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1

New transport properties of anisotropic holographic superfluids  

NASA Astrophysics Data System (ADS)

We complete the analysis of transport phenomena in p-wave superfluids within gauge/gravity duality, using the SU(2) Einstein-Yang-Mills model with backreaction. In particular, we analyze the fluctuation modes of helicity zero in addition to the helicity one and two modes studied earlier. We compute a further transport coefficient, associated to the first normal stress difference, not previously considered in the holographic context. In the unbroken phase this is related to a minimally coupled scalar on the gravity side. Moreover we find transport phenomena related to the thermoelectric and piezoelectric effects, in particular in the direction of the condensate, as well as the flexoelectric effect. These are similar to phenomena observed in condensed matter systems.

Erdmenger, Johanna; Fernández, Daniel; Zeller, Hansjörg

2013-04-01

2

Anisotropic Neutron Transport Analysis  

Microsoft Academic Search

This study is concerned with the analysis of the neutron transport equation with anisotropic phenomena. The mathematical method chosen for this analysis is the partial-range orthogonal function for the representation of the angular dependence of the pertinent angular neutronic functions. These functions are the neutron angular flux and the external sources of neutrons as well as the scattering functions. Of

El-Tantawy Abdel-Azim Attia

1976-01-01

3

Magnetically aligned single wall carbon nanotube films: Preferred orientation and anisotropic transport properties  

NASA Astrophysics Data System (ADS)

Thick films of single wall carbon nanotubes (SWNT) exhibiting in-plane preferred orientation have been produced by filter deposition from suspension in strong magnetic fields. We characterize the field-induced alignment with x-ray fiber diagrams and polarized Raman scattering, using a model which includes a completely unaligned fraction. We correlate the texture parameters with resistivity and thermal conductivity measured parallel and perpendicular to the alignment direction. Results obtained with 7 and 26 T fields are compared. We find no significant field dependence of the distribution width, while the aligned fraction is slightly greater at the higher field. Anisotropy in both transport properties is modest, with ratios in the range 5-9, consistent with the measured texture parameters assuming a simple model of rigid rod conductors. We suggest that further enhancements in anisotropic properties will require optimizing the filter deposition process rather than larger magnetic fields. We show that both x-ray and Raman data are required for a complete texture analysis of oriented SWNT materials.

Fischer, J. E.; Zhou, W.; Vavro, J.; Llaguno, M. C.; Guthy, C.; Haggenmueller, R.; Casavant, M. J.; Walters, D. E.; Smalley, R. E.

2003-02-01

4

Effect of Anisotropic Scattering on the Electron Transport Properties in CF4 Gas  

Microsoft Academic Search

The effects of anisotropy in scatterings in both elastic and inelastic collisions on the electron transport properties in CF4 gas have been examined using the extended FTI (flight time integral) method over a wide E\\/N range from 0.1 to 50 Td. Here, E and N are the electric field and the gas density, respectively and 1 Td is 1×10-17 Vcm2.

Akihide Takeda

1994-01-01

5

Anisotropic transport properties of zinc-blend ZnTe/CrTe heterogeneous junction nanodevices  

SciTech Connect

Motivated by the molecular-beam epitaxial growth of zinc-blend-type CrTe thin films on ZnTe, we present a theoretical study on the spin-polarized transport properties of ZnTe/CrTe p-n junction as spin diode and CrTe/ZnTe/CrTe magnetic tunnel junction for (001) and (011) surfaces. Both ZnTe(001)/CrTe(001) and ZnTe(011)/CrTe(011) p-n junctions show excellent spin diode effect, the majority spin current of positive voltage is much larger than that of negative voltage and the minority spin current is absolutely inhibited. The ZnTe(001)/CrTe(001) p-n junction has lower 'turn off' current and higher rectification ratio (about 10{sup 5}) than the ZnTe(011)/CrTe(011) which shows obvious anisotropy. We also find that the tunneling magneto resistance ratio of the CrTe/ZnTe/CrTe magnetic tunnel junction is up to about 4 Multiplication-Sign 10{sup 9}%.

Yao Wei; Gao, G. Y.; Zhu, S. C.; Fu, H. H. [School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074 (China); Yao, K. L. [School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074 (China); International Center of Materials Physics, Chinese Academy of Science, Shenyang 110015 (China)

2012-11-15

6

O the Transport Equations for Anisotropic Plasmas  

Microsoft Academic Search

First, I attempt to present a unified approach to the study of transport phenomena in multicoponent anisotropic space plasmas. In the limit of small temperature anisotropies this system of generalized transport equations reduces to Grad's 13-moment system of transport equations. In the collisionless limit, the generalized transport equations account for collisionless heat flow, collisionless viscosity, and large temperature anisotropies. Also,

Abdallah Rashied Barakat

1982-01-01

7

Variational nodal transport methods with anisotropic scattering  

Microsoft Academic Search

The variational nodal method is generalized to treat within-group and group-to-group anisotropic scattering in two- and three-dimensional eigenvalue and fixed source problems. The resulting formalism is implemented as the VARIational Anisotropic Nodal Transport code (VARIANT) within the shell of the Argonne National Laboratory production code DIF3D. The code is applied to a series of Cartesian and hexagonal geometry model problems

G. Palmiotti; C. B. Carrico; E. E. Lewis

1993-01-01

8

Anisotropic quantum Hall transport on misoriented substrates  

Microsoft Academic Search

Two years ago a new anisotropic Hall state was discovered at half integer filling factors.(M. P. Lilly, K. B. Cooper, J. P. Eisenstein, L. N. Pfeiffer, K. W. West, Phys. Rev. Lett. 82), 394 (1999) This effect may indicate the existence of a striped phase, whose origin remains unclear. The transport anisotropy is aligned along the principle crystallographic [0\\\\overline11] and

O. Jaeger; F. Ertl; R. A. Deutschmann; M. Bichler; M. Grayson; G. Abstreiter; E. Schuberth; C. Probst

2001-01-01

9

Comparative Calculation of Electron Transport Properties in Anisotropic Ramp Model Gas of Reid by Monte-Carlo Simulation  

NASA Astrophysics Data System (ADS)

Adopting the model differential cross sections used by Reid (1979) and by Haddad et al. (1981), an investigation to asses the discrepancies observed in the transverse diffusion coefficients D T and other transport properties are performed by the Monte-Carlo simulation. The results show that the values of ND T drastically vary with the change of anisotropy in the scattering property against the common sense that ND T is determined solely by the reduced field E/N under a given momentum transfer cross section. Cross sections so far derived from the D T/µ data may be necessary to be reassesed if anisotropy in the scattering properties is considered.

Yamamoto, Kohji; Ikuta, Nobuaki

1994-03-01

10

Quasi-diffusion and correlations in models of anisotropic transport  

NASA Astrophysics Data System (ADS)

This paper deals with scaling laws that describe transport and correlation effects in anisotropic mediums. Diffusion approximation of correlation effects is considered in a system of perpendicular random steady flows by using the Corrsin conjecture. The correlation properties of several well-known diffusive models in an anisotropic medium are investigated. We show that superdiffusive and subdiffusive behavior in the anisotropic medium with strong longitudinal correlations can be described by a single fractional differential equation. In the considered model we obtain the relationship between the Hurst exponent H, describing transverse diffusion and the correlation exponent ? by the simple expression, H=1-?/4. This result is in agreement with an analogous scaling law for isotropic medium. Permanent address: Russian Research Center ``Kurchatov Institute'', Nuclear Fusion Institute, sq. Kurchatova 1, Moscow 123182, Russia.

Bakunin, O. G.

2004-06-01

11

Variational nodal transport methods with anisotropic scattering  

SciTech Connect

The variational nodal method is generalized to treat within-group and group-to-group anisotropic scattering in two- and three-dimensional eigenvalue and fixed source problems. The resulting formalism is implemented as the VARIational Anisotropic Nodal Transport code (VARIANT) within the shell of the Argonne National Laboratory production code DIF3D. The code is applied to a series of Cartesian and hexagonal geometry model problems and the accuracy of the results compared to those from TWODANT and TWOHEX and to the Monte Carlo code VIM, respectively, in two and three dimensions. VARIANT is then applied to multigroup hexagonal representations of the Experimental Breeder Reactor II, and results are obtained for three-dimensional eigenvalue and for two-dimensional neutron-gamma heating problems.

Palmiotti, G. (Commissariat a l'Energie Atomique, Saint-Paul-les-Durance (France)); Carrico, C.B. (Argonne National Lab., Argonne, IL (United States)); Lewis, E.E. (Northwestern Univ., Evanston, IL (United States). Dept. of Mechanical Engineering)

1993-11-01

12

Anisotropic transport and magnetic properties and magnetic-field tuned states of CeZn11 single crystals  

NASA Astrophysics Data System (ADS)

We present detailed temperature- and field-dependent data obtained from magnetization, resistivity, heat capacity, Hall resistivity and thermoelectric power measurements performed on single crystals of CeZn11. The compound orders antiferromagnetically at ˜2 K. The zero-field resistivity and thermoelectric power data show features characteristic of a Ce-based intermetallic with crystal-electric-field splitting and possible Kondo lattice effects. We constructed the T-H phase diagram for the magnetic field applied along the easy [110] direction, which shows that the magnetic field required to suppress TN below 0.4 K is in the range of 45–47.5 kOe. A linear behavior of the ?(T) data, H? [110], was observed only for H=45 kOe for 0.46 K ?T? 1.96 K followed by the Landau–Fermi-liquid regime for a limited range of fields 47.5 kOe ?H? 60 kOe. From the analysis of our data, it appears that CeZn11 is a local moment compound with little or no electronic correlations arising from the Ce 4f shell. The thermoelectric and transport properties of CeZn11 are mostly governed by the crystal-electric-field effects. Given the very high quality of our single crystals, quantum oscillations are found for both CeZn11 and its nonmagnetic analog LaZn11.

Hodovanets, H.; Bud'ko, S. L.; Lin, X.; Taufour, V.; Kim, M. G.; Pratt, D. K.; Kreyssig, A.; Canfield, P. C.

2013-08-01

13

Synthesis of cubic SrCoO3 single crystal and its anisotropic magnetic and transport properties  

NASA Astrophysics Data System (ADS)

A large-size single crystal of nearly stoichiometric SrCoO3 was prepared with a two-step method combining the floating-zone technique and subsequent high oxygen pressure treatment. SrCoO3 crystallizes in a cubic perovskite structure with space group Pm\\bar {3}m , and displays an itinerant ferromagnetic behavior with the Curie temperature of 305 K. The easy magnetization axis is found to be along the [111] direction, and the saturation moment is 2.5 µB/f.u., in accord with the picture of the intermediate spin state. The resistivity at low temperatures (T) is proportional to T2, indicative of the possible effect of orbital fluctuation in the intermediate spin ferromagnetic metallic state. Unusual anisotropic magnetoresistance is also observed and its possible origin is discussed.

Long, Youwen; Kaneko, Yoshio; Ishiwata, Shintaro; Taguchi, Yasujiro; Tokura, Yoshinori

2011-06-01

14

Synthesis of cubic SrCoO3 single crystal and its anisotropic magnetic and transport properties.  

PubMed

A large-size single crystal of nearly stoichiometric SrCoO(3) was prepared with a two-step method combining the floating-zone technique and subsequent high oxygen pressure treatment. SrCoO(3) crystallizes in a cubic perovskite structure with space group Pm3m, and displays an itinerant ferromagnetic behavior with the Curie temperature of 305 K. The easy magnetization axis is found to be along the [111] direction, and the saturation moment is 2.5 µ(B)/f.u., in accord with the picture of the intermediate spin state. The resistivity at low temperatures (T) is proportional to T(2), indicative of the possible effect of orbital fluctuation in the intermediate spin ferromagnetic metallic state. Unusual anisotropic magnetoresistance is also observed and its possible origin is discussed. PMID:21628787

Long, Youwen; Kaneko, Yoshio; Ishiwata, Shintaro; Taguchi, Yasujiro; Tokura, Yoshinori

2011-06-01

15

Dephasing-induced diffusive transport in the anisotropic Heisenberg model  

NASA Astrophysics Data System (ADS)

In this work, we study the transport properties of the anisotropic Heisenberg model in a disordered magnetic field and in the presence of dephasing due to external degrees of freedom. Without dephasing, the model can display, depending on parameter values, the whole range of possible transport regimes: ideal ballistic conduction, diffusive, or ideal insulating behavior. We show that the presence of dephasing induces normal diffusive transport in a wide range of parameters. We also analyze the dependence of spin conductivity on the dephasing strength. In addition, by analyzing the decay of the spin-spin correlation function, we find a long-range order for finite chain sizes. All our results for a one-dimensional spin chain at infinite temperature can be equivalently rephrased for strongly interacting disordered spinless fermions.

Žnidari?, Marko

2010-04-01

16

Transport equations for multicomponent anisotropic space plasmas - A review  

Microsoft Academic Search

An attempt is made to present a unified approach to the study of transport phenomena in multicomponent anisotropic space plasmas. In particular, a system of generalized transport equations is presented that can be applied to widely different plasma flow conditions. The generalized transport equations can describe subsonic and supersonic flows, collision-dominated and collisionless flows, plasma flows in rapidly changing magnetic

A. R. Barakat; R. W. Schunk

1982-01-01

17

Transport equations for multicomponent anisotropic space plasmas: a review  

Microsoft Academic Search

The authors attempt to present a unified approach to the study of transport phenomena in multicomponent anisotropic space plasmas. In particular, a system of generalized transport equations is presented that can be applied to widely different plasma flow conditions. The generalized transport equations can describe subsonic and supersonic flows, collision-dominated and collisionless flows, plasma flows in rapidly changing magnetic field

A. R. BARAKAT; R. W. SCHUNK

1982-01-01

18

Anisotropic transport properties of nano-scale strips of YBa_(2)Cu_(3)O_(7) thin films grown on (110) SrTiO_(3) Substrate  

Microsoft Academic Search

Nano-scale superconducting strips have been fabricated by focused ion beam (FIB) from (110)- YBa_2Cu_3O7 (YBCO) thin films. In this study, combining standard optical lithography and FIB, we have prepared c-axis and ab-plane aligned YBCO wires of sub-100nm scale on (110) SrTiO3 substrates. Standard ac four-point probe method was used to investigate the electrical transport. Transverse and longitudinal magneto-transport properties were

Lixi Yuan; Hye-Won Seo; Chong Wang; Hongying Zhai; Quark Chen; Wei-Kan Chu

2000-01-01

19

Anisotropic transport processes in the chromosphere and overlying atmosphere  

NASA Astrophysics Data System (ADS)

Energy flow and transformation in the solar atmosphere is a complex process. Fluxes of particle kinetic and electromagnetic energy flow in both directions through the photosphere, and are transformed into one another in the overlying atmosphere. Diffusive transport processes such as electrical and thermal conduction, and viscous and thermoelectric effects play a major role in determining energy fluxes and transformation rates. Almost the entire atmosphere is strongly magnetized, meaning that charged particle cyclotron frequencies significantly exceed their collision frequencies. This causes transport processes to be anisotropic, so they must be described by tensors in MHD models. Only models that include the relevant transport tensors can reveal the processes that create and maintain the chromosphere, transition region, and corona because only such models can accurately describe energy flow and transformation. This paper outlines the importance of anisotropic transport processes in the atmosphere, especially of anisotropic electrical conduction in the weakly ionized, strongly magnetized chromosphere, and presents MHD model evidence that anisotropic electrical conduction plays a major role in shock wave and Alfvén wave heating in the chromosphere. It is proposed that magnetization induced resistivity increases with height from the photosphere, exceeds the Spitzer resistivity eta S near the height of the local temperature minimum, increases with height to orders of magnitude > eta S, and causes proton Pedersen current dissipation to be a major source of chromospheric heating.

Goodman, M. L.; Kazeminezhad, F.

20

Anisotropic Properties of Stainless Steel-Clad Aluminum Sheet  

NASA Astrophysics Data System (ADS)

The production of a stainless steel-clad aluminum sheet by the cold rolling process is a more efficient and economical approach compared with the other types of processes utilized for the production of such sheets. Because both the stainless steel and aluminum sheets show the highly anisotropic behavior, it is necessary to investigate anisotropic properties of clad sheets for the design of process. In this paper, to investigate the anisotropic properties of stainless steel-clad aluminum sheet, two kinds of clad sheets were considered: STS439/AA3003 and STS439/AA1050/STS304 clad sheets. The uni-axial tension tests at 0, 45 and 90 degrees for the rolling direction were performed to obtained yield stresses and R values. The strain ratio at balanced biaxial tension state was measured from compression disk test. In order to describe the anisotropic behavior of the clad sheet, nonquadratic anisotropic yield function Yld2000-2d was utilized.

Kim, Daeyong; Hwang, Bum Kyu; Lee, Young Seon; Kim, Ji Hoon; Kim, Min-Joong

2010-06-01

21

Synthetic acceleration methods for linear transport problems with highly anisotropic scattering  

Microsoft Academic Search

This paper reports on the diffusion synthetic acceleration (DSA) algorithm that effectively accelerates the iterative solution of transport problems with isotropic or mildly anisotropic scattering. However, DSA loses its effectiveness for transport problems that have strongly anisotropic scattering. Two generalizations of DSA are proposed, which, for highly anisotropic scattering problems, converge at least an order of magnitude (clock time) faster

K. M. Khattab; E. W. Larsen

1991-01-01

22

TOPICAL REVIEW: Textured silicon nitride: processing and anisotropic properties  

Microsoft Academic Search

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 beta-Si3N4, texture structure and texture analysis, processing methods and

Xinwen Zhu; Yoshio Sakka

2008-01-01

23

ANISOTROPIC DIFFUSIVE TRANSPORT IN ANNULUS FIBROSUS: EXPERIMENTAL DETERMINATION OF THE DIFFUSION TENSOR BY FRAP TECHNIQUE  

PubMed Central

The annulus fibrosus (AF) of the intervertebral disc (IVD) exhibits a fiber-organized structure which is responsible for anisotropic and inhomogeneous mechanical and transport properties. Due to its particular morphology, nutrient transport within AF is regulated by complex transport kinetics. This work investigates the diffusive transport of a small solute in the posterior and anterior regions of AF since diffusion is the major transport mechanism for low molecular weight nutrients (e.g., oxygen and glucose) in IVD. Diffusion coefficient (D) of fluorescein (332 Da) in bovine coccygeal AF was measured in the three major (axial, circumferential and radial) directions of the IVD by means of Fluorescence Recovery After Photobleaching (FRAP) technique. It was found that the diffusion coefficient was anisotropic and inhomogeneous. In both anterior and posterior regions, the diffusion coefficient in the radial direction was found to be lowest. Circumferential and axial diffusion coefficients were not significantly different in both posterior and anterior regions and their values were about 130% and 150% the value of the radial diffusion coefficient, respectively. The values of diffusion coefficients in the anterior region were in general higher than those of corresponding diffusion coefficients in the posterior region. This study represents the first quantitative analysis of anisotropic diffusion transport in AF by means of FRAP technique and provides additional knowledge on understanding the pathways of nutritional supply into IVD.

Travascio, Francesco; Gu, Wei Yong

2009-01-01

24

An engineered anisotropic nanofilm with unidirectional wetting properties  

NASA Astrophysics Data System (ADS)

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 80?N, 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.

Malvadkar, Niranjan A.; Hancock, Matthew J.; Sekeroglu, Koray; Dressick, Walter J.; Demirel, Melik C.

2010-12-01

25

An engineered anisotropic nanofilm with unidirectional wetting properties.  

PubMed

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 80 ?N, 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. PMID:20935657

Malvadkar, Niranjan A; Hancock, Matthew J; Sekeroglu, Koray; Dressick, Walter J; Demirel, Melik C

2010-10-10

26

Anisotropic properties in Fe-Pt thick film magnets  

SciTech Connect

As-deposited Fe-Pt thick films prepared by a pulsed laser deposition method with the laser power higher than 5 W had L1{sub 0} ordered phase without a substrate heating system. As the laser power increased, the properties of the obtained films changed from isotropic to anisotropic ones. It was also confirmed that x-ray diffraction analysis agrees with the anisotropic phenomenon in crystalline structure with increasing laser power.

Nakano, M.; Shibata, S.; Yanai, T.; Fukunaga, H. [Department of Electrical and Electronic Engineering, Nagasaki University, Nagasaki 852-8521 (Japan)

2009-04-01

27

Anisotropic electrical transport properties of a two-dimensional electron gas at SrTiO3-LaAlO3 interfaces  

SciTech Connect

Experimental evidence of strong in-plane anisotropy in electrical properties of the confined electron gas at the SrTiO{sub 3}-LaAlO{sub 3} interface on top of (LaAlO{sub 3}){sub 0.3}(Sr{sub 2}AlTaO{sub 3}){sub 0.7} substrates is provided by detailed transport measurements. Structured measurement geometries in multiple directions are used to show dependence of the sheet resistance with the in-plane angle {theta}, which is fitted with a sine function with a period of 180{sup o}. The carrier density remains constant and a directional dependence of the carrier mobility of more than one order of magnitude is determined with respect to the orientation of the unit cell height steps present at the SrTiO{sub 3}-LaAlO{sub 3} interface.

Brinks, Peter [University of Twente, Enschede, Netherlands; Siemons, Wolter [ORNL; Kleibeuker, Josee [University of Twente, Enschede, Netherlands; Koster, Gertjan [University of Twente, Enschede, Netherlands; Rijnders, Guus [MESA+ University of Twente, Enschede, Netherlands; Huijben, Mark [University of Twente, Enschede, Netherlands

2011-01-01

28

Anisotropic defect structure and transport properties of YBa2Cu3O7-? films on vicinal SrTiO3(001)  

NASA Astrophysics Data System (ADS)

The microstructure of YBa2Cu3O7-? thin films grown on vicinal SrTiO3(001) has been studied as a function of the vicinal angle by x-ray diffraction using the two-dimensional q-scan technique. Our results reveal a strong correlation between the miscut of a SrTiO3(001) substrate and the anisotropic defect structure of the film. Furthermore, we observed an anisotropy of the corresponding critical current density up to 4.6 depending on the angle of miscut.

Brötz, J.; Fuess, H.; Haage, T.; Zegenhagen, J.; Jooss, Ch.; Forkl, A.; Warthmann, R.

1999-01-01

29

Transport properties of the hard ellipsoid fluid  

Microsoft Academic Search

Transport properties of isotropic fluids composed of hard ellipsoids of revolution are studied using molecular dynamics simulation. The self-diffusion coefficient, the shear viscosity, and the thermal conductivity are evaluated for a range of densities and elongations and are compared with the results from an Enskog kinetic theory for nonspherical bodies. The full anisotropic pair correlation function, which is required input

Peter Bereolos; Julian Talbot; Michael P. Allen; Glenn T. Evans

1993-01-01

30

Vectorial Properties of Paraxial Beams Propagating in Anisotropic Metamaterials  

Microsoft Academic Search

On the basis of a suitable plane-wave angular spectrum representation of the electromagnetic field, the vectorial properties of paraxial beams propagating in anisotropic metamaterials (AMMs) are studied. It is found that the transverse field varies when the polarization or the distribution of initial electromagnetic field is changed. While the longitudinal component only dependent on the distribution of the input field.

Jingxiao Cao; Wei Hu; Hailu Luo; Xiangbo Yang

2006-01-01

31

Macroscopic electromagnetic properties of bi-anisotropic mixtures  

Microsoft Academic Search

This paper focuses on the effective properties of bi-anisotropic mixtures. The effective material parameters of mixtures are derived which consist of spherical, arbitrarily bianisotropic inclusions in an isotropic host medium. The parameters of the inclusions can have the full range of 36 components of a general linear electromagnetic medium. Six-vector notation is used to derive the results, but the final

A. H. Sihvola; J. O. Juntunen; P. Eratuuli

1996-01-01

32

Pulse shaping properties of volume holographic gratings in anisotropic media  

Microsoft Academic Search

Based on a modified coupled wave theory, the pulse shaping properties of volume holographic gratings (VHGs) in anisotropic media VHGs are studied systematically. Taking photorefractive LiNbO3 crystals as an example, the combined effect that the grating parameters, the dispersion and optical anisotropy of the crystal, the pulse width, and the polarization state of the input ultrashort pulsed beam (UPB) have

Chunhua Wang; Liren Liu; Aimin Yan; Dean Liu; Dashan Li; Weijuan Qu

2006-01-01

33

Quantum transport of atomic matter waves in anisotropic two-dimensional and three-dimensional disorder  

NASA Astrophysics Data System (ADS)

The macroscopic transport properties in a disordered potential, namely diffusion and weak/strong localization, closely depend on the microscopic and statistical properties of the disorder itself. This dependence is rich in counter-intuitive consequences. It can be particularly exploited in matter wave experiments, where the disordered potential can be tailored and controlled, and anisotropies are naturally present. In this work, we apply a perturbative microscopic transport theory and the self-consistent theory of Anderson localization to study the transport properties of ultracold atoms in anisotropic two-dimensional (2D) and three-dimensional (3D) speckle potentials. In particular, we discuss the anisotropy of single-scattering, diffusion and localization. We also calculate disorder-induced shift of the energy states and propose a method to include it, which amounts to renormalizing energies in the standard on-shell approximation. We show that the renormalization of energies strongly affects the prediction for the 3D localization threshold (mobility edge). We illustrate the theoretical findings with examples which are relevant for current matter wave experiments, where the disorder is created with laser speckle. This paper provides a guideline for future experiments aiming at the precise location of the 3D mobility edge and study of anisotropic diffusion and localization effects in 2D and 3D.

Piraud, M.; Pezzé, L.; Sanchez-Palencia, L.

2013-07-01

34

TOPICAL REVIEW: Textured silicon nitride: processing and anisotropic properties  

NASA Astrophysics Data System (ADS)

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 ?-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 ?-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 ?-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 ?-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 ?-Sialon is also reviewed, because the presence of elongated ?-Sialon grains allows the production of textured ?-Sialon using the same methods as those used for textured ?-Si3N4 and ?-Sialon. Corrections were made to this article on 24 September 2008.

Zhu, Xinwen; Sakka, Yoshio

2008-07-01

35

Origin of anisotropic nonmetallic transport in the Al80Cr15Fe5 decagonal approximant  

NASA Astrophysics Data System (ADS)

We present a study of the anisotropic transport properties (electrical resistivity, thermoelectric power, Hall coefficient, and thermal conductivity) of a single-crystalline Al80Cr15Fe5 complex metallic alloy that is an excellent approximant to the decagonal quasicrystal with six atomic layers in one periodic unit. Temperature-dependent electrical resistivity along the b and c crystalline directions shows a nonmetallic behavior with a broad maximum, whereas it shows a metallic positive temperature coefficient along the a direction perpendicular to the (b,c) atomic planes. Ab initio calculations of the electronic density of states reveal that the nonmetallic transport occurs in the presence of a high density of charge carriers. The very different temperature-dependent electrical resistivities along the three crystalline directions can all be treated within the same physical model of slow charge carriers due to weak dispersion of the electronic bands, where the increased electron-phonon scattering upon raising the temperature induces transition from dominant Boltzmann (metallic) to dominant non-Boltzmann (insulatinglike) regime. The temperature dependence of the resistivity is governed predominantly by the temperature dependence of the electronic diffusion constant D and the transition has no resemblance to the Anderson-type metal-to-insulator transition based on the gradual electron localization. Structural considerations of the Al80Cr15Fe5 phase show that the anisotropy of the transport properties is a consequence of anisotropic atomic order on the scale of nearest-neighbor atoms, suggesting that the role of quasiperiodicity in the anisotropic transport of decagonal quasicrystals is marginal. We also present a relaxed version of the Al4(Cr,Fe) structural model by Deng [J. Phys.: Condens. Matter 16, 2283 (2004)].

Dolinšek, J.; Jegli?, P.; Komelj, M.; Vrtnik, S.; Smontara, Ana; Smiljani?, I.; Biluši?, A.; Ivkov, J.; Stani?, D.; Zijlstra, E. S.; Bauer, Birgitta; Gille, P.

2007-11-01

36

Effects of highly anisotropic scattering on monoenergetic neutron transport at deep penetrations  

Microsoft Academic Search

The sensitivity of the flux in deep-penetration problems to anisotropic ; scattering was studied within the framework of monoenengetic transport theory. ; Several parameterized, anisotropic scattering kernels were used to represent a ; general class of anisotropies. The representation of these kernels in Legendre ; polynomial series of various orders was explored to determine their effect on ; calculated discrete

E. Oblow; K. Kin; H. Goldstein; J. J. Wagshal

1973-01-01

37

Description of hydraulic and strength properties of anisotropic geomaterials  

NASA Astrophysics Data System (ADS)

In this paper, a simple generalization of Darcy's law is proposed for the description of hydraulic properties of anisotropic porous materials. The coefficient of permeability is defined as a scalarvalued function of orientation. The principal directions of permeability are determined from a fabric descriptor specifying the distribution of average pore size. An example is provided for identification of material parameters, which is based on an idealized "pipe network model". A procedure for defining the anisotropy in strength properties, which incorporates a conceptually similar approach, is also reviewed and an illustrative example is provided.

Pietruszczak, S.; Pande, G. N.

2012-10-01

38

Elastic properties of anisotropic domain wall lattices  

SciTech Connect

Interest in the elastic properties of regular lattices constructed from domain walls has recently been motivated by cosmological applications as solid dark energy. This work investigates the particularly simple examples of triangular, hexagonal, and square lattices in two dimensions and a variety of more complicated lattices in three dimensions which have cubic symmetry. The relevant rigidity coefficients are computed taking into account nonaffine perturbations where necessary, and these are used to evaluate the propagation velocity for any macroscopic scale perturbation mode. Using this information we assess the stability of the various configurations. It is found that triangular lattices are isotropic and stable, whereas hexagonal lattices are unstable. It is argued that the simple orthonormal cases of a square in two dimensions and the cube in three are stable, except to perturbations of infinite extent. We also find that the more complicated case of a rhombic dodecahedral lattice is stable, except to the existence of transverse modes in certain directions, whereas a lattice formed from truncated octahedra is unstable.

Battye, Richard A.; Moss, Adam [Jodrell Bank Observatory, School of Physics and Astronomy, University of Manchester, Macclesfield, Cheshire SK11 9DL (United Kingdom); Chachoua, Elie [LuTh, Observatoire de Paris, Meudon 92195 (France)

2006-06-15

39

Anisotropic electron transport properties in sumanene crystal.  

PubMed

The high electron mobility with large anisotropy was attained in the needle-like single crystal of sumanene, which was indicated by time-resolved microwave conductivity (TRMC) measurement. PMID:19105693

Amaya, Toru; Seki, Shu; Moriuchi, Toshiyuki; Nakamoto, Kana; Nakata, Takuto; Sakane, Hiroyuki; Saeki, Akinori; Tagawa, Seiichi; Hirao, Toshikazu

2009-01-21

40

Anisotropic optical and thermoelectric properties of In4Se3 and In4Te3  

NASA Astrophysics Data System (ADS)

The anisotropic optical and thermoelectric properties of In4Se3 and In4Te3 are studied by the first-principles calculation using the full-potential linearized augmented plane-wave method and the semiclassical Boltzmann theory. The optical properties show highly anisotropic in the energy range between 0.0 and 12.0 eV for In4Se3 and between 0.0 and 10.0 eV for In4Te3 while it is isotropic in the higher energy range for In4Se3. In contrast to S, the anisotropies of the electrical conductivities and power factors are great affected by the change of the temperature. Their anisotropies become larger along three directions with the growth of the temperature. S2?/? along the y direction is much higher than that along the x and z directions for In4Se3, which shows that the thermoelectric thin films with excellent performance can be obtained along the (010) surface. By studying the anisotropy of transport properties, we find that the transport properties of In4Se3 are better than that of In4Te3, which mainly comes from the small band gap of In4Se3. The anisotropy of S2?/? for In4Se3 is larger than that for In4Te3, and the anisotropy of S2?/? is mainly due to the anisotropy of ?/?.

Li, Xingfu; Xu, Bin; Yu, Gongqi; Xue, Li; Yi, Lin

2013-05-01

41

Pulse shaping properties of volume holographic gratings in anisotropic media  

NASA Astrophysics Data System (ADS)

Based on a modified coupled wave theory, the pulse shaping properties of volume holographic gratings (VHGs) in anisotropic media VHGs are studied systematically. Taking photorefractive LiNbO3 crystals as an example, the combined effect that the grating parameters, the dispersion and optical anisotropy of the crystal, the pulse width, and the polarization state of the input ultrashort pulsed beam (UPB) have on the pulse shaping properties are considered when the input UPB with arbitrary polarization state propagates through the VHG. Under the combined effect, the diffraction bandwidth, pulse profiles of the diffracted and transmitted pulsed beams, and the total diffraction efficiency are shown. The studies indicate that the properties of the shaping of the o and e components of the input UPB in the crystal are greatly different; this difference can be used for pulse shaping applications.

Wang, Chunhua; Liu, Liren; Yan, Aimin; Liu, Dean; Li, Dashan; Qu, Weijuan

2006-12-01

42

Pulse shaping properties of volume holographic gratings in anisotropic media.  

PubMed

Based on a modified coupled wave theory, the pulse shaping properties of volume holographic gratings (VHGs) in anisotropic media VHGs are studied systematically. Taking photorefractive LiNbO(3) crystals as an example, the combined effect that the grating parameters, the dispersion and optical anisotropy of the crystal, the pulse width, and the polarization state of the input ultrashort pulsed beam (UPB) have on the pulse shaping properties are considered when the input UPB with arbitrary polarization state propagates through the VHG. Under the combined effect, the diffraction bandwidth, pulse profiles of the diffracted and transmitted pulsed beams, and the total diffraction efficiency are shown. The studies indicate that the properties of the shaping of the o and e components of the input UPB in the crystal are greatly different; this difference can be used for pulse shaping applications. PMID:17106475

Wang, Chunhua; Liu, Liren; Yan, Aimin; Liu, Dean; Li, Dashan; Qu, Weijuan

2006-12-01

43

Anisotropic magnetism and spin-dependent transport in Co nanoparticle embedded ZnO thin films  

NASA Astrophysics Data System (ADS)

Oriented Co nanoparticles were obtained by Co ion implantation in crystalline ZnO thin films grown by pulsed laser deposition. Transmission electron microscopy revealed the presence of elliptically shaped Co precipitates with nanometer size, which are embedded in the ZnO thin films, resulting in anisotropic magnetic behavior. The low-temperature resistance of the Co-implanted ZnO thin films follows the Efros-Shklovskii type variable-range-hopping. Large negative magnetoresistance (MR) exceeding 10% is observed in a magnetic field of 1 T at 2.5 K and the negative MR survives up to 250 K (0.3%). The negative MR reveals hysteresis as well as anisotropy that correlate well with the magnetic properties, clearly demonstrating the presence of spin-dependent transport.

Li, D. Y.; Zeng, Y. J.; Pereira, L. M. C.; Batuk, D.; Hadermann, J.; Zhang, Y. Z.; Ye, Z. Z.; Temst, K.; Vantomme, A.; Van Bael, M. J.; Van Haesendonck, C.

2013-07-01

44

VARIANT: VARIational anisotropic nodal transport for multidimensional Cartesian and hexadgonal geometry calculation  

Microsoft Academic Search

The theoretical basis, implementation information and numerical results are presented for VARIANT (VARIational Anisotropic Neutron Transport), a FORTRAN module of the DIF3D code system at Argonne National Laboratory. VARIANT employs the variational nodal method to solve multigroup steady-state neutron diffusion and transport problems. The variational nodal method is a hybrid finite element method that guarantees nodal balance and permits spatial

G. Palmiotti; C. B. Carrico; E. E. Lewis

1995-01-01

45

Optical properties of strongly coupled d-wave superconductors with an anisotropic momentum dependent interaction  

Microsoft Academic Search

We have studied within the Eliashberg framework properties of a two-dimensional d-wave superconductor where the electron-boson interaction leading to pairing in the superconducting state is a highly anisotropic function of momentum. Adding to the momentum anisotropy is an underlying single particle band structure based on a two-dimensional tight-binding model. The convolution of anisotropic interaction and anisotropic energy dispersion leads to

Dwayne Gordon Branch

1998-01-01

46

Optical Properties of Strongly-Coupled d-wave Superconductors with an Anisotropic Momentum Dependent Interaction  

Microsoft Academic Search

We have studied within the Eliashberg framework properties of a two-dimensional d-wave superconductor where the electron-boson interaction leading to pairing in the superconducting state is a highly anisotropic function of momentum. Adding to the momentum anisotropy is an underlying single particle band structure based on a two-dimensional tight-binding model. The convolution of anisotropic interaction and anisotropic energy dispersion leads to

Dwayne G Branch

1997-01-01

47

Crystal's anisotropic properties and tensor representation: a discussion  

NASA Astrophysics Data System (ADS)

For most applications, crystals need a careful selection to process an appropriate symmetry for a particular application. A crystal is innately symmetrical; hence it presents the same appearance from a number of different directions. Some of the physical properties of crystals which exhibit dependence on symmetry elements are presented. A method of using the inherent symmetry in order to simplify the formulation of the physical properties is needed. The use of tensors is one such tool. The authors review what tensors of different ranks are, and show how such tensors can be used to describe the directional variation of the physical properties within crystals. These arise when a tensor relates a vector to a second-rank tensor. Properties that involve third-rank tensors include the piezoelectric effect. However, to exhibit the reduction of the number of tensor components further, consider the fourth-rank tensors. Both stress and strain can be represented by second-rank tensors, the modulus can be represented by a fourth-rank tensor. Stress is the force acting in any direction divided by the area. The fourth-rank elasticity tensor of an anisotropic and linear elastic material of the material is considered.

Talebian, E.; Talebian, M.

2011-12-01

48

The generalized P{sub N} synthetic acceleration method for linear transport problems with highly anisotropic scattering  

Microsoft Academic Search

The diffusion synthetic acceleration (DSA) method has been known to be an effective tool for accelerating the iterative solution of transport equations with isotropic or mildly anisotropic scattering. However, the DSA method is not effective for transport equations that have strongly anisotropic scattering. A generalization of the modified DSA (MDSA) method is proposed that converges (clock time) faster than the

Khattab

1997-01-01

49

Local and nonlocal anisotropic transport in reversed shear magnetic fields: Shearless Cantori and nondiffusive transport  

NASA Astrophysics Data System (ADS)

A study of anisotropic heat transport in reversed shear (nonmonotonic q-profile) magnetic fields is presented. The approach is based on a recently proposed Lagrangian-Green's function method that allows an efficient and accurate integration of the parallel (i.e., along the magnetic field) heat transport equation. The magnetic field lines are described by a nontwist Hamiltonian system, known to exhibit separatrix reconnection and robust shearless (dq/dr=0) transport barriers. The changes in the magnetic field topology due to separatrix reconnection lead to bifurcations in the equilibrium temperature distribution. For perturbations of moderate amplitudes, magnetic chaos is restricted to bands flanking the shearless region. As a result, the temperature flattens in the chaotic bands and develops a very sharp radial gradient at the shearless region. For perturbations with larger amplitude, shearless Cantori (i.e., critical magnetic surfaces located at the minimum of the q profile) give rise to anomalous temperature relaxation involving widely different time scales. The first stage consists of the relatively fast flattening of the radial temperature profile in the chaotic bands with negligible flux across the shearless region that, for practical purposes, on a short time scale acts as an effective transport barrier despite the lack of magnetic flux surfaces. In the long-time scale, heat starts to flow across the shearless region, albeit at a comparatively low rate. The transport of a narrow temperature pulse centered at the reversed shear region exhibits weak self-similar scaling with non-Gaussian scaling functions indicating that transport at this scale cannot be modeled as a diffusive process with a constant diffusivity. Evidence of nonlocal effective radial transport is provided by the existence of regions with nonzero heat flux and zero temperature gradient. Parametric flux-gradient plots exhibit multivalued loops that question the applicability of the Fourier-Fick's prescription even in the presence of a finite pinch velocity.

Blazevski, Daniel; del-Castillo-Negrete, Diego

2013-06-01

50

Local and nonlocal anisotropic transport in reversed shear magnetic fields: shearless Cantori and nondiffusive transport.  

PubMed

A study of anisotropic heat transport in reversed shear (nonmonotonic q-profile) magnetic fields is presented. The approach is based on a recently proposed Lagrangian-Green's function method that allows an efficient and accurate integration of the parallel (i.e., along the magnetic field) heat transport equation. The magnetic field lines are described by a nontwist Hamiltonian system, known to exhibit separatrix reconnection and robust shearless (dq/dr=0) transport barriers. The changes in the magnetic field topology due to separatrix reconnection lead to bifurcations in the equilibrium temperature distribution. For perturbations of moderate amplitudes, magnetic chaos is restricted to bands flanking the shearless region. As a result, the temperature flattens in the chaotic bands and develops a very sharp radial gradient at the shearless region. For perturbations with larger amplitude, shearless Cantori (i.e., critical magnetic surfaces located at the minimum of the q profile) give rise to anomalous temperature relaxation involving widely different time scales. The first stage consists of the relatively fast flattening of the radial temperature profile in the chaotic bands with negligible flux across the shearless region that, for practical purposes, on a short time scale acts as an effective transport barrier despite the lack of magnetic flux surfaces. In the long-time scale, heat starts to flow across the shearless region, albeit at a comparatively low rate. The transport of a narrow temperature pulse centered at the reversed shear region exhibits weak self-similar scaling with non-Gaussian scaling functions indicating that transport at this scale cannot be modeled as a diffusive process with a constant diffusivity. Evidence of nonlocal effective radial transport is provided by the existence of regions with nonzero heat flux and zero temperature gradient. Parametric flux-gradient plots exhibit multivalued loops that question the applicability of the Fourier-Fick's prescription even in the presence of a finite pinch velocity. PMID:23848788

Blazevski, Daniel; del-Castillo-Negrete, Diego

2013-06-10

51

Thermal and transport properties of strongly correlated systems  

Microsoft Academic Search

We use a model-independent quasiparticle approach to the calculation of the properties of strongly correlated gap-anisotropic materials. In this framework we show how the measurement of thermal properties is insufficient to distinguish between different gap symmetries. The study of transport properties such as thermal conductivity and ultra-sound attenuation coefficients is essential to identify the gap symmetry. We have found that

Juana Moreno

1997-01-01

52

Time-dependent macrodispersion for solute transport in anisotropic heterogeneous aquifers  

Microsoft Academic Search

The expected values of the spatial second-order moments of a solute body transported by groundwater are derived for flow through heterogeneous formations of a stationary random anisotropic structure. They are based on a general formulation, which reduces to most existing results in the literature as particular cases. Detailed results are given for the spatial variance as a function of time

Gedeon Dagan

1988-01-01

53

Superdiffusive and Subdiffusive Transport of Energetic Particles in Solar Wind Anisotropic Magnetic Turbulence  

Microsoft Academic Search

The transport of energetic particles in a mean magnetic field and the presence of anisotropic magnetic turbulence are studied numerically, for parameter values relevant to the solar wind. A numerical realization of magnetic turbulence is set up in which we can vary the type of anisotropy by changing the correlation lengths lx, ly, lz. We find that for lx, ly>>lz,

G. Zimbardo; P. Pommois; P. Veltri

2006-01-01

54

New approximations of anisotropic scattering in neutron transport and diffusion equations  

SciTech Connect

A systematic approach to the problem of defining effective scattering cross sections for neutron diffusion equations is presented. In the authors' analysis, anisotropic scattering of the second order is assumed for the onespeed transport equation, and criterion of preserving both the diffusion length and the total absorption serves as a basis for the derivation of effective isotropic scattering cross sections for both transport and diffusion equations.

Duracz, T.; Zelazny, R.

1983-06-01

55

Anisotropic vanadium dioxide sculptured thin films with superior thermochromic properties  

PubMed Central

VO2 (M) STF through reduction of V2O5 STF was prepared. The results illustrate that V2O5 STF can be successfully obtained by oblique angle thermal evaporation technique. After annealing at 550°C/3?min, the V2O5 STF deposited at 85° can be easily transformed into VO2 STF with slanted columnar structure and superior thermochromic properties. After deposition SiO2 antireflective layer, Tlum of VO2 STF is enhanced 26% and ?Tsol increases 60% compared with that of normal VO2 thin films. Due to the anisotropic microstructure of VO2 STF, angular selectivity transmission of VO2 STF is observed and the solar modulation ability is further improved from 7.2% to 8.7% when light is along columnar direction. Moreover, the phase transition temperature of VO2 STF can be depressed into 54.5°C without doping. Considering the oblique incidence of sunlight on windows, VO2 STF is more beneficial for practical application as smart windows compared with normal homogenous VO2 thin films.

Sun, Yaoming; Xiao, Xiudi; Xu, Gang; Dong, Guoping; Chai, Guanqi; Zhang, Hua; Liu, Pengyi; Zhu, Hanmin; Zhan, Yongjun

2013-01-01

56

Anisotropic vanadium dioxide sculptured thin films with superior thermochromic properties.  

PubMed

VO2 (M) STF through reduction of V2O5 STF was prepared. The results illustrate that V2O5 STF can be successfully obtained by oblique angle thermal evaporation technique. After annealing at 550°C/3?min, the V2O5 STF deposited at 85° can be easily transformed into VO2 STF with slanted columnar structure and superior thermochromic properties. After deposition SiO2 antireflective layer, Tlum of VO2 STF is enhanced 26% and ?Tsol increases 60% compared with that of normal VO2 thin films. Due to the anisotropic microstructure of VO2 STF, angular selectivity transmission of VO2 STF is observed and the solar modulation ability is further improved from 7.2% to 8.7% when light is along columnar direction. Moreover, the phase transition temperature of VO2 STF can be depressed into 54.5°C without doping. Considering the oblique incidence of sunlight on windows, VO2 STF is more beneficial for practical application as smart windows compared with normal homogenous VO2 thin films. PMID:24067743

Sun, Yaoming; Xiao, Xiudi; Xu, Gang; Dong, Guoping; Chai, Guanqi; Zhang, Hua; Liu, Pengyi; Zhu, Hanmin; Zhan, Yongjun

2013-09-25

57

Electrical and thermal transport properties of magnetically aligned single wall carbon nanotube films  

Microsoft Academic Search

Bulk samples of parallel single-walled nanotubes ~SWNTs! would constitute a fascinating new material, with highly anisotropic electrical and thermal transport properties. In this letter we report quantitative measurements of the an- isotropic electrical and thermal transport properties of aligned thin films of SWNT ropes deposited from suspension in a high magnetic field. 1 The aligned samples show high electrical (

J. Hone; M. C. Llaguno; N. M. Nemes; A. T. Johnson; J. E. Fischera; D. A. Walters; M. J. Casavant; J. Schmidt; R. E. Smalley

2000-01-01

58

Coupled light transport-heat diffusion model for laser dosimetry with dynamic optical properties  

Microsoft Academic Search

The effect of dynamic optical properties on the spatial distribution of light in laser therapy is studied via numerical simulations. A 2D, time dependent computer program called LATIS is used. Laser light transport is simulated with a Monte Carlo technique including anisotropic scattering and absorption. Thermal heat transport is calculated with a finite difference algorithm. Material properties are specified on

Richard A. London; Michael E. Glinsky; George B. Zimmerman; David C. Eder; Steven L. Jacques

1995-01-01

59

Anisotropic heat transport in integrable and chaotic 3-D magnetic fields  

SciTech Connect

A study of anisotropic heat transport in 3-D chaotic magnetic fields is presented. The approach is based on the recently proposed Lagrangian-Green s function (LG) method in Ref. [1] that allows an efficient and accurate integration of the parallel transport equation applicable to general magnetic fields with local or non-local parallel flux closures. We focus on reversed shear magnetic field configurations known to exhibit separatrix reconnection and shearless transport barriers. The role of reconnection and magnetic field line chaos on temperature transport is studied. Numerical results are presented on the anomalous relaxation of radial temperature gradients in the presence of shearless Cantori partial barri- ers. Also, numerical evidence of non-local effective radial temperature transport in chaotic fields is presented. Going beyond purely parallel transport, the LG method is generalized to include finite perpendicular diffusivity, and the problem of temperature flattening inside a magnetic island is studied.

Del-Castillo-Negrete, Diego B [ORNL; Blazevski, D. [University of Texas, Austin; Chacon, Luis [ORNL

2012-01-01

60

Influence of anisotropic scattering on the size of time-dependent systems in monoenergetic neutron transport  

NASA Astrophysics Data System (ADS)

Criticality type eigenvalues of the one-speed transport equation in a homogeneous slab with anisotropic scattering and Marshak boundary conditions are considered. The connection between the transport equations for a critical and for a time-decaying system is established, and thus the time-dependent equation is reduced to the stationary one. Variation of the size of the time-dependent system with anisotropic scattering is studied numerically. Calculations for different combinations of the scattering parameters and the selected values of the time decay constant using the 0022-3727/32/3/020/img1 method are reported. Results are discussed and compared with those already obtained using various methods available in the literature.

Yildiz, Cemal

1999-02-01

61

Transport processes in an anisotropic near-earth plasma  

Microsoft Academic Search

Attention is given to the hydrodynamic theory of a plasma with a nonuniform particle thermal energy distribution with respect to degrees of freedom. A 16-moment approximation method for charged-particle distribution functions is presented and used to obtain a closed system of transport equations with allowance for the temperature anisotropy of partially ionized plasma in the earth's upper atmosphere.

V. N. Oraevskii; Iu. V. Konikov; G. V. Khazanov

1985-01-01

62

Optical symmetries and anisotropic transport in high-Tc superconductors  

NASA Astrophysics Data System (ADS)

A simple symmetry analysis of in-plane and out-of-plane transport in a family of high temperature superconductors is presented. It is shown that generalized scaling relations exist between the low frequency electronic Raman response and the low frequency in-plane and out-of-plane conductivities in both the normal and superconducting states of the cuprates. Specifically, for both the normal and superconducting state, the temperature dependence of the low frequency B_1g Raman slope scales with the c-axis conductivity, while the B_2g Raman slope scales with the in-plane conductivity. Comparison with experiments in the normal state of Bi-2212 and Y-123 imply that the nodal transport is largely doping independent and metallic, while transport near the BZ axes is governed by a quantum critical point near doping p ˜ 0.22 holes per CuO2 plaquette. Important differences for La-214 are discussed. It is also shown that the c- axis conductivity rise for T? Tc is a consequence of partial conservation of in-plane momentum for out-of-plane transport.

Devereaux, Thomas

2004-03-01

63

Optical symmetries and anisotropic transport in high-Tc superconductors  

NASA Astrophysics Data System (ADS)

A simple symmetry analysis of in-plane and out-of-plane transport in a family of high-temperature superconductors is presented. It is shown that generalized scaling relations exist between the low-frequency electronic Raman response and the low-frequency in-plane and out-of-plane conductivities in both normal and superconducting states of the cuprates. Specifically, for both normal and superconducting states, the temperature dependence of the low-frequency B1g Raman slope scales with the c-axis conductivity, while the B2g Raman slope scales with the in-plane conductivity. Comparison with experiments in the normal states of Bi-2212 and Y-123 implies that the nodal transport is largely doping independent and metallic, while transport near the Brillouin Zone axes is governed by a quantum critical point near doping p˜0.22 holes per CuO2 plaquette. Important differences for La-214 are discussed. It is also shown that the c-axis conductivity rise for T?Tc is a consequence of partial conservation of in-plane momentum for out-of-plane transport.

Devereaux, T. P.

