WorldWideScience

Sample records for two-dimensional growth mode

  1. Normal Modes of Magnetized Finite Two-Dimensional Yukawa Crystals

    Science.gov (United States)

    Marleau, Gabriel-Dominique; Kaehlert, Hanno; Bonitz, Michael

    2009-11-01

    The normal modes of a finite two-dimensional dusty plasma in an isotropic parabolic confinement, including the simultaneous effects of friction and an external magnetic field, are studied. The ground states are found from molecular dynamics simulations with simulated annealing, and the influence of screening, friction, and magnetic field on the mode frequencies is investigated in detail. The two-particle problem is solved analytically and the limiting cases of weak and strong magnetic fields are discussed.[4pt] [1] C. Henning, H. K"ahlert, P. Ludwig, A. Melzer, and M.Bonitz. J. Phys. A 42, 214023 (2009)[2] B. Farokhi, M. Shahmansouri, and P. K. Shukla. Phys.Plasmas 16, 063703 (2009)[3] L. Cândido, J.-P. Rino, N. Studart, and F. M. Peeters. J. Phys.: Condens. Matter 10, 11627--11644 (1998)

  2. Matrix method for two-dimensional waveguide mode solution

    Science.gov (United States)

    Sun, Baoguang; Cai, Congzhong; Venkatesh, Balajee Seshasayee

    2018-05-01

    In this paper, we show that the transfer matrix theory of multilayer optics can be used to solve the modes of any two-dimensional (2D) waveguide for their effective indices and field distributions. A 2D waveguide, even composed of numerous layers, is essentially a multilayer stack and the transmission through the stack can be analysed using the transfer matrix theory. The result is a transfer matrix with four complex value elements, namely A, B, C and D. The effective index of a guided mode satisfies two conditions: (1) evanescent waves exist simultaneously in the first (cladding) layer and last (substrate) layer, and (2) the complex element D vanishes. For a given mode, the field distribution in the waveguide is the result of a 'folded' plane wave. In each layer, there is only propagation and absorption; at each boundary, only reflection and refraction occur, which can be calculated according to the Fresnel equations. As examples, we show that this method can be used to solve modes supported by the multilayer step-index dielectric waveguide, slot waveguide, gradient-index waveguide and various plasmonic waveguides. The results indicate the transfer matrix method is effective for 2D waveguide mode solution in general.

  3. Two-dimensional modeling of conduction-mode laser welding

    International Nuclear Information System (INIS)

    Russo, A.J.

    1984-01-01

    WELD2D is a two-dimensional finite difference computer program suitable for modeling the conduction-mode welding process when the molten weld pool motion can be neglected. The code is currently structured to treat butt-welded geometries in a plane normal to the beam motion so that dissimilar materials may be considered. The surface heat transfer models used in the code include a Gaussian beam or uniform laser source, and a free electron theory reflectance calculation. Temperature-dependent material parameters are used in the reflectance calculation. Measured cold reflection data are used to include surface roughness or oxide effects until melt occurs, after which the surface is assumed to be smooth and clean. Blackbody reradiation and a simple natural convection model are also included in the upper surface boundary condition. Either an implicit or explicit finite-difference representation of the heat conduction equation in an enthalpy form is solved at each time step. This enables phase transition energies to be easily and accurately incorporated into the formulation. Temperature-dependent 9second-order polynominal dependence) thermal conductivities are used in the conduction calculations. Constant values of specific heat are used for each material phase. At present, material properties for six metals are included in the code. These are: aluminium, nickel, steel, molybdenum, copper and silicon

  4. Two-dimensional grating guided-mode resonance tunable filter.

    Science.gov (United States)

    Kuo, Wen-Kai; Hsu, Che-Jung

    2017-11-27

    A two-dimensional (2D) grating guided-mode resonance (GMR) tunable filter is experimentally demonstrated using a low-cost two-step nanoimprinting technology with a one-dimensional (1D) grating polydimethylsiloxane mold. For the first nanoimprinting, we precisely control the UV LED irradiation dosage and demold the device when the UV glue is partially cured and the 1D grating mold is then rotated by three different angles, 30°, 60°, and 90°, for the second nanoimprinting to obtain 2D grating structures with different crossing angles. A high-refractive-index film ZnO is then coated on the surface of the grating structure to form the GMR filter devices. The simulation and experimental results demonstrate that the passband central wavelength of the filter can be tuned by rotating the device to change azimuth angle of the incident light. We compare these three 2D GMR filters with differential crossing angles and find that the filter device with a crossing angle of 60° exhibits the best performance. The tunable range of its central wavelength is 668-742 nm when the azimuth angle varies from 30° to 90°.

  5. Strain-engineered growth of two-dimensional materials.

    Science.gov (United States)

    Ahn, Geun Ho; Amani, Matin; Rasool, Haider; Lien, Der-Hsien; Mastandrea, James P; Ager Iii, Joel W; Dubey, Madan; Chrzan, Daryl C; Minor, Andrew M; Javey, Ali

    2017-09-20

    The application of strain to semiconductors allows for controlled modification of their band structure. This principle is employed for the manufacturing of devices ranging from high-performance transistors to solid-state lasers. Traditionally, strain is typically achieved via growth on lattice-mismatched substrates. For two-dimensional (2D) semiconductors, this is not feasible as they typically do not interact epitaxially with the substrate. Here, we demonstrate controlled strain engineering of 2D semiconductors during synthesis by utilizing the thermal coefficient of expansion mismatch between the substrate and semiconductor. Using WSe 2 as a model system, we demonstrate stable built-in strains ranging from 1% tensile to 0.2% compressive on substrates with different thermal coefficient of expansion. Consequently, we observe a dramatic modulation of the band structure, manifested by a strain-driven indirect-to-direct bandgap transition and brightening of the dark exciton in bilayer and monolayer WSe 2 , respectively. The growth method developed here should enable flexibility in design of more sophisticated devices based on 2D materials.Strain engineering is an essential tool for modifying local electronic properties in silicon-based electronics. Here, Ahn et al. demonstrate control of biaxial strain in two-dimensional materials based on the growth substrate, enabling more complex low-dimensional electronics.

  6. Chemical vapor deposition growth of two-dimensional heterojunctions

    Science.gov (United States)

    Cui, Yu; Li, Bo; Li, JingBo; Wei, ZhongMing

    2018-01-01

    The properties of two-dimensional (2D) layered materials with atom-smooth surface and special interlayer van der Waals coupling are different from those of traditional materials. Due to the absence of dangling bonds from the clean surface of 2D layered materials, the lattice mismatch influences slightly on the growth of 2D heterojunctions, thus providing a flexible design strategy. 2D heterojunctions have attracted extensive attention because of their excellent performance in optoelectronics, spintronics, and valleytronics. The transfer method was utilized for the fabrication of 2D heterojunctions during the early stage of fundamental research on these materials. This method, however, has limited practical applications. Therefore, chemical vapor deposition (CVD) method was recently developed and applied for the preparation of 2D heterojunctions. The CVD method is a naturally down-top growth strategy that yields 2D heterojunctions with sharp interfaces. Moreover, this method effectively reduces the introduction of contaminants to the fabricated heterojunctions. Nevertheless, the CVD-growth method is sensitive to variations in growth conditions. In this review article, we attempt to provide a comprehensive overview of the influence of growth conditions on the fabrication of 2D heterojunctions through the direct CVD method. We believe that elucidating the effects of growth conditions on the CVD method is necessary to help control and improve the efficiency of the large-scale fabrication of 2D heterojunctions for future applications in integrated circuits.

  7. Two-Dimensional Edge Detection by Guided Mode Resonant Metasurface

    Science.gov (United States)

    Saba, Amirhossein; Tavakol, Mohammad Reza; Karimi-Khoozani, Parisa; Khavasi, Amin

    2018-05-01

    In this letter, a new approach to perform edge detection is presented using an all-dielectric CMOS-compatible metasurface. The design is based on guided-mode resonance which provides a high quality factor resonance to make the edge detection experimentally realizable. The proposed structure that is easy to fabricate, can be exploited for detection of edges in two dimensions due to its symmetry. Also, the trade-off between gain and resolution of edge detection is discussed which can be adjusted by appropriate design parameters. The proposed edge detector has also the potential to be used in ultrafast analog computing and image processing.

  8. A Bloch modal approach for engineering waveguide and cavity modes in two-dimensional photonic crystals

    DEFF Research Database (Denmark)

    de Lasson, Jakob Rosenkrantz; Kristensen, Philip Trøst; Mørk, Jesper

    2014-01-01

    uses no external excitation and determines the quasi-normal modes as unity eigenvalues of the cavity roundtrip matrix. We demonstrate the method and the quasi-normal modes for two types of two-dimensional photonic crystal structures, and discuss the quasi-normal mode eld distributions and Q-factors...

  9. Mode selection in two-dimensional Bragg resonators based on planar dielectric waveguides

    International Nuclear Information System (INIS)

    Baryshev, V R; Ginzburg, N S; Zaslavskii, V Yu; Malkin, A M; Sergeev, A S; Thumm, M

    2009-01-01

    Two-dimensional Bragg resonators based on planar dielectric waveguides are analysed. It is shown that the doubly periodic corrugation deposited on the dielectric surface in the form of two gratings with translational vectors directed perpendicular to each other ensures effective selection of modes along two coordinates at large Fresnel parameters. This result is obtained both by the method of coupled waves (geometrical optics approximation) and by the direct numerical simulations. Two-dimensional Bragg resonators make it possible to fabricate two-dimensional distributed feedback lasers and to provide generation of spatially coherent radiation in large-volume active media. (waveguides)

  10. Two-dimensional effects in the problem of tearing modes control by electron cyclotron current drive

    International Nuclear Information System (INIS)

    Comisso, L.; Lazzaro, E.

    2010-01-01

    The design of means to counteract robustly the classical and neoclassical tearing modes in a tokamak by localized injection of an external control current requires an ever growing understanding of the physical process, beyond the Rutherford-type zero-dimensional models. Here a set of extended magnetohydrodynamic nonlinear equations for four continuum fields is used to investigate the two-dimensional effects in the response of the reconnecting modes to specific inputs of the localized external current. New information is gained on the space- and time-dependent effects of the external action on the two-dimensional structure of magnetic islands, which is very important to formulate applicable control strategies.

  11. Growth and characterization of two-dimensional nanostructures

    International Nuclear Information System (INIS)

    Herrera Sancho, Oscar Andrey

    2008-01-01

    Two dimensional nanostructures of palladium, nickel, silver and gadolinium were grown by means of physical evaporation in atmospheres of high vacuum and ultra high vacuum. The qualitative characterization, in situ, of the nanostructures was carried out with techniques of surface analysis: Auger electron spectroscopy and X-ray photoelectron spectroscopy (XPS). The model for the quantification of contaminants in the nanostructures, was proposed by Seah and Shirley, and was made using the spectra XPS measured in situ in the atmospheres of vacuum. For the two-dimensional nanostructures of gadolinium of thicknesses 8 Å, 16 Å, 24 Å, 32 Å, 36 Å, 44 Å, 50 Å, 61 Å, 77 Å, 81 Å, 92 Å and 101 Å, were obtained optical spectra of transmission measured in situ. An band of absorption centered at approximately 2,40 eV is obtained by an increase in the dynamic conductivity from the optical constants, i.e. refractive index and extinction coefficient, of the nanostructure of gadolinium. In addition, the optical constants for the gadolinium nanostructures have presented a maximum of 80 Å of thickness and then it was continued a decreasing tendency toward the values that were reported in the literature for bulk of gadolinium. (author) [es

  12. Two-Dimensional Fuzzy Sliding Mode Control of a Field-Sensed Magnetic Suspension System

    Directory of Open Access Journals (Sweden)

    Jen-Hsing Li

    2014-01-01

    Full Text Available This paper presents the two-dimensional fuzzy sliding mode control of a field-sensed magnetic suspension system. The fuzzy rules include both the sliding manifold and its derivative. The fuzzy sliding mode control has advantages of the sliding mode control and the fuzzy control rules are minimized. Magnetic suspension systems are nonlinear and inherently unstable systems. The two-dimensional fuzzy sliding mode control can stabilize the nonlinear systems globally and attenuate chatter effectively. It is adequate to be applied to magnetic suspension systems. New design circuits of magnetic suspension systems are proposed in this paper. ARM Cortex-M3 microcontroller is utilized as a digital controller. The implemented driver, sensor, and control circuits are simpler, more inexpensive, and effective. This apparatus is satisfactory for engineering education. In the hands-on experiments, the proposed control scheme markedly improves performances of the field-sensed magnetic suspension system.

  13. Mode shape combination in a two-dimensional vibration energy harvester through mass loading structural modification

    Energy Technology Data Exchange (ETDEWEB)

    Sharpes, Nathan; Kumar, Prashant [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States); Abdelkefi, Abdessattar; Abdelmoula, Hichem [Department of Mechanical and Aerospace Engineering, New Mexico State University, Las Cruces, New Mexico 88003 (United States); Adler, Jan [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States); Institute of Dynamics and Vibration Research (IDS), Leibniz Universität, Hannover 30167 (Germany); Priya, Shashank [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States); Bio-Inspired Materials and Devices Laboratory (BMDL), Virginia Tech, Blacksburg, Virginia 24061 (United States)

    2016-07-18

    Mode shapes in the design of mechanical energy harvesters, as a means of performance increase, have been largely overlooked. Currently, the vast majority of energy harvester designs employ some variation of a single-degree-of-freedom cantilever, and the mode shapes of such beams are well known. This is especially true for the first bending mode, which is almost exclusively the chosen vibration mode for energy harvesting. Two-dimensional beam shapes (those which curve, meander, spiral, etc., in a plane) have recently gained research interest, as they offer freedom to modify the vibration characteristics of the harvester beam for achieving higher power density. In this study, the second bending mode shape of the “Elephant” two-dimensional beam shape is examined, and its interaction with the first bending mode is evaluated. A combinatory mode shape created by using mass loading structural modification to lower the second bending modal frequency was found to interact with the first bending mode. This is possible since the first two bending modes do not share common areas of displacement. The combined mode shape is shown to produce the most power of any of the considered mode shapes.

  14. Selective growth of two-dimensional phosphorene on catalyst surface.

    Science.gov (United States)

    Qiu, L; Dong, J C; Ding, F

    2018-02-01

    Although the study of black phosphorene (BP) and its isomers has attracted enormous attention, the method of synthesizing high-quality samples in a large area is still pending. Here we explore the potential of using the chemical vapor deposition method to synthesize large-area two-dimensional (2D) phosphorene films on metal surfaces. Our ab initio calculations show that BP can be synthesized by using tin (Sn) as a catalyst, while one of its isomers, blue phosphorene (BLP), is very possible to be synthesized by using most other metals, such as Ag and Au. Besides, our study also suggests that the large binding energy between the 2D phosphorene and the active metal substrate may prohibit the exfoliation of the 2D phosphorene for real applications and, therefore, tin, silver and gold are predicted to be the most suitable catalysts for the synthesis of BP and BLP.

  15. Two-dimensional spatial structure of the dissipative trapped-electron mode

    International Nuclear Information System (INIS)

    Rewoldt, G.; Tang, W.M.; Frieman, E.A.

    1976-09-01

    This paper deals with the complete two-dimensional structure of the dissipative trapped-electron mode over its full width, which may extend over several mode-rational surfaces. The complete integro-differential equation is studied in the limit k/sub r/rho/sub i/ less than 1, where rho/sub i/ is the ion gyroradius, and k/sub r/, the radial wavenumber, is regarded as a differential operator. This is converted into a matrix equation which is then solved by standard numerical methods

  16. Hole growth dynamics in a two dimensional Leidenfrost droplet

    Science.gov (United States)

    Raufaste, Christophe; Celestini, Franck; Barzyk, Alexandre; Frisch, Thomas

    2015-03-01

    We studied the behaviors of Leidenfrost droplets confined in a Hele-Shaw cell. These droplets are unstable above a critical size and a hole grows at their center. We experimentally investigate two different systems for which the hole growth dynamics exhibits peculiar features that are driven by capillarity and inertia. We report a first regime characterized by the liquid reorganization from a liquid sheet to a liquid torus with similarities to the burst of micron-thick soap films. In the second regime, the liquid torus expands and thins before fragmentation. Finally, we propose models to account for the experimental results.

  17. Two-dimensional diffusion limited system for cell growth

    International Nuclear Information System (INIS)

    Hlatky, L.

    1985-11-01

    A new cell system, the ''sandwich'' system, was developed to supplement multicellular spheroids as tumor analogues. Sandwiches allow new experimental approaches to questions of diffusion, cell cycle effects and radiation resistance in tumors. In this thesis the method for setting up sandwiches is described both theoretically and experimentally followed by its use in x-ray irradiation studies. In the sandwich system, cells are grown in a narrow gap between two glass slides. Where nutrients and waste products can move into or out of the local environment of the cells only by diffusing through the narrow gap between the slides. Due to the competition between cells, self-created gradients of nutrients and metabolic products are set up resulting in a layer of cells which resembles a living spheroid cross section. Unlike the cells of the spheroid, however, cells in all regions of the sandwich are visible. Therefore, the relative sizes of the regions and their time-dependent growth can be monitored visually without fixation or sectioning. The oxygen and nutrient gradients can be ''turned off'' at any time without disrupting the spatial arrangement of the cells by removing the top slide of the assembly and subsequently turned back on if desired. Removal of the top slide also provides access to all the cells, including those near the necrotic center, of the sandwich. The cells can then be removed for analysis outside the sandwich system. 61 refs., 17 figs

  18. Two-Dimensional Simulation of Mass Transfer in Unitized Regenerative Fuel Cells under Operation Mode Switching

    Directory of Open Access Journals (Sweden)

    Lulu Wang

    2016-01-01

    Full Text Available A two-dimensional, single-phase, isothermal, multicomponent, transient model is built to investigate the transport phenomena in unitized regenerative fuel cells (URFCs under the condition of switching from the fuel cell (FC mode to the water electrolysis (WE mode. The model is coupled with an electrochemical reaction. The proton exchange membrane (PEM is selected as the solid electrolyte of the URFC. The work is motivated by the need to elucidate the complex mass transfer and electrochemical process under operation mode switching in order to improve the performance of PEM URFC. A set of governing equations, including conservation of mass, momentum, species, and charge, are considered. These equations are solved by the finite element method. The simulation results indicate the distributions of hydrogen, oxygen, water mass fraction, and electrolyte potential response to the transient phenomena via saltation under operation mode switching. The hydrogen mass fraction gradients are smaller than the oxygen mass fraction gradients. The average mass fractions of the reactants (oxygen and hydrogen and product (water exhibit evident differences between each layer in the steady state of the FC mode. By contrast, the average mass fractions of the reactant (water and products (oxygen and hydrogen exhibit only slight differences between each layer in the steady state of the WE mode. Under either the FC mode or the WE mode, the duration of the transient state is only approximately 0.2 s.

  19. Temperature-dependent layer breathing modes in two-dimensional materials

    Science.gov (United States)

    Maity, Indrajit; Maiti, Prabal K.; Jain, Manish

    2018-04-01

    Relative out-of-plane displacements of the constituent layers of two-dimensional materials give rise to unique low-frequency breathing modes. By computing the height-height correlation functions from molecular dynamics simulations, we show that the layer breathing modes (LBMs) can be mapped consistently to vibrations of a simple linear chain model. Our calculated thickness dependence of LBM frequencies for few-layer (FL) graphene and molybdenum disulfide (MoS2) are in excellent agreement with available experiments. Our results show a redshift of LBM frequency with an increase in temperature, which is a direct consequence of anharmonicities present in the interlayer interaction. We also predict the thickness and temperature dependence of LBM frequencies for FL hexagonal boron nitride. Our Rapid Communication provides a simple and efficient way to probe the interlayer interaction for layered materials and their heterostructures with the inclusion of anharmonic effects.

  20. Measurement of correlations between low-frequency vibrational modes and particle rearrangements in quasi-two-dimensional colloidal glasses

    NARCIS (Netherlands)

    Chen, K.; Manning, M.L.; Yunker, P.J.; Ellenbroek, W.G.; Zhang, Zexin; Liu, Andrea J.; Yodh, A.G.

    2011-01-01

    We investigate correlations between low-frequency vibrational modes and rearrangements in two-dimensional colloidal glasses composed of thermosensitive microgel particles, which readily permit variation of the sample packing fraction. At each packing fraction, the particle displacement covariance

  1. Nonlinear localized modes in dipolar Bose–Einstein condensates in two-dimensional optical lattices

    International Nuclear Information System (INIS)

    Rojas-Rojas, Santiago; Naether, Uta; Delgado, Aldo; Vicencio, Rodrigo A.

    2016-01-01

    Highlights: • We study discrete two-dimensional breathers in dipolar Bose–Einstein Condensates. • Important differences in the properties of three fundamental modes are found. • Norm threshold for existence of 2D breathers varies with dipolar interaction. • The Effective Potential Method is implemented for stability analysis. • Uncommon mobility of 2D discrete solitons is observed. - Abstract: We analyze the existence and properties of discrete localized excitations in a Bose–Einstein condensate loaded into a periodic two-dimensional optical lattice, when a dipolar interaction between atoms is present. The dependence of the Number of Atoms (Norm) on the energy of solutions is studied, along with their stability. Two important features of the system are shown, namely, the absence of the Norm threshold required for localized solutions to exist in finite 2D systems, and the existence of regions in the parameter space where two fundamental solutions are simultaneously unstable. This feature enables mobility of localized solutions, which is an uncommon feature in 2D discrete nonlinear systems. With attractive dipolar interaction, a non-trivial behavior of the Norm dependence is obtained, which is well described by an analytical model.

  2. Nonlinear localized modes in dipolar Bose–Einstein condensates in two-dimensional optical lattices

    Energy Technology Data Exchange (ETDEWEB)

    Rojas-Rojas, Santiago, E-mail: srojas@cefop.cl [Center for Optics and Photonics and MSI-Nucleus on Advanced Optics, Universidad de Concepción, Casilla 160-C, Concepción (Chile); Departamento de Física, Universidad de Concepción, Casilla 160-C, Concepción (Chile); Naether, Uta [Instituto de Ciencia de Materiales de Aragón and Departamento de Física de la Materia Condensada, CSIC-Universidad de Zaragoza, 50009 Zaragoza (Spain); Delgado, Aldo [Center for Optics and Photonics and MSI-Nucleus on Advanced Optics, Universidad de Concepción, Casilla 160-C, Concepción (Chile); Departamento de Física, Universidad de Concepción, Casilla 160-C, Concepción (Chile); Vicencio, Rodrigo A. [Center for Optics and Photonics and MSI-Nucleus on Advanced Optics, Universidad de Concepción, Casilla 160-C, Concepción (Chile); Departamento de Física, Facultad de Ciencias, Universidad de Chile, Santiago (Chile)

    2016-09-16

    Highlights: • We study discrete two-dimensional breathers in dipolar Bose–Einstein Condensates. • Important differences in the properties of three fundamental modes are found. • Norm threshold for existence of 2D breathers varies with dipolar interaction. • The Effective Potential Method is implemented for stability analysis. • Uncommon mobility of 2D discrete solitons is observed. - Abstract: We analyze the existence and properties of discrete localized excitations in a Bose–Einstein condensate loaded into a periodic two-dimensional optical lattice, when a dipolar interaction between atoms is present. The dependence of the Number of Atoms (Norm) on the energy of solutions is studied, along with their stability. Two important features of the system are shown, namely, the absence of the Norm threshold required for localized solutions to exist in finite 2D systems, and the existence of regions in the parameter space where two fundamental solutions are simultaneously unstable. This feature enables mobility of localized solutions, which is an uncommon feature in 2D discrete nonlinear systems. With attractive dipolar interaction, a non-trivial behavior of the Norm dependence is obtained, which is well described by an analytical model.

  3. Two-dimensional performance of MIPAS observation modes in the upper-troposphere/lower-stratosphere

    Directory of Open Access Journals (Sweden)

    M. Carlotti

    2011-02-01

    Full Text Available In this paper we analyze the performance of the three MIPAS (Michelson Interferometer for Passive Atmospheric Sounding observation modes that sound the Upper-Troposphere/Lower-Stratosphere (UT/LS region. The two-dimensional (2-D tomographic retrieval approach is assumed to derive the atmospheric field of geophysical parameters. For each observation mode we have calculated the 2-D distribution of the information load quantifier relative to the main MIPAS targets. The performance of the observation modes has been evaluated in terms of strength and spatial coverage of the information-load distribution along the full orbit. The indications of the information-load analysis has been validated with simulated retrievals based on the observational parameters of real orbits. In the simulation studies we have assessed the precision and the spatial (both horizontal and vertical resolution of the retrieval products. The performance of the three observation modes has been compared for the MIPAS main products in both the UT/LS and the extended altitude range. This study shows that the two observation modes that were specifically designed for the UT/LS region are actually competitive with the third one, designed for the whole stratosphere, up to altitudes that far exceed the UT/LS. In the UT/LS the performance of the two specific observation modes is comparable even if the best performance in terms of horizontal resolution is provided by the observation mode that was excluded by the European Space Agency (ESA from the current MIPAS duty cycle. This paper reports the first application of the information-load analysis and highlights the worthiness of this approach to make qualitative considerations about retrieval potential and selection of retrieval grid.

  4. The multi-mode modulator: A versatile fluidic device for two-dimensional gas chromatography.

    Science.gov (United States)

    Seeley, John V; Schimmel, Nicolaas E; Seeley, Stacy K

    2018-02-09

    A fluidic device called the multi-mode modulator (MMM) has been developed for use as a comprehensive two-dimensional gas chromatography (GC x GC) modulator. The MMM can be employed in a wide range of capacities including as a traditional heart-cutting device, a low duty cycle GC x GC modulator, and a full transfer GC x GC modulator. The MMM is capable of producing narrow component pulses (widths <50ms) while operating at flows compatible with high resolution chromatography. The sample path of modulated components is confined to the interior of a joining capillary. The joining capillary dimensions and the position of the columns within the joining capillary can be optimized for the selected modulation mode. Furthermore, the joining capillary can be replaced easily and inexpensively if it becomes fouled due to sample matrix components or column bleed. The principles of operation of the MMM are described and its efficacy is demonstrated as a heart-cutting device and as a GC x GC modulator. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Growth and electronic properties of two-dimensional systems on (110) oriented GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, F.

    2005-07-01

    As the only non-polar plane the (110) surface has a unique role in GaAs. Together with Silicon as a dopant it is an important substrate orientation for the growth of n-type or p-type heterostructures. As a consequence, this thesis will concentrate on growth and research on that surface. In the course of this work we were able to realize two-dimensional electron systems with the highest mobilities reported so far on this orientation. Therefore, we review the necessary growth conditions and the accompanying molecular process. The two-dimensional electron systems allowed the study of a new, intriguing transport anisotropy not explained by current theory. Moreover, we were the first growing a two-dimensional hole gas on (110) GaAs with Si as dopant. For this purpose we invented a new growth modulation technique necessary to retrieve high mobility systems. In addition, we discovered and studied the metal-insulator transition in thin bulk p-type layers on (110) GaAs. Besides we investigated the activation process related to the conduction in the valence band and a parallelly conducting hopping band. The new two-dimensional hole gases revealed interesting physics. We studied the zero B-field spin splitting in these systems and compared it with the known theory. Furthermore, we investigated the anisotropy of the mobility. As opposed to the expectations we observed a strong persistent photoconductivity in our samples. Landau levels for two dimensional hole systems are non-linear and can show anticrossings. For the first time we were able to resolve anticrossings in a transport experiment and study the corresponding activation process. Finally, we compared these striking results with theoretical calculations. (orig.)

  6. Motion Mode and Two Dimensional Echocardiographic Measurements of Cardiac Dimensions of Indonesian Mongrel Dogs

    Directory of Open Access Journals (Sweden)

    DENI NOVIANA

    2011-03-01

    Full Text Available Prevalence of heart disease in dogs was very high and required early diagnosis through physical examination, electrocardiogram, and echocardiography. Normal reference values of echocardiography are highly breedspecific and need for comparison and evaluation of dogs suspected with heart disease. Therefore the aim of this study was to establish normal reference echocardiographic values for Indonesian mongrel dogs, specifically to find out intracardiac dimensions, wall thickness, and fractional shortening. Motion-mode and two-dimensional echocardiography from right parasternal short axis and long axis view were performed on nine clinically healthy dogs consisting of five males and four males. The results showed that wall thickness and fractional shortening of Indonesia mongrel dogs were higher compared with those in the other breed that have the same average weight. As opposite, the intracardiac dimensions and lumen dimensions of aorta and left atrial diameter were smaller. These differences might occur due to factors other than the dog's habits and functions such as working and hunting, but can also be caused by the existence of breed differences. There was no significant difference between male and female dogs in terms of intracardiac dimension systole (P = 0.53, diastole (P = 0.38, fractional shortening (P = 0.053, and the ratio of aorta and left atrial diameter (P = 0.06.

  7. Chiral zero energy modes in two-dimensional disordered Dirac semimetals

    Science.gov (United States)

    Liu, Lei; Yu, Yan; Wu, Hai-Bin; Zhang, Yan-Yang; Liu, Jian-Jun; Li, Shu-Shen

    2018-04-01

    The vacancy-induced chiral zero energy modes (CZEMs) of chiral-unitary-class (AIII) and chiral-symplectic-class (CII) two-dimensional (2 D ) disordered Dirac semimetals realized on a square bipartite lattice are investigated numerically by using the Kubo-Greenwood formula with the kernel polynomial method. The results show that, for both systems, the CZEMs exhibit the critical delocalization. The CZEM conductivity remains a robust constant (i.e., σ CZEM≈1.05 e2/h ), which is insensitive to the sample sizes, the vacancy concentrations, and the numbers of moments of Chebyshev polynomials, i.e., the dephasing strength. For both kinds of chiral systems, the CZEM conductivities are almost identical. However, they are not equal to that of graphene (i.e., 4 e2/π h ), which belongs to the chiral orthogonal class (BDI) semimetal on a 2 D hexagonal bipartite lattice. In addition, for the case that the vacancy concentrations are different in the two sublattices, the CZEM conductivity vanishes, and thus both systems exhibit localization at the Dirac point. Moreover, a band gap and a mobility gap open around zero energy. The widths of the energy gaps and mobility gaps are increasing with larger vacancy concentration difference. The width of the mobility gap is greater than that of the band gap, and a δ -function-like peak of density of states emerges at the Dirac point within the band gap, implying the existence of numerous localized states.

  8. Epitaxial Growth of Two-Dimensional Layered Transition-Metal Dichalcogenides: Growth Mechanism, Controllability, and Scalability

    KAUST Repository

    Li, Henan

    2017-07-06

    Recently there have been many research breakthroughs in two-dimensional (2D) materials including graphene, boron nitride (h-BN), black phosphors (BPs), and transition-metal dichalcogenides (TMDCs). The unique electrical, optical, and thermal properties in 2D materials are associated with their strictly defined low dimensionalities. These materials provide a wide range of basic building blocks for next-generation electronics. The chemical vapor deposition (CVD) technique has shown great promise to generate high-quality TMDC layers with scalable size, controllable thickness, and excellent electronic properties suitable for both technological applications and fundamental sciences. The capability to precisely engineer 2D materials by chemical approaches has also given rise to fascinating new physics, which could lead to exciting new applications. In this Review, we introduce the latest development of TMDC synthesis by CVD approaches and provide further insight for the controllable and reliable synthesis of atomically thin TMDCs. Understanding of the vapor-phase growth mechanism of 2D TMDCs could benefit the formation of complicated heterostructures and novel artificial 2D lattices.

  9. Nucleation of two-dimensional islands on Si (111) during high-temperature epitaxial growth

    Energy Technology Data Exchange (ETDEWEB)

    Sitnikov, S. V., E-mail: sitnikov@isp.nsc.ru; Kosolobov, S. S.; Latyshev, A. V. [Russian Academy of Sciences, Institute of Semiconductor Physics, Siberian Branch (Russian Federation)

    2017-02-15

    The process of two-dimensional island nucleation at the surface of ultra large Si (111) during hightemperature epitaxial growth is studied by in situ ultrahigh-vacuum reflection electron microscopy. The critical terrace size D{sub crit}, at which a two-dimensional island is nucleated in the center, is measured in the temperature range 900–1180°C at different silicon fluxes onto the surface. It is found that the parameter D{sub crit}{sup 2} is a power function of the frequency of island nucleation, with the exponent χ = 0.9 ± 0.05 in the entire temperature range under study. It is established that the kinetics of nucleus formation is defined by the diffusion of adsorbed silicon atoms at temperatures of up to 1180°C and the minimum critical nucleus size corresponds to 12 silicon atoms.

  10. Convergence of numerical schemes suitable for two dimensional nonlinear convection: application to the coupling of modes in a plasma

    International Nuclear Information System (INIS)

    Boukadida, T.

    1988-01-01

    The compatibility between accuracy and stability of the quasilinear equations is studied. Three stuations are analyzed: the discontinuous P-1 approximation of the first order quasilinear equation, the two dimensional version of the Lax-Friedrichs scheme and the coupling of modes in a plasma. For the one dimensional case, the proposed scheme matches the available data. In the two dimensional case, tests to show the explosion condition are performed. This investigation can be applied in laser-matter interactions, nonlinear optics and in many fields of physics [fr

  11. Optical microcavities based on surface modes in two-dimensional photonic crystals and silicon-on-insulator photonic crystals

    DEFF Research Database (Denmark)

    Xiao, Sanshui; Qiu, M.

    2007-01-01

    Surface-mode optical microcavities based on two-dimensional photonic crystals and silicon-on-insulator photonic crystals are studied. We demonstrate that a high-quality-factor microcavity can be easily realized in these structures. With an increasing of the cavity length, the quality factor is gr...... is gradually enhanced and the resonant frequency converges to that of the corresponding surface mode in the photonic crystals. These structures have potential applications such as sensing.......Surface-mode optical microcavities based on two-dimensional photonic crystals and silicon-on-insulator photonic crystals are studied. We demonstrate that a high-quality-factor microcavity can be easily realized in these structures. With an increasing of the cavity length, the quality factor...

  12. Dynamics of lava flow - Thickness growth characteristics of steady two-dimensional flow

    Science.gov (United States)

    Park, S.; Iversen, J. D.

