space.Then the problem is solved according to the procedure of combination and by the Green's function method. The horizontal surfaces of the two half spaces are loaded with undetermined anti-plane forces in order to satisfy continuity conditions at the linking section, or with some forces to recover cracks by means of crack-division technique. A series of Fredholm integral equations of first kind for determining the unknown forces can be set up through continuity conditions as expressed in terms of the Green's function. Moreover, some expressions are given in this paper, such as dynamic stress intensity factor (DSIF) at the tip of the interface crack and dynamic stress concentration factor (DSCF) around the circular cavity edge. Numerical examples are provided to show the influences of the wave numbers,the geometrical location of the interface crack and the circular cavity, and parameter combinations of different media upon DSIF and DSCF.
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
In this paper, by using the Brunn-Minkowski-Firey mixed volume theory and dual mixed volume theory, associated with Lp intersection body and dual mixed volume, some dual Brunn-Minkowski inequalities and their isolate forms are established for Lp intersection body about the normalized Lp radial addition and Lp radial linear combination. Some properties of operator Lp are given.
INEQUALITIES FOR MIXED INTERSECTION BODIES
Institute of Scientific and Technical Information of China (English)
YUAN SHUFENG; LENG GANGSONG
2005-01-01
In this paper, some properties of mixed intersection bodies are given, and inequalities from the dual Brunn-Minkowski theory (such as the dual Minkowski inequality, the dual Aleksandrov-Fenchel inequalities and the. dual Brunn-Minkowski inequalities) are established for mixed intersection bodies.
-Mixed Intersection Bodies and Star Duality
Indian Academy of Sciences (India)
Zhao Chang-jian; Wing-Sum Cheung
2010-09-01
The paper extends the two notions of the dual mixed volumes and -intersection body to -dual mixed volumes and -mixed intersection body, respectively. Inequalities for the star dual of -mixed intersection bodies are established.
Modelling of urban traffic networkof signalized intersections
2013-01-01
This report presents how traffic network of signalized intersection in a chosen urban area called Tema is synchronized. Using a modular approach, two different types of traffic intersection commonly found in an urban area were modelled i.e. a simple intersection and a complex intersection. A direct road, even though not an intersection, was also included in the modelling because it’s commonly found in an urban area plus it connects any two intersections. Each of these scenarios was modelled u...
Intersectional perspective in elderly care
Directory of Open Access Journals (Sweden)
Marta Cuesta
2016-05-01
Full Text Available Earlier research has shown that power relationships at workplaces are constructed by power structures. Processes related to power always influence the working conditions for (in this study in elderly care the working groups involved. Power structures are central for intersectional analysis, in the sense that the intersectional perspective highlights aspects such as gender and ethnicity (subjective dimensions and interrelates them to processes of power (objective dimension. This qualitative study aims to explore in what way an intersectional perspective could contribute to increased knowledge of power structures in a nursing home where the employees were mostly immigrants from different countries. By using reflexive dialogues related to an intersectional perspective, new knowledge which contributes to the employees’ well-being could develop. Narrative analysis was the method used to conduct this study. Through a multi-stage focus group on six occasions over 6 months, the staff were engaged in intersectional and critical reflections about power relationship with the researchers, by identifying patterns in their professional activities that could be connected to their subjectivities (gender, ethnicity, etc.. The result of this study presents three themes that express the staff's experiences and connect these experiences to structural discrimination. 1 Intersectionality, knowledge, and experiences of professionalism; 2 Intersectionality, knowledge, and experiences of collaboration; and 3 Intersectionality, knowledge, and experiences of discrimination. The result demonstrates that an intersectional perspective reinforces the involved abilities, during the conversations, into being clear about, for example, their experiences of discrimination, and consequently developing a better understanding of their professionalism and collaboration. Such deeper reflections became possible through a process of consciousness raising, strengthening the employee
Gear Crack Propagation Investigation
1995-01-01
Reduced weight is a major design goal in aircraft power transmissions. Some gear designs incorporate thin rims to help meet this goal. Thin rims, however, may lead to bending fatigue cracks. These cracks may propagate through a gear tooth or into the gear rim. A crack that propagates through a tooth would probably not be catastrophic, and ample warning of a failure could be possible. On the other hand, a crack that propagates through the rim would be catastrophic. Such cracks could lead to disengagement of a rotor or propeller from an engine, loss of an aircraft, and fatalities. To help create and validate tools for the gear designer, the NASA Lewis Research Center performed in-house analytical and experimental studies to investigate the effect of rim thickness on gear-tooth crack propagation. Our goal was to determine whether cracks grew through gear teeth (benign failure mode) or through gear rims (catastrophic failure mode) for various rim thicknesses. In addition, we investigated the effect of rim thickness on crack propagation life. A finite-element-based computer program simulated gear-tooth crack propagation. The analysis used principles of linear elastic fracture mechanics, and quarter-point, triangular elements were used at the crack tip to represent the stress singularity. The program had an automated crack propagation option in which cracks were grown numerically via an automated remeshing scheme. Crack-tip stress-intensity factors were estimated to determine crack-propagation direction. Also, various fatigue crack growth models were used to estimate crack-propagation life. Experiments were performed in Lewis' Spur Gear Fatigue Rig to validate predicted crack propagation results. Gears with various backup ratios were tested to validate crack-path predictions. Also, test gears were installed with special crack-propagation gages in the tooth fillet region to measure bending-fatigue crack growth. From both predictions and tests, gears with backup ratios
Shi, Yin; Wan, YongPing; Zhong, Zheng
2016-10-01
In this paper, we investigate the effective properties of three-phase (matrix/coating/fiber) cylindrical piezoelectric composites with imperfect interfaces under anti-plane mechanical and in-plane electrical loads. By using the electromechanically coupling spring-type interface model and the generalized self-consistent method (GSM), we analytically derived the effective electroelastic moduli. The present solutions include as special cases the three-phase cylindrical piezoelectric composites with perfect interfaces as well as the two-phase (matrix/fiber) case with imperfect or perfect interfaces. Selected calculations are graphically shown to demonstrate dependence of the effective moduli on the interfacial properties. The particular size-dependent characteristic due to the interfacial imperfection is also discussed.
Kusakabe, T.; Kame, N.
2015-12-01
We develop an extended boundary integral equation method (XBIEM) to analyse dynamic behavior of rupture crossing a medium interface in 2D. Many faults often lie near medium interfaces in the Earth's heterogeneous crust consisting of various types of rocks. Some faults cross the interfaces, and the theoretical analysis of their dynamic behavior has been awaited. In the development, we focus on the extended parts of XBIEM in comparison to the conventional BIEM, and derive all the 2D displacement and stress kernels in response to a unit boundary traction in explicit discretized forms, which are the ingredients in the extension of BIEM. The final forms of kernels are compact and easy to evaluate numerically. They are implemented in simulating dynamic anti-plane rupture propagation across a bimaterial interface allowing secondary interfacial rupture. Our analysis shows a significant effect of an interfacial medium contrast on the control of dynamic rupture propagation.
Modified Dugdale cracks and Fictitious cracks
DEFF Research Database (Denmark)
Nielsen, Lauge Fuglsang
1998-01-01
(displacement) respectively of material considered. The practical applicability of the two models is limited such that predicted strength sigma_CR must be less than sigma_L/3, which corresponds to an assumption that fictitious cracks are much smaller than real crack lengths considered. The reason......A number of theories are presented in the literature on crack mechanics by which the strength of damaged materials can be predicted. Among these are theories based on the well-known Dugdale model of a crack prevented from spreading by self-created constant cohesive flow stressed acting in local...... Dugdale crack is the same as if it has been weakened by the well-known Griffith crack, namely sigma_CR = (EG_CR/phi)^1/2 where E and 1 are Young's modulus and crack half-length respectively, and G_CR is the so-called critical energy release rate. The physical significance of G_CR, however, is different...
Intersectionality in European Union policymaking
DEFF Research Database (Denmark)
Lombardo, Emanuela; Agustin, Lise Rolandsen
2016-01-01
is particularly apt to deal with equality and diversity in policymaking. By analysing a selection of European Union policy documents on gender-based violence in the period 2000–2014, we attend to the question of what intersectionality can bring to policymaking in terms of strengthening inclusiveness and address...
Reconstructing surface triangulations by their intersection matrices
2014-01-01
The intersection matrix of a finite simplicial complex has as each of its entries the rank of the intersection of its respective simplices. We prove that such matrix defines the triangulation of a closed connected surface up to isomorphism.
Using Intersectionality in Student Affairs Research
Strayhorn, Terrell L.
2017-01-01
This chapter presents intersectionality as a useful heuristic for conducting research in higher education and student affairs contexts. Much more than just another theory, intersectionality can powerfully shape student affairs research in both obvious and tacit ways.
The Clique Problem in Ray Intersection Graphs
Cabello, Sergio; Langerman, Stefan
2011-01-01
Ray intersection graphs are intersection graphs of rays, or halflines, in the plane. We show that any planar graph has an even subdivision whose complement is a ray intersection graph. The construction can be done in polynomial time and implies that finding a maximum clique in a segment intersection graph is NP-hard. This solves a 21-year old open problem posed by Kratochv\\'il and Ne\\v{s}et\\v{r}il.
Institute of Scientific and Technical Information of China (English)
Zhen-yu ZHAO; Yan-ru GUO; Yan WANG; Hong LIU; Qing ZHANG
2014-01-01
This paper discusses the growth stages, spatial structures, quantitative fitting relationships among various parameters, growth patterns and influencing factors of mud cracks by field survey, core observation and SEM analysis. The study shows that:(1) Mud crack growth can go through three stages, i.e. the syndiagenetic stage, the burial diagenetic stage (including early diagenetic stage, middle-late diagenetic stage) and the epidiagenetic stage. (2) Quantitative fitting relationships among various parameters allow a great significance to describe the spatial structure, the regional distribution and the growth environment of mud cracks. (3) Mud crack growth has three models, such as the unilateral growth model including the linear growth pattern, the curvilinear growth pattern and the bifurcation growth pattern, the multilateral growth model including the intersectional growth pattern, the join growth pattern and the dispersed growth pattern, and the mixed growth model including the combination of any patterns listed above. (4) Modern mud crack growth usually undergoes four stages. Sand beds in sand-mud rhythmic strata can play a lubricative role on crack growth and provide enough sandy deposits for filling cracks. (5) Mud crack growth usually produces bifurcation and bifurcation angles which are mostly 120° or 90° that are related to sediment heterogeneity and released energy. (6) Factors affecting mud crack growth cover many aspects: clay content and salinity can control the number of mud cracks in different areas;terrain can control mud crack morphology;and different sedimentary cycles can control the growth patterns and filling models of mud cracks.
Institute of Scientific and Technical Information of China (English)
周彦斌; 刘官厅
2015-01-01
用复变函数方法和保角变换研究准晶压电材料中椭圆带不对称裂纹的栿型问题。根据压电准晶材料的基本方程，利用点群的对称性，导出一维六方准晶压电材料反平面问题的控制方程，并利用 Cauchy 积分公式，得到在电不可通边界下的裂纹尖端场的强度因子和机械能释放率的解析表达式。%This paper adopted variable function method and the technique of conformal mapping to study the anti-plane problem of two asymmetrical edge cracks emanating from an elliptical hole of piezoe-lectricity of onedimensional hexagonal quasicrystals.Based on the fundamental equations of peizoelasticity of quasicrystal materials and the symmetry of onedimensional hexagonal quasicrystals,one-dimensional piezoelectric crystal material control equations of antiplane problem were derived.Using Cauchy integral formula,the analytical expressions of the field intensity factors and the mechanical strain enegy rete were presented with the assumption that the crack were electrically impermeable.
Fatigue-crack-initiation numerical modelling of a Ni-base powder metallurgy alloy
Institute of Scientific and Technical Information of China (English)
2012-01-01
A simplified three-dimensional numerical model was presented to simulate the micro-crack nucleation and growth to some predefined dimension(approximately 0.38 mm) on the throat surface of a Ni-base powder metallurgy(PM) specimen.The numerical simulation of micro-crack initiation was based on the Tanaka-Mura micro-crack initiation models,where individual grains of the mesoscopic model were simulated using the Voronoi tessellation.Four improvements were made in the model.(1) Considering crack initiation along with 12 principal slip systems on octahedral slip planes of face centered cubic(FCC) crystal in three-dimensional(3-D) models.(2) Considering the effect of secondary phase precipitate due to impinging slip and dislocation pileup.(3) The Tanaka-Mura theory of fatigue-crack-initiation from notches was applied to simulate the crack initiation from another crack tip.(4) The coalescence of random initiated micro-cracks was simulated once they intersected with each other and a macro-crack was finally formed.The calculated results were in good agreement with the experimental data which verified the rationality of the simulation model.The applicability of the proposed model for treating fatigue-crack-initiation life in engineering structures was preliminarily achieved.%A simplified three-dimensional numerical model was presented to simulate the micro-crack nucleation and growth to some predefined dimension（approximately 0.38 mm） on the throat surface of a Ni-base powder metallurgy（PM） specimen.The numerical simulation of micro-crack initiation was based on the Tanaka-Mura micro-crack initiation models,where individual grains of the mesoscopic model were simulated using the Voronoi tessellation.Four improvements were made in the model.（1） Considering crack initiation along with 12 principal slip systems on octahedral slip planes of face centered cubic（FCC） crystal in three-dimensional（3-D） models.（2） Considering the effect of secondary phase
Point Lepreau primary heat transport pump wear ring cracking
Energy Technology Data Exchange (ETDEWEB)
Licina, G. [Structural Integrity Associates, Inc., San Jose, California (United States); Rankin, B. [Point Lepreau Nuclear Generating Station, Fredericton, New Brunswick (Canada)
2011-07-01
The number 3 Primary Heat Transport (PHT) pump from Point Lepreau Nuclear Generating Station (Point Lepreau) was disassembled after more than 30 years of service for inspection during station refurbishment. The disassembly and inspection were performed to provide assurance of continued satisfactory operation during life extension. The inspection revealed cracks in the wear ring, at and near the tack welds (Type 309 stainless steel weld metal) at the cap screws that attach the Type 420 stainless steel wear ring to the body of the pump. Investigative work consisted of on-site PT and replication of the microstructure at the surface of the wear ring, subsequent impressions of two crack faces, and hardness determinations. This paper describes the investigative work and conclusions associated with resolution of the following questions: 1. What is the most likely cause of the cracking? 2. Will the cracks propagate within the base metal of the wear ring? 3. If propagation is possible, what is the risk of cracks intersecting, such that a piece of metal could become dislodged? Question number 3 has clear ramifications with respect to foreign material entering and damaging a nuclear fuel-containing pressure tube. There are also questions associated with extent of condition, specifically, whether other PHT pumps may have similar or worse cracking and whether such cracks will grow. Results will be applied to wear rings in other PHT pumps at Point Lepreau and are likely to be applicable to similar components in other CANDU PHT pumps. (author)
Composite fluxbranes with general intersections
Ivashchuk, V D
2002-01-01
Generalized composite fluxbrane solutions for a wide class of intersection rules are obtained. The solutions are defined on a manifold which contains a product of n Ricci-flat spaces M_1 x ... x M_n with 1-dimensional M_1. They are defined up to a set of functions H_s obeying non-linear differential equations equivalent to Toda-type equations with certain boundary conditions imposed. A conjecture on polynomial structure of governing functions H_s for intersections related to semisimple Lie algebras is suggested. This conjecture is valid for Lie algebras: A_m, C_{m+1}, m > 0. For simple Lie algebras the powers of polynomials coincide with the components of the dual Weyl vector in the basis of simple roots. Explicit formulas for A_1 + ... + A_1 (orthogonal), "block-ortogonal" and A_2 solutions are obtained. Certain examples of solutions in D = 11 and D =10 (II A) supergravities (e.g. with A_2 intersection rules) and Kaluza-Klein dyonic A_2 flux tube, are considered.
Crack Characterisation for In-service Inspection Planning - An Update
Energy Technology Data Exchange (ETDEWEB)
Waale, Jan [lnspecta Technology AB, Stockholm (Sweden)
2006-05-15
; Mechanical fatigue; and Solidification cracking in weld metal. The evaluated parameters were divided into visually detectable and metallurgical parameters, which need to be evaluated from a cross-section. The visually detectable parameters are; location, orientation and shape in surface direction and finally the number of cracks in the cracked region. The metallurgical parameters are; orientation and shape in the through thickness direction, macroscopic branching, crack tip radius, crack surface roughness, crack width and finally discontinuous appearance. The morphology parameters were statistically processed and the results are presented as minimum, maximum. mean, median and scatter values for each data group, both in tables and in various graphs. Finally each morphology parameter is compared between the seven data groups. A brief description of typical characteristics of each data group is given below. Most IGSCC develop next to welds with straight or winding cracks oriented almost parallel to the weld. Single cracking is most common but occasionally two cracks are formed on each side of the weld. In the through thickness direction IGSCC is typically winding or lightly bend and macroscopic branching is rare. The surface roughness is normally on a grain size magnitude and the cracks are particularly narrow providing secondary corrosion is small. Similar characteristics to IGSCC in austenitic stainless steels may be expected. However, cracking close to weld are less frequent and macroscopic branching is more common for IGSCC in nickel base alloys compared to austenitic stainless steels. Typically IDSCC is winding or straight, single cracking in the weld metal transverse to the weld. In the through thickness direction IDSCC cause typically winding, non branched cracks with large surface roughness due to course solidification microstructure. The crack width often shows large variation along the crack and a width close to zero at the surface intersection is common. Typically
Chudnovsky, A.
1984-01-01
A damage parameter is introduced in addition to conventional parameters of continuum mechanics and consider a crack surrounded by an array of microdefects within the continuum mechanics framework. A system consisting of the main crack and surrounding damage is called crack layer (CL). Crack layer propagation is an irreversible process. The general framework of the thermodynamics of irreversible processes are employed to identify the driving forces (causes) and to derive the constitutive equation of CL propagation, that is, the relationship between the rates of the crack growth and damage dissemination from one side and the conjugated thermodynamic forces from another. The proposed law of CL propagation is in good agreement with the experimental data on fatigue CL propagation in various materials. The theory also elaborates material toughness characterization.
Projective modules and complete intersections
Mandal, Satya
1997-01-01
In these notes on "Projective Modules and Complete Intersections" an account on the recent developments in research on this subject is presented. The author's preference for the technique of Patching isotopic isomorphisms due to Quillen, formalized by Plumsted, over the techniques of elementary matrices is evident here. The treatment of Basic Element theory here incorporates Plumstead's idea of the "generalized dimension functions". These notes are highly selfcontained and should be accessible to any graduate student in commutative algebra or algebraic geometry. They include fully self-contained presentations of the theorems of Ferrand-Szpiro, Cowsik-Nori and the techniques of Lindel.
Effect of crack propagation on crack tip fields
Directory of Open Access Journals (Sweden)
F.V. Antunes
2013-07-01
Full Text Available Crack closure influences fatigue crack growth rate and must be included in the design of components. Plasticity induced crack closure is intimately linked with the crack tip plastic deformation, which becomes residual as the crack propagates. The objective here is to study numerically the effect of crack propagation on crack tip fields. The transient effect observed at the beginning of crack propagation is linked to the hardening behavior of material. The effect of mesh refinement is studied, and a singular behavior is evident, which is explained by the sharp crack associated with mesh topology, composed of a regular pattern of square elements. The plastic zone size measured perpendicularly to crack flank in the residual plastic wake is quantified and compared with literature models. Finally, the removal of material at the first node behind crack tip with load cycling was observed for plane strain state and some hardening models in plane stress state.
Larsen, James M.; Allison, John E.
This book contains chapters on fracture mechanics parameters for small fatigue cracks, monitoring small-crack growth by the replication method, measurement of small cracks by photomicroscopy (experiments and analysis), and experimental mechanics of microcracks. Other topics discussed are the real-time measurement of small-crack-opening behavior using an interferometric strain/displacement gage; direct current electrical potential measurement of the growth of small cracks; an ultrasonic method for the measurement of the size and opening behavior of small fatigue cracks; and the simulation of short crack and other low closure loading conditions, utilizing constant K(max) Delta-K-decreasing fatigue crack growth procedures.
Effect of crack surface geometry on fatigue crack closure
Energy Technology Data Exchange (ETDEWEB)
Drury, W.J. [P and L Technologies, Inc., Atlanta, GA (United States); Gokhale, A.M. [Georgia Inst. of Tech., Atlanta, GA (United States). School of Materials Science and Engineering; Antolovich, S.D. [Washington State Univ., Pullman, WA (United States). School of Mechanical and Materials Engineering
1995-10-01
The geometry of crack faces often plays a critical role in reducing crack extension forces when crack closure occurs during fatigue crack growth. Most previous studies of fatigue crack closure are concerned with mechanical measure of closure as related to the crack growth rate; very little attention has been given to the geometry of the crack surfaces. The objective is to identify those aspects of crack surface geometry that are important in the closure process, to develop quantitative fractographic techniques to estimate such attributes in a statistically significant and robust manner, and to correlate them to the physical process of crack closure. For this purpose, fatigue crack propagation experiments were performed on a Ni-base superalloy and crack growth rates and crack closure loads were measured. Digital image profilometry and software-based analysis techniques were used for statistically reliable and detailed quantitative characterization of fatigue crack profiles. It is shown that the dimensionless, scale-independent attributes, such a height-to-width ratio of asperities, fractal dimensions, dimensionless roughness parameters, etc., do not represent the aspects of crack geometry that are of primary importance in the crack closure phenomena. Furthermore, it is shown that the scale-dependent characteristics, such as average asperity height, do represent the aspects of crack geometry that play an interactive role in the closure process. These observations have implications concerning the validity of geometry-dependent, closure-based models for fatigue crack growth.
Tropical intersection theory on R^n
Flossmann, Simon
2014-01-01
In these notes we survey the tropical intersection theory on R^n by deriving the properties for tropical cycles from the corresponding properties in Chow cohomology. For this we review the stable intersection product introduced by Mikhalkin and the push forward of tropical cycles defined by Allermann and Rau. Furthermore we define a pull back for tropical cycles based on the pull back of Minkowski weights. This pull back commutes with the tropical intersection product and satisfies the projec...
Tropical intersection theory on R^n
Flossmann, Simon
2014-01-01
In these notes we survey the tropical intersection theory on R^n by deriving the properties for tropical cycles from the corresponding properties in Chow cohomology. For this we review the stable intersection product introduced by Mikhalkin and the push forward of tropical cycles defined by Allermann and Rau. Furthermore we define a pull back for tropical cycles based on the pull back of Minkowski weights. This pull back commutes with the tropical intersection product and satisfies the projec...
Institute of Scientific and Technical Information of China (English)
2008-01-01
In this paper the author first introduce a new concept of Lp-dual mixed volumes of star bodies which extends the classical dual mixed volumes. Moreover, we extend the notions of Lp- intersection body to Lp-mixed intersection body. Inequalities for Lp-dual mixed volumes of Lp-mixed intersection bodies are established and the results established here provide new estimates for these type of inequalities.
The clique problem in ray intersection graphs
Langerman, Stefan; Cardinal, Jean; Cabello, Sergio
2015-01-01
Ray intersection graphs are intersection graphs of rays, or halflines, in the plane. We show that any planar graph has an even subdivision whose complement is a ray intersection graph. The construction can be done in polynomial time and implies that finding a maximum clique in a segment intersection graph is NP-hard. This solves a 21-year old open problem posed by Kratochvíl and Nešetřil (Comment Math Univ Carolinae 31(1):85-93, 1990).
DESIGNING AN EFFECTIVE INTERSECTION USING CAD ENVIRONMENT
Directory of Open Access Journals (Sweden)
CRISAN George-Horea
2017-05-01
Full Text Available Ensuring the safety and streamline in road traffic are very important aims, with regard to the nowadays people mobility level. Road infrastructure is an essential element that can meet these requirements. Thus, it is proposed to develop an effective model of intersection by using CAD software tools. This type of intersection can be successfully used on almost any category of roads, increasing road traffic safety, reducing passing times through the intersection and in the same time, reducing conflict points and increase the intersection capacity.
POLES OF ZETA FUNCTIONS OF COMPLETE INTERSECTIONS
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
A vanishing theorem is proved for -adic cohomology with compact support on an affine (singular) complete intersection. As an application, it is shown that for an affine complete intersection defined over a finite field of q elements, the reciprocal "poles" of the zeta function are always divisible by q as algebraic integers. A p-adic proof is also given, which leads to further q-divisibility of the poles or equivalently an improvement of the polar part of the AxKatz theorem for an affine complete intersection. Similar results hold for a projective complete intersection.
Energy Technology Data Exchange (ETDEWEB)
Choi, Young Chul; Park, Tae Jin [KAERI, Daejeon (Korea, Republic of)
2016-05-15
Source localization in a dispersive medium has been carried out based on the time-of-arrival-differences (TOADs) method: a triangulation method and a circle intersection technique. Recent signal processing advances have led to calculation TOAD using a joint time-frequency analysis of the signal, where a short-time Fourier transform(STFT) and wavelet transform can be included as popular algorithms. The time-frequency analysis method is able to provide various information and more reliable results such as seismic-attenuation estimation, dispersive characteristics, a wave mode analysis, and temporal energy distribution of signals compared with previous methods. These algorithms, however, have their own limitations for signal processing. In this paper, the effective use of proposed algorithm in detecting crack wave arrival time and source localization in rock masses suggest that the evaluation and real-time monitoring on the intensity of damages related to the tunnels or other underground facilities is possible. Calculation of variances resulted from moving windows as a function of their size differentiates the signature from noise and from crack signal, which lead us to determine the crack wave arrival time. Then, the source localization is determined to be where the variance of crack wave velocities from real and virtual crack localization becomes a minimum. To validate our algorithm, we have performed experiments at the tunnel, which resulted in successful determination of the wave arrival time and crack localization.
Fatigue crack identification and lifetime prediction for steel bridge deck structures
Pahlavan, P.L.; Pijpers, R.J.M.; Hakkesteegt, H.C.; Jansen, T.H.; Peelen, W.H.A.
2015-01-01
Fatigue, as the governing degradation mechanism in steel bridge decks, can lead to non-inspectable cracks under the welded intersections of stiffeners to the deck plate. As a result, estimation of the remaining service life and optimization of the maintenance program of steel bridge decks become a g
Quantity effect of radial cracks on the cracking propagation behavior and the crack morphology.
Directory of Open Access Journals (Sweden)
Jingjing Chen
Full Text Available In this letter, the quantity effect of radial cracks on the cracking propagation behavior as well as the circular crack generation on the impacted glass plate within the sandwiched glass sheets are experimentally investigated via high-speed photography system. Results show that the radial crack velocity on the backing glass layer decreases with the crack number under the same impact conditions during large quantities of repeated experiments. Thus, the "energy conversion factor" is suggested to elucidate the physical relation between the cracking number and the crack propagation speed. Besides, the number of radial crack also takes the determinative effect in the crack morphology of the impacted glass plate. This study may shed lights on understanding the cracking and propagation mechanism in laminated glass structures and provide useful tool to explore the impact information on the cracking debris.
Opposed turns at signalized intersections
Energy Technology Data Exchange (ETDEWEB)
Akcelik, R.
1989-06-01
The 1985 Highway Capacity Manual (HCM) brought the U.S. and Australian methodologies for signalized intersections closer together. An important element in this methodology is the techniques used for the estimation of opposed (permissive) turn saturation flows. Although the basic modeling philosophies of the HCM and Australian methods are similar, there are significant differences in the procedures used and therefore in the results from the two methods. In particular, the latest methodology employed in the SIDRA software has eliminated the use of opposed turn adjustment factors for lane groups and adopted an explicit and direct method of modeling individual lanes. The purpose of this paper is to bring these new methods to the attention of the U.S. researchers since it is understood that efforts are being made to improve the 1985 HCM method.
Tracks, intersections and dead ends
DEFF Research Database (Denmark)
Siim, Birte; Skjeie, Hege
2008-01-01
of organisations of civil society in political power. The second part explores the framing of the hijab as a political issue of "intersections" of gender equality versus religious belongings. The third part investigates what we see as a "dead end" in policy making to prevent violations of women's rights......The article discusses multicultural challenges to state feminism in Denmark and Norway focusing both on similarities and differences in the two countries policy responses. In spite of important differences, we point towards similar problems and dilemmas in the public responses to multiculturalism......; that is the general, age based, restrictions on family unification as a means to combat forced marriages. Finally, in the conclusion, we emphasise the importance of participatory women-friendly politics that include all who are affected by political decisions. ...
DEFF Research Database (Denmark)
Thoft-Christensen, Palle
Modelling of corrosion cracking of reinforced concrete structures is complicated as a great number of uncertain factors are involved. To get a reliable modelling a physical and mechanical understanding of the process behind corrosion in needed.......Modelling of corrosion cracking of reinforced concrete structures is complicated as a great number of uncertain factors are involved. To get a reliable modelling a physical and mechanical understanding of the process behind corrosion in needed....
Framing Gender Intersections in the European Union
DEFF Research Database (Denmark)
Lombardo, Emanuela; Agustin, Lise Rolandsen
2012-01-01
This article explores the extent to which the emergence of an antidiscrimination policy in the European Union (EU) implies a shift in EU gender equality policies towards an intersectional approach. The frame analysis of EU gender equality policy documents shows that intersectional dimensions...
Computations in intersection rings of flag bundles
Grayson, Daniel R; Stillman, Michael E
2012-01-01
Intersection rings of flag varieties and of isotropic flag varieties are generated by Chern classes of the tautological bundles modulo the relations coming from multiplicativity of total Chern classes. In this paper we describe the Groebner bases of the ideals of relations and give applications to computation of intersections, as implemented in Macaulay2.
Framing Gender Intersections in the European Union
DEFF Research Database (Denmark)
Lombardo, Emanuela; Agustin, Lise Rolandsen
2012-01-01
This article explores the extent to which the emergence of an antidiscrimination policy in the European Union (EU) implies a shift in EU gender equality policies towards an intersectional approach. The frame analysis of EU gender equality policy documents shows that intersectional dimensions...
An intersection algorithm based on transformation
Institute of Scientific and Technical Information of China (English)
CHEN Xiao-xia; YONG Jun-hai; CHEN Yu-jian
2006-01-01
How to obtain intersection of curves and surfaces is a fundamental problem in many areas such as computer graphics,CAD/CAM,computer animation,and robotics.Especially,how to deal with singular cases,such as tangency or superposition,is a key problem in obtaining intersection results.A method for solving the intersection problem based on the coordinate transformation is presented.With the Lagrange multiplier method,the minimum distance between the center of a circle and a quadric surface is given as well.Experience shows that the coordinate transformation could significantly simplify the method for calculating intersection to the tangency condition.It can improve the stability of the intersection of given curves and surfaces in singularity cases.The new algorithm is applied in a three dimensional CAD software (GEMS),produced by Tsinghua University.
Energy Technology Data Exchange (ETDEWEB)
Nagano, K.; Sato, K. [Muroran Institute of Technology, Hokkaido (Japan); Niitsuma, H. [Tohoku University, Sendai (Japan)
1996-05-01
This paper reports experiments carried out to estimate subsurface-fracture orientation with the three-component crack-wave measurement. The experiments were performed by using existing subsurface cracks and two wells in the experimental field. An air gun as a sound source was installed directly above a subsurface crack intersection in one of the wells, and a three-component elastic wave detector was fixed in the vicinity of a subsurface crack intersection in the other well. Crack waves from the sound source were measured in a frequency bandwidth from 150 to 300 Hz. A coherence matrix was constituted relative to triaxial components of vibration in the crack waves; a coherent vector was sought that corresponds to a maximum coherent value of the matrix; and the direction of the longer axis in an ellipse (the direction being perpendicular to the crack face) was approximated in particle motions of the crack waves by using the vector. The normal line direction of the crack face estimated by using the above method was found to agree nearly well with the direction of the minimum crust compression stress measured in the normal line direction of the crack face existed in core samples collected from the wells, and measured at nearly the same position as the subsurface crack. 5 refs., 4 figs.
At the Intersection of Identities
Directory of Open Access Journals (Sweden)
Hidasi Judit
2016-12-01
Full Text Available It is assumed that part of today’s societal difficulties, uncertainties and crisis worldwide can be attributed to the competing of multiple identities, to their intersections and their overlapping nature – on the level of nations, on the level of communities and also on the level of the individual. We aim at presenting a typology of identities that come into play in the public and in the private domain of the individual. It is hypothesized that there is a strong interdependence of cultural heritage, human values and social traditions in the competition of identities. These questions, which are interrelated and interconnected with each other through a common denominator, namely “cultural-mental programming” and “reprogramming efforts,” are going to be pondered about in the presentation. In the context of globalization the relevance of this topic is reinforced by the need to adapt to changes within the ever-intensifying shift from intercultural to multicultural environment in communities, in business and in work places. Attempts will be made to articulate some projections with respect to future trends that are to be expected: the way to go from competing identities to establishing a competitive identity (Simon Anholt. The contribution does not offer ready solutions but rather serves as fuel for further discussions.
Session Types = Intersection Types + Union Types
Padovani, Luca
2011-01-01
We propose a semantically grounded theory of session types which relies on intersection and union types. We argue that intersection and union types are natural candidates for modeling branching points in session types and we show that the resulting theory overcomes some important defects of related behavioral theories. In particular, intersections and unions provide a native solution to the problem of computing joins and meets of session types. Also, the subtyping relation turns out to be a pre-congruence, while this is not always the case in related behavioral theories.
Elastic waves along a fracture intersection
Abell, Bradley Charles
Fractures and fracture networks play a significant role in the subsurface hydraulic connectivity within the Earth. While a significant amount of research has been performed on the seismic response of single fractures and sets of fractures, few studies have examined the effect of fracture intersections on elastic wave propagation. Intersections play a key role in the connectivity of a fracture network that ultimately affects the hydraulic integrity of a rock mass. In this dissertation two new types of coupled waves are examined that propagate along intersections. 1) A coupled wedge wave that propagates along a surface fracture with particle motion highly localized to the intersection of a fracture with a free surface, and 2) fracture intersection waves that propagate along the intersection between two orthogonal fractures. Theoretical formulations were derived to determine the particle motion and velocity of intersection waves. Vibrational modes calculated from the theoretical formulation match those predicted by group theory based on the symmetry of the problem. For the coupled wedge wave, two vibrational modes exist that range in velocity between the wedge wave and Rayleigh wave velocity and exhibit either wagging or breathing motion depending on the Poisson's ratio. For the intersection waves, the observed modes depend on the properties of the fractures forming the intersection. If both fractures have equal stiffness four modes exist, two with wagging and two with breathing motion. If the fractures have unequal stiffness, four modes also exist, but the motion depends on the Poisson's ratio. The velocity of intersection waves depends on the coupling or stiffness of the intersection and frequency of the signal. In general, the different modes travel with speeds between the wedge wave and bulk shear wave velocity. Laboratory experiments were performed on isotropic and anisotropic samples to verify the existence of these waves. For both waves, the observed signals
Conical intersections in an ultracold gas
Wüster, S; Rost, J M
2010-01-01
We find that energy surfaces of more than two atoms or molecules interacting via dipole-dipole po- tentials generically possess conical intersections (CIs). Typically only few atoms participate strongly in such an intersection. For the fundamental case, a circular trimer, we show how the CI affects adiabatic excitation transport via electronic decoherence or geometric phase interference. These phe- nomena may be experimentally accessible if the trimer is realized by light alkali atoms in a ring trap, whose dipole-dipole interactions are induced by off-resonant dressing with Rydberg states. Such a setup promises a direct probe of the full many-body density dynamics near a conical intersection.
Optimising Signalised Intersection Using Wireless Vehicle Detectors
DEFF Research Database (Denmark)
Adjin, Daniel Michael Okwabi; Torkudzor, Moses; Asare, Jack
Traffic congestion on roads wastes travel times. In this paper, we developed a vehicular traffic model to optimise a signalised intersection in Accra, using wireless vehicle detectors. Traffic volume gathered was extrapolated to cover 2011 and 2016 and were analysed to obtain the peak hour traffic...... volume causing congestion. The intersection was modelled and simulated in Synchro7 as an actuated signalised model using results from the analysed data. The model for morning peak periods gave optimal cycle lengths of 100s and 150s with corresponding intersection delay of 48.9s and 90.6s in 2011 and 2016...... respectively while that for the evening was 55s giving delay of 14.2s and 16.3s respectively. It is shown that the model will improve traffic flow at the intersection....
Hirzebruch-Milnor classes of complete intersections
Maxim, Laurentiu; Schuermann, Joerg
2012-01-01
We prove a new formula for the Hirzebruch-Milnor classes of global complete intersections with arbitrary singularities describing the difference between the Hirzebruch classes and the virtual ones. This generalizes a formula for the Chern-Milnor classes in the hypersurface case that was conjectured by S. Yokura and was proved by A. Parusinski and P. Pragacz. It also generalizes a formula of T. Suwa for the Chern-Milnor classes of complete intersections with isolated singularities.
Self-Localization at Street Intersections.
Fusco, Giovanni; Shen, Huiying; Coughlan, James M
2014-05-01
There is growing interest among smartphone users in the ability to determine their precise location in their environment for a variety of applications related to wayfinding, travel and shopping. While GPS provides valuable self-localization estimates, its accuracy is limited to approximately 10 meters in most urban locations. This paper focuses on the self-localization needs of blind or visually impaired travelers, who are faced with the challenge of negotiating street intersections. These travelers need more precise self-localization to help them align themselves properly to crosswalks, signal lights and other features such as walk light pushbuttons. We demonstrate a novel computer vision-based localization approach that is tailored to the street intersection domain. Unlike most work on computer vision-based localization techniques, which typically assume the presence of detailed, high-quality 3D models of urban environments, our technique harnesses the availability of simple, ubiquitous satellite imagery (e.g., Google Maps) to create simple maps of each intersection. Not only does this technique scale naturally to the great majority of street intersections in urban areas, but it has the added advantage of incorporating the specific metric information that blind or visually impaired travelers need, namely, the locations of intersection features such as crosswalks. Key to our approach is the integration of IMU (inertial measurement unit) information with geometric information obtained from image panorama stitchings. Finally, we evaluate the localization performance of our algorithm on a dataset of intersection panoramas, demonstrating the feasibility of our approach.
Effect of wetting-drying cycles on soil desiccation cracking behaviour
Directory of Open Access Journals (Sweden)
Tang Chao-Sheng
2016-01-01
Full Text Available Better understanding the desiccation cracking process is essential in analysing drought effects on soil hydraulic and mechanical properties through consideration of the atmosphere-ground interaction. Laboratory tests were conducted to investigate the consequence of wetting-drying cycles on the initiation and propagation characteristics of desiccation cracks on soil surface. Initially saturated slurry specimens were prepared and subjected to five subsequent wetting-drying cycles. Image processing technique was employed to quantitatively analyze the morphology characteristics of crack patterns formed during each drying path. The results show that the desiccation cracking behaviour of soil is significantly affected by the wetting-drying cycles. Before the third wetting-drying cycle is reached, the surface crack ratio and the average crack width increases while the average clod area decreases with increasing the number of wetting-drying cycles. The number of intersections and crack segments per unit area reaches the peak values after the second wetting-drying cycle. After the third wetting-drying cycle is reached, the effect of increasing wetting-drying cycles on crack patterns is insignificant. Moreover, it is observed that the applied wetting-drying cycles are accompanied by a continual reconstruction of soil structure. The initial homogenous slurry structure is completely replaced with aggregated structure after the third cycles, and a significant increase in the inter-aggregate porosity can be observed.
Stress corrosion crack initiation of alloy 600 in PWR primary water
Energy Technology Data Exchange (ETDEWEB)
Zhai, Ziqing; Toloczko, Mychailo B.; Olszta, Matthew J.; Bruemmer, Stephen M.
2017-07-01
Stress corrosion crack (SCC) initiation of three mill-annealed (MA) alloy 600 heats in simulated pressurized water reactor primary water has been investigated using constant load tests equipped with in-situ direct current potential drop (DCPD) measurement capabilities. SCC initiation times were greatly reduced by a small amount of cold work. Shallow intergranular (IG) attack and/or cracks were found on most high-energy grain boundaries intersecting the surface with only a small fraction evolving into larger cracks and IGSCC growth. Crack depth profiles were measured and related to DCPD-detected initiation response. Processes controlling the SCC initiation in MA alloy 600 are discussed. IN PRESS, CORRECTED PROOF, 05/02/2017 - mfl
Growth model for large branched three-dimensional hydraulic crack system in gas or oil shale.