2003-09-01

64

A generalized transport model for biased cell migration in an anisotropic environment  

Microsoft Academic Search

.  ?A generalized transport model is derived for cell migration in an anisotropic environment and is applied to the specific\\u000a cases of biased cell migration in a gradient of a stimulus (taxis; e.g.,?chemotaxis or haptotaxis) or along an axis of anisotropy (e.g.,?contact guidance). The model accounts for spatial or directional dependence of cell speed and cell turning behavior to predict a

Richard B. Dickinson

2000-01-01

65

Anisotropic eigenvalue spectrum calculations of the neutron transport operator with low-order spatial expansion methods  

Microsoft Academic Search

The results of a numerical analysis of the eigenvalue spectrum and eigenmodes of the monoenergetic integral transport equation are presented. Anisotropic scattering effects are explicitly considered with P[sub 1] and P[sub 2] expansions. Benchmark quality data are produced for three related one-dimensional homogeneous multiplying slab problems: fuel with vacuum boundary, fuel with reflectors, and fuel\\/reflector infinite lattice. Two low-order spatial

1993-01-01

66

Collisionless turbulent transport and anisotropic electron heating in coronal flare loops  

NASA Astrophysics Data System (ADS)

Context. One of the hypotheses about the generation of the hard X-ray emissions (HXR) of the sun is that a strong electron-beam is first accelerated near the looptop, and then propagated down to the chromosphere. There the HXR emissions are generated by the bombardment of electrons via thick-target bremsstrahlung. Recently, the beam-plasma model has been questioned because streaming instabilities make the beam propagation doubtful. Another open question in solar flare models is the generation of anisotropic electron distributions deduced from microwave emissions. The question is whether one can find a mechanism, in addition to the generally considered mirror motion, that may cause the electron anisotropy in flare loops. Aims: To understand the transport of coronal electron beams and the possible generation of electron anisotropic distribution in the course of the beam propagation, we simulated a beam-plasma return-current system. Our aim is to investigate the evolution of predicted streaming instabilities at the nonlinear stage and to determine the intensity of beam transport in coronal loops. Methods: The linear instabilities and wave coupling in the beam-plasma return-current system are investigated by a multi-fluid dispersion analysis. We performed a two-dimensional electromagnetic particle-in-cell simulation to understand the generation of turbulent transport and anisotropic electron heating at the nonlinear stage of the beam evolution. Results: The beam-plasma return-current system is stablized at a late stage of evolution by a combined effect of 1) a relaxation of electron bulk drifts; and 2) a fast thermalization of the beam and return-current electrons in the drift direction. As a result, the downward electron beam continues to propagate in the coronal loop. Distinguishable parallel and perpendicular electron heating is observed, which is caused by turbulent deflection of electron beams. The electron distribution becomes anisotropic through different heating rates. Conclusions: An electron beam injected from a solar flare looptop can continue to propagate stably despite a partial relaxation of its drift velocity. After drift relaxation and anisotropic electron heating, the slowed-down electron drifts and the ambient thermalized plasma create a stable beam-propagation environment because of the Landau damping effect. This electron beam can propagate stably at a modified drift speed down to the chromosphere, where it generates HXR radiation. We conclude that the beam plasma model is feasible for the HXR generation in a solar flare event. The observed anisotropic electron distribution is a direct consequence of turbulent deflections of the electron beams.

Lee, K. W.; Büchner, J.

2011-11-01

67

Transport in anisotropic model systems analyzed by a correlated projection superoperator technique.  

PubMed

By using a correlated projection operator, the time-convolutionless (TCL) method to derive a quantum master equation can be utilized to investigate the transport behavior of quantum systems as well. Here, we analyze a three-dimensional anisotropic quantum model system according to this technique. The system consists of Heisenberg coupled two-level systems in one direction and weak random interactions in all other ones. Depending on the partition chosen, we obtain ballistic behavior along the chains and normal transport in the perpendicular direction. These results are perfectly confirmed by the numerical solution of the full time-dependent Schrödinger equation. PMID:18351829

Weimer, Hendrik; Michel, Mathias; Gemmer, Jochen; Mahler, Günter

2008-01-16

68

Effective Transport Properties  

NASA Astrophysics Data System (ADS)

In this chapter we study a particular case of multiphase systems, namely two-phase materials in which one of the phases is randomly dispersed in the other, so that the composite can be viewed on a macroscale as an effective continuum, with well defined properties. In general, the theoretical determination of the parameter for an effective medium requires, as a rule, the solution of a corresponding transport problem at the microscale, which takes into account the morphology of the system and its evolution. As the mathematical problem is well-posed on a microscale, this can be accomplished using, for example, the multiple scale approach shown in Chap. 11 ; however, the task requires massive computations and is therefore difficult to implement from the practical standpoint. Here, instead, we focus on a deterministic approach to the problem, where the geometry and spatial configuration of the particles comprising the included phase are given and the solution to the microscale problem is therefore sought analytically. As examples, we study the effective thermal conductivity of solid reinforced materials (Sect. 10.1), the effective viscosity of non-colloidal suspensions (Sect. 10.2), the effective permeability of porous materials (10.3) and the effective self- and gradient diffusivities of colloidal suspensions (Sect. 10.4). Then, in Sect. 10.5, an alternative dynamic definition of the transport coefficients is considered, which can also serve as a basis to determine the effective properties of complex systems.

Mauri, Roberto

69

Anisotropic Pressure, Transport, and Shielding of Magnetic Perturbations  

SciTech Connect

We compute the effect on a tokamak of applying a nonaxisymmetric magnetic perturbation ??. An equilibrium with scalar pressure p yields zero net radial current, and therefore zero torque. Thus, the usual approach, which assumes scalar pressure, is not self-consistent, and masks the close connection which exists between that radial current and the in-surface currents, which provide shielding or amplification of ??. Here, we analytically compute the pressure anisoptropy, anisoptropy, pll, p? ? p, and from this, both the radial and in-surface currents. The surface-average of the radial current recovers earlier expressions for ripple transport, while the in-surface currents provide an expression for the amount of self-consistent shielding the plasma provides.

H.E. Mynick and A.H. Boozer

2008-05-23

70

Transport properties of geomaterials  

NASA Astrophysics Data System (ADS)

Many properties of real or reconstructed materials can be obtained by solving the relevant local equations such as the Stokes equations for low Reynolds number flow and then averaging over the sample to get the macroscopic properties such as permeability. Over the years our team has addressed a large number of transport properties and media and it has tried to rationalize the results obtained by a few correlations. This talk is focused on two groups of properties. The first one is concerned with diffusion (either stationary or not) and permeability. The second one addresses electrokinetic phenomena. The data are relative to unconsolidated materials such as packings of particles of complex shapes and to consolidated materials such as reconstructed media (either by the standard correlation function or by grain reconstruction) or media obtained by microtomography. 1. Permeability and macroscopic diffusion These properties were thoroughly investigated for a large number of different porous media. Let E be the local electrical field inside a porous medium submitted to a macroscopic field. A key quantity which can be used to unify the permeability K and the formation factor F (i.e. the inverse of the macroscopic dimensionless conductivity) is the Johnson length Lambda which is proportional to the ratio of the integral of E**2 over the pore volume divided by its integral over the surface of the pores. It was shown that Lambda is inversely proportional to the specific surface. Moreover, it was verified numerically that Lambda is equal to the square root of 8KF. This approach was extended to the apparent diffusion coefficient which can be measured by NMR, and it was shown that it could be renormalized in such a way to obtain a universal curve as a function of a universal time based on Lambda for all the media. This is also valid when two phases are present in the pore space. 2. Electroosmotic phenomena Electroosmotic phenomena, and more generally coupled transports, are generated at the local scale by the flow of an electrolyte close to charged solid surfaces while far from the walls, the solution can be considered as neutral. These phenomena may become very important when the characteristic length scales of the media are submicronic. The problem is most complex on the pore scale. The medium filled by an electrolyte is submitted to macroscopic gradients of pressure, of electrical potential and of concentration. They induce fluxes of mass, current and solute. Close to equilibrium, the macroscopic coefficients which relate the fluxes and the forces, can be obtained by solving three coupled partial differential equations. Numerical results can be rationalised again by means of Lambda. More precisely, when made dimensionless, the coupling coefficients only depend on the ratio of Lambda with the Debye-Hückel length kappa**-1, whatever the porous medium. Systematic experimental checks of these properties were performed on various sorts of finely divided materials, including clays. The data were in agreement with the previous numerical predictions. These properties can be extended to high values of the zeta potential. A universal curve is found for the electroosmotic coefficient which is valid for any porous medium and any value of zeta. These results are practically very important since good estimations of the coupling coefficients can be derived from the knowledge of F, K, kappa and zeta which are much easier to measure than the coupling coefficients themselves.

Thovert, Jean Francois; Adler, Pierre

2010-05-01

71

Reliability of in vivo measurements of the dielectric properties of anisotropic tissue: a simulative study  

NASA Astrophysics Data System (ADS)

A simulative study was performed to measure the dielectric properties of anisotropic tissue using several in vivo and in vitro probes. COMSOL Multiphysics was selected to carry out the simulation. Five traditional probes and a newly designed probe were used in this study. One of these probes was an in vitro measurement probe and the other five were in vivo. The simulations were performed in terms of the minimal tissue volume for in vivo measurements, the calibration of a probe constant, the measurement performed on isotropic tissue and the measurement performed on anisotropic tissue. Results showed that the in vitro probe can be used to measure the in-cell dielectric properties of isotropic and anisotropic tissues. When measured with the five in vivo probes, the dielectric properties of isotropic tissue were all measured accurately. For the measurements performed on anisotropic tissue, large errors were observed when the four traditional in vivo probes were used, but only a small error was observed when the new in vivo probe was used. This newly designed five-electrode in vivo probe may indicate the dielectric properties of anisotropic tissue more accurately than these four traditional in vivo probes.

Huo, Xuyang; Shi, Xuetao; You, Fusheng; Fu, Feng; Liu, Ruigang; Tang, Chi; Lu, Qiang; Dong, Xiuzhen

2013-05-01

72

Interaction effects and transport properties of Pt capped Co nanoparticles  

NASA Astrophysics Data System (ADS)

We studied the magnetic and transport properties of Co nanoparticles (NPs) being capped with varying amounts of Pt. Beside field and temperature dependent magnetization measurements, we performed ?? measurements to study the magnetic interactions between the Co NPs. We observe a transition from demagnetizing towards magnetizing interactions between the particles for an increasing amount of Pt capping. Resistivity measurements show a crossover from giant magnetoresistance towards anisotropic magnetoresistance.

Ludwig, A.; Agudo, L.; Eggeler, G.; Ludwig, A.; Wieck, A. D.; Petracic, O.

2013-01-01

73

Nonlinear optical properties of a three-dimensional anisotropic quantum dot  

NASA Astrophysics Data System (ADS)

The linear and nonlinear optical properties in a three-dimensional anisotropic quantum dot subjected to a uniform magnetic field directed with respect to the z-axis have been investigated within the compact-density matrix formalism and the iterative method. The dependence of the linear and nonlinear optical properties on the characteristic frequency of the parabolic potential, on the magnetic field, and on the incident optical intensity is studied in detail. Moreover, taking into account the position-dependent effective mass, the dependence of the linear and nonlinear optical properties on the dot radius is investigated. The results show that the optical absorption coefficients (ACs) and refractive index (RI) changes of the anisotropic quantum dot (QD) are strongly affected by these factors, and the position effect also plays an important role in the optical ACs and RI changes of the anisotropic QD.

Chen, Tairong; Xie, Wenfang

2012-02-01

74

Anisotropic thermal properties of talc under high temperature and pressure  

NASA Astrophysics Data System (ADS)

The anisotropic thermal conductivity and diffusivity of talc were simultaneously measured up to 5.3 GPa and 900 K using the pulse transient method. Although significant anisotropy was observed in the thermal conductivity of talc, the average thermal conductivity is comparable to that of olivine and roughly three times greater than that of antigorite. From the ratio of the thermal conductivity to the thermal diffusivity, the heat capacity of talc was evaluated. The pressure derivative of heat capacity was found to be positive, which is related to the anomaly of thermal expansivity of talc above 50 °C at atmospheric pressure.

Yoneda, Akira; Yonehara, Mitsuhide; Osako, Masahiro

2012-01-01

75

Anisotropic thermal property measurement of carbon-fiber/epoxy composite materials  

NASA Astrophysics Data System (ADS)

This work originated from a need for understanding heat transfer in carbon-fiber/epoxy natural-gas tanks undergoing rapid heating during refilling. The dissertation is focused on the determination of the anisotropic thermal properties of carbon-fiber/epoxy composite materials for in-plane and through-thickness directions. An effective anisotropic parameter estimation system consisting of the 3? experimental technique and an anisotropic two-dimensional heat transfer model is developed. In the present work, the 3? method, an experimental technique that has been well established to evaluate the thermal properties of isotropic materials, especially thin film materials, is extended to treat the thermal properties of bulk anisotropic materials. A platinum film deposited on the sample surface is periodically heated by a sinusoidally oscillating current at frequency ?, and thereby causes a time-harmonic electrical resistance variation at frequency 2?. The heat-induced resistance variation at frequency 2? coupled with the current at frequency ? produces a voltage variation component at frequency 3?. The phase and amplitude data of the voltage signal at frequency 3? are collected from the experiment. An impedance analysis model is employed to convert the voltage data to temperature data. The anisotropic thermal properties are deduced from an inverse parameter estimation model, which is a least-square systematic comparison between experimental data and the theoretical model. The anisotropic theoretical model is based on the Green's function approach. A careful sensitivity analysis is used to demonstrate the feasibility of simultaneous estimation of the in-plane and through-thickness thermal conductivities. Poly methyl methacrylate (PMMA) samples were applied as reference samples to verify the measurement system. The parameter estimation result for experimental data from PMMA samples agree very well with handbook values. Experimental results from carbon-fiber/epoxy samples are presented.

Tian, Tian

76

Lamé problem for a weakly anisotropic body with cubic symmetry of elastic properties  

NASA Astrophysics Data System (ADS)

The Lamé problem is solved for a body with cubic symmetry of elastic properties and the elastic anisotropy parameter is determined. In the case of plane deformation, the stresses in a ring are found to terms of the first order in the small anisotropic parameter. Stresses in a ring of KCl under internal pressure are calculated.

Solovei, V. D.

2010-12-01

77

The structure and properties of cellulose fibres spun from an anisotropic phosphoric acid solution  

Microsoft Academic Search

The structure and the mechanical properties of a newly developed highmodulus\\/high strength cellulose fibre spun from an anisotropic solution in phosphoric acid are discussed and compared with those of existing regenerated cellulose fibres. The crystal structure of the fibre is of the cellulose II modification, and the highly oriented and crystalline fibres have an initial filament modulus of 44GPa, a

M. G. Northolt; H. Boerstoel; H. Maatman; R. Huisman; J. Veurink; H. Elzerman

2001-01-01

78

Conservation properties for plane deformations of isotropic and anisotropic linearly elastic strips  

Microsoft Academic Search

Plane deformations of a rectangular strip, composed of an homogeneous fully anisotropic linearly elastic material, are considered. The strip is in equilibrium under the action of end loads, with the lateral sides traction-free. Two conservation properties for certain cross-sectional stress measures are established, generalizing previously known results for the isotropic case. It is noteworthy that in the first of these

Kristin L. Miller; Cornelius O. Horgan

1993-01-01

79

Impact of magnetic properties on the Casimir torque between anisotropic metamaterial plates  

Microsoft Academic Search

The quantized surface mode technique is used to calculate the Casimir torque between two parallel anisotropic metamaterial plates with in-plane optical axes, and our main concern is focused on the impact of the magnetic properties of the plates on the Casimir torque. Our result shows that at small separation, the Casimir torque between the two plates with frequency dependent permeabilities

Deng Gang; Liu Zhongzhu; Luo Jun

2009-01-01

80

Anisotropic optical property of a bio-medium with highly photon-scattering anisotropic bio-molecules  

Microsoft Academic Search

Tissues are optically anisotropic and highly photon scattering media. By using a simple ellipsoid model of bio-molecules with anisotropic distribution and using an effective mean-field theory, the principal anisotropic index of refraction nj(omega) and absorption extinction coefficient Kaj(omega), (j = x,y,z) are derived. The scattering extinction coefficient Ksj is calculated from our scattering depolarization theory of highly scattering bio-medium. The

Tsu-Wei Nee; Soe-Mie F. Nee

2010-01-01

81

TRANSPORT PROPERTIES OF CARTILAGINOUS TISSUES  

PubMed Central

Cartilaginous tissues, such as articular cartilage and intervertebral disc, are avascular tissues which rely on transport for cellular nutrition. Comprehensive knowledge of transport properties in such tissues is therefore necessary in the understanding of nutritional supply to cells. Furthermore, poor cellular nutrition in cartilaginous tissues is believed to be a primary source of tissue degeneration, which may result in osteoarthritis (OA) or disc degeneration. In this mini-review, we present an overview of the current status of the study of transport properties and behavior in cartilaginous tissues. The mechanisms of transport in these tissues, as well as experimental approaches to measuring transport properties and results obtained are discussed. The current status of bioreactors used in cartilage tissue engineering is also presented.

Jackson, AR; Gu, WY

2009-01-01

82

Benchmark values for monoenergetic neutron transport in one-dimensional cylindrical geometry with linearly anisotropic scattering  

Microsoft Academic Search

The integral transform method (IT \\/SUB N\\/ ) has been extended to the treatment of one-dimensional homogeneous media with linearly anisotropic scattering. A previously obtained formula linking the isotropic and the anisotropic one-dimensional kernels allows for calculation of the anisotropic matrix elements in the form of linear combinations of a few isotropic matrix elements. In practice, to solve the anisotropic

R. Sanchez; B. D. Ganapol

1983-01-01

83

VARIANT: VARIational anisotropic nodal transport for multidimensional Cartesian and hexadgonal geometry calculation  

SciTech Connect

The theoretical basis, implementation information and numerical results are presented for VARIANT (VARIational Anisotropic Neutron Transport), a FORTRAN module of the DIF3D code system at Argonne National Laboratory. VARIANT employs the variational nodal method to solve multigroup steady-state neutron diffusion and transport problems. The variational nodal method is a hybrid finite element method that guarantees nodal balance and permits spatial refinement through the use of hierarchical complete polynomial trial functions. Angular variables are expanded with complete or simplified P{sub 1}, P{sub 3} or P{sub 5}5 spherical harmonics approximations with full anisotropic scattering capability. Nodal response matrices are obtained, and the within-group equations are solved by red-black or four-color iteration, accelerated by a partitioned matrix algorithm. Fission source and upscatter iterations strategies follow those of DIF3D. Two- and three-dimensional Cartesian and hexagonal geometries are implemented. Forward and adjoint eigenvalue, fixed source, gamma heating, and criticality (concentration) search problems may be performed.

Palmiotti, G.; Carrico, C.B. [Argonne National Lab., IL (United States); Lewis, E.E. [Northwestern Univ., Evanston, IL (United States)

1995-10-01

84

Nonlinear and anisotropic tensile properties of graft materials used in soft tissue applications  

Microsoft Academic Search

BackgroundThe mechanical properties of extracellular matrix grafts that are intended to augment or replace soft tissues should be comparable to the native tissue. Such grafts are often used in fiber-reinforced tissue applications that undergo multi-axial loading and therefore knowledge of the anisotropic and nonlinear properties are needed, including the moduli and Poisson’s ratio in two orthogonal directions within the plane

Jonathon H. Yoder; Dawn M. Elliott

2010-01-01

85

Localized plastic flow, anisotropic mechanical properties and crystallographic texture in Zircaloy sheet  

Microsoft Academic Search

Mechanical properties of Zircaloys, like many other hexagonal close-packed (hcp) metals, are sensitive to the textures developed\\u000a during fabrication processes. These alloys exhibit highly anisotropic mechanical properties, a thorough knowledge of which\\u000a is needed for selecting materials with good formability characteristics as well as for the predictability of inservice behavior.\\u000a This paper describes texture analysis performed on recrystallized Zircaloy-4 sheet

Sheikh T. Mahmood; K. Linga Murty

1989-01-01

86

Anisotropic electronic properties of a-axis-oriented Sr2IrO4 epitaxial thin-films  

NASA Astrophysics Data System (ADS)

We have investigated the transport and optical properties along the c-axis of a-axis-oriented Sr2IrO4 epitaxial thin-films grown on LaSrGaO4 (100) substrates. The c-axis resistivity is approximately one order of magnitude larger than that of the ab-plane. Optical absorption spectra with E?c polarization show both Ir 5d intersite transitions and charge-transfer transitions (O 2p to Ir 5d), while E//c spectra show only the latter. The structural anisotropy created by biaxial strain in a-axis-oriented thin-films also changes the electronic structure and gap energy. These a-axis-oriented, epitaxial thin-films provide a powerful tool to investigate the highly anisotropic electronic properties of Sr2IrO4.

Nichols, J.; Korneta, O. B.; Terzic, J.; De Long, L. E.; Cao, G.; Brill, J. W.; Seo, S. S. A.

2013-09-01

87

Identifying the complete space of feasible anisotropic properties in polycrystalline microstructures  

NASA Astrophysics Data System (ADS)

Current engineering design focuses mainly on the geometrical optimization of a component, while the material selection is often limited to picking a material based on a set of properties reported in handbooks. The inherent anisotropic behavior of materials is often ignored in the design process, and is usually assumed to be addressed by the safety factor employed. This simple treatment of material selection in the design and optimization process often leads to inefficient design. In this study, we present a rigorous and a comprehensive procedure that facilitates the treatment of material microstructure as a continuous design variable in the elastic-plastic design of structural components made from anisotropic polycrystalline metals. The mechanical behavior of a metal is influenced by several details of its microstructure, including chemical composition, grain size distribution, crystallographic texture, among others. Here, we focus on the crystallographic texture (also called Orientation Distribution Function or ODF) as the main microstructural parameter controlling the anisotropic elastic-plastic properties of interest. The property closures that we have delineated describe the complete set of feasible property combinations for a given polycrystalline material system, while accounting for all possible textures. The property closures are obtained here using a spectral representation of ODF and its relationship with rigorous first order bounds on the effective properties of interest in design. Using the proposed methodology, we successfully developed a few examples of property closures for face centered cubic (fcc) and hexagonal close-packed (hcp) metals. The mechanical anisotropic behavior at the single crystal level for face centered cubic metals has been characterized using the nanoindentation technique along with orientation imaging mapping. This methodology shows promising possibilities to extract fundamental elastic and plastic parameters. However, the methods proposed in the literature to extract data from the load-displacement curves cause discrepancy between the experimental and expected values. The discrepancy could be attributed to the induced plastic deformation among other factors.

Proust, Gwenaelle

88

Evolution, Interaction, and Intrinsic Properties of Dislocations in Intermetallics: Anisotropic 3D Dislocation Dynamics Approach  

SciTech Connect

The generation, motion, and interaction of dislocations play key roles during the plastic deformation process of crystalline solids. 3D Dislocation Dynamics has been employed as a mesoscale simulation algorithm to investigate the collective and cooperative behavior of dislocations. Most current research on 3D Dislocation Dynamics is based on the solutions available in the framework of classical isotropic elasticity. However, due to some degree of elastic anisotropy in almost all crystalline solids, it is very necessary to extend 3D Dislocation Dynamics into anisotropic elasticity. In this study, first, the details of efficient and accurate incorporation of the fully anisotropic elasticity into 3D discrete Dislocation Dynamics by numerically evaluating the derivatives of Green's functions are described. Then the intrinsic properties of perfect dislocations, including their stability, their core properties and disassociation characteristics, in newly discovered rare earth-based intermetallics and in conventional intermetallics are investigated, within the framework of fully anisotropic elasticity supplemented with the atomistic information obtained from the ab initio calculations. Moreover, the evolution and interaction of dislocations in these intermetallics as well as the role of solute segregation are presented by utilizing fully anisotropic 3D dislocation dynamics. The results from this work clearly indicate the role and the importance of elastic anisotropy on the evolution of dislocation microstructures, the overall ductility and the hardening behavior in these systems.

Qian Chen

2008-08-18

89

Rotational positioning system adapted to atomic force microscope for measuring anisotropic surface properties.  

PubMed

The diverse atomic configurations induce the anisotropic surface properties. For investigating anisotropic phenomena, we developed a rotational positioning system adapted to atomic force microscope (AFM). This rotational positioning system is applied to revolve the measured sample to defined angular direction, and it composed of an inertial rotational stepper and a visual angular measurement. The inertial rotational stepper with diameter 30 mm and height 7.6 mm can be easily attached to the AFM-system built in any general optical microscope. Based on a clearance less bearing and the inertial driving method, its bidirectional angular resolution reaches 0.005° per step. For realizing a close-loop controlled angular positioning function, the visual measurement method is utilized. Through the feedback control, the angular positioning error is less than 0.01°. For verifying the system performance, we used it to investigate the anisotropic surface properties of graphite. Through a modified cantilever tip, the atomic-scale stick-slip, and the anisotropic friction phenomena can be distinctly detected. PMID:22128987

Liao, H-S; Juang, B-J; Chang, W-C; Lai, W-C; Huang, K-Y; Chang, C-S

2011-11-01

90

Nanoarchitectures with controllable anisotropic features in structures and properties from simple and robust holographic lithography.  

PubMed

Anisotropic nanostructures with precise orientations or sharp corners display unique properties that may be useful in a variety of applications; however, precise control over the anisotropy of geometric features, using a simple and reproducible large-area fabrication technique, remains a challenge. Here, we report the fabrication of highly uniform polymeric and metallic nanostructure arrays prepared using prism holographic lithography (HL) in such a way that the isotropy that can be readily and continuously tuned. The prism position on the sample stage was laterally translated to vary the relative intensities of the four split beams, thereby tuning the isotropy of the resulting polymer nanostructures through the following shapes: circular nanoholes, elliptical nanoholes, and zigzag-shaped nanoarrays. Corresponding large-area, defect-free anisotropic metallic nanostructures could then be fabricated using an HL-featured porous polymer structure as a milling mask. Removal of the polymer mask left zigzag-shaped metallic nanostructure arrays in which nanogaps separated adjacent sharp edges. These structures displayed two distinct optical properties, depending on the direction along which the excitation beam was polarized (longitudinal and transverse modes) incident on the array. Furthermore, bidirectional anisotropic wetting was observed on the anisotropic polymer nanowall array surface. PMID:24020508

Jeon, Hwan Chul; Jeon, Tae Yoon; Yang, Seung-Man

2013-09-24

91

Anisotropic magnetic properties of the KMo4O6  

NASA Astrophysics Data System (ADS)

Electrical resistivity measurements in the tetragonal KMo4O6 single crystals show a metal-insulator transition (MIT) near 100K. Magnetization measurements as a function of temperature show no evidence of magnetic ordering at this MIT [1]. Single crystals of KMo4O6 were obtained by electrolysis of a melt with a molar ratio of K2MoO4:MoO3 = 6:1. The process were carried out at 930 C with a current of 20-25mA for 52h in argon atmosphere. After that, electrodes were removed from the melt alloying the crystals to cool down to room temperature rapidly. Scanning Electron Microscopy (SEM) showed that the black single crystals were grown on the platinum cathode. Typical dimensions of the single crystals are 1x0.2x0.2mm^3. X-ray diffractometry confirmed that the single crystals have KMo4O6 tetragonal crystalline structure with space group P4. Magnetization measurements were performed parallel and perpendicular to the c-axis from 2 to 300K. The results show anisotropic behavior between both directions. Furthermore, the temperature independence of the magnetization at high temperature and the upturn at low temperature are observed in agreement with previous results [1]. MxH curves measured at several temperatures show nonlinear behavior and a small magnetic ordering. The magnetic ordering seems to be related to the MIT near 100K. This material is based upon support by FAPESP (2009/14524-6 and 2009/54001-6) and CNPq/NSF (490182/2009-7). M. Andrade is CAPES fellow and C.A.M. dos Santos is CNPq fellow. [4pt] [1] K. V. Ramanujachary et al., J. Sol. State Chem.102 (1993) 69.

Andrade, M.; Maffei, M. L.; Dos Santos, C. A. M.; Ferreira, B.; Sartori, A. F.

2012-02-01

92

Anisotropic nutrient transport in three-dimensional single species bacterial biofilms.  

PubMed

The ability for a biofilm to grow and function is critically dependent on the nutrient availability, and this in turn is dependent on the structure of the biofilm. This relationship is therefore an important factor influencing biofilm maturation. Nutrient transport in bacterial biofilms is complex; however, mathematical models that describe the transport of particles within biofilms have made three simplifying assumptions: the effective diffusion coefficient (EDC) is constant, the EDC is that of water, and/or the EDC is isotropic. Using a Monte Carlo simulation, we determined the EDC, both parallel to and perpendicular to the substratum, within 131 real, single species, three-dimensional biofilms that were constructed from confocal laser scanning microscopy images. Our study showed that diffusion within bacterial biofilms was anisotropic and depth dependent. The heterogeneous distribution of bacteria varied between and within species, reducing the rate of diffusion of particles via steric hindrance. In biofilms with low porosity, the EDCs for nutrient transport perpendicular to the substratum were significantly lower than the EDCs for nutrient transport parallel to the substratum. Here, we propose a reaction-diffusion model to describe the nutrient concentration within a bacterial biofilm that accounts for the depth dependence of the EDC. PMID:22124974

Van Wey, A S; Cookson, A L; Soboleva, T K; Roy, N C; McNabb, W C; Bridier, A; Briandet, R; Shorten, P R

2011-12-30

93

Nonlinear and Anisotropic Tensile Properties of Graft Materials used in Soft Tissue Applications  

PubMed Central

Background The mechanical properties of extracellular matrix grafts that are intended to augment or replace soft tissues should be comparable to the native tissue. Such grafts are often used in fiber-reinforced tissue applications that undergo multi-axial loading and therefore knowledge of the anisotropic and nonlinear properties are needed, including the moduli and Poisson's ratio in two orthogonal directions within the plane of the graft. The objective of this study was to measure the tensile mechanical properties of several marketed grafts: Alloderm, Restore, CuffPatch, and OrthADAPT. Methods The degree of anisotropy and nonlinearity within each graft was evaluated from uniaxial tensile tests and compared to their native tissue. Results The Alloderm graft was anisotropic in both the toe and linear-region of the stress-strain response, was highly nonlinear, and generally had low properties. The Restore and CuffPatch grafts had similar stress-strain responses, were largely isotropic, had a linear-region modulus of 18 MPa, and were nonlinear. OrthADAPT was anisotropic in the linear region (131 vs 47 MPa) and was highly nonlinear. The Poisson ratio for all grafts was between 0.4 and 0.7, except for the parallel orientation of Restore which was greater than 1.0. Interpretation Having an informed understanding of how the available grafts perform mechanically will allow for better assessment by the physician for which graft to apply depending upon its application.

Yoder, Jonathon H; Elliott, Dawn M

2010-01-01

94

Magnetic Properties of Isotropic and Anisotropic Linear Chains.  

NASA Astrophysics Data System (ADS)

The magnetic susceptibilities and magnetizations of three quasi one-dimensional magnetic systems have been studied at temperatures ranging between room temperature and 1.4 K, with a Vibrating Sample Magnetometer (VSM). X -ray diffraction at room temperature has been carried out to determine the crystal structures of the two new compounds. Mossbauer spectroscopy at temperatures ranging from room temperature to 0.4 K have been performed on the two iron compounds studied. The design and performance of a custom cryostat used in conjunction with the VSM is described in detail. An inner enclosure (hangdown tube) has been used to reduce temperature fluctuations and thermal gradients. Methods for eliminating rubbing-induced background signals, and field-induced errors in thermometry are discussed. The crystal structure of ((CH_3) _3NH) FeCl_3cdot2H _2O, FeTAC, consists of chains of Fe^{2+} ions extending along the b axis of the orthorhombic unit cell (space group Pnma). The low temperature magnetic susceptibilities are highly anisotropic, and can be fit to the 1-d Ising model with a small molecular field correction giving a ferromagnetic intrachain exchange (J_{rm b }/k = 17.4 K). The total interchain exchange is negative and small (Z^'J ^'/ZJ ~ 2 times 10^{-3}). Evidence of long range magnetic order is observed near 3.12 K. Low field magnetization data show metamagnetic transitions when small fields are applied along the b axis. The metamagnetic phase diagram indicates the critical field is 90 Oe at T = 0 K. High field magnetization data up to 150 kOe show the presence of spin canting. X-ray studies show (CH_3)_3 NHFeBr_3cdot2H _2O, FeTAB, to be isostructural with FeTAC. Low temperature powder susceptibility data agree with the predicted susceptibility for a ferromagnetic 1-d Ising magnet with an exchange constant of 4.0(1.0) K. Mossbauer spectroscopy has shown the ordering temperature to be near 1.3(1) K. Copper chloride bis(DMSO) (DMSO is dimethyl sulfoxide) consists of linear chains of antiferromagnetically coupled S = 1over2 ions. The single-crystal dc magnetic susceptibilities have been measured. The data were compared to the predictions of Bucher and Honerkamp for the susceptibilities of XXZ linear chains. Good agreement was found for an exchange strength of J/k = -8.25 K and an anisotropy parameter Delta = 1.1, slightly Ising-like.

Greeney, Robert Edgar

1988-12-01

95

Measurement of anisotropic energy transport in flowing polymers by using a holographic technique.  

PubMed

Almost no experimental data exist to test theories for the nonisothermal flow of complex fluids. To provide quantitative tests for newly proposed theories, we have developed a holographic grating technique to study energy transport in an amorphous polymer melt subject to flow. Polyisobutylene with weight-averaged molecular mass of 85 kDa is sheared at a rate of 10 s(-1), and all nonzero components of the thermal conductivity tensor are measured as a function of time, after cessation. Our results are consistent with proposed generalizations to the energy balance for microstructural fluids, including a generalized Fourier's law for anisotropic media. The data are also consistent with a proposed stress-thermal rule for amorphous polymer melts. Confirmation of the universality of these results would allow numerical modelers to make quantitative predictions for the nonisothermal flow of polymer melts. PMID:15340152

Schieber, Jay D; Venerus, David C; Bush, Kendall; Balasubramanian, Venkat; Smoukov, Stoyan

2004-08-30

96

The effect of anisotropic heat transport on magnetic islands in 3-D configurations  

SciTech Connect

An analytic theory of nonlinear pressure-induced magnetic island formation using a boundary layer analysis is presented. This theory extends previous work by including the effects of finite parallel heat transport and is applicable to general three dimensional magnetic configurations. In this work, particular attention is paid to the role of finite parallel heat conduction in the context of pressure-induced island physics. It is found that localized currents that require self-consistent deformation of the pressure profile, such as resistive interchange and bootstrap currents, are attenuated by finite parallel heat conduction when the magnetic islands are sufficiently small. However, these anisotropic effects do not change saturated island widths caused by Pfirsch-Schlueter current effects. Implications for finite pressure-induced island healing are discussed.

Schlutt, M. G.; Hegna, C. C. [University of Wisconsin-Madison, 1500 Engineering Drive, 510 ERB, Madison, Wisconsin 53706 (United States)

2012-08-15

97

The effect of anisotropic heat transport on magnetic islands in 3-D configurations  

NASA Astrophysics Data System (ADS)

An analytic theory of nonlinear pressure-induced magnetic island formation using a boundary layer analysis is presented. This theory extends previous work by including the effects of finite parallel heat transport and is applicable to general three dimensional magnetic configurations. In this work, particular attention is paid to the role of finite parallel heat conduction in the context of pressure-induced island physics. It is found that localized currents that require self-consistent deformation of the pressure profile, such as resistive interchange and bootstrap currents, are attenuated by finite parallel heat conduction when the magnetic islands are sufficiently small. However, these anisotropic effects do not change saturated island widths caused by Pfirsch-Schlüter current effects. Implications for finite pressure-induced island healing are discussed.

Schlutt, M. G.; Hegna, C. C.

2012-08-01

98

Anisotropic Mechanical Properties of Magnetically Aligned Fibrin Gels Measured by Magnetic Resonance Elastography  

PubMed Central

The anisotropic mechanical properties of magnetically aligned fibrin gels were measured by magnetic resonance elastography (MRE) and by a standard mechanical test: unconfined compression. Soft anisotropic biomaterials are notoriously difficult to characterize, especially in vivo. MRE is well-suited for efficient, non-invasive, and nondestructive assessment of shear modulus. Direction-dependent differences in shear modulus were found to be statistically significant for gels polymerized at magnetic fields of 11.7T and 4.7T compared to control gels. Mechanical anisotropy was greater in the gels polymerized at the higher magnetic field. These observations were consistent with results from unconfined compression tests. Analysis of confocal microscopy images of gels showed measurable alignment of fibrils in gels polymerized at 11.7T. This study provides direct, quantitative measurements of the anisotropy in mechanical properties that accompanies fibril alignment in fibrin gels.

Namani, Ravi; Wood, Matthew D.; Sakiyama-Elbert, Shelly E.; Bayly, Philip V.

2009-01-01

99

Diffraction Properties of Anisotropic Volume Gratings Formed in Polymer-Dispersed Liquid Crystal  

NASA Astrophysics Data System (ADS)

The diffraction properties of highly polarized holographic polymer-dispersed liquid crystal (HPDLC) gratings fabricated by various grating formations are investigated as functions of the incidence angle of light and polarization state. Dominant anisotropic diffraction characteristics are obtained in HPDLC gratings by controlling the grating formation. Phase separation by photopolymerization to form the gratings is studied by evaluating the anisotropic diffraction and configuration of the separated phase of the gratings. The diffraction efficiency and the characteristic ratio of diffraction efficiency in polarization parallel to the grating vector to that in polarization perpendicular to the grating vector are markedly affected by liquid crystal (LC) contents. Structural analysis by optical polarization microscopy and scanning electron microscopy (SEM) is carried out to investigate the effect of the morphology of HPDLC gratings on diffraction properties. The grating morphologies are composed of fine droplets. The resultant gratings show novel diffractive performance consisting of high diffraction efficiency and polarization dependence over a wide angular range of incident light.

Ogiwara, Akifumi; Minato, Masahiro; Horiguchi, Shogo; Ono, Hiroshi; Imai, Hideya; Kakiuchida, Hiroshi; Yoshimura, Kazuki

2008-08-01

100

Linear and nonlinear optical properties of anisotropic quantum dots in a magnetic field  

NASA Astrophysics Data System (ADS)

We have investigated the linear and nonlinear optical properties of a two-dimensional anisotropic quantum dot in a magnetic field. Based on the computed energies and wave functions, the linear, third-order nonlinear and total optical absorption coefficients as well as the refractive index changes have been examined. The results are presented as a function of the incident photon energy for the different cases of anisotropy, dot size and external magnetic field. The results show that the linear and nonlinear optical properties of anisotropic quantum dots are strongly affected by the degree of anisotropy, the dot size, the external magnetic field and the polarized direction of the incident electromagnetic wave. The result also shows that the size effect of anisotropy quantum dots on the optical absorptions is different from that of isotropic quantum dots.

Xie, Wenfang

2013-05-01

101

A new method for calculation of elastic properties of anisotropic material by constant pressure molecular dynamics  

Microsoft Academic Search

A new method based on constant pressure molecular dynamics (MD) with the software package Materials Studio (MS) was developed to calculate the anisotropic elastic properties of 1,3,5-tri-amino-2,4,6-tri-nitrobenzene (TATB) which is a typical and widely studied explosive molecular and its single crystal is a typical triclinic lattice. Key points of the method are introduced. Firstly, a P1 periodic super cell of

Kailiang Yin; Dinghui Zou; Jing Zhong; Duanjun Xu

2007-01-01

102

Influence of spherically anisotropic core on the optical properties of gold nanoshell  

Microsoft Academic Search

The optical properties of gold nanoshell with a core of spherically anisotropic material have been investigated by means of\\u000a quasi-static theory. It is found with increasing the extent of anisotropy of the core that the surface plasmon resonance for\\u000a the particle shows a red-shift and that the full width at half maximum (FWHM) of the plasmon resonance peak increases. The

D. J. Wu; X. J. Liu

2009-01-01

103

Anisotropic electronic properties of Ni nanowires in oriented mesoporous silica film  

NASA Astrophysics Data System (ADS)

The electronic behavior of Ni nanowires in an oriented mesoporous silica thin film was reported. The hybrid film was prepared using a facile method of airflow-induced mesopore orientation from silica sol solution containing Ni2+ cation, followed by H2 reduction. Because of the confinement effect, the Ni nanowires were aligned in the oriented mesochannels, which resulted in anisotropic electronic responses. Such a property would be of great importance in the design of nanodevices for advanced photoelectric applications.

Cui, Wei; Lu, Xuemin; Su, Bin; Lu, Qinghua; Wei, Yen

2009-10-01

104

Anisotropic material properties of fused deposition modeling ABS  

Microsoft Academic Search

Rapid Prototyping (RP) technologies provide the ability to fabricate initial prototypes from various model materials. Stratasys Fused Deposition Modeling (FDM) is a typical RP process that can fabricate prototypes out of ABS plastic. To predict the mechanical behavior of FDM parts, it is critical to understand the material properties of the raw FDM process material, and the effect that FDM

Sung-Hoon Ahn; Michael Montero; Dan Odell; Shad Roundy; Paul K. Wright

2002-01-01

105

Static and dynamic properties of vortices in anisotropic magnetic disks  

Microsoft Academic Search

We investigate the effect of the magnetic anisotropy (Kz) on the static and dynamic properties of magnetic vortices in small disks. Our micromagnetic calculations reveal that for a range of Kz there is an enlargement of the vortex core. We analyze the influence of Kz on the dynamics of the vortex core magnetization reversal under the excitation of a pulsed

Tiago S. Machado; Tatiana G. Rappoport; Luiz C. Sampaio

2008-01-01

106

Transport and thermal properties of heavy-fermion superconductors - A unified picture  

Microsoft Academic Search

The transport and thermal properties of heavy-fermion superconductors are explained in terms of: (1) an anisotropic order parameter with a line or lines of nodes and (2) an effective mean free path which, except for the lowest temperatures, is approximately temperature independent and of a similar magnitude as in the nominal state. Such a mean free path is shown to

S. Schmitt-Rink; K. Miyake; C. M. Varma

1986-01-01

107

Anisotropic magnetic properties and crystal electric field studies on CePd2Ge2 single crystal  

NASA Astrophysics Data System (ADS)

The anisotropic magnetic properties of the antiferromagnetic compound CePd2Ge2, crystallizing in the tetragonal crystal structure have been investigated in detail on a single crystal grown by the Czochralski method. From the electrical transport, magnetization and heat capacity data, the Néel temperature is confirmed to be 5.1 K. Anisotropic behaviour of the magnetization and resistivity is observed along the two principal crystallographic directions—namely, [100] and [001]. The isothermal magnetization measured in the magnetically ordered state at 2 K exhibits a spin reorientation at 13.5 T for the field applied along the [100] direction, whereas the magnetization is linear along the [001] direction attaining a value of 0.94 ?B/Ce at 14 T. The reduced value of the magnetization is attributed to the crystalline electric field (CEF) effects. A sharp jump in the specific heat at the magnetic ordering temperature is observed. After subtracting the phononic contribution, the jump in the heat capacity amounts to 12.5 J K-1mol-1 which is the expected value for a spin \\frac{1}{2} system. From the CEF analysis of the magnetization data the excited crystal field split energy levels were estimated to be at 120 K and 230 K respectively, which quantitatively explains the observed Schottky anomaly in the heat capacity. A magnetic phase diagram has been constructed based on the field dependence of magnetic susceptibility and the heat capacity data.

Maurya, Arvind; Kulkarni, R.; Dhar, S. K.; Thamizhavel, A.

2013-10-01

108

Anisotropic magnetic properties and crystal electric field studies on CePd2Ge2 single crystal.  

PubMed

The anisotropic magnetic properties of the antiferromagnetic compound CePd2Ge2, crystallizing in the tetragonal crystal structure have been investigated in detail on a single crystal grown by the Czochralski method. From the electrical transport, magnetization and heat capacity data, the Néel temperature is confirmed to be 5.1 K. Anisotropic behaviour of the magnetization and resistivity is observed along the two principal crystallographic directions-namely, [100] and [001]. The isothermal magnetization measured in the magnetically ordered state at 2 K exhibits a spin reorientation at 13.5 T for the field applied along the [100] direction, whereas the magnetization is linear along the [001] direction attaining a value of 0.94 ?B/Ce at 14 T. The reduced value of the magnetization is attributed to the crystalline electric field (CEF) effects. A sharp jump in the specific heat at the magnetic ordering temperature is observed. After subtracting the phononic contribution, the jump in the heat capacity amounts to 12.5 J K(-1)mol(-1) which is the expected value for a spin [Formula: see text] system. From the CEF analysis of the magnetization data the excited crystal field split energy levels were estimated to be at 120 K and 230 K respectively, which quantitatively explains the observed Schottky anomaly in the heat capacity. A magnetic phase diagram has been constructed based on the field dependence of magnetic susceptibility and the heat capacity data. PMID:24097258

Maurya, Arvind; Kulkarni, R; Dhar, S K; Thamizhavel, A

2013-10-04

109

Tuneable anisotropic transport in nitrogen-doped nanocrystalline diamond films: Evidence of a graphite-diamond hybrid superlattice  

NASA Astrophysics Data System (ADS)

We show strong evidence of superlattice-like carbon layered structures in heavily nitrogen-doped ultrananocrystalline diamond (UNCD) films through the experimental demonstration of temperature-dependent anisotropic diffusive transport. The superlattice periodicity, in the range of several nanometers, is derived from the analysis of both magneto-resistance and the temperature-dependent conductivity based on the generalized diffusive Fermi surface model. The effect of quasi-two-dimensionality on the magneto-transport of these films yields a weak temperature dependence of the electron dephasing length. These results explain a reasonably strong coupling between the conducting carbon layers separated by the insulating nanodiamond grains producing the anisotropic transport in UNCD films controlled by the level of nitrogen incorporation.

Churochkin, Dmitry; Bhattacharyya, Somnath

2012-12-01

110

Anomalous, non-Gaussian transport of charged particles in anisotropic magnetic turbulence  

SciTech Connect

The transport of energetic particles in a mean magnetic field and in the presence of anisotropic magnetic turbulence is studied numerically, for parameter values relevant to astrophysical plasmas. A numerical realization of magnetic turbulence is set up, in which the degree of anisotropy is varied by changing the correlation lengths l{sub x}, l{sub y}, and l{sub z}. The ratio {rho}/{lambda} of the particle Larmor radius {rho} over the turbulence correlation length {lambda} is also varied. It is found that for l{sub x},l{sub y}>>l{sub z}, and for {rho}/{lambda} < or approx. 10{sup -2} transport can be non-Gaussian, with superdiffusion along the average magnetic field and subdiffusion perpendicular to it. In addition, the spatial distribution of particles is clearly non-Gaussian. Such regimes are characterized by a Levy statistics, with diverging second-order moments. Decreasing the ratio l{sub x}/l{sub z}, nearly Gaussian (normal) diffusion is obtained, showing that the transport regime depends on the turbulence anisotropy. Changing the particle Larmor radius, normal diffusion is found for 10{sup -2} < or approx. {rho}/{lambda} < or approx. 1 because of increased pitch angle diffusion. New anomalous superdiffusive regimes appear when {rho}/{lambda} > or approx. 1 showing that the interaction between particles and turbulence decreases in these cases. A new regime, called generalized double diffusion, is proposed for the cases when particles are able to trace back field lines. A summary of the physical conditions which lead to non-Gaussian transport is given.

Pommois, P.; Zimbardo, G.; Veltri, P. [Physics Department, University of Calabria, Arcavacata di Rende, 87036 Rende (Italy)

2007-01-15

111

Characterization of the anisotropic mechanical properties of excised human skin.  

PubMed

The mechanical properties of skin are important for a number of applications including surgery, dermatology, impact biomechanics and forensic science. In this study, we have investigated the influence of location and orientation on the deformation characteristics of 56 samples of excised human skin. Uniaxial tensile tests were carried out at a strain rate of 0.012 s(-1) on skin from the back. Digital Image Correlation was used for 2D strain measurement and a histological examination of the dermis was also performed. The mean ultimate tensile strength (UTS) was 21.6±8.4 MPa, the mean failure strain 54%±17%, the mean initial slope 1.18±0.88 MPa, the mean elastic modulus 83.3±34.9 MPa and the mean strain energy was 3.6±1.6 MJ/m(3). A multivariate analysis of variance has shown that these mechanical properties of skin are dependent upon the orientation of the Langer lines (P<0.0001-P=0.046). The location of specimens on the back was also found to have a significant effect on the UTS (P=0.0002), the elastic modulus (P=0.001) and the strain energy (P=0.0052). The histological investigation concluded that there is a definite correlation between the orientation of the Langer lines and the preferred orientation of collagen fibres in the dermis (P<0.001). The data obtained in this study will provide essential information for those wishing to model the skin using a structural constitutive model. PMID:22100088

Ní Annaidh, Aisling; Bruyère, Karine; Destrade, Michel; Gilchrist, Michael D; Otténio, Mélanie

2011-08-31

112

Ground-state correlation properties of charged bosons trapped in strongly anisotropic harmonic potentials  

NASA Astrophysics Data System (ADS)

We study systems of a few charged bosons contained within a strongly anisotropic harmonic trap. A detailed examination of the ground-state correlation properties of two-, three-, and four-particle systems is carried out within the framework of the single-mode approximation of the transverse components. The linear correlation entropy of the quasi-1D systems is discussed in dependence on the confinement anisotropy and compared with a strictly 1D limit. Only at weak interaction the correlation properties depend strongly on the anisotropy parameter.

Ko?cik, P.; Okopi?ska, A.

2012-03-01

113

Thermodynamics properties of an anisotropic Ising antiferromagnet in both external longitudinal and transverse fields  

NASA Astrophysics Data System (ADS)

We have studied the anisotropic two-dimensional nearest-neighbor Ising model with competitive interactions in both uniform longitudinal field H and transverse magnetic field ?. Using the effective-field theory (EFT) with correlation in cluster with N=1 spin we calculate the thermodynamic properties as a function of temperature with values H and ? fixed. The model consists of ferromagnetic interaction Jx in the x direction and antiferromagnetic interaction Jy in the y direction, and it is found that for H/Jy?[0,2] the system exhibits a second-order phase transition. The thermodynamic properties are obtained for the particular case of ?=Jx/Jy=1 (isotropic square lattice).

do Nascimento, Denise A.; Neto, Minos A.; de Sousa, J. Ricardo; Pacobahyba, J. T. M.

2013-11-01

114

Anisotropic weakly localized transport in nitrogen-doped ultrananocrystalline diamond films  

NASA Astrophysics Data System (ADS)

We establish the dominant effect of anisotropic weak localization (WL) in three dimensions (3D) associated with a propagative Fermi surface on the conductivity correction in heavily nitrogen-doped ultrananocrystalline diamond (UNCD) films based on magnetoresistance studies at low temperatures. Also, low-temperature electrical conductivity can show weakly localized transport in 3D combined with the effect of electron-electron interactions in these materials, which is remarkably different from the conductivity in two-dimensional WL or strong localization regime. The corresponding dephasing time of electronic wave functions in these systems described as ˜T-p with p<1 , follows a relatively weak temperature dependence compared to the generally expected nature for bulk dirty metals having p?1 . The temperature dependence of Hall (electron) mobility together with an enhanced electron density has been used to interpret the unusual magnetotransport features and show delocalized electronic transport in these n -type UNCD films, which can be described as low-dimensional superlattice structures.

Shah, Kunjal V.; Churochkin, Dmitry; Chiguvare, Zivayi; Bhattacharyya, Somnath

2010-11-01

115

Optical Properties of Anisotropic Polycrystalline Ce(+3) activated LSO.  

