Failure in imperfect anisotropic materials
DEFF Research Database (Denmark)
Legarth, Brian Nyvang
2005-01-01
The fundamental cause of crack growth, namely nucleation and growth of voids, is investigated numerically for a two phase imperfect anisotropic material. A unit cell approach is adopted from which the overall stress strain is evaluated. Failure is observed as a sudden stress drop and depending...
Silicon as an anisotropic mechanical material
DEFF Research Database (Denmark)
Thomsen, Erik Vilain; Reck, Kasper; Skands, Gustav Erik
2014-01-01
While silicon is an anisotropic material it is often in literature treated as an isotropic material when it comes to plate calculations. This leads to considerable errors in the calculated deflection. To overcome this problem, we present an in-depth analysis of the bending behavior of thin...... analytical models involving crystalline plates, such as those often found in the field of micro electro mechanical systems. The effect of elastic boundary conditions is taken into account by using an effective radius of the plate....
Anisotropic Cloth Modeling for Material Fabric
Zhang, Mingmin; Pan, Zhigengx; Mi, Qingfeng
Physically based cloth simulation has been challenging the graphics community for more than three decades. With the developing of virtual reality and clothing CAD, it has become the key technique of virtual garment and try-on system. Although it has received considerable attention in computer graphics, due to its flexible property and realistic feeling that the textile engineers pay much attention to, there is not a successful methodology to simulate cloth both in visual realism and physical accuracy. We present a new anisotropic textile modeling method based on physical mass-spring system, which models the warps and wefts separately according to the different material fabrics. The simulation process includes two main steps: firstly the rigid object simulation and secondly the flexible mass simulation near to be equilibrium. A multiresolution modeling is applied to enhance the tradeoff fruit of the realistic presentation and computation cost. Finally, some examples and the analysis results show the efficiency of the proposed method.
PHENOMENOLOGICAL DAMAGE MODELS OF ANISOTROPIC STRUCTURAL MATERIALS
Bobyr, M.; Khalimon, O.; Bondarets, O.
2015-01-01
Damage in metals is mainly the process of the initiation and growth of voids. A formulation for anisotropic damage is established in the framework of the principle of strain equivalence, principle of increment complementary energy equivalence and principle of elastic energy equivalence. This paper presents the development of an anisotropic damage theory. This work is focused on the development of evolution anisotropic damage models which is based on a Young’s modulus/Poisson’s ratio change of...
Hybrid anisotropic materials for wind power turbine blades
Golfman, Yosif
2012-01-01
Based on rapid technological developments in wind power, governments and energy corporations are aggressively investing in this natural resource. Illustrating some of the crucial new breakthroughs in structural design and application of wind energy generation machinery, Hybrid Anisotropic Materials for Wind Power Turbine Blades explores new automated, repeatable production techniques that expand the use of robotics and process controls. These practices are intended to ensure cheaper fabrication of less-defective anisotropic material composites used to manufacture power turbine blades. This boo
Surface instabilities during straining of anisotropic materials
DEFF Research Database (Denmark)
Legarth, Brian Nyvang; Richelsen, Ann Bettina
2006-01-01
The development of instabilities in traction-free surfaces is investigated numerically using a unit cell model. Full finite strain analyses are conducted using isotropic as well as anisotropic yield criteria and both plane strain tension and compression are considered. In the load range of tension...
Debonding Analyses in Anisotropic Materials with Strain-Gradient Effects
DEFF Research Database (Denmark)
Legarth, Brian Nyvang
2012-01-01
A unit cell approach is adopted to numerically analyze the effect of plastic anisotropy on damage evolution in a microreinforced composite. The matrix material exhibit size effects and a visco-plastic anisotropic strain gradient plasticity model accounting for such size effects is adopted....... A conventional cohesive law is extended such that both the average as well as the jump in plastic strain across the fiber-matrix interface are accounted for. Results are shown for both conventional isotropic and anisotropic materials as well as for higher order isotropic and anisotropic materials...... with and without debonding. Generally, the strain gradient enhanced material exhibits higher load carry capacity compared to the corresponding conventional material. A sudden stress drop occurs in the macroscopic stress-strain response curve due to fiber-matrix debonding and the results show that a change in yield...
Debonding analyses in anisotropic materials with strain- gradient effects
DEFF Research Database (Denmark)
Legarth, Brian Nyvang
2012-01-01
A unit cell approach is adopted to numerically analyze the effect of plastic anisotropy on damage evolution in a micro-reinforced composite. The matrix material exhibit size effects and a visco-plastic anisotropic strain gradient plasticity model accounting for such size effects is adopted. A con...
Viscous inclusions in anisotropic materials: Theoretical development and perspective applications
Jiang, Dazhi
2016-12-01
Theories and numerical solutions for a viscous ellipsoid in an infinite anisotropic viscous medium subjected to far-field homogeneous deformation lie at the heart of self-consistent homogenization models and multiscale simulations of texture and fabric development in Earth's lithosphere. There is considerable literature on ellipsoid inclusions, focused on anisotropic elastic materials, published in multi-disciplinary fields. To make this body of work more accessible as well as to advance viscous inclusion studies, an effort is made here to summarize recent advances and to further develop formally more explicit and, where possible, analytic solutions for incompressible viscous materials. The point-force concept and equivalent inclusion method of Eshelby are used together with the Green function approach. This leads to generalized equations for ellipsoid inclusion behaviors in anisotropic materials. In the particular case of isotropic materials, the new mathematical development here enables the use of existing methods for elastic materials to get solutions for corresponding viscous inclusion problems efficiently and accurately. A 2D formulation is also presented for elliptic cylinders in plane-straining flows of anisotropic materials, using the same Green function method that is adopted for 3D inclusions. The 2D formulation is benchmarked with existing analytic solutions. A reconnaissance investigation to compare the behaviors of 2D elliptic inclusions and triaxial ellipsoids in a matrix of planar anisotropy undergoing far-field plane-straining flows suggests that conclusions drawn from 2D cannot be applied to 3D in anisotropic cases. The application of the viscous inclusion theory to the rheologically heterogeneous and non-linear lithosphere is discussed. By regarding a heterogeneous element as an ellipsoidal inclusion embedded in a hypothetical homogeneous equivalent matrix whose effective rheology is obtained through micromechanical homogenization and assuming
Development of an Anisotropic Thermal Transport Material
2014-01-13
Oxide” Materials Research Society Cancun Meeting, 2010. 4) Oyer, A. J.; Dobrynin, A. V.; Asandei, A. D.; Adamson, D. H., “High Concentration...Graphene Suspensions” International Materials Research Congress XX, Cancun MX, 2011. 5) Oyer, A. J.; Carrillo, J.-M. Y.; Hire, C. C.; Schniepp, H. C
WEIGHT FUNCTIONS FOR INTERFACE CRACKS IN DISSIMILAR ANISOTROPIC MATERIALS
Institute of Scientific and Technical Information of China (English)
MA Lifeng; CHEN Yiheng
2004-01-01
Bueckner's work conjugate integral customarily adopted for linear elastic materials is established for an interface crack in dissimilar anisotropic materials. The difficulties in separating Stroh's six complex arguments involved in the integral for the dissimilar materials are overcome and then the explicit function representations of the integral are given and studied in detail. It is found that the pseudo-orthogonal properties of the eigenfunction expansion form (EEF) for a crack presented previously in isotropic elastic cases, in isotopic bimaterial cases, and in orthotropic cases are also valid in the present dissimilar arbitrary anisotropic cases. The relation between Bueckner's work conjugate integral and the J-integral in these cases is obtained by introducing a complementary stressdisplacement state. Finally, some useful path-independent integrals and weight functions are proposed for calculating the crack tip parameters such as the stress intensity factors.
Analysis of Magneto-Piezoelastic Anisotropic Materials
Directory of Open Access Journals (Sweden)
Alexander L. Kalamkarov
2015-05-01
Full Text Available The paper is concerned with the analysis of magneto-piezoelastic anistropic materials. Analytical modeling of magneto-piezoelastic materials is essential for the design and applications in the smart composite structures incorporating them as actuating and sensing constituents. It is shown that Green’s function method is applicable to time harmonic magneto-elastic-piezoelectricity problems using the boundary integral technique, and the exact analytical solutions are obtained. As an application, a two-dimensional static plane-strain problem is considered to investigate the effect of magnetic field on piezoelectric materials. The closed-form analytical solutions are obtained for a number of boundary conditions for all components of the magneto-piezoelectric field. As a special case, numerical results are presented for two-dimensional static magneto-electroelastic field of a piezoelectric solid subjected to a concentrated line load and an electric charge. The numerical solutions are obtained for three different piezoelectric materials and they demonstrate a substantial dependence of the stress and electric field distribution on the constitutive properties and magnetic flux.
Debonding of perticles in anisotropic materials
DEFF Research Database (Denmark)
Legarth, Brian Nyvang
2003-01-01
is calculated. For increased triaxiality the onset of matrix-particle debonding occurs at a significantly reduced overall strain of the cell. The point of initial debonding is nearly unaffected by variations of the shape of the inclusions, but complete debonding occurs earlier if the inclusions are elongated...... if the material was plastically isotropic. It is found for mixed geometrical and plastic anisotropy, that plastic anisotropy promotes debonding initiation, whereas the occurrence of complete matrix-particle debonding is quite sensitive to the type of geometrical anisotropy....
Toward anisotropic materials via forced assembly coextrusion.
Burt, Tiffani M; Jordan, Alex M; Korley, LaShanda T J
2012-10-24
Multilayer coextrusion offers a diverse platform to examine layer dependent confinement effects on self-assembling nanomaterials via conventional extrusion technology. A triblock copolymer (BCP) with a cylindrical microstructure was processed via "forced assembly" to elucidate the effect of microdomain orientation on the mechanical behavior of multilayer films. The mechanical response was investigated in both the extrusion (ED) and transverse directions (TD) of the multilayer systems, revealing an influence of both cylinder-orientation and the interface on the mechanical response with decreasing layer thickness. The stress-strain curves for samples with the stress field along the cylinder axis revealed a sharp yielding phenomenon, while curves for specimens with the stress field applied perpendicular to the axis exhibited weak yielding behavior. The extensibility of the multilayer films stressed in the ED increases with decreasing layer thickness, but remains constant when deformed along the TD. Coextrusion technology allows for tunable mechanical toughness in industrial grade polymers via a continuous process. By altering the layer thickness of the two polymeric materials, we can tune the mechanics from strong, brittle behavior to a tough, ductile response by manipulation of the hierarchical structure. The enabling technology provides a unique platform to couple the inherent mechanical response of dissimilar polymers and allows for the design of composite materials with tailored mechanics.
Characteristics of surface waves in anisotropic left-handed materials
Institute of Scientific and Technical Information of China (English)
Jiang Yong-Yuan; Shi Hong-Yan; Zhang Yong-Qiang; Hou Chun-Feng; Sun Xiu-Dong
2007-01-01
We report the coexistence of TE and TM surface modes in certain same frequency domain at the interface between one isotropic regular medium and another biaxially anistotropic left-handed medium. The conditions for the existence of TE and TM polarized surface waves in biaxially anisotropic left-handed materials are identified, respectively.The Poynting vector and the energy density associated with surface modes are calculated. Depending on the system parameters, either TE or TM surface modes can have the time averaged Poynting vector directed to or opposite to the mode phase velocity. It is seen that the characteristics of surface waves in biaxially anisotropic left-handed media are significantly different from that in isotropic left-handed media.
Fracture of anisotropic materials with plastic strain-gradient effects
DEFF Research Database (Denmark)
Legarth, Brian Nyvang
2013-01-01
parameter is adopted. The fracture process along the fiber-matrix interface is modeled using a recently proposed cohesive law extension having an additional material length parameter. Due to the fiber-matrix fracture a sudden stress-drop is seen in the macroscopic stress-strain response which defines......A unit cell is adopted to numerically analyze the effect of plastic anisotropy on frac-ture evolution in a micro-reinforced fiber-composite. The matrix material exhibit size-effects and an anisotropic strain-gradient plasticity model accounting for such size-effects through a mate-rial length scale...... the failure strain of the composite. The effect of the two material length parameters on the failure strain of the composite is studied. For small values of the material length scale parameter conventional predictions are obtained. Larger values of the material length scale parameter result in corresponding...
Crowgey, Benjamin Reid
Rectangular waveguide methods are appealing for measuring isotropic and anisotropic materials because of high signal strength due to field confinement, and the ability to control the polarization of the applied electric field. As a stepping stone to developing methods for characterizing materials with fully-populated anisotropic tensor characteristics, techniques are presented in this dissertation to characterize isotropic, biaxially anisotropic, and gyromagnetic materials. Two characterization techniques are investigated for each material, and thus six different techniques are described. Additionally, a waveguide standard is introduced which may be used to validate the measurement of the permittivity and permeability of materials at microwave frequencies. The first characterization method examined is the Nicolson-Ross-Weir (NRW) technique for the extraction of isotropic parameters of a sample completely filling the cross-section of a rectangular waveguide. A second technique is proposed for the characterization of an isotropic conductor-backed sample filling the cross-section of a waveguide. If the sample is conductor-backed, and occupies the entire cross-section, a transmission measurement is not available, and thus a method must be found for providing two sufficiently different reflection measurements.The technique proposed here is to place a waveguide iris in front of the sample, exposing the sample to a spectrum of evanescent modes. By measuring the reflection coefficient with and without an iris, the necessary two data may be obtained to determine the material parameters. A mode-matching approach is used to determine the theoretical response of a sample placed behind the waveguide iris. This response is used in a root-searching algorithm to determine permittivity and permeability by comparing to measurements of the reflection coefficient. For the characterization of biaxially anisotropic materials, the first method considers an extension of the NRW technique
Direct Imaging of Anisotropic Material Properties using Photorefractive Laser Ultrasound
Energy Technology Data Exchange (ETDEWEB)
Telschow, Kenneth Louis; Deason, Vance Albert; Schley, Robert Scott; Watson, Scott Marshall
1999-07-01
Anisotropic properties of materials can be determined by measuring the propagation of elastic waves in different directions. A laser imaging approach is presented that utilizes the adaptive property of photorefractive materials to produce a real-time measurement of the antisymmetric Lamb or flexural traveling wave mode displacement and phase. Continuous excitation is employed and the data is recorded and displayed in all directions simultaneously at video camera frame rates. Fourier transform of the data produces an image of the wave slowness in all planar directions. The results demonstrate imaging of microstructural isotropy and anisotropy and stress induced ansiotropy in plates.
Direct Imaging of Anisotropic Material Properties using Photorefractive Laser Ultrasound
Energy Technology Data Exchange (ETDEWEB)
K.L. Telschow; R.S. Schley; S.M. Watson; V.A. Deason
1999-06-01
Anisotropic properties of materials can be determined by measuring the propagation of elastic waves in different directions. A laser imaging approach is presented that utilizes the adaptive property of photorefractive materials to produce a real-time measurement of the antisymmetric Lamb or flexural traveling wave mode displacement and phase. Continuous excitation is employed and the data is recorded and displayed in all directions simultaneously at video camera frame rates. Fourier transform of the data produces an image of the wave slowness in all planar directions. The results demonstrate imaging of microstructural isotropy and anisotropy and stress induced ansiotropy in plates.
Thije, ten R.H.W.; Akkerman, R.; Huetink, J.
2007-01-01
Large deformation finite element (FE) simulations of anisotropic material often show slow convergence or break down with increasing anisotropy and deformation. Large deformations are generally approximated by multiple small linearised steps. This leads to poor performance and contradicting formulati
Hou, Quanwen; Zhao, Xiaopeng; Meng, Tong; Liu, Cunliang
2016-09-01
Thermal metamaterials and devices based on transformation thermodynamics often require materials with anisotropic and inhomogeneous thermal conductivities. In this study, still based on the concept of transformation thermodynamics, we designed a planar illusion thermal device, which can delocalize a heat source in the device such that the temperature profile outside the device appears to be produced by a virtual source at another position. This device can be constructed by only one kind of material with constant anisotropic thermal conductivity. The condition which should be satisfied by the device is provided, and the required anisotropic thermal conductivity is then deduced theoretically. This study may be useful for the designs of metamaterials or devices since materials with constant anisotropic parameters have great facility in fabrication. A prototype device has been fabricated based on a composite composed by two naturally occurring materials. The experimental results validate the effectiveness of the device.
Laser ceramics with rare-earth-doped anisotropic materials.
Akiyama, Jun; Sato, Yoichi; Taira, Takunori
2010-11-01
The fabrication of laser-grade anisotropic ceramics by a conventional sintering process is not possible owing to optical scattering at randomly oriented grain boundaries. In this Letter, we report the first (to our knowledge) realization of transparent anisotropic ceramics by using a new crystal orientation process based on large magnetic anisotropy induced by 4f electrons. By slip casting in a 1.4 T magnetic field and subsequent heat treatments, we could successfully fabricate laser-grade calcium fluorapatite ceramics with a loss coefficient of 1.5 cm(-1).
Method of determining load in anisotropic non-crystalline materials using energy flux deviation
Prosser, William H. (Inventor); Kriz, Ronald D. (Inventor); Fitting, Dale W. (Inventor)
1994-01-01
An ultrasonic wave is applied to an anisotropic sample material in an initial direction and the intensity of the ultrasonic wave is measured on an opposite surface of the sample material by two adjacent receiving points located in an array of receiving points. A ratio is determined between the measured intensities of two adjacent receiving points, the ratio being indicative of an angle of flux deviation from the initial direction caused by an unknown applied load. This determined ratio is then compared to a plurality of ratios of a similarly tested, similar anisotropic reference material under a plurality of respective, known load conditions, whereby the load applied to the particular anisotropic sample material is determined. A related method is disclosed for determining the fiber orientation from known loads and a determined flux shift.
Lee, Hyung Jin; Lee, Heung Son; Ma, Pyung Sik; Kim, Yoon Young
2016-09-01
In this paper, the scattering (S-) parameter retrieval method is presented specifically for anisotropic elastic metamaterials; so far, no retrieval has been accomplished when elastic metamaterials exhibit fully anisotropic behavior. Complex constitutive property and intrinsic scattering behavior of elastic metamaterials make their characterization far more complicated than that for acoustic and electromagnetic metamaterials. In particular, elastic metamaterials generally exhibit anisotropic scattering behavior due to higher scattering modes associated with shear deformation. They also exhibit nonlocal responses to some degrees, which originate from strong multiple scattering interactions even in the long wavelength limit. Accordingly, the conventional S-parameter retrieval methods cannot be directly used for elastic metamaterials, because they determine only the diagonal components in effective tensor property. Also, the conventional methods simply use the analytic inversion formulae for the material characterization so that inherent nonlocality cannot be taken into account. To establish a retrieval method applicable to anisotropic elastic metamaterials, we propose an alternative S-parameter method to deal with full anisotropy of elastic metamaterials. To retrieve the whole effective anisotropic parameter, we utilize not only normal but also oblique wave incidences. For the retrieval, we first retrieve the ratio of the effective stiffness tensor to effective density and then determine the effective density. The proposed retrieval method is validated by characterizing the effective material parameters of various types of non-resonant anisotropic metamaterials. It is found that the whole effective parameters are retrieved consistently regardless of used retrieval conditions in spite of inherent nonlocality.
PO Solution for Scattering by the Complex Object Coated with Anisotropic Materials
Institute of Scientific and Technical Information of China (English)
殷红成; 黄培康; 刘学观; 郭辉萍
2003-01-01
The physical optics solution is presented for the calculation of scattering by the complex conducting bodies coated with anisotropic materials, which is based on the tangential plane approximation and the equivalent currents on an anisotropic material backed by an infinite metal surface illuminated by the plane wave given in our previous work. The analytical scheme is proposed to realize fast computation of the solution. Numerical results for several coated bodies such as dihedral corner reflector and cone-cylinder geometry are given and discussed.
Institute of Scientific and Technical Information of China (English)
GAO Xin; WANG Han-gong; KANG Xing-wu
2008-01-01
Based on the mechanics of anisotropic materials,the dynamic propagation problem of a mode Ⅲ crack in an infinite anisotropic body is investigated.Stress,strain and displacement around the crack tip are expressed as an analytical complex function,which can be represented in power series.Constant coefficients of series are determined by boundary conditions.Expressions of dynamic stress intensity factors for a mode Ⅲ crack are obtained.Components of dynamic stress,dynamic strain and dynamic displacement around the crack tip are derived.Crack propagation characteristics are represented by the mechanical properties of the anisotropic materials,i.e.,crack propagation velocity M and the parameter α.The faster the crack velocity is,the greater the maximums of stress components and dynamic displacement components around the crack tip are.In particular,the parameter α affects stress and dynamic displacement around the crack tip.
Implementation of an anisotropic damage material model using general second order damage tensor
Niazi, Muhammad; Wisselink, Harm; Meinders, Timo; Horn, ten Carel; Mori, K.; Pietrzyk, M.; Kusiak, J.; Majta, J.; Hartley, P.; Lin, J.
2010-01-01
Damage in metals is mainly the process of the initiation and growth of voids. With the growing complexity in materials and forming proc-esses, it becomes inevitable to include anisotropy in damage (tensorial damage variable). Most of the anisotropic damage models define the damage tensor in the prin
Repulsion of polarised particles from anisotropic materials with a near-zero permittivity component
Institute of Scientific and Technical Information of China (English)
Francisco J Rodríguez-Fortu(n)o; Anatoly V Zayats
2016-01-01
Reduction of adhesion and stiction is crucial for robust operation on nanomechanical and optofluidic devices as well as atom and molecule behaviour near surfaces.It can be achieved using electric charging,magnetic materials or light pressure and optical trapping.Here we show that a particle scattering or emitting in close proximity to an anisotropic substrate can experience a repulsive force if one of the diagonal components of the permittivity tensor is close to zero.We derive an analytic condition for the existence of such repulsive force depending on the optical properties of the substrate.We also demonstrate the effect using realistic anisotropic metamaterial implementations of a substrate.The anisotropic metamaterial approach using metal-dielectric and graphene-dielectric multilayers provides a tuneable spectral range and a very broad bandwidth of electromagnetic repulsion forces,in contrast to isotropic substrates.
Study of an anisotropic polymeric cellular material under compression loading
Directory of Open Access Journals (Sweden)
Mauricio Francisco Caliri Júnior
2012-06-01
Full Text Available This paper emphasizes the influence of micro mechanisms of failure of a cellular material on its phenomenological response. Most of the applications of cellular materials comprise a compression loading. Thus, the study focuses on the influence of the anisotropy in the mechanical behavior of cellular material under cyclic compression loadings. For this study, a Digital Image Correlation (DIC technique (named Correli was applied, as well as SEM (Scanning Electron Microscopy images were analyzed. The experimental results are discussed in detail for a closed-cell rigid poly (vinyl chloride (PVC foam, showing stress-strain curves in different directions and why the material can be assumed as transversely isotropic. Besides, the present paper shows elastic and plastic Poisson's ratios measured in different planes, explaining why the plastic Poisson's ratios approach to zero. Yield fronts created by the compression loadings in different directions and the influence of spring-back phenomenon on hardening curves are commented, also.
ASYMPTOTIC ELASTIC STRESS FIELD NEAR A BLUNT CRACK TIP IN AN ANISOTROPIC MATERIAL
Institute of Scientific and Technical Information of China (English)
HUANG; Zhen-yu(
2001-01-01
［1］Williams M L.Oh the stress distribution at the base of a stationary crack[J].ASME J App Mech,1957,24:109～114.［2］Creager M,Paris P C,Elastic field equations for blunt cracks with reference to stress corrosion crack-ing[J].Int J Fracture,1967,3:247～251［3］Kuang Z B.The stress field near the blunt crack tip and the fracture criterion[J].Engng Fracture Mech,1982,16:19～33.［4］Ting T C T.Anisotropic Elasticity and its applica-tion[M].London:Oxford University Press,1996.［5］Ting T C T ,Hwu C.Sextic formalism in anisotropic elasticity for almost non-semisimple matrix N[J].Int J S olids Structures,1988,24:65～76.［6］Yang X X,Shen S,Kuang Z B.The degenerate so-lution for piezothermoelastic materials[J].Eur J Mech A/Solid,1997,16:779～793［7］Hwu C,Yen W J.On the anisotropic elastic inclu-sions in plane elastostatics[J].ASME J A pp Mech,1993,60:626～632.［8］Lekhnitskii S G.Theory of elasticity of an anisotrop-ic elastic body[M].Moscow:Mir Publishers,1981.［9］Hoenig A.Near-tip behavior of a crack in a plane anisotropic elastic body[J].Engng Fracture Mech,1982,16:393～403.［10］匡震邦，马法尚。裂纹端部场[M].西安：西安交通大学出版社，2001
Energy Technology Data Exchange (ETDEWEB)
Lee, Dock Jin; Choi, Jae Boong; Kim, Moon Ki [Sungkyunkwan Univ., Suwon (Korea, Republic of); Chang, Yoon Suk [Kyunghee Univ., Suwon (Korea, Republic of)
2012-09-15
New advanced materials have received more attention from many scientists and engineers because of their outstanding chemical, electrical, thermal, optical, and mechanical properties. Since the design of advanced material by experiments requires high cost and time, numerical approaches have always been of great interest. In this paper, finite element analysis of anisotropic material behavior has been carried out based on a multiresolution continuum theory. Gurson Tvergaard Needleman (GTN) damage model has been applied as a constitutive model at macroscale. Effects of plastic anisotropy on deformation behavior are assessed using Hill's 48 yield function for anisotropic material and von Mises yield function for isotropic material, respectively. The material parameters for both isotropic and anisotropic damage models have systematically been determined from microstructure through unit cell modeling. The newly proposed linear approximation of local velocity gradient resolved the underdetermined problem of the previous homogenization process. Anisotropic material behaviors of a tensile specimen have been investigated by the proposed multiresolution continuum theory.
The effect of beam directivity on the inspection of anisotropic materials using ultrasonic arrays
Lane, C. J. L.; Wilcox, P. D.
2012-05-01
The beam directivity from an ultrasonic transducer in isotropic materials is well documented. However, beam directivities in elastically anisotropic materials and their effect on ultrasonic NDE inspection has been investigated far less extensively. In this paper, analytical and numerical finite element models are developed to predict the beam directivity in a single crystal nickel-based superalloy. This material is highly anisotropic and is used widely in the gas-turbine industry. The developed models are used to investigate the effect of the crystallographic orientation on the beam directivity. In turn, the effect of beam directivity on defect detection sensitivity and characterization capability using an ultrasonic array is demonstrated. It is shown that the effect is particularly important for the accurate sizing of small defects.
X-ray Birefringence Imaging of Materials with Anisotropic Molecular Dynamics.
Palmer, Benjamin A; Edwards-Gau, Gregory R; Kariuki, Benson M; Harris, Kenneth D M; Dolbnya, Igor P; Collins, Stephen P; Sutter, John P
2015-02-05
The X-ray birefringence imaging (XBI) technique, reported very recently, is a sensitive tool for spatially resolved mapping of the local orientational properties of anisotropic materials. In this paper, we report the first XBI measurements on materials that undergo anisotropic molecular dynamics. Using incident linearly polarized X-rays with energy close to the Br K-edge, the X-ray birefringence is dictated by the orientational properties of the C-Br bonds in the material. We focus on two materials (urea inclusion compounds containing 1,8-dibromooctane and 1,10-dibromodecane guest molecules) for which the reorientational dynamics of the brominated guest molecules (and hence the reorientational dynamics of the C-Br bonds) are already well characterized by other experimental techniques. The XBI results demonstrate clearly that, for the anisotropic molecular dynamics in these materials, the effective X-ray optic axis for the X-ray birefringence phenomenon is the time-averaged resultant of the orientational distribution of the C-Br bonds.
Al-Jabr, Ahmad Ali
2013-03-01
In this paper, an finite-difference time-domain (FDTD) algorithm for simulating propagation of EM waves in anisotropic material is presented. The algorithm is based on the auxiliary differential equation and the general polarization formulation. In anisotropic materials, electric fields are coupled and elements in the permittivity tensor are, in general, multiterm dispersive. The presented algorithm resolves the field coupling using a formulation based on electric polarizations. It also offers a simple procedure for the treatment of multiterm dispersion in the FDTD scheme. The algorithm is tested by simulating wave propagation in 1-D magnetized plasma showing excellent agreement with analytical solutions. Extension of the algorithm to multidimensional structures is straightforward. The presented algorithm is efficient and simple compared to other algorithms found in the literature. © 2012 IEEE.
Akinoglu, Eser M; Morfa, Anthony J; Giersig, Michael
2014-10-21
Anisotropic deformation of polystyrene particles in an oxygenated (O2/Ar) plasma is observed for radio frequency (rf) plasma and inductively coupled plasma (ICP). A facile model based on a ratio of completely isotropic and completely anisotropic etching is presented to describe the anisotropy of the etching process and is implemented to determine the height of the spheroid-shaped polystyrene particles. In our systems, we find the plasma etching to be 54% isotropic in the rf plasma and 79% isotropic in the ICP. With this model, the maximum material deposition thickness for nanofabrication with plasma-etched nanosphere lithography or colloid lithography can be predicted. Moreover, the etching of polystyrene particles in an oxygenated plasma is investigated versus the etching time, gas flow, gas composition, temperature, substrate material, and particle size. The results of this study allow precise shape tuning during the fabrication of nanostructured surfaces with size-dependent properties for bionic, medical, and photonic applications.
Prosser, William H. (Inventor); Kriz, Ronald D. (Inventor); Fitting, Dale W. (Inventor)
1993-01-01
An ultrasonic wave is applied to an anisotropic sample material in an initial direction and an angle of flux deviation of the ultrasonic wave front is measured from this initial direction. This flux deviation angle is induced by the unknown applied load. The flux shift is determined between this flux deviation angle and a previously determined angle of flux deviation of an ultrasonic wave applied to a similar anisotropic reference material under an initial known load condition. This determined flux shift is then compared to a plurality of flux shifts of a similarly tested, similar anisotropic reference material under a plurality of respective, known load conditions, whereby the load applied to the particular anisotropic sample material is determined. A related method is disclosed for determining the fiber orientation from known loads and a determined flux shift.
Energy Technology Data Exchange (ETDEWEB)
Fleury, W.H.; Rosinger, H.E.; Ritchie, I.G.
1975-09-01
A set of computer programs for the calculation of the flexural and torsional resonant frequencies of rectangular section bars of materials of orthotropic or high symmetry are described. The calculations are used in the experimental determination and verification of the elastic constants of anisotropic materials. The simple finite element technique employed separates the inertial and elastic properties of the beam element into station and field transfer matrices respectively. It includes the Timoshenko beam corrections for flexure and Lekhnitskii's theory for torsion-flexure coupling. The programs also calculate the vibration shapes and surface nodal contours or Chladni figures of the vibration modes. (auth)
Reflectance and reflection phase of photonic crystal with anisotropic left-handed materials
Kang, Yongqiang; Zhang, Chunmin; Yao, Baoli
2016-11-01
The reflectance and reflection phase properties of one dimensional photonic crystals with anisotropic left-handed materials is investigated by transfer matrix method. It is demonstrated that the width of zero- n band gap is influenced by the incident angle, polarization, the proportion of lattice and the ratio of thickness which is different from the zero- n band gap with isotropic left hand materials. The value of reflection phase is affected by incident angle and polarization and not affected by the proportion of lattice and the ratio of thickness. These characteristic may be useful for making photonic crystal phase compensators and the dispersion compensators.
Haider, Mohammad Faisal; Haider, Md. Mushfique; Yasmeen, Farzana
2016-07-01
Heterogeneous materials, such as composites consist of clearly distinguishable constituents (or phases) that show different electrical properties. Multifunctional composites have anisotropic electrical properties that can be tailored for a particular application. The effective anisotropic electrical conductivity of composites is strongly affected by many parameters including volume fractions, distributions, and orientations of constituents. Given the electrical properties of the constituents, one important goal of micromechanics of materials consists of predicting electrical response of the heterogeneous material on the basis of the geometries and properties of the individual phases, a task known as homogenization. The benefit of homogenization is that the behavior of a heterogeneous material can be determined without resorting or testing it. Furthermore, continuum micromechanics can predict the full multi-axial properties and responses of inhomogeneous materials, which are anisotropic in nature. Effective electrical conductivity estimation is performed by using classical micromechanics techniques (composite cylinder assemblage method) that investigates the effect of the fiber/matrix electrical properties and their volume fractions on the micro scale composite response. The composite cylinder assemblage method (CCM) is an analytical theory that is based on the assumption that composites are in a state of periodic structure. The CCM was developed to extend capabilities variable fiber shape/array availability with same volume fraction, interphase analysis, etc. The CCM is a continuum-based micromechanics model that provides closed form expressions for upper level length scales such as macro-scale composite responses in terms of the properties, shapes, orientations and constituent distributions at lower length levels such as the micro-scale.
Reliability of flip-chip bonded RFID die using anisotropic conductive paste hybrid material
Institute of Scientific and Technical Information of China (English)
Jun-Sik LEE; Jun-Ki KIM; Mok-Soon KIM; Namhyun KANG; Jong-Hyun LEE
2011-01-01
A reliability of flip-chip bonded die as a function of anisotropic conductive paste (ACP) hybrid materials. bonding conditions, and antenna pattern materials was investigated during the assembly of radio frequency identification(RFID) inlay. The optimization condition for flip-chip bonding was determined from the behavior of bonding strength. Under the optimized condition,the shear strength for the antenna printed with paste-type Ag ink was larger than that for Cu antenna. Furthermore, an identification distance was varied from the antenna materials. Comparing with the Ag antenna pattern, the as-bonded die on Cu antenna showed a larger distance of identification, However, the long-term reliability of inlay using the Cu antenna was decreased significantly as a function of aging time at room temperature because of the bended shape of Cu antenna formed during the flip-chip bonding process.
Ashkenazi, Y. K.
1981-01-01
The possibility of using general formulas for determining the strength of different anisotropic materials is considered, and theoretical formulas are applied and confirmed by results of tests on various nonmetallic materials. Data are cited on the strength of wood, plywood, laminated wood plastics, fiber glass-reinforced plastics and directed polymer films.
Measurement and inverse estimation of 3D anisotropic flow resistivity for porous materials
Göransson, Peter; Guastavino, Rémi; Hörlin, Nils-Erik
2009-11-01
This paper presents a new methodology for estimating the anisotropic flow resistivity for porous materials. From pressure measurements on a cubic or parallelepiped sample of a porous material, the flow resistivities are determined using inverse estimation. The core of the estimation is a series of 3D solutions to Darcy's law, where the flow resistivity tensor is varied until the sum of the quadratic errors between measured and computed pressures is minimised. The overall approach and experimental set-up used, enabling efficient measurements of high quality, are described in some detail together with the main steps of the measurement and estimation procedures. Results from a fibrous glass wool and a polyurethane foam are discussed and compared to standard measurement data.
Analytical solution of magnetothermoelastic interaction in a fiber-reinforced anisotropic material
Hobiny, Aatef D.; Abbas, Ibrahim A.
2016-12-01
The present paper is concerned with the investigation of the analytical solution of a fiber-reinforced anisotropic material under generalized magnetothermoelastic theory using the eigenvalue approach. Based on the Lord-Shulman theory, the formulation is applied to generalized magnetothermoelasticity with one relaxation time. Based on eigenvalue approach, exponential Fourier transform and Laplace techniques, the analytical solutions has been obtained. The inverses of Fourier transforms are obtained analytically. Numerical computations for a fiber-reinforced-like material have been performed and the results are presented graphically. The results of the temperature, displacement components and stress components have been verified numerically and are represented graphically. Comparisons are made with the results predicted by the presence and absence of reinforcement.
Numerical study of the thermal degradation of isotropic and anisotropic polymeric materials
Energy Technology Data Exchange (ETDEWEB)
Soler, E. [Departamento de Lenguajes y Ciencias de la Computacion, ETSI Informatica, Universidad de Malaga, 29071 Malaga (Spain); Ramos, J.I. [Room I-320-D, ETS Ingenieros Industriales, Universidad de Malaga, Plaza El Ejido, s/n, 29013 Malaga (Spain)
2005-08-01
The thermal degradation of two-dimensional isotropic, orthotropic and anisotropic polymeric materials is studied numerically by means of a second-order accurate (in both space and time) linearly implicit finite difference formulation which results in linear algebraic equations at each time step. It is shown that, for both isotropic and orthotropic composites, the monomer mass diffusion tensor plays a role in initiating the polymerization kinetics, the formation of a polymerization kernel and the initial front propagation, whereas the later stages of the polymerization are nearly independent of the monomer mass diffusion tensor. In anisotropic polymeric composites, it has been found that the monomer mass diffusion tensor plays a paramount role in determining the initial stages of the polymerization and the subsequent propagation of the polymerization front, the direction and speed of propagation of which are found to be related to the principal directions of both the monomer mass and the heat diffusion tensors. It is also shown that the polymerization time and temperatures depend strongly on the anisotropy of the mass and heat diffusion tensors. (authors)
Energy Technology Data Exchange (ETDEWEB)
Hutula, D.N.
1980-03-01
A finite element procedure is presented for finite deformation analysis of continuum structures with time-dependent anisotropic elastic-plastic material behavior. An updated Lagrangian formulation is used to describe the kinematics of deformation. Anisotropic constitutive relations are referred, at each material point, to a set of three mutually orthogonal axes which rotate as a unit with an angular velocity equal to the spin at the point. The time-history of the solution is generated by using a linear incremental procedure with residual force correction, along with an automatic time step control algorithm which chooses time step sizes to control the accuracy and numerical stability of the solution.
Raman and Photoluminescence Studies of In-plane Anisotropic Layered Materials
Pant, Anupum
This thesis presents systematic studies on angle dependent Raman and Photoluminescence (PL) of a new class of layered materials, Transition Metal Trichalcogenides (TMTCs), which are made up of layers possessing anisotropic structure within the van-der-Waals plane. The crystal structure of individual layer of MX3 compounds consists of aligned nanowire like 1D chains running along the b-axis direction. The work focuses on the growth of two members of this family - ZrS3 and TiS3 - through Chemical Vapor Transport Method (CVT), with consequent angle dependent Raman and PL studies which highlight their in-plane optically anisotropic properties. Results highlight that the optical properties of few-layer flakes are highly anisotropic as evidenced by large PL intensity variation with polarization direction (in ZrS3) and an intense variation in Raman intensity with variation in polarization direction (in both ZrS3 and TiS3). Results suggest that light is efficiently absorbed when E-field of the polarized incident excitation laser is polarized along the chain (b-axis). It is greatly attenuated and absorption is reduced when field is polarized perpendicular to the length of 1D-like chains, as wavelength of the exciting light is much longer than the width of each 1D chain. Observed PL variation with respect to the azimuthal flake angle is similar to what has been previously observed in 1D materials like nanowires. However, in TMTCs, since the 1D chains interact with each other, it gives rise to a unique linear dichroism response that falls between 2D and 1D like behavior. These results not only mark the very first demonstration of high PL polarization anisotropy in 2D systems, but also provide a novel insight into how interaction between adjacent 1D-like chains and the 2D nature of each layer influences the overall optical anisotropy of Quasi-1D materials. The presented results are anticipated to have impact in technologies involving polarized detection, near-field imaging
Directory of Open Access Journals (Sweden)
P.O. Judt
2015-10-01
Full Text Available In many engineering applications special requirements are directed to a material's fracture behavior and the prediction of crack paths. Especially if the material exhibits anisotropic elastic properties or fracture toughnesses, e.g. in textured or composite materials, the simulation of crack paths is challenging. Here, the application of path independent interaction integrals (I-integrals, J-, L- and M-integrals is beneficial for an accurate crack tip loading analysis. Numerical tools for the calculation of loading quantities using these path-invariant integrals are implemented into the commercial finite element (FE-code ABAQUS. Global approaches of the integrals are convenient considering crack tips approaching other crack faces, internal boundaries or material interfaces. Curved crack faces require special treatment with respect to integration contours. Numerical crack paths are predicted based on FE calculations of the boundary value problem in connection with an intelligent adaptive re-meshing algorithm. Considering fracture toughness anisotropy and accounting for inelastic effects due to small plastic zones in the crack tip region, the numerically predicted crack paths of different types of specimens with material interfaces and internal boundaries are compared to subcritically grown paths obtained from experiments.
Predicting the dielectric nonlinearity of anisotropic composite materials via tensorial analysis
Energy Technology Data Exchange (ETDEWEB)
Giordano, S [Department of Physics, University of Cagliari, Cittadella Universitaria, I-09042 Monserrato (Italy); Rocchia, W [NEST CNR-INFM, Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa (Italy)
2006-11-29
The discovery of new materials with peculiar optical properties as well as the prediction of their behaviour given the microstructure is a matter of remarkable interest in the community of material scientists. A complete theory allowing such a prediction is not yet available. We have formulated a theory able to analytically predict the effective second- and third-order nonlinear electrical behaviour of a dilute dispersion of randomly oriented anisotropic nonlinear spheres in a linear host. The inclusion medium has non-vanishing second- and third-order nonlinear hypersusceptibilities. As a result, the overall composite material is nonlinear but isotropic because of the random orientation of the inclusions. We derive the expressions for the equivalent permittivity and for the Kerr equivalent hypersusceptibility in terms of the characteristic electric tensors describing the electrical behaviour of the spheres. The complete averaging over inclusion positions and orientations led to general results in the dilute limit. We show that these results are consistent with earlier theories and that they provide null second-order hypersusceptibility as expected in a macroscopically isotropic medium. This theory generalizes the well-known Maxwell-Garnett formula and it can be easily specialized to any of the 32 crystallographic symmetry classes. Despite this study assuming static conditions, it can be generalized to the sinusoidal regime, pointing at an interesting way to engineer optically active materials with desired behaviour.
Directory of Open Access Journals (Sweden)
Zhao-Xia Tong
2013-01-01
Full Text Available The reliability of discrete element method (DEM numerical simulations is significantly dependent on the particle-scale parameters and boundary conditions. To verify the DEM models, two series of biaxial compression tests on ellipse-shaped steel rods are used. The comparisons on the stress-strain relationship, strength, and deformation pattern of experiments and simulations indicate that the DEM models are able to capture the key macro- and micromechanical behavior of inherently anisotropic granular materials with high fidelity. By using the validated DEM models, the boundary effects on the macrodeformation, strain localization, and nonuniformity of stress distribution inside the specimens are investigated using two rigid boundaries and one flexible boundary. The results demonstrate that the boundary condition plays a significant role on the stress-strain relationship and strength of granular materials with inherent fabric anisotropy if the stresses are calculated by the force applied on the wall. However, the responses of the particle assembly measured inside the specimens are almost the same with little influence from the boundary conditions. The peak friction angle obtained from the compression tests with flexible boundary represents the real friction angle of particle assembly. Due to the weak lateral constraints, the degree of stress nonuniformity under flexible boundary is higher than that under rigid boundary.
Focussing light in a bi-anisotropic slab with negatively refracting materials
Liu, Yan; Gralak, Boris; Ramakrishna, S Anantha
2013-01-01
We investigate the electromagnetic response of a pair of complementary bi-anisotropic media, which consist of a medium with positive refractive index ($+\\ep$, $+\\mu$, $+\\xi$) and a medium with negative refractive index($-\\ep$, $-\\mu$, $-\\xi$). We show that this idealized system has peculiar imaging properties in that it reproduces images of a source, in principle, with unlimited resolution. We then consider an infinite array of line sources regularly spaced in a one-dimensional photonic crystal (PC) consisting of 2n-layers of bi-anisotropic complementary media. Using coordinate transformation, we map this system into 2D corner chiral lenses of 2n heterogeneous anisotropic complementary media sharing a vertex, within which light circles around closed trajectories. Alternatively, one can consider corner lenses with homogeneous isotropic media and map them onto one dimensional PCs with heterogeneous bi-anisotropic layers. Interestingly, such complementary media are described by scalar, or matrix valued, sign-shi...
Thermal load leveling during silicon crystal growth from a melt using anisotropic materials
Energy Technology Data Exchange (ETDEWEB)
Carlson, Frederick M.; Helenbrook, Brian T.
2016-10-11
An apparatus for growing a silicon crystal substrate comprising a heat source, an anisotropic thermal load leveling component, a crucible, and a cold plate component is disclosed. The anisotropic thermal load leveling component possesses a high thermal conductivity and may be positioned atop the heat source to be operative to even-out temperature and heat flux variations emanating from the heat source. The crucible may be operative to contain molten silicon in which the top surface of the molten silicon may be defined as a growth interface. The crucible may be substantially surrounded by the anisotropic thermal load leveling component. The cold plate component may be positioned above the crucible to be operative with the anisotropic thermal load leveling component and heat source to maintain a uniform heat flux at the growth surface of the molten silicon.
The incremental response of a stressed, anisotropic granular material: loading and unloading
Ragione, Luigi La
2016-10-01
In this paper, we investigate the incremental response of a transversely isotropic granular material through numerical simulations (Distinct Element Method) and a theoretical model. A granular material is idealized by a random aggregate made of elastic, identical, frictional particles. We consider an initial isotropic compression followed by a uni-axial deformation, at constant pressure. The regime of deformation of our interest is quite narrow and it encompasses shear strains small compared to the volume strain associated with the pressure. In this regime, the contact network is almost the same as in the initial, isotropic, state, and anisotropy is induced by the applied strain through the contacts. In numerical simulations, particles deform according to local force and moment equilibrium, given an applied strain. In the theory, we do something similar and we allow a pair of contacting particles to deform while satisfying force and moment equilibrium, approximately. An average expression of the first moment of the contact forces is employed to obtain the stiffness tensor Aijkl relating the increments in stress with the increments in total average strain. We determine the non-zero components of Aijkl in stressed, anisotropic, states. The results refer to two cases: (a) when the contact friction coefficient is the same as in the uni-axial compression; (b) when a relatively high-contact friction coefficient is introduced (e.g. elastic response with a full mobilization of contact network). In the latter case, we recover, within a reasonable approximation, the typical structure of a transversely isotropic stiffness tensor Aijkl, itself a function of five independent constants; in the former, in case of forward incremental loading, we find the lack of major symmetry of the stiffness tensor, Aijkl ≠Aklij. We show that this occurs because particle deformation is not affine and because anisotropy is present in the aggregate. Theory and numerical DEM simulations agree
Directory of Open Access Journals (Sweden)
Abderraouf Messai
2013-01-01
Full Text Available A rigorous full-wave analysis of high Tc superconducting rectangular microstrip patch over ground plane with rectangular aperture in the case where the patch is printed on a uniaxially anisotropic substrate material is presented. The dyadic Green’s functions of the considered structure are efficiently determined in the vector Fourier transform domain. The effect of the superconductivity of the patch is taken into account using the concept of the complex resistive boundary condition. The accuracy of the analysis is tested by comparing the computed results with measurements and previously published data for several anisotropic substrate materials. Numerical results showing variation of the resonant frequency and the quality factor of the superconducting antenna with regard to operating temperature are given. Finally, the effects of uniaxial anisotropy in the substrate on the resonant frequencies of different TM modes of the superconducting microstrip antenna with rectangular aperture in the ground plane are presented.
Energy Technology Data Exchange (ETDEWEB)
Inampudi, Sandeep; Nazari, Mina; Forouzmand, Ali; Mosallaei, Hossein, E-mail: hosseinm@coe.neu.edu [Department of Electrical and Computer Engineering, Northeastern University, 360 Huntington Ave., Boston, Massachusetts 02115 (United States)
2016-01-14
We present a comprehensive analysis of surface plasmon polariton dispersion characteristics associated with isotropic and anisotropic two-dimensional atomically thin layered materials (2D sheets) coupled to h-BN heterostructures. A scattering matrix based approach is presented to compute the electromagnetic fields and related dispersion characteristics of stacked layered systems composed of anisotropic 2D sheets and uniaxial bulk materials. We analyze specifically the surface plasmon polariton (SPP) dispersion characteristics in case of isolated and coupled two-dimensional layers with isotropic and anisotropic conductivities. An analysis based on residue theorem is utilized to identify optimum optical parameters (surface conductivity) and geometrical parameters (separation between layers) to maximize the SPP field at a given position. The effect of type and degree of anisotropy on the shapes of iso-frequency curves and propagation characteristics is discussed in detail. The analysis presented in this paper gives an insight to identify optimum setup to enhance the SPP field at a given position and in a given direction on the surface of two-dimensional materials.
Ramirez, Sylvester
anisotropy of the thermal conductivity, K/K ⊥ ˜ 675, which is substantially larger even than in the high-quality graphite. The strongly anisotropic heat conduction properties of these films can be useful for the thermal filler applications. The results obtained for the nanostructured magnetic and hybrid materials are important for the renewable energy and electronic applications of permanent magnets.
A fully coupled elasto-plastic damage model applied to anisotropic materials
Wauters, M; Habraken, Anne; Duchene, Laurent
2000-01-01
In this paper, an elastoplastic energy-based anisotropic damage model for ductile fracture is described. A calibration method is also presented. The potential applicability of this model is illustrated by numerical examples of tensile test and Forming Limit Diagram establishment on a steel. Peer reviewed
Energy Technology Data Exchange (ETDEWEB)
Zhang, Hai-Feng, E-mail: hanlor@163.com, E-mail: lsb@nuaa.edu.cn [Key Laboratory of Radar Imaging and Microwave Photonics (Nanjing Univ. Aeronaut. Astronaut.), Ministry of Education, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Nanjing Artillery Academy, Nanjing 211132 (China); Liu, Shao-Bin, E-mail: hanlor@163.com, E-mail: lsb@nuaa.edu.cn; Tang, Yi-Jun [Key Laboratory of Radar Imaging and Microwave Photonics (Nanjing Univ. Aeronaut. Astronaut.), Ministry of Education, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Zhen, Jian-Ping [Nanjing Artillery Academy, Nanjing 211132 (China)
2014-03-15
In this paper, the properties of the right circular polarized (RCP) waves in the three-dimensional (3D) dispersive photonic crystals (PCs) consisting of the magnetized plasma and uniaxial material with face-centered-cubic (fcc) lattices are theoretically investigated by the plane wave expansion method, which the homogeneous anisotropic dielectric spheres (the uniaxial material) immersed in the magnetized plasma background, as the Faraday effects of magnetized plasma are considered (the incidence electromagnetic wave vector is parallel to the external magnetic field at any time). The equations for calculating the anisotropic photonic band gaps (PBGs) for the RCP waves in the first irreducible Brillouin zone are theoretically deduced. The anisotropic PBGs and a flatbands region can be obtained. The effects of the ordinary-refractive index, extraordinary-refractive index, anisotropic dielectric filling factor, plasma frequency, and plasma cyclotron frequency (the external magnetic field) on the properties of first two anisotropic PBGs for the RCP waves are investigated in detail, respectively. The numerical results show that the anisotropy can open partial band gaps in fcc lattices at U and W points, and the complete PBGs for the RCP waves can be achieved compared to the conventional 3D dispersive PCs composed of the magnetized plasma and isotropic material. It is also shown that the first two anisotropic PBGs can be tuned by those parameters as mentioned above. Those PBGs can be enlarged by introducing the uniaxial material into such 3D PCs as the Faraday effects are considered.
Torsion balance for study on anisotropic magnetic characteristics of superconducting materials
Ashimov, S M
2002-01-01
Paper describes low-temperature torsion balances to investigate into magnetic features of superconductors under rotation or oscillation of axisymmetric specimen as to the external magnetic field. The facility enables to measure tau specimen applied torsion moments within 1-10 sup - sup 8 N m limit. Because of high sensitivity one applies two-layer permalloy screens enabling to cool down superconductor in <= 10 sup - sup 3 Oe field. One demonstrates the most essential potentialities of the technique when studying critical parameters and anisotropic magnetic features of superconductors
GREEN'S FUNCTIONS FOR 2D PROBLEMS OF ANISOTROPIC PIEZOELECTRIC MATERIAL WITH A STRIP REGION
Institute of Scientific and Technical Information of China (English)
Hu Yiantai; Huang Yuying; Chen Chuanyao; Zhong Weifang
2000-01-01
By using Stroh's formalism and the conformal mapping technique, we derive the simple ex plicit elastic fields of a generalized line dislocation and a generalized line force in a general anisotropic piezo electric strip with fixed surfaces, which are two fixed conductor electrodes. The solutions obtained are usually considered as Green's functions which play important roles in the boundary element methods. The Coulomb forces of the distributed charges along the region boundaries on the line charge q at z0 are analysed in detail. The results are valid not only for plane and antiplane problems but also for the coupled problems between in plane and outplane deformations.
Optical correlation using isotropic and anisotropic self diffraction using photorefractive material
Buranasiri, Prathan
For two incident optical beams at different angles of incidence, a photorefractive cerium doped barium titanate crystal can facilitate different configurations of self-diffraction into higher orders. These configurations can be classified as isotropic and anisotropic, co-directional and contra-directional. Sometimes, a higher order resulting from an incident diverging object beam may comprise a converging beam, which then has the property of phase conjugation. Photorefractive fanning plays an important role in all these self-diffraction configurations. In this dissertation, we first explore the first higher order generated by forward three wave mixing. Only one higher order is observed when one of the incident beams is perpendicular to the surface of incidence. Not only the energy transfer via the first order grating has been observed but the energy transfer via the second order grating has been observed as well. With the angle between two incident beams less than 0.015 radians, the second configuration of self-diffraction has been investigated. With this configuration, codirectional isotropic self-diffraction (CODIS) and contradirectional isotropic self diffraction (CONDIS) have been observed. Phase conjugated beams which are responsible for CONDIS are the composite of mutual pumped phase conjugate (MPPC) and self pumped phase conjugate (SPPC). Due to the fanning effect, CONDIS usually forms before CODAS. In general, energy transfer between incident beams and CONDIS and CODIS occurs via first order and higher order gratings. For certain large but specific angles between the two incident extraordinarily polarized beams, it is possible to obtain anisotropic self-diffraction into ordinarily polarized higher orders. This third configuration for self-diffraction, called codirectional anisotropic self-diffraction (CODAS), can be generated most efficiently for the Bragg-matched case, although we have also observed CODAS with Bragg mismatch. In addition, CODAS has been
Cavitation for Incompressible Anisotropic Hyper-Elastic Materials%不可压各向异性超弹性材料中的空穴生成
Institute of Scientific and Technical Information of China (English)
任九生; 程昌钧
2002-01-01
The cavitation problem in a solid sphere composed of an incompressible anisotropic hyper-elastic material under a uniform radial tensile dead load was examined. A new analytical solution was obtained. The stress contributions were given and the jumping and concentration of stresses were discussed. The stability of solutions and the effect of the degree of anisotropy of the material were analyzed.