Chau, Viet T; Bažant, Zdeněk P; Su, Yewang
2016-10-13
Recent analysis of gas outflow histories at wellheads shows that the hydraulic crack spacing must be of the order of 0.1 m (rather than 1 m or 10 m). Consequently, the existing models, limited to one or several cracks, are unrealistic. The reality is 10(5)-10(6) almost vertical hydraulic cracks per fracking stage. Here, we study the growth of two intersecting near-orthogonal systems of parallel hydraulic cracks spaced at 0.1 m, preferably following pre-existing rock joints. One key idea is that, to model lateral cracks branching from a primary crack wall, crack pressurization, by viscous Poiseuille-type flow, of compressible (proppant-laden) frac water must be complemented with the pressurization of a sufficient volume of micropores and microcracks by Darcy-type water diffusion into the shale, to generate tension along existing crack walls, overcoming the strength limit of the cohesive-crack or crack-band model. A second key idea is that enforcing the equilibrium of stresses in cracks, pores and water, with the generation of tension in the solid phase, requires a new three-phase medium concept, which is transitional between Biot's two-phase medium and Terzaghi's effective stress and introduces the loading of the solid by pressure gradients of diffusing pore water. A computer program, combining finite elements for deformation and fracture with volume elements for water flow, is developed to validate the new model.This article is part of the themed issue 'Energy and the subsurface'.
1984-01-01
evaluating ciack initiation time and crack propagation, prgram I was used for performing the major fatigue test with the aircraft structure. In...advantage to begin with the end of the fracture, this is especially so in the case of the quantitative evaluation of striations. The overload fracture...Select the Measuring Line for Quantitative Evaluation Actually, the fatigue fracture should be inspected completely from the point of origin to the
Ledesma Alberto
2016-01-01
Soil shrinkage is produced typically under desiccating conditions. Eventually shrinkage may generate cracks in the soil mass, a phenomenon that is being studied by several researchers, because its prediction is far from being a routine in Soil Mechanics. Within this context, Unsaturated Soil Mechanics provides a promising framework to understand the mechanisms involved. In addition to that, physical modelling of desiccating soils constitutes a good tool to explore the nature of this problem. ...
2003-01-01
MGS MOC Release No. MOC2-339, 23 April 2003This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a pattern of polygonal cracks and aligned, elliptical pits in western Utopia Planitia. The picture covers an area about 3 km (about 1.9 mi) wide near 44.9oN, 274.7oW. Sunlight illuminates the scene from the left.
Intersection Logic in sequent calculus style
Della Rocca, Simona Ronchi; Stavrinos, Yiorgos; Veneti, Anastasia; 10.4204/EPTCS.45.2
2011-01-01
The intersection type assignment system has been designed directly as deductive system for assigning formulae of the implicative and conjunctive fragment of the intuitionistic logic to terms of lambda-calculus. But its relation with the logic is not standard. Between all the logics that have been proposed as its foundation, we consider ISL, which gives a logical interpretation of the intersection by splitting the intuitionistic conjunction into two connectives, with a local and global behaviour respectively, being the intersection the local one. We think ISL is a logic interesting by itself, and in order to support this claim we give a sequent calculus formulation of it, and we prove that it enjoys the cut elimination property.
Modeling aggressive driver behavior at unsignalized intersections.
Kaysi, Isam A; Abbany, Ali S
2007-07-01
The processing of vehicles at unsignalized intersections is a complex and highly interactive process, whereby each driver makes individual decisions about when, where, and how to complete the required maneuver, subject to his perceptions of distances, velocities, and own car's performance. Typically, the performance of priority-unsignalized intersections has been modeled with probabilistic approaches that consider the distribution of gaps in the major-traffic stream and their acceptance by the drivers of minor street vehicles based on the driver's "critical gap". This paper investigates the aggressive behavior of minor street vehicles at intersections that are priority-unsignalized but operate with little respect of control measures. The objective is to formulate a behavioral model that predicts the probability that a driver performs an aggressive maneuver as a function of a set of driver and traffic attributes. Parameters that were tested and modeled include driver characteristics (gender and age), car characteristics (performance and model year), and traffic attributes (number of rejected gaps, total waiting time at head of queue, and major-traffic speed). Binary probit models are developed and tested, based on a collected data set from an unsignalized intersection in the city of Beirut, to determine which of the studied variables are statistically significant in determining the aggressiveness of a specific driver. Primary conclusions reveal that age, car performance, and average speed on the major road are the major determinants of aggressive behavior. Another striking conclusion is that the total waiting time of the driver while waiting for an acceptable gap is of little significance in incurring the "forcing" behavior. The obtained model is incorporated in a simple simulation framework that reflects driver behavior and traffic stream interactions in estimating delay and conflict measures at unsignalized intersections. The simulation results were then compared
Simulation of intersecting black brane solutions
Ivashchuk, V D; Selivanov, A B
2003-01-01
A family of spherically symmetric solutions with horizon in the model with multi-component anisotropic fluid (MCAF) is obtained. The metric of any solution contains n-1 Ricci-flat ``internal space'' metrics and for certain equations of state (p_i = \\pm \\rho) coincides with the metric of intersecting black brane solution in the model with antisymmetric forms. Examples of simulation of intersecting M2 and M5 black branes are considered. The post-Newtonian parameters beta and gamma corresponding to the 4-dimensional section of the metric are calculated.
Switching exciton pulses through conical intersections
Leonhardt, K; Rost, J -M
2013-01-01
Exciton pulses transport excitation and entanglement adiabatically through Rydberg aggregates, assemblies of highly excited light atoms, which are set into directed motion by resonant dipole-dipole interaction. Here, we demonstrate the coherent splitting of such pulses as well as the spatial segregation of electronic excitation and atomic motion. Both mechanisms exploit local non-adiabatic effects at a conical intersection, turning them from a decoherence source into an asset. The intersection provides a sensitive knob controlling the propagation direction and coherence properties of exciton pulses.
Crack Tip Parameters for Growing Cracks in Linear Viscoelastic Materials
DEFF Research Database (Denmark)
Brincker, Rune
intensity factors. In the special case of a constant Poisson ratio only 2 deformation intensity factors are needed. Closed form solutions are given both for a slowly growing crack and for a crack that is suddenly arrested at a point at the crack extension path. Two examples are studied; a stress boundary...... value problem, and a displacement boundary value problem. The results show that the stress intensity factors and the displacement intensity factors do not depend explicitly upon the velocity of the crack tip....
Energy Technology Data Exchange (ETDEWEB)
Coe, Joshua D [Los Alamos National Laboratory; Levine, B G [U IL AT URBANA-CHAMPAIGN; Ong, M T [UIUC; Martinez, T J [UIUC
2008-01-01
We discuss the connectivity of intersection spaces and the role of minimal energy points within these intersection spaces (minimal energy conical intersections or MECIs) in promoting nonadiabatic transitions. We focus on malonaldeyde as a specific example, where there is a low-lying three-state conical intersection. This three-state intersection is the global minimum on the bright excited electronic state, but it plays a limited role in population transfer in our ab initio multiple spawning (AIMS) simulations because the molecule must traverse a series of two-state conical intersections to reach the three-state intersection. Due to the differences in seam space dimensionality separating conventional (two-state) and three-state intersections, we suggest that dynamical effects arising directly from a three-state intersection may prove difficult to observe in general. We also use a newly developed method for intersection optimization with geometric constraints to demonstrate the connectivity of all the stationary points in the intersection spaces for malonaldehyde. This supports the conjecture that all intersection spaces are connected, and that three-state intersections play a key role in extending this connectivity to all pairs of states, e.g. the S{sub 1}/S{sub 0} and S{sub 2}/S{sub 1} intersection spaces.
Intersection layout, traffic volumes and accidents.
Poppe, F.
1988-01-01
This paper reports on the accident research carried out as a part of a large project started in 1983. For this accident research an inventory was made of a large number of intersections.Recorded were layout features, accident data and estimates of traffic volumes. Attention will be given to the
The landscape of intersecting brane models
Douglas, M R; Douglas, Michael R.; Taylor, Washington
2007-01-01
We develop tools for analyzing the space of intersecting brane models. We apply these tools to a particular $T^6/Z^2_2$ orientifold which has been used for model building. We prove that there are a finite number of intersecting brane models on this orientifold which satisfy the Diophantine equations coming from supersymmetry. We give estimates for numbers of models with specific gauge groups, which we confirm numerically. We analyze the distributions and correlations of intersection numbers which characterize the numbers of generations of chiral fermions, and show that intersection numbers are roughly independent, with a characteristic distribution which is peaked around 0 and in which integers with fewer divisors are mildly suppressed. As an application, the number of models containing a gauge group $SU(3) \\times SU(2) \\times U(1)$ or $SU(4) \\times SU(2) \\times SU(2)$ and 3 generations of appropriate types of chiral matter is estimated to be order ${\\cal O} (10)$, in accord with previous explicit constructio...
Intersection of the Exponential and Logarithmic Curves
Boukas, Andreas; Valahas, Theodoros
2009-01-01
The study of the number of intersection points of y = a[superscript x] and y = log[subscript a]x can be an interesting topic to present in a single-variable calculus class. In this article, the authors present a classroom presentation outline involving the basic algebra and the elementary calculus of the exponential and logarithmic functions. The…
The Priority of Intersectionality in Academic Medicine.
Eckstrand, Kristen L; Eliason, Jennifer; St Cloud, Tiffani; Potter, Jennifer
2016-07-01
Recent societal events highlight inequities experienced by underrepresented and marginalized communities. These inequities are the impetus for ongoing efforts in academic medicine to create inclusive educational and patient care environments for diverse stakeholders. Frequently, approaches focus on singular populations or broad macroscopic concepts and do not always elucidate the complexities that arise at the intersection between multiple identities and life experiences. Intersectionality acknowledges multidimensional aspects of identity inclusive of historical, structural, and cultural factors. Understanding how multiple identity experiences impact different individuals, from patients to trainees to providers, is critical for improving health care education and delivery. Building on existing work within academic medicine, this Commentary outlines six key recommendations to advance intersectionality in academic medicine: embrace personal and collective loci of responsibility; examine and rectify unbalanced power dynamics; celebrate visibility and intersectional innovation; engage all stakeholders in the process of change; select and analyze meaningful metrics; and sustain the commitment to achieving health equity over time. Members of the academic medical community committed to advancing health equity can use these recommendations to promote and maintain meaningful changes that recognize and respond to the multidimensional voices and expressed needs of all individuals engaged in providing and receiving health care.
A Finite Model Property for Intersection Types
Directory of Open Access Journals (Sweden)
Rick Statman
2015-03-01
Full Text Available We show that the relational theory of intersection types known as BCD has the finite model property; that is, BCD is complete for its finite models. Our proof uses rewriting techniques which have as an immediate by-product the polynomial time decidability of the preorder <= (although this also follows from the so called beta soundness of BCD.
Grindr Culture: Intersectional and Socio-Sexual
DEFF Research Database (Denmark)
Shield, Andrew DJ
2017-01-01
and gender, (dis)ability and other socio-cultural categories intersect with users’ (homo)sexual identities while navigating the online subculture. The results and discussion sections integrate observations about Grindr culture ‘from below’ – such as the discourses circulated by Grindr’s users...
30 CFR 56.7055 - Intersecting holes.
2010-07-01
... Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Drilling and Rotary Jet Piercing Drilling § 56.7055 Intersecting holes. Holes shall not be drilled where there is a danger...
30 CFR 57.7055 - Intersecting holes.
2010-07-01
... Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Drilling and Rotary Jet Piercing Drilling-Surface and Underground § 57.7055 Intersecting holes. Holes shall not be...
Creating seamless connections: Intersecting the social and ...
African Journals Online (AJOL)
Intersecting the social and academic lives of students ... organised by the Centre for Student Support Services at the University of the Western ... benefits of improved performance in classrooms enhanced by this form of collaboration. ... university located in a big city is to create a “small college” life within a larger community.
Intersection numbers with Witten's top Chern class
Shadrin, S.; Zvonkine, D.
2008-01-01
Witten’s top Chern class is a particular cohomology class on the moduli space of Riemann surfaces endowed with r-spin structures. It plays a key role in Witten’s conjecture relating to the intersection theory on these moduli spaces. Our first goal is to compute the integral of Witten’s class over th
Improving the Performance of Urban Road Intersection.
Directory of Open Access Journals (Sweden)
Dr. Fareed M.A.Karim
2014-03-01
Full Text Available Road intersection is responsible for an important proportion of air pollution especially in urban areas, due to long queues of vehicles waiting for discharge. Therefore, it is necessary to quantify their emissions as accurately as possible. In this study an attempt was made to research on reducing the traffic air pollution such as CO, CO2, HC and NOx, fuel consumption and vehicle operating cost along with improving the traffic flow and delay at a road intersection. One major uncontrolled (un signalized intersection in capital city Sana'a (Yemen was chosen for the study. The traffic air pollution, fuel consumption and vehicle operating cost as well as vehicle delay was calculated for the base year 2012 using aaSIDRA 2.0 software developed in Australia. For the horizon year 2022, three scenarios were considered for investigation viz. (1 do nothing, (2 signalizing the intersection and (3 construction of flyover. The analysis shows that for the above mentioned parameters scenario (3 will be the best scenario followed by scenario (2, while worst case scenario will be do nothing.
Teaching Science from Cultural Points of Intersection
Grimberg, Bruna Irene; Gummer, Edith
2013-01-01
This study focuses on a professional development program for science teachers near or on American Indian reservations in Montana. This program was framed by culturally relevant pedagogy premises and was characterized by instructional strategies and content foci resulting from the intersection between three cultures: tribal, science teaching, and…
Inauguration ceremony for the Intersecting Storage Rings
1971-01-01
The inauguration ceremony for the Intersecting Storage Rings (ISR) was held on 16 October 1971. Kjell Johnsen is seen in the picture handing a symbolic key to the ISR to Edoardo Amaldi. From left to right on the podium: Victor Frederik Weisskopf, former Director-General; M Antonioz; Willibald Jentschke as Director-General of CERN, and on the other side Werner Heisenberg.
Triangle-intersecting families on eight vertices
Filmus, Yuval
2011-01-01
Simonovits and S\\'{o}s conjectured that the maximal size of a triangle-intersecting family of graphs on $n$ vertices is $2^{\\binom{n}{2}-3}$. Their conjecture has recently been proved using spectral methods. We provide an elementary proof of the special case of $8$ vertices using a partition argument.
Edge Effects in Line Intersect Sampling With
David L. R. Affleck; Timothy G. Gregoire; Harry T. Valentine
2005-01-01
Transects consisting of multiple, connected segments with a prescribed configuration are commonly used in ecological applications of line intersect sampling. The transect configuration has implications for the probability with which population elements are selected and for how the selection probabilities can be modified by the boundary of the tract being sampled. As...
First interactions from the Intersecting Storage Rings
1971-01-01
On 27 January 1971, Kjell Johnsen, who led the construction team which built the Intersecting Storage Rings (ISR), announced that the first ever interactions from colliding protons had been recorded. On the left are Franco Bonaudi, who was responsible for the civil engineering and Dirk Neet, who later took charge of ISR operations.
Vacuum chamber at intersection I-6
1971-01-01
The vacuum chamber at intersection region I-6, one of these where experiments in colliding-beam physics will be taking place. The "wheels" prevent the thin wall (1.5 mm) of the chamber from collapsing. The chamber is equipped with heating tapes and its wrapped in thermal insulation. Residual gas pressure at this and other similar regions is around 10_11.
2014-01-01
While cracking a code might seem like something few of us would encounter in our daily lives, it is actually far more prevalent than we may realize. Anyone who has had personal information taken because of a hacked email account can understand the need for cryptography and the importance of encryption-essentially the need to code information to keep it safe. This detailed volume examines the logic and science behind various ciphers, their real world uses, how codes can be broken, and the use of technology in this oft-overlooked field.
Extended MRI findings of intersection syndrome
Energy Technology Data Exchange (ETDEWEB)
Lee, Roger P.; Hatem, Stephen F.; Recht, Michael P. [Cleveland Clinic, Cleveland, OH (United States)
2009-02-15
The symptoms and physical findings of intersection syndrome have been well described in the clinical medical literature. However, the magnetic resonance imaging (MRI) findings in patients with intersection syndrome of the forearm have only recently been described in a small number of patients. We review our experience with imaging of intersection syndrome, describe previously unreported MRI findings, and emphasize modifications to MRI protocols for its evaluation. Institutional review board approval was obtained for this retrospective review of patients with MRI findings consistent with intersection syndrome of the forearm during the period from January 2004 to September 2006. Six patients were identified, three males and three females, with an average age of 39.3 years. The MRI examinations were reviewed to assess signal abnormalities within and adjacent to the first and second dorsal extensor tendon compartments (DETC): tendinosis, peritendinous edema or fluid, muscle edema, subcutaneous edema, and juxtacortical edema. The overall longitudinal extent of signal alterations was measured as well as the distance from Lister's tubercle to the crossover of the first and second DETC. Review of the MRIs showed increased intrasubstance tendon signal suggesting tendinosis in two of the six patients, peritendinous edema or fluid in all six patients, muscle edema in five of the six patients, and subcutaneous edema in three of the six patients. Juxtacortical edema was seen in one patient. Peritendinous edema or fluid extended distally beyond the radiocarpal joint in three of the six patients. The average distance from Lister's tubercle to the crossover of the first and second DETC was 3.95 cm, in keeping with recently published data. Intersection syndrome is an uncommon MRI diagnosis. In addition to the previously described MRI findings of edema adjacent to the first or second DETC, possibly with proximal extension and subcutaneous edema, we have identified
Intersectionality as a Framework for Inclusive Environments
Nunez, A. M.
2016-12-01
To create more inclusive environments for the advancement of scientific inquiry, it is critical to consider the role of intersectionality. Originating in activism and legal scholarship grounded in the realities of women of color, the concept of intersectionality emphasizes how societal power dynamics shape the differential construction of life opportunities of diverse demographic groups across a variety of social identities, contexts, and historical conditions. Importantly, intersectionality also recognizes that individuals can simultaneously hold privileged and marginalized identities. For example, while white women scientists are less represented in leadership and decision-making positions than their male counterparts, but they typically do not experience the marginalization of being mistaken for cleaning staff at their institutions, as many African American and Latina scientists report. Thus, white women are relatively privileged in this context. This case and national survey data demonstrate the critical importance of recognizing that the intersection of racial and gender identities creates complex and multi-faceted challenges for diverse women scientists in navigating the organizational culture of science. Educational research indicates that interventions seeking to create more inclusivity in science should take into account the relationships between various social identities, contexts, and broader historical conditions that affect the advancement of historically underrepresented minority groups. Therefore, this presentation will provide a conceptual framework of intersectionality to guide interventions to encourage all scientists to recognize the distinctive intellectual and social contributions of those from diverse gender, race, class, disability, sexual orientation, and other identity backgrounds. It will also address how this framework can be applied to develop programs, policies, and practices that transform organizational cultures to be more inclusive
Simulation of Intersection Rivet at Non-signalized Intersection in Housing Scheme
Nazmi, Mohd; Takaba, Sadao; Ohno, Sumio; Yusoff, Mohd Nazaruddin
Accident in the residential area are become serious case in Malaysia. Most of the incidents occur among pedestrians, bicycles, motorcycles and vehicles. Our research purpose is to avoid collision at the non-signalized intersection in the housing scheme. We committed to reduce injuries and increase pedestrians' safety. Our research provides important information that can help driver predict common problems and take steps to prevent collisions. Intersection rivet is proposed for this matter. This type of signal system can prevent any accident in a dangerous non-signalized intersection. Simulation tools and systems are developed to find and solve the problem in order to decrease any fatal incident. Investigation data were used to simulate the situation more precisely. The result will be effective as reference to set the parameter of control system of the intersection rivet.
Feuerbacher, Sven; Sommerfeld, Thomas; Cederbaum, Lorenz S
2004-02-15
Whereas conical intersections between potential energy surfaces of bound states are well known, the interaction of short-lived states has been investigated only rarely. Here, we present several systematically constructed model Hamiltonians to study the topology of intersecting complex potential energy surfaces describing short-lived states: We find the general phenomenon of doubly intersecting complex energy surfaces, i.e., there are two points instead of one as in the case of bound states where the potential energy surfaces coalesce. In addition, seams of intersections of the respective real and imaginary parts of the potential energy surfaces emanate from these two points. Using the Sigma* and Pi* resonance states of the chloroethene anion as a practical example, we demonstrate that our complete linear model Hamiltonian is able to reproduce all phenomena found in explicitly calculated ab initio complex potential energy surfaces.
Multiaxial mixed-mode cracking - small crack initiation and propagation
Energy Technology Data Exchange (ETDEWEB)
Freitas, M. de; Reis, L.; Li Bin [Lisbon Univ. (Portugal). ICEMS - Inst. of Material and Surface Science and Engineering
2006-07-01
Both the fatigue crack path and fatigue life of CK45 steel and 42CrMo4 steel under various multiaxial loading paths are studied in this paper. The replica method was applied to monitor the crack initiation and small crack growth, the fractographic analyses were carried out on the fracture surface and the crack initiation angle was measured. The effects of non-proportional loading on both the crack path and fatigue life were studied, and the flattening of asperities on the crack surface due to compressive normal stress was also observed. An improved model is proposed based on correcting the strain range parameter of the ASME code approach, taking into account the additional hardening caused by the non-proportional loading path, which can improve the predictions of the fatigue lives for various non-proportional loading paths and provide an easy way to overcome the drawbacks of the current ASME code approach for non-proportional fatigue. Based on these corrected strain range parameters, a strain intensity factor range is used to correlate with the experimental results of small crack growth rates. It is concluded that the orientation of the early crack growth can be predicted well by the critical damage plane, but the fatigue life can not be predicted accurately using only the parameters on the critical plane, since the damage on all the planes contributes to fatigue damage as stated by the integral approaches. (orig.)
Tomczak, Kamil; Jakubowski, Jacek; Fiołek, Przemysław
2017-06-01
Crack width measurement is an important element of research on the progress of self-healing cement composites. Due to the nature of this research, the method of measuring the width of cracks and their changes over time must meet specific requirements. The article presents a novel method of measuring crack width based on images from a scanner with an optical resolution of 6400 dpi, subject to initial image processing in the ImageJ development environment and further processing and analysis of results. After registering a series of images of the cracks at different times using SIFT conversion (Scale-Invariant Feature Transform), a dense network of line segments is created in all images, intersecting the cracks perpendicular to the local axes. Along these line segments, brightness profiles are extracted, which are the basis for determination of crack width. The distribution and rotation of the line of intersection in a regular layout, automation of transformations, management of images and profiles of brightness, and data analysis to determine the width of cracks and their changes over time are made automatically by own code in the ImageJ and VBA environment. The article describes the method, tests on its properties, sources of measurement uncertainty. It also presents an example of application of the method in research on autogenous self-healing of concrete, specifically the ability to reduce a sample crack width and its full closure within 28 days of the self-healing process.
Periodic points in the intersection of immediate attracting basins boundaries
Rossetti, Bastien
2014-01-01
We give sufficient conditions under which the set of eventually periodic points in the intersection of immediate attracting basins boundaries is non-empty. We give other conditions under which this set is dense in the intersection.
Catalytic cracking of lignites
Energy Technology Data Exchange (ETDEWEB)
Seitz, M.; Nowak, S.; Naegler, T.; Zimmermann, J. [Hochschule Merseburg (Germany); Welscher, J.; Schwieger, W. [Erlangen-Nuernberg Univ. (Germany); Hahn, T. [Halle-Wittenberg Univ., Halle (Germany)
2013-11-01
A most important factor for the chemical industry is the availability of cheap raw materials. As the oil price of crude oil is rising alternative feedstocks like coal are coming into focus. This work, the catalytic cracking of lignite is part of the alliance ibi (innovative Braunkohlenintegration) to use lignite as a raw material to produce chemicals. With this new one step process without an input of external hydrogen, mostly propylene, butenes and aromatics and char are formed. The product yield depends on manifold process parameters. The use of acid catalysts (zeolites like MFI) shows the highest amount of the desired products. Hydrogen rich lignites with a molar H/C ratio of > 1 are to be favoured. Due to primary cracking and secondary reactions the ratio between catalyst and lignite, temperature and residence time are the most important parameter to control the product distribution. Experiments at 500 C in a discontinuous rotary kiln reactor show yields up to 32 wt-% of hydrocarbons per lignite (maf - moisture and ash free) and 43 wt-% char, which can be gasified. Particularly, the yields of propylene and butenes as main products can be enhanced four times to about 8 wt-% by the use of catalysts while the tar yield decreases. In order to develop this innovative process catalyst systems fixed on beads were developed for an easy separation and regeneration of the used catalyst from the formed char. (orig.)
Statistical modeling of total crash frequency at highway intersections
Directory of Open Access Journals (Sweden)
Arash M. Roshandeh
2016-04-01
Full Text Available Intersection-related crashes are associated with high proportion of accidents involving drivers, occupants, pedestrians, and cyclists. In general, the purpose of intersection safety analysis is to determine the impact of safety-related variables on pedestrians, cyclists and vehicles, so as to facilitate the design of effective and efficient countermeasure strategies to improve safety at intersections. This study investigates the effects of traffic, environmental, intersection geometric and pavement-related characteristics on total crash frequencies at intersections. A random-parameter Poisson model was used with crash data from 357 signalized intersections in Chicago from 2004 to 2010. The results indicate that out of the identified factors, evening peak period traffic volume, pavement condition, and unlighted intersections have the greatest effects on crash frequencies. Overall, the results seek to suggest that, in order to improve effective highway-related safety countermeasures at intersections, significant attention must be focused on ensuring that pavements are adequately maintained and intersections should be well lighted. It needs to be mentioned that, projects could be implemented at and around the study intersections during the study period (7 years, which could affect the crash frequency over the time. This is an important variable which could be a part of the future studies to investigate the impacts of safety-related works at intersections and their marginal effects on crash frequency at signalized intersections.
Experiences on IGSCC crack manufacturing
Energy Technology Data Exchange (ETDEWEB)
Veron, P. [Equipos Nucleares, S.A., Maliano (Spain)
1997-02-01
The author presents his experience in manufacturing IGSCC realistic defects, mainly in INCONEL 600 MA Steam Generator Tubes. From that experience he extracts some knowledge about this cracking (influence of chemistry in the environment, stress state, crack growth rate, and occurrence in laboratory condition of break before leak).
HYDROGEN TRANSFER IN CATALYTIC CRACKING
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
Hydrogen transfer is an important secondary reaction of catalytic cracking reactions, which affects product yield distribution and product quality. It is an exothermic reaction with low activation energy around 43.3 kJ/mol. Catalyst properties and operation parameters in catalytic cracking greatly influence the hydrogen transfer reaction. Satisfactory results are expected through careful selection of proper catalysts and operation conditions.
Jackson, Heather; San Marchi, Chris; Balch, Dorian; Somerday, Brian; Michael, Joseph
2016-08-01
The objective of this study was to evaluate effects of low temperature on hydrogen-assisted crack propagation in forged 304L austenitic stainless steel. Fracture initiation toughness and crack-growth resistance curves were measured using fracture mechanics specimens that were thermally precharged with 140 wppm hydrogen and tested at 293 K or 223 K (20 °C or -50 °C). Fracture initiation toughness for hydrogen-precharged forgings decreased by at least 50 to 80 pct relative to non-charged forgings. With hydrogen, low-temperature fracture initiation toughness decreased by 35 to 50 pct relative to room-temperature toughness. Crack growth without hydrogen at both temperatures was microstructure-independent and indistinguishable from blunting, while with hydrogen microcracks formed by growth and coalescence of microvoids. Initiation of microvoids in the presence of hydrogen occurred where localized deformation bands intersected grain boundaries and other deformation bands. Low temperature additionally promoted fracture initiation at annealing twin boundaries in the presence of hydrogen, which competed with deformation band intersections and grain boundaries as sites of microvoid formation and fracture initiation. A common ingredient for fracture initiation was stress concentration that arose from the intersection of deformation bands with these microstructural obstacles. The localized deformation responsible for producing stress concentrations at obstacles was intensified by low temperature and hydrogen. Crack orientation and forging strength were found to have a minor effect on fracture initiation toughness of hydrogen-supersaturated 304L forgings.
Intersections and Unions of Session Types
Directory of Open Access Journals (Sweden)
Coşku Acay
2017-02-01
Full Text Available Prior work has extended the deep, logical connection between the linear sequent calculus and session-typed message-passing concurrent computation with equi-recursive types and a natural notion of subtyping. In this paper, we extend this further by intersection and union types in order to express multiple behavioral properties of processes in a single type. We prove session fidelity and absence of deadlock and illustrate the expressive power of our system with some simple examples. We observe that we can represent internal and external choice by intersection and union, respectively, which was previously suggested by Padovani for a different language of session types motivated by operational rather than logical concerns.
Birationally rigid Fano complete intersections. II
Pukhlikov, Aleksandr
2011-01-01
We prove that a generic (in the sense of Zariski topology) Fano complete intersection $V$ of the type $(d_1,...,d_k)$ in ${\\mathbb P}^{M+k}$, where $d_1+...+d_k=M+k$, is birationally superrigid if $M\\geq 7$, $M\\geq k+3$ and $\\mathop{\\rm max} \\{d_i\\}\\geq 4$. In particular, on the variety $V$ there is exactly one structure of a Mori fibre space (or a rationally connected fibre space), the groups of birational and biregular self-maps coincide, $\\mathop{\\rm Bir} V= \\mathop{\\rm Aut} V$, and the variety $V$ is non-rational. This fact covers a considerably larger range of complete intersections than the result of [J. reine angew. Math. {\\bf 541} (2001), 55-79], which required the condition $M\\geq 2k+1$. The paper is dedicated to the memory of Eckart Viehweg.
Planning of Autonomous Multi-agent Intersection
Directory of Open Access Journals (Sweden)
Viksnin Ilya I.
2016-01-01
Full Text Available In this paper, we propose a traffic management system with agents acting on behalf autonomous vehicle at the crossroads. Alternatively to existing solutions based on usage of semiautonomous control systems with the control unit, proposed in this paper algorithm apply the principles of decentralized multi-agent control. Agents during their collaboration generate intersection plan and determinate the optimal order of road intersection for a given criterion based on the exchange of information about them and their environment. The paper contains optimization criteria for possible routes selection and experiments that perform in order to estimate the proposed model. Experiment results show that this model can significantly reduce traffic density compared to the traditional traffic management systems. Moreover, the proposed algorithm efficiency increases with road traffic density. Furthermore, the availability of control unit in the system significantly reduces the negative impact of possible failures and hacker attacks.
Banerjee, Amit; Panigrahi, Brajesh; Pohit, G.
2016-04-01
In the present work, dynamic response of cracked Timoshenko beam with functionally graded material properties are obtained by a numerical technique using Ritz approximation. In order to verify the applicability and performance of the formulation, comparisons of the present numerical method with three-dimensional FEM models are made. Crack is assumed to be transverse and open throughout the vibration cycle. Two different crack detection techniques have been proposed. Results obtained by the numerical technique are used in both of the crack detection techniques. In the first technique, the frequency contours with respect to crack location and size are plotted and the intersection of contours of different modes helps in the prediction of crack location and size. In the second technique, crack is modelled using response surface methodology (RSM). The sum of the squared errors between the numerical and RSM regression model natural frequencies is used as the objective function. This objective function is minimised using genetic algorithm optimisation technique. Both the crack detection techniques and the numerical analysis have shown good agreement with each other.
Spiked Instantons from Intersecting D-branes
Nekrasov, Nikita
2016-01-01
The moduli space of spiked instantons that arises in the context of the BPS/CFT correspondence is realised as the moduli space of classical vacua, i.e. low-energy open string field configurations, of a certain stack of intersecting D1-branes and D5-branes in Type IIB string theory. The presence of a constant B-field induces an interesting dynamics involving the tachyon condensation.
Spiked instantons from intersecting D-branes
Directory of Open Access Journals (Sweden)
Nikita Nekrasov
2017-01-01
Full Text Available The moduli space of spiked instantons that arises in the context of the BPS/CFT correspondence [22] is realised as the moduli space of classical vacua, i.e. low-energy open string field configurations, of a certain stack of intersecting D1-branes and D5-branes in Type IIB string theory. The presence of a constant B-field induces an interesting dynamics involving the tachyon condensation.
Gender Equality, Intersectionality and Diversity in Europe
DEFF Research Database (Denmark)
Agustin, Lise Rolandsen
Analyzing the developments which have characterized EU gender equality policies and women's transnational activism since the introduction of multiple discrimination policies in the 1990s, this book identifies two interrelated challenges: diversity of women's interests, and degendering of policies....... Drawing on discursive policy analysis, it addresses the interaction between policies, institutions and civil society actors in relation to gender equality, diversity and intersectionality at the European level. Rolandsen Agustín successfully integrates the concepts of diversity and gender equality...
Spiked instantons from intersecting D-branes
Nekrasov, Nikita; Prabhakar, Naveen S.
2017-01-01
The moduli space of spiked instantons that arises in the context of the BPS/CFT correspondence [22] is realised as the moduli space of classical vacua, i.e. low-energy open string field configurations, of a certain stack of intersecting D1-branes and D5-branes in Type IIB string theory. The presence of a constant B-field induces an interesting dynamics involving the tachyon condensation.
A consistent partly cracked XFEM element for cohesive crack growth
DEFF Research Database (Denmark)
Asferg, Jesper L.; Poulsen, Peter Noe; Nielsen, Leif Otto
2007-01-01
capable of modelling variations in the discontinuous displacement field on both sides of the crack and hence also capable of modelling the case where equal stresses are present on each side of the crack. The enrichment was implemented for the 3-node constant strain triangle (CST) and a standard algorithm...... was used to solve the non-linear equations. The performance of the element is illustrated by modelling fracture mechanical benchmark tests. Investigations were carried out on the performance of the element for different crack lengths within one element. The results are compared with previously obtained...
Complete Intersection Fibers in F-Theory
Braun, Volker; Keitel, Jan
2014-01-01
Global F-theory compactifications whose fibers are realized as complete intersections form a richer set of models than just hypersurfaces. The detailed study of the physics associated with such geometries depends crucially on being able to put the elliptic fiber into Weierstrass form. While such a transformation is always guaranteed to exist, its explicit form is only known in a few special cases. We present a general algorithm for computing the Weierstrass form of elliptic curves defined as complete intersections of different codimensions and use it to solve all cases of complete intersections of two equations in an ambient toric variety. Using this result, we determine the toric Mordell-Weil groups of all 3134 nef partitions obtained from the 4319 three-dimensional reflexive polytopes and find new groups that do not exist for toric hypersurfaces. As an application, we construct several models that cannot be realized as toric hypersurfaces, such as the first toric SU(5) GUT model in the literature with disti...
Complete intersection fibers in F-theory
Energy Technology Data Exchange (ETDEWEB)
Braun, Volker [Mathematical Institute, University of Oxford,24-29 St Giles’, Oxford, OX1 3LB (United Kingdom); Grimm, Thomas W.; Keitel, Jan [Max-Planck-Institut für Physik,Föhringer Ring 6, 80805 Munich (Germany)
2015-03-24
Global F-theory compactifications whose fibers are realized as complete intersections form a richer set of models than just hypersurfaces. The detailed study of the physics associated with such geometries depends crucially on being able to put the elliptic fiber into Weierstrass form. While such a transformation is always guaranteed to exist, its explicit form is only known in a few special cases. We present a general algorithm for computing the Weierstrass form of elliptic curves defined as complete intersections of different codimensions and use it to solve all cases of complete intersections of two equations in an ambient toric variety. Using this result, we determine the toric Mordell-Weil groups of all 3134 nef partitions obtained from the 4319 three-dimensional reflexive polytopes and find new groups that do not exist for toric hypersurfaces. As an application, we construct several models that cannot be realized as toric hypersurfaces, such as the first toric SU(5) GUT model in the literature with distinctly charged 10 representations and an F-theory model with discrete gauge group ℤ{sub 4} whose dual fiber has a Mordell-Weil group with ℤ{sub 4} torsion.
Information point and saturation flow at signalized intersections
Directory of Open Access Journals (Sweden)
Lijun Gao
2016-08-01
Full Text Available This paper introduces an information point factor and attempts to identify how it affects saturation flow and their relationship at signalized intersections. An information point is defined as any object, structure, or activity located outside of a traveling vehicle that can potentially attract the visual attention of the driver. Saturation flow rates are studied at three pairs of signalized intersections in Toledo, Ohio, USA. Each pair of intersections consists of one intersection with a high number of information points and one intersection with a low number of information points. Study results reveal that, for each pair of intersections, the one with high information points has a lower saturation flow rate than the one with low information points. A statistical analysis shows that the differences are significant. Based on the saturation flow data of the paired intersections, information point effect models are developed and presented in this paper.
Institute of Scientific and Technical Information of China (English)
DONG Lihong; XU Binshi; DONG Shiyun; YE Minghui; CHEN Qunzhi
2006-01-01
Static tensile test and tensile-tensile fatigue test of medium carbon steel sheet specimens with surface crack precut were performed on MTS810 hydraulic testing machine to clear the meaning of the point of Hp( y ) value zero. Magnetic memory signals were measured during the test process. The results show that only one point of Hp( y ) zero value exists in all measured magnetic signal curves during the loading process, which should be a sign of intersection of positive-negative magnetic poles after magnetic ordered state appears and does not indicate the position of surface crack precut. The analysis shows that the surface crack precut can not interrupt the magnetic ordered state occurred during the test completely, hence its Hp( y ) value is not zero. However, the crack extending to a penetrated defect at the instant of specimen's fracture leads to the discontinuance of magnetic ordered state.
Xiao, Xia; Zhang, Yaoyuan; Jiang, Guiyuan; Liu, Jia; Han, Shanlei; Zhao, Zhen; Wang, Ruipu; Li, Cong; Xu, Chunming; Duan, Aijun; Wang, Yajun; Liu, Jian; Wei, Yuechang
2016-08-01
Nanosheet ZSM-5 zeolite with highly exposed (010) crystal planes demonstrates high reactivity and good anti-coking stability for the catalytic cracking of n-heptane, which is attributed to the synergy of high external surface area and acid sites, fully accessible channel intersection acid sites, and hierarchical porosity caused by the unique morphology.
Probabilistic Analysis of Crack Width
Directory of Open Access Journals (Sweden)
J. Marková
2000-01-01
Full Text Available Probabilistic analysis of crack width of a reinforced concrete element is based on the formulas accepted in Eurocode 2 and European Model Code 90. Obtained values of reliability index b seem to be satisfactory for the reinforced concrete slab that fulfils requirements for the crack width specified in Eurocode 2. However, the reliability of the slab seems to be insufficient when the European Model Code 90 is considered; reliability index is less than recommended value 1.5 for serviceability limit states indicated in Eurocode 1. Analysis of sensitivity factors of basic variables enables to find out variables significantly affecting the total crack width.
Analysis of Crack Arrest Toughness.
1988-01-15
vload(m) vp tn(m) Vertical Source Load (kN) on wedge HY80 Finite Element 0.0122 0.0099 3.81x10 -4 144 Steel Calculations Experiment 0.0122 --- 3.74x10-4...curve, are bona fide measures of the fracture arrest capability of tough ductile steels . The second is that the J-values represent the crack driving...fibrous mode of crack extension. (b) A new test method for studying fast fracture and arrest in tough steels . (c) Measurements of fast fracture and crack
A computational algorithm for crack determination: The multiple crack case
Bryan, Kurt; Vogelius, Michael
1992-01-01
An algorithm for recovering a collection of linear cracks in a homogeneous electrical conductor from boundary measurements of voltages induced by specified current fluxes is developed. The technique is a variation of Newton's method and is based on taking weighted averages of the boundary data. The method also adaptively changes the applied current flux at each iteration to maintain maximum sensitivity to the estimated locations of the cracks.
1999-01-01
Many of the craters found on the northern plains of Mars have been partly filled or buried by some material (possibly sediment). The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image presented here (MOC2-136b, above left) shows a high-resolution view of a tiny portion of the floor of one of these northern plains craters. The crater, located in Utopia Planitia at 44oN, 258oW, is shown on the right (MOC2-136a)with a small white box to indicate the location of the MOC image. The MOC image reveals that the material covering the floor of this crater is cracked and pitted. The origin and source of material that has been deposited in this crater is unknown.The MOC image was acquired in June 1999 and covers an area only 1.1 kilometers (0.7 miles) wide at a resolution of 1.8 meters (6 feet) per pixel. The context picture is a mosaic of Viking 2 orbiter images 010B53 and 010B55, taken in 1976. Both images are illuminated from the left. Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Peridynamic model for fatigue cracking.