PubMed

Polycrystalline cerium activated lutetium oxyorthosilicate (LSO:Ce) is highly desirable technique to make cost effective and highly reproducible radiation detectors for medical imaging. In this article methods to improve transparency in polycrystalline LSO:Ce were explored. Two commercially available powders of different particulate sizes (average particle size 30 and 1500 nm) were evaluated for producing dense LSO:Ce by pressure assisted densification routes, such as hot pressing and hot isostatic pressing. Consolidation of the powders at optimum conditions produced three polycrystalline ceramics with average grain sizes of 500 nm, 700 and 2000 nm. Microstructural evolution studies showed that for grain sizes larger than 1 µm, anisotropy in thermal expansion coefficient and elastic constants of LSO, resulted in residual stress at grain boundaries and triple points that led to intragranular microcracking. However, reducing the grain size below 1 µm effectively avoids microcracking, leading to more favorable optical properties. The optical scattering profiles generated by a Stover scatterometer, measured by a He-Ne laser of wavelength 633 nm, showed that by reducing the grain size from 2 µm to 500 nm, the in-line transmission increased by a factor of 10(3). Although these values were encouraging and showed that small changes in grain size could increase transmission by almost 3 orders of magnitude, even smaller grain sizes need to be achieved in order to get truly transparent material with high in-line transmission. PMID:23505329

Roy, Sudesna; Lingertat, Helmut; Brecher, Charles; Sarin, Vinod

2013-03-01

116

Optical properties of anisotropic polycrystalline Ce3+ activated LSO  

NASA Astrophysics Data System (ADS)

Polycrystalline cerium activated lutetium oxyorthosilicate (LSO:Ce) is highly desirable technique to make cost effective and highly reproducible radiation detectors for medical imaging. In this article methods to improve transparency in polycrystalline LSO:Ce were explored. Two commercially available powders of different particulate sizes (average particle size 30 and 1500 nm) were evaluated for producing dense LSO:Ce by pressure assisted densification routes, such as hot pressing and hot isostatic pressing. Consolidation of the powders at optimum conditions produced three polycrystalline ceramics with average grain sizes of 500 nm, 700 nm and 2000 nm. Microstructural evolution studies showed that for grain sizes larger than 1 ?m, anisotropy in thermal expansion coefficient and elastic constants of LSO, resulted in residual stress at grain boundaries and triple points that led to intragranular microcracking. However, reducing the grain size below 1 ?m effectively avoids microcracking, leading to more favorable optical properties. The optical scattering profiles generated by a Stover scatterometer, measured by a He-Ne laser of wavelength 633 nm, showed that by reducing the grain size from 2 ?m to 500 nm, the in-line transmission increased by a factor of 103. Although these values were encouraging and showed that small changes in grain size could increase transmission by almost three orders of magnitude, even smaller grain sizes need to be achieved in order to get truly transparent material with high in-line transmission.

Roy, Sudesna; Lingertat, Helmut; Brecher, Charles; Sarin, Vinod

2013-03-01

117

Anisotropic physical properties of myocardium characterized by ultrasonic measurements of backscatter, attenuation, and velocity  

NASA Astrophysics Data System (ADS)

The goal of elucidating the physical mechanisms underlying the propagation of ultrasonic waves in anisotropic soft tissue such as myocardium has posed an interesting and largely unsolved problem in the field of physics for the past 30 years. In part because of the vast complexity of the system being studied, progress towards understanding and modeling the mechanisms that underlie observed acoustic parameters may first require the guidance of careful experiment. Knowledge of the causes of observed ultrasonic properties in soft tissue including attenuation, speed of sound, and backscatter, and how those properties are altered with specific pathophysiologies, may lead to new noninvasive approaches to the diagnosis of disease. The primary aim of this Dissertation is to contribute to an understanding of the physics that underlies the mechanisms responsible for the observed interaction of ultrasound with myocardium. To this end, through-transmission and backscatter measurements were performed by varying acoustic properties as a function of angle of insonification relative to the predominant myofiber direction and by altering the material properties of myocardium by increased protein cross-linking induced by chemical fixation as an extreme form of changes that may occur in certain pathologies such as diabetes. Techniques to estimate acoustic parameters from backscatter were broadened and challenges to implementing these techniques in vivo were addressed. Provided that specific challenges identified in this Dissertation can be overcome, techniques to estimate attenuation from ultrasonic backscatter show promise as a means to investigate the physical interaction of ultrasound with anisotropic biological media in vivo. This Dissertation represents a step towards understanding the physics of the interaction of ultrasonic waves with anisotropic biological media.

Baldwin, Steven L.

118

Preparation of Large-Size Anisotropic Polypyrrole Film and Its Actuation Property  

NASA Astrophysics Data System (ADS)

A method of preparing a large-size anisotropic polypyrrole (PPy) film using a slab vessel consisting of poly(tetrafluoroethylene) (PTFE) walls as well as its actuation properties is reported. The PPy film can be grown along one side of the PTFE walls and exhibits a morphological anisotropy along the thickness direction. A piece of it bends and reverts in a regular direction during a redox cycle without the use of any addditional processes such as lamination. The actuation characteristics of the anisotropic PPy film strongly depend on the size of the cation in the driving electrolyte. The bending of this actuator at room temperature becomes slower for larger cations. The temperature dependence of the characteristics of the anisotropic PPy film as actuator has been investigated. As the temperature increases, the arrival time of the actuator becomes shorter in all electrolyte solutions. This can be understood in terms of the thermally activated microscopic movement of polymer chains. It is also found that this actuator can lift an object which weighs more than 25 times of the weight of the actuator itself.

Kato, Yoshiyuki; Tada, Kazuya; Onoda, Mitsuyoshi

2003-03-01

119

Electronic transport properties of topological insulator films and low dimensional superconductors  

NASA Astrophysics Data System (ADS)

In this review, we present a summary of some recent experiments on topological insulators (TIs) and superconducting nanowires and films. Electron-electron interaction (EEI), weak anti-localization (WAL) and anisotropic magneto-resistance (AMR) effect found in topological insulator films by transport measurements are reported. Then, transport properties of superconducting films, bridges and nanowires and proximity effect in non-superconducting nanowires are described. Finally, the interplay between topological insulators and superconductors (SCs) is also discussed.

Xing, Ying; Sun, Yi; Singh, Meenakshi; Zhao, Yan-Fei; Chan, Moses H. W.; Wang, Jian

2013-10-01

120

Effect of the Binder and Some Additives on Properties of the Anisotropic Injection Bonded Nd-Fe-B Magnets  

Microsoft Academic Search

This study is on the anisotropic Nd-Fe-B bonded magnets fabricated from HDDR powders by injection molding process under orientation magnetic field. The effects of polymer binder, chemicals such as coupling agent for surface modification of the powders, antioxidant and lubricant on the density, magnetic and mechanical properties of anisotropic Nd-Fe-B magnets were investigated. The corrosion resistance of the powder and

Xiaolei Zhang; Mingyuan Zhu; Ying Li; Hongming Jin; Ye Tian; Zhun Wang; Qiuping Yang

2008-01-01

121

Tuning the effects of Landau level mixing on anisotropic transport in quantum Hall systems.  

PubMed

Electron-electron interactions in half-filled high Landau levels in two-dimensional electron gases in a strong perpendicular magnetic field can lead to states with anisotropic longitudinal resistance. This longitudinal resistance is generally believed to arise from broken rotational invariance, which is indicated by charge density wave order in Hartree-Fock calculations. We use the Hartree-Fock approximation to study the influence of externally tuned Landau level mixing on the formation of interaction-induced states that break rotational invariance in two-dimensional electron and hole systems. We focus on the situation when there are two non-interacting states in the vicinity of the Fermi level and construct a Landau theory to study coupled charge density wave order that can occur as interactions are tuned and the filling or mixing are varied. We consider numerically a specific example where mixing is tuned externally through Rashba spin-orbit coupling. We calculate the phase diagram and find the possibility of ordering involving coupled striped or triangular charge density waves in the two levels. Our results may be relevant to recent transport experiments on quantum Hall nematics in which Landau level mixing plays an important role. PMID:22227599

Smith, Peter M; Kennett, Malcolm P

2012-01-06

122

New properties of magnon density in uniaxial anisotropic ferromagnet on the background of spin wave  

SciTech Connect

The N-soliton solutions of magnetization in uniaxial anisotropic ferromagnet on the background of spin wave are presented by using the effective Darboux transformation method. With the analytical solutions new properties of magnon density is studied in detail. On the ground state background the magnon density is constant for the spin wave solution and the magnetic soliton, respectively. However, on the spin wave background the magnon density possesses of temporal or spatial periodic oscillation. Moreover, the soliton solution possess the breather character in its propagation along the ferromagnet. These results show that during soliton propagation a periodic magnon exchange occurs between the magnetic soliton and the spin wave background.

Zheng Zhongxi [Key Laboratory of Instrumentation Science and Dynamic Measurement (North University of China), Ministry of Education, Taiyuan 030051 (China); National Key Laboratory For Electronic Measurement Technology, Taiyuan 030051 (China); College of Science, North University of China, Taiyuan 030051 (China); Li Qiuyan [Department of Applied Physics, Hebei University of Technology, Tianjin 300401 (China); School of Information Engineer, Hebei University of Technology, Tianjin 300401 (China); Li Zaidong [Department of Applied Physics, Hebei University of Technology, Tianjin 300401 (China)], E-mail: zdli2003@yahoo.com; Wang Shuxin [Department of Applied Physics, Hebei University of Technology, Tianjin 300401 (China); Xu Liping; Wen Tingdun [Key Laboratory of Instrumentation Science and Dynamic Measurement (North University of China), Ministry of Education, Taiyuan 030051 (China); National Key Laboratory For Electronic Measurement Technology, Taiyuan 030051 (China); College of Science, North University of China, Taiyuan 030051 (China)

2009-08-15

123

Anisotropic elastic properties of thermal spray coatings determined via resonant ultrasound spectroscopy  

SciTech Connect

The determination of elastic properties of plasma-sprayed ceramic and metallic coatings is difficult due to their complex microstructure, which involves a myriad array of pores, interfaces and other defects. Furthermore, the splat-based build-up of the coating results in transverse anisotropy in the elastic properties. In this paper, we report on the anisotropic elastic properties of these coatings determined by resonant ultrasound spectroscopy (RUS). This approach along with the analysis presented enables, for the first time, the determination of elastic properties as a function of direction and temperature for these complex systems with concomitant implications for design. The coating systems investigated included plasma-sprayed yttria-stabilized zirconia (YSZ) and nickel. An additional nickel coating deposited by high-velocity oxygen-fuel process was investigated and its elastic properties were compared to those of plasma-sprayed nickel. Average Young s moduli of the coatings were independently measured by using the instrumented indentation method. The elastic properties determined from the RUS and indentation methodologies allowed description of the microstructure elastic property relationships in the coatings.

Tan, Yang [Stony Brook University (SUNY); Shyam, Amit [ORNL; Choi, Wanhuk Brian [Stony Brook University (SUNY); Lara-Curzio, Edgar [ORNL; Sampath, Sanjay [Stony Brook University (SUNY)

2010-01-01

124

Optical properties of composite systems based on anisotropic fibers with axisymmetric stacking  

NASA Astrophysics Data System (ADS)

Simulation of optical properties of composite systems in the form of bundles consisting of anisotropic fibers with axisymmetric stacking is carried out in the ray-optics approximation. It is shown that such composite systems observed by the interference-polarization method for the case of crossed Nicol prisms produce figures in the form of a system of concentric light and dark rings, in the center of which there is a dark cross. The results of simulations applied to microsections of the human tooth taking into account the numerical values of the constituent components of the dentin (the sizes and optical properties of the dentinal tubules and of the matrix, etc.) are compared with the experiment. A good qualitative agreement between the calculation and the experiment for the observed patterns is found in the cases of some samples (molar and premolar).

Zolotarev, V. M.

2004-10-01

125

Impact of magnetic properties on the Casimir torque between anisotropic metamaterial plates  

SciTech Connect

The quantized surface mode technique is used to calculate the Casimir torque between two parallel anisotropic metamaterial plates with in-plane optical axes, and our main concern is focused on the impact of the magnetic properties of the plates on the Casimir torque. Our result shows that at small separation, the Casimir torque between the two plates with frequency dependent permeabilities is larger than that between two nonmagnetic plates, while at large separation it is smaller. This can be explained as a result of the impact of both magnetic properties and material dispersion of the plates. The impact of the Drude background in connected metallic metamaterial is also discussed. These phenomena provide us with new understanding about the Casimir effect and show great potential in application.

Deng Gang; Liu Zhongzhu; Luo Jun [Department of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)

2009-12-15

126

Localization for anisotropic sensor networks  

Microsoft Academic Search

In this paper, we consider the issue of localization in anisotropic sensor networks. Anisotropic networks are differentiated from isotropic networks in that they possess properties that vary according to the direction of measurement. Anisotropic characteristics result from various factors such as the geographic shape of the region (non-convex region), the different node densities, the irregular radio patterns, and the anisotropic

Hyuk Lim; Jennifer C. Hou

2005-01-01

127

Novel properties of wave propagation in biaxially anisotropic left-handed materials  

NASA Astrophysics Data System (ADS)

Some physically interesting properties and effects (including the quantum effects) of wave propagation in biaxially anisotropic left-handed materials are investigated in this paper: (i) we show that in the biaxially gyrotropic left-handed material, the left-right coupling of circularly polarized light arises due to the negative indices in permittivity and permeability tensors of gyrotropic media; (ii) it is well known that the geometric phases of photons inside a curved fiber in previous experiments often depend on the cone angles of solid angles subtended by a curve traced by the direction of wave vector of light, at the center of photon momentum space. Here, however, for the light propagating inside certain anisotropic left-handed media we will present a different geometric phase that is independent of the cone angles; (iii) the extra phases of electromagnetic wave resulting from the instantaneous helicity inversion at the interfaces between left- and right-handed (LRH) media is also studied in detail by using the Lewis-Riesenfeld invariant theory. Some interesting applications (e.g., controllable position-dependent frequency shift, detection of quantum-vacuum geometric phases and helicity reversals at the LRH interfaces etc.) of above effects and phenomena in left-handed media is briefly discussed.

Shen, J. Q.

2004-06-01

128

Study of the Anisotropic Properties of Argillite Under Moisture and Mechanical Loads  

NASA Astrophysics Data System (ADS)

Due to various factors, such as sedimentation, layered morphology of clay minerals, in situ stress, etc., argillite rocks often exhibit anisotropic behavior. In order to study the anisotropic properties of the Callovo-Oxfordian (COx) argillite of the Meuse-Haute-Marne site in France considered as a possible host rock for high-level radioactive nuclear waste repository, a series of tests including uniaxial compression and dehydration and hydration at different constant applied stress levels are carried out. In this study, a specific setup combining moisture and mechanical loading with optical observation is used and it allows to continuously capture surface images from which the full-field strains are determined by using Digital Image Correlation techniques. The results show evidence of the mechanical and hydric anisotropy of the material. The anisotropy parameters are identified, assuming the studied argillite as transversely isotropic. The shrinkage and swelling depend on the applied stress and the angle with respect to the vertical direction of the mechanical load and the stratification plane, and this dependence is quantified. The non-linearity and the hysteresis observed during dehydration and hydration cycles are discussed.

Yang, Diansen; Chanchole, Serge; Valli, Pierre; Chen, Liufeng

2013-03-01

129

Optimum condition of anisotropic plasma etching for improving bending properties of ionic polymer-metal composites.  

PubMed

We presented an anisotropic plasma etching technique by reactive ion etcher (RIE) as a new pretreatment method of fabrication of ionic polymer-metal composite (IPMC). We already found that the new technique provided large displacement to the fabricated IPMC in the presence of low applied voltage. However, we did not examine the optimum condition for the anisotropic plasma etching. In this research, we tried to figure out optimum treatment condition of film in etcher. Nafion (by DuPont) films were etched using various etching time and shadow masks with various slit and space sizes. The etched samples were plated with Pt at top and bottom side by Oguro's reduction method. The surface morphology of fabricated IPMCs was characterized by SEM. And, we've measured surface resistance, bending displacement, and driving force in order to check the IPMC properties out. Here, we found that optimum condition for pre-treatment of Nafion was 1 min for etching time under shadow mask with 200 microm slit and 100 microm space. PMID:20358943

Choi, N J; Lee, H K; Jung, S; Park, K H

2010-05-01

130

Single-crystal growth and anisotropic magnetic properties of nonstoichiometric three-layer sodium cobalt oxides  

SciTech Connect

Large single crystals of {alpha}-Na{sub x}CoO{sub 2} (x=0.91, 0.92, and 0.93) have been successfully fabricated by using the traveling solvent floating zone method. Details on the crystal growth are discussed. The crystal structures were characterized using powder x-ray diffraction and Rietveld refinement. The magnetic susceptibility measurements show that the magnetic properties depend strongly on x. The compound was found to be antiferromagnetic at T{sub N}{approx_equal}20 K for x=0.91 and x=0.92, and paramagnetic for x=0.93. The in-plane and out-of-plane anisotropies were observed for the x=0.91 crystals. In addition, the derived anisotropic g-factor ratios (g{sub ab}/g{sub c}) from the anisotropic susceptibility along H parallel ab and H parallel c decreased significantly as the sodium composition increased from x=0.91 to x=0.93.

Chen, D. P. [Institute for Superconducting and Electronic Materials, University of Wollongong, New South Wales 2500 (Australia); Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart (Germany); Wang, Xiaolin; Dou, S. X. [Institute for Superconducting and Electronic Materials, University of Wollongong, New South Wales 2500 (Australia); Lin, C. T. [Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart (Germany)

2007-10-01

131

Crystal growth and anisotropic magnetic properties of V{sub 3}O{sub 7}  

SciTech Connect

Needle-like crystals of V{sub 3}O{sub 7} up to 2 mm in length were grown by a chemical vapor transport method using NH{sub 4}Cl as a transport agent. The anisotropic magnetic susceptibility was measured for the first time. At 2 K, a spin-flop transition occurs under a magnetic field of 0.1 T. V{sub 3}O{sub 7} is proved to be a uniaxial antiferromagnet with its easy axis parallel to the b-axis of monoclinic structure. A spin structure with antiferromagnetic interaction between (101-bar) layers and ferromagnetic interaction in the layers below the Neel temperature (5.2 K) is suggested. - Graphical abstract: The temperature dependence of the magnetic susceptibility of V{sub 3}O{sub 7} for (H-parallel b) and (H-perpendicular b), respectively, at 0.1 T. The inset shows crystals of V{sub 3}O{sub 7} grown by using NH{sub 4}Cl as the transport agent.

Li, C. [Materials Design and Characterization Laboratory (MDCL), Institute for Solid State Physics (ISSP), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Isobe, M., E-mail: isobe@issp.u-tokyo.ac.j [Materials Design and Characterization Laboratory (MDCL), Institute for Solid State Physics (ISSP), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Ueda, H.; Matsushita, Y.; Ueda, Y. [Materials Design and Characterization Laboratory (MDCL), Institute for Solid State Physics (ISSP), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan)

2009-12-15

132

Ultrasonic Characterization of the Linear Elastic Properties of Myocardium and Other Anisotropic Soft Tissues  

NASA Astrophysics Data System (ADS)

This thesis seeks to contribute to a better understanding of the physics of interaction of ultrasonic waves with inhomogeneous and anisotropic media, one example of which is the human heart. The clinical success of echocardiography has generated a considerable interest in the development of ultrasonic techniques to measure the elastic properties of heart tissue. It is hypothesized that the elastic properties of myocardium are influenced by the interstitial content and organization of collagen. Collagen, which is the main component of tendon, interconnects the muscle cells of the heart to form locally unidirectional myofibers. This thesis therefore employs ultrasonic techniques to characterize the linear elastic properties of both heart and tendon. The linear elastic properties of tissues possessing a unidirectional arrangement of fibers may be described in terms of five independent elastic stiffness coefficients. Three of these coefficients were determined for formalin fixed specimens of bovine Achilles tendon and human myocardium by measuring the velocity of longitudinal mode ultrasonic pulses as a function of angle of propagation relative to the fiber axis of the tissue. The remaining two coefficients were determined by measuring the velocity of transverse mode ultrasonic waves through these tissues. To overcome technical difficulties associated with the extremely high attenuation of transverse mode waves at low megahertz frequencies, a novel measurement system was developed based on the sampled continuous wave technique. Results of these measurements were used to assess the influence of interstitial collagen, and to model the mechanical properties of heart wall.

Hoffmeister, Brentley Keith

1995-01-01

133

Oriented Morphology and Anisotropic Transport in Uniaxially Stretched Perfluorosulfonate Ionomer Membranes  

SciTech Connect

Relations between morphology and transport sensitively govern proton conductivity in perfluorsulfonate ionomers (PFSIs) and thus determine useful properties of these technologically important materials. In order to understand such relations, we have conducted a broad systematic study of H{sup +}-form PFSI membranes over a range of uniaxial extensions and water uptakes. On the basis of small-angle X-ray scattering (SAXS) and {sup 2}H NMR spectroscopy, uniaxial deformation induces a strong alignment of ionic domains along the stretching direction. We correlate ionic domain orientation to transport using pulsed-field-gradient {sup 1}H NMR measurements of water diffusion coefficients along the three orthogonal membrane directions. Intriguingly, we observe that uniaxial deformation enhances water transport in one direction (parallel-to-draw direction) while reducing it in the other two directions (two orthogonal directions relative to the stretching direction). We evaluate another important transport parameter, proton conductivity, along two orthogonal in-plane directions. In agreement with water diffusion experiments, orientation of ionic channels increases proton conduction along the stretching direction while decreasing it in the perpendicular direction. These findings provide valuable fodder for optimal application of PFSI membranes as well as for the design of next generation polymer electrolyte membranes.

J Park; J Li; G Divoux; L Madsen; R Moore

2011-12-31

134

Preparation and magnetic properties of anisotropic (Sm,Pr)Co5/Co composite particles  

NASA Astrophysics Data System (ADS)

Anisotropic (Sm,Pr)Co5/Co nanocomposite particles have been fabricated by chemical coating the 2 h ball milled (Sm,Pr)Co5 flakes with Co nanoparticles. The Co nanoparticles were synthesized with mean particle sizes in the range of 20-50 nm. The nanocomposite particles present [0 0 1] out-of-plane texture and improved magnetic properties, e.g., an enhanced remanent magnetization of 72 emu/g for (Sm,Pr)Co5/Co and 66 emu/g for (Sm,Pr)Co5. In addition, by using the 8 h ball milled powders (much smaller than the 2 h ball milled powders) as the starting materials, Co nanoparticles can also be successfully coated on the surface of the flakes. A plausible mechanism for the formation of Co nanoparticles on the surface of (Sm,Pr)Co5 flakes is discussed.

Wang, Xiaoliang; He, Huanlong; Wang, Fengqing; Chen, Yan; Xu, Lei; Li, Xiaohong; Zhang, Xiangyi

2012-03-01

135

Transport, thermal, and magnetic properties in heavy-fermion superconductor Ce 2CoIn 8  

Microsoft Academic Search

We have grown high purity single crystals of Ce2CoIn8 using the self-flux technique, and have investigated its transport, thermal, and magnetic properties, including the anisotropic features. Single crystals of Ce2CoIn8 were grown in the lower temperature region to avoid the formation of un-wanted phases such as CeCoIn5 and CeIn3 impurities. The results of the structural and physical measurements imply that

Tetsuro Yamashita; Shigeo Ohara; Isao Sakamoto

2011-01-01

136

Anisotropic electrical properties of thermal spray coatings: The role of splat-boundary interfaces  

NASA Astrophysics Data System (ADS)

A thermal spray coating is an assemblage of splats which are considered the building-blocks of the coating. Apart from the properties of the splats themselves, the physical properties of the coatings are strongly influenced by the nature of the regions between splats, the so-called splat-boundary (SB) interfaces. This dissertation is primarily an investigation of the role of SB interfaces in determining the properties of thermal spray coatings vis-a-vis processing conditions and post-process heat-treatments. The effect of process dependent differences in the nature of the SB interfaces and subsequent effects on coating properties was studied in Ni-5 wt %Al coatings made by different thermal spray processes. Measurement of in-plane and through-thickness electrical resistivities revealed the anisotropic nature of the coatings with anisotropies ranging from 1.1 to 2.2 across the processes. These results combined with the information on coating microstructures and chemical compositions showed the significant role of SBs in determining electrical behavior. These results also showed that electrical measurements could be used as a sensitive tool for microstructurel characterization. The effect of post-process heat-treatments was studied in plasma-sprayed TiO2 coatings which were subjected to a well-designed time-temperature scheme of air-annealing. Direct-current resistivity measurements in-plane and through-thickness of the coatings as a function of annealing time and temperature showed remarkably large anisotropies of up to 105. Impedance spectroscopy of the specimens coupled with microstructurel analysis revealed the relationship of this anisotropy with the SB interfaces: Due to rapid quenching, the high temperature deoxidation state is preserved in the SBs making them more conductive than the bulk of the splat in the as-sprayed coating. Upon annealing in air, the SBs get selectively oxidized due to faster surface diffusion of oxygen and become more insulating. This behavior of SBs, together with the layered morphology of plasma sprayed coatings results in anisotropic properties. Another aspect of the sprayed coatings is the thickness dependence of electrical resistivity which was observed in metallic coatings made of many different materials. A detailed analysis of this thickness dependence of resistivity in plasma-sprayed molybdenum coatings showed that this unusual effect is a percolation-conduction phenomenon associated with the evolution of porosity with thickness.

Sharma, Atin

137

Effect of quasiparticles on interlayer transport in highly anisotropic layered superconductors  

Microsoft Academic Search

We have performed a microscopic calculation of the dielectric response function in highly anisotropic layered superconductors and used the developed approach to obtain the frequency-dependent London penetration length and conductivity in the case of {ital d}-wave pairing for currents perpendicular to the layers. We consider a BCS model with coherent interlayer tunneling of electrons and take into account contributions from

S. N. Artemenko; L. N. Bulaevskii; M. P. Maley; V. M. Vinokur

1999-01-01

138

Effect of quasiparticles on interlayer transport in highly anisotropic layered superconductors  

Microsoft Academic Search

We have performed a microscopic calculation of the dielectric response function in highly anisotropic layered superconductors and used the developed approach to obtain the frequency-dependent London penetration length and conductivity in the case of d-wave pairing for currents perpendicular to the layers. We consider a BCS model with coherent interlayer tunneling of electrons and take into account contributions from both

S. N. Artemenko; L. N. Bulaevskii; M. P. Maley; V. M. Vinokur

1999-01-01

139

TRANSPORT PROPERTY MEASUREMENTS OF HFC-236EA  

EPA Science Inventory

The report gives results of an evaluation of transport properties of 1,1,1,2,3,3,-hexafluoropropane (HFC-236ea), with liquid viscosity and thermal conductivity being the two main transport properties of interest. In addition, the specific heat and density of refrigerant/lubrican...

140

TRANSPORT PROPERTY MEASUREMENTS OF HFC-236EA  

EPA Science Inventory

The report gives results of an evaluation of transport properties of 1, 1, 1, 2, 3, 3-hexafluoropropane (HFC-236ea), with liquid viscosity and thermal conductivity being the two main transport properties of interest. In addition, the specific heat and density of refrigerant/lubri...

141

Virtual Testing of Concrete Transport Properties  

Microsoft Academic Search

Synopsis: The transport properties of concrete are critical to its field performance. Commonly encountered degradation mechanisms are dependent on ionic diffusivity, sorptivity, and permeability. In this paper, virtual testing of two of these concrete transport properties, diffusivity and permeability, will be reviewed. Virtual evaluations of ionic diffusion (and equivalently conductivity) will be presented as one example that spans the full

D. P. Bentz; E. J. Garboczi; N. S. Martys; K. A. Snyder; W. S. Guthrie; K. Kyritsis; N. Neithalath

142

Transport properties of fission product vapors  

SciTech Connect

Kinetic theory of gases is used to calculate the transport properties of fission product vapors in a steam and hydrogen environment. Provided in tabular form is diffusivity of steam and hydrogen, viscosity and thermal conductivity of the gaseous mixture, and diffusivity of cesium iodide, cesium hydroxide, diatomic tellurium and tellurium dioxide. These transport properties are required in determining the thermal-hydraulics of and fission product transport in light water reactors.

Im, K.H.; Ahluwalia, R.K.

1983-07-01

143

Thermal transport properties of carbon nanotube  

Microsoft Academic Search

Because of their unique structure, novel properties and potential applications, carbon nanotubes (CNTs) have attracted significant attention since their discovery. The thermal properties of CNTs are of interest for basic science as well as for technological applications. In the present paper, our experimental studies of the thermal transport properties of CNTs in recent years were introduced. The measurement techniques and

Huaqing Xie; Yang Li

2009-01-01

144

Electron transport properties of magnetic granular films  

NASA Astrophysics Data System (ADS)

In this paper, we present a review of electron transport properties of magnetic granular films. Magnetic granular films are nanocomposite materials which consist of magnetic nanoparticles embedded in a nonmagnetic matrix or assembling of magnetic nanoparticles. According to the style of the nonmagnetic matrix, microstructure and the electron transport mechanism of the films, the magnetic granular films were divided into three groups: (1) magnetic metal-metal granular films, (2) magnetic metal-insulator granular films and (3) magnetic nanocluster-assembled granular films. Moreover, we also systematically review the magnetic properties, transport properties and magnetoresistance effect of size-monodispersed Co and Fe nanocluster-assembled films.

Peng, DongLiang; Wang, JunBao; Wang, LaiSen; Liu, XiaoLong; Wang, ZhenWei; Chen, YuanZhi

2013-01-01

145

Asymmetric transport property of fluorinated graphene  

NASA Astrophysics Data System (ADS)

Carrier transport properties of fluorinated graphene with various fluorination rates are presented. Onset of transition from insulating to metallic conduction is observed in dilute fluorinated graphene. Highly fluorinated graphene shows electron-hole asymmetry in transport properties and local resistivity maximum at the hole conduction region, which are presumably caused by the existence of resonant fluorine impurities. Drastic change of the asymmetric feature occurs after removing fluorine atoms and creating structural defects by thermal annealing. These results suggest that the type of impurities or defects in graphene is detectable by examining asymmetry in transport properties.

Tahara, Kosuke; Iwasaki, Takayuki; Furuyama, Satoko; Matsutani, Akihiro; Hatano, Mutsuko

2013-09-01

146

Impact of in-plane anisotropic strains on the dielectric and pyroelectric properties of Ba0.7Sr0.3TiO3 thin films  

NASA Astrophysics Data System (ADS)

A modified Landau-Devonshire phenomenological thermodynamic theory is used to describe the influence of in-plane anisotropic strains on the dielectric and pyroelectric properties of epitaxial Ba0.7Sr0.3TiO3 thin films grown on dissimilar tetragonal substrates. The in-plane anisotropic strain factor-temperature phase diagram is developed. The in-plane anisotropic strains play a crucial role in the dielectric and pyroelectric properties of BST thin films. The theoretical maximum dielectric tunability approaching 100% can be attained at the critical anisotropic strain factor corresponding to the structural phase transformation from ca1 to a1 phase. Moreover, the anisotropic strain factor has an opposite effect on the figure of merit and pyroelectric coefficient, respectively. Furthermore, in the case of isotropic strains, our theoretical results are well consistent with the experimental results.

Cao, Hai-Xia; Lo, Veng Cheong; Li, Zhen-Ya

2007-01-01

147

Synthesizing metamaterials with angularly independent effective medium properties based on an anisotropic parameter retrieval technique coupled with a genetic algorithm  

NASA Astrophysics Data System (ADS)

In this paper, we present a method to retrieve the effective electromagnetic parameters of a slab of anisotropic metamaterial from reflection and transmission coefficients (or scattering parameters). In this retrieval method, calculated or measured scattering parameters are employed for plane waves incident obliquely on a metamaterial slab at different angles. Useful analytical expressions are derived for extracting the homogeneous anisotropic medium parameters of a metamaterial. To validate the method, the effective permittivity and permeability tensor parameters for a composite split-ring resonator-wire array are retrieved and shown to be consistent with observations previously reported in the literature. This retrieval method is further incorporated into a genetic algorithm (GA) to synthesize an infrared zero-index-metamaterial with a wide field-of-view, demonstrating the utility of the new design approach. The anisotropic parameter retrieval algorithm, when combined with a robust optimizer such as GA, can provide a powerful design tool for exploiting the anisotropic properties in metamaterials to achieve specific angle dependant or independent responses.

Jiang, Zhi Hao; Bossard, Jeremy A.; Wang, Xiande; Werner, Douglas H.

2011-01-01

148

Transport properties of activated carbon fibers.  

National Technical Information Service (NTIS)

The transport properties of activated isotropic pitch-based carbon fibers with surface area 1000 m(sup 2)/g have been investigated. We report preliminary results on the electrical conductivity, the magnetoresistance, the thermal conductivity and the therm...

S. L. di Vittorio M. S. Dresselhaus M. Endo J. P. Issi L. Piraux

1990-01-01

149

Variational nodal perturbation theory with anisotropic scattering  

Microsoft Academic Search

The variational nodal perturbation method previously developed in two- and three-dimensional Cartesian and hexagonal geometries using the diffusion and full or simplified spherical harmonics transport approximations, is extended to treat problems with anisotropic scattering. The requisite solution to the adjoint transport equation with anisotropic scattering in formulated and incorporated into the VARIANT (VARIational Anisotropic Nodal Transport) option of the Argonne

K. F. Laurin-Kovitz; G. Palmiotti; E. E. Lewis

1997-01-01

150

Transport Properties in Alkali Azides.  

National Technical Information Service (NTIS)

Crystalline defects and ionic transport in potassium and rubidium azide have been studied by measuring the electrical conductivity with an a.c. bridge technique and the diffusion of cations by a tracer sectioning technique. Methods were developed to grow ...

A. L. Laskar

1975-01-01

151

Transport properties of Nafion®\\/cyclodextrin membranes  

Microsoft Academic Search

The transport properties of Nafion®\\/cyclodextrin membranes were studied for simple gases and water. Cyclodextrins (CD) in ionic form have been introduced as counter-ions in the ionic phase of Nafion® by solution exchange. The CD and Nafion® transport parameters were at first determined using sorption methods. The cyclodextrin gas and water solubility coefficients are higher than the Nafion® ones but the

N Grossi; E Espuche; M Escoubes

2001-01-01

152

Optical properties of phase shift on reflection and/or transmission through biaxial anisotropic thin films  

NASA Astrophysics Data System (ADS)

On the basis of theoretical analysis of biaxial birefringent thin films, this study investigates the optical properties of phase shift on reflection and/or transmission through slanted columnar TiO2 sculptured anisotropic thin film (ATF) deposited with glancing angle deposition (GLAD) technique via reactive electron-beam evaporation. The tilted nanocolumn microstructures of thin film induce the optical anisotropy. The optical constants dispersion equations of TiO2 ATF are determined from fitting the transmittance spectra for s- and p-polarized waves measured at normal and oblique incidence within 400-1200nm. With the extracted structure parameters, the phase shifts of polarized light are analyzed with the characteristic matrix and then measured with spectroscopic ellipsometry in the deposition plane. A reasonably good agreement between the theoretical studies and experimental measurements is obtained. In addition, the dependence of the phase shift on oblique incidence angle is also discussed. The results show a greater generality and superiority of the characteristic matrix method. Birefringence of the biaxial ATF performed a sophisticated phase modulation with varied incidence angles over a broad range to have a wide-angle phase shift.

Hou, Yongqiang; Qi, Hongji; Li, Xu; He, Kai; Fang, Ming; Yi, Kui; Shao, Jianda

2013-07-01

153

Fe-nanoparticle coated anisotropic magnet powders for composite permanent magnets with enhanced properties  

NASA Astrophysics Data System (ADS)

Utilizing the chemical reduction of FeCl2 with NaBH4 in the presence of 2:17 Sm-Co powders, we synthesized composite Sm(Co0.699Fe0.213Cu0.064Zr0.024)7.4/nano-Fe anisotropic hard magnetic powders. The average particle size of the hard magnetic core powder was 21 ?m while the soft magnetic Fe nanoparticles deposited uniformly on the core powder had a particle size smaller than 100 nm. Different reaction protocols, such as immersion of the hard magnetic core powder in each reagent, the use of microemulsion (micelle) technique, or doubling the weight ratio of FeCl2 to core powder, led to different degrees of magnetic coupling of the hard and soft magnetic components of the composite powder. A reaction time of 180 s led to deposition of 3.5 wt % Fe nanoparticles and improved magnetic properties of the composite powder compared to the uncoated Sm(Co0.699Fe0.213Cu0.064Zr0.024)7.4 powder. The respective magnetic hysteresis parameters were 4?M18 kOe=11.3 kG, 4?Mr=11 kG, and iHc>20 kOe with a smooth demagnetization curve.

Marinescu, M.; Liu, J. F.; Bonder, M. J.; Hadjipanayis, G. C.

2008-04-01

154

A Kinetic Theory for Nonanalog Monte Carlo Particle Transport Algorithms: Exponential Transform with Angular Biasing in Planar-Geometry Anisotropically Scattering Media  

Microsoft Academic Search

We show that Monte Carlo simulations of neutral particle transport in planar-geometry anisotropically scattering media, using the exponential transform with angular biasing as a variance reduction device, are governed by a new “Boltzmann Monte Carlo” (BMC) equation, which includes particle weight as an extra independent variable. The weight moments of the solution of the BMC equation determine the moments of

Taro Ueki; Edward W Larsen

1998-01-01

155

Strain-controlled anisotropic electronic transport in Bi0.4Ca0.6MnO3 films  

NASA Astrophysics Data System (ADS)

Structural and resistive anisotropy has been studied for the Bi0.4Ca0.6MnO3 films grown on (011)-oriented SrTiO3 substrates. Strong anisotropic transport behaviors are observed when significant lattice strains exist. The ratio of the two resistivities along the a and c axes of the films can be tuned between ~1 and ~13 by adjusting the a/c ratio between ~1.01 and ~1.04, which can be conducted simply by decreasing film thickness from 100 to 10 nm. Considerable anisotropy emerges and develops when film thickness drops below ~60 nm. With the decrease in film thickness, a change in preferred growth direction of the films is also observed. These features of the lattice effects could be useful for the design of artificial materials and devices.

Chen, Y. Z.; Sun, J. R.; Liang, S.; Lu, W. M.; Shen, B. G.

2008-12-01

156

Anisotropic superconducting and normal state magnetic properties of single crystals of RNi*2*B*2*C compounds (R = Y, Gd, Dy, Ho, Er, and Tm)  

SciTech Connect

The interaction of superconductivity with magnetism has been one of the most interesting and important phenomena in solid state physics since the 1950`s when small amounts of magnetic impurities were incorporated in superconductors. The discovery of the magnetic superconductors RNi{sub 2}B{sub 2}C (R = rare earth, Y) offers a new system to study this interaction. The wide ranges of superconducting transition (T{sub c}) and antiferromagnetic (AF) ordering temperatures (T{sub N}) (0 K {le} T{sub c} {le} 16 K, 0 K {le} T{sub N} {le} 20 K) give a good opportunity to observe a variety of interesting phenomena. Single crystals of high quality with appropriate size and mass are crucial in examining the anisotropic intrinsic properties. Single crystals have been grown successfully by an unusual high temperature flux method and characterized thoroughly by X-ray, electrical transport, magnetization, neutron scattering, scanning electron microscopy, and other measurements.

Cho, B.

1995-11-01

157

Transport properties of alumina nanofluids  

NASA Astrophysics Data System (ADS)

Recent studies have showed that nanofluids have significantly greater thermal conductivity compared to their base fluids. Large surface area to volume ratio and certain effects of Brownian motion of nanoparticles are believed to be the main factors for the significant increase in the thermal conductivity of nanofluids. In this paper all three transport properties, namely thermal conductivity, electrical conductivity and viscosity, were studied for alumina nanofluid (aluminum oxide nanoparticles in water). Experiments were performed both as a function of volumetric concentration (3-8%) and temperature (2-50 °C). Alumina nanoparticles with a mean diameter of 36 nm were dispersed in water. The effect of particle size was not studied. The transient hot wire method as described by Nagaska and Nagashima for electrically conducting fluids was used to test the thermal conductivity. In this work, an insulated platinum wire of 0.003 inch diameter was used. Initial calibration was performed using de-ionized water and the resulting data was within 2.5% of standard thermal conductivity values for water. The thermal conductivity of alumina nanofluid increased with both increase in temperature and concentration. A maximum thermal conductivity of 0.7351 W m-1 K-1 was recorded for an 8.47% volume concentration of alumina nanoparticles at 46.6 °C. The effective thermal conductivity at this concentration and temperature was observed to be 1.1501, which translates to an increase in thermal conductivity by 22% when compared to water at room temperature. Alumina being a good conductor of electricity, alumina nanofluid displays an increasing trend in electrical conductivity as volumetric concentration increases. A microprocessor-based conductivity/TDS meter was used to perform the electrical conductivity experiments. After carefully calibrating the conductivity meter's glass probe with platinum tip, using a standard potassium chloride solution, readings were taken at various volumetric concentrations. A 3457.1% increase in the electrical conductivity was measured for a small 1.44% volumetric concentration of alumina nanoparticles in water. The highest value of electrical conductivity, 314 µS cm-1, was recorded for a volumetric concentration of 8.47%. In the determination of the kinematic viscosity of alumina nanofluid, a standard kinematic viscometer with constant temperature bath was used. Calibrated capillary viscometers were used to measure flow under gravity at precisely controlled temperatures. The capillary viscometers were calibrated with de-ionized water at different temperatures, and the resulting kinematic viscosity values were found to be within 3% of the standard published values. An increase of 35.5% in the kinematic viscosity was observed for an 8.47% volumetric concentration of alumina nanoparticles in water. The maximum kinematic viscosity of alumina nanofluid, 2.901 42 mm2 s-1, was obtained at 0 °C for an 8.47% volumetric concentration of alumina nanoparticles. The experimental results of the present work will help researchers arrive at better theoretical models.

Wong, Kau-Fui Vincent; Kurma, Tarun

2008-08-01

158

Transport properties of alumina nanofluids.  

PubMed

Recent studies have showed that nanofluids have significantly greater thermal conductivity compared to their base fluids. Large surface area to volume ratio and certain effects of Brownian motion of nanoparticles are believed to be the main factors for the significant increase in the thermal conductivity of nanofluids. In this paper all three transport properties, namely thermal conductivity, electrical conductivity and viscosity, were studied for alumina nanofluid (aluminum oxide nanoparticles in water). Experiments were performed both as a function of volumetric concentration (3-8%) and temperature (2-50?°C). Alumina nanoparticles with a mean diameter of 36 nm were dispersed in water. The effect of particle size was not studied. The transient hot wire method as described by Nagaska and Nagashima for electrically conducting fluids was used to test the thermal conductivity. In this work, an insulated platinum wire of 0.003 inch diameter was used. Initial calibration was performed using de-ionized water and the resulting data was within 2.5% of standard thermal conductivity values for water. The thermal conductivity of alumina nanofluid increased with both increase in temperature and concentration. A maximum thermal conductivity of 0.7351 W m(-1) K(-1) was recorded for an 8.47% volume concentration of alumina nanoparticles at 46.6?°C. The effective thermal conductivity at this concentration and temperature was observed to be 1.1501, which translates to an increase in thermal conductivity by 22% when compared to water at room temperature. Alumina being a good conductor of electricity, alumina nanofluid displays an increasing trend in electrical conductivity as volumetric concentration increases. A microprocessor-based conductivity/TDS meter was used to perform the electrical conductivity experiments. After carefully calibrating the conductivity meter's glass probe with platinum tip, using a standard potassium chloride solution, readings were taken at various volumetric concentrations. A 3457.1% increase in the electrical conductivity was measured for a small 1.44% volumetric concentration of alumina nanoparticles in water. The highest value of electrical conductivity, 314 µS cm(-1), was recorded for a volumetric concentration of 8.47%. In the determination of the kinematic viscosity of alumina nanofluid, a standard kinematic viscometer with constant temperature bath was used. Calibrated capillary viscometers were used to measure flow under gravity at precisely controlled temperatures. The capillary viscometers were calibrated with de-ionized water at different temperatures, and the resulting kinematic viscosity values were found to be within 3% of the standard published values. An increase of 35.5% in the kinematic viscosity was observed for an 8.47% volumetric concentration of alumina nanoparticles in water. The maximum kinematic viscosity of alumina nanofluid, 2.901?42 mm(2) s(-1), was obtained at 0?°C for an 8.47% volumetric concentration of alumina nanoparticles. The experimental results of the present work will help researchers arrive at better theoretical models. PMID:21730657

Wong, Kau-Fui Vincent; Kurma, Tarun

2008-07-16

159

Low temperature transport properties and heat capacity of single-crystal Na8Si46.  

PubMed

The low temperature thermal conductivity, resistivity, and Seebeck coefficient of single-crystal Na(8)Si(46) are investigated revealing the intrinsic low temperature transport properties of this material. Metallic conduction is observed, with a higher residual resistance ratio than any other known type I clathrate. Heat capacity together with thermal conductivity provide insight into the Na disorder inside the polyhedra formed by the Si framework. Single-crystal structural refinement and thermal property analyses reveal anisotropic disorder for Na inside the tetrakaidecahedra due to a reduction in the symmetry inside these polyhedra, unlike that for Na inside the dodecahedra. PMID:21406746

Stefanoski, S; Martin, J; Nolas, G S

2010-11-17

160

Transport properties of molecular liquids  

Microsoft Academic Search

Dynamic processes in atomic liquids are nowadays very well understood in terms of kinetic theory and computer calculations. Transport coefficients and dynamic scattering functions of the example liquid argon are well reflected by kinetic theories and molecular dynamics calculations using the Lennard-Jones (LJ) pair potential. The present review gives a summarizing account of these results. The situation for molecular liquids

Claus Hoheisel

1994-01-01

161

Anisotropic physical properties of SC-15 epoxy reinforced with magnetic nanofillers under uniform magnetic field  

NASA Astrophysics Data System (ADS)

SC-15 epoxy is used in many industrial applications and it is well known that the mechanical and viscoelastic properties of epoxy can be significantly enhanced when reinforced with nanofillers. In this work, SC-15 epoxy is reinforced by loading with magnetically-active nanofillers and cured in a modest magnetic field. Because of the significant magnetic response of the nanofillers, this is a low cost and relatively easy technique for imposing a strong magnetic anisotropy to the system without the need of a superconducting magnet. It is also found that this method is an effective way of enhancing the mechanical properties of epoxy. Three systems were prepared and studied. The first is a dilute system of various concentrations of Fe2O3 nanoparticles in SC-15 epoxy. The second systems is a combination of Fe2O3 nanoparticles and chemically-functionalized single-walled carbon nanotubes (SWCNT(COOH)s) in SC-15 epoxy. The third is a dilute system of SWCNT(COOH)s decorated with Fe3O4 particles through a sonochemical oxidation process in SC-15 epoxy. Samples have an initial cure of 6 hrs in a magnetic filed of 10 kOe followed by an additional 24 hrs of post curing at room temperature. These are compared to the control samples that do not have initial field curing. Tensile and compressive stress-strain analysis of the prepared systems shows that mechanical properties such as tensile strength, tensile modulus and compressive strength are enhanced with the inclusion of these nanofillers. It is also found that there is an anisotropic enhancement of these properties with respect to the imposed curing field. An interesting phenomenon is observed with the increase in modulus of toughness and fracture strain with nanotube inclusion. These parameters are drastically enhanced after curing the systems in a magnetic field. While there is a modest shift in glass transition temperature during viscoelastic analysis, the thermal stability of the created systems is not compromised. Results of these mechanical enhancements will be compared with other nanoloading techniques from literature.

Malkina, Olga

162

Coupled light transport-heat diffusion model for laser dosimetry with dynamic optical properties  

SciTech Connect

The effect of dynamic optical properties on the spatial distribution of light in laser therapy is studied via numerical simulations. A two-dimensional, time dependent computer program called LATIS is used. Laser light transport is simulated with a Monte Carlo technique including anisotropic scattering and absorption. Thermal heat transport is calculated with a finite difference algorithm. Material properties are specified on a 2-D mesh and can be arbitrary functions of space and time. Arrhenius rate equations are solved for tissue damage caused by elevated temperatures. Optical properties are functions of tissue damage, as determined by previous measurements. Results are presented for the time variation of the light distribution and damage within the tissue as the optical properties of the tissue are altered.

London, R.A.; Glinsky, M.E.; Zimmerman, G.B.; Eder, D.C. [Lawrence Livermore National Lab., CA (United States); Jacques, S.L. [Texas Univ., Houston, TX (United States). M.D. Anderson Cancer Center

1995-03-01

163

Role of carrier density and disorder on anisotropic charge transport in polypyrrole  

NASA Astrophysics Data System (ADS)

Polypyrrole (PPy) has been synthesized electrochemically on platinum substrate by varying synthesis temperature and dopant concentration. The charge transport in PPy has been investigated as a function of temperature for both in-plane and out-of-plane geometry in a wide temperature range of 5 K-300 K. The charge transport showed strong anisotropy and various mechanisms were used to explain the transport. The conductivity ratio, ?r = ?(300 K)/?(5 K) is calculated for each sample to quantify the relative disorder. At all the temperatures, the conductivity values for in-plane transport are found to be more for PPy synthesized at lower temperature, while the behavior is found to be different for out-of-plane transport. The carrier density is found to play a crucial role in case of in-plane transport. An effort has been made to correlate charge transport to morphology by analyzing temperature and frequency dependence of conductivity. Charge transport in lateral direction is found to be dominated by hopping whereas tunneling mechanisms are dominated in vertical direction. Parameters such as density of states at the Fermi level [N(EF)], average hopping distance (R), and average hopping energy (W) have been estimated for each samples in both geometry.

Varade, Vaibhav; Anjaneyulu, P.; Suchand Sangeeth, C. S.; Ramesh, K. P.; Menon, Reghu

2013-01-01

164

Thermal Transport and Magnetic Properties of Superconductors  

Microsoft Academic Search

We address several aspects of the thermal transport and magnetic properties of conventional and high-T c superconductors. We first derive an expression for the effects of boundaries on phonon transport in small samples of circular and rectangular cross section. A variation of this treatment is then applied to calculate the thermal conductivity and phonon mean-free path of Y Ba_2Cu_3O_{7 -delta}

Raymond Adams Richardson

1993-01-01

165

Water transport properties of fuel cell ionomers  

SciTech Connect

We will report transport parameters measured for several available perfluorosulfonate membranes. The water sorption characteristics, diffusion coefficient of water, electroosmotic drag, and conductivity will be compared for these materials. The intrinsic properties of the membranes will be the basis of our comparison. An objective look at transport parameters should enable us to compare membranes without the skewing effects of extensive features such as membrane thickness. 8 refs., 4 figs., 2 tabs.

Zawodzinski, T.A. Jr.; Springer, T.E.; Davey, J.; Valerio, J.; Gottesfeld, S.