    1984-01-01

    The thickness growth characteristics of flowing lava are investigated using a heat balance model and a two-dimensional model for flow of a Bingham plastic fluid down an inclined plane. It is found that yield strength plays a crucial role in the thickening of a lava flow of given flow rate. To illustrate this point, downstream thickness profiles and yield strength distributions were calculated for flows with mass flow rates of 10,000 and 100,000 kg/m-sec. Higher flow rates led to slow cooling rates which resulted in slow rate of increase of yield strength and thus greater flow lengths.

  13. Entanglement of arbitrary superpositions of modes within two-dimensional orbital angular momentum state spaces

    International Nuclear Information System (INIS)

    Jack, B.; Leach, J.; Franke-Arnold, S.; Ireland, D. G.; Padgett, M. J.; Yao, A. M.; Barnett, S. M.; Romero, J.

    2010-01-01

    We use spatial light modulators (SLMs) to measure correlations between arbitrary superpositions of orbital angular momentum (OAM) states generated by spontaneous parametric down-conversion. Our technique allows us to fully access a two-dimensional OAM subspace described by a Bloch sphere, within the higher-dimensional OAM Hilbert space. We quantify the entanglement through violations of a Bell-type inequality for pairs of modal superpositions that lie on equatorial, polar, and arbitrary great circles of the Bloch sphere. Our work shows that SLMs can be used to measure arbitrary spatial states with a fidelity sufficient for appropriate quantum information processing systems.

  14. Growth and decay of a two-dimensional oxide quasicrystal: High-temperature in situ microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Foerster, Stefan [Physik-Institut, Universitaet Zuerich (Switzerland); Institute of Physics, Martin-Luther-Universitaet Halle-Wittenberg, Halle (Germany); Flege, Jan Ingo; Falta, Jens [Institute of Solid State Physics, University of Bremen (Germany); MAPEX Center for Materials and Processes, University of Bremen (Germany); Zollner, Eva Maria; Schumann, Florian Otto; Hammer, Rene; Bayat, Alireza; Schindler, Karl-Michael [Institute of Physics, Martin-Luther-Universitaet Halle-Wittenberg, Halle (Germany); Widdra, Wolf [Institute of Physics, Martin-Luther-Universitaet Halle-Wittenberg, Halle (Germany); Max-Planck-Institut fuer Mikrostrukturphysik, Halle (Germany)

    2017-01-15

    The recently discovered two-dimensional oxide quasicrystal (OQC) derived from BaTiO{sub 3} on Pt(111) is the first material in which a spontaneous formation of an aperiodic structure at the interface to a periodic support has been observed. Herein, we report in situ low-energy electron microscopy (LEEM) studies on the fundamental processes involved in the OQC growth. The OQC formation proceeds in two steps via of an amorphous two-dimensional wetting layer. At 1170 K the long-range aperiodic order of the OQC develops. Annealing in O{sub 2} induces the reverse process, the conversion of the OQC into BaTiO{sub 3} islands and bare Pt(111), which has been monitored by in situ LEEM. A quantitative analysis of the temporal decay of the OQC shows that oxygen adsorption on bare Pt patches is the rate limiting step of this dewetting process. (copyright 2016 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Multiple surface plasmon polaritons modes on thin silver film controlled by a two-dimensional lattice of silver nanodimers

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Ying; Jiang, Yongyuan, E-mail: jiangyy@hit.edu.cn [Harbin Institute of Technology, Department of Physics (China)

    2015-01-15

    We study the optical resonant spectrum of a two-dimensional periodic array of silver nanodimers on a thin silver film using multiple scattering formalism. The excited multiple plasmonic modes on two interfaces of the silver film reveal that the dispersion relationships of surface plasmon polaritons on metallic film are modified by doubly periodic lattice due to the fact that wave vectors matching conditions are satisfied. Moreover, we demonstrate that the plasmonic modes are directly controlled by the thickness of silver film, as well as the gap between nanodimer array and silver film. These effects provide novel high-efficient and steady way for excitation in future plasmonic nanodevices.

  16. One-pot growth of two-dimensional lateral heterostructures via sequential edge-epitaxy

    Science.gov (United States)

    Sahoo, Prasana K.; Memaran, Shahriar; Xin, Yan; Balicas, Luis; Gutiérrez, Humberto R.

    2018-01-01

    Two-dimensional heterojunctions of transition-metal dichalcogenides have great potential for application in low-power, high-performance and flexible electro-optical devices, such as tunnelling transistors, light-emitting diodes, photodetectors and photovoltaic cells. Although complex heterostructures have been fabricated via the van der Waals stacking of different two-dimensional materials, the in situ fabrication of high-quality lateral heterostructures with multiple junctions remains a challenge. Transition-metal-dichalcogenide lateral heterostructures have been synthesized via single-step, two-step or multi-step growth processes. However, these methods lack the flexibility to control, in situ, the growth of individual domains. In situ synthesis of multi-junction lateral heterostructures does not require multiple exchanges of sources or reactors, a limitation in previous approaches as it exposes the edges to ambient contamination, compromises the homogeneity of domain size in periodic structures, and results in long processing times. Here we report a one-pot synthetic approach, using a single heterogeneous solid source, for the continuous fabrication of lateral multi-junction heterostructures consisting of monolayers of transition-metal dichalcogenides. The sequential formation of heterojunctions is achieved solely by changing the composition of the reactive gas environment in the presence of water vapour. This enables selective control of the water-induced oxidation and volatilization of each transition-metal precursor, as well as its nucleation on the substrate, leading to sequential edge-epitaxy of distinct transition-metal dichalcogenides. Photoluminescence maps confirm the sequential spatial modulation of the bandgap, and atomic-resolution images reveal defect-free lateral connectivity between the different transition-metal-dichalcogenide domains within a single crystal structure. Electrical transport measurements revealed diode-like responses across the

  17. Orthonormal mode sets for the two-dimensional fractional Fourier transformation

    NARCIS (Netherlands)

    Alieva, T.; Bastiaans, M.J.

    2007-01-01

    A family of orthonormal mode sets arises when Hermite–Gauss modes propagate through lossless first-order optical systems. It is shown that the modes at the output of the system are eigenfunctions for the symmetric fractional Fourier transformation if and only if the system is described by an

  18. Progress on Crystal Growth of Two-Dimensional Semiconductors for Optoelectronic Applications

    Directory of Open Access Journals (Sweden)

    Bingqi Sun

    2018-06-01

    Full Text Available Two-dimensional (2D semiconductors are thought to belong to the most promising candidates for future nanoelectronic applications, due to their unique advantages and capability in continuing the downscaling of complementary metal–oxide–semiconductor (CMOS devices while retaining decent mobility. Recently, optoelectronic devices based on novel synthetic 2D semiconductors have been reported, exhibiting comparable performance to the traditional solid-state devices. This review briefly describes the development of the growth of 2D crystals for applications in optoelectronics, including photodetectors, light-emitting diodes (LEDs, and solar cells. Such atomically thin materials with promising optoelectronic properties are very attractive for future advanced transparent optoelectronics as well as flexible and wearable/portable electronic devices.

  19. Can M mode and two dimensional echocardiography give a sufficient evaluation for surgeray of patients with pure mitral stenosis

    International Nuclear Information System (INIS)

    Balbarini, A; Tartarini, G.; Mengozzi, G.; Mariani, M.; Salvatore, L.; Barsotti, A.

    1987-01-01

    One hundred and twenty-six patients with rheumatic mitral stenosis were studied by M-mode and/or two-dimensional echocardiography. Eighty-nine patients were also submetted to cardiac catheterization and all 126 patients subsequently underwent mitral valve surgery (51 valvulotomy and 75 valve replacement). The mitral valve area measured by two-dimensional echocardiography showed a significant correlation both with hemodynamic (r=0.803, p 2 , respectively; likewise there was non significant difference in pulmonary vascular resistances (3.9 and 3.4 mmHg/l/min/m 2 ) between patients who showed functional improvement after surgery comparison to those who showed no improvement. Finally, coronary arteriography appeared to be necessary, before operation, only in cardiography is able to provide a satisfactory preoperative assessment of patients with mitral stenosis and that therefore these patients need not necessarily to be submitted to cardiac catheterization

  20. Fermionic quasinormal modes for two-dimensional Horava-Lifshitz black holes

    Energy Technology Data Exchange (ETDEWEB)

    Stetsko, M.M. [Ivan Franko National University of Lviv, Department for Theoretical Physics, Lviv (Ukraine)

    2017-06-15

    To obtain fermionic quasinormal modes, the Dirac equation for two types of black holes is investigated. It is shown that two different geometries lead to distinctive types of quasinormal modes, while the boundary conditions imposed on the solutions in both cases are identical. For the first type of black hole, the quasinormal modes have continuous spectrum with negative imaginary part that provides the stability of perturbations. For the second type of the black hole, the quasinormal modes have a discrete spectrum and are completely imaginary. (orig.)

  1. Interface-guided mode of Lamb waves in a two-dimensional phononic crystal plate

    International Nuclear Information System (INIS)

    Huang Ping-Ping; Yao Yuan-Wei; Zhang Xin; Li Jing; Hu Ai-Zhen; Wu Fu-Gen

    2015-01-01

    We investigate the interface-guided mode of Lamb waves in a phononic crystal heterostructures plate, which is composed of two different semi-infinite phononic crystal (PC) plates. The interface-guided modes of the Lamb wave can be obtained by the lateral lattice slipping or by the interface longitudinal gliding. Significantly, it is observed that the condition to generate the interface-guided modes of the Lamb wave is more demanding than that of the studied fluid–fluid system. The interface-guided modes are strongly affected not only by the relative movement of the two semi-infinite PCs but also by the thickness of the PC plate. (paper)

  2. A two-dimensional problem of a mode-I crack in a rotating fibre ...

    Indian Academy of Sciences (India)

    AHMED E ABOUELREGAL

    2018-02-07

    Feb 7, 2018 ... Fibre-reinforced; mode-I crack; dual-phase-lag theory; rotation; normal mode analysis. 1. Introduction ... acki [2, 3] rests upon the hypothesis of the Fourier law of .... forcement and rotation on the variations of different field quantities inside ... The principle of balance of linear momentum leads to the following ...

  3. Numerical simulation of two-dimensional late-stage coarsening for nucleation and growth

    International Nuclear Information System (INIS)

    Akaiwa, N.; Meiron, D.I.

    1995-01-01

    Numerical simulations of two-dimensional late-stage coarsening for nucleation and growth or Ostwald ripening are performed at area fractions 0.05 to 0.4 using the monopole and dipole approximations of a boundary integral formulation for the steady state diffusion equation. The simulations are performed using two different initial spatial distributions. One is a random spatial distribution, and the other is a random spatial distribution with depletion zones around the particles. We characterize the spatial correlations of particles by the radial distribution function, the pair correlation functions, and the structure function. Although the initial spatial correlations are different, we find time-independent scaled correlation functions in the late stage of coarsening. An important feature of the late-stage spatial correlations is that depletion zones exist around particles. A log-log plot of the structure function shows that the slope at small wave numbers is close to 4 and is -3 at very large wave numbers for all area fractions. At large wave numbers we observe oscillations in the structure function. We also confirm the cubic growth law of the average particle radius. The rate constant of the cubic growth law and the particle size distribution functions are also determined. We find qualitatively good agreement between experiments and the present simulations. In addition, the present results agree well with simulation results using the Cahn-Hilliard equation

  4. Trimodal Mixed Mode Chromatography That Enables Efficient Offline Two-Dimensional Peptide Fractionation for Proteome Analysis.

    Science.gov (United States)

    Yu, Peng; Petzoldt, Svenja; Wilhelm, Mathias; Zolg, Daniel Paul; Zheng, Runsheng; Sun, Xuefei; Liu, Xiaodong; Schneider, Günter; Huhmer, Andreas; Kuster, Bernhard

    2017-09-05

    Offline two-dimensional chromatography is a common means to achieve deep proteome coverage. To reduce sample complexity and dynamic range and to utilize mass spectrometer (MS) time efficiently, high chromatographic resolution of and good orthogonality between the two dimensions are needed. Ion exchange and high pH reversed phase chromatography are often used for this purpose. However, the former requires desalting to be MS-compatible, and the latter requires fraction pooling to create orthogonality. Here, we report an alternative first-dimension separation technique using a commercial trimodal phase incorporating polar embedded reversed phase, weak anion exchange, and strong cation exchange material. The column is capable of retaining polar and nonpolar peptides alike without noticeable breakthrough. It allows separating ordinary and TMT-labeled peptides under mild acidic conditions using an acetonitrile gradient. The direct MS compatibility of solvents and good orthogonality to online coupled C18 columns enable a straightforward workflow without fraction pooling and desalting while showing comparable performance to the other techniques. The method scales from low to high microgram sample quantity and is amenable to full automation. To demonstrate practical utility, we analyzed the proteomes of 10 human pancreatic cancer cell lines to a depth of >8,700 quantified proteins.

  5. Fundamental and higher two-dimensional resonance modes of an Alpine valley

    Science.gov (United States)

    Ermert, Laura; Poggi, Valerio; Burjánek, Jan; Fäh, Donat

    2014-08-01

    We investigated the sequence of 2-D resonance modes of the sediment fill of Rhône Valley, Southern Swiss Alps, a strongly overdeepened, glacially carved basin with a sediment fill reaching a thickness of up to 900 m. From synchronous array recordings of ambient vibrations at six locations between Martigny and Sion we were able to identify several resonance modes, in particular, previously unmeasured higher modes. Data processing was performed with frequency domain decomposition of the cross-spectral density matrices of the recordings and with time-frequency dependent polarization analysis. 2-D finite element modal analysis was performed to support the interpretation of processing results and to investigate mode shapes at depth. In addition, several models of realistic bedrock geometries and velocity structures could be used to qualitatively assess the sensitivity of mode shape and particle motion dip angle to subsurface properties. The variability of modal characteristics due to subsurface properties makes an interpretation of the modes purely from surface observations challenging. We conclude that while a wealth of information on subsurface structure is contained in the modal characteristics, a careful strategy for their interpretation is needed to retrieve this information.

  6. Measurement of correlations between low-frequency vibrational modes and particle rearrangements in quasi-two-dimensional colloidal glasses.

    Science.gov (United States)

    Chen, Ke; Manning, M L; Yunker, Peter J; Ellenbroek, Wouter G; Zhang, Zexin; Liu, Andrea J; Yodh, A G

    2011-09-02

    We investigate correlations between low-frequency vibrational modes and rearrangements in two-dimensional colloidal glasses composed of thermosensitive microgel particles, which readily permit variation of the sample packing fraction. At each packing fraction, the particle displacement covariance matrix is measured and used to extract the vibrational spectrum of the "shadow" colloidal glass (i.e., the particle network with the same geometry and interactions as the sample colloid but absent damping). Rearrangements are induced by successive, small reductions in the packing fraction. The experimental results suggest that low-frequency quasilocalized phonon modes in colloidal glasses, i.e., modes that present low energy barriers for system rearrangements, are spatially correlated with rearrangements in this thermal system.

  7. A six-mode truncation of the Navier-Stokes equations on a two-dimensional torus: a numerical study

    International Nuclear Information System (INIS)

    Angelo, P.M.; Riela, G.

    1981-01-01

    We study a model obtained from a six-mode truncation of the Navier-Stokes equations for a two-dimensional incompressible fluid on a torus. We find that at low values of the Reynolds number R the dynamics is characterized by fixed points and, at large values of R, by two stable periodic orbits; at intermediate values of R two infinite sequences of bifurcations of periodic orbits into periodic orbits of doubled period lead to two regions of ''turbulent'' or ''chaotic'' behaviour. The turbulent regions end up for values of R for which stable periodic orbits appear. (author)

  8. Spontaneous creation of nonzero-angular-momentum modes in tunnel-coupled two-dimensional degenerate Bose gases

    International Nuclear Information System (INIS)

    Montgomery, T. W. A.; Scott, R. G.; Lesanovsky, I.; Fromhold, T. M.

    2010-01-01

    We investigate the dynamics of two tunnel-coupled two-dimensional degenerate Bose gases. The reduced dimensionality of the clouds enables us to excite specific angular momentum modes by tuning the coupling strength, thereby creating striking patterns in the atom density profile. The extreme sensitivity of the system to the coupling and initial phase difference results in a rich variety of subsequent dynamics, including vortex production, complex oscillations in relative atom number, and chiral symmetry breaking due to counter-rotation of the two clouds.

  9. Fringe-projection profilometry based on two-dimensional empirical mode decomposition.

    Science.gov (United States)

    Zheng, Suzhen; Cao, Yiping

    2013-11-01

    In 3D shape measurement, because deformed fringes often contain low-frequency information degraded with random noise and background intensity information, a new fringe-projection profilometry is proposed based on 2D empirical mode decomposition (2D-EMD). The fringe pattern is first decomposed into numbers of intrinsic mode functions by 2D-EMD. Because the method has partial noise reduction, the background components can be removed to obtain the fundamental components needed to perform Hilbert transformation to retrieve the phase information. The 2D-EMD can effectively extract the modulation phase of a single direction fringe and an inclined fringe pattern because it is a full 2D analysis method and considers the relationship between adjacent lines of a fringe patterns. In addition, as the method does not add noise repeatedly, as does ensemble EMD, the data processing time is shortened. Computer simulations and experiments prove the feasibility of this method.

  10. Oscillation mode transformation of edge magnetoplasmons in two-dimensional electron system on liquid-helium surface

    International Nuclear Information System (INIS)

    Yamanaka, Shuji; Yayama, Hideki; Arai, Toshikazau; Anju Sawada, Anju; Fukuda, Akira

    2013-01-01

    We measured the resonance spectra of edge magnetoplasmon (EMP) oscillations in a two-dimensional (2D) electron system located on a liquid-helium surface below 1.1 K. Systematic measurements of the resonance frequency and the damping rate as a function of the lateral confinement electric field strength shows clear evidence of the oscillation mode transformation. A pronounced change corresponding to the mode transformation was observed in the damping rate. When 2D electrons are confined in a strong lateral electric field, the damping is weak. As the lateral confinement electric field is reduced below a certain threshold value, an abrupt enhancement of the damping rate is observed. We hypothesize that the weak damping mode in the strong lateral confinement electric field is the compressive density oscillation of the electrons near the edge (conventional EMP) and the strong damping mode in the weak confinement field is the coupled mode of conventional EMP and the boundary displacement wave (BDW). The observation of the strong damping in the BDW-EMP coupled mode is a manifestation of the nearly incompressible feature of strongly interacting classical electrons, which agrees with earlier theoretical predictions.

  11. Evolutionary selection growth of two-dimensional materials on polycrystalline substrates

    Science.gov (United States)

    Vlassiouk, Ivan V.; Stehle, Yijing; Pudasaini, Pushpa Raj; Unocic, Raymond R.; Rack, Philip D.; Baddorf, Arthur P.; Ivanov, Ilia N.; Lavrik, Nickolay V.; List, Frederick; Gupta, Nitant; Bets, Ksenia V.; Yakobson, Boris I.; Smirnov, Sergei N.

    2018-03-01

    There is a demand for the manufacture of two-dimensional (2D) materials with high-quality single crystals of large size. Usually, epitaxial growth is considered the method of choice1 in preparing single-crystalline thin films, but it requires single-crystal substrates for deposition. Here we present a different approach and report the synthesis of single-crystal-like monolayer graphene films on polycrystalline substrates. The technological realization of the proposed method resembles the Czochralski process and is based on the evolutionary selection2 approach, which is now realized in 2D geometry. The method relies on `self-selection' of the fastest-growing domain orientation, which eventually overwhelms the slower-growing domains and yields a single-crystal continuous 2D film. Here we have used it to synthesize foot-long graphene films at rates up to 2.5 cm h-1 that possess the quality of a single crystal. We anticipate that the proposed approach could be readily adopted for the synthesis of other 2D materials and heterostructures.

  12. Raman Scattering from Higgs Mode Oscillations in the Two-Dimensional Antiferromagnet Ca_{2}RuO_{4}.

    Science.gov (United States)

    Souliou, Sofia-Michaela; Chaloupka, Jiří; Khaliullin, Giniyat; Ryu, Gihun; Jain, Anil; Kim, B J; Le Tacon, Matthieu; Keimer, Bernhard

    2017-08-11

    We present and analyze Raman spectra of the Mott insulator Ca_{2}RuO_{4}, whose quasi-two-dimensional antiferromagnetic order has been described as a condensate of low-lying spin-orbit excitons with angular momentum J_{eff}=1. In the A_{g} polarization geometry, the amplitude (Higgs) mode of the spin-orbit condensate is directly probed in the scalar channel, thus avoiding infrared-singular magnon contributions. In the B_{1g} geometry, we observe a single-magnon peak as well as two-magnon and two-Higgs excitations. Model calculations using exact diagonalization quantitatively agree with the observations. Together with recent neutron scattering data, our study provides strong evidence for excitonic magnetism in Ca_{2}RuO_{4} and points out new perspectives for research on the Higgs mode in two dimensions.

  13. Molecular Beam Epitaxial Growth and Characterization of Graphene and Hexagonal Boron Nitride Two-Dimensional Layers

    Science.gov (United States)

    Zheng, Renjing

    Van der Waals (vdW) materials (also called as two-dimensional (2D) material in some literature) systems have received extensive attention recently due to their potential applications in next-generation electronics platform. Exciting properties have been discovered in this field, however, the performance and properties of the systems rely on the materials' quality and interface significantly, leading to the urgent need for scalable synthesis of high-quality vdW crystals and heterostructures. Toward this direction, this dissertation is devoted on the study of Molecular Beam Epitaxy (MBE) growth and various characterization of vdW materials and heterostructures, especially graphene and hexagonal boron nitride (h-BN). The goal is to achieve high-quality vdW materials and related heterostructures. There are mainly four projects discussed in this dissertation. The first project (Chapter 2) is about MBE growth of large-area h-BN on copper foil. After the growth, the film was transferred onto SiO2 substrate for characterization. It is observed that as-grown film gives evident h-BN Raman spectrum; what's more, h-BN peak intensity and position is dependent on film thickness. N-1s and B-1s XPS peaks further suggest the formation of h-BN. AFM and SEM images show the film is flat and continuous over large area. Our synthesis method shows it's possible to use MBE to achieve h-BN growth and could also pave a way for some unique structure, such as h-BN/graphene heterostructures and doped h-BN films by MBE. The second project (Chapter 3) is focused on establishment of grapehene/h-BN heterostructure on cobalt (Co) film. In-situ epitaxial growth of graphene/h-BN heterostructures on Co film substrate was achieved by using plasma-assisted MBE. The direct graphene/h-BN vertical stacking structures were demonstrated and further confirmed by various characterizations, such as Raman spectroscopy, SEM, XPS and TEM. Large area heterostructures consisting of single- /bilayer graphene and

  14. Mode suppression of a two-dimensional potential relaxation instability in a weakly magnetized discharge plasma

    Science.gov (United States)

    Gyergyek, T.; Čerček, M.; Jelić, N.; Stanojević, M.

    1993-05-01

    A potential relaxation instability (PRI) is modulated by an external signal using an additional grid to modulate the radial plasma potential profile in a magnetized plasma column in a linear magnetized discharge plasma device. It is observed that the electrode current oscillations follow the van der Pol equation with an external forcing term, and the linear growth rate of the instability is measured.

  15. Low-Frequency Shear and Layer-Breathing Modes in Raman Scattering of Two-Dimensional Materials.

    Science.gov (United States)

    Liang, Liangbo; Zhang, Jun; Sumpter, Bobby G; Tan, Qing-Hai; Tan, Ping-Heng; Meunier, Vincent

    2017-12-26

    Ever since the isolation of single-layer graphene in 2004, two-dimensional layered structures have been among the most extensively studied classes of materials. To date, the pool of two-dimensional materials (2DMs) continues to grow at an accelerated pace and already covers an extensive range of fascinating and technologically relevant properties. An array of experimental techniques have been developed and used to characterize and understand these properties. In particular, Raman spectroscopy has proven to be a key experimental technique, thanks to its capability to identify minute structural and electronic effects in nondestructive measurements. While high-frequency (HF) intralayer Raman modes have been extensively employed for 2DMs, recent experimental and theoretical progress has demonstrated that low-frequency (LF) interlayer Raman modes are more effective at determining layer numbers and stacking configurations and provide a unique opportunity to study interlayer coupling. These advantages are due to 2DMs' unique interlayer vibration patterns where each layer behaves as an almost rigidly moving object with restoring forces corresponding to weak interlayer interactions. Compared to HF Raman modes, the relatively small attention originally devoted to LF Raman modes is largely due to their weaker signal and their proximity to the strong Rayleigh line background, which previously made their detection challenging. Recent progress in Raman spectroscopy with technical and hardware upgrades now makes it possible to probe LF modes with a standard single-stage Raman system and has proven crucial to characterize and understand properties of 2DMs. Here, we present a comprehensive and forward-looking review on the current status of exploiting LF Raman modes of 2DMs from both experimental and theoretical perspectives, revealing the fundamental physics and technological significance of LF Raman modes in advancing the field of 2DMs. We review a broad array of materials, with

  16. Two-dimensional photon-echo spectroscopy at a conical intersection: A two-mode pyrazine model with dissipation

    Energy Technology Data Exchange (ETDEWEB)

    Sala, Matthieu; Egorova, Dassia

    2016-12-20

    The multi-dimensional electronic spectroscopy of ultrafast nuclear dynamics at conical intersections (CI) is an emerging field of investigation, which profits also from the recent extension of the techniques to the UV domain. We present a detailed computational study of oscillatory signatures in two-dimensional (2D) photon-echo spectroscopy (also known as 2D electronic spectroscopy, 2DES) for the two-mode pyrazine model with dissipation. Conventional 2D signals as well as the resulting beating maps are considered. Although of a reduced character, the model captures quite well all the main signatures of the excited-state dynamics of the molecule. Due to the ultrafast relaxation via the CI and no excited-state absorption from the low-lying dark state, the oscillatory components of the signal are found to be predominantly determined by the ground state bleach contribution. They reflect, therefore, the ground-state vibrational coherence induced in the Raman active mode. Beating maps provide a way to experimentally differentiate between ground state bleach and stimulated emission oscillatory components. The ultrafast decay of the latter constitutes a clear indirect signature of the CI. In the considered model, because of the sign properties of the involved transition dipole moments, the dominance of the ground-state coherence leads to anti-correlated oscillations of cross peaks located at symmetric positions with respect to the main diagonal.

  17. Electromagnetic resonance modes on a two-dimensional tandem grating and its application for broadband absorption in the visible spectrum.

    Science.gov (United States)

    Han, Sunwoo; Lee, Bong Jae

    2016-01-25

    In this work, we numerically investigate the electromagnetic resonances on two-dimensional tandem grating structures. The base of a tandem grating consists of an opaque Au substrate, a SiO(2) spacer, and a Au grating (concave type); that is, a well-known fishnet structure forming Au/SiO(2)/Au stack. A convex-type Au grating (i.e., topmost grating) is then attached on top of the base fishnet structure with or without additional SiO(2) spacer, resulting in two types of tandem grating structures. In order to calculate the spectral reflectance and local magnetic field distribution, the finite-difference time-domain method is employed. When the topmost Au grating is directly added onto the base fishnet structure, the surface plasmon and magnetic polariton in the base structure are branched out due to the geometric asymmetry with respect to the SiO(2) spacer. If additional SiO(2) spacer is added between the topmost Au grating and the base fishnet structure, new magnetic resonance modes appear due to coupling between two vertically aligned Au/SiO(2)/Au stacks. With the understanding of multiple electromagnetic resonance modes on the proposed tandem grating structures, we successfully design a broadband absorber made of Au and SiO(2) in the visible spectrum.

  18. Spatial statistics of magnetic field in two-dimensional chaotic flow in the resistive growth stage

    Energy Technology Data Exchange (ETDEWEB)

    Kolokolov, I.V., E-mail: igor.kolokolov@gmail.com [Landau Institute for Theoretical Physics RAS, 119334, Kosygina 2, Moscow (Russian Federation); NRU Higher School of Economics, 101000, Myasnitskaya 20, Moscow (Russian Federation)

    2017-03-18

    The correlation tensors of magnetic field in a two-dimensional chaotic flow of conducting fluid are studied. It is shown that there is a stage of resistive evolution where the field correlators grow exponentially with time. The two- and four-point field correlation tensors are computed explicitly in this stage in the framework of Batchelor–Kraichnan–Kazantsev model. They demonstrate strong temporal intermittency of the field fluctuations and high level of non-Gaussianity in spatial field distribution.

  19. An investigation on a two-dimensional problem of Mode-I crack in a thermoelastic medium

    Science.gov (United States)

    Kant, Shashi; Gupta, Manushi; Shivay, Om Namha; Mukhopadhyay, Santwana

    2018-04-01

    In this work, we consider a two-dimensional dynamical problem of an infinite space with finite linear Mode-I crack and employ a recently proposed heat conduction model: an exact heat conduction with a single delay term. The thermoelastic medium is taken to be homogeneous and isotropic. However, the boundary of the crack is subjected to a prescribed temperature and stress distributions. The Fourier and Laplace transform techniques are used to solve the problem. Mathematical modeling of the present problem reduces the solution of the problem into the solution of a system of four dual integral equations. The solution of these equations is equivalent to the solution of the Fredholm's integral equation of the first kind which has been solved by using the regularization method. Inverse Laplace transform is carried out by using the Bellman method, and we obtain the numerical solution for all the physical field variables in the physical domain. Results are shown graphically, and we highlight the effects of the presence of crack in the behavior of thermoelastic interactions inside the medium in the present context, and its results are compared with the results of the thermoelasticity of type-III.

  20. Scalable solution-phase epitaxial growth of symmetry-mismatched heterostructures on two-dimensional crystal soft template.

    Science.gov (United States)

    Lin, Zhaoyang; Yin, Anxiang; Mao, Jun; Xia, Yi; Kempf, Nicholas; He, Qiyuan; Wang, Yiliu; Chen, Chih-Yen; Zhang, Yanliang; Ozolins, Vidvuds; Ren, Zhifeng; Huang, Yu; Duan, Xiangfeng

    2016-10-01

    Epitaxial heterostructures with precisely controlled composition and electronic modulation are of central importance for electronics, optoelectronics, thermoelectrics, and catalysis. In general, epitaxial material growth requires identical or nearly identical crystal structures with small misfit in lattice symmetry and parameters and is typically achieved by vapor-phase depositions in vacuum. We report a scalable solution-phase growth of symmetry-mismatched PbSe/Bi 2 Se 3 epitaxial heterostructures by using two-dimensional (2D) Bi 2 Se 3 nanoplates as soft templates. The dangling bond-free surface of 2D Bi 2 Se 3 nanoplates guides the growth of PbSe crystal without requiring a one-to-one match in the atomic structure, which exerts minimal restriction on the epitaxial layer. With a layered structure and weak van der Waals interlayer interaction, the interface layer in the 2D Bi 2 Se 3 nanoplates can deform to accommodate incoming layer, thus functioning as a soft template for symmetry-mismatched epitaxial growth of cubic PbSe crystal on rhombohedral Bi 2 Se 3 nanoplates. We show that a solution chemistry approach can be readily used for the synthesis of gram-scale PbSe/Bi 2 Se 3 epitaxial heterostructures, in which the square PbSe (001) layer forms on the trigonal/hexagonal (0001) plane of Bi 2 Se 3 nanoplates. We further show that the resulted PbSe/Bi 2 Se 3 heterostructures can be readily processed into bulk pellet with considerably suppressed thermal conductivity (0.30 W/m·K at room temperature) while retaining respectable electrical conductivity, together delivering a thermoelectric figure of merit ZT three times higher than that of the pristine Bi 2 Se 3 nanoplates at 575 K. Our study demonstrates a unique epitaxy mode enabled by the 2D nanocrystal soft template via an affordable and scalable solution chemistry approach. It opens up new opportunities for the creation of diverse epitaxial heterostructures with highly disparate structures and functions.

  1. A Bayesian network model for predicting aquatic toxicity mode of action using two dimensional theoretical molecular descriptors

    Energy Technology Data Exchange (ETDEWEB)

    Carriger, John F. [U.S. Environmental Protection Agency, Office of Research and Development, Gulf Ecology Division, Gulf Breeze, FL, 32561 (United States); Martin, Todd M. [U.S. Environmental Protection Agency, Office of Research and Development, Sustainable Technology Division, Cincinnati, OH, 45220 (United States); Barron, Mace G., E-mail: barron.mace@epa.gov [U.S. Environmental Protection Agency, Office of Research and Development, Gulf Ecology Division, Gulf Breeze, FL, 32561 (United States)

    2016-11-15

    Highlights: • A Bayesian network was developed to classify chemical mode of action (MoA). • The network was based on the aquatic toxicity MoA for over 1000 chemicals. • A Markov blanket algorithm selected a subset of theoretical molecular descriptors. • Sensitivity analyses found influential descriptors for classifying the MoAs. • Overall precision of the Bayesian MoA classification model was 80%. - Abstract: The mode of toxic action (MoA) has been recognized as a key determinant of chemical toxicity, but development of predictive MoA classification models in aquatic toxicology has been limited. We developed a Bayesian network model to classify aquatic toxicity MoA using a recently published dataset containing over one thousand chemicals with MoA assignments for aquatic animal toxicity. Two dimensional theoretical chemical descriptors were generated for each chemical using the Toxicity Estimation Software Tool. The model was developed through augmented Markov blanket discovery from the dataset of 1098 chemicals with the MoA broad classifications as a target node. From cross validation, the overall precision for the model was 80.2%. The best precision was for the AChEI MoA (93.5%) where 257 chemicals out of 275 were correctly classified. Model precision was poorest for the reactivity MoA (48.5%) where 48 out of 99 reactive chemicals were correctly classified. Narcosis represented the largest class within the MoA dataset and had a precision and reliability of 80.0%, reflecting the global precision across all of the MoAs. False negatives for narcosis most often fell into electron transport inhibition, neurotoxicity or reactivity MoAs. False negatives for all other MoAs were most often narcosis. A probabilistic sensitivity analysis was undertaken for each MoA to examine the sensitivity to individual and multiple descriptor findings. The results show that the Markov blanket of a structurally complex dataset can simplify analysis and interpretation by

  2. Fingerprinting of traditional Chinese medicines on the C18-Diol mixed-mode column in online or offline two-dimensional liquid chromatography on the single column modes.