Institute of Scientific and Technical Information of China (English)
LIU Yanfang; SHI Fazhong; XU Xiangyang
2006-01-01
Two algorithms of computing stress increment by using the elasto-plasticity constitutive model are firstly formulated, which are the Euler integration method and the radial return method.Hill'48 anisotropic yield criterion is used. The Euler integration method can not obtain more accurate computation of the stress increment as the radial return method unless enough subintervals are taken,by which the Euler integration method will take excessive computing time. Without decreasing any accuracy, the radial return method can save much time. Finally, a square cup deep drawing from NUMISHEET'93 benchmarks is simulated with a self-developed code SheetForm in order to investigate the accuracy and efficiency of the radial return method.
Mityushev, V.; Rogosin, S.; Rutkauskas, S.
2009-01-01
Our work is devoted to the study of dependence of the effective conductivity of 2D composite material on the perturbation of inclusions. We consider the case of bounded composite material with finite number of inclusions.
Anisotropic elasticity and abnormal Poisson’s ratios in super-hard materials
Directory of Open Access Journals (Sweden)
Chuanwei Huang
2014-12-01
Full Text Available We theoretically investigated the variable mechanical properties such as Young’s modulus, Poisson’s ratios and compressibility in super-hard materials. Our tensorial analysis reveals that the mechanical properties of super-hard materials are strongly sensitive to the anisotropy index of materials. In sharp contrast to the traditional positive constant as thought before, the Poisson’s ratio of super-hard materials could be unexpectedly negative, zero, or even positive with a value much larger than the isotropic upper limit of 0.5 along definite directions. Our results uncover a correlation between compressibility and hardness, which offer insights on the prediction of new super-hard materials.
导热系数各向异性建筑材料的节能分析%Energy saving analysis of anisotropic building material of thermal conductivity
Institute of Scientific and Technical Information of China (English)
苏顺玉; 黄钦; 龚建伍
2013-01-01
The steady-state heat conductive mechanism of anisotropic material was analyzed in this paper. It indicated that heat conduction in anisotropic material is quite different from that in isotropic material. And temperature gradient of one direction at one point in the anisotropic material could cause partial heat flux in perpendicular direction. There are advantages and disadvantages while the anisotropic material of thermal conductivity is alone applied to building envelope. And the technique of double skin envelope has been successfully applied in many building designs. Basing on the heat conductive characteristics of anisotropic material, it was applied to double skin envelope in this paper. The combined building envelope of anisotropic material and double skin envelope was constructed. And heat transfer in it was analyzed. The results indicated that it is more economical of energy than traditional double skin envelope.%通过坐标变换法分析了各向异性材料的稳态导热机理,并指出各向异性材料内部的导热不同于各向同性材料,各向异性材料内部一点处某一方向上的温度梯度会在垂直方向上引发热流分量.导热系数各向异性材料单独用于建筑围护结构中有其优势但也存在不足之处,而双层幕墙技术已成功地应用于许多建筑设计中.针对各向异性材料的传热特性,将各向异性材料应用于双层幕墙,构建了各向异性材料和双层幕墙相结合的建筑围护结构,同时对其内部的热量传递进行了分析,结果表明,它比传统的双层幕墙更加节能.
Lourenço, P.B.; Rots, J.G.
1998-01-01
Results of using recently developed material models for the analysis of masonry structures are shown. Both interface modeling, in which masonry components (units and joints) are represented, as continuum modeling, in which masonry is represented as a homogeneous continuum, are addressed. It is shown
Biaxial Anisotropic Material Development and Characterization using Rectangular to Square Waveguide
2015-03-26
transition’s taper produces a magnitude response that is equivalent to a series of waveguide apertures that have capacitive equivalent circuits [13]. The ca...number of cell columns, y = number of cell rows, l, w, h = sample edge length, hc =cell height, wc =cell width, lc =cell length. Material definitions ...permittivity 57 of Teflonr, and the WRWS results exhibit significant ripple due to the reflections caused by the WRWS’s tapered transitions, as observed
Unit-Sphere Multiaxial Stochastic-Strength Model Applied to Anisotropic and Composite Materials
Nemeth, Noel, N.
2013-01-01
Models that predict the failure probability of brittle materials under multiaxial loading have been developed by authors such as Batdorf, Evans, and Matsuo. These "unit-sphere" models assume that the strength-controlling flaws are randomly oriented, noninteracting planar microcracks of specified geometry but of variable size. This methodology has been extended to predict the multiaxial strength response of transversely isotropic brittle materials, including polymer matrix composites (PMCs), by considering (1) flaw-orientation anisotropy, whereby a preexisting microcrack has a higher likelihood of being oriented in one direction over another direction, and (2) critical strength, or K (sub Ic) orientation anisotropy, whereby the level of critical strength or fracture toughness for mode I crack propagation, K (sub Ic), changes with regard to the orientation of the microstructure. In this report, results from finite element analysis of a fiber-reinforced-matrix unit cell were used with the unit-sphere model to predict the biaxial strength response of a unidirectional PMC previously reported from the World-Wide Failure Exercise. Results for nuclear-grade graphite materials under biaxial loading are also shown for comparison. This effort was successful in predicting the multiaxial strength response for the chosen problems. Findings regarding stress-state interactions and failure modes also are provided.
Alexander, C. S.; Key, C. T.; Schumacher, S. C.
2014-05-01
Recently there has been renewed interest in the dynamic response of composite materials; specifically low density epoxy matrix binders strengthened with continuous reinforcing fibers. This is in part due to the widespread use of carbon fiber composites in military, commercial, industrial, and aerospace applications. The design community requires better understanding of these materials in order to make full use of their unique properties. Planar impact testing was performed resulting in pressures up to 15 GPa on a unidirectional carbon fiber - epoxy composite, engineered to have high uniformity and low porosity. Results illustrate the anisotropic nature of the response under shock loading. Along the fiber direction, a two-wave structure similar to typical elastic-plastic response is observed, however, when shocked transverse to the fibers, only a single bulk shock wave is detected. At higher pressures, the epoxy matrix dissociates resulting in a loss of anisotropy. Greater understanding of the mechanisms responsible for the observed response has been achieved through numerical modeling of the system at the micromechanical level using the CTH hydrocode. From the simulation results it is evident that the observed two-wave structure in the longitudinal fiber direction is the result of a fast moving elastic precursor wave traveling in the carbon fibers ahead of the bulk response in the epoxy resin. Similarly, in the transverse direction, results show a collapse of the resin component consistent with the experimental observation of a single shock wave traveling at speeds associated with bulk carbon. Experimental and simulation results will be discussed and used to show where additional mechanisms, not fully described by the currently used models, are present.
Quantum storage of polarization qubits in birefringent and anisotropically absorbing materials
Clausen, Christoph; Afzelius, Mikael; Gisin, Nicolas
2012-01-01
Storage of quantum information encoded into true single photons is an essential constituent of long-distance quantum communication based on quantum repeaters and of optical quantum information processing. The storage of photonic polarization qubits is, however, complicated by the fact that many materials are birefringent and have polarization-dependent absorption. Here we present and demonstrate a simple scheme that allows compensating for these polarization effects. The scheme is demonstrated using a solid-state quantum memory implemented with an ensemble of rare-earth ions doped into a biaxial yttrium orthosilicate (Y_{2}SiO_{5}) crystal. Heralded single photons generated from a filtered spontaneous parametric downconversion source are stored, and quantum state tomography of the retrieved polarization state reveals an average fidelity of 97.5 \\pm 0.4%, which is significantly higher than what is achievable with a measure-and-prepare strategy.
Dropping the Ball: The effect of anisotropic granular materials on ejecta and impact crater shape
Drexler, Philip; Arratia, Paulo
2013-01-01
In this fluid dynamics video, we present an experimental investigation of the shape of impact craters in granular materials. Complex crater shapes, including polygons, have been observed in many terrestrial planets as well as moons and asteroids. We release spherical projectiles from different heights above a granular bed (sand). The experiments demonstrate two different techniques to create non-circular impact craters, which we measure by digitizing the final crater topography. In the first method, we create trenches in the sand to mimic fault lines or valleys on a planetary target. During impact, ejecta move faster in the direction of the trenches, creating nearly elliptical craters with the major axis running parallel to the trench. Larger trenches lead to more oblong craters. In the second method, a hose beneath the surface of the sand injects nitrogen gas. The pressure of the gas counters the hydrostatic pressure of the sand, greatly reducing static friction between grains above the injection point, with...
Sun, Bao-Zhen; Ma, Zuju; He, Chao; Wu, Kechen
2015-11-28
Thermoelectrics interconvert heat to electricity and are of great interest in waste heat recovery, solid-state cooling and so on. Here we assessed the potential of SnS2 and SnSe2 as thermoelectric materials at the temperature gradient from 300 to 800 K. Reflecting the crystal structure, the transport coefficients are highly anisotropic between a and c directions, in particular for the electrical conductivity. The preferred direction for both materials is the a direction in TE application. Most strikingly, when 800 K is reached, SnS2 can show a peak power factor (PF) of 15.50 μW cm(-1) K(-2) along the a direction, while a relatively low value (11.72 μW cm(-1) K(-2)) is obtained in the same direction of SnSe2. These values are comparable to those observed in thermoelectrics such as SnSe and SnS. At 300 K, the minimum lattice thermal conductivity (κmin) along the a direction is estimated to be about 0.67 and 0.55 W m(-1) K(-1) for SnS2 and SnSe2, respectively, even lower than the measured lattice thermal conductivity of Bi2Te3 (1.28 W m(-1) K(-1) at 300 K). The reasonable PF and κmin suggest that both SnS2 and SnSe2 are potential thermoelectric materials. Indeed, the estimated peak ZT can approach 0.88 for SnSe2 and a higher value of 0.96 for SnS2 along the a direction at a carrier concentration of 1.94 × 10(19) (SnSe2) vs. 2.87 × 10(19) cm(-3) (SnS2). The best ZT values in SnX2 (X = S, Se) are comparable to that in Bi2Te3 (0.8), a typical thermoelectric material. We hope that this theoretical investigation will provide useful information for further experimental and theoretical studies on optimizing the thermoelectric properties of SnX2 materials.
Electrical dissipation and material properties of in-plane anisotropic superconducting YBCO films
Czerwinka, P S
2001-01-01
vortex liquid-to-glass phase transition model (VG). In all cases, the data can be successfully collapsed when scaled under the VG algorithm forming the expected master curves for temperatures above and below the vortex-glass 'transition' temperature T sub V sub G (B). However, between film systems we observe wide variations of the critical exponent z(theta,B) and T sub V sub G (B) as a function of field strength (B) and field orientation (theta). This lack of 'universality' does not allow interpretation of the scaling as evidence for a vortex liquid-to-glass phase transition. We find quantitative evidence in support of alternative scaling models which are based upon conventional flux-flow/creep theories and distributions of vortex-pinning strength. We investigate the growth, material and electrical properties of a wide variety of YBa sub 2 Cu sub 3 O sub 7 sub - subdelta films (40-480nm). The films range from c-axis normal to c-axis parallel to the film plane and were grown upon SrTiO sub 3 (STO) and LaSrGaO ...
Molecular anisotropic magnetoresistance
Otte, Fabian; Heinze, Stefan; Mokrousov, Yuriy
2015-12-01
Using density functional theory calculations, we demonstrate that the effect of anisotropic magnetoresistance (AMR) can be enhanced by orders of magnitude with respect to conventional bulk ferromagnets in junctions containing molecules sandwiched between ferromagnetic leads. We study ballistic transport in metal-benzene complexes contacted by 3 d transition-metal wires. We show that a gigantic AMR can arise from spin-orbit coupling effects in the leads, drastically enhanced by orbital-symmetry filtering properties of the molecules. We further discuss how this molecular anisotropic magnetoresistance (MAMR) can be tuned by the proper choice of materials and their electronic properties.
Hwu, Chyanbin
2010-01-01
As structural elements, anisotropic elastic plates find wide applications in modern technology. The plates here are considered to be subjected to not only in plane load but also transverse load. In other words, both plane and plate bending problems as well as the stretching-bending coupling problems are all explained in this book. In addition to the introduction of the theory of anisotropic elasticity, several important subjects have are discussed in this book such as interfaces, cracks, holes, inclusions, contact problems, piezoelectric materials, thermoelastic problems and boundary element a
Kang, Joon Sang; Ke, Ming; Hu, Yongjie
2017-03-08
Two-dimensional van der Waals materials have shown novel fundamental properties and promise for wide applications. Here, we report for the first time an experimental demonstration of the in situ characterization and highly reversible control of the anisotropic thermal conductivity of black phosphorus. We develop a novel platform based on lithium ion batteries that integrates ultrafast optical spectroscopy and electrochemical control to investigate the interactions between lithium ions and the lattices of the black phosphorus electrode. We discover a strong dependence of the thermal conductivity on battery charge states (lithium concentrations) during the discharge/charge process. The thermal conductivity of black phosphorus is reversibly tunable over a wide range of 2.45-3.86, 62.67-85.80, and 21.66-27.58 W·m(-1)·K(-1) in the cross-plan, zigzag, and armchair directions, respectively. The modulation in thermal conductivity is attributed to phonon scattering introduced by the ionic intercalation in between the interspacing layers and shows anisotropic phonon scattering mechanism based on semiclassical model. At the fully discharged state (x ∼ 3 in LixP), a dramatic reduction of thermal conductivity by up to 6 times from that of the pristine crystal has been observed. This study provides a unique approach to explore the fundamental energy transport involving lattices and ions in the layered structures and may open up new opportunities in controlling energy transport based on novel operation mechanisms and the rational design of nanostructures.
Institute of Scientific and Technical Information of China (English)
陈宜亨; 马浩
1997-01-01
The explicit formulation of the J2-integral in anisotropic bodies and its application in microcrack shielding problems are discussed. With analytical treatments and numerical examinations, it is proved that there is a redistribution law for the remote J-integral in a discrete model of microcrack shielding problems, i.e. the projected conservation law of the Jk-vector. In this law, the J2-integral which was disregarded by Herrmann (1981) is proved to be of the same significance as the J1-integral. It is also concluded that the two energy dissipative processes due to the mi crocrack damage, i. e. the reduction in the effective moduli and the release of residual stresses, can be described by using the dissipation of the remote J-integral spreading across the microcrack damage zone.
Energy Technology Data Exchange (ETDEWEB)
Ouar, Nassima; Schoenstein, Frédéric; Mercone, Silvana; Farhat, Samir; Jouini, Noureddine [Laboratoire des Sciences des Procédés et des Matériaux, CNRS, LSPM—UPR 3407, Université Paris 13, Sorbonne-Paris-Cité, 99 Avenue J.-B. Clément, 93430 Villetaneuse (France); Villeroy, Benjamin [Institut de Chimie et des Matériaux Paris Est, CNRS, ICMPE—UMR 7182, Equipe de Chimie Métallurgique des Terres Rares, 2-8 rue Henri Dunant, 94320 Thiais Cedex (France); Leridon, Brigitte [Laboratoire de Physique et d’Étude des Matériaux, LPEM, ESPCI-ParisTech, CNRS, UPMC, 10 rue Vauquelin, F-75231 Paris Cedex 5 (France)
2013-10-28
We developed a two-step process showing the way for sintering anisotropic nanostructured bulk ferromagnetic materials. A new reactor has been optimized allowing the synthesis of several grams per batch of nanopowders via a polyol soft chemistry route. The feasibility of the scale-up has been successfully demonstrated for Co{sub 80}Ni{sub 20} nanowires and a massic yield of ∼97% was obtained. The thus obtained nanowires show an average diameter of ∼6 nm and a length of ∼270 nm. A new bottom-up strategy allowed us to compact the powder into a bulk nanostructured system. We used a spark-plasma-sintering technique under uniaxial compression and low temperature assisted by a permanent magnetic field of 1 T. A macroscopic pellet of partially aligned nanowire arrays has been easily obtained. This showed optimized coercive properties along the direction of the magnetic field applied during compaction (i.e., the nanowires' direction)
Koontz, Steve L.; Leger, Lubert J.; Wu, Corina; Cross, Jon B.; Jurgensen, Charles W.
1994-01-01
Neutral atomic oxygen is the most abundant component of the ionospheric plasma in the low Earth orbit environment (LEO; 200 to 700 kilometers altitude) and can produce significant degradation of some spacecraft materials. In order to produce a more complete understanding of the materials chemistry of atomic oxygen, the chemistry and physics of O-atom interactions with materials were determined in three radically different environments: (1) The Space Shuttle cargo bay in low Earth orbit (the EOIM-3 space flight experiment), (2) a high-velocity neutral atom beam system (HVAB) at Los Alamos National Laboratory (LANL), and (3) a microwave-plasma flowing-discharge system at JSC. The Space Shuttle and the high velocity atom beam systems produce atom-surface collision energies ranging from 0.1 to 7 eV (hyperthermal atoms) under high-vacuum conditions, while the flowing discharge system produces a 0.065 eV surface collision energy at a total pressure of 2 Torr. Data obtained in the three different O-atom environments referred to above show that the rate of O-atom reaction with polymeric materials is strongly dependent on atom kinetic energy, obeying a reactive scattering law which suggests that atom kinetic energy is directly available for overcoming activation barriers in the reaction. General relationships between polymer reactivity with O atoms and polymer composition and molecular structure have been determined. In addition, vacuum ultraviolet photochemical effects have been shown to dominate the reaction of O atoms with fluorocarbon polymers. Finally, studies of the materials chemistry of O atoms have produced results which may be of interest to technologists outside the aerospace industry. Atomic oxygen 'spin-off' or 'dual use' technologies in the areas of anisotropic etching in microelectronic materials and device processing, as well as surface chemistry engineering of porous solid materials are described.
Fractures in anisotropic media
Shao, Siyi
theory and experimental results in this report demonstrate that the presence of fractures in anisotropic material can be unambiguously interpreted if experimental measurements are made as a function of stress, which eliminates many fracture-generated discrete modes (e.g., interface waves, and leaky guided-modes). Orthogonal fracture networks that are often encountered in field exploration bring in additional challenges for seismic/acoustic data interpretation. An innovative wavefront imaging system with a bi-axial load frame was designed and implemented on orthogonally-fractured samples to determine the effect of fracture networks on elastic wave propagation. The effects of central wave guiding and extra time delays along a fracture intersection were observed in experiments and was analyzed. Interpreting data from media with intersecting fracture sets must account for fracture intersections and the non-uniformity of fracture properties caused by local tectonic conditions or other physical process such as non-uniform fluid distributions within a network and/or chemical alterations.
Modelling of CMUTs with Anisotropic Plates
DEFF Research Database (Denmark)
la Cour, Mette Funding; Christiansen, Thomas Lehrmann; Jensen, Jørgen Arendt;
2012-01-01
Traditionally, CMUTs are modelled using the isotropic plate equation and this leads to deviations between analytical calculations and FEM simulations. In this paper, the deflection profile and material parameters are calculated using the anisotropic plate equation. It is shown that the anisotropic...
Energy Technology Data Exchange (ETDEWEB)
Pudovikov, Sergey
2013-11-21
Austenitic and dissimilar welds with respect to the ultrasonic testing (UT) methods are considered normally as ''difficult-to-test'' objects. During the solidification process in such welds a distinct dendrite microstructure evolves, which is coarse-grained, anisotropic and inhomogeneous simultaneously. The reliability of available ultrasonic methods on austenitic welds depends significantly on the selected UT-parameters as well as on the inspection personnel experience. In the present dissertation, an ultrasonic testing method was developed, which allows the flaw detection and evaluation in acoustically anisotropic inhomogeneous materials, especially in austenitic and dissimilar welds with a quantitative statement to the defect size, type, and location. The principle of synthetic focusing with taking into account the material anisotropy and inhomogeneity along with two- and three-dimensional visualization provides a reliable and quantitative assessment of the inspection results in acoustically anisotropic inhomogeneous test objects. Among others, an iterative algorithm for the determination of unknown elastic properties of inhomogeneous anisotropic materials has been developed. It allows practical application of the developed UT method, since the anisotropy of most of austenitic and dissimilar welds (especially of hand-welded joints) in practice is usually unknown. The functionality of the developed inspection technique has been validated by many experiments on welded austenitic specimens having artificial and natural defects. For the practical application of the new ultrasonic technique different testing strategies are proposed, which can be used depending on the current inspection task.
Anisotropically structured magnetic aerogel monoliths
Heiligtag, Florian J.; Airaghi Leccardi, Marta J. I.; Erdem, Derya; Süess, Martin J.; Niederberger, Markus
2014-10-01
Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture.Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture. Electronic supplementary information (ESI) available: Digital photographs of dispersions and gels with different water-to-ethanol ratios; magnetic measurements of an anatase aerogel containing 0.25 mol% Fe3O4 nanoparticles; XRD patterns of the iron oxide and
Enhancement of non-resonant dielectric cloaks using anisotropic composites
Takezawa, Akihiro
2014-01-01
The effectiveness of homogenized anisotropic materials in non-resonant dielectric multilayer cloaking is studied. Because existing multilayer cloaking by isotropic materials can be regarded as homogenous anisotropic cloaking from a macroscopic view, they can be efficiently designed by handling the physical properties of anisotropic materials directly. Anisotropic properties can be realized in two-phase composites if the physical properties of the material are within appropriate bounds. The optimized anisotropic physical properties are identified by a numerical optimization technique based on a full-wave simulation using the finite element method. The cloaking performance measured by the total scattering width is improved by about 10% compared with existing multilayer cloaking by isotropic materials in eight-layer cylindrical cloaking materials. The same performance with eight-layer cloaking by isotropic materials is achieved by three-layer cloaking using anisotropic materials. Cloaking with a about 50% reduct...
Zhang, Xiao-Yu; Huang, Jin-Dou; Yu, Juan-Juan; Li, Peng; Zhang, Wei-Ping; Frauenheim, Thoma
2015-10-14
In this study, the electron-transfer properties of alkynylated indenofluorene-diones with various substituents (SiMe3, SiPr3, and SiPh3) that function as n-type organic semiconductors were comparatively investigated at the first-principles DFT level based on the Marcus-Hush theory. The reorganization energies are calculated by the adiabatic potential-energy surface method, and the coupling terms are evaluated through a direct adiabatic model. The maximum value of the electron-transfer mobility of SiPr3 is 0.485 cm(2) V(-1) s(-1), which appears at the orientation angle of the conducting channel on the reference plane a-b near to 172°/352°. The predicted maximum electron mobility value of SiPr3 is nearly 26 times larger than that of SiPh3. This may be attributed to the largest number of intermolecular π-π interactions. In addition, the mobilities in all three crystals show remarkable anisotropic behavior. The calculated results indicate that SiPr3 could be an ideal candidate as a high-performance n-type organic semiconductor material. Our investigations not only give us an opportunity to completely understand the charge transport mechanisms, but also provide guidelines for designing materials for electronic applications.
2015-01-24
endosteal and periosteal formative surfaces [23]. We chose one of these sites (the Antero-Medial or AM cortex) for our study. The growth of the...figure, instead of a uniform expansion of the cortex around the periosteal or endosteal surfaces, bone formation and resorption take place as a...mechanisms of bovine tibial cortical bone. Journal of Materials Science: Materials in Medicine, 2005. 16(10): p. 947-959. 3. Goodwin, K.J. and N.A
Magnetic relaxation in anisotropic magnets
DEFF Research Database (Denmark)
Lindgård, Per-Anker
1971-01-01
The line shape and the kinematic and thermodynamic slowing down of the critical and paramagnetic relaxation in axially anisotropic materials are discussed. Kinematic slowing down occurs only in the longitudinal relaxation function. The thermodynamic slowing down occurs in either the transverse or...
Energy Technology Data Exchange (ETDEWEB)
Chang, Jiwon [SEMATECH, 257 Fuller Rd #2200, Albany, New York 12203 (United States)
2015-06-07
Ballistic transport characteristics of metal-oxide semiconductor field effect transistors (MOSFETs) based on anisotropic two-dimensional materials monolayer HfS{sub 2} and phosphorene are explored through quantum transport simulations. We focus on the effects of the channel crystal orientation and the channel length scaling on device performances. Especially, the role of degenerate conduction band (CB) valleys in monolayer HfS{sub 2} is comprehensively analyzed. Benchmarking monolayer HfS{sub 2} with phosphorene MOSFETs, we predict that the effect of channel orientation on device performances is much weaker in monolayer HfS{sub 2} than in phosphorene due to the degenerate CB valleys of monolayer HfS{sub 2}. Our simulations also reveal that at 10 nm channel length scale, phosphorene MOSFETs outperform monolayer HfS{sub 2} MOSFETs in terms of the on-state current. However, it is observed that monolayer HfS{sub 2} MOSFETs may offer comparable, but a little bit degraded, device performances as compared with phosphorene MOSFETs at 5 nm channel length.
A Modified PUFF Equation of State for Anisotropic Materials%一种适用于各向异性材料的修正PUFF物态方程
Institute of Scientific and Technical Information of China (English)
黄霞; 汤文辉; 蒋邦海; 王道荣
2011-01-01
给出一种适用于各向异性材料的修正PUFF物态方程,既能体现各向异性材料在压缩和膨胀过程中材料体积变化的非线性特征,又能反映材料的各向异性强度效应.以正交各向异性材料二维碰撞问题和X射线辐照下的二维热击波为例,利用有限元方法编写程序进行数值模拟,对根据传统PUFF物态方程和修正PUFF物态方程计算得到的平均正应力值作对比研究,结果表明,低压和拉伸状态下二者存在明显差异,在高压下二者趋于一致.%A modified PUFF equation of state is proposed with considenation of both non-linear volume change and anisotropic strength of material under compression and dilation. Taking 2-D impact of orthotropic material and thermal shock wave under X-ray radiation as examples, a finite element program is developed. The mean stresses obtained by traditional and modified PUFF equation of state are compared. They are obviously different at low compression and tension states. With increase of stress, they tends to be consistent gradually.
van Kats, C. M.
2008-10-01
The driving forces for fundamental research in colloid science are the ability to manage the material properties of colloids and to unravel the forces that play a role between colloids to be able to control and understand the processes where colloids play an important role. Therefore we are searching for colloidal materials with specific physical properties to better understand our surrounding world.Until recently research in colloid science was mainly focused on spherical (isotropic) particles. Monodisperse spherical colloids serve as a model system as they exhibit similar phase behaviour as molecular and atomic systems. Nevertheless, in many cases the spherical shape is not sufficient to reach the desired research goals. Recently the more complex synthesis methods of anisotropic model colloids has strongly developed. This thesis should be regarded as a contribution to this research area. Anisotropic colloids can be used as a building block for complex structures and are expected not only to lead to the construction of full photonic band gap materials. They will also serve as new, more realistic, models systems for their molecular analogues. Therefore the term ‘molecular colloids” is sometimes used to qualify these anisotropic colloidal particles. In the introduction of this thesis, we give an overview of the main synthesis techniques for anisotropic colloids. Chapter 2 describes the method of etching silicon wafers to construct monodisperse silicon rods. They subsequently were oxidized and labeled (coated) with a fluorescent silica layer. The first explorative phase behaviour of these silica rods was studied. The particles showed a nematic ordering in charge stabilized suspensions. Chapter 3 describes the synthesis of colloidal gold rods and the (mesoporous) silica coating of gold rods. Chapter 4 describes the physical and optical properties of these particles when thermal energy is added. This is compared to the case where the particles are irradiated with
Fronts of Stress Wave in Anisotropic Piezoelectric Media
Institute of Scientific and Technical Information of China (English)
刘颖; 刘凯欣; 高凌天
2004-01-01
The characteristic of wave fronts in anisotropic piezoelectric media is analysed by adopting the generalized characteristic theory. Analytical expressions for wave velocities and wave fronts are formulated. Apart from the ordinary characteristics, a new phenomenon, energy velocity funnel, is formed on the wave fronts of quasitransverse waves in anisotropic piezoelectric materials. A three-dimensional representation of wave fronts in anisotropic piezoelectric materials is given for a better understanding of the new phenomena.
Placidi, Luca; Seddik, Hakime; Faria, Sergio H
2009-01-01
A complete theoretical presentation of the CAFFE model (Continuum-mechanical, Anisotropic Flow model, based on an anisotropic Flow Enhancement factor) is given. The CAFFE model is an application of the theory of mixtures with continuous diversity for the case of large ice masses in which the induced anisotropy can not be neglected. The anisotropic response of the material is considered via a simple anisotropic generalization of Glen's flow law based on a scalar anisotropic enhancement factor. Such an enhancement factor depends upon the orientation mass density, that corresponds to the distribution of lattice orientations or simply to the orientation distribution function. The evolution of anisotropy is assumed to be modeled by the evolution of the orientation mass density, that is governed by the balance of mass of the present mixture with continuous diversity and explicitly depends upon four distinct effects interpreted, respectively, with grain rotation, local rigid body rotation, grain boundary migration (...
Reformulation of Nonlinear Anisotropic Crystal Elastoplasticity for Impact Physics
2015-03-01
Clayton JD, McDowell DL. Homogenized finite elastoplasticity and damage : theory and computations. Mechanics of Materials. 2004;36:799–824. 23. Clayton...ARL-TR-7231 ● MAR 2015 US Army Research Laboratory Reformulation of Nonlinear Anisotropic Crystal Elastoplasticity for Impact...of Nonlinear Anisotropic Crystal Elastoplasticity for Impact Physics by JD Clayton Weapons and Materials Research Directorate, ARL
Fast Anisotropic Gauss Filtering
Geusebroek, J.M.; Smeulders, A.W.M.; van de Weijer, J.; Heyden, A.; Sparr, G.; Nielsen, M.; Johansen, P.
2002-01-01
We derive the decomposition of the anisotropic Gaussian in a one dimensional Gauss filter in the x-direction followed by a one dimensional filter in a non-orthogonal direction phi. So also the anisotropic Gaussian can be decomposed by dimension. This appears to be extremely efficient from a computin
Fast Anisotropic Gauss Filters
Geusebroek, J.M.; Smeulders, A.W.M.; van de Weijer, J.
2003-01-01
We derive the decomposition of the anisotropic Gaussian in a one dimensional Gauss filter in the x-direction phi. So also the anisotropic Gaussian can be decomposed by dimension. This appears to be extremely efficient from a computing perspective. An implementation scheme for normal covolution and f
Anisotropic nanomaterials preparation, properties, and applications
Li, Quan
2015-01-01
In this book anisotropic one-dimensional and two-dimensional nanoscale building blocks and their assembly into fascinating and qualitatively new functional structures embracing both hard and soft components are explained. Contributions from leading experts regarding important aspects like synthesis, assembly, properties and applications of the above materials are compiled into a reference book. The anisotropy, i.e. the direction-dependent physical properties, of materials is fascinating and elegant and has sparked the quest for anisotropic materials with useful properties. With such a curiosi
Frontiers in Anisotropic Shock-Wave Modeling
2012-02-01
contact info: Tel.: +44 07840355383, Fax: +44 (0) 1234 758217. Studies of anisotropic materials and the discovery of various novel and unexpected phenomena...19 Figure 4. The Kevlar ...Epoxy IFPT simulated and experimental back surface velocities for 572, 788, and 1015 m/s. The experimental data Kevlar /Epoxy materials recovered after
Radar velocity tomography in anisotropic media
Energy Technology Data Exchange (ETDEWEB)
Kim, Jung Ho; Cho, Seong Jun; Yi Myeong Jong; Chung, Seung Hwan [Korea Institute of Geology Mining and Materials, Taejon (Korea, Republic of)
1996-12-01
Radar tomography inversion method was developed in the elliptic anisotropic environment with the parametrization of maximum, minimum velocity, and the direction of symmetry axis. Nonlinear least-square method with smoothness constraint was adopted as inversion scheme. Newly developed algorithm was successfully tested with the 2-D numerical cross-borehole data in isotropic environment. Seismic data from physical modelling in partially anisotropic environment was also inverted and compared with the reconstruction technique assuming isotropic media. We could confirm the effectiveness of our algorithm, even though the tested data were generated from isotropic or partially anisotropic media. Cross-hole radar field data in limestone area in Korea was analyzed that the limestone bedrock is systematically anisotropic in the sense of radar application. The data set was inverted with the new anisotropy algorithm. The anisotropic effect in the data was corrected and also inverted for the comparison through the algorithm with isotropic assumption. Applying two different algorithm and comparing the various images, the tomographic image of maximum velocity from anisotropic inversion could give the most excellent way to visualize underground. An addition to the high resolution image, we could grasp some information on the material type from the feature of maximum velocity distribution the degree of anisotropy which can be inferred from the ratio of maximum and minimum velocity. The newly developed algorithm will be expected to provide a good way to image underground, especially in sedimentary or metamorphosed bedrock. (author). 9 refs., 21 figs.
Effective medium theory for anisotropic metamaterials
Zhang, Xiujuan
2015-01-20
Materials with anisotropic material parameters can be utilized to fabricate many fascinating devices, such as hyperlenses, metasolids, and one-way waveguides. In this study, we analyze the effects of geometric anisotropy on a two-dimensional metamaterial composed of a rectangular array of elliptic cylinders and derive an effective medium theory for such a metamaterial. We find that it is possible to obtain a closed-form analytical solution for the anisotropic effective medium parameters, provided the aspect ratio of the lattice and the eccentricity of the elliptic cylinder satisfy certain conditions. The derived effective medium theory not only recovers the well-known Maxwell-Garnett results in the quasi-static regime, but is also valid beyond the long-wavelength limit, where the wavelength in the host medium is comparable to the size of the lattice so that previous anisotropic effective medium theories fail. Such an advance greatly broadens the applicable realm of the effective medium theory and introduces many possibilities in the design of structures with desired anisotropic material characteristics. A real sample of a recently theoretically proposed anisotropic medium, with a near-zero index to control the flux, is achieved using the derived effective medium theory, and control of the electromagnetic waves in the sample is clearly demonstrated.
Anisotropic Contrast Optical Microscope
Peev, D; Kananizadeh, N; Wimer, S; Rodenhausen, K B; Herzinger, C M; Kasputis, T; Pfaunmiller, E; Nguyen, A; Korlacki, R; Pannier, A; Li, Y; Schubert, E; Hage, D; Schubert, M
2016-01-01
An optical microscope is described that reveals contrast in the Mueller matrix images of a thin, transparent or semi-transparent specimen located within an anisotropic object plane (anisotropic filter). The specimen changes the anisotropy of the filter and thereby produces contrast within the Mueller matrix images. Here we use an anisotropic filter composed of a semi-transparent, nanostructured thin film with sub-wavelength thickness placed within the object plane. The sample is illuminated as in common optical microscopy but the light is modulated in its polarization using combinations of linear polarizers and phase plate (compensator) to control and analyze the state of polarization. Direct generalized ellipsometry data analysis approaches permit extraction of fundamental Mueller matrix object plane images dispensing with the need of Fourier expansion methods. Generalized ellipsometry model approaches are used for quantitative image analyses. We demonstrate the anisotropic contrast optical microscope by mea...
Generalized Fractional Derivative Anisotropic Viscoelastic Characterization
Directory of Open Access Journals (Sweden)
Harry H. Hilton
2012-01-01
Full Text Available Isotropic linear and nonlinear fractional derivative constitutive relations are formulated and examined in terms of many parameter generalized Kelvin models and are analytically extended to cover general anisotropic homogeneous or non-homogeneous as well as functionally graded viscoelastic material behavior. Equivalent integral constitutive relations, which are computationally more powerful, are derived from fractional differential ones and the associated anisotropic temperature-moisture-degree-of-cure shift functions and reduced times are established. Approximate Fourier transform inversions for fractional derivative relations are formulated and their accuracy is evaluated. The efficacy of integer and fractional derivative constitutive relations is compared and the preferential use of either characterization in analyzing isotropic and anisotropic real materials must be examined on a case-by-case basis. Approximate protocols for curve fitting analytical fractional derivative results to experimental data are formulated and evaluated.
Micromechanics and dislocation theory in anisotropic elasticity
Lazar, Markus
2016-01-01
In this work, dislocation master-equations valid for anisotropic materials are derived in terms of kernel functions using the framework of micromechanics. The second derivative of the anisotropic Green tensor is calculated in the sense of generalized functions and decomposed into a sum of a $1/R^3$-term plus a Dirac $\\delta$-term. The first term is the so-called "Barnett-term" and the latter is important for the definition of the Green tensor as fundamental solution of the Navier equation. In addition, all dislocation master-equations are specified for Somigliana dislocations with application to 3D crack modeling. Also the interior Eshelby tensor for a spherical inclusion in an anisotropic material is derived as line integral over the unit circle.
Anisotropic nanomaterials: structure, growth, assembly, and functions.
Sajanlal, Panikkanvalappil R; Sreeprasad, Theruvakkattil S; Samal, Akshaya K; Pradeep, Thalappil
2011-01-01
Comprehensive knowledge over the shape of nanomaterials is a critical factor in designing devices with desired functions. Due to this reason, systematic efforts have been made to synthesize materials of diverse shape in the nanoscale regime. Anisotropic nanomaterials are a class of materials in which their properties are direction-dependent and more than one structural parameter is needed to describe them. Their unique and fine-tuned physical and chemical properties make them ideal candidates for devising new applications. In addition, the assembly of ordered one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) arrays of anisotropic nanoparticles brings novel properties into the resulting system, which would be entirely different from the properties of individual nanoparticles. This review presents an overview of current research in the area of anisotropic nanomaterials in general and noble metal nanoparticles in particular. We begin with an introduction to the advancements in this area followed by general aspects of the growth of anisotropic nanoparticles. Then we describe several important synthetic protocols for making anisotropic nanomaterials, followed by a summary of their assemblies, and conclude with major applications.
Anisotropic nanomaterials: structure, growth, assembly, and functions
Directory of Open Access Journals (Sweden)
Panikkanvalappil R. Sajanlal
2011-02-01
Full Text Available Comprehensive knowledge over the shape of nanomaterials is a critical factor in designing devices with desired functions. Due to this reason, systematic efforts have been made to synthesize materials of diverse shape in the nanoscale regime. Anisotropic nanomaterials are a class of materials in which their properties are direction-dependent and more than one structural parameter is needed to describe them. Their unique and fine-tuned physical and chemical properties make them ideal candidates for devising new applications. In addition, the assembly of ordered one-dimensional (1D, two-dimensional (2D, and three-dimensional (3D arrays of anisotropic nanoparticles brings novel properties into the resulting system, which would be entirely different from the properties of individual nanoparticles. This review presents an overview of current research in the area of anisotropic nanomaterials in general and noble metal nanoparticles in particular. We begin with an introduction to the advancements in this area followed by general aspects of the growth of anisotropic nanoparticles. Then we describe several important synthetic protocols for making anisotropic nanomaterials, followed by a summary of their assemblies, and conclude with major applications.
Electrochemical Impedance of a Battery Electrode with Anisotropic Active Particles
Song, J
2013-01-01
Electrochemical impedance spectra for battery electrodes are usually interpreted using models that assume isotropic active particles, having uniform current density and symmetric diffusivities. While this can be reasonable for amorphous or polycrystalline materials with randomly oriented grains, modern electrode materials increasingly consist of highly anisotropic, single-crystalline, nanoparticles, with different impedance characteristics. In this paper, analytical expressions are derived for the impedance of anisotropic particles with tensorial diffusivities and orientation-dependent surface reaction rates and capacitances. The resulting impedance spectrum contains clear signatures of the anisotropic material properties and aspect ratio, as well as statistical variations in any of these parameters.
Statistical Anisotropy from Anisotropic Inflation
Soda, Jiro
2012-01-01
We review an inflationary scenario with the anisotropic expansion rate. An anisotropic inflationary universe can be realized by a vector field coupled with an inflaton, which can be regarded as a counter example to the cosmic no-hair conjecture. We show generality of anisotropic inflation and derive a universal property. We formulate cosmological perturbation theory in anisotropic inflation. Using the formalism, we show anisotropic inflation gives rise to the statistical anisotropy in primordial fluctuations. We also explain a method to test anisotropic inflation using the cosmic microwave background radiation (CMB).
Raman Tensor Formalism for Optically Anisotropic Crystals.
Kranert, Christian; Sturm, Chris; Schmidt-Grund, Rüdiger; Grundmann, Marius
2016-03-25
We present a formalism for calculating the Raman scattering intensity dependent on the polarization configuration for optically anisotropic crystals. It can be applied to crystals of arbitrary orientation and crystal symmetry measured in normal incidence backscattering geometry. The classical Raman tensor formalism cannot be used for optically anisotropic materials due to birefringence causing the polarization within the crystal to be depth dependent. We show that in the limit of averaging over a sufficiently large scattering depth, the observed Raman intensities converge and can be described by an effective Raman tensor given here. Full agreement with experimental results for uniaxial and biaxial crystals is demonstrated.
Anisotropic hydrodynamics -- basic concepts
Florkowski, Wojciech; Ryblewski, Radoslaw; Strickland, Michael
2013-01-01
Due to the rapid longitudinal expansion of the quark-gluon plasma created in relativistic heavy ion collisions, potentially large local rest frame momentum-space anisotropies are generated. The magnitude of these momentum-space anisotropies can be so large as to violate the central assumption of canonical viscous hydrodynamical treatments which linearize around an isotropic background. In order to better describe the early-time dynamics of the quark gluon plasma, one can consider instead expanding around a locally anisotropic background which results in a dynamical framework called anisotropic hydrodynamics. In this proceedings contribution we review the basic concepts of the anisotropic hydrodynamics framework presenting viewpoints from both the phenomenological and microscopic points of view.
Quasiparticle anisotropic hydrodynamics
Alqahtani, Mubarak
2016-01-01
We study an azimuthally-symmetric boost-invariant quark-gluon plasma using quasiparticle anisotropic hydrodynamics including the effects of both shear and bulk viscosities. We compare results obtained using the quasiparticle method with the standard anisotropic hydrodynamics and viscous hydrodynamics. We consider the predictions of the three methods for the differential particle spectra and mean transverse momentum. We find that the three methods agree for small shear viscosity to entropy density ratio, $\\eta/s$, but show differences at large $\\eta/s$. Additionally, we find that the standard anisotropic hydrodynamics method shows suppressed production at low transverse-momentum compared to the other two methods, and the bulk-viscous correction can drive the primordial particle spectra negative at large $p_T$ in viscous hydrodynamics.
Gravitational stresses in anisotropic rock masses
Amadei, B.; Savage, W.Z.; Swolfs, H.S.
1987-01-01
This paper presents closed-form solutions for the stress field induced by gravity in anisotropic rock masses. These rocks are assumed to be laterally restrained and are modelled as a homogeneous, orthotropic or transversely isotropic, linearly elastic material. The analysis, constrained by the thermodynamic requirement that strain energy be positive definite, gives the following important result: inclusion of anisotropy broadens the range of permissible values of gravity-induced horizontal stresses. In fact, for some ranges of anisotropic rock properties, it is thermodynamically admissible for gravity-induced horizontal stresses to exceed the vertical stress component; this is not possible for the classical isotropic solution. Specific examples are presented to explore the nature of the gravity-induced stress field in anisotropic rocks and its dependence on the type, degree and orientation of anisotropy with respect to the horizontal ground surface. ?? 1987.
Anisotropic Hanle line shape via magnetothermoelectric phenomena
Das, K. S.; Dejene, F. K.; van Wees, B. J.; Vera-Marun, I. J.
2016-11-01
We observe anisotropic Hanle line shape with unequal in-plane and out-of-plane nonlocal signals for spin precession measurements carried out on lateral metallic spin valves with transparent interfaces. The conventional interpretation for this anisotropy corresponds to unequal spin relaxation times for in-plane and out-of-plane spin orientations as for the case of two-dimensional materials like graphene, but it is unexpected in a polycrystalline metallic channel. Systematic measurements as a function of temperature and channel length, combined with both analytical and numerical thermoelectric transport models, demonstrate that the anisotropy in the Hanle line shape is magnetothermal in origin, caused by the anisotropic modulation of the Peltier and Seebeck coefficients of the ferromagnetic electrodes. Our results call for the consideration of such magnetothermoelectric effects in the study of anisotropic spin relaxation.
Anisotropic contrast optical microscope
Peev, D.; Hofmann, T.; Kananizadeh, N.; Beeram, S.; Rodriguez, E.; Wimer, S.; Rodenhausen, K. B.; Herzinger, C. M.; Kasputis, T.; Pfaunmiller, E.; Nguyen, A.; Korlacki, R.; Pannier, A.; Li, Y.; Schubert, E.; Hage, D.; Schubert, M.
2016-11-01
An optical microscope is described that reveals contrast in the Mueller matrix images of a thin, transparent, or semi-transparent specimen located within an anisotropic object plane (anisotropic filter). The specimen changes the anisotropy of the filter and thereby produces contrast within the Mueller matrix images. Here we use an anisotropic filter composed of a semi-transparent, nanostructured thin film with sub-wavelength thickness placed within the object plane. The sample is illuminated as in common optical microscopy but the light is modulated in its polarization using combinations of linear polarizers and phase plate (compensator) to control and analyze the state of polarization. Direct generalized ellipsometry data analysis approaches permit extraction of fundamental Mueller matrix object plane images dispensing with the need of Fourier expansion methods. Generalized ellipsometry model approaches are used for quantitative image analyses. These images are obtained from sets of multiple images obtained under various polarizer, analyzer, and compensator settings. Up to 16 independent Mueller matrix images can be obtained, while our current setup is limited to 11 images normalized by the unpolarized intensity. We demonstrate the anisotropic contrast optical microscope by measuring lithographically defined micro-patterned anisotropic filters, and we quantify the adsorption of an organic self-assembled monolayer film onto the anisotropic filter. Comparison with an isotropic glass slide demonstrates the image enhancement obtained by our method over microscopy without the use of an anisotropic filter. In our current instrument, we estimate the limit of detection for organic volumetric mass within the object plane of ≈49 fg within ≈7 × 7 μm2 object surface area. Compared to a quartz crystal microbalance with dissipation instrumentation, where contemporary limits require a total load of ≈500 pg for detection, the instrumentation demonstrated here improves
Pérez-Nadal, Guillem
2016-01-01
We consider a non-relativistic free scalar field theory with a type of anisotropic scale invariance in which the number of coordinates "scaling like time" is generically greater than one. We propose the Cartesian product of two curved spaces, with the metric of each space parameterized by the other space, as a notion of curved background to which the theory can be extended. We study this type of geometries, and find a family of extensions of the theory to curved backgrounds in which the anisotropic scale invariance is promoted to a local, Weyl-type symmetry.
Florkowski, W.; Maj, R.
The recently introduced approach describing coupled quark and gluon anisotropic fluids is generalized to include explicitly the transitions between quarks and gluons. We study the effects of such processes on the thermalization rate of anisotropic systems. We find that the quark-gluon transitions may enhance the overall thermalization rate in the cases where the initial momentum anisotropies correspond to mixed oblate-prolate or prolate configurations. On the other hand, no effect on the thermalization rate is found in the case of oblate configurations. The observed regularities are connected with the late-time behavior of the analyzed systems which is described either by the exponential decay or the power law.
Florkowski, Wojciech
2013-01-01
The recently introduced approach describing coupled quark and gluon anisotropic fluids is generalized to include explicitly the transitions between quarks and gluons. We study the effects of such processes on the thermalization rate of anisotropic systems. We find that the quark-gluon transitions may enhance the overall thermalization rate in the cases where the initial momentum anisotropies correspond to mixed oblate-prolate or prolate configurations. On the other hand, no effect on the thermalization rate is found in the case of oblate configurations. The observed regularities are connected with the late-time behavior of the analyzed systems which is described either by the exponential decay or the power law.
Anisotropic models for compact stars
Maurya, S K; Ray, Saibal; Dayanandan, Baiju
2015-01-01
In the present paper we obtain an anisotropic analogue of Durgapal-Fuloria (1985) perfect fluid solution. The methodology consists of contraction of anisotropic factor $\\Delta$ by the help of both metric potentials $e^{\
Indian Academy of Sciences (India)
B B Bhowmik; A Rajput
2004-06-01
Anisotropic Bianchi Type-I cosmological models have been studied on the basis of Lyra's geometry. Two types of models, one with constant deceleration parameter and the other with variable deceleration parameter have been derived by considering a time-dependent displacement field.
Wave propagation and radiation in gyrotropic and anisotropic media
Eroglu, Abdullah
2010-01-01
""Wave Propagation and Radiation in Gyrotropic and Anisotropic Media"" fills the gap in the area of applied electromagnetics for the design of microwave and millimeter wave devices using composite structures where gyrotropic, anisotropic materials are used. The book provides engineers with the information on theory and practical skills they need to understand wave propagation and radiation characteristics of materials and the ability to design devices at higher frequencies with optimum device performance.
Anisotropic nanomaterials: structure, growth, assembly, and functions
Panikkanvalappil R. Sajanlal; Theruvakkattil S. Sreeprasad; Samal, Akshaya K.; Thalappil Pradeep
2011-01-01
Comprehensive knowledge over the shape of nanomaterials is a critical factor in designing devices with desired functions. Due to this reason, systematic efforts have been made to synthesize materials of diverse shape in the nanoscale regime. Anisotropic nanomaterials are a class of materials in which their properties are direction-dependent and more than one structural parameter is needed to describe them. Their unique and fine-tuned physical and chemical properties make them ideal candidates...
Energy Technology Data Exchange (ETDEWEB)
Munikoti, V.K.
2001-03-01
In this work the propagation behaviour of ultrasound in austenitic weld metal has been analyzed by the time-harmonic plane wave approach. Bounded beam and pulse propagation as occurring in ultrasonic testing can be sufficiently dealt with by this approach. More sophisticated approaches principally do not offer any improvements in the results of plane wave modeling except for diffraction and aperture effects and, therefore, the subject matter of this work has been limited to plane wave propagation in the bulk of the medium and at different types of interfaces. Inspite of the fact, that the individual columnar grains of the weld metal have cubic symmetry, the austenitic weld metal as a whole exhibits cylinder-symmetrical texture, as substantiated by metallurgical examination, and therefore has been treated as an anisotropic poly-crystalline medium with transverse isotropic symmetry. (orig.) [German] In der vorliegenden Arbeit wird die Ultraschallausbreitung in akustisch anisotropen, homogenen Werkstoffen mit stengelkristalliner Textur wie austenitischen Plattierungen und Schweissverbindungen, austenitischem Guss oder geschweissten Komponenten aus austenitischem Guss modelliert. Wie die in dieser Arbeit referierten metallurgischen Untersuchungen gezeigt haben, koennen austenitisches Schweissgut und stengelkristallin erstarrter austenitischer Guss makroskopisch als polykristallines Medium mit zylindersymmetrischer Textur behandelt werden, also als Medium mit transversal isotroper Symmetrie, obwohl mikroskopisch die einzelnen Stengelkristallite kubische Symmetrie aufweisen. Die Schallausbreitung wird mit Hilfe des Ansatzes ebener Wellen modelliert. Obwohl bei der Ultraschallpruefung gepulste und begrenzte Schallbuendel verwendet werden, liefert dieser Ansatz die bei der Ultraschallpruefung beobachteten Wellenarten mit Geschwindigkeiten und Polarisationen, Schallbuendelablenkung und Reflexion und Brechnung nach Richtung und Amplitude, so dass ueber das Modell der ebenen
Spatially anisotropic Heisenberg kagome antiferromagnet
Apel, W.; Yavors'kii, T.; Everts, H.-U.
2007-04-01
In the search for spin-1/2 kagome antiferromagnets, the mineral volborthite has recently been the subject of experimental studies (Hiroi et al 2001 J. Phys. Soc. Japan 70 3377; Fukaya et al 2003 Phys. Rev. Lett. 91 207603; Bert et al 2004 J. Phys.: Condens. Matter 16 S829; Bert et al 2005 Phys. Rev. Lett. 95 087203). It has been suggested that the magnetic properties of this material are described by a spin-1/2 Heisenberg model on the kagome lattice with spatially anisotropic exchange couplings. We report on investigations of the {\\mathrm {Sp}}(\\mathcal {N}) symmetric generalization of this model in the large \\mathcal {N} limit. We obtain a detailed description of the dependence of possible ground states on the anisotropy and on the spin length S. A fairly rich phase diagram with a ferrimagnetic phase, incommensurate phases with and without long-range order and a decoupled chain phase emerges.
Q-factor and absorption enhancement for plasmonic anisotropic nanoparticles
Liu, Wei; Miroshnichenko, Andrey E
2016-01-01
We investigate the scattering and absorption properties of anisotropic metal-dielectric core-shell nanoparticles. It is revealed that the radially anisotropic dielectric layer can accelerate the evanescent decay of the localized resonant surface modes, leading to Q-factor and absorption rate enhancement. Moreover, the absorption cross section can be maximized to reach the single resonance absorption limit. We further show that such artificial anisotropic cladding materials can be realized by isotropic layered structures, which may inspire many applications based on scattering and absorption of plasmonic nanoparticles.
Designing novel anisotropic lenses with transformation optics
Jiang, Wei Xiang; Bao, Di; Cui, Tie Jun
2016-04-01
Transformation optics (TO), based on the formally invariant property of Maxwell’s equations, has provided a powerful strategy to design anisotropic or nearly-isotropic devices, in both time-varied and static fields. In this paper, we present and investigate the negative refraction or reflection phenomena by positive-index anisotropic materials based on transformation-optics design. First, we propose and design an inhomogeneous transformed planar lens, in which we will show the negative-refraction-like properties of transformation media. Secondly, we present a homogeneous transformed lens based on linear spatial transformation, in which we will reveal the negative-reflection properties of positive transformation media. Both transformed lenses have unusual properties which are different from those in natural materials.
Anisotropic Thermal Conductivity of Exfoliated Black Phosphorus.
Jang, Hyejin; Wood, Joshua D; Ryder, Christopher R; Hersam, Mark C; Cahill, David G
2015-12-22
The anisotropic thermal conductivity of passivated black phosphorus (BP), a reactive two-dimensional material with strong in-plane anisotropy, is ascertained. The room-temperature thermal conductivity for three crystalline axes of exfoliated BP is measured by time-domain thermo-reflectance. The thermal conductivity along the zigzag direction is ≈2.5 times higher than that of the armchair direction.