1991-01-01

166

Asymptotic-preserving Lagrangian approach for modeling anisotropic transport in magnetized plasmas  

NASA Astrophysics Data System (ADS)

Modeling electron transport in magnetized plasmas is extremely challenging due to the extreme anisotropy introduced by the presence of the magnetic field (?/?˜10^10 in fusion plasmas). Recently, a novel Lagrangian method has been proposedootnotetextD. del-Castillo-Negrete, L. Chac'on, PRL, 106, 195004 (2011); DPP11 invited talk by del-Castillo-Negrete to solve the local and non-local purely parallel transport equation in general 3D magnetic fields. The approach avoids numerical pollution (in fact, it respects transport barriers --flux surfaces-- exactly by construction), is inherently positivity-preserving, and is scalable algorithmically (i.e., work per degree-of-freedom is grid-independent). In this poster, we discuss the extension of the Lagrangian approach to include perpendicular transport and sources. We present an asymptotic-preserving numerical formulation that ensures a consistent numerical discretization temporally and spatially for arbitrary ?/? ratios. This is of importance because parallel and perpendicular transport terms in the transport equation may become comparable in regions of the plasma (e.g., at incipient islands), while remaining disparate elsewhere. We will demonstrate the potential of the approach with various challenging configurations, including the case of transport across a magnetic island in cylindrical geometry.

Chacon, Luis; Del-Castillo-Negrete, Diego

2011-11-01

167

Macroscopic properties of isotropic and anisotropic fracture networks from the percolation threshold to very large densities  

NASA Astrophysics Data System (ADS)

The main purpose of this review paper is to summarize some recent studies of fracture networks. Progress has been made possible thanks to a very versatile numerical technique based on a three-dimensional discrete description of the fracture networks. Any network geometry, any boundary condition, and any distribution of the fractures can be addressed. The first step is to mesh the fracture network as it is by triangles of a controlled size. The second step consists in the discretization of the conservation equations by the finite volume technique. Two important properties were systematically studied, namely the percolation threshold rho_c and the macroscopic permeability K_n of the fracture network. Dimensionless quantities are denoted by a prime. The numerical results are interpreted in a systematic way with the concept of excluded volume which enables us to define a dimensionless fracture density rho' equal in the average to the average number of intersections per fracture. 1. Isotropic networks of identical fractures The dimensionless percolation threshold rho'_c of such networks was systematically studied for fractures of various shapes. rho'_c was shown to be almost independent of the shape except when one has very elongated rectangles. A formula is proposed for rho'_c. The permeability of these networks was calculated for a wide range of fracture densities and shapes. K'_n(rho') is almost independent of the fracture shape; an empirical formula is proposed for any value of rho' between rho'_c and infinity. For large rho', K_n is well approximated by the Snow formula initially derived for infinite fractures. 2. Anisotropic networks of identical fractures The fracture orientations are supposed to follow a Fisher distribution characterized by the parameter kappa; when kappa=0, the fractures are isotropic; when kappa=infinity, the fractures are perpendicular to a given direction. rho'_c does not depend significantly on kappa and the general formula proposed in 1 can be used as a first approximation. A considerable simplification occurs for permeability. The dependence on kappa can be determined analytically for infinite fractures as an extension of the Snow formula and is a tensor K'_S. Numerically, K'_n is equal to the product K'_n,i K'_S. 3. Extensions Two important extensions were already worked out. rho'_c and K'_n were determined for fracture networks with power law size distribution wether they are anisotropic or not. So far only fractures which are uniformly distributed in space were considered. However, in Excavation Damaged Zones, the density decreases exponentially from the wall. The previous analysis has been recently extended to this case. Results for both extensions are conveniently analyzed in the same framework. 4. Conclusions Our studies can be summarized as follows. rho'_c and K'_n(rho') do not depend significantly of the fracture shape. Moreover, semi empirical formulae are proposed to predict these quantities for all densities. Further studies closer to geophysical reality will be performed.

Adler, P. M.; Thovert, J.; Mourzenko, V.

2011-12-01

168

Stress-dependent permeability evolution in sandstones with anisotropic physical properties  

NASA Astrophysics Data System (ADS)

Fluid flow in reservoir rocks is strongly dependent on stress path and rock microstructure which may present a significant anisotropy. We present recent experimental data on the evolution of permeability with applied stress for three sandstones tested under triaxial conditions in the low confining pressure range (<10 MPa). Samples with diameter 40 mm and length 80 mm were cored in three orthogonal directions in blocks retrieved from quarries. One coring direction was perpendicular to the bedding plane whereas the other directions were arbitrarily chosen within the bedding plane. The selected rocks are the Bentheim sandstone (BNT), a quartz-rich cretaceous sandstone from Germany with 24% porosity, and two different varieties of a same jurassic formation in Northern Spain, the La Marina sandstone. The Yellow La Marina sandstone (YLM) with porosity 28% has a low cohesion and is the weathered form of the well-consolidated Grey La Marina sandstone (GLM) with porosity 17%. When loaded up to the failure stress, the more porous sandstones (BNT, YLM) exhibited a monotonic decrease of permeability even when the rock was dilating at deviatoric stresses close to the failure stress. On the other hand the permeability of the less porous sandstone (GLM) increased during the dilating phase. These results are in agreement with previous studies. In addition we observed that all three sandstones are anisotropic with respect to several physical properties including permeability. We systematically found a lower permeability in the direction perpendicular to the bedding plane, but the ratio of "vertical" to "horizontal" permeability varies from one sandstone to the other. The permeability anisotropy is compared to the anisotropy of electrical conductivity, acoustic velocity, capillary imbibition and elastic moduli: in general good correlations are found for all the properties. For the Bentheim sandstone, a microstructural study on thin sections revealed that the rock anisotropy is due to the anisotropy of intergranular pores which statistically are found to be elongated within the bedding plane. This result is in agreement with the prediction of Kachanov's model for the anisotropy of acoustic velocity in Bentheim sandstone.

Metz, V.; David, C.; Louis, L.; Rodriguez Rey, A.; Ruiz de Argandona, V. G.

2003-04-01

169

Anomalous and Gaussian transport regimes in anisotropic three-dimensional magnetic turbulence  

Microsoft Academic Search

The effects of the anisotropy of magnetic turbulence on the transport of magnetic field lines are investigated numerically. The three-dimensional magnetic turbulence is represented by a Fourier expansion with a power law band spectrum, and anisotropy is introduced by considering different correlation lengths lcx and lcy in the plane perpendicular to the average magnetic field B0=B0e⁁z. Transport in this plane

P. Pommois; P. Veltri; G. Zimbardo

1999-01-01

170

Solvothermal synthesis, growth mechanism, and photoluminescence property of sub-micrometer PbS anisotropic structures  

PubMed Central

The sub-micrometer PbS with anisotropic microstructures including fishbone-like dendrites, multipods, cubes, corallines, and hopper cubes were successfully prepared by the solvothermal process. Different morphologies can be obtained by adjusting the reaction temperatures or using the nontoxic controlled reagents which can tune the relative growth rate in the <100> direction and the <111> direction of PbS nuclei. Based on the viewpoint of crystallography about face-centered cubic crystal structure, the possible formation mechanism for sub-micrometer anisotropic structures has been discussed. The difference between the enhanced growth rates on the {100} and {111} planes induced the change of ratio between the growth rates in the <100> and <111> directions, which resulted in the formation of the different PbS anisotropic microstructures. The PbS anisotropic structures exhibited the different visible emission with a peak in the red regions mainly attributed to the variation of shape, size, and the trap state of as-obtained PbS.

2012-01-01

171

Solvothermal synthesis, growth mechanism, and photoluminescence property of sub-micrometer PbS anisotropic structures  

NASA Astrophysics Data System (ADS)

The sub-micrometer PbS with anisotropic microstructures including fishbone-like dendrites, multipods, cubes, corallines, and hopper cubes were successfully prepared by the solvothermal process. Different morphologies can be obtained by adjusting the reaction temperatures or using the nontoxic controlled reagents which can tune the relative growth rate in the <100> direction and the <111> direction of PbS nuclei. Based on the viewpoint of crystallography about face-centered cubic crystal structure, the possible formation mechanism for sub-micrometer anisotropic structures has been discussed. The difference between the enhanced growth rates on the {100} and {111} planes induced the change of ratio between the growth rates in the <100> and <111> directions, which resulted in the formation of the different PbS anisotropic microstructures. The PbS anisotropic structures exhibited the different visible emission with a peak in the red regions mainly attributed to the variation of shape, size, and the trap state of as-obtained PbS.

Cao, Yali; Hu, Pengfei; Jia, Dianzeng

2012-12-01

172

Transport of angular momentum and chemical species by anisotropic mixing in stellar radiative interiors  

NASA Astrophysics Data System (ADS)

Small levels of turbulence can be present in stellar radiative interiors due to, e.g., the instability of rotational shear. In this paper we estimate turbulent transport coefficients for stably stratified rotating stellar radiation zones. Stable stratification induces strong anisotropy with a very small ratio of radial-to-horizontal turbulence intensities. Angular momentum is transported mainly due to the correlation between azimuthal and radial turbulent motions induced by the Coriolis force. This non-diffusive transport known as the ?-effect has outward direction in radius and is much more efficient compared to the effect of radial eddy viscosity. Chemical species are transported by small radial diffusion only. This result is confirmed using direct numerical simulations combined with the test-scalar method. As a consequence of the non-diffusive transport of angular momentum, the estimated characteristic time of rotational coupling (?100 Myr) between radiative core and convective envelope in young solar-type stars is much shorter compared to the time-scale of Lithium depletion (˜1 Gyr).

Kitchatinov, L. L.; Brandenburg, A.

2012-04-01

173

Anisotropic magnetothermal resistance in Ni nanowires  

NASA Astrophysics Data System (ADS)

We present measurements of the electrical and thermal transport properties of individual Ni nanowires as a function of the applied magnetic field, recorded in the temperature range between 78 and 380 K. In analogy to the anisotropic magnetoresistance (AMR) effect observed in ferromagnetic conductors, we find that the thermal resistance of Ni nanowires depends on the angle between magnetization vector and current direction. This anisotropic magnetothermal resistance effect turns out to be weaker than the AMR effect in Ni nanowires over the temperature range investigated. As a consequence, also the Lorenz number is found to be anisotropic with respect to the magnetization direction. To explain our observation, we propose a simple model that considers spin mixing due to electron-magnon scattering.

Kimling, Johannes; Gooth, Johannes; Nielsch, Kornelius

2013-03-01

174

Electrical transport properties of some liquid metals  

Microsoft Academic Search

In the present article, we report the electrical transport properties viz. the electrical resistivity (?), the thermoelectric power and thermal conductivity (?) of several monovalent, divalent and polyvalent liquid metals of the different groups of the periodic table on the basis of model potential formalism. The well-known empty core model potential of Ashcroft is used for the first time with

Aditya M. Vora

2008-01-01

175

Quantum transport properties of zigzag graphene nanoribbons  

Microsoft Academic Search

We have studied the quantum transport properties of zigzag graphene nanoribbons under periodic or Möbius boundary conditions connected to one-dimensional leads using the nonequilibrium Green's function method with a tight-binding scheme. We reveal the existence of a current path originating from the edge states of the graphene nanoribbons. We have found that the conduction channel at the Fermi energy under

Hirokazu Takaki; Nobuhiko Kobayashi

2011-01-01

176

Transport properties of liquid hydrogen fluoride  

Microsoft Academic Search

The dynamical properties of liquid hydrogen fluoride are investigated by a molecular dynamics study of the correlation functions relevant for a generalized hydrodynamics description of transport coefficients. The results are compared with the corresponding ones in liquid water in order to understand the role of hydrogen bonding in the two systems. The different behavior can ultimately be attributed to the

Umberto Balucani; Davide Bertolini; Alessandro Tani; Renzo Vallauri

2000-01-01

177

Transport and Deformation-Potential Theory for Many-Valley Semiconductors with Anisotropic Scattering  

Microsoft Academic Search

A transport theory which allows for anisotropy in the scattering processes is developed for semiconductors with multiple nondegenerate band edge points. It is found that the main effects of scattering on the distribution function over each ellipsoidal constant-energy surface can be described by a set of three relaxation times, one for each principal direction; these are the principal components of

Conyers Herring; Erich Vogt

1956-01-01

178

Inverse estimation of the elastic and anelastic properties of the porous frame of anisotropic open-cell foams.  

PubMed

This paper presents a method for simultaneously identifying both the elastic and anelastic properties of the porous frame of anisotropic open-cell foams. The approach is based on an inverse estimation procedure of the complex stiffness matrix of the frame by performing a model fit of a set of transfer functions of a sample of material subjected to compression excitation in vacuo. The material elastic properties are assumed to have orthotropic symmetry and the anelastic properties are described using a fractional-derivative model within the framework of an augmented Hooke's law. The inverse estimation problem is formulated as a numerical optimization procedure and solved using the globally convergent method of moving asymptotes. To show the feasibility of the approach a numerically generated target material is used here as a benchmark. It is shown that the method provides the full frequency-dependent orthotropic complex stiffness matrix within a reasonable degree of accuracy. PMID:22894184

Cuenca, Jacques; Göransson, Peter

2012-08-01

179

Measurement of anisotropic energy transport in flowing polymers by using a holographic technique  

Microsoft Academic Search

Almost no experimental data exist to test theories for the nonisothermal flow of complex fluids. To provide quantitative tests for newly proposed theories, we have developed a holographic grating technique to study energy transport in an amorphous polymer melt subject to flow. Polyisobutylene with weight-averaged molecular mass of 85 kDa is sheared at a rate of 10 s-1, and all

Jay D. Schieber; David C. Venerus; Kendall Bush; Venkat Balasubramanian; Stoyan Smoukov

2004-01-01

180

Magnetic properties of isotropic and anisotropic Nd-Fe-B bonded magnets  

NASA Astrophysics Data System (ADS)

A trial to make Nd-Fe-B rapidly quenched flakes anisotropic by grain growth during heat treatment in the magnetic field has been carried out. No magnetic anisotropy is observed, but the optimum heat treatment temperature is lowered by about 100°C by applying 14 kOe of magnetic field. There is, as yet, no explanation of this phenomenon. Another way of making anisotropic bonded magnets is to use pulverized powders of anisotropic dense die-upset magnets as a starting material. By examination of the process parameters for Nd-Fe-B die-upset magnets it was found from stress-strain curves that the Nd14Fe80B6 ternary composition has the best workability and to achieve aligned material the compression ratio (defined as the inverse of reduction in height) should be larger than 4. Grain coarsening resulted in a decrease in coercivity (iHc) during die upsetting. Ga is the best additional element for enhancing iHc with a little sacrifice of remanence (Br) and no deterioration in hot workability. Further improvement of thermal stability by raising the Curie temperature (Tc) of the Nd-Fe-B-Ga alloy can be achieved by Co substitution. The iHc of the powder made by pulverizing the die-upset magnets is nearly independent of particle size. Anisotropic bonded magnets were developed using this powder. The (BH)max of compression-moulded magnet with Ga addition and Co substitution, Nd14Fe71.75Co7.5B6Ga0.075, is 15 MGOe. The irreversible losses after exposure up to 140°C is lower than 5% (Pc=2), which is sufficient thermal stability for polymer-bonded magnets.

Tokunaga, M.; Nozawa, Y.; Iwasaki, K.; Tanigawa, S.; Harada, H.

1989-08-01

181

Quantifying transport properties by exchange matrix method  

NASA Astrophysics Data System (ADS)

The exchange matrix method is described to study of transport properties in chaotic geophysical flows. This study is important for applying in problems of pollutants transport (such as petroleum patches) in tidal flows and others. In order to construct this special exchange matrix (first suggested by Spencer & Wiley) we use an approximation of such flows made by Zimmerman, who adopted the idea of chaotic advection, first put forward by Aref. Then for a quantitative estimation of the transport properties we explore a coarse-grained density description introduced by Gibbs and Welander. Such coarse-grained representations over an investigation area, show a ``residence place'' for the pollutant material at any instant. The orbit expansion method, exploited an assumption that the contributions of tidal and residual currents are of different orders (the tidal is much stronger), does not give answers in many real situations. The exchange matrix can show transport of patches or particles from any place in the area under consideration to an arbitrary location in the tidal sea and time if it happens.

Krasnopolskaya, Tatyana; Meleshko, Vyacheslav

2005-11-01

182

Transport properties of the quark gluon plasma  

Microsoft Academic Search

We use kinetic theory to investigate two transport properties of high temperature Quark Gluon Plasma (QGP) in the weak coupling limit. Bulk viscosity of QGP is calculated along with the splitting\\/joining functions in the deep Landau-Pomeranchuk-Migdal (LPM) regime. Within the framework of kinetic theory and in particular using the linearized Boltzmann equation we calculate the bulk viscosity of QGP to

Caglar Dogan

2008-01-01

183

Electrical transport properties of some liquid metals  

Microsoft Academic Search

In the present article, we report the electrical transport properties, namely, the electrical resistivity ( ?), the thermoelectric\\u000a power (TEP) ( ?), and the thermal conductivity (?) of several monovalent, divalent and polyvalent liquid metals of the different\\u000a groups of the periodic table on the basis of model potential formalism. The well known empty core model (EMC) potential of\\u000a Ashcroft

A. M. Vora

2008-01-01

184

Transport properties of nonconventional lead cuprate glass  

Microsoft Academic Search

The dc electrical transport properties of the nonconventional lead cuprate glasses of compositions (CuO)x(PbO)100?x for x=15–50 mol % are reported in the temperature range 150–500 K. The experimental results have been analyzed in the light of existing theoretical models. It has been observed that the high-temperature conductivity data are consistent with Mott’s nearest-neighbor hopping model, while at low temperatures Mott’s

S. Hazra; A. Ghosh

1995-01-01

185

Role of transport properties in corrosion product growth  

Microsoft Academic Search

The tendency for corrosion and the observed rate of corrosion are determined in large part by the transport properties of thin corrosion product layers. Both ionic and electronic transport are important. For continued corrosion, a corrosion product film capable of high ionic transport is required at the metal surface. The electronic transport properties will affect the spatial distribution of reduction

J. H. Payer; G. Ball; B. I. Rickett; H. S. Kim

1995-01-01

186

Anisotropic noise samples.  

PubMed

We present a practical approach to generate stochastic anisotropic samples with Poisson-disk characteristic over a two-dimensional domain. In contrast to isotropic samples, we understand anisotropic samples as non-overlapping ellipses whose size and density match a given anisotropic metric. Anisotropic noise samples are useful for many visualization and graphics applications. The spot samples can be used as input for texture generation, e.g., line integral convolution (LIC), but can also be used directly for visualization. The definition of the spot samples using a metric tensor makes them especially suitable for the visualization of tensor fields that can be translated into a metric. Our work combines ideas from sampling theory and mesh generation. To generate these samples with the desired properties we construct a first set of non-overlapping ellipses whose distribution closely matches the underlying metric. This set of samples is used as input for a generalized anisotropic Lloyd relaxation to distribute noise samples more evenly. Instead of computing the Voronoi tessellation explicitly, we introduce a discrete approach which combines the Voronoi cell and centroid computation in one step. Our method supports automatic packing of the elliptical samples, resulting in textures similar to those generated by anisotropic reaction-diffusion methods. We use Fourier analysis tools for quality measurement of uniformly distributed samples. The resulting samples have nice sampling properties, for example, they satisfy a blue noise property where low frequencies in the power spectrum are reduced to a minimum. PMID:18192714

Feng, Louis; Hotz, Ingrid; Hamann, Bernd; Joy, Kenneth

187

Transport properties of nonlinear photonic crystals  

NASA Astrophysics Data System (ADS)

Keen interest has been shown in exploiting the transport properties of nonlinear photonic crystals for modulation, switching and routing applications at telecommunication frequencies. This is due to the rich anisotropy evidenced by a highly-textured dispersion surface, and its dependence on the permittivity profile of the structure. We consider a two-dimensional photonic crystal, presume an instantaneous change in profile due to an optical Kerr effect, and show how the beam's refraction angle depends on its intensity. For computational simplicity, we employ a self-consistent approach and the linear eigenvalue equation, which we solve using a finite element method. Previous studies have extracted directions of optical power flow from equifrequency contour gradients. Such gradients, more formally the group velocity, lack local definition and are only meaningful in the context of a spatial average over the unit cell. As a result, the relationship between the local character of the optical transport and the induced permittivity profile is obscured. By contrast, we explicitly consider the spatial dependence of the Poynting's vector, from which we also extract mean transport directions with much greater computational efficiency. We thereby demonstrate the interrelationship between optical transport and nonlinear response at the nanoscale. A consequent analysis of refraction in the context of the superprism effect reveals new aspects to the optical transport in such nonlinear systems.

Schriemer, Henry P.; Wheeldon, Jeffrey; Hall, Trevor

2005-09-01

188

Anisotropic properties of ultrafast laser-driven microexplosions in lithium niobate crystal  

SciTech Connect

Smooth voids are achieved in an anisotropic Fe:LiNbO{sub 3} crystal with a high refractive index by use of a femtosecond laser-driven microexplosion method. Due to the anisotropy of the crystal, the maximum fabrication depth and the fabrication power threshold are different in different crystal directions, indicating that the direction perpendicular to the crystal axis is more suitable for thick three-dimensional structure fabrication. The dependence of the threshold power on the illumination wavelength shows that the microexplosion mechanism is caused by a two-photon absorption process. As a result, a near threshold fabrication method can be used to generate quasispherical voids.

Zhou Guangyong; Gu Min [center for Micro-Photonics and center for Ultrahigh-bandwidth Devices for Optical Systems (CUDOS), Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, PO Box 218, Hawthorn, Victoria 3122 (Australia)

2005-12-12

189

NMR properties of 3He-A in biaxially anisotropic aerogel  

NASA Astrophysics Data System (ADS)

Theoretical model of G.E. Volovik for A-like phase of 3He in aerogel suggests formation of Larkin-Imry-Ma state of Anderson-Brinkmann-Morel order parameter. Most of results of NMR studies of A-like phase are in a good agreement with this model in assumption of uniaxial anisotropy, except for some of experiments in weakly anisotropic aerogel samples. We demonstrate that these results can be described in frames of the same model in assumption of biaxial anisotropy. Parameters of anisotropy in these experiments can be determined from the NMR data.

Dmitriev, V. V.; Krasnikhin, D. A.; Senin, A. A.; Yudin, A. N.

2012-12-01

190

Anisotropic thermal transport in Bi2223/Ag superconducting tape with sandwiched structure  

NASA Astrophysics Data System (ADS)

The thermal conductivity, ?(T), of the Bi2223/Ag tape reinforced by metal tapes (stainless steel (SS) or copper-based alloy (CA)) from both side was evaluated along the length (l) and width (w) directions. ?(T) along the l-direction was measured directly using a single tape and that along the w-direction was estimated from the ?(T) measured for a stacked bundle which consists of several sandwiched Bi2223/Ag tapes. We analyzed the obtained ?(T) curves using an equivalent heat current circuit, and found that the heat transports along both directions were nearly the same and that the route of heat-flow depended on the species of the reinforcing metal. The absolute values of ?(T) at 77 K along the l- and w- directions for the Bi2223/Ag-SS tape were 174 and 140 W m-1 K-1 and those for the Bi2223/Ag-CA tape were 206 and 206 W m-1 K-1, respectively, the values of which were approximately 30-40% and 10-15% smaller than those of the standard Bi2223/Ag tape.

Naito, Tomoyuki; Fujishiro, Hiroyuki; Osabe, Goro; Fujikami, Jun

2013-01-01

191

Study of Low Temperature Magnetic Properties of a Single Chain Magnet with Alternate Isotropic and Non-collinear Anisotropic Units  

NASA Astrophysics Data System (ADS)

Here we study thermodynamic properties of an important class of single-chain magnets (SCMs), where alternate units are isotropic and anisotropic with anisotropy axes being non-collinear. This class of SCMs shows slow relaxation at low temperatures which results from the interplay of two different relaxation mechanisms, namely dynamical and thermal. Here anisotropy is assumed to be large and negative, as a result, anisotropic units behave like canted spins at low temperatures; but even then simple Ising-type model does not capture the essential physics of the system due to quantum mechanical nature of the isotropic units. We here show how statistical behavior of this class of SCMs can be studied using a transfer matrix (TM) method. We also, for the first time, discuss in detail how weak inter-chain interactions can be treated by a TM method. The finite size effect is also discussed which becomes important for low temperature dynamics. At the end of this paper, we apply this technique to study a real helical chain magnet.

Sahoo, Shaon; Sutter, Jean-Pascal; Ramasesha, S.

2012-04-01

192

ANALYTIC SOLUTIONS FOR CURRENT SHEET STRUCTURE DETERMINED BY SELF-CONSISTENT, ANISOTROPIC TRANSPORT PROCESSES IN A GRAVITATIONAL FIELD  

SciTech Connect

A Harris sheet magnetic field with maximum magnitude B{sub 0} and length scale L is combined with the anisotropic electrical conductivity, viscosity, and thermoelectric tensors for an electron-proton plasma to define a magnetohydrodynamic model that determines the steady state of the plasma. The transport tensors are functions of temperature, density, and magnetic field strength, and are computed self-consistently as functions of position x normal to the current sheet. The flow velocity, magnetic field, and gravitational force lie along the z-axis. The plasma is supported against gravity by the viscous force. Analytic solutions are obtained for temperature, density, and velocity. They are valid over a broad range of temperature, density, and magnetic field strength, and so may be generally useful in astrophysical applications. Numerical examples of solutions in the parameter range of the solar atmosphere are presented. The objective is to compare Joule and viscous heating rates, determine the velocity shear that generates viscous forces that support the plasma and are self-consistent with a mean outward mass flux comparable to the solar wind mass flux, and compare the thermoelectric and conduction current contributions to the Joule heating rate. The ratio of the viscous to Joule heating rates per unit mass can exceed unity by orders of magnitude, and increases rapidly with L. The viscous heating rate can be concentrated outside the region where the current density is localized, corresponding to a resistively heated layer of plasma bounded by viscously heated plasma. The temperature gradient drives a thermoelectric current density that can have a magnitude greater than that of the electric-field-driven conduction current density, so thermoelectric effects are important in determining the Joule heating rate.

Goodman, Michael L., E-mail: mgoodman@wvhtf.org [Advanced Technologies Group, West Virginia High Technology Consortium Foundation, 1000 Galliher Drive, Fairmont, WV 26554 (United States)

2011-04-10

193

Energy Migration in a Poly(phenylene ethynylene):  Determination of Interpolymer Transport in Anisotropic Langmuir?Blodgett Films  

Microsoft Academic Search

The photophysical and energy transport properties of a poly(p-ethynylene), 1, were investigated in thin films. Highly aligned films of a precise thickness, prepared by sequential monolayer deposition using the Langmuir-Blodgett technique, were surface modified with luminescent traps (acridine orange, AO) for energy transfer studies. The degree of energy transfer to the traps was investigated as a function of the AO

Igor A. Levitsky; Jinsang Kim; Timothy M. Swager

1999-01-01

194

In Vivo IVUS-Based 3-D Fluid-Structure Interaction Models With Cyclic Bending and Anisotropic Vessel Properties for Human Atherosclerotic Coronary Plaque Mechanical Analysis  

PubMed Central

In this paper, a modeling approach combining in vivo intravascular ultrasound (IVUS) imaging, computational modeling, angiography, and mechanical testing is proposed to perform mechanical analysis for human coronary atherosclerotic plaques for potential more accurate plaque vulnerability assessment. A 44-slice in vivo IVUS dataset of a coronary plaque was acquired from one patient, and four 3-D models with fluid–structure interactions (FSIs) based on the data were constructed to quantify effects of anisotropic vessel properties and cyclic bending of the coronary plaque on flow and plaque stress/strain conditions. Compared to the isotropic model (model 1, no bending, no axial stretch), maximum stress-P1 (maximum principal stress) values on the cut surface with maximum bending (where applicable) from model 2 (anisotropic, no bending, no stretch), model 3 (anisotropic, with bending, no stretch), and model 4 (anisotropic with bending and stretch) were, respectively, 63%, 126%, and 345% higher than that from model 1. Effects of cyclic bending on flow behaviors were modest (5%–15%). Our preliminary results indicated that in vivo IVUS-based FSI models with cyclic bending and anisotropic material properties could improve the accuracies of plaque stress/strain predictions and plaque vulnerability assessment. Large-scale patient studies are needed to further validate our findings.

Yang, Chun; Bach, Richard G.; Zheng, Jie; Naqa, Issam Ei; Woodard, Pamela K.; Teng, Zhongzhao; Billiar, Kristen

2010-01-01

195

Research on propagation properties of elastic waves in two-phase anisotropic media  

NASA Astrophysics Data System (ADS)

With the development of seismic engineering and seismic exploration of energy, the underground media that we study are more and more complicated. Conventional anisotropy theory or two-phase isotropy theory is difficult to describe anisotropic media containing fluid, such as fractures containing gas, shales containing water. Based on Biot theory about two-phase anisotropy, with the use of elastic plane wave equations, we get Christoffel equations. We calculate and analyze the effects of frequency on phase velocity, attenuation, amplitude ratio and polarization direction of elastic waves of two-phase, transversely isotropic media. Results show that frequency affects slow P wave the greatest among the four kinds of waves, i.e., fast P wave, slow P wave, fast S wave and slow S wave. Fluid phase amplitude to solid phase amplitude ratio of fast P wave, fast S wave and slow S wave approaches unit for large dissipation coefficients. Polarization analysis shows that polarization direction of fluid phase displacement is different from, not parallel to or reverse to, that of solid phase displacement in two-phase anisotropic media.

Liu, Yang; Li, Cheng-Chu

1999-07-01

196

Blind inversion method using Lamb waves for the complete elastic property characterization of anisotropic plates.  

PubMed

A novel blind inversion method using Lamb wave S(0) and A(0) mode velocities is proposed for the complete determination of elastic moduli, material symmetries, as well as principal plane orientations of anisotropic plates. The approach takes advantage of genetic algorithm, introduces the notion of "statistically significant" elastic moduli, and utilizes their sensitivities to velocity data to reconstruct the elastic moduli. The unknown material symmetry and the principal planes are then evaluated using the method proposed by Cowin and Mehrabadi [Q. J. Mech. Appl. Math. 40, 451-476 (1987)]. The blind inversion procedure was verified using simulated ultrasonic velocity data sets on materials with transversely isotropic, orthotropic, and monoclinic symmetries. A modified double ring configuration of the single transmitter and multiple receiver compact array was developed to experimentally validate the blind inversion approach on a quasi-isotropic graphite-epoxy composite plate. This technique finds application in the area of material characterization and structural health monitoring of anisotropic platelike structures. PMID:19206853

Vishnuvardhan, J; Krishnamurthy, C V; Balasubramaniam, Krishnan

2009-02-01

197

Angular momentum transport in a multicomponent solar wind with differentially flowing, thermally anisotropic ions  

NASA Astrophysics Data System (ADS)

Context: The Helios measurements of the angular momentum flux L of the fast solar wind lead to a tendency for the fluxes associated with individual ion angular momenta of protons and alpha particles, Lp and L_?, to be negative (i.e., in the sense of counter-rotation with the Sun). However, the opposite holds for the slow wind, and the overall particle contribution LP = L_p+L_? tends to exceed the magnetic contribution L_M. These two aspects are at variance with previous models. Aims: We examine whether introducing realistic ion temperature anisotropies can resolve this discrepancy. Methods: From a general set of multifluid transport equations with gyrotropic species pressure tensors, we derive the equations governing both the meridional and azimuthal dynamics of outflows from magnetized, rotating stars. The equations are not restricted to radial flows in the equatorial plane but valid for general axisymmetric winds that include two major ion species. The azimuthal dynamics are examined in detail, using the empirical meridional flow profiles for the solar wind, constructed mainly according to measurements made in situ. Results: The angular momentum flux L is determined by the requirement that the solution to the total angular momentum conservation law is unique and smooth in the vicinity of the Alfvén point, defined as where the combined Alfvénic Mach number M_T=1. MT has to consider the contributions from both protons and alpha particles. Introducing realistic ion temperature anisotropies may introduce a change of up to 10% in L and up to ~1.8 km~s-1 in azimuthal speeds of individual ions between 0.3 and 1 AU, compared with the isotropic case. The latter has strong consequences on the relative importance of LP and LM in the angular momentum budget. Conclusions: However, introducing ion temperature anisotropies cannot resolve the discrepancy between in situ measurements and model computations. For the fast-wind solutions, while in extreme cases LP may become negative, Lp never does. On the other hand, for the slow solar wind solutions examined, LP never exceeds L_M, even though LM may be less than the individual ion contribution, since Lp and L_? always have opposite signs for the slow and fast wind alike.

Li, B.; Li, X.

2009-01-01

198

Anisotropic Thermal and Electrical Properties of Thin Thermal Interface Layers of Graphite Nanoplatelet-Based Composites  

NASA Astrophysics Data System (ADS)

Thermal interface materials (TIMs) are crucial components of high density electronics and the high thermal conductivity of graphite makes this material an attractive candidate for such applications. We report an investigation of the in-plane and through-plane electrical and thermal conductivities of thin thermal interface layers of graphite nanoplatelet (GNP) based composites. The in-plane electrical conductivity exceeds its through-plane counterpart by three orders of magnitude, whereas the ratio of the thermal conductivities is about 5. Scanning electron microscopy reveals that the anisotropy in the transport properties is due to the in-plane alignment of the GNPs which occurs during the formation of the thermal interface layer. Because the alignment in the thermal interface layer suppresses the through-plane component of the thermal conductivity, the anisotropy strongly degrades the performance of GNP-based composites in the geometry required for typical thermal management applications and must be taken into account in the development of GNP-based TIMs.

Tian, Xiaojuan; Itkis, Mikhail E.; Bekyarova, Elena B.; Haddon, Robert C.

2013-04-01

199

Anisotropic properties and conduction mechanism of TlInSe2 chain semiconductor  

NASA Astrophysics Data System (ADS)

TlInSe2 chain crystals were prepared using the modification of the Bridgman technique. The grown crystals were identified by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX), and X-ray diffraction (XRD). We investigate the anisotropy of transport properties for the first time for TlInSe2 crystals. Temperature dependence of the dc electrical conductivity, Hall coefficient, Hall mobility, and charge carrier concentration were investigated in the temperature range 184-455 K. The conduction mechanism of TlInSe2 crystals was studied, and measurements revealed that the dc behavior of the grown crystals can be described by Mott's variable range hopping (VRH) model in the low temperature range, while it is due to thermoionic emission of charge carriers over the chain boundaries above 369 K. The Mott temperature, the density of states at the Fermi level, and the average hopping distance are estimated in the two crystallographic directions. The temperature dependence of the ac conductivity and the frequency exponent, s, is reasonably well interpreted in terms of the correlated barrier-hopping CBH model.

Ebnalwaled, A. A.; Al-Orainy, R. H.

2013-09-01

200

Transport properties of graphene quantum dots  

NASA Astrophysics Data System (ADS)

In this work we present a theoretical study of transport properties of a double crossbar junction composed of segments of graphene ribbons with different widths forming a graphene quantum dot structure. The systems are described by a single-band tight binding Hamiltonian and the Green’s function formalism using real space renormalization techniques. We show calculations of the local density of states, linear conductance, and I-V characteristics. Our results depict a resonant behavior of the conductance in the quantum dot structures, which can be controlled by changing geometrical parameters such as the nanoribbon segment widths and the distance between them. By application of a gate voltage on determined regions of the structure, it is possible to modulate the transport response of the systems. We show that negative differential resistance can be obtained for low values of applied gate and bias voltages.

González, J. W.; Pacheco, M.; Rosales, L.; Orellana, P. A.

2011-04-01

201

Transport properties of graphene containing structural defects  

NASA Astrophysics Data System (ADS)

We propose an extensive report on the simulation of electronic transport in two-dimensional graphene in presence of structural defects. Amongst the large variety of such defects in sp2 carbon-based materials, we focus on the Stone-Wales defect and on two divacancy-type reconstructed defects. Based on ab initio calculations, a tight-binding model is derived to describe the electronic structure of these defects. Semiclassical transport properties including the elastic mean-free paths, mobilities, and conductivities are computed using an order-N real-space Kubo-Greenwood method. A plateau of minimum conductivity (?scmin=4e2/?h) is progressively observed as the density of defects increases. This saturation of the decay of conductivity to ?scmin is associated with defect-dependent resonance energies. Finally, localization phenomena are captured beyond the semiclassical regime. An Anderson transition is predicted with localization lengths of the order of tens of nanometers for defect densities around 1%.

Lherbier, Aurélien; Dubois, Simon M.-M.; Declerck, Xavier; Niquet, Yann-Michel; Roche, Stephan; Charlier, Jean-Christophe

2012-08-01

202

Electronic transport properties of carbon nanotoroids  

NASA Astrophysics Data System (ADS)

We investigate the electronic transport properties of carbon nanotori covalently connected to external electrodes made up of carbon nanotubes of various chiralities. The study is based on computing ballistic transport characteristics within the framework of Green's function theory using a simple ?-orbital tight-binding model. The calculations focus on the effect of the relative angle made by the electrodes as they are placed at different positions along the nanoring. The conductance behavior is found to depend on the details of the atomic structure of the torus but also on the positions of the electrodes. Our findings are rationalized using an elementary quantum mechanical interference model, which reproduces well the main features of the numerical data.

Costa Girão, Eduardo; Gomes Souza Filho, Antônio; Meunier, Vincent

2011-02-01

203

Analysis of the three-phase transformer considering the nonlinear and anisotropic properties using the transmission line modeling method and FEM  

Microsoft Academic Search

The transmission line modeling (TLM) method applied to the nonlinear finite element analysis yields a great reduction of calculation time. This method, however, has a shortcoming that the anisotropic property of a material cannot be considered. In this paper, a novel topology using TLM method which can consider both nonlinearity and anisotropy is developed. This new algorithm is applied to

Chang-Hwan Im; Hong-Kyu Kim; Chang-Hwan Lee; Hyun-Kyo Jung

2001-01-01

204

Physical principles pertaining to ultrasonic and mechanical properties of anisotropic media and their application to nondestructive evaluation of fiber-reinforced composite materials  

SciTech Connect

The central theme of this thesis is to contribute to the physics underlying the mechanical properties of highly anisotropic materials. The hypothesis is that a fundamental understanding of the physics involved in the interaction of interrogating ultrasonic waves with anisotropic media will provide useful information applicable to quantitative ultrasonic measurement techniques employed for the determination of material properties. The desired characteristics of practical fiber-reinforced composites depend on average mechanical properties achieved by placing fibers at specific angles relative to the external surfaces of the finished part. The author examines the physics underlying the use of ultrasound as an interrogation probe for determination of ultrasonic and mechanical properties of anisotropic materials such as fiber-reinforced composites. Fundamental constituent parameters, such as elastic stiffness coefficients, are experimentally determined from ultrasonic time-of-flight measurements. Mechanical moduli descriptive of the anisotropic mechanical properties of unidirectional graphite/epoxy composites are obtained from the ultrasonically determined stiffness coefficients. Three-dimensional visualizations of the anisotropic ultrasonic and mechanical properties of unidirectional graphite/epoxy composites are generated. A goal of the research is to strengthen the connection between practical ultrasonic nondestructive evaluation methods and the physics underlying quantitative ultrasonic measurements for the assessment of manufactured fiber-reinforced composites. Production defects have proven to be of substantial concern in the manufacturing of composites. The author investigates the applicability of ultrasonic interrogation techniques for the detection and characterization of porosity in graphite/epoxy laminates. Complementary ultrasonic parameters based on the frequency dependence of ultrasonic attenuation and integrated polar backscatter are investigated.

Handley, S.M.

1992-01-01

205

Magnetic properties of resin-bonded magnets of anisotropic Nd-Fe-B-Cu powder  

SciTech Connect

Anisotropic Nd-Fe-B-Cu powder was fabricated by grinding melt-spun and subsequently hot-rolled materials. The authors prepared two types of powder with different particle shapes: one isotropic shape, and the other a flat shape with the c-axis perpendicular to the flat face. Perpendicular-field pressing experiments show that isotropic particles are better aligned in the bonded magnet than are flat particles. Radial-field pressing using isotropic particles yields high (BH)[sub max] values of up to 16 MGOe for bonded magnets with a density of 6.0 g/cm[sup 3]. Nd-Fe-B-Cu powder has been found to be well aligned in a relatively weak magnetic field. This fact is useful when fabricating ring magnets with larger height to diameter aspect ratios.

Inaguma, T.; Sakamoto, H.; Mukai, T.

1993-01-01

206

Anisotropic elastic properties of flexible metal-organic frameworks: how soft are soft porous crystals?  

PubMed

We performed ab initio calculations of the elastic constants of five flexible metal-organic frameworks (MOFs): MIL-53(Al), MIL-53(Ga), MIL-47, and the square and lozenge structures of DMOF-1. Tensorial analysis of the elastic constants reveals a highly anisotropic elastic behavior, some deformation directions exhibiting very low Young's modulus and shear modulus. This anisotropy can reach a 400:1 ratio between the most rigid and weakest directions, in stark contrast to the case of nonflexible MOFs such as MOF-5 and ZIF-8. In addition, we show that flexible MOFs can display extremely large negative linear compressibility. These results uncover the microscopic roots of stimuli-induced structural transitions in flexible MOFs, by linking the local elastic behavior of the material and its multistability. PMID:23215398

Ortiz, Aurélie U; Boutin, Anne; Fuchs, Alain H; Coudert, François-Xavier

2012-11-07

207

Anisotropic Elastic Properties of Flexible Metal-Organic Frameworks: How Soft are Soft Porous Crystals?  

NASA Astrophysics Data System (ADS)

We performed ab initio calculations of the elastic constants of five flexible metal-organic frameworks (MOFs): MIL-53(Al), MIL-53(Ga), MIL-47, and the square and lozenge structures of DMOF-1. Tensorial analysis of the elastic constants reveals a highly anisotropic elastic behavior, some deformation directions exhibiting very low Young’s modulus and shear modulus. This anisotropy can reach a 400?1 ratio between the most rigid and weakest directions, in stark contrast to the case of nonflexible MOFs such as MOF-5 and ZIF-8. In addition, we show that flexible MOFs can display extremely large negative linear compressibility. These results uncover the microscopic roots of stimuli-induced structural transitions in flexible MOFs, by linking the local elastic behavior of the material and its multistability.

Ortiz, Aurélie U.; Boutin, Anne; Fuchs, Alain H.; Coudert, François-Xavier

2012-11-01

208

Methods for conditioning anisotropic, operator-scaling, fractal random fields, and the effect on solute transport simulations  

NASA Astrophysics Data System (ADS)

The fractal scaling of aquifer materials have been observed in many data sets. Typically, the scaling coefficient is different in different directions. To date, only unconditional realizations with these properties can be generated. We present and analyze two methods of creating conditional operator-scaling fractal random fields (OSFRF) which have the ability to condition any number and geometry of measurements into each realization. One method is based on the theory of Orthographic Projection (Feller, 1971) and requires the continuous checking of a conditional probability function. The other method uses a best linear unbiased estimate (i.e., a kriged mean surface between known points) and an unconditional realization to create each conditional field. These two methods are analyzed for computational difficulty and their ability to recreate the desired fractal scaling along different (eigenvector) directions. Finally these methods are applied to a transport experiment through a slab of Massillon sandstone to show the advantage of using conditional OSFRF in solute transport modeling.

Revielle, J.; Benson, D. A.

2008-12-01

209

Anisotropic Autocorrelation in House Prices  

Microsoft Academic Search

This article examines anisotropic spatial autocorrelation in single-family house prices and in hedonic house-price equation residuals using a spherical semivariogram and transactions data for one county in the Philadelphia, Pennsylvania, MSA. Isotropic semivariograms model spatial relationships as a function of the distance separating properties in space. Anisotropic semivariograms model spatial relationships as a function of both the distance and the

Kevin Gillen; Thomas Thibodeau; Susan Wachter

2001-01-01

210

Electronic transport properties of graphene nanoribbons  

NASA Astrophysics Data System (ADS)

We will present a brief overview of the electronic and transport properties of graphene nanoribbons focusing on the effect of edge shapes and impurity scattering. The low-energy electronic states of graphene have two non-equivalent massless Dirac spectra. The relative distance between these two Dirac points in the momentum space and edge states due to the existence of zigzag-type graphene edges is a deciding factor in the electronic and transport properties of graphene nanoribbons. In graphene nanoribbons with zigzag edges (zigzag nanoribbons), two valleys related to each Dirac spectrum are well separated in momentum space. The propagating modes in each valley contain a single chiral mode originating from a partially flat band at the band center. This feature gives rise to a perfectly conducting channel in the disordered system, if impurity scattering does not connect the two valleys, i.e. for long-range impurity (LRI) potentials. Ribbons with short-range impurity potentials, however, display ordinary localization behavior through inter-valley scattering. On the other hand, the low-energy spectrum of graphene nanoribbons with armchair edges (armchair nanoribbons) is described as the superposition of two non-equivalent Dirac points of graphene. In spite of the lack of two well separated valley structures, the single-channel transport subjected to LRIs is nearly perfectly conducting, where the backward scattering matrix elements in the lowest order vanish as a manifestation of internal phase structures of the wave function. For the multi-channel energy regime, however, conventional exponential decay of the averaged conductance occurs. Symmetry considerations lead to the classification of disordered zigzag ribbons into the unitary class for LRIs, and the orthogonal class for short-range impurities. Since inter-valley scattering is not completely absent, armchair nanoribbons can be classified into the orthogonal universality class irrespective of the range of impurities.

Wakabayashi, Katsunori; Takane, Yositake; Yamamoto, Masayuki; Sigrist, Manfred

2009-09-01

211

Distributed localization for anisotropic sensor networks  

Microsoft Academic Search

In this paper, we address the issue of localization in anisotropic sensor networks. Anisotropic networks are differ- entiated from isotropic networks in that they possess properties that vary according to the direction of measurement. Anisotropic characteristics result from various factors such as the geographic shape of the region (non-convex region), the different node densities, the irregular radio patterns, and the

Hyuk Lim; Jennifer C. Hou

2009-01-01

212

Correlations among magnetic, electrical and magneto-transport properties of NiFe nanohole arrays  

NASA Astrophysics Data System (ADS)

In this work, we use anodic aluminum oxide (AAO) templates to build NiFe magnetic nanohole arrays. We perform a thorough study of their magnetic, electrical and magneto-transport properties (including the resistance R(T), and magnetoresistance MR(T)), enabling us to infer the nanohole film morphology, and the evolution from granular to continuous film with increasing thickness. In fact, different physical behaviors were observed to occur in the thickness range of the study (2 nm < t < 100 nm). For t < 10 nm, an insulator-to-metallic crossover was visible in R(T), pointing to a granular film morphology, and thus being consistent with the presence of electron tunneling mechanisms in the magnetoresistance. Then, for 10 nm < t < 50 nm a metallic R(T) allied with a larger anisotropic magnetoresistance suggests the onset of morphological percolation of the granular film. Finally, for t > 50 nm, a metallic R(T) and only anisotropic magnetoresistance behavior were obtained, characteristic of a continuous thin film. Therefore, by combining simple low-cost bottom-up (templates) and top-down (sputtering deposition) techniques, we are able to obtain customized magnetic nanostructures with well-controlled physical properties, showing nanohole diameters smaller than 35 nm.

Leitao, D. C.; Ventura, J.; Teixeira, J. M.; Sousa, C. T.; Pinto, S.; Sousa, J. B.; Michalik, J. M.; De Teresa, J. M.; Vazquez, M.; Araujo, J. P.

2013-02-01

213

Transport Properties of the Quantum Hall State  

NASA Astrophysics Data System (ADS)

In this thesis, I analyze the transport properties of the two-dimensional electron gas(2DEG) in the quantum Hall regime. This analysis is based on the model in which the 2DEG breaks into compressible and incompressible regions. ^1 I first describe the progress in the study of the quantum Hall effect from its experimental discovery to the point where the role of the compressible liquid became crucial. The key concept here is the existence of the incompressible state. In Chapter 2 I show through a self-consistent electrostatic calculation that wide compressible strips are present parallel to the edges of a sample. ^2 This leads to an explanation of certain data from equilibration experiments. In Chapter 3 I analyze the effect of compressible strips on the conductance of a narrow wire.^3 The presence of the compressible state leads to narrow plateaus in conductance vs. magnetic field plots. These predictions are yet to be tested. The model of compressible and incompressible regions is used in Chapter 4 to study transport properties of the 2DEG in the bulk.^4 I show that depending on the level of disorder in a sample one can have either narrow or wide compressible regions. In the first case the conventional network model analysis applies, while in the second case I use the composite fermion approach to obtain transport properties. This provides a way of understanding the nature of the compressible state. The main predictions of this part are on the longitudinal resistivity peak values in the quantum Hall effect in the limit of zero temperature. These predictions are compatible with existing experimental data. ftn^1A. L. Efros, Solid State Commun. 67, 1019 (1988), S. Luryi in High Magnetic fields in Semiconductor Physics, edited by Landwehr (Springer, New York, 1987). ^2D. B. Chklovskii, B. I. Shklovskii, and L. I. Glazman, Phys. Rev. 46, 4026 (1992); 46, 15606(E) (1992). ^3D. B. Chklovskii, K. A. Matveev, and B. I. Shklovskii Phys. Rev. B 47, 12605 (1993). ^4D. B. Chklovskii and P. A. Lee, Phys. Rev. B 48, 18060 (1993). (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253 -1690.).

Chklovskii, Dmitri Boris

214

Documentation and verification of VST2D; a model for simulating transient, Variably Saturated, coupled water-heat-solute Transport in heterogeneous, anisotropic 2-Dimensional, ground-water systems with variable fluid density  

USGS Publications Warehouse

This report describes a model for simulating transient, Variably Saturated, coupled water-heatsolute Transport in heterogeneous, anisotropic, 2-Dimensional, ground-water systems with variable fluid density (VST2D). VST2D was developed to help understand the effects of natural and anthropogenic factors on quantity and quality of variably saturated ground-water systems. The model solves simultaneously for one or more dependent variables (pressure, temperature, and concentration) at nodes in a horizontal or vertical mesh using a quasi-linearized general minimum residual method. This approach enhances computational speed beyond the speed of a sequential approach. Heterogeneous and anisotropic conditions are implemented locally using individual element property descriptions. This implementation allows local principal directions to differ among elements and from the global solution domain coordinates. Boundary conditions can include time-varying pressure head (or moisture content), heat, and/or concentration; fluxes distributed along domain boundaries and/or at internal node points; and/or convective moisture, heat, and solute fluxes along the domain boundaries; and/or unit hydraulic gradient along domain boundaries. Other model features include temperature and concentration dependent density (liquid and vapor) and viscosity, sorption and/or decay of a solute, and capability to determine moisture content beyond residual to zero. These features are described in the documentation together with development of the governing equations, application of the finite-element formulation (using the Galerkin approach), solution procedure, mass and energy balance considerations, input requirements, and output options. The VST2D model was verified, and results included solutions for problems of water transport under isohaline and isothermal conditions, heat transport under isobaric and isohaline conditions, solute transport under isobaric and isothermal conditions, and coupled water-heat-solute transport. The first three problems considered in model verification were compared to either analytical or numerical solutions, whereas the coupled problem was compared to measured laboratory results for which no known analytic solutions or numerical models are available. The test results indicate the model is accurate and applicable for a wide range of conditions, including when water (liquid and vapor), heat (sensible and latent), and solute are coupled in ground-water systems. The cumulative residual errors for the coupled problem tested was less than 10-8 cubic centimeter per cubic centimeter, 10-5 moles per kilogram, and 102 calories per cubic meter for liquid water content, solute concentration and heat content, respectively. This model should be useful to hydrologists, engineers, and researchers interested in studying coupled processes associated with variably saturated transport in ground-water systems.

Friedel, Michael J.