    Science.gov (United States)

    Wang, Qing; Tong, Ling; Yao, Lin; Zhang, Peng; Xu, Li

    2016-06-05

    In the present study, a mixed-mode stationary phase, C18-Diol, was applied for fingerprint analysis of traditional Chinese medicines. Hydrophobic, hydrogen bonding and electrostatic interactions were demonstrated to contribute the retention separately or jointly, which endowed the C18-Diol stationary phase with distinct selectivity compared to the bare C18 one. The separation of total alkaloids extracted from Fritillaria hupehensis was compared on the C18-Diol and conventional C18 column with the greater resolving power and better symmetry responses on the former one. Besides, a novel two-dimensional liquid chromatography on the single column (2D-LC-1C) was realized on C18-Diol with the offline mode for the alcohol extract of Fritillaria hupehensis and online mode for Ligusticum chuanxiong Hort. The early co-eluted extracted components with great polarity on the first dimension were reinjected on the same column and well separated on the second dimension. The results exhibited that the two complementary RPLC and HILIC modes on C18-Diol stationary phase enhanced the separation capacity and revealed more abundant chemical information of the sample, which was a powerful tool in analyzing complex herbal medicines. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. X-ray studies on a two-dimensional diffusion limited system for cell growth

    International Nuclear Information System (INIS)

    Hlatky, L.R.; Alpen, E.L.

    1985-01-01

    X-ray studies were performed on cells grown in a new type of in vitro multicellular system, the ''sandwich'' system. This system is a two-dimensional array of cells, sandwiched between transparent slides which are impermeable to oxygen. The cell system is subject to self-created diffusion gradients of nutrients, metabolic products and, most importantly, oxygen. Sandwiches are analogous to living cross sections of multicellular spheroids or of poorly vascularized tumors. They contain a necrotic center, which the authors show to be due to diffusion limitations, an intermediate region which has a large fraction of quiescent cells and a cycling outer rim. One advantage sandwiches have over three-dimensional tumor models (sheproids) is that can control the amount of cell to cell contact and thereby separate effects due to oxygen or other gradients from effects due to contact. The authors present x-ray survival curves for sandwiches of various cell densities and compare them to x-ray survival curves done for spheroids and monolayers of the same cell line

  4. Growth of two-dimensional Ge crystal by annealing of heteroepitaxial Ag/Ge(111) under N2 ambient

    Science.gov (United States)

    Ito, Koichi; Ohta, Akio; Kurosawa, Masashi; Araidai, Masaaki; Ikeda, Mitsuhisa; Makihara, Katsunori; Miyazaki, Seiichi

    2018-06-01

    The growth of a two-dimensional crystal of Ge atoms on an atomically flat Ag(111) surface has been demonstrated by the thermal annealing of a heteroepitaxial Ag/Ge structure in N2 ambient at atmospheric pressure. The surface morphology and chemical bonding features of heteroepitaxial Ag(111) grown on wet-cleaned Ge(111) after annealing at different temperatures and for various times have been systematically investigated to control the surface segregation of Ge atoms and the planarization of the heteroepitaxial Ag(111) surface.

  5. Simulation of diffusion in a two-dimensional lattice gas cellular automaton: a test of mode-coupling theory

    NARCIS (Netherlands)

    Frenkel, D.; Ernst, M.H.

    1989-01-01

    We compute the velocity autocorrelation function of a tagged particle in a two-dimensional lattice-gas cellular automaton using a method that is about a million times more efficient than existing techniques. A t-1 algebraic tail in the tagged-particle velocity autocorrelation function is clearly

  6. Study of Growth Kinetics in One Dimensional and Two Dimensional ZnO Nanostructures

    Science.gov (United States)

    Yin, Xin

    Because of the merits arising from the unique geometry, nanostructure materials have been an essential class of materials, which have shown great potentials in the fields of electronics, photonics, and biology. With various nanostructures being intensively investigated and successfully complemented into device applications, there has been one increasing demand to the investigation of the growth mechanism devoted to the controlled nanostructure synthesis. Motivated by this situation, this thesis is focused on the fundamental understanding of the nanostructure growth. Specifically, by taking zinc oxide as an example material, through controlling the basic driving force, that is, the supersaturation, I have rationally designed and synthesized various of nanostructures, and further applied the classical layer-by-layer growth mechanism to the understanding on the formation of these nanostructures, they are, the convex-plate-capped nanowires, the concave-plate-capped nanowires, the facet evolution at the tip of the nanowires, and the ultrathin 2D nanosheets.

  7. On impossibility of limit cycles in certain two-dimensional countinuous-time growth models

    Czech Academy of Sciences Publication Activity Database

    Slobodyan, Sergey

    2001-01-01

    Roč. 5, č. 1 (2001), s. 33-40 ISSN 1081-1826 Institutional research plan: CEZ:AV0Z7085904 Keywords : growth model Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 0.150, year: 2001

  8. A two-dimensional simulation model of phosphorus uptake including crop growth and P-response

    NARCIS (Netherlands)

    Mollier, A.; Willigen, de P.; Heinen, M.; Morel, C.; Schneider, A.; Pellerin, S.

    2008-01-01

    Modelling nutrient uptake by crops implies considering and integrating the processes controlling the soil nutrient supply, the uptake by the root system and relationships between the crop growth response and the amount of nutrient absorbed. We developed a model that integrates both dynamics of maize

  9. Emulation of two-dimensional photonic crystal defect modes in a photonic crystal with a three-dimensional photonic band gap

    International Nuclear Information System (INIS)

    Povinelli, M. L.; Johnson, Steven G.; Fan, Shanhui; Joannopoulos, J. D.

    2001-01-01

    Using numerical simulations, we demonstrate the construction of two-dimensional- (2D-) like defect modes in a recently proposed 3D photonic crystal structure. These modes, which are confined in all three dimensions by a complete photonic band gap, bear a striking similarity to those in 2D photonic crystals in terms of polarization, field profile, and projected band structures. It is expected that these results will greatly facilitate the observation of widely studied 2D photonic-crystal phenomena in a realistic, 3D physical system

  10. Emulation of two-dimensional photonic crystal defect modes in a photonic crystal with a three-dimensional photonic band gap

    Energy Technology Data Exchange (ETDEWEB)

    Povinelli, M. L.; Johnson, Steven G.; Fan, Shanhui; Joannopoulos, J. D.

    2001-08-15

    Using numerical simulations, we demonstrate the construction of two-dimensional- (2D-) like defect modes in a recently proposed 3D photonic crystal structure. These modes, which are confined in all three dimensions by a complete photonic band gap, bear a striking similarity to those in 2D photonic crystals in terms of polarization, field profile, and projected band structures. It is expected that these results will greatly facilitate the observation of widely studied 2D photonic-crystal phenomena in a realistic, 3D physical system.

  11. Collective excitations in semiconductor superlattices and plasma modes of a two-dimensional electron gas with spatially modulated charge density

    International Nuclear Information System (INIS)

    Eliasson, G.L.

    1987-01-01

    The theory of collective excitations in semiconductor superlattices is formulated by using linear response theory. Different kinds of collective excitations in type I (GaAs-GaAlAs) and type II (GaSb-InAs) superlattices are surveyed. Special attention is paid to the presence of surface and finite-size effects. In calculating the dielectric matrix, the effect of different approximations of the system is discussed. The theory for inelastic length scattering (Raman scattering), and for Electron Energy Loss (EEL) due to collective excitations, is formulated. Calculations for several model systems are presented and the main features of the spectra are discussed. In part II the theory of collective excitations of a two-dimensional electron gas with a spatially periodic equilibrium density is formulated. As a first example a periodic array of two-dimensional electron gas strips with constant equilibrium density is studied. The integral equation that describes the charge fluctuations on the strips is derived and solved numerically. The spatial dependence of the density fluctuation across a single strip can be in the form of either propagating or evanescent waves

  12. A two-dimensional continuum model of biofilm growth incorporating fluid flow and shear stress based detachment

    KAUST Repository

    Duddu, Ravindra

    2009-05-01

    We present a two-dimensional biofilm growth model in a continuum framework using an Eulerian description. A computational technique based on the eXtended Finite Element Method (XFEM) and the level set method is used to simulate the growth of the biofilm. The model considers fluid flow around the biofilm surface, the advection-diffusion and reaction of substrate, variable biomass volume fraction and erosion due to the interfacial shear stress at the biofilm-fluid interface. The key assumptions of the model and the governing equations of transport, biofilm kinetics and biofilm mechanics are presented. Our 2D biofilm growth results are in good agreement with those obtained by Picioreanu et al. (Biotechnol Bioeng 69(5):504-515, 2000). Detachment due to erosion is modeled using two continuous speed functions based on: (a) interfacial shear stress and (b) biofilm height. A relation between the two detachment models in the case of a 1D biofilm is established and simulated biofilm results with detachment in 2D are presented. The stress in the biofilm due to fluid flow is evaluated and higher stresses are observed close to the substratum where the biofilm is attached. © 2008 Wiley Periodicals, Inc.

  13. Evaluation and application of a mixed-mode chromatographic stationary phase in two-dimensional liquid chromatography for the separation of traditional Chinese medicine.

    Science.gov (United States)

    Wei, Zhishen; Fu, Qing; Cai, Jianfeng; Huan, Liyun; Zhao, Jianchao; Shi, Hui; Jin, Yu; Liang, Xinmiao

    2016-06-01

    In this study, two mixed-mode chromatography stationary phases (C8SAX and C8SCX) were evaluated and used to establish a two-dimensional liquid chromatography system for the separation of traditional Chinese medicine. The chromatographic properties of the mixed-mode columns were systematically evaluated by comparing with other three columns of C8, strong anion exchanger, and strong cation exchanger. The result showed that C8SAX and C8SCX had a mixed-mode retention mechanism including electrostatic interaction and hydrophobic interaction. Especially, they were suitable for separating acidic and/or basic compounds and their separation selectivities could be easily adjusted by changing pH value. Then, several off-line 2D-LC systems based on the C8SAX in the first dimension and C8SAX, C8SCX, or C8 columns in the second dimension were developed to analyze a traditional Chinese medicine-Uncaria rhynchophylla. The two-dimensional liquid chromatography system of C8SAX (pH 3.0) × C8SAX (pH 6.0) exhibited the most effective peak distribution. Finally, fractions of U. rhynchophylla prepared from the first dimension were successfully separated on the C8SAX column with a gradient pH. Thus, the mixed-mode stationary phase could provide a platform to separate the traditional Chinese medicine in practical applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. New approach in two-dimensional fluid modeling of edge plasma transport with high intermittency due to blobs and edge localized modes

    International Nuclear Information System (INIS)

    Pigarov, A. Yu.; Krasheninnikov, S. I.; Rognlien, T. D.

    2011-01-01

    A new approach is proposed to simulate intermittent, non-diffusive plasma transport (via blobs and filaments of edge localized modes (ELMs)) observed in the tokamak edge region within the framework of two-dimensional transport codes. This approach combines the inherently three-dimensional filamentary structures associated with an ensemble of blobs into a macro-blob in the two-dimensional poloidal cross-section and advects the macro-blob ballistically across the magnetic field, B. Intermittent transport is represented as a sequence of macro-blobs appropriately seeded in the edge plasma according to experimental statistics. In this case, the code is capable of reproducing both the long-scale temporal evolution of the background plasma and the fast spatiotemporal dynamics of blobs. We report the results from a two-dimensional edge plasma code modeling of a single macro-blob dynamics, and its interaction with initially stationary background plasma as well as with material surfaces. The mechanisms of edge plasma particle and energy losses from macro-blobs are analyzed. The effects of macro-blob sizes and advection velocity on edge plasma profiles are studied. The macro-blob impact on power loading and sputtering rates on the chamber wall and on inner and outer divertor plates is discussed. Temporal evolution of particle inventory of the edge plasma perturbed by macro-blobs is analyzed. Application of macro-blobs to ELM modeling is highlighted.

  15. Superconductivity induced by flexural modes in non-σh-symmetric Dirac-like two-dimensional materials: A theoretical study for silicene and germanene

    Science.gov (United States)

    Fischetti, Massimo V.; Polley, Arup

    2018-04-01

    In two-dimensional crystals that lack symmetry under reflections on the horizontal plane of the lattice (non-σh-symmetric), electrons can couple to flexural modes (ZA phonons) at first order. We show that in materials of this type that also exhibit a Dirac-like electron dispersion, the strong coupling can result in electron pairing mediated by these phonons, as long as the flexural modes are not damped or suppressed by additional interactions with a supporting substrate or gate insulator. We consider several models: The weak-coupling limit, which is applicable only in the case of gapped and parabolic materials, like stanene and HfSe2, thanks to the weak coupling; the full gap-equation, solved using the constant-gap approximation and considering statically screened interactions; its extensions to energy-dependent gap and to dynamic screening. We argue that in the case of silicene and germanene superconductivity mediated by this process can exhibit a critical temperature of a few degrees K, or even a few tens of degrees K when accounting for the effect of a high-dielectric-constant environment. We conclude that the electron/flexural-modes coupling should be included in studies of possible superconductivity in non-σh-symmetric two-dimensional crystals, even if alternative forms of coupling are considered.

  16. Controlled growth of high-density CdS and CdSe nanorod arrays on selective facets of two-dimensional semiconductor nanoplates

    KAUST Repository

    Wu, Xue-Jun; Chen, Junze; Tan, Chaoliang; Zhu, Yihan; Han, Yu; Zhang, Hua

    2016-01-01

    . Here, we report a seeded growth approach for the controlled epitaxial growth of three types of hierarchical one-dimensional (1D)/two-dimensional (2D) nanostructures, where nanorod arrays of II-VI semiconductor CdS or CdSe are grown on the selective

  17. Vibrational correlation between conjugated carbonyl and diazo modes studied by single- and dual-frequency two-dimensional infrared spectroscopy

    International Nuclear Information System (INIS)

    Maekawa, Hiroaki; Sul, Soohwan; Ge, Nien-Hui

    2013-01-01

    Highlights: ► Vibrational dynamics of conjugated C=O and N=N modes of ethyl diazoacetate was studied. ► Their frequency–frequency correlation functions are different. ► The dual-frequency 2D IR spectrum indicates anticorrelated frequency fluctuations. ► Correlation effects on dual-frequency 2D IR spectra are discussed. ► The existence of cis and trans conformers is revealed in 2D IR spectra. - Abstract: We have applied infrared three-pulse photon echo and single- and dual-frequency 2D IR spectroscopy to the ester C=O and diazo N=N stretching modes in ethyl diazoacetate (EDA), and investigated their vibrational frequency fluctuations and correlation. The two modes exhibit different vibrational dynamics and 2D lineshape, which are well simulated by frequency–frequency correlation functions (FFCFs) with two decaying components. Although the FT IR spectrum shows a single C=O band, absolute magnitude 2D IR nonrephasing spectrum displays spectral signatures supporting the presence of cis and trans conformations. The cross-peak inclined toward the anti-diagonal in the dual-frequency 2D IR spectrum, indicating that the frequency fluctuations of the two modes are anticorrelated. This behavior is attributed to anticorrelated change in the bond orders when solvent and structural fluctuations causes EDA to adopt a different mixture of the two dominant resonance structures. The effects of cross FFCF on the cross-peak line shape are discussed

  18. Vibrational correlation between conjugated carbonyl and diazo modes studied by single- and dual-frequency two-dimensional infrared spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Maekawa, Hiroaki; Sul, Soohwan [Department of Chemistry, University of California at Irvine, Irvine, CA 92697-2025 (United States); Ge, Nien-Hui, E-mail: nhge@uci.edu [Department of Chemistry, University of California at Irvine, Irvine, CA 92697-2025 (United States)

    2013-08-30

    Highlights: ► Vibrational dynamics of conjugated C=O and N=N modes of ethyl diazoacetate was studied. ► Their frequency–frequency correlation functions are different. ► The dual-frequency 2D IR spectrum indicates anticorrelated frequency fluctuations. ► Correlation effects on dual-frequency 2D IR spectra are discussed. ► The existence of cis and trans conformers is revealed in 2D IR spectra. - Abstract: We have applied infrared three-pulse photon echo and single- and dual-frequency 2D IR spectroscopy to the ester C=O and diazo N=N stretching modes in ethyl diazoacetate (EDA), and investigated their vibrational frequency fluctuations and correlation. The two modes exhibit different vibrational dynamics and 2D lineshape, which are well simulated by frequency–frequency correlation functions (FFCFs) with two decaying components. Although the FT IR spectrum shows a single C=O band, absolute magnitude 2D IR nonrephasing spectrum displays spectral signatures supporting the presence of cis and trans conformations. The cross-peak inclined toward the anti-diagonal in the dual-frequency 2D IR spectrum, indicating that the frequency fluctuations of the two modes are anticorrelated. This behavior is attributed to anticorrelated change in the bond orders when solvent and structural fluctuations causes EDA to adopt a different mixture of the two dominant resonance structures. The effects of cross FFCF on the cross-peak line shape are discussed.

  19. Two-dimensional Schrödinger symmetry and three-dimensional breathers and Kelvin-ripple complexes as quasi-massive-Nambu-Goldstone modes

    Science.gov (United States)

    Takahashi, Daisuke A.; Ohashi, Keisuke; Fujimori, Toshiaki; Nitta, Muneto

    2017-08-01

    Bose-Einstein condensates (BECs) confined in a two-dimensional (2D) harmonic trap are known to possess a hidden 2D Schrödinger symmetry, that is, the Schrödinger symmetry modified by a trapping potential. Spontaneous breaking of this symmetry gives rise to a breathing motion of the BEC, whose oscillation frequency is robustly determined by the strength of the harmonic trap. In this paper, we demonstrate that the concept of the 2D Schrödinger symmetry can be applied to predict the nature of three-dimensional (3D) collective modes propagating along a condensate confined in an elongated trap. We find three kinds of collective modes whose existence is robustly ensured by the Schrödinger symmetry, which are physically interpreted as one breather mode and two Kelvin-ripple complex modes, i.e., composite modes in which the vortex core and the condensate surface oscillate interactively. We provide analytical expressions for the dispersion relations (energy-momentum relation) of these modes using the Bogoliubov theory [D. A. Takahashi and M. Nitta, Ann. Phys. 354, 101 (2015), 10.1016/j.aop.2014.12.009]. Furthermore, we point out that these modes can be interpreted as "quasi-massive-Nambu-Goldstone (NG) modes", that is, they have the properties of both quasi-NG and massive NG modes: quasi-NG modes appear when a symmetry of a part of a Lagrangian, which is not a symmetry of a full Lagrangian, is spontaneously broken, while massive NG modes appear when a modified symmetry is spontaneously broken.

  20. Vibrational correlation between conjugated carbonyl and diazo modes studied by single- and dual-frequency two-dimensional infrared spectroscopy

    Science.gov (United States)

    Maekawa, Hiroaki; Sul, Soohwan; Ge, Nien-Hui

    2013-08-01

    We have applied infrared three-pulse photon echo and single- and dual-frequency 2D IR spectroscopy to the ester Cdbnd O and diazo Ndbnd N stretching modes in ethyl diazoacetate (EDA), and investigated their vibrational frequency fluctuations and correlation. The two modes exhibit different vibrational dynamics and 2D lineshape, which are well simulated by frequency-frequency correlation functions (FFCFs) with two decaying components. Although the FT IR spectrum shows a single Cdbnd O band, absolute magnitude 2D IR nonrephasing spectrum displays spectral signatures supporting the presence of cis and trans conformations. The cross-peak inclined toward the anti-diagonal in the dual-frequency 2D IR spectrum, indicating that the frequency fluctuations of the two modes are anticorrelated. This behavior is attributed to anticorrelated change in the bond orders when solvent and structural fluctuations causes EDA to adopt a different mixture of the two dominant resonance structures. The effects of cross FFCF on the cross-peak line shape are discussed.

  1. Two-dimensional environmental profiles of growth and fumonisin production by Fusarium proliferatum on a wheat-based substrate.

    Science.gov (United States)

    Cendoya, Eugenia; Farnochi, María Cecilia; Chulze, Sofia Noemi; Ramirez, María Laura

    2014-07-16

    The effect of water activity (aW; 0.995, 0.99, 0.98, 0.96, 0.94, 0.92, and 0.90), temperature (15, 25, and 30°C), incubation time (7, 14, 21 and 28days), and their interactions on mycelial growth and fumonisin production on wheat-based medium by three Fusarium proliferatum strains isolated from wheat in Argentina was evaluated. Maximum growth rates were obtained at the highest aW (0.995) and 30°C, with growth decreasing as the aW of the medium was reduced. Maximum amounts of total fumonisins (FB1, FB2 and FB3) were produced at 0.99 aW and 25°C after 21 and 28days of incubation for 2 strains, and at 15°C and 0.98 aW after 28days of incubation for the third strain. The fumonisin concentrations varied considerably depending on the aW and temperature interactions assayed. The studied strains had different fumonisin production profiles. F. proliferatum ITEM 15661 and ITEM 15664 produced FB1 and FB2 whereas F. proliferatum ITEM 15654 was able to produce FB1, FB2 and FB3. Interestingly, fumonisin production profiles for each particular strain were related to incubation temperatures. Fumonisins were produced from 15 to 30°C and at aW values of 0.92 to 0.995 after 21 to 28days of incubation. However at 7 and 14days of incubation small amounts of fumonisin were produced at aW lower than 0.94. Two-dimensional profiles of aW by temperature interactions were developed from these data to identify areas where conditions indicate a significant risk from fumonisin accumulation on wheat. Temperature and aW conditions that resulted in fumonisin production are those found during wheat grain development (especially milk and dough stages) in the field. This study provides useful base line data on conditions representing a high and a low risk for contamination of wheat by fumonisins which is becoming of greater concern because this cereal is destined mainly for human consumption. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. Highly Oriented Growth of Piezoelectric Thin Films on Silicon using Two-Dimensional Nanosheets as Growth Template Layer

    NARCIS (Netherlands)

    Nguyen, Duc Minh; Yuan, H.; Houwman, Evert Pieter; Dekkers, Jan M.; Koster, Gertjan; ten Elshof, Johan E.; Rijnders, Augustinus J.H.M.

    2016-01-01

    Ca2Nb3O10 (CNOns) and Ti0.87O2 (TiOns) metal oxide nanosheets (ns) are used as a buffer layer for epitaxial growth of piezoelectric capacitor stacks on Si and Pt/Ti/SiO2/Si (Pt/Si) substrates. Highly (001)- and (110)-oriented Pb(Zr0.52Ti0.48)O3 (PZT) films are achieved by utilizing CNOns and TiOns,

  3. Turbulence growth and its dependency of wake vortices on excitation frequency by local body-force around two-dimensional hump

    Science.gov (United States)

    Yakeno, Aiko; Abe, Yoshiaki; Nonomura, Taku; Kawai, Soshi; Fujii, Kozo

    2017-11-01

    We investigated details of wake vortex dynamics to cause turbulence increase and early flow-reattachment under excitation forcing by a plasma actuator setting around a 2D hump numerically. The local body-force was homogeneous in the spanwise direction and bursting temporally. That actuation generates two-dimensional roll vortices and other turbulence motions such like three-dimensional rib structure in downstream. These dynamics depended on the excitation frequency. We tried to discuss multi-scaled vortices separately with considering the temporal phaseaveraged statistics of the excitation frequency and others, those are related to roll vortices and others with rib structure between rolls. It was found that the maximum value of non-periodic fluctuation in downstream correlated with flow-reattachment performance more than that of periodic fluctuation of roll vortices. The amplitude becomes large around separation position in early reattachment cases. The spacial growth rates of peak values in the wall-normal direction are same for high frequency cases, K-H instability modes, however not true for low frequency cases. In high frequency cases, amplitude in the early state of separation plays a significant rule to increase it in downstream. Strategic Programs for Innovative Research of the High Performance Computing Initiative (No. hp120296,hp130001,hp140207, hp150219) Grant-in-Aid for Scientific Research(B) (No. 15K21677) by the MEXT.

  4. Highly Oriented Growth of Piezoelectric Thin Films on Silicon Using Two-Dimensional Nanosheets as Growth Template Layer.

    Science.gov (United States)

    Nguyen, Minh D; Yuan, Huiyu; Houwman, Evert P; Dekkers, Matthijn; Koster, Gertjan; Ten Elshof, Johan E; Rijnders, Guus

    2016-11-16

    Ca 2 Nb 3 O 10 (CNOns) and Ti 0.87 O 2 (TiOns) metal oxide nanosheets (ns) are used as a buffer layer for epitaxial growth of piezoelectric capacitor stacks on Si and Pt/Ti/SiO 2 /Si (Pt/Si) substrates. Highly (001)- and (110)-oriented Pb(Zr 0.52 Ti 0.48 )O 3 (PZT) films are achieved by utilizing CNOns and TiOns, respectively. The piezoelectric capacitors are characterized by polarization and piezoelectric hysteresis loops and by fatigue measurements. The devices fabricated with SrRuO 3 top and bottom electrodes directly on nanosheets/Si have ferroelectric and piezoelectric properties well comparable with devices that use more conventional oxide buffer layers (stacks) such as YSZ, CeO 2 /YSZ, or SrTiO 3 on Si. The devices grown on nanosheets/Pt/Si with Pt top electrodes show significantly improved polarization fatigue properties over those of similar devices grown directly on Pt/Si. The differences in properties are ascribed to differences in the crystalline structures and the density of the films. These results show a route toward the fabrication of single crystal piezoelectric thin films and devices with high quality, long-lifetime piezoelectric capacitor structures on nonperovskite and even noncrystalline substrates such as glass or polished metal surfaces.

  5. Two-dimensional errors

    International Nuclear Information System (INIS)

    Anon.

    1991-01-01

    This chapter addresses the extension of previous work in one-dimensional (linear) error theory to two-dimensional error analysis. The topics of the chapter include the definition of two-dimensional error, the probability ellipse, the probability circle, elliptical (circular) error evaluation, the application to position accuracy, and the use of control systems (points) in measurements

  6. The Use of Sparse Direct Solver in Vector Finite Element Modeling for Calculating Two Dimensional (2-D) Magnetotelluric Responses in Transverse Electric (TE) Mode

    Science.gov (United States)

    Yihaa Roodhiyah, Lisa’; Tjong, Tiffany; Nurhasan; Sutarno, D.

    2018-04-01

    The late research, linear matrices of vector finite element in two dimensional(2-D) magnetotelluric (MT) responses modeling was solved by non-sparse direct solver in TE mode. Nevertheless, there is some weakness which have to be improved especially accuracy in the low frequency (10-3 Hz-10-5 Hz) which is not achieved yet and high cost computation in dense mesh. In this work, the solver which is used is sparse direct solver instead of non-sparse direct solverto overcome the weaknesses of solving linear matrices of vector finite element metod using non-sparse direct solver. Sparse direct solver will be advantageous in solving linear matrices of vector finite element method because of the matrix properties which is symmetrical and sparse. The validation of sparse direct solver in solving linear matrices of vector finite element has been done for a homogen half-space model and vertical contact model by analytical solution. Thevalidation result of sparse direct solver in solving linear matrices of vector finite element shows that sparse direct solver is more stable than non-sparse direct solver in computing linear problem of vector finite element method especially in low frequency. In the end, the accuracy of 2D MT responses modelling in low frequency (10-3 Hz-10-5 Hz) has been reached out under the efficient allocation memory of array and less computational time consuming.

  7. Two dimensional unstable scar statistics.

    Energy Technology Data Exchange (ETDEWEB)

    Warne, Larry Kevin; Jorgenson, Roy Eberhardt; Kotulski, Joseph Daniel; Lee, Kelvin S. H. (ITT Industries/AES Los Angeles, CA)

    2006-12-01

    This report examines the localization of time harmonic high frequency modal fields in two dimensional cavities along periodic paths between opposing sides of the cavity. The cases where these orbits lead to unstable localized modes are known as scars. This paper examines the enhancements for these unstable orbits when the opposing mirrors are both convex and concave. In the latter case the construction includes the treatment of interior foci.

  8. Study of long-range orders of hard-core bosons coupled to cooperative normal modes in two-dimensional lattices

    Science.gov (United States)

    Ghosh, A.; Yarlagadda, S.

    2017-09-01

    Understanding the microscopic mechanism of coexisting long-range orders (such as lattice supersolidity) in strongly correlated systems is a subject of immense interest. We study the possible manifestations of long-range orders, including lattice-supersolid phases with differently broken symmetry, in a two-dimensional square lattice system of hard-core bosons (HCBs) coupled to archetypal cooperative/coherent normal-mode distortions such as those in perovskites. At strong HCB-phonon coupling, using a duality transformation to map the strong-coupling problem to a weak-coupling one, we obtain an effective Hamiltonian involving nearest-neighbor, next-nearest-neighbor, and next-to-next-nearest-neighbor hoppings and repulsions. Using stochastic series expansion quantum Monte Carlo, we construct the phase diagram of the system. As coupling strength is increased, we find that the system undergoes a first-order quantum phase transition from a superfluid to a checkerboard solid at half-filling and from a superfluid to a diagonal striped solid [with crystalline ordering wave vector Q ⃗=(2 π /3 ,2 π /3 ) or (2 π /3 ,4 π /3 )] at one-third filling without showing any evidence of supersolidity. On tuning the system away from these commensurate fillings, checkerboard supersolid is generated near half-filling whereas a rare diagonal striped supersolid is realized near one-third filling. Interestingly, there is an asymmetry in the extent of supersolidity about one-third filling. Within our framework, we also provide an explanation for the observed checkerboard and stripe formations in La2 -xSrxNiO4 at x =1 /2 and x =1 /3 .

  9. Application of the lattice Boltzmann model to simulated stenosis growth in a two-dimensional carotid artery

    International Nuclear Information System (INIS)

    Boyd, J; Buick, J; Cosgrove, J A; Stansell, P

    2005-01-01

    The lattice Boltzmann model is used to observe changes in the velocity flow and shear stress in a carotid artery model during a simulated stenosis growth. Near wall shear stress in the unstenosed artery is found to agree with literature values. The model also shows regions of low velocity, rotational flow and low near wall shear stress along parts of the walls of the carotid artery that have been identified as being prone to atherosclerosis. These regions persist during the simulated stenosis growth, suggesting that atherosclerotic plaque build-up creates regions of flow with properties that favour atherosclerotic progression

  10. Growth optimization and characterization of high mobility two-dimensional electron systems in AlAs quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Dasgupta, Shivaji

    2009-02-15

    In this work two-dimensional electron systems (2DESs) based on AlAs/AlGaAs heterostructures doped with Si are investigated. The electrons are confined in AlAs quantum wells (QWs) sandwiched between AlGaAs buffers. Analytical calculations and simulations for AlAs QWs are presented in the first chapter. The results show a cross-over width, above which the wide (001)-oriented QWs show double valley occupancy and wide (110)-oriented QWs show single valley occupancy. We solve the Schroedinger equation analytically for anisotropic masses. The solution shows the orientation dependence of the elliptical cyclotron orbit due to the anisotropic mass. We also present an introduction to the Landau level crossings based on g{sup *}m{sup *} product. In the next chapter, we present experimental results for the double-valley (001)-oriented AlAs QWs. We present the different structures of the deep AlAs QWs along with the low temperature magnetotransport data for these QWs. Thereafter, we present the results on shallow AlAs QWs. We achieved a mobility of 4.2 x 10{sup 5} cm{sup 2}/Vs at 330 mK for the deep backside doped AlAs QW. For the shallow QWs, we achieved a mobility of2.3 x 10{sup 5} cm{sup 2}/Vs at 330 mK, for a density of 2.9 x 10{sup 11} cm{sup -2}. From the magneto-transport data, we see evidence of the double-valley occupation for the (001)-oriented AlAs wide QWs. In the next chapter, we present experimental results for the single-valley (110)-oriented AlAs QWs. We deduced the donor binding energy and the doping efficiency for this facet from a doping series of double-sided doped QWs. Thereafter, we designed different structures for the (110)-oriented AlAs QWs, which we present along with their respective low temperature magneto-transport data. We measured one of the double-sided doped AlAs QWs at very high magnetic fields and low temperatures, down to 60 mK. At the end of the chapter, we present a spike feature observed in the magneto-transport data of these QWs. This

  11. Sediment transport, light and algal growth in the Markermeer : a two-dimensional water quality model for a shallow lake

    NARCIS (Netherlands)

    Duin, van E.H.S.

    1992-01-01

    This thesis reports on a study of the water quality in the Markermeer, focusing on the relationships between sediment transport, the light field and the growth of Oscillatoria agardhii . The study comprises two aspects: an extensive data collection program with the data

  12. Growth of large-size-two-dimensional crystalline pentacene grains for high performance organic thin film transistors

    Directory of Open Access Journals (Sweden)

    Chuan Du

    2012-06-01

    Full Text Available New approach is presented for growth of pentacene crystalline thin film with large grain size. Modification of dielectric surfaces using a monolayer of small molecule results in the formation of pentacene thin films with well ordered large crystalline domain structures. This suggests that pentacene molecules may have significantly large diffusion constant on the modified surface. An average hole mobility about 1.52 cm2/Vs of pentacene based organic thin film transistors (OTFTs is achieved with good reproducibility.

  13. Dynamical scaling, domain-growth kinetics, and domain-wall shapes of quenched two-dimensional anisotropic XY models

    DEFF Research Database (Denmark)

    Mouritsen, Ole G.; Praestgaard, Eigil

    1988-01-01

    obeys dynamical scaling and the shape of the dynamical scaling function pertaining to the structure factor is found to depend on P. Specifically, this function is described by a Porod-law behavior, q-ω, where ω increases with the wall softness. The kinetic exponent, which describes how the linear domain...... infinite to zero temperature as well as to nonzero temperatures below the ordering transition. The continuous nature of the spin variables causes the domain walls to be ‘‘soft’’ and characterized by a finite thickness. The steady-state thickness of the walls can be varied by a model parameter, P. At zero...... size varies with time, R(t)∼tn, is for both models at zero temperature determined to be n≃0.25, independent of P. At finite temperatures, the growth kinetics is found to cross over to the Lifshitz-Allen-Cahn law characterized by n≃0.50. The results support the idea of two separate zero...