On the relativistic anisotropic configurations
Energy Technology Data Exchange (ETDEWEB)
Shojai, F. [University of Tehran, Department of Physics, Tehran (Iran, Islamic Republic of); Institute for Research in Fundamental Sciences (IPM), Foundations of Physics Group, School of Physics, Tehran (Iran, Islamic Republic of); Kohandel, M. [Alzahra University, Department of Physics and Chemistry, Tehran (Iran, Islamic Republic of); Stepanian, A. [University of Tehran, Department of Physics, Tehran (Iran, Islamic Republic of)
2016-06-15
In this paper we study anisotropic spherical polytropes within the framework of general relativity. Using the anisotropic Tolman-Oppenheimer-Volkov equations, we explore the relativistic anisotropic Lane-Emden equations. We find how the anisotropic pressure affects the boundary conditions of these equations. Also we argue that the behavior of physical quantities near the center of star changes in the presence of anisotropy. For constant density, a class of exact solution is derived with the aid of a new ansatz and its physical properties are discussed. (orig.)
Directory of Open Access Journals (Sweden)
Daniela Lehr
2015-11-01
Full Text Available Numerous applications in optoelectronics require electrically conducting materials with high optical transparency over the entire visible light range. A solid solution of indium oxide and substantial amounts of tin oxide for electronic doping (ITO is currently the most prominent example for the class of so-called TCOs (transparent conducting oxides. Due to the limited, natural occurrence of indium and its steadily increasing price, it is highly desired to identify materials alternatives containing highly abundant chemical elements. The doping of other metal oxides (e.g., zinc oxide, ZnO is a promising approach, but two problems can be identified. Phase separation might occur at the required high concentration of the doping element, and for successful electronic modification it is mandatory that the introduced heteroelement occupies a defined position in the lattice of the host material. In the case of ZnO, most attention has been attributed so far to n-doping via substitution of Zn2+ by other metals (e.g., Al3+. Here, we present first steps towards n-doped ZnO-based TCO materials via substitution in the anion lattice (O2− versus halogenides. A special approach is presented, using novel single-source precursors containing a potential excerpt of the target lattice 'HalZn·Zn3O3' preorganized on the molecular scale (Hal = I, Br, Cl. We report about the synthesis of the precursors, their transformation into halogene-containing ZnO materials, and finally structural, optical and electronic properties are investigated using a combination of techniques including FT-Raman, low-T photoluminescence, impedance and THz spectroscopies.
Inhomogeneous anisotropic cosmology
Kleban, Matthew; Senatore, Leonardo
2016-10-01
In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here, we prove that arbitrarily inhomogeneous and anisotropic cosmologies with ``flat'' (including toroidal) and ``open'' (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region at a rate bounded from below by a positive number, despite the presence of arbitrarily large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are ``flat'' or ``open''. Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potential) and initial conditions for the inflaton, cosmologies with ``flat'' or ``open'' topology must expand forever in some region at least as fast as de Sitter space, and are therefore very likely to begin inflationary expansion eventually, regardless of the scale of the inflationary energy or the spectrum and amplitude of initial inhomogeneities and gravitational waves. Our result is also significant for numerical general relativity, which often makes use of periodic (toroidal) boundary conditions.
Gardiner, Thomas
2013-10-01
Anisotropic thermal diffusion in magnetized plasmas is an important physical phenomena for a diverse set of physical conditions ranging from astrophysical plasmas to MFE and ICF. Yet numerically simulating this phenomenon accurately poses significant challenges when the computational mesh is misaligned with respect to the magnetic field. Particularly when the temperature gradients are unresolved, one frequently finds entropy violating solutions with heat flowing from cold to hot zones for χ∥ /χ⊥ >=102 which is substantially smaller than the range of interest which can reach 1010 or higher. In this talk we present a new implicit algorithm for solving the anisotropic thermal diffusion equations and demonstrate its characteristics on what has become a fairly standard set of test problems in the literature. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND2013-5687A.
Inhomogeneous anisotropic cosmology
Energy Technology Data Exchange (ETDEWEB)
Kleban, Matthew [Center for Cosmology and Particle Physics, New York University,4 Washington Place, New York, NY 10003 (United States); Senatore, Leonardo [Stanford Institute for Theoretical Physics and Department of Physics, Stanford University,382 Via Pueblo Mall, Stanford, CA 94306 (United States); Kavli Institute for Particle Astrophysics and Cosmology, Stanford University and SLAC,2575 Sand Hill Road, M/S 29, Menlo Park, CA 94025 (United States)
2016-10-12
In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here, we prove that arbitrarily inhomogeneous and anisotropic cosmologies with “flat” (including toroidal) and “open” (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region at a rate bounded from below by a positive number, despite the presence of arbitrarily large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are “flat” or “open”. Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potential) and initial conditions for the inflaton, cosmologies with “flat” or “open” topology must expand forever in some region at least as fast as de Sitter space, and are therefore very likely to begin inflationary expansion eventually, regardless of the scale of the inflationary energy or the spectrum and amplitude of initial inhomogeneities and gravitational waves. Our result is also significant for numerical general relativity, which often makes use of periodic (toroidal) boundary conditions.
Institute of Scientific and Technical Information of China (English)
陈云; 谢秀峰; 李俊林
2011-01-01
对各向异性复合材料板的周期性Ⅱ型裂纹尖端应力场进行了有关的力学分析,通过求解一类线性偏微分方程的边值问题,引入Westergaard应力函数、采用复变函数方法及待定系数法,给出在无穷远处受对称载荷τ作用下,周期性Ⅱ型裂纹尖端的应力强度因子,推出了各向异性复合材料板周期性Ⅱ型裂纹尖端附近应力场的理论计算公式。%The stress fields near Mode-Ⅱ periodic cracks tip of anisotropic composite materials were analyzed.The boundary value problem of one kind of partial differential equation was solved.The stress intensity factors at the crack tip for mode Ⅱ periodic cracks were presented under symmetric loading by introducing Westergaard＇s stress function and using complex function method and the approach of undetermined coefficients.The theoretical formulae for computing stress field of mode II periodic crack tips were obtained.
Institute of Scientific and Technical Information of China (English)
谢秀峰; 李俊林; 杨维阳
2011-01-01
对各向异性复合材料板的周期性I型裂纹尖端应力场进行了力学分析.通过求解一类线性偏微分方程的边值问题,引入Westergaard应力函数,采用复变函数方法及待定系数法,给出在无穷远处受对称载荷σ作用下,周期性Ⅰ型裂纹尖端的应力强度因子,推出了各向异性复合材料板周期性Ⅰ型裂纹尖端附近应力场的理论计算公式.%Mode-I stress fields near periodic cracks tip of anisotropic composite materials were analyzed. The boundary value problem of one kind of partial differential equation was solved. By introducing Westergaard' s stress function, using complex function method and approach of undetermined coefficients, the stress intensity factors at the crack tip for mode I periodic cracks were presented under symmetrical loading a. The stress field theoretical computing formulae of mode I periodic cracks near crack tip were obtained.
Anisotropic Power-law Inflation
Kanno, Sugumi; Watanabe, Masa-aki
2010-01-01
We study an inflationary scenario in supergravity model with a gauge kinetic function. We find exact anisotropic power-law inflationary solutions when both the potential function for an inflaton and the gauge kinetic function are exponential type. The dynamical system analysis tells us that the anisotropic power-law inflation is an attractor for a large parameter region.
Anisotropic viscoelastic models in large deformation for architectured membranes
Rebouah, Marie; Chagnon, Gregory; Heuillet, Patrick
2016-08-01
Due to the industrial elaboration process, membranes can have an in-plane anisotropic mechanical behaviour. In this paper, anisotropic membranes elaborated with two different materials were developed either by calendering or by inducing a force in one direction during the process. Experimental tests are developed to measure the differences of mechanical behaviour for both materials in different in-plane properties: stiffness, viscoelasticity and stress-softening. A uniaxial formulation is developed, and a homogenisation by means of a sphere unit approach is used to propose a three-dimensional formulation to represent the materials behaviour. An evolution of the mechanical parameters, depending on the direction, is imposed to reproduce the anisotropic behaviour of the materials. Comparison with experimental data highlights very promising results.
Autofocus imaging: Experimental results in an anisotropic austenitic weld
Zhang, J.; Drinkwater, B. W.; Wilcox, P. D.; Hunter, A.
2012-05-01
The quality of an ultrasonic array image, especially for anisotropic material, depends on accurate information about acoustic properties. Inaccuracy of acoustic properties causes image degradation, e.g., blurring, errors in locating of reflectors and introduction of artifacts. In this paper, for an anisotropic austenitic steel weld, an autofocus imaging technique is presented. The array data from a series of beacons is captured and then used to statistically extract anisotropic weld properties by using a Monte-Carlo inversion approach. The beacon and imaging systems are realized using two separated arrays; one acts as a series of beacons and the other images these beacons. Key to the Monte-Carlo inversion scheme is a fast forward model of wave propagation in the anisotropic weld and this is based on the Dijkstra algorithm. Using this autofocus approach a measured weld map was extracted from an austenitic weld and used to reduce location errors, initially greater than 6mm, to less than 1mm.
Anisotropic Optical Properties of Layered Germanium Sulfide
Tan, Dezhi; Wang, Feijiu; Mohamed, Nur Baizura; Mouri, Shinichiro; Sandhaya, Koirala; Zhang, Wenjing; Miyauchi, Yuhei; Ohfuchi, Mari; Matsuda, Kazunari
2016-01-01
Two-dimensional (2D) layered materials, transition metal dichalcogenides and black phosphorus, have attracted much interest from the viewpoints of fundamental physics and device applications. The establishment of new functionalities in anisotropic layered 2D materials is a challenging but rewarding frontier, owing to their remarkable optical properties and prospects for new devices. Here, we report the anisotropic optical properties of layered 2D monochalcogenide of germanium sulfide (GeS). Three Raman scattering peaks corresponding to the B3g, A1g, and A2g modes with strong polarization dependence are demonstrated in the GeS flakes, which validates polarized Raman spectroscopy as an effective method for identifying the crystal orientation of anisotropic layered GeS. Photoluminescence (PL) is observed with a peak at around 1.66 eV that originates from the direct optical transition in GeS at room temperature. Moreover, determination of the polarization dependent characteristics of the PL and absorption reveals...
Anisotropic silica mesostructures for DNA encapsulation
Indian Academy of Sciences (India)
Aparna Ganguly; Ashok K Ganguli
2013-04-01
The encapsulation of biomolecules in inert meso or nanostructures is an important step towards controlling drug delivery agents. Mesoporous silica nanoparticles (MSN) are of immense importance owing to their high surface area, large pore size, uniform particle size and chemical inertness. Reverse micellar method with CTAB as the surfactant has been used to synthesize anisotropic mesoporous silica materials. We have used the anisotropic silica nanostructures for DNA encapsulation studies and observed a loading capacity of ∼8 g mg-1 of the sample. On functionalizing the pores of silica with amine group, the amount of DNA loaded on the rods decreases which is due to a reduction in the pore size upon grafting of amine groups.
Rubin, M. B.; Vorobiev, O.; Vitali, E.
2016-07-01
A large deformation thermomechanical model is developed for shock loading of a material that can exhibit elastic and inelastic anisotropy. Use is made of evolution equations for a triad of microstructural vectors mathbf{m}i (hbox {i}=1,2,3) which model elastic deformations and directions of anisotropy. Specific constitutive equations are presented for a material with orthotropic elastic response. The rate of inelasticity depends on an orthotropic yield function that can be used to model weak fault planes with failure in shear and which exhibits a smooth transition to isotropic response at high compression. Moreover, a robust, strongly objective numerical algorithm is proposed for both rate-independent and rate-dependent response. The predictions of the continuum model are examined by comparison with exact steady-state solutions. Also, the constitutive equations are used to obtain a simplified continuum model of jointed rock which is compared with high fidelity numerical solutions that model a persistent system of joints explicitly in the rock medium.
Anisotropic Inflation with General Potentials
Shi, Jiaming; Qiu, Taotao
2015-01-01
Anomalies in recent observational data indicate that there might be some "anisotropic hair" generated in an inflation period. To obtain general information about the effects of this anisotropic hair to inflation models, we studied anisotropic inflation models that involve one vector and one scalar using several types of potentials. We determined the general relationship between the degree of anisotropy and the fraction of the vector and scalar fields, and concluded that the anisotropies behave independently of the potentials. We also generalized our study to the case of multi-directional anisotropies.
Anisotropic and Hierarchical Porosity in Multifunctional Ceramics
Lichtner, Aaron Zev
The performance of multifunctional porous ceramics is often hindered by the seemingly contradictory effects of porosity on both mechanical and non-structural properties and yet a sufficient body of knowledge linking microstructure to these properties does not exist. Using a combination of tailored anisotropic and hierarchical materials, these disparate effects may be reconciled. In this project, a systematic investigation of the processing, characterization and properties of anisotropic and isotropic hierarchically porous ceramics was conducted. The system chosen was a composite ceramic intended as the cathode for a solid oxide fuel cell (SOFC). Comprehensive processing investigations led to the development of approaches to make hierarchical, anisotropic porous microstructures using directional freeze-casting of well dispersed slurries. The effect of all the important processing parameters was investigated. This resulted in an ability to tailor and control the important microstructural features including the scale of the microstructure, the macropore size and total porosity. Comparable isotropic porous ceramics were also processed using fugitive pore formers. A suite of characterization techniques including x-ray tomography and 3-D sectional scanning electron micrographs (FIB-SEM) was used to characterize and quantify the green and partially sintered microstructures. The effect of sintering temperature on the microstructure was quantified and discrete element simulations (DEM) were used to explain the experimental observations. Finally, the comprehensive mechanical properties, at room temperature, were investigated, experimentally and using DEM, for the different microstructures.
The design of metamaterial cloaks embedded in anisotropic medium
Institute of Scientific and Technical Information of China (English)
Ma Hua; Qu Shao-Bo; Xu Zhuo; Zhang Jie-Qiu; Wang Jia-Fu
2009-01-01
By using coordinate transformation method, this paper obtains an useful equation of designing meta-material cloaks embedded in anisotropic medium. This equation is the generalization of what was introduced early by Pendry et al (2006 Science 312 1780) and can be more widely used. As an example of its applications, this paper deduces the material parameter equation for cylinder cloaks embedded in anisotropic medium, and then offers the numerical simulation. The results show that such a cylinder cloak has perfect cloaking performance and therefore verifies the method proposed in this paper.
Gradient expansion for anisotropic hydrodynamics
Florkowski, Wojciech; Ryblewski, Radoslaw; Spaliński, Michał
2016-12-01
We compute the gradient expansion for anisotropic hydrodynamics. The results are compared with the corresponding expansion of the underlying kinetic-theory model with the collision term treated in the relaxation time approximation. We find that a recent formulation of anisotropic hydrodynamics based on an anisotropic matching principle yields the first three terms of the gradient expansion in agreement with those obtained for the kinetic theory. This gives further support for this particular hydrodynamic model as a good approximation of the kinetic-theory approach. We further find that the gradient expansion of anisotropic hydrodynamics is an asymptotic series, and the singularities of the analytic continuation of its Borel transform indicate the presence of nonhydrodynamic modes.
Gradient expansion for anisotropic hydrodynamics
Florkowski, Wojciech; Spaliński, Michał
2016-01-01
We compute the gradient expansion for anisotropic hydrodynamics. The results are compared with the corresponding expansion of the underlying kinetic-theory model with the collision term treated in the relaxation time approximation. We find that a recent formulation of anisotropic hydrodynamics based on an anisotropic matching principle yields the first three terms of the gradient expansion in agreement with those obtained for the kinetic theory. This gives further support for this particular hydrodynamic model as a good approximation of the kinetic-theory approach. We further find that the gradient expansion of anisotropic hydrodynamics is an asymptotic series, and the singularities of the analytic continuation of its Borel transform indicate the presence of non-hydrodynamic modes.
Photon states in anisotropic media
Indian Academy of Sciences (India)
Deepak Kumar
2002-08-01
Quantum aspects of optical polarization are discussed for waves traveling in anisotropic dielectric media with a view to relate the dynamics of polarization with that of photon spin and its manipulation by classical polarizers.
Anisotropic assembly and pattern formation
von Brecht, James H.; Uminsky, David T.
2017-01-01
We investigate the role of anisotropy in two classes of individual-based models for self-organization, collective behavior and self-assembly. We accomplish this via first-order dynamical systems of pairwise interacting particles that incorporate anisotropic interactions. At a continuum level, these models represent the natural anisotropic variants of the well-known aggregation equation. We leverage this framework to analyze the impact of anisotropic effects upon the self-assembly of co-dimension one equilibrium structures, such as micelles and vesicles. Our analytical results reveal the regularizing effect of anisotropy, and isolate the contexts in which anisotropic effects are necessary to achieve dynamical stability of co-dimension one structures. Our results therefore place theoretical limits on when anisotropic effects can be safely neglected. We also explore whether anisotropic effects suffice to induce pattern formation in such particle systems. We conclude with brief numerical studies that highlight various aspects of the models we introduce, elucidate their phase structure and partially validate the analysis we provide.
Mean field magnetization of gapped anisotropic multiplet
Paixão, L. S.; Reis, M. S.
2014-06-01
Some materials have a large gap between the ground and first excited states. At temperatures smaller than the gap value, the thermodynamic properties of such materials are mainly ruled by the ground state. It is also common to find materials with magnetocrystalline anisotropy, which arises due to interatomic interactions. The present paper uses a classical approach to deal large angular momenta in such materials. Based on analytical expressions for the thermodynamics of paramagnetic gapped anisotropic multiplets, we use mean field theory to study the influence of the anisotropy upon the properties of interacting systems. We also use Landau theory to determine the influence of the anisotropy in first and second order phase transitions. It is found that the anisotropy increases the critical temperature, and enlarges the hysteresis of first order transitions. We present analytical expressions for the quantities analyzed.
Advances in Anisotropic Materials for Optical Switching
2010-09-16
overcome this cha llcnge we have developed a fundamentally new concept of optica ll y switchable clements based 011 dim’active wave plates (OWs). DWs...doped liquid crysta ls," J. Phys. D.: Appl. Phys., 25, 492-499 ( 1992). 17. T . Ikeda, O. Tsutsumi , " Optica l switching and image storage by
Graphical Retrieval Method for Orthorhombic Anisotropic Materials
2010-07-01
Nat. Mater. 7, 31–37 (2008). 7. S. Zhang, W. Fan, N. C. Panoiu, K. J. Malloy , R. M. Osgood, and S. R. J. Brueck, “Experimental demonstration of near... Roberts , S. Feng, M. Moran, and L. Johnson, “Effective permittivity near zero in nanolaminates of silver and amorphous polycarbonate,” J. Nanophoton. 4
An Anisotropic Hardening Model for Springback Prediction
Zeng, Danielle; Xia, Z. Cedric
2005-08-01
As more Advanced High-Strength Steels (AHSS) are heavily used for automotive body structures and closures panels, accurate springback prediction for these components becomes more challenging because of their rapid hardening characteristics and ability to sustain even higher stresses. In this paper, a modified Mroz hardening model is proposed to capture realistic Bauschinger effect at reverse loading, such as when material passes through die radii or drawbead during sheet metal forming process. This model accounts for material anisotropic yield surface and nonlinear isotropic/kinematic hardening behavior. Material tension/compression test data are used to accurately represent Bauschinger effect. The effectiveness of the model is demonstrated by comparison of numerical and experimental springback results for a DP600 straight U-channel test.
Anisotropic metamaterials with simultaneous attenuation and amplification
Mackay, Tom G
2015-01-01
Anisotropic metamaterials that are neither wholly dissipative nor wholly active at a specific frequency are permitted by classical electromagnetic theory. Well-established formalisms for the homogenization of particulate composite materials indicate that such a metamaterial may be conceptualized quite simply as a random mixture of electrically small spheroidal particles of at least two different isotropic dielectric materials, one of which must be dissipative but the other active. The realization of this metametarial is influenced by the volume fraction, spatial distribution, particle shape and size, and the relative permittivities of the component materials. Metamaterials displaying both dissipation and amplification at the same frequency with more complicated linear as well as nonlinear constitutive properties are possible.
Light propagation through anisotropic turbulence.
Toselli, Italo; Agrawal, Brij; Restaino, Sergio
2011-03-01
A wealth of experimental data has shown that atmospheric turbulence can be anisotropic; in this case, a Kolmogorov spectrum does not describe well the atmospheric turbulence statistics. In this paper, we show a quantitative analysis of anisotropic turbulence by using a non-Kolmogorov power spectrum with an anisotropic coefficient. The spectrum we use does not include the inner and outer scales, it is valid only inside the inertial subrange, and it has a power-law slope that can be different from a Kolmogorov one. Using this power spectrum, in the weak turbulence condition, we analyze the impact of the power-law variations α on the long-term beam spread and scintillation index for several anisotropic coefficient values ς. We consider only horizontal propagation across the turbulence cells, assuming circular symmetry is maintained on the orthogonal plane to the propagation direction. We conclude that the anisotropic coefficient influences both the long-term beam spread and the scintillation index by the factor ς(2-α).
Influence of anisotropic piezoelectric actuators on wing aerodynamic forces
Institute of Scientific and Technical Information of China (English)
2008-01-01
Changing the shape of an airfoil to enhance overall aircraft performance has always been a goal of aircraft designers. Using smart material to reshape the wing can improve aerodynamic performance. The influence of anisotropic effects of piezoelectric actuators on the aerodynamic characteristics of a simplified HALE wing model was investigated. Test verification was conducted.
Influence of anisotropic piezoelectric actuators on wing aerodynamic forces
Institute of Scientific and Technical Information of China (English)
GUAN De; LI Min; LI Wei; WANG MingChun
2008-01-01
Changing the shape of an airfoil to enhance overall aircraft performance has always been s goal of aircraft designers.Using smart material to reshape the wing can improve aerodynamic performance.The influence of anisotropic effects of piezo-electric actuators on the aerodynamic characteristics of a simplified HALE wing model was investigated.Test verification was conducted.
Autofocus imaging : Experimental results in an anisotropic austenitic weld
Zhang, J.; Drinkwater, B.W.; Wilcox, P.D.; Hunter, A.J.
2012-01-01
The quality of an ultrasonic array image, especially for anisotropic material, depends on accurate information about acoustic properties. Inaccuracy of acoustic properties causes image degradation, e.g., blurring, errors in locating of reflectors and introduction of artifacts. In this paper, for an
The thermoelectric magnetic field of isotropic inclusions in anisotropic metals
Faidi, W. I.; Nayfeh, A. H.
2006-02-01
In this paper we model the thermoelectric magnetic field around isotropic inclusions in anisotropic media. It is demonstrated that while the presence of the inclusion will be the dominant source of the thermoelectric signal, the anisotropy of the host material will affect the signal. Although such a phenomenon will occur for all shapes of inclusions, for simplicity we shall demonstrate our theoretical and numerical modeling on the more mathematically tractable case of a cylindrical inclusion aligned along an axis of symmetry of an anisotropic metal medium.
Anisotropic thermoelement in emf and current generation mode
Directory of Open Access Journals (Sweden)
Anatychuk L. I.
2011-06-01
Full Text Available Computer methods for the description of the anisotropic thermoelement (AT properties with regard to all necessary model approximations have been elaborated. Configurations of eddy thermoelectric currents in the anisotropic thermoele-ment caused by current contacts have been found. The pro-perties of the AT with regard to temperature dependences of material properties, contact resistances and current contacts have been determined for concrete cases. Optimal dimensions of current contacts have been found. The optimization of AT construction allowed to increase its efficiency by 15%.
Surface waves in ﬁbre-reinforced anisotropic elastic media
Indian Academy of Sciences (India)
P R Sengupta; Sisir Nath
2001-08-01
The aim of this paper is to investigate surface waves in anisotropic ﬁbre-reinforced solid elastic media. First, the theory of general surface waves has been derived and applied to study the particular cases of surface waves – Rayleigh, Love and Stoneley types. The wave velocity equations are found to be in agreement with the corresponding classical result when the anisotropic elastic parameters tends to zero. It is important to note that the Rayleigh type of wave velocity in the ﬁbre-reinforced elastic medium increases to a considerable amount in comparison with the Rayleigh wave velocity in isotropic materials.
Timoshenko beam element with anisotropic cross-sectional properties
DEFF Research Database (Denmark)
Stäblein, Alexander; Hansen, Morten Hartvig
2016-01-01
Beam models are used for the aeroelastic time and frequency domain analysis of wind turbines due to their computational efficiency. Many current aeroelastic tools for the analysis of wind turbines rely on Timoshenko beam elements with classical crosssectional properties (EA, EI, etc.). Those cross......-sectional properties do not reflect the various couplings arising from the anisotropic behaviour of the blade material. A twonoded, three-dimensional Timoshenko beam element was therefore extended to allow for anisotropic cross-sectional properties. For an uncoupled beam, the resulting shape functions are identical...
Hyperspherical theory of anisotropic exciton
Muljarov, E A; Tikhodeev, S G; Bulatov, A E; Birman, Joseph L; 10.1063/1.1286772
2012-01-01
A new approach to the theory of anisotropic exciton based on Fock transformation, i.e., on a stereographic projection of the momentum to the unit 4-dimensional (4D) sphere, is developed. Hyperspherical functions are used as a basis of the perturbation theory. The binding energies, wave functions and oscillator strengths of elongated as well as flattened excitons are obtained numerically. It is shown that with an increase of the anisotropy degree the oscillator strengths are markedly redistributed between optically active and formerly inactive states, making the latter optically active. An approximate analytical solution of the anisotropic exciton problem taking into account the angular momentum conserving terms is obtained. This solution gives the binding energies of moderately anisotropic exciton with a good accuracy and provides a useful qualitative description of the energy level evolution.
Anisotropic inflation in Finsler spacetime
Li, Xin; Chang, Zhe
2015-01-01
We suggest the universe is Finslerian in the stage of inflation. The Finslerian background spacetime breaks rotational symmetry and induces parity violation. The primordial power spectrum is given for quantum fluctuation of the inflation field. It depends not only on the magnitude of wavenumber but also on the preferred direction. We derive the gravitational field equations in the perturbed Finslerian background spacetime, and obtain a conserved quantity outside the Hubble horizon. The angular correlation coefficients are presented in our anisotropic inflation model. The parity violation feature of Finslerian background spacetime requires that the anisotropic effect only appears in angular correlation coefficients if $l'=l+1$. The numerical results of the angular correlation coefficients are given to describe the anisotropic effect.
The Derived Equivalent Circuit Model for Magnetized Anisotropic Graphene
Cao, Ying S; Ruehli, Albert E
2015-01-01
Due to the static magnetic field, the conductivity for graphene becomes a dispersive and anisotropic tensor, which complicates most modeling methodologies. In this paper, a novel equivalent circuit model is proposed for graphene with the magnetostatic bias based on the electric field integral equation (EFIE). To characterize the anisotropic property of the biased graphene, the resistive part of the unit circuit is replaced by a resistor in series with current control voltage sources (CCVSs). The CCVSs account for the off-diagonal parts of the surface conductivity tensor for the magnetized graphene. Furthermore, the definitions of the absorption cross section and the scattering cross section are revisited to make them feasible for derived circuit analysis. This proposed method is benchmarked with several numerical examples. This paper also provides a new equivalent circuit model to deal with dispersive and anisotropic materials.
Anisotropic hydrodynamics: Motivation and methodology
Energy Technology Data Exchange (ETDEWEB)
Strickland, Michael
2014-06-15
In this proceedings contribution I review recent progress in our understanding of the bulk dynamics of relativistic systems that possess potentially large local rest frame momentum-space anisotropies. In order to deal with these momentum-space anisotropies, a reorganization of relativistic viscous hydrodynamics can be made around an anisotropic background, and the resulting dynamical framework has been dubbed “anisotropic hydrodynamics”. I also discuss expectations for the degree of momentum-space anisotropy of the quark–gluon plasma generated in relativistic heavy ion collisions at RHIC and LHC from second-order viscous hydrodynamics, strong-coupling approaches, and weak-coupling approaches.
Anisotropic Poisson Processes of Cylinders
Spiess, Malte
2010-01-01
Main characteristics of stationary anisotropic Poisson processes of cylinders (dilated k-dimensional flats) in d-dimensional Euclidean space are studied. Explicit formulae for the capacity functional, the covariance function, the contact distribution function, the volume fraction, and the intensity of the surface area measure are given which can be used directly in applications.
Wave propagation in layered anisotropic media with application to composites
Nayfeh, AH
1995-01-01
Recent advances in the study of the dynamic behavior of layered materials in general, and laminated fibrous composites in particular, are presented in this book. The need to understand the microstructural behavior of such classes of materials has brought a new challenge to existing analytical tools. This book explores the fundamental question of how mechanical waves propagate and interact with layered anisotropic media. The chapters are organized in a logical sequence depending upon the complexity of the physical model and its mathematical treatment.
Quantum electrodynamics of inhomogeneous anisotropic media
Energy Technology Data Exchange (ETDEWEB)
Lopez, Adrian E.R.; Lombardo, Fernando C. [Ciudad Universitaria, Departamento de Fisica Juan Jose Giambiagi, Buenos Aires (Argentina); IFIBA CONICET-UBA, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina)
2015-02-01
In this work we calculate the closed time path generating functional for the electromagnetic (EM) field interacting with inhomogeneous anisotropic matter. For this purpose, we first find a general expression for the electromagnetic field's influence action from the interaction of the field with a composite environment consisting in the quantum polarization degrees of freedom in each point of space, at arbitrary temperatures, connected to thermal baths. Then we evaluate the generating functional for the gauge field, in the temporal gauge, by implementing the Faddeev-Popov procedure. Finally, through the point-splitting technique, we calculate closed expressions for the energy, the Poynting vector, and the Maxwell tensor in terms of the Hadamard propagator. We show that all the quantities have contributions from the field's initial conditions and also from the matter degrees of freedom. Throughout the whole work we discuss how the gauge invariance must be treated in the formalism when the EM-field is interacting with inhomogeneous anisotropic matter. We study the electrodynamics in the temporal gauge, obtaining the EM-field's equation and a residual condition. Finally we analyze the case of the EM-field in bulk material and also discuss several general implications of our results in relation with the Casimir physics in a non-equilibrium scenario. (orig.)
Electrically Anisotropic Layered Perovskite Single Crystal
Li, Ting-You
2016-04-01
Organic-inorganic hybrid perovskites (OIHPs), which are promising materials for electronic and optoelectronic applications (1-10), have made into layered organic-inorganic hybrid perovskites (LOIHPs). These LOIHPs have been applied to thin-film transistors, solar cells and tunable wavelength phosphors (11-18). It is known that devices fabricated with single crystal exhibit the superior performance, which makes the growth of large-sized single crystals critical for future device applications (19-23). However, the difficulty in growing large-sized LOIHPs single crystal with superior electrical properties limits their practical applications. Here, we report a method to grow the centimeter-scaled LOIHP single crystal of [(HOC2H4NH3)2PbI4], demonstrating the potentials in mass production. After that, we reveal anisotropic electrical and optoelectronic properties which proved the carrier propagating along inorganic framework. The carrier mobility of in-inorganic-plane (in-plane) devices shows the average value of 45 cm2 V–1 s–1 which is about 100 times greater than the record of LOIHP devices (15), showing the importance of single crystal in device application. Moreover, the LOIHP single crystals show its ultra-short carrier lifetime of 42.7 ps and photoluminescence quantum efficiency (PLQE) of 25.4 %. We expect this report to be a start of LOIHPs for advanced applications in which the anisotropic properties are needed (24-25), and meets the demand of high-speed applications and fast-response applications.
Anisotropic Internal Friction Damping
Peters, R D
2003-01-01
The mechanical damping properties of sheet polaroid material have been studied with a physical pendulum. The polaroid samples were placed under the knife-edges of the pendulum, which was operated in free-decay at a period in the vicinity of 10 s. With the edges oriented parallel to the direction of the long molecular chains in the polaroid, it was found that the damping was more than 10% smaller than when oriented perpendicular to the chains.
What is the Brillouin Zone of an Anisotropic Photonic Crystal?
Sivarajah, P; Ofori-Okai, B K; Nelson, K A
2015-01-01
The concept of the Brillouin zone (BZ) in relation to a photonic crystal fabricated in an optically anisotropic material is explored both experimentally and theoretically. In experiment, we used femtosecond laser pulses to excite THz polaritons and image their propagation in lithium niobate and lithium tantalate photonic crystal (PhC) slabs. We directly measured the dispersion relation inside PhCs and observed that the lowest bandgap expected to form at the BZ boundary forms inside the BZ in the anisotropic lithium niobate PhC. Our analysis shows that in an anisotropic material the BZ - defined as the Wigner-Seitz cell in the reciprocal lattice - is no longer bounded by Bragg planes and thus does not conform to the original definition of the BZ by Brillouin. We construct an alternative Brillouin zone defined by Bragg planes and show its utility in identifying features of the dispersion bands. We show that for an anisotropic 2D PhC without dispersion, the Bragg plane BZ can be constructed by applying the Wigne...
Anisotropic metamaterials for microwave antennas and infrared nanostructured thin films
Jian, Zhihao
Wave-matter interactions have long been investigated to discover unknown physical phenomena and exploited to achieve improved device performance throughout the electromagnetic spectrum ranging from quasi-static limit to microwave frequencies, and even at infrared and optical wavelengths. As a nascent but fast growing field, metamaterial technology, which relies on clusters of artificially engineered subwavelength structures, has been demonstrated to provide a wide variety of exotic electromagnetic properties unattainable in natural materials. This dissertation presents the research on novel anisotropic metamaterials for tailoring microwave radiation and infrared scattering of nanostructured thin films. First, a new inversion algorithm is proposed for retrieving the anisotropic effective medium parameters of a slab of metamaterial. Secondly, low-loss anisotropic metamaterial lenses and coatings are introduced for improving the gain and/or bandwidth for a variety of antennas. In particular, a quad-beam high-gain lens for a quarter-wave monopole, a low-profile grounded leaky metamaterial coating for slot antenna, and an ultra-thin anisotropic metamaterial bandwidth-enhancing coating for a quarter-wave monopole are experimentally demonstrated. In the infrared regime, novel nanostructured metamaterial free-standing thin-films, which are inherently anisotropic, are introduced for achieving exotic index properties and further for practical photonic devices. In particular, a low-loss near-infrared fishnet zero-index metamaterial, a dispersionengineered optically-thin, low-loss broadband metamaterial filter with a suppressed group delay fluctuation in the mid-infrared, and a conformal dual-band near-perfectly absorbing coating in the mid-infrared are experimentally demonstrated. These explorations show the great promise anisotropic metamaterials hold for the flexible manipulation of electromagnetic waves and their broad applicability in a wide spectrum range.
Optimal anisotropic three-phase conducting composites: Plane problem
Cherkaev, Andrej
2010-01-01
The paper establishes tight lower bound for effective conductivity tensor $K_*$ of two-dimensional three-phase conducting anisotropic composites and defines optimal microstructures. It is assumed that three materials are mixed with fixed volume fractions and that the conductivity of one of the materials is infinite. The bound expands the Hashin-Shtrikman and Translation bounds to multiphase structures, it is derived using the technique of {\\em localized polyconvexity} that is a combination of Translation method and additional inequalities on the fields in the materials; similar technique was used by Nesi (1995) and Cherkaev (2009) for isotropic multiphase composites. This paper expands the bounds to the anisotropic composites. The lower bound of conductivity (G-closure) is a piece-wise analytic function of eigenvalues of $K_*$, that depends only on conductivities of components and their volume fractions. Also, we find optimal microstructures that realize the bounds, developing the technique suggested earlier ...
Recent progress in anisotropic hydrodynamics
Strickland, Michael
2016-01-01
The quark-gluon plasma created in a relativistic heavy-ion collisions possesses a sizable pressure anisotropy in the local rest frame at very early times after the initial nuclear impact and this anisotropy only slowly relaxes as the system evolves. In a kinetic theory picture, this translates into the existence of sizable momentum-space anisotropies in the underlying partonic distribution functions, . In such cases, it is better to reorganize the hydrodynamical expansion by taking into account momentum-space anisotropies at leading-order in the expansion instead of as a perturbative correction to an isotropic distribution. The resulting anisotropic hydrodynamics framework has been shown to more accurately describe the dynamics of rapidly expanding systems such as the quark-gluon plasma. In this proceedings contribution, I review the basic ideas of anisotropic hydrodynamics, recent progress, and present a few preliminary phenomenological predictions for identified particle spectra and elliptic flow.
Conductivities in an anisotropic medium
Khimphun, Sunly; Lee, Bum-Hoon; Park, Chanyong
2016-10-01
In order to imitate the anisotropic medium of a condensed matter system, we take into account an Einstein-Maxwell-dilaton-axion model as a dual gravity theory where the anisotropy is caused by different momentum relaxations. This gravity model allows an anisotropic charged black hole solution. On this background, we investigate how the linear responses of vector modes like electric, thermoelectric, and thermal conductivities rely on the anisotropy. We find that the electric conductivity in the low frequency limit shows a Drude peak and that, in the intermediate frequency regime, it reveals the power law behavior. Specifically, when the anisotropy increases, the exponent of the power law becomes smaller. In addition, we find that a critical value for the anisotropy exists at which the dc conductivity reaches to its maximum value.
Anisotropic Inflation and Cosmological Observations
Emami, Razieh
2015-01-01
Recent observations opened up a new window on the inflationary model building. As it was firstly reported by the WMAP data, there may be some indications of statistical anisotropy on the CMB map, although the statistical significance of these findings are under debate. Motivated by these observations, people begun considering new inflationary models which may lead to statistical anisotropy. The simplest possible way to construct anisotropic inflation is to introduce vector fields. During the course of this thesis, we study models of anisotropic inflation and their observational implications such as power spectrum, bispectrum etc. Firstly we build a new model, which contains the gauge field which breaks the conformal invariance while preserving the gauge invariance. We show that in these kind of models, there can be an attractor phase in the evolution of the system when the back-reaction of the gauge field becomes important in the evolution of the inflaton field. We then study the cosmological perturbation the...
Conductivities in an anisotropic medium
Khimphun, Sunly; Park, Chanyong
2016-01-01
In order to imitate anisotropic medium of a condensed matter system, we take into account an Einstein-Maxwell-dilaton-axion model as a dual gravity theory where the anisotropy is caused by different momentum relaxations. This gravity model allows an anisotropic charged black hole solution. On this background, we investigate how the linear responses of vector modes like electric, thermoelectric, and thermal conductivities rely on the anisotropy. We find that the electric conductivity in low frequency limit shows a Drude peak and that in the intermediate frequency regime it reveals the power law behavior. Especially, when the anisotropy increases the exponent of the power law becomes smaller. In addition, we find that there exist a critical value for the anisotropy at which the DC conductivity reaches to its maximum value.
Equivalent Antisymmetry Performance of Three-Dimensional Heterogeneous Anisotropic Composites
Institute of Scientific and Technical Information of China (English)
李永; 宋健; 张志民
2003-01-01
Starting from the physical features of materials, heterogeneous anisotropic composites (HACs) are analysed on the basis of the understanding and applications of its equivalent antisymmetry performance. Moreover, the design parameter is optimized to attain the goal of maximizing the use of materials, which is quite meaningful. The HAC structure is defined as a kind of equivalent structures according to the structure and properties of materials.We apply the mature plate theory and the composite materials laminate theory in analysis of the HAC structure,and in this way a new concept and a new idea are expected.
Transient motion of thick anisotropic plates
Nayfeh, Adnan H.; Taylor, Timothy W.
1991-01-01
Analyses are developed for the response of anisotropic plate strips to a transient load. The load is taken in the form of a line load of normal stress on the surface or within the body of the strip. The characteristic free vibrational modes of the strip are derived and used to derive the secular equation for this case in closed form and to isolate the mathematical conditions for symmetric and antisymmetric wave mode propagation in completely separate terms. The applied loads are expanded in terms of these normal modes and the response of the plate is obtained by superposition of the appropriate components. Material systems of higher symmetry are contained implicitly in the analysis.
Anisotropic criteria for the type of superconductivity
Energy Technology Data Exchange (ETDEWEB)
Kogan, Vladimir G [Ames Laboratory; Prozorov, Ruslan [Ames Laboratory
2014-08-01
The classical criterion for classification of superconductors as type I or type II based on the isotropic Ginzburg-Landau theory is generalized to arbitrary temperatures for materials with anisotropic Fermi surfaces and order parameters. We argue that the relevant quantity for this classification is the ratio of the upper and thermodynamic critical fields Hc2/Hc, rather than the traditional ratio of the penetration depth and the coherence length λ/ξ. Even in the isotropic case, Hc2/Hc coincides with 2√λ/ξ only at the critical temperature Tc and they differ as T decreases, the long-known fact. Anisotropies of Fermi surfaces and order parameters may amplify this difference and render false the criterion based on the value of κ=λ/ξ.
Anisotropic criteria for the type of superconductivity
Kogan, V. G.; Prozorov, R.
2014-08-01
The classical criterion for classification of superconductors as type I or type II based on the isotropic Ginzburg-Landau theory is generalized to arbitrary temperatures for materials with anisotropic Fermi surfaces and order parameters. We argue that the relevant quantity for this classification is the ratio of the upper and thermodynamic critical fields Hc2/Hc, rather than the traditional ratio of the penetration depth and the coherence length λ /ξ. Even in the isotropic case, Hc2/Hc coincides with √2 λ /ξ only at the critical temperature Tc and they differ as T decreases, the long-known fact. Anisotropies of Fermi surfaces and order parameters may amplify this difference and render false the criterion based on the value of κ =λ/ξ.
Institute of Scientific and Technical Information of China (English)
黄超超; 吴晓迪; 杨华; 蒋剑锋
2013-01-01
Object's surface Bidirectional Reflectance Distribution Function(BRDF) was studied,the wavelength factor was introduced on the basis of anisotropic Gaussian model,the modified Anisotropic Gaussian calculation model of BRDF with was put forward.The BRDF of satellite's solar panel and multilayer insulation was calculated by using this model.The numerical results indicate that the modified model has univocal parameters and high efficiency,which can calculate object's surface BRDF effectively.%对目标表面双向反射分布函数(BRDF)进行研究,在各向异性Gaussian模型的基础上引入波长因子,提出了改进的BRDF各向异性Gaussian计算模型.运用该模型对卫星太阳能板及包裹多层隔热材料进行了BRDF计算,结果表明该模型参数物理意义明确、简洁高效,能够有效地计算物体表面材料BRDF数值.
Anisotropic artificial substrates for microwave applications
Shahvarpour, Attieh
The perfect electromagnetic conductor (PEMC) boundary is a novel fundamental electromagnetic concept. It is a generalized description of the electromagnetic boundary conditions including the perfect electric conductor (PEC) and the perfect magnetic conductor (PMC) and due to its fundamental properties, it has the potential of enabling several electromagnetic applications. However, the PEMC boundaries concept had remained at the theoretical level and has not been practically realized. Therefore, motivated by the importance of this electromagnetic fundamental concept and its potential applications, the first contribution of this thesis is focused on the practical implementation of the PEMC boundaries by exploiting Faraday rotation principle and ground reflection in the ferrite materials which are intrinsically anisotropic. As a result, this thesis reports the first practical approach for the realization of PEMC boundaries. A generalized scattering matrix (GSM) is used for the analysis of the grounded-ferrite PEMC boundaries structure. As an application of the PEMC boundaries, a transverse electromagnetic (TEM) waveguide is experimentally demonstrated using grounded ferrite PMC (as particular case of the PEMC boundaries) side walls. Perfect electromagnetic conductor boundaries may find applications in various types of sensors, reflectors, polarization convertors and polarization-based radio frequency identifiers. Leaky-wave antennas perform as high directivity and frequency beam scanning antennas and as a result they enable applications in radar, point-to-point communications and MIMO systems. The second contribution of this thesis is introducing and analysing a novel broadband and highly directive two-dimensional leaky-wave antenna. This antenna operates differently in the lower and higher frequency ranges. Toward its lower frequencies, it allows full-space conical-beam scanning while at higher frequencies, it provides fixed-beam radiation (at a designable angle
Institute of Scientific and Technical Information of China (English)
SHU Wei-Xing; LUO Hai-Lu; LI Fei; REN Zhong-Zhou
2006-01-01
@@ We investigate the propagation of electromagnetic waves at the interface between an isotropic material and the anisotropic medium with a unique dispersion relation. We show that the refraction behaviour of E-polarized waves is opposite to that of H-polarized waves, though the dispersion relations for E- and H-polarized waves are the same. It is found that waves exhibit different propagation properties in anisotropic media with different sign combinations of the permittivity and permeability tensors. Some interesting properties of propagation are also found in the special anisotropic media, leading to potential applications.
Biermann, Mark L.; Walters, Matthew; Diaz-Barriga, James; Rabinovich, W. S.
2003-10-01
Anisotropic in-plane strain in quantum wells leads to an optical polarization anisotropy that can be exploited for device applications. We have determined that for many anisotropic compressive strain cases, the dependence of the optical anisotropy is linear in the strain anisotropy. This result holds for a variety of well and barrier materials and widths and for various overall strain conditions. Further, the polarization anisotropy per strain anisotropy varies as the reciprocal of the energy separation of the relevant hole sub-bands. Hence, a general result for the polarization anisotropy per strain anisotropy is avialable for cases of compressive anisotropic in-plane strain.
Energy Technology Data Exchange (ETDEWEB)
Biermann, Mark L [Physics Department, 566 Brownson Rd., U.S. Naval Academy, Annapolis, MD 21402 (United States); Walters, Matthew [Physics Department, 566 Brownson Rd., U.S. Naval Academy, Annapolis, MD 21402 (United States); Diaz-Barriga, James [Physics Department, 566 Brownson Rd., U.S. Naval Academy, Annapolis, MD 21402 (United States); Rabinovich, W S [Naval Research Laboratory, Code 5652, 4555 Overlook Ave. SW, Washington, DC 20375-5320 (United States)
2003-10-21
Anisotropic in-plane strain in quantum wells leads to an optical polarization anisotropy that can be exploited for device applications. We have determined that for many anisotropic compressive strain cases, the dependence of the optical anisotropy is linear in the strain anisotropy. This result holds for a variety of well and barrier materials and widths and for various overall strain conditions. Further, the polarization anisotropy per strain anisotropy varies as the reciprocal of the energy separation of the relevant hole sub-bands. Hence, a general result for the polarization anisotropy per strain anisotropy is available for cases of compressive anisotropic in-plane strain.
Heat Flow Pattern and Thermal Resistance Modeling of Anisotropic Heat Spreaders
Falakzaadeh, F.; Mehryar, R.
2017-01-01
To ensure safe operating temperatures of the ever smaller heat generating electronic devices, drastic measures should be taken. Heat spreaders are used to increase surface area, by spreading the heat without necessarily transferring it to the ambient in the first place. The heat flow pattern is investigated in heat spreaders and the fundamental differences regarding how heat conducts in different materials is addressed. Isotropic materials are compared with anisotropic ones having a specifically higher in-plane thermal conductivity than through plane direction. Thermal resistance models are proposed for anisotropic and isotropic heat spreaders in compliance with the order of magnitude of dimensions used in electronics packaging. After establishing thermal resistance models for both the isotropic and anisotropic cases, numerical results are used to find a correlation for predicting thermal resistance in anisotropic heat spreaders with high anisotropy ratios.
Biferale, Luca; Toschi, Federico
2001-01-01
We present the first measurements of anisotropic statistical fluctuations in perfectly homogeneous turbulent flows. We address both problems of intermittency in anisotropic sectors and hierarchical ordering of anisotropies on a direct numerical simulation of a three dimensional random Kolmogorov flo
Doubly Periodic Cracks in the Anisotropic Medium with the Account of Contact of Their Faces
Directory of Open Access Journals (Sweden)
Maksymovych Olesya
2014-09-01
Full Text Available The paper presents complex variable integral formulae and singular boundary integral equations for doubly periodic cracks in anisotropic elastic medium. It utilizes the numerical solution procedure, which accounts for the contact of crack faces and produce accurate results for SIF evaluation. It is shown that the account of contact effects significantly influence the SIF of doubly periodic curvilinear cracks both for isotropic and anisotropic materials.
Anisotropic Paramagnetic Meissner Effect by Spin-Orbit Coupling
Espedal, Camilla; Yokoyama, Takehito; Linder, Jacob
2016-03-01
Conventional s -wave superconductors repel an external magnetic field. However, a recent experiment [A. Di Bernardo et al., Phys. Rev. X 5, 041021 (2015)] has tailored the electromagnetic response of superconducting correlations via adjacent magnetic materials. We consider another route of altering the Meissner effect where spin-orbit interactions induce an anisotropic Meissner response that changes sign depending on the field orientation. The tunable electromagnetic response opens new paths in the utilization of hybrid systems comprising magnets and superconductors.
A Reformulation of Nonlinear Anisotropic Elasticity for Impact Physics
2014-02-01
Polycrystals. International Journal of Plasticity 2003, 19, 1401–1444. 26. Clayton, J. D.; McDowell, D. L. Homogenized Finite Elastoplasticity and Damage ...Materials and Technology 2002, 124, 302– 313. 25. Clayton, J. D.; McDowell, D. L. A Multiscale Multiplicative Decomposition for Elastoplasticity of...29. Clayton, J. D. Continuum Multiscale Modeling of Finite Deformation Plasticity and Anisotropic Damage in Polycrystals. Theoretical and Applied
Magnetostriction simulation using anisotropic vector Preisach-type models
Energy Technology Data Exchange (ETDEWEB)
Adly, A.A. [Cairo Univ., Giza (Egypt). Electric Power and Machines Dept.; Mayergoyz, I.D. [Univ. of Maryland, College Park, MD (United States). Electrical Engineering Dept.
1996-09-01
Magnetic materials exhibiting gigantic magnetostriction, especially Terfenol, are currently being widely used in fine positioning and active vibration damping devices. By involving accurate magnetostriction models during design stages, precision of such devices may be significantly enhanced. In this paper a straight-forward approach that employs anisotropic vector Preisach-type hysteresis models in simulating field-stress effects on magnetic materials is presented. Formulation of the proposed model is given and its identification problem is solved. The presented approach has been numerically implemented and numerous digital computer simulations have been performed for Terfenol material. Sample simulation results as well as comparisons with experimentally observed magnetostriction curves are reported in the paper.
Analyzing spinodal decomposition of an anisotropic fluid mixture
Gruhn, Thomas; Pogorelov, Evgeny; Seiferling, Felix; Emmerich, Heike
2017-02-01
Spinodal decomposition leads to spontaneous fluctuations of the local concentration. In the early stage, the resulting pattern provides explicit information about the material properties of the mixture. In the case of two isotropic fluids, the static structure factor shows the characteristic ring shape. If one component is a liquid crystal, the pattern is typically anisotropic and the structure factor is more complex. Using numerical methods, we investigate how structure factors can be used to extract information about material properties like the diffusion constant or the isotropic and the anisotropic contributions to the interfacial tension. The method is based on momenta taken from structure factors in the early stage of the spinodal demixing. We perform phase field calculations for an isotropic and an anisotropic spinodal decomposition. A comparison of the extracted results with analytic values is made. The calculations show that linear modes dominate in the beginning of the growth process, while non-linear modes grow monotonously in the region of the k-space for which damping is predicted by the linearized theory. As long as non-linear modes are small enough, linearized theory can be applied to extract material properties from the structure factor.
Contrôle de l'apparence des matériaux anisotropes
Raymond, Boris
2016-01-01
In computer graphics, material appearance is a fundamental component of the final image quality. Many models have contributed to improve material appearance. Today, some materials remains hard to represent because of their complexity. Among them, anisotopic materials are especially complex and little studied. In this thesis, we propose a better comprehension of anisotropic materials providing a representation model and an editing tool to control their appearance. Our scratched material model ...
Remarks on inhomogeneous anisotropic cosmology
Kaya, Ali
2016-08-01
Recently a new no-global-recollapse argument was given for some inhomogeneous and anisotropic cosmologies that utilizes surface deformation by the mean curvature flow. In this paper we discuss important properties of the mean curvature flow of spacelike surfaces in Lorentzian manifolds. We show that singularities may form during cosmic evolution, and the theorems forbidding the global recollapse lose their validity. The time evolution of the spatial scalar curvature that may kinematically prevent the recollapse is determined in normal coordinates, which shows the impact of inhomogeneities explicitly. Our analysis indicates a caveat in numerical solutions that give rise to inflation.
Spin precession in anisotropic cosmologies
Energy Technology Data Exchange (ETDEWEB)
Kamenshchik, A.Yu. [Universita di Bologna, Dipartimento di Fisica e Astronomia, Bologna (Italy); L. D. Landau Institute for Theoretical Physics, Moscow (Russian Federation); INFN, Bologna (Italy); Teryaev, O.V. [Joint Institute for Nuclear Research, Bogoliubov Laboratory of Theoretical Physics, Dubna (Russian Federation); Lomonosov Moscow State University, Moscow (Russian Federation)
2016-05-15
We consider the precession of a Dirac particle spin in some anisotropic Bianchi universes. This effect is present already in the Bianchi-I universe. We discuss in some detail the geodesics and the spin precession for both the Kasner and the Heckmann-Schucking solutions. In the Bianchi-IX universe the spin precession acquires the chaotic character due to the stochasticity of the oscillatory approach to the cosmological singularity. The related helicity flip of fermions in the very early universe may produce the sterile particles contributing to dark matter. (orig.)
Anisotropic and nonlinear optical waveguides
Someda, CG
1992-01-01
Dielectric optical waveguides have been investigated for more than two decades. In the last ten years they have had the unique position of being simultaneously the backbone of a very practical and fully developed technology, as well as an extremely exciting area of basic, forefront research. Existing waveguides can be divided into two sets: one consisting of waveguides which are already in practical use, and the second of those which are still at the laboratory stage of their evolution. This book is divided into two separate parts: the first dealing with anisotropic waveguides, an
Comments on inhomogeneous anisotropic cosmology
Kaya, Ali
2016-01-01
Recently a new no-global-recollapse argument is given for some inhomogeneous and anisotropic cosmologies that utilizes surface deformation by the mean curvature flow. In this note we point out a few important issues about the proposed deformations and in particular indicate that in the presence of large spatial variations the mean curvature flow may deform an initially spacelike surface to a surface with null or timelike portions. The time evolution of the spatial scalar curvature that prevents recollapse is determined in normal coordinates, which shows the impact of inhomogeneities explicitly. Our analysis also indicates a possible caveat in numerical solutions that give rise to inflation.
Recent progress in anisotropic hydrodynamics
Directory of Open Access Journals (Sweden)
Strickland Michael
2017-01-01
Full Text Available The quark-gluon plasma created in a relativistic heavy-ion collisions possesses a sizable pressure anisotropy in the local rest frame at very early times after the initial nuclear impact and this anisotropy only slowly relaxes as the system evolves. In a kinetic theory picture, this translates into the existence of sizable momentum-space anisotropies in the underlying partonic distribution functions, 〈 pL2〉 ≪ 〈 pT2〉. In such cases, it is better to reorganize the hydrodynamical expansion by taking into account momentum-space anisotropies at leading-order in the expansion instead of as a perturbative correction to an isotropic distribution. The resulting anisotropic hydrodynamics framework has been shown to more accurately describe the dynamics of rapidly expanding systems such as the quark-gluon plasma. In this proceedings contribution, I review the basic ideas of anisotropic hydrodynamics, recent progress, and present a few preliminary phenomenological predictions for identified particle spectra and elliptic flow.