2001-01-01

215

Calculation of Thermoelectric Transport Properties in Heterostructures  

NASA Astrophysics Data System (ADS)

We present a model that can predict the Seebeck coefficient of different interfaces. Within this model we solve the Poisson equation and Schrödinger equation self-consistently to obtain the potential profile across the interface. Then we use the nonequilibrium Green's function (NEGF) method to calculate the transport properties across the interface. We apply our model to a ZnO grain boundary, describing the boundary as a back-to-back Schottky barrier. The potential profile in the considered system is similar to a rigid-shift potential, and thus the Seebeck coefficient obtained from the rigid-shift potential shows no deviation in comparison with the Seebeck coefficient obtained from the self-consistent potential.

Bachmann, M.; Czerner, M.; Heiliger, C.

2011-05-01

216

Studies on transport properties of copper doped tungsten diselenide single crystals  

NASA Astrophysics Data System (ADS)

During recent years, transition metal dichalcogenides of groups IVB, VB and VIB have received considerable attention because of the great diversity in their transport properties. 2H-WSe2 (Tungsten diselenide) is an interesting member of the transition metal dichalcogenide (TMDC's) family and known to be a semiconductor useful for photovoltaic and optoelectronic applications. The anisotropy usually observed in this diamagnetic semiconductor material is a result of the sandwich structure of Se-W-Se layers interacting with each other, loosely bonded by the weak Van der Waals forces. Recent efforts in studying the influence of the anisotropic electrical and optical properties of this layered-type transition metal dichalcogenides have been implemented by doping the samples with different alkali group elements. Unfortunately, little work is reported on doping of metals in WSe2. Therefore, it is proposed in this work to carry out a systematic growth of single crystals of WSe2 by doping it with copper in different proportions i.e. CuxWSe2 (x=0, 0.5, 1.0) by direct vapour transport technique. Transport properties like low and high temperature resistivity measurements, high pressure resistivity, Seebeck coefficient measurements at low temperature and Hall Effect at room temperature were studied in detail on all these samples. These measurements show that tungsten diselenide single crystals are p-type whereas doped with copper makes it n-type in nature. The results obtained and their implications are discussed in this paper.

Deshpande, M. P.; Parmar, M. N.; Pandya, Nilesh N.; Chaki, Sunil; Bhatt, Sandip V.

2012-02-01

217

Mechanical properties of cancellous bone in the human mandibular condyle are anisotropic  

Microsoft Academic Search

The objective of the present study was (1) to test the hypothesis that the elastic and failure properties of the cancellous bone of the mandibular condyle depend on the loading direction, and (2) to relate these properties to bone density parameters. Uniaxial compression tests were performed on cylindrical specimens (n=47) obtained from the condyles of 24 embalmed cadavers. Two loading

E. B. W. Giesen; M. Ding; M. Dalstra; T. M. G. J van Eijden

2001-01-01

218

Architecture and properties of anisotropic polymer composite scaffolds for bone tissue engineering  

Microsoft Academic Search

Bone is a complex porous composite structure with specific characteristics such as viscoelasticity and anisotropy, both in morphology and mechanical properties. Bone defects are regularly filled with artificial tissue grafts, which should ideally have properties similar to those of natural bone. Open cell composite foams made of bioresorbable poly(l-lactic acid) (PLA) and ceramic fillers, hydroxyapatite (HA) or ?-tricalcium phosphate (?-TCP),

Laurence Marcelle Mathieu; Thomas L. Mueller; Pierre-Etienne Bourban; Dominique P. Pioletti; Ralph Müller; Jan-Anders E. Månson

2006-01-01

219

Anisotropic transport of two-dimensional electron gas modulated by embedded elongated GaSb/GaAs quantum dots  

NASA Astrophysics Data System (ADS)

Geometrically anisotropic GaSb/GaAs quantum dots (QDs) that are elongated along the [110] direction are embedded in the vicinity of a modulation-doped AlGaAs/GaAs heterointerface. At 4.2 K, the electron mobilities ?? and ??, which are parallel and perpendicular to the QD elongation axis, respectively, are systematically investigated as a function of the electron concentration NS by both experimental measurements and theoretical simulations. In the experiments, the mobility ratio ??/?? increased with increasing NS. The mobility anisotropy, attributed to the anisotropic scattering potential of the elongated GaSb QDs, is calculated under the theoretical model of a rectangular scattering potential of GaSb QDs.

Li, Guodong; Jiang, Chao; Zhu, Qinsheng; Sakaki, Hiroyuki

2011-01-01

220

Anisotropic transport of two-dimensional electron gas modulated by embedded elongated GaSb\\/GaAs quantum dots  

Microsoft Academic Search

Geometrically anisotropic GaSb\\/GaAs quantum dots (QDs) that are elongated along the [110] direction are embedded in the vicinity of a modulation-doped AlGaAs\\/GaAs heterointerface. At 4.2 K, the electron mobilities mu|| and mu?, which are parallel and perpendicular to the QD elongation axis, respectively, are systematically investigated as a function of the electron concentration NS by both experimental measurements and theoretical

Guodong Li; Chao Jiang; Qinsheng Zhu; Hiroyuki Sakaki

2011-01-01

221

Correlation of self-organized surface nanostructures and anisotropic electron transport in nonpolar ZnO (10-10) homoepitaxy  

Microsoft Academic Search

Self-organized surface nanostructures were formed during laser molecular beam epitaxy of nonpolar ZnO (10-10). The growth mechanism of the nanostructures was related to a Schwoebel barrier effect generated during ZnO homoepitaxy. Small islands elongated along the [001] direction were generated on two-dimensional (2D) growing surfaces above the critical thickness. With increasing film thickness, the anisotropic islands developed homogeneous nanostripe arrays

Hiroaki Matsui; Hitoshi Tabata

2006-01-01

222

Transport properties of dense matter. II  

Microsoft Academic Search

Exact solutions for the transport coefficients of a multicomponent system of several interacting Fermi liquids are given in the low temperature limit. The transport coefficients are found by solving a set of coupled Boltzmann transport equations. These solutions for the transport coefficients are used to evaluate the thermal conductivity and viscosity of neutron star matter in the density regime where

E. Flowers; N. Itoh

1979-01-01

223

Determination of the anisotropic elastic properties of Ge1Sb2Te4  

NASA Astrophysics Data System (ADS)

The elastic properties of Ge-Sb-Te (GST) alloys are important for phase-change devices (such as CD-RW, DVD-RW, Blu-ray, or phase-change random access memory) because the transition between the crystalline and amorphous phases involves a volume change accommodated by a strain estimated to be between 150 MPa and 10 GPa. However, the elastic properties of GST alloys are poorly characterized and the experimental and theoretical values show large discrepancies. We carry out a careful analysis of the elastic properties of a model system, crystalline Ge1Sb2Te4, using density functional theory and elastic anisotropy considerations. We show that Ge1Sb2Te4 exhibits significant anisotropy in its elastic properties.

Marmier, Arnaud; Kohary, Krisztian; Wright, C. David

2011-06-01

224

Anisotropic electrical properties of thermal spray coatings: The role of splat-boundary interfaces  

Microsoft Academic Search

A thermal spray coating is an assemblage of splats which are considered the building-blocks of the coating. Apart from the properties of the splats themselves, the physical properties of the coatings are strongly influenced by the nature of the regions between splats, the so-called splat-boundary (SB) interfaces. This dissertation is primarily an investigation of the role of SB interfaces in

Atin Sharma

2006-01-01

225

In-plane anisotropy in the magnetic and transport properties of manganite ultrathin films  

SciTech Connect

To analyze the conducting and magnetic properties near the film and substrate interface in manganites, ultrathin films (thickness{<=}100 A ) of La{sub 0.7}Sr{sub 0.3}MnO{sub 3} were epitaxially grown by molecular-beam epitaxy on single-crystal (001) LaAlO{sub 3} (110) NdGaO{sub 3}, and (001) SrTiO{sub 3} substrates. Structural, magnetic, and magnetoresistive properties were investigated. All samples exhibit a substrate-independent decrease of the c-lattice parameter for thinnest films. Highly anisotropic behavior in both transport and magnetic properties were measured along the in-plane directions parallel to the substrate crystallographic axes. In particular, for the thinnest films (60 A ), the negative magnetoresistance at about 120 K with the average current along one of the crystallographic directions, is larger than the room-temperature colossal value. In the same low-temperature range, with the current along the other in-plane crystallographic direction, the magnetoresistance changes sign (resulting to be magnetic field independent for T{approx}150 K). Such an in-plane anisotropy of transport and magnetic properties is investigated with respect to possible intrinsic and extrinsic physical mechanisms.

Orgiani, P.; Polichetti, M.; Zola, D. [CNR-INFM SuperMat and Department of Physics, University of Salerno, Via S. Allende, I - 84081 Baronissi (Saudi Arabia) (Italy); Petrov, A. Yu.; Adamo, C.; Aruta, C.; Barone, C.; De Luca, G. M.; Galdi, A.; Maritato, L. [CNR-INFM Coherentia and Department of Physics, University of Salerno, Via S. Allende, I - 84081 Baronissi (Saudi Arabia) (Italy)

2006-10-01

226

A review of some charge transport properties of silicon  

Microsoft Academic Search

Basic bulk transport properties of charge carriers in silicon are reviewed, with particular reference to their use in designing solid-state components. The current theoretical model for transport in silicon is outlined, along with experimental techniques for determining most important transport parameters such as the drift velocity and diffusion coefficient. Phenomenological expressions are presented, which are in good agreement with experimental

C. Jacoboni; C. Canali; G. Ottaviani; A. Alberigi Quaranta

1977-01-01

227

Transport properties of supercooled confined water  

NASA Astrophysics Data System (ADS)

This article presents an overview of recent experiments performed on transport properties of water in the deeply supercooled region, a temperature region of fundamental importance in the science of water. We report data of nuclear magnetic resonance, quasi-elastic neutron scattering, Fourier-transform infrared spectroscopy, and Raman spectroscopy, studying water confined in nanometer-scale environments. When contained within small pores, water does not crystallise, and can be supercooled well below its homogeneous nucleation temperature Th. On this basis it is possible to carry out a careful analysis of the well known thermodynamical anomalies of water. Studying the temperature and pressure dependencies of water dynamics, we show that the liquid-liquid phase transition (LLPT) hypothesis represents a reliable model for describing liquid water. In this model, water in the liquid state is a mixture of two different local structures, characterised by different densities, namely the low density liquid (LDL) and the high-density liquid (HDL). The LLPT line should terminate at a special transition point: a low-T liquid-liquid critical point. We discuss the following experimental findings on liquid water: (i) a crossover from non-Arrhenius behaviour at high T to Arrhenius behaviour at low T in transport parameters; (ii) a breakdown of the Stokes-Einstein relation; (iii) the existence of a Widom line, which is the locus of points corresponding to maximum correlation length in the p-T phase diagram and which ends in the liquid-liquid critical point; (iv) the direct observation of the LDL phase; (v) a minimum in the density at approximately 70 K below the temperature of the density maximum. In our opinion these results represent the experimental proofs of the validity of the LLPT hypothesis.

Mallamace, F.; Branca, C.; Broccio, M.; Corsaro, C.; Gonzalez-Segredo, N.; Spooren, J.; Stanley, H. E.; Chen, S.-H.

2008-07-01

228

Crystal growth and anisotropic magnetic properties of RAg2Ge2 (R=Pr, Nd and Sm) single crystals  

NASA Astrophysics Data System (ADS)

We report the single crystal growth and anisotropic magnetic properties of the tetragonal RAg2Ge2 (R=Pr, Nd and Sm) compounds which crystallize in the ThCr2Si2 -type crystal structure with the space group I4/mmm. The single crystals of RAg2Ge2 (R=Pr, Nd and Sm) were grown by self-flux method using Ag:Ge binary alloy as flux. From the magnetic studies on single crystalline samples we have found that PrAg2Ge2 and NdAg2Ge2 order antiferromagnetically at 12 and 2 K, respectively, thus corroborating the earlier polycrystalline results. SmAg2Ge2 also orders antiferromagnetically at 9.2 K. The magnetic susceptibility and magnetization show a large anisotropy and the easy axis of magnetization for PrAg2Ge2 and NdAg2Ge2 is along the [1 0 0] direction whereas it changes to [0 0 1] direction for SmAg2Ge2. Two metamagnetic transitions were observed in NdAg2Ge2 at H=1.25T and H=3.56T for the field parallel to [1 0 0] direction whereas the magnetization along [0 0 1] direction was linear indicating the hard axis of magnetization.

Joshi, Devang A.; Nagalakshmi, R.; Kulkarni, R.; Dhar, S. K.; Thamizhavel, A.

2009-10-01

229

Magnetic properties of isotropic and anisotropic CoFe2O4 -based ferrogels and their application as torsional and rotational actuators  

Microsoft Academic Search

CoFe2O4 -based ferrogels were prepared with both isotropic and anisotropic orientation of the magnetic anisotropy axis of the magnetic particles. In contrast to the superparamagnetic properties of the ferrofluid, the ferrogels exhibit hysteresis, indicating that (i) a significant fraction of magnetic particles has volumes beyond the critical value that allows Néelian relaxation, and (ii) a mechanical interaction between the particles

S. Monz; A. Tschöpe; R. Birringer

2008-01-01

230

Architecture and properties of anisotropic polymer composite scaffolds for bone tissue engineering.  

PubMed

Bone is a complex porous composite structure with specific characteristics such as viscoelasticity and anisotropy, both in morphology and mechanical properties. Bone defects are regularly filled with artificial tissue grafts, which should ideally have properties similar to those of natural bone. Open cell composite foams made of bioresorbable poly(L-lactic acid) (PLA) and ceramic fillers, hydroxyapatite (HA) or beta-tricalcium phosphate (beta-TCP), were processed by supercritical CO2 foaming. Their internal 3D-structure was then analysed by micro-computed tomography (microCT), which evidenced anisotropy in morphology with pores oriented in the foaming direction. Furthermore compressive tests demonstrated anisotropy in mechanical behaviour, with an axial modulus up to 1.5 times greater than the transverse modulus. Composite scaffolds also showed viscoelastic behaviour with increased modulus for higher strain rates. Such scaffolds prepared by gas foaming of polymer composite materials therefore possess suitable architecture and properties for bone tissue engineering applications. PMID:16051346

Mathieu, Laurence Marcelle; Mueller, Thomas L; Bourban, Pierre-Etienne; Pioletti, Dominique P; Müller, Ralph; Månson, Jan-Anders E

2005-07-27

231

Transport and mechanical properties of Yb-filled skutterudites  

Microsoft Academic Search

A series of Yb-filled skutterudites were produced and powder samples consolidated using spark plasma sintering (SPS). The effect of different heating cycles on the resulting transport properties of the consolidated samples was explored. Specifically, the effect of sample uniformity on the electrical and thermal transport properties was explored. In addition to the optimal Yb-filling fraction, other factors, such as heating

J. R. Salvador; J. Yang; X. Shi; H. Wang; A. A. Wereszczak; H. Kong; C. Uher

2009-01-01

232

Investigating linkages between atmospheric and terrain properties and spatial anisotropic multiscaling in orographic convective precipitation  

NASA Astrophysics Data System (ADS)

The solutions of idealized fully nonlinear cloud resolving numerical simulations of orographic convective precipitation display statistical multiscaling, similar to what is commonly found in observations in the atmosphere. This result is verified even in the absence of scaling in the initial conditions or terrain forcing, suggesting that this scaling behavior should be a general property of the nonlinear solutions of the Navier-Stokes like equations governing the atmospheric dynamics. By taking advantage of this scale invariance property, statistical downscaling methods can be constructed which can be used as sub-grid scale parameterizations and provide a way to bridge between coarser resolution numerical simulations and the high resolution needs of hydrological applications. However, the horizontal scaling exponent function (and respective multifractal parameters) varies with atmospheric and terrain properties, particularly small scale terrain spectra, atmospheric stability and mean wind speed. This result qualitatively agrees with the predictions of linear stability analysis that suggests the governing role of these parameters in embedded convective structures. Hence multiscaling statistical parameters should be computed for each particular geographical location and atmospheric conditions, bringing the necessity of development of relationships to predict them from coarse grid atmospheric data and terrain spectra. The spatial anisotropy (both vertical and horizontal) of the scaling exponent function for rain, cloud and velocity fields is also investigated. Based on the computed statistical multifractal exponents, multifractal simulations are performed to test the ability of these cascade models in reproducing the statistical properties of the atmospheric fields and the sensitivity of the statistical properties of the fields to variations in the multifractal parameters. Finally, simulations with scaling terrain forcing are created and the relationship between scaling of rain, cloud and wind fields and topography is explored.

Nogueira, M.; Barros, A. P.; Miranda, P. M.

2011-12-01

233

Anisotropic transport behavior of orbital-ordered Nd0.48Sr0.52MnO3 films  

NASA Astrophysics Data System (ADS)

Anisotropic magnetoresistance (AMR) and Hall effect have been studied for the (110)-oriented Nd0.48Sr0.52MnO3 film. The most remarkable results are the significant enhancement of the AMR accompanying the orbital ordering and the appearance of four-fold symmetry of the AMR along the [1-10] direction. Analysis of the Hall data indicates the absence of any visible increase in spin-orbit coupling corresponding to the AMR growth. This suggests a different mechanism for the AMR of Nd0.48Sr0.52MnO3 from that of the conventional ferromagnetic metals/alloys.

Liang, S.; Sun, J. R.; Chen, Y. Z.; Shen, B. G.

2011-11-01

234

Theoretical studies on leaky-SAW properties influenced by layers on anisotropic piezoelectric crystals.  

PubMed

Theoretical studies on the behavior of leaky-SAW (LSAW) properties in layered structures were performed. For these calculations rotYX LiTaO (3) and rotYX LiNbO(3) LSAW crystal cuts were used, assuming different layer materials. For LSAWs both the velocity and the inherent loss due to bulk wave emission into the substrate are strongly influenced by distinct layer parameters. As a result, these layer properties like elastic constants or thickness have shown a strong influence on the crystal cut angle of minimum LSAW loss. Moreover, for soft and stiff layer materials, a different shift of the LSAW loss minimum can occur. Therefore, using double-layer structures, the shift of the LSAW loss minimum can be influenced by appropriate chosen layers and ratios. PMID:18238665

Wallner, P; Ruile, W; Weigel, R

2000-01-01

235

Characterisation by Inverse Techniques of Elastic, Viscoelastic and Piezoelectric Properties of Anisotropic Sandwich Adaptive Structures  

Microsoft Academic Search

In this article we present recent developments regarding parameter estimation in sandwich structures with viscoelastic frequency\\u000a dependent core and elastic laminated skin layers, with piezoelectric patch sensors and actuators bonded to the exterior surfaces\\u000a of the sandwich. The frequency dependent viscoelastic properties of the core material are modelled using fractional derivative\\u000a models, with unknown parameters that are to be estimated

Aurelio L. Araújo; Cristovao M. Mota Soares; Carlos A. Mota Soares; Jose Herskovits

2010-01-01

236

Anisotropic conductivity of the Si(111)4 × 1-In surface: Transport mechanism determined by the temperature dependence  

NASA Astrophysics Data System (ADS)

The temperature dependence of anisotropic conductivity of a quasi-one-dimensional metallic surface, Si(111)4 × 1-In, was measured by a variable-temperature four-tip scanning tunneling microscope. Using the square four-point probe method, we succeeded in measuring the conductivity parallel and perpendicular to the In chains independently as a function of temperature. It was shown that the conductivity perpendicular to the In chains was mainly the conductivity of the space-charge layer of the substrate. Moreover, it was clarified that it strongly depends on the substrate flashing temperature and this sometimes hindered the anisotropic conductivity at low temperatures. In contrast, the conductivity parallel to In chains was clearly dominated by the surface states and decreased drastically around 110 K by the well-known 4×1 to 8×2 metal-insulator transition. The low temperature 8×2 phase had an energy gap as large as ˜250 meV, consistent with previous photoemission reports.

Uetake, Tomoya; Hirahara, Toru; Ueda, Yoichi; Nagamura, Naoka; Hobara, Rei; Hasegawa, Shuji

2012-07-01

237

Anisotropic thermal properties of the polar crystal Cs2TeMo3O12  

NASA Astrophysics Data System (ADS)

A Cs2TeMo3O12 single crystal with dimensions of 17 mm×17 mm×18 mm was grown using the top-seeded solution growth method. Thermal properties, including thermal expansion, specific heat, thermal diffusivity and thermal conductivity, were investigated as a function of temperature. The average linear thermal expansion coefficients along different crystallographic directions were measured to be ?a=7.34×10-6 K-1 and ?c=32.02×10-6 K-1 over the temperature range of 30-430 °C. The specific heat was measured to be 0.400-0.506 J g-1 K-1 from 22 °C to 440 °C. The thermal conductivity was calculated to be 1.86 and 0.76 W m-1 K-1 at 22 °C along the a and c axes, respectively. With increasing temperature from 22 to 430 °C, the thermal conductivity decreases by 33.0% along the a axis, while it decreases by 18.5% below 200 °C and then remains unchanged along the c axis. The relationship between structure and the thermal properties is also discussed.

Zhang, Junjie; Zhang, Zhonghan; Sun, Youxuan; Zhang, Chengqian; Tao, Xutang

2012-11-01

238

Models of two level systems for anisotropic glassy materials  

NASA Astrophysics Data System (ADS)

We use an extended version of the standard tunneling model to explain the sound absorption in anisotropic glassy materials and heat transport in mesoscopic slabs and bridges. The glassy properties are determined by an ensemble of two level systems (TLS). In our model a TLS is characterized by a 3x3 symmetric tensor, [T], which couples to the strain field, [S], through a 3x3x3x3 tensor of coupling constants, [[R

Anghel, Dragos-Victor; Dumitru, Irina Mihaela; Nemnes, Alexandru George; Churochkin, Dmitrii

2013-03-01

239

Unusual Transport and Strongly Anisotropic Thermopower in PtCoO2 and PdCoO2  

SciTech Connect

We show, using Boltzmann transport calculations and analysis of experimental data, that hexagonal PdCoO2 and PtCoO2 have a highly unusual metallic transport. The in-plane transport is typical of a very good metal, with high conductivity and low positive thermopower. The c-axis transport is completely different, with 2 orders of magnitude lower, but still coherent, conductivity and remarkably a very large negative thermopower. This large anisotropy of the thermopower provides an opportunity for investigating transport in a highly unusual regime using bulk materials.

Singh, David J.; Wu, Ping; Ong, Khuong P.

2010-01-01

240

Anisotropic magnetic properties in Åkermanite Sr2 MSi2O7 ( M=Co, Mn) crystals  

NASA Astrophysics Data System (ADS)

We have investigated the magnetic and the dielectric properties of åkermanite Sr2CoSi2O7 and Sr2MnSi2O7 single crystals. Sr2CoSi2O7 shows a canted antiferromagnetism with a large magnetic anisotropy at temperatures below 7 K. By applying a magnetic field along the [110] direction, an electric polarization emerges along the c axis at temperatures below the magnetic transition temperature. In high magnetic fields, the saturation magnetization becomes enhanced only when the electric polarization appears. In contrast, the magnetization of Sr2MnSi2O7 is isotropic at all temperatures, and its magnetic-field-induced electric polarization is very small. These results suggest that the electronic configuration of the transition-metal ion is of crucial importance for the appearance of electric polarization.

Akaki, Mitsuru; Tadokoro, Tomoya; Kuwahara, Hideki; Kihara, Takumi; Tokunaga, Masashi

2013-06-01

241

Effective Hydraulic Properties Determined from Transient Unsaturated Flow in Anisotropic Soils  

SciTech Connect

Hydraulic parameters including the pore connectivity/tortuosity tensor (L_i) were inversely estimated using the STOMP numerical simulator coupled with the parameter estimation code, UCODE. Results show that six of eight parameters required for a modified van Genuchten-Mualem model could be inversely estimated using water content measured during transient infiltration from a surface line source and approximated prior information. Soils showed evidence of saturation-dependent anisotropy that was well described with the connectivity tensor. Variability of the vertical saturated hydraulic conductivity was larger than the horizontal. The autocorrelation ranges for the horizonatal and vertical Ks; the inverse of the air-entry value, and the horizontal connectivity were between 2.4 and 4.6 m whereas the van Genuchten shape parameter, n, and saturated water content showed no autocorrelation. Accurate upscaling of hydraulic properties requires the correct assessment of the connectivity of facies.

Ward, Andy L.; Zhang, Z. F.

2007-11-01

242

Float zone growth and anisotropic spectral properties of Nd:LaVO4 single crystals  

NASA Astrophysics Data System (ADS)

Nd:LaVO4 single crystals were successfully grown by the floating zone method and their optical properties along each optic elasticity axis were investigated. The crystals grown at 10 mm/h in air did not contain any macroscopic defects for Nd-concentrations upto 5 at%. The optic elasticity axes were determined by the conoscopic figures with a polarizing microscope. The absorption cross-section along the Z-axis was 2.6×10-20 cm2 near 800 nm and the FWHM was 20 nm. The absorption cross-sections along other directions were much the same as that along the Z-axis. The fluorescence lifetime of the 5 at%-doped crystal was approximately 80 ?s. All the polarized fluorescence spectra of the Nd:LaVO4 single crystal had a broadened band around 1060 nm with FWHMs of 7-10 nm, which are wide enough to generate femtosecond order pulses.

Yomogida, Shohei; Higuchi, Mikio; Ogawa, Takayo; Wada, Satoshi; Takahashi, Junichi

2012-11-01

243

Thermodynamic and transport properties of sodium liquid and vapor  

Microsoft Academic Search

Data have been reviewed to obtain thermodynamically consistent equations for thermodynamic and transport properties of saturated sodium liquid and vapor. Recently published Russian recommendations and results of equation of state calculations on thermophysical properties of sodium have been included in this critical assessment. Thermodynamic properties of sodium liquid and vapor that have been assessed include: enthalpy, heat capacity at constant

J. K. Fink; L. Leibowitz

1995-01-01

244

Functional Properties and Genomics of Glucose Transporters  

PubMed Central

Glucose is the major energy source for mammalian cells as well as an important substrate for protein and lipid synthesis. Mammalian cells take up glucose from extracellular fluid into the cell through two families of structurallyrelated glucose transporters. The facilitative glucose transporter family (solute carriers SLC2A, protein symbol GLUT) mediates a bidirectional and energy-independent process of glucose transport in most tissues and cells, while the NaM+/glucose cotransporter family (solute carriers SLC5A, protein symbol SGLT) mediates an active, Na+-linked transport process against an electrochemical gradient. The GLUT family consists of thirteen members (GLUT1-12 and HMIT). Phylogenetically, the members of the GLUT family are split into three classes based on protein similarities. Up to now, at least six members of the SGLT family have been cloned (SGLT1-6). In this review, we report both the genomic structure and function of each transporter as well as intra-species comparative genomic analysis of some of these transporters. The affinity for glucose and transport kinetics of each transporter differs and ranges from 0.2 to 17mM. The ability of each protein to transport alternative substrates also differs and includes substrates such as fructose and galactose. In addition, the tissue distribution pattern varies between species. There are different regulation mechanisms of these transporters. Characterization of transcriptional control of some of the gene promoters has been investigated and alternative promoter usage to generate different protein isoforms has been demonstrated. We also introduce some pathophysiological roles of these transporters in human.

Zhao, Feng-Qi; Keating, Aileen F

2007-01-01

245

Rotationally anisotropic second-harmonic generation studies of the structure and electronic properties of bimetallic interfaces, Ag on Cu(110)  

SciTech Connect

Rotationally anisotropic surface second-harmonic generation (SHG) has been measured from a clean, well-ordered Cu(110) single-crystal surface as a function of both surface temperature and Ag coverage. For the clean Cu(110) surface, the temperature dependence of the SH response at a fixed azimuthal angle can be correlated with a surface phase transformation. A large decrease in the rotationally anisotropic SH response as a function of surface temperature can be related to changes in the surface disorder. The results are compared with other studies of Cu(110) surface structure using both x-ray and He-atom scattering. The rotationally anisotropic SH response has also been measured as a function of Ag coverage with the Cu(110) surface temperature fixed at 300 K. The results closely follow the formation of an ordered Ag(111)-like overlayer, the nucleation of three-dimensional Ag nanoclusters (<20 {angstrom} thick) that enhance the anisotropic SH response, and the subsequent growth of a {approximately}10 monolayer thick Ag film. Variations in the rotationally anisotropic SH response as a function of Ag coverage are used to separate the resonant surface electronic contributions to the nonlinear susceptibility of the interface. 22 refs., 4 figs.

Hoffbauer, M.A.; McVeigh, V.J.

1990-01-01

246

Nematic Ordering and Anisotropic Viscoelastic Properties in a Main-Chain Polymer System.  

NASA Astrophysics Data System (ADS)

The fundamental features of macroscopic phenomena in polymer nematics formed from solutions of long rigid or semirigid macromolecules are studied from theoretical and experimental points of view. Firstly, the theoretical study of nematic ordering, curvature elasticity, and nematodynamic behavior in main -chain polymer systems is completely carried out. Analytical formulations as well as numerical analyses are performed for basic understanding of the phenomena in terms of the intrinsic material parameters such as the great length of the polymers and the degree of their flexibility. The Onsager-type free energy are formulated for studying the effect of charge, chain flexibility, and an external flow field on the stability of the nematic phase. A self-consistent functional scaling is also proposed to analyze the phase behavior and elastic properties of liquid-density nematics in which the low density approximation is obviously not appropriate. The generalized molecular kinetic theory is described, and molecular expressions for the Leslie coefficients are obtained. Secondly, quasi-elastic Rayleigh scattering on well oriented nematic liquid crystals of Poly- gamma-Benzyl-Glutamate (PBG), which belongs to a class of synthetic polypeptides, is performed to determine their elastic and nematodynamic viscosity coefficients as a function of molecular chain length. The first observation of the crossover from rigid to semiflexible behavior of the viscoelastic coefficients for a PBG nematic system is reported. The experimental results are compared with existing theoretical predictions in detail. The speculative and qualitative ideas are also presented.

Lee, Sin-Doo

247

26 CFR 49.4271-1 - Tax on transportation of property by air.  

Code of Federal Regulations, 2013 CFR

... 2013-04-01 false Tax on transportation of property by air. 49.4271-1...FACILITIES AND SERVICES EXCISE TAXES Transportation of Property § 49.4271-1 Tax on transportation of property by air. (a)...

2013-04-01

248

67 FR 4318 - Revised Requirement for Material Strength Properties and Design Values for Transport Airplanes  

Federal Register 2010, 2011, 2012, 2013

...Requirement for Material Strength Properties and Design Values for Transport Airplanes and Notice...Requirement for Material Strength Properties and Design Values for Transport Airplanes AGENCY...material strength properties and material design values requirement for transport...

2002-01-29

249

Rapid Salt Exchange by Coupled Ultrafiltration and Dialysis in Anisotropic Hollow Fibers  

Microsoft Academic Search

Anisotropic hollow fibers allow construction of a dialyzing system that provides extremely large membrane surface in a small laboratory-sized system. Possessing the added property of high ultrafiltration flux, these fibers reduce salt exchange times from days to hours. In this system the exchange of salt by dialytic transport is largely unaffected by recirculation rate, solute type, or content, but is

William F. Blatt; Lita Nelsen; Eliseo M. Zipilivan; Mark C. Porter

1972-01-01

250

Anisotropic enhanced backscattering induced by anisotropic diffusion.  

PubMed

The enhanced backscattering cone displaying a strong anisotropy from a material with anisotropic diffusion is reported. The constructive interference of the wave is preserved in the helicity preserving polarization channel and completely lost in the nonpreserving one. The internal reflectivity at the interface modifies the width of the backscatter cone. The reflectivity coefficient is measured by angular-resolved transmission. This interface property is found to be isotropic, simplifying the backscatter cone analysis. The material used is a macroporous semiconductor, gallium phosphide, in which pores are etched in a disordered position but with a preferential direction. PMID:15524650

Bret, B P J; Lagendijk, A

2004-09-03

251

Anisotropic branes  

NASA Astrophysics Data System (ADS)

We present a class of anisotropic brane configurations which shows BKL oscillations near their cosmological singularities. Near horizon limits of these solutions represent Kasner space embedded in AdS background. Dynamical probe branes in these geometries inherit anisotropies from the background. Amusingly, for a probe M5 brane, we find that there exists a parameter region where three of its world-volume directions expand while the rest contract.

Banerjee, Souvik; Bhowmick, Samrat; Mukherji, Sudipta

2013-10-01

252

A Novel Multigrid Method for Sn Discretizations of the Mono-Energetic Boltzmann Transport Equation in the Optically Thick and Thin Regimes with Anisotropic Scattering, Part I  

SciTech Connect

This paper presents a new multigrid method applied to the most common Sn discretizations (Petrov-Galerkin, diamond-differenced, corner-balanced, and discontinuous Galerkin) of the mono-energetic Boltzmann transport equation in the optically thick and thin regimes, and with strong anisotropic scattering. Unlike methods that use scalar DSA diffusion preconditioners for the source iteration, this multigrid method is applied directly to an integral equation for the scalar flux. Thus, unlike the former methods that apply a multigrid strategy to the scalar DSA diffusion operator, this method applies a multigrid strategy to the integral source iteration operator, which is an operator for 5 independent variables in spatial 3-d (3 in space and 2 in angle) and 4 independent variables in spatial 2-d (2 in space and 2 in angle). The core smoother of this multigrid method involves applications of the integral operator. Since the kernel of this integral operator involves the transport sweeps, applying this integral operator requires a transport sweep (an inversion of an upper triagular matrix) for each of the angles used. As the equation is in 5-space or 4-space, the multigrid approach in this paper coarsens in both angle and space, effecting efficient applications of the coarse integral operators. Although each V-cycle of this method is more expensive than a V-cycle for the DSA preconditioner, since the DSA equation does not have angular dependence, the overall computational efficiency is about the same for problems where DSA preconditioning {\\it is} effective. This new method also appears to be more robust over all parameter regimes than DSA approaches. Moreover, this new method is applicable to a variety of Sn spatial discretizations, to problems involving a combination of optically thick and thin regimes, and more importantly, to problems with anisotropic scattering cross-sections, all of which DSA approaches perform poorly or not applicable at all. This multigrid approach is most effective in neutron scattering applications, where the total cross-section coefficient $\\sigma_t$ and spatial meshsize $h$ satisfies $\\sigma_t h\\approx 1.$ For this case, coarsening can be done aggressively. For problems with $\\sigma_t h\\approx 10,$ this multigrid scheme requires a moderately coarsened multiple-coarsening scheme. An even slow coarsening, an angle semi-coarsening, is required for problems with $\\sigma_t h$ ranges between 100 and 1000, which occur in high-energy photon applications.

Lee, Barry

2010-05-01

253

Transport properties of small spherical particles.  

PubMed

Recently, a theoretical framework for nanoparticle transport in the laminar flow regime has been proposed. The theory features a rigorous gas-kinetic theory analysis. It considers the effect of nonrigid body collision, and the theory is shown to reproduce the Chapman-Enskog theory of molecular transport in the small particle size limit, Epstein's model of particle drag in the rigid-body limit, and the Stokes-Cunningham equation for the drag on micrometer size particles. This theoretical framework provides the hope that bits and pieces of particle transport theories formulated over the last century can now be unified into a generalized theory. This paper discusses an unresolved fundamental issue related to this generalized theory, namely, the transition from specular scattering applicable to molecule-molecule collision to diffuse scattering governing molecule-"particle" collision. PMID:19426341

Wang, Hai

2009-04-01

254

Transport properties of clean quantum point contacts  

NASA Astrophysics Data System (ADS)

Quantum point contacts are fundamental building blocks for mesoscopic transport experiments and play an important role in recent interference and fractional quantum Hall experiments. However, it is unclear how electron-electron interactions and the random disorder potential influence the confinement potential and give rise to phenomena such as the mysterious 0.7 anomaly. Novel growth techniques of AlXGa1-XAs heterostructures for high-mobility two-dimensional electron gases enable us to investigate quantum point contacts with a strongly suppressed disorder potential. These clean quantum point contacts indeed show transport features that are obscured by disorder in standard samples. From these transport data, we are able to extract those parameters of the confinement potential that describe its shape in the longitudinal and transverse directions. Knowing the shape (and hence the slope) of the confinement potential might be crucial for predicting which interaction-induced states can best form in quantum point contacts.

Rössler, C.; Baer, S.; de Wiljes, E.; Ardelt, P.-L.; Ihn, T.; Ensslin, K.; Reichl, C.; Wegscheider, W.

2011-11-01

255

Anisotropic magnetic and superconducting properties of aligned weak-ferromagnetic superconductor RuSr$_2$RCu$_2$O$_8$ (R = rare earths)  

Microsoft Academic Search

The powder alignment method is used to investigate the anisotropic physical properties of the weak-ferromagnetic superconductor system RuSr2RCu2O8 (R = Pr, Nd, Sm, Eu, Gd, Gd0.5Dy0.5). The RuSr2GdCu2O8 cuprate is a weak-ferromagnetic superconductor with a magnetic ordering of Ru moments at TN(Ru) = 131 K, a superconducting transition in the CuO2 layers at Tc = 56 K, and a low

B. C. Chang; C. H. Hsu; M. F. Tai; H. C. Ku; Y. Y. Hsu

2008-01-01

256

Carrier density dependences of anisotropic optical properties in closely stacked InAs/GaAs one-dimensional quantum dot superlattices  

NASA Astrophysics Data System (ADS)

We theoretically study the carrier density dependences of optical properties of closely stacked InAs/GaAs one-dimensional quantum dot superlattices based on the eight-band k.p theory. We find that the phonon assisted carrier injection into the ground state of both conduction and valence minibands is possible for small interdot spacings. We also predict that optical gain and spontaneous emission spectra show strongly anisotropic characters and can be controlled between [001]-, [110]-, [110]-polarization by injected carrier densities as well as interdot spacing. Our findings reveal interesting possibilities of quantum dot-based optoelectronic devices applications.

Kotani, Teruhisa; Lugli, Paolo; Hamaguchi, Chihiro

2013-07-01

257

Transport properties of molecular wires from ab initio calculations  

NASA Astrophysics Data System (ADS)

Understanding of electron transport through nanostructures becomes important with the advancement of fabrication process to construct atomic-scale devices. Due to the drastic change of transport properties by contact conditions to electrodes in local electric fields, first-principles calculation approaches are indispensable to understand and characterize the transport properties of nanometer-scale molecular devices. Here we focus on the transport properties of molecular wires bridged between metallic electrodes, especially on the effects of contacts to electrodes and on the dependence of the length of molecular wires on transport properties. We use an ab initio calculation method based on the scattering waves, which are obtained by the recursion-transfer-matrix (RTM) method, combined with non-equilibrium Green's function (NEGF) method. We find that conductance shows exponential behaviors as a function of the length of molecular wires due to tunneling process determined by the HOMO-LUMO energy gap. From the voltage drop behaviors inside the molecular wires, we show that the contact resistances are well separated for the long molecular wires. We will present detailed data of electronic states at contacts to metallic electrodes under strong electronic fields and will discuss the polarization, screening effect, and potential barrier formation at contacts on the transport properties of molecular wires, comparing them with those of metallic atomic wires.

Hirose, Kenji; Kobayashi, Nobuhiko

2008-03-01

258

Volume transport and property distributions of the Mozambique Channel  

Microsoft Academic Search

We summarize previous estimates of volume transport and property distributions through the Mozambique Channel and offer additional estimates and measurements based on recently acquired hydrographic and float data. Previously published property distributions are consistent with southward spreading through the Channel. Waters of the Mozambique Channel are characterized by shallow and intermediate oxygen minima separated by a relative maximum. Based on

Steven F. DiMarcoa; Piers Chapmana; Worth D. Nowlin Jr; Peter Hackerb; Gregory C. Johnsone; John Toolef

259

`Confined coherence' in strongly correlated anisotropic metals  

NASA Astrophysics Data System (ADS)

We present a detailed discussion of both theoretical and experimental evidence in favour of the existence of states of ‘confined coherence’ in metals of sufficiently high anisotropy and with sufficiently strong correlations. The defining property of such a state is that single electron coherence is confined to lower dimensional subspaces (planes or chains) so that it is impossible to observe interference effects between histories which involve electrons moving between these subspaces. The most dramatic experimental manifestation of such a state is the coexistence of incoherent non-metallic transport in one or two directions (transverse to the lower dimensional subspaces) with coherent transport in at least one other direction (within the subspaces). The magnitude of the Fermi surface warping due to transverse (intersubspace) momentum plays the role of an order parameter (in a state of confined coherence, this order parameter vanishes) and the effect can occur in a pure system at zero temperature. Our theoretical approach is to treat an anisotropic two (2D)- or three (3D)-dimensional electronic system as a collection of one (1D)- or two-dimensional electron liquids coupled by weak interliquid single-particle hopping. We find that a necessary condition for the destruction of coherent interliquid transport is that the intraliquid state be a non-Fermi liquid. We present a very detailed discussion of coupled 1D Luttinger liquids and the reasons for believing in the existence of a phase of confined coherence in that model. This provides a paradigm for incoherent transport between weakly coupled 2D non-Fermi liquids, the case relevant to the experiments of which we are aware. Specifically, anomalous transport data in the (normal state of the) cuprate superconductors and in the low temperature metallic state of the highly anisotropic organic conductor (TMTSF)2PF6 cannot be understood within a Fermi liquid framework, and, we argue, the only plausible way to understand that transport is in terms of a state of confined coherence.

Clarke, David G.; Strong, S. P.

1997-11-01

260

Ultrasonic polarization measurements of elastic-anisotropic properties of metamorphized rocks on the slit of the German KTB superdeep well in the 4100-7100 m depth range  

NASA Astrophysics Data System (ADS)

The KTB German Superdeep Well (Germany, Windischeschenbach) has limiting depth of 9101 m. It is one of the world deepest well among the continental boreholes. A study of physical parameters including elastic ones of the massif intersected by the well allowed to represent a real pattern of changing properties and the state of crystalline rocks in upper and middle part of the Earth crust. Such a deep section enables performing analyses of large spectrum of geological and geophysical objects, such as minerals, crystalline rocks, geological strata, formation complexes et al. Recently obtained results permit to get a general idea of elastic-anisotropic properties of crystalline rocks extracted from great depths. A study of properties and state of rocks along the KTB section will make it possible to most precisely determine regular changes of the Earth's rock properties within a large range of depths. Below are the results of investigation of elastic-anisotropic properties for 13 core samples of the KTB rocks in the range of 4.1 to 7.1 km. In this interval the well has penetrated metamorphosed rocks [1]. The measurements have been done by an acoustopolarization method with recent improvements and with devices for determination of sample elastic properties [2 3]. The data obtained are the result of extended study into the KTB rock samples by the method [4]. Study of rock samples from the KTB Superdeep Well in the 4100-7100 m depth range showed that they all are elastic anisotropic and pertain to a orthorhombic symmetry type. Virtually the degree of linear acoustic anisotropic absorption (LAAA) effect has been detected in all samples. Its appearance is likely related to directional orientation of mineral grains as well as to the generation of microcracks during drilling and lithostatic stress release. The several samples showed an angular unconformity between the LAAA orientation and elastic symmetry elements. The shear waves depolarization (DSW) effect was detected in garnet amphibolites samples. There was observed a tendency to persistence in propagation rate of compression and shear wave velocities. The pattern of change in anisotropy factors for compression and shear waves in depth shows itself in a similar way. There is an inverse correlation between density and anisotropy. R E F E R E N C E S 1. Emmermann R., Althaus E., Giese P., Stockhert B.. KTB Hauptbohrung. Results of Geoscientific Investigation in the KTB Field Laboratory. Final Report: 0-9101m. KTB Report 95-2. Hannover. 1995. 2. Gorbatsevich F.F. Acoustopolariscopy of rock forming minerals and crystalline rocks. Apatity, Kola Science Centre RAS, 2002, p. 140. (In Russian) 3. Kovalevskiy M.V. Automated hardware-software complex Acoustpol: Tutorial: Apatity, «K & M» Publ., 2009. 54p. (In Russian). 4. Kovalevsky M.V., Gorbatsevich F.F., Harms U., Dahlheim H.-A. Ultrasonic polarization measurements of elastic-anisotropic properties of metamorphized rocks on the slit of German KTB Superdeep Well // Geophysical magazine.- Geophysics Institute of NAS of Ukraine. -2012.- Issue 34.-#2.-P. 36-48. (In Russian)

Kovalevskiy, Mikhail

2013-04-01

261

Magnetic and transport properties of the ? alloys  

Microsoft Academic Search

Magnetization and transport measurements have been performed to study the martensitic and pre-martensitic transitions for a series of ferromagnetic Heusler 0953-8984\\/11\\/13\\/016\\/img10 alloys. Both magnetization and resistivity measurements show a clear jump at the martensitic transition and a discontinuous slope change at the pre-martensitic transition. The characteristic temperatures correspond well with those derived from previous direct structural results from neutron scattering,

F. Zuo; X. Su; P. Zhang; G. C. Alexandrakis; F. Yang; K. H. Wu

1999-01-01

262

Lagrangian transport properties of pulmonary interfacial flows.  

PubMed

Disease states characterized by airway fluid occlusion and pulmonary surfactant insufficiency, such as respiratory distress syndrome, have a high mortality rate. Understanding the mechanics of airway reopening, particularly involving surfactant transport, may provide an avenue to increase patient survival via optimized mechanical ventilation waveforms. We model the occluded airway as a liquid-filled rigid tube with the fluid phase displaced by a finger of air that propagates with both mean and sinusoidal velocity components. Finite-time Lyapunov exponent (FTLE) fields are employed to analyse the convective transport characteristics, taking note of Lagrangian coherent structures (LCSs) and their effects on transport. The Lagrangian perspective of these techniques reveals flow characteristics that are not readily apparent by observing Eulerian measures. These analysis techniques are applied to surfactant-free velocity fields determined computationally, with the boundary element method, and measured experimentally with micro particle image velocimetry (?-PIV). We find that the LCS divides the fluid into two regimes, one advected upstream (into the thin residual film) and the other downstream ahead of the advancing bubble. At higher oscillatory frequencies particles originating immediately inside the LCS experience long residence times at the air-liquid interface, which may be conducive to surfactant transport. At high frequencies a well-mixed attractor region is identified; this volume of fluid cyclically travels along the interface and into the bulk fluid. The Lagrangian analysis is applied to velocity data measured with 0.01 mg ml(-1) of the clinical pulmonary surfactant Infasurf in the bulk fluid, demonstrating flow field modifications with respect to the surfactant-free system that were not visible in the Eulerian frame. PMID:23049141

Smith, Bradford J; Lukens, Sarah; Yamaguchi, Eiichiro; Gaver, Donald P

2011-11-01

263

Properties of intracellular transport: the role of cytoskeleton topology  

NASA Astrophysics Data System (ADS)

The eukaryotic cytoskeleton is composed of polarized filaments forming a complex, intertwined network. Various motor proteins such as kinesins or myosins convert ATP into mechanical work and are able to walk processively or even diffuse along the cytoskeleton. Large organelles such as vesicles or mitochondria can randomly bind and unbind to one or several motors and their transport in the cell can be described as alternating phases of diffusion in the cytoplasm and phases of directed or diffusive transport along the cytoskeletal network. Intracellular transport has been the focus of extensive studies both experimentally and theoretically. However, the impact of the cytoskeleton network structure on transport properties, which is expected to be significant, is not fully understood. We develop a computational model of intracellular transport, and explore the impact of the cytoskeletal structure on transport properties. We show that transport can be enhanced even by diffusional motion along the cytoskeleton after memory effects due to cytoskeletal structure are taken into account. We also explore the influence of the network structure on the first passage time distributions for a cargo to reach the cell membrane after being exported from the nucleus and for transport from the membrane to the nucleus.

Korabel, Nickolay; Huang, Kerwyn C.; Gopinathan, Ajay

2013-03-01

264

Structure and properties of anisotropic gels and plasticized networks containing molecules with a smectic-A phase  

NASA Astrophysics Data System (ADS)

Liquid-crystal (LC) mixtures of a low-molar-mass LC diacrylate and 4-cyano-4'-octylbiphenyl (8CB) showing a smectic-A phase in the bulk were produced. The mixtures were aligned macroscopically and the polymerization was induced photochemically. In this way, anisotropic networks containing molecules which are not chemically attached to the network (anisotropic gels and plasticized networks) were produced. Using IR dichroism, it was found that, above the nematic-to-isotropic transition temperature of 8CB, a fraction of the molecules remained oriented. This behavior was associated with the presence of two populations of 8CB molecules within anisotropic gels and plasticized networks. One of the populations showed the same behavior as in the bulk (unbound fraction), while the other population was found to be influenced to a large extent by the network (bound fraction) and did not show a first-order nematic-to-isotropic transition. The behavior as observed by IR dichroism was simulated using a theoretical model and the fractions of the bound and unbound 8CB were estimated in systems containing various amounts of networks.

Hikmet, R. A. M.; Howard, R.

1993-10-01

265

Magnetic properties of isotropic and anisotropic CoFe2O4 -based ferrogels and their application as torsional and rotational actuators  

NASA Astrophysics Data System (ADS)

CoFe2O4 -based ferrogels were prepared with both isotropic and anisotropic orientation of the magnetic anisotropy axis of the magnetic particles. In contrast to the superparamagnetic properties of the ferrofluid, the ferrogels exhibit hysteresis, indicating that (i) a significant fraction of magnetic particles has volumes beyond the critical value that allows Néelian relaxation, and (ii) a mechanical interaction between the particles and the polymer network exists, which prevents the particles from Brownian relaxation. The contribution of such particles was investigated by field cooling field warming and zero field cooling field warming measurements as well as temperature-dependent magnetization measurements. By application of an external field during gel polymerization, a magnetic texture was induced as confirmed by the angular dependence of mR/mS and HC . The net-magnetic torque, exerted on the magnetic particles in an anisotropic ferrogel in combination with the soft elastic properties of the gel matrix enables the application as torsional soft actuator as demonstrated.

Monz, S.; Tschöpe, A.; Birringer, R.

2008-08-01

266

Magnetic properties of isotropic and anisotropic CoFe2O4-based ferrogels and their application as torsional and rotational actuators.  

PubMed

CoFe2O4-based ferrogels were prepared with both isotropic and anisotropic orientation of the magnetic anisotropy axis of the magnetic particles. In contrast to the superparamagnetic properties of the ferrofluid, the ferrogels exhibit hysteresis, indicating that (i) a significant fraction of magnetic particles has volumes beyond the critical value that allows Néelian relaxation, and (ii) a mechanical interaction between the particles and the polymer network exists, which prevents the particles from Brownian relaxation. The contribution of such particles was investigated by field cooling field warming and zero field cooling field warming measurements as well as temperature-dependent magnetization measurements. By application of an external field during gel polymerization, a magnetic texture was induced as confirmed by the angular dependence of mRmS and HC . The net-magnetic torque, exerted on the magnetic particles in an anisotropic ferrogel in combination with the soft elastic properties of the gel matrix enables the application as torsional soft actuator as demonstrated. PMID:18850833

Monz, S; Tschöpe, A; Birringer, R

2008-08-15

267

Thermodynamic and transport properties of sodium liquid and vapor  

SciTech Connect

Data have been reviewed to obtain thermodynamically consistent equations for thermodynamic and transport properties of saturated sodium liquid and vapor. Recently published Russian recommendations and results of equation of state calculations on thermophysical properties of sodium have been included in this critical assessment. Thermodynamic properties of sodium liquid and vapor that have been assessed include: enthalpy, heat capacity at constant pressure, heat capacity at constant volume, vapor pressure, boiling point, enthalpy of vaporization, density, thermal expansion, adiabatic and isothermal compressibility, speed of sound, critical parameters, and surface tension. Transport properties of liquid sodium that have been assessed include: viscosity and thermal conductivity. For each property, recommended values and their uncertainties are graphed and tabulated as functions of temperature. Detailed discussions of the analyses and determinations of the recommended equations include comparisons with recommendations given in other assessments and explanations of consistency requirements. The rationale and methods used in determining the uncertainties in the recommended values are also discussed.