Energy Technology Data Exchange (ETDEWEB)
Silling, Stewart Andrew; Abe Askari (Boeing)
2014-10-01
The peridynamic theory is an extension of traditional solid mechanics in which the field equations can be applied on discontinuities, such as growing cracks. This paper proposes a bond damage model within peridynamics to treat the nucleation and growth of cracks due to cyclic loading. Bond damage occurs according to the evolution of a variable called the "remaining life" of each bond that changes over time according to the cyclic strain in the bond. It is shown that the model reproduces the main features of S-N data for typical materials and also reproduces the Paris law for fatigue crack growth. Extensions of the model account for the effects of loading spectrum, fatigue limit, and variable load ratio. A three-dimensional example illustrates the nucleation and growth of a helical fatigue crack in the torsion of an aluminum alloy rod.
21 CFR 137.190 - Cracked wheat.
2010-04-01
... 21 Food and Drugs 2 2010-04-01 2010-04-01 false Cracked wheat. 137.190 Section 137.190 Food and... Related Products § 137.190 Cracked wheat. Cracked wheat is the food prepared by so cracking or cutting into angular fragments cleaned wheat other than durum wheat and red durum wheat that, when tested by...
The crack growth mechanism in asphaltic mixes
Jacobs, .M.M.J.; Hopman, P.C.; Molenaar, A.A.A.
1995-01-01
The crack growth mechanism in asphalt concrete (Ac) mixes is studied. In cyclic tests on several asphaltic mixes crack growth is measured, both with crack foils and with cOD-gauges. It is found that crack growth in asphaltic mixes is described by three processes which are parallel in time: cohesive
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
The stress-induced martensitic transformation and its relation with crack nucleation and propagation in CuNiAl shape memory alloy were investigated through in-situ tensile tests by SEM and TEM.The results indicated that the stress concentration ahead of the crack tip could induce formation of stacking faults and different types of martensites.TEM observations showed that the martensites could transform from one type to another and even reversely to the parent during loading.The micro-cracks nucleated along the martensite/parent interface and intersection between two martensites.When the crack propagated a certain distance,the stress concentration ahead of the crack tip was large enough to result in formation of slip bands,and in this condition the microcrack nucleated along slip bands more easily.
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
Optical fiber sensors are used for sensing micro-cracking in composite and metal materials in aerospace applications. The sensing mechanism is based on the detection of acoustic emission signals, which are known to emanate from micro-cracks when they grow under further loading. The sensor head consists of a fiber Bragg grating that is capable of detecting acoustic emission signals generated by pencil lead breaking, of frequencies up to 200 kHz.
Reactive chemical dynamics through conical intersections
Indian Academy of Sciences (India)
S Ghosal; B Jayachander Rao; S Mahapatra
2007-09-01
Reaction dynamics of prototypical, D + H2 and Cl (2P) + H2, chemical reactions occurring through the conical intersections of the respective coupled multi-sheeted potential energy surfaces is examined here. In addition to the electronic coupling, nonadiabatic effects due to relativistic spin-orbit coupling are also considered for the latter reaction. A time-dependent wave packet propagation approach is undertaken and the quantum dynamical observables viz., energy resolved reaction probabilities, integral reaction cross-sections and thermal rate constants are reported.
Bicone vacuum chamber for ISR intersection
1975-01-01
This is one of the bicone chambers made of titanium for experiment R 702. The central corrugated part had a very thin titanium wall (0.28 mm). The first of these chambers collapsed in its central part when baked at 300 C (August 1975). After an intensive effort to develop better quality and reproducible welds for this special material, the ISR workshop was able to build two new chambers of this type. One of them was installed at I 7 for R 702 in 1976 and worked perfectly. It was at that time the most "transparent" intersection vacuum chamber. See also 7609219, 7609221.
An Optimal Online Algorithm for Halfplane Intersection
Institute of Scientific and Technical Information of China (English)
WU Jigang; JI Yongchang; CHEN Guoliang
2000-01-01
The intersection of N halfplanes is a basic problem in computational geometry and computer graphics. The optimal offiine algorithm for this problem runs in time O(N log N). In this paper, an optimal online algorithm which runs also in time O(N log N) for this problem is presented. The main idea of the algorithm is to give a new definition for the left side of a given line, to assign the order for the points of a convex polygon, and then to use binary search method in an ordered vertex set. The data structure used in the algorithm is no more complex than array.
Minimal free resolutions over complete intersections
Eisenbud, David
2016-01-01
This book introduces a theory of higher matrix factorizations for regular sequences and uses it to describe the minimal free resolutions of high syzygy modules over complete intersections. Such resolutions have attracted attention ever since the elegant construction of the minimal free resolution of the residue field by Tate in 1957. The theory extends the theory of matrix factorizations of a non-zero divisor, initiated by Eisenbud in 1980, which yields a description of the eventual structure of minimal free resolutions over a hypersurface ring. Matrix factorizations have had many other uses in a wide range of mathematical fields, from singularity theory to mathematical physics.
Charting Relations between Intersectionality Theory and the Neurodiversity Paradigm
Directory of Open Access Journals (Sweden)
Lauren Rose Strand
2017-06-01
Full Text Available This essay explores central elements and applications of intersectionality theory and the neurodiversity paradigm. First, the histories and tenets of intersectionality theory and neurodiversity paradigm are provided. Then, areas are explored where each of the two approaches might further engage with the principles of the other. Finally, the essay concludes by broadly considering the efforts made by the Black Lives Matter movement and the Autistic Self Advocacy Network to bring attention to and end police violence as both networks employ and attend to elements of intersectionality and neurodiversity. The way these two networks draw on both intersectionality and neurodiversity to further their mission could be a possible site for scholars to consider in the interest of advancing dialogues between intersectionality theory and the neurodiversity paradigm. Ultimately, the essay calls for a continued exploration of the potentials for intersectionality and neurodiversity to complement and complicate one another, both in terms of theoretical development and coalition building.
Aircraft recognition based on the discrepancy of polygon intersection area
Deng, Xiujian; Wang, Yanfang; Feng, Qi
2017-01-01
In this paper, a new algorithm that based on discrepancy of polygon intersection area for aircraft recognition is presented. The recognition algorithm process involves three parts: generating polygon of aircraft, placing overlapping plane polygons and computing the area of total intersecting polygons. For the purpose of getting the polygon of aircraft, the picture that was ready to be recognized has gone through a series of pre-processing and the smallest circumference polygon algorithm was used to get approximate polygon of the target contour. To make the two compared polygons have the approximate area, the similar principle was utilized. The matching procedure was divided into four steps including computing intersecting points, computing polygon intersecting sets, computing the intersecting area and getting the intersecting rate to recognize the aircraft. The data structure of algorithm is based on doubly liked list principle. A mass of simulations illustrate that the proposed algorithm is effective and reasonable.
Study on Optimization of Phase Offset at Adjacent Intersections
Directory of Open Access Journals (Sweden)
Yuanli GU
2010-11-01
Full Text Available Optimization of the phase offset at adjacent intersections is the key parameter regarding coordinated control of traffic signal for adjacent intersections, which decides the effect of the coordinated control for adjacent intersections. According to characters of saturated traffic flow of Chinese urban road, this thesis establishes a model for optimization of phase offset for adjacent interactions and finds a solution from such model by adopting genetic algorithm. The model is verified by actual traffic flow datum of two adjacent signal intersections on Changan Avenue. Then a comparison is made between the optimization result of such model and that of the existing mathematical method and SYNCHRO model, which indicates that the model established by this thesis can reduce the delay suffered by vehicles at the intersections and increase the traffic efficiency of the intersections.
Surface/Surface Intersection Using Simulated Annealing Genetic Algorithm
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
The genetic algorithm and marching method are integrated into a novel algorithm to solve the surface intersection problem. By combining genetic algorithm with local searching method the efficiency of evolution is greatly improved. By fully utilizing the global searching ability and instinct attribute for parallel computation of genetic algorithm and the local rapid convergency of marching method, the algorithm can compute the intersection robustly and generate correct topology of intersection curves. The details of the new algorithm are discussed here.
Landscaping of highway medians and roadway safety at unsignalized intersections.
Chen, Hongyun; Fabregas, Aldo; Lin, Pei-Sung
2016-05-01
Well-planted and maintained landscaping can help reduce driving stress, provide better visual quality, and decrease over speeding, thus improving roadway safety. Florida Department of Transportation (FDOT) Standard Index (SI-546) is one of the more demanding standards in the U.S. for landscaping design criteria at highway medians near intersections. The purposes of this study were to (1) empirically evaluate the safety results of SI-546 at unsignalized intersections and (2) quantify the impacts of geometrics, traffic, and landscaping design features on total crashes and injury plus fatal crashes. The studied unsignalized intersections were divided into (1) those without median trees near intersections, (2) those with median trees near intersections that were compliant with SI-546, and (3) those with median trees near intersections that were non-compliant with SI-546. A total of 72 intersections were selected, for which five-year crash data from 2006-2010 were collected. The sites that were compliant with SI-546 showed the best safety performance in terms of the lowest crash counts and crash rates. Four crash predictive models-two for total crashes and two for injury crashes-were developed. The results indicated that improperly planted and maintained median trees near highway intersections can increase the total number of crashes and injury plus fatal crashes at a 90% confidence level; no significant difference could be found in crash rates between sites that were compliant with SI-546 and sites without trees. All other conditions remaining the same, an intersection with trees that was not compliant with SI-546 had 63% more crashes and almost doubled injury plus fatal crashes than those at intersections without trees. The study indicates that appropriate landscaping in highway medians near intersections can be an engineering technology that not only improves roadway environmental quality but also maintains intersection safety.
Intersecting Solitons, Amoeba and Tropical Geometry
Fujimori, Toshiaki; Ohta, Kazutoshi; Sakai, Norisuke; Yamazaki, Masahito
2008-01-01
We study generic intersection (or web) of vortices with instantons inside, which is a 1/4 BPS state in the Higgs phase of five-dimensional N=1 supersymmetric U(Nc) gauge theory on R_t \\times (C^\\ast)^2 \\simeq R^{2,1} \\times T^2 with Nf=Nc Higgs scalars in the fundamental representation. In the case of the Abelian-Higgs model (Nf=Nc=1), the intersecting vortex sheets can be beautifully understood in a mathematical framework of amoeba and tropical geometry, and we propose a dictionary relating solitons and gauge theory to amoeba and tropical geometry. A projective shape of vortex sheets is described by the amoeba. Vortex charge density is uniformly distributed among vortex sheets, and negative contribution to instanton charge density is understood as the complex Monge-Ampere measure with respect to a plurisubharmonic function on (C^\\ast)^2. The Wilson loops in T^2 are related with derivatives of the Ronkin function. The general form of the Kahler potential and the asymptotic metric of the moduli space of a vort...
Locating conical intersections relevant to photochemical reactions
Energy Technology Data Exchange (ETDEWEB)
Dick, Bernhard [Institut fuer Physikalische und Theoretische Chemie, Universitaet Regensburg, D 93040 Regensburg (Germany)], E-mail: Bernhard.Dick@chemie.uni-regensburg.de; Haas, Yehuda; Zilberg, Shmuel [Department of Physical Chemistry and the Farkas Center for Light-induced Processes, The Hebrew University of Jerusalem, Jerusalem 91904 (Israel)
2008-05-23
A new computerized method for locating conical intersections of interest in photochemistry is presented. The search is based on the Longuet-Higgins phase change theorem (Berry phase) which provides the subspace required for the initial search. The subspace is approximated as a plane containing three stable structures lying on a Longuet-Higgins loop. The search is conducted for a minimum of {delta}E, the energy difference between two electronic states. It is started using up to three points within the circle defined by the three structures; symmetry, if relevant, is helpful but not essential. Since a two-dimensional subspace of the large 3N - 6 space is used, the search that uses either Cartesian or internal coordinates is efficient and yields a degeneracy after a few iterations. Given that not all degrees of freedom are included in the search, usually a high lying part of the conical intersection is initially located. The system is subsequently optimized along all coordinates keeping {delta}E as close to zero as desired. The method is demonstrated for the symmetric H{sub 3} system and also for the butadiene-cyclobutene-bicyclobutane system in which the three stable structures are not equivalent. The method is general and can be extended to any photochemical system.
Volume of intersection of two cones
Balogun, F A; Cesareo, R
2000-01-01
Radiation measurements utilising collimated source and detector systems invariably result in a target volume described by the overlap of their fields of view. When these collimators are cylindrical, this is derived from the volume of intersection of two cones. In general, analysis of this volume does not lend itself to a direct analytical process. Here, numerical methods of estimating the common volume of two intersecting right cones are presented. These include methods which employ, (a) a sequential scanning of an elemental volume with a predetermined size across a defined space containing the volume of interest and (b) a Monte Carlo technique. The accuracy obtainable and the execution time in the first type of algorithm depend on the size of the elemental volume (bin-size). On the other hand, these two parameters are independent of the bin-size but dependent on the number of histories sampled, for the Monte Carlo technique. At 0 deg. angle of inclination, where an analytical estimation is easily obtained, t...
Fatigue reliability of cracked engineering structures
Lanning, David Bruce, Jr.
1997-12-01
This study investigates the reliability of engineering structures containing fatigue cracks. Stress concentrations and welded joints are probable locations for the initiation and propagation of fatigue cracks. Due to the many unknowns of loading, materials properties, crack sizes and crack shapes present at these locations, a statistics-based reliability analysis is valuable in the careful consideration of these many different random factors involved in a fatigue life analysis, several of which are expanded upon in this study. The basic problem of a crack near a stress concentration is first considered. A formulation for the aspect ratio (a/c) of a propagating semi-elliptical fatigue crack located at the toe of a welded T-joint is developed using Newman and Raju's stress intensity factor for a cracked flat plate with a weld magnification factor and compared to that of a cracked flat plate, and the reliability in terms of fatigue lifetime is calculated with the aid of Paris' crack propagation equation for membrane and bending loadings. Crack closure effects are then introduced in the consideration of short crack effects, where crack growth rates typically may exceed those found using traditional linear elastic fracture mechanics solutions for long cracks. The probability of a very small, microstructurally influenced crack growing to a size influenced by local plastic conditions is calculated utilizing the probability of a crack continuing to grow past an obstacle, such as a grain boundary. The result is then combined with the probability for failure defined using the crack closure-modified Paris equation to find an overall reliability for the structure. Last, the probability of fracture is determined when a crack front encounters regions of non-uniform toughness, such as typical in the heat affected zone of a welded joint. An expression for the effective crack lengths of the dissimilar regions is derived, and used in a weakest-link fracture model in the evaluation
Inequalities for Dual Quermassintegrals of Mixed Intersection Bodies
Indian Academy of Sciences (India)
Zhao Chang-jian; Leng Gang-song
2005-02-01
In this paper, we first introduce a new concept of dual quermassintegral sum function of two star bodies and establish Minkowski’s type inequality for dual quermassintegral sum of mixed intersection bodies, which is a general form of the Minkowski inequality for mixed intersection bodies. Then, we give the Aleksandrov–Fenchel inequality and the Brunn–Minkowski inequality for mixed intersection bodies and some related results. Our results present, for intersection bodies, all dual inequalities for Lutwak’s mixed prosection bodies inequalities.
OPTIMASI KINERJA PROTOKOL AODV DENGAN STATIC INTERSECTION NODE
Directory of Open Access Journals (Sweden)
Johan Ericka Wahyu Prakasa
2016-07-01
Full Text Available VANET adalah sebuah pengembangan teknologi yang memungkinkan komunikasi antar kendaraan meskipun tidak terdapat koneksi secara langsung antara kendaraan yang berkomunikasi. Untuk meningkatkan performa protokol routing, maka pada penelitian ini akan ditambahkan SIN (Static Intersection Node. Static Intersection Node adalah RSU (Road Side Unit yang diletakkan di persimpangan jalan (intersection. Fungsi dari Static Intersection Node pada penelitian ini adalah sebagai repeater untuk membantu mengirimkan paket data ke kendaraan lain yang berada disekitarnya sehingga dapat meningkatkan Packet Delivery Ratio serta meminimalkan Packet Loss dan End to End Delay.
SHORT FATIGUE CRACK PARAMETER BASED ON THE TOTAL CRACK AREA
Institute of Scientific and Technical Information of China (English)
Z.X.Wu; X.C.Wu
2001-01-01
The progressive fatigue damage of a material is closely related to the whole populationof cracks on the surface of an un-notched specimen.In order to understand whichparameter is a more useful indicator of fatigue damage,rotatory bending fatigue testswere carried out using smooth specimens of medium-carbon steel.The behavior ofshort crack propagation during fatigue was examined and a new parameter "totalcrack area" was suggested.The aim of this paper is to extend the research on fatiguedamage in the already studied steel and to study how these damage parameters arecorrelated with the process of fatigue damage in order to evaluate the effectiveness ofdamage detection methods.
IDENTIFICATION OF CRACKED ROTOR BY WAVELET TRANSFORM
Institute of Scientific and Technical Information of China (English)
邹剑; 陈进; 蒲亚鹏
2002-01-01
The dynamic equation of cracked rotor in rotational frame was modelled, the numerical simulation solutions of the cracked rotor and the uncracked rotor were obtained. By the wavelet transform, the time-frequency properties of the cracked rotor and the uncracked rotor were discussed, the difference of the time-frequency properties between the cracked rotor and the uncracked rotor was compared. A new detection algorithm using wavelet transform to identify crack was proposed. The experiments verify the availability and validity of the wavelet transform in identification of crack.
Measurements of radiated elastic wave energy from dynamic tensile cracks
Boler, Frances M.
1990-01-01
The role of fracture-velocity, microstructure, and fracture-energy barriers in elastic wave radiation during a dynamic fracture was investigated in experiments in which dynamic tensile cracks of two fracture cofigurations of double cantilever beam geometry were propagating in glass samples. The first, referred to as primary fracture, consisted of fractures of intact glass specimens; the second configuration, referred to as secondary fracture, consisted of a refracture of primary fracture specimens which were rebonded with an intermittent pattern of adhesive to produce variations in fracture surface energy along the crack path. For primary fracture cases, measurable elastic waves were generated in 31 percent of the 16 fracture events observed; the condition for radiation of measurable waves appears to be a local abrupt change in the fracture path direction, such as occurs when the fracture intersects a surface flaw. For secondary fractures, 100 percent of events showed measurable elastic waves; in these fractures, the ratio of radiated elastic wave energy in the measured component to fracture surface energy was 10 times greater than for primary fracture.
Review of Environmentally Assisted Cracking
Sadananda, K.; Vasudevan, A. K.
2011-02-01
Many efforts have been made in the past by several researchers to arrive at some unifying principles governing the embrittlement phenomena. An inescapable conclusion reached by all these efforts was that the behavior is very complex. Hence, recognizing the complexity of material/environment behavior, we focus our attention here only in extracting some similarities in the experimental trends to arrive at some generic principles of behavior. Crack nucleation and growth are examined under static load in the presence of internal and external environments. Stress concentration, either pre-existing or in-situ generated, appears to be a requirement for embrittlement. A chemical stress concentration factor is defined for a given material/environment system as the ratio of failure stress with and without the damaging chemical environment. All factors that affect the buildup of the required stress concentration, such as planarity of slip, stacking fault energy, etc., also affect the stress-corrosion behavior. The chemical stress concentration factor is coupled with the mechanical stress concentration factor. In addition, generic features for all systems appear to be (a) an existence of a threshold stress as a function of concentration of the damaging environment and flow properties of the material, and (b) an existence of a limiting threshold as a function of concentration, indicative of a damage saturation for that environment. Kinetics of crack growth also depends on concentration and the mode of crack growth. In general, environment appears to enhance crack tip ductility on one side by the reduction of energy for dislocation nucleation and glide, and to reduce cohesive energy for cleavage, on the other. These two opposing factors are coupled to provide environmentally induced crack nucleation and growth. The relative ratio of these two opposing factors depends on concentration and flow properties, thereby affecting limiting thresholds. The limiting concentration or
ON INTERSECTIONS OF INDEPENDENT NONDEGENERATE DIFFUSION PROCESSES
Institute of Scientific and Technical Information of China (English)
Zhenlong CHEN
2014-01-01
Let X(1) = {X(1)(s), s ∈ R+} and X(2) = {X(2)(t), t ∈ R+} be two inde-pendent nondegenerate diffusion processes with values in Rd. The existence and fractal dimension of intersections of the sample paths of X (1) and X (2) are studied. More gener-ally, let E1, E2⊆(0,∞) and F ⊂Rd be Borel sets. A necessary condition and a suffcient condition for P{X(1)(E1)∩X(2)(E2)∩F 6=∅}>0 are proved in terms of the Bessel-Riesz type capacity and Hausdorff measure of E1 × E2 × F in the metric space (R+× R+× Rd,ρb), whereρb is an unsymmetric metric defined in R+× R+× Rd. Under reasonable conditions, results resembling those of Browian motion are obtained.
Belonging and Unbelonging from an Intersectional Perspective
DEFF Research Database (Denmark)
Christensen, Ann-Dorte
2009-01-01
The article is primarily theoretical and conceptual. It focuses on the notion of belonging from an intersectional perspective. The purpose is to discuss different dimensions of the concept of ‘belonging' and its rooting at different analytical levels. The first part of the article outlines...... the theoretical framework. The point of departure is multilayered citizenship and different notions of belonging. Second, the notion of belonging is divided into three analytical levels: (a) the macro level: imagined communities; (b) the meso level: collective organizations; and (c) the micro level: everyday......, for instance how to combine analysis of model citizenship/migration regimes with perspectives on everyday life. Another question relates to dilemmas within studies of everyday life. On the one hand, these studies are based on voices from below and a high degree of authenticity, but on the other hand, they tend...
Cracking and corrosion recovery boiler
Energy Technology Data Exchange (ETDEWEB)
Suik, H. [Tallinn Technical University, Horizon Pulp and Paper, Tallinn (Estonia)
1998-12-31
The corrosion of heat surfaces and the cracking the drums are the main problems of the recovery boiler. These phenomena have been appeared during long-term operation of boiler `Mitsubishi - 315` erected at 1964. Depth of the crack is depending on the number of shutdowns and on operation time. Corrosion intensity of different heat surfaces is varying depend on the metal temperature and the conditions at place of positioning of tube. The lowest intensity of corrosion is on the bank tubes and the greatest is on the tubes of the second stage superheater and on the tubes at the openings of air ports. (orig.) 5 refs.
Modified Dugdale crack models - some easy crack relations
DEFF Research Database (Denmark)
Nielsen, Lauge Fuglsang
1997-01-01
are assumed to be self created by local materials flow. The strength sigma_CR predictid by the Dugdale model is sigma_CR =(E Gamma_CR/phi1)^½ where E and 1 are Young’s modulus and crack half-length respectively of the material considered. The so-called critical strain energy rate is Gamma_CR = sigma......_Ldelta_CR where sigma_L is strength, and at the same time constant flow stress, of the uncracked material while delta_CR is flow limit (displacement).Obviously predictions by the Dugdale model are most reliable for materials with stress-strain relations where flow can actually be described (or well approximated......) by a constant flow stress (sigma_L). A number of materials, however, do not at all exhibit this kind of flow. Such materials are considered in this paper by Modified Dugdale crack models which apply for any cohesive stress distribution in crack front areas. Formally modified Dugdale crack models exhibit...
Intersectional perspectives on intimate technology, solutionism, and privilege
DEFF Research Database (Denmark)
Søndergaard, Marie Louise Juul; Hansen, Lone Koefoed
In this text, we discuss if and how an intersectional perspective on design may be critically practiced from a privileged position. More precisely, we ask how intersectional perspectives on race, gender and class may be useful in reflecting on and critically intervening in a privileged, Northern ...
A new proof of Faber's intersection number conjecture
Buryak, A
2009-01-01
We give a new proof of Faber's intersection number conjecture concerning the top intersections in the tautological ring of the moduli space of curves $\\M_g$. The proof is based on a very straightforward geometric and combinatorial computation with double ramification cycles.
Intersection of Three Planes Revisited--An Algebraic Approach
Trenkler, Götz; Trenkler, Dietrich
2017-01-01
Given three planes in space, a complete characterization of their intersection is provided. Special attention is paid to the case when the intersection set does not exist of one point only. Besides the vector cross product, the tool of generalized inverse of a matrix is used extensively.
Intersectionality and the Canadian Museum for Human Rights
Dhamoon, Rita Kaur; Hankivsky, Olena
2015-01-01
In this commentary, the authors propose than an intersectionality perspective can transform understandings of the contentious content of the Canadian Museum for Human Rights (CMHR). The use of an intersectionality perspective starts from the position that such discourses as racialization, gendering, capitalism, and ableism are mutually…
The Structure Theorem for Complete Intersections of Grade 4
Institute of Scientific and Technical Information of China (English)
Oh-Jin Kang; Hyoung J. Ko
2005-01-01
Serre showed that a Gorenstein ideal of grade 2 is a complete intersection, and Buchsbaum and Eisenbud proved a structure theorem for Gorenstein ideals of grade 3. It is found that a certain complete matrix defines a perfect ideal K3(f).As an application,we present a structure theorem for complete intersections of grade 4.
The Intersection of Gender and Age: An Exploration
Gander, Michelle
2014-01-01
The understanding of gender inequality for women entering work has not been subject to significant research or theorizing. This small study indicated that young women entering the workplace are subject to direct discrimination and by using an intersectionality approach this paper proposes that the intersection of gender and young age results in…
4-manifolds and intersection forms with local coefficients
DEFF Research Database (Denmark)
Frøyshov, Kim Anders
2012-01-01
We extend Donaldson's diagonalization theorem to intersection forms with certain local coefficients, under some constraints. This provides new examples of non-smoothable topological 4-manifolds.......We extend Donaldson's diagonalization theorem to intersection forms with certain local coefficients, under some constraints. This provides new examples of non-smoothable topological 4-manifolds....
Modal intersection types, two-level languages, and staged synthesis
DEFF Research Database (Denmark)
Henglein, Fritz; Rehof, Jakob
2016-01-01
A typed λ-calculus, λ∩ ⎕, is introduced, combining intersection types and modal types. We develop the metatheory of λ∩ ⎕, with particular emphasis on the theory of subtyping and distributivity of the modal and intersection type operators. We describe how a stratification of λ∩ ⎕ leads to a multi-linguistic...
The Ideal Intersection Property for Groupoid Graded Rings
DEFF Research Database (Denmark)
Öinert, Per Johan; Lundström, Patrik
2012-01-01
We show that, if a groupoid graded ring has a grading satisfying a certain nondegeneracy property, then the commutant of the center of the principal component of the ring has the ideal intersection property, that is it intersects nontrivially every nonzero ideal of the ring. Furthermore, we show ...
The Intersection of Gender and Age: An Exploration
Gander, Michelle
2014-01-01
The understanding of gender inequality for women entering work has not been subject to significant research or theorizing. This small study indicated that young women entering the workplace are subject to direct discrimination and by using an intersectionality approach this paper proposes that the intersection of gender and young age results in…
Self-Intersecting Periodic Curves in the Plane
Howie, J
2010-01-01
Suppose a smooth planar curve $\\gamma$ is $2\\pi$-periodic in the $x$ direction and the length of one period is $\\ell$. It is shown that if $\\gamma$ self-intersects, then it has a segment of length $\\ell- 2\\pi$ on which it self-intersects and somewhere its curvature is at least $2\\pi/(\\ell - 2\\pi)$. The proof involves the projection $\\Gamma$ of $\\gamma$ onto a cylinder. (The complex relation between $\\gamma$ and $\\Gamma$ was recently observed analytically by T. M. Apostol and M. A. Mnatsakanian. When $\\gamma$ is in general position there is a bijection between self-intersection points of $\\gamma$ modulo the periodicity, and self-intersection points of $\\Gamma$ with winding number 0 around the cylinder. However, our proof depends on the observation that a loop in $\\Gamma$ with winding number 1 leads to a self-intersection point of $\\gamma$.
FRACTAL KINEMATICS OF CRACK PROPAGATION IN GEOMATERIALS
Institute of Scientific and Technical Information of China (English)
谢和平
1995-01-01
Experimental results indicate that propagation paths of cracks in geomaterials are often irregular, producing rough fracture surfaces which are fractal. A formula is derived for the fractal kinematics of crack propagation in geomaterials. The formula correlates the dynamic and static fracture toughnesses with crack velocity, crack length and a microstructural parameter, and allows the fractal dimension to be obtained. From the equations for estimating crack velocity and fractal dimension it can be shown that the measured crack velocity, Vo , should be much smaller than the fractal crack velocity, V. It can also be shown that the fractal dimension of the crack propagation path can be calculated directly from Vo and from the fracture toughness.
Interacting Cracks in an Environmentally Assisted Fracture
Levandovsky, Artem; Balazs, Anna
2006-03-01
We perform the study of environmentally assisted fracture within the framework of a lattice model. Formation of an ensemble of environmentally assisted microcracks, their coalescence and formation of crack ``avalanches'' lead to a very rich dynamical picture. Under specific condition crack healing can occur due to cohesive forces, which hold material together and tend to pull atoms together even if they are separated by a crack over several lattice units. We investigate the dynamical interplay between crack formation, arrest, healing and re-cracking. The goal here is to provide an understanding of the conditions leading to the phenomena of crack healing that happens along with the crack formation. We study the morphology of crack patterns with the intentions to establish a way to enhance the healing property of a material sample.
On multiple crack detection in beam structures
Energy Technology Data Exchange (ETDEWEB)
Moradi, Shapour; Kargozarfard, Mohammad [Shahid Chamran University, Ahvaz (Iran, Islamic Republic of)
2013-01-15
This study presents an inverse procedure to identify multiple cracks in beams using an evolutionary algorithm. By considering the crack detection procedure as an optimization problem, an objective function can be constructed based on the change of the eigenfrequencies and some strain energy parameters. Each crack is modeled by a rotational spring. The changes in natural frequencies due to the presence of the cracks are related to a damage index vector. Then, the bees algorithm, a swarm-based evolutionary optimization technique, is used to optimize the objective function and find the damage index vector, whose positive components show the number and position of the cracks. A second objective function is also optimized to find the crack depths. Several experimental studies on cracked cantilever beams are conducted to ensure the integrity of the proposed method. The results show that the number of cracks as well as their sizes and locations can be predicted well through this method.
Energy Technology Data Exchange (ETDEWEB)
Kuk, Y.; Pickering, H.W.; Sakurai, T.
1980-01-01
With the greatly improved resolution now available in energy focused atom probes, hydrogen can be readily resolved even when combined with metals having several isotopes. In addition to finding that H, H/sub 2/, FeH and TiH/sub 2/ accumulate at segregated grain boundaries in Fe-0.29 wt % Ti, a striking observation was made - the formation and propagation of a microcrack when the (field ion microscope) tip was exposed to hydrogen gas at elevated temperature. A small crack (approx. 200 A in length) was first noticed at a grain-boundary intersection during field ion imaging. This was an open crack, formed by detachment of metal between the intersecting grain boundaries, which was observed to be much larger after the tip was reheated to 1300/sup 0/K for 10 min. in the presence of 10/sup 2/ Pa (1 torr) H/sub 2/. This crack could be easily reduced in size by gradually field evaporating the surface. Its propagation was repeated several times and reproducible results were obtained. Hydrogen was identified in quantity in the crack surface, though not elsewhere. The observation of H/sub 2/ is taken to mean that H/sub 2/ gas was trapped in the grain boundary. The grain boundary was also observed to be enriched in Ti, O, C and S, in agreement with earlier results for Fe-Ti.
DEFF Research Database (Denmark)
Agustin, Lise Rolandsen; Lombardo, Emanuela
This paper explores the extent to which the emergence of an anti-discrimination policy in the European Union (EU) implies a shift in EU gender equality policies towards an intersectional approach. The frame analysis of EU gender equality policy documents shows that intersectional dimensions are i...
Crack and flip phacoemulsification technique.
Fine, I H; Maloney, W F; Dillman, D M
1993-11-01
The crack and flip phacoemulsification technique combines the advantages of circumferential division of the nucleus and nucleofactis techniques. As such, it adds safety and control to the procedure. We describe each of the surgical maneuvers, including machine settings, and explain the rationale for maneuvers and machine settings.
China Cracks Down Internet Piracy
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
National Copyright Administration of China carried out a special operation to crack down on behaviors involving network infringement and piracy from September to December in 2005 ,according to the speech of Yan Xiaohong,Deputy Commissioner of National Copyright Administration on the Press Conference of the State Council.Now the relevant conditions are as follows:……
China Cracks Down Internet Piracy
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
@@ National Copyright Administration of China carried out a special operation to crack down on behaviors involving network infringement and piracy from September to December in 2005 ,according to the speech of Yan Xiaohong,Deputy Commissioner of National Copyright Administration on the Press Conference of the State Council.Now the relevant conditions are as follows:
HYDROTHERMAL CRACKING OF RESIDUAL OILS
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
The hydrothermal cracking of heavy oils, such as Canadian oil sand bitumen and Arabian heavy vacuum residue, as well as their model compound were performed over sulfided Ni/Al2O3 and NiMo/Al2O3 catalysts under 663～703 K and 6.0～8.0 MPa of hydrogen pressure in a batch autoclave reactor. According to the reaction mechanism of hydrothermal cracking, a small amount of free redical initiators, such as di-tert-peroxide, sulfur, etc., was added into the feed to generate free redicals at lower temperature, and obviously showed promotional effect on the conversion of hydrocarbons. The reaction mechanisms of hydrothermal cracking as well as the enhancing effect of initiators were studied by a probe reaction with 1-phenyldodecane as a model compound. The hydrothermal cracking of hydrocarbon proceeded via free redical mechanism and hydrogenating quench. The initiators might easily generate free redicals under reaction temperature, these redicals might abstract H from hydrocarbon molecule and reasonably initiate the chain reactions, therefore, promote the conversion of hydrocarbon even at lower reaction temperature.
Confining crack propagation in defective graphene.
López-Polín, Guillermo; Gómez-Herrero, Julio; Gómez-Navarro, Cristina
2015-03-11
Crack propagation in graphene is essential to understand mechanical failure in 2D materials. We report a systematic study of crack propagation in graphene as a function of defect content. Nanoindentations and subsequent images of graphene membranes with controlled induced defects show that while tears in pristine graphene span microns length, crack propagation is strongly reduced in the presence of defects. Accordingly, graphene oxide exhibits minor crack propagation. Our work suggests controlled defect creation as an approach to avoid catastrophic failure in graphene.
Correction to the crack extension direction in numerical modelling of mixed mode crack paths
DEFF Research Database (Denmark)
Lucht, Tore; Aliabadi, M.H.
2007-01-01
In order to avoid introduction of an error when a local crack-growth criterion is used in an incremental crack growth formulation, each straight crack extension would have to be infinitesimal or have its direction corrected. In this paper a new procedure to correct the crack extension direction i...
Mesh sensitivity effects on fatigue crack growth by crack-tip blunting and re-sharpening
DEFF Research Database (Denmark)
Tvergaard, Viggo
2007-01-01
Crack-tip blunting under tensile loads and re-sharpening of the crack-tip during unloading is one of the basic mechanisms for fatigue crack growth in ductile metals. Based on an elastic–perfectly plastic material model, crack growth computations have been continued up to 700 full cycles by using...
Fatigue crack growth from a cracked elastic particle into a ductile matrix
Groh, S.; Olarnrithinun, S.; Curtin, W. A.; Needleman, A.; Deshpande, V. S.; Van der Giessen, E.
2008-01-01
The monotonic and cyclic crack growth rate of cracks is strongly influenced by the microstructure. Here, the growth of cracks emanating from pre-cracked micron-scale elastic particles and growing into single crystals is investigated, with a focus on the effects of (i) plastic confinement due to the
Twisting cracks in Bouligand structures.
Suksangpanya, Nobphadon; Yaraghi, Nicholas A; Kisailus, David; Zavattieri, Pablo
2017-06-10
The Bouligand structure, which is found in many biological materials, is a hierarchical architecture that features uniaxial fiber layers assembled periodically into a helicoidal pattern. Many studies have highlighted the high damage-resistant performance of natural and biomimetic Bouligand structures. One particular species that utilizes the Bouligand structure to achieve outstanding mechanical performance is the smashing Mantis Shrimp, Odontodactylus Scyllarus (or stomatopod). The mantis shrimp generates high speed, high acceleration blows using its raptorial appendage to defeat highly armored preys. The load-bearing part of this appendage, the dactyl club, contains an interior region [16] that consists of a Bouligand structure. This region is capable of developing a significant amount of nested twisting microcracks without exhibiting catastrophic failure. The development and propagation of these microcracks are a source of energy dissipation and stress relaxation that ultimately contributes to the remarkable damage tolerance properties of the dactyl club. We develop a theoretical model to provide additional insights into the local stress intensity factors at the crack front of twisting cracks formed within the Bouligand structure. Our results reveal that changes in the local fracture mode at the crack front leads to a reduction of the local strain energy release rate, hence, increasing the necessary applied energy release rate to propagate the crack, which is quantified by the local toughening factor. Ancillary 3D simulations of the asymptotic crack front field were carried out using a J-integral to validate the theoretical values of the energy release rate and the local stress intensity factors. Copyright © 2017 Elsevier Ltd. All rights reserved.
Fatigue crack growth simulations of 3-D linear elastic cracks under thermal load by XFEM
Institute of Scientific and Technical Information of China (English)
Himanshu PATHAK[1; Akhilendra SINGH[2; I.V. SINGH[3; S. K. YADAV[3
2015-01-01
This paper deals with the fatigue crack growth simulations of three-dimensional linear elastic cracks by XFEM under cyclic thermal load. Both temperature and displacement approximations are extrinsically enriched by Heaviside and crack front enrichment functions. Crack growth is modelled by successive linear extensions, and the end points of these linear extensions are joined by cubic spline segments to obtain a modified crack front. Different crack geometries such as planer, non-planer and arbitrary spline shape cracks are simulated under thermal shock, adiabatic and isothermal loads to reveal the sturdiness and versatility of the XFEM approach.
Spanners for geometric intersection graphs with applications
Directory of Open Access Journals (Sweden)
Martin Fürer
2012-05-01
Full Text Available A ball graph is an intersection graph of a set of balls with arbitrary radii. Given a real numbert>1, we say that a subgraph G' of a graph G is a t-spanner of G, if for every pair of verticesu,v in G, there exists a path in G' of length at most t times the distance between u and v inG. In this paper, we consider the problem of efficiently constructing sparse spanners of ball graphs which supports fast shortest path distance queries.We present the first algorithm for constructing spanners of ball graphs. For a ball graph in Rk, we construct a (1+ε-spanner for any ε>0 with O(nε-k+1 edges in O(n2ℓ+δε-k logℓ S time, using an efficient partitioning of space into hypercubes and solving intersection problems. Here ℓ=1-1/(⌊k/2⌋+2, δ is any positive constant, and S is the ratio between the largest and smallest radius. For the special case when the balls all have unit size, we show that the complexity of constructing a (1+ε-spanner is almost equal to the complexity of constructing a Euclidean minimum spanning tree. The algorithm extends naturally to other disk-likeobjects, also in higher dimensions.The algorithm uses an efficient subdivision of space to construct a sparse graph having many of the same distance properties as the input ball graph. Additionally, the constructed spanners have a small vertex separator decomposition (hereditary. In dimension k=2, the disk graph spanner has an O(n1/2ε-3/2+ε-3log S separator. The presence of a small separator is then exploited to obtain very efficient data structures for approximate distance queries. The results on geometric graph separators might be of independent interest. For example, since complete Euclidean graphs are just a special case of (unit ball graphs, our results also provide a new approach for constructing spanners with small separators in these graphs.