Sur, Shouvik; Lee, Sung-Sik
2016-11-01
We study non-Fermi-liquid states that arise at the quantum critical points associated with the spin density wave (SDW) and charge density wave (CDW) transitions in metals with twofold rotational symmetry. We use the dimensional regularization scheme, where a one-dimensional Fermi surface is embedded in (3 -ɛ ) -dimensional momentum space. In three dimensions, quasilocal marginal Fermi liquids arise both at the SDW and CDW critical points: the speed of the collective mode along the ordering wave vector is logarithmically renormalized to zero compared to that of Fermi velocity. Below three dimensions, however, the SDW and CDW critical points exhibit drastically different behaviors. At the SDW critical point, a stable anisotropic non-Fermi-liquid state is realized for small ɛ , where not only time but also different spatial coordinates develop distinct anomalous dimensions. The non-Fermi liquid exhibits an emergent algebraic nesting as the patches of Fermi surface are deformed into a universal power-law shape near the hot spots. Due to the anisotropic scaling, the energy of incoherent spin fluctuations disperse with different power laws in different momentum directions. At the CDW critical point, on the other hand, the perturbative expansion breaks down immediately below three dimensions as the interaction renormalizes the speed of charge fluctuations to zero within a finite renormalization group scale through a two-loop effect. The difference originates from the fact that the vertex correction antiscreens the coupling at the SDW critical point whereas it screens at the CDW critical point.
ANISOTROPIC BIQUADRATIC ELEMENT WITH SUPERCLOSE RESULT
Institute of Scientific and Technical Information of China (English)
Dongyang SHI; Shipeng MAO; Hui LIANG
2006-01-01
The main aim of this paper is to study the convergence of biquadratic finite element for the second order problem on anisotropic meshes. By using some novel approaches and techniques, the optimal error estimates are obtained. At the same time, the anisotropic superclose results are also achieved. Furthermore, the numerical results are given to demonstrate our theoretical analysis.
Radiation of planar electromagnetic waves by a line source in anisotropic metamaterials
Cheng, Qiang; Jiang, Wei Xiang; Cui, Tie Jun
2010-08-01
We show experimentally that a line source in an anisotropic metamaterial directly radiates planar electromagnetic waves instead of cylindrical waves, when one component of the permeability tensor approaches zero. The impedance of this material can be perfectly matched to that of free space, which can significantly reduce the reflections between the source and the superstrate, as in traditional highly directive antennas based on zero index metamaterials. Such a unique property determines the two-way propagation of electromagnetic waves excited by a line source, instead of all-way propagation. From this feature, a highly directive emission of electromagnetic waves is achieved using the anisotropic metamaterial with arbitrary shape. We have designed and fabricated the anisotropic metamaterial in the microwave region, and observed the generation of plane waves and their highly directive emission. The proposed plane-wave emission is independent of the shape variance of the anisotropic metamaterial, which can be utilized in the design of conformal antennas.
CONSTITUTIVE EQUATION OF CO-ROTATIONAL DERIVATIVE TYPE FOR ANISOTROPIC-VISCOELASTIC FLUID
Institute of Scientific and Technical Information of China (English)
HAN Shifang
2004-01-01
A constitutive equation theory of Oldroyd fluid B type, i.e. the co-rotational derivative type, is developed for the anisotropic-viscoelastic fluid of liquid crystalline (LC) polymer. Analyzing the influence of the orientational motion on the material behavior and neglecting the influence, the constitutive equation is applied to a simple case for the hydrodynamic motion when the orientational contribution is neglected in it and the anisotropic relaxation, retardation times and anisotropic viscosities are introduced to describe the macroscopic behavior of the anisotropic LC polymer fluid. Using the equation for the shear flow of LC polymer fluid, the analytical expressions of the apparent viscosity and the normal stress differences are given which are in a good agreement with the experimental results of Baek et al. For the fiber spinning flow of the fluid, the analytical expression of the extensional viscosity is given.
Radiation of planar electromagnetic waves by a line source in anisotropic metamaterials
Energy Technology Data Exchange (ETDEWEB)
Cheng Qiang; Jiang Weixiang; Cui Tiejun, E-mail: tjcui@seu.edu.c [State Key Laboratory of Millimeter Waves, Department of Radio Engineering, Southeast University, Nanjing 210096 (China)
2010-08-25
We show experimentally that a line source in an anisotropic metamaterial directly radiates planar electromagnetic waves instead of cylindrical waves, when one component of the permeability tensor approaches zero. The impedance of this material can be perfectly matched to that of free space, which can significantly reduce the reflections between the source and the superstrate, as in traditional highly directive antennas based on zero index metamaterials. Such a unique property determines the two-way propagation of electromagnetic waves excited by a line source, instead of all-way propagation. From this feature, a highly directive emission of electromagnetic waves is achieved using the anisotropic metamaterial with arbitrary shape. We have designed and fabricated the anisotropic metamaterial in the microwave region, and observed the generation of plane waves and their highly directive emission. The proposed plane-wave emission is independent of the shape variance of the anisotropic metamaterial, which can be utilized in the design of conformal antennas.
Efficient Wavefield Extrapolation In Anisotropic Media
Alkhalifah, Tariq
2014-07-03
Various examples are provided for wavefield extrapolation in anisotropic media. In one example, among others, a method includes determining an effective isotropic velocity model and extrapolating an equivalent propagation of an anisotropic, poroelastic or viscoelastic wavefield. The effective isotropic velocity model can be based upon a kinematic geometrical representation of an anisotropic, poroelastic or viscoelastic wavefield. Extrapolating the equivalent propagation can use isotopic, acoustic or elastic operators based upon the determined effective isotropic velocity model. In another example, non-transitory computer readable medium stores an application that, when executed by processing circuitry, causes the processing circuitry to determine the effective isotropic velocity model and extrapolate the equivalent propagation of an anisotropic, poroelastic or viscoelastic wavefield. In another example, a system includes processing circuitry and an application configured to cause the system to determine the effective isotropic velocity model and extrapolate the equivalent propagation of an anisotropic, poroelastic or viscoelastic wavefield.
Designing Anisotropic Inflation with Form Fields
Ito, Asuka
2015-01-01
We study inflation with anisotropic hair induced by form fields. In four dimensions, the relevant form fields are gauge (one-form) fields and two-form fields. Assuming the exponential form of potential and gauge kinetic functions, we find new exact power-law solutions endowed with anisotropic hair. We also explore the phase space of anisotropic inflation and find fixed points corresponding to the exact power-law solutions. Moreover, we perform the stability analysis around the fixed points to reveal the structure of the phase space. It turns out that one of the fixed points becomes an attractor and others (if any) are saddle points. In particular, the one corresponding to anisotropic inflation becomes an attractor when it exists. We also argue that various anisotropic inflation models can be designed by choosing coupling constants.
Characteristics of Plane Wave Propagation in Biaxially Anisotropic Gyrotropic Media
Institute of Scientific and Technical Information of China (English)
PAN Wei-Tao; LIU Song-Hua; QIU Zhi-Liang
2012-01-01
Propagation characteristics of electromagnetic waves at the interface between an isotropic regular medium and a biaxially anisotropic gyrotropic medium are investigated.The results indicate that the reflection and refract ionproperties of electromagnetic waves are closely dependent on the dispersion relation of the gyrotropic media,and that anomalous total reflection and negative refraction may occur.The existence conditions of total transmission are also considered.It is found that total transmission arises when the TE-polarized incident waves are normal to the interface and the physical parameters of the two media are chosen properly,which are quite different from the existence conditions of total transmission at the anisotropic left-handed material interface.Numerical resul tsare given to validate our theoretical analysis.
Characterization of highly anisotropic three-dimensionally nanostructured surfaces
Schmidt, Daniel
2013-01-01
Generalized ellipsometry, a non-destructive optical characterization technique, is employed to determine geometrical structure parameters and anisotropic dielectric properties of highly spatially coherent three-dimensionally nanostructured thin films grown by glancing angle deposition. The (piecewise) homogeneous biaxial layer model approach is discussed, which can be universally applied to model the optical response of sculptured thin films with different geometries and from diverse materials, and structural parameters as well as effective optical properties of the nanostructured thin films are obtained. Alternative model approaches for slanted columnar thin films, anisotropic effective medium approximations based on the Bruggeman formalism, are presented, which deliver results comparable to the homogeneous biaxial layer approach and in addition provide film constituent volume fraction parameters as well as depolarization or shape factors. Advantages of these ellipsometry models are discussed on the example ...
Anisotropic electronic conduction in stacked two-dimensional titanium carbide
Hu, Tao; Zhang, Hui; Wang, Jiemin; Li, Zhaojin; Hu, Minmin; Tan, Jun; Hou, Pengxiang; Li, Feng; Wang, Xiaohui
2015-11-01
Stacked two-dimensional titanium carbide is an emerging conductive material for electrochemical energy storage which requires an understanding of the intrinsic electronic conduction. Here we report the electronic conduction properties of stacked Ti3C2T2 (T = OH, O, F) with two distinct stacking sequences (Bernal and simple hexagonal). On the basis of first-principles calculations and energy band theory analysis, both stacking sequences give rise to metallic conduction with Ti 3d electrons contributing most to the conduction. The conduction is also significantly anisotropic due to the fact that the effective masses of carriers including electrons and holes are remarkably direction-dependent. Such an anisotropic electronic conduction is evidenced by the I-V curves of an individual Ti3C2T2 particulate, which demonstrates that the in-plane electrical conduction is at least one order of magnitude higher than that vertical to the basal plane.
Modeling of CMUTs with Multiple Anisotropic Layers and Residual Stress
DEFF Research Database (Denmark)
Engholm, Mathias; Thomsen, Erik Vilain
2014-01-01
Usually the analytical approach for modeling CMUTs uses the single layer plate equation to obtain the deflection and does not take anisotropy and residual stress into account. A highly accurate model is developed for analytical characterization of CMUTs taking an arbitrary number of layers...... and residual stress into account. Based on the stress-strain relation of each layer and balancing stress resultants and bending moments, a general multilayered anisotropic plate equation is developed for plates with an arbitrary number of layers. The exact deflection profile is calculated for a circular...... clamped plate of anisotropic materials with residual bi-axial stress. From the deflection shape the critical stress for buckling is calculated and by using the Rayleigh-Ritz method the natural frequency is estimated....
Modeling of plates with multiple anisotropic layers and residual stress
DEFF Research Database (Denmark)
Engholm, Mathias; Pedersen, Thomas; Thomsen, Erik Vilain
2016-01-01
Usually the analytical approach for modeling of plates uses the single layer plate equation to obtain the deflection and does not take anisotropy and residual stress into account. Based on the stress–strain relation of each layer and balancing stress resultants and bending moments, a general...... multilayered anisotropic plate equation is developed for plates with an arbitrary number of layers. The exact deflection profile is calculated for a circular clamped plate of anisotropic materials with residual bi-axial stress.From the deflection shape the critical stress for buckling is calculated......, and an excellent agreement between the two models is seen with a relative difference of less than 2% for all calculations. The model was also used to extract the cell capacitance, the parasitic capacitance and the residual stress of a pressure sensor composed of a multilayered plate of silicon and silicon oxide...
Anisotropic hypersonic phonon propagation in films of aligned ellipsoids.
Beltramo, Peter J; Schneider, Dirk; Fytas, George; Furst, Eric M
2014-11-14
A material with anisotropic elastic mechanical properties and a direction-dependent hypersonic band gap is fabricated using ac electric field-directed convective self-assembly of colloidal ellipsoids. The frequency of the gap, which is detected in the direction perpendicular to particle alignment and entirely absent parallel to alignment, and the effective sound velocities can be tuned by the particle aspect ratio. We hypothesize that the band gap originates from the primary eigenmode peak, the m-splitted (s,1,2) mode, of the particle resonating with the effective medium. These results reveal the potential for powerful control of the hypersonic phononic band diagram by combining anisotropic particles and self-assembly.
Theoretical assessment of sound absorption coefficient for anisotropic nonwovens
Directory of Open Access Journals (Sweden)
Klara Kalinova
2012-03-01
Full Text Available The anisotropy factor as a function of fiber arrangement, fiber fineness and sample thickness has been derived from the theories of soundwave transformation due to phase changing. The sound absorption coefficient of the anisotropic fibrous material is then theoretically calculated. The fibrous materials were prepared so that the fibers are arranged parallel (perpendicularly laid fiber web called STRUTO technology in the direction of soundwave propagation or perpendicularly (longitudinally laid fiber web to the direction of sound propagation. The sound absorption coefficient was measured due to the Impedance tube. The theoretical results are in good agreement with experimental findings.
Warm anisotropic inflationary universe model
Energy Technology Data Exchange (ETDEWEB)
Sharif, M.; Saleem, Rabia [University of the Punjab, Department of Mathematics, Lahore (Pakistan)
2014-02-15
This paper is devoted to the study of warm inflation using vector fields in the background of a locally rotationally symmetric Bianchi type I model of the universe. We formulate the field equations, and slow-roll and perturbation parameters (scalar and tensor power spectra as well as their spectral indices) in the slow-roll approximation. We evaluate all these parameters in terms of the directional Hubble parameter during the intermediate and logamediate inflationary regimes by taking the dissipation factor as a function of the scalar field as well as a constant. In each case, we calculate the observational parameter of interest, i.e., the tensor-scalar ratio in terms of the inflaton. The graphical behavior of these parameters shows that the anisotropic model is also compatible with WMAP7 and the Planck observational data. (orig.)
Warm Anisotropic Inflationary Universe Model
Sharif, M
2014-01-01
This paper is devoted to study the warm inflation using vector fields in the background of locally rotationally symmetric Bianchi type I universe model. We formulate the field equations, slow-roll and perturbation parameters (scalar and tensor power spectra as well as their spectral indices) under slow-roll approximation. We evaluate all these parameters in terms of directional Hubble parameter during intermediate and logamediate inflationary regimes by taking the dissipation factor as a function of scalar field as well as a constant. In each case, we calculate the observational parameter of interest, i.e., tensor-scalar ratio in terms of inflation. The graphical behavior of these parameters shows that the anisotropic model is also compatible with WMAP7 and Planck observational data.
Gravitational Baryogenesis after Anisotropic Inflation
Fukushima, Mitsuhiro; Maeda, Kei-ichi
2016-01-01
The gravitational baryogensis may not generate a sufficient baryon asymmetry in the standard thermal history of the Universe when we take into account the gravitino problem. Hence it has been suggested that anisotropy of the Universe can enhance the generation of the baryon asymmetry through the increase of the time change of the Ricci scalar curvature. We study the gravitational baryogenesis in the presence of anisotropy, which is produced at the end of an anisotropic inflation. Although we confirm that the generated baryon asymmetry is enhanced compared with the original isotropic cosmological model, taking into account the constraint on the anisotropy by the recent CMB observations, we find that it is still difficult to obtain the observed baryon asymmetry only through the gravitational baryogenesis without suffering from the gravitino problem.
Anisotropic inflation from extra dimensions
Litterio, M; Amendola, L; Dyrek, A; Litterio, Marco; Amendola, Luca; Dyrek, Andrzej
1995-01-01
Vacuum multidimensional cosmological models with internal spaces being compact n-dimensional Lie group manifolds are considered. Products of 3-spheres and SU(3) manifold (a novelty in cosmology) are studied. It turns out that the dynamical evolution of the internal space drives an accelerated expansion of the external world (power law inflation). This generic solution (attractor in a phase space) is determined by the Lie group space without any fine tuning or arbitrary inflaton potentials. Matter in the four dimensions appears in the form of a number of scalar fields representing anisotropic scale factors for the internal space. Along the attractor solution the volume of the internal space grows logarithmically in time. This simple and natural model should be completed by mechanisms terminating the inflationary evolution and transforming the geometric scalar fields into ordinary particles.
Gravitational baryogenesis after anisotropic inflation
Fukushima, Mitsuhiro; Mizuno, Shuntaro; Maeda, Kei-ichi
2016-05-01
The gravitational baryogensis may not generate a sufficient baryon asymmetry in the standard thermal history of the Universe when we take into account the gravitino problem. Hence, it has been suggested that anisotropy of the Universe can enhance the generation of the baryon asymmetry through the increase of the time change of the Ricci scalar curvature. We study the gravitational baryogenesis in the presence of anisotropy, which is produced at the end of an anisotropic inflation. Although we confirm that the generated baryon asymmetry is enhanced compared with the original isotropic cosmological model, taking into account the constraint on the anisotropy by the recent CMB observations, we find that it is still difficult to obtain the observed baryon asymmetry only through the gravitational baryogenesis without suffering from the gravitino problem.
Anisotropic grid adaptation in LES
Toosi, Siavash; Larsson, Johan
2016-11-01
The modeling errors depend directly on the grid (or filter) spacing in turbulence-resolving simulations (LES, DNS, DES, etc), and are typically at least as significant as the numerical errors. This makes adaptive grid-refinement complicated, since it prevents the estimation of the local error sources through numerical analysis. The present work attempts to address this difficulty with a physics-based error-source indicator that accounts for the anisotropy in the smallest resolved scales, which can thus be used to drive an anisotropic grid-adaptation process. The proposed error indicator is assessed on a sequence of problems, including turbulent channel flow and flows in more complex geometries. The formulation is geometrically general and applicable to complex geometries.
Yagi, Kent
2015-01-01
Certain physical quantities that characterize neutron stars and quark stars (e.g. their mass, spin angular momentum and quadrupole moment) are interrelated in a way that is approximately insensitive to their internal structure. Such approximately universal relations are useful to break degeneracies in data analysis for future radio, X-ray and gravitational wave observations. Although the pressure inside compact stars is most likely nearly isotropic, certain scenarios have been put forth that suggest otherwise, for example due to phase transitions. We here investigate whether pressure anisotropy affects the approximate universal relations and whether it prevents their use in future observations. We achieve this by numerically constructing slowly-rotating and tidally-deformed, anisotropic, compact stars in General Relativity to third order in spin. We find that anisotropy affects the universal relations only weakly; the relations become less universal by a factor of 1.5-3 relative to the isotropic case, but rem...
Anisotropic microstructure near the sun
Coles, W. A.; Grall, R. R.; Spangler, S. R.; Sakurai, T.; Harmon, J. K.
1996-07-01
Radio scattering observations provide a means of measuring a two-dimensional projection of the three-dimensional spatial spectrum of electron density, i.e., in the plane perpendicular to the line of sight. Earlier observations have shown that the microstructure at scales of the order of 10 km becomes highly field-aligned inside of 10 Rsolar [Armstrong et al., 1990]. Earlier work has also shown that density fluctuations at scales larger than 1000 km have a Kolmogorov spectrum, whereas the smaller scale structure has a flatter spectrum and is considerably enhanced above the Kolmogorov ``background'' [Coles et al., 1991]. Here we present new observations made during 1990 and 1992. These confirm the earlier work, which was restricted to one source on a few days, but they suggest that the anisotropy changes abruptly near 6 Rsolar which was not clear in the earlier data. The axial ratio measurements are shown on Figure 1 below. The new observations were made with a more uniform sampling of the spatial plane. They show that contours of constant correlation are elliptical. This is apparently inconsistent with the spatial correlation of the ISEE-3 magnetic field which shows a ``Maltese Cross'' shape [Matthaeus et al., 1990]. However this inconsistency may be only apparent: the magnetic field and density correlations need not have the same shape; the scale of the magnetic field correlations is at least 4 orders of magnitude larger; they are much further from the sun; and they are point measurements whereas ours are path-integrated. We also made two simultaneous measurements, at 10 Rsolar, of the anisotropy on scales of 200 to 4000 km. Significant anisotropy was seen on the smaller scales, but the larger scale structure was essentially isotropic. This suggests that the process responsible for the anisotropic microstructure is independent of the larger scale isotropic turbulence. It is then tempting to speculate that the damping of this anisotropic process inside of 6 Rsolar
Effective stress law for anisotropic double porous media
Institute of Scientific and Technical Information of China (English)
ZHAO Ying; CHEN Mian; ZHANG Guangqing
2004-01-01
An effective stress law is derived analytically to describe the effect of pore (fracture pore and matrix-block pore) fluid pressure on the linearly elastic response of anisotropic saturated dual-porous rocks, which exhibit anisotropy. For general anisotropy the difference between the effective stress and the applied stress is not hydrostatic simply multiplied by Biot coefficient. The effective stress law involves four constants for transversely isotropic response; these constants can be expressed in terms of the moduli of the single porous material, double porous material and of the solid material. These expressions are simplified considerably when the anisotropy is structural rather than intrinsic, i.e. in the case of an isotropic solid material with an anisotropic pore structure. In this case the effective stress law involves grain bulk modulus, four moduli and two compliances of the porous material for transverse isotropy. The law reduces, in the case of isotropic response, to that suggested by Li Shuiquan (2001). And reduction to the single-porosity (derived analytically by Carroll (1979)) is presented to demonstrate the conceptual consistency of the proposed law.
Shaped beam scattering by an anisotropic particle
Chen, Zhenzhen; Zhang, Huayong; Huang, Zhixiang; Wu, Xianliang
2017-03-01
An exact semi-analytical solution to the electromagnetic scattering from an optically anisotropic particle illuminated by an arbitrarily shaped beam is proposed. The scattered fields and fields within the anisotropic particle are expanded in terms of spherical vector wave functions. The unknown expansion coefficients are determined by using the boundary conditions and the method of moments scheme. For incidence of a Gaussian beam, zero-order Bessel beam and Hertzian electric dipole radiation, numerical results of the normalized differential scattering cross section are given to a uniaxial, gyrotropic anisotropic spheroid and circular cylinder of finite length. The scattering properties are analyzed concisely.
Research on anisotropic parameters by synthetic seismogram
Institute of Scientific and Technical Information of China (English)
FAN Xiao-ping; LI Qing-he; YANG Cong-jie
2005-01-01
ased on the extensive-dilatancy anisotropy theory, the method of synthetic seismogram is used to estimate the anisotropic parameters. The advantages of the method lie in that it avoids the singularity resolution and saves calculation time of computer by using the eigenvalue and eigenvector analytical expressions of Christoffel equation, at the same time, the result is tested by coherence function. The test result reveals there exists a fine linear relation between original records and synthetic records, indicating the anisotropic parameters estimated by synthetic seismogram can reflect and describe the anisotropic characteristics of the given region medium.
Finite-volume scheme for anisotropic diffusion
Energy Technology Data Exchange (ETDEWEB)
Es, Bram van, E-mail: bramiozo@gmail.com [Centrum Wiskunde & Informatica, P.O. Box 94079, 1090GB Amsterdam (Netherlands); FOM Institute DIFFER, Dutch Institute for Fundamental Energy Research, The Netherlands" 1 (Netherlands); Koren, Barry [Eindhoven University of Technology (Netherlands); Blank, Hugo J. de [FOM Institute DIFFER, Dutch Institute for Fundamental Energy Research, The Netherlands" 1 (Netherlands)
2016-02-01
In this paper, we apply a special finite-volume scheme, limited to smooth temperature distributions and Cartesian grids, to test the importance of connectivity of the finite volumes. The area of application is nuclear fusion plasma with field line aligned temperature gradients and extreme anisotropy. We apply the scheme to the anisotropic heat-conduction equation, and compare its results with those of existing finite-volume schemes for anisotropic diffusion. Also, we introduce a general model adaptation of the steady diffusion equation for extremely anisotropic diffusion problems with closed field lines.
A new algorithm for anisotropic solutions
Indian Academy of Sciences (India)
M Chaisi; S D Maharaj
2006-02-01
We establish a new algorithm that generates a new solution to the Einstein field equations, with an anisotropic matter distribution, from a seed isotropic solution. The new solution is expressed in terms of integrals of an isotropic gravitational potential; and the integration can be completed exactly for particular isotropic seed metrics. A good feature of our approach is that the anisotropic solutions necessarily have an isotropic limit. We find two examples of anisotropic solutions which generalise the isothermal sphere and the Schwarzschild interior sphere. Both examples are expressed in closed form involving elementary functions only.
Anisotropic inflation in Gauss-Bonnet gravity
Energy Technology Data Exchange (ETDEWEB)
Lahiri, Sayantani [ZARM, University of Bremen,Am Falltrum, 28359 Bremen (Germany)
2016-09-19
We study anisotropic inflation with Gauss-Bonnet correction in presence of a massless vector field. In this scenario, exact anisotropic power-law inflation is realized when the inflaton potential, gauge coupling function and the Gauss-Bonnet coupling are exponential functions. We show that anisotropy becomes proportional to two slow-roll parameters of the theory and hence gets enhanced in presence of quadratic curvature corrections. The stability analysis reveals that anisotropic power-law solutions remain stable over a substantially large parameter region.
Imprints of Anisotropic Inflation on the CMB
Watanabe, Masa-aki; Soda, Jiro
2010-01-01
We study the imprints of anisotropic inflation on the CMB temperature fluctuations and polarizations. The statistical anisotropy stems not only from the direction dependence of curvature and tensor perturbations, but also from the cross correlation between curvature and tensor perturbations, and the linear polarization of tensor perturbations. We show that off-diagonal $TB$ and $EB$ spectrum as well as on- and off-diagonal $TT, EE, BB, TE$ spectrum are induced from anisotropic inflation. We emphasize that the off-diagonal spectrum induced by the cross correlation could be a characteristic signature of anisotropic inflation.
Tungsten based Anisotropic Metamaterial as an Ultra-broadband Absorber
Lin, Yinyue; Ding, Fei; Fung, Kin Hung; Ji, Ting; Li, Dongdong; Hao, Yuying
2016-01-01
The trapped rainbow effect has been mostly found on tapered anisotropic metamaterials (MMs) made of low loss noble metals, such as gold, silver, etc. In this work, we demonstrate that an anisotropic MM waveguide made of high loss metal tungsten can also support the trapped rainbow effect similar to the noble metal based structure. We show theoretically that an array of tungsten/germanium anisotropic nano-cones placed on top of a reflective substrate can absorb light at the wavelength range from 0.3 micrometer to 9 micrometer with an average absorption efficiency approaching 98%. It is found that the excitation of multiple orders of slow-light resonant modes is responsible for the efficient absorption at wavelengths longer than 2 micrometer, and the anti-reflection effect of tapered lossy material gives rise to the near perfect absorption at shorter wavelengths. The absorption spectrum suffers a small dip at around 4.2 micrometer where the first order and second order slow-light modes get overlapped, but we ca...
Biodirected synthesis and nanostructural characterization of anisotropic gold nanoparticles.
Plascencia-Villa, Germán; Torrente, Daniel; Marucho, Marcelo; José-Yacamán, Miguel
2015-03-24
Gold nanoparticles with anisotropic structures have tunable absorption properties and diverse bioapplications as image contrast agents, plasmonics, and therapeutic-diagnostic materials. Amino acids with electrostatically charged side chains possess inner affinity for metal ions. Lysine (Lys) efficiently controlled the growing into star-shape nanoparticles with controlled narrow sizes (30-100 nm) and produced in high yields (85-95%). Anisotropic nanostructures showed tunable absorbance from UV to NIR range, with extraordinary colloidal stability (-26 to -42 mV) and surface-enhanced Raman scattering properties. Advanced electron microscopy characterization through ultra-high-resolution SEM, STEM, and HR-TEM confirmed the size, nanostructure, crystalline structure, and chemical composition. Molecular dynamics simulations revealed that Lys interacted preferentially with Au(I) through the -COOH group instead of their positive side chains with a binding free energy (BFE) of 3.4 kcal mol(-1). These highly monodisperse and colloidal stable anisotropic particles prepared with biocompatible compounds may be employed in biomedical applications.
Influence of copper foil polycrystalline structure on graphene anisotropic etching
Sharma, Kamal P.; Mahyavanshi, Rakesh D.; Kalita, Golap; Tanemura, Masaki
2017-01-01
Anisotropic etching of graphene and other two dimensional materials is an important tool to understand the growth process as well as enabling fabrication of various well-defined structures. Here, we reveal the influence of copper foil polycrystalline structure on anisotropic etching process of as-synthesized graphene. Graphene crystals were synthesized on the polycrystalline Cu foil by a low-pressure chemical vapor deposition (LPCVD) system. Microscopic analysis shows difference in shape, size and stripes alignment of graphene crystals with dissimilar nucleation within closure vicinity of neighboring Cu grains. Post-growth etching of such graphene crystals also significantly affected by the crystallographic nature of Cu grains as observed by the field emission scanning electron microscope (FE-SEM) and electron back scattered diffraction (EBSD) analysis. Hexagonal hole formation with anisotropic etching is observed to be independent of the stripes and wrinkles in the synthesized graphene. We also observed variation in etched pattern of the graphene depending on the base Cu grain orientations, attributing to difference in nucleation and growth process. The findings can facilitate to understand the nature of microscopic etched pattern depending on metal catalyst crystallographic structure.
Phenomenological Anisotropic Study of Surface Finish in Pack Rolling
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
A phenomenological anisotropic model has been presented for the surface roughness modeling of pack rolling. The model is an assembly of grains in different orientations and sizes. The grain size is assumed to be in log-normal distribution. To model the macro anisotropic mechanical behavior of the grains induced by the slip deformation, the grains are assumed as isolated anisotropic units. The units have different mechanic behavior, and depend on the crystallographic orientations and the external loading as well as the interaction of the adjunctive grains. In the paper,the material properties of the grains are assumed as uniform distributions. The roughness of the contact surfaces depends on the distribution types and the scatters of the distributions. It is found that the initial roughness of the contact surfaces has a little influence on the surface roughness when the rolling deformation is large. The comparison between the phenomenological model and crystallographic model shows that the phenomenological model can also give out a reasonable result, while it only takes much less CPU time. The agreement between the single sheet model and the pack rolling model shows that in a certain degree the pack rolling model can be replaced by the single sheet model to decrease the CPU time.
Anisotropism of the Non-Smooth Surface of Butterfly Wing
Institute of Scientific and Technical Information of China (English)
Gang Sun; Yan Fang; Qian Cong; Lu-quan Ren
2009-01-01
Twenty-nine species of butterflies were collected for observation and determination of the wing surfaces using a Scanning Electron Microscope (SEM). Butterfly wing surface displays structural anisotropism in micro-, submicro- and nano-scales. The scales on butterfly wing surface arrange like overlapping roof tiles. There are submicrometric vertical gibbosities, horizontal links, and nano-protuberances on the scales. First-incline-then-drip method and first-drip-then-incline method were used to measure the Sliding Angle (SA) of droplet on butterfly wing surface by an optical Contact Angle (CA) measuring system.Relatively smaller sliding angles indicate that the butterfly wing surface has fine self-cleaning property. Significantly different SAs in various directions indicate the anisotropic self-cleaning property of butterfly wing surface. The SAs on the butterfly wing surface without scales are remarkably larger than those with scales, which proves the crucial role of scales in determining the self-cleaning property. Butterfly wing surface is a template for design and fabrication of biomimetic materials and self-cleaning substrates. This work may offer insights into how to design directional self-cleaning coatings and anisotropic wetting surface.
Jung, Chan Woo; Jalani, Ghulam; Ko, Juhui; Choo, Jaebum; Lim, Dong Woo
2014-01-01
Anisotropic microarchitectures with different physicochemical properties have been developed as advanced materials for challenging industrial and biomedical applications including switchable displays, multiplexed biosensors and bioassays, spatially-controlled drug delivery systems, and tissue engineering scaffolds. In this study, anisotropic biohybrid microparticles (MPs) spatio-selectively conjugated with two different antibodies (Abs) are first developed for fluorescence-based, multiplexed sensing of biological molecules. Poly(acrylamide-co-acrylic acid) is chemically modified with maleimide- or acetylene groups to introduce different targeting biological moieties into each compartment of anisotropic MPs. Modified polymer solutions containing two different fluorescent dyes are separately used for electrohydrodynamic co-jetting with side-by-side needle geometry. The anisotropic MPs are chemically stabilized by thermal imidization, followed by bioconjugation of two different sets of polyclonal Abs with two individual compartments via maleimide-thiol coupling reaction and Huisgen 1,3-dipolar cycloaddition. Finally, two compartments of the anisotropic biohybrid MPs are spatio-selectively associated with the respective monoclonal Ab-immobilized substrate in the presence of the antigen by sandwich-type immunocomplex formation, resulting in their ordered orientation due to the spatio-specific molecular interaction, as confirmed by confocal laser scanning microscopy. In conclusion, anisotropic biohybrid MPs capable of directional binding have great potential as a new fluorescence-based multiplexing biosensing system.
Spatial interpolation approach based on IDW with anisotropic spatial structures
Li, Jia; Duan, Ping; Sheng, Yehua; Lv, Haiyang
2015-12-01
In many interpolation methods, with its simple interpolation principle, Inverse distance weighted (IDW) interpolation is one of the most common interpolation method. There are anisotropic spatial structures with actual geographical spatial phenomenon. When the IDW interpolation is used, anisotropic spatial structures should be considered. Geostatistical theory has a characteristics of exploring anisotropic spatial structures. In this paper, spatial interpolation approach based on IDW with anisotropic spatial structures is proposed. The DEM data is tested in this paper to prove reliability of the IDW interpolation considering anisotropic spatial structures. Experimental results show that IDW interpolation considering anisotropic spatial structures can improve interpolation precision when sampling data has anisotropic spatial structures feature.
Energy Technology Data Exchange (ETDEWEB)
Clancy, S.P.; Burkett, M.W.; Maudlin, P.J.
1997-05-01
Previously developed constitutive models and solution algorithms for anisotropic elastoplastic material strength are implemented in the two-dimensional MESA hydrodynamics code. Quadratic yield functions fitted from polycrystal simulations for a metallic hexagonal-close-packed structure are utilized. An associative flow strength formulation incorporating these yield functions is solved using a geometric normal return method. A stretching rod problem is selected to investigate the effects of material anisotropy on a tensile plastic instability (necking). The rod necking rate and topology are compared for MESA simulations performed for both isotropic and anisotropic cases utilizing the Mechanical Threshold Stress flow stress model.
Failure Criteria for Reinforced Materials
DEFF Research Database (Denmark)
Rathkjen, Arne
Failure of materials is often characterized as ductile yielding, brittle fracture, creep rupture, etc., and different criteria given in terms of different parameters have been used to describe different types of failure. Only criteria expressing failure in terms of stress are considered in what...... place until the matrix, the continuous component of the composite, fails. When an isotropic matrix is reinforced as described above, the result is an anisotropic composite material. Even if the material is anisotropic, it usually exhibits a rather high degree of symmetry and such symmetries place...... certain restrictions on the form of the failure criteria for anisotropic materials. In section 2, some failure criteria for homogenous materials are reviewed. Both isotropic and anisotropic materials are described, and in particular the constraints imposed on the criteria from the symmetries orthotropy...
Anisotropic Thermal Behavior of Silicone Polymer, DC 745
Energy Technology Data Exchange (ETDEWEB)
Adams, Jillian Cathleen [Univ. of Oregon, Eugene, OR (United States). Dept. of Chemistry; Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Torres, Joseph Angelo [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Volz, Heather Michelle [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Gallegos, Jennifer Marie [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Yang, Dali [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-09-02
In material applications, it is important to understand how polymeric materials behave in the various environments they may encounter. One factor governing polymer behavior is processing history. Differences in fabrication will result in parts with varied or even unintended properties. In this work, the thermal expansion behavior of silicone DC 745 is studied. Thermomechanical analysis (TMA) is used to determine changes in sample dimension resulting from changes in temperature. This technique can measure thermal events such as the linear coefficient of thermal expansion (CTE), melting, glass transitions, cure shrinkage, and internal relaxations. Using a thermomechanical analyzer (Q400 TMA), it is determined that DC 745 expands anisotropically when heated. This means that the material has a different CTE depending upon which direction is being measured. In this study, TMA experiments were designed in order to confirm anisotropic thermal behavior in multiple DC 745 samples of various ages and lots. TMA parameters such as temperature ramp rate, preload force, and temperature range were optimized in order to ensure the most accurate and useful data. A better understanding of the thermal expansion of DC 745 will allow for more accurate modeling of systems using this material.
Polarizing interference coatings made with anisotropic thin films
Flory, Francois; Defay, Celine
1998-07-01
It is now well known that the microstructure of materials in thin film form can be slightly different from that of corresponding bulk materials. Conventional evaporation using a heated crucible or an electron beam gun generally leads to a lacunar structure in columns. Some consequences of this microstructure on the optical properties of the films are well-known. The refractive indices are slightly smaller than that of the bulk material; water adsorption-desorption in the voids leads to variations of the spectral reflection and transmission of the coatings. But apart from these disadvantages, the columnar structure can present advantages because it also induces anisotropy of refractive index. When deposited with an ion beam assistance the microstructure of the material is modify and so is its anisotropy. The anisotropy can then be controlled through the ion energy, making it possible to construct multilayer filters combining both isotropic films and anisotropic films. This opens the way for the making of components acting on the polarization state of light. Results of calculation for different components are presented. Planar non absorbing monochromatic polarizers or polarization rotators can be made in this way. The difficulty in controlling the deposition comes from the fact that the anisotropic layers must be deposited on non rotating substrates. This problem is discussed and examples of measured optical properties of multilayer filters will be given.
Anisotropic rectangular metric for polygonal surface remeshing
Pellenard, Bertrand
2013-06-18
We propose a new method for anisotropic polygonal surface remeshing. Our algorithm takes as input a surface triangle mesh. An anisotropic rectangular metric, defined at each triangle facet of the input mesh, is derived from both a user-specified normal-based tolerance error and the requirement to favor rectangle-shaped polygons. Our algorithm uses a greedy optimization procedure that adds, deletes and relocates generators so as to match two criteria related to partitioning and conformity.
Overview of anisotropic flow measurements from ALICE
Directory of Open Access Journals (Sweden)
Zhou You
2016-01-01
Full Text Available Anisotropic flow is an important observable to study the properties of the hot and dense matter, the Quark Gluon Plasma (QGP, created in heavy-ion collisions. Measurements of anisotropic flow for inclusive and identified charged hadrons are reported in Pb–Pb, p–Pb and pp collisions with the ALICE detector. The comparison of experimental measurements to various theoretical calculations are also presented in these proceedings.
Inflation in anisotropic scalar-tensor theories
Energy Technology Data Exchange (ETDEWEB)
Pimentel, L.O.; Stein-Schabes, J.
1989-01-05
The existence of an inflationary phase in anisotropic scalar-tensor theories is investigated by means of a conformal transformation that allows us to rewrite these theories as gravity minimally coupled to a scalar field with a non-trivial potential. We then use the explicit form of the potential and the no hair theorem to conclude that there is an inflationary phase in all open or flat anisotropic spacetimes in these theories. Several examples are constructed where the effect becomes manifest.
Inflation in anisotropic scalar-tensor theories
Pimentel, Luis O.; Stein-Schabes, Jaime
1988-01-01
The existence of an inflationary phase in anisotropic Scalar-Tensor Theories is investigated by means of a conformal transformation that allows us to rewrite these theories as gravity minimally coupled to a scalar field with a nontrivial potential. The explicit form of the potential is then used and the No Hair Theorem concludes that there is an inflationary phase in all open or flat anisotropic spacetimes in these theories. Several examples are constructed where the effect becomes manifest.
Progress in Anisotropic Plasma Physics
Romatschke, P; Romatschke, Paul; Strickland, Michael
2004-01-01
In 1959 Weibel demonstrated that when a QED plasma has a temperature anisotropy there exist unstable transverse magnetic excitations which grow exponentially fast. In this paper we will review how to determine the growth rates for these unstable modes in the weak-coupling and ultrarelativistic limits in which the collective behavior is describable in terms are so-called "hard-loops". We will show that in this limit QCD is subject to instabilities which are analogous to the Weibel instability in QED. The presence of such instabilities dominates the early time evolution of a highly anisotropic plasma; however, at longer times it is expected that these instabilities will saturate (condense). I will discuss how the presence of non-linear interactions between the gluons complicates the determination of the saturated state. In order to discuss this I present the generalization of the Braaten-Pisarski isotropic hard-thermal-loop effective action to a system with a temperature anisotropy in the parton distribution fu...
Spin precession in anisotropic media
Raes, B.; Cummings, A. W.; Bonell, F.; Costache, M. V.; Sierra, J. F.; Roche, S.; Valenzuela, S. O.
2017-02-01
We generalize the diffusive model for spin injection and detection in nonlocal spin structures to account for spin precession under an applied magnetic field in an anisotropic medium, for which the spin lifetime is not unique and depends on the spin orientation. We demonstrate that the spin precession (Hanle) line shape is strongly dependent on the degree of anisotropy and on the orientation of the magnetic field. In particular, we show that the anisotropy of the spin lifetime can be extracted from the measured spin signal, after dephasing in an oblique magnetic field, by using an analytical formula with a single fitting parameter. Alternatively, after identifying the fingerprints associated with the anisotropy, we propose a simple scaling of the Hanle line shapes at specific magnetic field orientations that results in a universal curve only in the isotropic case. The deviation from the universal curve can be used as a complementary means of quantifying the anisotropy by direct comparison with the solution of our generalized model. Finally, we applied our model to graphene devices and find that the spin relaxation for graphene on silicon oxide is isotropic within our experimental resolution.
PURCELL EFFECT IN EXTREMELY ANISOTROPIC ELLIPTIC METAMATERIALS
Directory of Open Access Journals (Sweden)
Alexander V. Chebykin
2014-11-01
Full Text Available The paper deals with theoretical demonstration of Purcell effect in extremely anisotropic metamaterials with elliptical isofrequency surface. This effect is free from association with divergence in density of states unlike the case of hyperbolic metamaterials. It is shown that a large Purcell factor can be observed without excitation of modes with large wave vectors in one direction, and the component of the wave vector normal to the layers is less than k0. For these materials the possibility is given for increasing of the power radiated in the medium, as well as the power radiated from material into free space across the medium border situated transversely to the layers. We have investigated isofrequency contours and the dependence of Purcell factor from the frequency for infinite layered metamaterial structure. In the visible light range strong spatial dispersion gives no possibility to obtain enhancement of spontaneous emission in metamaterial with unit cell which consists of two layers. This effect can be achieved in periodic metal-dielectric layered nanostructures with a unit cell containing two different metallic layers and two dielectric ones. Analysis of the dependences for Purcell factor from the frequency shows that the spontaneous emission is enhanced by a factor of ten or more only for dipole orientation along metamaterial layers, but in the case of the transverse orientation radiation can be enhanced only 2-3 times at most. The results can be used to create a new type of metamaterials with elliptical isofrequency contours, providing a more efficient light emission in the far field.
Anisotropic Finite Element Modeling Based on a Harmonic Field for Patient-Specific Sclera
Directory of Open Access Journals (Sweden)
Xu Jia
2017-01-01
Full Text Available Purpose. This study examined the influence of anisotropic material for human sclera. Method. First, the individual geometry of patient-specific sclera was reproduced from a laser scan. Then, high quality finite element modeling of individual sclera was performed using a convenient automatic hexahedral mesh generator based on harmonic field and integrated with anisotropic material assignment function. Finally, comparison experiments were designed to investigate the effects of anisotropy on finite element modeling of sclera biomechanics. Results. The experimental results show that the presented approach can generate high quality anisotropic hexahedral mesh for patient-specific sclera. Conclusion. The anisotropy shows significant differences for stresses and strain distribution and careful consideration should be given to its use in biomechanical FE studies.
Anisotropic Finite Element Modeling Based on a Harmonic Field for Patient-Specific Sclera.
Jia, Xu; Liao, Shenghui; Duan, Xuanchu; Zheng, Wanqiu; Zou, Beiji
2017-01-01
Purpose. This study examined the influence of anisotropic material for human sclera. Method. First, the individual geometry of patient-specific sclera was reproduced from a laser scan. Then, high quality finite element modeling of individual sclera was performed using a convenient automatic hexahedral mesh generator based on harmonic field and integrated with anisotropic material assignment function. Finally, comparison experiments were designed to investigate the effects of anisotropy on finite element modeling of sclera biomechanics. Results. The experimental results show that the presented approach can generate high quality anisotropic hexahedral mesh for patient-specific sclera. Conclusion. The anisotropy shows significant differences for stresses and strain distribution and careful consideration should be given to its use in biomechanical FE studies.
Synthesis of anisotropic gold shell on carbon nanotube
Energy Technology Data Exchange (ETDEWEB)
Minati, L., E-mail: luminati@fbk.eu [CNR-IFN, CSMFO Lab. (Italy); Torrengo, S. [FBK (Italy); Ischia, G. [University of Trento, Department of Industrial Engineering (Italy); Speranza, G. [FBK (Italy)
2013-11-15
This paper reports a simple procedure to synthesize gold-coated carbon nanotubes. The method involves the reduction of gold precursor on oxidized carbon nanotubes. UV–Visible absorption spectroscopy and electron microscopy were used to study the gold precursor reduction on the carbon nanotubes. Scanning and transmission electron microscopy analysis showed the formation of an irregular gold layer around the CNT surface. The resulting nanoparticles show an anisotropic shape with dimensions between 100 and 200 nm. This hybrid material displays an intense absorption in the near infrared range with an absorption maximum at 840 nm.
Elasticity tensor and ultrasonic velocities for anisotropic cubic polycrystal
Institute of Scientific and Technical Information of China (English)
2008-01-01
The orientation distribution of crystallites in a polycrystal can be described by the orientation distribution function(ODF) . The ODF can be expanded under the Wigner D-bases. The expanded coefficients in the ODF are called the texture coefficients. In this paper,we use the Clebsch-Gordan expression to derive an explicit expression of the elasticity tensor for an anisotropic cubic polycrystal. The elasticity tensor contains three material constants and nine texture coefficients. In order to measure the nine texture coefficients by ultrasonic wave,we give relations between the nine texture coefficients and ultrasonic propagation velocities. We also give a numerical example to check the relations.
Energy Technology Data Exchange (ETDEWEB)
Harzallah, H.S.; Zegnani, A.; Slimi, K.; Mhimid, A. [Ecole Nationale D' Ingenieurs de Monastir, Monastir (Tunisia)
2009-07-01
Natural convection through anisotropic porous media is of significant interest in a wide variety of applications such as in geophysics, hydrology, oil extraction, and reservoir engineering. Anisotropy is basically a consequence of a preferential orientation and/or asymmetric geometry of the grains or fibres. Despite its broad range of applications, natural problems involving anisotropic effects in the presence of porous materials coupled with the effect of the bounding walls have received relatively little attention. This paper examined the effects of both thermal and mechanical anisotropies, as well as the effect of the conductive walls on the unsteady heat transfer and fluid flow through a porous material sandwiched between two vertical finite thickness walls maintained at constant but different temperatures. The remaining two horizontal walls were thermally insulated. The influencing non-dimensional parameters governing heat and fluid flow in the presented system were the wall thickness, wall-to-porous medium thermal conductivity ratio, wall-to-porous medium heat capacity ratio, anisotropic thermal conductivity ratio and anisotropic permeability ratio according to x-axis, and Rayleigh number. The purpose of the study was to demonstrate the effects of heat conduction within solid boundaries as well as both thermal and mechanical anisotropies on flow and heat transfer rates. It was concluded that as the anisotropic thermal conductivity ratio along the x-axis increases, the conductive mode becomes stronger than the convective one. 13 refs., 7 figs.
An anisotropic hydrogel with electrostatic repulsion between cofacially aligned nanosheets
Liu, Mingjie; Ishida, Yasuhiro; Ebina, Yasuo; Sasaki, Takayoshi; Hikima, Takaaki; Takata, Masaki; Aida, Takuzo
2015-01-01
Machine technology frequently puts magnetic or electrostatic repulsive forces to practical use, as in maglev trains, vehicle suspensions or non-contact bearings. In contrast, materials design overwhelmingly focuses on attractive interactions, such as in the many advanced polymer-based composites, where inorganic fillers interact with a polymer matrix to improve mechanical properties. However, articular cartilage strikingly illustrates how electrostatic repulsion can be harnessed to achieve unparalleled functional efficiency: it permits virtually frictionless mechanical motion within joints, even under high compression. Here we describe a composite hydrogel with anisotropic mechanical properties dominated by electrostatic repulsion between negatively charged unilamellar titanate nanosheets embedded within it. Crucial to the behaviour of this hydrogel is the serendipitous discovery of cofacial nanosheet alignment in aqueous colloidal dispersions subjected to a strong magnetic field, which maximizes electrostatic repulsion and thereby induces a quasi-crystalline structural ordering over macroscopic length scales and with uniformly large face-to-face nanosheet separation. We fix this transiently induced structural order by transforming the dispersion into a hydrogel using light-triggered in situ vinyl polymerization. The resultant hydrogel, containing charged inorganic structures that align cofacially in a magnetic flux, deforms easily under shear forces applied parallel to the embedded nanosheets yet resists compressive forces applied orthogonally. We anticipate that the concept of embedding anisotropic repulsive electrostatics within a composite material, inspired by articular cartilage, will open up new possibilities for developing soft materials with unusual functions.
TOPICAL REVIEW Textured silicon nitride: processing and anisotropic properties
Directory of Open Access Journals (Sweden)
Xinwen Zhu and Yoshio Sakka
2008-01-01
Full Text Available Textured silicon nitride (Si3N4 has been intensively studied over the past 15 years because of its use for achieving its superthermal and mechanical properties. In this review we present the fundamental aspects of the processing and anisotropic properties of textured Si3N4, with emphasis on the anisotropic and abnormal grain growth of β-Si3N4, texture structure and texture analysis, processing methods and anisotropic properties. On the basis of the texturing mechanisms, the processing methods described in this article have been classified into two types: hot-working (HW and templated grain growth (TGG. The HW method includes the hot-pressing, hot-forging and sinter-forging techniques, and the TGG method includes the cold-pressing, extrusion, tape-casting and strong magnetic field alignment techniques for β-Si3N4 seed crystals. Each processing technique is thoroughly discussed in terms of theoretical models and experimental data, including the texturing mechanisms and the factors affecting texture development. Also, methods of synthesizing the rodlike β-Si3N4 single crystals are presented. Various anisotropic properties of textured Si3 N4 and their origins are thoroughly described and discussed, such as hardness, elastic modulus, bending strength, fracture toughness, fracture energy, creep behavior, tribological and wear behavior, erosion behavior, contact damage behavior and thermal conductivity. Models are analyzed to determine the thermal anisotropy by considering the intrinsic thermal anisotropy, degree of orientation and various microstructure factors. Textured porous Si3N4 with a unique microstructure composed of oriented elongated β-Si3N4 and anisotropic pores is also described for the first time, with emphasis on its unique mechanical and thermal-mechanical properties. Moreover, as an important related material, textured α-Sialon is also reviewed, because the presence of elongated α-Sialon grains allows the production of textured
Anisotropic matching principle for the hydrodynamic expansion
Tinti, Leonardo
2016-10-01
Following the recent success of anisotropic hydrodynamics, I propose here a new, general prescription for the hydrodynamic expansion around an anisotropic background. The anisotropic distribution fixes exactly the complete energy-momentum tensor, just like the effective temperature fixes the proper energy density in the ordinary expansion around local equilibrium. This means that momentum anisotropies are already included at the leading order, allowing for large pressure anisotropies without the need of a next-to-leading-order treatment. The first moment of the Boltzmann equation (local four-momentum conservation) provides the time evolution of the proper energy density and the four-velocity. Differently from previous prescriptions, the dynamic equations for the pressure corrections are not derived from the zeroth or second moment of the Boltzmann equation, but they are taken directly from the exact evolution given by the Boltzmann equation. As known in the literature, the exact evolution of the pressure corrections involves higher moments of the Boltzmann distribution, which cannot be fixed by the anisotropic distribution alone. Neglecting the next-to-leading-order contributions corresponds to an approximation, which depends on the chosen form of the anisotropic distribution. I check the the effectiveness of the leading-order expansion around the generalized Romatschke-Stricklad distribution, comparing with the exact solution of the Boltzmann equation in the Bjorken limit with the collisional kernel treated in the relaxation-time approximation, finding an unprecedented agreement.
Anisotropic thermal conductivity of magnetic fluids
Institute of Scientific and Technical Information of China (English)
Xiaopeng Fang; Yimin Xuan; Qiang Li
2009-01-01
Considering the forces acting on the particles and the motion of the particles, this study uses a numerical simulation to investigate the three-dimensional microstructure of the magnetic fluids in the presence of an external magnetic field. A method is proposed for predicting the anisotropic thermal conductivity of magnetic fluids. By introducing an anisotropic structure parameter which characterizes the non-uniform distribution of particles suspended in the magnetic fluids, the traditional Maxwell formula is modified and extended to calculate anisotropic thermal conductivity of the magnetic fluids. The results show that in the presence of an external magnetic field the magnetic nanoparticles form chainlike clusters along the direction of the external magnetic field, which leads to the fact that the thermal conduc-tivity of the magnetic fluid along the chain direction is bigger than that along other directions. The thermal conductivity of the magnetic fluids presents an anisotropic feature. With the increase of the magnetic field strength the chainlike clusters in the magnetic fluid appear to be more obvious, so that the anisotropic feature of heat conduction in the fluids becomes more evident.
Textile-templated electrospun anisotropic scaffolds for regenerative cardiac tissue engineering.
Şenel Ayaz, H Gözde; Perets, Anat; Ayaz, Hasan; Gilroy, Kyle D; Govindaraj, Muthu; Brookstein, David; Lelkes, Peter I
2014-10-01
For patients with end-stage heart disease, the access to heart transplantation is limited due to the shortage of donor organs and to the potential for rejection of the donated organ. Therefore, current studies focus on bioengineering approaches for creating biomimetic cardiac patches that will assist in restoring cardiac function, by repairing and/or regenerating the intrinsically anisotropic myocardium. In this paper we present a simplified, straightforward approach for creating bioactive anisotropic cardiac patches, based on a combination of bioengineering and textile-manufacturing techniques in concert with nano-biotechnology based tissue-engineering stratagems. Using knitted conventional textiles, made of cotton or polyester yarns as template targets, we successfully electrospun anisotropic three-dimensional scaffolds from poly(lactic-co-glycolic) acid (PLGA), and thermoplastic polycarbonate-urethane (PCU, Bionate(®)). The surface topography and mechanical properties of textile-templated anisotropic scaffolds significantly differed from those of scaffolds electrospun from the same materials onto conventional 2-D flat-target electrospun scaffolds. Anisotropic textile-templated scaffolds electrospun from both PLGA and PCU, supported the adhesion and proliferation of H9C2 cardiac myoblasts cell line, and guided the cardiac tissue-like anisotropic organization of these cells in vitro. All cell-seeded PCU scaffolds exhibited mechanical properties comparable to those of a human heart, but only the cells on the polyester-templated scaffolds exhibited prolonged spontaneous synchronous contractility on the entire engineered construct for 10 days in vitro at a near physiologic frequency of ∼120 bpm. Taken together, the methods described here take advantage of straightforward established textile manufacturing strategies as an efficient and cost-effective approach to engineering 3D anisotropic, elastomeric PCU scaffolds that can serve as a cardiac patch.