Fink, J.K.; Leibowitz, L.

1995-01-01

268

Transport properties of n-type ultrananocrystalline diamond films  

Microsoft Academic Search

We investigate transport properties of ultrananocrystalline diamond films for\\u000aa broad range of temperatures. Addition of nitrogen during plasma-assisted\\u000agrowth increases the conductivity of ultrananocrystalline diamond films by\\u000aseveral orders of magnitude. We show that films produced at low concentration\\u000aof nitrogen in the plasma are very resistive and electron transport occurs via\\u000aa variable range hopping mechanism while in

I. S. Beloborodov; P. Zapol; D. M. Gruen; L. A. Curtiss

2006-01-01

269

Transport properties of high-temperature Jupiter atmosphere components  

SciTech Connect

Transport properties of high-temperature helium and hydrogen plasmas as well as Jupiter atmosphere have been calculated for equilibrium and nonequilibrium conditions using higher approximations of the Chapman-Enskog method. A complete database of transport cross sections for relevant interactions has been derived, including minority species, by using both ab initio and phenomenological potentials. Inelastic collision integrals terms, due to resonant charge-exchange channels, have been also considered.

Bruno, D.; Colonna, G.; De Pascale, O.; Laricchiuta, A. [Department of Chemistry, University of Bari, via Orabona 4 Bari 70125 (Italy); Catalfamo, C.; Diomede, P. [CNR-IMIP Bari, via Orabona 4 Bari 70125 (Italy); Capitelli, M.; Gorse, C.; Longo, S. [Department of Chemistry, University of Bari, via Orabona 4 Bari 70125 (Italy); CNR-IMIP Bari, via Orabona 4 Bari 70125 (Italy); Giordano, D. [Aerothermodynamics Section, ESA-ESTEC, Keplerlaan 1 2200 AG Noordwijk (Netherlands); Pirani, F. [Department of Chemistry, University of Perugia, via Elce di Sotto 8 Perugia 06123 (Italy)

2010-11-15

270

Momentum and spin transport properties of spin polarized Fermi systems  

Microsoft Academic Search

We carried out experiments on a spin polarized 3He- 4He mixture with 3He concentration x 3 = 6.26 x 10-4, and on pure 3He liquid. Spin polarization affects the transport properties of these Fermi systems. The effect on momentum transport was studied by using a vibrating-wire viscometer to measure viscosity of the 3He-4He mixture over the temperature range 6.09 mK--100

Lijuan Wei

2001-01-01

271

Applying distributions of hydraulic conductivity for anisotropic systems and applications to Tc Transport at the U.S. Department of Energy Hanford Site  

SciTech Connect

43Tc99 is spreading mostly laterally through the U.S. Department of Energy Hanford site sediments. At higher tensions in the unsaturated zone, the hydraulic conductivity may be strongly anisotropic as a consequence of finer soils to retain more water than coarser ones, and for these soils to have been deposited primarily in horizontal structures. We have tried to develop a consistent modeling procedure that could predict the behavior of Tc plumes. Our procedure consists of: (1) Adapting existing numerical recipes based on critical path analysis to calculate the hydraulic conductivity, K, as a function of tension, h, (2) Statistically correlating the predicted K at various values of the tension with fine content, (3) Seeking a tension value, for which the anisotropy and the horizontal K values are both sufficiently large to accommodate multi-kilometer spreading, (4) Predicting the distribution of K values for vertical flow as a function of system support volume, (5) Comparing the largest likely K value in the vertical direction with the expected K in the horizontal direction, (6) Finding the length scale at which the two K values are roughly equal, (7) Comparing that length scale with the horizontal spreading of the plume. We find that our predictions of the value of the tension at which the principle spreading is likely occurring compares very well with experiment. However, we seem to underestimate the physical length scale at which the predominantly horizontal spreading begins to take on significant vertical characteristics. Our data and predictions would seem to indicate that this should happen after horizontal transport of somewhat over a km, but the chiefly horizontal transport appears to continue out to scales of 10km or so.

Allen G Hunt

2008-06-09

272

Floating zone growth and anisotropic magnetic properties of Pr1/2+ySr1/2-yMnO3 single crystal  

NASA Astrophysics Data System (ADS)

Single crystal bar of Pr1/2+ySr1/2-yMnO3 was successfully prepared by the floating zone growth method, which shows evident anisotropic properties, indicating good quality of crystal. Magnetic measurements were performed on several chips taken from the crystal and three kinds of different magnetic behaviors were found at low temperatures for the half doped Pr1/2+ySr1/2-yMnO3 system. The results reveal that slight inhomogeneous element distribution of the crystal obtained by floating zone growth method may be inevitable, but even a slight change of Sr ratio does affect the physical properties of the sample ultimately. Therefore, doped rare-earth manganites is a system strongly depends on the ratio of Mn3+/Mn4+, i.e., the content of the divalent alkaline-earth element.

Kang, Baojuan; Cao, Shixun; Wang, Xinyan; Yuan, Shujuan; Qin, Xiaoling; Zhang, Jincang

2013-01-01

273

TRANSPORT  

EPA Science Inventory

Presentation outline: transport principles, effective solubility; gasoline composition; and field examples (plume diving). Presentation conclusions: MTBE transport follows from - phyiscal and chemical properties and hydrology. Field examples show: MTBE plumes > benzene plu...

274

Thermal transport properties of rolled graphene nanoribbons  

NASA Astrophysics Data System (ADS)

Using nonequilibrium Green's function method, we investigate the influence of the curvature and edge effects on the thermal transport during the process of rolling graphene nanoribbons (GNRs) into carbon nanotubes (CNTs) in the transverse direction. The curvature effect results in a slight decrease in the thermal conductance of GNRs, which is remarkably different from that in the longitudinal direction. The curvature and edge effects show a strong size and chirality dependence, while the curvature effect is more sensitive to the size. When the size equals to 12.8 nm (49.2 nm) with the zigzag (armchair) edge, the edge effect results in the reduction of thermal conductance of 2.4% (13.0%) as compared to the corresponding CNT, but the curvature effect vanishes.

Li, Dengfeng; Li, Bolin; Luo, Min; Feng, Chunbao; Ouyang, Tao; Gao, Fei

2013-08-01

275

Exact quantum scattering calculations of transport properties: CH2(X~3B1, a~1A1)-helium  

NASA Astrophysics Data System (ADS)

Transport properties for collisions of methylene, in both its ground X~3B1 and low-lying a~1A1 electronic states, with helium have been computed using recently computed high-quality ab initio potential energy surfaces (PESs). Because of the difference in the orbital occupancy of the two electronic states, the anisotropies of the PESs are quite different. The CH2(a~)-He PES is very anisotropic because of the strong interaction of the electrons on the helium atom with the unoccupied CH2 orbital perpendicular to the molecular plane, while the anisotropy of the CH2(X~)-He PES is significantly less since this orbital is singly occupied in this case. To investigate the importance of the anisotropy on the transport properties, calculations were performed with the full potential and with the spherical average of the potential for both electronic states. Significant differences (over 20% for the a~ state at the highest temperatures considered) in the computed transport properties were found.

Dagdigian, Paul J.; Alexander, Millard H.

2013-04-01

276

Exact quantum scattering calculations of transport properties: CH2(X?3B1, a?1A1)-helium.  

PubMed

Transport properties for collisions of methylene, in both its ground X?(3)B1 and low-lying a?(1)A1 electronic states, with helium have been computed using recently computed high-quality ab initio potential energy surfaces (PESs). Because of the difference in the orbital occupancy of the two electronic states, the anisotropies of the PESs are quite different. The CH2(a?)-He PES is very anisotropic because of the strong interaction of the electrons on the helium atom with the unoccupied CH2 orbital perpendicular to the molecular plane, while the anisotropy of the CH2(X?)-He PES is significantly less since this orbital is singly occupied in this case. To investigate the importance of the anisotropy on the transport properties, calculations were performed with the full potential and with the spherical average of the potential for both electronic states. Significant differences (over 20% for the a? state at the highest temperatures considered) in the computed transport properties were found. PMID:23635136

Dagdigian, Paul J; Alexander, Millard H

2013-04-28

277

Transport Properties of Ni and PbTe Under Pressure  

NASA Astrophysics Data System (ADS)

The high-pressure transport properties have been determined for nickel and PbTe. Nickel shows a reduction in electrical resistivity, an increase in thermal conductivity, and a variable effect on the Seebeck coefficient with pressure. In PbTe, a dramatic decrease in resistivity and a slow increase in thermal conductivity have been observed with increasing pressure. The three transport properties in PbTe are affected by a pressure-induced structural phase transition. The measurements show that the high-pressure phase is likely a more effective thermoelectric material than the ambient-pressure phase.

Jacobsen, Matthew K.; Kumar, Ravhi S.; Cornelius, Andrew L.

2012-04-01

278

68 FR 46428 - Revised Requirement for Material Strength Properties and Design Values for Transport Airplanes  

Federal Register 2010, 2011, 2012, 2013

...Requirement for Material Strength Properties and Design Values for Transport Airplanes; Final...Requirement for Material Strength Properties and Design Values for Transport Airplanes AGENCY...material strength properties and material design values. It incorporates changes...

2003-08-05

279

Variational nodal perturbation theory with anisotropic scattering  

SciTech Connect

The variational nodal perturbation method previously developed in two- and three-dimensional Cartesian and hexagonal geometries using the diffusion and full or simplified spherical harmonics transport approximations, is extended to treat problems with anisotropic scattering. The requisite solution to the adjoint transport equation with anisotropic scattering in formulated and incorporated into the VARIANT (VARIational Anisotropic Nodal Transport) option of the Argonne National Laboratory DIF3D production code. The method, which calculates changes in the critical eigenvalue due to perturbations arising from changes in the material cross sections, is demonstrated by applying perturbations to an anisotropic hexagonal benchmark. Exact and first order perturbation theory are used to calculate changes in the critical eigenvalue and compared to the change obtained by direct calculation in VARIANT. The time savings obtained by using perturbation theory is substantial; times for base forward and adjoint calculations are much greater than the times for perturbation calculations.

Laurin-Kovitz, K.F.; Palmiotti, G. [Argonne National Lab., IL (United States); Lewis, E.E. [Northwestern Univ., Evanston, IL (United States). Dept. of Mechanical Engineering

1997-09-01

280

Single tube electric transport properties of synthesized Titania nanotubes  

NASA Astrophysics Data System (ADS)

Titania nanotube arrays fabricated by means of electrochemical anodization is currently the main interest of several research groups due to its promising applications. The high aspect ratio, durability, cheap and scalable fabrication technique make it highly attractive material for efficient solar cell. In this regard extensive research work is being carried out to investigate its properties. In our previous work we were able to find a mechanism for separating a single titania nanotube from the titania nanotube arrays and to measure its electric transport properties using e-beam lithography technique, In this work we investigated the effect of thermal annealing on the transport properties, we studied the effect of different annealing temperatures, heating and cooling rates, and in different gases. As a result, we were able to find the optimal annealing conditions to enhance the transport properties in blank titania nanotube. Under these optimal conditions, we were able to study the effect of coating TNTs with N719 dye and gold nanoparticles on the transport properties. As a result of our work we were able to optimize the treatments for more efficient solar cell fabrication.

Abdelmoula, Mohamed; Menon, Latika

2011-03-01

281

Methods for conditioning anisotropic, operator-scaling, fractal random fields, and the effect on solute transport simulations  

Microsoft Academic Search

The fractal scaling of aquifer materials have been observed in many data sets. Typically, the scaling coefficient is different in different directions. To date, only unconditional realizations with these properties can be generated. We present and analyze two methods of creating conditional operator-scaling fractal random fields (OSFRF) which have the ability to condition any number and geometry of measurements into

J. Revielle; D. A. Benson

2008-01-01

282

Transport properties of strong-interaction matter  

NASA Astrophysics Data System (ADS)

The properties of matter under conditions dominated by the strong-interaction are probed in ultra-relativistic heavyion collisions. In connection with measurements of the elliptic flow at RHIC and the LHC the shear viscosity is of particular interest. In this talk I discuss recent results for ?/s in hadronic matter at vanishing baryo-chemical potential within kinetic theory. Using the Nambu Jona-Lasinio model, special attention is paid to effects arising from the restoration of spontaneously broken chiral symmetry with increasing temperature.

Wambach, Jochen

2012-04-01

283

A nonlinear anisotropic model for porcine aortic heart valves  

Microsoft Academic Search

The anisotropic property of porcine aortic valve leaflet has potentially significant effects on its mechanical behaviour and the failure mechanisms. However, due to its complex nature, testing and modelling the anisotropic porcine aortic valves remains a continuing challenge to date. This study has developed a nonlinear anisotropic finite element model for porcine heart valves. The model is based on the

J. Li; X. Y. Luo; Z. B. Kuang

2001-01-01

284

Active transport properties of porcine choroid plexus cells in culture.  

PubMed

We have investigated the transport properties of cultured porcine choroid plexus cells grown on permeable membranes and in serum-free medium. Withdrawal of serum yielded cell cultures with permeabilities low enough to establish and maintain a pH-gradient between the two compartments of the filter system and to allow apical fluid secretion. This became possible because of ten-fold increased electrical resistance of 1700 Omega cm2 in the absence of serum. These plexus epithelial cells transported phenol red, fluorescein, riboflavin and penicillin G from the apical to the basolateral side. KM values and vmax were determined and come close to in vivo values. Competitive inhibition with probenicid showed that the organic anion transporter is involved. Riboflavin transport however was not completely inhibited and did not respond quantitatively to the stilben derivate SITS that blocks the Cl-/HCO3--exchanger. We assume that an additional transport system exists for riboflavin. Ascorbic acid and myo-inositol were transported from the basolateral to the apical side in vitro which strongly resembles the in vivo transport from the blood to the cerebrospinal fluid. Again the experimental in vitro KM values come close to the in vivo values. The established epithelial cell culture model thus closely mimics the blood-CSF-barrier and may be a useful tool to further elucidate transport to and from the brain. PMID:9622643

Hakvoort, A; Haselbach, M; Galla, H J

1998-06-01

285

High pressure studies of the transport properties of ionic liquids.  

PubMed

High pressure measurements have been made of viscosities, ion self-diffusion coefficients and electrical conductivities of ionic liquids, mainly of imidazolium salts. We review how these properties have been analysed in terms of the empirical Stokes-Einstein, Walden and Nernst-Einstein equations, and examine trends revealed by the phenomenological approach of velocity correlation coefficients and the more general theory of density scaling. Finally we examine the possibility of dynamic crossover in the transport properties of ionic liquids. PMID:22455034

Harris, Kenneth R; Kanakubo, Mitsuhiro

2012-01-01

286

Hybrid silica-polyimide composite membranes: gas transport properties  

Microsoft Academic Search

The gas permeability, diffusivity, and selectivity properties of gases such as He, O2, N2, CH4, and CO2 were evaluated for a series of hybrid inorganic–organic composites based on 6FDA-6FpDA and 6FDA-6FpDA-DABA polyimides and various organo-silica structures. The organo-silica domains were introduced into the polymer matrix via sol–gel reactions. The gas transport properties of these hybrid membranes were dependent on the

Chris J. Cornelius; Eva Marand

2002-01-01

287

Multiple-pumped-well aquifer test to determine the anisotropic properties of a karst limestone aquifer in Pasco County, Florida, USA  

NASA Astrophysics Data System (ADS)

Groundwater-level data from an aquifer test utilizing four pumped wells conducted in the South Pasco wellfield in Pasco County, Florida, USA, were analyzed to determine the anisotropic transmissivity tensor, storativity, and leakance in the vicinity of the wellfield. A weighted least-squares procedure was used to analyze drawdowns measured at eight observation wells, and it was determined that the major axis of transmissivity extends approximately from north to south and the minor axis extends approximately from west to east with an angle of anisotropy equal to N4.54°W. The transmissivity along the major axis {( {T_{{? ? }} } )} is 14,019 m2 day-1, and the transmissivity along the minor axis {( {T_{{? ? }} } )} is 4,303 m2 day-1. The equivalent transmissivity Te = {( {T_{{? ? }} T_{{? ? }} } )}^{1/2} = 7,767{{m}2 } day^{-1}, and the ratio of anisotropy is 3.26. The storativity of the aquifer is 7.52 × 10-4, and the leakance of the overlying confining unit is 1.37 × 10-4 day-1. The anisotropic properties determined for the South Pasco wellfield in this investigation confirm the results of previous aquifer tests conducted in the wellfield and help to quantify the NW-SE to NE-SW trends for regional fracture patterns and inferred solution-enhanced flow zones in west-central Florida.

Motz, Louis H.

2009-06-01

288

Application of differential effective medium, magnetic pore fabric analysis, and X-ray microtomography to calculate elastic properties of porous and anisotropic rock aggregates  

NASA Astrophysics Data System (ADS)

A differential effective medium (DEM) model is used to predict elastic properties for a set of porous and anisotropic aggregates, comprised of mixtures of calcite and muscovite. The DEM takes into consideration an anisotropic background medium with triclinic or higher symmetry, in which inclusions of idealized ellipsoidal shape are added incrementally. In general, the calculated elastic properties of a solid that contains inclusions representing "dry" pores/cracks are strongly dependent on the orientation and aspect ratio of the inclusions. Aspect ratios of inclusions in the synthetic aggregates, which consist of air-filled pores, are estimated from anisotropy of magnetic susceptibility (AMS) of samples whose pore space has been impregnated with a colloidal ferrofluid. The AMS derived pore shape geometry is used as an input value for inclusions in the DEM. Modeling results are compared with laboratory determined elastic properties, measured with ultrasonic waves. Calculated shear wave velocities agree in general well with laboratory measured S wave velocities, whereas calculated P wave velocities are typically 0.5-1.1 km/s higher than measured values. Differences between calculated and measured P wave velocities are attributed mainly to incomplete and biased ferrofluid saturation of pores. Spherical pores are preferably filled during imbibition, in comparison to thin cracks, which leads to overprediction of the calculated P wave velocities. The amount of ferrofluid that fills the pore space is dependent on the ratio of calcite to muscovite and the load used for compaction during sample synthesis. The permeability decreases with increasing muscovite content and increasing compaction load. Incomplete saturation of samples with high-muscovite content is confirmed by X-ray microtomography density contrast imaging of dry and ferrofluid saturated specimens.

Almqvist, Bjarne S. G.; Mainprice, David; Madonna, Claudio; Burlini, Luigi; Hirt, Ann M.

2011-01-01

289

Transport properties of Nb/PdNi bilayers  

NASA Astrophysics Data System (ADS)

The transport properties of superconductor/weak ferromagnet Nb/Pd86Ni14 sputtered bilayers have been studied. The critical thickness needed for superconductivity to develop is determined from the dependence of the transition temperature Tc on dNb.

Cirillo, C.; Prischepa, S. L.; Salvato, M.; Attanasio, C.

2006-01-01

290

Thermal Transport Properties of Polycrystalline Diamond Films and Other Composites  

Microsoft Academic Search

The thermal transport properties of three chemical vapor deposition (CVD) polycrystalline diamond films of different isotopic compositions and other advanced composites have been measured as a function of temperature by using steady and non-steady state techniques. The results of these measurements have been analyzed by using existing theories and models. The Klemens-Callaway model has been used to fit the thermal

Kalayu G. Belay

1994-01-01

291

Economic Growth, Property Valuation Change, and Transportation Investments  

Microsoft Academic Search

Transportation related infrastructure investment is closely linked to economic performance of a region. In assessing the role of transporta- tion investment in economic growth, it is important to refine the spatial detail of analysis and to use effective data analysis techniques. As an alternative to county level data, property tax data that is collected an- nually can be used to

DAVID SWENSON; LIESL EATHINGTON; DANIEL OTTO

292

Transport properties of solid oxide electrolyte ceramics: a brief review  

Microsoft Academic Search

This work is centered on the comparative analysis of oxygen ionic conductivity, electronic transport properties and thermal expansion of solid electrolyte ceramics, providing a brief overview of the materials having maximum potential performance in various high-temperature electrochemical devices, such as solid oxide fuel cells (SOFCs). Particular emphasis is focused on the oxygen ionic conductors reported during the last 10–15 years,

V. V. Kharton; F. M. B. Marques; A. Atkinson

2004-01-01

293

Investigation of mass transport properties of microfibrillated cellulose (MFC) films  

Microsoft Academic Search

The structure and transport properties of a four different films based on two different generations of microfibrillated cellulose (MFC), alone or in combination with glycerol as plasticizer, were investigated through FE-SEM analysis and sorption or permeation experiments. FE-SEM revealed the existence of complex structures in the different samples. A porous, closely packed fiber network, more homogeneous in the samples containing

Matteo Minelli; Marco Giacinti Baschetti; Ferruccio Doghieri; Mikael Ankerfors; Tom Lindström; István Siró; David Plackett

2010-01-01

294

Electronic and Transport Properties of Boron-Doped Graphene Nanoribbons  

Microsoft Academic Search

We report a spin polarized density functional theory study of the electronic and transport properties of graphene nanoribbons doped with boron atoms. We considered hydrogen terminated graphene (nano)ribbons with width up to 3.2 nm. The substitutional boron atoms at the nanoribbon edges (sites of lower energy) suppress the metallic bands near the Fermi level, giving rise to a semiconducting system.

T. B. Martins; R. H. Miwa; Antônio J. R. da Silva; A. Fazzio

2007-01-01

295

Receptor and transport properties of imprinted polymer membranes – a review  

Microsoft Academic Search

Over the last 10 years new types of polymeric materials with molecular recognition sites for low-weight organic substances have been prepared using the molecular imprinting approach. In this review paper, in particular, the recognition and transport properties of molecularly imprinted polymer (MIP) membranes prepared thus far are summarized and analyzed. Microporous and macroporous MIP membranes show the same receptor but

S. A Piletsky; T. L Panasyuk; E. V Piletskaya; I. A Nicholls; M Ulbricht

1999-01-01

296

Transport properties of single wall carbon nanotubes  

NASA Astrophysics Data System (ADS)

In this thesis, we study the properties of macroscopic samples of single walled carbon nanotubes (SWNT) in the form of buckypapers and fibers, and how these properties are affected by doping, alignment and C60 filling. A metal-insulator (MI) transition in macroscopic SWNT conductors is revealed by systematic measurements of resistivity, rho(T), and transverse magnetoresistance, MR(B), as a function of p-type redox doping. In the insulating regime, the rho( T) can be described by variable-range hopping (VRH) mechanism. The MR(B) and rho(T) of strongly doped samples are best described by a weak localization (WL) model. The 1D character of the electronic and phonon spectra becomes apparent in the thermopower (TEP) of strongly doped samples. In contrast to weakly doped samples, TEP is small at the lowest temperatures, and then increases at a characteristic temperature which depends on the position of the Fermi energy. We attribute this unusual behavior to 1D phonon drag, in which the electron-phonon interaction is restricted to phonons with the appropriate wave-vector. This idea is supported by a model calculation in which the low T behavior of phonon drag is specifically related to the one-dimensional character of the electronic spectrum. TEP data are correlated with optical reflectivity, Raman spectroscopy, mass loss and resistivity measurements. We performed the careful dedoping of H2SO4 doped samples and in situ measurements of the temperature dependence of TEP. It is found that the effect of H2SO4 doping is to change the Fermi energy and not to introduce new features into DOS of SWNTs. A model is developed which can explain some of the features observed in the diffusion TEP. Filling SWNTs with C60 molecules does not have a considerable effect on p and TEP of macroscopic samples and only very weak effect on heat capacity and thermal conductivity is expected. A possibility of observing cluster dynamics using diffraction methods is discussed. We show that the conduction mechanism in bulk SWNT samples is not affected by a partial nanotube alignment. The effect of alignment on rho can be described by a proportionality factor, which depends on the number of rope-rope contacts along the most probable conduction path.

Vavro, Juraj

297

Measurement of gas transport properties for chemical vapor infiltration  

SciTech Connect

In the chemical vapor infiltration (CVI) process for fabricating ceramic matrix composites (CMCs), transport of gas phase reactant into the fiber preform is a critical step. The transport can be driven by pressure or by concentration. This report describes methods for measuring this for CVI preforms and partially infiltrated composites. Results are presented for Nicalon fiber cloth layup preforms and composites, Nextel fiber braid preforms and composites, and a Nicalon fiber 3-D weave composite. The results are consistent with a percolating network model for gas transport in CVI preforms and composites. This model predicts inherent variability in local pore characteristics and transport properties, and therefore, in local densification during processing; this may lead to production of gastight composites.

Starr, T.L.; Hablutzel, N. [Georgia Inst. of Tech., Atlanta, GA (United States). School of Materials Science and Engineering

1996-12-01

298

Local transport properties of ferromagnetic tunnel junctions  

NASA Astrophysics Data System (ADS)

The local electrical properties were measured simultaneously with the topography for a SiO2/Ta(3nm)/ Fe20Ni80(3nm) /Pt(20nm)/Fe20Ni80(3nm) /IrMn(10nm)/Co75Fe25(4nm)/Al(0.8nm)-oxide junction. The current image became very homogeneous and smooth after annealing at around 300?C for 1h. Increase of tunneling magnetoresistance ratio of the junction after annealing can be well explained by taking into account both increase of the barrier height and decrease of the barrier height variation. After further annealing over 350?C, the barrier height decreased and leak currents were detected. Reduction of spin polarization of the ferromagnetic electrodes due to interface mixing or damage of the insulator due to the growth of grains of bottom electrode is a possible reason for the drastic decrease of TMR ratio for annealing at temperatures higher than 350?C.

Ando, Y.; Hayashi, M.; Kamijo, M.; Kubota, H.; Miyazaki, T.

2001-05-01

299

Epitaxial growth and electrical transport properties of Cr2GeC thin films  

NASA Astrophysics Data System (ADS)

Cr2GeC thin films were grown by magnetron sputtering from elemental targets. Phase-pure Cr2GeC was grown directly onto Al2O3(0001) at temperatures of 700-800 °C. These films have an epitaxial component with the well-known epitaxial relationship Cr2GeC(0001)//Al2O3(0001) and Cr2GeC(112¯0)//Al2O3(11¯00) or Cr2GeC(112¯0)//Al2O3(1¯21¯0). There is also a large secondary grain population with (101¯3) orientation. Deposition onto Al2O3(0001) with a TiN(111) seed layer and onto MgO(111) yielded growth of globally epitaxial Cr2GeC(0001) with a virtually negligible (101¯3) contribution. In contrast to the films deposited at 700-800 °C, the ones grown at 500-600 °C are polycrystalline Cr2GeC with (101¯0)-dominated orientation; they also exhibit surface segregations of Ge as a consequence of fast Ge diffusion rates along the basal planes. The room-temperature resistivity of our samples is 53-66 ??cm. Temperature-dependent resistivity measurements from 15-295 K show that electron-phonon coupling is important and likely anisotropic, which emphasizes that the electrical transport properties cannot be understood in terms of ground state electronic structure calculations only.

Eklund, Per; Bugnet, Matthieu; Mauchamp, Vincent; Dubois, Sylvain; Tromas, Christophe; Jensen, Jens; Piraux, Luc; Gence, Loïk; Jaouen, Michel; Cabioc'H, Thierry

2011-08-01

300

Electronic transport properties through ZGNR/BNAM/ZGNR  

NASA Astrophysics Data System (ADS)

We present a theoretical study of electron transport properties through boron-nitride aromatic molecules (BNAMs) embedded between two zig-zag graphene nanoribbons (ZGNRs), which are considered as electrodes. The work is based on a tight-binding Hamiltonian model within the framework of a generalized Green's function technique and relies on the Landauer-Bütikker formalism as the basis for studying the current-voltage characteristic of this system. It is shown that the current can decrease at a finite value of voltage and the electron transport can open a conduction gap in the ZGNR/BNAM/ZGNR structure.

Ashhadi, M.; Ketabi, S. A.

2012-09-01

301

Intrinsic electronic and transport properties of graphyne sheets and nanoribbons  

NASA Astrophysics Data System (ADS)

Graphyne, a two-dimensional carbon allotrope like graphene but containing doubly and triply bonded carbon atoms, has been proven to possess amazing electronic properties as graphene. Although the electronic, optical, and mechanical properties of graphyne and graphyne nanoribbons (NRs) have been previously studied, their electron transport behaviors have not been understood. Here we report a comprehensive study of the intrinsic electronic and transport properties of four distinct polymorphs of graphyne (?, ?, ?, and 6,6,12-graphynes) and their nanoribbons (GyNRs) using density functional theory coupled with the non-equilibrium Green's function (NEGF) method. Among the four graphyne sheets, 6,6,12-graphyne displays notable directional anisotropy in the transport properties. Among the GyNRs, those with armchair edges are nonmagnetic semiconductors whereas those with zigzag edges can be either antiferromagnetic or nonmagnetic semiconductors. Among the armchair GyNRs, the ?-GyNRs and 6,6,12-GyNRs exhibit distinctive negative differential resistance (NDR) behavior. On the other hand, the zigzag ?-GyNRs and zigzag 6,6,12-GyNRs exhibit symmetry-dependent transport properties, that is, asymmetric zigzag GyNRs behave as conductors with nearly linear current-voltage dependence, whereas symmetric GyNRs produce very weak currents due to the presence of a conductance gap around the Fermi level under finite bias voltages. Such symmetry-dependent behavior stems from different coupling between ?* and ? subbands. Unlike ?- and 6,6,12-GyNRs, both zigzag ?-GyNRs and zigzag ?-GyNRs exhibit NDR behavior regardless of the symmetry.Graphyne, a two-dimensional carbon allotrope like graphene but containing doubly and triply bonded carbon atoms, has been proven to possess amazing electronic properties as graphene. Although the electronic, optical, and mechanical properties of graphyne and graphyne nanoribbons (NRs) have been previously studied, their electron transport behaviors have not been understood. Here we report a comprehensive study of the intrinsic electronic and transport properties of four distinct polymorphs of graphyne (?, ?, ?, and 6,6,12-graphynes) and their nanoribbons (GyNRs) using density functional theory coupled with the non-equilibrium Green's function (NEGF) method. Among the four graphyne sheets, 6,6,12-graphyne displays notable directional anisotropy in the transport properties. Among the GyNRs, those with armchair edges are nonmagnetic semiconductors whereas those with zigzag edges can be either antiferromagnetic or nonmagnetic semiconductors. Among the armchair GyNRs, the ?-GyNRs and 6,6,12-GyNRs exhibit distinctive negative differential resistance (NDR) behavior. On the other hand, the zigzag ?-GyNRs and zigzag 6,6,12-GyNRs exhibit symmetry-dependent transport properties, that is, asymmetric zigzag GyNRs behave as conductors with nearly linear current-voltage dependence, whereas symmetric GyNRs produce very weak currents due to the presence of a conductance gap around the Fermi level under finite bias voltages. Such symmetry-dependent behavior stems from different coupling between ?* and ? subbands. Unlike ?- and 6,6,12-GyNRs, both zigzag ?-GyNRs and zigzag ?-GyNRs exhibit NDR behavior regardless of the symmetry. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03167e

Wu, Wenzhi; Guo, Wanlin; Zeng, Xiao Cheng

2013-09-01

302

Anisotropic etching of silicon  

Microsoft Academic Search

Anisotropic etching of silicon has become an important technology in silicon semiconductor processing during the past ten years. It will continue to gain stature and acceptance as standard processing technology in the next few years. Anisotropic etching of

K. E. Bean

1978-01-01

303

Transport properties of two finite armchair graphene nanoribbons  

NASA Astrophysics Data System (ADS)

In this work, we present a theoretical study of the transport properties of two finite and parallel armchair graphene nanoribbons connected to two semi-infinite leads of the same material. Using a single ?-band tight binding Hamiltonian and based on Green's function formalisms within a real space renormalization techniques, we have calculated the density of states and the conductance of these systems considering the effects of the geometric confinement and the presence of a uniform magnetic field applied perpendicularly to the heterostructure. Our results exhibit a resonant tunneling behaviour and periodic modulations of the transport properties as a function of the geometry of the considered conductors and as a function of the magnetic flux that crosses the heterostructure. We have observed Aharonov-Bohm type of interference representing by periodic metal-semiconductor transitions in the DOS and conductance curves of the nanostructures.

Rosales, Luis; González, Jhon W.

2013-01-01

304

Considerations on the transport-theorem for extensive flow properties  

NASA Astrophysics Data System (ADS)

Two methods are presented for derivation of the transport theorem for volume and line properties, particularly the Reynolds transport and Thomson circulation theorems. The substantial time derivatives of the velocity field (including the density), the fluid volume, mass, momentum, kinetic and internal energies, enthalpy, and entropy, and a constant mass line that continually flows with the fluid are defined. The volume integral is then used to obtain the Reynolds transort theorem on a time differencing basis, allowing integration to be performed for a volume fixed in space. Alternatively, the volume can be treated as constant and the mass can be integrated over time within the bounds of the integration. For the Thomson theorem, the substantial time derivatives are volume properties determined from the line integral of the velocity of the circulation along a closed material line, or of the mass over a length of the flow.

Truckenbrodt, E.

305

Generalized thermodynamic and transport properties. I. Simple liquids.  

PubMed

We propose a method by which the generalized transport properties and coefficients at all wavelengths and frequencies can be obtained by inversion of an exact kinetic equation. The necessary data are the density-density, energy-energy, and density-energy time correlation functions, which can be obtained by molecular-dynamics simulation. In addition, also the coupling between viscous stress tensor and energy flux vector can be obtained without approximation. This allows one to check the validity of the Markov assumption in a straightforward way. As a first test case, the theory is applied to liquid argon in two thermodynamic states. For this system, we calculate and discuss generalized thermodynamic (enthalpy, specific heats, and thermal expansion) and transport properties (longitudinal viscosity, thermal conductivity). PMID:21517485

Bertolini, D; Tani, A

2011-03-11

306

LFN and LSCFN perovskites — structure and transport properties  

Microsoft Academic Search

Structural, electronic and transport properties of LFN (LaFe1?zNizO3) and LSCFN (La1?xSrxCo1?y?zFeyNizO3) perovskites synthesized by a modified citric acid method were studied. Structure of the samples was characterized by X-ray studies with Rietveld method analysis. Magnetic properties and valence states of iron ions were characterized by 57Fe Moessbauer spectroscopy performed at RT, which were found to be greatly dependent on the

K. ?wierczek; J. Marzec; D. Pa?ubiak; W. Zaj?c; J. Molenda

2006-01-01

307

Engineered microstructures and transport properties in YBCO coated conductors.  

SciTech Connect

Each process used to deposit or make the bi-axially textured template, buffer layer(s), and the superconductor in a coated conductor creates interfaces along which defects or interfacial reactions may result. These defects can be additive and propagate through the entire film structure to affect the growth and properties of the superconducting film. Defects within the films and their corresponding transport properties have been correlated with the differences in the thickness of the underlying buffer layer material. This knowledge can be used to control and engineer the structure of the coated conductor to maximize critical current densities.

Holesinger, T. G. (Terry G.); Gibbons, B. J. (Brady J.); Coulter, J. Y. (James Y.); Foltyn, S. R. (Stephen R.); Arendt, P. N. (Paul N.)

2001-01-01

308

Transport Properties of Carbon-Nanotube/Cement Composites  

NASA Astrophysics Data System (ADS)

This paper preliminarily investigates the general transport properties (i.e., water sorptivity, water permeability, and gas permeability) of carbon-nanotube/cement composites. Carboxyl multi-walled carbon nanotubes (MWNTs) are dispersed into cement mortar to fabricate the carbon nanotubes (CNTs) reinforced cement-based composites by applying ultrasonic energy in combination with the use of surfactants (sodium dodecylbenzene sulfonate and sodium dodecyl sulfate). Experimental results indicate that even at a very small dosage the addition of MWNTs can help decrease water sorptivity coefficient, water permeability coefficient, and gas permeability coefficient of cement mortar, which suggests that CNTs can effectively improve the durability properties of cement-based composites.

Han, Baoguo; Yang, Zhengxian; Shi, Xianming; Yu, Xun

2013-01-01

309

Mechanical and transport properties of carbon nanotube systems  

Microsoft Academic Search

The mechanical and transport properties of carbon nanotube systems are studied by large-scale ab initio, tight-binding and classical molecular dynamics simulations. The ultimate strength of carbon nanotubes is investigated theoretically. While the formation energy of strain-induced topological defects determines the thermodynamic limits of the elastic response and of mechanical resistance to applied tension, it is found that the activation barriers

Qingzhong Zhao

2003-01-01

310

Preparation and gas transport properties of dense fluoroaniline copolymer membranes  

Microsoft Academic Search

The first evaluation of gas transport properties of dense polyfluoroaniline and fluoroaniline copolymer membranes was presented. First of all, a series of fluoroaniline copolymers containing different feeding ratio of ortho-fluoroaniline\\/aniline were prepared by oxidative copolymerizations in CaCl2\\/HCl medium. These polymers were amorphous and could afford flexible films in high molecular weight, obtained by casting from solution. The results for gas

Kuan-Yeh Huang; Chang-Lung Shiu; Yu-An Su; Chia-Chi Yang; Jui-Ming Yeh; Yen Wei; Kueir-Rarn Lee

2009-01-01

311

Gas Transport Properties of Asymmetric Block Copolyimide Membranes  

Microsoft Academic Search

We have synthesized fluorinated block copolyimides with different block chain lengths by chemical imidization in a two-pot procedure and prepared the asymmetric coployimide membranes using the dry-wet phase inversion process. The gas transport properties of the asymmetric membranes were measured using a high vacuum apparatus equipped with a Baratron absolute pressure gauge at 76 cmHg and 35 °C. We demonstrated

Yumi Kashimura; Satoshi Aoyama; Hiroyoshi Kawakami

2009-01-01

312

Gas transport properties and molecular motions of 6FDA copolyimides  

Microsoft Academic Search

The gas transport properties of 6FDA copolyimide membranes have been studied by examining their interaction such as the charge transfer complex between donor and acceptor molecules or the ?–? aromatic stacking and their molecular motion in the solid-state. The interaction and the molecular motion in the membranes have been measured using fluorescence spectroscopy and solid-state 13C NMR spectroscopy, respectively. The

Masato Mikawa; Shoji Nagaoka; Hiroyoshi Kawakami

1999-01-01

313

Magnetic and transport properties of superconductor/ferromagnet bilayer microbridges  

NASA Astrophysics Data System (ADS)

We investigated magnetic and transport properties of variable-thickness bridges (VTBs) having a Nb/Pd0.85Ni0.15 bilayer microbridges. It was found that the superconducting critical current Ic of the VTBs monotonically decreased with increasing PdNi thickness dF, while nonmonotonic behavior of the superconducting transition temperature Tc was observed as a function of dF in large Nb/PdNi bilayer films.

Matsuda, Ken-Ichi; Akimoto, Yosuke; Uemura, Tetsuya; Yamamoto, Masafumi

2008-04-01

314

Thermal transport properties of strontium intercalated titanium diselenide  

NASA Astrophysics Data System (ADS)

Polycrystalline SrxTiSe2 (x = 0.04, 0.14, 0.2) alloy was prepared using solid state reaction method and hot press sintering. The effects Sr content were studied on the thermal transport properties of the material. As grown material shows pure TiSe2 phase. Increasing the strontium content reduces thermal conductivity of the material. This is attributed to large number of interfaces and weakly bound Sr atom which acts like a phonon scatterer.

Patel, M.; Bhatt, R.; Bhattacharya, S.; Basu, R.; Haque, F. Z.; Singh, A.; Aswal, D. K.; Gupta, S. K.

2013-06-01

315

Transport properties of antidot superlattices of graphene nanoribbons  

Microsoft Academic Search

In this work we show a theoretical study of the electronic and transport properties of superlattices formed by a periodic structure of vacancies (antidots) on graphene nanoribbons. The systems are described by a single-band tight-binding Hamiltonian and also by ab initio total energy density-functional theory calculations. The quantum conductance is determined within the Green's function formalism, calculated by real-space renormalization

L. Rosales; M. Pacheco; Z. Barticevic; A. León; A. Latgé; P. A. Orellana

2009-01-01

316

Macroscopic Properties of a Multipolar Electron Cyclotron Resonance Microwave-Cavity Plasma Source for Anisotropic Silicon Etching.  

NASA Astrophysics Data System (ADS)

Although electron cyclotron resonance (ECR) plasmas have been studied extensively in the context of nuclear fusion, many aspects of plasma-reactor design, discharge physics, and plasma processing physics in ECR plasmas which are specifically engineered for plasma-aided manufacturing are not well understood. This work experimentally investigates the discharge characteristics and develops a process for the anisotropic etching of silicon using a novel microwave -cavity ECR plasma-disk reactor (MPDR). This dissertation begins with an experimental investigation of the interaction of 2.45 GHz microwave radiation within the microwave cavity with the discharge. Electric field strengths within the cavity typically range from 7 kV/m to 22 kV/m and the E-field within the discharge is estimated at 7 kV/m for a 0.9 mTorr, 20 sccm argon discharge absorbing 260 W of microwave power. The plasma diffuses into a downstream processing chamber where the ion density and the electron and ion energy distribution functions have been measured. Peak ion densities in the processing region are 6 times 10^ {11} cm^{-3} in a 0.9 mTorr, 20 sccm argon, 260 watt discharge. The alignment of the ECR magnetic field and the cavity mode is an important factor in low power discharge stability. The spatial distribution of ions in the system shows that the MPDR discharge region is a free-fall diffusion dominated discharge and the processing region is an ambipolar diffusion dominated discharge. Electron energy distribution functions (EEDFs) measured in the processing zone show no signs of potentially-damaging, high energy electron populations. In argon the EEDFs are nearly Maxwellian. Unusual EEDF shapes in SF_6 plasmas are attributed to inelastic electron collisions rather than ECR energy transfer processes. The spectrum of ion energies impinging on a conducting substrate in the processing chamber shows a divergent ion flux emerges from the discharge. The average energy of the ions varies from 15-35 eV. Actinometry reveals a uniform distribution of radical fluorine and an Ar ^{+} density of 1.2 times 10^{12} cm ^{-3} in the ECR regions. Anisotropic plasma etching of silicon in SF_6 + Ar is demonstrated at rates of 0.3 mum/minute.

Hopwood, Jeffrey Alan

1990-01-01

317

Transport properties of polymer solutions. A comparative approach.  

PubMed Central

A variety of transport properties have been measured for solutions of the water soluble polymer poly(ethylene oxide)(PEO) with molecular weights ranging from 200 to 14,000, and volume fractions ranging from 0-80%. The transport properties are thermal conductivity, electrical conductivity at audio frequencies (in solutions containing dilute electrolyte), and water self-diffusion. These data, together with dielectric relaxation data previously reported, are amenable to analysis by the same mixture theory. The ionic conductivity and water self-diffusion coefficient, but not the thermal conductivity, are substantially smaller than predicted by the Maxwell and Hanai mixture relations, calculated using the known transport properties of pure liquid water. A 25% (by volume) solution of PEO exhibits an average dielectric relaxation frequency of the suspending water of one half that of pure water, with clear evidence of a distribution of relaxation times present. The limits of the cumulative distribution of dielectric relaxation times that are consistent with the data are obtained using a linear programming technique. The application of simple mixture theory, under appropriate limiting conditions, yields hydration values for the more dilute polymer solutions that are somewhat larger than values obtained from thermodynamic measurements.

Foster, K R; Cheever, E; Leonard, J B; Blum, F D

1984-01-01

318

Influence of transport properties in electric field gradient focusing.  

PubMed

Miniaturized devices for electric field gradient focusing (EFGF) were developed that consist of a cylindrical separation channel surrounded by an acrylic-based polymer hydrogel. The ionic transport properties of the hydrogel enable the manipulation of the electric field inside the separation channel. A changing cross-section design was used in which the hydrogel is shaped such that an electric field gradient is established in the separation channel. One of the challenges with this type of EFGF device has been that experimental resolution between protein analytes is lower than theoretically predicted. In order to investigate this phenomenon, a mathematical transport model was developed using FEMLAB. Model results and experimental observations showed that the reduced performance was caused by concentration gradients formed in the EFGF channel, and that these concentration gradients were the result of an imbalance in cation transport between the open separation channel and the hydrogel. Removing acidic impurities from the monomers that form the hydrogel reduced this tendency and improved the resolution. These transport-induced concentration gradients can be used to establish electric field gradients that may be useful for sample pre-concentration. Both the results of simulation and experiments demonstrate how transport-induced concentration gradients lead to the establishment of electric field gradients. PMID:17481644

Humble, Paul H; Harb, John N; Tolley, H Dennis; Woolley, Adam T; Farnsworth, Paul B; Lee, Milton L

2007-04-13

319

Anisotropic Cartesian Grid Adaptation  

NASA Astrophysics Data System (ADS)

A three-dimensional grid adaptation method using the concept of anisotropic Cartesian grid has been developed to improve the efficiency of an existing Cartesian grid adaptation method by reducing the total number of cells needed to compute a flow field. The present grid adaptation is carried out by performing both grid coarsening and refinement in such a way that the cell aspect ratio can take an arbitrary value, keeping the grid smoothness. This flexibility necessitates the concept of unstructured approach. Two test cases: a cylinder in supersonic flow and an ONERA M6 wing in transonic flow show that the present method can well capture 2D and 3D flow features. In the cylinder case, the number of cells after the final adaptation cycle is one or two orders of magnitude less than that of the corresponding isotropic grid; in the ONERA M6 case it becomes about half as many. This remarkable saving in the 2D case is achieved because the spanwise domain is covered by only one cell in the present method, unlike conventional isotropic approaches. As a result of the decrease in the number of cells, the anisotropic grid requires less time to solve the flow and less amount of total memory, though the amount of memory per cell actually increases because of its unstructured property.

Lahur, Paulus R.; Nakamura, Yoshiaki

320

Surface and transport properties of Ag Cu liquid alloys  

NASA Astrophysics Data System (ADS)

The applicability of quasi-lattice theory (QLT) to describe surface and transport properties of Ag Cu liquid alloys is substantiated by surface tension experimental data. The surface tension of molten Ag, Cu and Ag Cu alloys has been measured by the pinned-sessile drop method over a temperature range. The results obtained are in good agreement with other reported measurements on pure elements and their alloys as well as with calculated surface tension values. The phase diagram of Ag Cu system shows the existence of a simple eutectic indicating a tendency towards phase separation. The mixing behaviour of Ag Cu regular alloys has been analysed through the study of surface properties (surface tension and surface composition), dynamic properties (chemical diffusion and viscosity) and microscopic functions (concentration fluctuations in the long-wavelength limit and chemical short-range order parameter) in the frame of quasi-lattice theory combined with a statistical mechanical theory.

Novakovic, R.; Ricci, E.; Giuranno, D.; Passerone, A.

2005-02-01

321

Space radiation transport properties of polyethylene-based composites.  

PubMed

Composite materials that can serve as both effective shielding materials against cosmic-ray and energetic solar particles in deep space, as well as structural materials for habitat and spacecraft, remain a critical and mission enabling component in mission planning and exploration. Polyethylene is known to have excellent shielding properties due to its low density, coupled with high hydrogen content. Polyethylene-fiber reinforced composites promise to combine this shielding effectiveness with the required mechanical properties of structural materials. Samples of polyethylene-fiber reinforced epoxy matrix composite 1-5 cm thick were prepared at the NASA Marshall Space Flight Center and tested against a 500 MeV/nucleon Fe beam at the HIMAC facility of NIRS in Chiba, Japan. This paper presents measured and calculated results for the radiation transport properties of these samples. PMID:15644352

Kaul, R K; Barghouty, A F; Dahche, H M

2004-11-01

322

Anisotropic Gent–McWilliams Parameterization for Ocean Models  

Microsoft Academic Search

ABSTRACT An anisotropic generalization of the Gent?McWilliams (GM) parameterization is presented for eddy-induced tracer transport and diffusion in ocean models, and it is implemented in an ocean general circulation model using a functional formalism,to derive the spatial discretization. This complements,the anisotropic viscosity parameterization,recently developed,by Smith and McWilliams. The anisotropic GM operator is potentially useful in both coarse- and high-resolution ocean

Richard D. Smith; Peter R. Gent

2004-01-01

323

The determination of the elastic properties of an anisotropic polycrystalline graphite using neutron diffraction and ultrasonic measurements  

Microsoft Academic Search

The elastic properties of an extruded graphite (GR-280) used in nuclear industry have been examined. The lattice preferred orientation was determined by time-of-flight neutron diffraction that revealed weak texture with a texture index of less than 1.2. The bulk elastic properties of polycrystalline graphite with such a texture have been calculated using various averaging methods and compared with the properties

Tomas Lokajicek; Petr Lukas; Anatoly N. Nikitin; Igor V. Papushkin; Vyacheslav V. Sumin; Roman N. Vasin

2011-01-01

324

Small molecules with ambipolar transporting properties for efficient OLEDs  

NASA Astrophysics Data System (ADS)

For stable and efficienct organic light-emitting diodes, it is essential to find molecules with high photoluminescent efficiency, little self-quenching and balanced charge transporting properties. Recently, we've designed and synthesized some highly emissive naphtho[2,3-c][1,2,5]thiadiazole (NTD) derivatives and naphtho[2,3-c][1,2,5]selenadiazole (NSeD) derivatives with unusual ambipolar transporting properties. The ambipolar transporting properties of the NTDs were explained by Marcus theory with carrier reorganization energies and charge-transfer integrals. We obtained high quality single crystals of 4,9-di(biphenyl-4-yl)-naphtho[2,3-c][1,2,5]thiadiazole (NTD02) and 4,9-bis(4-(2,2-diphenylvinyl)phenyl)-naphtho[2,3-c][1,2,5]thiadiazole (NTD05). They have disordered NTD rings' orientation with the opposite directions in the center of the molecule because of NTD's planar configuration and the single-bond connection with the phenyl substituents. The packing structure of NTD02 shows the planar arrangement of NTD rings, forming a "charge transporting channel". Quantum calculation also confirms that the ?-? stacking interaction in NTD derivatives benefits the charge transporting via intermolecular hopping on NTD rings. The hole and electron mobilities of NTD05 are 7.16×10-4 cm2/V.s and 6.19×10-4 cm2/V•s at an electronic field E = 2.0×105 V/cm, respectively. The hole mobility of NTD05 is close to that of N,N'-diphenyl-N,N'-bis(1-naphthyl)(1,1'-biphenyl)-4,4'-diamine (NPB) and the electron mobility of NTD05 is two orders-of-magnitude higher than that of tris(8-hydroxyquinoline) aluminum (Alq3). For the NTD derivatives, NTD05 also shows the best performance in non-doped OLEDs. CIE coordinates of (0.65, 0.35) and a peak efficiency of 2.4% are achieved for a double layer OLED with NPB as the hole transporting layer and NTD05 as the emitting layer. Moreover, we get ultimate red emission with CIE coordinates of (0.71, 0.29) for some of the NSeD based non-doped OLEDs.