Institute of Scientific and Technical Information of China (English)
丁晓浩; 齐辉; 赵元博
2016-01-01
利用Green函数法、复变函数法及保角映射技术研究了SH波作用下直角域中直线裂纹对椭圆形夹杂动应力集中系数的影响.采用保角映射法和镜像叠加原理构造了一个能自动满足直角平面两个直线边界应力自由边界条件的散射位移场,并取含有椭圆形夹杂的直角域中任意一点承受时间谐和的出平面线源载荷作用下的位移基本解作为适合的Green函数.利用裂纹"切割"技术构造直线裂纹,进而得出裂纹与椭圆形夹杂共存时的位移场和应力场.通过具体算例讨论了入射波数、裂纹角度、裂纹长度等因素对椭圆形夹杂周边动应力集中系数的影响.%The scattering problem of SH-wave by elliptic inclusion in right-angle plane with an arbitrary beeline crack was analyzed by Green's function,complex function method and conformal mapping method.The conformal map-ping method and image method were employed to construct the scattering wave function,which satisfies the condi-tion that stress is free on the straight boundaries of the right angle planes.An essential solution to the displacement field of an elastic right-angle plane containing an elliptic inclusion,whose any point bore an anti-plane harmonic line source load,was taken as Green's function.The beeline crack was constructed with crack-division technique,and the expressions of displacement and stress fields were given when crack and elliptic inclusion co-exist.The dynamic stress concentration factor(DSCF)on the edge of elliptic inclusion was given and the influences of incident wave number,crack angle,crack length and other parameters on DSCF of elliptic inclusion were discussed.
Simulation of queue with cyclic service in signalized intersection system
Directory of Open Access Journals (Sweden)
Muhammad Dermawan Mulyodiputro
2015-03-01
Full Text Available The simulation was implemented by modeling the queue with cyclic service in the signalized intersection system. The service policies used in this study were exhaustive and gated, the model was the M/M/1 queue, the arrival rate used was Poisson distribution and the services rate used was Exponential distribution. In the gated service policy, the server served only vehicles that came before the green signal appears at an intersection. Considered that there were 2 types of exhaustive policy in the signalized intersection system, namely normal exhaustive (vehicles only served during the green signal was still active, and exhaustive (there was the green signal duration addition at the intersection, when the green signal duration at an intersection finished. The results of this queueing simulation program were to obtain characteristics and performance of the system, i.e. average number of vehicles and waiting time of vehicles in the intersection and in the system, as well as system utilities. Then from these values, it would be known which of the cyclic service policies (normal exhaustive, exhaustive and gated was the most suitable when applied to a signalized intersection system
Tur\\'an and Ramsey Properties of Subcube Intersection Graphs
Johnson, J Robert
2011-01-01
The discrete cube $\\{0,1\\}^d$ is a fundamental combinatorial structure. A subcube of $\\{0,1\\}^d$ is a subset of $2^k$ of its points formed by fixing $k$ coordinates and allowing the remaining $d-k$ to vary freely. The subcube structure of the discrete cube is surprisingly complicated and there are many open questions relating to it. This paper is concerned with patterns of intersections among subcubes of the discrete cube. Two sample questions along these lines are as follows: given a family of subcubes in which no $r+1$ of them have non-empty intersection, how many pairwise intersections can we have? How many subcubes can we have if among them there are no $k$ which have non-empty intersection and no $l$ which are pairwise disjoint? These questions are naturally expressed as Tur\\'an and Ramsey type questions in intersection graphs of subcubes where the intersection graph of a family of sets has one vertex for each set in the family with two vertices being adjacent if the corresponding subsets intersect. Tur\\...
Tracer Flux Balance at an Urban Canyon Intersection
Carpentieri, Matteo; Robins, Alan G.
2010-05-01
Despite their importance for pollutant dispersion in urban areas, the special features of dispersion at street intersections are rarely taken into account by operational air quality models. Several previous studies have demonstrated the complex flow patterns that occur at street intersections, even with simple geometry. This study presents results from wind-tunnel experiments on a reduced scale model of a complex but realistic urban intersection, located in central London. Tracer concentration measurements were used to derive three-dimensional maps of the concentration field within the intersection. In combination with a previous study (Carpentieri et al., Boundary-Layer Meteorol 133:277-296, 2009) where the velocity field was measured in the same model, a methodology for the calculation of the mean tracer flux balance at the intersection was developed and applied. The calculation highlighted several limitations of current state-of-the-art canyon dispersion models, arising mainly from the complex geometry of the intersection. Despite its limitations, the proposed methodology could be further developed in order to derive, assess and implement street intersection dispersion models for complex urban areas.
Claros, Sharon Chia; Garcia, Gina A.; Johnston-Guerrero, Marc P.; Mata, Christine
2017-01-01
In this chapter, the authors share insights from a dialogue project focused on intersectionality within a residential life setting and discuss additional strategies for helping students understand intersectionality.
Photoelastic studies of crack propagation and crack arrest. [Homalite 100
Energy Technology Data Exchange (ETDEWEB)
Irwin, G.R.; Dally, J.W.; Kobayashi, T.; Fourney, W.L.; Etheridge, J.M.
1977-09-01
This report describes the third year effort on research programs dealing with the characterization of dynamic aspects of fracture. The results included in this report are (1) verification of the BCL one-dimensional computer code; (2) determination of a-dot--K relationship from modified compact-tension specimen of Homalite 100; (3) verification of the MRL procedure for K/sub Ia/ measurement with machine-loaded C-DCB specimen of Homalite 100; (4) influence of adhesive toughness, adhesive thickness, and toughness of the arrest section on crack behavior in duplex specimens of both the M-CT and R-DCB types; (5) crack propagation in a thermally stressed ring specimen; and (6) development of a two-dimensional finite-difference code to predict fracture behavior in specimens of rectangular geometry under various a-dot vs K relationships. 118 figures, 53 tables.
Inhibiting Corrosion Cracking: Crack Tip Chemistry and Physics.
1986-03-14
5 5. Swuzary 113 Rferences 114 wl NO 4L iv . List of Figuring 1. Microipette pulling machine . 29 2. Anodic polarization of 7075-T6 Al alloy in dilute...environment has a strong effect on microplastic behavior at the tip of a fatigue crack. Stolz and Pelloux suggest that nitrate ion competes with chloride...Crystalline Na2 N 20 29H20 precipitates when the filtrate is placed in a vacunm desiccator over sulfuric acid. The filtered precipitate is washed
Crack branching in carbon steel. Fracture mechanisms
Syromyatnikova, A. S.; Alekseev, A. A.; Levin, A. I.; Lyglaev, A. V.
2010-04-01
The fracture surfaces of pressure vessels made of carbon steel that form during crack branching propagation are examined by fractography. Crack branching is found to occur at a crack velocity higher than a certain critical value V > V c . In this case, the material volume that is involved in fracture and depends on the elastoplastic properties of the material and the sample width has no time to dissipate the energy released upon crack motion via the damage mechanisms intrinsic in the material under given deformation conditions (in our case, via cracking according to intragranular cleavage).
Strength of Cracked Reinforced Concrete Disks
DEFF Research Database (Denmark)
Hoang, Cao Linh; Nielsen, Mogens Peter
1999-01-01
The paper deals with models, based on the theory of plasticity, to be used in strength assessments of reinforced concrete disks suffering from different kinds of cracking. Based on the assumption that the sliding strength of concrete is reduced in sections where cracks are located, solutions...... for the shear strength of disks with initial cracks and disks suffering from isotropic cracking are presented. Furthermore, in the case of isotropicly cracked disks subjected to arbitrary in-plane loading, a general yield condition is derived....
CRACK REASON ANALYSIS OF DAMAGED CARBONITRIDED PART
Directory of Open Access Journals (Sweden)
Karin Kocúrová
2010-03-01
Full Text Available The article deals with the analysis of a damaged part, which was designed for use in a mechanical clutch of a car. The crack in the part was found during the production inspection. The aim of metallographic and fractography analyses of the fracture surfaces was to discover the reasons for the crack. The reason for creating the crack was the formation of smaller cracks in the production during pressing process of the semiproduct. These cracks even grew after the following thermochemical treatment. The fracture was initiated during the straightening process of quenched part.
Component evolution in general random intersection graphs
Energy Technology Data Exchange (ETDEWEB)
Bradonjic, Milan [Los Alamos National Laboratory; Hagberg, Aric [Los Alamos National Laboratory; Hengartner, Nick [Los Alamos National Laboratory; Percus, Allon G [CLAREMONT GRADUATE UNIV.
2010-01-01
We analyze component evolution in general random intersection graphs (RIGs) and give conditions on existence and uniqueness of the giant component. Our techniques generalize the existing methods for analysis on component evolution in RIGs. That is, we analyze survival and extinction properties of a dependent, inhomogeneous Galton-Watson branching process on general RIGs. Our analysis relies on bounding the branching processes and inherits the fundamental concepts from the study on component evolution in Erdos-Renyi graphs. The main challenge becomes from the underlying structure of RIGs, when the number of offsprings follows a binomial distribution with a different number of nodes and different rate at each step during the evolution. RIGs can be interpreted as a model for large randomly formed non-metric data sets. Besides the mathematical analysis on component evolution, which we provide in this work, we perceive RIGs as an important random structure which has already found applications in social networks, epidemic networks, blog readership, or wireless sensor networks.
Narrating the Intersectionalities of Gender Violence: Editorial
Directory of Open Access Journals (Sweden)
Floretta Boonzaier
2015-12-01
Full Text Available The telling, sharing and, most critically, the hearing of stories related to gender violence has been a critical part of the project of feminism as well as the refuge movement (Dobash and Dobash 1979, Kelly 1988. This an introduction to a set of papers that represent highlights from the conference entitled “International Congress on Gender Violence: Intersectionalities” in terms of how the intersections of gender violence have been narrated. Contar, compartir, y, más críticamente, escuchar historias relacionadas con la violencia de género ha sido una parte fundamental del proyecto del feminismo, así como del movimiento de refugio (Dobash y Dobash 1979, Kelly 1988. Esta es una introducción a una serie de artículos representativos del Congreso Internacional sobre Violencia de Género: Intersecciones, que abordan cómo se han relatado las intersecciones de la violencia de género. DOWNLOAD THIS PAPER FROM SSRN: http://ssrn.com/abstract=2710203
The probability that a complete intersection is smooth
Bucur, Alina
2010-01-01
Given a smooth subscheme of a projective space over a finite field, we compute the probability that its intersection with a fixed number of hypersurface sections of large degree is smooth of the expected dimension. This generalizes the case of a single hypersurface, due to Poonen. We use this result to give a probabilistic model for the number of rational points of such a complete intersection. A somewhat surprising corollary is that the number of rational points on a random smooth intersection of two curves in projective 3-space is strictly less than the number of points on the projective line.
Political Intersectionality and Democratic Politics in the European Public Sphere
DEFF Research Database (Denmark)
Siim, Birte
2015-01-01
intersections of gender and ethnic diversity in political life at the national and transnational levels across Europe. In this context, political intersectionality refers to the framing of gender and ethnic diversity by major political actors as well as by activities of women’s and anti-racist organisations...... Public Sphere (EPS). It is inspired by results and reflections from the European Gender Project (EGP) , where intersectionality was used as an approach for analysing negotiations between gender and ethno-national diversity in selected European countries and in relation to the European Public Sphere...
An efficient quantum scheme for Private Set Intersection
Shi, Run-hua; Mu, Yi; Zhong, Hong; Cui, Jie; Zhang, Shun
2016-01-01
Private Set Intersection allows a client to privately compute set intersection with the collaboration of the server, which is one of the most fundamental and key problems within the multiparty collaborative computation of protecting the privacy of the parties. In this paper, we first present a cheat-sensitive quantum scheme for Private Set Intersection. Compared with classical schemes, our scheme has lower communication complexity, which is independent of the size of the server's set. Therefore, it is very suitable for big data services in Cloud or large-scale client-server networks.
Open intersection numbers, matrix models and MKP hierarchy
Alexandrov, A
2014-01-01
In this paper we claim that the generating function of the intersection numbers on the moduli spaces of Riemann surfaces with boundary, constructed recently by R. Pandharipande, J. Solomon and R. Tessler and extended by A. Buryak, is a tau-function of the KP integrable hierarchy. Moreover, it is given by a simple modification of the Kontsevich matrix integral so that the generating functions of open and closed intersection numbers are described by the MKP integrable hierarchy. Virasoro constraints for the open intersection numbers naturally follow from the matrix integral representation.
ANALYTICAL AND MATHCAD INTERSECTION BETWEEN TWO PERPENDICULAR AXES CYLINDERS
Directory of Open Access Journals (Sweden)
PETRESCU Ligia
2015-06-01
Full Text Available The intersection of two surfaces is a common line to both surfaces. This line is often called transition line. The authors propose an analytical and a computer graphics intersection between two perpendicular axes cylinders. The analytical expression of such intersection will be obtained and transposed on the development of one cylinder. The distance between the two cylinders axes is essential in the aspect of the transition line. This transition line can be also obtained, using the computer, by the MathCAD programme. Some samples are relevant in this subject, according to the distance between the cylinders.
Open intersection numbers, matrix models and MKP hierarchy
Energy Technology Data Exchange (ETDEWEB)
Alexandrov, A. [Freiburg Institute for Advanced Studies (FRIAS), University of Freiburg,Albertstrasse 19, 79104 Freiburg (Germany); Mathematics Institute, University of Freiburg,Eckerstrasse 1, 79104 Freiburg (Germany); ITEP,Bolshaya Cheremushkinskaya 25, 117218 Moscow (Russian Federation)
2015-03-09
In this paper we conjecture that the generating function of the intersection numbers on the moduli spaces of Riemann surfaces with boundary, constructed recently by R. Pandharipande, J. Solomon and R. Tessler and extended by A. Buryak, is a tau-function of the KP integrable hierarchy. Moreover, it is given by a simple modification of the Kontsevich matrix integral so that the generating functions of open and closed intersection numbers are described by the MKP integrable hierarchy. Virasoro constraints for the open intersection numbers naturally follow from the matrix integral representation.
Inkjet patterning of multiline intersections for wirings in printed electronics.
Diaz, Elkin; Ramon, Eloi; Carrabina, Jordi
2013-10-08
Inkjet printed electronics using thermo-curable liquid inks exhibit particular geometrical characteristics in terms of regularity. This article presents a morphological analysis for inkjet printed multi line intersections that are critical structures for building circuits. We studied thin-film structures of silver conductive ink and printed by inkjet technology. Instability of the ink during printing causes the thickness irregularity of vertex, normally with peaks at these areas. We propose the usage of specific patterns for intersections as thickness regularity compensations. The results show that some patterns help to reduce this instability and improve the thickness regularity of intersections morphology.
Alternating grain orientation and weld solidification cracking
Kou, S.; Le, Y.
1985-10-01
A new mechanism for reducing weld solidification cracking was proposed, based on the concept of the crack path and resistance to crack propagation, and its effectiveness was verified in magnetically oscillated GTA welds of a rather crack susceptible material 2014 aluminum alloy. This mechanism, i.e., alternating grain orientation, was most pronounced in welds made with transverse arc oscillation of low frequency and high amplitude, and solidification cracking was dramatically reduced in these welds. The effect of the arc oscillation pattern, amplitude, and frequency on the formation of alternating columnar grains and the reduction of solidification cracking in GTA welds of 2014 aluminum alloy was examined and explained. The present study demonstrated for the first time that columnar grains can, in fact, be very effective in reducing solidification cracking, provided that they are oriented favorably.
Biaxial Fatigue Cracking from Notch
2013-03-04
Leevers (reference 11) noticed that the variation in from 0 to 2 has little effect on the da/dN in PVC ( polyvinyl - chloride ), but reduces the da/dN...under biaxial rotating and bending. Ahmad (reference 2) formulated a model for the biaxial fatigue crack growth in aggressive environment, outlined by...1962, Vol. 90, pp. 238-239. 20. ASM Handbook , Vol. 12 Fractography: 1992, p. 430, 438. 21. Metals Handbook , Vol. 9 Fractography and Atlas of
The Growth of Small Corrosion Fatigue Cracks in Alloy 7075
Piascik, Robert S.
2015-01-01
The corrosion fatigue crack growth characteristics of small (greater than 35 micrometers) surface and corner cracks in aluminum alloy 7075 is established. The early stage of crack growth is studied by performing in situ long focal length microscope (500×) crack length measurements in laboratory air and 1% sodium chloride (NaCl) environments. To quantify the "small crack effect" in the corrosive environment, the corrosion fatigue crack propagation behavior of small cracks is compared to long through-the-thickness cracks grown under identical experimental conditions. In salt water, long crack constant K(sub max) growth rates are similar to small crack da/dN.
Fatigue cracks in Eurofer 97 steel: Part II. Comparison of small and long fatigue crack growth
Kruml, T.; Hutař, P.; Náhlík, L.; Seitl, S.; Polák, J.
2011-05-01
The fatigue crack growth rate in the Eurofer 97 steel at room temperature was measured by two different methodologies. Small crack growth data were obtained using cylindrical specimens with a shallow notch and no artificial crack starters. The growth of semicircular cracks of length between 10-2000 μm was followed in symmetrical cycling with constant strain amplitude ( R ɛ = -1). Long crack data were measured using standard CT specimen and ASTM methodology, i.e. R = 0.1. The growth of cracks having the length in the range of 10-30 mm was measured. It is shown that the crack growth rates of both types of cracks are in a very good agreement if J-integral representation is used and usual assumptions of the crack closure effects are taken into account.
Fatigue cracks in Eurofer 97 steel: Part II. Comparison of small and long fatigue crack growth
Energy Technology Data Exchange (ETDEWEB)
Kruml, T., E-mail: kruml@ipm.cz [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Zizkova 22, CZ 61662 Brno (Czech Republic); Hutar, P.; Nahlik, L.; Seitl, S.; Polak, J. [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Zizkova 22, CZ 61662 Brno (Czech Republic)
2011-05-01
The fatigue crack growth rate in the Eurofer 97 steel at room temperature was measured by two different methodologies. Small crack growth data were obtained using cylindrical specimens with a shallow notch and no artificial crack starters. The growth of semicircular cracks of length between 10-2000 {mu}m was followed in symmetrical cycling with constant strain amplitude (R{sub {epsilon}} = -1). Long crack data were measured using standard CT specimen and ASTM methodology, i.e. R = 0.1. The growth of cracks having the length in the range of 10-30 mm was measured. It is shown that the crack growth rates of both types of cracks are in a very good agreement if J-integral representation is used and usual assumptions of the crack closure effects are taken into account.
Reconstructing Surface Triangulations by Their Intersection Matrices 26 September 2014
2015-01-01
The intersection matrix of a simplicial complex has entries equal to the rank of the intersecction of its facets. We prove that this matrix is enough to define up to isomorphism a triangulation of a surface.
A Unified Algorithm for Finding the Intersection Curve of Surfaces
Institute of Scientific and Technical Information of China (English)
谭建荣; 郑建民; 等
1994-01-01
In this papaer,an INTEGRAL CURVE ALGORITHM is presented,which turns the intersection curve of surfaces into the form of integral one and then uses “PREDICTORCORRECTOR” technique to evaluate the intersection of surfaces.No matter how the surfaces are defined,the method always deals with the intersection curves in the same way.To find a point on the curve one need only to calculate the JACOBI determinants of “PREDICTOR point”and “CORRECTOR point” while the second order precision is guatanteed.Thus,not only is the problem of finding the intersection of surfaces resolved,but also the algorithms for generating both plane curve and space curve are unified.
Intersection patterns of convex sets via simplicial complexes, a survey
Tancer, Martin
2011-01-01
The task of this survey is to present various results on intersection patterns of convex sets. One of main tools for studying intersection patterns is a point of view via simplicial complexes. We recall the definitions of so called $d$-representable, $d$-collapsible and $d$-Leray simplicial complexes which are very useful for this study. We study the differences among these notions and we also focus on computational complexity for recognizing them. A list of Helly-type theorems is presented in the survey and it is also discussed how (important) role play the above mentioned notions for the theorems. We also consider intersection patterns of good covers which generalize collections of convex sets (the sets may be `curvy'; however, their intersections cannot be too complicated). We mainly focus on new results.
Deformation of Singularities and the Homology of Intersection Spaces
Banagl, Markus
2011-01-01
While intersection cohomology is stable under small resolutions, both ordinary and intersection cohomology are unstable under smooth deformation of singularities. For complex projective algebraic hypersurfaces with an isolated singularity, we show that the first author's cohomology of intersection spaces is stable under smooth deformations in all degrees except possibly the middle, and in the middle degree precisely when the monodromy action on the cohomology of the Milnor fiber is trivial. In many situations, the isomorphism is shown to be a ring homomorphism induced by a continuous map. This is used to show that the rational cohomology of intersection spaces can be endowed with a mixed Hodge structure compatible with Deligne's mixed Hodge structure on the ordinary cohomology of the singular hypersurface.
Reduced Hamiltonian for intersecting shells and Hawking radiation
Menotti, Pietro
2010-01-01
We consider the dynamics of one or more self gravitating shells of matter in a centrally symmetric gravitational field in the Painleve' family of gauges. We give the reduced hamiltonian for two intersecting shells, both massless and massive. Such a formulation is applied to the computation of the semiclassical action of two intersecting shells. The relation of the imaginary part of the space-part of the action to the computation of the Bogoliubov coefficients is revisited.
MATHEMATICAL METHODS TO DETERMINE THE INTERSECTION CURVES OF THE CYLINDERS
Directory of Open Access Journals (Sweden)
POPA Carmen
2010-07-01
Full Text Available The aim of this paper is to establish the intersection curves between cylinders, by using the Mathematica program. This thing can be obtained by introducing the curves equations, which are inferred, in Mathematica program. This paper take into discussion three right cylinders and another inclined to 45 degrees. The intersection curves can also be obtained by using the classical methods of the descriptive geometry.
The OAFM magnet for ISR intersection I-8
CERN PhotoLab
1979-01-01
The Open Axial Field Magnet (OAFM), weighing in at 300 tons, was installed in ISR intersection I-8 and brought into operation early in 1979. Fitted with a highly transparent "flat-fish" vacuum chamber, it served experiment R807 (large transverse momentum). Flat-fish vacuum chambers were originally developed for use inside the Split-Field Magnet (SFM) at intersection I-4: see 8310325 and references there.
INTERSECTION OF MCMULLEN SET WITH ITS RATIONAL TRANSLATION
Institute of Scientific and Technical Information of China (English)
Meifeng Dai; Lixin Tang
2008-01-01
In this paper,we study the intersection of Mcmullen set with its rational translation.The main difficulty is that the generating structure of the intersection.By the radix expansion of translating vector,we give its fractal characterization.We find that the Hausdorff measure of these sets forms a discrete spectrum whose non-zero values come only from translating the vector(x,y)with its radix expansion.
Proceedings Sixth Workshop on Intersection Types and Related Systems
Graham-Lengrand, Stéphane; Paolini, Luca
2013-01-01
This volume contains the proceedings of the Sixth Workshop on Intersection Types and Related Systems (ITRS 2012). The workshop was held in Dubrovnik (Croatia) on June 29th, 2012, affiliated to Twenty-Seventh Annual ACM/IEEE Symposium on Logic in Computer Science (LICS 2012). The ITRS workshop aims to bring together researchers working on both the theory and practical applications of systems based on intersection types and related approaches (e.g., union types, refinement types, behavioural ty...
Institute of Scientific and Technical Information of China (English)
杨娟; 李星; 丁生虎
2016-01-01
This paper employes variable function method and the technique of conformal map-ping to discuss the anti-plane problem of a circular hole with three unequal cracks in a one-dimensional (1D) hexagonal piezoelectric quasicrystal. Based on the piezo-electricity fundamental equations of quasicrystal materials and the symmetry of 1D hexagonal quasicrystal and its linear piezoelectricity effect, 1D hexagonal qua-sicrystal control equations of anti-plane problem are derived. Applying Cauchy integral formula, the analytical expressions for the crack tip filed intensity factors are presented with the assumption that the crack are electrical impermeable and electrical permeable. With the variation of the hole-size and the crack length, some of the new model of crack are obtained. In the absence of the electric load, the results match with the classical ones. The numerical results indicate the effects of geometric parameters on the field intensity factors. It is verified that the horizon-tal crack length and the circle radius can easily promote crack growth. Research on such issues will provide reliable theoretical value for the engineering materials preparation and application.%本文利用复变函数方法和保角映射，研究一维六方压电准晶材料中带不对称三裂纹的圆形孔口的的断裂问题。根据准晶压电材料基本方程的基础上，利用点群的对称性和一维六方准晶的线性压电效应，导出了一维六方准晶压电材料反平面问题的控制方程，并结合Cauchy积分公式，得到电非渗透与电渗透边界条件下的裂纹尖端场强度因子的解析表达式。当改变裂纹长度和孔口半径时，所得结果可以模拟出一些新裂纹模型。在不考虑电载荷作用时，所得结果和原有结果是一致的。通过数值算例讨论了材料的几何参数对场强度因子的影响，得出水平裂纹长度和圆半径可以促进裂纹增长。本研究为工程中材料的制备与
Modeling signalized intersection safety with corridor-level spatial correlations.
Guo, Feng; Wang, Xuesong; Abdel-Aty, Mohamed A
2010-01-01
Intersections in close spatial proximity along a corridor should be considered as correlated due to interacted traffic flows as well as similar road design and environmental characteristics. It is critical to incorporate this spatial correlation for assessing the true safety impacts of risk factors. In this paper, several Bayesian models were developed to model the crash data from 170 signalized intersections in the state of Florida. The safety impacts of risk factors such as geometric design features, traffic control, and traffic flow characteristics were evaluated. The Poisson and Negative Binomial Bayesian models with non-informative priors were fitted but the focus is to incorporate spatial correlations among intersections. Two alternative models were proposed to capture this correlation: (1) a mixed effect model in which the corridor-level correlation is incorporated through a corridor-specific random effect and (2) a conditional autoregressive model in which the magnitude of correlations is determined by spatial distances among intersections. The models were compared using the Deviance Information Criterion. The results indicate that the Poisson spatial model provides the best model fitting. Analysis of the posterior distributions of model parameters indicated that the size of intersection, the traffic conditions by turning movement, and the coordination of signal phase have significant impacts on intersection safety.
Estimation of air quality improvement at road and street intersections
Energy Technology Data Exchange (ETDEWEB)
Hoeglund, P.G. [Royal Inst. of Technology, Stockholm (Sweden). Traffic and Transport Planning
1995-12-31
There has always been a very great problem to quantify the detrimental exhaust air pollution related to the traffic flow, especially at road and street intersections. Until now model calculations have been developed mainly for the links between the intersections. In an attempt to remedy this situation the author has developed a method of estimating emissions on the micro level from motor vehicles at intersections as a help for infrastructural design related to improved environmental conditions. Very parsimonious knowledge exists regarding the deceleration and acceleration patterns at road- and street intersections. Not many surveys are done neither in Sweden nor within other countries. Evidently, the need for knowledge regarding deceleration and acceleration behaviour on the micro level has until now not been given priority. In traffic safety related research studies have been done describing the drivers` deceleration and acceleration behaviour and the vehicles` braking performance. Those results give deceleration data for extreme situations and are not useful for describing normal decelerations and accelerations at road- and street intersections. Environment related problems within the traffic flow analysis are now accentuating the need for the studying of special deceleration and acceleration behaviours in combination with an alternative design of the road and street infrastructure. There is a big difference in different vehicles` amount of emitted exhaust pollutions during the passing of intersections depending on the vehicles` speed levels related to their deceleration and acceleration levels. (author)
Intersecting Surface Defects and Two-Dimensional CFT
Gomis, Jaume; Pan, Yiwen; Peelaers, Wolfger
2016-01-01
We initiate the study of intersecting surface operators/defects in four-dimensional quantum field theories (QFTs). We characterize these defects by coupled 4d/2d/0d theories constructed by coupling the degrees of freedom localized at a point and on intersecting surfaces in spacetime to each other and to the four-dimensional QFT. We construct supersymmetric intersecting surface defects preserving just two supercharges in N = 2 gauge theories. These defects are amenable to exact analysis by localization of the partition function of the underlying 4d/2d/0d QFT. We identify the 4d/2d/0d QFTs that describe intersecting surface operators in N = 2 gauge theories realized by intersecting M2-branes ending on N M5-branes wrapping a Riemann surface. We conjecture and provide evidence for an explicit equivalence between the squashed four-sphere partition function of these intersecting defects and correlation functions in Liouville/Toda CFT with the insertion of arbitrary degenerate vertex operators, which are labeled by ...
Subsidence crack closure: rate, magnitude and sequence
Energy Technology Data Exchange (ETDEWEB)
De Graff, J.V.; Romesburg, H.C.
1981-06-01
Tension cracks are a major surface disturbance resulting from subsidence and differential settlement above underground coal mines. Recent engineering studies of subsidence indicate that cracks may close where tensile stresses causing the cracks are reduced or relaxed. This stress reduction occurs as mining in the area is completed. Crack closure was confirmed by a study in the Wasatch Plateau coal field of central Utah. Cracks occurred in both exposed bedrock and regolith in an area with maximum subsidence of 3 m. Mean closure rate was 0.3 cm per week with individual crack closure rates between 0.2 cm and 1.0 cm per week. The mean crack closure magnitude was 80% with closure magnitudes varying between 31% and 100%. Actual magnitude values ranged from 0.6 cm to 6.5 cm with a mean value of 3.8 cm. Statistical analysis compared width change status among cracks over time. It was found that: 1) a 41% probability existed that a crack would exhibit decreasing width per weekly measurement, 2) closure state sequences seem random over time, and 3) real differences in closure state sequence existed among different cracks. (6 refs.) (In English)
Crack propagation in fracture mechanical graded structures
Directory of Open Access Journals (Sweden)
B. Schramm
2015-10-01
Full Text Available The focus of manufacturing is more and more on innovative and application-oriented products considering lightweight construction. Hence, especially functional graded materials come to the fore. Due to the application-matched functional material gradation different local demands such as absorbability, abrasion and fatigue of structures are met. However, the material gradation can also have a remarkable influence on the crack propagation behavior. Therefore, this paper examines how the crack propagation behavior changes when a crack grows through regions which are characterized by different fracture mechanical material properties (e.g. different threshold values KI,th, different fracture toughness KIC. In particular, the emphasis of this paper is on the beginning of stable crack propagation, the crack velocity, the crack propagation direction as well as on the occurrence of unstable crack growth under static as well as cyclic loading. In this context, the developed TSSR-concept is presented which allows the prediction of crack propagation in fracture mechanical graded structures considering the loading situation (Mode I, Mode II and plane Mixed Mode and the material gradation. In addition, results of experimental investigations for a mode I loading situation and numerical simulations of crack growth in such graded structures confirm the theoretical findings and clarify the influence of the material gradation on the crack propagation behavior.
Li, Bo; Liu, Richeng; Jiang, Yujing
2016-07-01
Fluid flow tests were conducted on two crossed fracture models for which the geometries of fracture segments and intersections were measured by utilizing a visualization technique using a CCD (charged coupled device) camera. Numerical simulations by solving the Navier-Stokes equations were performed to characterize the fluid flow at fracture intersections. The roles of hydraulic gradient, surface roughness, intersecting angle, and scale effect in the nonlinear fluid flow behavior through single fracture intersections were investigated. The simulation results of flow rate agreed well with the experimental results for both models. The experimental and simulation results showed that with the increment of the hydraulic gradient, the ratio of the flow rate to the hydraulic gradient, Q/J, decreases and the relative difference of Q/J between the calculation results employing the Navier-Stokes equations and the cubic law, δ, increases. When taking into account the fracture surface roughness quantified by Z2 ranging 0-0.42 for J = 1, the value of δ would increase by 0-10.3%. The influences of the intersecting angle on the normalized flow rate that represents the ratio of the flow rate in a segment to the total flow rate, Ra, and the ratio of the hydraulic aperture to the mechanical aperture, e/E, are negligible when J 10-2. Based on the regression analysis on simulation results, a mathematical expression was proposed to quantify e/E, involving variables of J and Rr, where Rr is the radius of truncating circles centered at an intersection. For E/Rr > 10-2, e/E varies significantly and the scale of model has large impacts on the nonlinear flow behavior through intersections, while for E/Rr < 10-3, the scale effect is negligibly small. Finally, a necessary condition to apply the cubic law to fluid flow through fracture intersections is suggested as J < 10-3, E/Rr < 10-3, and Z2 = 0.
Controlling fatigue crack paths for crack surface marking and growth investigations
Directory of Open Access Journals (Sweden)
S. Barter
2016-01-01
Full Text Available While it is well known that fatigue crack growth in metals that display confined slip, such as high strength aluminium alloys, develop crack paths that are responsive to the loading direction and the local microstructural orientation, it is less well known that such paths are also responsive to the loading history. In these materials, certain loading sequences can produce highly directional slip bands ahead of the crack tip and by adjusting the sequence of loads, distinct fracture surface features or progression marks, even at very small crack depths can result. Investigating the path a crack selects in fatigue testing when particular combinations of constant and variable amplitude load sequences are applied is providing insight into crack growth. Further, it is possible to design load sequences that allow very small amounts of crack growth to be measured, at very small crack sizes, well below the conventional crack growth threshold in the aluminium alloy discussed here. This paper reports on observations of the crack path phenomenon and a novel test loading method for measuring crack growth rates for very small crack depths in aluminium alloy 7050-T7451 (an important aircraft primary structural material. The aim of this work was to firstly generate short- crack constant amplitude growth data and secondly, through the careful manipulation of the applied loading, to achieve a greater understanding of the mechanisms of fatigue crack growth in the material being investigated. A particular focus of this work is the identification of the possible sources of crack growth retardation and closure in these small cracks. Interpreting these results suggests a possible mechanism for why small fatigue crack growth through this material under variable amplitude loading is faster than predicted from models based on constant amplitude data alone.
Online Bridge Crack Monitoring with Smart Film
Directory of Open Access Journals (Sweden)
Benniu Zhang
2013-01-01
Full Text Available Smart film crack monitoring method, which can be used for detecting initiation, length, width, shape, location, and propagation of cracks on real bridges, is proposed. Firstly, the fabrication of the smart film is developed. Then the feasibility of the method is analyzed and verified by the mechanical sensing character of the smart film under the two conditions of normal strain and crack initiation. Meanwhile, the coupling interference between parallel enameled wires of the smart film is discussed, and then low-frequency detecting signal and the custom communication protocol are used to decrease interference. On this basis, crack monitoring system with smart film is designed, where the collected crack data is sent to the remote monitoring center and the cracks are simulated and recurred. Finally, the monitoring system is applied to six bridges, and the effects are discussed.
Crack Propagation in Bamboo's Hierarchical Cellular Structure
Habibi, Meisam K.; Lu, Yang
2014-07-01
Bamboo, as a natural hierarchical cellular material, exhibits remarkable mechanical properties including excellent flexibility and fracture toughness. As far as bamboo as a functionally graded bio-composite is concerned, the interactions of different constituents (bamboo fibers; parenchyma cells; and vessels.) alongside their corresponding interfacial areas with a developed crack should be of high significance. Here, by using multi-scale mechanical characterizations coupled with advanced environmental electron microscopy (ESEM), we unambiguously show that fibers' interfacial areas along with parenchyma cells' boundaries were preferred routes for crack growth in both radial and longitudinal directions. Irrespective of the honeycomb structure of fibers along with cellular configuration of parenchyma ground, the hollow vessels within bamboo culm affected the crack propagation too, by crack deflection or crack-tip energy dissipation. It is expected that the tortuous crack propagation mode exhibited in the present study could be applicable to other cellular natural materials as well.
Air flow through smooth and rough cracks
Energy Technology Data Exchange (ETDEWEB)
Kula, H.-G.; Sharples, S. [Sheffield Univ. (United Kingdom). Dept. of Building Science
1994-12-31
A series of laboratory experiments are described which investigated the effect of surface roughness on the air flow characteristics of simple, straight-through, no-bend cracks with smooth and rough internal surfaces. The crack thicknesses used in the study were 1.0, 1.5 and 2.0mm. The crack lengths, in the direction of flow, were 50.8mm and 76.2mm. For the rough cracks the roughness was simulated with two different grades of commercially available energy-cloth (grade 60 and 100). The experimental results were satisfactorily fitted to a quadratic relationship between {Delta}p and Q of the form {Delta}p = AQ + BQ{sup 2} for both the smooth and rough crack data. The effect of roughness on the reduction of air flowing through a crack is also discussed. (author)
Crack problem in a long cylindrical superconductor
Yong, Hua-Dong; Zhou, You-He; Zeng, Jun
2008-12-01
In this work, the general problem of a center crack in a long cylindrical superconductor is studied. The dependence of the stress intensity factor on the parameters, including the crack length and the applied field, is investigated. We presented a simple model in which the effect of the crack on the critical current is taken into account. It is assumed that the crack forms a perfect barrier to the flow of current. The Bean model and the Kim model are considered for the critical state. Based on the complex potential and boundary collocation methods, the stress intensity factor under the magnetic field is obtained for a long cylindrical superconductor containing a central crack. The results show that the crack length and the applied field have significant effects on the fracture behavior of the superconductor.
Numerical Study of Corrosion Crack Opening
DEFF Research Database (Denmark)
Thoft-Christensen, Palle; Frandsen, Henrik Lund; Svensson, Staffan
2008-01-01
for the corrosion crack opening. Experiments and theoretical analysis by a numerical method, FEM, support that the relation between the reduction of the reinforcement bar diameter due to corrosion and the corresponding increase in crack width for a given time interval, measured on the surface of a concrete specimen...... is proportional. More recently, the constant of proportionality, the so-called crack-corrosion index, has been studied further with respect to its dependence on the diameter of the reinforcement and the concrete cover. In the present paper the above-mentioned work is presented and extended with more realistic 3D......-models of the cracked concrete beam. The crack-corrosion index is evaluated for a variation of different parameters, i.e. bar diameter, concrete cover, crack length and type of corrosion product. This paper is an extended version of a paper by Thoft-Christensen et al. (2005) presented at the IFIP WG 7.5 Conference...
Institute of Scientific and Technical Information of China (English)
刘广萍; 丁建梅
2004-01-01
Vehicle delay is an important measure to evaluate the signal timings of signalized intersections.When optimization the signal control parameters, delays of vehicles from all approach directions of an intersection should be considered. Based on the analysis of the vehicle delay on an approach of intersection, directed against the typical condition of a congested intersection-over-saturated condition, the paper has analyzed and inferred the intersection delay dynamic formulation, and has established the relation between intersection delay,the signal timings, vehicle arrival rate and the queue lengths, and that provides useful information for understanding vehicle delay of signalized intersection and for establishing performance index function of signal timing optimization.
Gendered Violence, Intersectionalities and Resisting Gender Neutrality
Directory of Open Access Journals (Sweden)
Julie Stubbs
2015-12-01
Full Text Available Developments in feminist theory and research towards a more complex approach to gender relations and a more differentiated understanding of gendered violence have been positive but also have been the subject of significant debate. Some debates have long histories, while others mark more newly emergent concerns. In this paper I reflect on three areas of debate: intersectionality, complex gendering and complex inequalities; differentiating between forms of gendered violence (with a focus on intimate partner violence (IPV, and criminalisation. In each of these areas, feminist frameworks and knowledge concerning gendered violence have been challenged and the resurgence of gender neutral accounts has been notable. I argue that keeping a structural analysis to the fore provides the best way forward for constructive debate in the field aligned with feminist aspirations for the achievement of substantive equality. El desarrollo de la teoría feminista y la investigación hacia un enfoque más complejo de las relaciones de género y una comprensión más diferenciada de la violencia de género ha sido positivo, pero también ha sido objeto de un importante debate. Algunos debates tienen una larga historia, mientras que otros marcan preocupaciones emergentes surgidas en los últimos tiempos. En este trabajo se reflexiona sobre tres áreas de debate: interseccionalidad, configuración de géneros compleja y desigualdades complejas; diferenciación entre formas de violencia de género (fijándose en la violencia de pareja (VP; y la criminalización. En cada una de estas áreas, se han cuestionado los marcos feministas y el conocimiento relativo a la violencia de género, y ha sido notable el resurgimiento de cuentas de género neutro. Se defiende que fomentar un análisis estructural ofrece la mejor forma de fomentar un debate constructivo en el campo alineado con las aspiraciones feministas para el logro de una igualdad sustantiva. DOWNLOAD THIS PAPER FROM
DBEM crack propagation for nonlinear fracture problems
Directory of Open Access Journals (Sweden)
R. Citarella
2015-10-01
Full Text Available A three-dimensional crack propagation simulation is performed by the Dual Boundary Element Method (DBEM. The Stress Intensity Factors (SIFs along the front of a semi elliptical crack, initiated from the external surface of a hollow axle, are calculated for bending and press fit loading separately and for a combination of them. In correspondence of the latter loading condition, a crack propagation is also simulated, with the crack growth rates calculated using the NASGRO3 formula, calibrated for the material under analysis (steel ASTM A469. The J-integral and COD approaches are selected for SIFs calculation in DBEM environment, where the crack path is assessed by the minimum strain energy density criterion (MSED. In correspondence of the initial crack scenario, SIFs along the crack front are also calculated by the Finite Element (FE code ZENCRACK, using COD, in order to provide, by a cross comparison with DBEM, an assessment on the level of accuracy obtained. Due to the symmetry of the bending problem a pure mode I crack propagation is realised with no kinking of the propagating crack whereas for press fit loading the crack propagation becomes mixed mode. The crack growth analysis is nonlinear because of normal gap elements used to model the press fit condition with added friction, and is developed in an iterative-incremental procedure. From the analysis of the SIFs results related to the initial cracked configuration, it is possible to assess the impact of the press fit condition when superimposed to the bending load case.