Energy Technology Data Exchange (ETDEWEB)
NONE
2001-03-01
The pitch between electrodes in electric parts, for example semiconductor devices, is becoming increasingly fine, with electronic appliances, which are portable information terminals mainly, growing higher in performance and smaller in size and weight. Efforts were exerted to develop an anisotropic conductive material capable of dealing with fine pitch designs and provided with an insulating structure having an insulating lattice of pores formed by photolithography generally applied to the manufacture of semiconductor devices. For the manufacture of homogeneous particles, a special emulsification method (membrane emulsification) was applied for making the particles as homogeneous as possible. A special classifier was used to shape them into particles of the intended size. The particles were made conductive by coatings of nickel and gold. For their organization into a membrane, a technology of building a lattice with pores of the several {mu}m rule and another for filling the pores with conductive particles were required. A lattice with pores arranged therein was completed using two technologies of photolithography and laser application. A technology for guiding conductive particles into the lattice pores was also established. (NEDO)
Bound dipole solitary solutions in anisotropic nonlocal self-focusing media
DEFF Research Database (Denmark)
Mamaev, A.V.; Zozulya, A.A.; Mezentsev, V.K.;
1997-01-01
We find and analyze bound dipole solitary solutions in media with anisotropic nonlocal photorefractive material response. The dipole solutions consist of two elliptically shaped Gaussian-type beams separated by several diameters, and with a pi phase shift between their fields. Spatial evolution...... of two initially round Gaussian beams and their convergence to the above dipole solution is demonstrated experimentally....
The Stress Distribution in an Infinite Anisotropic Plate with Co-Linear Cracks
DEFF Research Database (Denmark)
Krenk, Steen
1975-01-01
A general solution of the plane problem of a finite number of co-linear cracks in an anisotropic material is presented. The solution is obtained by reducing the problem to four very simple Riemann-Hilbert problems. From the solution it is concluded that if the loads acting on the cracks have the ...
Institute of Scientific and Technical Information of China (English)
王庆兵
2004-01-01
展示一种新型含有超薄液晶层( 小于1 μm) 的快速响应液晶盒, 总的响应时间( τon+τoff) 可以达到1.3 ms.这种液晶器件可以通过对一种液晶和聚合物混合材料的各向异性相分离制备获得. 偏光显微镜和扫描电子显微镜的观测结果确认了一种液晶/聚合物的双层膜机构的形成. 实验结果表明液晶层的厚度可以简单地通过改变液晶在混合材料中的含量来精确调节.这种制备方法可以用来制作含有超薄液晶层的快速显示液晶器件用于视频显示方面的应用.%It is demonstrated that a nematic liquid crystal (LC) cell containing a very thin (《1 μm) LC film can perform very fast switching, with a total response time as fast as 1.3 ms. Such type of LC devices can be prepared by a photo-induced anisotropic phase-separation from a nematic LC and polymer composite material. The formation of the LC/polymer bi-layer structure in the cell after the anisotropic phase-separation was confirmed by employing polarized light microscope and scanning electron microscope. It is also found that LC layer thickness can be fine tuned by adjusting the LC concentration in the composite mixture. Such a technique can be used to fabricate LC devices containing very thin LC film and performing fast switching for TV and Video applications where fast response time is required.
Necking of anisotropic micro-films with strain-gradient effects
DEFF Research Database (Denmark)
Legarth, Brian Nyvang
2008-01-01
Necking of stubby micro-films of aluminum is investigated numerically by considering tension of a specimen with an initial imperfection used to onset localisation. Plastic anisotropy is represented by two different yield criteria and strain-gradient effects are accounted for using the visco......-plastic finite strain model. Furthermore, the model is extended to isotropic anisotropic hardening (evolving anisotropy). For isotropic hardening plastic anisotropy affects the predicted overall nominal stress level, while the peak stress remains at an overall logarithmic strain corresponding to the hardening...... exponent. This holds true for both local and nonlocal materials. Anisotropic hardening delays the point of maximum overall nominal stress....
BUECKNER'S WORK CONJUGATE INTEGRALS AND WEIGHT FUNCTIONS FOR A CRACKIN ANISOTROPIC SOLIDS
Institute of Scientific and Technical Information of China (English)
Chen Yiheng; Ma Lifeng
2000-01-01
The Bueckner work conjugate integrals are studied for cracks in anisotropic elastic solids. The difficulties in separating Lekhnitskii's two complex arguments involved in the integrals are overcome and explicit functional representations of the integrals are given for several typical cases. It is found that the pseudoorthogonal property of the eigenfunction expansion forms presented previously for isotropic cases, isotropic bimaterials, and orthotropic cases, are proved to be also valid in the present case of anisotropic material. Finally, Some useful path-independent integrals and weight functions are proposed.
Crack growth resistance for anisotropic plasticity with non-normality effects
DEFF Research Database (Denmark)
Tvergaard, Viggo; Legarth, Brian Nyvang
2006-01-01
For a plastically anisotropic solid a plasticity model using a plastic flow rule with non-normality is applied to predict crack growth. The fracture process is modelled in terms of a traction–separation law specified on the crack plane. A phenomenological elastic–viscoplastic material model...... is applied, using one of two different anisotropic yield criteria to account for the plastic anisotropy, and in each case the effect of the normality flow rule is compared with the effect of non-normality. Conditions of small scale yielding are assumed, with mode I loading conditions far from the crack...
Influence of spherically anisotropic core on the optical properties of gold nanoshell
Energy Technology Data Exchange (ETDEWEB)
Wu, D.J. [Nanjing University, Department of Electronic Science and Engineering, Key Laboratory of Modern Acoustics of MOE, Nanjing (China); Jiangsu University, Faculty of Science, Zhenjiang (China); Liu, X.J. [Nanjing University, Department of Electronic Science and Engineering, Key Laboratory of Modern Acoustics of MOE, Nanjing (China)
2009-03-15
The optical properties of gold nanoshell with a core of spherically anisotropic material have been investigated by means of quasi-static theory. It is found with increasing the extent of anisotropy of the core that the surface plasmon resonance for the particle shows a red-shift and that the full width at half maximum (FWHM) of the plasmon resonance peak increases. The local electric field of the particle with anisotropic core is found to be enhanced compared to that with isotropic core. The larger enhancement of the local electric field for the particle is observed in the particle with smaller extent of anisotropy. (orig.)
An anisotropic constitutive model with biaxial-tension coupling for woven composite reinforcements
Yao, Yuan; Huang, Xiaoshuang; Peng, Xiongqi; Gong, Youkun
2016-10-01
Based on fiber reinforced continuum mechanics theory, an anisotropic hyperelastic constitutive model with biaxial tension coupling for woven composite reinforcements is developed. Experimental data from literature are used to identify material parameters in the constitutive model for a specific balanced plain woven fabric. The developed model is validated by comparing numerical results with experimental biaxial tension data under different stretch ratios and picture-frame shear data, demonstrating that the developed constitutive model is highly suitable to characterize the highly non-linear and strongly anisotropic mechanical behaviors of woven composite reinforcements under large deformation.
Anisotropic non-gaussianity with noncommutative spacetime
Energy Technology Data Exchange (ETDEWEB)
Nautiyal, Akhilesh
2014-01-20
We study single field inflation in noncommutative spacetime and compute two-point and three-point correlation functions for the curvature perturbation. We find that both power spectrum and bispectrum for comoving curvature perturbation are statistically anisotropic and the bispectrum is also modified by a phase factor depending upon the noncommutative parameters. The non-linearity parameter f{sub NL} is small for small statistical anisotropic corrections to the bispectrum coming from the noncommutative geometry and is consistent with the recent PLANCK bounds. There is a scale dependence of f{sub NL} due to the noncommutative spacetime which is different from the standard single field inflation models and statistically anisotropic vector field inflation models. Deviations from statistical isotropy of CMB, observed by PLANCK can tightly constraint the effects due to noncommutative geometry on power spectrum and bispectrum.
Leith diffusion model for homogeneous anisotropic turbulence
Rubinstein, Robert; Clark, Timothy; Kurien, Susan
2016-11-01
A new spectral closure model for homogeneous anisotropic turbulence is proposed. The systematic development begins by closing the third-order correlation describing nonlinear interactions by an anisotropic generalization of the Leith diffusion model for isotropic turbulence. The correlation tensor is then decomposed into a tensorially isotropic part, or directional anisotropy, and a trace-free remainder, or polarization anisotropy. The directional and polarization components are then decomposed using irreducible representations of the SO(3) symmetry group. Under the ansatz that the decomposition is truncated at quadratic order, evolution equations are derived for the directional and polarization pieces of the correlation tensor. Numerical simulation of the model equations for a freely decaying anisotropic flow illustrate the non-trivial effects of spectral dependencies on the different return-to-isotropy rates of the directional and polarization contributions.
Theory of Compton scattering by anisotropic electrons
Poutanen, Juri
2010-01-01
Compton scattering plays an important role in various astrophysical objects such as accreting black holes and neutron stars, pulsars, and relativistic jets, clusters of galaxies as well as the early Universe. In most of the calculations it is assumed that the electrons have isotropic angular distribution in some frame. However, there are situations where the anisotropy may be significant due to the bulk motions, or anisotropic cooling by synchrotron radiation, or anisotropic source of seed soft photons. We develop here an analytical theory of Compton scattering by anisotropic distribution of electrons that can simplify significantly the calculations. Assuming that the electron angular distribution can be represented by a second order polynomial over cosine of some angle (dipole and quadrupole anisotropy), we integrate the exact Klein-Nishina cross-section over the angles. Exact analytical and approximate formulae valid for any photon and electron energies are derived for the redistribution functions describin...
Anisotropic inflation in the Finsler spacetime
Energy Technology Data Exchange (ETDEWEB)
Li, Xin [Chongqing University, Department of Physics, Chongqing (China); Institute of Theoretical Physics, Chinese Academy of Sciences, State Key Laboratory of Theoretical Physics, Beijing (China); Wang, Sai [Institute of Theoretical Physics, Chinese Academy of Sciences, State Key Laboratory of Theoretical Physics, Beijing (China); Chang, Zhe [Institute of Theoretical Physics, Chinese Academy of Sciences, State Key Laboratory of Theoretical Physics, Beijing (China); Institute of High Energy Physics, Chinese Academy of Sciences, Beijing (China)
2015-06-15
We suggest the universe is Finslerian in the stage of inflation. The Finslerian background spacetime breaks rotational symmetry and induces parity violation. The primordial power spectrum is given for the quantum fluctuation of the inflation field. It depends not only on the magnitude of the wavenumber but also on the preferred direction. We derive the gravitational field equations in the perturbed Finslerian background spacetime, and we obtain a conserved quantity outside the Hubble horizon. The angular correlation coefficients are presented in our anisotropic inflation model. The parity violation feature of Finslerian background spacetime requires that the anisotropic effect only appears in the angular correlation coefficients if l' = l + 1. The numerical results of the angular correlation coefficients are given describing the anisotropic effect. (orig.)
Convective dissolution in anisotropic porous media
de Paoli, Marco; Zonta, Francesco; Soldati, Alfredo
2016-11-01
Solute convection in porous media at high Rayleigh-Darcy numbers has important fundamental features and may also bear implications for geological CO2 sequestration processes. With the aid of direct numerical simulations, we examine the role of anisotropic permeability γ (the vertical-to-horizontal permeability ratio) on the distribution of solutal concentration in fluid saturated porous medium. Interestingly, we find that the finite-time (short-term) amount of solute that can be dissolved in anisotropic sedimentary rocks (γ < 1 , i.e. vertical permeability smaller than horizontal permeability) is much larger than in isotropic rocks. We link this seemingly counterintuitive effect with the occurring modifications to the flow topology in the anisotropic conditions. CINECA Supercomputing Centre and ISCRA Computing Initiative are gratefully acknowledged for generous allowance of computer resources. Support from Regione Autonoma Friuli Venezia Giulia under Grant PAR FSC 2007/2013 is also gratefully acknowledged.
Anisotropic selection in cellular genetic algorithms
Simoncini, David; Collard, Philippe; Clergue, Manuel
2008-01-01
In this paper we introduce a new selection scheme in cellular genetic algorithms (cGAs). Anisotropic Selection (AS) promotes diversity and allows accurate control of the selective pressure. First we compare this new scheme with the classical rectangular grid shapes solution according to the selective pressure: we can obtain the same takeover time with the two techniques although the spreading of the best individual is different. We then give experimental results that show to what extent AS promotes the emergence of niches that support low coupling and high cohesion. Finally, using a cGA with anisotropic selection on a Quadratic Assignment Problem we show the existence of an anisotropic optimal value for which the best average performance is observed. Further work will focus on the selective pressure self-adjustment ability provided by this new selection scheme.
Quasiparticle anisotropic hydrodynamics for central collisions
Alqahtani, Mubarak; Strickland, Michael
2016-01-01
We use quasiparticle anisotropic hydrodynamics to study an azimuthally-symmetric boost-invariant quark-gluon plasma including the effects of both shear and bulk viscosities. In quasiparticle anisotropic hydrodynamics, a single finite-temperature quasiparticle mass is introduced and fit to the lattice data in order to implement a realistic equation of state. We compare results obtained using the quasiparticle method with the standard method of imposing the equation of state in anisotropic hydrodynamics and viscous hydrodynamics. Using these three methods, we extract the primordial particle spectra, total number of charged particles, and average transverse momentum for various values of the shear viscosity to entropy density ratio eta/s. We find that the three methods agree well for small shear viscosity to entropy density ratio, eta/s, but differ at large eta/s. We find, in particular, that when using standard viscous hydrodynamics, the bulk-viscous correction can drive the primordial particle spectra negative...
Obtuse triangle suppression in anisotropic meshes
Sun, Feng
2011-12-01
Anisotropic triangle meshes are used for efficient approximation of surfaces and flow data in finite element analysis, and in these applications it is desirable to have as few obtuse triangles as possible to reduce the discretization error. We present a variational approach to suppressing obtuse triangles in anisotropic meshes. Specifically, we introduce a hexagonal Minkowski metric, which is sensitive to triangle orientation, to give a new formulation of the centroidal Voronoi tessellation (CVT) method. Furthermore, we prove several relevant properties of the CVT method with the newly introduced metric. Experiments show that our algorithm produces anisotropic meshes with much fewer obtuse triangles than using existing methods while maintaining mesh anisotropy. © 2011 Elsevier B.V. All rights reserved.
Constraining the Anisotropic Expansion of Universe
Cai, Rong-Gen; Tang, Bo; Tuo, Zhong-Liang
2013-01-01
We study the possibly existing anisotropy in the accelerating expansion Universe with the Union2 Type Ia supernovae data and Gamma-ray burst data. We construct a direction-dependent dark energy model and constrain the anisotropy direction and strength of modulation. We find that the maximum anisotropic deviation direction is $(l,\\,b)=(126^{\\circ},\\,13^{\\circ})$ (or equivalently $(l,\\,b)=(306^{\\circ},\\,-13^{\\circ})$), and the anisotropy level is $g_0=0.030_{+0.010}^{-0.030}$ (obtained using Union2 data, at $1\\sigma$ confidence level). Our results do not show strong evidence for the anisotropic dark energy model. We also discuss potential methods that may distinguish the peculiar velocity field from the anisotropic dark energy model.
Anisotropic magnetostrictive metal-polymer composites for functional devices
Kiseleva, T. Yu.; Zholudev, S. I.; Il'inykh, I. A.; Novakova, A. A.
2013-12-01
New metal-polymer composites based on mechanochemically synthesized magnetostrictive Fe-Ga phase particles with dimensions of up to 2 μm dispersed and spatially oriented in a polymer matrix have been studied. The polymer matrix for spatial anisotropic stabilization of particles was represented by modified polyurethane (PU). An increase in the magnetostrictive effect was achieved by directed orientation of particles in a magnetic field applied during polymerization of the PU matrix. The spatial anisotropy of the composite has been studied by the methods of conversion Mössbauer spectroscopy with resonant X-ray detection and scanning electron microscopy. It is shown that the mechanochemical synthesis is an effective method of obtaining particles with microstress-enhanced magnetostriction. The use of these particles for the formation of a functional elastomer composite provides a material with significant magnetostrictive effect, which can be several-fold increased due to orientation of particles in an applied magnetic field. The obtained anisotropic magnetostrictive composite is a promising material for the creation of smart functional components of positioning systems, attenuators, and sensors.
Ciancio, P. M.; Rossit, C. A.; Laura, P. A. A.
2007-05-01
This study is concerned with the vibration analysis of a cantilevered rectangular anisotropic plate when a concentrated mass is rigidly attached to its center point. Based on the classical theory of anisotropic plates, the Ritz method is employed to perform the analysis. The deflection of the plate is approximated by a set of beam functions in each principal coordinate direction. The influence of the mass magnitude on the natural frequencies and modal shapes of vibration is studied for a boron-epoxy plate and also in the case of a generic anisotropic material. The classical Ritz method with beam functions as the spatial approximation proved to be a suitable procedure to solve a problem of this analytical complexity.
Experimental study of the anisotropic magneto-Seebeck effect in (Ga,Mn)As thin films
Energy Technology Data Exchange (ETDEWEB)
Althammer, Matthias; Krupp, Alexander T.; Brenninger, Thomas; Venkateshvaran, Deepak; Opel, Matthias; Gross, Rudolf; Goennenwein, Sebastian T.B. [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Dreher, Lukas [Walter Schottky Institut, Technische Universitaet Muenchen, Garching (Germany); Schoch, Wladimir; Limmer, Wolfgang [Abteilung Halbleiterphysik, Universitaet Ulm, Ulm (Germany)
2011-07-01
In analogy to anisotropic magnetoresistance (AMR), the thermopower of ferromagnetic materials also characteristically depends on the orientation of the magnetization vector. This anisotropic magneto-thermopower - or anisotropic magneto-Seebeck effect (AMS) - has only scarcely been studied to date. Taking the ferromagnetic semiconductor (Ga,Mn)As with its large magneto-resistive effects as a prototype example, we have measured the evolution of both the AMR and the AMS effects at liquid He temperatures as a function of the orientation of a magnetic field applied in the (Ga,Mn)As film plane, for different, fixed magnetic field magnitudes. Our data show that the AMS effect can be adequately modeled only if the symmetry of the (Ga,Mn)As crystal is explicitly taken into account. We quantitatively compare our AMR and AMS measurements with corresponding model calculations, and address the validity of the Mott relations linking the magneto-resistance and the magneto-Seebeck coefficients.
Anisotropic Heisenberg model in thin film geometry
Energy Technology Data Exchange (ETDEWEB)
Akıncı, Ümit
2014-01-01
The effect of the anisotropy in the exchange interaction on the phase diagrams and magnetization behavior of the Heisenberg thin film has been investigated with effective field formulation in a two spin cluster using the decoupling approximation. Phase diagrams and magnetization behaviors have been obtained for several different cases, by grouping the systems in accordance with, whether the surfaces/interior of the film has anisotropic exchange interaction or not. - Highlights: • Phase diagrams of the anisotropic Heisenberg model on the thin film obtained • Dependence of the critical properties on the film thickness obtained • Effect of the anisotropy on the magnetic properties obtained.
Enhanced-transmission metamaterials as anisotropic plates
Baida, F. I.; Boutria, M.; Oussaid, R.; van Labeke, D.
2011-07-01
We present an original design of anisotropic metamaterial plates exhibiting extraordinary transmission through perfectly conductor metallic screens perforated by a subwavelength double-pattern rectangular aperture array. The polarization properties of the fundamental guided mode inside the apertures are at the origin of the anisotropy. The metal thickness is a key parameter that is adjusted in order to get the desired value of the phase difference between the two transversal electromagnetic field components. As an example, we treat the case of a half-wave plate having 92% transmission coefficient. Such a study can be easily extended to design anisotropic plates operating in terahertz or microwave domains.
One-Dimensional Anisotropic Band Gap Structure
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
The band gap structure of one-dimensional anisotropic photonic crystal has been studied by means of the transfer matrix formalism. From the analytic expressions and numeric calculations we see some general characteristics of the band gap structure of anisotropic photonic crystals, each band separates into two branches and the two branches react to polarization sensitively. In the practical case of oblique incidence, gaps move towards high frequency when the angle of incidence increases. Under some special conditions, the two branches become degenerate again.
Anisotropic Gold Nanocrystals:. Synthesis and Characterization
Stiufiuc, R.; Toderas, F.; Iosin, M.; Stiufiuc, G.
In this letter we report on successful preparation and characterization of anisotropic gold nanocrystals bio-synthesized by reduction of aqueous chloroaurate ions in pelargonium plant extract. The nanocrystals have been characterized by means of Transmission Electron Microscopy (TEM), UV-VIS absorption spectroscopy and tapping mode atomic force microscopy (TM-AFM). Using these investigation techniques, the successful formation of anisotropic single nanocrystals with the preferential growth direction along the gold (111) plane has been confirmed. The high detail phase images could give us an explanation concerning the growth mechanism of the nanocrystals.
Anisotropic strange star with de Sitter spacetime
Kalam, Mehedi; Rahaman, Farook; Ray, Saibal; Hossein, Sk. Monowar; Karar, Indrani; Naskar, Jayanta
2012-12-01
Stars can be treated as self-gravitating fluid. Krori and Barua (J. Phys. A., Math. Gen. 8:508, 1975) gave an analytical solution to that kind of fluids. In this connection, we propose a de Sitter model for an anisotropic strange star with the Krori-Barua spacetime. We incorporate the existence of the cosmological constant on a small scale to study the structure of anisotropic strange stars and come to the conclusion that this doping is very well compatible with the well-known physical features of strange stars.
Relativistic Solutions of Anisotropic Compact Objects
Paul, Bikash Chandra
2016-01-01
We present a class of new relativistic solutions with anisotropic fluid for compact stars in hydrostatic equilibrium. The interior space-time geometry considered here for compact objects are described by parameters namely, $\\lambda$, $k$, $A$, $R$ and $n$. The values of the geometrical parameters are determined here for obtaining a class of physically viable stellar models. The energy-density, radial pressure and tangential pressure are finite and positive inside the anisotropic stars. Considering some stars of known mass we present stellar models which describe compact astrophysical objects with nuclear density.
Institute of Scientific and Technical Information of China (English)
韩式方
2008-01-01
Research advances of un-symmetric constitutive equation of anisotropic fluid,influence of un-symmetric stress tensor on material functions,vibrational shear flow of the fluid with small amplitudes and rheology of anisotropic suspension were reported.A new concept of simple anisotropic fluid was introduced.On the basis of anisotropic principle,the simple fluid stress behaviour was described by velocity gradient tensor F and spin tensor W instead of velocity gradient tensor D in the classic Leslie-Ericksen continuum theory.Two relaxation times analyzing rheological nature of the fluid and using tensor analysis a general form of the constitutive equation of co-rotational type was introduced.More general model LCP-H for the fluid was developed.The unsymmetry of the shear stress was predicted by the present continuum theory for anisotropic viscoelastic fluid-LC polymer liquids.The influence of the relaxation times on material functions was specially studied.It is important to study the unsteady vibrational rotating flow with small amplitudes,as it is a best way to obtain knowledge of elasticity of the LC polymer,i.e.dynamic viscoelasticity.For the shear-unsymmetric stresses,two shear stresses were obtained thus two complex viscosities and two complex shear modulus(i.e.first and second one) were introduced by the constitutive equation which was defined by rotating shear rate introduced by author.For the two stability problems of fluid,such as stability of hydrodynamic flow and orientational motion,were discussed.The results show that the polymer suspension systems exhibit anisotropic character.The PNC systems can exhibit significant shear-thinning effects.For more concentrated polymer nano-suspensions,the first normal stress difference change from positive to negative,which is similar to LC polymer behavior.
Anisotropic fractal media by vector calculus in non-integer dimensional space
Energy Technology Data Exchange (ETDEWEB)
Tarasov, Vasily E., E-mail: tarasov@theory.sinp.msu.ru [Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow 119991 (Russian Federation)
2014-08-15
A review of different approaches to describe anisotropic fractal media is proposed. In this paper, differentiation and integration non-integer dimensional and multi-fractional spaces are considered as tools to describe anisotropic fractal materials and media. We suggest a generalization of vector calculus for non-integer dimensional space by using a product measure method. The product of fractional and non-integer dimensional spaces allows us to take into account the anisotropy of the fractal media in the framework of continuum models. The integration over non-integer-dimensional spaces is considered. In this paper differential operators of first and second orders for fractional space and non-integer dimensional space are suggested. The differential operators are defined as inverse operations to integration in spaces with non-integer dimensions. Non-integer dimensional space that is product of spaces with different dimensions allows us to give continuum models for anisotropic type of the media. The Poisson's equation for fractal medium, the Euler-Bernoulli fractal beam, and the Timoshenko beam equations for fractal material are considered as examples of application of suggested generalization of vector calculus for anisotropic fractal materials and media.
Starinshak, David P.; Smith, Nathan D.; Wilson, Jeffrey D.
2008-01-01
The electromagnetic effects of conventional dielectrics, anisotropic dielectrics, and metamaterials were modeled in a terahertz-frequency folded-waveguide slow-wave circuit. Results of attempts to utilize these materials to increase efficiency are presented.
Anisotropic Differential Reflectance Spectroscopy of Thin GeSe
Matson, Joseph; Woods, Grace; Churchill, Hugh
2017-01-01
Atomically thin monochalcogenides are predicted to exhibit a two-dimensional structural phase transition. This phase transition could be useful for designing new phase change memory devices. The critical temperature is dependent on the material as well as the thickness, and is predicted to occur just above room temperature for monolayer GeSe. We used differential reflectance spectroscopy on thin samples of GeSe to measure changes in the optical anisotropy with temperature as a signature of this phase transition. We constructed an apparatus for temperature-depedendent spectroscopy of micro-scale GeSe samples, and measured anisotropic optical absorption of thin GeSe. We observed a decrease in optical anisotropy of GeSe at elevated temperatures, which may be a first indication of the continuous transition from a rectangular to a square lattice in that material. This work was supported by NSF REU Grant #EEC-1359306.
Lee, Hee Jung; Cho, Yea Jin; Cho, Won; Oh, Moonhyun
2013-01-22
The ability to fabricate multicompositional hybrid materials in a precise and controlled manner is one of the primary goals of modern materials science research. In addition, an understanding of the phenomena associated with the systematic growth of one material on another can facilitate the evolution of multifunctional hybrid materials. Here, we demonstrate precise manipulation of the isotropic and/or anisotropic nanoscale growth of various coordination polymers (CPs) to obtain heterocompositional hybrid coordination polymer particles. Chemical composition analyses conducted at every growth step reveal the formation of accurately assembled hybrid nanoscale CPs, and microscopy images are used to examine the morphology of the particles and visualize the hybrid structures. The dissimilar growth behavior, that is, growth in an isotropic or anisotropic fashion, is found to be dependent on the size of the metal ions involved within the CPs.
Observational signatures of anisotropic inflationary models
Ohashi, Junko; Tsujikawa, Shinji
2013-01-01
We study observational signatures of two classes of anisotropic inflationary models in which an inflaton field couples to (i) a vector kinetic term F_{mu nu}F^{mu nu} and (ii) a two-form kinetic term H_{mu nu lambda}H^{mu nu lambda}. We compute the corrections from the anisotropic sources to the power spectrum of gravitational waves as well as the two-point cross correlation between scalar and tensor perturbations. The signs of the anisotropic parameter g_* are different depending on the vector and the two-form models, but the statistical anisotropies generally lead to a suppressed tensor-to-scalar ratio r and a smaller scalar spectral index n_s in both models. In the light of the recent Planck bounds of n_s and r, we place observational constraints on several different inflaton potentials such as those in chaotic and natural inflation in the presence of anisotropic interactions. In the two-form model we also find that there is no cross correlation between scalar and tensor perturbations, while in the vector ...
Spin Wave Theory of Strongly Anisotropic Magnets
DEFF Research Database (Denmark)
Lindgård, Per-Anker
1977-01-01
A strong anisotropy gives rise to a non-spherical precession of the spins with different amplitudes in the x and y directions. The highly anharmonic exchange interaction thereby becomes effectively anisotropic. The possibility of detecting a genuine two-ion anisotropy is discussed, and comments a...
ANISOTROPIC PARABOLIC EQUATIONS WITH MEASURE DATA
Institute of Scientific and Technical Information of China (English)
Li Fengquan; Zhao Huixiu
2001-01-01
In this paper, we prove the existence of solutions to anisotropic parabolic equations with right hand side term in the bounded Radon measure M(Q) and the initial condition in M(Ω) or in Lm space (with m "small").
Orphan-Free Anisotropic Voronoi Diagrams
Canas, Guillermo D
2011-01-01
We describe conditions under which an appropriately-defined anisotropic Voronoi diagram of a set of sites in Euclidean space is guaranteed to be composed of connected cells in any number of dimensions. These conditions are natural for problems in optimization and approximation, and algorithms already exist to produce sets of sites that satisfy them.
Anisotropic Interactions between Cold Rydberg Atoms
2015-09-28
AFRL-AFOSR-CL-TR-2015-0002 Anisotropic interactions between cold Rydberg atoms Luis Marcassa INSTITUTO DE FISICA DE SAO CARLOS Final Report 09/28...problem with the report +551633739806 Organization / Institution name Instituto de Fisica de Sao Carlos Grant/Contract Title The full title of the
The Kepler Problem with Anisotropic Perturbations
Diacu, Florin; Santoprete, Manuele
2009-01-01
We study a 2-body problem given by the sum of the Newtonian potential and an anisotropic perturbation that is a homogeneous function of degree $-\\beta$, $\\beta\\ge 2$. For $\\beta>2$, the sets of initial conditions leading to collisions/ejections and the one leading to escapes/captures have positive measure. For $\\beta>2$ and $\\beta\
A discrete anisotropic model for Scheibe aggregates
Directory of Open Access Journals (Sweden)
O. Bang
1991-05-01
Full Text Available A discrete anisotropic nonlinear model for the dynamics of Scheibe aggregates is investigated. The collapse of the collective excitations found by Möbius and Kuhn is described as a shrinking ring wave, which is eventually absorbed by an acceptor molecule. An optimal acceptor loss is found.
Extensional structures in anisotropic rocks
Platt, J.P.; Vissers, R.L.M.
1980-01-01
A distinct class of structures can form as a result of extension along a plane of anisotropy (foliation). The effect of the foliation is to decrease the ductility of the material in this orientation so that brittle fractures or shear-bands develop. Foliation boudinage is caused by brittle failure; e
Anisotropic Elastoplastic Damage Mechanics Method to Predict Fatigue Life of the Structure
Hualiang Wan; Qizhi Wang; Zheng Zhang
2016-01-01
New damage mechanics method is proposed to predict the low-cycle fatigue life of metallic structures under multiaxial loading. The microstructure mechanical model is proposed to simulate anisotropic elastoplastic damage evolution. As the micromodel depends on few material parameters, the present method is very concise and suitable for engineering application. The material parameters in damage evolution equation are determined by fatigue experimental data of standard specimens. By employing fu...
Anisotropic thermal conductivity in epoxy-bonded magnetocaloric composites
Weise, Bruno; Sellschopp, Kai; Bierdel, Marius; Funk, Alexander; Bobeth, Manfred; Krautz, Maria; Waske, Anja
2016-09-01
Thermal management is one of the crucial issues in the development of magnetocaloric refrigeration technology for application. In order to ensure optimal exploitation of the materials "primary" properties, such as entropy change and temperature lift, thermal properties (and other "secondary" properties) play an important role. In magnetocaloric composites, which show an increased cycling stability in comparison to their bulk counterparts, thermal properties are strongly determined by the geometric arrangement of the corresponding components. In the first part of this paper, the inner structure of a polymer-bonded La(Fe, Co, Si)13-composite was studied by X-ray computed tomography. Based on this 3D data, a numerical study along all three spatial directions revealed anisotropic thermal conductivity of the composite: Due to the preparation process, the long-axis of the magnetocaloric particles is aligned along the xy plane which is why the in-plane thermal conductivity is larger than the thermal conductivity along the z-axis. Further, the study is expanded to a second aspect devoted to the influence of particle distribution and alignment within the polymer matrix. Based on an equivalent ellipsoids model to describe the inner structure of the composite, numerical simulation of the thermal conductivity in different particle arrangements and orientation distributions were performed. This paper evaluates the possibilities of microstructural design for inducing and adjusting anisotropic thermal conductivity in magnetocaloric composites.
Linear and nonlinear optical response of spherical anisotropic semiconductor microcrystallites
Ramaniah, Lavanya M.; Nair, Selvakumar V.; Rustagi, Kailash C.
1989-12-01
We present a phenomenological theory of the linear and nonlinear optical properties associated with the Fröhlich resonances of an optically anisotropic, spherical semiconductor crystallite. Using the Maxwell-Garnett approach, we calculate the effective dielectric function of a composite medium containing such crystallites. To study the effect of anisotropy, we take CdS and CdSe quantum dots as examples for the inclusions, and use a two-resonance model for the dielectric function. Even for randomly oriented inclusions, the Fröhlich resonances split as a result of anisotropic local-field corrections. At higher laser intensities, absorption saturation leads to bistability or tristability in the optical response of individual crystallites, while the response of the composite medium with randomly oriented inclusions shows multistability, with many intermediate branches. The nonlinear response of such a composite medium also exhibits a new kind of orientation-induced broadening of resonances. We also find that tristability is possible in another kind of inhomogeneous material, viz., a composite medium containing two types of isotropic spherical crystallites.
Anisotropic Tuning of Graphite Thermal Conductivity by Lithium Intercalation.
Qian, Xin; Gu, Xiaokun; Dresselhaus, Mildred S; Yang, Ronggui
2016-11-17
Understanding thermal transport in lithium intercalated layered materials is not only important for managing heat generation and dissipation in lithium ion batteries but also the understanding potentially provides a novel way to design materials with reversibly tunable thermal conductivity. In this work, the thermal conductivity of lithium-graphite intercalation compounds (LixC6) is calculated using molecular dynamics simulations as a function of the amount of lithium intercalated. We found that intercalation of lithium has an anisotropic effect on tuning the thermal conductivity: the thermal conductivity in the basal plane decreases monotonically from 1232 W/m·K of pristine graphite to 444 W/m·K of the fully lithiated LiC6, while the thermal conductivity along the c-axis decreases first from 6.5 W/m·K for graphite to 1.3 W/m·K for LiC18 and then increases to 5.0 W/m·K for LiC6 as the lithium composition increases. More importantly, we provide the very first atomic-scale insight into the effect of lithium intercalation on the spectral phonon properties of graphite. The intercalated lithium ions are found to suppress the phonon lifetime and to reduce the group velocity of phonons parallel to the basal plane but significantly to increase the phonon group velocity along the c-axis, which anisotropically tunes the thermal conductivity of lithiated graphite compounds. This work could shed some light on the search for tunable thermal conductivity materials and might have strong impacts on the thermal management of lithium ion batteries.
Views on the Anisotropic Nature of Ilva Valley Region
Directory of Open Access Journals (Sweden)
GABRIELA-ALINA MUREŞAN
2012-01-01
Full Text Available There are two concepts important for the authors of this article: anisotropic region and anisotropic space. Anisotropic region is defined by A. Dauphiné, the geographer (-mathematician, as a territorial unit whose structure results from the organisation of space along one or more axes. From the point of view of a territorial system, this type of region has some characteristics which differentiate it both from the homogeneous region and from the polarised one. These specificities have been analysed for Ilva Valley. The region of Ilva Valley is formed along the morphological axis represented by the Ilva River. The aim is to identify these specificities or their absence within this region. In this way we can determine whether this region is an anisotropic one or just an anisotropic space, namely whether it can be considered as evolving towards an anisotropic region, not yet complying with all characteristics of anisotropic regions.
Angle-Resolved Light-Matter Interaction in Anisotropic Layered Black Phosphorus
Huang, Shengxi; Ling, Xi; Hasdeo, Eddwi; Liang, Liangbo; Parkin, William; Tatsumi, Yuki; Nugraha, Ahmad; Puretzky, Alexander; Das, Paul; Sumpter, Bobby; Geohegan, David; Kong, Jing; Saito, Riichiro; Drndic, Marija; Meunier, Vincent; Dresselhaus, Mildred
Orthorhombic black phosphorus (BP) and other layered materials, such as gallium telluride and tin selenide, stand out among two-dimensional (2D) materials owing to their anisotropic in-plane structure. This anisotropy adds a new dimension to the properties of 2D materials and stimulates the development of angle-resolved photonics and electronics. However, understanding the effect of anisotropy has remained unsatisfactory to-date, as shown by a number of inconsistencies in the recent literature. We use angle-resolved absorption and Raman spectroscopies to investigate the role of anisotropy on the electron-photon and electron-phonon interactions in BP. We highlight, both experimentally and theoretically, a non-trivial dependence between anisotropies and flake thickness, photon and phonon energies. We show that the anisotropic optical absorption is a reliable and simple way to identify the crystalline orientation of BP, which cannot be determined from Raman spectroscopy without the explicit consideration of excitation wavelength and flake thickness.
Energy Technology Data Exchange (ETDEWEB)
Lazar, Markus, E-mail: lazar@fkp.tu-darmstadt.de [Heisenberg Research Group, Department of Physics, Darmstadt University of Technology, Hochschulstr. 6, D-64289 Darmstadt (Germany); Po, Giacomo, E-mail: gpo@ucla.edu [Department of Mechanical and Aerospace Engineering, University of California Los Angeles, Los Angeles, CA 90095 (United States)
2015-07-31
In this paper, we derive the Green tensor of anisotropic gradient elasticity with separable weak non-locality, a special version of Mindlin's form II anisotropic gradient elasticity theory with up to six independent length scale parameters. The framework models materials where anisotropy is twofold, namely the bulk material anisotropy and a weak non-local anisotropy relevant at the nano-scale. In contrast with classical anisotropic elasticity, it is found that both the Green tensor and its gradient are non-singular at the origin, and that they rapidly converge to their classical counterparts away from the origin. Therefore, the Green tensor of Mindlin's anisotropic gradient elasticity with separable weak non-locality can be used as a physically-based regularization of the classical Green tensor for materials with strong anisotropy. - Highlights: • Theory of Mindlin's anisotropic gradient elasticity with separable weak non-locality is presented. • The non-singular (3D) Green tensor is given. • The gradient of the non-singular Green tensor is calculated.
Glaessgen, Edward H.; Schoeppner, Gregory A.
2006-01-01
NASA Langley Research Center has successfully developed an electron beam freeform fabrication (EBF3) process, a rapid metal deposition process that works efficiently with a variety of weldable alloys. The EBF3 process can be used to build a complex, unitized part in a layer-additive fashion, although the more immediate payoff is for use as a manufacturing process for adding details to components fabricated from simplified castings and forgings or plate products. The EBF3 process produces structural metallic parts with strengths comparable to that of wrought product forms and has been demonstrated on aluminum, titanium, and nickel-based alloys to date. The EBF3 process introduces metal wire feedstock into a molten pool that is created and sustained using a focused electron beam in a vacuum environment. Operation in a vacuum ensures a clean process environment and eliminates the need for a consumable shield gas. Advanced metal manufacturing methods such as EBF3 are being explored for fabrication and repair of aerospace structures, offering potential for improvements in cost, weight, and performance to enhance mission success for aircraft, launch vehicles, and spacecraft. Near-term applications of the EBF3 process are most likely to be implemented for cost reduction and lead time reduction through addition of details onto simplified preforms (casting or forging). This is particularly attractive for components with protruding details that would require a significantly large volume of material to be machined away from an oversized forging, offering significant reductions to the buy-to-fly ratio. Future far-term applications promise improved structural efficiency through reduced weight and improved performance by exploiting the layer-additive nature of the EBF3 process to fabricate tailored unitized structures with functionally graded microstructures and compositions.
Observation of an Anisotropic Wigner Crystal
Liu, Yang; Hasdemir, S.; Pfeiffer, L. N.; West, K. W.; Baldwin, K. W.; Shayegan, M.
2016-09-01
We report a new correlated phase of two-dimensional charged carriers in high magnetic fields, manifested by an anisotropic insulating behavior at low temperatures. It appears in a large range of low Landau level fillings 1 /3 ≲ν ≲2 /3 in hole systems confined to wide GaAs quantum wells when the sample is tilted in magnetic field to an intermediate angle. The parallel field component (B∥) leads to a crossing of the lowest two Landau levels, and an elongated hole wave function in the direction of B∥. Under these conditions, the in-plane resistance exhibits an insulating behavior, with the resistance along B∥ about 10 times smaller than the resistance perpendicular to B∥. We interpret this anisotropic insulating phase as a two-component, striped Wigner crystal.
Formation of Anisotropic Block Copolymer Gels
Liaw, Chya Yan; Shull, Kenneth; Henderson, Kevin; Joester, Derk
2011-03-01
Anisotropic, fibrillar gels are important in a variety of processes. Biomineralization is one example, where the mineralization process often occurs within a matrix of collagen or chitin fibers that trap the mineral precursors and direct the mineralization process. We wish to replicate this type of behavior within block copolymer gels. Particularly, we are interested in employing gels composed of cylindrical micelles, which are anisotropic and closely mimic biological fibers. Micelle geometry is controlled in our system by manipulating the ratio of molecular weights of the two blocks and by controlling the detailed thermal processing history of the copolymer solutions. Small-Angle X-ray Scattering and Dynamic Light Scattering are used to determine the temperature dependence of the gel formation process. Initial experiments are based on a thermally-reversible alcohol-soluble system, that can be subsequently converted to a water soluble system by hydrolysis of a poly(t-butyl methacrylate) block to a poly (methacrylic acid) block. MRSEC.
Anisotropic Spin Splitting in Step Quantum Wells
Institute of Scientific and Technical Information of China (English)
HAO Ya-Fei; CHEN Yong-Hai; HAO Guo-Dong; WANG Zhan-Guo
2009-01-01
By the method of finite difference,the anisotropic spin splitting of the Alx Ga1-x As/GaAs/Aly Ga1-y As/Alx Ga1-x As step quantum wells (QWs) are theoretically investigated considering the interplay of the bulk inversion asymmetry and structure inversion asymmetry induced by step quantum well structure and external electric field.We demonstrate that the anisotropy of the total spin splitting can be controlled by the shape of the QWs and the external electric field.The interface related Rashba effect plays an important effect on the anisotropic spin splitting by influencing the magnitude of the spin splitting and the direction of electron spin.The Rashba spin splitting presents in the step quantum wells due to the interface related Rashba effect even without external electric field or magnetic field.
Bond diluted anisotropic quantum Heisenberg model
Energy Technology Data Exchange (ETDEWEB)
Akıncı, Ümit, E-mail: umit.akinci@deu.edu.tr
2013-10-15
Effects of the bond dilution on the critical temperatures, phase diagrams and the magnetization behaviors of the isotropic and anisotropic quantum Heisenberg model have been investigated in detail. For the isotropic case, bond percolation threshold values have been determined for several numbers of two (2D) and three (3D) dimensional lattices. In order to investigate the effect of the anisotropy in the exchange interaction on the results obtained for the isotropic model, a detailed investigation has been made on a honeycomb lattice. Some interesting results, such as second order reentrant phenomena in the phase diagrams have been found. - Highlights: • Anisotropic quantum Heisenberg model with bond dilution investigated. • Bond percolation threshold values given for 2D and 3D lattices in isotropic case. • Phase diagrams and ground state magnetizations investigated in detail. • Variation of the bond percolation threshold values with anisotropy determined.
Rainbow metric from quantum gravity: anisotropic cosmology
Assanioussi, Mehdi
2016-01-01
In this paper we present a construction of effective cosmological models which describe the propagation of a massive quantum scalar field on a quantum anisotropic cosmological spacetime. Each obtained effective model is represented by a rainbow metric in which particles of distinct momenta propagate on different classical geometries. Our analysis shows that upon certain assumptions and conditions on the parameters determining such anisotropic models, we surprisingly obtain a unique deformation parameter $\\beta$ in the modified dispersion relation of the modes. Hence inducing an isotropic deformation despite the general starting considerations. We then ensure the recovery of the dispersion relation realized in the isotropic case, studied in [arXiv:1412.6000], when some proper symmetry constraints are imposed, and we estimate the value of the deformation parameter for this case in loop quantum cosmology context.
Rainbow metric from quantum gravity: Anisotropic cosmology
Assanioussi, Mehdi; Dapor, Andrea
2017-03-01
In this paper we present a construction of effective cosmological models which describe the propagation of a massive quantum scalar field on a quantum anisotropic cosmological spacetime. Each obtained effective model is represented by a rainbow metric in which particles of distinct momenta propagate on different classical geometries. Our analysis shows that upon certain assumptions and conditions on the parameters determining such anisotropic models, we surprisingly obtain a unique deformation parameter β in the modified dispersion relation of the modes, hence, inducing an isotropic deformation despite the general starting considerations. We then ensure the recovery of the dispersion relation realized in the isotropic case, studied in [M. Assanioussi, A. Dapor, and J. Lewandowski, Phys. Lett. B 751, 302 (2015), 10.1016/j.physletb.2015.10.043], when some proper symmetry constraints are imposed, and we estimate the value of the deformation parameter for this case in loop quantum cosmology context.
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.
Anisotropic dark energy and CMB anomalies
Battye, Richard
2009-01-01
We investigate the breaking of global statistical isotropy caused by a dark energy component with an energy-momentum tensor which has point symmetry, that could represent a cubic or hexagonal crystalline lattice. In such models Gaussian, adiabatic initial conditions created during inflation can lead to anisotropies in the cosmic microwave background whose spherical harmonic coefficients are correlated, contrary to the standard assumption. We develop an adaptation of the line of sight integration method that can be applied to models where the background energy-momentum tensor is isotropic, but whose linearized perturbations are anisotropic. We then show how this can be applied to the cases of cubic and hexagonal symmetry. We compute quantities which show that such models are indistinguishable from isotropic models even in the most extreme parameter choices, in stark contrast to models with anisotropic initial conditions based on inflation. The reason for this is that the dark energy based models contribute to ...
Anisotropic permeability in deterministic lateral displacement arrays
Vernekar, Rohan; Loutherback, Kevin; Morton, Keith; Inglis, David
2016-01-01
We investigate anisotropic permeability of microfluidic deterministic lateral displacement (DLD) arrays. A DLD array can achieve high-resolution bimodal size-based separation of micro-particles, including bioparticles such as cells. Correct operation requires that the fluid flow remains at a fixed angle with respect to the periodic obstacle array. We show via experiments and lattice-Boltzmann simulations that subtle array design features cause anisotropic permeability. The anisotropy, which indicates the array's intrinsic tendency to induce an undesired lateral pressure gradient, can lead to off-axis flows and therefore local changes in the critical separation size. Thus, particle trajectories can become unpredictable and the device useless for the desired separation duty. We show that for circular posts the rotated-square layout, unlike the parallelogram layout, does not suffer from anisotropy and is the preferred geometry. Furthermore, anisotropy becomes severe for arrays with unequal axial and lateral gaps...
Comparing anisotropic displacement parameters in protein structures.
Merritt, E A
1999-12-01
The increasingly widespread use of synchrotron-radiation sources and cryo-preparation of samples in macromolecular crystallography has led to a dramatic increase in the number of macromolecular structures determined at atomic or near-atomic resolution. This permits expansion of the structural model to include anisotropic displacement parameters U(ij) for individual atoms. In order to explore the physical significance of these parameters in protein structures, it is useful to be able to compare quantitatively the electron-density distribution described by the refined U(ij) values associated with corresponding crystallographically independent atoms. This paper presents the derivation of an easily calculated correlation coefficient in real space between two atoms modeled with anisotropic displacement parameters. This measure is used to investigate the degree of similarity between chemically equivalent but crystallographically independent atoms in the set of protein structural models currently available from the Protein Data Bank.
Dynamics of anisotropic f(R) cosmology
Leon, Genly
2010-01-01
We construct general anisotropic cosmological scenarios governed by an f(R) gravitational sector. Focusing then on Kantowski-Sachs geometries in the case of $R^n$-gravity we perform a detailed phase-space analysis. We find that at late times the universe can result to a state of accelerating expansion, and additionally, for a particular n-range (2
Anomalous anisotropic magnetoresistance effects in graphene
Directory of Open Access Journals (Sweden)
Yiwei Liu
2014-09-01
Full Text Available We investigate the effect of external stimulus (temperature, magnetic field, and gases adsorptions on anisotropic magnetoresistance (AMR in multilayer graphene. The graphene sample shows superlinear magnetoresistance when magnetic field is perpendicular to the plane of graphene. A non-saturated AMR with a value of −33% is found at 10 K under a magnetic field of 7 T. It is surprisingly to observe that a two-fold symmetric AMR at high temperature is changed into a one-fold one at low temperature for a sample with an irregular shape. The anomalous AMR behaviors may be understood by considering the anisotropic scattering of carriers from two asymmetric edges and the boundaries of V+(V- electrodes which serve as active adsorption sites for gas molecules at low temperature. Our results indicate that AMR in graphene can be optimized by tuning the adsorptions, sample shape and electrode distribution in the future application.
Electromagnetic effects on cracking of anisotropic polytropes
Energy Technology Data Exchange (ETDEWEB)
Sharif, Muhammad; Sadiq, Sobia [University of the Punjab, Department of Mathematics, Lahore (Pakistan)
2016-10-15
In this paper, we study the electromagnetic effects on the stability of a spherically symmetric anisotropic fluid distribution satisfying two polytropic equations of state and construct the corresponding generalized Tolman-Oppenheimer-Volkoff equations. We apply perturbations on matter variables via the polytropic constant as well as the polytropic index and formulate the force distribution function. It is found that the compact object is stable for a feasible choice of perturbed polytropic index in the presence of charge. (orig.)
Crossing Statistics of Anisotropic Stochastic Surface
Nezhadhaghighi, M Ghasemi; Yasseri, T; Allaei, S M Vaez
2015-01-01
We use crossing statistics and its generalization to determine the anisotropic direction imposed on a stochastic fields in $(2+1)$Dimension. This approach enables us to examine not only the rotational invariance of morphology but also we can determine the Gaussianity of underlying stochastic field in various dimensions. Theoretical prediction of up-crossing statistics (crossing with positive slope at a given threshold $\\alpha$ of height fluctuation), $\
Symmetry analysis for anisotropic field theories
Energy Technology Data Exchange (ETDEWEB)
Parra, Lorena; Vergara, J. David [Instituto de Ciencias Nucleares, UNAM, Circuito Exterior s/n, Ciudad Universitaria. Delg. Coyoacan. C.P. 04510 Mexico DF (Mexico)
2012-08-24
The purpose of this paper is to study with the help of Noether's theorem the symmetries of anisotropic actions for arbitrary fields which generally depend on higher order spatial derivatives, and to find the corresponding current densities and the Noether charges. We study in particular scale invariance and consider the cases of higher derivative extensions of the scalar field, electrodynamics and Chern-Simons theory.
Electromagnetic field representation in inhomogeneous anisotropic media
Mohsen, A.
1973-01-01
Some of the basic developments in the theory of electromagnetic field representation in terms of Hertz vectors are reviewed. A solution for the field in an inhomogeneous anisotropic medium is given in terms of the two Hertz vectors. Conditions for presentation of the field in terms of uncoupled transverse electric and transverse magnetic modes, in a general orthogonal coordinate system, are derived when the permeability and permittivity tensors have only diagonal components. These conditions are compared with some known special cases.
Effect of inflation on anisotropic cosmologies
Energy Technology Data Exchange (ETDEWEB)
Jensen, L.G.; Stein-Schabes, J.A.
1986-03-01
The effects of anisotropic cosmologies on inflation are studied. By properly formulating the field equations it is possible to show that any model that undergoes sufficient inflation will become isotropic on scales greater than the horizon today. Furthermore, we shall show that it takes a very long time for anisotropies to become visible in the observable part of the Universe. It is interesting to note that the time scale will be independent of the Bianchi Model and of the initial anisotropy. 6 refs.
Electromagnetic Effects on Cracking of Anisotropic Polytropes
Sharif, M
2016-01-01
In this paper, we study the electromagnetic effects on stability of spherically symmetric anisotropic fluid distribution satisfying two polytropic equations of state and construct the corresponding generalized Tolman Oppenheimer Volkoff equations. We apply perturbations on matter variables via polytropic constant as well as polytropic index and formulate the force distribution function. It is found that the compact object is stable for feasible choice of perturbed polytropic index in the presence of charge.
On anisotropic black branes with Lifshitz scaling
Directory of Open Access Journals (Sweden)
Dibakar Roychowdhury
2016-08-01
Full Text Available In this paper, based on the method of scalar perturbations, we construct the anisotropic charged Lifshitz background perturbatively up to leading order in the anisotropy. We perform our analysis both in the extremal as well as in the non-extremal limit. Finally, we probe the so called superfluid phase of the boundary theory and explore the effects of anisotropy on the superconducting condensate.
Anisotropic magnetocapacitance in ferromagnetic-plate capacitors
Haigh, J. A.; Ciccarelli, C.; Betz, A. C.; Irvine, A.; Novák, V.; Jungwirth, T.; Wunderlich, J.
2015-04-01
The capacitance of a parallel-plate capacitor can depend on the applied magnetic field. Previous studies have identified capacitance changes induced via classical Lorentz force or spin-dependent Zeeman effects. Here we measure a magnetization direction-dependent capacitance in parallel-plate capacitors where one plate is a ferromagnetic semiconductor, gallium manganese arsenide. This anisotropic magnetocapacitance is due to the anisotropy in the density of states dependent on the magnetization through the strong spin-orbit interaction.
Effect of inflation on anisotropic cosmologies
Energy Technology Data Exchange (ETDEWEB)
Jensen, L.G.; Stein-Schabes, J.A.
1986-08-15
We study the effects of anisotropic cosmologies on inflation. By properly formulating the field equations it is possible to show that any model that undergoes sufficient inflation will become isotropic on scales greater than the horizon today. Furthermore, we shall show that it takes a very long time for anisotropies to become visible in the observable part of the Universe. It is interesting to note that the time scale will be independent of the Bianchi model and of the initial anisotropy.