  14. Controlled growth of high-density CdS and CdSe nanorod arrays on selective facets of two-dimensional semiconductor nanoplates

    KAUST Repository

    Wu, Xue-Jun

    2016-03-14

    The rational synthesis of hierarchical three-dimensional nanostructures with specific compositions, morphologies and functionalities is important for applications in a variety of fields ranging from energy conversion and electronics to biotechnology. Here, we report a seeded growth approach for the controlled epitaxial growth of three types of hierarchical one-dimensional (1D)/two-dimensional (2D) nanostructures, where nanorod arrays of II-VI semiconductor CdS or CdSe are grown on the selective facets of hexagonal-shaped nanoplates, either on the two basal facets of the nanoplate, or on one basal facet, or on the two basal facets and six side facets. The seed engineering of 2D hexagonal-shaped nanoplates is the key factor for growth of the three resulting types of 1D/2D nanostructures. The wurtzite- and zinc-blende-type polymorphs of semiconductors are used to determine the facet-selective epitaxial growth of 1D nanorod arrays, resulting in the formation of different hierarchical three-dimensional (3D) nanostructures. © 2016 Macmillan Publishers Limited. All rights reserved.

  15. Two-dimensional calculus

    CERN Document Server

    Osserman, Robert

    2011-01-01

    The basic component of several-variable calculus, two-dimensional calculus is vital to mastery of the broader field. This extensive treatment of the subject offers the advantage of a thorough integration of linear algebra and materials, which aids readers in the development of geometric intuition. An introductory chapter presents background information on vectors in the plane, plane curves, and functions of two variables. Subsequent chapters address differentiation, transformations, and integration. Each chapter concludes with problem sets, and answers to selected exercises appear at the end o

  16. Two-dimensional models

    International Nuclear Information System (INIS)

    Schroer, Bert; Freie Universitaet, Berlin

    2005-02-01

    It is not possible to compactly review the overwhelming literature on two-dimensional models in a meaningful way without a specific viewpoint; I have therefore tacitly added to the above title the words 'as theoretical laboratories for general quantum field theory'. I dedicate this contribution to the memory of J. A. Swieca with whom I have shared the passion of exploring 2-dimensional models for almost one decade. A shortened version of this article is intended as a contribution to the project 'Encyclopedia of mathematical physics' and comments, suggestions and critical remarks are welcome. (author)

  17. Two-dimensional ferroelectrics

    Energy Technology Data Exchange (ETDEWEB)

    Blinov, L M; Fridkin, Vladimir M; Palto, Sergei P [A.V. Shubnikov Institute of Crystallography, Russian Academy of Sciences, Moscow, Russian Federaion (Russian Federation); Bune, A V; Dowben, P A; Ducharme, Stephen [Department of Physics and Astronomy, Behlen Laboratory of Physics, Center for Materials Research and Analysis, University of Nebraska-Linkoln, Linkoln, NE (United States)

    2000-03-31

    The investigation of the finite-size effect in ferroelectric crystals and films has been limited by the experimental conditions. The smallest demonstrated ferroelectric crystals had a diameter of {approx}200 A and the thinnest ferroelectric films were {approx}200 A thick, macroscopic sizes on an atomic scale. Langmuir-Blodgett deposition of films one monolayer at a time has produced high quality ferroelectric films as thin as 10 A, made from polyvinylidene fluoride and its copolymers. These ultrathin films permitted the ultimate investigation of finite-size effects on the atomic thickness scale. Langmuir-Blodgett films also revealed the fundamental two-dimensional character of ferroelectricity in these materials by demonstrating that there is no so-called critical thickness; films as thin as two monolayers (1 nm) are ferroelectric, with a transition temperature near that of the bulk material. The films exhibit all the main properties of ferroelectricity with a first-order ferroelectric-paraelectric phase transition: polarization hysteresis (switching); the jump in spontaneous polarization at the phase transition temperature; thermal hysteresis in the polarization; the increase in the transition temperature with applied field; double hysteresis above the phase transition temperature; and the existence of the ferroelectric critical point. The films also exhibit a new phase transition associated with the two-dimensional layers. (reviews of topical problems)

  18. Effect of Temperature and Fluid Flow on Dendrite Growth During Solidification of Al-3 Wt Pct Cu Alloy by the Two-Dimensional Cellular Automaton Method

    Science.gov (United States)

    Gu, Cheng; Wei, Yanhong; Liu, Renpei; Yu, Fengyi

    2017-12-01

    A two-dimensional cellular automaton-finite volume model was developed to simulate dendrite growth of Al-3 wt pct Cu alloy during solidification to investigate the effect of temperature and fluid flow on dendrite morphology, solute concentration distribution, and dendrite growth velocity. Different calculation conditions that may influence the results of the simulation, including temperature and flow, were considered. The model was also employed to study the effect of different undercoolings, applied temperature fields, and forced flow velocities on solute segregation and dendrite growth. The initial temperature and fluid flow have a significant impact on the dendrite morphologies and solute profiles during solidification. The release of energy is operated with solidification and results in the increase of temperature. A larger undercooling leads to larger solute concentration near the solid/liquid interface and solute concentration gradient at the same time-step. Solute concentration in the solid region tends to increase with the increase of undercooling. Four vortexes appear under the condition when natural flow exists: the two on the right of the dendrite rotate clockwise, and those on the left of the dendrite rotate counterclockwise. With the increase of forced flow velocity, the rejected solute in the upstream region becomes easier to be washed away and enriched in the downstream region, resulting in acceleration of the growth of the dendrite in the upstream and inhibiting the downstream dendrite growth. The dendrite perpendicular to fluid flow shows a coarser morphology in the upstream region than that of the downstream. Almost no secondary dendrite appears during the calculation process.

  19. Two-dimensional Kagome photonic bandgap waveguide

    DEFF Research Database (Denmark)

    Nielsen, Jens Bo; Søndergaard, Thomas; Libori, Stig E. Barkou

    2000-01-01

    The transverse-magnetic photonic-bandgap-guidance properties are investigated for a planar two-dimensional (2-D) Kagome waveguide configuration using a full-vectorial plane-wave-expansion method. Single-moded well-localized low-index guided modes are found. The localization of the optical modes...... is investigated with respect to the width of the 2-D Kagome waveguide, and the number of modes existing for specific frequencies and waveguide widths is mapped out....

  20. Concordance and reproducibility between M-mode, tissue Doppler imaging, and two-dimensional strain imaging in the assessment of mitral annular displacement and velocity in patients with various heart conditions

    DEFF Research Database (Denmark)

    de Knegt, Martina Chantal; Biering-Sorensen, Tor; Sogaard, Peter

    2014-01-01

    AIMS: Mitral annular (MA) displacement reflects longitudinal left ventricular (LV) deformation and systolic velocity measurements reflect the rate of contraction; both are valuable in the diagnosis and prognosis of cardiac disease. The aim of this study was to test the agreement and reproducibility...... between motion mode (M-mode), colour tissue Doppler imaging (TDI), and two-dimensional strain imaging (2DSI) when measuring MA displacement and systolic velocity. METHODS AND RESULTS: Using GE Healthcare Vivid 7 and E9 and Echopac BT11 software, MA displacement and velocity measurements by 2DSI, TDI...

  1. Characterization of pH titration shifts for all the nonlabile proton resonances in a protein by two-dimensional NMR: The case of mouse epidermal growth factor

    International Nuclear Information System (INIS)

    Kohda, Daisuke; Sawada, Toshie; Inagaki, Fuyuhiko

    1991-01-01

    The pH titration shifts for all the nonlabile proton resonances in a 53-residue protein (mouse epidermal growth factor) were measured in the p 2 H range 1.5-9 with two-dimensional (2D) 1 H NMR. The 2D NMR pH titration experiment made it possible to determine the pK values for all the ionizable group which were titrated in the pH range 1.5-9 in the protein. The pK values of the nine ionizable groups (α-amino group, four Asp, two Glu, one His, and α-carboxyl group) were found to be near their normal values. The 2D titration experiment also provided a detailed description of the pH-dependent behavior of the proton chemical shifts and enabled us to characterize the pH-dependent changes of protein conformation. Analysis of the pH-dependent shifts of ca. 200 proton resonances offered evidence of conformational changes in slightly basic pH solution: The deprotonation of the N-terminal α-amino group induced a widespread conformational change over the β-sheet structure in the protein, while the effects of deprotonation of the His22 imidazole group were relatively localized. The authors found that the 2D NMR pH titration experiment is a powerful tool for investigating the structural and dynamic properties of proteins

  2. Mixed-Mode Crack Growth in Wood

    Directory of Open Access Journals (Sweden)

    Octavian POP

    2012-09-01

    Full Text Available In timber elements the mixed mode dependsessentially of wood anatomy and load configuration.In these conditions, in order to evaluate the materialbehavior and the fracture process, it’s necessary toseparate the part of each mode. The mixed modeseparation allows evaluating the amplitude offracture mode. In the present paper, using a mixedmodecrack growth specimen made in Douglas fir,the mixed mode crack growth process is studythanks to marks tracking method. Using the markstracking method the characteristic displacementsassociated to opening and shear mode aremeasured. From the experimental measurements,the energy release rate associated to opening andshear modes is calculated into to account the crackadvancement during the test.

  3. Formation of large-scale structures with sharp density gradient through Rayleigh-Taylor growth in a two-dimensional slab under the two-fluid and finite Larmor radius effects

    International Nuclear Information System (INIS)

    Goto, R.; Hatori, T.; Miura, H.; Ito, A.; Sato, M.

    2015-01-01

    Two-fluid and the finite Larmor effects on linear and nonlinear growth of the Rayleigh-Taylor instability in a two-dimensional slab are studied numerically with special attention to high-wave-number dynamics and nonlinear structure formation at a low β-value. The two effects stabilize the unstable high wave number modes for a certain range of the β-value. In nonlinear simulations, the absence of the high wave number modes in the linear stage leads to the formation of the density field structure much larger than that in the single-fluid magnetohydrodynamic simulation, together with a sharp density gradient as well as a large velocity difference. The formation of the sharp velocity difference leads to a subsequent Kelvin-Helmholtz-type instability only when both the two-fluid and finite Larmor radius terms are incorporated, whereas it is not observed otherwise. It is shown that the emergence of the secondary instability can modify the outline of the turbulent structures associated with the primary Rayleigh-Taylor instability

  4. Constraints on mechanisms for the growth of gully alcoves in Gasa crater, Mars, from two-dimensional stability assessments of rock slopes

    Science.gov (United States)

    Okubo, C.H.; Tornabene, L.L.; Lanza, N.L.

    2011-01-01

    The value of slope stability analyses for gaining insight into the geologic conditions that would facilitate the growth of gully alcoves on Mars is demonstrated in Gasa crater. Two-dimensional limit equilibrium methods are used in conjunction with high-resolution topography derived from stereo High Resolution Imaging Science Experiment (HiRISE) imagery. These analyses reveal three conditions that may produce observed alcove morphologies through slope failure: (1) a ca >10m thick surface layer that is either saturated with H2O ground ice or contains no groundwater/ice at all, above a zone of melting H2O ice or groundwater and under dynamic loading (i.e., seismicity), (2) a 1-10m thick surface layer that is saturated with either melting H2O ice or groundwater and under dynamic loading, or (3) a >100m thick surface layer that is saturated with either melting H2O ice or groundwater and under static loading. This finding of three plausible scenarios for slope failure demonstrates how the triggering mechanisms and characteristics of future alcove growth would be affected by prevailing environmental conditions. HiRISE images also reveal normal faults and other fractures tangential to the crowns of some gully alcoves that are interpreted to be the result of slope instability, which may facilitate future slope movement. Stability analyses show that the most failure-prone slopes in this area are found in alcoves that are adjacent to crown fractures. Accordingly, crown fractures appear to be a useful indicator of those alcoves that should be monitored for future landslide activity. ?? 2010.

  5. Zero modes and the vacuum problem: A study of scalar adjoint matter in two-dimensional Yang-Mills theory via light-cone quantization

    International Nuclear Information System (INIS)

    Kalloniatis, A.C.

    1996-01-01

    SU(2) Yang-Mills theory coupled to massive adjoint scalar matter is studied in 1+1 dimensions using discretized light-cone quantization. This theory can be obtained from pure Yang-Mills theory in 2+1 dimensions via dimensional reduction. On the light cone, the vacuum structure of this theory is encoded in the dynamical zero mode of a gluon and a constrained mode of the scalar field. The latter satisfies a linear constraint, suggesting no nontrivial vacua in the present paradigm for symmetry breaking on the light cone. I develop a diagrammatic method to solve the constraint equation. In the adiabatic approximation I compute the quantum-mechanical potential governing the dynamical gauge mode. Because of a condensation of the lowest momentum modes of the dynamical gluons, a centrifugal barrier is generated in the adiabatic potential. In the present theory, however, the barrier height appears too small to make any impact in this model. Although the theory is superrenormalizable on naive power-counting grounds, the removal of ultraviolet divergences is nontrivial when the constrained mode is taken into account. The solution of this problem is discussed. copyright 1996 The American Physical Society

  6. Two-dimensional NMR spectrometry

    International Nuclear Information System (INIS)

    Farrar, T.C.

    1987-01-01

    This article is the second in a two-part series. In part one (ANALYTICAL CHEMISTRY, May 15) the authors discussed one-dimensional nuclear magnetic resonance (NMR) spectra and some relatively advanced nuclear spin gymnastics experiments that provide a capability for selective sensitivity enhancements. In this article and overview and some applications of two-dimensional NMR experiments are presented. These powerful experiments are important complements to the one-dimensional experiments. As in the more sophisticated one-dimensional experiments, the two-dimensional experiments involve three distinct time periods: a preparation period, t 0 ; an evolution period, t 1 ; and a detection period, t 2

  7. Quasi-two-dimensional holography

    International Nuclear Information System (INIS)

    Kutzner, J.; Erhard, A.; Wuestenberg, H.; Zimpfer, J.

    1980-01-01

    The acoustical holography with numerical reconstruction by area scanning is memory- and time-intensive. With the experiences by the linear holography we tried to derive a scanning for the evaluating of the two-dimensional flaw-sizes. In most practical cases it is sufficient to determine the exact depth extension of a flaw, whereas the accuracy of the length extension is less critical. For this reason the applicability of the so-called quasi-two-dimensional holography is appropriate. The used sound field given by special probes is divergent in the inclined plane and light focussed in the perpendicular plane using cylindrical lenses. (orig.) [de

  8. Two-dimensional metamaterial optics

    International Nuclear Information System (INIS)

    Smolyaninov, I I

    2010-01-01

    While three-dimensional photonic metamaterials are difficult to fabricate, many new concepts and ideas in the metamaterial optics can be realized in two spatial dimensions using planar optics of surface plasmon polaritons. In this paper we review recent progress in this direction. Two-dimensional photonic crystals, hyperbolic metamaterials, and plasmonic focusing devices are demonstrated and used in novel microscopy and waveguiding schemes

  9. Proteomic analysis of Bacillus thuringiensis at different growth phases by using an automated online two-dimensional liquid chromatography-tandem mass spectrometry strategy.

    Science.gov (United States)

    Huang, Shaoya; Ding, Xuezhi; Sun, Yunjun; Yang, Qi; Xiao, Xiuqing; Cao, Zhenping; Xia, Liqiu

    2012-08-01

    The proteome of a new Bacillus thuringiensis subsp. kurstaki strain, 4.0718, from the middle vegetative (T(1)), early sporulation (T(2)), and late sporulation (T(3)) phases was analyzed using an integrated liquid chromatography (LC)-based protein identification system. The system comprised two-dimensional (2D) LC coupled with nanoscale electrospray ionization (ESI) tandem mass spectrometry (MS/MS) on a high-resolution hybrid mass spectrometer with an automated data analysis system. After deletion of redundant proteins from the different batches and B. thuringiensis subspecies, 918, 703, and 778 proteins were identified in the respective three phases. Their molecular masses ranged from 4.6 Da to 477.4 Da, and their isoelectric points ranged from 4.01 to 11.84. Function clustering revealed that most of the proteins in the three phases were functional metabolic proteins, followed by proteins participating in cell processes. Small molecular and macromolecular metabolic proteins were further classified according to the Kyoto Encyclopedia of Genes and Genome and BioCyc metabolic pathway database. Three protoxins (Cry2Aa, Cry1Aa, and Cry1Ac) as well as a series of potential intracellular active factors were detected. Many significant proteins related to spore and crystal formation, including sporulation proteins, help proteins, chaperones, and so on, were identified. The expression patterns of two identified proteins, CotJc and glutamine synthetase, were validated by Western blot analysis, which further confirmed the MS results. This study is the first to use shotgun technology to research the proteome of B. thuringiensis. Valuable experimental data are provided regarding the methodology of analyzing the B. thuringiensis proteome (which can be used to produce insecticidal crystal proteins) and have been added to the related protein database.

  10. Two-dimensional flexible nanoelectronics

    Science.gov (United States)

    Akinwande, Deji; Petrone, Nicholas; Hone, James

    2014-12-01

    2014/2015 represents the tenth anniversary of modern graphene research. Over this decade, graphene has proven to be attractive for thin-film transistors owing to its remarkable electronic, optical, mechanical and thermal properties. Even its major drawback--zero bandgap--has resulted in something positive: a resurgence of interest in two-dimensional semiconductors, such as dichalcogenides and buckled nanomaterials with sizeable bandgaps. With the discovery of hexagonal boron nitride as an ideal dielectric, the materials are now in place to advance integrated flexible nanoelectronics, which uniquely take advantage of the unmatched portfolio of properties of two-dimensional crystals, beyond the capability of conventional thin films for ubiquitous flexible systems.

  11. Two-dimensional topological photonics

    Science.gov (United States)

    Khanikaev, Alexander B.; Shvets, Gennady

    2017-12-01

    Originating from the studies of two-dimensional condensed-matter states, the concept of topological order has recently been expanded to other fields of physics and engineering, particularly optics and photonics. Topological photonic structures have already overturned some of the traditional views on wave propagation and manipulation. The application of topological concepts to guided wave propagation has enabled novel photonic devices, such as reflection-free sharply bent waveguides, robust delay lines, spin-polarized switches and non-reciprocal devices. Discrete degrees of freedom, widely used in condensed-matter physics, such as spin and valley, are now entering the realm of photonics. In this Review, we summarize the latest advances in this highly dynamic field, with special emphasis on the experimental work on two-dimensional photonic topological structures.

  12. Two-dimensional thermofield bosonization

    International Nuclear Information System (INIS)

    Amaral, R.L.P.G.; Belvedere, L.V.; Rothe, K.D.

    2005-01-01

    The main objective of this paper was to obtain an operator realization for the bosonization of fermions in 1 + 1 dimensions, at finite, non-zero temperature T. This is achieved in the framework of the real-time formalism of Thermofield Dynamics. Formally, the results parallel those of the T = 0 case. The well-known two-dimensional Fermion-Boson correspondences at zero temperature are shown to hold also at finite temperature. To emphasize the usefulness of the operator realization for handling a large class of two-dimensional quantum field-theoretic problems, we contrast this global approach with the cumbersome calculation of the fermion-current two-point function in the imaginary-time formalism and real-time formalisms. The calculations also illustrate the very different ways in which the transmutation from Fermi-Dirac to Bose-Einstein statistics is realized

  13. Two-dimensional critical phenomena

    International Nuclear Information System (INIS)

    Saleur, H.

    1987-09-01

    Two dimensional critical systems are studied using transformation to free fields and conformal invariance methods. The relations between the two approaches are also studied. The analytical results obtained generally depend on universality hypotheses or on renormalization group trajectories which are not established rigorously, so numerical verifications, mainly using the transfer matrix approach, are presented. The exact determination of critical exponents; the partition functions of critical models on toruses; and results as the critical point is approached are discussed [fr

  14. Finding two-dimensional peaks

    International Nuclear Information System (INIS)

    Silagadze, Z.K.

    2007-01-01

    Two-dimensional generalization of the original peak finding algorithm suggested earlier is given. The ideology of the algorithm emerged from the well-known quantum mechanical tunneling property which enables small bodies to penetrate through narrow potential barriers. We merge this 'quantum' ideology with the philosophy of Particle Swarm Optimization to get the global optimization algorithm which can be called Quantum Swarm Optimization. The functionality of the newborn algorithm is tested on some benchmark optimization problems

  15. Growth Kinematics of Opening-Mode Fractures

    Science.gov (United States)

    Eichhubl, P.; Alzayer, Y.; Laubach, S.; Fall, A.

    2014-12-01

    Fracture aperture is a primary control on flow in fractured reservoirs of low matrix permeability including unconventional oil and gas reservoirs and most geothermal systems. Guided by principles of linear elastic fracture mechanics, fracture aperture is generally assumed to be a linear function of fracture length and elastic material properties. Natural opening-mode fractures with significant preserved aperture are observed in core and outcrop indicative of fracture opening strain accommodated by permanent solution-precipitation creep. Fracture opening may thus be decoupled from length growth if the material effectively weakens after initial elastic fracture growth by either non-elastic deformation processes or changes in elastic properties. To investigate the kinematics of fracture length and aperture growth, we reconstructed the opening history of three opening-mode fractures that are bridged by crack-seal quartz cement in Travis Peak Sandstone of the SFOT-1 well, East Texas. Similar crack-seal cement bridges had been interpreted to form by repeated incremental fracture opening and subsequent precipitation of quartz cement. We imaged crack-seal cement textures for bridges sampled at varying distance from the tips using scanning electron microscope cathodoluminescence, and determined the number and thickness of crack-seal cement increments as a function of position along the fracture length and height. Observed trends in increment number and thickness are consistent with an initial stage of fast fracture propagation relative to aperture growth, followed by a stage of slow propagation and pronounced aperture growth. Consistent with fluid inclusion observations indicative of fracture opening and propagation occurring over 30-40 m.y., we interpret the second phase of pronounced aperture growth to result from fracture opening strain accommodated by solution-precipitation creep and concurrent slow, possibly subcritical, fracture propagation. Similar deformation

  16. Multistable selection equations of pattern formation type in the case of inhomogeneous growth rates: With applications to two-dimensional assignment problems

    International Nuclear Information System (INIS)

    Frank, T.D.

    2011-01-01

    We study the stability of solutions of a particular type of multistable selection equations proposed by Starke, Schanz and Haken in the case of an inhomogeneous spectrum of growth parameters. We determine how the stability of feasible solutions depends on the inhomogeneity of the spectrum. We show that the strength of the competitive interaction between feasible solutions can act as a control parameter that induces bifurcations reducing the degree of multistability. - Research highlights: → Feasible solutions can be stable in the case of inhomogeneous growth parameters. → Changing coupling strength can induce bifurcations of feasible solutions. → Optimal solutions are obtained when selected winnings are relatively large.

  17. Mechanical exfoliation of two-dimensional materials

    Science.gov (United States)

    Gao, Enlai; Lin, Shao-Zhen; Qin, Zhao; Buehler, Markus J.; Feng, Xi-Qiao; Xu, Zhiping

    2018-06-01

    Two-dimensional materials such as graphene and transition metal dichalcogenides have been identified and drawn much attention over the last few years for their unique structural and electronic properties. However, their rise begins only after these materials are successfully isolated from their layered assemblies or adhesive substrates into individual monolayers. Mechanical exfoliation and transfer are the most successful techniques to obtain high-quality single- or few-layer nanocrystals from their native multi-layer structures or their substrate for growth, which involves interfacial peeling and intralayer tearing processes that are controlled by material properties, geometry and the kinetics of exfoliation. This procedure is rationalized in this work through theoretical analysis and atomistic simulations. We propose a criterion to assess the feasibility for the exfoliation of two-dimensional sheets from an adhesive substrate without fracturing itself, and explore the effects of material and interface properties, as well as the geometrical, kinetic factors on the peeling behaviors and the torn morphology. This multi-scale approach elucidates the microscopic mechanism of the mechanical processes, offering predictive models and tools for the design of experimental procedures to obtain single- or few-layer two-dimensional materials and structures.

  18. Two dimensional infinite conformal symmetry

    International Nuclear Information System (INIS)

    Mohanta, N.N.; Tripathy, K.C.

    1993-01-01

    The invariant discontinuous (discrete) conformal transformation groups, namely the Kleinian and Fuchsian groups Gamma (with an arbitrary signature) of H (the Poincare upper half-plane l) and the unit disc Delta are explicitly constructed from the fundamental domain D. The Riemann surface with signatures of Gamma and conformally invariant automorphic forms (functions) with Peterson scalar product are discussed. The functor, where the category of complex Hilbert spaces spanned by the space of cusp forms constitutes the two dimensional conformal field theory. (Author) 7 refs

  19. Two-dimensional liquid chromatography

    DEFF Research Database (Denmark)

    Græsbøll, Rune

    -dimensional separation space. Optimization of gradients in online RP×RP is more difficult than in normal HPLC as a result of the increased number of parameters and their influence on each other. Modeling the coverage of the compounds across the two-dimensional chromatogram as a result of a change in gradients could...... be used for optimization purposes, and reduce the time spend on optimization. In this thesis (chapter 6), and manuscript B, a measure of the coverage of the compounds in the twodimensional separation space is defined. It is then shown that this measure can be modeled for changes in the gradient in both...

  20. Two-dimensional capillary origami

    Energy Technology Data Exchange (ETDEWEB)

    Brubaker, N.D., E-mail: nbrubaker@math.arizona.edu; Lega, J., E-mail: lega@math.arizona.edu

    2016-01-08

    We describe a global approach to the problem of capillary origami that captures all unfolded equilibrium configurations in the two-dimensional setting where the drop is not required to fully wet the flexible plate. We provide bifurcation diagrams showing the level of encapsulation of each equilibrium configuration as a function of the volume of liquid that it contains, as well as plots representing the energy of each equilibrium branch. These diagrams indicate at what volume level the liquid drop ceases to be attached to the endpoints of the plate, which depends on the value of the contact angle. As in the case of pinned contact points, three different parameter regimes are identified, one of which predicts instantaneous encapsulation for small initial volumes of liquid. - Highlights: • Full solution set of the two-dimensional capillary origami problem. • Fluid does not necessarily wet the entire plate. • Global energy approach provides exact differential equations satisfied by minimizers. • Bifurcation diagrams highlight three different regimes. • Conditions for spontaneous encapsulation are identified.

  1. Two-dimensional capillary origami

    International Nuclear Information System (INIS)

    Brubaker, N.D.; Lega, J.

    2016-01-01

    We describe a global approach to the problem of capillary origami that captures all unfolded equilibrium configurations in the two-dimensional setting where the drop is not required to fully wet the flexible plate. We provide bifurcation diagrams showing the level of encapsulation of each equilibrium configuration as a function of the volume of liquid that it contains, as well as plots representing the energy of each equilibrium branch. These diagrams indicate at what volume level the liquid drop ceases to be attached to the endpoints of the plate, which depends on the value of the contact angle. As in the case of pinned contact points, three different parameter regimes are identified, one of which predicts instantaneous encapsulation for small initial volumes of liquid. - Highlights: • Full solution set of the two-dimensional capillary origami problem. • Fluid does not necessarily wet the entire plate. • Global energy approach provides exact differential equations satisfied by minimizers. • Bifurcation diagrams highlight three different regimes. • Conditions for spontaneous encapsulation are identified.

  2. Two dimensional solid state NMR

    International Nuclear Information System (INIS)

    Kentgens, A.P.M.

    1987-01-01

    This thesis illustrates, by discussing some existing and newly developed 2D solid state experiments, that two-dimensional NMR of solids is a useful and important extension of NMR techniques. Chapter 1 gives an overview of spin interactions and averaging techniques important in solid state NMR. As 2D NMR is already an established technique in solutions, only the basics of two dimensional NMR are presented in chapter 2, with an emphasis on the aspects important for solid spectra. The following chapters discuss the theoretical background and applications of specific 2D solid state experiments. An application of 2D-J resolved NMR, analogous to J-resolved spectroscopy in solutions, to natural rubber is given in chapter 3. In chapter 4 the anisotropic chemical shift is mapped out against the heteronuclear dipolar interaction to obtain information about the orientation of the shielding tensor in poly-(oxymethylene). Chapter 5 concentrates on the study of super-slow molecular motions in polymers using a variant of the 2D exchange experiment developed by us. Finally chapter 6 discusses a new experiment, 2D nutation NMR, which makes it possible to study the quadrupole interaction of half-integer spins. 230 refs.; 48 figs.; 8 tabs

  3. Two-dimensional turbulent convection

    Science.gov (United States)

    Mazzino, Andrea

    2017-11-01

    We present an overview of the most relevant, and sometimes contrasting, theoretical approaches to Rayleigh-Taylor and mean-gradient-forced Rayleigh-Bénard two-dimensional turbulence together with numerical and experimental evidences for their support. The main aim of this overview is to emphasize that, despite the different character of these two systems, especially in relation to their steadiness/unsteadiness, turbulent fluctuations are well described by the same scaling relationships originated from the Bolgiano balance. The latter states that inertial terms and buoyancy terms balance at small scales giving rise to an inverse kinetic energy cascade. The main difference with respect to the inverse energy cascade in hydrodynamic turbulence [R. H. Kraichnan, "Inertial ranges in two-dimensional turbulence," Phys. Fluids 10, 1417 (1967)] is that the rate of cascade of kinetic energy here is not constant along the inertial range of scales. Thanks to the absence of physical boundaries, the two systems here investigated turned out to be a natural physical realization of the Kraichnan scaling regime hitherto associated with the elusive "ultimate state of thermal convection" [R. H. Kraichnan, "Turbulent thermal convection at arbitrary Prandtl number," Phys. Fluids 5, 1374-1389 (1962)].

  4. Two-dimensional Semiconductor-Superconductor Hybrids

    DEFF Research Database (Denmark)

    Suominen, Henri Juhani

    This thesis investigates hybrid two-dimensional semiconductor-superconductor (Sm-S) devices and presents a new material platform exhibiting intimate Sm-S coupling straight out of the box. Starting with the conventional approach, we investigate coupling superconductors to buried quantum well....... To overcome these issues we integrate the superconductor directly into the semiconducting material growth stack, depositing it in-situ in a molecular beam epitaxy system under high vacuum. We present a number of experiments on these hybrid heterostructures, demonstrating near unity interface transparency...

  5. Study on two-dimensional induced signal readout of MRPC

    International Nuclear Information System (INIS)

    Wu Yucheng; Yue Qian; Li Yuanjing; Ye Jin; Cheng Jianping; Wang Yi; Li Jin

    2012-01-01

    A kind of two-dimensional readout electrode structure for the induced signal readout of MRPC has been studied in both simulation and experiments. Several MRPC prototypes are produced and a series of test experiments have been done to compare with the result of simulation, in order to verify the simulation model. The experiment results are in good agreement with those of simulation. This method will be used to design the two-dimensional signal readout mode of MRPC in the future work.

  6. Two-dimensional quantum repeaters

    Science.gov (United States)

    Wallnöfer, J.; Zwerger, M.; Muschik, C.; Sangouard, N.; Dür, W.

    2016-11-01

    The endeavor to develop quantum networks gave rise to a rapidly developing field with far-reaching applications such as secure communication and the realization of distributed computing tasks. This ultimately calls for the creation of flexible multiuser structures that allow for quantum communication between arbitrary pairs of parties in the network and facilitate also multiuser applications. To address this challenge, we propose a two-dimensional quantum repeater architecture to establish long-distance entanglement shared between multiple communication partners in the presence of channel noise and imperfect local control operations. The scheme is based on the creation of self-similar multiqubit entanglement structures at growing scale, where variants of entanglement swapping and multiparty entanglement purification are combined to create high-fidelity entangled states. We show how such networks can be implemented using trapped ions in cavities.

  7. Two dimensional generalizations of the Newcomb equation

    International Nuclear Information System (INIS)

    Dewar, R.L.; Pletzer, A.

    1989-11-01

    The Bineau reduction to scalar form of the equation governing ideal, zero frequency linearized displacements from a hydromagnetic equilibrium possessing a continuous symmetry is performed in 'universal coordinates', applicable to both the toroidal and helical cases. The resulting generalized Newcomb equation (GNE) has in general a more complicated form than the corresponding one dimensional equation obtained by Newcomb in the case of circular cylindrical symmetry, but in this cylindrical case , the equation can be transformed to that of Newcomb. In the two dimensional case there is a transformation which leaves the form of the GNE invariant and simplifies the Frobenius expansion about a rational surface, especially in the limit of zero pressure gradient. The Frobenius expansions about a mode rational surface is developed and the connection with Hamiltonian transformation theory is shown. 17 refs

  8. Equilibrium: two-dimensional configurations

    International Nuclear Information System (INIS)

    Anon.

    1987-01-01

    In Chapter 6, the problem of toroidal force balance is addressed in the simplest, nontrivial two-dimensional geometry, that of an axisymmetric torus. A derivation is presented of the Grad-Shafranov equation, the basic equation describing axisymmetric toroidal equilibrium. The solutions to equations provide a complete description of ideal MHD equilibria: radial pressure balance, toroidal force balance, equilibrium Beta limits, rotational transform, shear, magnetic wall, etc. A wide number of configurations are accurately modeled by the Grad-Shafranov equation. Among them are all types of tokamaks, the spheromak, the reversed field pinch, and toroidal multipoles. An important aspect of the analysis is the use of asymptotic expansions, with an inverse aspect ratio serving as the expansion parameter. In addition, an equation similar to the Grad-Shafranov equation, but for helically symmetric equilibria, is presented. This equation represents the leading-order description low-Beta and high-Beta stellarators, heliacs, and the Elmo bumpy torus. The solutions all correspond to infinitely long straight helices. Bending such a configuration into a torus requires a full three-dimensional calculation and is discussed in Chapter 7

  9. Study of two-dimensional interchange turbulence

    International Nuclear Information System (INIS)

    Sugama, Hideo; Wakatani, Masahiro.

    1990-04-01

    An eddy viscosity model describing enstrophy transfer in two-dimensional turbulence is presented. This model is similar to that of Canuto et al. and provides an equation for the energy spectral function F(k) as a function of the energy input rate to the system per unit wavenumber, γ s (k). In the enstrophy-transfer inertial range, F(k)∝ k -3 is predicted by the model. The eddy viscosity model is applied to the interchange turbulence of a plasma in shearless magnetic field. Numerical simulation of the two-dimensional interchange turbulence demonstrates that the energy spectrum in the high wavenumber region is well described by this model. The turbulent transport driven by the interchange turbulence is expressed in terms of the Nusselt number Nu, the Rayleigh number Ra and Prantl number Pr in the same manner as that of thermal convection problem. When we use the linear growth rate for γ s (k), our theoretical model predicts that Nu ∝ (Ra·Pr) 1/2 for a constant background pressure gradient and Nu ∝ (Ra·Pr) 1/3 for a self-consistent background pressure profile with the stress-free slip boundary conditions. The latter agrees with our numerical result showing Nu ∝ Ra 1/3 . (author)

  10. Influence of index contrast in two dimensional photonic crystal lasers

    DEFF Research Database (Denmark)

    Jørgensen, Mette Marie; Petersen, Sidsel Rübner; Christiansen, Mads Brøkner

    2010-01-01

    The influence of index contrast variations for obtaining single-mode operation and low threshold in dye doped polymer two dimensional photonic crystal (PhC) lasers is investigated. We consider lasers made from Pyrromethene 597 doped Ormocore imprinted with a rectangular lattice PhC having a cavity...