Transition from Multiple Macro-Cracking to Multiple Micro-Cracking in Cementitious Composites
Institute of Scientific and Technical Information of China (English)
ZHANG Jun; LENG Bing
2008-01-01
This paper presents an experimental study of the possibility of transition from multiple macro-cracking to multiple micro-cracking in cementitious composites.Conventional polyvinyl alcohol fiber reinforced cementitious composites normally exhibit macroscopic strain-hardening and multiple cracking after the first cracks appear.However,the individual crack width at the saturated stage is normally 60 to 80 μm.In the current study,the effect of fine aggregate size on the cracking performance,especially the individual crack width in the strain-hardening stage was studied by bending tests.The results show that the individual crack widths can be reduced from 60-80 μm to 10-30 μm by modifying the particle size of the fine aggregates used in the composites.
Fatigue Crack Closure Analysis Using Digital Image Correlation
Leser, William P.; Newman, John A.; Johnston, William M.
2010-01-01
Fatigue crack closure during crack growth testing is analyzed in order to evaluate the critieria of ASTM Standard E647 for measurement of fatigue crack growth rates. Of specific concern is remote closure, which occurs away from the crack tip and is a product of the load history during crack-driving-force-reduction fatigue crack growth testing. Crack closure behavior is characterized using relative displacements determined from a series of high-magnification digital images acquired as the crack is loaded. Changes in the relative displacements of features on opposite sides of the crack are used to generate crack closure data as a function of crack wake position. For the results presented in this paper, remote closure did not affect fatigue crack growth rate measurements when ASTM Standard E647 was strictly followed and only became a problem when testing parameters (e.g., load shed rate, initial crack driving force, etc.) greatly exceeded the guidelines of the accepted standard.
... rate, breathing rate, blood pressure , and body temperature decreased appetite and less need for sleep feelings of restlessness, ... effects include: gangrene in the bowels resulting from decreased blood ... chest pain reduced appetite, plus health problems associated with not eating a ...
SPIRALING CRACKS IN THIN SHEETS
2010-01-01
En este trabajo de tesis presentamos dos experimentos en que trayectorias de fracturas sumamente reproducibles son obtenidas en láminas delgadas frágiles. En ambos casos, a partir de configuraciones iniciales sumamente simples y pequeñas, las trayectorias obtenidas son espirales logarítmicas de gran tamao. Nuestro primer experimento consiste en un crack que se inicia desde un corte recto hecho en una lámina delgada y que es forzado a propagarse por medio de empujar con un objeto sólido....
Fatigue Crack Closure - A Review
1990-09-01
gauge along the crack line. They used CCT speci- mens of high tensile strength steel ( HY80 ). The measured value of U was found to be a minimum at the...ultrasonic surface wave technique on 12.5mm thick specimens of 2024-T851, 2024-T351, Al 2219, Ti-6AI-4V and 17-4 PH steel . Most of the results were...medium and high strength steels . Exami- nation of the fracture surfaces suggested that raising the mean stress in low fracture toughness steels could
Expansive Soil Crack Depth under Cumulative Damage
Directory of Open Access Journals (Sweden)
Bei-xiao Shi
2014-01-01
Full Text Available The crack developing depth is a key problem to slope stability of the expansive soil and its project governance and the crack appears under the roles of dry-wet cycle and gradually develops. It is believed from the analysis that, because of its own cohesion, the expansive soil will have a certain amount of deformation under pulling stress but without cracks. The soil body will crack only when the deformation exceeds the ultimate tensile strain that causes cracks. And it is also believed that, due to the combined effect of various environmental factors, particularly changes of the internal water content, the inherent basic physical properties of expansive soil are weakened, and irreversible cumulative damages are eventually formed, resulting in the development of expansive soil cracks in depth. Starting from the perspective of volumetric strain that is caused by water loss, considering the influences of water loss rate and dry-wet cycle on crack developing depth, the crack developing depth calculation model which considers the water loss rate and the cumulative damages is established. Both the proposal of water loss rate and the application of cumulative damage theory to the expansive soil crack development problems try to avoid difficulties in matrix suction measurement, which will surely play a good role in promoting and improving the research of unsaturated expansive soil.
Nonlinear modal method of crack localization
Ostrovsky, Lev; Sutin, Alexander; Lebedev, Andrey
2004-05-01
A simple scheme for crack localization is discussed that is relevant to nonlinear modal tomography based on the cross-modulation of two signals at different frequencies. The scheme is illustrated by a theoretical model, in which a thin plate or bar with a single crack is excited by a strong low-frequency wave and a high-frequency probing wave (ultrasound). The crack is assumed to be small relative to all wavelengths. Nonlinear scattering from the crack is studied using a general matrix approach as well as simplified models allowing one to find the nonlinear part of crack volume variations under the given stress and then the combinational wave components in the tested material. The nonlinear response strongly depends on the crack position with respect to the peaks or nodes of the corresponding interacting signals which can be used for determination of the crack position. Juxtaposing various resonant modes interacting at the crack it is possible to retrieve both crack location and orientation. Some aspects of inverse problem solutions are also discussed, and preliminary experimental results are presented.
Wettability Induced Crack Dynamics and Morphology
Ghosh, Udita Uday; Bhandari, Aditya Bikram; Chakraborty, Suman; DasGupta, Sunando
2014-01-01
Substrate wettability alteration induced control over crack formation process in thin colloidal films has been addressed in the present study. Colloidal nanosuspension (53nm, mean particle diameter) droplets have been subjected to natural drying to outline the effects of substrate surface energies over the dry-out characteristics with emphasis on crack dynamics, crack morphology and underlying particle arrangements. Experimental findings indicate that number of cracks formed decreases with increase in substrate hydrophobicity. These physical phenomena have been explained based on the magnitude of stress dissipation incurred by the substrate. DLVO predictions are also found to be in tune with the reported experimental investigations.
Crack depth determination with inductive thermography
Oswald-Tranta, B.; Schmidt, R.
2015-05-01
Castings, forgings and other steel products are nowadays usually tested with magnetic particle inspection, in order to detect surface cracks. An alternative method is active thermography with inductive heating, which is quicker, it can be well automated and as in this paper presented, even the depth of a crack can be estimated. The induced eddy current, due to its very small penetration depth in ferro-magnetic materials, flows around a surface crack, heating this selectively. The surface temperature is recorded during and after the short inductive heating pulse with an infrared camera. Using Fourier transformation the whole IR image sequence is evaluated and the phase image is processed to detect surface cracks. The level and the local distribution of the phase around a crack correspond to its depth. Analytical calculations were used to model the signal distribution around cracks with different depth and a relationship has been derived between the depth of a crack and its phase value. Additionally, also the influence of the heating pulse duration has been investigated. Samples with artificial and with natural cracks have been tested. Results are presented comparing the calculated and measured phase values depending on the crack depth. Keywords: inductive heating, eddy current, infrared
Fatigue crack growth detect, assess, avoid
Richard, Hans Albert
2016-01-01
This book offers a concise introduction to fatigue crack growth, based on practical examples. It discusses the essential concepts of fracture mechanics, fatigue crack growth under constant and variable amplitude loading and the determination of the fracture-mechanical material parameters. The book also introduces the analytical and numerical simulation of fatigue crack growth as well as crack initiation. It concludes with a detailed description of several practical case studies and some exercises. The target group includes graduate students, researchers at universities and practicing engineers.
Investigations of Low Temperature Time Dependent Cracking
Energy Technology Data Exchange (ETDEWEB)
Van der Sluys, W A; Robitz, E S; Young, B A; Bloom, J
2002-09-30
The objective of this project was to investigate metallurgical and mechanical phenomena associated with time dependent cracking of cold bent carbon steel piping at temperatures between 327 C and 360 C. Boiler piping failures have demonstrated that understanding the fundamental metallurgical and mechanical parameters controlling these failures is insufficient to eliminate it from the field. The results of the project consisted of the development of a testing methodology to reproduce low temperature time dependent cracking in laboratory specimens. This methodology was used to evaluate the cracking resistance of candidate heats in order to identify the factors that enhance cracking sensitivity. The resultant data was integrated into current available life prediction tools.
Cracking of open traffic rigid pavement
Directory of Open Access Journals (Sweden)
Niken Chatarina
2017-01-01
Full Text Available The research is done by observing the growth of real structure cracking in Natar, Lampung, Indonesia compared to C. Niken’s et al research and literature study. The rigid pavement was done with open traffic system. There are two main crack types on Natar rigid pavement: cracks cross the road, and cracks spreads on rigid pavement surface. The observation of cracks was analyzed by analyzing material, casting, curing, loading and shrinkage mechanism. The relationship between these analysis and shrinkage mechanism was studied in concrete micro structure. Open traffic make hydration process occur under vibration; therefore, fresh concrete was compressed and tensioned alternately since beginning. High temperature together with compression, cement dissociation, the growth of Ca2+ at very early age leads abnormal swelling. No prevention from outside water movement leads hydration process occur with limited water which caused spreads fine cracks. Limited water improves shrinkage and plastic phase becomes shorter; therefore, rigid pavement can’t accommodate the abnormal swelling and shrinking alternately and creates the spread of cracks. Discontinuing casting the concrete makes both mix under different condition, the first is shrink and the second is swell and creates weak line on the border; so, the cracks appear as cracks across the road.
Crack spacing of unsaturated soils in the critical state
Institute of Scientific and Technical Information of China (English)
SUN JiChao; WANG GuangQian; SUN QiCheng
2009-01-01
The cracking mechanism of unsaturated soils due to evaporation is poorly understood, and the magnitude of crack spacing is usually hard to estimate. In this work, cracks were postulated to occur suc-cedently rather than simultaneously, that is, secondary cracks appear after primary cracks as evaporation continues. Formulae of the secondary crack spacing and secondary trend crack spacing were then derived after stress analysis. The calculated spacing values were consistent with the published experimental data. Meanwhile, the effect of the Poisson ratio on the crack spacing was analyzed, which showed that the magnitude of crack spacing was proportional to the Poisson ratio in the range of [0.30,0.35].
On the application of cohesive crack modeling in cementitious materials
DEFF Research Database (Denmark)
Stang, Henrik; Olesen, John Forbes; Poulsen, Peter Noe;
2007-01-01
Cohesive crack models-in particular the Fictitious Crack Model - are applied routinely in the analysis of crack propagation in concrete and mortar. Bridged crack models-where cohesive stresses are assumed to exist together with a stress singularity at the crack tip-on the other hand, are used....... Further, a quantitative condition is established indicating when a bridged crack model can be approximated with a cohesive crack model with smooth crack closure in terms of the ratio between the energy dissipation associated with the crack tip and the process zone....
Effect of Crack Closure on Ultrasonic Detection of Fatigue Cracks at Fastener Holes
Bowles, S. J.; Harding, C. A.; Hugo, G. R.
2009-03-01
The ultrasonic response from closed fatigue cracks grown in aluminium alloy specimens using a representative aircraft spectrum loading has been characterised as a function of tensile applied load using pulse-echo 45° shear-wave ultrasonic C-scans with focused immersion transducers. Observed trends with crack size and applied load are described and compared to results for artificial machined defects. The results demonstrate that crack closure significantly reduces the ultrasonic response compared to open cracks or machined defects.
Mode Ⅰ Plane Crack Interacting with an Interfacial Crack Along a Circular Inhomogeneity
Institute of Scientific and Technical Information of China (English)
WANG Rui; MA Jian-jun; LIU Zheng-guang
2006-01-01
The elastic interaction of the mode Ⅰ plane crack with an interfacial crack along a circular inhomogeneity is dealt with. The dislocation density and the stress intensity factors (SIFs) of the mode I plane crack are obtained numerically. A new kind of dislocation equilibrium equation about the plane crack is applied. The influence of some material parameters on the dislocation density and SIFs are analyzed.
Extended propagation model for interfacial crack in composite material structure
Institute of Scientific and Technical Information of China (English)
闫相桥; 冯希金
2002-01-01
An interfacial crack is a common damage in a composite material structure . An extended propaga-tion model has been established for an interfacial crack to study the dependence of crack growth on the relativesizes of energy release rates at left and right crack tips and the properties of interfacial material characterize thegrowth of interfacial crack better.
Directory of Open Access Journals (Sweden)
In-Seok Yoon
2012-01-01
Full Text Available For enhancing the service life of concrete structures, it is very important to minimize crack at surface. Even if these cracks are very small, the problem is to which extend these cracks may jeopardize the durability of these decks. It was proposed that crack depth corresponding with critical crack width from the surface is a crucial factor in view of durability design of concrete structures. It was necessary to deal with chloride penetration through microcracks characterized with the mixing features of concrete. This study is devoted to examine the effect of high strength concrete and reinforcement of steel fiber on chloride penetration through cracks. High strength concrete is regarded as an excellent barrier to resist chloride penetration. However, durability performance of cracked high strength concrete was reduced seriously up to that of ordinary cracked concrete. Steel fiber reinforcement is effective to reduce chloride penetration through cracks because steel fiber reinforcement can lead to reduce crack depth significantly. Meanwhile, surface treatment systems are put on the surface of the concrete in order to seal the concrete. The key-issue is to which extend a sealing is able to ensure that chloride-induced corrosion can be prevented. As a result, penetrant cannot cure cracks, however, coating and combined treatment can prevent chloride from flowing in concrete with maximum crack width of 0.06 mm and 0.08 mm, respectively.
On fatigue crack growth in ductile materials by crack-tip blunting
DEFF Research Database (Denmark)
Tvergaard, Viggo
2004-01-01
One of the basic mechanisms for fatigue crack growth in ductile metals is that depending on crack-tip blunting under tensile loads and re-sharpening of the crack-tip during unloading. In a standard numerical analysis accounting for finite strains it is not possible to follow this process during...
Exploring the promises of intersectionality for advancing women's health research.
Hankivsky, Olena; Reid, Colleen; Cormier, Renee; Varcoe, Colleen; Clark, Natalie; Benoit, Cecilia; Brotman, Shari
2010-02-11
Women's health research strives to make change. It seeks to produce knowledge that promotes action on the variety of factors that affect women's lives and their health. As part of this general movement, important strides have been made to raise awareness of the health effects of sex and gender. The resultant base of knowledge has been used to inform health research, policy, and practice. Increasingly, however, the need to pay better attention to the inequities among women that are caused by racism, colonialism, ethnocentrism, heterosexism, and able-bodism, is confronting feminist health researchers and activists. Researchers are seeking new conceptual frameworks that can transform the design of research to produce knowledge that captures how systems of discrimination or subordination overlap and "articulate" with one another. An emerging paradigm for women's health research is intersectionality. Intersectionality places an explicit focus on differences among groups and seeks to illuminate various interacting social factors that affect human lives, including social locations, health status, and quality of life. This paper will draw on recently emerging intersectionality research in the Canadian women's health context in order to explore the promises and practical challenges of the processes involved in applying an intersectionality paradigm. We begin with a brief overview of why the need for an intersectionality approach has emerged within the context of women's health research and introduce current thinking about how intersectionality can inform and transform health research more broadly. We then highlight novel Canadian research that is grappling with the challenges in addressing issues of difference and diversity. In the analysis of these examples, we focus on a largely uninvestigated aspect of intersectionality research - the challenges involved in the process of initiating and developing such projects and, in particular, the meaning and significance of social
Exploring the promises of intersectionality for advancing women's health research
Directory of Open Access Journals (Sweden)
Clark Natalie
2010-02-01
Full Text Available Abstract Women's health research strives to make change. It seeks to produce knowledge that promotes action on the variety of factors that affect women's lives and their health. As part of this general movement, important strides have been made to raise awareness of the health effects of sex and gender. The resultant base of knowledge has been used to inform health research, policy, and practice. Increasingly, however, the need to pay better attention to the inequities among women that are caused by racism, colonialism, ethnocentrism, heterosexism, and able-bodism, is confronting feminist health researchers and activists. Researchers are seeking new conceptual frameworks that can transform the design of research to produce knowledge that captures how systems of discrimination or subordination overlap and "articulate" with one another. An emerging paradigm for women's health research is intersectionality. Intersectionality places an explicit focus on differences among groups and seeks to illuminate various interacting social factors that affect human lives, including social locations, health status, and quality of life. This paper will draw on recently emerging intersectionality research in the Canadian women's health context in order to explore the promises and practical challenges of the processes involved in applying an intersectionality paradigm. We begin with a brief overview of why the need for an intersectionality approach has emerged within the context of women's health research and introduce current thinking about how intersectionality can inform and transform health research more broadly. We then highlight novel Canadian research that is grappling with the challenges in addressing issues of difference and diversity. In the analysis of these examples, we focus on a largely uninvestigated aspect of intersectionality research - the challenges involved in the process of initiating and developing such projects and, in particular, the meaning
Ceunynck, T. de Polders, E. Daniels, S. Hermans, E. Brijs, T. & Wets, G.
2014-01-01
This study analyzes interactions between two vehicles at right-hand priority intersections and priority-controlled intersections and will help to gain a better insight into safety differences between both types of intersections. Data about yielding, looking behavior, drivers' age and gender,
PowerSet: A Comprehensive Visualization of Set Intersections.
Alsallakh, Bilal; Ren, Liu
2017-01-01
When analyzing a large amount of data, analysts often define groups over data elements that share certain properties. Using these groups as the unit of analysis not only reduces the data volume, but also allows detecting various patterns in the data. This involves analyzing intersection relations between these groups, and how the element attributes vary between these intersections. This kind of set-based analysis has various applications in a variety of domains, due to the generic and powerful notion of sets. However, visualizing intersections relations is challenging because their number grows exponentially with the number of sets. We present a novel technique based on Treemaps to provide a comprehensive overview of non-empty intersections in a set system in a scalable way. It enables gaining insight about how elements are distributed across these intersections as well as performing fine-grained analysis to explore and compare their attributes both in overview and in detail. Interaction allows querying and filtering these elements based on their set memberships. We demonstrate how our technique supports various use cases in data exploration and analysis by providing insights into set-based data, beyond the limits of state-of-the-art techniques.
Mitigating gas emissions at signalised intersections using wireless vehicle detectors
Directory of Open Access Journals (Sweden)
Moses Kwasi Torkudzor
2015-09-01
Full Text Available Traffic congestion on roads wastes travel times and increases fuel consumption as well as gas emissions which are dangerous to human health. This has led to growing concern about environmental protection and energy conservation and a number of studies to increase fuel economy and reduce gas emissions. To increase travel times so as to reduce fuel consumption and gas emissions, traffic signals at intersections must be well implemented. It is therefore necessary to employ the current technology of wireless sensor networks to enhance the optimisation of the signalised intersections so as to address such a concern. In this study, a vehicular traffic control model was developed to optimise a signalised intersection, using wireless vehicle detectors. Real-time traffic volume gathered were analysed to obtain the peak hour traffic volume causing congestion. The intersection was modelled and simulated in Synchro7 as an actuated signalised model using results from the analysed data. The model for morning peak and evening peak periods gave optimal cycle lengths which result in the reduction of gas emissions, fuel consumption and delay at the intersection.
Modeling Driver Behavior near Intersections in Hidden Markov Model.
Li, Juan; He, Qinglian; Zhou, Hang; Guan, Yunlin; Dai, Wei
2016-12-21
Intersections are one of the major locations where safety is a big concern to drivers. Inappropriate driver behaviors in response to frequent changes when approaching intersections often lead to intersection-related crashes or collisions. Thus to better understand driver behaviors at intersections, especially in the dilemma zone, a Hidden Markov Model (HMM) is utilized in this study. With the discrete data processing, the observed dynamic data of vehicles are used for the inference of the Hidden Markov Model. The Baum-Welch (B-W) estimation algorithm is applied to calculate the vehicle state transition probability matrix and the observation probability matrix. When combined with the Forward algorithm, the most likely state of the driver can be obtained. Thus the model can be used to measure the stability and risk of driver behavior. It is found that drivers' behaviors in the dilemma zone are of lower stability and higher risk compared with those in other regions around intersections. In addition to the B-W estimation algorithm, the Viterbi Algorithm is utilized to predict the potential dangers of vehicles. The results can be applied to driving assistance systems to warn drivers to avoid possible accidents.
MATLAB Simulation of Fuzzy Traffic Controller for Multilane Isolated Intersection
Directory of Open Access Journals (Sweden)
Azura Che Soh/Lai Guan Rhung
2010-07-01
Full Text Available This paper presents a MATLAB simulation of fuzzy traffic controller for controlling traffic flow at multilane isolated signalized intersection. The controller is developed based on the waiting time and vehicles queue length at current green phase, and vehicles queue lengths at the other phases. For control strategy, the controllercontrols the traffic light timings and phase sequence to ensure smooth flow of traffic with minimal waiting time, queue length and delay time. In this research, the isolated intersection model used consists of two lanes in each approach. Each approach has two different values of vehicles queue length and waiting time, respectively, at the intersection. The maximum values of vehicles queue length and waiting times are selected as the inputs to controller for optimized control of traffic flows at the intersection. A traffic model and fuzzy traffic controller are developed to evaluate the performance of traffic controllers underdifferent conditions. In the end, by comparing the experimental result obtained by the vehicle-actuated controller (VAC and fuzzy traffic controller (FTC which improves significant performance for intersections, we confirmed the efficiency of our intelligent controller based fuzzy inference system.
Numerical simulations of Mach stem formation via intersecting bow shocks
Hansen, E. C.; Frank, A.; Hartigan, P.; Yirak, K.
2015-12-01
Hubble Space Telescope observations show bright knots of Hα emission within outflowing young stellar jets. Velocity variations in the flow create secondary bow shocks that may intersect and lead to enhanced emission. When the bow shocks intersect at or above a certain critical angle, a planar shock called a Mach stem is formed. These shocks could produce brighter Hα emission since the incoming flow to the Mach stem is parallel to the shock normal. In this paper we report first results of a study using 2-D numerical simulations designed to explore Mach stem formation at the intersection of bow shocks formed by hypersonic "bullets" or "clumps". Our 2-D simulations show how the bow shock shapes and intersection angles change as the adiabatic index γ changes. We show that the formation or lack of a Mach stem in our simulations is consistent with the steady-state Mach stem formation theory. Our ultimate goal, which is part of an ongoing research effort, is to characterize the physical and observational consequences of bow shock intersections including the formation of Mach stems.
Recombination of Intersecting D-Branes and Cosmological Inflation
Gómez-Reino, Marta
2002-01-01
We consider the interactions between Dp-branes intersecting at an arbitrary number of angles in the context of type II string theory. For cosmology purposes we concentrate in the theory on R^{3,1} x T^6. Interpreting the distance between the branes as the inflaton field, the branes can intersect at most at two angles in the compact space. If the configuration is non-supersymmetric we will have an interbrane potential that provides an effective cosmological inflationary epoch at the four dimensional intersection between the branes. The end of inflation occurs when the interbrane distance becomes small compared with the string scale, where a tachyon develops triggering the recombination of the branes. We study this recombination due to tachyon instabilities and we find the possibility for the final configuration to be again branes intersecting at two angles. This preserves the interesting features that are present in the intersecting brane models from the string model building point of view also after the end o...
Faurschou Hviid, Stubbe; Hüttig, Christian; Groussin, Olivier; Mottola, Stefano; Keller, Horst Uwe; OSIRIS Team
2016-10-01
Since the middle of 2014 the OSIRIS cameras on the ESA Rosetta mission have been monitoring the evolution of the comet 67P/Churyumov-Gerasimenko as it passed through perihelion. During the perihelion passage several change events have been observed on the nucleus surface. For example existing large scale cracks have expanded and new large scale cracks have been created. Also several large scale "wave pattern" like change events have been observed in the Imhotep and Hapi regions. These are events not directly correlated with any normal visible cometary activity. One interpretation is that these are events likely caused by "seismic" activity. The seismic activity is created by the self-gravity stress of the non-spherical comet nucleus and stress created by the non-gravitational forces acting on the comet. The non-gravitational forces are changing the rotation period of the comet (~20min/perihelion passage) which induces a changing mechanical stress pattern through the perihelion passage. Also the diurnal cycle with its changing activity pattern is causing a periodic wobble in the stress pattern that can act as a trigger for a comet quake. The stress pattern has been modeled using a finite element model that includes self-gravity, the comet spin and the non-gravitational forces based on a cometary activity model. This paper will discuss what can be learned about the comet nucleus structure and about the cometary material properties from these events and from the FEM model.
Jiao, Kexin; Zhou, Chuanhong; Kohli, Punit; Poudel, Anish; Chu, Tsuchin
2015-03-01
Buckling, delamination, and cracking are very well known phenomenon observed in most thin films. They were theoretically explained by the existence of mechanical instability due to the residue stress generated when a thin film is deposited on substrates or undergoing environmental stimulus. Buckled structures at micro- or nano-scale have been of great interests and have been used extensively in many applications including particles self-assembling, surface wettability modification, and micro-electronic device fabrication. However, peeling of a layer from a substrate due to delamination or fractures on a thin film due to cracking is mostly taken as an undesirable result. Therefore, strategies are inspired for preventing or removing these often undesired structures. We found that after being heated above its decomposition temperature and then cooled to room temperature, a PDMS thin film showed micro-fibers of 100 μm width and up to 1.5 cm in length. By studying the formation mechanism, control of the dimensions and of the growth pattern on a substrate for PDMS micro-fibers were realized. Giving credit to their high flexibility and optical transparency, a PDMS micro-fiber were utilized in high resolution near field imaging achieved by attaching a micro-lens on the fiber. Interestingly, a surface covered by PDMS micro-fibers will turn from superhydrophobic into superhydrophilic by further heating providing potential applications in surface wettability modification. In future, we will investigate and simulate the growth of PDMS micro-fiber and look for more possible applications.
Development of crack shape: LBB methodology for cracked pipes
Energy Technology Data Exchange (ETDEWEB)
Moulin, D.; Chapuliot, S.; Drubay, B. [Commissariat a l Energie Atomique, Gif sur Yvette (France)
1997-04-01
For structures like vessels or pipes containing a fluid, the Leak-Before-Break (LBB) assessment requires to demonstrate that it is possible, during the lifetime of the component, to detect a rate of leakage due to a possible defect, the growth of which would result in a leak before-break of the component. This LBB assessment could be an important contribution to the overall structural integrity argument for many components. The aim of this paper is to review some practices used for LBB assessment and to describe how some new R & D results have been used to provide a simplified approach of fracture mechanics analysis and especially the evaluation of crack shape and size during the lifetime of the component.
Tools for analyzing intersecting tracks: The x2sys package
Wessel, Paul
2010-03-01
I present a new set of tools for detection of intersections among tracks in 2-D Cartesian or geographic coordinates. These tools allow for evaluation of crossover errors at intersections, analysis of such crossover errors to determine appropriate linear models of systematic corrections for each track, and application of these corrections and further adjustments to data that completely eliminates crossover discrepancies from final 2-D data compilations. Unlike my older x_system tools, the new x2sys tools implement modern algorithms for detecting track intersections and are capable of reading a wide range of data file formats, including data files following the netCDF COARDS convention. The x2sys package contains several programs that address the various tasks needed to undertake a comprehensive crossover analysis and is distributed as a supplement to the Generic Mapping Tools, making them available for all computer platforms and architectures.
The intersection of Finite State Automata and Definite Clause Grammars
Van Noord, G
1995-01-01
Bernard Lang defines parsing as the calculation of the intersection of a FSA (the input) and a CFG. Viewing the input for parsing as a FSA rather than as a string combines well with some approaches in speech understanding systems, in which parsing takes a word lattice as input (rather than a word string). Furthermore, certain techniques for robust parsing can be modelled as finite state transducers. In this paper we investigate how we can generalize this approach for unification grammars. In particular we will concentrate on how we might the calculation of the intersection of a FSA and a DCG. It is shown that existing parsing algorithms can be easily extended for FSA inputs. However, we also show that the termination properties change drastically: we show that it is undecidable whether the intersection of a FSA and a DCG is empty (even if the DCG is off-line parsable). Furthermore we discuss approaches to cope with the problem.
Research on Driver Behavior in Yellow Interval at Signalized Intersections
Directory of Open Access Journals (Sweden)
Zhaosheng Yang
2014-01-01
Full Text Available Vehicles are often caught in dilemma zone when they approach signalized intersections in yellow interval. The existence of dilemma zone which is significantly influenced by driver behavior seriously affects the efficiency and safety of intersections. This paper proposes the driver behavior models in yellow interval by logistic regression and fuzzy decision tree modeling, respectively, based on camera image data. Vehicle’s speed and distance to stop line are considered in logistic regression model, which also brings in a dummy variable to describe installation of countdown timer display. Fuzzy decision tree model is generated by FID3 algorithm whose heuristic information is fuzzy information entropy based on membership functions. This paper concludes that fuzzy decision tree is more accurate to describe driver behavior at signalized intersection than logistic regression model.
Optimal Locations of Bus Stops Connecting Subways near Urban Intersections
Directory of Open Access Journals (Sweden)
Yuan Cui
2015-01-01
Full Text Available Unsuitable locations of bus stops which provide feeder transportation connecting subways near urban intersections usually lead to the low efficiency of public transport and level of passenger service. A multiobjective optimization model to distribute such stop locations is proposed to attain the shortest total walk distance of passengers and minimum delay time of cars through intersections and travel time of buses. The Pareto frontier and optimal solutions for the proposed model are given by the distance-based and enumerative methods. The Xizhimen bus stop is selected to implement case studies for verifying the validity of the proposed model. The analysis of sensitivity on possible solutions is also carried out in the case studies. The results show that the proposed model is capable of optimizing the locations of bus stops connecting subways near intersections and helpful to improve the level of passengers service and operational efficiency of public transportation.
Self-organizing traffic lights at multiple-street intersections
Gershenson, Carlos
2011-01-01
Summary: Traffic light coordination is a complex problem. In this paper, we extend previous work on an abstract model of city traffic to allow for multiple street intersections. We test a self-organizing method in our model, showing that it is close to theoretical optima and superior to a traditional method of traffic light coordination. Abstract: The elementary cellular automaton following rule 184 can mimic particles flowing in one direction at a constant speed. This automaton can therefore model highway traffic. In a recent paper, we have incorporated intersections regulated by traffic lights to this model using exclusively elementary cellular automata. In such a paper, however, we only explored a rectangular grid. We now extend our model to more complex scenarios employing an hexagonal grid. This extension shows first that our model can readily incorporate multiple-way intersections and hence simulate complex scenarios. In addition, the current extension allows us to study and evaluate the behavior of two...
Beyond dichotomies: Gender and intersecting inequalities in climate change studies.
Djoudi, Houria; Locatelli, Bruno; Vaast, Chloe; Asher, Kiran; Brockhaus, Maria; Basnett Sijapati, Bimbika
2016-12-01
Climate change and related adaptation strategies have gender-differentiated impacts. This paper reviews how gender is framed in 41 papers on climate change adaptation through an intersectionality lens. The main findings show that while intersectional analysis has demonstrated many advantages for a comprehensive study of gender, it has not yet entered the field of climate change and gender. In climate change studies, gender is mostly handled in a men-versus-women dichotomy and little or no attention has been paid to power and social and political relations. These gaps which are echoed in other domains of development and gender research depict a 'feminization of vulnerability' and reinforce a 'victimization' discourse within climate change studies. We argue that a critical intersectional assessment would contribute to unveil agency and emancipatory pathways in the adaptation process by providing a better understanding of how the differential impacts of climate change shape, and are shaped by, the complex power dynamics of existing social and political relations.
On the intersections of Fibonacci, Pell, and Lucas numbers
Alekseyev, Max A
2010-01-01
We describe how to compute the intersection of two Lucas sequences of the forms $\\{U_n(P,\\pm 1) \\}_{n=0}^{\\infty}$ or $\\{V_n(P,\\pm 1) \\}_{n=0}^{\\infty}$ with $P\\in\\mathbb{Z}$ that includes sequences of Fibonacci, Pell, Lucas, and Lucas-Pell numbers. We prove that such an intersection is finite except for the case $U_n(1,-1)$ and $U_n(3,1)$ and the case of two $V$-sequences when the product of their discriminants is a perfect square. Moreover, the intersection in these cases also forms a Lucas sequence. Our approach relies on solving homogeneous quadratic Diophantine equations and Thue equations. In particular, we prove that 0, 1, 2, and 5 are the only numbers that are both Fibonacci and Pell, and list similar results for many other pairs of Lucas sequences. We further extend our results to Lucas sequences with arbitrary initial terms.
Dynamical Outcomes of Quenching: Reflections on a Conical Intersection
Lehman, Julia H.; Lester, Marsha I.
2014-04-01
This review focuses on experimental studies of the dynamical outcomes following collisional quenching of electronically excited OH A2Î£+ radicals by molecular partners. The experimental observables include the branching between reactive and nonreactive decay channels, kinetic energy release, and quantum state distributions of the products. Complementary theoretical investigations reveal regions of strong nonadiabatic coupling, known as conical intersections, which facilitate the quenching process. The dynamical outcomes observed experimentally are connected to the local forces and geometric properties of the nuclei in the conical intersection region. Dynamical calculations for the benchmark OH-H2 system are in good accord with experimental observations, demonstrating that the outcomes reflect the strong coupling in the conical intersection region as the system evolves from the excited electronic state to quenched products.
Characterization of crack growth under combined loading
Feldman, A.; Smith, F. W.; Holston, A., Jr.
1977-01-01
Room-temperature static and cyclic tests were made on 21 aluminum plates in the shape of a 91.4x91.4-cm Maltese cross with 45 deg flaws to develop crack growth and fracture toughness data under mixed-mode conditions. During cyclic testing, it was impossible to maintain a high proportion of shear-mode deformation on the crack tips. Cracks either branched or turned. Under static loading, cracks remained straight if shear stress intensity exceeded normal stress intensity. Mixed-mode crack growth rate data compared reasonably well with published single-mode data, and measured crack displacements agreed with the straight and branched crack analyses. Values of critical strain energy release rate at fracture for pure shear were approximately 50% higher than for pure normal opening, and there was a large reduction in normal stress intensity at fracture in the presence of high shear stress intensity. Net section stresses were well into the inelastic range when fracture occurred under high shear on the cracks.
Locating a leaking crack by safe stimulation
Energy Technology Data Exchange (ETDEWEB)
Coleman, C.E.; Sagat, S. (Atomic Energy of Canada Ltd., Chalk River, ON (Canada). Chalk River Nuclear Labs.); Shek, G.K.; Graham, D.B.; Durand, M.A. (Ontario Hydro, Toronto, ON (Canada))
1990-01-01
A few Zr-2.5 Nb alloy pressure tubes in CANDU nuclear reactors have leaked through cracks that have grown by delayed hydride cracking (DHC). In some instances, tubes contained confirmed leaks that were leaking at a rate too low for precise identification of the leaking channel. Controlled stimulation of DHC can be used to help locate these leaks by extending the crack and increasing the leak rate without approaching crack instability. In the event of a leak being detected, a plant operator can gain time for leak location by a heating and unloading manoeuvre that will arrest crack growth and increase the critical crack length. This manoeuvre increases the safety margin against tube rupture. If required, the operator can then stimulate cracking in a controlled manner to aid in leak identification. Sequences of temperature and load manoeuvres for safe crack stimulation have been found by laboratory tests on dry specimens and the efficacy of the process has been demonstrated, partly in a power reactor, and partly in a full-scale simulation of a leaking pressure tube. (author).
Entering a Crack: An Encounter with Gossip
Henderson, Linda
2014-01-01
In this paper, I enter a crack to think otherwise about the concept "gossip". Drawing on previous scholarship engaging with Deleuzian concepts to inform research methodologies, this paper builds on this body of work. Following Deleuze and Guattari, the paper undertakes a mapping of gossip, subsequent to an encounter with a crack.…
Crack propagation directions in unfilled resins.
Baran, G; Sadeghipour, K; Jayaraman, S; Silage, D; Paul, D; Boberick, K
1998-11-01
Posterior composite restorative materials undergo accelerated wear in the occlusal contact area, primarily through a fatigue mechanism. To facilitate the timely development of new and improved materials, a predictive wear model is desirable. The objective of this study was to develop a finite element model enabling investigators to predict crack propagation directions in resins used as the matrix material in composites, and to verify these predictions by observing cracks formed during the pin-on-disc wear of a 60:40 BISGMA:TEGDMA resin and an EBPADMA resin. Laser confocal scanning microscopy was used to measure crack locations. Finite element studies were done by means of ABAQUS software, modeling a cylinder sliding on a material with pre-existing surface-breaking cracks. Variables included modulus, cylinder/material friction coefficient, crack face friction, and yield behavior. Experimental results were surprising, since most crack directions were opposite previously published observations. The majority of surface cracks, though initially orthogonal to the surface, changed direction to run 20 to 30 degrees from the horizontal in the direction of indenter movement. Finite element modeling established the importance of subsurface shear stresses, since calculations provided evidence that cracks propagate in the direction of maximum K(II)(theta), in the same direction as the motion of the indenter, and at an angle of approximately 20 degrees. These findings provide the foundation for a predictive model of sliding wear in unfilled glassy resins.
Uncertainty Quantification in Fatigue Crack Growth Prognosis
Directory of Open Access Journals (Sweden)
Shankar Sankararaman
2011-01-01
Full Text Available This paper presents a methodology to quantify the uncertainty in fatigue crack growth prognosis, applied to structures with complicated geometry and subjected to variable amplitude multi-axial loading. Finite element analysis is used to address the complicated geometry and calculate the stress intensity factors. Multi-modal stress intensity factors due to multi-axial loading are combined to calculate an equivalent stress intensity factor using a characteristic plane approach. Crack growth under variable amplitude loading is modeled using a modified Paris law that includes retardation effects. During cycle-by-cycle integration of the crack growth law, a Gaussian process surrogate model is used to replace the expensive finite element analysis. The effect of different types of uncertainty – physical variability, data uncertainty and modeling errors – on crack growth prediction is investigated. The various sources of uncertainty include, but not limited to, variability in loading conditions, material parameters, experimental data, model uncertainty, etc. Three different types of modeling errors – crack growth model error, discretization error and surrogate model error – are included in analysis. The different types of uncertainty are incorporated into the crack growth prediction methodology to predict the probability distribution of crack size as a function of number of load cycles. The proposed method is illustrated using an application problem, surface cracking in a cylindrical structure.
Entering a Crack: An Encounter with Gossip
Henderson, Linda
2014-01-01
In this paper, I enter a crack to think otherwise about the concept "gossip". Drawing on previous scholarship engaging with Deleuzian concepts to inform research methodologies, this paper builds on this body of work. Following Deleuze and Guattari, the paper undertakes a mapping of gossip, subsequent to an encounter with a crack.…
Investigation of Cracked Lithium Hydride Reactor Vessels
Energy Technology Data Exchange (ETDEWEB)
bird, e.l.; mustaleski, t.m.
1999-06-01
Visual examination of lithium hydride reactor vessels revealed cracks that were adjacent to welds, most of which were circumferentially located in the bottom portion of the vessels. Sections were cut from the vessels containing these cracks and examined by use of the metallograph, scanning electron microscope, and microprobe to determine the cause of cracking. Most of the cracks originated on the outer surface just outside the weld fusion line in the base material and propagated along grain boundaries. Crack depths of those examined sections ranged from {approximately}300 to 500 {micro}m. Other cracks were reported to have reached a maximum depth of 1/8 in. The primary cause of cracking was the creation of high tensile stresses associated with the differences in the coefficients of thermal expansion between the filler metal and the base metal during operation of the vessel in a thermally cyclic environment. This failure mechanism could be described as creep-type fatigue, whereby crack propagation may have been aided by the presence of brittle chromium carbides along the grain boundaries, which indicates a slightly sensitized microstructure.
Fracture Mechanical Markov Chain Crack Growth Model
DEFF Research Database (Denmark)
Gansted, L.; Brincker, Rune; Hansen, Lars Pilegaard
1991-01-01
On the basis of the B-model developed in [J. L. Bogdanoff and F. Kozin, Probabilistic Models of Cumulative Damage. John Wiley, New York (1985)] a new numerical model incorporating the physical knowledge of fatigue crack propagation is developed. The model is based on the assumption that the crack...