Acoustic anisotropic wavefields through perturbation theory
Alkhalifah, Tariq Ali
2013-09-01
Solving the anisotropic acoustic wave equation numerically using finite-difference methods introduces many problems and media restriction requirements, and it rarely contributes to the ability to resolve the anisotropy parameters. Among these restrictions are the inability to handle media with η<0 and the presence of shear-wave artifacts in the solution. Both limitations do not exist in the solution of the elliptical anisotropic acoustic wave equation. Using perturbation theory in developing the solution of the anisotropic acoustic wave equation allows direct access to the desired limitation-free solutions, that is, solutions perturbed from the elliptical anisotropic background medium. It also provides a platform for parameter estimation because of the ability to isolate the wavefield dependency on the perturbed anisotropy parameters. As a result, I derive partial differential equations that relate changes in the wavefield to perturbations in the anisotropy parameters. The solutions of the perturbation equations represented the coefficients of a Taylor-series-type expansion of the wavefield as a function of the perturbed parameter, which is in this case η or the tilt of the symmetry axis. The expansion with respect to the symmetry axis allows use of an acoustic transversely isotropic media with a vertical symmetry axis (VTI) kernel to estimate the background wavefield and the corresponding perturbation coefficients. The VTI extrapolation kernel is about one-fourth the cost of the transversely isotropic model with a tilt in the symmetry axis kernel. Thus, for a small symmetry axis tilt, the cost of migration using a first-order expansion can be reduced. The effectiveness of the approach was demonstrated on the Marmousi model.
Anisotropic cosmological solutions in massive vector theories
Heisenberg, Lavinia; Kase, Ryotaro; Tsujikawa, Shinji
2016-11-01
In beyond-generalized Proca theories including the extension to theories higher than second order, we study the role of a spatial component v of a massive vector field on the anisotropic cosmological background. We show that, as in the case of the isotropic cosmological background, there is no additional ghostly degrees of freedom associated with the Ostrogradski instability. In second-order generalized Proca theories we find the existence of anisotropic solutions on which the ratio between the anisotropic expansion rate Σ and the isotropic expansion rate H remains nearly constant in the radiation-dominated epoch. In the regime where Σ/H is constant, the spatial vector component v works as a dark radiation with the equation of state close to 1/3. During the matter era, the ratio Σ/H decreases with the decrease of v. As long as the conditions |Σ| ll H and v2 ll phi2 are satisfied around the onset of late-time cosmic acceleration, where phi is the temporal vector component, we find that the solutions approach the isotropic de Sitter fixed point (Σ = 0 = v) in accordance with the cosmic no-hair conjecture. In the presence of v and Σ the early evolution of the dark energy equation of state wDE in the radiation era is different from that in the isotropic case, but the approach to the isotropic value wDE(iso) typically occurs at redshifts z much larger than 1. Thus, apart from the existence of dark radiation, the anisotropic cosmological dynamics at low redshifts is similar to that in isotropic generalized Proca theories. In beyond-generalized Proca theories the only consistent solution to avoid the divergence of a determinant of the dynamical system corresponds to v = 0, so Σ always decreases in time.
Effective dielectric response of graded composite materials containing anisotropic particles
Institute of Scientific and Technical Information of China (English)
Sang Zhi-Fang; Li Zhen-Ya
2005-01-01
The effective dielectric response of granular composites, in which spheroidal particles with graded shells are randomly distributed in a host matrix, is investigated. General expressions for the effective dielectric constant of the composites and partial resonant condition are obtained in the dilute limit by use of a quasi-static approximation. In particular, spheroidal particles with a power-law gradation profile in the shells are studied in detail. We find that, by adjusting the dielectric gradient profile in the shells, the shape and structure of particles, it is possible to enhance the effective dielectric constant of the composite and to realize partial resonance. Under the partial resonant conditions,the coated spheroidal particles with graded shells within the host matrix can be regarded as equivalent homogeneous spheroids embedded in the same host. The equivalent spheroids have the same dielectric constant as the original cores and semiaxes equal to those of the original shells: i.e., the partial resonant system behaves as if the cores of the particles were enlarged and the shells were absent.
Multiple small-angle neutron scattering studies of anisotropic materials
Allen, A J; Long, G G; Ilavsky, J
2002-01-01
Building on previous work that considered spherical scatterers and randomly oriented spheroidal scatterers, we describe a multiple small-angle neutron scattering (MSANS) analysis for nonrandomly oriented spheroids. We illustrate this with studies of the multi-component void morphologies found in plasma-spray thermal barrier coatings. (orig.)
Mathematical Foundations of Limit Criterion for Anisotropic Materials
Directory of Open Access Journals (Sweden)
Ostrovvska-Maciejewska J.
2013-12-01
Full Text Available Artykuł przedstawia nową propozycję kryterium stanu granicznego dla anizotropowych ciał stałych wykazujących różną wytrzymałość przy rozciąganiu i ściskaniu. Propozycja ta opiera się na koncepcji energetycznie ortogonalnych rozkładów stanu naprężenia zaproponowanej przez Rychlewskiego. Pomysł wykorzystania zależnych od stanu naprężenia parametrów określających wpływ konkretnych form naprężenia na całkowitą miarę wytężenia materiału po raz pierwszy został przedstawiony przez Burzyńskiego. W pracy omówione są obydwie koncepcje. Przedstawione jest ogólne sformułowanie nowego warunku granicznego, jak również jego specyfikacja dla wybranych symetrii sprężystych. Kryterium to zostało porównane z niektórymi innymi spośród znanych kryteriów granicznych dla ciał anizotropowych. Przedstawiono ogólną metodologię pozyskiwania danych wymaganych do specyfikacji kryterium.
Derivation of the Optical Constants of Anisotropic Materials
2011-06-30
1,2,3 (69) aPk Qk -1 Dk I +ip, k - P3k( 170) aPIk D aL L k Lk -i V (71) a P2k Dk ak --1. (72) aP 3 k Dk *1 " aavk avT " But (vkvTL) = vT + v. Lk...8217 = 4.5 (73) aPk aP2 k aP~k/ Y .i-. 17 AXArthur D. Little, Inc. aVk (Cos P4k COS P5k COS P4k s P5k 4- P k) (74) aP 4 k k - (-sin P4k sin P5k sin P4k O P5k...0C) (75) Obviously avk T aVT \\T- V I = k (76) apk 2k. A Fortran program embodying these methods was written and used to fit the observed spectra
Micro-macro modelling of stress-dependent anisotropic magnetoresistance
Energy Technology Data Exchange (ETDEWEB)
Bartok, A; Daniel, L; Razek, A, E-mail: andras.bartok@lgep.supelec.fr, E-mail: laurent.daniel@u-psud.fr [Laboratoire de Genie Electrique de Paris (LGEP), CNRS (UMR 8507)-SUPELEC-UPMC Paris 6-Univ Paris-Sud 11, 11 rue Joliot-Curie, Plateau de Moulon, 91192 Gif-sur-Yvette (France)
2011-04-06
Anisotropic magnetoresistance (AMR) is the basic phenomenon of a spread class of sensors. AMR effect has a strong mechanical stress dependence. Micromagnetic simulations are often used for modelling the magnetoresistance of ferromagnetic materials, but these approaches do not allow us to investigate macroscopic effects (for example behaviour of a polycrystal under stress) due to the high number of interactions and degrees of freedom. On the other hand macroscopic phenomenological approaches fail in describing the main role of microstructure on the effective behaviour. In this work a micro-macro model is proposed to describe the effect of stress on the AMR in ferromagnetic polycrystals. Results are discussed and compared with experimental data from the literature.
Polymer Nanocomposites Containing Anisotropic Metal Nanostructures as Internal Strain Indicators
Directory of Open Access Journals (Sweden)
Giacomo Ruggeri
2010-02-01
Full Text Available Polymer/metal nanocomposite containing intrinsically anisotropic metal nanostructures such as metal nanorods and nanowires appeared extremely more sensitive and responsive to mechanical stimuli than nanocomposites containing spherical nanoparticles. After uniaxial stretching of the supporting polymer matrix (poly(vinyl alcohol, the elongated silver nanostructures embedded at low concentration into the polymer matrix (<1 wt % of Ag assume the direction of the drawing, yielding materials with a strong dichroic response of the absorption behavior. Accordingly, the film changed its color when observed under linearly polarized light already at moderate drawings. The results obtained suggest that nanocomposite films have potential in applications such as color polarizing filters, radiation responsive polymeric objects and smart flexible films in packaging applications.
Anisotropic cosmological solutions in massive vector theories
Heisenberg, Lavinia; Tsujikawa, Shinji
2016-01-01
In beyond-generalized Proca theories including the extension to theories higher than second order, we study the role of a spatial component $v$ of a massive vector field on the anisotropic cosmological background. We show that, as in the case of the isotropic cosmological background, there is no additional ghostly degrees of freedom associated with the Ostrogradski instability. In second-order generalized Proca theories we find the existence of anisotropic solutions on which the ratio between the anisotropic expansion rate $\\Sigma$ and the isotropic expansion rate $H$ remains nearly constant in the radiation-dominated epoch. In the regime where $\\Sigma/H$ is constant, the spatial vector component $v$ works as a dark radiation with the equation of state close to $1/3$. During the matter era, the ratio $\\Sigma/H$ decreases with the decrease of $v$. As long as the conditions $|\\Sigma| \\ll H$ and $v^2 \\ll \\phi^2$ are satisfied around the onset of late-time cosmic acceleration, where $\\phi$ is the temporal vector ...
Anisotropic properties of TaS2
Institute of Scientific and Technical Information of China (English)
Qiao Yan-Bin; Li Yan-Ling; Zhong Guo-Hua; Zeng Zhi; Qin Xiao-Ying
2007-01-01
The anisotropic properties of 1T- and 2H-TaS2 are investigated by the density functional theory within the framework of full-potential linearized augmented plane wave method. The band structures of 1T- and 2H-TaS2 exhibit anisotropic properties and the calculated electronic specific-heat coefficient γ of 2H-TaS2 accords well with the existing experimental value. The anisotropic frequency-dependent dielectric functions including the effect of the Drude term are analysed, where the εxx(ω) spectra corresponding to the electric field E perpendicular to the z axis show excellent agreement with the measured results except for the ε1xx(ω) of 1T-TaS2 below the energy level of 2.6 eV which is due to the lack of the enough CDW information for reference in our calculation. Furthermore, based on the values of optical effective mass ratio P of 1T and 2H phases it is found that the anisotropy in 2H-TaS2 is stronger than that in 1T-TaS2.
Anisotropic power-law k-inflation
Ohashi, Junko; Tsujikawa, Shinji
2013-01-01
It is known that power-law k-inflation can be realized for the Lagrangian $P=Xg(Y)$, where $X=-(\\partial \\phi)^2/2$ is the kinetic energy of a scalar field $\\phi$ and $g$ is an arbitrary function in terms of $Y=Xe^{\\lambda \\phi/M_{pl}}$ ($\\lambda$ is a constant and $M_{pl}$ is the reduced Planck mass). In the presence of a vector field coupled to the inflaton with an exponential coupling $f(\\phi) \\propto e^{\\mu \\phi/M_{pl}}$, we show that the models with the Lagrangian $P=Xg(Y)$ generally give rise to anisotropic inflationary solutions with $\\Sigma/H=constant$, where $\\Sigma$ is an anisotropic shear and $H$ is an isotropic expansion rate. Provided these anisotropic solutions exist in the regime where the ratio $\\Sigma/H$ is much smaller than 1, they are stable attractors irrespective of the forms of $g(Y)$. We apply our results to concrete models of k-inflation such as the generalized dilatonic ghost condensate/the DBI model and we numerically show that the solutions with different initial conditions converge...
ARTc: Anisotropic reflectivity and transmissivity calculator
Malehmir, Reza; Schmitt, Douglas R.
2016-08-01
While seismic anisotropy is known to exist within the Earth's crust and even deeper, isotropic or even highly symmetric elastic anisotropic assumptions for seismic imaging is an over-simplification which may create artifacts in the image, target mis-positioning and hence flawed interpretation. In this paper, we have developed the ARTc algorithm to solve reflectivity, transmissivity as well as velocity and particle polarization in the most general case of elastic anisotropy. This algorithm is able to provide reflectivity solution from the boundary between two anisotropic slabs with arbitrary symmetry and orientation up to triclinic. To achieve this, the algorithm solves full elastic wave equation to find polarization, slowness and amplitude of all six wave-modes generated from the incident plane-wave and welded interface. In the first step to calculate the reflectivity, the algorithm solves properties of the incident wave such as particle polarization and slowness. After calculation of the direction of generated waves, the algorithm solves their respective slowness and particle polarization. With this information, the algorithm then solves a system of equations incorporating the imposed boundary conditions to arrive at the scattered wave amplitudes, and thus reflectivity and transmissivity. Reflectivity results as well as slowness and polarization are then tested in complex computational anisotropic models to ensure their accuracy and reliability. ARTc is coded in MATLAB ® and bundled with an interactive GUI and bash script to run on single or multi-processor computers.
Longitudinal fluctuations and decorrelation of anisotropic flow
Pang, Long-Gang; Petersen, Hannah; Qin, Guang-You; Roy, Victor; Wang, Xin-Nian
2016-12-01
We investigate the decorrelation of 2nd and 3rd order anisotropic flow for charged particles in two different pseudo rapidity (η) windows by varying the pseudo rapidity gap, in an event-by-event (3+1)D ideal hydrodynamic model, with fluctuating initial conditions from A Multi-Phase Transport (AMPT) model. We visualize the parton distribution at initial state for Pb+Pb collisions at LHC and Au+Au collisions at RHIC, and demonstrate the longitudinal fluctuations originating from the asymmetry between forward and backward going participants, the fluctuations of the string length and the fluctuations due to finite number of partons at different beam energies. The decorrelation of anisotropic flow of final hadrons with large η gaps is found to originate from the spatial decorrelation along the longitudinal direction in the AMPT initial conditions through hydrodynamic evolution. The agreement between our results and recent CMS data in most centralities suggests that the string-like mechanism of initial parton production in AMPT model captures the initial longitudinal fluctuation that is responsible for the measured decorrelation of anisotropic flow in Pb+Pb collisions at LHC. Our predictions for Au+Au collisions at the highest RHIC energy show stronger longitudinal decorrelation than at LHC, indicating larger longitudinal fluctuations at lower beam energies.
Anisotropic microsrheology of self-assembling collagen networks
Dutov, Pavel
Collagen is the main component of human connective tissue and extracellular matrix. Here we report multiple novel methods for utilizing optical tweezers to measure mechanical properties of different hierarchical levels of collagenous materials. First, we introduce a method for optical trap calibration that is suitable for viscoelastic material. The method is designed for use on experimental setups with two optical tweezers and is based on pulling a trapped particle with one trap while holding it with the other. The method combines advantages of commonly known PSD-fitting and fast-sweeping methods, allowing calibration of a completely fixed trap in a fluid of unknown viscosity/viscoelasticity without additional expensive equipment. Then we report an approach to measure the longitudinal component of the elastic moduli of biological fibers under conditions close to those found in vivo and apply it to type I collagen from rat tail tendon. This approach combines optical tweezers, atomic force microscopy, and exploits Euler-Bernoulli elasticity theory for data analysis. The approach also avoids the traditional drying-soaking cycle, since samples are freshly extracted. Importantly, strains are kept below 0.5%, which appear consistent with the linear elastic regime. We find, surprisingly, that the longitudinal elastic modulus of type I collagen cannot be represented by a single quantity but rather is a distribution that is broader than the uncertainty of our experimental technique. Lastly, we report a new method for characterizing anisotropic viscoelastic response of collagenous matrices. Anisotropic collagenous extracellular matrices are used in biomedicine to enhance the wound healing process by directing fibroblast proliferation. We utilize an optical trap to monitor the thermal fluctuations of microspheres embedded into collagenous network to extract a viscoelastic response function of the network along the principal axes of anisotropy.
Li, Xianping
2010-01-01
Heterogeneous anisotropic diffusion problems arise in the various areas of science and engineering including plasma physics, petroleum engineering, and image processing. Standard numerical methods can produce spurious oscillations when they are used to solve those problems. A common approach to avoid this difficulty is to design a proper numerical scheme and/or a proper mesh so that the numerical solution validates the discrete counterpart (DMP) of the maximum principle satisfied by the continuous solution. A well known mesh condition for the DMP satisfaction by the linear finite element solution of isotropic diffusion problems is the non-obtuse angle condition that requires the dihedral angles of mesh elements to be non-obtuse. In this paper, a generalization of the condition, the so-called anisotropic non-obtuse angle condition, is developed for the finite element solution of heterogeneous anisotropic diffusion problems. The new condition is essentially the same as the existing one except that the dihedral ...
Majhi, S.; Pal, P. C.; Kumar, S.
2017-01-01
This study investigates the reflection and transmission of plane SH-waves in two semi-infinite anisotropic magnetoelastic media. The lower half-space is considered as initially stressed and inhomogeneous. The density of lower half-space is taken exponentially varying with depth. The solutions for half-spaces are obtained analytically. The expressions for reflection and transmission coefficient are obtained in the closed form subject to continuity conditions at the interfaces of anisotropic magnetoelastic half-spaces and the Snell's law. It is found that these coefficients depend on the initial stress, inhomogeneity parameter, the magnetoelastic coupling parameter, and the angle at which wave crosses the magnetic field of the half-spaces. Numerical computations are performed for these coefficients for a specific model of two different anisotropic magnetoelastic half-spaces. The numerical results are illustrated by the graph of reflection and transmission coefficient versus the angle of incidence. In general, as the initial stress increases the reflection and transmission coefficient increases, the affect is more prominent for more than 10 GPa. Inhomogeneity in the density of the material also increases the reflection and transmission coefficient. The anisotropic magnetoelastic parameter and the angle at which the wave crosses the magnetic field for both the half-spaces have a quite significant effect on the reflection and transmission coefficient.
Majhi, S.; Pal, P. C.; Kumar, S.
2016-06-01
This study investigates the reflection and transmission of plane SH-waves in two semi-infinite anisotropic magnetoelastic media. The lower half-space is considered as initially stressed and inhomogeneous. The density of lower half-space is taken exponentially varying with depth. The solutions for half-spaces are obtained analytically. The expressions for reflection and transmission coefficient are obtained in the closed form subject to continuity conditions at the interfaces of anisotropic magnetoelastic half-spaces and the Snell's law. It is found that these coefficients depend on the initial stress, inhomogeneity parameter, the magnetoelastic coupling parameter, and the angle at which wave crosses the magnetic field of the half-spaces. Numerical computations are performed for these coefficients for a specific model of two different anisotropic magnetoelastic half-spaces. The numerical results are illustrated by the graph of reflection and transmission coefficient versus the angle of incidence. In general, as the initial stress increases the reflection and transmission coefficient increases, the affect is more prominent for more than 10 GPa. Inhomogeneity in the density of the material also increases the reflection and transmission coefficient. The anisotropic magnetoelastic parameter and the angle at which the wave crosses the magnetic field for both the half-spaces have a quite significant effect on the reflection and transmission coefficient.
Modelling of a compact anisotropic star as an anisotropic fluid sphere in $f(T)$ gravity
Momeni, D; Qaisar, S; Zaz, Zaid; Myrzakulov, R
2016-01-01
In this paper, we have studied the new exact model of anisotropic star in $f(T)$ theory of gravity. The dynamical equations in $f(T)$ theory with the anisotropic fluid have been solved by using Krori-Barua solution. We have determined that all the obtained solutions are free from central singularity and potentially stable. The observed values of mass and radius of the different strange stars RX J 1856-37, Her X-1, and Vela X-12 have been used to calculate the values of unknown constants in Krori and Barua metric. The physical parameters like anisotropy, stability and redshift of the stars have been investigated in detail.
Sayem, Ayed Al; Rahman, Md Saifur
2015-01-01
In this article, it has been theoretically shown that broad angle negative refraction is possible with asymmetric anisotropic metamaterials constructed by only dielectrics or loss less semiconductors at the telecommunication and relative wavelength range. Though natural uniaxial materials can exhibit negative refraction, the maximum angle of negative refraction and critical incident angle lie in a very narrow range. This notable problem can be overcome by our proposed structure. In our structures, negative refraction originates from the highly asymmetric elliptical iso-frequency.This is artificially created by the rotated multilayer sub-wavelength dielectric/semiconductor stack, which act as an effective asymmetric anisotropic metamaterial.This negative refraction is achieved without using any negative permittivity materials such as metals. As we are using simple dielectrics, fabrication of such structures would be less complex than that of the metal based metamaterials. Our proposed ideas have been validated...
A multiscale framework for the simulation of the anisotropic mechanical behavior of shale
Li, Weixin; Jin, Congrui; Zhou, Xinwei; Cusatis, Gianluca
2016-01-01
Shale, like many other sedimentary rocks, is typically heterogeneous, anisotropic, and is characterized by partial alignment of anisotropic clay minerals and naturally formed bedding planes. In this study, a micromechanical framework based on the Lattice Discrete Particle Model (LDPM) is formulated to capture these features. Material anisotropy is introduced through an approximated geometric description of shale internal structure, which includes representation of material property variation with orientation and explicit modeling of parallel lamination. The model is calibrated by carrying out numerical simulations to match various experimental data, including the ones relevant to elastic properties, Brazilian tensile strength, and unconfined compressive strength. Furthermore, parametric study is performed to investigate the relationship between the mesoscale parameters and the macroscopic properties. It is shown that the dependence of the elastic stiffness, strength, and failure mode on loading orientation ca...
DEFF Research Database (Denmark)
Li, Fan; Yoo, Won Cheol; Beernink, Molly B;
2009-01-01
-specific tethers. Amorphous sol-gel materials were molded by the template into shaped NPs that mimic tetravalent atoms but on the length scale of colloids. Synthetic methods were developed to modify only the tips of the tetrapods with a range of possible functional groups to generate anisotropic NPs capable......Multipodal nanoparticles (NPs) with controlled tethers are promising principal building blocks, useful for constructing more complex materials, much like atoms are connected into more complex molecules. Here we report colloidal sphere templating as a viable means to create tetrapodal NPs with site...... of directional bonding to other NPs. We also illustrate that sets of tethered "colloidal atoms" can assemble themselves into "colloidal molecules" with precise placement of the modifying colloids. The templating and tethering approaches to these anisotropic colloidal building blocks and the assembly methods...
Solitary attractors and low-order filamentation in anisotropic self-focusing media
DEFF Research Database (Denmark)
Zozulya, A.A.; Anderson, D.Z.; Mamaev, A.V.;
1998-01-01
We present a detailed theoretical analysis of the properties and formation of single solitons and higher-order bound dipole pairs in media with anisotropic nonlocal photorefractive material response. The single solitons are elliptical beams, whereas the dipole pairs are formed by a pair of displa......We present a detailed theoretical analysis of the properties and formation of single solitons and higher-order bound dipole pairs in media with anisotropic nonlocal photorefractive material response. The single solitons are elliptical beams, whereas the dipole pairs are formed by a pair...... of displaced elliptical beams with a rr phase shift between their fields. The theory predicts convergence of Gaussian beams to the solitary states within a certain basin of attraction. Experimental observation of these solitons has been presented elsewhere. The experimental portion of the present paper...
Anisotropic Elastoplastic Damage Mechanics Method to Predict Fatigue Life of the Structure
Directory of Open Access Journals (Sweden)
Hualiang Wan
2016-01-01
Full Text Available New damage mechanics method is proposed to predict the low-cycle fatigue life of metallic structures under multiaxial loading. The microstructure mechanical model is proposed to simulate anisotropic elastoplastic damage evolution. As the micromodel depends on few material parameters, the present method is very concise and suitable for engineering application. The material parameters in damage evolution equation are determined by fatigue experimental data of standard specimens. By employing further development on the ANSYS platform, the anisotropic elastoplastic damage mechanics-finite element method is developed. The fatigue crack propagation life of satellite structure is predicted using the present method and the computational results comply with the experimental data very well.
Saving Moore’s Law Down To 1 nm Channels With Anisotropic Effective Mass
Ilatikhameneh, Hesameddin; Ameen, Tarek; Novakovic, Bozidar; Tan, Yaohua; Klimeck, Gerhard; Rahman, Rajib
2016-08-01
Scaling transistors’ dimensions has been the thrust for the semiconductor industry in the last four decades. However, scaling channel lengths beyond 10 nm has become exceptionally challenging due to the direct tunneling between source and drain which degrades gate control, switching functionality, and worsens power dissipation. Fortunately, the emergence of novel classes of materials with exotic properties in recent times has opened up new avenues in device design. Here, we show that by using channel materials with an anisotropic effective mass, the channel can be scaled down to 1 nm and still provide an excellent switching performance in phosphorene nanoribbon MOSFETs. To solve power consumption challenge besides dimension scaling in conventional transistors, a novel tunnel transistor is proposed which takes advantage of anisotropic mass in both ON- and OFF-state of the operation. Full-band atomistic quantum transport simulations of phosphorene nanoribbon MOSFETs and TFETs based on the new design have been performed as a proof.
Grooved organogel surfaces towards anisotropic sliding of water droplets.
Zhang, Pengchao; Liu, Hongliang; Meng, Jingxin; Yang, Gao; Liu, Xueli; Wang, Shutao; Jiang, Lei
2014-05-21
Periodic micro-grooved organogel surfaces can easily realize the anisotropic sliding of water droplets attributing to the formed slippery water/oil/solid interface. Different from the existing anisotropic surfaces, this novel surface provides a versatile candidate for the anisotropic sliding of water droplets and might present a promising way for the easy manipulation of liquid droplets for water collection, liquid-directional transportation, and microfluidics.
Orthonormal bases for anisotropic α-modulation spaces
DEFF Research Database (Denmark)
Rasmussen, Kenneth Niemann
2012-01-01
In this article we construct orthonormal bases for bi-variate anisotropic α-modulation spaces. The construction is based on generating a nice anisotropic α-covering and using carefully selected tensor products of univariate brushlet functions with regards to this covering. As an application, we...... show that n-term nonlinear approximation with the orthonormal bases in certain anisotropic α-modulation spaces can be completely characterized....
Orthonormal bases for anisotropic α-modulation spaces
DEFF Research Database (Denmark)
Rasmussen, Kenneth Niemann
In this article we construct orthonormal bases for bi-variate anisotropic α-modulation spaces. The construction is based on generating a nice anisotropic α-covering and using carefully selected tensor products of univariate brushlet functions with regards to this covering. As an application, we...... show that n-term nonlinear approximation with the orthonormal bases in certain anisotropic α-modulation spaces can be completely characterized....
Sayem, Ayed Al; Mahdy, Mahdy Rahman Chowdhury; Rahman, Md. Saifur
2015-01-01
In this article, it has been theoretically shown that broad angle negative refraction is possible with asymmetric anisotropic metamaterials constructed by only dielectrics or loss less semiconductors at the telecommunication and relative wavelength range. Though natural uniaxial materials can exhibit negative refraction, the maximum angle of negative refraction and critical incident angle lie in a very narrow range. This notable problem can be overcome by our proposed structure. In our struct...
Accurate finite-difference time-domain simulation of anisotropic media by subpixel smoothing.
Oskooi, Ardavan F; Kottke, Chris; Johnson, Steven G
2009-09-15
Finite-difference time-domain methods suffer from reduced accuracy when discretizing discontinuous materials. We previously showed that accuracy can be significantly improved by using subpixel smoothing of the isotropic dielectric function, but only if the smoothing scheme is properly designed. Using recent developments in perturbation theory that were applied to spectral methods, we extend this idea to anisotropic media and demonstrate that the generalized smoothing consistently reduces the errors and even attains second-order convergence with resolution.
Buranasiri, Prathan
2005-04-01
Using barium titanate as the photorefractive material, we demonstrate phase conjugation, beam coupling, higher diffraction order generation. At small incident angles less than 0.015 radian, both codirectional isotropic self-diffraction (CODIS) and contradirectional isotropic self-diffraction (CONDIS) are generated simultaneously. At bigger incident angles approximately more than 0.2094 radian, only codirectional anisotropic-self diffraction (CODAS) are generated. On going imaging correlation is also showing.
Safety Factor of Anisotropic Bars in the Space of Generalized Forces
Sibgatullin, K. E.; Sibgatullin, E. S.
2017-01-01
Bars of arbitrary shape made of a homogeneous anisotropic material are considered. In the general case, in their cross section, nonzero are all internal force factors (IFF) — three forces and three moments. The values of the IFF are known from solutions of the corresponding problem. The safety factor for the load-carrying capacity of the beams is determined by comparing the known vector R ∗ of IFF with the corresponding desired strength vector R in the IFF space.
Barrett, John W; Nürnberg, Robert
2012-01-01
We introduce unconditionally stable finite element approximations for anisotropic Allen--Cahn and Cahn--Hilliard equations. These equations frequently feature in phase field models that appear in materials science. On introducing the novel fully practical finite element approximations we prove their stability and demonstrate their applicability with some numerical results. We dedicate this article to the memory of our colleague and friend Christof Eck (1968--2011) in recognition of his fundamental contributions to phase field models.
An eigen theory of static electromagnetic field for anisotropic media
Institute of Scientific and Technical Information of China (English)
Shao-hua GUO
2009-01-01
Static electromagnetic fields are studied based on standard spaces of the physical presentation,and the modal equations of static electromagnetic fields for anisotropic media are derived. By introducing a new set of first-order potential functions,several novel theoretical results are obtained. It is found that,for isotropic media,electric or magnetic potentials are scalar; while for anisotropic media,they are vectors. Magnitude and direction of the vector potentials are related to the anisotropic subspaces. Based on these results,we discuss the laws of static electromagnetic fields for anisotropic media.
ON THE ORIENTATION OF BUCKLING DIRECTION OF ANISOTROPIC ELASTIC PLATE UNDER UNIAXIAL COMPRESSION
Institute of Scientific and Technical Information of China (English)
Zhang Yitong
2001-01-01
The theory of small deformation superimposed on a large deformation of an elastic solid is used to investigate the buckling of anisotropic elastic plate under uniaxial compression. The buckling direction (the direction of buckling wave) is generally not aligned with the compression direction. The equation for determining the buckling direction is obtained. It is found that the out-of-plane buckling of anisotropic elastic plate is possible and both buckling conditions for flexural and extensional modes are presented. As a specific case of buckling of anisotropic elastic plate, the buckling of an orthotropic elastic plate subjected to a compression in a direction that forms an arbitrary angle with an elastic principal axis of the materials is analyzed. It is found that the buckling direction depends on the angle between the compression direction and the principal axis of the materials, the critical compressive force and plate-thickness parameters.In the case that the compression direction is aligned with the principal axis of the materials, the buckling direction will be aligned with the compression one irrespective of critical compressive force and plate-thickness.
Directory of Open Access Journals (Sweden)
V. C. Motresc
2004-01-01
Full Text Available The exposure of human body to electromagnetic fields has in the recent years become a matter of great interest for scientists working in the area of biology and biomedicine. Due to the difficulty of performing measurements, accurate models of the human body, in the form of a computer data set, are used for computations of the fields inside the body by employing numerical methods such as the method used for our calculations, namely the Finite Integration Technique (FIT. A fact that has to be taken into account when computing electromagnetic fields in the human body is that some tissue classes, i.e. cardiac and skeletal muscles, have higher electrical conductivity and permittivity along fibers rather than across them. This property leads to diagonal conductivity and permittivity tensors only when expressing them in a local coordinate system while in a global coordinate system they become full tensors. The Finite Integration Technique (FIT in its classical form can handle diagonally anisotropic materials quite effectively but it needed an extension for handling fully anisotropic materials. New electric voltages were placed on the grid and a new averaging method of conductivity and permittivity on the grid was found. In this paper, we present results from electrostatic computations performed with the extended version of FIT for fully anisotropic materials.
Motresc, V. C.; van Rienen, U.
2004-05-01
The exposure of human body to electromagnetic fields has in the recent years become a matter of great interest for scientists working in the area of biology and biomedicine. Due to the difficulty of performing measurements, accurate models of the human body, in the form of a computer data set, are used for computations of the fields inside the body by employing numerical methods such as the method used for our calculations, namely the Finite Integration Technique (FIT). A fact that has to be taken into account when computing electromagnetic fields in the human body is that some tissue classes, i.e. cardiac and skeletal muscles, have higher electrical conductivity and permittivity along fibers rather than across them. This property leads to diagonal conductivity and permittivity tensors only when expressing them in a local coordinate system while in a global coordinate system they become full tensors. The Finite Integration Technique (FIT) in its classical form can handle diagonally anisotropic materials quite effectively but it needed an extension for handling fully anisotropic materials. New electric voltages were placed on the grid and a new averaging method of conductivity and permittivity on the grid was found. In this paper, we present results from electrostatic computations performed with the extended version of FIT for fully anisotropic materials.
Anisotropic expansion and SNIa: An open issue
Directory of Open Access Journals (Sweden)
Jose Beltrán Jiménez
2015-02-01
Full Text Available We review the appropriateness of using SNIa observations to detect potential signatures of anisotropic expansion in the Universe. We focus on Union2 and SNLS3 SNIa datasets and use the hemispherical comparison method to detect possible anisotropic features. Unlike some previous works where non-diagonal elements of the covariance matrix were neglected, we use the full covariance matrix of the SNIa data, thus obtaining more realistic and not underestimated errors. As a matter of fact, the significance of previously claimed detections of a preferred direction in the Union2 dataset completely disappears once we include the effects of using the full covariance matrix. Moreover, we also find that such a preferred direction is aligned with the orthogonal direction of the SDSS observational plane and this suggests a clear indication that the SDSS subsample of the Union2 dataset introduces a significant bias, making the detected preferred direction unphysical. We thus find that current SNIa surveys are inappropriate to test anisotropic features due to their highly non-homogeneous angular distribution in the sky. In addition, after removal of the highest inhomogeneous sub-samples, the number of SNIa is too low. Finally, we take advantage of the particular distribution of SNLS SNIa sub-sample in the SNLS3 data set, in which the observations were taken along four different directions. We fit each direction independently and find consistent results at the 1σ level. Although the likelihoods peak at relatively different values of Ωm, the low number of data along each direction gives rise to large errors so that the likelihoods are sufficiently broad as to overlap within 1σ.
Computation of Large Anisotropic Seismic Heterogeneities (CLASH)
Beucler, Éric; Montagner, Jean-Paul
2006-05-01
A general tomographic technique is designed in order (i) to operate in anisotropic media; (ii) to account for the uneven seismic sampling and (iii) to handle massive data sets in a reasonable computing time. One modus operandi to compute a 3-D body wave velocity model relies on surface wave phase velocity measurements. An intermediate step, shared by other approaches, consists in translating, for each period of a given mode branch, the phase velocities integrated along ray paths into local velocity perturbations. To this end, we develop a method, which accounts for the azimuthal anisotropy in its comprehensive form. The weakly non-linear forward problem allows to use a conjugate gradient optimization. The Earth's surface is regularly discretized and the partial derivatives are assigned to the individual grid points. Possible lack of lateral resolution, due to the inescapable uneven ray path coverage, is taken into account through the a priori covariances on parameters with laterally variable correlation lengths. This method allows to efficiently separate the 2ψ and the 4ψ anisotropic effects from the isotropic perturbations. Fundamental mode and overtone phase velocity maps, derived with real Rayleigh wave data sets, are presented and compared with previous maps. The isotropic models concur well with the results of Trampert & Woodhouse. Large 4ψ heterogeneities are located in the tectonically active regions and over the continental lithospheres such as North America, Antarctica or Australia. At various periods, a significant 4ψ signature is correlated with the Hawaii hotspot track. Finally, concurring with the conclusions of Trampert & Woodhouse, our phase velocity maps show that Rayleigh wave data sets do need both 2ψ and 4ψ anisotropic terms.
Steady needle growth with 3-D anisotropic surface tension
Institute of Scientific and Technical Information of China (English)
Xiao-jun CHEN; Yong-qiang CHEN; Jian-pu XU; Jian-jun XU
2008-01-01
The effect of the anisotropic interracial en-ergy on dendritic growth has been an important sub-ject, and has preoccupied many researchers in the field of materials science and condensed matter physics. The present paper is dedicated to the study of the effect of full 3-D anisotropic Surface tension on the steady state solution of dendritic growth. We obtain the analytical form of the first order approximation solution in the reg-ular asymptotic expansion around the Ivantsov's nee-dle growth solution, which extends the steady needle growth solution of the system with isotropic surface ten-sion obtained by Xu and Yu (J. J. Xu and D. S. Yu, J. Cryst. Growth, 1998, 187: 314; J. J. Xu, Interfa-cial Wave Theory of Pattern Formation: Selection of Dendrite Growth and Viscous Fingering in a Hele-Shaw Flow, Berlin: Springer-Verlag, 1997).The solution is expanded in the general Laguerre se-ries in any finite region around the needle-tip, and it is also expanded in a power series in the far field behind the tip. Both solutions are then numerically matched in the intermediate region. Based on this global valid solution, the dependence of Peclet number Pe and the interface's morphology on the anisotropy parameter of surface ten-sion as well as other physical parameters involved are determined. On the basis of this global valid solution, we explore the effect of the anisotropy parameter on the Peclet number of growth, as well as the morphology of the interface.
On the Deflexion of Anisotropic Structural Composite Aerodynamic Components
Directory of Open Access Journals (Sweden)
J. Whitty
2014-01-01
Full Text Available This paper presents closed form solutions to the classical beam elasticity differential equation in order to effectively model the displacement of standard aerodynamic geometries used throughout a number of industries. The models assume that the components are constructed from in-plane generally anisotropic (though shown to be quasi-isotropic composite materials. Exact solutions for the displacement and strains for elliptical and FX66-S-196 and NACA 63-621 aerofoil approximations thin wall composite material shell structures, with and without a stiffening rib (shear-web, are presented for the first time. Each of the models developed is rigorously validated via numerical (Runge-Kutta solutions of an identical differential equation used to derive the analytical models presented. The resulting calculated displacement and material strain fields are shown to be in excellent agreement with simulations using the ANSYS and CATIA commercial finite element (FE codes as well as experimental data evident in the literature. One major implication of the theoretical treatment is that these solutions can now be used in design codes to limit the required displacement and strains in similar components used in the aerospace and most notably renewable energy sectors.
Ultrasonic Linear Motor with Anisotropic Composite
Institute of Scientific and Technical Information of China (English)
曾周末; 王新辉; 赵伯雷
2004-01-01
An idea to make up the vibrating body of ultrasonic motor with anisotropic composite is proposed and a linear piezoelectric motor is developed in this paper. Relative problems such as actuating mechanism, resonant frequency are discussed theoretically. According to the feature that impulse exists between the elastic body of composite ultrasonic linear motor and the base, an impulse analysis is presented to calculate the motor′s friction driving force and frictional conversion efficiency. The impulse analysis essentially explains the reason why the ultrasonic motor has great driving force, and can be applied to analyze the non-linear ultrasonic motor.
Wireless energy transfer between anisotropic metamaterials shells
Diaz-Rubio, Ana; Sanchez-Dehesa, Jose
2013-01-01
The behavior of strongly coupled Radial Photonic Crystals shells is investigated as a potential alternative to transfer electromagnetic energy wirelessly. These sub-wavelength resonant microstructures, which are based on anisotropic metamaterials, can produce efficient coupling phenomena due to their high quality factor. A configuration of selected constitutive parameters (permittivity and permeability) is analyzed in terms of its resonant characteristics. The coupling to loss ratio between two coupled resonators is calculated as a function of distance, the maximum (in excess of 300) is obtained when the shells are separated by three times their radius. Under practical conditions an 83% of maximum power transfer has been also estimated.
Anisotropic Density Estimation in Global Illumination
DEFF Research Database (Denmark)
Schjøth, Lars
2009-01-01
Density estimation employed in multi-pass global illumination algorithms gives cause to a trade-off problem between bias and noise. The problem is seen most evident as blurring of strong illumination features. This thesis addresses the problem, presenting four methods that reduce both noise...... and bias in estimates. Good results are obtained by the use of anisotropic filtering. Two methods handles the most common cases; filtering illumination reflected from object surfaces. One methods extends filtering to the temporal domain and one performs filtering on illumination from participating media...
On Radiative Fluids in Anisotropic Spacetimes
Shogin, Dmitry
2016-01-01
We apply the second-order Israel-Stewart theory of relativistic fluid- and thermodynamics to a physically realistic model of a radiative fluid in a simple anisotropic cosmological background. We investigate the asymptotic future of the resulting cosmological model and review the role of the dissipative phenomena in the early Universe. We demonstrate that the transport properties of the fluid alone, if described appropriately, do not explain the presently observed accelerated expansion of the Universe. Also, we show that, in constrast to the mathematical fluid models widely used before, the radiative fluid does approach local thermal equilibrium at late times, although very slowly, due to the cosmological expansion.
Multichannel image regularization using anisotropic geodesic filtering
Energy Technology Data Exchange (ETDEWEB)
Grazzini, Jacopo A [Los Alamos National Laboratory
2010-01-01
This paper extends a recent image-dependent regularization approach introduced in aiming at edge-preserving smoothing. For that purpose, geodesic distances equipped with a Riemannian metric need to be estimated in local neighbourhoods. By deriving an appropriate metric from the gradient structure tensor, the associated geodesic paths are constrained to follow salient features in images. Following, we design a generalized anisotropic geodesic filter; incorporating not only a measure of the edge strength, like in the original method, but also further directional information about the image structures. The proposed filter is particularly efficient at smoothing heterogeneous areas while preserving relevant structures in multichannel images.
Temperature and Polarization Patterns in Anisotropic Cosmologies
Sung, Rockhee
2010-01-01
We study the coherent temperature and polarization patterns produced in homogeneous but anisotropic cosmological models. We show results for all Bianchi types with a Friedman-Robertson-Walker limit (i.e. Types I, V, VII$_{0}$, VII$_{h}$ and IX) to illustrate the range of possible behaviour. We discuss the role of spatial curvature, shear and rotation in the geodesic equations for each model and establish some basic results concerning the symmetries of the patterns produced. We also give examples of the time-evolution of these patterns in terms of the Stokes parameters $I$, $Q$ and $U$.
Relativistic Cyclotron Instability in Anisotropic Plasmas
López, Rodrigo A.; Moya, Pablo S.; Navarro, Roberto E.; Araneda, Jaime A.; Muñoz, Víctor; Viñas, Adolfo F.; Alejandro Valdivia, J.
2016-11-01
A sufficiently large temperature anisotropy can sometimes drive various types of electromagnetic plasma micro-instabilities, which can play an important role in the dynamics of relativistic pair plasmas in space, astrophysics, and laboratory environments. Here, we provide a detailed description of the cyclotron instability of parallel propagating electromagnetic waves in relativistic pair plasmas on the basis of a relativistic anisotropic distribution function. Using plasma kinetic theory and particle-in-cell simulations, we study the influence of the relativistic temperature and the temperature anisotropy on the collective and noncollective modes of these plasmas. Growth rates and dispersion curves from the linear theory show a good agreement with simulations results.
Hydrodynamics of anisotropic quark and gluon fluids
Florkowski, Wojciech; Maj, Radoslaw; Ryblewski, Radoslaw; Strickland, Michael
2013-03-01
The recently developed framework of anisotropic hydrodynamics is generalized to describe the dynamics of coupled quark and gluon fluids. The quark and gluon components of the fluids are characterized by different dynamical anisotropy parameters. The dynamical equations describing such mixtures are derived from kinetic theory, with the collisional kernel treated in the relaxation-time approximation, allowing for different relaxation times for quarks and gluons. Baryon number conservation is enforced in the quark and antiquark components of the fluid, but overall parton number nonconservation is allowed in the system. The resulting equations are solved numerically in the (0+1)-dimensional boost-invariant case at zero and finite baryon density.
Hydrodynamics of anisotropic quark and gluon fluids
Florkowski, Wojciech; Ryblewski, Radoslaw; Strickland, Michael
2012-01-01
The recently developed framework of anisotropic hydrodynamics is generalized to describe the dynamics of coupled quark and gluon fluids. The quark and gluon components of the fluids are characterized by different dynamical anisotropy parameters. The dynamical equations describing such mixtures are derived from kinetic theory with the collisional kernel treated in the relaxation-time approximation. Baryon number conservation is enforced in the quark and anti-quark components of the fluid, but overall parton number non-conservation is allowed in the system. The resulting equations are solved numerically in the (0+1)-dimensional boost-invariant case at zero and finite baryon density.
Anisotropic Spin Cluster as a Qubit
Institute of Scientific and Technical Information of China (English)
YAN Xiao-Bo; WANG Ming-Ji
2007-01-01
We study an anisotropic spin cluster of 3 spin S=1/2 particles with antiferromagnetic exchange interaction with non-uniform coupling constants. A time-dependent magnetic field is applied to control the time evolution of the cluster. It is well known that for an odd number og sites a spin cluster qubit can be defined in terms of the ground state doublet. The universal one-qubit logic gate can be constructed from the time evolution operator of the non-autonomous many-body system, and the six basic one-qubit gates can be realized by adjusting the applied time-dependent magnetic field.
Generalized Jones matrices for anisotropic media.
Ortega-Quijano, Noé; Arce-Diego, José Luis
2013-03-25
The interaction of arbitrary three-dimensional light beams with optical elements is described by the generalized Jones calculus, which has been formally proposed recently [Azzam, J. Opt. Soc. Am. A 28, 2279 (2011)]. In this work we obtain the parametric expression of the 3×3 differential generalized Jones matrix (dGJM) for arbitrary optical media assuming transverse light waves. The dGJM is intimately connected to the Gell-Mann matrices, and we show that it provides a versatile method for obtaining the macroscopic GJM of media with either sequential or simultaneous anisotropic effects. Explicit parametric expressions of the GJM for some relevant optical elements are provided.
Charged Anisotropic Star on Paraboloidal Spacetime
Ratanpal, B S
2015-01-01
The charged anisotropic star on paraboloidal spacetime is reported by choosing particular form of radial pressure and electric field intensity. The non-singular solution of Einstein-Maxwell system of equation have been derived and it is shown that model satisfy all the physical plausibility conditions. It is observed that in the absence of electric field intensity, model reduces to particular case of uncharged Sharma \\& Ratanpal model. It is also observed that the parameter used in electric field intensity directly effects the mass of the star.
Self-organized motion in anisotropic swarms
Institute of Scientific and Technical Information of China (English)
Tianguang CHU; Long WANG; Tongwen CHEN
2003-01-01
This paper considers an anisotropic swarm model with a class of attraction and repulsion functions. It is shown that the members of the swarm will aggregate and eventually form a cohesive cluster of finite size around the swarm center. Moreover,It is also proved that under certain conditions, the swarm system can be completely stable, i. e., every solution converges to the equilibrium points of the system. The model and results of this paper extend a recent work on isotropic swarms to more general cases and provide further insight into the effect of the interaction pattern on self-organized motion in a swarm system.
A.V. Strizhachenko; Shul'ga, S. N.
2010-01-01
The electrodynamic and numerical analysis of eigen Q-factor of electromagnetic modes of E-type in waveguide junction of plain waveguides, fulfilled with anisotropic dielectric in depending on a permittivity tensor components and dielectric loss have been carried out in the paper. The recommendations on using of waveguide junctions for measurement of dielectric losses of the materials are given.
Energy Technology Data Exchange (ETDEWEB)
Gelinas, R.J.; Doss, S.K.; Carlson, N.N.
1985-01-01
This report describes a totally Eulerian code for anisotropic thermoelasticity (code name TECATE) which may be used in evaluations of prospective crystal media for high-average-power lasers. The present TECATE code version computes steady-state distributions of material temperatures, stresses, strains, and displacement fields in 2-D slab geometry. Numerous heat source and coolant boundary condition options are available in the TECATE code for laser design considerations. Anisotropic analogues of plane stress and plane strain evaluations can be executed for any and all crystal symmetry classes. As with all new and/or large physics codes, it is likely that some code imperfections will emerge at some point in time.
Scaling Argument of Anisotropic Random Walk
Institute of Scientific and Technical Information of China (English)
XU Bing-Zhen; JIN Guo-Jun; WANG Fei-Feng
2005-01-01
In this paper, we analytically discuss the scaling properties of the average square end-to-end distance for anisotropic random walk in D-dimensional space ( D ≥ 2), and the returning probability Pn(ro) for the walker into a certain neighborhood of the origin. We will not only give the calculating formula for and Pn (ro), but also point out that if there is a symmetric axis for the distribution of the probability density of a single step displacement, we always obtain ～ n, where ⊥ refers to the projections of the displacement perpendicular to each symmetric axes of the walk; in D-dimensional space with D symmetric axes perpendicular to each other, we always have ～ n and the random walk will be like a purely random motion; if the number of inter-perpendicular symmetric axis is smaller than the dimensions of the space, we must have ～ n2 for very large n and the walk will be like a ballistic motion. It is worth while to point out that unlike the isotropic random walk in one and two dimensions, which is certain to return into the neighborhood of the origin, generally there is only a nonzero probability for the anisotropic random walker in two dimensions to return to the neighborhood.
Finite-difference schemes for anisotropic diffusion
Energy Technology Data Exchange (ETDEWEB)
Es, Bram van, E-mail: es@cwi.nl [Centrum Wiskunde and Informatica, P.O. Box 94079, 1090GB Amsterdam (Netherlands); FOM Institute DIFFER, Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM (Netherlands); Koren, Barry [Eindhoven University of Technology (Netherlands); Blank, Hugo J. de [FOM Institute DIFFER, Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM (Netherlands)
2014-09-01
In fusion plasmas diffusion tensors are extremely anisotropic due to the high temperature and large magnetic field strength. This causes diffusion, heat conduction, and viscous momentum loss, to effectively be aligned with the magnetic field lines. This alignment leads to different values for the respective diffusive coefficients in the magnetic field direction and in the perpendicular direction, to the extent that heat diffusion coefficients can be up to 10{sup 12} times larger in the parallel direction than in the perpendicular direction. This anisotropy puts stringent requirements on the numerical methods used to approximate the MHD-equations since any misalignment of the grid may cause the perpendicular diffusion to be polluted by the numerical error in approximating the parallel diffusion. Currently the common approach is to apply magnetic field-aligned coordinates, an approach that automatically takes care of the directionality of the diffusive coefficients. This approach runs into problems at x-points and at points where there is magnetic re-connection, since this causes local non-alignment. It is therefore useful to consider numerical schemes that are tolerant to the misalignment of the grid with the magnetic field lines, both to improve existing methods and to help open the possibility of applying regular non-aligned grids. To investigate this, in this paper several discretization schemes are developed and applied to the anisotropic heat diffusion equation on a non-aligned grid.
Radial stability of anisotropic strange quark stars
Arbañil, José D. V.; Malheiro, M.
2016-11-01
The influence of the anisotropy in the equilibrium and stability of strange stars is investigated through the numerical solution of the hydrostatic equilibrium equation and the radial oscillation equation, both modified from their original version to include this effect. The strange matter inside the quark stars is described by the MIT bag model equation of state. For the anisotropy two different kinds of local anisotropic σ = pt-pr are considered, where pt and pr are respectively the tangential and the radial pressure: one that is null at the star's surface defined by pr(R) = 0, and one that is nonnull at the surface, namely, σs = 0 and σs ≠ 0. In the case σs = 0, the maximum mass value and the zero frequency of oscillation are found at the same central energy density, indicating that the maximum mass marks the onset of the instability. For the case σs ≠ 0, we show that the maximum mass point and the zero frequency of oscillation coincide in the same central energy density value only in a sequence of equilibrium configurations with the same value of σs. Thus, the stability star regions are determined always by the condition dM/dρc > 0 only when the tangential pressure is maintained fixed at the star surface's pt(R). These results are also quite important to analyze the stability of other anisotropic compact objects such as neutron stars, boson stars and gravastars.
DECAY OF ENERGY FOR A DISSIPATIVE ANISOTROPIC ELASTIC SYSTEM
Institute of Scientific and Technical Information of China (English)
Qin Yuming; Liu Xin; Deng Shuxian
2011-01-01
In this article, we study the large-time behavior of energy for a N-dimensional dissipative anisotropic elastic system. By means of multiplicative techniques, energy method, and Zuazua's estimate technique, we prove the decay property of energy for anisotropic elastic system.
Some Weighted Hardy-Type Inequalities on Anisotropic Heisenberg Groups
Directory of Open Access Journals (Sweden)
Yang Qiao-Hua
2011-01-01
Full Text Available We prove some weighted Hardy type inequalities associated with a class of nonisotropic Greiner-type vector fields on anisotropic Heisenberg groups. As an application, we get some new Hardy type inequalities on anisotropic Heisenberg groups which generalize a result of Yongyang Jin and Yazhou Han.
SUPERCONVERGENCE ANALYSIS OF A NONCONFORMING TRIANGULAR ELEMENT ON ANISOTROPIC MESHES
Institute of Scientific and Technical Information of China (English)
Dongyang SHI; Hui LIANG; Caixia WANG
2007-01-01
The class of anisotropic meshes we conceived abandons the regular assumption. Some distinct properties of Carey's element are used to deal with the superconvergence for a class of twodimensional second-order elliptic boundary value problems on anisotropic meshes. The optimal results are obtained and numerical examples are given to confirm our theoretical analysis.
Optical anisotropic reflectance from W720 LIPSS surface
Silvennoinen, Martti; Penttinen, Niko; Hasoň, Stanislav; Silvennoinen, Raimo
2013-05-01
Optical anisotropic reflectance from laser induced periodic surface structures (LIPSS) of stainless steel (W720LIPSS), which were produced by a femtosecond laser, were investigated by using polarized probe beam in a spectrophotometer. Remarkable repeatability in optical anisotropic reflectance was recognized.
Holographic Wilson loops in anisotropic quark-gluon plasma.
Ageev, Dmitry
2016-10-01
The nonequilibrium properties of the anisotropic quark-gluon plasma are condidered from the holographic viewpoint. Lifshitz-like solution is considered as a holographic dual of anisotropic QGP. The black brane formation in such background is considered as a thermalization in dual theory. As a probe of thermalization we consider rectangular spatial Wilson loops with different orientation.
Holographic Wilson loops in anisotropic quark-gluon plasma.
Directory of Open Access Journals (Sweden)
Ageev Dmitry
2016-01-01
Full Text Available The nonequilibrium properties of the anisotropic quark-gluon plasma are condidered from the holographic viewpoint. Lifshitz-like solution is considered as a holographic dual of anisotropic QGP. The black brane formation in such background is considered as a thermalization in dual theory. As a probe of thermalization we consider rectangular spatial Wilson loops with different orientation.