  11. Influence of Different Interlayers on Growth Mode and Properties of InN by MOVPE

    International Nuclear Information System (INIS)

    Ri-Qing, Zhang; Xiang-Lin, Liu; Ting-Ting, Kang; Wei-Guo, Hu; Shao-Yan, Yang; Chun-Mei, Jiao; Qing-Sheng, Zhu

    2008-01-01

    We grow InN epilayers on different interlayers by metal organic vapour phase epitaxy (MOVPE) method, and investigate the effect of interlayer on the properties and growth mode of InN films. Three InN samples were deposited on nitrided sapphire, low-temperature InN (LT-InN) and high-temperature GaN (HT-GaN), respectively. The InN layer grown directly on nitrided sapphire owns the narrowest x-ray diffraction rocking curve (XRC) width of 300 arcsec among the three samples, and demonstrates a two-dimensional (2D) step-flow-like lateral growth mode, which is much different from the three-dimensional (3D) pillar-like growth mode of LT-InN and HT-GaN buffered samples. It seems that mismatch tensile strain is helpful for the lateral epitaxy of InN film, whereas compressive strain promotes the vertical growth of InN films

  12. Two-dimensional analysis of trapped-ion eigenmodes

    International Nuclear Information System (INIS)

    Marchand, R.; Tang, W.M.; Rewoldt, G.

    1979-11-01

    A fully two-dimensional eigenmode analysis of the trapped-ion instability in axisymmetric toroidal geometry is presented. The calculations also takes into account the basic dynamics associated with other low frequency modes such as the trapped-electron instability and the ion-temperature-gradient instability. The poloidal structure of the mode is taken into account by Fourier expanding the perturbed electrostatic potential, PHI, in theta

  13. Topology optimization of two-dimensional waveguides

    DEFF Research Database (Denmark)

    Jensen, Jakob Søndergaard; Sigmund, Ole

    2003-01-01

    In this work we use the method of topology optimization to design two-dimensional waveguides with low transmission loss.......In this work we use the method of topology optimization to design two-dimensional waveguides with low transmission loss....

  14. Two-dimensional vibrational-electronic spectroscopy

    Science.gov (United States)

    Courtney, Trevor L.; Fox, Zachary W.; Slenkamp, Karla M.; Khalil, Munira

    2015-10-01

    Two-dimensional vibrational-electronic (2D VE) spectroscopy is a femtosecond Fourier transform (FT) third-order nonlinear technique that creates a link between existing 2D FT spectroscopies in the vibrational and electronic regions of the spectrum. 2D VE spectroscopy enables a direct measurement of infrared (IR) and electronic dipole moment cross terms by utilizing mid-IR pump and optical probe fields that are resonant with vibrational and electronic transitions, respectively, in a sample of interest. We detail this newly developed 2D VE spectroscopy experiment and outline the information contained in a 2D VE spectrum. We then use this technique and its single-pump counterpart (1D VE) to probe the vibrational-electronic couplings between high frequency cyanide stretching vibrations (νCN) and either a ligand-to-metal charge transfer transition ([FeIII(CN)6]3- dissolved in formamide) or a metal-to-metal charge transfer (MMCT) transition ([(CN)5FeIICNRuIII(NH3)5]- dissolved in formamide). The 2D VE spectra of both molecules reveal peaks resulting from coupled high- and low-frequency vibrational modes to the charge transfer transition. The time-evolving amplitudes and positions of the peaks in the 2D VE spectra report on coherent and incoherent vibrational energy transfer dynamics among the coupled vibrational modes and the charge transfer transition. The selectivity of 2D VE spectroscopy to vibronic processes is evidenced from the selective coupling of specific νCN modes to the MMCT transition in the mixed valence complex. The lineshapes in 2D VE spectra report on the correlation of the frequency fluctuations between the coupled vibrational and electronic frequencies in the mixed valence complex which has a time scale of 1 ps. The details and results of this study confirm the versatility of 2D VE spectroscopy and its applicability to probe how vibrations modulate charge and energy transfer in a wide range of complex molecular, material, and biological systems.

  15. Two-dimensional vibrational-electronic spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Courtney, Trevor L.; Fox, Zachary W.; Slenkamp, Karla M.; Khalil, Munira, E-mail: mkhalil@uw.edu [Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195 (United States)

    2015-10-21

    Two-dimensional vibrational-electronic (2D VE) spectroscopy is a femtosecond Fourier transform (FT) third-order nonlinear technique that creates a link between existing 2D FT spectroscopies in the vibrational and electronic regions of the spectrum. 2D VE spectroscopy enables a direct measurement of infrared (IR) and electronic dipole moment cross terms by utilizing mid-IR pump and optical probe fields that are resonant with vibrational and electronic transitions, respectively, in a sample of interest. We detail this newly developed 2D VE spectroscopy experiment and outline the information contained in a 2D VE spectrum. We then use this technique and its single-pump counterpart (1D VE) to probe the vibrational-electronic couplings between high frequency cyanide stretching vibrations (ν{sub CN}) and either a ligand-to-metal charge transfer transition ([Fe{sup III}(CN){sub 6}]{sup 3−} dissolved in formamide) or a metal-to-metal charge transfer (MMCT) transition ([(CN){sub 5}Fe{sup II}CNRu{sup III}(NH{sub 3}){sub 5}]{sup −} dissolved in formamide). The 2D VE spectra of both molecules reveal peaks resulting from coupled high- and low-frequency vibrational modes to the charge transfer transition. The time-evolving amplitudes and positions of the peaks in the 2D VE spectra report on coherent and incoherent vibrational energy transfer dynamics among the coupled vibrational modes and the charge transfer transition. The selectivity of 2D VE spectroscopy to vibronic processes is evidenced from the selective coupling of specific ν{sub CN} modes to the MMCT transition in the mixed valence complex. The lineshapes in 2D VE spectra report on the correlation of the frequency fluctuations between the coupled vibrational and electronic frequencies in the mixed valence complex which has a time scale of 1 ps. The details and results of this study confirm the versatility of 2D VE spectroscopy and its applicability to probe how vibrations modulate charge and energy transfer in a

  16. Piezoelectricity in Two-Dimensional Materials

    KAUST Repository

    Wu, Tao; Zhang, Hua

    2015-01-01

    Powering up 2D materials: Recent experimental studies confirmed the existence of piezoelectricity - the conversion of mechanical stress into electricity - in two-dimensional single-layer MoS2 nanosheets. The results represent a milestone towards

  17. Construction of two-dimensional quantum chromodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Klimek, S.; Kondracki, W.

    1987-12-01

    We present a sketch of the construction of the functional measure for the SU(2) quantum chromodynamics with one generation of fermions in two-dimensional space-time. The method is based on a detailed analysis of Wilson loops.

  18. Development of Two-Dimensional NMR

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 20; Issue 11. Development of Two-Dimensional NMR: Strucure Determination of Biomolecules in Solution. Anil Kumar. General Article Volume 20 Issue 11 November 2015 pp 995-1002 ...

  19. Logarithmic Superdiffusion in Two Dimensional Driven Lattice Gases

    Science.gov (United States)

    Krug, J.; Neiss, R. A.; Schadschneider, A.; Schmidt, J.

    2018-03-01

    The spreading of density fluctuations in two-dimensional driven diffusive systems is marginally anomalous. Mode coupling theory predicts that the diffusivity in the direction of the drive diverges with time as (ln t)^{2/3} with a prefactor depending on the macroscopic current-density relation and the diffusion tensor of the fluctuating hydrodynamic field equation. Here we present the first numerical verification of this behavior for a particular version of the two-dimensional asymmetric exclusion process. Particles jump strictly asymmetrically along one of the lattice directions and symmetrically along the other, and an anisotropy parameter p governs the ratio between the two rates. Using a novel massively parallel coupling algorithm that strongly reduces the fluctuations in the numerical estimate of the two-point correlation function, we are able to accurately determine the exponent of the logarithmic correction. In addition, the variation of the prefactor with p provides a stringent test of mode coupling theory.

  20. Nonlinear growth of strongly unstable tearing modes

    International Nuclear Information System (INIS)

    Waelbroeck, F.L.

    1993-11-01

    Rutherford's theory of the tearing instability is extended to cases where current nonlinearities are important, such as long wavelength modes in current slabs and the m = 1 instability in tokamaks with moderately large aspect-ratios. Of particular interest is the possibility that the associated magnetic islands, as a result of secondary instabilities, have a singular response to the Ohmic diffusion of the current. A family of islands is used to test this possibility; it is found that the response remains bounded

  1. Phase transitions in two-dimensional systems

    International Nuclear Information System (INIS)

    Salinas, S.R.A.

    1983-01-01

    Some experiences are related using synchrotron radiation beams, to characterize solid-liquid (fusion) and commensurate solid-uncommensurate solid transitions in two-dimensional systems. Some ideas involved in the modern theories of two-dimensional fusion are shortly exposed. The systems treated consist of noble gases (Kr,Ar,Xe) adsorbed in the basal plane of graphite and thin films formed by some liquid crystal shells. (L.C.) [pt

  2. Mode I and Mode II Interlaminar Crack Growth Resistances of Ceramic Matrix Composites at Ambient Temperature

    National Research Council Canada - National Science Library

    Choi, Sung R; Kowalik, Robert W; Alexander, Donald J

    2007-01-01

    ...) including three gas-turbine grade melt-infiltrated SiC/SiC composites. Modes I and II crack growth resistances, GI and GII, were evaluated at ambient temperature using double cantilever beam and end notched flexure methods, respectively...

  3. Two-dimensional silica opens new perspectives

    Science.gov (United States)

    Büchner, Christin; Heyde, Markus

    2017-12-01

    In recent years, silica films have emerged as a novel class of two-dimensional (2D) materials. Several groups succeeded in epitaxial growth of ultrathin SiO2 layers using different growth methods and various substrates. The structures consist of tetrahedral [SiO4] building blocks in two mirror symmetrical planes, connected via oxygen bridges. This arrangement is called a silica bilayer as it is the thinnest 2D arrangement with the stoichiometry SiO2 known today. With all bonds saturated within the nano-sheet, the interaction with the substrate is based on van der Waals forces. Complex ring networks are observed, including hexagonal honeycomb lattices, point defects and domain boundaries, as well as amorphous domains. The network structures are highly tuneable through variation of the substrate, deposition parameters, cooling procedure, introducing dopants or intercalating small species. The amorphous networks and structural defects were resolved with atomic resolution microscopy and modeled with density functional theory and molecular dynamics. Such data contribute to our understanding of the formation and characteristic motifs of glassy systems. Growth studies and doping with other chemical elements reveal ways to tune ring sizes and defects as well as chemical reactivities. The pristine films have been utilized as molecular sieves and for confining molecules in nanocatalysis. Post growth hydroxylation can be used to tweak the reactivity as well. The electronic properties of silica bilayers are favourable for using silica as insulators in 2D material stacks. Due to the fully saturated atomic structure, the bilayer interacts weakly with the substrate and can be described as quasi-freestanding. Recently, a mm-scale film transfer under structure retention has been demonstrated. The chemical and mechanical stability of silica bilayers is very promising for technological applications in 2D heterostacks. Due to the impact of this bilayer system for glass science

  4. Two-dimensional nuclear magnetic resonance spectroscopy

    International Nuclear Information System (INIS)

    Bax, A.; Lerner, L.

    1986-01-01

    Great spectral simplification can be obtained by spreading the conventional one-dimensional nuclear magnetic resonance (NMR) spectrum in two independent frequency dimensions. This so-called two-dimensional NMR spectroscopy removes spectral overlap, facilitates spectral assignment, and provides a wealth of additional information. For example, conformational information related to interproton distances is available from resonance intensities in certain types of two-dimensional experiments. Another method generates 1 H NMR spectra of a preselected fragment of the molecule, suppressing resonances from other regions and greatly simplifying spectral appearance. Two-dimensional NMR spectroscopy can also be applied to the study of 13 C and 15 N, not only providing valuable connectivity information but also improving sensitivity of 13 C and 15 N detection by up to two orders of magnitude. 45 references, 10 figures

  5. Two-dimensional x-ray diffraction

    CERN Document Server

    He, Bob B

    2009-01-01

    Written by one of the pioneers of 2D X-Ray Diffraction, this useful guide covers the fundamentals, experimental methods and applications of two-dimensional x-ray diffraction, including geometry convention, x-ray source and optics, two-dimensional detectors, diffraction data interpretation, and configurations for various applications, such as phase identification, texture, stress, microstructure analysis, crystallinity, thin film analysis and combinatorial screening. Experimental examples in materials research, pharmaceuticals, and forensics are also given. This presents a key resource to resea

  6. Equivalence of two-dimensional gravities

    International Nuclear Information System (INIS)

    Mohammedi, N.

    1990-01-01

    The authors find the relationship between the Jackiw-Teitelboim model of two-dimensional gravity and the SL(2,R) induced gravity. These are shown to be related to a two-dimensional gauge theory obtained by dimensionally reducing the Chern-Simons action of the 2 + 1 dimensional gravity. The authors present an explicit solution to the equations of motion of the auxiliary field of the Jackiw-Teitelboim model in the light-cone gauge. A renormalization of the cosmological constant is also given

  7. Network patterns in exponentially growing two-dimensional biofilms

    Science.gov (United States)

    Zachreson, Cameron; Yap, Xinhui; Gloag, Erin S.; Shimoni, Raz; Whitchurch, Cynthia B.; Toth, Milos

    2017-10-01

    Anisotropic collective patterns occur frequently in the morphogenesis of two-dimensional biofilms. These patterns are often attributed to growth regulation mechanisms and differentiation based on gradients of diffusing nutrients and signaling molecules. Here, we employ a model of bacterial growth dynamics to show that even in the absence of growth regulation or differentiation, confinement by an enclosing medium such as agar can itself lead to stable pattern formation over time scales that are employed in experiments. The underlying mechanism relies on path formation through physical deformation of the enclosing environment.

  8. Full melting of a two-dimensional complex plasma crystal triggered by localized pulsed laser heating

    Science.gov (United States)

    Couëdel, L.; Nosenko, V.; Rubin-Zuzic, M.; Zhdanov, S.; Elskens, Y.; Hall, T.; Ivlev, A. V.

    2018-04-01

    The full melting of a two-dimensional plasma crystal was induced in a principally stable monolayer by localized laser stimulation. Two distinct behaviors of the crystal after laser stimulation were observed depending on the amount of injected energy: (i) below a well-defined threshold, the laser melted area recrystallized; (ii) above the threshold, it expanded outwards in a similar fashion to mode-coupling instability-induced melting, rapidly destroying the crystalline order of the whole complex plasma monolayer. The reported experimental observations are due to the fluid mode-coupling instability, which can pump energy into the particle monolayer at a rate surpassing the heat transport and damping rates in the energetic localized melted spot, resulting in its further growth. This behavior exhibits remarkable similarities with impulsive spot heating in ordinary reactive matter.

  9. Two-dimensional simulation of the hydromagnetic Rayleigh-Taylor instability in an imploding foil plasma

    International Nuclear Information System (INIS)

    Roderick, N.F.; Hussey, T.W.; Faehl, R.J.; Boyd, R.W.

    1978-01-01

    Two-dimensional (r-z) magnetohydrodynamic simulations of the electromagnetic implosion of metallic foil plasmas show, for certain initial configurations, a tendency to develop large-amplitude perturbations characteristic of the hydromagnetic Rayleigh-Taylor instability. These perturbations develop at the plasma magnetic field interface for plasma configurations where the density gradient scale length, the characteristic dimension for the instability, is short. The effects on the plasma dynamics of the implosion will be discussed for several initial foil configurations. In general, the growth rates and linear mode structure are found to be influenced by the plasma shell thickness and density gradient scale length, in agreement with theory. The most destructive modes are found to be those with wavelengths of the order of the plasma shell thickness

  10. Analytical simulation of two dimensional advection dispersion ...

    African Journals Online (AJOL)

    The study was designed to investigate the analytical simulation of two dimensional advection dispersion equation of contaminant transport. The steady state flow condition of the contaminant transport where inorganic contaminants in aqueous waste solutions are disposed of at the land surface where it would migrate ...

  11. Analytical Simulation of Two Dimensional Advection Dispersion ...

    African Journals Online (AJOL)

    ADOWIE PERE

    ABSTRACT: The study was designed to investigate the analytical simulation of two dimensional advection dispersion equation of contaminant transport. The steady state flow condition of the contaminant transport where inorganic contaminants in aqueous waste solutions are disposed of at the land surface where it would ...

  12. Sums of two-dimensional spectral triples

    DEFF Research Database (Denmark)

    Christensen, Erik; Ivan, Cristina

    2007-01-01

    construct a sum of two dimensional modules which reflects some aspects of the topological dimensions of the compact metric space, but this will only give the metric back approximately. At the end we make an explicit computation of the last module for the unit interval in. The metric is recovered exactly...

  13. Stability of two-dimensional vorticity filaments

    International Nuclear Information System (INIS)

    Elhmaidi, D.; Provenzale, A.; Lili, T.; Babiano, A.

    2004-01-01

    We discuss the results of a numerical study on the stability of two-dimensional vorticity filaments around a circular vortex. We illustrate how the stability of the filaments depends on the balance between the strain associated with the far field of the vortex and the local vorticity of the filament, and we discuss an empirical criterion for filament stability

  14. Two-Dimensional Motions of Rockets

    Science.gov (United States)

    Kang, Yoonhwan; Bae, Saebyok

    2007-01-01

    We analyse the two-dimensional motions of the rockets for various types of rocket thrusts, the air friction and the gravitation by using a suitable representation of the rocket equation and the numerical calculation. The slope shapes of the rocket trajectories are discussed for the three types of rocket engines. Unlike the projectile motions, the…

  15. Two-dimensional microstrip detector for neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Oed, A [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)

    1997-04-01

    Because of their robust design, gas microstrip detectors, which were developed at ILL, can be assembled relatively quickly, provided the prefabricated components are available. At the beginning of 1996, orders were received for the construction of three two-dimensional neutron detectors. These detectors have been completed. The detectors are outlined below. (author). 2 refs.

  16. Conformal invariance and two-dimensional physics

    International Nuclear Information System (INIS)

    Zuber, J.B.

    1993-01-01

    Actually, physicists and mathematicians are very interested in conformal invariance: geometric transformations which keep angles. This symmetry is very important for two-dimensional systems as phase transitions, string theory or node mathematics. In this article, the author presents the conformal invariance and explains its usefulness

  17. Matching Two-dimensional Gel Electrophoresis' Spots

    DEFF Research Database (Denmark)

    Dos Anjos, António; AL-Tam, Faroq; Shahbazkia, Hamid Reza

    2012-01-01

    This paper describes an approach for matching Two-Dimensional Electrophoresis (2-DE) gels' spots, involving the use of image registration. The number of false positive matches produced by the proposed approach is small, when compared to academic and commercial state-of-the-art approaches. This ar...

  18. Two-dimensional membranes in motion

    NARCIS (Netherlands)

    Davidovikj, D.

    2018-01-01

    This thesis revolves around nanomechanical membranes made of suspended two - dimensional materials. Chapters 1-3 give an introduction to the field of 2D-based nanomechanical devices together with an overview of the underlying physics and the measurementtools used in subsequent chapters. The research

  19. Extended Polymorphism of Two-Dimensional Material

    NARCIS (Netherlands)

    Yoshida, Masaro; Ye, Jianting; Zhang, Yijin; Imai, Yasuhiko; Kimura, Shigeru; Fujiwara, Akihiko; Nishizaki, Terukazu; Kobayashi, Norio; Nakano, Masaki; Iwasa, Yoshihiro

    When controlling electronic properties of bulk materials, we usually assume that the basic crystal structure is fixed. However, in two-dimensional (2D) materials, atomic structure or to functionalize their properties. Various polymorphs can exist in transition metal dichalcogenides (TMDCs) from

  20. Piezoelectricity in Two-Dimensional Materials

    KAUST Repository

    Wu, Tao

    2015-02-25

    Powering up 2D materials: Recent experimental studies confirmed the existence of piezoelectricity - the conversion of mechanical stress into electricity - in two-dimensional single-layer MoS2 nanosheets. The results represent a milestone towards embedding low-dimensional materials into future disruptive technologies. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA.

  1. A new algebraic growth of nonlinear tearing mode

    International Nuclear Information System (INIS)

    Li, D.

    1995-01-01

    It is found that the quasilinear modification of magnetic field produces a nonlinear Lorentz force opposing the linear driving force and slowing down the vortex flow. A new algebraic growth appears due to this damping mechanism to oppose the linear growth of the tearing mode. This effect was eliminated in Rutherford's model [Phys. Fluids 16, 1903 (1973)] under the flux average operation and the assumption ∂/∂t much-lt η/δ 2 (here η is the resistivity, δ is the resistive layer width). A unified analytical model is developed by using standard perturbation theory for the linear and nonlinear growth of the tearing mode. The inertia effect and quasilinear effects of both the current density and the magnetic field have been included. A nonlinear evolution equation is analytically derived for the tearing mode to describe the linear growth, Rutherford's behavior, and the new behavior. The classical linear result is exactly recovered as the quasilinear effects are negligible. It is shown that a more slowly algebraic growth like Ψ 1 ∝t can become dominant in the nonlinear phase instead of Rutherford behavior like Ψ 1 ∝t 2 , provided the tearing mode in the linear phase is strongly unstable. Here Ψ 1 is the magnetic flux perturbation. copyright 1995 American Institute of Physics

  2. Two-Dimensional Raman Correlation Spectroscopy Study of Poly[(R)-3-hydroxybutyrate- co-(R)-3-hydroxyhexanoate] Copolymers.

    Science.gov (United States)

    Noda, Isao; Roy, Anjan; Carriere, James; Sobieski, Brian J; Chase, D Bruce; Rabolt, John F

    2017-07-01

    Two-dimensional correlation analysis was applied to the time-dependent evolution of Raman spectra during the isothermal crystallization of bioplastic, poly[(R)-3-hydroxybutyrate- co-(R)-3-hydroxyhexanoate] or PHBHx copolymer. Simultaneous Raman measurement of both carbonyl stretching and low-frequency crystalline lattice mode regions made it possible to carry out the highly informative hetero-mode correlation analysis. The crystallization process of PHBHx involves: (1) the early nucleation stage; (2) the primary growth of well-ordered crystals of PHBHx; and (3) the secondary crystal growth phase. The latter stage probably occurs in the inter-lamellar region, with an accompanying reduction of the amorphous component, which occurs most dominantly during the primary crystal growth. The development of a fully formed lamellar structure comprising the 2 1 helices occurs after the primary growth of crystals. In the later stage, secondary inter lamellar space crystallization occurs after the full formation of packed helices comprising the lamellae.

  3. Tracer particles in two-dimensional elastic networks diffuse logarithmically slow

    International Nuclear Information System (INIS)

    Lizana, Ludvig; Ambjörnsson, Tobias; Lomholt, Michael A

    2017-01-01

    Several experiments on tagged molecules or particles in living systems suggest that they move anomalously slow—their mean squared displacement (MSD) increase slower than linearly with time. Leading models aimed at understanding these experiments predict that the MSD grows as a power law with a growth exponent that is smaller than unity. However, in some experiments the growth is so slow (fitted exponent  ∼0.1–0.2) that they hint towards other mechanisms at play. In this paper, we theoretically demonstrate how in-plane collective modes excited by thermal fluctuations in a two dimensional membrane lead to logarithmic time dependence for the the tracer particle’s MSD. (paper)

  4. Relations among the crack growth modes resulting from tensor splitting

    Czech Academy of Sciences Publication Activity Database

    Kafka, Vratislav

    2015-01-01

    Roč. 60, č. 4 (2015), s. 319-335 ISSN 0001-7043 Institutional support: RVO:68378297 Keywords : fracture mechanics * combination of crack-growth modes * non-local effect * tensor splitting Subject RIV: JL - Materials Fatigue, Friction Mechanics http://journal.it.cas.cz/60(15)4-Contents/60(15)4a.pdf

  5. Friction stress effects on mode I crack growth predictions

    NARCIS (Netherlands)

    Chen, Q.; Deshpande, V.S.; Giessen, E. van der; Needleman, A.

    2003-01-01

    The effect of a lattice friction stress on the monotonic growth of a plane strain mode I crack under small-scale yielding conditions is analyzed using discrete dislocation plasticity. When the friction stress is increased from zero to half the dislocation nucleation stress, the crack tip stress

  6. Universal growth modes of high-elevation conifers

    Czech Academy of Sciences Publication Activity Database

    Datsenko, N. M.; Sonechkin, D. M.; Büntgen, Ulf; Yang, B.

    2016-01-01

    Roč. 38, JUN (2016), s. 38-50 ISSN 1125-7865 Institutional support: RVO:67179843 Keywords : tree-ring chronologies * summer temperature-variations * northeastern tibetan plateau * climate signal * fennoscandian summers * annual precipitation * density * variability * qinghai * Growth modes * Ring width and maximum latewood density * Eigenvector analysis Subject RIV: EF - Botanics Impact factor: 2.259, year: 2016

  7. Two-dimensional plasma photonic crystals in dielectric barrier discharge

    International Nuclear Information System (INIS)

    Fan Weili; Dong Lifang; Zhang Xinchun

    2010-01-01

    A series of two-dimensional plasma photonic crystals have been obtained by filaments' self-organization in atmospheric dielectric barrier discharge with two water electrodes, which undergo the transition from square to square superlattice and finally to the hexagon. The spatio-temporal behaviors of the plasma photonic crystals in nanosecond scale have been studied by optical method, which show that the plasma photonic crystal is actually an integration of different transient sublattices. The photonic band diagrams of the transverse electric (TE) mode and transverse magnetic mode for each sublattice of these plasma photonic crystals have been investigated theoretically. A wide complete band gap is formed in the hexagonal plasma photonic crystal with the TE mode. The changes of the band edge frequencies and the band gap widths in the evolvement of different structures are studied. A kind of tunable plasma photonic crystal which can be controlled both in space and time is suggested.

  8. Graphene and Two-Dimensional Materials for Optoelectronic Applications

    Directory of Open Access Journals (Sweden)

    Andreas Bablich

    2016-03-01

    Full Text Available This article reviews optoelectronic devices based on graphene and related two-dimensional (2D materials. The review includes basic considerations of process technology, including demonstrations of 2D heterostructure growth, and comments on the scalability and manufacturability of the growth methods. We then assess the potential of graphene-based transparent conducting electrodes. A major part of the review describes photodetectors based on lateral graphene p-n junctions and Schottky diodes. Finally, the progress in vertical devices made from 2D/3D heterojunctions, as well as all-2D heterostructures is discussed.

  9. Two-dimensional confinement of heavy fermions

    International Nuclear Information System (INIS)

    Shishido, Hiroaki; Shibauchi, Takasada; Matsuda, Yuji; Terashima, Takahito

    2010-01-01

    Metallic systems with the strongest electron correlations are realized in certain rare-earth and actinide compounds whose physics are dominated by f-electrons. These materials are known as heavy fermions, so called because the effective mass of the conduction electrons is enhanced via correlation effects up to as much as several hundreds times the free electron mass. To date the electronic structure of all heavy-fermion compounds is essentially three-dimensional. Here we report on the first realization of a two-dimensional heavy-fermion system, where the dimensionality is adjusted in a controllable fashion by fabricating heterostructures using molecular beam epitaxy. The two-dimensional heavy fermion system displays striking deviations from the standard Fermi liquid low-temperature electronic properties. (author)

  10. Two-dimensional sensitivity calculation code: SENSETWO

    International Nuclear Information System (INIS)

    Yamauchi, Michinori; Nakayama, Mitsuo; Minami, Kazuyoshi; Seki, Yasushi; Iida, Hiromasa.

    1979-05-01

    A SENSETWO code for the calculation of cross section sensitivities with a two-dimensional model has been developed, on the basis of first order perturbation theory. It uses forward neutron and/or gamma-ray fluxes and adjoint fluxes obtained by two-dimensional discrete ordinates code TWOTRAN-II. The data and informations of cross sections, geometry, nuclide density, response functions, etc. are transmitted to SENSETWO by the dump magnetic tape made in TWOTRAN calculations. The required input for SENSETWO calculations is thus very simple. The SENSETWO yields as printed output the cross section sensitivities for each coarse mesh zone and for each energy group, as well as the plotted output of sensitivity profiles specified by the input. A special feature of the code is that it also calculates the reaction rate with the response function used as the adjoint source in TWOTRAN adjoint calculation and the calculated forward flux from the TWOTRAN forward calculation. (author)

  11. Two-dimensional ranking of Wikipedia articles

    Science.gov (United States)

    Zhirov, A. O.; Zhirov, O. V.; Shepelyansky, D. L.

    2010-10-01

    The Library of Babel, described by Jorge Luis Borges, stores an enormous amount of information. The Library exists ab aeterno. Wikipedia, a free online encyclopaedia, becomes a modern analogue of such a Library. Information retrieval and ranking of Wikipedia articles become the challenge of modern society. While PageRank highlights very well known nodes with many ingoing links, CheiRank highlights very communicative nodes with many outgoing links. In this way the ranking becomes two-dimensional. Using CheiRank and PageRank we analyze the properties of two-dimensional ranking of all Wikipedia English articles and show that it gives their reliable classification with rich and nontrivial features. Detailed studies are done for countries, universities, personalities, physicists, chess players, Dow-Jones companies and other categories.

  12. Toward two-dimensional search engines

    International Nuclear Information System (INIS)

    Ermann, L; Shepelyansky, D L; Chepelianskii, A D

    2012-01-01

    We study the statistical properties of various directed networks using ranking of their nodes based on the dominant vectors of the Google matrix known as PageRank and CheiRank. On average PageRank orders nodes proportionally to a number of ingoing links, while CheiRank orders nodes proportionally to a number of outgoing links. In this way, the ranking of nodes becomes two dimensional which paves the way for the development of two-dimensional search engines of a new type. Statistical properties of information flow on the PageRank–CheiRank plane are analyzed for networks of British, French and Italian universities, Wikipedia, Linux Kernel, gene regulation and other networks. A special emphasis is done for British universities networks using the large database publicly available in the UK. Methods of spam links control are also analyzed. (paper)

  13. Acoustic phonon emission by two dimensional plasmons

    International Nuclear Information System (INIS)

    Mishonov, T.M.

    1990-06-01

    Acoustic wave emission of the two dimensional plasmons in a semiconductor or superconductor microstructure is investigated by using the phenomenological deformation potential within the jellium model. The plasmons are excited by the external electromagnetic (e.m.) field. The power conversion coefficient of e.m. energy into acoustic wave energy is also estimated. It is shown, the coherent transformation has a sharp resonance at the plasmon frequency of the two dimensional electron gas (2DEG). The incoherent transformation of the e.m. energy is generated by ohmic dissipation of 2DEG. The method proposed for coherent phonon beam generation can be very effective for high mobility 2DEG and for thin superconducting layers if the plasmon frequency ω is smaller than the superconducting gap 2Δ. (author). 21 refs, 1 fig

  14. Confined catalysis under two-dimensional materials

    OpenAIRE

    Li, Haobo; Xiao, Jianping; Fu, Qiang; Bao, Xinhe

    2017-01-01

    Small spaces in nanoreactors may have big implications in chemistry, because the chemical nature of molecules and reactions within the nanospaces can be changed significantly due to the nanoconfinement effect. Two-dimensional (2D) nanoreactor formed under 2D materials can provide a well-defined model system to explore the confined catalysis. We demonstrate a general tendency for weakened surface adsorption under the confinement of graphene overlayer, illustrating the feasible modulation of su...

  15. Two-Dimensional Extreme Learning Machine

    Directory of Open Access Journals (Sweden)

    Bo Jia

    2015-01-01

    (BP networks. However, like many other methods, ELM is originally proposed to handle vector pattern while nonvector patterns in real applications need to be explored, such as image data. We propose the two-dimensional extreme learning machine (2DELM based on the very natural idea to deal with matrix data directly. Unlike original ELM which handles vectors, 2DELM take the matrices as input features without vectorization. Empirical studies on several real image datasets show the efficiency and effectiveness of the algorithm.

  16. Superintegrability on the two dimensional hyperboloid

    International Nuclear Information System (INIS)

    Akopyan, E.; Pogosyan, G.S.; Kalnins, E.G.; Miller, W. Jr

    1998-01-01

    This work is devoted to the investigation of the quantum mechanical systems on the two dimensional hyperboloid which admit separation of variables in at least two coordinate systems. Here we consider two potentials introduced in a paper of C.P.Boyer, E.G.Kalnins and P.Winternitz, which haven't been studied yet. An example of an interbasis expansion is given and the structure of the quadratic algebra generated by the integrals of motion is carried out

  17. Repulsion of polarized particles from two-dimensional materials

    Science.gov (United States)

    Rodríguez-Fortuño, Francisco J.; Picardi, Michela F.; Zayats, Anatoly V.

    2018-05-01

    Repulsion of nanoparticles, molecules, and atoms from surfaces can have important applications in nanomechanical devices, microfluidics, optical manipulation, and atom optics. Here, through the solution of a classical scattering problem, we show that a dipole source oscillating at a frequency ω can experience a robust and strong repulsive force when its near-field interacts with a two-dimensional material. As an example, the case of graphene is considered, showing that a broad bandwidth of repulsion can be obtained at frequencies for which propagation of plasmon modes is allowed 0 chemical potential tunable electrically or by chemical doping.