Duan, Lian; Wei, Peng; Qiu, Yong

2007-10-01

325

Morphologic and transport properties of natural organic floc  

NASA Astrophysics Data System (ADS)

The morphology, entrainment, and settling of suspended aggregates ("floc") significantly impact fluxes of organic carbon, nutrients, and contaminants in aquatic environments. However, transport properties of highly organic floc remain poorly understood. In this study detrital floc was collected in the Florida Everglades from two sites with different abundances of periphyton for use in a settling column and in racetrack flume entrainment experiments. Although Everglades flocs are similar to other organic aggregates in terms of morphology and settling rates, they tend to be larger and more porous than typical mineral flocs because of biostabilization processes and relatively low prevailing shear stresses typical of wetlands. Flume experiments documented that Everglades floc was entrained at a low bed shear stress of 1.0 × 10-2 Pa, which is considerably smaller than the typical entrainment threshold of mineral floc. Because of similarities between Everglades floc and other organic floc populations, floc transport characteristics in the Everglades typify the behavior of floc in other organic-rich shallow-water environments. Highly organic floc is more mobile than less organic floc, but because bed shear stresses in wetlands are commonly near the entrainment threshold, wetland floc dynamics are often transport-limited rather than supply limited. Organic floc transport in these environments is therefore governed by the balance between entrainment and settling fluxes, which has implications for ecosystem metabolism, materials cycling, and even landscape evolution.

Larsen, Laurel G.; Harvey, Judson W.; Crimaldi, John P.

2009-01-01

326

Nonlocal transport properties of nanoscale conductor–microwave cavity systems  

NASA Astrophysics Data System (ADS)

Recent experimental progress in coupling nanoscale conductors to superconducting microwave cavities has opened up for transport investigations of the deep quantum limit of light-matter interactions, with tunneling electrons strongly coupled to individual cavity photons. We have investigated theoretically the most basic cavity-conductor system with strong, single photon induced nonlocal transport effects: two spatially separated double quantum dots (DQDs) resonantly coupled to the fundamental cavity mode. The system, described by a generalized Tavis-Cummings model, is investigated within a quantum master equation formalism, allowing us to account for both the electronic transport properties through the DQDs as well as the coherent, nonequilibrium cavity photon state. We find sizable nonlocally induced current and current cross-correlations mediated by individual photons. From a full statistical description of the electron transport we further reveal a dynamical channel blockade in one DQD lifted by photon emission due to tunneling through the other DQD. Moreover, large entanglement between the orbital states of electrons in the two DQDs is found for small DQD-lead temperatures.

Bergenfeldt, C.; Samuelsson, P.

2013-05-01

327

Effect of CO 2 treated polycarbonate membranes on gas transport and sorption properties  

Microsoft Academic Search

The effect of polycarbonate (PC) membranes treated with super critical carbon dioxide on gas sorption and transport properties was studied. It was found that the gas permeability of PC membranes hardly changed after the CO2 treatment. However, the gas sorption and diffusion properties showed a significant change. The transport properties were determined by measuring the sorption and permeation properties. The

Shih-Hsiung Chen; Shih-Liang Huang; Kuang-Chang Yua; Juin-Yih Lai; Ming-Tsai Liang

2000-01-01

328

Structural, electronic, and transport properties of silicane nanoribbons  

NASA Astrophysics Data System (ADS)

Silicane ribbons do not suffer from aromatic dependence of the band gap making them a more promising candidate for near-term nanoelectronic application compared to armchair graphene nanoribbons. The structural, electronic, and transport properties of free-standing sp3-hybridized armchair- and zigzag-edge silicane nanoribbons have been investigated using ab initio and nonlocal empirical pseudopotential calculations. Under ambient conditions, two-dimensional silicane sheets will spontaneously break into stable one-dimensional ribbons similar to density functional theory studies of graphene ribbons. The calculated low-field electron mobility and ballistic conductance show a strong edge dependence, due to differences in the effective mass and momentum relaxation rates along the two transport directions. The mobility in zigzag-edge ribbons is found to be approximately twenty times higher than in armchair-edge ribbons.

Kim, Jiseok; Fischetti, Massimo V.; Aboud, Shela

2012-11-01

329

Transport properties of the hot quark-gluon plasma  

NASA Astrophysics Data System (ADS)

A phase where quark and gluon are the relevant degrees of freedom is expected for nuclear matter at energy density epsilon >= 1 GeV/fm3 and a temperature T > 160 MeV. A transient state state of such a matter can be created by mean of ultra-relativistic heavy-ion collisions. We briefly overview some main results on the properties of the quark-gluon plasma emphasizing the necessity to develop a transport theory for quarks and gluons able to incorporate the main developments in lattice QCD and perturbative QCD. First results show that Boltzmann-Vlasov transport theory correctly predict the elliptic flow observed at both RHIC and LHC energies.

Greco, Vincenzo

2011-12-01

330

Transport properties in a line defect superlattice of graphene  

NASA Astrophysics Data System (ADS)

It was recently reported that a kind of graphene line defect can be fabricated in a controllable experimental way. In the present work we theoretically investigate the band structure and the electronic transport properties of a graphene superlattice formed by embedding periodically line defects in the graphene lattice. Based on the calculated results, we suggest that such a superlattice can be used as a quantum wire array which can carry much larger current than a single graphene nanoribbon. A remarkable advantage of this superlattice over other quantum wires is that the electronic transport in it is insensitive to scattering effects except that the scattering potential range is smaller than the graphene lattice constant. Moreover, we find that the anisotropy of the Dirac cone presented in this superlattice has a nontrivial influence on the universal minimal conductivity and the sub-Poissonian shot noise of graphene.

Lü, Xiaoling; Jiang, Liwei; Zheng, Yisong

2013-11-01

331

Scattering and transport properties of tight-binding random networks  

NASA Astrophysics Data System (ADS)

We study numerically scattering and transport statistical properties of tight-binding random networks characterized by the number of nodes N and the average connectivity ?. We use a scattering approach to electronic transport and concentrate on the case of a small number of single-channel attached leads. We observe a smooth crossover from insulating to metallic behavior in the average scattering matrix elements <|Smn|2>, the conductance probability distribution w(T), the average conductance , the shot noise power P, and the elastic enhancement factor F by varying ? from small (??0) to large (??1) values. We also show that all these quantities are invariant for fixed ?=?N. Moreover, we proposes a heuristic and universal relation between <|Smn|2>, , and P and the disorder parameter ?.

Martínez-Mendoza, A. J.; Alcazar-López, A.; Méndez-Bermúdez, J. A.

2013-07-01

332

Low temperature carrier transport properties in isotopically controlled germanium  

SciTech Connect

Investigations of electronic and optical properties of semiconductors often require specimens with extremely homogeneous dopant distributions and precisely controlled net-carrier concentrations and compensation ratios. The previous difficulties in fabricating such samples are overcome as reported in this thesis by growing high-purity Ge single crystals of controlled {sup 75}Ge and {sup 70}Ge isotopic compositions, and doping these crystals by the neutron transmutation doping (NTD) technique. The resulting net-impurity concentrations and the compensation ratios are precisely determined by the thermal neutron fluence and the [{sup 74}Ge]/[{sup 70}Ge] ratios of the starting Ge materials, respectively. This method also guarantees unprecedented doping uniformity. Using such samples the authors have conducted four types of electron (hole) transport studies probing the nature of (1) free carrier scattering by neutral impurities, (2) free carrier scattering by ionized impurities, (3) low temperature hopping conduction, and (4) free carrier transport in samples close to the metal-insulator transition.

Itoh, K.

1994-12-01

333

Anisotropic Model Colloids  

NASA Astrophysics Data System (ADS)

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 femtosecond laserpulses of variable wavelengths. We show that we can grow a silica layer on the gold rods with controllable thickness. In future this can be used to control the alignment of the gold rods a 3D crystal in an electric field. The silica coated gold rods can be used in optical switches. In chapter 4 we show to have a very local control of changing the aspect ratio of gold rods by irradiation with femtosecond laserpulses of 82 MHz with a threshold of ~ 2 picojoules to deform the particles. In chapter 5 and 6 we show how, starting from spherical particles, dimers (dumbbells), trimers and multimers can be formed by controlled aggregation. Chapter 7 finally shows an overview of syntheses where the pores of (mainly) silica particles is decreased. We show that the pores of the given particles could be decreased from macroporous to (ultra)microporous. Through a full control of pore size particles can selectively be filled with materials (for instance a drug) and be controllably closed. This opens a route for synthesis of particles that can be used as molecular filters or in biomedical applications such as smart drug delivery.

van Kats, C. M.

2008-10-01

334

Gas transport properties in thermally cured aromatic polyimide membranes  

Microsoft Academic Search

Aromatic polyimide derived from 2,2?-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 3,3?-diaminodiphenylsulfone (m-DDS) has been synthesized to facilitate the study of relationships between the polymer structure and the gas transport properties (permeability and selectivity). The gas permeability and selectivity of CO2, O2, N2, and CH4 for the 6FDA-m-DDS membranes cured at 150, 200, and 250°C have been determined at 35°C and at pressures

Hiroyoshi Kawakami; Masato Mikawa; Shoji Nagaoka

1996-01-01

335

Synthesis and electrical transport properties of SnS nanoparticles  

NASA Astrophysics Data System (ADS)

The SnS nanoparticles were synthesized at ambient temperature by simple wet chemical method. The stoichiometric and structural characterization was done by EDAX and XRD techniques respectively. The crystallite size was determined using Scherrer's formula and Hall-Williamson plot using XRD data. The electrical transport properties studies were carried out on pellets prepared by hydraulic pressing of SnS nanoparticles. The thermoelectric power and dc resistivity variation with temperature was studied on the pellets. Room temperature Hall effect measurement was made on the pellet. The obtained results are discussed in details.

Chaki, S. H.; Deshpande, M. P.; Chaudhary, M. D.; Tailor, J. P.; Mahato, K. S.

2013-02-01

336

Stacking-order dependent transport properties of trilayer graphene  

NASA Astrophysics Data System (ADS)

We report markedly different transport properties of ABA- and ABC-stacked trilayer graphenes. Our experiments in double-gated trilayer devices provide evidence that a perpendicular electric field opens an energy gap in the ABC trilayer, while it causes the increase of a band overlap in the ABA trilayer. In a perpendicular magnetic field, the ABA trilayer develops quantum Hall plateaus at filling factors of ?=2,4,6,... with a step of ??=2, whereas the inversion-symmetric ABC trilayer exhibits plateaus at ?=6 and 10 with fourfold spin and valley degeneracy.

Jhang, S. H.; Craciun, M. F.; Schmidmeier, S.; Tokumitsu, S.; Russo, S.; Yamamoto, M.; Skourski, Y.; Wosnitza, J.; Tarucha, S.; Eroms, J.; Strunk, C.

2011-10-01

337

Geometrical and Transport Properties of Sequential Adsorption Clusters  

NASA Astrophysics Data System (ADS)

We investigate transport properties of percolating clusters generated by irreversible cooperative sequential adsorption (CSA) on square lattices with Arrhenius rates given by ki ? qni, where ni is the number of occupied neighbors of the site i, and q a controlling parameter. Our results show a dependence of the prefactors non q and a strong finite size effect for small values of this parameter, both impacting the size of the backbone and the global conductance of the system. These results might be pertinent to practical applications in processes involving adsorption of particles.

Araújo, E. B.; Moreira, A. A.; Herrmann, H. J.; da Silva, L. R.; Andrade, J. S.

2013-06-01

338

Magnetic and Transport Properties of doped half-Heusler alloys.  

NASA Astrophysics Data System (ADS)

We present results of a study of small-gap semiconductors which crystallize in the MgAgAs half-Heusler structure. In particular TiNiSn and ScNiSb have been studied. We report the results of doping into the metallic state via substitution onto each of the three sublattices. We have also studied the role of magnetic impurities, for example, Ce, in the otherwise non-magnetic host. Magnetic and transport properties of flux-grown single crystals of Ti_1-xCe_xNiSn and Sc_1-xCe_xNiSb which display small-moment ferromagnetism will be reported.

Torelli, M. E.; Sarrao, J. L.; Fisk, Z.

1996-03-01

339

Transport Properties for Triangular Barriers in Graphene Nanoribbon  

NASA Astrophysics Data System (ADS)

We theoretically study the electronic transport properties of Dirac fermions through one and double triangular barriers in graphene nanoribbon. Using the transfer matrix method, we determine the transmission, conductance and Fano factor. They are obtained to be various parameters dependent such as well width, barrier height and barrier width. Therefore, different discussions are given and comparison with the previous significant works is done. In particular, it is shown that at Dirac point the Dirac fermions always own a minimum conductance associated with a maximum Fano factor and change their behaviors in an oscillatory way (irregularly periodical tunneling peaks) when the potential of applied voltage is increased.

El Mouhafid, Abderrahim; Jellal, Ahmed

2013-10-01

340

Band structure effects of transport properties in icosahedral quasicrystals  

NASA Astrophysics Data System (ADS)

Transport properties and optical conductivity are calculated for the crystalline approximant AlMn alloy. The number of electrons at the Fermi energy is very small and, based on the band structure, the anomalously small dc conductivity and temperature dependent thermoelectric power are explained. A model calculation for the two-dimensional Penrose lattice with random phason strain shows that it becomes more conductive than the perfect Penrose lattice. We propose the mechanism of the interband transition by phason randomness and inelastic scattering for the origin of the anomalous conductivity in real quasicrystals.

Fujiwara, Takeo; Yamamoto, Susumu; Trambly de Laissardière, Guy

1993-12-01

341

Transport properties of Ni-interacted armchair graphene nanoribbons  

NASA Astrophysics Data System (ADS)

The present first principles investigations explore the transport properties of Ni-interacted armchair graphene nanoribbons (Ni-AGNR) and compare the findings with pristine AGNR. Our calculations revealed that Ni-interaction could be a possible way to enhance the metallicity of AGNR. The transmission spectra show that high metallicity is preserved in the ribbon irrespective of doping site which is further supported by the I-V characteristics. The observed enhanced metallicity of Ni-AGNR can play an important role particularly for the interconnect applications in nanoelectronic devices.

Jaiswal, Neeraj K.; Srivastava, Pankaj; Kumar, Sanodh

2013-06-01

342

Predicting the transport properties of sedimentary rocks from microgeometry  

SciTech Connect

We investigate through analysis and experiment how pore geometry, topology, and the physics and chemistry of mineral-fluid and fluid-fluid interactions affect the flow of fluids through consolidated/partially consolidated porous media. Our approach is to measure fluid permeability and electrical conductivity of rock samples using single and multiple fluid phases that can be frozen in place (wetting and nonwetting) over a range of pore pressures. These experiments are analyzed in terms of the microphysics and microchemistry of the processes involved to provide a theoretical basis for the macroscopic constitutive relationships between fluid-flow and geophysical properties that we develop. The purpose of these experiments and their analyses is to advance the understanding of the mechanisms and factors that control fluid transport in porous media. This understanding is important in characterizing porous media properties and heterogeneities before simulating and monitoring the progress of complex flow processes at the field scale in permeable media.

Schlueter, E.M.

1993-01-01

343

Generalized thermodynamic and transport properties. II. Molecular liquids.  

PubMed

In the present paper, we extend the method described in paper I [D. Bertolini and A. Tani, preceding paper, Phys. Rev. E 83, 031201 (2011)] to molecular liquids, which allows us to solve the exact kinetic equation proposed by de Schepper et al. [Phys. Rev. A 38, 271 (1988)] without approximations. In particular, generalized thermodynamic properties (enthalpy, specific heat, and thermal expansion coefficient) and transport properties (longitudinal viscosity, thermal conductivity) have been calculated for three liquids of increasing complexity, namely dimethyl sulfoxide, hydrogen fluoride, and SPC/E water. All results have been obtained by the molecular formalism as well as the atomic one, corrected for intramolecular correlations that are due to the models adopted. As done for simple liquids, the coupling between the viscous stress tensor and the energy flux vector has been calculated exactly. We also show that the Markov assumption for the dynamics related to thermal conductivity can only be adopted with caution. PMID:21517486

Bertolini, D; Tani, A

2011-03-11

344

Electron transport properties of carbon nanotube-graphene contacts  

NASA Astrophysics Data System (ADS)

The properties of carbon nanotube-graphene junctions are investigated with first-principles electronic structure and electron transport calculations. Contact properties are found to be key factors in determining the performance of nanotube based electronic devices. In a typical single-walled carbon nanotube-metal junction, there is a p-type Schottky barrier of up to ~0.4 eV which depends on the nanotube diameter. Calculations of the Schottky barrier height in carbon nanotube-graphene contacts indicate that low barriers of 0.09 eV and 0.04 eV are present in nanotube-graphene contacts ((8,0) and (10,0) nanotubes, respectively). Junctions with a finite contact region are investigated with simulations of the current-voltage characteristics. The results suggest the suitability of the junctions for applications and provide insight to explain recent experimental findings.

Cook, Brandon G.; French, William R.; Varga, Kálmán

2012-10-01

345

Epitaxial growth and electrical transport properties of Cr{sub 2}GeC thin films  

SciTech Connect

Cr{sub 2}GeC thin films were grown by magnetron sputtering from elemental targets. Phase-pure Cr{sub 2}GeC was grown directly onto Al{sub 2}O{sub 3}(0001) at temperatures of 700-800 deg. C. These films have an epitaxial component with the well-known epitaxial relationship Cr{sub 2}GeC(0001)//Al{sub 2}O{sub 3}(0001) and Cr{sub 2}GeC(1120)//Al{sub 2}O{sub 3}(1100) or Cr{sub 2}GeC(1120)//Al{sub 2}O{sub 3}(1210). There is also a large secondary grain population with (1013) orientation. Deposition onto Al{sub 2}O{sub 3}(0001) with a TiN(111) seed layer and onto MgO(111) yielded growth of globally epitaxial Cr{sub 2}GeC(0001) with a virtually negligible (1013) contribution. In contrast to the films deposited at 700-800 deg. C, the ones grown at 500-600 deg. C are polycrystalline Cr{sub 2}GeC with (1010)-dominated orientation; they also exhibit surface segregations of Ge as a consequence of fast Ge diffusion rates along the basal planes. The room-temperature resistivity of our samples is 53-66 {mu}{Omega}cm. Temperature-dependent resistivity measurements from 15-295 K show that electron-phonon coupling is important and likely anisotropic, which emphasizes that the electrical transport properties cannot be understood in terms of ground state electronic structure calculations only.

Eklund, Per [Institut Pprime, UPR 3346, Universite de Poitiers, SP2MI-Boulevard 3, Teleport 2-BP 30179, 86962 Futuroscope Chasseneuil Cedex (France); Thin Film Physics Division, Linkoeping University, IFM, 581 83 Linkoeping (Sweden); Bugnet, Matthieu; Mauchamp, Vincent; Dubois, Sylvain; Tromas, Christophe; Jaouen, Michel; Cabioc'h, Thierry [Institut Pprime, UPR 3346, Universite de Poitiers, SP2MI-Boulevard 3, Teleport 2-BP 30179, 86962 Futuroscope Chasseneuil Cedex (France); Jensen, Jens [Thin Film Physics Division, Linkoeping University, IFM, 581 83 Linkoeping (Sweden); Piraux, Luc; Gence, Loiek [Institute of Condensed Matter and Nanosciences, Universite Catholique de Louvain, B-1348 Louvain la Neuve (Belgium)

2011-08-15

346

Procedures for construction of anisotropic elastic plastic property closures for face-centered cubic polycrystals using first-order bounding relations  

NASA Astrophysics Data System (ADS)

Microstructure-sensitive design (MSD) is a novel mathematical framework that facilitates a rigorous consideration of the material microstructure as a continuous design variable in the engineering design enterprise [Adams, B.L., Henrie, A., Henrie, B., Lyon, M., Kalidindi, S.R., Garmestani, H., 2001. Microstructure-sensitive design of a compliant beam. J. Mech. Phys. Solids 49(8), 1639 1663; Adams, B.L., Lyon, M., Henrie, B., 2004. Microstructures by design: linear problems in elastic plastic design. Int. J. Plasticity 20(8 9), 1577 1602; Kalidindi, S.R., Houskamp, J.R., Lyons, M., Adams, B.L., 2004. Microstructure sensitive design of an orthotropic plate subjected to tensile load. Int. J. Plasticity 20(8 9), 1561 1575]. MSD employs spectral representations of the local state distribution functions in describing the microstructure quantitatively, and these in turn enable development of invertible linkages between microstructure and effective properties using established homogenization (composite) theories. As a natural extension of the recent publications in MSD, we provide in this paper a detailed account of the methods that can be readily used by mechanical designers to construct first-order elastic plastic property closures. The main focus in this paper is on the crystallographic texture (also called Orientation Distribution Function or ODF) as the main microstructural parameter controlling the elastic and yield properties of cubic (fcc and bcc) polycrystalline metals. The following specific advances are described in this paper: (i) derivation of rigorous first-order bounds for the off-diagonal terms of the effective elastic stiffness tensor and their incorporation in the MSD framework, (ii) delineation of the union of the property closures corresponding to both the upper and lower bound theories resulting in comprehensive first-order closures, (iii) development of generalized and readily usable expressions for effective anisotropic elastic plastic properties that could be applied to all cubic polycrystals, and (iv) identification of the locations of readily available or easily processable ODFs (e.g. textures that are produced by rolling, drawing, etc.) on the property closures. It is anticipated that the advances communicated in this paper will make the mathematical framework of MSD highly accessible to the mechanical designers.

Proust, Gwénaëlle; Kalidindi, Surya R.

2006-08-01

347

Electronic structures and transport properties of silicene on Ag surface  

NASA Astrophysics Data System (ADS)

It has been predicted from first-principle that ``silicene'', a two-dimensional buckled honeycomb structure of silicon, is thermally stable and has a graphene-like band structure. In experiments, epitaxial silicene were observed to form at hexagonal Ag(111) and ZrB2(0001) surfaces. However, electronic structure and transport properties related to silicene have not been thoroughly studied. In this work, we have studied band structures of silicene on top of Ag surface using density-functional theory. The effective band structure mapped onto 1x1 unit cell of monolayer silicene on Ag(111) surface could be compared directly with Angle-Resolved Photoemission Spectra (ARPES). We have also studied electronic transport property across monolayer and bilayer silicene sheets using the Non-Equilibrium Green's Function (NEGF) method. The transmission curve shows a maximum at Fermi energy for the monolayer silicene case, but shows a minimum for the bilayer silicene case, which can be explained by their band structures.

Wang, Yun-Peng; Cheng, Hai-Ping

2013-03-01

348

Growth and transport properties of fractionally ?-doped oxide superlattices  

NASA Astrophysics Data System (ADS)

LaTiO3/SrTiO3 (LTO/STO) heterostructures are interesting as they show an intriguing 2D conduction, and their bulk counterpart, LaxSr1-xTiO3 (LSTO), exhibits a filling-controlled insulator-metal transition (IMT). In this study, we investigated the filling controlled IMT in 2D geometry by fabricating monolayer-thick fractionally ?--doped LSTO/STO superlattices (SLs), in order to find ways to enhancing the carrier mobility of two dimensional electron gas (2DEG). Fractional layers of LSTO have been grown in between STO using advanced PLD. It is found that the SLs' transport properties are governed by a multichannel conduction with at least two distinctly different carriers: (1) High-density-low-mobility carriers presenting at the LSTO interface layer and (2) low-density-high-mobility carriers residing in the STO layers away from the ?--doped layer. By optimizing x, we could tune the effective mass and carrier density to enhance the carrier mobility by about an order of magnitude, selectively for the high-density-low-mobility carriers. This proves that the fractional ?--doping is an effective way to controlling the filling controlled IMT, resulting in highly improved transport properties

Lee, Ho Nyung; Choi, Woo Seok; Lee, Suyoun; Cooper, Valentino

2012-02-01

349

[Some properties of transport ATPases in functionally different muscles].  

PubMed

The properties of Ca-transporting system in sarcoplasmic reticulum membranes in fast and slow frog muscles as well as some properties of sarcolemma Na, K-ATPase of the same object were investigated. The rate of Ca2+ uptake, Ca-ATPase activity and Ca/ATP ratio for the reticulum of fast muscle demonstrated higher values than those for the reticulum of slow muscle. The rate of Ca2+ accumulation by the fragments of the rectus reticulum and Ca/ATP ratio were found to decrease under the influence of acetylcholine (0.05-5 mM). The transport system of the sartorius reticulum was found to be less sensitive to acetylcholine. The peak activity of Na, K-ATPase in femoral muscles of the frog occurred at 80 mM NaCl and 60 mM KCl, whereas in the rectus abdominal muscle it equalled 100 mM NaCl and 40 mM KCl. Thus, Na, K-ATPase activity in the slow muscle was predominantly higher than that in the mixed (femoral) muscles. If the sarcolemma preparations of the muscles of both types the inhibitory effect of acetylcholine on Na; K-ATPase was registered. The enzyme of slow muscles exhibited higher sensibility to acetylcholine. PMID:139169

Esyrev, O V; Uspanova AhK; Omarova, R D; Sarsenova, Sh S; Kniazevskaia, I B

1976-11-01

350

Studies on magneto-transport properties of dilute magnetic semiconductors  

NASA Astrophysics Data System (ADS)

Diluted magnetic semiconductors (DMS) are rare group of promising semiconductors in which a fraction of the constituent ions is replaced by magnetic ions. This study is aimed to understand the magneto-transport properties of magnetic ion doped In2O3 thin films. The films were grown under different temperature and partial oxygen pressures by pulsed laser deposition. The films were characterized using various techniques such as X-ray diffraction, UV-VIS spectroscopy and magneto-transport. Anomalous magneto-resistive (MR) behavior has been observed for these films, which largely depends on growth conditions. For example, Co doped In2O3 films show presence of negative as well as positive MR at low temperatures. However, the film grown at 400 0C at a partial oxygen pressure of 1x10-4 mbar shows negative MR with a maximum value of around -0.3%. Films grown under higher partial oxygen pressures show large positive MR. Maximum positive MR of 8.9% is seen for the film grown at partial oxygen pressure of 4.3x10- 4 mbar at 400 0C. The effect of growth conditions on MR properties of these films will be presented in detailed. This work is supported by National Science Foundation (Award Number DMR-0907037).

Gupta, R.; Ghosh, A.; Kolekar, Y.; Ghosh, K.; Kahol, P.

2011-03-01

351

Anisotropic surface properties of micro/nanostructured a-C:H:F thin films with self-assembly applications  

NASA Astrophysics Data System (ADS)

The singular properties of hydrogenated amorphous carbon (a-C:H) thin films deposited by pulsed DC plasma enhanced chemical vapor deposition (PECVD), such as hardness and wear resistance, make it suitable as protective coating with low surface energy for self-assembly applications. In this paper, we designed fluorine-containing a-C:H (a-C:H:F) nanostructured surfaces and we characterized them for self-assembly applications. Sub-micron patterns were generated on silicon through laser lithography while contact angle measurements, nanotribometer, atomic force microscopy (AFM), and scanning electron microscopy (SEM) were used to characterize the surface. a-C:H:F properties on lithographied surfaces such as hydrophobicity and friction were improved with the proper relative quantity of CH4 and CHF3 during deposition, resulting in ultrahydrophobic samples and low friction coefficients. Furthermore, these properties were enhanced along the direction of the lithography patterns (in-plane anisotropy). Finally, self-assembly properties were tested with silica nanoparticles, which were successfully assembled in linear arrays following the generated patterns. Among the main applications, these surfaces could be suitable as particle filter selector and cell colony substrate.

Freire, V.-M.; Corbella, C.; Bertran, E.; Portal-Marco, S.; Rubio-Roy, M.; Andújar, J.-L.

2012-06-01

352

Pipette aspiration technique for the measurement of nonlinear and anisotropic mechanical properties of blood vessel walls under biaxial stretch  

Microsoft Academic Search

A pipette aspiration technique was proposed for the measurement of nonlinear mechanical properties of arteries under biaxial stretching. A cross-shaped specimen of porcine thoracic aorta whose principal axes corresponded with the axial and circumferential directions of the aortic walls was excised. The intraluminal surface of the specimen was aspirated with a circular cross-sectioned glass pipette while the specimen was stretching

Toshiro Ohashi; Hironobu Abe; Takeo Matsumoto; Masaaki Sato

2005-01-01

353

Transport properties of the clathrate BaGe5  

NASA Astrophysics Data System (ADS)

We report on the synthesis, crystallographic and transport properties of the Zintl phase BaGe5, which crystallizes in a new clathrate-type structure. This compound was synthesized by the decomposition of the type-I clathrate Ba8Ge43 squarelg 3 subjected to annealing treatment at 623, 673 and 793 K. Electrical resistivity, thermopower and thermal conductivity measurements were performed in the temperature range 2 - 773 K and complemented by magnetization, specific heat and Hall experiments below room temperature. Additional information on the chemical bonding and electronic band structure in BaGe5 was obtained through the electron localizability indicator (ELI) and the total density of states, all calculated within the all-electron full-potential local orbital method (FLPO). In agreement with the chemical bonding and electronic band structure calculations, electrical resistivity and specific heat data show that BaGe5 is a semiconductor. The complex crystal structure of BaGe5 contributes to the low thermal conductivity which displays a conventional crystalline-like behavior. Further measurements were carried out on samples annealed at 623, 673 and 793 K for four up to 30 days to probe possible variations of the crystal structure and electronic properties as a function of the annealing temperature and time. Even though the annealing temperature does not alter the semiconducting nature of this material, differences in the absolute values of the transport properties were unveiled in samples annealed for short-time periods. These differences are significantly reduced in samples which underwent long-time annealing treatment even though the measured curves do not merge completely.

Candolfi, C.; Aydemir, U.; Ormeci, A.; Carrillo-Cabrera, W.; Burkhardt, U.; Baitinger, M.; Oeschler, N.; Steglich, F.; Grin, Yu.

2011-08-01

354

Relationship between Cell Surface Properties and Transport of Bacteria through Soil.  

National Technical Information Service (NTIS)

A study was conducted to relate the properties of Enterobacter, Pseudomonas, Bacillus, Achromobacter, Flavobacterium, and Arthrobacter strains to their transport with water moving through soil. The bacteria differed markedly in their extent of transport; ...

J. T. Cannon V. B. Manilal M. Alexander

1991-01-01

355

Incidence, reflection and transmission angles in anisotropic media  

Microsoft Academic Search

The mathematical description of phenomena related to wave propagation in anisotropic media is considerably more complicated\\u000a than that for isotropic media. This complexity stems from many physical properties distinguishing the anisotropic from isotropic\\u000a medium. Therefore, calculating the angles of reflection and transmission for a ray impining on a boundary between two anisotropic\\u000a media become more complicated in mathematical implication. Snell

Bing-Ming Zhang; Min-Yu Dong; Zhong-Ping Qian

1999-01-01

356

Anisotropic Diffraction from Inclined Silver Nanorod Arrays on Grating Templates  

Microsoft Academic Search

Inclined silver nanorods (AgNRs) are highly anisotropic, with various applications in energy conversion, plasmonic and photonic devices, and sensing. So far, related studies have focused on the reflection or transmission, whereas studies on the diffraction and scattering from anisotropic AgNRs are still lacking. We investigate the anisotropic radiative properties of novel micro\\/nanoscale hybrid structures of inclined AgNRs deposited on compact

X. J. Wang; A. M. Haider; J. L. Abell; Y.-P. Zhao; Z. M. Zhang

2012-01-01

357

An Investigation on Transport Properties Near the Wall in Porous Media by Fractal Models  

Microsoft Academic Search

A comprehensive investigation on the wall effects on the transport properties, permeability, thermal conductivity, and thermal dispersion conductivity is performed, based on the fractal models for these properties and the porosity variations near the wall in porous media. The results show that the fractal models for transport properties of porous media can provide good agreement with the conventional models in

Boming Yu; Yongjin Feng; Mingqing Zou; Mingtao Huang

2006-01-01

358

A comparison of anisotropic PML to Berenger's PML and its application to the finite-element method for EM scattering  

Microsoft Academic Search

The use of an anisotropic material for the boundary truncation of the finite-element method is considered. The anisotropic material properties can be chosen such that a plane-wave incident from free space into the anisotropic halfspace has no reflection. Because there is no reflection, the material is referred to as a perfectly matched layer (PML). The relationship between the anisotropic PML

Jo-Yu Wu; David M. Kingsland; Jin-Fa Lee; Robert Lee

1997-01-01

359

Transport properties of ribbon-shaped carbon fibers: Property-structure relationship  

NASA Astrophysics Data System (ADS)

Mesophase pitch-based carbon fibers are an ideal material for applications in which high rates of heat dissipation and low mass are required. Unfortunately, the high cost of current commercial high thermal conductivity mesophase pitch-based carbon fibers has limited their use in high volume applications. Understanding how the structure develops during the fiber formation process and how this structure relates to the final fiber properties is the way to optimizing the fiber properties while reducing the processing costs. Ribbon-shaped fibers have been developed at Clemson University and are being evaluated as a low-cost high thermal conductivity alternative fiber to traditional round-shaped fibers. However, the characterization of the thermal transport properties of carbon fibers is a difficult and time-consuming process. The objectives of this study were to evaluate the transport (both thermal and electronic) properties of ribbon-shaped fibers produced from an AR mesophase at different processing conditions, to characterize the structure of these fibers, to study their structure-property relationships, and to develop a model capable of estimating the thermal conductivity of carbon fibers based upon their structural parameters. For this purpose, several sets of ribbon fibers were produced from an AR mesophase at different spinning temperatures and shear rates and heat treated at a final temperature of 2400°C. The electrical resistivities, magnetoresistances and thermal conductivities of these fibers were measured and the structural parameters were determined with x-ray techniques. Two approaches (a short-fiber composite, and a periodic composite) were utilized to model the relationship between the structure of the fiber and its thermal conductivity. The results of this study confirmed that ribbon-shaped fibers develop excellent transport properties at lower graphitization temperatures than those used commercially for round-shaped fibers. Additionally, for the first time, two models that directly relate the structure of the carbon fiber to its thermal conductivity were developed.

Gallego, Nidia Constanza

360

The study of thermodynamic properties and transport properties of multicomponent systems with chemical reactions  

NASA Astrophysics Data System (ADS)

In case of system with chemical reaction the most important properties are heat conductivity and heat capacity. In this work we have considered the equation for estimate the component of these properties caused by chemical reaction and ionization processes. We have evaluated the contribution of this part in heat conductivity and heat capacity too. At the high temperatures contribution in heat conductivity from ionization begins to play an important role. We have created a model, which describe partial and full ionization of gases and gas mixtures. In addition, in this work we present the comparison of our result with experimental data and data from numerical simulation. We was used the data about transport properties of middle composition of Russian coals and the data of thermophysical properties of natural gas for comparison.

Shmelkov, Y.; Samujlov, E.

2013-04-01

361

Controlling anisotropic nanoparticle growth through plasmon excitation  

Microsoft Academic Search

Inorganic nanoparticles exhibit size-dependent properties that are of interest for applications ranging from biosensing and catalysis to optics and data storage. They are readily available in a wide variety of discrete compositions and sizes. Shape-selective synthesis strategies now also yield shapes other than nanospheres, such as anisotropic metal nanostructures with interesting optical properties. Here we demonstrate that the previously described

Rongchao Jin; Y. Charles Cao; Encai Hao; Gabriella S. Métraux; George C. Schatz; Chad A. Mirkin

2003-01-01

362

Anisotropic Porous Structure of Pharmaceutical Compacts Evaluated by PGSTE-NMR in Relation to Mechanical Property Anisotropy  

Microsoft Academic Search

Purpose  The pore space anisotropy of pharmaceutical compacts was evaluated in relation to the mechanical property anisotropy.\\u000a \\u000a \\u000a \\u000a Methods  The topology and the pore space anisotropy were characterized by PGSTE-NMR measurements. Parallelepipedical compacts of anhydrous\\u000a calcium phosphate (aCP) and microcrystalline cellulose (MCC) were tested on top, bottom and side faces. A microindentation\\u000a and three-point single beam tests were used to measure Brinell hardness,

Patrice Porion; Virginie Busignies; Vincent Mazel; Bernard Leclerc; Pierre Evesque; Pierre Tchoreloff

2010-01-01

363

Consideration for the dynamic depolarization in the effective-medium model for description of optical properties for anisotropic nanostructured semiconductors  

SciTech Connect

The effective-medium model has been generalized within the dipole approximation, with allowance for the shape anisotropy and dynamic depolarization of semiconductor nanoparticles. The calculations revealed nonmonotonic dependences for the birefringence and dichroism on the nanoparticle size. Comparison of the measured and calculated refractive index dispersion of birefringent porous silicon layers in the near-IR region indicates that consideration for the dynamic depolarization gives a better description of the optical properties for this material in comparison with the generally used effective-medium electrostatic approximation.

Golovan, L. A.; Zabotnov, S. V., E-mail: zabotnov@vega.phys.msu.ru; Timoshenko, V. Yu.; Kashkarov, P. K. [Moscow State University (Russian Federation)

2009-02-15

364

Robust anisotropic diffusion  

Microsoft Academic Search

Relations between anisotropic diffusion and robust statis tics are described in this pa- per. Specifically, we show that anisotropic diffusion can be seen as a robust estimation procedure that estimates a piecewise smooth image from a noi sy input image. The \\

Michael J. Black; Guillermo Sapiro; David H. Marimont; David Heeger

1998-01-01

365

Transient waves in inhomogeneous anisotropic elastic plates  

Microsoft Academic Search

Summary This paper considers the problem of transient wave propagation in elastic Cosserat plates that may be anisotropic, inhomogeneous, or of variable thickness. The methods of rays and of singular wave curves are combined to find and integrate the transport equations governing growth-decay behaviour of the extensional and bending wave modes to derive a common general formula involving the material

H. Cohen; R. S. D. Thomas

1986-01-01

366

Orientation of bone mineral and its role in the anisotropic mechanical properties of bone--transverse anisotropy.  

PubMed

An orientation of hydroxyapatite (HAP) crystals in bovine femur mineral was investigated by means of X-ray pole figure analysis (XPFA). It was found that the c-axis of HAP generally orients parallel to the longitudinal axis of bone (bone axis) and a significant amount of c-axis was oriented in other directions, in particular, perpendicular to the bone axis. Comparing these results with those of the small angle X-ray scattering (SAXS) investigation by Matsushima et al. (Jap. J. appl. Phys. 21, 186-189, 1982) at least two types of morphology of bone mineral were found; rod like bone mineral having the c-axis of HAP crystal parallel to the longitudinal axis of the rod and that having the c-axis not parallel, in a particular case, perpendicular to its longitudinal axis. Transverse anisotropy in mechanical properties of bone was reproduced by the estimation of Young's moduli by using the structural results mainly from XPFA. It is concluded that the anisotropy in mechanical properties of bone is well explained by taking account of the non-longitudinal (off-bone) axial distribution of orientation of bone mineral. PMID:2540205

Sasaki, N; Matsushima, N; Ikawa, T; Yamamura, H; Fukuda, A

1989-01-01

367

Characterization of fluid transport properties of reservoirs using induced microseismicity  

Microsoft Academic Search

We systematically describe an approach to estimate the large-scale permeability of reservoirs using seismic emission (microseismicity) induced by fluid injection. We call this approach seismicity-based reservoir char- acterization (SBRC). A simple variant of the approach is based on the hypothesis that the triggering front of hydraulically-induced microseismicity propagates like a diffusive process (pore pressure relaxation) in an effective homogeneous anisotropic

Serge A. Shapiro; Elmar Rothert; Volker Rath; Jan Rindschwentner

2002-01-01

368

Thermodynamic and transport properties of infinite U Hubbard model  

NASA Astrophysics Data System (ADS)

The infinite U Hubbard model, which excludes double occupancy of electrons on a lattice site, can be considered as an exactly solvable non-interacting orthofermion model. We obtained several thermodynamic and transport properties like specific heat, entropy, magnetization, magnetic susceptibility and thermoelectric power for the non-interacting orthofermions. It is found that in one dimension our results coincides with that of known exact results. In case of thermoelectric power, we have also obtained the generalized Heikes formula in high temperature limits and Stafford results at low temperatures. Since the non-interacting orthofermion model is exactly solvable in any dimension, our results can be used as a guide to ascertain the accuracy of the approximations, used to solve the finite U Hubbard model, frequently employed for the study of the strongly correlated electron systems.

Kishore, R.; Mishra, A. K.

2010-01-01

369

Transport properties of AA-stacking bilayer graphene nanoribbons  

NASA Astrophysics Data System (ADS)

The transport properties of AA-stacking bilayer graphene nanoribbons (GNs) have been explored by using the nonequilibrium Green's function method and the Landauer-Büttiker formalism. It is found that in the case of zero bias, the interlayer coupling has pronounced effects on the conductance of bilayer GNs. The zigzag bilayer GNs remain metallic, but metallic armchair bilayer GNs will be semiconductor as the strength of interlayer coupling exceeds critical value. The first Van Hove singularities move close to the Dirac point for both armchair and zigzag bilayer GNs with the strength of interlayer coupling increasing. Some prominent conductance peaks around the Fermi energy are observed in zigzag bilayer GNs, when the top layer and bottom layer have different widths. In the presence of bias voltage, the I-V curves show that for armchair bilayer GNs, the interlayer interactions suppress current, while the interlayer interactions have almost no effect on the current for zigzag bilayer GNs. The ripples in bilayer GNs suppress electronic transport, especially for zigzag bilayer GNs.

Xu, Ning; Wang, B. L.; Shi, Daning; Zhang, Chao

2012-06-01

370

Transport properties and stability of molecular break junctions  

NASA Astrophysics Data System (ADS)

The electrode-molecule interface in a break junction is known to be crucial to understand its electronic and transport properties. Using first-principles calculations we first probe a comprehensive set of mechanisms responsible for the stability of the prototype junction of a benzene-dithiol (BDT) between gold electrodes. We find that by pulling the electrodes apart the geometry of the molecule depends drastically on the electrode-surface morphology. We next report results of the quantum transport calculations for several stable junction configurations. The calculations are performed using the recently developed technique based on density functional theory and complex absorbing potentials[1]. The molecular junction is treated as a closed system with a set of complex potentials mimicking the source and the drain electrodes. We find that the conductance of the BDT molecule varies significantly within the different junction configurations. We will compare the results with recent experiments on BDT break junctions. [1]. K. Varga and S.T. Pantelides, PRL 98, 076804 (2007).

Sergueev, Nikolai; Tsetseris, Leonidas; Varga, Kalman; Pantelides, Sokrates

2009-03-01

371

Transport Properties of SAM Molecular Diodes with Structural Tunability  

NASA Astrophysics Data System (ADS)

A new molecular engineering approach is used to fabricate molecular junctions from self-assembled-monolayers (SAM) sandwiched between gold electrodes, with structural tunability based on two-component solid-state mixtures of molecular wires (1,4 methane benzene-dithiol; Me-BDT, and molecular insulator spacers (1-pentanethiol; PT). The electrical transport of the fabricated SAM diodes was investigated at various temperatures versus the ratio r between the molecular wires and insulators. At r < 10-3 the diodes are dominated by the isolated molecular wires dispersed in the dielectric spacer matrix; from the conductivity vs. r we determined the value for the Me-BDT molecular resistance to be 4x10^8 Ohm. We also found that the activation energy in these devices is ˜50 meV at low bias and high temperatures; and injection barrier of ˜1.5 eV at intermediate bias and low temperatures. At r > 10-3 Me-BDT aggregates are formed in the PT matrix resulting in additional in-plane order and substantive changes in the transport properties.

Burtman, Vladimir; Vardeny, Valy Z.; Ndobe, Alex

2006-03-01

372

Electron Transport Materials: Synthesis, Properties and Device Performance  

SciTech Connect

We report the design, synthesis and characterization, thermal and photophysical properties of two silane based electron transport materials, dibenzo[b,d]thiophen-2-yltriphenylsilane (Si{phi}87) and (dibenzo[b,d]thiophen-2-yl)diphenylsilane (Si{phi}88) and their performance in blue organic light emitting devices (OLEDs). The utility of these materials in blue OLEDs with iridium (III) bis[(4,6-difluorophenyl)-pyridinato-N,C']picolinate (Firpic) as the phosphorescent emitter was demonstrated. Using the silane Si{phi}87 as the electron transport material (ETm) an EQE of 18.2% was obtained, with a power efficiency of 24.3 lm/W (5.8V at 1mA/cm{sup 2}), in a heterostructure. When Si{phi}88 is used, the EQE is 18.5% with a power efficiency of 26.0 lm/W (5.5V at 1mA/cm{sup 2}).

Cosimbescu, Lelia; Wang, Liang; Helm, Monte L.; Polikarpov, Evgueni; Swensen, James S.; Padmaperuma, Asanga B.

2012-06-01

373

The anisotropic effect of functional groups in 1H NMR spectra is the molecular response property of spatial nucleus independent chemical shifts (NICS)--conformational equilibria of exo/endo tetrahydrodicyclopentadiene derivatives.  

PubMed

The inversion of the flexible five-membered ring in tetrahydrodicyclopentadiene (TH-DCPD) derivatives remains fast on the NMR timescale even at 103 K. Since the intramolecular exchange process could not be sufficiently slowed for spectroscopic evaluation, the conformational equilibrium is thus inaccessible by dynamic NMR. Fortunately, the spatial magnetic properties of the aryl and carbonyl groups attached to the DCPD skeleton can be employed in order to evaluate the conformational state of the system. In this context, the anisotropic effects of the functional groups in the (1)H NMR spectra prove to be the molecular response property of spatial nucleus independent chemical shifts (NICS). PMID:21152640

Kleinpeter, Erich; Lämmermann, Anica; Kühn, Heiner

2010-12-13

374

Predicting the transport properties of sedimentary rocks from microstructure  

SciTech Connect

Understanding transport properties of sedimentary rocks, including permeability, relative permeability, and electrical conductivity, is of great importance for petroleum engineering, waste isolation, environmental restoration, and other applications. These transport properties axe controlled to a great extent by the pore structure. How pore geometry, topology, and the physics and chemistry of mineral-fluid and fluid-fluid interactions affect the flow of fluids through consolidated/partially consolidated porous media are investigated analytically and experimentally. Hydraulic and electrical conductivity of sedimentary rocks are predicted from the microscopic geometry of the pore space. Cross-sectional areas and perimeters of individual pores are estimated from two-dimensional scanning electron microscope (SEM) photomicrographs of rock sections. Results, using Berea, Boise, Massilon, and Saint-Gilles sandstones show close agreement between the predicted and measured permeabilities. Good to fair agreement is found in the case of electrical conductivity. In particular, good agreement is found for a poorly cemented rock such as Saint-Gilles sandstone, whereas the agreement is not very good for well-cemented rocks. The possible reasons for this are investigated. The surface conductance contribution of clay minerals to the overall electrical conductivity is assessed. The effect of partial hydrocarbon saturation on overall rock conductivity, and on the Archie saturation exponent, is discussed. The region of validity of the well-known Kozeny-Carman permeability formulae for consolidated porous media and their relationship to the microscopic spatial variations of channel dimensions are established. It is found that the permeabilities predicted by the Kozeny-Carman equations are valid within a factor of three of the observed values methods.

Schlueter, E.M.

1995-01-01

375

Influence of raw materials and milling technological process on magnetic properties of sintered anisotropic Sr-ferrite magnet  

SciTech Connect

It is necessary to reduce the Sr-ferrite grain size below 1 {mu}m for high coercivity, besides a high degree of density and orientation for high residual induction. However, submicron Sr-ferrite particles are difficult to orient in a magnetic field at pressing stage because of their cohesion. For preventing this cohesion, treatments with dispersants and reducing coercive force of S-ferrite particles are very effective. In this research, a study was done correlating purity and aggregation state of raw materials with intrinsic coercive force and microstructure of presintered Sr-ferrite sample, and a presintered sample with uniform grain size distribution and lower coercivity was gained. The classical pulverizing process is composed of coarse dry milling and fine wet milling. The results confirm that compared with wet milling, a long dry milling time promotes the development of crystal deformation and reduces the coercive force of the powders effectively; hence the viscosity is also lowered. By enhancing dry-milling time to control average particle size under 1.8 {mu}m and fine wet milling up to 0.75 {mu}m with optimum amount of dispersant, a well dispersed Sr-ferrite slurry is prepared. By these methods, a remarkable improvement of magnetic properties was achieved. {copyright} {ital 1997 American Institute of Physics.}

Teng, Y.; Lu, B.; Yao, J. [Beijing General Research Institute of Mining and Metallurgy, Research Center for Magnetic Materials, Beijing, 100054 (China)

1997-04-01

376

Magnetic and transport properties of Fe-based nanocrystalline materials  

NASA Astrophysics Data System (ADS)

Fe-rich amorphous alloys containing late transition metals like Nb, V, Zr,..., sometimes with the addition of Cu, can crystallize in ultrafine grains of a crystalline phase, a few nanometers in diameter, embedded in a disordered matrix. In such state they have shown excellent soft magnetic properties for technical applications, rising the interest for deep studies. In this paper, recent work on some Fe-Nb and Fe-Zr based alloys both in amorphous state and after several degrees of nanocrystallization is presented. The nanocrystallization process has been achieved by conventional heat treatments (about 1 h at temperatures around 400-500 °C in a controlled atmosphere furnance) as well as by Joule heating using an electrical current flowing through the sample. Magnetic measurements, electrical resistivity, x-rays diffraction and 57Fe Mössbauer spectroscopy were used in the study of the crystalline phases appearing after the thermal treatments. The basic magnetic and transport properties of the nanocrystals do not differ appreciably from their bulk values. The magnetic anisotropy, however, is very sensitive to grain size and to the intergranular magnetic coupling. The effect of such coupling is deduced from the coercivity changes at the Curie Temperature of the amorphous matrix remaining after nanocrystallization.

Barandiarán, J. M.

1994-01-01

377

Elastic and transport properties in polycrystals of crackedgrains: Cross-property relations and microstructure  

SciTech Connect

Some arguments of Bristow (1960) concerning the effects of cracks on elastic and transport (i.e., electrical or thermal conduction) properties of cold-worked metals are reexamined. The discussion is posed in terms of a modern understanding of bounds and estimates for physical properties of polycrystals--in contrast to Bristow's approach using simple mixture theory. One type of specialized result emphasized here is the cross-property estimates and bounds that can be obtained using the methods presented. Our results ultimately agree with those of Bristow, i.e., confirming that microcracking is not likely to be the main cause of the observed elastic behavior of cold-worked metals. However, it also becomes clear that the mixture theory approach to the analysis is too simple and that crack-crack interactions are necessary for proper quantitative study of Bristow's problem.

Berryman, J.G.

2007-10-02

378

Shear induced transport property in impermeable fault rocks and its effect on the mechanical property  

NASA Astrophysics Data System (ADS)

Transport property in fault zone will change by shear deformation during and after earthquakes, and the change in transport property may lead to the fault strength transition as well. Previous study by Tanikawa et al. (2012) revealed that, for permeable rocks, shear induced permeability in medium to high slip velocity is mainly controlled by the fluid viscosity that changes due to frictional heating. However, impermeable fault rocks may show different evolution process for the fluid transport property compared to permeable fault rock. In this study, rock-to-rock friction tests was conducted on granite samples to see a shear induced transport property in impermeable fault rocks. We measured flow rate during and after friction test using a rotary shear apparatus. Two 20-mm-long hollow cylindrical specimens (outer and inner diameters of 25 and 9.5 mm, respectively) of low permeable Aji Granite (permeability of 10^-19 m^2) were used in all tests. One cylindrical specimen was fixed and the other rotated under a fixed axial stress of 2 MPa. We applied the total slip displacements of 1.5 and 3 m at various constant slip rates from 0.076 to 150 mm/s. To measure shear-induced fluid transport property, radial flow from the inner wall to the outer wall of the specimen was induced by applying a differential pore pressure between the inner and outer walls. Nitrogen gas was used as a pore fluid. Friction coefficient typically decreased from 0.9 to 0.5 with an increase of slip velocity. At the same slip rate, friction coefficient increased with an increase in apparent permeability of specimen. Apparent permeability during and after friction test were over one order of magnitude larger than that of intact granite. At slower slip rate below 0.01 m/s, permeability decreased soon after sliding ceased, though at high slip rate, permeability increased after sliding. By comparing initial permeability and permeability after 10 minutes of friction tests, results show a reduction in permeability that occurred when initial permeability is high. In contrast, permeability increases with sliding when initial permeability is low. This transition transport property is (intrinsic) transmissivity of ~2*10^-21 m3 that is equivalent to fracture aperture of ~0.3 ?m assuming that threshold aperture is equivalent to hydraulic aperture evaluated by cubic law. We assume that the permeability change during sliding is caused by the production of gouge and smoothing of slip surface that changes aperture size and real contact area of specimens. The change of surface property resulted in change of friction property as well. The reduction of permeability immediately after sliding is probably caused by the thermo-elastic effect on aperture due to frictional heating.