Anisotropic Flow Measurements in ALICE at the Large Hadron Collider
Bilandzic, A.
2012-01-01
Anisotropic ﬂow is one of the observables which is sensitive to the properties of the created hot and dense system in heavy-ion collisions. In noncentral heavy-ion collisions the initial volume of the interacting system is anisotropic in coordinate space. Due to multiple interactions this anisotropy
Interpolation theory of anisotropic finite elements and applications
Institute of Scientific and Technical Information of China (English)
2008-01-01
Interpolation theory is the foundation of finite element methods.In this paper,after reviewing some existed interpolation theorems of anisotropic finite element methods,we present a new way to analyse the interpolation error of anisotropic elements based on Newton’s formula of polynomial interpolation as well as its applications.
Symmetric Periodic Solutions of the Anisotropic Manev Problem
Santoprete, Manuele
2002-01-01
We consider the Manev Potential in an anisotropic space, i.e., such that the force acts differently in each direction. Using a generalization of the Poincare' continuation method we study the existence of periodic solutions for weak anisotropy. In particular we find that the symmetric periodic orbits of the Manev system are perturbed to periodic orbits in the anisotropic problem.
Interpolation theory of anisotropic finite elements and applications
Institute of Scientific and Technical Information of China (English)
CHEN ShaoChun; XIAO LiuChao
2008-01-01
Interpolation theory is the foundation of finite element methods. In this paper, after reviewing some existed interpolation theorems of anisotropic finite element methods, we present a new way to analyse the interpolation error of anisotropic elements based on Newton's formula of polynomial interpolation as well as its applications.
THE SUPERCONVERGENCE ANALYSIS OF AN ANISOTROPIC FINITE ELEMENT
Institute of Scientific and Technical Information of China (English)
SHI Dongyang; ZHU Huiqing
2005-01-01
This paper deals with the high accuracy analysis of bilinear finite element on the class of anisotropic rectangular meshes. The inverse inequalities on anisotropic meshes are established. The superclose and the superconvergence are obtained for the second order elliptic problem. A numerical test is given, which coincides with our theoretical analysis.
Photoconductivity in Dirac materials
Energy Technology Data Exchange (ETDEWEB)
Shao, J. M.; Yang, G. W., E-mail: stsygw@mail.sysu.edu.cn [State Key Laboratory of Optoelectronic Materials and Technologies, Nanotechnology Research Center, School of Materials & Engineering, School of Physics & Engineering, Sun Yat-sen University, Guangzhou 510275, Guangdong (China)
2015-11-15
Two-dimensional (2D) Dirac materials including graphene and the surface of a three-dimensional (3D) topological insulator, and 3D Dirac materials including 3D Dirac semimetal and Weyl semimetal have attracted great attention due to their linear Dirac nodes and exotic properties. Here, we use the Fermi’s golden rule and Boltzmann equation within the relaxation time approximation to study and compare the photoconductivity of Dirac materials under different far- or mid-infrared irradiation. Theoretical results show that the photoconductivity exhibits the anisotropic property under the polarized irradiation, but the anisotropic strength is different between 2D and 3D Dirac materials. The photoconductivity depends strongly on the relaxation time for different scattering mechanism, just like the dark conductivity.
Photoconductivity in Dirac materials
Directory of Open Access Journals (Sweden)
J. M. Shao
2015-11-01
Full Text Available Two-dimensional (2D Dirac materials including graphene and the surface of a three-dimensional (3D topological insulator, and 3D Dirac materials including 3D Dirac semimetal and Weyl semimetal have attracted great attention due to their linear Dirac nodes and exotic properties. Here, we use the Fermi’s golden rule and Boltzmann equation within the relaxation time approximation to study and compare the photoconductivity of Dirac materials under different far- or mid-infrared irradiation. Theoretical results show that the photoconductivity exhibits the anisotropic property under the polarized irradiation, but the anisotropic strength is different between 2D and 3D Dirac materials. The photoconductivity depends strongly on the relaxation time for different scattering mechanism, just like the dark conductivity.
Umeda, Minoru; Katagiri, Mitsuhiko; Shironita, Sayoko; Nagayama, Norio
2016-12-01
This paper reports the anisotropic hole transport at the triphenylamine-derivative single crystal surface prepared by a solution method. Triphenylamine derivatives are commonly used in a hole-transport material for organic photoconductors of laser-beam printers, in which the materials are used as an amorphous form. For developing organic photovoltaics using the photoconductor's technology, preparation of a single crystal seems to be a specific way by realizing the high mobility of an organic semiconductor. In this study, a single crystal of 4-(2,2-diphenylethenyl)-N,N-bis(4-methylphenyl)-benzenamine (TPA) was prepared and its anisotropic hole-transport property measured. First, the hole-transport property of the TPA was investigated based on its chemical structure and electrochemical redox characteristics. Next, a large-scale single crystal formation at a high rate was developed by employing a solution method based on its solubility and supersolubility curves. The grown TPA was found to be a single crystal based on the polarization micrograph observation and crystallographic analysis. For the TPA single crystal, an anisotropic surface conduction was found, which was well explained by its molecular stack structure. The measured current in the long-axis direction is one order of magnitude greater than that of amorphous TPA.
Kottke, Chris; Farjadpour, Ardavan; Johnson, Steven G
2008-03-01
We derive a correct first-order perturbation theory in electromagnetism for cases where an interface between two anisotropic dielectric materials is slightly shifted. Most previous perturbative methods give incorrect results for this case, even to lowest order, because of the complicated discontinuous boundary conditions on the electric field at such an interface. Our final expression is simply a surface integral, over the material interface, of the continuous field components from the unperturbed structure. The derivation is based on a "localized" coordinate-transformation technique, which avoids both the problem of field discontinuities and the challenge of constructing an explicit coordinate transformation by taking the limit in which the coordinate perturbation is infinitesimally localized around the boundary. Not only is our result potentially useful in evaluating boundary perturbations, e.g., from fabrication imperfections, in highly anisotropic media such as many metamaterials, but it also has a direct application in numerical electromagnetism. In particular, we show how it leads to a subpixel smoothing scheme to ameliorate staircasing effects in discretized simulations of anisotropic media, in such a way as to greatly reduce the numerical errors compared to other proposed smoothing schemes.
Anisotropic Diffusion in Mesh-Free Numerical Magnetohydrodynamics
Hopkins, Philip F
2016-01-01
We extend recently-developed mesh-free Lagrangian methods for numerical magnetohydrodynamics (MHD) to arbitrary anisotropic diffusion equations, including: passive scalar diffusion, Spitzer-Braginskii conduction and viscosity, cosmic ray diffusion/streaming, anisotropic radiation transport, non-ideal MHD (Ohmic resistivity, ambipolar diffusion, the Hall effect), and turbulent 'eddy diffusion.' We study these as implemented in the code GIZMO for both new meshless finite-volume Godunov schemes (MFM/MFV) as well as smoothed-particle hydrodynamics (SPH). We show the MFM/MFV methods are accurate and stable even with noisy fields and irregular particle arrangements, and recover the correct behavior even in arbitrarily anisotropic cases. They are competitive with state-of-the-art AMR/moving-mesh methods, and can correctly treat anisotropic diffusion-driven instabilities (e.g. the MTI and HBI, Hall MRI). We also develop a new scheme for stabilizing anisotropic tensor-valued fluxes with high-order gradient estimators ...
An anisotropic negative refractive index medium operated at multiple-angle incidences.
Yang, Tien-Chung; Yang, Yu-Hang; Yen, Ta-Jen
2009-12-21
Recently metamaterials have been demonstrating new physics to enable various unprecedented electromagnetic properties, but pratically they are so sensitive to incident angles of the external excitation that their applications are restricted. Therefore, we present an anisotropic negative refractive index medium operated at multiple-angle incidences (NRIM for MAI) to ease such a burden. Both the simulated and measured transmittance, reflectance and the corresponding material parameters indicate that our structure does possess the anisotropic negative refractive index with respect to different incident angles. In addition, the opposite directions of group and phase velocities are also demonstrated under both grazing-angle, normal and 45-degree incidences to further verify the negative refractive index of the designed monolithic NRIM structure for multiple-angle incidences.
Yoshida, Satoru; Takinoue, Masahiro; Iwase, Eiji; Onoe, Hiroaki
2016-08-01
This paper describes a system through which the self-assembly of anisotropic hydrogel microparticles is achieved, which also enables dynamic transformation of the assembled structures. Using a centrifuge-based microfluidic device, anisotropic hydrogel microparticles encapsulating superparamagnetic materials on one side are fabricated, which respond to a magnetic field. We successfully achieve dynamic assembly using these hydrogel microparticles and realize three different self-assembled structures (single and double pearl chain structures, and close-packed structures), which can be transformed to other structures dynamically via tuning of the precessional magnetic field. We believe that the developed system has potential application as an effective platform for a dynamic cell manipulation and cultivation system, in biomimetic autonomous microrobot organization, and that it can facilitate further understanding of the self-organization and complex systems observed in nature.
Energy Technology Data Exchange (ETDEWEB)
Cheng, Guang; Sun, Xin; Wang, Yuxin; Tay, See Leng; Gao, Wei
2017-01-01
A new inverse method was proposed to calculate the anisotropic elastic-plastic properties (flow stress) of thin electrodeposited Ag coating utilizing nanoindentation tests, previously reported inverse method for isotropic materials and three-dimensional (3-D) finite element analyses (FEA). Indentation depth was ~4% of coating thickness (~10 μm) to avoid substrate effect and different indentation responses were observed in the longitudinal (L) and the transverse (T) directions. The estimated elastic-plastic properties were obtained in the newly developed inverse method by matching the predicted indentation responses in the L and T directions with experimental measurements considering indentation size effect (ISE). The results were validated with tensile flow curves measured from free-standing (FS) Ag film. The current method can be utilized to characterize the anisotropic elastic-plastic properties of coatings and to provide the constitutive properties for coating performance evaluations.
Necking of anisotropic micro-films with strain-gradient effects
Institute of Scientific and Technical Information of China (English)
Brian Nyvang Legarth
2008-01-01
Necking of stubby micro-films of aluminum is investigated numerically by considering tension of a speci-men with an initial imperfection used to onset localisation. Plastic anisotropy is represented by two different yield cri-teria and strain-gradient effects are accounted for using the visco-plastic finite strain model. Furthermore, the model is extended to isotropic anisotropic hardening (evolving aniso-tropy). For isotropic hardening plastic anisotropy affects the predicted overall nominal stress level, while the peak stress remains at an overall logarithmic strain corresponding to the hardening exponent. This holds true for both local and non-local materials. Anisotropic hardening delays the point of maximum overall nominal stress.
Radial vibration of free anisotropic nanoparticles based on nonlocal continuum mechanics.
Ghavanloo, Esmaeal; Fazelzadeh, S Ahmad
2013-02-22
Radial vibration of spherical nanoparticles made of materials with anisotropic elasticity is theoretically investigated using nonlocal continuum mechanics. The anisotropic elastic model is reformulated using the nonlocal differential constitutive relations of Eringen. The nonlocal differential equation of radial motion is derived in terms of radial displacement. Cubic, hexagonal, trigonal and tetragonal symmetries of the elasticity are discussed. The suggested model is justified by a good agreement between the results given by the present model and available experimental data. Furthermore, the model is used to elucidate the effect of small scale on the vibration of several nanoparticles. Our results show that the small scale is essential for the radial vibration of the nanoparticles when the nanoparticle radius is smaller than 1.5 nm.
Jisha, Chandroth Pannian; Marrucci, Lorenzo; Assanto, Gaetano
2016-01-01
We discuss the propagation of an electromagnetic field in a inhomogeneously rotated anisotropic material. Rotation is taken invariant along the propagation direction, the latter corresponding to the rotation axis as well. In such a configuration, electromagnetic evolution is dictated by the Pancharatnam-Berry phase (PBP), responsible for the appearance of an effective photonic potential. In the accompanying paper [A. Alberucci et al., "Electromagnetic confinement via spin-orbit interaction in anisotropic dielectrics"] we demonstrate that the effective potential support transverse confinement of light. Here we find the profile of the quasi-modes and we show that the photonic potential arises from the Kapitza effect. Theoretical results are confirmed by numerical simulations, with particular attention to the dependence on the medium birefringence. Finally, we investigate a configuration capable to support non-leaky guided modes.
Baryshevsky, V G
2013-01-01
This paper considers the refraction and diffraction of waves in three-dimensional crystals formed by anisotropically scattering centers. The partial wave expansion method is used to consider the effect of multiple rescattering of waves by centers composing a crystal. The expression for the refractive index of a crystal is derived. It is shown that instead of the diagonal elements of the scattering matrix $\\mathbf{T}$, appearing in the expression for the refractive index of a chaotic medium, the derived expression includes the diagonal elements of the reaction matrix $\\mathbf{K}$. This fact is taken into account in writing the equations describing the dynamical diffraction of waves in a crystal. The results can be of interest for research into, e.g., diffraction of cold neutrons and photons in crystals, nanocrystalline materials, as well as for the description of parametric and diffraction radiation in electromagnetic crystals formed by anisotropically scattering centers.
Group classification and conservation laws of anisotropic wave equations with a source
Ibragimov, N. H.; Gandarias, M. L.; Galiakberova, L. R.; Bruzon, M. S.; Avdonina, E. D.
2016-08-01
Linear and nonlinear waves in anisotropic media are useful in investigating complex materials in physics, biomechanics, biomedical acoustics, etc. The present paper is devoted to investigation of symmetries and conservation laws for nonlinear anisotropic wave equations with specific external sources when the equations in question are nonlinearly self-adjoint. These equations involve two arbitrary functions. Construction of conservation laws associated with symmetries is based on the generalized conservation theorem for nonlinearly self-adjoint partial differential equations. First we calculate the conservation laws for the basic equation without any restrictions on the arbitrary functions. Then we make the group classification of the basic equation in order to specify all possible values of the arbitrary functions when the equation has additional symmetries and construct the additional conservation laws.
Thermal Stresses in an Anisotropic Thin Plate Subjected to Moving Plane Heat Sources
Directory of Open Access Journals (Sweden)
Malak Naji
2014-04-01
Full Text Available The aim of this study is to numerically simulate the plane moving heat source through anisotropic mild steal thin plate. Heat conduction problems in anisotropic material, where the thermal conductivity varies with direction and involving a moving heat source have several industrial applications, such like metal cutting, flame or laser hardening of metals, welding and others. The parabolic heat conduction model is used for the prediction of the temperature history. The temperature distribution inside the plate is determined from the solution of heat equation. Thus, the heat equation is solved numerically using finite deference method and the temperature distributions are determined. The thermal stresses in this case are, also, investigated and computed numerically. It is found that the thermal conductivity ratio affect in both temperature and thermal stresses distributions, in additional to the speed and heat source intensity.
Constitutive relation of weakly anisotropic polycrystal with microstructure and initial stress
Institute of Scientific and Technical Information of China (English)
Mojia Huang; Hua Zhan; Xiuqiao Lin; Hai Tang
2007-01-01
Man (Nondestr Test Eval 15:191-214, 1999) derived the constitutive relation of a weakly-textured orthorhombic aggregate of cubic crystallites with effects of microstructure and initial stress. In this paper, a computational expression on the integration ∫SO(3)Qh× Dl m0 is given. Then, by means of the computational expression, the general constitutive relation of a weakly-textured anisotropic polycrystal with the consideration of microstructure and initial stress is derived. As special cases of our general constitutive relation, two constitutive relations are given for an isotropic polycrystal and a weakly-textured anisotropic aggregate of cubic crystallites. The acoustoelastic tensor of the reference cubic crystal is derived to determine the material constants of the polycrystal. Two examples are given for understanding the physical meaning of the texture coefficients and the constitutive relations.
Ultrasonic guided wave nondestructive evaluation using generalized anisotropic interface waves
Gardner, Michael D.
The motivation for this work is a goal to inspect interfaces between thick layers of materials that can be anisotropic. The specific application is a thick composite bonded to a metal substrate. The interface is inspected for disbonds between the metal and composite. The large thickness allows the problem to be modeled as a half space. The theory behind guided waves in plates is presented. This theory includes the calculation and analysis of dispersion curves and the resulting wave structure. It is noted that for high frequency-thickness values, certain modes will converge to the half-space waves, e.g. the Rayleigh wave and the Stoneley wave. Points of high energy, especially shear energy, at the interface are desirable for interfacial inspection. Therefore, the wave structure for all modes and frequencies is searched for ideal inspection points. Interface waves are inherently good modes to use for interface inspection. Results from the dispersion curves and wave structures are verified in the finite element model software package called Abaqus. It is confirmed that the group speeds and wave structures of the modes match the predicted values. A theoretical development of interface waves is given wherein Rayleigh, Stoneley, and generalized interface waves are discussed. This is applied to both isotropic and anisotropic materials. It is shown that the Stoneley wave only exists for a certain range of material parameters. Because the Stoneley wave is the interface wave between two solid half spaces, it might appear that only certain pairs of solids would allow for inspection via interface wave. However, it is shown that for perturbations of the Stoneley-wave-valid material properties, interface waves which leak energy away from the interface can still propagate. They can also be used for inspection. Certain choices of materials will leak less energy and will therefore allow for longer inspection distances. The solutions to the isotropic leaky wave problem exist on
Anisotropic phenomena in gauge/gravity duality
Energy Technology Data Exchange (ETDEWEB)
Zeller, Hansjoerg
2014-05-26
In this thesis we use gauge/gravity duality to model anisotropic effects realised in nature. Firstly we analyse transport properties in holographic systems with a broken rotational invariance. Secondly we discuss geometries dual to IR fixed points with anisotropic scaling behaviour, which are related to quantum critical points in condensed matter systems. Gauge/gravity duality relates a gravity theory in Anti-de Sitter space to a lower dimensional strongly coupled quantum field theory in Minkowski space. Over the past decade this duality provided many insights into systems at strong coupling, e.g. quark-gluon plasma and condensed matter close to quantum critical points. One very important result computed in this framework is the value of the shear viscosity divided by the entropy density in strongly coupled theories. The quantitative result agrees very well with measurements of the ratio in quark-gluon plasma. However, for isotropic two derivative Einstein gravity it is temperature independent. We show that by breaking the rotational symmetry of a system we obtain a temperature dependent shear viscosity over entropy density. This is important to make contact with real world systems, since substances in nature display such dependence. In addition, we derive various transport properties in strongly coupled anisotropic systems using the gauge/gravity dictionary. The most notable results include an electrical conductivity with Drude behaviour in the low frequency region. This resembles conductors with broken translational invariance. However, we did not implement the breaking explicitly. Furthermore, our analysis shows that this setup models effects, resembling the piezoelectric and exoelectric effects, known from liquid crystals. In a second project we discuss a geometry with non-trivial scaling behaviour in order to model an IR fixed point of condensed matter theories. We construct the UV completion of this geometry and analyse its properties by computing the
Then, C; Stassen, B; Depta, K; Silber, G
2017-02-21
Mechanical characterization of human superficial facial tissue has important applications in biomedical science, computer assisted forensics, graphics, and consumer goods development. Specifically, the latter may include facial hair removal devices. Predictive accuracy of numerical models and their ability to elucidate biomechanically relevant questions depends on the acquisition of experimental data and mechanical tissue behavior representation. Anisotropic viscoelastic behavioral characterization of human facial tissue, deformed in vivo with finite strain, however, is sparse. Employing an experimental-numerical approach, a procedure is presented to evaluate multidirectional tensile properties of superficial tissue layers of the face in vivo. Specifically, in addition to stress relaxation, displacement-controlled multi-step ramp-and-hold protocols were performed to separate elastic from inelastic properties. For numerical representation, an anisotropic hyperelastic material model in conjunction with a time domain linear viscoelasticity formulation with Prony series was employed. Model parameters were inversely derived, employing finite element models, using multi-criteria optimization. The methodology provides insight into mechanical superficial facial tissue properties. Experimental data shows pronounced anisotropy, especially with large strain. The stress relaxation rate does not depend on the loading direction, but is strain-dependent. Preconditioning eliminates equilibrium hysteresis effects and leads to stress-strain repeatability. In the preconditioned state tissue stiffness and hysteresis insensitivity to strain rate in the applied range is evident. The employed material model fits the nonlinear anisotropic elastic results and the viscoelasticity model reasonably reproduces time-dependent results. Inversely deduced maximum anisotropic long-term shear modulus of linear elasticity is G∞,max(aniso)=2.43kPa and instantaneous initial shear modulus at an
Takizawa, Hideo; Kuwabara, Toshihiko; Oide, Kai; Yoshida, Junji
2016-08-01
Numerous types of yield functions have been proposed to describe the shape of a realistic yield surface. Major commercial finite element codes include few anisotropic functions. Alternatively, the codes allow users to implement material models through user- subroutines. We develop the Unified Material Model Driver for Plasticity (UMMDp) subroutine library, which enables users to implement an arbitrary yield function easily. In this paper, the framework of the UMMDp is presented and its availabilities is shown through examples of sheet metal forming analyses.
Creating Statistically Anisotropic and Inhomogeneous Perturbations
Armendariz-Picon, C
2007-01-01
In almost all structure formation models, primordial perturbations are created within a homogeneous and isotropic universe, like the one we observe. Because their ensemble averages inherit the symmetries of the spacetime in which they are seeded, cosmological perturbations then happen to be statistically isotropic and homogeneous. Certain anomalies in the cosmic microwave background on the other hand suggest that perturbations do not satisfy these statistical properties, thereby challenging perhaps our understanding of structure formation. In this article we relax this tension. We show that if the universe contains an appropriate triad of scalar fields with spatially constant but non-zero gradients, it is possible to generate statistically anisotropic and inhomogeneous primordial perturbations, even though the energy momentum tensor of the triad itself is invariant under translations and rotations.
Anisotropic compact stars in Karmarkar spacetime
Singh, Ksh Newton; Govender, M
2016-01-01
We present a new class of solutions to the Einstein field equations for an anisotropic matter distribution in which the interior space-time obeys the Karmarkar condition. The necessary and sufficient condition required for a spherically symmetric space-time to be of class one reduces the gravitational behavior of the model to a single metric function. By assuming a physically viable form for the $g_{rr}$ metric potential we obtain an exact solution of the Einstein field equations which is free from any singularities and satisfies all the physical criteria. We utilize this solution to predict the masses and radii of well-known compact objects such as Cen X-3, PSR J0348+0432, PSRB0943+10 and XTE J1739-285. To be publish in Chinese Physics C (Accepted)
Plasmons in Anisotropic Quark-Gluon Plasma
Carrington, Margaret E; Mrowczynski, Stanislaw
2014-01-01
Plasmons of quark-gluon plasma - gluon collective modes - are systematically studied. The plasma is, in general, non-equilibrium but homogeneous. We consider anisotropic momentum distributions of plasma constituents which are obtained from the isotropic one by stretching or squeezing in one direction. This leads to prolate or oblate distributions, respectively. We study all possible degrees of one dimensional deformation from the extremely prolate case, when the momentum distribution is infinitely elongated in one direction, to the extremely oblate distribution, which is infinitely squeezed in the same direction. In between these extremes we discuss arbitrarily prolate, weakly prolate, isotropic, weakly oblate and arbitrarily oblate distributions. For each case, the number of modes is determined using a Nyquist analysis and the complete spectrum of plasmons is found analytically if possible, and numerically when not. Unstable modes are shown to exist in all cases except that of isotropic plasma. We derive con...
Quench dynamics of the anisotropic Heisenberg model.
Liu, Wenshuo; Andrei, Natan
2014-06-27
We develop an analytical approach for the study of the quench dynamics of the anisotropic Heisenberg model (XXZ model) on the infinite line. We present the exact time-dependent wave functions after a quench in an integral form for any initial state and for any anisotropy Δ by means of a generalized Yudson contour representation. We calculate the evolution of several observables from two particular initial states: starting from a local Néel state we calculate the time evolution of the antiferromagnetic order parameter-staggered magnetization; starting from a state with consecutive flipped spins (1) we calculate the evolution of the local magnetization and express it in terms of the propagation of magnons and bound state excitations, and (2) we predict the evolution of the induced spin currents. These predictions can be confronted with experiments in ultracold gases in optical lattices. We also show how the "string" solutions of Bethe ansatz equations emerge naturally from the contour approach.
Anisotropic magnetic fluctuations in 3-k antiferromagnets
Energy Technology Data Exchange (ETDEWEB)
Caciuffo, R. [European Commission, Joint Research Center, Institute for Transuranium Elements, Postfach 2340, Karlsruhe D-76125 (Germany)]. E-mail: roberto.caciuffo@ec.europa.eu; Magnani, N. [European Commission, Joint Research Center, Institute for Transuranium Elements, Postfach 2340, Karlsruhe D-76125 (Germany); Istituto dei Materiali per l' Elettronica ed il Magnetismo, Consiglio Nazionale delle Ricerche, I-43010 Fontanini (PR) (Italy); Santini, P. [Dipartimento di Fisica, Universita di Parma, Viale G. P. Usberti 7/A, I-43100 Parma (Italy); Carretta, S. [Dipartimento di Fisica, Universita di Parma, Viale G. P. Usberti 7/A, I-43100 Parma (Italy); Amoretti, G. [Dipartimento di Fisica, Universita di Parma, Viale G. P. Usberti 7/A, I-43100 Parma (Italy); Blackburn, E. [European Commission, Joint Research Center, Institute for Transuranium Elements, Postfach 2340, Karlsruhe D-76125 (Germany); Institute Laue-Langevin, Boite Postal 156-X, F-38042 Grenoble Cedex (France); Enderle, M. [Institute Laue-Langevin, Boite Postal 156-X, F-38042 Grenoble Cedex (France); Brown, P.J. [Institute Laue-Langevin, Boite Postal 156-X, F-38042 Grenoble Cedex (France); Lander, G.H. [European Commission, Joint Research Center, Institute for Transuranium Elements, Postfach 2340, Karlsruhe D-76125 (Germany)
2007-03-15
The anisotropy of magnetic fluctuations propagating along the high-symmetry directions in cubic systems with 3-k magnetic order is analyzed within the random-phase approximation assuming anisotropic exchange interactions. Both transverse and longitudinal structures are considered, with reference to the UO{sub 2} and USb compounds, respectively. In the case of UO{sub 2}, the spin-waves polarizations calculated for acoustic and optical branches are favorably compared with three-dimensional polarization analysis experiments carried out on a triple axis spectrometer. The overall spin-waves polarization behavior emerges as a consequence of the 3-k nature of the magnetic order, whatever the strength of the exchange coupling assumed.
Transport processes in anisotropic gravitational collapse
Martínez, J
1996-01-01
In this paper we introduce a new method to study the influence of thermal conduction and viscous processes in anisotropic gravitational collapse. To this end we employ the HJR method to solve the Einstein equations. The Maxwell-Cattaneo type transport equations are used to find the temperature and bulk and shear viscous pressures. Under some conditions Maxwell-Cattaneo transport equations comply with relativistic causality. Thus, it is advisable to use them instead of Eckart transport equations. In the inner layers of the star the temperature ceases to be sensitive to the boundary condition. This behavior, which can be explained in terms of the Eddington approximation, allows us to find the thickness of the neutrinosphere. The dynamics of collapsing dense stars is deeply influenced by the neutrino emission/absorption processes. These cool the star and drive it to a new equilibrium state. Therefore, the calculation of transport coefficients is based on these processes.
Particle Behavior at Anisotropically Curved Liquid Interfaces
McEnnis, Kathleen; Zeng, Chuan; Davidovitch, Benny; Dinsmore, Anthony; Russell, Thomas
2011-03-01
A particle bound to an anisotropically curved liquid interface, such as a cylinder or catenoid, cannot maintain a constant contact angle without deforming the interface. Theory suggests that the particles will experience a force that depends on the interfacial shape and migrate to minimize the total interfacial energy. To test these predictions, particles were deposited on top of liquid semi-cylinders of ionic liquid or melted polystyrene confined on chemically patterned surfaces. Particles were also deposited on liquid catenoid structures created by placing a melted polymer film under an electric field. The location of the particles on these structures was observed by optical, confocal, and scanning electron microscopy. The implications for the directed assembly of particles and stability of Pickering emulsions are also discussed.
Recent developments in anisotropic heterogeneous shell theory
Grigorenko, Alexander Ya; Grigorenko, Yaroslav M; Vlaikov, Georgii G
2016-01-01
This volume focuses on the relevant general theory and presents some first applications, namely those based on classical shell theory. After a brief introduction, during which the history and state-of-the-art are discussed, the first chapter presents the mechanics of anisotropic heterogeneous shells, covering all relevant assumptions and the basic relations of 3D elasticity, classical and refined shell models. The second chapter examines the numerical techniques that are used, namely discrete orthogonalization, spline-collocation and Fourier series, while the third highlights applications based on classical theory, in particular, the stress-strain state of shallow shells, non-circular shells, shells of revolution, and free vibrations of conical shells. The book concludes with a summary and an outlook bridging the gap to the second volume.
Anisotropic dynamic mass density for fluidsolid composites
Wu, Ying
2012-10-01
By taking the low frequency limit of multiple-scattering theory, we obtain the dynamic effective mass density of fluidsolid composites with a two-dimensional rectangular lattice structure. The anisotropic mass density can be described by an angle-dependent dipole solution, to the leading-order of solid concentration. The angular dependence vanishes for the square lattice, but at high solid concentrations there is a structure-dependent factor that contributes to the leading-order solution. In all cases, Woods formula is found to be accurately valid for the effective bulk modulus, independent of the structures. Numerical evaluations from the solutions are shown to be in excellent agreement with finite-element simulations. © 2012 Elsevier B.V.
Anisotropic turbulence in weakly stratified rotating magnetoconvection
Giesecke, A
2010-01-01
Numerical simulations of the 3D MHD-equations that describe rotating magnetoconvection in a Cartesian box have been performed using the code NIRVANA. The characteristics of averaged quantities like the turbulence intensity and the turbulent heat flux that are caused by the combined action of the small-scale fluctuations are computed. The correlation length of the turbulence significantly depends on the strength and orientation of the magnetic field and the anisotropic behavior of the turbulence intensity induced by Coriolis and Lorentz force is considerably more pronounced for faster rotation. The development of isotropic behavior on the small scales -- as it is observed in pure rotating convection -- vanishes even for a weak magnetic field which results in a turbulent flow that is dominated by the vertical component. In the presence of a horizontal magnetic field the vertical turbulent heat flux slightly increases with increasing field strength, so that cooling of the rotating system is facilitated. Horizont...
A model for anisotropic strange stars
Deb, Debabrata; Ray, Saibal; Rahaman, Farook; Guha, B K
2016-01-01
We attempt to find a singularity free interior solution for a neutral and static stellar model. We consider that (i) the star is made up of anisotropic fluid and (ii) the MIT bag model can be used. The total system is defined by assuming the density profile given by Mak and Harko \\cite{Mak2002}, which satisfies all the physical conditions of a stellar system and is stable by nature. We find that those stellar systems which obey such a non-linear density function must have maximum anisotropy at the surface. We also perform several tests for physical features of the proposed model and show that these are mostly acceptable within certain range. As a special mention, from our investigation we find that the maximum mass and radius of the quark star are $11.811 km$ and $3.53 {M}_{\\odot}$ respectively.
Anisotropic plasmas from axion and dilaton deformations
Donos, Aristomenis; Sosa-Rodriguez, Omar
2016-01-01
We construct black hole solutions of type IIB supergravity that are holographically dual to anisotropic plasmas arising from deformations of an infinite class of four-dimensional CFTs. The CFTs are dual to $AdS_5\\times X_5$, where $X_5$ is an Einstein manifold, and the deformations involve the type IIB axion and dilaton, with non-trivial periodic dependence on one of the spatial directions of the CFT. At low temperatures the solutions approach smooth domain wall solutions with the same $AdS_5\\times X_5$ solution appearing in the far IR. For sufficiently large deformations an intermediate scaling regime appears which is governed by a Lifshitz-like scaling solution. We calculate the DC thermal conductivity and some components of the shear viscosity tensor.
Theory of Random Anisotropic Magnetic Alloys
DEFF Research Database (Denmark)
Lindgård, Per-Anker
1976-01-01
A mean-field-crystal-field theory is developed for random, multicomponent, anisotropic magnetic alloys. It is specially applicable to rare-earth alloys. A discussion is given of multicritical points and phase transitions between various states characterized by order parameters with different...... spatial directions or different ordering wave vectors. Theoretical predictions based on known parameters for the phase diagrams and magnetic moments for the binary rare-earth alloys of Tb, Dy, Ho, and Er, Tb-Tm, Nd-Pr, and pure double-hcp Nd agree qualitatively with the experimental observations....... Quantitative agreement can be obtained by increasing the interaction between different alloy elements, in particular for alloys with very different axial anisotropy, e.g., Tb-Tm. A model system consisting of a singlet-singlet and singlet-doublet alloy is discussed in detail. A simple procedure to include...
Quantum electrodynamics of inhomogeneous anisotropic media
Lopez, Adrian E Rubio
2014-01-01
In this work we calculate the closed time path (CTP) generating functional for the electromagnetic (EM) field interacting with inhomogeneous anisotropic matter. For this purpose, we first find a general expression for the electromagnetic field's influence action from the interaction of the field with a composite environment consisting in the quantum polarization degrees of freedom in each point of space, at arbitrary temperatures, connected to thermal baths. Then, we evaluate the generating functional for the gauge field, in the temporal gauge, by implementing the Faddeev-Popov procedure. Finally, through the point-splitting technique, we calculate closed expressions for the energy, the Poynting vector and the Maxwell tensor in terms of the Hadamard propagator. We show that all the quantities have contributions from the field's initial conditions and also from the matter degrees of freedom. Throughout the whole work we discuss and give insights about how the gauge invariance must be treated in the formalism w...
Anisotropic plasmas from axion and dilaton deformations
Donos, Aristomenis; Gauntlett, Jerome P.; Sosa-Rodriguez, Omar
2016-11-01
We construct black hole solutions of type IIB supergravity that are holographically dual to anisotropic plasmas arising from deformations of an infinite class of four-dimensional CFTs. The CFTs are dual to AdS 5 × X 5, where X 5 is an Einstein manifold, and the deformations involve the type IIB axion and dilaton, with non-trivial periodic dependence on one of the spatial directions of the CFT. At low temperatures the solutions approach smooth domain wall solutions with the same AdS 5 × X 5 solution appearing in the far IR. For sufficiently large deformations an intermediate scaling regime appears which is governed by a Lifshitz-like scaling solution. We calculate the DC thermal conductivity and some components of the shear viscosity tensor.
Spectral functions from anisotropic lattice QCD
Aarts, G.; Allton, C.; Amato, A.; Evans, W.; Giudice, P.; Harris, T.; Kelly, A.; Kim, S. Y.; Lombardo, M. P.; Praki, K.; Ryan, S. M.; Skullerud, J.-I.
2016-12-01
The FASTSUM collaboration has been carrying out lattice simulations of QCD for temperatures ranging from one third to twice the crossover temperature, investigating the transition region, as well as the properties of the Quark Gluon Plasma. In this contribution we concentrate on quarkonium correlators and spectral functions. We work in a fixed scale scheme and use anisotropic lattices which help achieving the desirable fine resolution in the temporal direction, thus facilitating the (ill posed) integral transform from imaginary time to frequency space. We contrast and compare results for the correlators obtained with different methods, and different temporal spacings. We observe robust features of the results, confirming the sequential dissociation scenario, but also quantitative differences indicating that the methods' systematic errors are not yet under full control. We briefly outline future steps towards accurate results for the spectral functions and their associated statistical and systematic errors.
Translation correlations in anisotropically scattering media
Judkewitz, Benjamin; Vellekoop, Ivo M; Yang, Changhuei
2014-01-01
Controlling light propagation across scattering media by wavefront shaping holds great promise for a wide range of applications in biomedical imaging. However finding the right wavefront to shape is a challenge when the scattering transmission matrix is not known. Correlations in transmission matrices, especially the so-called memory-effect, have been exploited to address this limitation. However, the traditional memory-effect applies to thin scattering layers at a distance from the target, which precludes its use within thick scattering media. Here, we report on analogous transmission matrix correlations within thick anisotropically scattering media, with wide-ranging implications for biomedical imaging. We use a simple conceptual framework to explain these findings and relate them to the traditional memory effect.
Long-range interaction of anisotropic systems
Zhang, Junyi
2015-02-01
The first-order electrostatic interaction energy between two far-apart anisotropic atoms depends not only on the distance between them but also on their relative orientation, according to Rayleigh-Schrödinger perturbation theory. Using the first-order interaction energy and the continuum model, we study the long-range interaction between a pair of parallel pristine graphene sheets at zero temperature. The asymptotic form of the obtained potential density, &epsi:(D) &prop: ?D ?3 ?O(D?4), is consistent with the random phase approximation and Lifshitz theory. Accordingly, neglectance of the anisotropy, especially the nonzero first-order interaction energy, is the reason why the widely used Lennard-Jones potential approach and dispersion corrections in density functional theory give a wrong asymptotic form ε(D) &prop: ?D?4. © EPLA, 2015.
Effective orthorhombic anisotropic models for wavefield extrapolation
Ibanez-Jacome, W.
2014-07-18
Wavefield extrapolation in orthorhombic anisotropic media incorporates complicated but realistic models to reproduce wave propagation phenomena in the Earth\\'s subsurface. Compared with the representations used for simpler symmetries, such as transversely isotropic or isotropic, orthorhombic models require an extended and more elaborated formulation that also involves more expensive computational processes. The acoustic assumption yields more efficient description of the orthorhombic wave equation that also provides a simplified representation for the orthorhombic dispersion relation. However, such representation is hampered by the sixth-order nature of the acoustic wave equation, as it also encompasses the contribution of shear waves. To reduce the computational cost of wavefield extrapolation in such media, we generate effective isotropic inhomogeneous models that are capable of reproducing the firstarrival kinematic aspects of the orthorhombic wavefield. First, in order to compute traveltimes in vertical orthorhombic media, we develop a stable, efficient and accurate algorithm based on the fast marching method. The derived orthorhombic acoustic dispersion relation, unlike the isotropic or transversely isotropic ones, is represented by a sixth order polynomial equation with the fastest solution corresponding to outgoing P waves in acoustic media. The effective velocity models are then computed by evaluating the traveltime gradients of the orthorhombic traveltime solution, and using them to explicitly evaluate the corresponding inhomogeneous isotropic velocity field. The inverted effective velocity fields are source dependent and produce equivalent first-arrival kinematic descriptions of wave propagation in orthorhombic media. We extrapolate wavefields in these isotropic effective velocity models using the more efficient isotropic operator, and the results compare well, especially kinematically, with those obtained from the more expensive anisotropic extrapolator.
Quantization of the radiation field in an anisotropic dielectric medium
Institute of Scientific and Technical Information of China (English)
Li Wei; Liu Shi-Bing; Yang Wei
2009-01-01
There are both loss and dispersion characteristics for most dielectric media. In quantum theory the loss in medium is generally described by Langevin force in the Langevin noise (LN) scheme by which the quantization of the radiation field in various homogeneous absorbing dielectrics can be successfully actualized. However, it is invalid for the anisotropic dispersion medium. This paper extends the LN theory to an anisotropic dispersion medium and presented the quantization of the radiation field as well as the transformation relation between the homogeneous and anisotropic dispersion media.
Magnetic Anisotropic Energy Gap and Strain Effect in Au Nanoparticles
Directory of Open Access Journals (Sweden)
Shih Po-Hsun
2009-01-01
Full Text Available Abstract We report on the observation of the size effect of thermal magnetization in Au nanoparticles. The thermal deviation of the saturation magnetization departs substantially from that predicted by the Bloch T3/2-law, indicating the existence of magnetic anisotropic energy. The results may be understood using the uniaxial anisotropy Heisenberg model, in which the surface atoms give rise to polarized moments while the magnetic anisotropic energy decreases as the size of the Au nanoparticles is reduced. There is a significant maximum magnetic anisotropic energy found for the 6 nm Au nanoparticles, which is associated with the deviation of the lattice constant due to magnetocrystalline anisotropy.
Design of anisotropic reflector with birefringent thin films
Institute of Scientific and Technical Information of China (English)
Jianguo Wang; Kui Yi; Jianda Shao; Zhengxiu Fan
2005-01-01
A novel design for dielectric anisotropic mirrors with birefringent thin films for normal incidence is presented. This mirror consists of a stack of quarter-wave biaxial layers. The biaxial anisotropic layers can be fabricated by oblique deposition. The reflectance is different for two linear polarizations of light incidence on the mirrors. As a numerical example, the design is carried out on glass with TiO2 and ZrO2. These thin films could be applied to anisotropic reflective devices for lasers.
Development of laser ablation plasma by anisotropic self-radiation
Directory of Open Access Journals (Sweden)
Ohnishi Naofumi
2013-11-01
Full Text Available We have proposed a method for reproducing an accurate solution of low-density ablation plasma by properly treating anisotropic radiation. Monte-Carlo method is employed for estimating Eddington tensor with limited number of photon samples in each fluid time step. Radiation field from ablation plasma is significantly affected by the anisotropic Eddington tensor. Electron temperature around the ablation surface changes with the radiation field and is responsible for the observed emission. An accurate prediction of the light emission from the laser ablation plasma requires a careful estimation of the anisotropic radiation field.
Black phosphorus plasmonics: anisotropic elliptical propagation and nonlocality-induced canalization
Correas-Serrano, D.; Gomez-Diaz, J. S.; Alvarez Melcon, A.; Alù, Andrea
2016-10-01
We investigate unusual surface plasmons polariton (SPP) propagation and light-matter interactions in ultrathin black phosphorus (BP) films, a 2D material that exhibits exotic electrical and physical properties due to its extremely anisotropic crystal structure. Recently, it has been speculated that the ultra-confined surface plasmons supported by BP may present various topologies of wave propagation bands, ranging from anisotropic elliptic to hyperbolic, across the mid- and near-infrared regions of the electromagnetic spectrum. By carefully analyzing the natural nonlocal anisotropic optical conductivity of BP, derived using the Kubo formalism and an effective low-energy Hamiltonian, we demonstrate here that the SPP wavenumber cutoff imposed by nonlocality prohibits that they acquire an arbitrary hyperbolic topology, forcing operation in the canalization regime. The resulting nonlocality-induced canalization presents interesting properties, as it is inherently broadband, enables large light-matter interactions in the very near field, and allows extreme device miniaturization. We also determine fundamental bounds to the confinement of BP plasmons, which are significantly weaker than for graphene, thus allowing a larger local density of states. Our results confirm the potential of BP as a promising reconfigurable plasmonic platform, with exciting applications, such as planar hyperlenses, optoelectronic components, imaging, and communication systems.
Atomic Layer Thermopile Materials: Physics and Application
Directory of Open Access Journals (Sweden)
P. X. Zhang
2008-01-01
Full Text Available New types of thermoelectric materials characterized by highly anisotropic Fermi surfaces and thus anisotropic Seebeck coefficients are reviewed. Early studies revealed that there is an induced voltage in high TC oxide superconductors when the surface of the films is exposed to short light pulses. Subsequent investigations proved that the effect is due to anisotropic components of the Seebeck tensor, and the type of materials is referred to atomic layer thermopile (ALT. Our recent studies indicate that multilayer thin films at the nanoscale demonstrate enhanced ALT properties. This is in agreement with the prediction in seeking the larger figure of merit (ZT thermoelectric materials in nanostructures. The study of ALT materials provides both deep insight of anisotropic transport property of these materials and at the same time potential materials for applications, such as light detector and microcooler. By measuring the ALT properties under various perturbations, it is found that the information on anisotropic transport properties can be provided. The information sometimes is not easily obtained by other tools due to the nanoscale phase coexistence in these materials. Also, some remained open questions and future development in this research direction have been well discussed.
Weibel instability driven by spatially anisotropic density structures
Tomita, Sara
2016-01-01
Observations of afterglows of gamma-ray bursts suggest (GRBs) that post-shock magnetic fields are strongly amplified to about 100 times the shock-compressed value. The Weibel instability appears to play an important role in generating of the magnetic field. However, recent simulations of collisionless shocks in homogeneous plasmas show that the magnetic field generated by the Weibel instability rapidly decays. There must be some density fluctuations in interstellar and circumstellar media. The density fluctuations are anisotropically compressed in the downstream region of relativistic shocks. In this paper, we study the Weibel instability in electron--positron plasmas with the spatially anisotropic density distributions by means of two-dimensional particle-in-cell simulations. We find that large magnetic fields are maintained for a longer time by the Weibel instability driven by the spatially anisotropic density structure. Particles anisotropically escape from the high density region, so that the temperature ...
Anisotropic thermal conduction in galaxy clusters with MHD in Gadget
Arth, Alexander; Beck, Alexander M; Petkova, Margarita; Lesch, Harald
2014-01-01
We present an implementation of thermal conduction including the anisotropic effects of magnetic fields for SPH. The anisotropic thermal conduction is mainly proceeding parallel to magnetic fields and suppressed perpendicular to the fields. We derive the SPH formalism for the anisotropic heat transport and solve the corresponding equation with an implicit conjugate gradient scheme. We discuss several issues of unphysical heat transport in the cases of extreme ansiotropies or unmagnetized regions and present possible numerical workarounds. We implement our algorithm into the GADGET code and study its behaviour in several test cases. In general, we reproduce the analytical solutions of our idealised test problems, and obtain good results in cosmological simulations of galaxy cluster formations. Within galaxy clusters, the anisotropic conduction produces a net heat transport similar to an isotropic Spitzer conduction model with an efficiency of one per cent. In contrast to isotropic conduction our new formalism ...
Modelling of anisotropic compact stars of embedding class one
Energy Technology Data Exchange (ETDEWEB)
Bhar, Piyali [Government General Degree College, Department of Mathematics, Singur, Hooghly, West Bengal (India); Maurya, S.K. [University of Nizwa, Department of Mathematical and Physical Sciences, College of Arts and Science, Nizwa (Oman); Gupta, Y.K. [Raj Kumar Goel Institute of Technology, Department of Mathematics, Ghaziabad, U.P. (India); Manna, Tuhina [St. Xavier' s College, Department of Commerce (Evening), Kolkata, West Bengal (India)
2016-10-15
In the present article, we have constructed static anisotropic compact star models of Einstein field equations for the spherical symmetric metric of embedding class one. By assuming the particular form of the metric function ν, we have solved the Einstein field equations for anisotropic matter distribution. The anisotropic models represent the realistic compact objects such as SAX J 1808.4-3658 (SS1), Her X-1, Vela X-12, PSR J1614-2230 and Cen X-3. We have reported our results in details for the compact star Her X-1 on the ground of physical properties such as pressure, density, velocity of sound, energy conditions, TOV equation and red-shift etc. Along with these, we have also discussed about the stability of the compact star models. Finally we made a comparison between our anisotropic stars with the realistic objects on the key aspects as central density, central pressure, compactness and surface red-shift. (orig.)
Numerical study of domain coarsening in anisotropic stripe patterns.
Boyer, Denis
2004-06-01
We study the coarsening of two-dimensional smectic polycrystals characterized by grains of oblique stripes with only two possible orientations. For this purpose, an anisotropic Swift-Hohenberg equation is solved. For quenches close enough to the onset of stripe formation, the average domain size increases with time as t(1/2). Further from onset, anisotropic pinning forces similar to Peierls stresses in solid crystals slow down defects, and growth becomes anisotropic. In a wide range of quench depths, dislocation arrays remain mobile and dislocation density roughly decays as t(-1/3), while chevron boundaries are totally pinned. We discuss some agreements and disagreements found with recent experimental results on the coarsening of anisotropic electroconvection patterns.
The Nature of Primordial Fluctuations from Anisotropic Inflation
Watanabe, Masa-aki; Soda, Jiro
2010-01-01
We study the statistical nature of primordial fluctuations from an anisotropic inflation which is realized by a vector field coupled to an inflaton. We find a suitable gauge, which we call the canonical gauge, for anisotropic inflation by generalizing the flat slicing gauge in conventional isotropic inflation. Using the canonical gauge, we reveal the structure of the couplings between curvature perturbations, vector waves, and gravitational waves. We identify two sources of anisotropy, i.e. the anisotropy due to the anisotropic expansion of the universe and that due to the anisotropic couplings among variables. It turns out that the latter effect is dominant. Since the coupling between the curvature perturbations and vector waves is the strongest one, the statistical anisotropy in the curvature perturbations is larger than that in gravitational waves. We find the cross correlation between the curvature perturbations and gravitational waves which never occurs in conventional inflation. We also find the linear ...
An engineered anisotropic nanofilm with unidirectional wetting properties
Malvadkar, Niranjan A.; Hancock, Matthew J.; Sekeroglu, Koray; Dressick, Walter J.; Demirel, Melik C.
2010-12-01
Anisotropic textured surfaces allow water striders to walk on water, butterflies to shed water from their wings and plants to trap insects and pollen. Capturing these natural features in biomimetic surfaces is an active area of research. Here, we report an engineered nanofilm, composed of an array of poly(p-xylylene) nanorods, which demonstrates anisotropic wetting behaviour by means of a pin-release droplet ratchet mechanism. Droplet retention forces in the pin and release directions differ by up to 80μN, which is over ten times greater than the values reported for other engineered anisotropic surfaces. The nanofilm provides a microscale smooth surface on which to transport microlitre droplets, and is also relatively easy to synthesize by a bottom-up vapour-phase technique. An accompanying comprehensive model successfully describes the film's anisotropic wetting behaviour as a function of measurable film morphology parameters.
Neutron transport with anisotropic scattering: theory and applications
Van den Eynde, Gert
2005-01-01
This thesis is a blend of neutron transport theory and numerical analysis. We start with the study of the problem of the Mika/Case eigenexpansion used in the solution process of the homogeneous one-speed Boltzmann neutron transport equation with anisotropic scattering for plane symmetry. The anisotropic scattering is expressed as a finite Legendre series in which the coefficients are the ``scattering coefficients'. This eigenexpansion consists of a discrete spectrum of eigenvalues with its co...
ON THE ANISOTROPIC ACCURACY ANALYSIS OF ACM'S NONCONFORMING FINITE ELEMENT
Institute of Scientific and Technical Information of China (English)
Dong-yang Shi; Shi-peng Mao; Shao-chun Chen
2005-01-01
The main aim of this paper is to study the superconvergence accuracy analysis of the famous ACM's nonconforming finite element for biharmonic equation under anisotropic meshes. By using some novel approaches and techniques, the optimal anisotropic interpolation error and consistency error estimates are obtained. The global error is of order O(h2). Lastly, some numerical tests are presented to verify the theoretical analysis.
Holographic study of the jet quenching parameter in anisotropic systems
Energy Technology Data Exchange (ETDEWEB)
Wang, Luying [Shanghai University, Department of Physics, Shanghai (China); Wu, Shang-Yu [National Chiao Tung University, Department of Electrophysics, Hsinchu (China)
2016-11-15
We first calculate the jet quenching parameter of an anisotropic plasma with a U(1) chemical potential via AdS/CFT duality. The effects of charge, anisotropy parameter, and quark motion direction on the jet quenching parameter are investigated. We then discuss the situation of an anisotropic black brane in the IR region. We study both the jet quenching parameters along the longitudinal direction and the transverse plane. (orig.)
Duals of Orphan-Free Anisotropic Voronoi Diagrams are Triangulations
Canas, Guillermo D
2011-01-01
We show that, under mild conditions on the underlying metric, duals of appropriately defined anisotropic Voronoi diagrams are embedded triangulations. Furthermore, they always triangulate the convex hull of the vertices, and have other properties that parallel those of ordinary Delaunay triangulations. These results apply to the duals of anisotropic Voronoi diagrams of any set of vertices, so long as the diagram is orphan-free.
Modeling and Measurements of CMUTs with Square Anisotropic Plates
DEFF Research Database (Denmark)
la Cour, Mette Funding; Christiansen, Thomas Lehrmann; Dahl-Petersen, Christian;
2013-01-01
The conventional method of modeling CMUTs use the isotropic plate equation to calculate the deflection, leading to deviations from FEM simulations including anisotropic effects of around 10% in center deflection. In this paper, the deflection is found for square plates using the full anisotropic...... plate equation and the Galerkin method. Utilizing the symmetry of the silicon crystal, a compact and accurate expression for the deflection can be obtained. The deviation from FEM in center deflection is
Anisotropic static solutions in modelling highly compact bodies
Indian Academy of Sciences (India)
M Chaisi; S D Maharaj
2006-03-01
Einstein field equations for static anisotropic spheres are solved and exact interior solutions obtained. This paper extends earlier treatments to include anisotropic models which accommodate a wider variety of physically viable energy densities. Two classes of solutions are possible. The first class contains the limiting case ∝ -2 for the energy density which arises in many astrophysical applications. In the second class the singularity at the centre of the star is not present in the energy density
Holographic study on the jet quenching parameter in anisotropic systems
Wang, Luying
2016-01-01
We first calculate the jet quenching parameter of an anisotropic plasma with a U(1) chemical potential via the AdS/CFT duality. The effects of charge, anisotropy parameter and quark motion direction on the jet quenching parameter are investigated. We then discuss the situation of anisotropic black brane in the IR region. We study both the jet quenching parameters along the longitudinal direction and transverse plane.
Biomimetic collagen scaffolds with anisotropic pore architecture.
Davidenko, N; Gibb, T; Schuster, C; Best, S M; Campbell, J J; Watson, C J; Cameron, R E
2012-02-01
Sponge-like matrices with a specific three-dimensional structural design resembling the actual extracellular matrix of a particular tissue show significant potential for the regeneration and repair of a broad range of damaged anisotropic tissues. The manipulation of the structure of collagen scaffolds using a freeze-drying technique was explored in this work as an intrinsically biocompatible way of tailoring the inner architecture of the scaffold. The research focused on the influence of temperature gradients, imposed during the phase of crystallisation of collagen suspensions, upon the degree of anisotropy in the microstructures of the scaffolds produced. Moulding technology was employed to achieve differences in heat transfer rates during the freezing processes. For this purpose various moulds with different configurations were developed with a view to producing uniaxial and multi-directional temperature gradients across the sample during this process. Scanning electron microscopy analysis of different cross-sections (longitudinal and horizontal) of scaffolds revealed that highly aligned matrices with axially directed pore architectures were obtained where single unidirectional temperature gradients were induced. Altering the freezing conditions by the introduction of multiple temperature gradients allowed collagen scaffolds to be produced with complex pore orientations, and anisotropy in pore size and alignment.