  18. Wave dispersion relations in two-dimensional Yukawa systems

    International Nuclear Information System (INIS)

    Liu Yanhong; Liu Bin; Chen Yanping; Yang Size; Wang Long; Wang Xiaogang

    2003-01-01

    Collective modes in a two-dimensional Yukawa system are investigated by molecular dynamics simulation in a wide range of coupling parameter Γ and screening strength κ. The dispersion relations and sound speeds of the transverse and longitudinal waves obtained for hexagonal lattice are in agreement with the theoretical results. The negative dispersion of the longitudinal wave is demonstrated. Frequency gaps are found on the dispersion curves of the transverse wave due to scattering of the waves on lattice defects for proper values of Γ. The common frequency of transverse and longitudinal waves drops dramatically with the increasing screening strength κ

  19. Linear and nonlinear viscous flow in two-dimensional fluids

    International Nuclear Information System (INIS)

    Gravina, D.; Ciccotti, G.; Holian, B.L.

    1995-01-01

    We report on molecular dynamics simulations of shear viscosity η of a dense two-dimensional fluid as a function of the shear rate γ. We find an analytic dependence of η on γ, and do not find any evidence whatsoever of divergence in the Green-Kubo (GK) value that would be caused by the well-known long-time tail for the shear-stress autocorrelation function, as predicted by the mode-coupling theory. In accordance with the linear response theory, the GK value of η agrees remarkably well with nonequilibrium values at small shear rates. (c) 1995 The American Physical Society

  20. Characterization of Mode I and Mode II delamination growth and thresholds in AS4/PEEK composites

    Science.gov (United States)

    Martin, Roderick H.; Murri, Gretchen Bostaph

    1990-01-01

    Composite materials often fail by delamination. The onset and growth of delamination in AS4/PEEK, a tough thermoplastic matrix composite, was characterized for mode 1 and mode 2 loadings, using the Double Cantilever Beam (DCB) and the End Notched Flexure (ENF) test specimens. Delamination growth per fatigue cycle, da/dN, was related to strain energy release rate, G, by means of a power law. However, the exponents of these power laws were too large for them to be adequately used as a life prediction tool. A small error in the estimated applied loads could lead to large errors in the delamination growth rates. Hence strain energy release rate thresholds, G sub th, below which no delamination would occur were also measured. Mode 1 and 2 threshold G values for no delamination growth were found by monitoring the number of cycles to delamination onset in the DCB and ENF specimens. The maximum applied G for which no delamination growth had occurred until at least 1,000,000 cycles was considered the threshold strain energy release rate. Comments are given on how testing effects, facial interference or delamination front damage, may invalidate the experimental determination of the constants in the expression.

  1. Characterization of Mode 1 and Mode 2 delamination growth and thresholds in graphite/peek composites

    Science.gov (United States)

    Martin, Roderick H.; Murri, Gretchen B.

    1988-01-01

    Composite materials often fail by delamination. The onset and growth of delamination in AS4/PEEK, a tough thermoplastic matrix composite, was characterized for mode 1 and mode 2 loadings, using the Double Cantilever Beam (DCB) and the End Notched Flexure (ENF) test specimens. Delamination growth per fatigue cycle, da/dN, was related to strain energy release rate, G, by means of a power law. However, the exponents of these power laws were too large for them to be adequately used as a life prediction tool. A small error in the estimated applied loads could lead to large errors in the delamination growth rates. Hence strain energy release rate thresholds, G sub th, below which no delamination would occur were also measured. Mode 1 and 2 threshold G values for no delamination growth were found by monitoring the number of cycles to delamination onset in the DCB and ENF specimens. The maximum applied G for which no delamination growth had occurred until at least 1,000,000 cycles was considered the threshold strain energy release rate. Comments are given on how testing effects, facial interference or delamination front damage, may invalidate the experimental determination of the constants in the expression.

  2. Vector (two-dimensional) magnetic phenomena

    International Nuclear Information System (INIS)

    Enokizono, Masato

    2002-01-01

    In this paper, some interesting phenomena were described from the viewpoint of two-dimensional magnetic property, which is reworded with the vector magnetic property. It shows imperfection of conventional magnetic property and some interested phenomena were discovered, too. We found magnetic materials had the strong nonlinearity both magnitude and spatial phase due to the relationship between the magnetic field strength H-vector and the magnetic flux density B-vector. Therefore, magnetic properties should be defined as the vector relationship. Furthermore, the new Barukhausen signal was observed under rotating flux. (Author)

  3. Optimized two-dimensional Sn transport (BISTRO)

    International Nuclear Information System (INIS)

    Palmiotti, G.; Salvatores, M.; Gho, C.

    1990-01-01

    This paper reports on an S n two-dimensional transport module developed for the French fast reactor code system CCRR to optimize algorithms in order to obtain the best performance in terms of computational time. A form of diffusion synthetic acceleration was adopted, and a special effort was made to solve the associated diffusion equation efficiently. The improvements in the algorithms, along with the use of an efficient programming language, led to a significant gain in computational time with respect to the DOT code

  4. Binding energy of two-dimensional biexcitons

    DEFF Research Database (Denmark)

    Singh, Jai; Birkedal, Dan; Vadim, Lyssenko

    1996-01-01

    Using a model structure for a two-dimensional (2D) biexciton confined in a quantum well, it is shown that the form of the Hamiltonian of the 2D biexciton reduces into that of an exciton. The binding energies and Bohr radii of a 2D biexciton in its various internal energy states are derived...... analytically using the fractional dimension approach. The ratio of the binding energy of a 2D biexciton to that of a 2D exciton is found to be 0.228, which agrees very well with the recent experimental value. The results of our approach are compared with those of earlier theories....

  5. Airy beams on two dimensional materials

    Science.gov (United States)

    Imran, Muhammad; Li, Rujiang; Jiang, Yuyu; Lin, Xiao; Zheng, Bin; Dehdashti, Shahram; Xu, Zhiwei; Wang, Huaping

    2018-05-01

    We propose that quasi-transverse-magnetic (quasi-TM) Airy beams can be supported on two dimensional (2D) materials. By taking graphene as a typical example, the solution of quasi-TM Airy beams is studied under the paraxial approximation. The analytical field intensity in a bilayer graphene-based planar plasmonic waveguide is confirmed by the simulation results. Due to the tunability of the chemical potential of graphene, the self-accelerating behavior of the quasi-TM Airy beam can be steered effectively. 2D materials thus provide a good platform to investigate the propagation of Airy beams.

  6. Two-dimensional heat flow apparatus

    Science.gov (United States)

    McDougall, Patrick; Ayars, Eric

    2014-06-01

    We have created an apparatus to quantitatively measure two-dimensional heat flow in a metal plate using a grid of temperature sensors read by a microcontroller. Real-time temperature data are collected from the microcontroller by a computer for comparison with a computational model of the heat equation. The microcontroller-based sensor array allows previously unavailable levels of precision at very low cost, and the combination of measurement and modeling makes for an excellent apparatus for the advanced undergraduate laboratory course.

  7. Two dimensional kinetic analysis of electrostatic harmonic plasma waves

    Energy Technology Data Exchange (ETDEWEB)

    Fonseca-Pongutá, E. C.; Ziebell, L. F.; Gaelzer, R. [Instituto de Física, UFRGS, 91501-970 Porto Alegre, RS (Brazil); Yoon, P. H. [IPST, University of Maryland, College Park, Maryland 20742 (United States); SSR, Kyung Hee University, Yongin, Gyeonggi 446-701 (Korea, Republic of)

    2016-06-15

    Electrostatic harmonic Langmuir waves are virtual modes excited in weakly turbulent plasmas, first observed in early laboratory beam-plasma experiments as well as in rocket-borne active experiments in space. However, their unequivocal presence was confirmed through computer simulated experiments and subsequently theoretically explained. The peculiarity of harmonic Langmuir waves is that while their existence requires nonlinear response, their excitation mechanism and subsequent early time evolution are governed by essentially linear process. One of the unresolved theoretical issues regards the role of nonlinear wave-particle interaction process over longer evolution time period. Another outstanding issue is that existing theories for these modes are limited to one-dimensional space. The present paper carries out two dimensional theoretical analysis of fundamental and (first) harmonic Langmuir waves for the first time. The result shows that harmonic Langmuir wave is essentially governed by (quasi)linear process and that nonlinear wave-particle interaction plays no significant role in the time evolution of the wave spectrum. The numerical solutions of the two-dimensional wave spectra for fundamental and harmonic Langmuir waves are also found to be consistent with those obtained by direct particle-in-cell simulation method reported in the literature.

  8. High power blue LED development using different growth modes

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Dong S.; Florescu, Doru I.; Ramer, Jeff C.; Merai, Vinod; Parekh, Aniruddh; Begarney, Michael J.; Armour, Eric A. [Veeco TurboDisc Operations, 394 Elizabeth Avenue, Somerset, NJ 08873 (United States); Lu Dong [Veeco TurboDisc Operations, 394 Elizabeth Avenue, Somerset, NJ 08873 (United States); School of Engineering, Rutgers University, Piscataway, NJ 08854 (United States)

    2004-09-01

    Blue high brightness light emitting diodes (HB-LEDs) have been developed using different growth modes in the active layers. Piezoelectric field engineering improves the optical output power in multiple quantum well (MQW) LEDs by inserting an optimized transitional superlattice (TSL) before the active MQW layers. Within single quantum well (SQW) LEDs, quasi-Quantum Dot (QD) growth for Indium localization has been realized. The SQW LED output power exceeds the strain engineered MQW LEDs. The experimental data indicates that Indium localization enhances overall quantum efficiency and results in increased output power for HB-LEDs. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Single-mode, Rayleigh-Taylor growth-rate measurements on the OMEGA laser system

    International Nuclear Information System (INIS)

    Knauer, J. P.; Betti, R.; Bradley, D. K.; Boehly, T. R.; Collins, T. J. B.; Goncharov, V. N.; McKenty, P. W.; Meyerhofer, D. D.; Smalyuk, V. A.; Verdon, C. P.

    2000-01-01

    The results from a series of single-mode, Rayleigh-Taylor (RT) instability growth experiments performed on the OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] using planar targets are reported. Planar targets with imposed mass perturbations were accelerated using five or six 351 nm laser beams overlapped with total intensities up to 2.5x10 14 W/cm 2 . Experiments were performed with both 3 ns ramp and 3 ns flat-topped temporal pulse shapes. The use of distributed phase plates and smoothing by spectral dispersion resulted in a laser-irradiation nonuniformity of 4%-7% over a 600 μm diam region defined by the 90% intensity contour. The temporal growth of the modulation in optical depth was measured using throughfoil radiography and was detected with an x-ray framing camera for CH targets. Two-dimensional (2-D) hydrodynamic simulations (ORCHID) [R. L. McCrory and C. P. Verdon, in Inertial Confinement Fusion (Editrice Compositori, Bologna, 1989), pp. 83-124] of the growth of 20, 31, and 60 μm wavelength perturbations were in good agreement with the experimental data when the experimental details, including noise, were included. The amplitude of the simulation optical depth is in good agreement with the experimental optical depth; therefore, great care must be taken when the growth rates are compared to dispersion formulas. Since the foil's initial condition just before it is accelerated is not that of a uniformly compressed foil, the optical density measurement does not accurately reflect the amplitude of the ablation surface but is affected by the initial nonuniform density profile. (c) 2000 American Institute of Physics

  10. Single-mode, Rayleigh-Taylor growth-rate measurements on the OMEGA laser system

    Energy Technology Data Exchange (ETDEWEB)

    Knauer, J. P. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States); Betti, R. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States); Bradley, D. K. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States); Boehly, T. R. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States); Collins, T. J. B. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States); Goncharov, V. N. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States); McKenty, P. W. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States); Meyerhofer, D. D. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States); Smalyuk, V. A. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States); Verdon, C. P. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)] (and others)

    2000-01-01

    The results from a series of single-mode, Rayleigh-Taylor (RT) instability growth experiments performed on the OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] using planar targets are reported. Planar targets with imposed mass perturbations were accelerated using five or six 351 nm laser beams overlapped with total intensities up to 2.5x10{sup 14} W/cm{sup 2}. Experiments were performed with both 3 ns ramp and 3 ns flat-topped temporal pulse shapes. The use of distributed phase plates and smoothing by spectral dispersion resulted in a laser-irradiation nonuniformity of 4%-7% over a 600 {mu}m diam region defined by the 90% intensity contour. The temporal growth of the modulation in optical depth was measured using throughfoil radiography and was detected with an x-ray framing camera for CH targets. Two-dimensional (2-D) hydrodynamic simulations (ORCHID) [R. L. McCrory and C. P. Verdon, in Inertial Confinement Fusion (Editrice Compositori, Bologna, 1989), pp. 83-124] of the growth of 20, 31, and 60 {mu}m wavelength perturbations were in good agreement with the experimental data when the experimental details, including noise, were included. The amplitude of the simulation optical depth is in good agreement with the experimental optical depth; therefore, great care must be taken when the growth rates are compared to dispersion formulas. Since the foil's initial condition just before it is accelerated is not that of a uniformly compressed foil, the optical density measurement does not accurately reflect the amplitude of the ablation surface but is affected by the initial nonuniform density profile. (c) 2000 American Institute of Physics.

  11. Two dimensional radiated power diagnostics on Alcator C-Mod

    International Nuclear Information System (INIS)

    Reinke, M. L.; Hutchinson, I. H.

    2008-01-01

    The radiated power diagnostics for the Alcator C-Mod tokamak have been upgraded to measure two dimensional structure of the photon emissivity profile in order to investigate poloidal asymmetries in the core radiation. Commonly utilized unbiased absolute extreme ultraviolet (AXUV) diode arrays view the plasma along five different horizontal planes. The layout of the diagnostic set is shown and the results from calibrations and recent experiments are discussed. Data showing a significant, 30%-40%, inboard/outboard emissivity asymmetry during ELM-free H-mode are presented. The ability to use AXUV diode arrays to measure absolute radiated power is explored by comparing diode and resistive bolometer-based emissivity profiles for highly radiative L-mode plasmas seeded with argon. Emissivity profiles match in the core but disagree radially outward resulting in an underprediction of P rad of nearly 50% by the diodes compared to P rad determined using resistive bolometers.

  12. Two dimensional radiated power diagnostics on Alcator C-Moda)

    Science.gov (United States)

    Reinke, M. L.; Hutchinson, I. H.

    2008-10-01

    The radiated power diagnostics for the Alcator C-Mod tokamak have been upgraded to measure two dimensional structure of the photon emissivity profile in order to investigate poloidal asymmetries in the core radiation. Commonly utilized unbiased absolute extreme ultraviolet (AXUV) diode arrays view the plasma along five different horizontal planes. The layout of the diagnostic set is shown and the results from calibrations and recent experiments are discussed. Data showing a significant, 30%-40%, inboard/outboard emissivity asymmetry during ELM-free H-mode are presented. The ability to use AXUV diode arrays to measure absolute radiated power is explored by comparing diode and resistive bolometer-based emissivity profiles for highly radiative L-mode plasmas seeded with argon. Emissivity profiles match in the core but disagree radially outward resulting in an underprediction of Prad of nearly 50% by the diodes compared to Prad determined using resistive bolometers.

  13. Two-dimensional simulation of the MHD stability, (2)

    International Nuclear Information System (INIS)

    Kurita, Gen-ichi; Amano, Tsuneo.

    1977-09-01

    Growth rate and eigen-function of the MHD instability of a toroidal plasma were calculated numerically as an initial-boundary value problem. When a conducting shell is away from the plasma, toroidicity hardly influences growth rate of the external kink modes in a slender tokamak, but it stabilizes the modes in a fat tokamak. On the other hand, when the shell is near to the plasma, the unstable external modes are stabilized by both toroidicity and shell effect. (auth.)

  14. Decoherence in two-dimensional quantum walks

    International Nuclear Information System (INIS)

    Oliveira, A. C.; Portugal, R.; Donangelo, R.

    2006-01-01

    We analyze the decoherence in quantum walks in two-dimensional lattices generated by broken-link-type noise. In this type of decoherence, the links of the lattice are randomly broken with some given constant probability. We obtain the evolution equation for a quantum walker moving on two-dimensional (2D) lattices subject to this noise, and we point out how to generalize for lattices in more dimensions. In the nonsymmetric case, when the probability of breaking links in one direction is different from the probability in the perpendicular direction, we have obtained a nontrivial result. If one fixes the link-breaking probability in one direction, and gradually increases the probability in the other direction from 0 to 1, the decoherence initially increases until it reaches a maximum value, and then it decreases. This means that, in some cases, one can increase the noise level and still obtain more coherence. Physically, this can be explained as a transition from a decoherent 2D walk to a coherent 1D walk

  15. Two-Dimensional Theory of Scientific Representation

    Directory of Open Access Journals (Sweden)

    A Yaghmaie

    2013-03-01

    Full Text Available Scientific representation is an interesting topic for philosophers of science, many of whom have recently explored it from different points of view. There are currently two competing approaches to the issue: cognitive and non-cognitive, and each of them claims its own merits over the other. This article tries to provide a hybrid theory of scientific representation, called Two-Dimensional Theory of Scientific Representation, which has the merits of the two accounts and is free of their shortcomings. To do this, we will argue that although scientific representation needs to use the notion of intentionality, such a notion is defined and realized in a simply structural form contrary to what cognitive approach says about intentionality. After a short introduction, the second part of the paper is devoted to introducing theories of scientific representation briefly. In the third part, the structural accounts of representation will be criticized. The next step is to introduce the two-dimensional theory which involves two key components: fixing and structural fitness. It will be argued that fitness is an objective and non-intentional relation, while fixing is intentional.

  16. Two-dimensional simulations of magnetically-driven instabilities

    International Nuclear Information System (INIS)

    Peterson, D.; Bowers, R.; Greene, A.E.; Brownell, J.

    1986-01-01

    A two-dimensional Eulerian MHD code is used to study the evolution of magnetically-driven instabilities in cylindrical geometry. The code incorporates an equation of state, resistivity, and radiative cooling model appropriate for an aluminum plasma. The simulations explore the effects of initial perturbations, electrical resistivity, and radiative cooling on the growth and saturation of the instabilities. Comparisons are made between the 2-D simulations, previous 1-D simulations, and results from the Pioneer experiments of the Los Alamos foil implosion program

  17. Study of two-dimensional Debye clusters using Brownian motion

    International Nuclear Information System (INIS)

    Sheridan, T.E.; Theisen, W.L.

    2006-01-01

    A two-dimensional Debye cluster is a system of n identical particles confined in a parabolic well and interacting through a screened Coulomb (i.e., a Debye-Hueckel or Yukawa) potential with a Debye length λ. Experiments were performed for 27 clusters with n=3-63 particles (9 μm diam) in a capacitively coupled 9 W rf discharge at a neutral argon pressure of 13.6 mTorr. In the strong-coupling regime each particle exhibits small amplitude Brownian motion about its equilibrium position. These motions were projected onto the center-of-mass and breathing modes and Fourier analyzed to give resonance curves from which the mode frequencies, amplitudes, and damping rates were determined. The ratio of the breathing frequency to the center-of-mass frequency was compared with theory to self-consistently determine the Debye shielding parameter κ, Debye length λ, particle charge q, and mode temperatures. It is found that 1 < or approx. κ < or approx. 2, and κ decreases weakly with n. The particle charge averaged over all measurements is -14 200±200 e, and q decreases slightly with n. The two center-of-mass modes and the breathing mode are found to have the same temperature, indicating that the clusters are in thermal equilibrium with the neutral gas. The average cluster temperature is 399±5 K

  18. Design, Fabrication, and Measurement of Two-Dimensional Photonic Crystal Slab Waveguides

    International Nuclear Information System (INIS)

    Chao, Zhang; Xuan, Tang; Xiao-Yu, Mao; Kai-Yu, Cui; Lei, Cao; Yi-Dong, Huang; Wei, Zhang; Jiang-De, Peng

    2008-01-01

    Two-dimensional photonic crystal slab waveguides on SOI wafer are designed and fabricated. Photonic band gap, band gap guided mode, and index guided mode are observed by measuring the transmission spectra. The experimental results are in good agreement with the theoretical ones

  19. Two-dimensional simulation of sintering process

    International Nuclear Information System (INIS)

    Vasconcelos, Vanderley de; Pinto, Lucio Carlos Martins; Vasconcelos, Wander L.

    1996-01-01

    The results of two-dimensional simulations are directly applied to systems in which one of the dimensions is much smaller than the others, and to sections of three dimensional models. Moreover, these simulations are the first step of the analysis of more complex three-dimensional systems. In this work, two basic features of the sintering process are studied: the types of particle size distributions related to the powder production processes and the evolution of geometric parameters of the resultant microstructures during the solid-state sintering. Random packing of equal spheres is considered in the sintering simulation. The packing algorithm does not take into account the interactive forces between the particles. The used sintering algorithm causes the densification of the particle set. (author)

  20. Pressure of two-dimensional Yukawa liquids

    International Nuclear Information System (INIS)

    Feng, Yan; Wang, Lei; Tian, Wen-de; Goree, J; Liu, Bin

    2016-01-01

    A simple analytic expression for the pressure of a two-dimensional Yukawa liquid is found by fitting results from a molecular dynamics simulation. The results verify that the pressure can be written as the sum of a potential term which is a simple multiple of the Coulomb potential energy at a distance of the Wigner–Seitz radius, and a kinetic term which is a multiple of the one for an ideal gas. Dimensionless coefficients for each of these terms are found empirically, by fitting. The resulting analytic expression, with its empirically determined coefficients, is plotted as isochores, or curves of constant area. These results should be applicable to monolayer dusty plasmas. (paper)

  1. Two dimensional nanomaterials for flexible supercapacitors.

    Science.gov (United States)

    Peng, Xu; Peng, Lele; Wu, Changzheng; Xie, Yi

    2014-05-21

    Flexible supercapacitors, as one of most promising emerging energy storage devices, are of great interest owing to their high power density with great mechanical compliance, making them very suitable as power back-ups for future stretchable electronics. Two-dimensional (2D) nanomaterials, including the quasi-2D graphene and inorganic graphene-like materials (IGMs), have been greatly explored to providing huge potential for the development of flexible supercapacitors with higher electrochemical performance. This review article is devoted to recent progresses in engineering 2D nanomaterials for flexible supercapacitors, which survey the evolution of electrode materials, recent developments in 2D nanomaterials and their hybrid nanostructures with regulated electrical properties, and the new planar configurations of flexible supercapacitors. Furthermore, a brief discussion on future directions, challenges and opportunities in this fascinating area is also provided.

  2. Geometrical aspects of solvable two dimensional models

    International Nuclear Information System (INIS)

    Tanaka, K.

    1989-01-01

    It was noted that there is a connection between the non-linear two-dimensional (2D) models and the scalar curvature r, i.e., when r = -2 the equations of motion of the Liouville and sine-Gordon models were obtained. Further, solutions of various classical nonlinear 2D models can be obtained from the condition that the appropriate curvature two form Ω = 0, which suggests that these models are closely related. This relation is explored further in the classical version by obtaining the equations of motion from the evolution equations, the infinite number of conserved quantities, and the common central charge. The Poisson brackets of the solvable 2D models are specified by the Virasoro algebra. 21 refs

  3. Two-dimensional materials for ultrafast lasers

    International Nuclear Information System (INIS)

    Wang Fengqiu

    2017-01-01

    As the fundamental optical properties and novel photophysics of graphene and related two-dimensional (2D) crystals are being extensively investigated and revealed, a range of potential applications in optical and optoelectronic devices have been proposed and demonstrated. Of the many possibilities, the use of 2D materials as broadband, cost-effective and versatile ultrafast optical switches (or saturable absorbers) for short-pulsed lasers constitutes a rapidly developing field with not only a good number of publications, but also a promising prospect for commercial exploitation. This review primarily focuses on the recent development of pulsed lasers based on several representative 2D materials. The comparative advantages of these materials are discussed, and challenges to practical exploitation, which represent good future directions of research, are laid out. (paper)

  4. Two-dimensional phase fraction charts

    International Nuclear Information System (INIS)

    Morral, J.E.

    1984-01-01

    A phase fraction chart is a graphical representation of the amount of each phase present in a system as a function of temperature, composition or other variable. Examples are phase fraction versus temperature charts used to characterize specific alloys and as a teaching tool in elementary texts, and Schaeffler diagrams used to predict the amount of ferrite in stainless steel welds. Isothermal-transformation diagrams (TTT diagrams) are examples that give phase (or microconstituent) amount versus temperature and time. The purpose of this communication is to discuss the properties of two-dimensional phase fraction charts in more general terms than have been reported before. It is shown that they can represent multi-component, multiphase equilibria in a way which is easier to read and which contains more information than the isotherms and isopleths of multi-component phase diagrams

  5. Two-dimensional motions of rockets

    International Nuclear Information System (INIS)

    Kang, Yoonhwan; Bae, Saebyok

    2007-01-01

    We analyse the two-dimensional motions of the rockets for various types of rocket thrusts, the air friction and the gravitation by using a suitable representation of the rocket equation and the numerical calculation. The slope shapes of the rocket trajectories are discussed for the three types of rocket engines. Unlike the projectile motions, the descending parts of the trajectories tend to be gentler and straighter slopes than the ascending parts for relatively large launching angles due to the non-vanishing thrusts. We discuss the ranges, the maximum altitudes and the engine performances of the rockets. It seems that the exponential fuel exhaustion can be the most potent engine for the longest and highest flights

  6. Two dimensional NMR studies of polysaccharides

    International Nuclear Information System (INIS)

    Byrd, R.A.; Egan, W.; Summers, M.F.

    1987-01-01

    Polysaccharides are very important components in the immune response system. Capsular polysaccharides and lipopolysaccharides occupy cell surface sites of bacteria, play key roles in recognition and some have been used to develop vaccines. Consequently, the ability to determine chemical structures of these systems is vital to an understanding of their immunogenic action. The authors have been utilizing recently developed two-dimensional homonuclear and heteronuclear correlation spectroscopy for unambiguous assignment and structure determination of a number of polysaccharides. In particular, the 1 H-detected heteronuclear correlation experiments are essential to the rapid and sensitive determination of these structures. Linkage sites are determined by independent polarization transfer experiments and multiple quantum correlation experiments. These methods permit the complete structure determination on very small amounts of the polysaccharides. They present the results of a number of structural determinations and discuss the limits of these experiments in terms of their applications to polysaccharides

  7. Two-Dimensional Homogeneous Fermi Gases

    Science.gov (United States)

    Hueck, Klaus; Luick, Niclas; Sobirey, Lennart; Siegl, Jonas; Lompe, Thomas; Moritz, Henning

    2018-02-01

    We report on the experimental realization of homogeneous two-dimensional (2D) Fermi gases trapped in a box potential. In contrast to harmonically trapped gases, these homogeneous 2D systems are ideally suited to probe local as well as nonlocal properties of strongly interacting many-body systems. As a first benchmark experiment, we use a local probe to measure the density of a noninteracting 2D Fermi gas as a function of the chemical potential and find excellent agreement with the corresponding equation of state. We then perform matter wave focusing to extract the momentum distribution of the system and directly observe Pauli blocking in a near unity occupation of momentum states. Finally, we measure the momentum distribution of an interacting homogeneous 2D gas in the crossover between attractively interacting fermions and bosonic dimers.

  8. Two-dimensional electroacoustic waves in silicene

    Science.gov (United States)

    Zhukov, Alexander V.; Bouffanais, Roland; Konobeeva, Natalia N.; Belonenko, Mikhail B.

    2018-01-01

    In this letter, we investigate the propagation of two-dimensional electromagnetic waves in a piezoelectric medium built upon silicene. Ultrashort optical pulses of Gaussian form are considered to probe this medium. On the basis of Maxwell's equations supplemented with the wave equation for the medium's displacement vector, we obtain the effective governing equation for the vector potential associated with the electromagnetic field, as well as the component of the displacement vector. The dependence of the pulse shape on the bandgap in silicene and the piezoelectric coefficient of the medium was analyzed, thereby revealing a nontrivial triadic interplay between the characteristics of the pulse dynamics, the electronic properties of silicene, and the electrically induced mechanical vibrations of the medium. In particular, we uncovered the possibility for an amplification of the pulse amplitude through the tuning of the piezoelectric coefficient. This property could potentially offer promising prospects for the development of amplification devices for the optoelectronics industry.

  9. Versatile two-dimensional transition metal dichalcogenides

    DEFF Research Database (Denmark)

    Canulescu, Stela; Affannoukoué, Kévin; Döbeli, Max

    ), a strategy for the fabrication of 2D heterostructures must be developed. Here we demonstrate a novel approach for the bottom-up synthesis of TMDC monolayers, namely Pulsed Laser Deposition (PLD) combined with a sulfur evaporation beam. PLD relies on the use of a pulsed laser (ns pulse duration) to induce...... material transfer from a solid source (such as a sintered target of MoS2) to a substrate (such as Si or sapphire). The deposition rate in PLD is typically much less than a monolayer per pulse, meaning that the number of MLs can be controlled by a careful selection of the number of laser pulses......Two-dimensional transition metal dichalcogenides (2D-TMDCs), such as MoS2, have emerged as a new class of semiconducting materials with distinct optical and electrical properties. The availability of 2D-TMDCs with distinct band gaps allows for unlimited combinations of TMDC monolayers (MLs...

  10. Two-dimensional heterostructures for energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Gogotsi, Yury G. [Drexel Univ., Philadelphia, PA (United States); Pomerantseva, Ekaterina [Drexel Univ., Philadelphia, PA (United States)

    2017-06-12

    Two-dimensional (2D) materials provide slit-shaped ion diffusion channels that enable fast movement of lithium and other ions. However, electronic conductivity, the number of intercalation sites, and stability during extended cycling are also crucial for building high-performance energy storage devices. While individual 2D materials, such as graphene, show some of the required properties, none of them can offer all properties needed to maximize energy density, power density, and cycle life. Here we argue that stacking different 2D materials into heterostructured architectures opens an opportunity to construct electrodes that would combine the advantages of the individual building blocks while eliminating the associated shortcomings. We discuss characteristics of common 2D materials and provide examples of 2D heterostructured electrodes that showed new phenomena leading to superior electrochemical performance. As a result, we also consider electrode fabrication approaches and finally outline future steps to create 2D heterostructured electrodes that could greatly expand current energy storage technologies.

  11. Two-dimensional fourier transform spectrometer

    Science.gov (United States)

    DeFlores, Lauren; Tokmakoff, Andrei

    2013-09-03

    The present invention relates to a system and methods for acquiring two-dimensional Fourier transform (2D FT) spectra. Overlap of a collinear pulse pair and probe induce a molecular response which is collected by spectral dispersion of the signal modulated probe beam. Simultaneous collection of the molecular response, pulse timing and characteristics permit real time phasing and rapid acquisition of spectra. Full spectra are acquired as a function of pulse pair timings and numerically transformed to achieve the full frequency-frequency spectrum. This method demonstrates the ability to acquire information on molecular dynamics, couplings and structure in a simple apparatus. Multi-dimensional methods can be used for diagnostic and analytical measurements in the biological, biomedical, and chemical fields.

  12. Equivalency of two-dimensional algebras

    International Nuclear Information System (INIS)

    Santos, Gildemar Carneiro dos; Pomponet Filho, Balbino Jose S.

    2011-01-01

    Full text: Let us consider a vector z = xi + yj over the field of real numbers, whose basis (i,j) satisfy a given algebra. Any property of this algebra will be reflected in any function of z, so we can state that the knowledge of the properties of an algebra leads to more general conclusions than the knowledge of the properties of a function. However structural properties of an algebra do not change when this algebra suffers a linear transformation, though the structural constants defining this algebra do change. We say that two algebras are equivalent to each other whenever they are related by a linear transformation. In this case, we have found that some relations between the structural constants are sufficient to recognize whether or not an algebra is equivalent to another. In spite that the basis transform linearly, the structural constants change like a third order tensor, but some combinations of these tensors result in a linear transformation, allowing to write the entries of the transformation matrix as function of the structural constants. Eventually, a systematic way to find the transformation matrix between these equivalent algebras is obtained. In this sense, we have performed the thorough classification of associative commutative two-dimensional algebras, and find that even non-division algebra may be helpful in solving non-linear dynamic systems. The Mandelbrot set was used to have a pictorial view of each algebra, since equivalent algebras result in the same pattern. Presently we have succeeded in classifying some non-associative two-dimensional algebras, a task more difficult than for associative one. (author)

  13. Growth of the double Tearing mode in a plasma cylinder

    International Nuclear Information System (INIS)

    Gatilov, V.V.; Sagalakov, A.M.; Ul'chenko, V.F.

    1989-01-01

    Within the framework of the linear theory the growth of Tearing modes in collisional plasma of a cylindrical filament with a free boundary in the presence of two resonance surfaces is studied. The boundary problems for the system of Kadomtsev-Pogutse equation were solved numerically using the method of differential run which was widely used to study the stability of viscous liquid flows. The asymptotic dependences for the increments are determined. The regular behaviour of increments in the case of drawing together of resonance surfaces is fiound. A very strong destabilizing factor of conductivity inhomogeneity on modes 1/1, 2/1 connected with the resonance surface in the near-the-boundary plasma region is found

  14. Tearing mode growth in a regime of weak magnetic shear

    International Nuclear Information System (INIS)

    Riyopoulos, S.; Hazeltine, R.D.

    1987-06-01

    The nonlinear growth for the m/n ≥ 2 resistive tearing mode is studied in case when the rational surface q(r 0 ) = m/n falls in a regime of weak magnetic shear, q'(r 0 ) ≅ 0. The island width is determined self-consistently from the nonlinear, zero-helicity component of the perturbed magnetic flux that provides the local shear. It is found that the magnetic perturbation keeps growing exponentially in the nonlinear regime on a hybrid resistive-Alfvenic time scale, while the island width and the vorticity grow on a much slower time scale. Accordingly, much faster release of magnetic energy results for modes growing near minima of hollow q profiles

  15. Monitoring of biofilm growth using ATR-leaky mode spectroscopy

    International Nuclear Information System (INIS)

    Leitz, M.; Franke, H.; Grattan, K.T.V.; Tamachkiarow, A.

    2002-01-01

    An approach to the in situ monitoring of biofilm formation using the technique of ATR-leaky mode spectroscopy is given as an example for the case of Cytophaga. The biofilm growth was studied on an aluminium layer and on a bilayer of the hydrogel agarose on aluminium. This metal was chosen because of its chemical stability in aqueous systems. The spectra obtained have been recorded using a flow cell to contain the suspension and nutrients over a period of several days. In the case considered using a prism surface coated with agarose, the experiments were performed by breeding in an incubator. (author)

  16. Growth modes of pentacene films obtained by pulsed laser deposition

    International Nuclear Information System (INIS)

    Wisz, G.; Kuzma, M.; Virt, I.; Sagan, P.; Rudyj, I.