Tanikawa, Wataru; Tadai, Osamu; Mukoyoshi, Hideki; Hirose, Takehiro

2013-04-01

379

ANISOTROPIC STRAIN-DEPENDENT MATERIAL PROPERTIES OF BOVINE ARTICULAR CARTILAGE IN THE TRANSITIONAL RANGE FROM TENSION TO COMPRESSION  

PubMed Central

Articular cartilage exhibits complex mechanical properties such as anisotropy, inhomogeneity and tension-compression nonlinearity. This study proposes and demonstrates that the application of compressive loading in the presence of osmotic swelling can be used to acquire a spectrum of incremental cartilage moduli (EYi) and Poisson’s ratios (?ij) from tension to compression. Furthermore, the anisotropy of the tissue can be characterized in both tension and compression by conducting these experiments along 3 mutually perpendicular loading directions: Parallel to split-line (1-direction), perpendicular to split-line (2-direction) and along the depth direction (3-direction, perpendicular to articular surface), accounting for tissue inhomogeneity between the surface and deep layers in the latter direction. Tensile moduli were found to be strain-dependent while compressive moduli were nearly constant. The peak tensile (+) Young’s moduli in 0.15 M NaCl were E+Y1 =3.1±2.3 MPa, E+Y2 =1.3±0.3 MPa, E+Y3Surface=0.65±0.29MPa and E+Y3Deep=2.1±1.2MPa. The corresponding compressive (?) Young’s moduli were E?Y1 =0.23±0.07 MPa, E?Y2 =0.22±0.07 MPa, E?Y3Surface=0.18±0.07MPa and E?Y3Deep=0.35±0.11MPa. Peak tensile Poisson’s ratios were ?+12 =0.22±0.06, ?+21 =0.13±0.07, ?+31Surface=0.10±0.03 and ?+31Deep=0.20±0.05 while compressive Poisson’s ratios were ??12 =0.027±0.012, ??21 =0.017±0.007, ??31Surface=0.034±0.009 and ??31Deep=0.065±0.024. Similar measurements were also performed at 0.015 M and 2 M NaCl, showing strong variations with ionic strength. Results indicate that (a) a smooth transition occurs in the stress-strain and modulus-strain responses between the tensile and compressive regimes, and (b) cartilage exhibits orthotropic symmetry within the framework of tension-compression nonlinearity. The strain-softening behavior of cartilage (the initial decrease in EYi with increasing compressive strain) can be interpreted in the context of osmotic swelling and tension-compression nonlinearity.

Chahine, Nadeen O.; Wang, Christopher C-B.; Hung, Clark T.; Ateshian, Gerard A.

2010-01-01

380

Review of Anisotropic Terahertz Material Response  

NASA Astrophysics Data System (ADS)

Anisotropy is ubiquitous in solids and enhanced in low-dimensional materials. In response to an electromagnetic wave, anisotropic absorptive and refractive properties result in dichroic and birefringent optical phenomena both in the linear and nonlinear optics regimes. Such material properties have led to a diverse array of useful polarization components in the visible and near-infrared, but mature technology is non-existent in the terahertz (THz). Here, we review several novel types of anisotropic material responses observed in the THz frequency range, including both linear and circular anisotropy, which have long-term implications for the development of THz polarization optics. We start with the extreme linear anisotropy of macroscopically aligned carbon nanotubes, arising from their intrinsically anisotropic dynamic conductivity. Magnetically induced anisotropy will then be reviewed, including the giant Faraday effects observed in semiconductors, semimetals, and two-dimensional electron systems.

Arikawa, Takashi; Zhang, Qi; Ren, Lei; Belyanin, Alexey A.; Kono, Junichiro

2013-08-01

381

Review of Anisotropic Terahertz Material Response  

NASA Astrophysics Data System (ADS)

Anisotropy is ubiquitous in solids and enhanced in low-dimensional materials. In response to an electromagnetic wave, anisotropic absorptive and refractive properties result in dichroic and birefringent optical phenomena both in the linear and nonlinear optics regimes. Such material properties have led to a diverse array of useful polarization components in the visible and near-infrared, but mature technology is non-existent in the terahertz (THz). Here, we review several novel types of anisotropic material responses observed in the THz frequency range, including both linear and circular anisotropy, which have long-term implications for the development of THz polarization optics. We start with the extreme linear anisotropy of macroscopically aligned carbon nanotubes, arising from their intrinsically anisotropic dynamic conductivity. Magnetically induced anisotropy will then be reviewed, including the giant Faraday effects observed in semiconductors, semimetals, and two-dimensional electron systems.

Arikawa, Takashi; Zhang, Qi; Ren, Lei; Belyanin, Alexey A.; Kono, Junichiro

2013-11-01

382

Momentum and spin transport properties of spin polarized Fermi systems  

NASA Astrophysics Data System (ADS)

We carried out experiments on a spin polarized 3He- 4He mixture with 3He concentration x 3 = 6.26 x 10-4, and on pure 3He liquid. Spin polarization affects the transport properties of these Fermi systems. The effect on momentum transport was studied by using a vibrating-wire viscometer to measure viscosity of the 3He-4He mixture over the temperature range 6.09 mK--100 mK in 7.96 T and 1.00 T magnetic fields. A large viscosity increase was observed upon application of the 7.96 T magnetic field for temperature T < TF(TF = 19.5 mK is the Fermi temperature). The observed viscosity is in very good agreement with theoretical calculations for a dilute Fermi gas by Jeon and Mullin [1988, 1989] and Mullin and Jeon [1992]. The polarization effect on spin transport was investigated by measuring the transverse diffusion coefficient D ? in pure 3He liquid at saturated vapor pressure and at 15.85 bar over the temperature range 4.5 mK--159 mK in a 7.96 T magnetic field. We used a pulsed NMR spin echo technique in a field gradient of 16.0 G/cm to do the measurements and fits to the Leggett equations [1970] to obtain D?. For T < 20 mK, we found D? is less than measured in earlier experiments at lower magnetic fields. D? does not increase with decreasing temperature as 1/T2, but appears to approach a constant as T ? 0 while it is expected that the longitudinal spin diffusion coefficient D? ? 1/ T2. This is called spin diffusion anisotropy and it was observed for the first time in our 3He liquid experiments. The anisotropy temperature we determined for 3He liquid was Ta = 16.4 +/- 2.2 mK at saturated vapor pressure and in a 7.96 T magnetic field. The transverse spin diffusion in 3 He results agree qualitatively with theories proposed by Meyerovich and Musaeflan [1992, 1994]. They also agree qualitatively with theories proposed by Golosov and Ruckenstein [1995, 1998] by extrapolation of the dilute theory to a strongly interacting system.

Wei, Lijuan

383

Electron transport properties of carbon-based nanostructures  

NASA Astrophysics Data System (ADS)

Grapheme and graphene-related systems have been the focus of intensive research due to their exceptional electronic behavior. Their properties have been studied for decades, from the unique band structure predicted for a single layer of graphite, to the unexpected linear magnetoresistance observed in its bulk form. Since its experimental isolation in 2004, studies on graphene monolayer, bilayer, and few-layer systems garnered an overwhelming amount of attention from the scientific community, with studies focusing on multilayers with nanometer thicknesses paling in comparison. The main motivation of this study is to further the understanding of systems consisting of multilayer graphene and ultrathin graphite (graphitic multilayers) through electron transport experiments. Uniquely designed and fabricated devices based on carbon nanostructures were used to study the transport of charge carriers under high electric and magnetic fields. For short-channel suspended graphitic multilayer devices, the two-terminal differential conductance dI/dV as a function of drain-source bias Vd displays a pronounced dip pinned at Vd=0, explained by the hot electron effect. The dip is attenuated under high magnetic fields, likely due to intra-Landau level cyclotron phonon scattering. Also, distinct high-energy dI/dV anomalies have been observed and shown to be related to intrinsic phonon-emission processes in graphite. The evolution of such dI/dV anomalies under magnetic fields is understood as a consequence of the inter-Landau level cyclotron-phonon resonance scattering. The magnetoresistance (MR) of this system shows Shubnikov-de Haas oscillations on top of a strong positive nearly-linear background. Upon the introduction of a significant amount of short-range disorders through ion implantation, the positive MR transforms into a negative MR. The results for the MR of pure and implanted graphitic multilayers can be understood by considering a recent magneto-transport theory for two-dimensional systems. Four terminal measurements on unique multi-terminal devices with suspended multilayer graphene grown by ambient-pressure chemical vapor deposition also display the dI/dV dip related to the hot electron effect, and its attenuation at high magnetic fields, confirming its intrinsic nature for multilayer graphene systems.

Diaz Pinto, Carlos A.

384

Tuning the electronic transport properties of graphene through functionalisation with fluorine  

Microsoft Academic Search

Engineering the electronic properties of graphene has triggered great interest for potential applications in electronics and opto-electronics. Here we demonstrate the possibility to tune the electronic transport properties of graphene monolayers and multilayers by functionalisation with fluorine. We show that by adjusting the fluorine content different electronic transport regimes can be accessed. For monolayer samples, with increasing the fluorine content,

F. Withers; S. Russo; M. Dubois; M. F. Craciun

2011-01-01

385

Effect of hydrochloric acid on the transport properties of tin through ion-exchange membranes  

Microsoft Academic Search

This work presents a study of the transport properties of two ion-exchange membranes present in an electrochemical reactor used to process the wasted and rinse baths of the electroless plating of polymers industry. The influence of the hydrochloric acid on the transport properties of tin through both cation- and anion-exchange membranes has been evaluated by chronopotentiometry. The shape of the

M. García-Gabaldón; V. Pérez-Herranz; J. García-Antón; J. L. Guiñón

2009-01-01

386

Experimental studies of the relationship between DNA structure and chemical modification, and its charge transport properties  

Microsoft Academic Search

We experimentally investigate the influence of the physico-chemical properties of DNA molecules on its charge transport capabilities. By performing comparative rather than absolute charge transport measurements, we probe the effect of chemical modifications on the electronic properties of the molecule. Modifications include the introduction of phosphodiester bond breaks, and intercalation of metal cations, as probes to ascertain the relationship between

V. Soghomonian; D. E. Davis; A. A. Belak; J. F. Dowd; J. J. Heremans

2007-01-01

387

Implications of hole vs electron transport properties for high speed Pnp heterojunction bipolar transistors  

Microsoft Academic Search

This paper examines the implications of differences in hole and electron transport properties on the microwave performance potential of InP-based Pnp HBTs. In particular, the carrier mobility, diffusion length, saturation velocity and ballistic transport properties for holes vs electrons are compared and their implications for Pnp device performance, such as the current gain and high frequency performance. The effects of

S. Datta; K. P Roenker; M. M Cahay; William E Stanchina

1999-01-01

388

The effects of vacancies on the transport properties of zigzag graphene nanoribbons  

Microsoft Academic Search

The transport properties of zigzag graphene nanoribbons (ZGNRs) with different patterns of vacancies are investigated by using density functional theory and nonequilibrium Green's function (NEGF) formalism. It is found that the transport properties are different with a different lattice type vacancy (A-type or B-type vacancy). The conductance of ZGNRs is more sensitive to an interior vacancy than an edge vacancy.

Yu Zhang; Lianqing Liu; Niandong Jiao; Ning Xi; Yuechao Wang; Zaili Dong

2010-01-01

389

Molecular Simulation of Phase Equilibria and Transport Properties  

NASA Astrophysics Data System (ADS)

Molecular simulations are used to test models and theories through comparison with experimental results and theoretical predictions. Three areas are covered: transport properties, free energy measurement, and phase diagram calculation. Transport properties of isotropic fluids composed of hard ellipsoids of revolution are studied using molecular dynamics simulation. The self diffusion coefficient, the shear viscosity, and the thermal conductivity are evaluated for a range of densities and elongations and are compared to the predictions of an Enskog kinetic theory for nonspherical bodies. The simulation and the kinetic theory values for the shear viscosity and the thermal conductivity show the same qualitative behavior, that is, increasing with density and with particle nonsphericity. Quantitatively, there is good agreement at low densities (up to 30% of closest packing); at higher densities (60% of closest packing) deviations from Enskog theory are larger than, and in the opposite direction to those seen for hard spheres. The Stokes-Einstein and Debye relations are tested, and indicate a transition from a kinetic theory region towards the hydrodynamic limit as density increases. A new Monte Carlo method of free energy calculation, which does not rely on particle insertion is analyzed. The justification for the use of the method in the NVT ensemble is shown. The method is extended into the isothermal-isobaric ensemble where it is successfully applied to a variety of hard molecules. Analysis shows that the single particle sampling portion of the method should not be extended to the NPT ensemble. Isothermal phase diagrams for a variety of mixtures are determined by a combination of semi-grand ensemble simulation and orthogonal collocation integration. The semi-grand ensemble avoids problems of particle insertion that are encountered in some other widely used techniques. Orthogonal collocation allows the simulations to be run in parallel as opposed to stepwise integration techniques. The orthogonal collocation method is first studied numerically on an ideal system to demonstrate its superiority in suppressing error propagation. Next, Lennard-Jones mixtures, including some which form azeotropes, are examined and compared with prior works. Finally, three systems of real molecules, Krypton-Argon Methane-Ethane, and Ethane -Carbon Dioxide are simulated and compared with experimental results.

Bereolos, Peter James

1995-01-01

390

Effect of recording conditions on the anisotropic diffraction of volume holographic gratings  

Microsoft Academic Search

The anisotropic Bragg diffraction of the volume holographic gratings in photorefractive crystals are investigated based on the model of anisotropic coupled-wave theory. The effect of the initial intensity ratio and the recording angles of the two recording waves on the anisotropic Bragg diffraction properties is discussed. It is shown that both the ratio of the initial intensity and the incident

Xin Wang; Aimin Yan; De’an Liu; Liren Liu; Zhijuan Hu

2007-01-01

391

Transport properties of pure and doped MNiSn (M=Zr, Hf)  

Microsoft Academic Search

We have studied the transport properties in a family of pure and doped intermetallics of the form MNiSi (M=Zr, Hf), the structures known as the half-Heusler alloys. We have shown that the transport is very sensitive to structural arrangements of the constituent atoms, and this can be manipulated by annealing, isostructural alloying, and doping. The unusual transport properties are viewed

C. Uher; J. Yang; S. Hu; D. T. Morelli; G. P. Meisner

1999-01-01

392

Oxygen nonstoichiometry and transport properties of strontium substituted lanthanum ferrite  

SciTech Connect

This study presents an investigation of the properties of (La{sub 0.6}Sr{sub 0.4}){sub 0.99}FeO{sub 3-{delta}} (LSF40) covering thermomechanical properties, oxygen nonstoichiometry and electronic and ionic conductivity. Finally, oxygen permeation experiments have been carried out and the oxygen flux has been determined as a function of temperature and driving force. The electrical conductivity was measured using a 4 probe method. It is shown that the electrical conductivity is a function of the charge carrier concentration only. The electron hole mobility is found to decrease with increasing charge carrier concentration in agreement with recent literature. Values of the chemical diffusion coefficient, D{sub Chem}, and the surface exchange coefficient, k{sub Ex}, have been determined using electrical conductivity relaxation. At 800 deg. CD{sub Chem} is determined to be 6.2x10{sup -6}cm{sup 2}s{sup -1} with an activation energy of 137kJmol{sup -1}. The surface exchange coefficient is found to decrease with decreasing oxygen partial pressure. Oxygen permeation experiments were carried out. The flux through a membrane placed between air and wet hydrogen/nitrogen was J{sub O{sub 2}}{approx}1.8x10{sup -6}molcm{sup -2}s{sup -1} (corresponding to an equivalent electrical current density of 670mAcm{sup -2}). The oxygen permeation measurements are successfully interpreted based on the oxygen nonstoichiometry data and the determined transport parameters.

Sogaard, Martin [Fuel Cells and Solid State Chemistry Department, Riso National Laboratory, Frederiksborgvej 399, DK-4000 Roskilde (Denmark)], E-mail: martin.soegaard@risoe.dk; Vang Hendriksen, Peter [Fuel Cells and Solid State Chemistry Department, Riso National Laboratory, Frederiksborgvej 399, DK-4000 Roskilde (Denmark); Mogensen, Mogens [Fuel Cells and Solid State Chemistry Department, Riso National Laboratory, Frederiksborgvej 399, DK-4000 Roskilde (Denmark)

2007-04-15

393

Superconducting and dielectric instabilities in Tl2Mo6Se6: Unusual transport properties and unsaturating critical field  

NASA Astrophysics Data System (ADS)

The Hall effect of the quasi-one-dimensional compound Tl2Mo6Se6 undergoes a progressive transition between an electronlike metallic regime at 300 K and a holelike semimetallic regime just above the superconducting transition (Tc~=6.5 K). We show that, above ~=80 K, the paradoxical transport properties can be explained by an unusual anisotropic electron scattering related to the low dimensionality of the system and to its instability. A spin-density-wave (SDW) or charge-density-wave (CDW) state certainly builds up below ~80 K-leading also to a change of regime in the thermopower but not in the conductivity-which is accompanied, at lower temperatures, by a magnetic-field dependence of the Hall coefficient and by a significant transverse magnetoresistance. The superconducting (SC) state therefore arises after the electron spectrum has been partly dielectrized by the CDW (or SDW) condensation, and it involves a very small density of states. A large paraconductivity which we attribute to superconducting fluctuations is detected just above Tc and the transverse upper critical field H?c2 does not saturate down to 50 mK, which confirms that we are dealing with a very unusual superconducting state, intricately connected with the other competing instabilities.

Brusetti, R.; Briggs, A.; Laborde, O.; Potel, M.; Gougeon, P.

1994-04-01

394

Effects of interlayer coupling on the magnetic and transport properties of superconducting multilayers and high-temperature superconductors  

SciTech Connect

The effect of interlayer coupling on the transport properties and dissipation in a magnetic field is reviewed for superconducting multilayers including highly-anisotropic high-temperature superconductors (HTS). For the applied field parallel to the superconducting layers the absence of any Lorentz-force dependence of the dissipation leads to an explanation other than flux motion. This is consistent with a Josephson junction dissipation which dominates flux motion of the insulating regions between layers. However, in is seen to cross over from phase slips at Josephson junctions to depinning of vortices from the external field at high fields and temperatures. For fields perpendicular to the superconducting layers the much greater resistive broadening in HTS is due to dissipation by thermally-activated flux motion, consistent with a lack of intrinsic pinning. We show experimental evidence that the associated flux motion occurs as a result of a crossover from three dimensional (3D) vortex lines to 2D independent pancake-like vortices, residing in the Cu-O layers. This 3D to 2D crossover occurs after k{sub B}T exceeds the Josephson coupling energy.

Gray, K.E.; Hettinger, J.D.; Kim, D.H.

1994-06-01

395

REVIEWS OF TOPICAL PROBLEMS: Transport properties of carbon nanotubes  

NASA Astrophysics Data System (ADS)

The current status of experimental research on the transport characteristics of carbon nanotubes (CNTs) has been reviewed. Methods for measuring transport coefficients of CNTs have been considered. The available experimental data on the temperature dependence of thermal conductivity and electroconductivity of single-walled and multi-walled CNTs have been analyzed in terms of the ballistic mechanism of charge and heat transport.

Eletskii, Aleksandr V.

2009-03-01

396

Anisotropic Bragg diffraction of finite-sized volume holographic grating in photorefractive crystals  

Microsoft Academic Search

Anisotropic diffraction of uniform plane wave by finite-sized volume holographic grating in photorefractive crystals is considered. It is found that the anisotropic diffraction can take place when some special conditions are satisfied. The diffracted image is obtained in experiment for the anisotropic Bragg diffraction in Fe:LiNbO3 crystals. A coupled wave analysis is presented to study the properties of anisotropic diffraction.

Aimin Yan; Lingyu Wan; De’an Liu; Liren Liu

2007-01-01

397

Novel Transport Properties of Intercalated Graphite Films Prepared by CVD  

NASA Astrophysics Data System (ADS)

With primary focus on possible thermoelectric applications, Se, Te, and Bi were selected for intercalation into graphite via an open-tube CVD approach. Benzene and Ph_2Se_2, Ph_2Te_2, or Ph_3Bi (Ph = phenyl group, C_6H_5) were used for the carbon and intercalant sources. Experiments employing polycrystalline Ni substrates and Ph_2Se2 will be emphasized. Film growth was found to be very sensitive to the orientation of individual grains in the Ni substrate: faces of grains with a poor lattice match to the a-b plane of graphite were generally coated by amorphous material or nickel selenide, while (111) faces readily seeded formation of graphite intercalation compounds, as confirmed by electron microscopy. Due to the experimental geometry, transport properties of our films were measured along c-axis, normal to the substrate surface. The conductivity ?e was two orders of magnitude greater than in pristine graphite at 300 K, while the c-axis Seebeck coefficient Sc exceeded -50 ?V/K, roughly five times greater than in graphite. These two factors in conjunction lead to significantly improved power factors for the intercalated materials as compared to pristine graphite. Whereas graphite has Sc increasing with temperature in the range 100 K to 300 K, our intercalated samples showed more complex behavior over this range, increasing sharply at lower temperatures. This work was supported by ARPA MDA 972-95-1-0021

Williams, K. A.; Grigorian, L.; Sumanasekera, G. U.; Eklund, P. C.

1998-03-01

398

Thermal Transport Properties of Polycrystalline Diamond Films and Other Composites.  

NASA Astrophysics Data System (ADS)

The thermal transport properties of three chemical vapor deposition (CVD) polycrystalline diamond films of different isotopic compositions and other advanced composites have been measured as a function of temperature by using steady and non-steady state techniques. The results of these measurements have been analyzed by using existing theories and models. The Klemens-Callaway model has been used to fit the thermal conductivity data of diamond samples as a function of temperature. Isotopic composition has been found to have significant effect on the thermal conductivity of diamond. Around room temperature, while the thermal conductivities of the isotopically pure ^{12} C and the natural abundant samples were comparable to each other they were about three times higher than that of the sample which was composed of 50% of each ^{12}C and ^{13 }C isotopes. The differences in the thermal conductivities are explained in terms of crystal defects. The thermal conductivity of the composite samples were obtained by measuring their thermal diffisivity. The thermal conductivity of the composites of has been analyzed by using different mixing models.

Belay, Kalayu G.

399

Strain dependence of the heat transport properties of graphene nanoribbons  

NASA Astrophysics Data System (ADS)

Using a combination of accurate density-functional theory and a nonequilibrium Green’s function method, we calculate the ballistic thermal conductance characteristics of tensile-strained armchair (AGNR) and zigzag (ZGNR) edge graphene nanoribbons, with widths between 3 and 50 Å. The optimized lateral lattice constants for AGNRs of different widths display a three-family behavior when the ribbons are grouped according to N modulo 3, where N represents the number of carbon atoms across the width of the ribbon. Two lowest-frequency out-of-plane acoustic modes play a decisive role in increasing the thermal conductance of AGNR-N at low temperatures. At high temperatures the effect of tensile strain is to reduce the thermal conductance of AGNR-N and ZGNR-N. These results could be explained by the changes in force constants in the in-plane and out-of-plane directions with the application of strain. This fundamental atomistic understanding of the heat transport in graphene nanoribbons paves a way to effect changes in their thermal properties via strain at various temperatures.

Emmeline Yeo, Pei Shan; Loh, Kian Ping; Gan, Chee Kwan

2012-12-01

400

Transport Properties of Ce, Sm, and Ho Doped Bismuth Antimony  

NASA Astrophysics Data System (ADS)

Bi88Sb12 alloy has been doped with Ce, Sm, and Ho prepared under two different fabrication conditions. The first being ball milled for 12 hours and a hot pressed at 240 ^oC and the second ball milled for 6 hours and hot pressed at 200 ^oC. It is found that Ce, Sm, and Ho dopants all have a similar impact on the transport properties. A ZT enhancement is seen due to doping which is an effect of an enhanced Seebeck coefficient as a result of a decrease in the carrier concentration most likely caused by a widening band gap. The alteration of the band gap does not appear to be caused by the magnetic moments of Ce, Sm, and Ho based on the similar change to the gap size with the widely varying magnetic moments of the dopants. Also, similar results were not obtained with Fe doped samples, where Fe has a magnetic moment similar to Ce and greater than Sm.

Lukas, K. C.; Zhao, H.; Ren, Z. F.; Opeil, C. P.

2013-03-01

401

Strain dependence of the heat transport properties of graphene nanoribbons.  

PubMed

Using a combination of accurate density-functional theory and a nonequilibrium Green's function method, we calculate the ballistic thermal conductance characteristics of tensile-strained armchair (AGNR) and zigzag (ZGNR) edge graphene nanoribbons, with widths between 3 and 50 ?. The optimized lateral lattice constants for AGNRs of different widths display a three-family behavior when the ribbons are grouped according to N modulo 3, where N represents the number of carbon atoms across the width of the ribbon. Two lowest-frequency out-of-plane acoustic modes play a decisive role in increasing the thermal conductance of AGNR-N at low temperatures. At high temperatures the effect of tensile strain is to reduce the thermal conductance of AGNR-N and ZGNR-N. These results could be explained by the changes in force constants in the in-plane and out-of-plane directions with the application of strain. This fundamental atomistic understanding of the heat transport in graphene nanoribbons paves a way to effect changes in their thermal properties via strain at various temperatures. PMID:23149343

Yeo, Pei Shan Emmeline; Loh, Kian Ping; Gan, Chee Kwan

2012-11-13

402

Thermodynamic and Transport Properties of Superconducting Mg10B2  

NASA Astrophysics Data System (ADS)

Transport and thermodynamic properties of a sintered pellet of the newly discovered MgB2 superconductor have been measured to determine the characteristic critical magnetic fields and critical current densities. Both resistive transition and magnetization data give similar values of the upper critical field, Hc2, with magnetization data giving dHc2/dT = 0.44 T/K at the transition temperature of Tc = 40.2 K. Close to the transition temperature, magnetization curves are thermodynamically reversible, but at low temperatures the trapped flux can be on the order of 1 T. The value of dHc/dT at Tc is estimated to be about 12 mT/K, a value similar to classical superconductors like Sn. Hence, the Ginzburg-Landau parameter ?~26. Estimates of the critical supercurrent density, Jc, using hysteresis loops and the Bean model, give critical current densities on the order of 105 A/cm2. Hence the supercurrent coupling through the grain boundaries is comparable to intermetallics like Nb3Sn.

Finnemore, D. K.; Ostenson, J. E.; Bud'Ko, S. L.; Lapertot, G.; Canfield, P. C.

2001-03-01

403

Interrelation Between Elastic Properties Determined by Brillouin Spectroscopy and Thermal Transport Properties of Garnets  

NASA Astrophysics Data System (ADS)

Both thermal diffusivity and elastic constants are mineral properties of major relevance to understand the dynamics of the solid earth. It is expected that a relation between sound wave velocities, elastic constants, and thermal transport properties exist. The goal of this study is to improve our understanding of the correlation between elastic properties, thermal transport properties and the mean free path lengths of phonons. We are determining the entire set of elastic constants of different synthetic and natural garnets, for instance the solid solution series Y3Al5O12-Yb3Al5O12, with the recently installed Brillouin scattering system at the GeoForschungsZentrum Potsdam. This system consists of a Nd:YVO4 solid state Laser with a wavelength of 532 nm as light source and a Sandercock-type tandem multipass Fabry-Perot interferometer equipped with a photomultiplier tube for signal detection as spectrometer. All measurements were performed in a 90 degree symmetric forward scattering geometry. An anisotropy in shear sound wave velocities of about 3 % and an anisotropy in compressional sound wave velocity of about 1 % is observed for the Yb-rich garnets, which is in agreement with literature data for Y3Al5O12. We reported the thermal diffusivity of the same garnet single crystals in a previous study using a transient method[1]. Knowledge of both the elastic constants and the thermal diffusivities allows the calculation of the mean free path lengths of phonons. [1] Schilling, F. R. (1999): Eur. J. Mineral. 11, 1115-1124

Marquardt, H.; Speziale, S.; Schilling, F.

2007-05-01

404

Anisotropic periodic structure exhibiting gigantic field enhancements  

NASA Astrophysics Data System (ADS)

A strongly anisotropic photonic crystal structure was designed using form birefringence. It has a low group velocity close to a split band edge (SBE) and large field enhancements proportional to the fourth power of the number of periods are predicted. Numerical results are presented illustrating the bandgap behavior as a function of anisotropy and an effective negative index property is discussed.

Shenk, J. O.; Ingel, R. P.; Cao, Y.; Fiddy, M. A.

2008-05-01

405

Rayleigh type bending waves in anisotropic media  

Microsoft Academic Search

The existence, dispersion properties, velocities and energy of waves, localized near the stress-free edge of thin anisotropic plates are investigated. As shown, some qualitatively new effects occur: the velocity of Rayleigh type waves can be not minimal between bending waves; wave decay takes place with oscillations; under some type of anisotropy, power flow can equal zero and can change the

D. D. Zakharov; W. Becker

2003-01-01

406

Influence of material synthesis and doping on the transport properties of WSe 2 single crystals grown by selenium transport  

Microsoft Academic Search

Resistivity and Hall effect measurements of WSe2 single crystals grown with excess selenium as transport agent in chemical vapor transport are presented. The electronic properties are shown to depend strongly on the materials selected for synthesizing polycrystalline powder used in the crystal growth procedure. Compensated high-resistivity samples of p-type doping were obtained with room-temperature carrier concentrations of p ? 1012

A. Klein; P. Dolatzoglou; M. Lux-Steiner; E. Bucher

1997-01-01

407

Monotonic solution of heterogeneous anisotropic diffusion problems  

NASA Astrophysics Data System (ADS)

Anisotropic problems arise in various areas of science and engineering, for example groundwater transport and petroleum reservoir simulations. The pure diffusive anisotropic time-dependent transport problem is solved on a finite number of nodes, that are selected inside and on the boundary of the given domain, along with possible internal boundaries connecting some of the nodes. An unstructured triangular mesh, that attains the Generalized Anisotropic Delaunay condition for all the triangle sides, is automatically generated by properly connecting all the nodes, starting from an arbitrary initial one. The control volume of each node is the closed polygon given by the union of the midpoint of each side with the "anisotropic" circumcentre of each final triangle. A structure of the flux across the control volume sides similar to the standard Galerkin Finite Element scheme is derived. A special treatment of the flux computation, mainly based on edge swaps of the initial mesh triangles, is proposed in order to obtain a stiffness M-matrix system that guarantees the monotonicity of the solution. The proposed scheme is tested using several literature tests and the results are compared with analytical solutions, as well as with the results of other algorithms, in terms of convergence order. Computational costs are also investigated.

Aricò, Costanza; Tucciarelli, Tullio

2013-11-01

408

Cloak for curvilinearly anisotropic media in conduction  

NASA Astrophysics Data System (ADS)

We explore the possibility to cloak a region in curvilinearly anisotropic background materials in the context of conductivity. Materials with curvilinear anisotropy possess constant properties in specific curvilinear coordinate. For cylindrically and spherically anisotropic solids, the cloak center and the origin of material coordinate are generally not collocated. We show that in combination with a rigid-body translation from the cloak center to the material origin, the previous coordinate transformation procedure remains applicable. But now the transformed material specifications depend on the position of cloak center. The validity of the cloak parameters is verified by finite element simulations.

Chen, Tungyang; Weng, Chung-Ning; Chen, Jun-Shan

2008-09-01

409

Anisotropic flow analysis in the ALICE experiment  

SciTech Connect

Anisotropic flow is one of the observables which is sensitive to the properties of the created hot and dense system in heavy-ion collisions. Unfortunately detailed measurements of anisotropic flow are difficult due to contributions from nonflow correlations. In these proceedings a recently developed method for flow analysis, called Q-cumulants (a.k.a. direct cumulants), will be presented. This new method is used to study azimuthal correlations in p-p collisions at 7 TeV with the ALICE detector.

Bilandzic, Ante [Nikhef, Science Park 105, 1098 XG Amsterdam (Netherlands); Utrecht University, P.O. Box 80000, 3508 TA Utrecht (Netherlands)

2011-05-23

410

Anisotropic epitaxial ZnO/CdO core/shell heterostructure nanorods  

PubMed Central

Various surface structures and polarities of one-dimensional nanostructures offer additional control in synthesizing heterostructures suitable for optoelectronic and electronic applications. In this work, we report synthesis and characterization of ZnO-CdO nanorod-based heterostructures grown on a-plane sapphire. The heterojunction formed on the sidewall surface of the nanorod shows that wurtzite ZnO {1010} planes are interfaced with rocksalt CdO {100}. This is evidently different from the heterojunction formed on the nanorod top surface, where a ZnO (0001) top plane is interfaced with a CdO (111) plane. Such anisotropic heterostructures are determined by different surface structures of the nanorods and their polarities. Revelation of such anisotropic heterojunctions will provide a clue for understanding charge transport properties in electronic and optoelectronic nanodevices.

2012-01-01

411

Temperature-dependent thermal transport properties of Archean rocks  

NASA Astrophysics Data System (ADS)

Heat transfer controls the rates and styles of fundamental planetary processes including the formation and differentiation of planetary crust, the rheological behavior of the lithosphere and asthenosphere, and the secular cooling of the Earth following its accretion. The Earth's first few hundred million years were characterized by much higher radiogenic heat production and heat flow out of the mantle than seen today, and early continental crust was comprised of rock associations such as granite-greenstone belts and intrusions of tonalite-trondhjemite-granodiorite (TTG). The composition of Archean crustal rocks, and likely variations in radiogenic heat production, have been well documented in past studies. However, the thermal transport properties of these rocks, thermal diffusivity D and thermal conductivity (k=D?CP, where ? is density and CP is isobaric heat capacity), are less well constrained, especially at high temperatures. High temperature measurements of D and k are few, and contact methods may suffer from a combination of imperfect physical contacts and unwanted direct radiative transfer. Using the laser flash analysis (LFA) technique, we determined D of a suite of 14 granite-greenstone and TTG rocks including samples from the Abitibi and Barberton greenstone belts, over a range of crustal temperatures at atmospheric pressure. Dehydration and devolatilization of amphiboles and biotite prevented direct measurement of D for most samples above ~750K, however previous studies of T-dependent D have shown that values of bulk rock diffusivity asymptotically approach a constant value above the ?-? quartz transition (846K). Our measurements yielded a range of D at room temperature from ~3.8 mm2 s-1 for banded iron to ~1 mm2 s-1 for granodiorite. D for all samples decreases with increasing T, and the range of D for the suite narrows to ~0.45 and 0.70 mm2 s-1 for granodiorite and tholeiite basalt respectively by ~1000K. Density of each sample was measured using the Archimedean method and was assumed ~constant over crustal P and T. The T-dependence of CP was calculated from modal mineralogy and published CP data for mineral end-members. Calculated values of k ranged from ~5.7 Wm-1k-1 for a quartz-rich (~38%) tonalite to ~1.7 Wm-1k-1 for a quartz-free syenite at 280K. The range of k at higher temperatures is less restricted than D, as a result of the general increase in CP at higher temperatures and varied between ~2.5 Wm-1k-1 for amphibolite and ~1.5 Wm-1k-1 for syenite. These results show that the T-dependence of D and k cannot be ignored, and variations in thermal transport properties between different rock types, and for a single rock type at different temperatures, may be more important than differences in their radiogenic heat production. This has important implications for the geothermal gradient of Archean crust, its rheological behavior and potential for partial melting.

Merriman, J. D.; Hofmeister, A.; Nabelek, P. I.; Whittington, A. G.; Benn, K.

2010-12-01

412

Spectral and transport properties of quantum wires with bond disorder  

NASA Astrophysics Data System (ADS)

Systems with bond disorder are defined through lattice Hamiltonians that are of pure nearest neighbour hopping type, i.e., do not contain on-site contributions. They stand representative for the general family of disordered systems with chiral symmetries. Application of the Dorokhov-Mello-Pereyra-Kumar transfer matrix technique P.W. Brouwer et al. [Phys. Rev. Lett 81 (1998) 862; Phys. Rev. Lett. 84 (2000) 1913] has shown that both spectral and transport properties of quasi one-dimensional systems belonging to this category are highly unusual. Most notably, regimes with absence of exponential Anderson localization are observed, the single particle density of states exhibits singular structure in the vicinity of the band centre, and the manifestation of these phenomena depends in an apparently topological manner on the even- or oddness of the channel number. In this paper we re-consider the problem from the complementary perspective of the nonlinear /?-model. Relying on the standard analogy between one-dimensional statistical field theories and zero-dimensional quantum mechanics, we will relate the problem to the behaviour of a quantum point particle subject to an Aharonov-Bohm flux. We will build on this analogy to re-derive earlier DMPK results, identify a new class of even/odd staggering phenomena (now dependent on the total number of sites in the system) and trace back the anomalous behaviour of the bond disordered system to a simple physical mechanism, viz. the flux periodicity of the quantum Aharonov-Bohm system. We will also touch upon connections to the low energy physics of other lattice systems, notably disordered chiral systems in /0 and /2 dimensions and antiferromagnetic spin chains.

Altland, A.; Merkt, R.

2001-07-01

413

Tuning the electronic transport properties of graphene through functionalisation with fluorine  

NASA Astrophysics Data System (ADS)

We demonstrate the possibility to tune the electronic transport properties of graphene mono-layers and multi-layers by functionalisation with fluorine. For mono-layer samples, with increasing the fluorine content, we observe a transition from electronic transport through Mott variable range hopping (VRH) in two dimensions to Efros-Shklovskii VRH. Multi-layer fluorinated graphene with high concentration of fluorine show two-dimensional Mott VRH transport, whereas CF0.28 multi-layer flakes exhibit thermally activated transport through near neighbour hopping. Our experimental findings demonstrate that the ability to control the degree of functionalisation of graphene is instrumental to engineer different electronic properties in graphene materials.

Withers, Freddie; Russo, Saverio; Dubois, Marc; Craciun, Monica F.

2011-09-01

414

Tuning the electronic transport properties of grapheme through functionalisation with fluorine  

PubMed Central

We demonstrate the possibility to tune the electronic transport properties of graphene mono-layers and multi-layers by functionalisation with fluorine. For mono-layer samples, with increasing the fluorine content, we observe a transition from electronic transport through Mott variable range hopping (VRH) in two dimensions to Efros-Shklovskii VRH. Multi-layer fluorinated graphene with high concentration of fluorine show two-dimensional Mott VRH transport, whereas CF0.28 multi-layer flakes exhibit thermally activated transport through near neighbour hopping. Our experimental findings demonstrate that the ability to control the degree of functionalisation of graphene is instrumental to engineer different electronic properties in graphene materials.

2011-01-01

415

Crude Oil Emulsion Properties and Their Application to Heavy Oil Transportation  

Microsoft Academic Search

Crude Oil Emulsion Properties and their Application to Heavy Oil Transportation — Many advances have been made in the field of emulsions in recent years. Emulsion behavior is largely controlled by the properties of the adsorbed layers that stabilize the oil-water surfaces. The knowledge of surface tension alone is not sufficient to understand emulsion properties, and surface rheology plays an

D. Langevin; S. Poteau; I. Hénaut; J. F. Argillier

2004-01-01

416

Investigation of Microstructural Change by X-ray Tomography and Anisotropic Effect on Thermal Property of Thermally Oxidized 2DC\\/C Composite for Very High Temperature Reactor  

Microsoft Academic Search

Two-dimensional carbon fiber reinforced carbon composite (2D-C\\/C composite) is one of the candidate materials for reactor internals, e.g., control rod element, of Very High Temperature Reactor (VHTR) because of its high strength at high temperature and thermal stability. From the viewpoint of its application to the reactor internals of the VHTR, it is important to investigate the anisotropic effect on

Junya SUMITA; Taiju SHIVARA; Eiji KUNIMOTO; Masatoshi YAMAJI; Takashi KONISHI; Kazuhiro SAWA

2010-01-01

417

Measurement of gas transport properties for chemical vapor infiltration  

Microsoft Academic Search

In the chemical vapor infiltration (CVI) process for fabricating ceramic matrix composites (CMCs), transport of gas phase reactant into the fiber preform is a critical step. The transport can be driven by pressure or by concentration. This report describes methods for measuring this for CVI preforms and partially infiltrated composites. Results are presented for Nicalon fiber cloth layup preforms and

T. L. Starr; N. Hablutzel

1996-01-01

418

Méthode particulaire anisotrope pour des écoulements de fluide visqueux  

NASA Astrophysics Data System (ADS)

The anisotropic particle method has been extended to the case of viscous flows. The moment transport equation is modified to account for viscous effects. The diffusion term has been evaluated by using the PSE method and the particle moments. The modified transport equation includes geometrical moments for which a specific transport equation has been introduced. The study of the evolution of two corotating vortices allowed the comparison of the anisotropic particle method with the usual particle method. To cite this article: A. Beaudoin et al., C. R. Mecanique 332 (2004).

Beaudoin, Anthony; Huberson, Serge; Rivoalen, Elie

2004-07-01

419

Solution phase synthesis of anisotropic multicomponent nanoparticles  

Microsoft Academic Search

This dissertation presents research on the synthesis of anisotropic and multicomponent nanoparticles by liquid-phase approaches. Nanoparticles have attracted broad attention from researchers in various fields for both their fundamental size-dependent properties and their many potential applications. These nanomaterials exhibit size and shape-dependent characteristics, including novel electronic, magnetic, optical, chemical, and mechanical properties that cannot be achieved using their bulk counterparts.

Ken-Tye Yong

2006-01-01

420

Effect of impurity layers on the electric transport properties of Ni thin films  

NASA Astrophysics Data System (ADS)

The evolution of the electrical properties of Ni thin films is reported as a function of the distance L between periodically inserted impurity layers of different elements. In all the cases the resistivity of the films increases with the decrease of L. The anisotropic magnetoresistance (AMR) is modified when L becomes comparable to the electron mean free path ?. The effect depends drastically on the magnetic nature of the impurity element. While an enhancement of the AMR with decreasing L is observed with 3d impurity elements, the insertion of Ho 4f impurity layers gives rise to a decrease of the AMR factor with decreasing L. The dependence of the magnetotransport properties with L has been analyzed and discussed within the Fuchs-Sondheimer approach.

Prados, C.; Dimitrov, D. V.; Hadjipanayis, G. C.

1999-05-01

421

Magnetic and transport properties of Sm7Rh3 single crystal  

NASA Astrophysics Data System (ADS)

A Sm7Rh3 single crystal with Th7Fe3-type hexagonal structure was grown by the Czochralski method. The magnetic and transport measurements revealed a uniaxial magnetocrystalline anisotropy in the magnetic susceptibility, magnetization and electrical resistivity. Sm7Rh3 was found to exhibit antiferromagnetic transition at TN=54.0 K and another magnetic transition at Tt=25.0 K. The specific heat data clearly showed the bulk nature of paramagnetic to ordered magnetic phase transition by the presence of a sharp peak at TN and a small anomaly at Tt. The paramagnetic susceptibility does not obey the Curie-Weiss law, attributing to the temperature independent Van Vleck contribution and Pauli paramagnetism of conduction electrons. Metamagnetic phase transitions were observed along the c-axis in the ordered states. The magnetic field H-temperature T phase diagram was constructed. Anisotropic paramagnetic electrical resistivity showed the small negative temperature coefficients.

Tsutaoka, Takanori; Noguchi, Daisuke; Nakamori, Yuko; Nakamoto, Go; Kurisu, Makio

2013-10-01

422

Magnetic and transport properties of Sm7Rh3 single crystal  

NASA Astrophysics Data System (ADS)

A Sm7Rh3 single crystal with Th7Fe3-type hexagonal structure was grown by the Czochralski method. The magnetic and transport measurements revealed a uniaxial magnetocrystalline anisotropy in the magnetic susceptibility, magnetization and electrical resistivity. Sm7Rh3 was found to exhibit antiferromagnetic transition at TN=54.0 K and another magnetic transition at Tt=25.0 K. The specific heat data clearly showed the bulk nature of paramagnetic to ordered magnetic phase transition by the presence of a sharp peak at TN and a small anomaly at Tt. The paramagnetic susceptibility does not obey the Curie–Weiss law, attributing to the temperature independent Van Vleck contribution and Pauli paramagnetism of conduction electrons. Metamagnetic phase transitions were observed along the c-axis in the ordered states. The magnetic field H–temperature T phase diagram was constructed. Anisotropic paramagnetic electrical resistivity showed the small negative temperature coefficients.

Tsutaoka, Takanori; Noguchi, Daisuke; Nakamori, Yuko; Nakamoto, Go; Kurisu, Makio

2013-10-01

423

Model anisotropic quantum Hall states  

NASA Astrophysics Data System (ADS)

Model quantum Hall states including Laughlin, Moore-Read, and Read-Rezayi states are generalized into appropriate anisotropic form. The generalized states are exact zero-energy eigenstates of corresponding anisotropic two- or multibody Hamiltonians, and explicitly illustrate the existence of geometric degree of freedom in the fractional quantum Hall effect. These generalized model quantum Hall states can provide a good description of the quantum Hall system with anisotropic interactions. Some numeric results of these anisotropic quantum Hall states are also presented.

Qiu, R.-Z.; Haldane, F. D. M.; Wan, Xin; Yang, Kun; Yi, Su

2012-03-01

424

Transport Properties of Sedimentary Rocks. Phase 3 Report, July 1993-December 1994.  

National Technical Information Service (NTIS)

The project is aimed at understanding the relationships between electrical and fluid transport properties in sedimentary rock from which we can make better estimates of gas saturation and producibility in low to moderate permeability shaly sandstone forma...

P. Z. Wong

1995-01-01

425

Evaluation of transport properties of ozonized poly\\/mono interfaces in polysilicon emitter bipolar transistors  

Microsoft Academic Search

Temperature-dependent electrical measurements have been performed to determine hole and electron transport properties across the poly\\/mono interface in polysilicon emitter bipolar transistors. A tunneling probability has been extracted, and the results are correlated with noise parameters.

S. Niel; A. Chantre; P. Llinarès; M. Laurens; G. Vincent

2000-01-01

426

Nuclear Microprobe Studies of the Electronic Transport Properties of Cadmium Zinc Telluride (CZT) Radiation Detectors.  

National Technical Information Service (NTIS)

Beam Induced Charge Collection (IBICC) is a proven albeit relatively new method to measure the electronic transport properties of room temperature radiation detectors. Using an ion microbeam the charge collection efficiency of CZT detectors can be mapped ...

G. Vizkelethy B. L. Doyle D. S. Walsh R. B. James

2000-01-01

427

General polarized ray-tracing method for inhomogeneous uniaxially anisotropic media.  

PubMed

Uniaxial optical anisotropy in the geometrical-optics approach is a classical problem, and most of the theory has been known for at least fifty years. Although the subject appears frequently in the literature, wave propagation through inhomogeneous anisotropic media is rarely addressed. The rapid advances in liquid-crystal lenses call for a good overview of the theory on wave propagation via anisotropic media. Therefore, we present a novel polarized ray-tracing method, which can be applied to anisotropic optical systems that contain inhomogeneous liquid crystals. We describe the propagation of rays in the bulk material of inhomogeneous anisotropic media in three dimensions. In addition, we discuss ray refraction, ray reflection, and energy transfer at, in general, curved anisotropic interfaces with arbitrary orientation and/or arbitrary anisotropic properties. The method presented is a clear outline of how to assess the optical properties of uniaxially anisotropic media. PMID:18516136

Sluijter, Maarten; de Boer, Dick K G; Braat, Joseph J M

2008-06-01

428

Influence of phosphate on the transport properties of lead in sand  

Microsoft Academic Search

Temporal moment analysis was used to examine the transport of lead species in sand columns. The influence of sodium phosphate (PO4(aq)) and hydroxyapatite (HA) on lead transport was also evaluated. Transport properties of lead microparticles (diameter>0.45?m) were a function of electrophoretic mobility: those particles with electrophoretic mobility less than ?1×10?8m2\\/Vs exhibited significantly lower dimensionless first temporal moment (?) and second

Michael A. Butkus; Marie C. Johnson

2011-01-01

429

Tables of thermodynamic and transport properties of UO/sub 2/  

SciTech Connect

The thermodynamic and transport properties of solid and liquid UO/sub 2/ are tabulated as a function of temperature. Properties are given for the temperature range 298.15 K to 3120 K for solid UO/sub 2/ and from 3120 to 6000 K for liquid UO/sub 2/. Thermodynamic properties tabulated include enthalpy, heat capacity, pressure, density, instantaneous thermal expansion coefficient, compressibility, thermal pressure coefficient, and speed of sound. Tabulated transport properties include thermal conductivity, thermal diffusivity, emissivity, electrical conductivity, and viscosity. Tables are given in SI units and cgs units.

Fink, J.K.

1982-06-01

430

Effect of Alignment on Transport Properties of Carbon Nanotube\\/Metallic Junctions  

Microsoft Academic Search

Ballistic and spin coherent transport in single walled carbon nanotubes (SWCNT) are predicted to enable high sensitivity single-nanotube devices for strain and magnetic field sensing. Based upon these phenomena, electron beam lithography procedures have been developed to study the transport properties of purified HiPCO single walled carbon nanotubes for development into sensory materials for nondestructive evaluation. Purified nanotubes are dispersed

Buzz Wincheski; Min Namkung; Jan Smits; Phillip Williams; Robert Harvey

431

Role of Symmetry in the Transport Properties of Graphene Nanoribbons under Bias  

Microsoft Academic Search

The intrinsic transport properties of zigzag graphene nanoribbons (ZGNRs) are investigated using first-principles calculations. It is found that although all ZGNRs have similar metallic band structure, they show distinctly different transport behaviors under bias voltages, depending on whether they are mirror symmetric with respect to the midplane between two edges. Asymmetric ZGNRs behave as conventional conductors with linear current-voltage dependence,

Zuanyi Li; Haiyun Qian; Jian Wu; Bing-Lin Gu; Wenhui Duan

2008-01-01

432

Effect of heavy-ion irradiation on transport properties of YBa2Cu3Ox films  

Microsoft Academic Search

We have investigated the effect of heavy-ion irradiation on the transport properties of YBa2Cu3Ox thin films. Parallel columnar defects to the c axis and crossed columnar defects were introduced into films by heavy-ion irradiation with dose equivalent to 1 or 2 T vortex density. The electrical transport properties including resistivity, critical current density, and the Hall resistivity were measured as

Dong Ho Kim; Seong Yup Shim; Jong Hyeog Park; Young Hwan Kim; Chang Hoon Kim; Jin Wook Jang; Taek Sang Hahn; Sang Sam Choi; Jeffrey D. Hettinger; David G. Steel; Kenneth E. Gray

1997-01-01