Solute transport in cracking clay soils
Bronswijk, J.J.B.; Ritsema, C.J.; Oostindie, K.; Hamminga, P.
1996-01-01
A bromide tracer applied to a cracked clay soil was adsorbed in the soil matrix close to the soil surface. Upon subsequent precipitation, a small part of the bromide dissolved and flowed rapidly through cracks to the subsoil and the groundwater. As a result, the groundwater and the drain discharge
Strength of Cracked Reinforced Concrete Disks
DEFF Research Database (Denmark)
Hoang, Cao Linh; Nielsen, Mogens Peter
1999-01-01
The paper deals with models, based on the theory of plasticity, to be used in strength assessments of reinforced concrete disks suffering from different kinds of cracking. Based on the assumption that the sliding strength of concrete is reduced in sections where cracks are located, solutions...
Corrosion and Cracking of Reinforced Concrete
DEFF Research Database (Denmark)
Thoft-Christensen, Palle
Modelling of the deterioration of reinforced concrete has in recent years changed from being a deterministic modelling based on experience to be stochastic modelling based on sound and consistent physical, chemical and mechanical principles. In this paper is presented a brief review of modern mod...... for time to initial corrosion, time to initial cracking, and time to a given crack width may be obtained....
Teleparallel loop quantum cosmology in a system of intersecting branes
Directory of Open Access Journals (Sweden)
Alireza Sepehri
2016-09-01
Full Text Available Recently, some authors have removed the big bang singularity in teleparallel Loop Quantum Cosmology (LQC and have shown that the universe may undergo a number of oscillations. We investigate the origin of this type of teleparallel theory in a system of intersecting branes in M-theory in which the angle between them changes with time. This system is constructed by two intersecting anti-D8-branes, one compacted D4-brane and a D3-brane. These branes are built by joining M0-branes which develop in decaying fundamental strings. The compacted D4-brane is located between two intersecting anti-D8 branes and glues to one of them. Our universe is located on the D3 brane which wraps around the D4 brane from one end and sticks to one of the anti-D8 branes from the other one. In this system, there are three types of fields, corresponding to compacted D4 branes, intersecting branes and D3-branes. These fields interact with each other and make the angle between branes oscillate. By decreasing this angle, the intersecting anti-D8 branes approach each other, the D4 brane rolls, the D3 brane wraps around the D4 brane, and the universe contracts. By separating the intersecting branes and increasing the angle, the D4 brane rolls in the opposite direction, the D3 brane separates from it and the expansion branch begins. Also, the interaction between branes in this system gives us the exact form of the relevant Lagrangian for teleparallel LQC.
Teleparallel loop quantum cosmology in a system of intersecting branes
Sepehri, Alireza; Pradhan, Anirudh; Beesham, Aroonkumar; de Haro, Jaume
2016-09-01
Recently, some authors have removed the big bang singularity in teleparallel Loop Quantum Cosmology (LQC) and have shown that the universe may undergo a number of oscillations. We investigate the origin of this type of teleparallel theory in a system of intersecting branes in M-theory in which the angle between them changes with time. This system is constructed by two intersecting anti-D8-branes, one compacted D4-brane and a D3-brane. These branes are built by joining M0-branes which develop in decaying fundamental strings. The compacted D4-brane is located between two intersecting anti-D8 branes and glues to one of them. Our universe is located on the D3 brane which wraps around the D4 brane from one end and sticks to one of the anti-D8 branes from the other one. In this system, there are three types of fields, corresponding to compacted D4 branes, intersecting branes and D3-branes. These fields interact with each other and make the angle between branes oscillate. By decreasing this angle, the intersecting anti-D8 branes approach each other, the D4 brane rolls, the D3 brane wraps around the D4 brane, and the universe contracts. By separating the intersecting branes and increasing the angle, the D4 brane rolls in the opposite direction, the D3 brane separates from it and the expansion branch begins. Also, the interaction between branes in this system gives us the exact form of the relevant Lagrangian for teleparallel LQC.
Crack spacing threshold of double cracks propagation for large-module rack
Institute of Scientific and Technical Information of China (English)
赵铁柱; 石端伟; 姚哲皓; 毛宏勇; 程术潇; 彭惠
2015-01-01
Large-module rack of the Three Gorges shiplift is manufactured by casting and machining, which is unable to avoid slag inclusions and surface cracks. To ensure its safety in the future service, studying on crack propagation rule and the residual life estimation method of large-module rack is of great significance. The possible crack distribution forms of the rack in the Three Gorges shiplift were studied. By applying moving load on the model in FRANC3D and ANSYS, quantitative analyses of interference effects on double cracks in both collinear and offset conditions were conducted. The variation rule of the stress intensity factor (SIF) influence factor,RK, of double collinear cracks changing with crack spacing ratio,RS, was researched. The horizontal and vertical crack spacing threshold of double cracks within the design life of the shiplift were obtained, which are 24 and 4 times as large as half of initial crack length,c0, respectively. The crack growth rates along the length and depth directions in the process of coalescence on double collinear cracks were also studied.
Unsaturated Seepage Analysis of Cracked Soil including Development Process of Cracks
Directory of Open Access Journals (Sweden)
Ling Cao
2016-01-01
Full Text Available Cracks in soil provide preferential pathways for water flow and their morphological parameters significantly affect the hydraulic conductivity of the soil. To study the hydraulic properties of cracks, the dynamic development of cracks in the expansive soil during drying and wetting has been measured in the laboratory. The test results enable the development of the relationships between the cracks morphological parameters and the water content. In this study, the fractal model has been used to predict the soil-water characteristic curve (SWCC of the cracked soil, including the developmental process of the cracks. The cracked expansive soil has been considered as a crack-pore medium. A dual media flow model has been developed to simulate the seepage characteristics of the cracked expansive soil. The variations in pore water pressure at different part of the model are quite different due to the impact of the cracks. This study proves that seepage characteristics can be better predicted if the impact of cracks is taken into account.
Probabilistic analysis of linear elastic cracked structures
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
This paper presents a probabilistic methodology for linear fracture mechanics analysis of cracked structures. The main focus is on probabilistic aspect related to the nature of crack in material. The methodology involves finite element analysis; statistical models for uncertainty in material properties, crack size, fracture toughness and loads; and standard reliability methods for evaluating probabilistic characteristics of linear elastic fracture parameter. The uncertainty in the crack size can have a significant effect on the probability of failure, particularly when the crack size has a large coefficient of variation. Numerical example is presented to show that probabilistic methodology based on Monte Carlo simulation provides accurate estimates of failure probability for use in linear elastic fracture mechanics.
Strain rate effects in stress corrosion cracking
Energy Technology Data Exchange (ETDEWEB)
Parkins, R.N. (Newcastle upon Tyne Univ. (UK). Dept. of Metallurgy and Engineering Materials)
1990-03-01
Slow strain rate testing (SSRT) was initially developed as a rapid, ad hoc laboratory method for assessing the propensity for metals an environments to promote stress corrosion cracking. It is now clear, however, that there are good theoretical reasons why strain rate, as opposed to stress per se, will often be the controlling parameter in determining whether or not cracks are nucleated and, if so, are propagated. The synergistic effects of the time dependence of corrosion-related reactions and microplastic strain provide the basis for mechanistic understanding of stress corrosion cracking in high-pressure pipelines and other structures. However, while this may be readily comprehended in the context of laboratory slow strain tests, its extension to service situations may be less apparent. Laboratory work involving realistic stressing conditions, including low-frequency cyclic loading, shows that strain or creep rates give good correlation with thresholds for cracking and with crack growth kinetics.
Crack front propagation by kink formation
Energy Technology Data Exchange (ETDEWEB)
Roesch, Frohmut; Trebin, Hans-Rainer [Universitaet Stuttgart, Institut fuer Theoretische und Angewandte Physik, 70550 Stuttgart (Germany)
2010-07-01
In a brittle material a travelling crack generates an upper and a lower fracture surface, which meet at a one-dimensional crack front. From a macroscopic point of view there is no reason why this curve should deviate from a straight line, contrary to the atomistic point of view, where a crack propagates by successive rupture of cohesive bonds. We investigate fracture of the C15 NbCr{sub 2} Friauf-laves phase on an atomic level by means of molecular dynamics simulations. The numerical experiments highlight that crack fronts in general do not form a straight line and propagate by kink-pair formation at low loads (EPL 87 (2009) 66004). This mechanism should be relevant for crack propagation in any ordered brittle solid.
XFEM for Thermal Crack of Massive Concrete
Directory of Open Access Journals (Sweden)
Guowei Liu
2013-01-01
Full Text Available Thermal cracking of massive concrete structures occurs as a result of stresses caused by hydration in real environment conditions. The extended finite element method that combines thermal fields and creep is used in this study to analyze the thermal cracking of massive concrete structures. The temperature field is accurately simulated through an equivalent equation of heat conduction that considers the effect of a cooling pipe system. The time-dependent creep behavior of massive concrete is determined by the viscoelastic constitutive model with Prony series. Based on the degree of hydration, we consider the main properties related to cracking evolving with time. Numerical simulations of a real massive concrete structure are conducted. Results show that the developed method is efficient for numerical calculations of thermal cracks on massive concrete. Further analyses indicate that a cooling system and appropriate heat preservation measures can efficiently prevent the occurrence of thermal cracks.
The geometry of soil crack networks
Chertkov, V Y
2014-01-01
The subject of this work is the modification and specification of an approach to detail the estimation of soil crack network characteristics. The modification aims at accounting for the corrected soil crack volume based on the corrected shrinkage geometry factor compared to known estimates of crack volume and shrinkage geometry factor. The mode of the correction relies on recent results of the soil reference shrinkage curve. The main exposition follows the preliminary brief review of available approaches to dealing with the geometry of soil crack networks and gives a preliminary brief summary of the approach to be modified and specified. To validate and illustrate the modified approach the latter is used in the analysis of available data on soil cracking in a lysimeter.
Field cracking performance of airfield rigid pavements
Directory of Open Access Journals (Sweden)
Yusuf Mehta
2017-08-01
Full Text Available This paper discusses cracking in airport pavements as studied in Construction Cycle 6 of testing carried out at the National Airport Pavement Testing Facility by the Federal Aviation Administration. Pavements of three different flexural strengths as well as two different subgrades, a soft bituminous layer and a more rigid layer known as econocrete, were tested. In addition to this, cracking near two types of isolated transition joints, a reinforced edge joint and a thickened edge joint, was considered. The pavement sections were tested using a moving load simulating that of an aircraft. It has been determined that the degree of cracking was reduced as the flexural strength of the pavement was increased and that fewer cracks formed over the econocrete base than over the bituminous base. In addition, the thickened edge transition joint was more effective in preventing cracking at the edges compared to the reinforced edge joint.
Crack Growth in Concrete Gravity Dams Based on Discrete Crack Method
Directory of Open Access Journals (Sweden)
A. R. Lohrasbi
2008-01-01
Full Text Available Seepage is the most parameter in water management safety and in stable agricultural. This seepage is passed through the cracks that are present to some degree in hydraulic structures. They may exist as basic defects in the constituent materials or may be induced in construction or during service life. To avoid such failure in concrete dams, safety would be an important factor. Over-design carries heavy penalty in terms of excess weight. So the fracture mechanics theory is a principal necessity of evaluating the stability of such crack propagation. For the process of crack propagation analysis in concrete structures, there are two general models: discrete crack and smeared crack. This study surveys the crack propagation in concrete gravity dams based on discrete crack methods. Moreover, we use a program provided specifically for this purpose.
Crack shape developments and leak rates for circumferential complex-cracked pipes
Energy Technology Data Exchange (ETDEWEB)
Brickstad, B.; Bergman, M. [SAQ Inspection Ltd., Stockholm (Sweden)
1997-04-01
A computerized procedure has been developed that predicts the growth of an initial circumferential surface crack through a pipe and further on to failure. The crack growth mechanism can either be fatigue or stress corrosion. Consideration is taken to complex crack shapes and for the through-wall cracks, crack opening areas and leak rates are also calculated. The procedure is based on a large number of three-dimensional finite element calculations of cracked pipes. The results from these calculations are stored in a database from which the PC-program, denoted LBBPIPE, reads all necessary information. In this paper, a sensitivity analysis is presented for cracked pipes subjected to both stress corrosion and vibration fatigue.
Fully plastic crack opening analyses of complex-cracked pipes for Ramberg-Osgood materials
Energy Technology Data Exchange (ETDEWEB)
Jeong, Jae Uk; Choi, Jae Boong [Sungkyunkwan University, Suwon (Korea, Republic of); Huh, Nam Su [Seoul National University, Seoul (Korea, Republic of); Kim, Yun Jae [Korea University, Seoul (Korea, Republic of)
2016-04-15
The plastic influence functions for calculating fully plastic Crack opening displacement (COD) of complex-cracked pipes were newly proposed based on systematic 3-dimensional (3-D) elastic-plastic Finite element (FE) analyses using Ramberg-Osgood (R-O) relation, where global bending moment, axial tension and internal pressure are considered separately as a loading condition. Then, crack opening analyses were performed based on GE/EPRI concept by using the new plastic influence functions for complex-cracked pipes made of SA376 TP304 stainless steel, and the predicted CODs were compared with FE results based on deformation plasticity theory of tensile material behavior. From the comparison, the confidence of the proposed fully plastic crack opening solutions for complex-cracked pipes was gained. Therefore, the proposed engineering scheme for COD estimation using the new plastic influence functions can be utilized to estimate leak rate of a complex-cracked pipe for R-O material.
General forms of elastic-plastic matching equations for mode-Ⅲ cracks near crack line
Institute of Scientific and Technical Information of China (English)
Zhi-jian YI; Chao-hua ZHAO; Qing-guo YANG; Kai PENG; Zong-ming HUANG
2009-01-01
Crack line analysis is an effective way to solve elastic-plastic crack problems.Application of the method does not need the traditional small-scale yielding conditions and can obtain sufficiently accurate solutions near the crack line. To address mode-Ⅲ crack problems under the perfect elastic-plastic condition,matching procedures of the crack line analysis method are summarized and refined to give general forms and formulation steps of plastic field,elastic-plastic boundary,and elastic-plastic matching equations near the crack line. The research unifies mode-Ⅲ crack problems under different conditions into a problem of determining four integral constants with four matching equations.An example is given to verify correctness,conciseness,and generality of the procedure.
Viewing equitable practices through the lens of intersecting identities
Lyons, Renée; Dsouza, Nikeetha; Quigley, Cassie
2016-04-01
This review explores Archer, Dawson, Seakins, and Wong's "Disorienting, fun or meaningful? Disadvantaged families' experiences of a science museum visit" by examining the analytic frameworks guiding this study. To expand on Archer et al.'s use of feminist post-structuralist theories of identity we draw from the theory of intersectionality to provide a more robust framework for analyzing barriers to engagement within an informal learning space. Our response to this work ends by exploring the types of solutions generated from an intersectionality framework—solutions aimed at transforming institutional programs and practices to create more equitable spaces for learning.
Viewing equitable practices through the lens of intersecting identities
Lyons, Renée; Dsouza, Nikeetha; Quigley, Cassie
2016-12-01
This review explores Archer, Dawson, Seakins, and Wong's "Disorienting, fun or meaningful? Disadvantaged families' experiences of a science museum visit" by examining the analytic frameworks guiding this study. To expand on Archer et al.'s use of feminist post-structuralist theories of identity we draw from the theory of intersectionality to provide a more robust framework for analyzing barriers to engagement within an informal learning space. Our response to this work ends by exploring the types of solutions generated from an intersectionality framework—solutions aimed at transforming institutional programs and practices to create more equitable spaces for learning.
New Approach to Measuring Traffic Queue at Intersections
Institute of Scientific and Technical Information of China (English)
SONG Lei; SHI Zhong-ke
2008-01-01
To measure the length of traffic queue, a vehicle motion model at intersections was built, and based on it the effective traffic queue was defined. Color images segmentation and frame differencing technique were used to detect the foreground and the moving vehicles by detecting regions of the images, and then measure the length of effective traffic queue. By processing the image sequence acquired at certain intersection, the results prove that it is able to work out the traffic queue effectively by using the two techniques.
Intersection democracy for winding branes and stabilization of extra dimensions
Rador, Tonguc
2005-01-01
We show that, in the context of pure Einstein gravity, a democratic principle for intersection possibilities of branes winding around extra dimensions in a given partitioning yield stabilization, while what the observed space follows is matter-like dust evolution . Here democracy is used in the sense that, in a given decimation of extra dimensions, all possible wrappings and hence all possible intersections are allowed. Generally, the necessary and sufficient condition for this is that the dimensionality $m$ of the observed space dimensions obey $3\\leqm \\le N$ where $N$ is the decimation order of the extra dimensions.
Third Wave Feminism's Unhappy Marriage of Poststructuralism and Intersectionality Theory
Directory of Open Access Journals (Sweden)
Susan Archer Mann
2013-06-01
Full Text Available This article first traces the history of unhappy marriages of disparate theoretical perspectives in US feminism. In recent decades, US third-wave authors have arranged their own unhappy marriage in that their major publications reflect an attempt to wed poststructuralism with intersectionality theory. Although the standpoint epistemology of intersectionality theory shares some common ground with the epistemology of poststructuralism, their epistemological assumptions conflict on a number of important dimensions. This contested terrain has generated serious debates within the third wave and between second- and thirdwave feminists. The form, content, and political implications of their "unhappy marriage" are the subject of this article.
Combined effect of matrix cracking and stress-free edge on delamination
Salpekar, S. A.; Obrien, T. K.
1990-01-01
The effect of the stress-free edge on the growth of local delaminations initiating from a matrix crack in (0 sub 2/90 sub 4) sub s and (+ or - 45.90 sub 4) sub s glass epoxy laminates is investigated using 3-D finite element analysis. The presence of high interlaminar normal stresses at the intersection (corner) of the matrix crack with the stress-free edge, suggests that a mode I delamination may initiate at the corners. The strain energy release rates (G) were calculated by modeling a uniform through-width delamination and two inclined delaminations at 10.6 deg and 45 deg to the matrix crack. All components of G have high values near the free edges. The mode I component of G is high at small delamination length and becomes zero for a delamination length of one-ply thickness. The total G values near the free edge agreed well with previously derived closed form solution. The quasi-3D solutions agreed well with the 3-D interior solutions.
Investigating Reaction-Driven Cracking
Kelemen, P. B.; Hirth, G.; Savage, H. M.
2013-12-01
Many metamorphic reactions lead to large volume changes, and potentially to reaction-driven cracking [1,2]. Large-scale hydration of mantle peridotite to produce serpentine or talc is invoked to explain the rheology of plate boundaries, the nature of earthquakes, and the seismic properties of slow-spread ocean crust and the 'mantle wedge' above subduction zones. Carbonation of peridotite may be an important sink in the global carbon cycle. Zones of 100% magnesite + quartz replacing peridotite, up to 200 m thick, formed where oceanic mantle was thrust over carbonate-bearing metasediments in Oman. Talc + carbonate is an important component of the matrix in subduction mélanges at Santa Catalina Island , California, and the Sanbagawa metamorphic belt, Japan. Engineered systems to emulate natural mineral carbonation could provide relatively inexpensive CO2 capture and storage [3]. More generally, engineered reaction-driven cracking could supplement or replace hydraulic fracture in geothermal systems, solution mining, and extraction of tight oil and gas. The controls on reaction-driven cracking are poorly understood. Hydration and carbonation reactions can be self-limiting, since they potentially reduce permeability and armor reactive surfaces [4]. Also, in some cases, hydration or carbonation may take place at constant volume. Small changes in volume due to precipitation of solid products increases stress, destabilizing solid reactants, until precipitation and dissolution rates become equal at a steady state stress [5]. In a third case, volume change due to precipitation of solid products causes brittle failure. This has been invoked on qualitative grounds to explain, e.g., complete serpentinization of mantle peridotite [6]. Below ~ 300°C, the available potential energy for hydration and carbonation of olivine could produce stresses of 100's of MPa [2], sufficient to fracture rocks to 10 km depth or more, causing brittle failure below the steady state stress required
Cracks assessment using ultrasonic technology
Energy Technology Data Exchange (ETDEWEB)
Martinez, Maria Pia; Tomasella, Marcelo [OLDELVAL S.A. Oleoductos del Valle, Rio Negro (Argentina). Pipeline Integrity Dept.
2005-07-01
The goal of Oldelval Integrity Program is to prevent ruptures and leaks, developing strategies for a better handling of the integrity of our pipelines. In order to achieve it we have studied and modeled each process that involved in the integrity pipeline. Those processes are mainly based on defects reported by an internal inspection tool and supplied with field inspection and monitoring data. Years of evaluation, study and the continuous effort overturned towards a phenomenon that worries to the industry, as it is the SCC. Since 1998 up to 2004 SCC was included in the integrity program with some preventive maintenance programs. The accomplishment of the inspection based on ultrasound tools, is the culmination of years of evaluation and investigations supported by field digs and materials susceptibility. This paper describes Oldelval's results with ultrasonic crack detection tool, and how it can be reliably to detect SCC. (author)
Institute of Scientific and Technical Information of China (English)
李冬; 王慧聪; 宋天舒
2016-01-01
采用 Green 函数法对压电材料中多个孔边径向裂纹在 SH 波作用下的相互作用问题进行了研究。首先利用复变函数方法构造出具有多个半圆形凹陷的半无限压电介质的位移 Green 函数和电场 Green 函数，然后采用裂纹“切割”技术构造孔边径向裂纹，根据界面上的位移和应力连续性条件建立求解问题的第一类 Fredholm 定解积分方程。最后作为算例，给出了裂纹尖端动应力强度因子随缺陷几何尺寸、材料物理参数和入射波频率的变化特征图并进行了讨论。%Based on the method of Green's function,this work studied the interaction of the radial cracks emanating from the edges of the circular cavities in piezoelectric material,which was subjected to the dynamic incident anti-plane shearing wave(SH-wave).Firstly,coupled Green's functions for displacement and electric potential were established by using a complex variable method.Secondly,crack-division technique was used to construct the model of radial cracks. The problem was reduced to a series of Fredholm integral equations of the first type according to the continuity conditions of the displacement and stress at the interface.Finally,numerical results were provided by solving the equations to show the influences of the geometry parameters,piezoelectric characteristic parameters,and the wave frequencies of incident wave on the dynamic stress intensity factors(DSIFs)at the crack tips.
Three-Dimensional Gear Crack Propagation Studied
Lewicki, David G.
1999-01-01
Gears used in current helicopters and turboprops are designed for light weight, high margins of safety, and high reliability. However, unexpected gear failures may occur even with adequate tooth design. To design an extremely safe system, the designer must ask and address the question, "What happens when a failure occurs?" With gear-tooth bending fatigue, tooth or rim fractures may occur. A crack that propagates through a rim will be catastrophic, leading to disengagement of the rotor or propeller, loss of an aircraft, and possible fatalities. This failure mode should be avoided. A crack that propagates through a tooth may or may not be catastrophic, depending on the design and operating conditions. Also, early warning of this failure mode may be possible because of advances in modern diagnostic systems. One concept proposed to address bending fatigue fracture from a safety aspect is a splittooth gear design. The prime objective of this design would be to control crack propagation in a desired direction such that at least half of the tooth would remain operational should a bending failure occur. A study at the NASA Lewis Research Center analytically validated the crack-propagation failsafe characteristics of a split-tooth gear. It used a specially developed three-dimensional crack analysis program that was based on boundary element modeling and principles of linear elastic fracture mechanics. Crack shapes as well as the crack-propagation life were predicted on the basis of the calculated stress intensity factors, mixed-mode crack-propagation trajectory theories, and fatigue crack-growth theories. The preceding figures show the effect of the location of initial cracks on crack propagation. Initial cracks in the fillet of the teeth produced stress intensity factors of greater magnitude (and thus, greater crack growth rates) than those in the root or groove areas of the teeth. Crack growth was simulated in a case study to evaluate crack-propagation paths. Tooth
Effects of Weaving Laser on Weld Microstructure and Crack for Al 6k21-T4 Alloy
Institute of Scientific and Technical Information of China (English)
B.H. Kim; N.Y. Kang; W.T. Oh; C.H. Kim; J.H. Kim; Y.S. Kim; Y.H. Park
2011-01-01
For Al 6k21-T4 overlap weld joint, the shear-tensile strength by using the weaving laser was improved as compared to the case of linear laser. For the specimen of low strength, the porosity was distributed continuously along the intersection between the plates and fusion line. However, for the optimized welding condition, large oval-shaped porosities were located only in the advancing track of the concave part. Therefore, the continuity of cracks and porosities played a key role to determine the strength. And, the weaving width was also the important parameter to control the strength. Furthermore, the concave part had more significant hot and cold cracking in the weld and heat-affected zone (HAZ), respectively, than the convex part.
Institute of Scientific and Technical Information of China (English)
袁泽帅; 郭俊宏; 卢子兴
2012-01-01
通过构造新保角映射，利用stroh公式研究了远场受反平面剪应力和面内电载荷共同作用下无限大压电复合材料中幂函数型曲线裂纹的断裂行为。给出了电不可渗透边界条件下裂纹尖端场强度因子和机械应变能释放率的解析解。该解析解在幂函数的幂次为零时，可退化为已有文献中无限大压电复合材料含直线裂纹的结果，证明了其合理性。由解析解可知，裂纹几何形状一定时，电场分布将不受机械载荷的影响。最后，通过数值算例讨论了幂函数的幂次、系数及其在X1轴上的投影长度对机械应变能释放率的影响。结果表明，当压电体仅受X2方向载荷作用时，对于给定幂次与开口的曲线裂纹，在X1轴上的投影长度存在一临界值使其最容易开裂；而对于给定投影长度与幂次的曲线裂纹，开口越大裂纹越容易扩展。%By proposing a new conformal mapping and using the Stroh formula the fracture problem of a power function curved crack in an infinite piezoelectric coposite is studied under anti-plane shear stress and in-plane electric load at infinity The analytical solutions of the field intensity factors and the mechanical strain energy relrase rate are presented with the assumptio that the surface of the crack is electrically impermeable When the power of the curve is zero the present results can be reduced to the solutions of a Griffith crack in an infinite piezoelectric comosite Based on the analytical solutions it is found that the distribution of electric field is independent on the mechanics load under a fixed shape of the curve,Numerical examples are finally conducted to analyze the influences of the projected length along the X1-axis power and coefficient of curved cracks on the mechanical strain energy release rate The results show that if the plezoelectrlc composlte is subjected to the only load along the direction ot X2-axis there exists a
Crack detection in a beam with an arbitrary number of transverse cracks using genetic algorithms
Energy Technology Data Exchange (ETDEWEB)
Khaji, N. [Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Mehrjoo, M. [Islamic Azad University, Tehran (Iran, Islamic Republic of)
2014-03-15
In this paper, a crack detection approach is presented for detecting depth and location of cracks in beam-like structures. For this purpose, a new beam element with an arbitrary number of embedded transverse edge cracks, in arbitrary positions of beam element with any depth, is derived. The components of the stiffness matrix for the cracked element are computed using the conjugate beam concept and Betti's theorem, and finally represented in closed-form expressions. The proposed beam element is efficiently employed for solving forward problem (i.e., to gain precise natural frequencies and mode shapes of the beam knowing the cracks' characteristics). To validate the proposed element, results obtained by new element are compared with two-dimensional (2D) finite element results and available experimental measurements. Moreover, by knowing the natural frequencies and mode shapes, an inverse problem is established in which the location and depth of cracks are determined. In the inverse approach, an optimization problem based on the new finite element and genetic algorithms (GAs) is solved to search the solution. It is shown that the present algorithm is able to identify various crack configurations in a cracked beam. The proposed approach is verified through a cracked beam containing various cracks with different depths.
Identification of cracks in thick beams with a cracked beam element model
Hou, Chuanchuan; Lu, Yong
2016-12-01
The effect of a crack on the vibration of a beam is a classical problem, and various models have been proposed, ranging from the basic stiffness reduction method to the more sophisticated model involving formulation based on the additional flexibility due to a crack. However, in the damage identification or finite element model updating applications, it is still common practice to employ a simple stiffness reduction factor to represent a crack in the identification process, whereas the use of a more realistic crack model is rather limited. In this paper, the issues with the simple stiffness reduction method, particularly concerning thick beams, are highlighted along with a review of several other crack models. A robust finite element model updating procedure is then presented for the detection of cracks in beams. The description of the crack parameters is based on the cracked beam flexibility formulated by means of the fracture mechanics, and it takes into consideration of shear deformation and coupling between translational and longitudinal vibrations, and thus is particularly suitable for thick beams. The identification procedure employs a global searching technique using Genetic Algorithms, and there is no restriction on the location, severity and the number of cracks to be identified. The procedure is verified to yield satisfactory identification for practically any configurations of cracks in a beam.
Subcritical crack growth in two titanium alloys.
Williams, D. N.
1973-01-01
Measurement of subcritical crack growth during static loading of precracked titanium alloys in salt water using samples too thin for plane strain loading to predominate was examined as a method for determining the critical stress intensity for crack propagation in salt water. Significant internal crack growth followed by arrest was found at quite low stress intensities, but crack growth rates were relatively low. Assuming these techniques provided a reliable measurement of the critical stress intensity, the value for annealed Ti-4Al-1.5Mo-0.5V alloy was apparently about 35 ksi-in. to the 1/2 power, while that for annealed Ti-4Al-3Mo-1V was below 45 ksi-in. to the 1/2 power. Crack growth was also observed in tests conducted in both alloys in an air environment. At 65 ksi-in. to the 1/2 power, the extent of crack growth was greater in air than in salt water. Ti-4Al-3Mo-1V showed arrested crack growth in air at a stress intensity of 45 ksi-in. to the 1/2 power.
Dyslexia, Mothering and Work: Intersecting Identities, Reframing, "Drowning" and Resistance
Skinner, Tina
2011-01-01
This paper focuses on the ways in which mothering, work and dyslexia intersect in lived experience. The theoretical framework used to interpret these experiences draws on competing discourses variously imposed on and internalised by the individual; however, it also stresses the ability (however limited) of the individual to reframe and therefore…
MULTIAGENT PLANNING OF INTERSECTION PASSAGE BY AUTONOMOUS VEHICLES
Directory of Open Access Journals (Sweden)
I. A. Zikratov
2016-09-01
Full Text Available We propose a traffic management system for autonomous vehicles that are agents at the intersection. In contrast to the known solutions based on the usage of semiautonomous control systems in assembly with the control unit, this algorithm is based on the principles of decentralized multiagent control. The best travel plan for intersection passage is produced by means of optimization methods jointly by all agents belonging to a dynamic collaboration of autonomous vehicles. The order of road intersection optimal for a given criterion is determined by the agents in the process of information exchange about themselves and environment. Our experiments show that this protocol can reduce significantly the traffic density as compared to the traditional systems of traffic management. Moreover, the effectiveness of the proposed algorithm increases with increasing density of road traffic. In addition, the absence of the critical object, that is the control unit, in the control system, reduces significantly the effectiveness of possible failures and hacker attacks on the intersection control system.
Exploring Driver Injury Severity at Intersection: An Ordered Probit Analysis
Directory of Open Access Journals (Sweden)
Yaping Zhang
2015-02-01
Full Text Available It is well known that intersections are the most hazardous locations; however, only little is known about driver injury severity in intersection crashes. Hence, the main goal of this study was to further examine the different factors contributing to driver injury severity involved in fatal crashes at intersections. Data used for the present analysis was from the US DOT-Fatality Analysis Reporting System (FARS crash database from the year 2011. An ordered probit model was employed to fit the fatal crash data and analyze the factors impacting each injury severity level. The analysis results displayed that driver injury severity is significantly affected by many factors. They include driver age and gender, driver ethnicity, vehicle type and age (years of use, crash type, driving drunk, speeding, violating stop sign, cognitively distracted driving, and seat belt usage. These findings from the current study are beneficial to form a solid basis for adopting corresponding measures to effectively drop injury severity suffering from intersection crash. More insights into the effects of risk factors on driver injury severity could be acquired using more advanced statistical models.
Intersectional Identity Negotiation: The Case of Young Immigrant Children
Compton-Lilly, Catherine; Papoi, Kristin; Venegas, Patricia; Hamman, Laura; Schwabenbauer, Briana
2017-01-01
We cast our lens on intersectional networks of identity negotiated by young children in immigrant families. Although some scholars discuss identity construction, we reference identity negotiation to capture the active, strategic, and agential work that we witnessed in our study. We begin by synthesizing relevant research on children's identity…
Intersecting Scapes and New Millennium Identities in Language Learning
Higgins, Christina
2015-01-01
This paper examines how flows of people, media, money, technology, and ideologies move through the world, with attention to how these scapes (Appadurai 1990, 1996, 2013) shape identity construction among language learners, both in and out of classrooms. After illustrating intersecting scapes in sociolinguistic terms, I explore the relevance of…
Simulation of Traffic on Intersection After Change of Traffic Priority
Directory of Open Access Journals (Sweden)
Vladislav KŘIVDA
2011-06-01
Full Text Available This paper deals with problem of capacity calculation of intersection after change of traffic priority and with simulation of traffic using simulation software PTV VISSIM. This paper was prepared with financial support for project FRVŠ č. 2206/2011/F1/d “Innovation of Learning of Subjects from the Design of Urban Roads and Intersections”.
Conclusion: The Intersection of Student Voice and Policy Research
Mitra, Dana L.
2015-01-01
This concluding chapter examines how this book on student voice intersects with previous research about policy, especially policy implementation and sustainability. Mapping onto the themes of this volume, Discovering, Developing, and Demonstrating the power of student voice, I focus on three issues--legitimizing the role of young people in the…
INTERSECTION OF PRIME SUBMODULES AND DIMENSION OF MODULES
Institute of Scientific and Technical Information of China (English)
A. Azizi
2005-01-01
The aim of this paper is to study the conditions by which a P-prime submodule can be expressed as a finite intersection or union of P-prime submodules. Also corresponding to dimension and rank of modules, some equivalent conditions for a ring to be a Dedekind domain are given.
Intersectional Identity Negotiation: The Case of Young Immigrant Children
Compton-Lilly, Catherine; Papoi, Kristin; Venegas, Patricia; Hamman, Laura; Schwabenbauer, Briana
2017-01-01
We cast our lens on intersectional networks of identity negotiated by young children in immigrant families. Although some scholars discuss identity construction, we reference identity negotiation to capture the active, strategic, and agential work that we witnessed in our study. We begin by synthesizing relevant research on children's identity…
Intersecting Scapes and New Millennium Identities in Language Learning
Higgins, Christina
2015-01-01
This paper examines how flows of people, media, money, technology, and ideologies move through the world, with attention to how these scapes (Appadurai 1990, 1996, 2013) shape identity construction among language learners, both in and out of classrooms. After illustrating intersecting scapes in sociolinguistic terms, I explore the relevance of…
Acoustic analysis of a semi-anechoic chamber with intersection
Directory of Open Access Journals (Sweden)
P. Nassiri
2014-05-01
.Conclusion: According to the results, it can be concluded that the suggested intersection layout of rectangular fibrous absorbents can be used as a reliable method in order to reduce the reverberation time and to gain lower cut-off frequency for construct a semi anechoic chamber with the high efficiency.
Becoming Black Women: Intimate Stories and Intersectional Identities
Wilkins, Amy C.
2012-01-01
In this article, I argue that intimate stories are an important resource for the achievement of intersectional identities. Drawing on in-depth interviews with black college students at two predominantly white universities, I examine the stories black college women tell about interracial relationships between black men and white women. I argue that…
Intersections of Spirituality, Religion and Gender in Children's Literature
Trousdale, Ann M.
2005-01-01
This paper explores the intersections of spirituality, religion and gender in contemporary children's books published in the United States. Background for the discussion includes a history of religion in children's literature and the history of women's roles in the Christian tradition. Representative works of realistic fiction--historical and…
Leaf-wise intersections and Rabinowitz Floer homology
Albers, Peter
2008-01-01
In this article we explain how critical points of a perturbed Rabinowitz action functional give rise to leaf-wise intersection points in hypersurfaces of restricted contact type. This is used to derive existence results for hypersurfaces in general exact symplectic manifolds.
Precision of Points Computed from Intersections of Lines or Planes
DEFF Research Database (Denmark)
Cederholm, Jens Peter
2004-01-01
estimates the precision of the points. When using laser scanning a similar problem appears. A laser scanner captures a 3-D point cloud, not the points of real interest. The suggested method can be used to compute three-dimensional coordinates of the intersection of three planes estimated from the point...
Design unbiased estimation in line intersect sampling using segmented transects
David L.R. Affleck; Timothy G. Gregoire; Harry T. Valentine; Harry T. Valentine
2005-01-01
In many applications of line intersect sampling. transects consist of multiple, connected segments in a prescribed configuration. The relationship between the transect configuration and the selection probability of a population element is illustrated and a consistent sampling protocol, applicable to populations composed of arbitrarily shaped elements, is proposed. It...
Traffic noise and vehicle movement at a controlled intersection
Salomons, E.M.
2014-01-01
Traffic noise at an intersection controlled by traffic lights shows noise level variations due to the alternating green and red lights for the different trafficstreams. Noise peaks caused by automobiles pulling up or passing by at highspeed may be quite annoying for people living near the intersecti
Intersections of Loops and the Andersen-Mattes-Reshetikhin Algebra
Cahn, Patricia
2011-01-01
Given two free homotopy classes $\\alpha_1, \\alpha_2$ of loops on an oriented surface, it is natural to ask how to compute the minimum number of intersection points $m(\\alpha_1, \\alpha_2)$ of loops in these two classes. We show that for $\\alpha_1\
Using Dynamic Geometry Software for the Intersection Surfaces
Koparan, Timur; Yilmaz, Gül Kaleli
2015-01-01
The purpose of this study is to define prospective teacher views about using dynamic geometry software for intersection surfaces. The study was conducted as a case study. For this purpose, data collection tool was developed based on the opinion of two experts. The data collection tool consists of 4 open-ended questions related to the intersection…
Teleparallel loop quantum cosmology in a system of intersecting branes
Sepehri, Alireza; Beesham, A; de Haro, Jaume
2016-01-01
Recently, some authors have removed the big bang singularity in teleparallel Loop Quantum Cosmology (LQC) and have shown that the universe may undergo a number of oscillations. We investigate the origin of this type of teleparallel theory in a system of intersecting branes in M-theory in which the angle between them changes with time. This system is constructed by two intersecting anti-D8-branes, one compacted D4-brane and the other a D3-brane. These branes are built by joining M0-branes which develop in decaying fundamental strings. The compacted D4-brane is located between two intersecting anti-D8 branes and glues to one of them. Our universe is located on the D3 brane which wraps the D4 brane from one end and sticks to one of the anti-D8 branes from another one. In this system, there are three types of ?elds, corresponding to compacted D4 branes, intersecting branes and D3-branes. These ?elds interact with each other and make the angle between branes oscillate. By decreasing this angle and approaching the ...
Disciplinarity and Methodology in Intersectionality Theory and Research
Syed, Moin
2010-01-01
Comments on the original article, "Intersectionality and research in psychology," by E. R. Cole. Cole's article, says the current author, makes a welcome and valuable contribution to the field of psychology. Particularly useful are the three questions that she posed, highlighting how these questions are relevant and pressing for all researchers,…
Response to Mary J. Reichling, "Intersections: Form, Feeling, and Isomorphism"
Sinclair, Anne
2004-01-01
In her response to Mary Reichling's article "Intersections: Form, Feeling, and Isomorphism, Anne Sinclair believes that the exploration of form, feeling, and isomorphism in the writings of Susanne Langer accomplishes its goal to examine and elucidate aspects of these concepts. Sinclair finds several of the ideas presented very engaging. Musical…
Threshold Functions in Random s-Intersection Graphs
Zhao, Jun; Gligor, Virgil
2015-01-01
Random $s$-intersection graphs have recently received considerable attention in a wide range of application areas. In such a graph, each vertex is equipped with a set of items in some random manner, and any two vertices establish an undirected edge in between if and only if they have at least $s$ common items. In particular, in a uniform random $s$-intersection graph, each vertex independently selects a fixed number of items uniformly at random from a common item pool, while in a binomial random $s$-intersection graph, each item in some item pool is independently attached to each vertex with the same probability. For binomial/uniform random $s$-intersection graphs, we establish threshold functions for perfect matching containment, Hamilton cycle containment, and $k$-robustness, where $k$-robustness is in the sense of Zhang and Sundaram [IEEE Conf. on Decision & Control '12]. We show that these threshold functions resemble those of classical Erd\\H{o}s-R\\'{e}nyi graphs, where each pair of vertices has an un...