    2011-01-01

    Thin pentacene films were deposited on KCl and ITO/glass substrates by the pulsed laser deposition method (PLD) using a YAG:Nd 3+ laser with a second harmonic (λ = 532 nm). We compared the structure of the layer on differently oriented substrates with respect to the pentacene plasma plume - vertical and parallel orientation. The structure of the layers formed was examined using SEM, RHEED and THEED methods. The lattice parameters of the layer deposited on KCl were determined from THEED pattern (a = 5.928 A, b 7.874 A, c = 14,98 A, α = 76.54 o , β 75.17 o , γ = 89.20 o ). The preferred direction [11-bar 0] of the layer growth on KCl substrate was addressed. The effect of the substrate orientation results in a different growth mode of the layers.

  17. Two-dimensional photonic crystal accelerator structures

    Directory of Open Access Journals (Sweden)

    Benjamin M. Cowan

    2003-10-01

    Full Text Available Photonic crystals provide a method of confining a synchronous speed-of-light mode in an all-dielectric structure, likely a necessary feature in any optical accelerator. We explore computationally a class of photonic crystal structures with translational symmetry in a direction transverse to the electron beam. We demonstrate synchronous waveguide modes and discuss relevant parameters of such modes. We then explore how accelerator parameters vary as the geometry of the structure is changed and consider trade-offs inherent in the design of an accelerator of this type.

  18. Bifurcated equilibria in two-dimensional MHD with diamagnetic effects

    International Nuclear Information System (INIS)

    Ottaviani, M.; Tebaldi, C.

    1998-12-01

    In this work we analyzed the sequence of bifurcated equilibria in two-dimensional reduced magnetohydrodynamics. Diamagnetic effects are studied under the assumption of a constant equilibrium pressure gradient, not altered by the formation of the magnetic island. The formation of an island when the symmetric equilibrium becomes unstable is studied as a function of the tearing mode stability parameter Δ' and of the diamagnetic frequency, by employing fixed-points numerical techniques and an initial value code. At larger values of Δ' a tangent bifurcation takes place, above which no small island solutions exist. This bifurcation persists up to fairly large values of the diamagnetic frequency (of the order of one tenth of the Alfven frequency). The implications of this phenomenology for the intermittent MHD dynamics observed in tokamaks is discussed. (authors)

  19. A spectroelectrochemical cell for ultrafast two-dimensional infrared spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    El Khoury, Youssef; Van Wilderen, Luuk J. G. W.; Vogt, Tim; Winter, Ernst; Bredenbeck, Jens, E-mail: bredenbeck@biophysik.uni-frankfurt.org, E-mail: bredenbeck@biophysik.uni-frankfurt.de [Institut für Biophysik, Johann Wolfgang Goethe-Universität, Max-von-Laue-Strasse 1, 60438 Frankfurt (Germany)

    2015-08-15

    A spectroelectrochemical cell has been designed to combine electrochemistry and ultrafast two-dimensional infrared (2D-IR) spectroscopy, which is a powerful tool to extract structure and dynamics information on the femtosecond to picosecond time scale. Our design is based on a gold mirror with the dual role of performing electrochemistry and reflecting IR light. To provide the high optical surface quality required for laser spectroscopy, the gold surface is made by electron beam evaporation on a glass substrate. Electrochemical cycling facilitates in situ collection of ultrafast dynamics of redox-active molecules by means of 2D-IR. The IR beams are operated in reflection mode so that they travel twice through the sample, i.e., the signal size is doubled. This methodology is optimal for small sample volumes and successfully tested with the ferricyanide/ferrocyanide redox system of which the corresponding electrochemically induced 2D-IR difference spectrum is reported.

  20. Two-dimensional random arrays for real time volumetric imaging

    DEFF Research Database (Denmark)

    Davidsen, Richard E.; Jensen, Jørgen Arendt; Smith, Stephen W.

    1994-01-01

    real time volumetric imaging system, which employs a wide transmit beam and receive mode parallel processing to increase image frame rate. Depth-of-field comparisons were made from simulated on-axis and off-axis beamplots at ranges from 30 to 160 mm for both coaxial and offset transmit and receive......Two-dimensional arrays are necessary for a variety of ultrasonic imaging techniques, including elevation focusing, 2-D phase aberration correction, and real time volumetric imaging. In order to reduce system cost and complexity, sparse 2-D arrays have been considered with element geometries...... selected ad hoc, by algorithm, or by random process. Two random sparse array geometries and a sparse array with a Mills cross receive pattern were simulated and compared to a fully sampled aperture with the same overall dimensions. The sparse arrays were designed to the constraints of the Duke University...

  1. Acoustic resonances in two-dimensional radial sonic crystal shells

    Energy Technology Data Exchange (ETDEWEB)

    Torrent, Daniel; Sanchez-Dehesa, Jose, E-mail: jsdehesa@upvnet.upv.e [Wave Phenomena Group, Departamento de Ingenieria Electronica, Universidad Politecnica de Valencia, C/Camino de Vera s.n., E-46022 Valencia (Spain)

    2010-07-15

    Radial sonic crystals (RSC) are fluidlike structures infinitely periodic along the radial direction that verify the Bloch theorem and are possible only if certain specially designed acoustic metamaterials with mass density anisotropy can be engineered (see Torrent and Sanchez-Dehesa 2009 Phys. Rev. Lett. 103 064301). A comprehensive analysis of two-dimensional (2D) RSC shells is reported here. A given shell is in fact a circular slab with a central cavity. These finite crystal structures contain Fabry-Perot-like resonances and modes strongly localized at the central cavity. Semi-analytical expressions are developed to obtain the quality factors of the different resonances, their symmetry features and their excitation properties. The results reported here are completely general and can be extended to equivalent 3D spherical shells and to their photonic counterparts.

  2. A spectroelectrochemical cell for ultrafast two-dimensional infrared spectroscopy

    International Nuclear Information System (INIS)

    El Khoury, Youssef; Van Wilderen, Luuk J. G. W.; Vogt, Tim; Winter, Ernst; Bredenbeck, Jens

    2015-01-01

    A spectroelectrochemical cell has been designed to combine electrochemistry and ultrafast two-dimensional infrared (2D-IR) spectroscopy, which is a powerful tool to extract structure and dynamics information on the femtosecond to picosecond time scale. Our design is based on a gold mirror with the dual role of performing electrochemistry and reflecting IR light. To provide the high optical surface quality required for laser spectroscopy, the gold surface is made by electron beam evaporation on a glass substrate. Electrochemical cycling facilitates in situ collection of ultrafast dynamics of redox-active molecules by means of 2D-IR. The IR beams are operated in reflection mode so that they travel twice through the sample, i.e., the signal size is doubled. This methodology is optimal for small sample volumes and successfully tested with the ferricyanide/ferrocyanide redox system of which the corresponding electrochemically induced 2D-IR difference spectrum is reported

  3. Electronic Transport in Two-Dimensional Materials

    Science.gov (United States)

    Sangwan, Vinod K.; Hersam, Mark C.

    2018-04-01

    Two-dimensional (2D) materials have captured the attention of the scientific community due to the wide range of unique properties at nanometer-scale thicknesses. While significant exploratory research in 2D materials has been achieved, the understanding of 2D electronic transport and carrier dynamics remains in a nascent stage. Furthermore, because prior review articles have provided general overviews of 2D materials or specifically focused on charge transport in graphene, here we instead highlight charge transport mechanisms in post-graphene 2D materials, with particular emphasis on transition metal dichalcogenides and black phosphorus. For these systems, we delineate the intricacies of electronic transport, including band structure control with thickness and external fields, valley polarization, scattering mechanisms, electrical contacts, and doping. In addition, electronic interactions between 2D materials are considered in the form of van der Waals heterojunctions and composite films. This review concludes with a perspective on the most promising future directions in this fast-evolving field.

  4. Stress distribution in two-dimensional silos

    Science.gov (United States)

    Blanco-Rodríguez, Rodolfo; Pérez-Ángel, Gabriel

    2018-01-01

    Simulations of a polydispersed two-dimensional silo were performed using molecular dynamics, with different numbers of grains reaching up to 64 000, verifying numerically the model derived by Janssen and also the main assumption that the walls carry part of the weight due to the static friction between grains with themselves and those with the silo's walls. We vary the friction coefficient, the radii dispersity, the silo width, and the size of grains. We find that the Janssen's model becomes less relevant as the the silo width increases since the behavior of the stresses becomes more hydrostatic. Likewise, we get the normal and tangential stress distribution on the walls evidencing the existence of points of maximum stress. We also obtained the stress matrix with which we observe zones of concentration of load, located always at a height around two thirds of the granular columns. Finally, we observe that the size of the grains affects the distribution of stresses, increasing the weight on the bottom and reducing the normal stress on the walls, as the grains are made smaller (for the same total mass of the granulate), giving again a more hydrostatic and therefore less Janssen-type behavior for the weight of the column.

  5. Asymptotics for Two-dimensional Atoms

    DEFF Research Database (Denmark)

    Nam, Phan Thanh; Portmann, Fabian; Solovej, Jan Philip

    2012-01-01

    We prove that the ground state energy of an atom confined to two dimensions with an infinitely heavy nucleus of charge $Z>0$ and $N$ quantum electrons of charge -1 is $E(N,Z)=-{1/2}Z^2\\ln Z+(E^{\\TF}(\\lambda)+{1/2}c^{\\rm H})Z^2+o(Z^2)$ when $Z\\to \\infty$ and $N/Z\\to \\lambda$, where $E^{\\TF}(\\lambd......We prove that the ground state energy of an atom confined to two dimensions with an infinitely heavy nucleus of charge $Z>0$ and $N$ quantum electrons of charge -1 is $E(N,Z)=-{1/2}Z^2\\ln Z+(E^{\\TF}(\\lambda)+{1/2}c^{\\rm H})Z^2+o(Z^2)$ when $Z\\to \\infty$ and $N/Z\\to \\lambda$, where $E......^{\\TF}(\\lambda)$ is given by a Thomas-Fermi type variational problem and $c^{\\rm H}\\approx -2.2339$ is an explicit constant. We also show that the radius of a two-dimensional neutral atom is unbounded when $Z\\to \\infty$, which is contrary to the expected behavior of three-dimensional atoms....

  6. Seismic isolation of two dimensional periodic foundations

    International Nuclear Information System (INIS)

    Yan, Y.; Mo, Y. L.; Laskar, A.; Cheng, Z.; Shi, Z.; Menq, F.; Tang, Y.

    2014-01-01

    Phononic crystal is now used to control acoustic waves. When the crystal goes to a larger scale, it is called periodic structure. The band gaps of the periodic structure can be reduced to range from 0.5 Hz to 50 Hz. Therefore, the periodic structure has potential applications in seismic wave reflection. In civil engineering, the periodic structure can be served as the foundation of upper structure. This type of foundation consisting of periodic structure is called periodic foundation. When the frequency of seismic waves falls into the band gaps of the periodic foundation, the seismic wave can be blocked. Field experiments of a scaled two dimensional (2D) periodic foundation with an upper structure were conducted to verify the band gap effects. Test results showed the 2D periodic foundation can effectively reduce the response of the upper structure for excitations with frequencies within the frequency band gaps. When the experimental and the finite element analysis results are compared, they agree well with each other, indicating that 2D periodic foundation is a feasible way of reducing seismic vibrations.

  7. Two-dimensional transport of tokamak plasmas

    International Nuclear Information System (INIS)

    Hirshman, S.P.; Jardin, S.C.

    1979-01-01

    A reduced set of two-fluid transport equations is obtained from the conservation equations describing the time evolution of the differential particle number, entropy, and magnetic fluxes in an axisymmetric toroidal plasma with nested magnetic surfaces. Expanding in the small ratio of perpendicular to parallel mobilities and thermal conductivities yields as solubility constraints one-dimensional equations for the surface-averaged thermodynamic variables and magnetic fluxes. Since Ohm's law E +u x B =R', where R' accounts for any nonideal effects, only determines the particle flow relative to the diffusing magnetic surfaces, it is necessary to solve a single two-dimensional generalized differential equation, (partial/partialt) delpsi. (delp - J x B) =0, to find the absolute velocity of a magnetic surface enclosing a fixed toroidal flux. This equation is linear but nonstandard in that it involves flux surface averages of the unknown velocity. Specification of R' and the cross-field ion and electron heat fluxes provides a closed system of equations. A time-dependent coordinate transformation is used to describe the diffusion of plasma quantities through magnetic surfaces of changing shape

  8. Two-dimensional topological photonic systems

    Science.gov (United States)

    Sun, Xiao-Chen; He, Cheng; Liu, Xiao-Ping; Lu, Ming-Hui; Zhu, Shi-Ning; Chen, Yan-Feng

    2017-09-01

    The topological phase of matter, originally proposed and first demonstrated in fermionic electronic systems, has drawn considerable research attention in the past decades due to its robust transport of edge states and its potential with respect to future quantum information, communication, and computation. Recently, searching for such a unique material phase in bosonic systems has become a hot research topic worldwide. So far, many bosonic topological models and methods for realizing them have been discovered in photonic systems, acoustic systems, mechanical systems, etc. These discoveries have certainly yielded vast opportunities in designing material phases and related properties in the topological domain. In this review, we first focus on some of the representative photonic topological models and employ the underlying Dirac model to analyze the edge states and geometric phase. On the basis of these models, three common types of two-dimensional topological photonic systems are discussed: 1) photonic quantum Hall effect with broken time-reversal symmetry; 2) photonic topological insulator and the associated pseudo-time-reversal symmetry-protected mechanism; 3) time/space periodically modulated photonic Floquet topological insulator. Finally, we provide a summary and extension of this emerging field, including a brief introduction to the Weyl point in three-dimensional systems.

  9. Turbulent equipartitions in two dimensional drift convection

    International Nuclear Information System (INIS)

    Isichenko, M.B.; Yankov, V.V.

    1995-01-01

    Unlike the thermodynamic equipartition of energy in conservative systems, turbulent equipartitions (TEP) describe strongly non-equilibrium systems such as turbulent plasmas. In turbulent systems, energy is no longer a good invariant, but one can utilize the conservation of other quantities, such as adiabatic invariants, frozen-in magnetic flux, entropy, or combination thereof, in order to derive new, turbulent quasi-equilibria. These TEP equilibria assume various forms, but in general they sustain spatially inhomogeneous distributions of the usual thermodynamic quantities such as density or temperature. This mechanism explains the effects of particle and energy pinch in tokamaks. The analysis of the relaxed states caused by turbulent mixing is based on the existence of Lagrangian invariants (quantities constant along fluid-particle or other orbits). A turbulent equipartition corresponds to the spatially uniform distribution of relevant Lagrangian invariants. The existence of such turbulent equilibria is demonstrated in the simple model of two dimensional electrostatically turbulent plasma in an inhomogeneous magnetic field. The turbulence is prescribed, and the turbulent transport is assumed to be much stronger than the classical collisional transport. The simplicity of the model makes it possible to derive the equations describing the relaxation to the TEP state in several limits

  10. Radiation effects on two-dimensional materials

    Energy Technology Data Exchange (ETDEWEB)

    Walker, R.C. II; Robinson, J.A. [Department of Materials Science, Penn State, University Park, PA (United States); Center for Two-Dimensional Layered Materials, Penn State, University Park, PA (United States); Shi, T. [Department of Mechanical and Nuclear Engineering, Penn State, University Park, PA (United States); Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI (United States); Silva, E.C. [GlobalFoundries, Malta, NY (United States); Jovanovic, I. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI (United States)

    2016-12-15

    The effects of electromagnetic and particle irradiation on two-dimensional materials (2DMs) are discussed in this review. Radiation creates defects that impact the structure and electronic performance of materials. Determining the impact of these defects is important for developing 2DM-based devices for use in high-radiation environments, such as space or nuclear reactors. As such, most experimental studies have been focused on determining total ionizing dose damage to 2DMs and devices. Total dose experiments using X-rays, gamma rays, electrons, protons, and heavy ions are summarized in this review. We briefly discuss the possibility of investigating single event effects in 2DMs based on initial ion beam irradiation experiments and the development of 2DM-based integrated circuits. Additionally, beneficial uses of irradiation such as ion implantation to dope materials or electron-beam and helium-beam etching to shape materials have begun to be used on 2DMs and are reviewed as well. For non-ionizing radiation, such as low-energy photons, we review the literature on 2DM-based photo-detection from terahertz to UV. The majority of photo-detecting devices operate in the visible and UV range, and for this reason they are the focus of this review. However, we review the progress in developing 2DMs for detecting infrared and terahertz radiation. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Buckled two-dimensional Xene sheets.

    Science.gov (United States)

    Molle, Alessandro; Goldberger, Joshua; Houssa, Michel; Xu, Yong; Zhang, Shou-Cheng; Akinwande, Deji

    2017-02-01

    Silicene, germanene and stanene are part of a monoelemental class of two-dimensional (2D) crystals termed 2D-Xenes (X = Si, Ge, Sn and so on) which, together with their ligand-functionalized derivatives referred to as Xanes, are comprised of group IVA atoms arranged in a honeycomb lattice - similar to graphene but with varying degrees of buckling. Their electronic structure ranges from trivial insulators, to semiconductors with tunable gaps, to semi-metallic, depending on the substrate, chemical functionalization and strain. More than a dozen different topological insulator states are predicted to emerge, including the quantum spin Hall state at room temperature, which, if realized, would enable new classes of nanoelectronic and spintronic devices, such as the topological field-effect transistor. The electronic structure can be tuned, for example, by changing the group IVA element, the degree of spin-orbit coupling, the functionalization chemistry or the substrate, making the 2D-Xene systems promising multifunctional 2D materials for nanotechnology. This Perspective highlights the current state of the art and future opportunities in the manipulation and stability of these materials, their functions and applications, and novel device concepts.

  12. Broken ergodicity in two-dimensional homogeneous magnetohydrodynamic turbulence

    International Nuclear Information System (INIS)

    Shebalin, John V.

    2010-01-01

    Two-dimensional (2D) homogeneous magnetohydrodynamic (MHD) turbulence has many of the same qualitative features as three-dimensional (3D) homogeneous MHD turbulence. These features include several ideal (i.e., nondissipative) invariants along with the phenomenon of broken ergodicity (defined as nonergodic behavior over a very long time). Broken ergodicity appears when certain modes act like random variables with mean values that are large compared to their standard deviations, indicating a coherent structure or dynamo. Recently, the origin of broken ergodicity in 3D MHD turbulence that is manifest in the lowest wavenumbers was found. Here, we study the origin of broken ergodicity in 2D MHD turbulence. It will be seen that broken ergodicity in ideal 2D MHD turbulence can be manifest in the lowest wavenumbers of a finite numerical model for certain initial conditions or in the highest wavenumbers for another set of initial conditions. The origins of broken ergodicity in an ideal 2D homogeneous MHD turbulence are found through an eigenanalysis of the covariance matrices of the probability density function and by an examination of the associated entropy functional. When the values of ideal invariants are kept fixed and grid size increases, it will be shown that the energy in a few large modes remains constant, while the energy in any other mode is inversely proportional to grid size. Also, as grid size increases, we find that broken ergodicity becomes manifest at more and more wavenumbers.

  13. Analysis of Mode I and Mode II Crack Growth Arrest Mechanism with Z-Fibre Pins in Composite Laminated Joint

    Science.gov (United States)

    Jeevan Kumar, N.; Ramesh Babu, P.

    2018-04-01

    This paper presents the numerical study of the mode I and mode II interlaminar crack growth arrest in hybrid laminated curved composite stiffened joint with Z-fibre reinforcement. A FE model of hybrid laminated skin-stiffener joint reinforced with Z-pins is developed to investigate the effect of Z- fibre pins on mode I and mode II crack growth where the delamination is embedded inbetween the skin and stiffener interface. A finite element model was developed using S4R element of a 4-node doubly curved thick shell elements to model the composite laminates and non linear interface elements to simulate the reinforcements. The numerical analyses revealed that Z-fibre pinning were effective in suppressing the delamination growth when propagated due to applied loads. Therefore, the Z-fibre technique effectively improves the crack growth resistance and hence arrests or delays crack growth extension.

  14. Non-Linear Non Stationary Analysis of Two-Dimensional Time-Series Applied to GRACE Data, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed innovative two-dimensional (2D) empirical mode decomposition (EMD) analysis was applied to NASA's Gravity Recovery and Climate Experiment (GRACE)...

  15. Atomically thin two-dimensional organic-inorganic hybrid perovskites

    Science.gov (United States)

    Dou, Letian; Wong, Andrew B.; Yu, Yi; Lai, Minliang; Kornienko, Nikolay; Eaton, Samuel W.; Fu, Anthony; Bischak, Connor G.; Ma, Jie; Ding, Tina; Ginsberg, Naomi S.; Wang, Lin-Wang; Alivisatos, A. Paul; Yang, Peidong

    2015-09-01

    Organic-inorganic hybrid perovskites, which have proved to be promising semiconductor materials for photovoltaic applications, have been made into atomically thin two-dimensional (2D) sheets. We report the solution-phase growth of single- and few-unit-cell-thick single-crystalline 2D hybrid perovskites of (C4H9NH3)2PbBr4 with well-defined square shape and large size. In contrast to other 2D materials, the hybrid perovskite sheets exhibit an unusual structural relaxation, and this structural change leads to a band gap shift as compared to the bulk crystal. The high-quality 2D crystals exhibit efficient photoluminescence, and color tuning could be achieved by changing sheet thickness as well as composition via the synthesis of related materials.

  16. Two-dimensional computer simulation of high intensity proton beams

    CERN Document Server

    Lapostolle, Pierre M

    1972-01-01

    A computer program has been developed which simulates the two- dimensional transverse behaviour of a proton beam in a focusing channel. The model is represented by an assembly of a few thousand 'superparticles' acted upon by their own self-consistent electric field and an external focusing force. The evolution of the system is computed stepwise in time by successively solving Poisson's equation and Newton's law of motion. Fast Fourier transform techniques are used for speed in the solution of Poisson's equation, while extensive area weighting is utilized for the accurate evaluation of electric field components. A computer experiment has been performed on the CERN CDC 6600 computer to study the nonlinear behaviour of an intense beam in phase space, showing under certain circumstances a filamentation due to space charge and an apparent emittance growth. (14 refs).

  17. Two-dimensional PCA-based human gait identification

    Science.gov (United States)

    Chen, Jinyan; Wu, Rongteng

    2012-11-01

    It is very necessary to recognize person through visual surveillance automatically for public security reason. Human gait based identification focus on recognizing human by his walking video automatically using computer vision and image processing approaches. As a potential biometric measure, human gait identification has attracted more and more researchers. Current human gait identification methods can be divided into two categories: model-based methods and motion-based methods. In this paper a two-Dimensional Principal Component Analysis and temporal-space analysis based human gait identification method is proposed. Using background estimation and image subtraction we can get a binary images sequence from the surveillance video. By comparing the difference of two adjacent images in the gait images sequence, we can get a difference binary images sequence. Every binary difference image indicates the body moving mode during a person walking. We use the following steps to extract the temporal-space features from the difference binary images sequence: Projecting one difference image to Y axis or X axis we can get two vectors. Project every difference image in the difference binary images sequence to Y axis or X axis difference binary images sequence we can get two matrixes. These two matrixes indicate the styles of one walking. Then Two-Dimensional Principal Component Analysis(2DPCA) is used to transform these two matrixes to two vectors while at the same time keep the maximum separability. Finally the similarity of two human gait images is calculated by the Euclidean distance of the two vectors. The performance of our methods is illustrated using the CASIA Gait Database.

  18. Numerical simulation of growth of flames formed in two-dimensional mixing layer. 2nd Report. Effect of dilution of fuel; Nijigen kongo sonai ni keiseisareta kaen no seicho ni kansuru suchi simulation. 2. Nenryo no kishaku ni yoru eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Noda, S [Toyohashi University of Technology, Aichi (Japan); Hashimoto, K [Sumitomo Metal Industries, Ltd., Osaka (Japan); Nakajima, T [Kobe University, Kobe (Japan). Faculty of Engineering

    1994-07-25

    The effect of fuel dilution on growth of flames formed in 2-D mixing layers was studied by numerical simulation. The methane mass fraction of fuel was adjusted to 1.0, 0.3 and 0.2 through dilution by nitrogen, while the oxygen mass fraction of an oxidizer was fixed at 0.27. Flame structure was complicated due to the flows separated by flame at the leading edge of flames, and three peaks of the second Damkohler number were observed. Fuel dilution by nitrogen caused blow-off of flames, and the mixing ratio of the fuel and oxidizer at the leading edge of flames was essential to blow-off of diffused flames. In the case where vortices were observed in a flow field, the first Damkohler number was important which was determined by the hydrodynamic characteristic time of coherent vortices and the chemical characteristic time of flame propagation based on the mixing ratio of the fuel and oxidizer at the leading edge of flames. The diffused flames were elongated by shearing force, and an exothermic reaction was suppressed and a flame stabilization decreased with a decrease in second Damkohler number. 10 refs., 9 figs., 1 tab.

  19. Two-dimensional beam-profile monitor using the Reticon MC510A array camera

    International Nuclear Information System (INIS)

    Gottschalk, B.

    1981-08-01

    A quantitative two-dimensional beam profile may be obtained from a scintillator viewed by a Reticon camera which uses a 32 x 32 array of photodiodes as its sensing element. In this note, CAMAC-oriented data acquisition electronics which allow one either to transmit the profile to a computer, or to use the monitor in a stand-alone mode are described

  20. Two-dimensional Nonlinear Simulations of Temperature-anisotropy Instabilities with a Proton-alpha Drift

    Science.gov (United States)

    Markovskii, S. A.; Chandran, Benjamin D. G.; Vasquez, Bernard J.

    2018-04-01

    We present two-dimensional hybrid simulations of proton-cyclotron and mirror instabilities in a proton-alpha plasma with particle-in-cell ions and a neutralizing electron fluid. The instabilities are driven by the protons with temperature perpendicular to the background magnetic field larger than the parallel temperature. The alpha particles with initially isotropic temperature have a nonzero drift speed with respect to the protons. The minor ions are known to influence the relative effect of the proton-cyclotron and mirror instabilities. In this paper, we show that the mirror mode can dominate the power spectrum at the nonlinear stage even if its linear growth rate is significantly lower than that of the proton-cyclotron mode. The proton-cyclotron instability combined with the alpha-proton drift is a possible cause of the nonzero magnetic helicity observed in the solar wind for fluctuations propagating nearly parallel to the magnetic field. Our simulations generally confirm this concept but reveal a complex helicity spectrum that is not anticipated from the linear theory of the instability.

  1. Evaluation of the secretion and release of vascular endothelial growth factor from two-dimensional culture and three-dimensional cell spheroids formed with stem cells and osteoprecursor cells.

    Science.gov (United States)

    Lee, Hyunjin; Lee, Sung-Il; Ko, Youngkyung; Park, Jun-Beom

    2018-05-18

    Co-culture has been applied in cell therapy, including stem cells, and has been reported to give enhanced functionality. In this study, stem-cell spheroids were formed in concave micromolds at different ratios of stem cells to osteoprecursor cells, and the amount of secretion of vascular endothelial growth factor (VEGF) was evaluated. Gingiva-derived stem cells and osteoprecursor cells in the amount of 6 × 105 were seeded on a 24-well culture plate or concave micromolds. The ratios of stem cells to osteoprecursor cells included: 0:4 (group 1), 1:3 (group 2), 2:2 (group 3), 3:1 (group 4), and 4:0 (group 5). The morphology of cells in a 2-dimensional culture (groups 1-5) showed a fibroblast-like appearance. The secretion of VEGF increased with the increase in stem cells, and a statistically significant increase was noted in groups 3, 4 and 5 when compared with the media-only group (p cells formed spheroids in concave microwells, and no noticeable change in the morphology was noted with the increase in stem cells. Spheroids containing stem cells were positive for the stem-cell markers SSEA-4. The secretion of VEGF from cell spheroids increased with the increase in stem cells. This study showed that cell spheroids formed with stem cells and osteoprecursor cells with different ratios, using microwells, had paracrine effects on the stem cells. The secretion of VEGF increased with the increase in stem cells. This stem-cell spheroid may be applied for tissue-engineering purposes.

  2. Topotactic transformations of superstructures: from thin films to two-dimensional networks to nested two-dimensional networks.

    Science.gov (United States)

    Guo, Chuan Fei; Cao, Sihai; Zhang, Jianming; Tang, Haoying; Guo, Shengming; Tian, Ye; Liu, Qian

    2011-06-01

    Design and synthesis of super-nanostructures is one of the key and prominent topics in nanotechnology. Here we propose a novel methodology for synthesizing complex hierarchical superstructures using sacrificial templates composed of ordered two-dimensional (2D) nanostructures through lattice-directed topotactic transformations. The fabricated superstructures are nested 2D orthogonal Bi(2)S(3) networks composed of nanorods. Further investigation indicates that the lattice matching between the product and sacrificial template is the dominant mechanism for the formation of the superstructures, which agrees well with the simulation results based on an anisotropic nucleation and growth analysis. Our approach may provide a promising way toward a lattice-directed nonlithographic nanofabrication technique for making functional porous nanoarchitectures and electronic devices. © 2011 American Chemical Society

  3. Dynamics of a two-dimensional order-disorder transition

    International Nuclear Information System (INIS)

    Sahni, P.S.; Dee, G.; Gunton, J.D.; Phani, M.; Lebowitz, J.L.; Kalos, M.

    1981-01-01

    We present results of a Monte Carlo study of the time development of a two-dimensional order-disorder model binary alloy following a quench to low temperature from a disordered, high-temperature state. The behavior is qualitatively quite similar to that seen in a recent study of a three-dimensional system. The structure function exhibits a scaling of the form K 2 (t)S(k,t) = G(k/K(t)) where the moment K(t) decreases with time approximately like t/sup -1/2/. If one interprets this moment as being inversely proportional to the domain size, the characteristic domain growth rate is proportional to t/sup -1/2/. Additional insight into this time evolution is obtained from studying the development of the short-range order, as well as from monitoring the growth of a compact ordered domain embedded in a region of opposite order. All these results are consistent with the picture of domain growth as proposed by Lifshitz and by Cahn and Allen

  4. Lie algebra contractions on two-dimensional hyperboloid

    International Nuclear Information System (INIS)

    Pogosyan, G. S.; Yakhno, A.

    2010-01-01

    The Inoenue-Wigner contraction from the SO(2, 1) group to the Euclidean E(2) and E(1, 1) group is used to relate the separation of variables in Laplace-Beltrami (Helmholtz) equations for the four corresponding two-dimensional homogeneous spaces: two-dimensional hyperboloids and two-dimensional Euclidean and pseudo-Euclidean spaces. We show how the nine systems of coordinates on the two-dimensional hyperboloids contracted to the four systems of coordinates on E 2 and eight on E 1,1 . The text was submitted by the authors in English.

  5. Numerical study of two-dimensional moist symmetric instability

    Directory of Open Access Journals (Sweden)

    M. Fantini

    2008-06-01

    Full Text Available The 2-D version of the non-hydrostatic fully compressible model MOLOCH developed at ISAC-CNR was used in idealized set-up to study the start-up and finite amplitude evolution of symmetric instability. The unstable basic state was designed by numerical integration of the equation which defines saturated equivalent potential vorticity qe*. We present the structure and growth rates of the linear modes both for a supersaturated initial state ("super"-linear mode and for a saturated one ("pseudo"-linear mode and the modifications induced on the base state by their finite amplitude evolution.

  6. Surface and Interface Engineering of Organometallic and Two Dimensional Semiconductor

    Science.gov (United States)

    Park, Jun Hong

    For over half a century, inorganic Si and III-V materials have led the modern semiconductor industry, expanding to logic transistor and optoelectronic applications. However, these inorganic materials have faced two different fundamental limitations, flexibility for wearable applications and scaling limitation as logic transistors. As a result, the organic and two dimensional have been studied intentionally for various fields. In the present dissertation, three different studies will be presented with followed order; (1) the chemical response of organic semiconductor in NO2 exposure. (2) The surface and stability of WSe2 in ambient air. (3) Deposition of dielectric on two dimensional materials using organometallic seeding layer. The organic molecules rely on the van der Waals interaction during growth of thin films, contrast to covalent bond inorganic semiconductors. Therefore, the morphology and electronic property at surface of organic semiconductor in micro scale is more sensitive to change in gaseous conditions. In addition, metal phthalocyanine, which is one of organic semiconductor materials, change their electronic property as reaction with gaseous analytes, suggesting as potential chemical sensing platforms. In the present part, the growth behavior of metal phthalocyanine and surface response to gaseous condition will be elucidated using scanning tunneling microscopy (STM). In second part, the surface of layered transition metal dichalcogenides and their chemical response to exposure ambient air will be investigated, using STM. Layered transition metal dichalcogenides (TMDs) have attracted widespread attention in the scientific community for electronic device applications because improved electrostatic gate control and suppression of short channel leakage resulted from their atomic thin body. To fabricate the transistor based on TMDs, TMDs should be exposed to ambient conditions, while the effect of air exposure has not been understood fully. In this part

  7. Growth of two-dimensional arrays of uncapped gold nanoparticles ...

    Indian Academy of Sciences (India)

    These nanoparticles have been prepared without using any kind of capping agent. Analysis by TEM showed discrete Au nanoparticles of 4 nm average diameter. AFM analysis also showed similar result. The TEM studies showed that these nanoparticles formed self-assembled coherent patterns with dimensions exceeding ...

  8. Particle simulation of a two-dimensional electrostatic plasma

    International Nuclear Information System (INIS)

    Patel, K.

    1989-01-01

    Computer simulation is a growing field of research and plasma physics is one of the important areas where it is being applied today. This report describes the particle method of simulating a two-dimensional electrostatic plasma. The methods used to discretise the plasma equations and integrate the equations of motion are outlined. The algorithm used in building a simulation program is described. The program is applied to simulating the Two-stream Instability occurring within an infinite plasma. The results of the simulation are presented. The growth rate of the instability as simulated is in excellent agreement with the growth rate as calculated using linear theory. Diagnostic techniques used in interpreting the data generated by the simulation program are discussed. A comparison of the computing environment of the ND and PC from a user's viewpoint is presented. It is observed that the PC is an acceptable computing tool for certain (non-trivial) physics problems, and that more extensive use of its computing power should be made. (author). 5 figs

  9. Beginning Introductory Physics with Two-Dimensional Motion

    Science.gov (United States)

    Huggins, Elisha

    2009-01-01

    During the session on "Introductory College Physics Textbooks" at the 2007 Summer Meeting of the AAPT, there was a brief discussion about whether introductory physics should begin with one-dimensional motion or two-dimensional motion. Here we present the case that by starting with two-dimensional motion, we are able to introduce a considerable…

  10. Two-dimensional black holes and non-commutative spaces

    International Nuclear Information System (INIS)

    Sadeghi, J.