Lattice Study of Anisotropic QED-3
Hands, S; Hands, Simon; Thomas, Iorwerth Owain
2004-01-01
We present results from a Monte Carlo simulation of non-compact lattice QED in 3 dimensions on a $16^3$ lattice in which an explicit anisotropy between $x$ and $y$ hopping terms has been introduced into the action. This formulation is inspired by recent formulations of anisotropic QED$_3$ as an effective theory of the non-superconducting portion of the cuprate phase diagram, with relativistic fermion degrees of freedom defined near the nodes of the gap function on the Fermi surface, and massless photon degrees of freedom reproducing the dynamics of the phase disorder of the superconducting order parameter. Using a parameter set corresponding to broken chiral symmetry in the isotropic limit, our results show that the renormalised anisotropy, defined in terms of the ratio of correlation lengths of gauge invariant bound states in the $x$ and $y$ directions, exceeds the explicit anisotropy $\\kappa$ introduced in the lattice action, implying in contrast to recent analytic results that anisotropy is a relevant defo...
Coefficient adaptive triangulation for strongly anisotropic problems
Energy Technology Data Exchange (ETDEWEB)
D`Azevedo, E.F.; Romine, C.H.; Donato, J.M.
1996-01-01
Second order elliptic partial differential equations arise in many important applications, including flow through porous media, heat conduction, the distribution of electrical or magnetic potential. The prototype is the Laplace problem, which in discrete form produces a coefficient matrix that is relatively easy to solve in a regular domain. However, the presence of anisotropy produces a matrix whose condition number is increased, making the resulting linear system more difficult to solve. In this work, we take the anisotropy into account in the discretization by mapping each anisotropic region into a ``stretched`` coordinate space in which the anisotropy is removed. The region is then uniformly triangulated, and the resulting triangulation mapped back to the original space. The effect is to generate long slender triangles that are oriented in the direction of ``preferred flow.`` Slender triangles are generally regarded as numerically undesirable since they tend to cause poor conditioning; however, our triangulation has the effect of producing effective isotropy, thus improving the condition number of the resulting coefficient matrix.
Details of tetrahedral anisotropic mesh adaptation
Jensen, Kristian Ejlebjerg; Gorman, Gerard
2016-04-01
We have implemented tetrahedral anisotropic mesh adaptation using the local operations of coarsening, swapping, refinement and smoothing in MATLAB without the use of any for- N loops, i.e. the script is fully vectorised. In the process of doing so, we have made three observations related to details of the implementation: 1. restricting refinement to a single edge split per element not only simplifies the code, it also improves mesh quality, 2. face to edge swapping is unnecessary, and 3. optimising for the Vassilevski functional tends to give a little higher value for the mean condition number functional than optimising for the condition number functional directly. These observations have been made for a uniform and a radial shock metric field, both starting from a structured mesh in a cube. Finally, we compare two coarsening techniques and demonstrate the importance of applying smoothing in the mesh adaptation loop. The results pertain to a unit cube geometry, but we also show the effect of corners and edges by applying the implementation in a spherical geometry.
Experimental evidence for anisotropic double-gap behavior in MgB2.
Cubitt, R; Levett, S; Bud'ko, S L; Anderson, N E; Canfield, P C
2003-04-18
The behavior of a type II superconductor in the presence of a magnetic field is governed by two characteristic length scales, the London penetration depth and the coherence length. We present magnetization measurements on MgB2 powder showing an anisotropy in the upper critical field and hence the coherence length of 6. Using the technique of small angle neutron scattering we show that this anisotropy is not mirrored in the London penetration depth, which is almost isotropic. This result can be explained by the superconductivity residing in two distinct electronic bands of the material, only one of which is highly anisotropic.
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The bending problem of a functionally graded anisotropic cantilever beam subjected to thermal and uniformly distributed load is investigated, with material parameters being arbitrary functions of the thickness coordinate. The heat conduction problem is treated as a 1D problem through the thickness. Based on the elementary formulations for plane stress problem, the stress function is assumed to be in the form of polynomial of the longitudinal coordinate variable, from which the stresses can be derived.The stress function is then determined completely with the compatibility equation and boundary conditions. A practical example is presented to show the application of the method.
Interface crack growth for anisotropic plasticity with non-normality effects
DEFF Research Database (Denmark)
Tvergaard, Viggo; Legarth, Brian Nyvang
2007-01-01
elastic–viscoplastic material model is applied, using an anisotropic yield criterion, and in each case analyzed the effect of non-normality is compared with results for the standard normality flow rule. Due to the mismatch of elastic properties across the interface the corresponding elastic solution has...... an oscillating stress singularity, and with conditions of small scale yielding this solution is applied as boundary conditions on the outer edge of the region analyzed. Crack growth resistance curves are calculated numerically, and the effect of the near-tip mode mixity on the steady-state fracture toughness...
The anisotropic Kerr nonlinear refractive index of \\beta-BaB_2O_4
Bache, Morten; Zhou, Binbin; Zeng, Xianglong
2012-01-01
We study the anisotropic nature of the Kerr nonlinear response in a \\beta-BaB_2O_4 (BBO) crystal. The focus is on determining the relevant $\\chi^{(3)}$ cubic tensor component in connection with type I cascaded quadratic interaction, which is done by analyzing various experiments in the literature. We correct the data from some of the experiments for contributions from cascading as well as for updated material parameters, and find that the Kerr nonlinear refractive index used to model self-phase modulation in cascading is considerably larger than what has been used to date.
Magnon nodal-line semimetals and drumhead surface states in anisotropic pyrochlore ferromagnets
Mook, Alexander; Mertig, Ingrid
2016-01-01
We introduce a new type of topological magnon matter: the magnonic pendant to electronic nodal-line semimetals. Magnon spectra of anisotropic pyrochlore ferromagnets feature twofold degeneracies of magnon bands along a closed loop in reciprocal space. These magnon nodal lines are topologically protected by the coexistence of inversion and time-reversal symmetry; they require the absence of spin-orbit interaction (no Dzyaloshinskii-Moriya interaction). We calculate the topological invariants of the nodal lines and show that details of the associated magnon drumhead surface states depend strongly on the termination of the surface. Magnon nodal-line semimetals complete the family of topological magnons in three-dimensional ferromagnetic materials.
Polarimetric investigation of materials with both linear and circular anisotropy
DEFF Research Database (Denmark)
Naydenova, I.; Nikolova, L.; Todorov, T.;
1997-01-01
We investigate light propagation through materials with both linear and circular anisotropy and find the relation of the amplitude and polarization transfer functions to the four anisotropic characteristics: linear circular birefringence, and linear and circular dichroism. We determine these four...
Mietta, José L.; Jorge, Guillermo; Martín Negri, R.
2014-08-01
A flexible, anisotropic and portable stress sensor (logarithmic reversible response between 40-350 kPa) was fabricated, in which i) the sensing material, ii) the electrical contacts and iii) the encapsulating material, were based on polydimethylsiloxane (PDMS) composites. The sensing material is a slide of an anisotropic magnetorheological elastomer (MRE), formed by dispersing silver-covered magnetite particles (Fe3O4@Ag) in PDMS and by curing in the presence of a uniform magnetic field. Thus, the MRE is a structure of electrically conducting pseudo-chains (needles) aligned in a specific direction, in which electrical conductivity increases when stress is exclusively applied in the direction of the needles. Electrical conductivity appears only between contact points that face each other at both sides of the MRE slide. An array of electrical contacts was implemented based on PDMS-silver paint metallic composites. The array was encapsulated with PDMS. Using Fe3O4 superparamagnetic nanoparticles also opens up possibilities for a magnetic field sensor, due to the magnetoresistance effects.
Fracture Interface Waves in an Anisotropic Medium
Pyrak-Nolte, L. J.; Shao, S.; Abell, B.
2011-12-01
The detection of fractures in an anisotropic medium is complicated by discreet modes that are guided or confined by fractures and that travel with velocities close (~92%) to the shear wave velocity. For instance, fractures can mask the presence of textural anisotropy in a rock, and can increase the apparent shear wave velocity anisotropy. In this study, we examine how fracture interface waves affect the interpretation of shear wave velocities for two orthogonal polarizations propagating parallel to the layers. Samples with textural anisotropy measuring 100 x 100 x 100 mm were fabricated from garolite, an epoxy - cloth laminate, with layer thickness on the order of 0.5 mm. Three fracture samples were created with: (1) a fracture oriented parallel to layering, (2) a fracture oriented perpendicular to layering, and (3) two intersecting orthogonal fractures. An intact sample without fractures was used a standard. A seismic array, consisting of source and receiver arrays, was used to perform full waveform measurements. Each array contained two compressional and five shear wave piezoelectric contact transducers with a central frequency of 1 MHz. Shear wave transducers were polarized both perpendicular and parallel to the layering as well as to the fracture. Measurements were made for a range of stresses (0.4 - 4MPa). When the shear wave was polarized parallel to a fracture, the shear wave traveled at the bulk shear velocity respective to the layering. However, when the shear wave was polarized perpendicular to a fracture, the measured velocity ranged between the Rayleigh wave velocity at low stress and the bulk shear wave at high stress. The shear wave velocities perpendicular and parallel to the layering (propagation direction parallel to the layers) were ~1500 m/s and ~1600 m/s, respectively, in the intact sample. However, in the fractured samples, the observed shear wave anisotropy depended on the stress and fracture orientation relative to the layering. When the
Collisionless magnetic reconnection under anisotropic MHD approximation
Hirabayashi, Kota; Hoshino, Masahiro
We study the formation of slow-mode shocks in collisionless magnetic reconnection by using one- and two-dimensional collisionless magneto-hydro-dynamic (MHD) simulations based on the double adiabatic approximation, which is an important step to bridge the gap between the Petschek-type MHD reconnection model accompanied by a pair of slow shocks and the observational evidence of the rare occasion of in-situ slow shock observation. According to our results, a pair of slow shocks does form in the reconnection layer. The resultant shock waves, however, are quite weak compared with those in an isotropic MHD from the point of view of the plasma compression and the amount of the magnetic energy released across the shock. Once the slow shock forms, the downstream plasma are heated in highly anisotropic manner and a firehose-sense (P_{||}>P_{⊥}) pressure anisotropy arises. The maximum anisotropy is limited by the marginal firehose criterion, 1-(P_{||}-P_{⊥})/B(2) =0. In spite of the weakness of the shocks, the resultant reconnection rate is kept at the same level compared with that in the corresponding ordinary MHD simulations. It is also revealed that the sequential order of propagation of the slow shock and the rotational discontinuity, which appears when the guide field component exists, changes depending on the magnitude of the guide field. Especially, when no guide field exists, the rotational discontinuity degenerates with the contact discontinuity remaining at the position of the initial current sheet, while with the slow shock in the isotropic MHD. Our result implies that the slow shock does not necessarily play an important role in the energy conversion in the reconnection system and is consistent with the satellite observation in the Earth's magnetosphere.
Molecular Location Sensing Approach by Anisotropic Magnetism of an Endohedral Metallofullerene.
Takano, Yuta; Tashita, Ryo; Suzuki, Mitsuaki; Nagase, Shigeru; Imahori, Hiroshi; Akasaka, Takeshi
2016-06-29
Location recognition at the molecular scale provides valuable information about the nature of functional molecular materials. This study presents a novel location sensing approach based on an endohedral metallofullerene, Ce@C82, using its anisotropic magnetic properties, which lead to temperature-dependent paramagnetic shifts in (1)H NMR spectra. Five site-isomers of Ce@C82CH2-3,5-C6H3Me2 were synthesized to demonstrate the spatial sensing ability of Ce@C82. Single-crystal structures, absorption spectra, and density functional theory calculations were used to select the plausible addition positions in the radical coupling reaction, which preferentially happens on the carbon atoms with high electron density of the singly occupied molecular orbital (SOMO) and positive charge. Temperature-dependent NMR measurements demonstrated unique paramagnetic shifts of the (1)H peaks, which were derived from the anisotropic magnetism of the f-electron in the Ce atom of the isomers. It was found that the magnetic anisotropy axes can be easily predicted by theoretical calculations using the Gaussian 09 package. Further analysis revealed that the temperature-dependent trend in the shifts is clearly predictable from the distance and relative position of the proton from the Ce atom. Hence, the Ce-encapsulated metallofullerene Ce@C82 can provide spatial location information about nearby atoms through the temperature-dependent paramagnetic shifts of its NMR signals. It can act as a molecular probe for location sensing by utilizing the anisotropic magnetism of the encapsulated Ce atom. The potentially low toxicity and stability of the endohedral fullerene would make Ce@C82 suitable for applications in biology and material science.
Golykh, R. N.
2016-06-01
Progress of technology and medicine dictates the ever-increasing requirements (heat resistance, corrosion resistance, strength properties, impregnating ability, etc.) for non-Newtonian fluids and materials produced on their basis (epoxy resin, coating materials, liquid crystals, etc.). Materials with improved properties obtaining is possible by modification of their physicochemical structure. One of the most promising approaches to the restructuring of non-Newtonian fluids is cavitation generated by high-frequency acoustic vibrations. The efficiency of cavitation in non-Newtonian fluid is determined by dynamics of gaseous bubble. Today, bubble dynamics in isotropic non-Newtonian fluids, in which cavitation bubble shape remains spherical, is most full investigated, because the problem reduces to ordinary differential equation for spherical bubble radius. However, gaseous bubble in anisotropic fluids which are most wide kind of non-Newtonian fluids (due to orientation of macromolecules) deviates from spherical shape due to viscosity dependence on shear rate direction. Therefore, the paper presents the mathematical model of gaseous bubble dynamics in anisotropic non-Newtonian fluids. The model is based on general equations for anisotropic non-Newtonian fluid flow. The equations are solved by asymptotic decomposition of fluid flow parameters. It allowed evaluating bubble size and shape evolution depending on rheological properties of liquid and acoustic field characteristics.
Loss-induced Enhanced Transmission in Anisotropic Density-near-zero Acoustic Metamaterials
Shen, Chen; Jing, Yun
2016-11-01
Anisotropic density-near-zero (ADNZ) acoustic metamaterials are investigated theoretically and numerically in this paper and are shown to exhibit extraordinary transmission enhancement when material loss is induced. The enhanced transmission is due to the enhanced propagating and evanescent wave modes inside the ADNZ medium thanks to the interplay of near-zero density, material loss, and high wave impedance matching in the propagation direction. The equi-frequency contour (EFC) is used to reveal whether the propagating wave mode is allowed in ADNZ metamaterials. Numerical simulations based on plate-type acoustic metamaterials with different material losses were performed to demonstrate collimation and subwavelength imaging enabled by the induced loss in ADNZ media. This work provides a different way for manipulating acoustic waves.
Loss-induced enhanced transmission in anisotropic density-near-zero acoustic metamaterials
Shen, Chen
2016-01-01
Anisotropic density-near-zero (ADNZ) acoustic metamaterials are investigated theoretically and numerically in this letter and are shown to exhibit extraordinary transmission enhancement when material loss is induced. The enhanced transmission is due to the enhanced propagating and evanescent wave modes inside the ADNZ medium thanks to the interplay of near-zero density, material loss, and high wave impedance matching in the propagation direction. The equi-frequency contour (EFC) is used to reveal whether the propagating wave mode is allowed in ADNZ metamaterials. Numerical simulations based on plate-type acoustic metamaterials with different material losses were performed to demonstrate collimation enabled by the induced loss in ADNZ media. This work provides a different way for manipulating acoustic waves.
Lee, Dock-Jin; Kim, Young-Jin; Kim, Moon-Ki; Choi, Jae-Boong; Chang, Yoon-Suk; Liu, Wing Kam
2011-01-01
New advanced composite materials have recently been of great interest. Especially, many researchers have studied on nano/micro composites based on matrix filled with nano-particles, nano-tubes, nano-wires and so forth, which have outstanding characteristics on thermal, electrical, optical, chemical and mechanical properties. Therefore, the need of numerical approach for design and development of the advanced materials has been recognized. In this paper, finite element analysis based on multi-resolution continuum theory is carried out to predict the anisotropic behavior of nano/micro composites based on damage mechanics with a cell modeling. The cell modeling systematically evaluates constitutive relationships from microstructure of the composite material. Effects of plastic anisotropy on deformation behavior and damage evolution of nano/micro composite are investigated by using Hill's 48 yield function and also compared with those obtained from Gurson-Tvergaard-Needleman isotropic damage model based on von Mises yield function.
Selection Theory of Dendritic Growth with Anisotropic Diffusion
Directory of Open Access Journals (Sweden)
Martin von Kurnatowski
2015-01-01
Full Text Available Dendritic patterns frequently arise when a crystal grows into its own undercooled melt. Latent heat released at the two-phase boundary is removed by some transport mechanism, and often the problem can be described by a simple diffusion model. Its analytic solution is based on a perturbation expansion about the case without capillary effects. The length scale of the pattern is determined by anisotropic surface tension, which provides the mechanism for stabilizing the dendrite. In the case of liquid crystals, diffusion can be anisotropic too. Growth is faster in the direction of less efficient heat transport (inverted growth. Any physical solution should include this feature. A simple spatial rescaling is used to reduce the bulk equation in 2D to the case of isotropic diffusion. Subsequently, an eigenvalue problem for the growth mode results from the interface conditions. The eigenvalue is calculated numerically and the selection problem of dendritic growth with anisotropic diffusion is solved. The length scale is predicted and a quantitative description of the inverted growth phenomenon is given. It is found that anisotropic diffusion cannot take the stabilizing role of anisotropic surface tension.
Anisotropic diffusion in mesh-free numerical magnetohydrodynamics
Hopkins, Philip F.
2017-04-01
We extend recently developed mesh-free Lagrangian methods for numerical magnetohydrodynamics (MHD) to arbitrary anisotropic diffusion equations, including: passive scalar diffusion, Spitzer-Braginskii conduction and viscosity, cosmic ray diffusion/streaming, anisotropic radiation transport, non-ideal MHD (Ohmic resistivity, ambipolar diffusion, the Hall effect) and turbulent 'eddy diffusion'. We study these as implemented in the code GIZMO for both new meshless finite-volume Godunov schemes (MFM/MFV). We show that the MFM/MFV methods are accurate and stable even with noisy fields and irregular particle arrangements, and recover the correct behaviour even in arbitrarily anisotropic cases. They are competitive with state-of-the-art AMR/moving-mesh methods, and can correctly treat anisotropic diffusion-driven instabilities (e.g. the MTI and HBI, Hall MRI). We also develop a new scheme for stabilizing anisotropic tensor-valued fluxes with high-order gradient estimators and non-linear flux limiters, which is trivially generalized to AMR/moving-mesh codes. We also present applications of some of these improvements for SPH, in the form of a new integral-Godunov SPH formulation that adopts a moving-least squares gradient estimator and introduces a flux-limited Riemann problem between particles.
Weibel Instability Driven by Spatially Anisotropic Density Structures
Tomita, Sara; Ohira, Yutaka
2016-07-01
Observations of afterglows of gamma-ray bursts (GRBs) suggest that post-shock magnetic fields are strongly amplified to about 100 times the shock-compressed value. The Weibel instability appears to play an important role in generating the magnetic field. However, recent simulations of collisionless shocks in homogeneous plasmas show that the magnetic field generated by the Weibel instability rapidly decays. There must be some density fluctuations in interstellar and circumstellar media. The density fluctuations are anisotropically compressed in the downstream region of relativistic shocks. In this paper, we study the Weibel instability in electron-positron plasmas with spatially anisotropic density distributions by means of two-dimensional particle-in-cell simulations. We find that large magnetic fields are maintained for a longer time by the Weibel instability driven by spatially anisotropic density structure. Particles anisotropically escape from the high density region, so that a temperature anisotropy is generated and the Weibel instability becomes unstable. Our simulation results suggest that the Weibel instability driven by an anisotropic density structure can generate sufficiently large magnetic fields and they can cover sufficiently large regions to explain the afterglow emission of GRBs.
2D seismic reflection tomography in strongly anisotropic media
Huang, Guangnan; Zhou, Bing; Li, Hongxi; Zhang, Hua; Li, Zelin
2014-12-01
Seismic traveltime tomography is an effective method to reconstruct underground anisotropic parameters. Currently, most anisotropic tomographic methods were developed under the assumption of weak anisotropy. The tomographic method proposed here can be implemented for imaging subsurface targets in strongly anisotropic media with a known tilted symmetry axis, since the adopted ray tracing method is suitable for anisotropic media with arbitrary degree. There are three kinds of reflection waves (qP, qSV and qSH waves) that were separately used to invert the blocky abnormal body model. The reflection traveltime tomographiy is developed here because a surface observation system is the most economical and practical way compared with crosswell and VSP. The numerical examples show that the traveltimes of qP reflection wave have inverted parameters {{c}11},{{c}13},{{c}33} \\text{and} {{c}44} successfully. Traveltimes of qSV reflection wave have inverted parameters {{c}11},{{c}33} \\text{and} {{c}44} successfully, with the exception of the {{c}13}, since it is less sensitive than other parameters. Traveltimes of qSH reflection wave also have inverted parameters {{c}44} \\text{and} {{c}66} successfully. In addition, we find that the velocity sensitivity functions (derivatives of phase velocity with respect to elastic moduli parameters) and raypath illuminating angles have a great influence on the qualities of tomograms according to the inversion of theoretical models. Finally, the numerical examples confirm that the reflection traveltime tomography can be applied to invert strongly anisotropic models.
Multiple anisotropic collisions for advection-diffusion Lattice Boltzmann schemes
Ginzburg, Irina
2013-01-01
This paper develops a symmetrized framework for the analysis of the anisotropic advection-diffusion Lattice Boltzmann schemes. Two main approaches build the anisotropic diffusion coefficients either from the anisotropic anti-symmetric collision matrix or from the anisotropic symmetric equilibrium distribution. We combine and extend existing approaches for all commonly used velocity sets, prescribe most general equilibrium and build the diffusion and numerical-diffusion forms, then derive and compare solvability conditions, examine available anisotropy and stable velocity magnitudes in the presence of advection. Besides the deterioration of accuracy, the numerical diffusion dictates the stable velocity range. Three techniques are proposed for its elimination: (i) velocity-dependent relaxation entries; (ii) their combination with the coordinate-link equilibrium correction; and (iii) equilibrium correction for all links. Two first techniques are also available for the minimal (coordinate) velocity sets. Even then, the two-relaxation-times model with the isotropic rates often gains in effective stability and accuracy. The key point is that the symmetric collision mode does not modify the modeled diffusion tensor but it controls the effective accuracy and stability, via eigenvalue combinations of the opposite parity eigenmodes. We propose to reduce the eigenvalue spectrum by properly combining different anisotropic collision elements. The stability role of the symmetric, multiple-relaxation-times component, is further investigated with the exact von Neumann stability analysis developed in diffusion-dominant limit.
Experimental Characterization and Micromechanical Modelling of Anisotropic Slates
Chen, Yi-Feng; Wei, Kai; Liu, Wu; Hu, Shao-Hua; Hu, Ran; Zhou, Chuang-Bing
2016-09-01
Laboratory tests were performed in this study to examine the anisotropic physical and mechanical properties of the well-foliated Jiujiang slate. The P-wave velocity and the apparent Young's modulus were found to increase remarkably with the foliation angle θ, and the compressive strength at any confining pressure varies in a typical U-shaped trend, with the maximum strength consistently attained at θ = 90° and the minimum strength at θ = 45°. The slate samples failed in three typical patterns relevant to the foliation angle, i.e. shear failure across foliation planes for θ ≤ 15°, sliding along foliation planes for 30° ≤ θ ≤ 60° and axial splitting along foliation planes for θ = 90°. The stress-strain curves at any given foliation angle and confining pressure display an initial nonlinear phase, a linear elastic phase, a crack initiation and growth phase, as well as a rapid stress drop phase and a residual stress phase. Based on the experimental evidences, a micromechanical damage-friction model was proposed for the foliated slate by simply modelling the foliation planes as a family of elastic interfaces and by characterizing the interaction between the foliation planes and the rock matrix with a nonlinear damage evolution law associated with the inclination angle. The proposed model was applied to predict the deformational and strength behaviours of the foliated slate under triaxial compressive conditions using the material parameters calibrated with the uniaxial and/or triaxial test data, with good agreement between the model predictions and the laboratory measurements.
Unusually High and Anisotropic Thermal Conductivity in Amorphous Silicon Nanostructures.
Kwon, Soonshin; Zheng, Jianlin; Wingert, Matthew C; Cui, Shuang; Chen, Renkun
2017-02-02
Amorphous Si (a-Si) nanostructures are ubiquitous in numerous electronic and optoelectronic devices. Amorphous materials are considered to possess the lower limit to the thermal conductivity (κ), which is ∼1 W·m(-1) K(-1) for a-Si. However, recent work suggested that κ of micrometer-thick a-Si films can be greater than 3 W·m(-1) K(-1), which is contributed to by propagating vibrational modes, referred to as "propagons". However, precise determination of κ in a-Si has been elusive. Here, we used structures of a-Si nanotubes and suspended a-Si films that enabled precise in-plane thermal conductivity (κ∥) measurement within a wide thickness range of 5 nm to 1.7 μm. We showed unexpectedly high κ∥ in a-Si nanostructures, reaching ∼3.0 and 5.3 W·m(-1) K(-1) at ∼100 nm and 1.7 μm, respectively. Furthermore, the measured κ∥ is significantly higher than the cross-plane κ on the same films. This unusually high and anisotropic thermal conductivity in the amorphous Si nanostructure manifests the surprisingly broad propagon mean free path distribution, which is found to range from 10 nm to 10 μm, in the disordered and atomically isotropic structure. This result provides an unambiguous answer to the century-old problem regarding mean free path distribution of propagons and also sheds light on the design and performance of numerous a-Si based electronic and optoelectronic devices.
Nonconforming rotated Q1 element on non-tensor product anisotropic meshes
Institute of Scientific and Technical Information of China (English)
MAO; Shipeng; SHI; Zhongci
2006-01-01
In this paper, we consider the nonconforming rotated Q1 element for the second order elliptic problem on the non-tensor product anisotropic meshes, i.e. the anisotropic affine quadrilateral meshes. Though the interpolation error is divergent on the anisotropic meshes,we overcome this difficulty by constructing another proper operator. Then we give the optimal approximation error and the consistency error estimates under the anisotropic affine quadrilateral meshes. The results of this paper provide some hints to derive the anisotropic error of some finite elements whose interpolations do not satisfy the anisotropic interpolation properties. Lastly, a numerical test is carried out, which coincides with our theoretical analysis.
Kang, Hosung; Kim, Duckjong; Baik, Seunghyun
2014-09-21
One-dimensional conductive fillers such as single-walled carbon nanotubes (SWNTs) can be aggregated and aligned during transparent conductive film (TCF) formation by the vacuum filtration method. The potential error of analysing the average sheet resistance of these anisotropic films, using the four-point probe in-line method and the conversion formula developed assuming uniform isotropic material properties, was systematically investigated by finite element analysis and experiments. The finite element analysis of anisotropic stripe-patterned TCFs with alternating low (ρ1) and high (ρ2) resistivities revealed that the estimated average sheet resistance approached ρ1/t when the probes were parallel to the aligned nanotubes. The thickness of the film is t. It was more close to ρ2/t when the probes were perpendicular to the aligned tubes. Indeed, TCFs fabricated by the vacuum filtration method using metal-enriched SWNTs exhibited highly anisotropic local regions where tubes were aggregated and aligned. The local sheet resistances of randomly oriented, aligned, and perpendicular tube regions of the TCF at a transmittance of 89.9% were 5000, 2.4, and 12 300 Ω □(-1), respectively. Resistivities of the aggregated and aligned tube region (ρ1 = 1.2 × 10(-5) Ω cm) and the region between tubes (ρ2 = 6.2 × 10(-2) Ω cm) could be approximated with the aid of finite element analysis. This work demonstrates the potential error of characterizing the average sheet resistance of anisotropic TCFs using the four-point probe in-line method since surprisingly high or low values could be obtained depending on the measurement angle. On the other hand, a better control of aggregation and alignment of nanotubes would realize TCFs with a very small anisotropic resistivity and a high transparency.
Anisotropic shrinkage characteristics of tape cast alumina
Patwardhan, Jaideep Suresh
Dimensional control during sintering is a major issue in ceramics processing to avoid high post-sintering costs associated with machining of the fired ceramic part to desired tolerances and dimensions. Ceramic forming processes such as tape casting, injection molding, and extrusion involve shear of anisotropic particles resulting in preferential alignment of the particles in the green body. This preferential alignment causes directionality in mechanical, electrical, optical, and magnetic properties and most importantly warpage or distortion during sintering. A large effort has been devoted to synthesizing ceramic green bodies with minimal density gradients and uniform packing and modeling the sintering behavior evolution but little effort has been devoted to characterizing orientation of particles and the effect of preferential alignment on sintering shrinkage anisotropy. A systematic study was initiated to study the effect of processing variables such as shear rate, solids loading, temperature, and binder content on aqueous tape cast alumina. Three different alumina systems: A16-SG, Baikowski RC-UFX DBM and RC-LS DBM were investigated. Aqueous tapes of high solids loading alumina (56 vol. %) were tape cast at various speeds and thicknesses and assuming plane Couette flow a shear rate regime of 21--270 s-1 was investigated. Higher shear rates and high solids loading resulted in higher in-plane anisotropy whereas the anisotropy in the thickness direction was higher for low solids loading systems. The anisotropy was found to be fairly constant above a certain critical shear rate (˜100 s-1) irrespective of the temperature and the solids loading and this correlated with the viscosity-shear rate relationship of the cast slips. The higher shrinkage anisotropy in the thickness direction for the low solids loading systems (35 and 45 vol. %) was attributed to the higher amount of organics in the slip required to sustain the suitable viscosity for tape casting and
Directory of Open Access Journals (Sweden)
Uğur Mazlum
2015-12-01
Full Text Available Magneto-rheological (MR materials are in a smart material class that has the rheological properties to be quickly and reversibly controlled with the external magnetic field applications. Considering the technological developments the rubber-like smart materials has had a more functional usage area with magneto- rheological effect. This study investigates the axial mechanical properties of magneto-rheological Ethylene Propylene Diene Monomer (EPDM and Natural Rubber (NR type synthetic rubbers for isotropic and anisotropic situations. Also, these composite materials were built by means of hot press systems as either isotropic or anisotropic using magnetic field application after addition of ferromagnetic powders. The influence of magnetic field was investigated. In this study, NR rubber was found to be more susceptible in terms of smart material properties unlike EPDM synthetic rubber.
Small-angle neutron scattering in materials science - an introduction
Energy Technology Data Exchange (ETDEWEB)
Fratzl, P. [Vienna Univ., Inst. fuer Materialphysik, Vienna (Austria)
1996-12-31
The basic principles of the application of small-angle neutron scattering to materials research are summarized. The text focusses on the classical methods of data evaluation for isotropic and for anisotropic materials. Some examples of applications to the study of alloys, porous materials, composites and other complex materials are given. (author) 9 figs., 38 refs.
Yao, Xin; Guo, Guilue; Ma, Xing; Zhao, Yang; Ang, Chung Yen; Luo, Zhong; Nguyen, Kim Truc; Li, Pei-Zhou; Yan, Qingyu; Zhao, Yanli
2015-12-01
Three-dimensional (3D) graphene aerogel (GA) has emerged as an outstanding support for metal oxides to enhance the overall energy-storage performance of the resulting hybrid materials. In the current stage of the studies, metals/metal oxides inside GA are in uncrafted geometries. Introducing structure-controlled metal oxides into GA may further push electrochemical properties of metal oxide-GA hybrids. Using rutile SnO2 as an example, we demonstrated here a facile hydrothermal strategy combined with a preconditioning technique named vacuum-assisted impregnation for in situ construction of controlled anisotropic SnO2 heterostructures inside GA. The obtained hybrid material was fully characterized in detail, and its formation mechanism was investigated by monitoring the phase-transformation process. Rational integration of the two advanced structures, anisotropic SnO2 and 3D GA, synergistically led to enhanced lithium-storage properties (1176 mAh/g for the first cycle and 872 mAh/g for the 50th cycle at 100 mA/g) as compared with its two counterparts, namely, rough nanoparticles@3D GA and anisotropic SnO2@2D graphene sheets (618 and 751 mAh/g for the 50th cycle at 100 mA/g, respectively). It was also well-demonstrated that this hybrid material was capable of delivering high specific capacity at rapid charge/discharge cycles (1044 mAh/g at 100 mA/g, 847 mAh/g at 200 mA/g, 698 mAh/g at 500 mA/g, and 584 mAh/g at 1000 mA/g). The in situ integration strategy along with vacuum-assisted impregnation technique presented here shows great potential as a versatile tool for accessing a variety of sophisticated smart structures in the form of anisotropic metals/metal oxides within 3D GA toward useful applications.
Well behaved anisotropic compact star models in general relativity
Jasim, M. K.; Maurya, S. K.; Gupta, Y. K.; Dayanandan, B.
2016-11-01
Anisotropic compact star models have been constructed by assuming a particular form of a metric function e^{λ}. We solved the Einstein field equations for determining the metric function e^{ν}. For this purpose we have assumed a physically valid expression of radial pressure (pr). The obtained anisotropic compact star model is representing the realistic compact objects such as PSR 1937 +21. We have done an extensive study about physical parameters for anisotropic models and found that these parameters are well behaved throughout inside the star. Along with these we have also determined the equation of state for compact star which gives the radial pressure is purely the function of density i.e. pr=f(ρ).
Anisotropic Electron Tail Generation during Tearing Mode Magnetic Reconnection
DuBois, Ami M.; Almagri, Abdulgader F.; Anderson, Jay K.; Den Hartog, Daniel J.; Lee, John David; Sarff, John S.
2017-02-01
The first experimental evidence of anisotropic electron energization during magnetic reconnection that favors a direction perpendicular to the guide magnetic field in a toroidal, magnetically confined plasma is reported in this Letter. Magnetic reconnection plays an important role in particle heating, energization, and transport in space and laboratory plasmas. In toroidal devices like the Madison Symmetric Torus, discrete magnetic reconnection events release large amounts of energy from the equilibrium magnetic field. Fast x-ray measurements imply a non-Maxwellian, anisotropic energetic electron tail is formed at the time of reconnection. The tail is well described by a power-law energy dependence. The expected bremsstrahlung from an electron distribution with an anisotropic energetic tail (v⊥>v∥ ) spatially localized in the core region is consistent with x-ray emission measurements. A turbulent process related to tearing fluctuations is the most likely cause for the energetic electron tail formation.
Nonlinear analysis of traffic jams in an anisotropic continuum model
Institute of Scientific and Technical Information of China (English)
Arvind Kumar Gupta; Sapna Sharma
2010-01-01
This paper presents our study of the nonlinear stability of a new anisotropic continuum traffic flow model in which the dimensionless parameter or anisotropic factor controls the non-isotropic character and diffusive influence. In order to establish traffic flow stability criterion or to know the critical parameters that lead, on one hand, to a stable response to perturbations or disturbances or, on the other hand, to an unstable response and therefore to a possible congestion, a nonlinear stability criterion is derived by using a wavefront expansion technique. The stability criterion is illustrated by numerical results using the finite difference method for two different values of anisotropic parameter. It is also been observed that the newly derived stability results are consistent with previously reported results obtained using approximate linearisation methods. Moreover, the stability criterion derived in this paper can provide more refined information from the perspective of the capability to reproduce nonlinear traffic flow behaviors observed in real traffic than previously established methodologies.
Generation of Curvature Perturbations with Extra Anisotropic Stress
Kojima, Kazuhiko; Mathews, Grant J
2009-01-01
We study the evolution of curvature perturbations and the cosmic microwave background (CMB) power spectrum in the presence of an hypothesized extra anisotropic stress in the early universe. Such extra anisotropic stress terms might arise, for example, from the presence of the dark radiation term in brane-world cosmology. For the first time we evolve the scalar modes of such perturbations before and after neutrino decoupling and analyze their effects on the CMB spectrum. A novel result of this work is that the cancellation of the neutrino and extra anisotropic stress could lead to a spectrum of residual curvature perturbations which by themselves could reproduce the observed CMB power spectrum. This possibility may be testable as it would generate non-Gaussian fluctuations which could be constrained by future observations of density fluctuations.
Geodesic acoustic mode in anisotropic plasma with heat flux
Energy Technology Data Exchange (ETDEWEB)
Ren, Haijun, E-mail: hjren@ustc.edu.cn [CAS Key Laboratory of Geospace Environment and Department of Modern Physics, University of Science and Technology of China, Hefei 230026 (China)
2015-10-15
Geodesic acoustic mode (GAM) in an anisotropic tokamak plasma is investigated in fluid approximation. The collisionless anisotropic plasma is described within the 16-momentum magnetohydrodynamic (MHD) fluid closure model, which takes into account not only the pressure anisotropy but also the anisotropic heat flux. It is shown that the GAM frequency agrees better with the kinetic result than the standard Chew-Goldberger-Low (CGL) MHD model. When zeroing the anisotropy, the 16-momentum result is identical with the kinetic one to the order of 1/q{sup 2}, while the CGL result agrees with the kinetic result only on the leading order. The discrepancies between the results of the CGL fluid model and the kinetic theory are well removed by considering the heat flux effect in the fluid approximation.
3-D waveform tomography sensitivity kernels for anisotropic media
Djebbi, R.
2014-01-01
The complications in anisotropic multi-parameter inversion lie in the trade-off between the different anisotropy parameters. We compute the tomographic waveform sensitivity kernels for a VTI acoustic medium perturbation as a tool to investigate this ambiguity between the different parameters. We use dynamic ray tracing to efficiently handle the expensive computational cost for 3-D anisotropic models. Ray tracing provides also the ray direction information necessary for conditioning the sensitivity kernels to handle anisotropy. The NMO velocity and η parameter kernels showed a maximum sensitivity for diving waves which results in a relevant choice of those parameters in wave equation tomography. The δ parameter kernel showed zero sensitivity; therefore it can serve as a secondary parameter to fit the amplitude in the acoustic anisotropic inversion. Considering the limited penetration depth of diving waves, migration velocity analysis based kernels are introduced to fix the depth ambiguity with reflections and compute sensitivity maps in the deeper parts of the model.
Strongly interacting particles on an anisotropic kagome lattice
Energy Technology Data Exchange (ETDEWEB)
Hotta, Chisa; Pollmann, Frank, E-mail: chisa@cc.kyoto-su.ac.j [Kyoto Sangyo University, Department of Physics, Faculty of Science, Kyoto 603-8555, Japan Department of Physics, University of California, Berkeley, CA94720 (United States)
2009-01-01
We study a model of strongly interacting spinless fermions and hard-core bosons on an anisotropic kagome lattice near 2/3-filling. Our main focus lies on the strongly anisotropic case in which the nearest-neighbor repulsions V and V' are large compared to the hopping amplitudes |t| and |t'|. When t = t' = 0, the system has a charge ordered insulating ground state where the charges align in striped configurations. Doping one electron or hole into the ground state yields an anisotropic metal at V' > V, where the particle fractionalizes along the V'-bonds while propagates along the V-bonds in a one-body like manner. The sixth order ring exchange processes around the hexagonal unit of the lattice play a crucial role in forming a bound state of fractional charges.
Strongly interacting particles on an anisotropic kagome lattice
Hotta, Chisa; Pollmann, Frank
2009-01-01
We study a model of strongly interacting spinless fermions and hard-core bosons on an anisotropic kagome lattice near 2/3-filling. Our main focus lies on the strongly anisotropic case in which the nearest-neighbor repulsions V and V' are large compared to the hopping amplitudes |t| and |t'|. When t = t' = 0, the system has a charge ordered insulating ground state where the charges align in striped configurations. Doping one electron or hole into the ground state yields an anisotropic metal at V' > V, where the particle fractionalizes along the V'-bonds while propagates along the V-bonds in a one-body like manner. The sixth order ring exchange processes around the hexagonal unit of the lattice play a crucial role in forming a bound state of fractional charges.
Reduction of noise in diffusion tensor images using anisotropic smoothing.
Ding, Zhaohua; Gore, John C; Anderson, Adam W
2005-02-01
To improve the accuracy of tissue structural and architectural characterization with diffusion tensor imaging, a novel smoothing technique is developed for reducing noise in diffusion tensor images. The technique extends the traditional anisotropic diffusion filtering method by allowing isotropic smoothing within homogeneous regions and anisotropic smoothing along structure boundaries. This is particularly useful for smoothing diffusion tensor images in which direction information contained in the tensor needs to be restored following noise corruption and preserved around tissue boundaries. The effectiveness of this technique is quantitatively studied with experiments on simulated and human in vivo diffusion tensor data. Illustrative results demonstrate that the anisotropic smoothing technique developed can significantly reduce the impact of noise on the direction as well as anisotropy measures of the diffusion tensor images.
Vacuum self similar anisotropic cosmologies in $F(R)-$gravity
Apostolopoulos, Pantelis S
2016-01-01
The implications from the existence of a proper Homothetic Vector Field (HVF) on the dynamics of vacuum anisotropic models in $F(R)$ gravitational theory are studied. The fact that \\emph{every} Spatially Homogeneous vacuum model is equivalent, formally, with a \\textquotedblleft flux\\textquotedblright -free anisotropic fluid model in standard gravity and the induced power-law form of the functional $F(R)$ due to self-similarity enable us to close the system of equations. We found some new exact anisotropic solutions that arise as fixed points in the associated dynamical system. The non-existence of Kasner-like (Bianchi type I) solutions in proper $F(R)-$gravity (i.e. $R\
Anisotropic Smoothing Improves DT-MRI-Based Muscle Fiber Tractography.
Directory of Open Access Journals (Sweden)
Amanda K W Buck
Full Text Available To assess the effect of anisotropic smoothing on fiber tracking measures, including pennation angle, fiber tract length, and fiber tract number in the medial gastrocnemius (MG muscle in healthy subjects using diffusion-weighted magnetic resonance imaging (DW-MRI.3T DW-MRI data were used for muscle fiber tractography in the MG of healthy subjects. Anisotropic smoothing was applied at three levels (5%, 10%, 15%, and pennation angle, tract length, fiber tract number, fractional anisotropy, and principal eigenvector orientation were quantified for each smoothing level.Fiber tract length increased with pre-fiber tracking smoothing, and local heterogeneities in fiber direction were reduced. However, pennation angle was not affected by smoothing.Modest anisotropic smoothing (10% improved fiber-tracking results, while preserving structural features.
Wave velocities in a pre-stressed anisotropic elastic medium
Indian Academy of Sciences (India)
M D Sharma; Neetu Garg
2006-04-01
Modiﬁed Christoffel equations are derived for three-dimensional wave propagation in a general anisotropic medium under initial stress.The three roots of a cubic equation deﬁne the phase velocities of three quasi-waves in the medium.Analytical expressions are used to calculate the directional derivatives of phase velocities.These derivatives are,further,used to calculate the group velocities and ray directions of the three quasi-waves in a pre-stressed anisotropic medium.Effect of initial stress on wave propagation is observed through the deviations in phase velocity,group velocity and ray direction for each of the quasi-waves.The variations of these deviations with the phase direction are plotted for a numerical model of general anisotropic medium with triclinic/ monoclinic/orthorhombic symmetry.
Anisotropic models are unitary: A rejuvenation of standard quantum cosmology
Pal, Sridip
2016-01-01
The present work proves that the folk-lore of the pathology of non-conservation of probability in quantum anisotropic models is wrong. It is shown in full generality that all operator ordering can lead to a Hamiltonian with a self-adjoint extension as long as it is constructed to be a symmetric operator, thereby making the problem of non-unitarity in context of anisotropic homogeneous model a ghost. Moreover, it is indicated that the self-adjoint extension is not unique and this non-uniqueness is suspected not to be a feature of Anisotropic model only, in the sense that there exists operator orderings such that Hamiltonian for an isotropic homogeneous cosmological model does not have unique self-adjoint extension, albeit for isotropic model, there is a special unique extension associated with quadratic form of Hamiltonian i.e {\\it Friedrichs extension}. Details of calculations are carried out for a Bianchi III model.
Scattering of electromagnetic light waves from a deterministic anisotropic medium
Li, Jia; Chang, Liping; Wu, Pinghui
2015-11-01
Based on the weak scattering theory of electromagnetic waves, analytical expressions are derived for the spectral densities and degrees of polarization of an electromagnetic plane wave scattered from a deterministic anisotropic medium. It is shown that the normalized spectral densities of scattered field is highly dependent of changes of the scattering angle and degrees of polarization of incident plane waves. The degrees of polarization of scattered field are also subjective to variations of these parameters. In addition, the anisotropic effective radii of the dielectric susceptibility can lead essential influences on both spectral densities and degrees of polarization of scattered field. They are highly dependent of the effective radii of the medium. The obtained results may be applicable to determine anisotropic parameters of medium by quantitatively measuring statistics of a far-zone scattered field.
Modeling anisotropic Maxwell-Jüttner distributions: derivation and properties
Livadiotis, George
2016-12-01
In this paper we develop a model for the anisotropic Maxwell-Jüttner distribution and examine its properties. First, we provide the characteristic conditions that the modeling of consistent and well-defined anisotropic Maxwell-Jüttner distributions needs to fulfill. Then, we examine several models, showing their possible advantages and/or failures in accordance to these conditions. We derive a consistent model, and examine its properties and its connection with thermodynamics. We show that the temperature equals the average of the directional temperature-like components, as it holds for the classical, anisotropic Maxwell distribution. We also derive the internal energy and Boltzmann-Gibbs entropy, where we show that both are maximized for zero anisotropy, that is, the isotropic Maxwell-Jüttner distribution.
Self-force on dislocation segments in anisotropic crystals
Energy Technology Data Exchange (ETDEWEB)
Fitzgerald, S P [EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); Aubry, S, E-mail: steve.fitzgerald@ccfe.ac.u [Department of Mechanical Engineering, Stanford University, Stanford, CA (United States)
2010-07-28
A dislocation segment in a crystal experiences a 'self-force', by virtue of the orientation dependence of its elastic energy. If the crystal is elastically isotropic, this force is manifested as a couple acting to rotate the segment toward the lower energy of the pure screw orientation (i.e. acting to align the dislocation line with its Burgers vector). If the crystal is anisotropic, there are additional contributions to the couple, arising from the more complex energy landscape of the lattice itself. These effects can strongly influence the dynamic evolution of dislocation networks, and via their governing role in dislocation multiplication phenomena, control plastic flow in metals. In this paper we develop a model for dislocation self-forces in a general anisotropic crystal, and briefly consider the technologically important example of {alpha}-iron, which becomes increasingly anisotropic as the temperature approaches that of the {alpha}-{gamma} phase transition at 912 {sup 0}C.
Cosmological MHD simulations of cluster formation with anisotropic thermal conduction
Ruszkowski, M; Bruggen, M; Parrish, I; Oh, S Peng
2010-01-01
(abridged) The ICM has been suggested to be buoyantly unstable in the presence of magnetic field and anisotropic thermal conduction. We perform first cosmological simulations of galaxy cluster formation that simultaneously include magnetic fields, radiative cooling and anisotropic thermal conduction. In isolated and idealized cluster models, the magnetothermal instability (MTI) tends to reorient the magnetic fields radially. Using cosmological simulations of the Santa Barbara cluster we detect radial bias in the velocity and magnetic fields. Such radial bias is consistent with either the inhomogeneous radial gas flows due to substructures or residual MTI-driven field rearangements that are expected even in the presence of turbulence. Although disentangling the two scenarios is challenging, we do not detect excess bias in the runs that include anisotropic thermal conduction. The anisotropy effect is potentially detectable via radio polarization measurements with LOFAR and SKA and future X-ray spectroscopic stu...
The Shear Viscosity in an Anisotropic Unitary Fermi Gas
Samanta, Rickmoy; Trivedi, Sandip P
2016-01-01
We consider a system consisting of a strongly interacting, ultracold unitary Fermi gas under harmonic confinement. Our analysis suggests the possibility of experimentally studying, in this system, an anisotropic shear viscosity tensor driven by the anisotropy in the trapping potential. In particular, we suggest that this experimental setup could mimic some features of anisotropic geometries that have recently been studied for strongly coupled field theories which have a gravitational dual. Results using the AdS/CFT correspondence in these theories show that in systems with a background linear potential, certain viscosity components can be made much smaller than the entropy density, parametrically violating the KSS bound. This intuition, along with results from a Boltzmann analysis that we perform, suggests that a violation of the KSS bound can perhaps occur in the unitary Fermi gas system when it is subjected to a suitable anisotropic trapping potential. We give a concrete proposal for an experimental setup w...
Energy Technology Data Exchange (ETDEWEB)
Assadi, Abbas, E-mail: assadi@aut.ac.ir; Salehi, Manouchehr, E-mail: msalehi@aut.ac.ir; Akhlaghi, Mehdi, E-mail: makhlagi@aut.ac.ir
2015-07-17
In this work, size dependent behavior of single crystalline normal and auxetic anisotropic nanoplates is discussed with consideration of material surface stresses via a generalized model. Bending of pressurized nanoplates and their fundamental resonant frequency are discussed for different crystallographic directions and anisotropy degrees. It is explained that the orientation effects are considerable when the nanoplates' edges are pinned but for clamped nanoplates, the anisotropy effect may be ignored. The size effects are the highest when the simply supported nanoplates are parallel to [110] direction but as the anisotropy gets higher, the size effects are reduced. The orientation effect is also discussed for possibility of self-instability occurrence in nanoplates. The results in simpler cases are compared with previous experiments for nanowires but with a correction factor. There are still some open questions for future studies. - Highlights: • Size effects in single crystalline anisotropic nanoplates are discussed. • A generalized model is established containing some physical assumptions. • Orientation dependent size effects due to material anisotropy are explained. • Bending, instability and frequencies are studied at normal/auxetic domain.
Anisotropic ferromagnetic behaviors in highly orientated epitaxial NiO-based thin films
Directory of Open Access Journals (Sweden)
Yu-Jun Zhang
2015-07-01
Full Text Available Antiferromagnetic materials attract a great amount of attention recently for promising antiferromagnet-based spintronics applications. NiO is a conventional antiferromagnetic semiconductor material and can show ferromagnetism by doping other magnetic elements. In this work, we synthesized epitaxial Fe-doped NiO thin films on SrTiO3 substrates with various crystal orientations by pulsed laser deposition. The room-temperature ferromagnetism of these films is anisotropic, including the saturated magnetization and the coercive field. The anisotropic magnetic behaviors of Fe-doped NiO diluted magnetic oxide system should be closely correlated to the magnetic structure of antiferromagnetic NiO base. Within the easy plane of NiO, the coercive field of the films becomes smaller, and larger coercive field while tested out of the easy plane of NiO. The saturated magnetization anisotropy is due to different strain applied by different substrates. These results lead us to more abundant knowledge of the exchange interactions in this conventional antiferromagnetic system.
Decorrelation of anisotropic flow along the longitudinal direction
Energy Technology Data Exchange (ETDEWEB)
Pang, Long-Gang [Frankfurt Institute for Advanced Studies, Frankfurt am Main (Germany); Petersen, Hannah [Frankfurt Institute for Advanced Studies, Frankfurt am Main (Germany); Goethe University, Institute for Theoretical Physics, Frankfurt am Main (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany); Qin, Guang-You [Central China Normal University, Key Laboratory of Quark and Lepton Physics (MOE) and Institute of Particle Physics, Wuhan (China); Roy, Victor [Goethe University, Institute for Theoretical Physics, Frankfurt am Main (Germany); Wang, Xin-Nian [Central China Normal University, Key Laboratory of Quark and Lepton Physics (MOE) and Institute of Particle Physics, Wuhan (China); Lawrence Berkeley National Laboratory, Nuclear Science Division MS70R0319, Berkeley, CA (United States)
2016-04-15
The initial energy density distribution and fluctuations in the transverse direction lead to anisotropic flow of final hadrons through collective expansion in high-energy heavy-ion collisions. Fluctuations along the longitudinal direction, on the other hand, can result in decorrelation of anisotropic flow in different regions of pseudorapidity (η). Decorrelation of the 2nd- and 3rd-order anisotropic flow with different η gaps for final charged hadrons in high-energy heavy-ion collisions is studied in an event-by-event (3+1)D ideal hydrodynamic model with fully fluctuating initial conditions from A Multi-Phase Transport (AMPT) model. The decorrelation of anisotropic flow of final hadrons with large η gaps is found to originate from the spatial decorrelation along the longitudinal direction in the AMPT initial conditions through hydrodynamic evolution. The decorrelation is found to consist of both a linear twist and random fluctuation of the event plane angles. The agreement between our results and recent CMS data in most centralities suggests that the string-like mechanism of initial parton production in AMPT model captures the initial longitudinal fluctuation that is responsible for the measured decorrelation of anisotropic flow in Pb+Pb collisions at LHC. Our predictions for Au+Au collisions at the highest RHIC energy show stronger longitudinal decorrelation, indicating larger longitudinal fluctuations at lower beam energies. Our study also calls into question some of the current experimental methods for measuring anisotropic flow and the quantitative extraction of transport coefficients through comparisons to hydrodynamic simulations that do not include longitudinal fluctuations. (orig.)
Decorrelation of anisotropic flow along the longitudinal direction
Pang, Long-Gang; Petersen, Hannah; Qin, Guang-You; Roy, Victor; Wang, Xin-Nian
2016-04-01
The initial energy density distribution and fluctuations in the transverse direction lead to anisotropic flow of final hadrons through collective expansion in high-energy heavy-ion collisions. Fluctuations along the longitudinal direction, on the other hand, can result in decorrelation of anisotropic flow in different regions of pseudorapidity ( η . Decorrelation of the 2nd- and 3rd-order anisotropic flow with different η gaps for final charged hadrons in high-energy heavy-ion collisions is studied in an event-by-event (3+1)D ideal hydrodynamic model with fully fluctuating initial conditions from A Multi-Phase Transport (AMPT) model. The decorrelation of anisotropic flow of final hadrons with large η gaps is found to originate from the spatial decorrelation along the longitudinal direction in the AMPT initial conditions through hydrodynamic evolution. The decorrelation is found to consist of both a linear twist and random fluctuation of the event plane angles. The agreement between our results and recent CMS data in most centralities suggests that the string-like mechanism of initial parton production in AMPT model captures the initial longitudinal fluctuation that is responsible for the measured decorrelation of anisotropic flow in Pb+Pb collisions at LHC. Our predictions for Au+Au collisions at the highest RHIC energy show stronger longitudinal decorrelation, indicating larger longitudinal fluctuations at lower beam energies. Our study also calls into question some of the current experimental methods for measuring anisotropic flow and the quantitative extraction of transport coefficients through comparisons to hydrodynamic simulations that do not include longitudinal fluctuations.