Revisiting Street Intersections Using Slot-Based Systems.
Directory of Open Access Journals (Sweden)
Remi Tachet
Full Text Available Since their appearance at the end of the 19th century, traffic lights have been the primary mode of granting access to road intersections. Today, this centuries-old technology is challenged by advances in intelligent transportation, which are opening the way to new solutions built upon slot-based systems similar to those commonly used in aerial traffic: what we call Slot-based Intersections (SIs. Despite simulation-based evidence of the potential benefits of SIs, a comprehensive, analytical framework to compare their relative performance with traffic lights is still lacking. Here, we develop such a framework. We approach the problem in a novel way, by generalizing classical queuing theory. Having defined safety conditions, we characterize capacity and delay of SIs. In the 2-road crossing configuration, we provide a capacity-optimal SI management system. For arbitrary intersection configurations, near-optimal solutions are developed. Results theoretically show that transitioning from a traffic light system to SI has the potential of doubling capacity and significantly reducing delays. This suggests a reduction of non-linear dynamics induced by intersection bottlenecks, with positive impact on the road network. Such findings can provide transportation engineers and planners with crucial insights as they prepare to manage the transition towards a more intelligent transportation infrastructure in cities.
Revisiting Street Intersections Using Slot-Based Systems.
Tachet, Remi; Santi, Paolo; Sobolevsky, Stanislav; Reyes-Castro, Luis Ignacio; Frazzoli, Emilio; Helbing, Dirk; Ratti, Carlo
2016-01-01
Since their appearance at the end of the 19th century, traffic lights have been the primary mode of granting access to road intersections. Today, this centuries-old technology is challenged by advances in intelligent transportation, which are opening the way to new solutions built upon slot-based systems similar to those commonly used in aerial traffic: what we call Slot-based Intersections (SIs). Despite simulation-based evidence of the potential benefits of SIs, a comprehensive, analytical framework to compare their relative performance with traffic lights is still lacking. Here, we develop such a framework. We approach the problem in a novel way, by generalizing classical queuing theory. Having defined safety conditions, we characterize capacity and delay of SIs. In the 2-road crossing configuration, we provide a capacity-optimal SI management system. For arbitrary intersection configurations, near-optimal solutions are developed. Results theoretically show that transitioning from a traffic light system to SI has the potential of doubling capacity and significantly reducing delays. This suggests a reduction of non-linear dynamics induced by intersection bottlenecks, with positive impact on the road network. Such findings can provide transportation engineers and planners with crucial insights as they prepare to manage the transition towards a more intelligent transportation infrastructure in cities.
Numerical Simulations of Mach Stem Formation via Intersecting Bow Shocks
Hansen, Edward C; Hartigan, Patrick
2014-01-01
Hubble Space Telescope observations show bright knots of H$\\alpha$ emission within outflowing young stellar jets. Velocity variations in the flow create secondary bow shocks that may intersect and lead to enhanced emission. When the bow shocks intersect at or above a certain critical angle, a planar shock called a Mach stem is formed. These shocks could produce brighter H$\\alpha$ emission since the incoming flow to the Mach stem is parallel to the shock normal. In this paper we report first results of a study using 2-D numerical simulations designed to explore Mach stem formation at the intersection of bow shocks formed by hypersonic "bullets" or "clumps". Our 2-D simulations show how the bow shock shapes and intersection angles change as the adiabatic index $\\gamma$ changes. We show that the formation or lack of a Mach stem in our simulations is consistent with the steady-state Mach stem formation theory. Our ultimate goal, which is part of an ongoing research effort, is to characterize the physical and obse...
Crack growth monitoring at CFRP bond lines
Rahammer, M.; Adebahr, W.; Sachse, R.; Gröninger, S.; Kreutzbruck, M.
2016-02-01
With the growing need for lightweight technologies in aerospace and automotive industries, fibre-reinforced plastics, especially carbon-fibre (CFRP), are used with a continuously increasing annual growth rate. A promising joining technique for composites is adhesive bonding. While rivet holes destroy the fibres and cause stress concentration, adhesive bond lines distribute the load evenly. Today bonding is only used in secondary structures due to a lack of knowledge with regard to long-term predictability. In all industries, numerical simulation plays a critical part in the development process of new materials and structures, while it plays a vital role when it comes to CFRP adhesive bondings conducing the predictability of life time and damage tolerance. The critical issue with adhesive bondings is crack growth. In a dynamic tensile stress testing machine we dynamically load bonded CFRP coupon specimen and measure the growth rate of an artificially started crack in order to feed the models with the results. We also investigate the effect of mechanical crack stopping features. For observation of the bond line, we apply two non-contact NDT techniques: Air-coupled ultrasound in slanted transmission mode and active lockin-thermography evaluated at load frequencies. Both methods give promising results for detecting the current crack front location. While the ultrasonic technique provides a slightly higher accuracy, thermography has the advantage of true online monitoring, because the measurements are made while the cyclic load is being applied. The NDT methods are compared to visual inspection of the crack front at the specimen flanks and show high congruence. Furthermore, the effect of crack stopping features within the specimen on the crack growth is investigated. The results show, that not all crack fronts are perfectly horizontal, but all of them eventually come to a halt in the crack stopping feature vicinity.
Slow crack growth in spinel in water
Schwantes, S.; Elber, W.
1983-01-01
Magnesium aluminate spinel was tested in a water environment at room temperature to establish its slow crack-growth behavior. Ring specimens with artificial flaws on the outside surface were loaded hydraulically on the inside surface. The time to failure was measured. Various precracking techniques were evaluated and multiple precracks were used to minimize the scatter in the static fatigue tests. Statistical analysis techniques were developed to determine the strength and crack velocities for a single flaw. Slow crack-growth rupture was observed at stress intensities as low as 70 percent of K sub c. A strengthening effect was observed in specimens that had survived long-time static fatigue tests.
Mitigation strategies for autogenous shrinkage cracking
DEFF Research Database (Denmark)
Bentz, Dale P.; Jensen, Ole Mejlhede
2004-01-01
, the fundamental parameters contributing to the autogenous shrinkage and resultant early-age cracking of concrete are presented. Basic characteristics of the cement paste that contribute to or control the autogenous shrinkage response include the surface tension of the pore solution, the geometry of the pore...... of early-age cracking due to autogenous shrinkage. Mitigation strategies discussed in this paper include: the addition of shrinkage-reducing admixtures more commonly used to control drying shrinkage, control of the cement particle size distribution, modification of the mineralogical composition......, it should be possible to minimize cracking due to autogenous shrinkage via some combination of the presented approaches....
Prediction of Crack Growth in Aqueous Environments.
1986-07-01
Impedance for the Propagation of a Crack Through HY80 Steel in 3.5Z NaCl Solution at 25*C Under Sinusoidal Loading Condi t ions...THE PROPAGATION OF A CRACK THROUGH HY80 STEEL IN 3.5% NaCI SOLUTION AT 25°C UNDER SINUSOIDAL LOADING CONDITIONS 49 and the properties of greatest...VELOCITY AS A FUNCTION OF TIME FOR A CRACK GROWN AT CONSTANT CURRENT IN HY80 STEEL Initial conditions CI in Table 5. 66 400 UJ x v> l/> L. 0
Safety performance models for urban intersections in Brazil.
Barbosa, Heloisa; Cunto, Flávio; Bezerra, Bárbara; Nodari, Christine; Jacques, Maria Alice
2014-09-01
This paper presents a modeling effort for developing safety performance models (SPM) for urban intersections for three major Brazilian cities. The proposed methodology for calibrating SPM has been divided into the following steps: defining the safety study objective, choosing predictive variables and sample size, data acquisition, defining model expression and model parameters and model evaluation. Among the predictive variables explored in the calibration phase were exposure variables (AADT), number of lanes, number of approaches and central median status. SPMs were obtained for three cities: Fortaleza, Belo Horizonte and Brasília. The SPM developed for signalized intersections in Fortaleza and Belo Horizonte had the same structure and the most significant independent variables, which were AADT entering the intersection and number of lanes, and in addition, the coefficient of the best models were in the same range of values. For Brasília, because of the sample size, the signalized and unsignalized intersections were grouped, and the AADT was split in minor and major approaches, which were the most significant variables. This paper also evaluated SPM transferability to other jurisdiction. The SPM for signalized intersections from Fortaleza and Belo Horizonte have been recalibrated (in terms of the Cx) to the city of Porto Alegre. The models were adjusted following the Highway Safety Manual (HSM) calibration procedure and yielded Cx of 0.65 and 2.06 for Fortaleza and Belo Horizonte SPM respectively. This paper showed the experience and future challenges toward the initiatives on development of SPMs in Brazil, that can serve as a guide for other countries that are in the same stage in this subject.
A mathematical model of traffic noise at a signalized intersection
Directory of Open Access Journals (Sweden)
Sorawit Narupiti
2005-05-01
Full Text Available This research aims at modeling interrupted flow traffic noise at a signalized intersection. The models are mathematically derived by applying the inverse square law of sound pressure incorporating with theories of traffic flow at an intersection. The traffic flow theories utilized for developing the model consist of characteristics of individual vehicle motion at intersection, shock wave model, and queuing analysis. The modelformulation is divided into two different approaches and takes into account of all regimes of vehicle movement while traversing an intersection (i.e. idling, decelerating, accelerating, and cruising conditions. The first approach assumes a constant acceleration/deceleration rate for each type of vehicle. Another appliesinconstant acceleration/deceleration which comes from speed-distance relationship. The final models are expressed in LAeq (1 hr.Eventually, the developed models are validated by collecting equivalent continuous noise level in 1 min as well as traffic parameters (i.e. red time, number of vehicle in the queue, queue length, time of queue dissipation, and final cruise speed from fifteen vehicle platoons. The noise levels predicted from the developed models are compared with the measured ones. The results show that the inconstant acceleration model gives the predicted levels closer to the measured ones than constant acceleration model. The error of inconstant acceleration model ranges from 0.1-3.9 dB(A with the average value of 2 dB(A overestimated and that of constant acceleration model ranges from 1.8-6.5 dB(A with the average value of 3 dB(A underestimated. It might be concluded that movement characteristic of vehicle is an important factor that apparently affects the accuracy of traffic noise prediction at an intersection.
van der Bij, Hendrik E; Meirer, Florian; Kalirai, Sam; Wang, Jian; Weckhuysen, Bert M
2014-12-15
The nature behind the promotional effect of phosphorus on the catalytic performance and hydrothermal stability of zeolite H-ZSM-5 has been studied using a combination of (27) Al and (31) P MAS NMR spectroscopy, soft X-ray absorption tomography and n-hexane catalytic cracking, complemented with NH3 temperature-programmed desorption and N2 physisorption. Phosphated H-ZSM-5 retains more acid sites and catalytic cracking activity after steam treatment than its non-phosphated counterpart, while the selectivity towards propylene is improved. It was established that the stabilization effect is twofold. First, the local framework silico-aluminophosphate (SAPO) interfaces, which form after phosphatation, are not affected by steam and hold aluminum atoms fixed in the zeolite lattice, preserving the pore structure of zeolite H-ZSM-5. Second, the four-coordinate framework aluminum can be forced into a reversible sixfold coordination by phosphate. These species remain stationary in the framework under hydrothermal conditions as well. Removal of physically coordinated phosphate after steam-treatment leads to an increase in the number of strong acid sites and increased catalytic activity. We propose that the improved selectivity towards propylene during catalytic cracking can be attributed to local SAPO interfaces located at channel intersections, where they act as impediments in the formation of bulky carbenium ions and therefore suppress the bimolecular cracking mechanism.
Some insights into the intersection of physical planning and governance in Zimbabwe
CSIR Research Space (South Africa)
Chakwizira, J
2008-04-01
Full Text Available This paper presents some insights into the intersection of physical planning and governance in Zimbabwe. It argues that the major theoretical, policy and practice discourses - explaining the intersection of physical planning and governance - relate...
EnviroAtlas - Paterson, NJ - Estimated Intersection Density of Walkable Roads
U.S. Environmental Protection Agency — This EnviroAtlas dataset estimates the intersection density of walkable roads within a 750 meter radius of any given 10 meter pixel in the community. Intersections...
EnviroAtlas - Minneapolis/St. Paul, MN - Estimated Intersection Density of Walkable Roads
U.S. Environmental Protection Agency — This EnviroAtlas dataset estimates the intersection density of walkable roads within a 750 meter radius of any given 10 meter pixel in the community. Intersections...
EnviroAtlas - New Bedford, MA - Estimated Intersection Density of Walkable Roads
U.S. Environmental Protection Agency — This EnviroAtlas dataset estimates the intersection density of walkable roads within a 750 meter radius of any given 10 meter pixel in the community. Intersections...
EnviroAtlas - Pittsburgh, PA - Estimated Intersection Density of Walkable Roads
U.S. Environmental Protection Agency — This EnviroAtlas dataset estimates the intersection density of walkable roads within a 750 meter radius of any given 10 meter pixel in the community. Intersections...
EnviroAtlas - New York, NY - Estimated Intersection Density of Walkable Roads
U.S. Environmental Protection Agency — This EnviroAtlas dataset estimates the intersection density of walkable roads within a 750 meter radius of any given 10 meter pixel in the community. Intersections...
EnviroAtlas - Memphis, TN - Estimated Intersection Density of Walkable Roads
U.S. Environmental Protection Agency — This EnviroAtlas dataset estimates the intersection density of walkable roads within a 750 meter radius of any given 10 meter pixel in the community. Intersections...
EnviroAtlas - Cleveland, OH - Estimated Intersection Density of Walkable Roads
U.S. Environmental Protection Agency — This EnviroAtlas dataset estimates the intersection density of walkable roads within a 750 meter radius of any given 10 meter pixel in the community. Intersections...
EnviroAtlas - Fresno, CA - Estimated Intersection Density of Walkable Roads
U.S. Environmental Protection Agency — This EnviroAtlas dataset estimates the intersection density of walkable roads within a 750 meter radius of any given 10 meter pixel in the community. Intersections...
EnviroAtlas - Green Bay, WI - Estimated Intersection Density of Walkable Roads
U.S. Environmental Protection Agency — This EnviroAtlas dataset estimates the intersection density of walkable roads within a 750 meter radius of any given 10 meter pixel in the community. Intersections...
EnviroAtlas - Tampa, FL - Estimated Intersection Density of Walkable Roads
U.S. Environmental Protection Agency — This EnviroAtlas dataset estimates the intersection density of walkable roads within a 750 meter radius of any given 10 meter pixel in the community. Intersections...
EnviroAtlas - Portland, ME - Estimated Intersection Density of Walkable Roads
U.S. Environmental Protection Agency — This EnviroAtlas dataset estimates the intersection density of walkable roads within a 750 meter radius of any given 10 meter pixel in the community. Intersections...
EnviroAtlas - Phoenix, AZ - Estimated Intersection Density of Walkable Roads
U.S. Environmental Protection Agency — This EnviroAtlas dataset estimates the intersection density of walkable roads within a 750 meter radius of any given 10 meter pixel in the community. Intersections...
EnviroAtlas - Des Moines, IA - Estimated Intersection Density of Walkable Roads
U.S. Environmental Protection Agency — This EnviroAtlas dataset estimates the intersection density of walkable roads within a 750 meter radius of any given 10 meter pixel in the community. Intersections...
EnviroAtlas - Austin, TX - Estimated Intersection Density of Walkable Roads
U.S. Environmental Protection Agency — This EnviroAtlas dataset estimates the intersection density of walkable roads within a 750 meter radius of any given 10 meter pixel in the community. Intersections...
EnviroAtlas - Woodbine, IA - Estimated Intersection Density of Walkable Roads
U.S. Environmental Protection Agency — This EnviroAtlas dataset estimates the intersection density of walkable roads within a 750 meter radius of any given 10 meter pixel in the community. Intersections...
EnviroAtlas - Milwaukee, WI - Estimated Intersection Density of Walkable Roads
U.S. Environmental Protection Agency — This EnviroAtlas dataset estimates the intersection density of walkable roads within a 750 meter radius of any given 10 meter pixel in the community. Intersections...
EnviroAtlas - Portland, OR - Estimated Intersection Density of Walkable Roads
U.S. Environmental Protection Agency — This EnviroAtlas dataset estimates the intersection density of walkable roads within a 750 meter radius of any given 10 meter pixel in the community. Intersections...
EnviroAtlas - Durham, NC - Estimated Intersection Density of Walkable Roads
U.S. Environmental Protection Agency — This EnviroAtlas dataset estimates the intersection density of walkable roads within a 750 meter radius of any given 10 meter pixel in the community. Intersections...
Martakos, G.; Andreasen, J. H.; Berggreen, C.; Thomsen, O. T.
2017-02-01
A novel crack arresting device has been implemented in sandwich panels and tested using a special rig to apply out-of-plane loading on the sandwich panel face-sheets. Fatigue crack propagation was induced in the face-core interface of the sandwich panels which met the crack arrester. The effect of the embedded crack arresters was evaluated in terms of the achieved enhancement of the damage tolerance of the tested sandwich panels. A finite element (FE) model of the experimental setup was used for predicting propagation rates and direction of the crack growth. The FE simulation was based on the adoption of linear fracture mechanics and a fatigue propagation law (i.e. Paris law) to predict the residual fatigue life-time and behaviour of the test specimens. Finally, a comparison between the experimental results and the numerical simulations was made to validate the numerical predictions as well as the overall performance of the crack arresters.
Martakos, G.; Andreasen, J. H.; Berggreen, C.; Thomsen, O. T.
2016-08-01
A novel crack arresting device has been implemented in sandwich panels and tested using a special rig to apply out-of-plane loading on the sandwich panel face-sheets. Fatigue crack propagation was induced in the face-core interface of the sandwich panels which met the crack arrester. The effect of the embedded crack arresters was evaluated in terms of the achieved enhancement of the damage tolerance of the tested sandwich panels. A finite element (FE) model of the experimental setup was used for predicting propagation rates and direction of the crack growth. The FE simulation was based on the adoption of linear fracture mechanics and a fatigue propagation law (i.e. Paris law) to predict the residual fatigue life-time and behaviour of the test specimens. Finally, a comparison between the experimental results and the numerical simulations was made to validate the numerical predictions as well as the overall performance of the crack arresters.
On Cracking of Charged Anisotropic Polytropes
Azam, M
2016-01-01
Recently in \\cite{34}, the role of electromagnetic field on the cracking of spherical polytropes has been investigated without perturbing charge parameter explicitly. In this study, we have examined the occurrence of cracking of anisotropic spherical polytropes through perturbing parameters like anisotropic pressure, energy density and charge. We consider two different types of polytropes in this study. We discuss the occurrence of cracking in two different ways $(i)$ by perturbing polytropic constant, anisotropy and charge parameter $(ii)$ by perturbing polytropic index, anisotropy and charge parameter for each case. We conclude that cracking appears for a wide range of parameters in both cases. Also, our results are reduced to \\cite{33} in the absence of charge.
Struggling with Fitzgerald's "Crack-Up" Essays.
Fulcher, James
1998-01-01
Ponders F. Scott Fitzgerald's essays about his "crack-up" and relates them to the many complex aspects of the struggles of a teacher using post-structural literary theory and teaching two-year college students. (SR)
The Effect of Water on Crack Interaction
Gaede, O.; Regenauer-Lieb, K.
2009-04-01
While the mechanical coupling between pore fluid and solid phase is relatively well understood, quantitative studies dealing with chemical-mechanical weakening in geological materials are rare. Many classical poroelastic problems can be addressed with the simple law of effective stress. Experimental studies show that the presence of a chemically active fluid can have effects that exceed the predictions of the law of effective stress. These chemical fluid-rock interactions alter the mechanical properties of the solid phase. Especially chemical-mechanical weakening has important ramifications for many areas of applied geosciences ranging from nuclear waste disposal over reservoir enhancement to fault stability. In this study, we model chemically induced changes of the size of the process zone around a crack tip. The knowledge of the process zone size is used to extend existing effective medium approximations of cracked solids. The stress distribution around a crack leads to a chemical potential gradient. This gradient will be a driver for mass diffusion through the solid phase. As an example, mass diffusion is towards the crack tip for a mode I crack. In this case a chemical reaction, that weakens the solid phase, will increase the size of the process zone around the crack tip. We apply our model to the prominent hydrolytic weakening effect observed in the quartz-water system (Griggs and Blacic, 1965). Hydrolytic weakening is generally attributed to water hydrolyzing the strong Si-O bonds of the quartz crystal. The hydrolysis replaces a Si-O-Si bridge with a relatively weak hydrogen bridge between two silanol groups. This enhances dislocation mobility and hence the yield stress is reduced. The plastic process zone around a crack tip is therefore larger in a wet crystal than in a dry crystal. We calculate the size of the process zone by solving this coupled mechanical-chemical problem with the Finite Element code ABAQUS. We consider single crack, collinear crack and
Inner Crack Detection Method for Cantilever Beams
Li, Zheng; Zhang, Wei; Li, Yixuan; Su, Xianyue
2008-02-01
In this paper, continuous wavelet transform has been performed to extract the inner crack information from the guided waves in cantilever beams, and the location and size of crack can be detected exactly. Considering its best time-frequency property, Gabor continuous wavelet transform is employed to analyze the complicated flexible wave signals in cantilever beam, which is inspirited by an impact on the free end. Otherwise, in order to enhance the sensitivity of detection for some small cracks, an improved method is discussed. Here, both computational and experimental methods are carried out for comparing the influence of different crack location in beam. Therefore, the method proposed can be expected to expand to a powerful damage detection method in a broad engineering application.
Initiating, growing and cracking of hydrogen blisters
Institute of Scientific and Technical Information of China (English)
REN Xuechong; SHAN Guangbin; CHU Wuyang; SU Yanjing; GAO Kewei; QIAO Lijie; JIANG Bo; CHEN Gang; CUI Yinhui
2005-01-01
The growing process of a hydrogen blister in a wheel steel was observed in situ with an optical microscope, and the fracture surfaces formed from broken blisters on a wheel steel and bulk metallic glass were investigated. The initiating, growing, cracking and breaking of hydrogen blisters are as follows. Supersaturated vacancies can increase greatly during charging and gather together into a vacancy cluster (small cavity). Hydrogen atoms become hydrogen molecules in the vacancy cluster and hydrogen molecules can stabilize the vacancy cluster. The small cavity becomes the nucleus of hydrogen blister. The blister will grow with entering of vacancies and hydrogen atoms. With increasing hydrogen pressure, plastic deformation occurs first, the hydrogen blister near the surface extrudes, and then cracks initiate along the wall of the blister with further increasing hydrogen pressure. A cracked blister can grow further through propagating of cracks until it breaks.
Dynamic Strain and Crack Monitoring Sensor Project
National Aeronautics and Space Administration — Los Gatos Research proposes to develop a new automated vehicle health monitoring sensor system capable of measuring loads and detecting crack, corrosion, and...
Finite Element Analysis of the Effect of Crack Depth and Crack Opening On the Girder
Directory of Open Access Journals (Sweden)
Md. Kamrul Hassan
2011-01-01
Full Text Available In order to identify the effect of crack depth and opening on the girder, finite element method (FEM has been used in this paper. In FE analysis, six nodded two dimensional plane elements (PLANE-2 are considered. Each node has two degree of freedom such as UX and UY. For the plane elements, a plane stress width/thickness option is chosen. For analytical model of crack of the concrete bridge girder, crack opening was increased from 0.2 mm to 1mm at an interval 0.2 mm and crack depth also increased from 30 mm to 150 mm at an interval 30 mm. The models were discreatized by a triangular mesh and convergence test was executed to obtain satisfactory results from the Plane-2 element. From the numerical result, it is seen that the principal stress become a higher with increased the crack depth and also crack opening with respect to load increasing. But the crack depth at 90 mm and crack opening at 0.6 mm, it has more effect on the girder because the stress concentration is higher than other crack depth and opening.
Calculation of the crack tip opening displacement of a crack lying in a subsurface layer
Higashida, Y.; Kamada, K.
1985-11-01
Crack tip opening displacement of a crack lying parallel to a free surface is calculated by counting the number of dislocations emitted into the plastic zone from a crack tip. A discrete dislocation model was used to simulate the crack, while varying the strength of dislocations so as to satisfy the boundary condition. The result coincides numerically with the predictions made in a previous paper, in which the stress intensity factor appearing in a theory of bulk materials was replaced with the one which includes the surface correction.
Directory of Open Access Journals (Sweden)
José A. F. O. Correia
2016-01-01
Full Text Available Structural design taking into account fatigue damage requires a thorough knowledge of the behaviour of materials. In addition to the monotonic behaviour of the materials, it is also important to assess their cyclic response and fatigue crack propagation behaviour under constant and variable amplitude loading. Materials whenever subjected to fatigue cracking may exhibit mean stress effects as well as crack closure effects. In this paper, a theoretical model based on the same initial assumptions of the analytical models proposed by Hudak and Davidson and Ellyin is proposed to estimate the influence of the crack closure effects. This proposal based further on Walker’s propagation law was applied to the P355NL1 steel using an inverse analysis (back-extrapolation of experimental fatigue crack propagation results. Based on this proposed model it is possible to estimate the crack opening stress intensity factor, Kop, the relationship between U=ΔKeff/ΔK quantity and the stress intensity factor, the crack length, and the stress ratio. This allows the evaluation of the influence of the crack closure effects for different stress ratio levels, in the fatigue crack propagation rates. Finally, a good agreement is found between the proposed theoretical model and the analytical models presented in the literature.
Hydration Process and Crack Tendency of Concrete Based on Resistivity and Restrained Shrinkage Crack
Institute of Scientific and Technical Information of China (English)
MUAZU Bawa Samaila; WEI Xiaosheng; WANG Lei
2016-01-01
Hydration process, crack potential and setting time of concrete grade C30, C40 and C50 were monitored by using a non-contact electrical resistivity apparatus, a novel plastic ring mould and penetration resistance methods, respectively. The results show the highest resistivity of C30 at the early stage until a point when C50 accelerated and overtook the others. It has been experimentally conifrmed that the crossing point of C30 and C50 corresponds to the ifnal setting time of C50. From resistivity derivative curve, four different stages were observed upon which the hydration process is classiifed; these are dissolution, induction, acceleration and deceleration periods. Consequently, restrained shrinkage crack and setting time results demonstrated that C50 set and cracked the earliest. The cracking time of all the samples occurred within a reasonable experimental period thus the novel plastic ring is a convenient method for predicting concrete’s crack potential. The highest inlfection time (ti) obtained from resistivity curve and the ifnal setting time (tf) were used with crack time (tc) in coming up with mathematical models for the prediction of concrete’s cracking age for the range of concrete grade considered. Finally, an ANSYS numerical simulation supports the experimental ifndings in terms of the earliest crack age of C50 and the crack location.
Directory of Open Access Journals (Sweden)
COTRUMBĂ Mirela
2015-06-01
Full Text Available This paper presents how descriptive geometry contributes to the achievement of intersections of simple objects and isometric axonometric representation of these intersections. It also highlights the role of descriptive geometry on acquiring skills in Technical Drawing, in representation of objects intersection. All illustrations in this paper are made using Microsoft Office Word Drawing Toolbar and AutoCAD software.
Molecular dynamics simulation of propagating cracks
Mullins, M.
1982-01-01
Steady state crack propagation is investigated numerically using a model consisting of 236 free atoms in two (010) planes of bcc alpha iron. The continuum region is modeled using the finite element method with 175 nodes and 288 elements. The model shows clear (010) plane fracture to the edge of the discrete region at moderate loads. Analysis of the results obtained indicates that models of this type can provide realistic simulation of steady state crack propagation.
Fatigue Crack Initiation Analysis in 1060 Steel
Directory of Open Access Journals (Sweden)
L. Gyansah
2010-07-01
Full Text Available This study investigates initiation of small cracks on dumble-shaped plate type specimens of 1060steel at the load ratio of R = 0 under varied cyclic stress amplitudes between 0.6 and 1.0 of yield stress usingthe Instron machine (model: 8501. Sinusoidal wave of a frequency of 10 Hz was used in the experiment. Theexperiment was conducted at a room temperature of 23ºC. Each test for different applied stress ranges wascarried out for 2×104 cycles. Microstructure and fractography of the fractured specimen were also analyzed.Nucleations of cracks were observed at Ferrite-Ferrite G rain Boundary (FFGB as well as inside Ferrite GrainBody (FGB, but the FFGB location was preferred. Results show that the average length of FFGB cracks isfound larger than that of the average length of cracks initiated inside FGB at the same cyclic loading conditions.The formation of slip band inside grain body, slip band impingement at grain boundary and elastic-plasticincompatibility synergistically have significant influence on fatigue crack initiation in 1060 steel. Additionally,the formation of irregular voids inside slip bands, initiation and growth of small voids at grain boundary andthe subsequent joining of these with other voids were seen as specific characteristics of 1060 steel. It was alsoestablished that cracks nucleate both at grain boundary and inside grain body in 1060 steel in the investigateddomain of 0.6 to 1.0Fy.It was further established that the orientation of the grain body cracks at low stress levelis greater than 45º and the average angle of orientation of these cracks increases like that of grain boundarycracks with increased magnitude of stress range.
Molecular dynamics simulation of propagating cracks
Mullins, M.
1982-01-01
Steady state crack propagation is investigated numerically using a model consisting of 236 free atoms in two (010) planes of bcc alpha iron. The continuum region is modeled using the finite element method with 175 nodes and 288 elements. The model shows clear (010) plane fracture to the edge of the discrete region at moderate loads. Analysis of the results obtained indicates that models of this type can provide realistic simulation of steady state crack propagation.
Atomistic observation of a crack tip approaching coherent twin boundaries.
Liu, L; Wang, J; Gong, S K; Mao, S X
2014-03-18
Coherent twin boundaries (CTBs) in nano-twinned materials could improve crack resistance. However, the role of the CTBs during crack penetration has never been explored at atomic scale. Our in situ observation on nano-twinned Ag under a high resolution transmission electron microscope (HRTEM) reveals the dynamic processes of a crack penetration across the CTBs, which involve alternated crack tip blunting, crack deflection, twinning/detwinning and slip transmission across the CTBs. The alternated blunting processes are related to the emission of different types of dislocations at the crack tip and vary with the distance of the crack tip from the CTBs.
Crack shape analysis of PWSCC in S/G tubings
Energy Technology Data Exchange (ETDEWEB)
Park, I. K. [Sunmon Univ., Chonan (Korea, Republic of)
2000-10-01
Crack shape of PWSCC was analyzed, based on the fractured pulled-out S/G tubings of Ulchin-1 steam generator. The shape of the cracks in kiss roll transitions was elliptical shape for short cracks, and car shape for long cracks with flat crack front. The bulging was observed under the inner wall after shot-peening. Crack shape change after shot-peening was resulted from the crack growth restraint in axial direction due to compressive residual stresses on the primary side surface.
Thermally activated processes of fatigue crack growth in steels
Tanaka, Masaki; Fujii, Atsushi; Noguchi, Hiroshi; Higashida, Kenji
2014-02-01
Fatigue crack growth rates in steels at high and low temperatures have been investigated using Paris curves. The fatigue crack growth rates at high temperatures are quite different from those at low temperatures. Arrhenius plots between fatigue crack growth rate (da/dN) and test temperatures at constant stress intensity factor range (ΔKI) indicate a difference of the rate-controlling process for fatigue crack growth with temperature. Slip deformation at the crack tip governs fatigue crack growth at high temperatures, while hydrogen diffusion is associated with crack growth at low temperatures.
Hierarchical Formation of Intrasplat Cracks in Thermal Spray Ceramic Coatings
Chen, Lin; Yang, Guan-Jun; Li, Cheng-Xin; Li, Chang-Jiu
2016-06-01
Intrasplat cracks, an essential feature of thermally sprayed ceramic coatings, play important roles in determining coating properties. However, final intrasplat crack patterns are always considered to be disordered and irregular, resulting from random cracking during splat cooling, since the detailed formation process of intrasplat cracks has scarcely been considered. In the present study, the primary formation mechanism for intrasplat cracking was explored based on both experimental observations and mechanical analysis. The results show that the intrasplat crack pattern in thermally sprayed ceramic splats presents a hierarchical structure with four sides and six neighbors, indicating that intrasplat crack patterns arise from successive domain divisions due to sequential cracking during splat cooling. The driving forces for intrasplat cracking are discussed, and the experimental data quantitatively agree well with theoretical results. This will provide insight for further coating structure designs and tailoring by tuning of intrasplat cracks.
Electromagnetic pulsed thermography for natural cracks inspection
Gao, Yunlai; Tian, Gui Yun; Wang, Ping; Wang, Haitao; Gao, Bin; Woo, Wai Lok; Li, Kongjing
2017-02-01
Emerging integrated sensing and monitoring of material degradation and cracks are increasingly required for characterizing the structural integrity and safety of infrastructure. However, most conventional nondestructive evaluation (NDE) methods are based on single modality sensing which is not adequate to evaluate structural integrity and natural cracks. This paper proposed electromagnetic pulsed thermography for fast and comprehensive defect characterization. It hybrids multiple physical phenomena i.e. magnetic flux leakage, induced eddy current and induction heating linking to physics as well as signal processing algorithms to provide abundant information of material properties and defects. New features are proposed using 1st derivation that reflects multiphysics spatial and temporal behaviors to enhance the detection of cracks with different orientations. Promising results that robust to lift-off changes and invariant features for artificial and natural cracks detection have been demonstrated that the proposed method significantly improves defect detectability. It opens up multiphysics sensing and integrated NDE with potential impact for natural understanding and better quantitative evaluation of natural cracks including stress corrosion crack (SCC) and rolling contact fatigue (RCF).
Nonlinear modal methods for crack localization
Sutin, Alexander; Ostrovsky, Lev; Lebedev, Andrey
2003-10-01
A nonlinear method for locating defects in solid materials is discussed that is relevant to nonlinear modal tomography based on the signal cross-modulation. The scheme is illustrated by a theoretical model in which a thin plate or bar with a single crack is excited by a strong low-frequency wave and a high-frequency probing wave (ultrasound). A crack is considered as a small contact-type defect which does not perturb the modal structure of sound in linear approximation but creates combinational-frequency components whose amplitudes depend on their closeness to a resonance and crack position. Using different crack models, including the hysteretic ones, the nonlinear part of its volume variations under the given stress and then the combinational wave components in the bar can be determined. Evidently, their amplitude depends strongly on the crack position with respect to the peaks or nodes of the corresponding linear signals which can be used for localization of the crack position. Exciting the sample by sweeping ultrasound frequencies through several resonances (modes) reduces the ambiguity in the localization. Some aspects of inverse problem solution are also discussed, and preliminary experimental results are presented.
Electromagnetic pulsed thermography for natural cracks inspection
Gao, Yunlai; Tian, Gui Yun; Wang, Ping; Wang, Haitao; Gao, Bin; Woo, Wai Lok; Li, Kongjing
2017-01-01
Emerging integrated sensing and monitoring of material degradation and cracks are increasingly required for characterizing the structural integrity and safety of infrastructure. However, most conventional nondestructive evaluation (NDE) methods are based on single modality sensing which is not adequate to evaluate structural integrity and natural cracks. This paper proposed electromagnetic pulsed thermography for fast and comprehensive defect characterization. It hybrids multiple physical phenomena i.e. magnetic flux leakage, induced eddy current and induction heating linking to physics as well as signal processing algorithms to provide abundant information of material properties and defects. New features are proposed using 1st derivation that reflects multiphysics spatial and temporal behaviors to enhance the detection of cracks with different orientations. Promising results that robust to lift-off changes and invariant features for artificial and natural cracks detection have been demonstrated that the proposed method significantly improves defect detectability. It opens up multiphysics sensing and integrated NDE with potential impact for natural understanding and better quantitative evaluation of natural cracks including stress corrosion crack (SCC) and rolling contact fatigue (RCF). PMID:28169361
Dynamic behaviour of a rotating cracked beam
Yashar, Ahmed; Ghandchi-Tehrani, Maryam; Ferguson, Neil
2016-09-01
This paper presents a new approach to investigate and analyse the vibrational behaviour of cracked rotating cantilever beams, which can for example represent helicopter or wind turbine blades. The analytical Hamiltonian method is used in modelling the rotating beam and two numerical methods, the Rayleigh-Ritz and FEM, are used to study the natural frequencies and the mode shapes of the intact rotating beams. Subsequently, a crack is introduced into the FE model and simulations are performed to identify the modal characteristics for an open cracked rotating beam. The effect of various parameters such as non-dimensional rotating speed, hub ratio and slenderness ratio are investigated for both the intact and the cracked rotating beam, and in both directions of chordwise and flapwise motion. The veering phenomena in the natural frequencies as a function of the rotational speed and the buckling speed are considered with respect to the slenderness ratio. In addition, the mode shapes obtained for the flapwise vibration are compared using the modal assurance criterion (MAC). Finally, a new three dimensional design chart is produced, showing the effect of crack location and depth on the natural frequencies of the rotating beam. This chart will be subsequently important in identifying crack defects in rotating blades.
Protection of brittle film against cracking
Musil, J.; Sklenka, J.; Čerstvý, R.
2016-05-01
This article reports on the protection of the brittle Zrsbnd Sisbnd O film against cracking in bending by the highly elastic top film (over-layer). In experiments the Zrsbnd Sisbnd O films with different elemental composition and structure were used. Both the brittle and highly elastic films were prepared by magnetron sputtering using a dual magnetron. The brittle film easily cracks in bending. On the other hand, the highly elastic film exhibits enhanced resistance to cracking in bending. Main characteristic parameters of both the brittle and highly elastic films are given. Special attention is devoted to the effect of the structure (crystalline, amorphous) of both the brittle and highly elastic top film on the resistance of cracking of the brittle film. It was found that (1) both the X-ray amorphous and crystalline brittle films easily crack in bending, (2) the highly elastic film can have either X-ray amorphous or crystalline structure and (3) both the X-ray amorphous and crystalline, highly elastic top films perfectly protect the brittle films against cracking in bending. The structure, mechanical properties and optical transparency of the brittle and highly elastic sputtered Zrsbnd Sisbnd O films are described in detail. At the end of this article, the principle of the low-temperature formation of the highly elastic films is also explained.
Fatigue crack propagation analysis of plaque rupture.
Pei, Xuan; Wu, Baijian; Li, Zhi-Yong
2013-10-01
Rupture of atheromatous plaque is the major cause of stroke or heart attack. Considering that the cardiovascular system is a classic fatigue environment, plaque rupture was treated as a chronic fatigue crack growth process in this study. Fracture mechanics theory was introduced to describe the stress status at the crack tip and Paris' law was used to calculate the crack growth rate. The effect of anatomical variation of an idealized plaque cross-section model was investigated. The crack initiation was considered to be either at the maximum circumferential stress location or at any other possible locations around the lumen. Although the crack automatically initialized at the maximum circumferential stress location usually propagated faster than others, it was not necessarily the most critical location where the fatigue life reached its minimum. We found that the fatigue life was minimum for cracks initialized in the following three regions: the midcap zone, the shoulder zone, and the backside zone. The anatomical variation has a significant influence on the fatigue life. Either a decrease in cap thickness or an increase in lipid pool size resulted in a significant decrease in fatigue life. Comparing to the previously used stress analysis, this fatigue model provides some possible explanations of plaque rupture at a low stress level in a pulsatile cardiovascular environment, and the method proposed here may be useful for further investigation of the mechanism of plaque rupture based on in vivo patient data.
Stress corrosion cracking of copper canisters
Energy Technology Data Exchange (ETDEWEB)
King, Fraser (Integrity Corrosion Consulting Limited (Canada)); Newman, Roger (Univ. of Toronto (Canada))
2010-12-15
A critical review is presented of the possibility of stress corrosion cracking (SCC) of copper canisters in a deep geological repository in the Fennoscandian Shield. Each of the four main mechanisms proposed for the SCC of pure copper are reviewed and the required conditions for cracking compared with the expected environmental and mechanical loading conditions within the repository. Other possible mechanisms are also considered, as are recent studies specifically directed towards the SCC of copper canisters. The aim of the review is to determine if and when during the evolution of the repository environment copper canisters might be susceptible to SCC. Mechanisms that require a degree of oxidation or dissolution are only possible whilst oxidant is present in the repository and then only if other environmental and mechanical loading conditions are satisfied. These constraints are found to limit the period during which the canisters could be susceptible to cracking via film rupture (slip dissolution) or tarnish rupture mechanisms to the first few years after deposition of the canisters, at which time there will be insufficient SCC agent (ammonia, acetate, or nitrite) to support cracking. During the anaerobic phase, the supply of sulphide ions to the free surface will be transport limited by diffusion through the highly compacted bentonite. Therefore, no HS. will enter the crack and cracking by either of these mechanisms during the long term anaerobic phase is not feasible. Cracking via the film-induced cleavage mechanism requires a surface film of specific properties, most often associated with a nano porous structure. Slow rates of dissolution characteristic of processes in the repository will tend to coarsen any nano porous layer. Under some circumstances, a cuprous oxide film could support film-induced cleavage, but there is no evidence that this mechanism would operate in the presence of sulphide during the long-term anaerobic period because copper sulphide
Biogenic Cracks in Porous Rock
Hemmerle, A.; Hartung, J.; Hallatschek, O.; Goehring, L.; Herminghaus, S.
2014-12-01
Microorganisms growing on and inside porous rock may fracture it by various processes. Some of the mechanisms of biofouling and bioweathering are today identified and partially understood but most emphasis is on chemical weathering, while mechanical contributions have been neglected. However, as demonstrated by the perseverance of a seed germinating and cracking up a concrete block, the turgor pressure of living organisms can be very significant. Here, we present results of a systematic study of the effects of the mechanical forces of growing microbial populations on the weathering of porous media. We designed a model porous medium made of glass beads held together by polydimethylsiloxane (PDMS), a curable polymer. The rheological properties of the porous medium, whose shape and size are tunable, can be controlled by the ratio of crosslinker to base used in the PDMS (see Fig. 1). Glass and PDMS being inert to most chemicals, we are able to focus on the mechanical processes of biodeterioration, excluding any chemical weathering. Inspired by recent measurements of the high pressure (~0.5 Mpa) exerted by a growing population of yeasts trapped in a microfluidic device, we show that yeast cells can be cultured homogeneously within porous medium until saturation of the porous space. We investigate then the effects of such an inner pressure on the mechanical properties of the sample. Using the same model system, we study also the complex interplay between biofilms and porous media. We focus in particular on the effects of pore size on the penetration of the biofilm within the porous sample, and on the resulting deformations of the matrix, opening new perspectives into the understanding of life in complex geometry. Figure 1. Left : cell culture growing in a model porous medium. The white spheres represent the grains, bonds are displayed in grey, and microbes in green. Right: microscopy picture of glass beads linked by PDMS bridges, scale bar: 100 μm.
Road Impedance Model Study under the Control of Intersection Signal
Directory of Open Access Journals (Sweden)
Yunlin Luo
2015-01-01
Full Text Available Road traffic impedance model is a difficult and critical point in urban traffic assignment and route guidance. The paper takes a signalized intersection as the research object. On the basis of traditional traffic wave theory including the implementation of traffic wave model and the analysis of vehicles’ gathering and dissipating, the road traffic impedance model is researched by determining the basic travel time and waiting delay time. Numerical example results have proved that the proposed model in this paper has received better calculation performance compared to existing model, especially in flat hours. The values of mean absolute percentage error (MAPE and mean absolute deviation (MAD are separately reduced by 3.78% and 2.62 s. It shows that the proposed model has feasibility and availability in road traffic impedance under intersection signal.
Thermodynamics of Intersecting Black Branes from Interacting Elementary Branes
Morita, Takeshi
2015-01-01
If an Einstein-Maxwell-Dilaton system admits the extreme brane solution in which no force works between the parallel branes, the collective motion of nearly parallel branes exhibits the thermodynamical properties which are coincident with those of the corresponding black branes at low energy regime (up to unfixed numerical factors). Hence it may provide the microscopic description of the black branes ($p$-soup proposal). This fact motivates us to test this proposal in the intersecting black branes which have multiple brane charges and/or momentum along the brane direction. We consider the case that the multiple branes satisfy the intersection rule and feel no force when they are static, and find the agreement to the black hole thermodynamics.
Fat People of Color: Emergent Intersectional Discourse Online
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Apryl A. Williams
2017-02-01
Full Text Available Though the general populace has been introduced to the idea of thin privilege, the fat activist movement has been slow in gaining momentum. This is due, in part, to the symbolic annihilation of “fat” people in media. Within the fat activist framework, women of color are often further excluded from the overarching discourse and white privilege is sometimes unacknowledged. Taking an intersectional approach, I examine the Tumblr page, Fat People of Color. I use Critical Technocultural Discourse Analysis (CTDA to examine the images and conversations posted by users. Findings reveal that Fat People of Color uses an intersectional, communal approach to posit counter-narratives against normative ideas about white thinness. This research contributes to an understudied area of sociological inquiry by presenting an analysis of the experience of “fat” women of color within a feminist framework. Ignoring the variation of experiences strengthens the types of privileges that fat activism and feminism hope to dismantle.
A New Data Layout For Set Intersection on GPUs
DEFF Research Database (Denmark)
Amossen, Rasmus Resen; Pagh, Rasmus
2011-01-01
Set intersection is the core in a variety of problems, e.g. frequent itemset mining and sparse boolean matrix multiplication. It is well-known that large speed gains can, for some computational problems, be obtained by using a graphics processing unit (GPU) as a massively parallel computing device....... However, GPUs require highly regular control flow and memory access patterns, and for this reason previous GPU methods for intersecting sets have used a simple bitmap representation. This representation requires excessive space on sparse data sets. In this paper we present a novel data layout, BATMAP....... The main finding is that our method is able to achieve speedups over both Apriori and FP-growth when the number of distinct items is large, and the density of the problem instance is above 1%. Previous implementations of frequent itemset mining on GPU have not been able to show speedups over the best...
Intersections of S-branes with waves and monopoles
Energy Technology Data Exchange (ETDEWEB)
Besken, Mert, E-mail: mbesken@physics.ucla.edu [Dept. of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Deger, Nihat Sadik, E-mail: sadik.deger@boun.edu.tr [Dept. of Mathematics, Bogazici University, Bebek, 34342 Istanbul (Turkey)
2015-05-15
We construct intersections of S-branes with waves and Kaluza–Klein monopoles. There are several possible ways to add a monopole to an S-brane solution similar to p-branes. On the other hand, one may add a wave only to the transverse space of an S-brane unlike a p-brane where wave resides on its worldvolume. The metric function of the wave is a harmonic function of the remaining transverse directions and an extra condition on integration constants is needed. We also show that it is not possible to add an S-brane to p-brane intersections whose near horizon geometry has an AdS part.
Intersection of a Sure Ellipsoid and a Random Ellipsoid
Directory of Open Access Journals (Sweden)
Arjun K. Gupta
2012-07-01
Full Text Available Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif";} An Expression for the expected value of the intersection of a sure sphere and a random sphere has been derived by Laurent (1974. In the present paper we derive the expression for the expected intersection volume of a sure ellipsoid and a random ellipsoid
SOFTWARE FOR SYNTHESIS OF COMPLIANT MECHANISMS WITHOUT INTERSECTING ELEMENTS
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Andrija P. Milojević
2014-01-01
Full Text Available A compliant mechanism is defined as a single piece structure that transfer motion or force through elastic deformation. The synthesis of this kind of mechanisms represents a challenging task, especially because their flexible segments usually must undergo large, nonlinear deflections which include difficult nonlinear analysis. In this paper the new software for synthesis of compliant mechanisms is developed. The software uses an improved topology optimization technique that is especially useful when the designer does not have a particular compliant mechanism already in mind. Intersection between elements in the compliant mechanisms obtained by using existing topology optimization technique often increases stiffness of the structure which need to be flexible. The topology optimization technique is improved in the software so that compliant mechanisms without intersecting elements are obtained. The methodology that software uses and its capability will be shown on the examples of synthesis of the compliant gripper and the compliant displacement inverter.
From r-spin intersection numbers to Hodge integrals
Energy Technology Data Exchange (ETDEWEB)
Ding, Xiang-Mao; Li, Yuping [Institute of Applied Mathematics, Academy of Mathematics and Systems Science,Chinese Academy of Sciences,Beijing 100190, People’s Republic of (China); Meng, Lingxian [Institute of Applied Mathematics, Academy of Mathematics and Systems Science,Chinese Academy of Sciences,Beijing 100190, People’s Republic of (China); College of Mathematics and Information Science, Zhengzhou University of Light Industry,Zhengzhou 450002, People’s Republic of (China)
2016-01-04
Generalized Kontsevich Matrix Model (GKMM) with a certain given potential is the partition function of r-spin intersection numbers. We represent this GKMM in terms of fermions and expand it in terms of the Schur polynomials by boson-fermion correspondence, and link it with a Hurwitz partition function and a Hodge partition by operators in a (GL)-hat (∞) group. Then, from a W{sub 1+∞} constraint of the partition function of r-spin intersection numbers, we get a W{sub 1+∞} constraint for the Hodge partition function. The W{sub 1+∞} constraint completely determines the Schur polynomials expansion of the Hodge partition function.
The Standard Model from Stable Intersecting Brane World Orbifolds
Blumenhagen, R; Lüst, Dieter; Ott, T; Blumenhagen, Ralph; Kors, Boris; Lust, Dieter; Ott, Tassilo
2001-01-01
We analyze the perturbative stability of non-supersymmetric intersecting brane world models on tori. Besides the dilaton tadpole, a dynamical instability in the complex structure moduli space occurs at string disc level, which drives the background geometry to a degenerate limit. We show that in certain orbifold models this latter instability is absent as the relevant moduli are frozen. We construct explicit examples of such orbifold intersecting brane world models and discuss the phenomenological implications of a three generation Standard Model which descends naturally from an SU(5) GUT theory. It turns out that various phenomenological issues require the string scale to be at least of the order of the GUT scale. As a major difference compared to the Standard Model, some of the Yukawa couplings are excluded so that the standard electroweak Higgs mechanism with a fundamental Higgs scalar is not realized in this set-up.
Intersection of a Sure Ellipsoid and a Random Ellipsoid
Directory of Open Access Journals (Sweden)
Arjun K. Gupta
2012-07-01
Full Text Available Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif";} An Expression for the expected value of the intersection of a sure sphere and a random sphere has been derived by Laurent (1974. In the present paper we derive the expression for the expected intersection volume of a sure ellipsoid and a random ellipsoid
Sigma-model soliton intersections from exceptional calibrations
Portugues, R
2002-01-01
A first-order `BPS' equation is obtained for 1/8 supersymmetric intersections of soliton-membranes (lumps) of supersymmetric (4+1)-dimensional massless sigma models, and a special non-singular solution is found that preserves 1/4 supersymmetry. For 4-dimensional hyper-K\\"ahler target spaces ($HK_4$) the BPS equation is shown to be the low-energy limit of the equation for a Cayley-calibrated 4-surface in $\\bE^4\\times HK_4$. Similar first-order equations are found for stationary intersections of Q-lump-membranes of the massive sigma model, but now generic solutions preserve either 1/8 supersymmetry or no supersymmetry, depending on the time orientation.
The Standard Model from stable intersecting brane world orbifolds
Energy Technology Data Exchange (ETDEWEB)
Blumenhagen, Ralph E-mail: blumenha@physik.hu-berlin.de; Koers, Boris E-mail: koers@physik.hu-berlin.de; Luest, Dieter E-mail: luest@physik.hu-berlin.de; Ott, Tassilo E-mail: ott@physik.hu-berlin.de
2001-11-19
We analyze the perturbative stability of non-supersymmetric intersecting brane world models on tori. Besides the dilaton tadpole, a dynamical instability in the complex structure moduli space occurs at string disc level, which drives the background geometry to a degenerate limit. We show that in certain orbifold models this latter instability is absent as the relevant moduli are frozen. We construct explicit examples of such orbifold intersecting brane world models and discuss the phenomenological implications of a three generation Standard Model which descends naturally from an SU(5) GUT theory. It turns out that various phenomenological issues require the string scale to be at least of the order of the GUT scale. As a major difference compared to the Standard Model, some of the Yukawa couplings are excluded so that the standard electroweak Higgs mechanism with a fundamental Higgs scalar is not realized in this set-up.
Infiuence of Bicycle Traffic on Capacity of Typical Signalized Intersection
Institute of Scientific and Technical Information of China (English)
CHEN Xiaoming; SHAO Chunfu; YUE Hao
2007-01-01
Bicycle traffic has a significant effect on the capacity of signalized intersections. This paper divides the influence of bicyclists on vehicular flow into four types with the time durations estimated based on probability, shock wave, and gap acceptance theory. Vehicular saturation flow rate is predicted for various conditions on the basis of the speed-flow curve for the capacity of typical intersections influenced by bicycle traffic.The model overcomes the limitations of the Highway Capacity Manual (HCM, 2000) method for left-turns due to data collection, and takes into account the effect of trapped bicycles on the through vehicular traffic.The numerical results show that the left-turn and through capacities predicted by the model are lower than those of the HCM method. The right-turn capacity is close to that of the HCM method at Iow bicycle volumes and higher than that of the HCM method at high bicycle volumes.
Environmentally assisted cracking in light water reactors.
Energy Technology Data Exchange (ETDEWEB)
Chopra, O. K.; Chung, H. M.; Clark, R. W.; Gruber, E. E.; Shack, W. J.; Soppet, W. K.; Strain, R. V.
2007-11-06
This report summarizes work performed by Argonne National Laboratory on fatigue and environmentally assisted cracking (EAC) in light water reactors (LWRs) from January to December 2002. Topics that have been investigated include: (a) environmental effects on fatigue crack initiation in carbon and low-alloy steels and austenitic stainless steels (SSs), (b) irradiation-assisted stress corrosion cracking (IASCC) of austenitic SSs in BWRs, (c) evaluation of causes and mechanisms of irradiation-assisted cracking of austenitic SS in PWRs, and (d) cracking in Ni-alloys and welds. A critical review of the ASME Code fatigue design margins and an assessment of the conservation in the current choice of design margins are presented. The existing fatigue {var_epsilon}-N data have been evaluated to define the effects of key material, loading, and environmental parameters on the fatigue lives of carbon and low-alloy steels and austenitic SSs. Experimental data are presented on the effects of surface roughness on fatigue crack initiation in these materials in air and LWR environments. Crack growth tests were performed in BWR environments on SSs irradiated to 0.9 and 2.0 x 10{sup 21} n x cm{sup -2}. The crack growth rates (CGRs) of the irradiated steels are a factor of {approx}5 higher than the disposition curve proposed in NUREG-0313 for thermally sensitized materials. The CGRs decreased by an order of magnitude in low-dissolved oxygen (DO) environments. Slow-strain-rate tensile (SSRT) tests were conducted in high-purity 289 C water on steels irradiated to {approx}3 dpa. The bulk S content correlated well with the susceptibility to intergranular SCC in 289 C water. The IASCC susceptibility of SSs that contain >0.003 wt. % S increased drastically. bend tests in inert environments at 23 C were conducted on broken pieces of SSRT specimens and on unirradiated specimens of the same materials after hydrogen charging. The results of the tests and a review of other data in the literature
Evaluation method of cracking resistance of lightweight aggregate concrete
Institute of Scientific and Technical Information of China (English)
季韬; 张彬彬; 陈永波; 庄一舟
2014-01-01
The cracking behavior of lightweight aggregate concrete (LWAC) was investigated by mechanical analysis, SEM and cracking-resistant test where a shrinkage-restrained ring with a clapboard was used. The relationship between the ceramsite type and the cracking resistance of LWAC was built up and compared with that of normal-weight coarse aggregate concrete (NWAC). A new method was proposed to evaluate the cracking resistance of concrete, where the concepts of cracking coefficient ζt(t) and the evaluation index Acr(t) were proposed, and the development of micro-cracks and damage accumulation were recognized. For the concrete with an ascending cracking coefficient curve, the larger Acr(t) is, the lower cracking resistance of concrete is. For the concrete with a descending cracking coefficient curve, the larger Acr(t) is, the stronger the cracking resistance of concrete is. The evaluation results show that in the case of that all the three types of coarse aggregates in concrete are pre-soaked for 24 h, NWAC has the lowest cracking resistance, followed by the LWAC with lower water absorption capacity ceramsite and the LWAC with higher water absorption capacity ceramsite has the strongest cracking resistance. The proposed method has obvious advantages over the cracking age method, because it can evaluate the cracking behavior of concrete even if the concrete has not an observable crack.
Intersection Theory, Integrable Hierarchies and Topological Field Theory
Dijkgraaf, Robbert
1992-01-01
In these lecture notes we review the various relations between intersection theory on the moduli space of Riemann surfaces, integrable hierarchies of KdV type, matrix models, and topological quantum field theories. We explain in particular why matrix integrals of the type considered by Kontsevich naturally appear as tau-functions associated to minimal models. Our starting point is the extremely simple form of the string equation for the topological (p,1) models, where the so-called Baker-Akhi...
Cryptanalysis and improvement of a quantum private set intersection protocol
Cheng, Xiaogang; Guo, Ren; Chen, Yonghong
2017-02-01
A recent Quantum Private Set Intersection (QPSI) scheme is crypt-analyzed. The original claimed communication overhead is shown to be not accurate. And the original security definition is passive and not fair. To ensure fairness, a passive third party is introduced. It is also shown that unconditional fairness of QPSI protocol is impossible. Since otherwise, it would violate a well-known impossible quantum cryptography result.
Intersecting D-branes and black hole entropy
Behrndt, Klaus; Bergshoeff, Eric
1996-01-01
In four dimensions there are 4 different types of extremal Maxwell/scalar black holes characterized by a scalar coupling parameter a with a = 0, 1/âˆš3, 1, âˆš3. These black holes can be described as intersections of ten-dimensional non-singular Ramond-Ramond objects, i.e, D-branes, waves and Taub-N
Nonempty intersection theorems in topological spaces with applications
Institute of Scientific and Technical Information of China (English)
Min FANG; Nan-jing HUANG
2009-01-01
In this paper,we establish some new nonempty intersection theorems for generalized L-KKM mappings and prove some new fixed point theorems for set-valued mappings under suitable conditions in topological spaces.As applications,an existence theorem for an equilibrium problem with lower and upper bounds and two existence theorems for a quasi-equilibrium problem with lower and upper bounds are obtained in topological spaces.Our results generalize some known results in the literature.
Conical intersection dynamics of the primary photoisomerization event in vision.
Polli, Dario; Altoè, Piero; Weingart, Oliver; Spillane, Katelyn M; Manzoni, Cristian; Brida, Daniele; Tomasello, Gaia; Orlandi, Giorgio; Kukura, Philipp; Mathies, Richard A; Garavelli, Marco; Cerullo, Giulio
2010-09-23
Ever since the conversion of the 11-cis retinal chromophore to its all-trans form in rhodopsin was identified as the primary photochemical event in vision, experimentalists and theoreticians have tried to unravel the molecular details of this process. The high quantum yield of 0.65 (ref. 2), the production of the primary ground-state rhodopsin photoproduct within a mere 200 fs (refs 3-7), and the storage of considerable energy in the first stable bathorhodopsin intermediate all suggest an unusually fast and efficient photoactivated one-way reaction. Rhodopsin's unique reactivity is generally attributed to a conical intersection between the potential energy surfaces of the ground and excited electronic states enabling the efficient and ultrafast conversion of photon energy into chemical energy. But obtaining direct experimental evidence for the involvement of a conical intersection is challenging: the energy gap between the electronic states of the reacting molecule changes significantly over an ultrashort timescale, which calls for observational methods that combine high temporal resolution with a broad spectral observation window. Here we show that ultrafast optical spectroscopy with sub-20-fs time resolution and spectral coverage from the visible to the near-infrared allows us to follow the dynamics leading to the conical intersection in rhodopsin isomerization. We track coherent wave-packet motion from the photoexcited Franck-Condon region to the photoproduct by monitoring the loss of reactant emission and the subsequent appearance of photoproduct absorption, and find excellent agreement between the experimental observations and molecular dynamics calculations that involve a true electronic state crossing. Taken together, these findings constitute the most compelling evidence to date for the existence and importance of conical intersections in visual photochemistry.
MATLAB Simulation of Fuzzy Traffic Controller for Multilane Isolated Intersection
2010-01-01
This paper presents a MATLAB simulation of fuzzy traffic controller for controlling traffic flow at multilane isolated signalized intersection. The controller is developed based on the waiting time and vehicles queue length at current green phase, and vehicles queue lengths at the other phases. For control strategy, the controllercontrols the traffic light timings and phase sequence to ensure smooth flow of traffic with minimal waiting time, queue length and delay time. In this research, the ...
SELF-INTERSECTION LOCAL TIME OF ADDITIVE LEVY PROCESS
Institute of Scientific and Technical Information of China (English)
钟玉泉; 胡迪鹤
2002-01-01
This article discusses the problem of existence of jointly continuous self-process X = {X(t), t ∈ RN+)} which has the decomposition X = X1 X2 ... Xv, eachThey prove that if Nrα＞ d(r - 1), then a jointly continuous local time of Z, i.e. theself-intersection local time of X, can be obtained.
Precision of Points Computed from Intersections of Lines or Planes
DEFF Research Database (Denmark)
Cederholm, Jens Peter
2004-01-01
estimates the precision of the points. When using laser scanning a similar problem appears. A laser scanner captures a 3-D point cloud, not the points of real interest. The suggested method can be used to compute three-dimensional coordinates of the intersection of three planes estimated from the point...... cloud. The method can also be used to predict the precision of the points prior to a survey. An example is given....
Fuels Performance: Navigating the Intersection of Fuels and Combustion (Brochure)
Energy Technology Data Exchange (ETDEWEB)
2014-12-01
Researchers at the National Renewable Energy Laboratory (NREL), the only national laboratory dedicated 100% to renewable energy and energy efficiency, recognize that engine and infrastructure compatibility can make or break the impact of even the most promising fuel. NREL and its industry partners navigate the intersection of fuel chemistry, ignition kinetics, combustion, and emissions, with innovative approaches to engines and fuels that meet drivers' expectations, while minimizing petroleum use and GHGs.
Imploded test-chamber for an ISR intersection
1977-01-01
At the ISR intersection points the vacuum chambers had to be as "transparent" as possible, for the p-p collision product particles to reach the detectors with minimum hindrance. This meant the choice of a light, yet very strong, metal; minimum thickness; and corrugation for mechanical strength. The test-chamber seen here was made of 0.6 mm thick corrugated titanium, obviously not strong enough to withstand the atmospheric pressure.
Some phenomenology of intersecting D-brane models
Energy Technology Data Exchange (ETDEWEB)
Kane, Gordon L.; Kumar, Piyush; /Michigan U., MCTP; Lykken, Joseph D.; /Fermilab; Wang, Ting T.; /Michigan U., MCTP
2004-11-01
We present some phenomenology of a new class of intersecting D-brane models. Soft SUSY breaking terms for these models are calculated in the complex structure (u)-moduli dominant SUSY breaking approach (in type IIA). In this case, the dependence of the soft terms on the Yukawas and Wilson lines drops out. These soft terms have a different pattern compared to the usual heterotic string models. Phenomenological implications for dark matter are discussed.
Some Intersections and Identifications in Integral Group Rings
Indian Academy of Sciences (India)
Ram Karan; Deepak Kumar
2002-05-01
Let be the integral group ring of a group and () its augmentation ideal. For a free group and a normal subgroup of , the intersection $I^{n+1}(F) \\cap I^n(R)$ is determined for all ≥ 1. The subgroups $F \\cap (1+ZFI(R)I(F)I(S))$ and $F \\cap (1+I(R)I^3(F))$ of are identified when and are arbitrary subgroups of .
Ranking the types of intersections for assessing the safety of pedestrians using TOPSIS method
Directory of Open Access Journals (Sweden)
Călin ŞERBU
2014-11-01
Full Text Available Every year, more than 1500 accidents with pedestrian occur in the intersections in Romania. The number of accidents involving pedestrians in roundabouts intersections type increased approximately three times in 2013 compared to 2009 in Romania. This alarming increase led to the need of assessing the safety of pedestrians in intersections with or without safety systems. The safety systems for pedestrians and drivers include: the road marking, the pedestrian crossings marking, signal intersections with road signs, traffic lights or pedestrian safety barriers. We propose to assess the types of intersections with TOPSIS method.
The Research of Vehicle Acceleration at Signalized Intersections
Directory of Open Access Journals (Sweden)
Vuk Bogdanović
2013-02-01
Full Text Available Vehicle acceleration is an important parameter used in planning various road elements, traffic signalization, geometric elements of an intersection, signal plans of traffic lights, etc. The knowledge of vehicle acceleration values is also necessary in using simulation softwares for more accurate analysis of the total situation at an intersection, on a road section or in a traffic network. In a lot of earlier studies, acceleration values were analysed and defined, mostly in optimal conditions for traffic functioning. However, values of almost all traffic flow parameters have been changed over time, due to changes in driving-dynamic vehicle characteristics, pneumatic tyres, material used for building road surface, etc. Besides, local environment influence and changes in drivers’ behaviour also significantly affect values of this parameter. According to HCM, it is advisable to perform local research for all values of the parameters recommended within the framework of this handbook, and to adapt their values to local conditions as well. The results of measuring the values of vehicles acceleration at signalized intersections in Novi Sad, Serbia, have been shown in this paper, using the procedure based on video recording processing.
Remote Sensing Image Registration with Line Segments and Their Intersections
Directory of Open Access Journals (Sweden)
Chengjin Lyu
2017-05-01
Full Text Available Image registration is a basic but essential step for remote sensing image processing, and finding stable features in multitemporal images is one of the most considerable challenges in the field. The main shape contours of artificial objects (e.g., roads, buildings, farmlands, and airports can be generally described as a group of line segments, which are stable features, even in images with evident background changes (e.g., images taken before and after a disaster. In this study, a registration method that uses line segments and their intersections is proposed for multitemporal remote sensing images. First, line segments are extracted in image pyramids to unify the scales of the reference image and the test image. Then, a line descriptor based on the gradient distribution of local areas is constructed, and the segments are matched in image pyramids. Lastly, triplets of intersections of matching lines are selected to estimate affine transformation between two images. Additional corresponding intersections are provided based on the estimated transformation, and an iterative process is adopted to remove outliers. The performance of the proposed method is tested on a variety of optical remote sensing image pairs, including synthetic and real data. Compared with existing methods, our method can provide more accurate registration results, even in images with significant background changes.
Complete intersections K-theory and Chern classes
Mandal, S S
1996-01-01
Throughout this abstruct A will denote a noetherian commutative ring of dimension n. The paper has two parts. Among the interesting results in Part-1 are the following: 1) {\\it suppose that f_1, f_2, \\ldots, f_r (with r \\leq n) is a regular sequence in A and suppose Q is a projective A-module of rank r that maps onto the ideal (f_1, f_2, \\ldots, f_{r-1},f_r^{(r-1)!}). Then [Q]=[Q_0 \\oplus A] in K_0(A) for some projective A-module~Q_0 of rank r-1.} 2) The set F_0K_0(A) = \\{[A/I] \\in K_0(A): I~ is~ a~ locally~ complete ~intersection~ ideal~ in~ A~ of~ height~n \\} is a {\\it subgroup} of K_0(A). We also show that if A is a reduced affine algebra over a field k then F_0K_0(A) {\\it is indeed the Zero Cycle Subgroup of} K_0(A) {\\it that is generated by smooth maximal ideals} \\Cal M {\\it of height} n. 3){\\it let A be such that whenever I is a locally complete intersection ideal of height n with [A/I]=0 then I is the image of a projective A-module of rank n. Then for any locally complete intersection ideal J of height...
Droplets coalescence at microchannel intersection chambers with different shapes
Liu, Zhaomiao; Wang, Xiang; Cao, Rentuo; Pang, Yan
2016-11-01
The influence of microchannel intersection chamber shape on droplets coalescence process is investigated in this study. Three kinds of chamber shapes (half-round, triangle and camber) are designed to realize head-on droplets coalescence. The coalescence processes are visualized with high-speed camera system and the internal flow patterns are resolved with micro-PIV system. Experimental analyses on droplets coalescence position, coalescence time and the critical conditions are discussed. Both direct coalescence and late coalescence can be observed in the camber junction while only the late coalescence is present for the half-round and the triangle junction. The critical capillary number Ca* varies for different working systems or intersection shapes. Ca* in the camber junction is larger than that in the other two junctions for each working system and it decreases with the increase of the viscosity ratios for each intersection shape. Moreover, the characteristics of the velocity fields for different coalescence cases are analyzed for in-depth understanding of the process. The authors do appreciate the financial support of No.11572013 of National Nature Scicence Funding of China.
Conical intersection seams in polyenes derived from their chemical composition
Energy Technology Data Exchange (ETDEWEB)
Nenov, Artur; Vivie-Riedle, Regina de [Department Chemie, Ludwig-Maximilians-Univerisitaet, Muenchen Butenandtstr. 11, 81377 Muenchen (Germany)
2012-08-21
The knowledge of conical intersection seams is important to predict and explain the outcome of ultrafast reactions in photochemistry and photobiology. They define the energetic low-lying reachable regions that allow for the ultrafast non-radiative transitions. In complex molecules it is not straightforward to locate them. We present a systematic approach to predict conical intersection seams in multifunctionalized polyenes and their sensitivity to substituent effects. Included are seams that facilitate the photoreaction of interest as well as seams that open competing loss channels. The method is based on the extended two-electron two-orbital method [A. Nenov and R. de Vivie-Riedle, J. Chem. Phys. 135, 034304 (2011)]. It allows to extract the low-lying regions for non-radiative transitions, which are then divided into small linear segments. Rules of thumb are introduced to find the support points for these segments, which are then used in a linear interpolation scheme for a first estimation of the intersection seams. Quantum chemical optimization of the linear interpolated structures yields the final energetic position. We demonstrate our method for the example of the electrocyclic isomerization of trifluoromethyl-pyrrolylfulgide.
Conical intersection seams in polyenes derived from their chemical composition
Nenov, Artur; de Vivie-Riedle, Regina
2012-08-01
The knowledge of conical intersection seams is important to predict and explain the outcome of ultrafast reactions in photochemistry and photobiology. They define the energetic low-lying reachable regions that allow for the ultrafast non-radiative transitions. In complex molecules it is not straightforward to locate them. We present a systematic approach to predict conical intersection seams in multifunctionalized polyenes and their sensitivity to substituent effects. Included are seams that facilitate the photoreaction of interest as well as seams that open competing loss channels. The method is based on the extended two-electron two-orbital method [A. Nenov and R. de Vivie-Riedle, J. Chem. Phys. 135, 034304 (2011)], 10.1063/1.3608924. It allows to extract the low-lying regions for non-radiative transitions, which are then divided into small linear segments. Rules of thumb are introduced to find the support points for these segments, which are then used in a linear interpolation scheme for a first estimation of the intersection seams. Quantum chemical optimization of the linear interpolated structures yields the final energetic position. We demonstrate our method for the example of the electrocyclic isomerization of trifluoromethyl-pyrrolylfulgide.
Caregiver Well-Being: Intersections of Relationship and Gender.
Chappell, Neena L; Dujela, Carren; Smith, André
2015-08-01
We know much about caregiving women compared with caregiving men and caregiving spouses compared with caregiving adult children. We know less about the intersections of relationship and gender. This article explores this intersection through the well-being (burden and self-esteem) of caregivers to family members with dementia. Throughout British Columbia, Canada, 873 caregivers were interviewed in person for on average, over 1½ hours. The results reveal that daughters experience the highest burden but also the highest self-esteem, suggesting the role is less salient for their self-identities. Wives emerge as the most vulnerable of the four groups when both burden and self-esteem are considered. The data confirm the usefulness of the intersectionality framework for understanding co-occupancy of more than one status and indicate that positive cognitive well-being and negative affective well-being can be differentially related. Multivariate analyses confirm the importance of caregiver, not patient, characteristics for burden and self-esteem. © The Author(s) 2014.
Traffic light detection and intersection crossing using mobile computer vision
Grewei, Lynne; Lagali, Christopher
2017-05-01
The solution for Intersection Detection and Crossing to support the development of blindBike an assisted biking system for the visually impaired is discussed. Traffic light detection and intersection crossing are key needs in the task of biking. These problems are tackled through the use of mobile computer vision, in the form of a mobile application on an Android phone. This research builds on previous Traffic Light detection algorithms with a focus on efficiency and compatibility on a resource-limited platform. Light detection is achieved through blob detection algorithms utilizing training data to detect patterns of Red, Green and Yellow in complex real world scenarios where multiple lights may be present. Also, issues of obscurity and scale are addressed. Safe Intersection crossing in blindBike is also discussed. This module takes a conservative "assistive" technology approach. To achieve this blindBike use's not only the Android device but, an external bike cadence Bluetooth/Ant enabled sensor. Real world testing results are given and future work is discussed.
Firebox modeling of SRT cracking heaters
Energy Technology Data Exchange (ETDEWEB)
Sundaram, K.M.; Albano, J.V. [ABB Lummus Crest Inc., Bloomfield, NJ (United States)
1994-12-31
Thermal cracking of hydrocarbons remains the most economically attractive route for the production of ethylene. The heat for the endothermic cracking reaction is supplied in high capacity fired heaters which are designed specifically to have high selectivity to olefins. In the cracking process, coke is deposited within the tubes of the radiant coil. The rate of coke deposition in a cracking furnace is a function not only of process conditions but of other factors as well. High tube metal temperatures in certain areas of the coil or hot spots can cause locally high coking rate leading to partial blockage of the tubes and consequently, short runs. The small diameter tubes used in modern high selectivity heaters are more sensitive than older large tube designs. The occurrence of these hot zones is a strong function of fireside conditions. For satisfactory performance, the heat flux profile in a cracking heater must be maintained as uniform as possible. In addition, it is important to minimize the variation of process temperatures entering the various cracking coils. These fireside variables are not only a function of the type of burners, excess air, type of fuel(s) and distribution of air and fuel but depend significantly on the air and flue gas flow patterns associated with the firebox, i.e., the firebox aerodynamics. Poor aerodynamics can adversely affect firing patterns and hence heat flux profiles in commercial furnaces. A variety of modeling techniques have been used to evaluate the firebox aerodynamics of Lummus, Short Residence Time, cracking heaters. These include flow visualization, physical cold flow modeling, and computational techniques. These approaches are discussed in this paper.
Crack propagation modeling using Peridynamic theory
Hafezi, M. H.; Alebrahim, R.; Kundu, T.
2016-04-01
Crack propagation and branching are modeled using nonlocal peridynamic theory. One major advantage of this nonlocal theory based analysis tool is the unifying approach towards material behavior modeling - irrespective of whether the crack is formed in the material or not. No separate damage law is needed for crack initiation and propagation. This theory overcomes the weaknesses of existing continuum mechanics based numerical tools (e.g. FEM, XFEM etc.) for identifying fracture modes and does not require any simplifying assumptions. Cracks grow autonomously and not necessarily along a prescribed path. However, in some special situations such as in case of ductile fracture, the damage evolution and failure depend on parameters characterizing the local stress state instead of peridynamic damage modeling technique developed for brittle fracture. For brittle fracture modeling the bond is simply broken when the failure criterion is satisfied. This simulation helps us to design more reliable modeling tool for crack propagation and branching in both brittle and ductile materials. Peridynamic analysis has been found to be very demanding computationally, particularly for real-world structures (e.g. vehicles, aircrafts, etc.). It also requires a very expensive visualization process. The goal of this paper is to bring awareness to researchers the impact of this cutting-edge simulation tool for a better understanding of the cracked material response. A computer code has been developed to implement the peridynamic theory based modeling tool for two-dimensional analysis. A good agreement between our predictions and previously published results is observed. Some interesting new results that have not been reported earlier by others are also obtained and presented in this paper. The final objective of this investigation is to increase the mechanics knowledge of self-similar and self-affine cracks.
ENDOFEM INTEGRATED METHODOLOGY FOR FATIGUE CRACK GROWTH
Institute of Scientific and Technical Information of China (English)
C.F.Lee; L.T.Hsiao
2002-01-01
In this paper, the FEM with the incremental endochronic cyclic plasticity (EndoFEM) and the rc controlled node-released strategy are employed to study the fatigue crack opened/closed load (Pop) of A1 2024-T3 CCT specimens provided by Mageed and Pandey under several crack lengths and the constant amplitude with various load ratio (R). After statisfactory results are achieved by comparisons of computed Pop values and cited experimental data, the simulations will be extended to the crack lengths with significant bending effect due to short ligaments or high peak (Pmax) or high positive or very low negative R cyclic loads. Through these simulations, the complete map of Pop/Pmax vs. Kmax and R can be constructed and thereafter its correspondant empirical formulae can be proposed. Using these formulae and selecting the traditional fatigue crack growth parameter ΔKeff, the A1 2024-T3 fatigue crack growth rate da/dN vs. ΔK and R data, provided by Hiroshi and Schijve, can be employed to proposed empirical formulae of da/dN vs. ΔKeff and R. After integration, fatigue-crack-growth length a vs. N curves computed by EndoFEM can be obtained. The results are agreed very well with the existing experimental curves. According to the above procedures of simulation and steps of comparions with experiment, this paper may provides an integrate methodology of numerical simulation in the studies of fatigue crack growth for academic and industrial researches and design analysis.
TRANSPORT THROUGH CRACKED CONCRETE: LITERATURE REVIEW
Energy Technology Data Exchange (ETDEWEB)
Langton, C.
2012-05-11
Concrete containment structures and cement-based fills and waste forms are used at the Savannah River Site to enhance the performance of shallow land disposal systems designed for containment of low-level radioactive waste. Understanding and measuring transport through cracked concrete is important for describing the initial condition of radioactive waste containment structures at the Savannah River Site (SRS) and for predicting performance of these structures over time. This report transmits the results of a literature review on transport through cracked concrete which was performed by Professor Jason Weiss, Purdue University per SRR0000678 (RFP-RQ00001029-WY). This review complements the NRC-sponsored literature review and assessment of factors relevant to performance of grouted systems for radioactive waste disposal. This review was performed by The Center for Nuclear Waste Regulatory Analyses, San Antonio, TX, and The University of Aberdeen, Aberdeen Scotland and was focused on tank closure. The objective of the literature review on transport through cracked concrete was to identify information in the open literature which can be applied to SRS transport models for cementitious containment structures, fills, and waste forms. In addition, the literature review was intended to: (1) Provide a framework for describing and classifying cracks in containment structures and cementitious materials used in radioactive waste disposal, (2) Document the state of knowledge and research related to transport through cracks in concrete for various exposure conditions, (3) Provide information or methodology for answering several specific questions related to cracking and transport in concrete, and (4) Provide information that can be used to design experiments on transport through cracked samples and actual structures.
Recent evaluations of crack-opening-area in circumferentially cracked pipes
Energy Technology Data Exchange (ETDEWEB)
Rahman, S.; Brust, F.; Ghadiali, N.; Wilkowski, G.; Miura, N.
1997-04-01
Leak-before-break (LBB) analyses for circumferentially cracked pipes are currently being conducted in the nuclear industry to justify elimination of pipe whip restraints and jet shields which are present because of the expected dynamic effects from pipe rupture. The application of the LBB methodology frequently requires calculation of leak rates. The leak rates depend on the crack-opening area of the through-wall crack in the pipe. In addition to LBB analyses which assume a hypothetical flaw size, there is also interest in the integrity of actual leaking cracks corresponding to current leakage detection requirements in NRC Regulatory Guide 1.45, or for assessing temporary repair of Class 2 and 3 pipes that have leaks as are being evaluated in ASME Section XI. The objectives of this study were to review, evaluate, and refine current predictive models for performing crack-opening-area analyses of circumferentially cracked pipes. The results from twenty-five full-scale pipe fracture experiments, conducted in the Degraded Piping Program, the International Piping Integrity Research Group Program, and the Short Cracks in Piping and Piping Welds Program, were used to verify the analytical models. Standard statistical analyses were performed to assess used to verify the analytical models. Standard statistical analyses were performed to assess quantitatively the accuracy of the predictive models. The evaluation also involved finite element analyses for determining the crack-opening profile often needed to perform leak-rate calculations.
DEFF Research Database (Denmark)
Pereira, Gilmar Ferreira; Mikkelsen, Lars Pilgaard; McGugan, Malcolm
2015-01-01
This article presents a novel method to asses a crack growing/damage event in fibre reinforced plastic, or adhesive using Fibre Bragg Grating (FBG) sensors embedded in a host material. Different features of the crack mechanism that induce a change in the FBG response were identified. Double Canti...