    2008-01-01

    We study the effects of non-commutative spaces on two-dimensional black hole. The event horizon of two-dimensional black hole is obtained in non-commutative space up to second order of perturbative calculations. A lower limit for the non-commutativity parameter is also obtained. The observer in that limit in contrast to commutative case see two horizon

  11. Solution of the two-dimensional spectral factorization problem

    Science.gov (United States)

    Lawton, W. M.

    1985-01-01

    An approximation theorem is proven which solves a classic problem in two-dimensional (2-D) filter theory. The theorem shows that any continuous two-dimensional spectrum can be uniformly approximated by the squared modulus of a recursively stable finite trigonometric polynomial supported on a nonsymmetric half-plane.

  12. Two-dimensional Navier-Stokes turbulence in bounded domains

    NARCIS (Netherlands)

    Clercx, H.J.H.; van Heijst, G.J.F.

    In this review we will discuss recent experimental and numerical results of quasi-two-dimensional decaying and forced Navier–Stokes turbulence in bounded domains. We will give a concise overview of developments in two-dimensional turbulence research, with emphasis on the progress made during the

  13. Two-dimensional Navier-Stokes turbulence in bounded domains

    NARCIS (Netherlands)

    Clercx, H.J.H.; Heijst, van G.J.F.

    2009-01-01

    In this review we will discuss recent experimental and numerical results of quasi-two-dimensional decaying and forced Navier–Stokes turbulence in bounded domains. We will give a concise overview of developments in two-dimensional turbulence research, with emphasis on the progress made during the

  14. Photon management in two-dimensional disordered media.

    Science.gov (United States)

    Vynck, Kevin; Burresi, Matteo; Riboli, Francesco; Wiersma, Diederik S

    2012-12-01

    Elaborating reliable and versatile strategies for efficient light coupling between free space and thin films is of crucial importance for new technologies in energy efficiency. Nanostructured materials have opened unprecedented opportunities for light management, notably in thin-film solar cells. Efficient coherent light trapping has been accomplished through the careful design of plasmonic nanoparticles and gratings, resonant dielectric particles and photonic crystals. Alternative approaches have used randomly textured surfaces as strong light diffusers to benefit from their broadband and wide-angle properties. Here, we propose a new strategy for photon management in thin films that combines both advantages of an efficient trapping due to coherent optical effects and broadband/wide-angle properties due to disorder. Our approach consists of the excitation of electromagnetic modes formed by multiple light scattering and wave interference in two-dimensional random media. We show, by numerical calculations, that the spectral and angular responses of thin films containing disordered photonic patterns are intimately related to the in-plane light transport process and can be tuned through structural correlations. Our findings, which are applicable to all waves, are particularly suited for improving the absorption efficiency of thin-film solar cells and can provide a new approach for high-extraction-efficiency light-emitting diodes.

  15. Coherent and radiative couplings through two-dimensional structured environments

    Science.gov (United States)

    Galve, F.; Zambrini, R.

    2018-03-01

    We study coherent and radiative interactions induced among two or more quantum units by coupling them to two-dimensional (2D) lattices acting as structured environments. This model can be representative of atoms trapped near photonic crystal slabs, trapped ions in Coulomb crystals, or to surface acoustic waves on piezoelectric materials, cold atoms on state-dependent optical lattices, or even circuit QED architectures, to name a few. We compare coherent and radiative contributions for the isotropic and directional regimes of emission into the lattice, for infinite and finite lattices, highlighting their differences and existing pitfalls, e.g., related to long-time or large-lattice limits. We relate the phenomenon of directionality of emission with linear-shaped isofrequency manifolds in the dispersion relation, showing a simple way to disrupt it. For finite lattices, we study further details such as the scaling of resonant number of lattice modes for the isotropic and directional regimes, and relate this behavior with known van Hove singularities in the infinite lattice limit. Furthermore, we export the understanding of emission dynamics with the decay of entanglement for two quantum, atomic or bosonic, units coupled to the 2D lattice. We analyze in some detail completely subradiant configurations of more than two atoms, which can occur in the finite lattice scenario, in contrast with the infinite lattice case. Finally, we demonstrate that induced coherent interactions for dark states are zero for the finite lattice.

  16. Almost two-dimensional treatment of drift wave turbulence

    International Nuclear Information System (INIS)

    Albert, J.M.; Similon, P.L.; Sudan, R.N.

    1990-01-01

    The approximation of two-dimensionality is studied and extended for electrostatic drift wave turbulence in a three-dimensional, magnetized plasma. It is argued on the basis of the direct interaction approximation that in the absence of parallel viscosity, purely 2-D solutions exist for which only modes with k parallel =0 are excited, but that the 2-D spectrum is unstable to perturbations at nonzero k parallel . A 1-D equation for the parallel profile g k perpendicular (k parallel ) of the saturated spectrum at steady state is derived and solved, allowing for parallel viscosity; the spectrum has finite width in k parallel , and hence finite parallel correlation length, as a result of nonlinear coupling. The enhanced energy dissipation rate, a 3-D effect, may be incorporated in the 2-D approximation by a suitable renormalization of the linear dissipation term. An algorithm is presented that reduces the 3-D problem to coupled 1- and 2-D problems. Numerical results from a 2-D spectral direct simulation, thus modified, are compared with the results from the corresponding 3-D (unmodified) simulation for a specific model of drift wave excitation. Damping at high k parallel is included. It is verified that the 1-D solution for g k perpendicular (k parallel ) accurately describes the shape and width of the 3-D spectrum, and that the modified 2-D simulation gives a good estimate of the 3-D energy saturation level and distribution E(k perpendicular )

  17. Theory of boundary-free two-dimensional dust clusters

    International Nuclear Information System (INIS)

    Tsytovich, V.N.; Gousein-zade, N.G.; Morfill, G.E.

    2006-01-01

    It is shown theoretically that a stable two-dimensional (2D) grain cluster can exist in plasmas without external confinement if the shadow attraction of grains is taken into account. These are considered as boundary-free clusters. The equilibrium radius of the clusters is investigated numerically. It is found that it is rapidly decreasing with an increase of the attraction coefficient and with an increase of the number of grains N in the cluster. Comparison of energies of one shell cluster containing N grains with the energies of a cluster with N-1 grains in the shell and an additional one grain in the center as functions of the attraction coefficient is used to find the magic numbers for new shell creation. It is demonstrated that a dissociation of the cluster in several smaller clusters requires less energy than a removal of one of the grains from the cluster. The computations were performed for the Debye screening and for the nonlinear screening models and show that the structure of the clusters is sensitive to the type of screening. Frequencies of all collective modes of the 2D boundary-free clusters are calculated up to N=7 grains in the cluster for the case where all grains form one shell cluster and for the case where N=6 grains form one shell cluster and one of the grains is located at the center of the cluster. The frequencies of the modes increase with a decrease of the cluster radius. Stable and unstable modes are investigated as a function of the attraction coefficient. The presence of instability indicates that this type of equilibrium cluster does not correspond to the minimum energy in all directions and will be converted into another stable configuration. The universal magic number N m of grains in one shell cluster, such that for N=N m +1 the modes of the shell start to be unstable and the cluster converts to the cluster with N m grains in the shell and one grain in the center, is found for both the Yukawa screening and for the nonlinear screening

  18. Optimizing separations in online comprehensive two-dimensional liquid chromatography.

    Science.gov (United States)

    Pirok, Bob W J; Gargano, Andrea F G; Schoenmakers, Peter J

    2018-01-01

    Online comprehensive two-dimensional liquid chromatography has become an attractive option for the analysis of complex nonvolatile samples found in various fields (e.g. environmental studies, food, life, and polymer sciences). Two-dimensional liquid chromatography complements the highly popular hyphenated systems that combine liquid chromatography with mass spectrometry. Two-dimensional liquid chromatography is also applied to the analysis of samples that are not compatible with mass spectrometry (e.g. high-molecular-weight polymers), providing important information on the distribution of the sample components along chemical dimensions (molecular weight, charge, lipophilicity, stereochemistry, etc.). Also, in comparison with conventional one-dimensional liquid chromatography, two-dimensional liquid chromatography provides a greater separation power (peak capacity). Because of the additional selectivity and higher peak capacity, the combination of two-dimensional liquid chromatography with mass spectrometry allows for simpler mixtures of compounds to be introduced in the ion source at any given time, improving quantitative analysis by reducing matrix effects. In this review, we summarize the rationale and principles of two-dimensional liquid chromatography experiments, describe advantages and disadvantages of combining different selectivities and discuss strategies to improve the quality of two-dimensional liquid chromatography separations. © 2017 The Authors. Journal of Separation Science published by WILEY-VCH Verlag GmbH & Co. KGaA.

  19. Exploring two-dimensional electron gases with two-dimensional Fourier transform spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Paul, J.; Dey, P.; Karaiskaj, D., E-mail: karaiskaj@usf.edu [Department of Physics, University of South Florida, 4202 East Fowler Ave., Tampa, Florida 33620 (United States); Tokumoto, T.; Hilton, D. J. [Department of Physics, University of Alabama at Birmingham, Birmingham, Alabama 35294 (United States); Reno, J. L. [CINT, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

    2014-10-07

    The dephasing of the Fermi edge singularity excitations in two modulation doped single quantum wells of 12 nm and 18 nm thickness and in-well carrier concentration of ∼4 × 10{sup 11} cm{sup −2} was carefully measured using spectrally resolved four-wave mixing (FWM) and two-dimensional Fourier transform (2DFT) spectroscopy. Although the absorption at the Fermi edge is broad at this doping level, the spectrally resolved FWM shows narrow resonances. Two peaks are observed separated by the heavy hole/light hole energy splitting. Temperature dependent “rephasing” (S{sub 1}) 2DFT spectra show a rapid linear increase of the homogeneous linewidth with temperature. The dephasing rate increases faster with temperature in the narrower 12 nm quantum well, likely due to an increased carrier-phonon scattering rate. The S{sub 1} 2DFT spectra were measured using co-linear, cross-linear, and co-circular polarizations. Distinct 2DFT lineshapes were observed for co-linear and cross-linear polarizations, suggesting the existence of polarization dependent contributions. The “two-quantum coherence” (S{sub 3}) 2DFT spectra for the 12 nm quantum well show a single peak for both co-linear and co-circular polarizations.

  20. Raman scattering in a two-dimensional Fermi liquid with spin-orbit coupling

    Science.gov (United States)

    Maiti, Saurabh; Maslov, Dmitrii L.

    2017-04-01

    We present a microscopic theory of Raman scattering in a two-dimensional Fermi liquid (FL) with Rashba and Dresselhaus types of spin-orbit coupling and subject to an in-plane magnetic field (B ⃗). In the long-wavelength limit, the Raman spectrum probes the collective modes of such a FL: the chiral spin waves. The characteristic features of these modes are a linear-in-q term in the dispersion and the dependence of the mode frequency on the directions of both q ⃗ and B ⃗. All of these features have been observed in recent Raman experiments on Cd1 -xMnxTe quantum wells.

  1. Elementary excitations and quasi-two-dimensional behaviour in a GaAs field effect transistor

    International Nuclear Information System (INIS)

    Tomak, M.; Sernelius, B.E.; Berggren, K.F.

    1983-09-01

    The elementary excitation modes in a narrow channel of conducting electrons in a special GaAs FET are evaluated within the RPA-approximation. The system is found to be quasi-two-dimensional when the width of the channel is small, i.e. there are collective excitations with a dispersion very close to the strictly 2D form. In addition to the low-lying quasi-2D-mode there are higher collective modes associated with the sub-band structure of the device. (author)

  2. Functional inks and printing of two-dimensional materials.

    Science.gov (United States)

    Hu, Guohua; Kang, Joohoon; Ng, Leonard W T; Zhu, Xiaoxi; Howe, Richard C T; Jones, Christopher G; Hersam, Mark C; Hasan, Tawfique

    2018-05-08

    Graphene and related two-dimensional materials provide an ideal platform for next generation disruptive technologies and applications. Exploiting these solution-processed two-dimensional materials in printing can accelerate this development by allowing additive patterning on both rigid and conformable substrates for flexible device design and large-scale, high-speed, cost-effective manufacturing. In this review, we summarise the current progress on ink formulation of two-dimensional materials and the printable applications enabled by them. We also present our perspectives on their research and technological future prospects.

  3. Third sound in one and two dimensional modulated structures

    International Nuclear Information System (INIS)

    Komuro, T.; Kawashima, H., Shirahama, K.; Kono, K.

    1996-01-01

    An experimental technique is developed to study acoustic transmission in one and two dimensional modulated structures by employing third sound of a superfluid helium film. In particular, the Penrose lattice, which is a two dimensional quasiperiodic structure, is studied. In two dimensions, the scattering of third sound is weaker than in one dimension. Nevertheless, the authors find that the transmission spectrum in the Penrose lattice, which is a two dimensional prototype of the quasicrystal, is observable if the helium film thickness is chosen around 5 atomic layers. The transmission spectra in the Penrose lattice are explained in terms of dynamical theory of diffraction

  4. ONE-DIMENSIONAL AND TWO-DIMENSIONAL LEADERSHIP STYLES

    Directory of Open Access Journals (Sweden)

    Nikola Stefanović

    2007-06-01

    Full Text Available In order to motivate their group members to perform certain tasks, leaders use different leadership styles. These styles are based on leaders' backgrounds, knowledge, values, experiences, and expectations. The one-dimensional styles, used by many world leaders, are autocratic and democratic styles. These styles lie on the two opposite sides of the leadership spectrum. In order to precisely define the leadership styles on the spectrum between the autocratic leadership style and the democratic leadership style, leadership theory researchers use two dimensional matrices. The two-dimensional matrices define leadership styles on the basis of different parameters. By using these parameters, one can identify two-dimensional styles.

  5. Two-dimensional materials for novel liquid separation membranes

    Science.gov (United States)

    Ying, Yulong; Yang, Yefeng; Ying, Wen; Peng, Xinsheng

    2016-08-01

    Demand for a perfect molecular-level separation membrane with ultrafast permeation and a robust mechanical property for any kind of species to be blocked in water purification and desalination is urgent. In recent years, due to their intrinsic characteristics, such as a unique mono-atom thick structure, outstanding mechanical strength and excellent flexibility, as well as facile and large-scale production, graphene and its large family of two-dimensional (2D) materials are regarded as ideal membrane materials for ultrafast molecular separation. A perfect separation membrane should be as thin as possible to maximize its flux, mechanically robust and without failure even if under high loading pressure, and have a narrow nanochannel size distribution to guarantee its selectivity. The latest breakthrough in 2D material-based membranes will be reviewed both in theories and experiments, including their current state-of-the-art fabrication, structure design, simulation and applications. Special attention will be focused on the designs and strategies employed to control microstructures to enhance permeation and selectivity for liquid separation. In addition, critical views on the separation mechanism within two-dimensional material-based membranes will be provided based on a discussion of the effects of intrinsic defects during growth, predefined nanopores and nanochannels during subsequent fabrication processes, the interlayer spacing of stacking 2D material flakes and the surface charge or functional groups. Furthermore, we will summarize the significant progress of these 2D material-based membranes for liquid separation in nanofiltration/ultrafiltration and pervaporation. Lastly, we will recall issues requiring attention, and discuss existing questionable conclusions in some articles and emerging challenges. This review will serve as a valuable platform to provide a compact source of relevant and timely information about the development of 2D material-based membranes as

  6. Two-dimensional materials for novel liquid separation membranes.

    Science.gov (United States)

    Ying, Yulong; Yang, Yefeng; Ying, Wen; Peng, Xinsheng

    2016-08-19

    Demand for a perfect molecular-level separation membrane with ultrafast permeation and a robust mechanical property for any kind of species to be blocked in water purification and desalination is urgent. In recent years, due to their intrinsic characteristics, such as a unique mono-atom thick structure, outstanding mechanical strength and excellent flexibility, as well as facile and large-scale production, graphene and its large family of two-dimensional (2D) materials are regarded as ideal membrane materials for ultrafast molecular separation. A perfect separation membrane should be as thin as possible to maximize its flux, mechanically robust and without failure even if under high loading pressure, and have a narrow nanochannel size distribution to guarantee its selectivity. The latest breakthrough in 2D material-based membranes will be reviewed both in theories and experiments, including their current state-of-the-art fabrication, structure design, simulation and applications. Special attention will be focused on the designs and strategies employed to control microstructures to enhance permeation and selectivity for liquid separation. In addition, critical views on the separation mechanism within two-dimensional material-based membranes will be provided based on a discussion of the effects of intrinsic defects during growth, predefined nanopores and nanochannels during subsequent fabrication processes, the interlayer spacing of stacking 2D material flakes and the surface charge or functional groups. Furthermore, we will summarize the significant progress of these 2D material-based membranes for liquid separation in nanofiltration/ultrafiltration and pervaporation. Lastly, we will recall issues requiring attention, and discuss existing questionable conclusions in some articles and emerging challenges. This review will serve as a valuable platform to provide a compact source of relevant and timely information about the development of 2D material-based membranes as

  7. Multisoliton formula for completely integrable two-dimensional systems

    International Nuclear Information System (INIS)

    Chudnovsky, D.V.; Chudnovsky, G.V.

    1979-01-01

    For general two-dimensional completely integrable systems, the exact formulae for multisoliton type solutions are given. The formulae are obtained algebrically from solutions of two linear partial differential equations

  8. Two-dimensional electronic femtosecond stimulated Raman spectroscopy

    Directory of Open Access Journals (Sweden)

    Ogilvie J.P.

    2013-03-01

    Full Text Available We report two-dimensional electronic spectroscopy with a femtosecond stimulated Raman scattering probe. The method reveals correlations between excitation energy and excited state vibrational structure following photoexcitation. We demonstrate the method in rhodamine 6G.

  9. Micromachined two dimensional resistor arrays for determination of gas parameters

    NARCIS (Netherlands)

    van Baar, J.J.J.; Verwey, Willem B.; Dijkstra, Mindert; Dijkstra, Marcel; Wiegerink, Remco J.; Lammerink, Theodorus S.J.; Krijnen, Gijsbertus J.M.; Elwenspoek, Michael Curt

    A resistive sensor array is presented for two dimensional temperature distribution measurements in a micromachined flow channel. This allows simultaneous measurement of flow velocity and fluid parameters, like thermal conductivity, diffusion coefficient and viscosity. More general advantages of

  10. Generalized similarity method in unsteady two-dimensional MHD ...

    African Journals Online (AJOL)

    user

    International Journal of Engineering, Science and Technology. Vol. 1, No. 1, 2009 ... temperature two-dimensional MHD laminar boundary layer of incompressible fluid. ...... Φ η is Blasius solution for stationary boundary layer on the plate,. ( ). 0.

  11. Negative refraction imaging of solid acoustic waves by two-dimensional three-component phononic crystal

    International Nuclear Information System (INIS)

    Li Jing; Liu Zhengyou; Qiu Chunyin

    2008-01-01

    By using of the multiple scattering methods, we study the negative refraction imaging effect of solid acoustic waves by two-dimensional three-component phononic crystals composed of coated solid inclusions placed in solid matrix. We show that localized resonance mechanism brings on a group of flat single-mode bands in low-frequency region, which provides two equivalent frequency surfaces (EFS) close to circular. The two constant frequency surfaces correspond to two Bloch modes, a right-handed and a left-handed, whose leading mode are respectively transverse (T) and longitudinal (L) modes. The negative refraction behaviors of the two kinds of modes have been demonstrated by simulation of a Gaussian beam through a finite system. High-quality far-field imaging by a planar lens for transverse or longitudinal waves has been realized separately. This three-component phononic crystal may thus serve as a mode selector in negative refraction imaging of solid acoustic waves

  12. Topological aspect of disclinations in two-dimensional crystals

    International Nuclear Information System (INIS)

    Wei-Kai, Qi; Tao, Zhu; Yong, Chen; Ji-Rong, Ren

    2009-01-01

    By using topological current theory, this paper studies the inner topological structure of disclinations during the melting of two-dimensional systems. From two-dimensional elasticity theory, it finds that there are topological currents for topological defects in homogeneous equation. The evolution of disclinations is studied, and the branch conditions for generating, annihilating, crossing, splitting and merging of disclinations are given. (the physics of elementary particles and fields)

  13. Structures of two-dimensional three-body systems

    International Nuclear Information System (INIS)

    Ruan, W.Y.; Liu, Y.Y.; Bao, C.G.

    1996-01-01

    Features of the structure of L = 0 states of a two-dimensional three-body model system have been investigated. Three types of permutation symmetry of the spatial part, namely symmetric, antisymmetric, and mixed, have been considered. A comparison has been made between the two-dimensional system and the corresponding three-dimensional one. The effect of symmetry on microscopic structures is emphasized. (author)

  14. Controlled Interactions between Two Dimensional Layered Inorganic Nanosheets and Polymers

    Science.gov (United States)

    2016-06-15

    AFRL-AFOSR-JP-TR-2016-0071 Controlled Interactions between Two Dimensional Layered Inorganic Nanosheets and Polymers Cheolmin Park YONSEI UNIVERSITY...Interactions between Two Dimensional Layered Inorganic Nanosheets and Polymers 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA2386-14-1-4054 5c.  PROGRAM ELEMENT...prospects for a variety of emerging applications in a broad range of fields, such as electronics, energy conversion and storage, catalysis and polymer

  15. Border-crossing model for the diffusive coarsening of two-dimensional and quasi-two-dimensional wet foams

    Science.gov (United States)

    Schimming, C. D.; Durian, D. J.

    2017-09-01

    For dry foams, the transport of gas from small high-pressure bubbles to large low-pressure bubbles is dominated by diffusion across the thin soap films separating neighboring bubbles. For wetter foams, the film areas become smaller as the Plateau borders and vertices inflate with liquid. So-called "border-blocking" models can explain some features of wet-foam coarsening based on the presumption that the inflated borders totally block the gas flux; however, this approximation dramatically fails in the wet or unjamming limit where the bubbles become close-packed spheres and coarsening proceeds even though there are no films. Here, we account for the ever-present border-crossing flux by a new length scale defined by the average gradient of gas concentration inside the borders. We compute that it is proportional to the geometric average of film and border thicknesses, and we verify this scaling by numerical solution of the diffusion equation. We similarly consider transport across inflated vertices and surface Plateau borders in quasi-two-dimensional foams. And we show how the d A /d t =K0(n -6 ) von Neumann law is modified by the appearance of terms that depend on bubble size and shape as well as the concentration gradient length scales. Finally, we use the modified von Neumann law to compute the growth rate of the average bubble area, which is not constant.

  16. Influence of Mixed Mode I-Mode II Loading on Fatigue Delamination Growth Characteristics of a Graphite Epoxy Tape Laminate

    Science.gov (United States)

    Ratcliffe, James G.; Johnston, William M., Jr.

    2014-01-01

    Mixed mode I-mode II interlaminar tests were conducted on IM7/8552 tape laminates using the mixed-mode bending test. Three mixed mode ratios, G(sub II)/G(sub T) = 0.2, 0.5, and 0.8, were considered. Tests were performed at all three mixed-mode ratios under quasi-static and cyclic loading conditions, where the former static tests were used to determine initial loading levels for the latter fatigue tests. Fatigue tests at each mixed-mode ratio were performed at four loading levels, Gmax, equal to 0.5G(sub c), 0.4G(sub c), 0.3G(sub c), and 0.2G(sub c), where G(sub c) is the interlaminar fracture toughness of the corresponding mixed-mode ratio at which a test was performed. All fatigue tests were performed using constant-amplitude load control and delamination growth was automatically documented using compliance solutions obtained from the corresponding quasi-static tests. Static fracture toughness data yielded a mixed-mode delamination criterion that exhibited monotonic increase in Gc with mixed-mode ratio, G(sub II)/G(sub T). Fatigue delamination onset parameters varied monotonically with G(sub II)/G(sub T), which was expected based on the fracture toughness data. Analysis of non-normalized data yielded a monotonic change in Paris law exponent with mode ratio. This was not the case when normalized data were analyzed. Fatigue data normalized by the static R-curve were most affected in specimens tested at G(sub II)/G(sub T)=0.2 (this process has little influence on the other data). In this case, the normalized data yielded a higher delamination growth rate compared to the raw data for a given loading level. Overall, fiber bridging appeared to be the dominant mechanism, affecting delamination growth rates in specimens tested at different load levels and differing mixed-mode ratios.

  17. The theory of critical phenomena in two-dimensional systems

    International Nuclear Information System (INIS)

    Olvera de la C, M.

    1981-01-01

    An exposition of the theory of critical phenomena in two-dimensional physical systems is presented. The first six chapters deal with the mean field theory of critical phenomena, scale invariance of the thermodynamic functions, Kadanoff's spin block construction, Wilson's renormalization group treatment of critical phenomena in configuration space, and the two-dimensional Ising model on a triangular lattice. The second part of this work is made of four chapters devoted to the application of the ideas expounded in the first part to the discussion of critical phenomena in superfluid films, two-dimensional crystals and the two-dimensional XY model of magnetic systems. Chapters seven to ten are devoted to the following subjects: analysis of long range order in one, two, and three-dimensional physical systems. Topological defects in the XY model, in superfluid films and in two-dimensional crystals. The Thouless-Kosterlitz iterated mean field theory of the dipole gas. The renormalization group treatment of the XY model, superfluid films and two-dimensional crystal. (author)

  18. Two-dimensional multifractal cross-correlation analysis

    International Nuclear Information System (INIS)

    Xi, Caiping; Zhang, Shuning; Xiong, Gang; Zhao, Huichang; Yang, Yonghong

    2017-01-01

    Highlights: • We study the mathematical models of 2D-MFXPF, 2D-MFXDFA and 2D-MFXDMA. • Present the definition of the two-dimensional N 2 -partitioned multiplicative cascading process. • Do the comparative analysis of 2D-MC by 2D-MFXPF, 2D-MFXDFA and 2D-MFXDMA. • Provide a reference on the choice and parameter settings of these methods in practice. - Abstract: There are a number of situations in which several signals are simultaneously recorded in complex systems, which exhibit long-term power-law cross-correlations. This paper presents two-dimensional multifractal cross-correlation analysis based on the partition function (2D-MFXPF), two-dimensional multifractal cross-correlation analysis based on the detrended fluctuation analysis (2D-MFXDFA) and two-dimensional multifractal cross-correlation analysis based on the detrended moving average analysis (2D-MFXDMA). We apply these methods to pairs of two-dimensional multiplicative cascades (2D-MC) to do a comparative study. Then, we apply the two-dimensional multifractal cross-correlation analysis based on the detrended fluctuation analysis (2D-MFXDFA) to real images and unveil intriguing multifractality in the cross correlations of the material structures. At last, we give the main conclusions and provide a valuable reference on how to choose the multifractal algorithms in the potential applications in the field of SAR image classification and detection.

  19. Two-Dimensional Materials for Sensing: Graphene and Beyond

    Directory of Open Access Journals (Sweden)

    Seba Sara Varghese

    2015-09-01

    Full Text Available Two-dimensional materials have attracted great scientific attention due to their unusual and fascinating properties for use in electronics, spintronics, photovoltaics, medicine, composites, etc. Graphene, transition metal dichalcogenides such as MoS2, phosphorene, etc., which belong to the family of two-dimensional materials, have shown great promise for gas sensing applications due to their high surface-to-volume ratio, low noise and sensitivity of electronic properties to the changes in the surroundings. Two-dimensional nanostructured semiconducting metal oxide based gas sensors have also been recognized as successful gas detection devices. This review aims to provide the latest advancements in the field of gas sensors based on various two-dimensional materials with the main focus on sensor performance metrics such as sensitivity, specificity, detection limit, response time, and reversibility. Both experimental and theoretical studies on the gas sensing properties of graphene and other two-dimensional materials beyond graphene are also discussed. The article concludes with the current challenges and future prospects for two-dimensional materials in gas sensor applications.

  20. Pulsating strings from two-dimensional CFT on (T4N/S(N

    Directory of Open Access Journals (Sweden)

    Carlos Cardona

    2015-04-01

    Full Text Available We propose a state from the two-dimensional conformal field theory on the orbifold (T4N/S(N as a dual description for a pulsating string moving in AdS3. We show that, up to first order in the deforming parameter, the energy in both descriptions has the same dependence on the mode number, but with a non-trivial function of the coupling.

  1. Fatigue crack growth in mode II of adhesively joined composites

    DEFF Research Database (Denmark)

    Biel, Anders; Toftegaard, Helmuth Langmaack

    2017-01-01

    , experiments are performed to derive material data for a crack propagation in shear i.e. in mode II. The shear loading of the crack is achieved by use of double cantilever beam specimens loaded with uneven bending moments. The experiments are performed under a constant cyclic displacement. An initial mode I...... loading is used to make the crack start in the adhesive. The crack length is measured using a load synchronized camera. Due to the shear loading the crack deviates from the adhesive layer into the laminate. A stable crack propagation is detected in the laminate. No influence have been detected due...... to an increasing crack length. It is also observed that the crack is trapped in the laminate; if the loading is changed to mode I the crack continues to propagate in the laminate....

  2. Common mode noise on the main Tevatron bus and associated beam emittance growth

    International Nuclear Information System (INIS)

    Zhang, P.; Johnson, R.P.; Kuchnir, M.; Siergiej, D.; Wolff, D.

    1991-05-01

    Overlap of betatron tune frequencies with the power supply noise spectrum can cause transverse beam emittance growth in a storage ring. We have studied this effect for tunes near the integer, where the betatron frequency is low. By injecting noise onto the main power supply bus, it was determined that common mode noise was the dominant source of emittance growth. A noise suppression feed-back loop was then used to reduce the noise and the emittance growth. These experiments are described as are investigations of the common mode propagation along the Tevatron bus and measurements of the fields generated by common mode excitation of isolated Tevatron magnets. 3 refs., 4 figs

  3. Temperature-Driven Change in the Unstable Growth Mode on Patterned GaAs(001)

    International Nuclear Information System (INIS)

    Tadayyon-Eslami, T.; Phaneuf, R. J.; Kan, H.-C.; Calhoun, L. C.

    2006-01-01

    We observe a dramatic change in the unstable growth mode during GaAs molecular beam epitaxy on patterned GaAs(001) as the temperature is lowered through approximately 540 deg. C, roughly coincident with the preroughening temperature. Observations of the As 2 flux dependence, however, rule out thermodynamic preroughening as driving the growth mode change. Similar observations rule out the change in surface reconstruction as the cause. Instead, we find evidence that the change in the unstable growth mode can be explained by a competition between the decreased adatom collection rate on small terraces and a small anisotropic barrier to adatom diffusion downward across step bunches

  4. Traditional Semiconductors in the Two-Dimensional Limit.

    Science.gov (United States)

    Lucking, Michael C; Xie, Weiyu; Choe, Duk-Hyun; West, Damien; Lu, Toh-Ming; Zhang, S B

    2018-02-23

    Interest in two-dimensional materials has exploded in recent years. Not only are they studied due to their novel electronic properties, such as the emergent Dirac fermion in graphene, but also as a new paradigm in which stacking layers of distinct two-dimensional materials may enable different functionality or devices. Here, through first-principles theory, we reveal a large new class of two-dimensional materials which are derived from traditional III-V, II-VI, and I-VII semiconductors. It is found that in the ultrathin limit the great majority of traditional binary semiconductors studied (a series of 28 semiconductors) are not only kinetically stable in a two-dimensional double layer honeycomb structure, but more energetically stable than the truncated wurtzite or zinc-blende structures associated with three dimensional bulk. These findings both greatly increase the landscape of two-dimensional materials and also demonstrate that in the double layer honeycomb form, even ordinary semiconductors, such as GaAs, can exhibit exotic topological properties.

  5. Two-dimensional analytic weighting functions for limb scattering

    Science.gov (United States)

    Zawada, D. J.; Bourassa, A. E.; Degenstein, D. A.

    2017-10-01

    Through the inversion of limb scatter measurements it is possible to obtain vertical profiles of trace species in the atmosphere. Many of these inversion methods require what is often referred to as weighting functions, or derivatives of the radiance with respect to concentrations of trace species in the atmosphere. Several radiative transfer models have implemented analytic methods to calculate weighting functions, alleviating the computational burden of traditional numerical perturbation methods. Here we describe the implementation of analytic two-dimensional weighting functions, where derivatives are calculated relative to atmospheric constituents in a two-dimensional grid of altitude and angle along the line of sight direction, in the SASKTRAN-HR radiative transfer model. Two-dimensional weighting functions are required for two-dimensional inversions of limb scatter measurements. Examples are presented where the analytic two-dimensional weighting functions are calculated with an underlying one-dimensional atmosphere. It is shown that the analytic weighting functions are more accurate than ones calculated with a single scatter approximation, and are orders of magnitude faster than a typical perturbation method. Evidence is presented that weighting functions for stratospheric aerosols calculated under a single scatter approximation may not be suitable for use in retrieval algorithms under solar backscatter conditions.

  6. Atom-field interaction in the single-quantum limit in a two dimensional travelling-wave cavity

    International Nuclear Information System (INIS)

    Youn, Sun Hyun; Chough, Young Tak; An, Kyung Won

    2003-01-01

    We analyze the interaction of an atom with two dimensional travelling-wave cavity modes in the strong coupling region, with the quantized atomic center of mass motion taken into account. Analytic and numerical calculation shows that the atom in two independent pairs of travelling wave modes can be made to interact only with a particular travelling mode by matching the initial momentum and the detuning of the cavities. We also numerically investigate the atomic momentum deflection in the cavities

  7. Dynamical class of a two-dimensional plasmonic Dirac system.

    Science.gov (United States)

    Silva, Érica de Mello

    2015-10-01

    A current goal in plasmonic science and technology is to figure out how to manage the relaxational dynamics of surface plasmons in graphene since its damping constitutes a hinder for the realization of graphene-based plasmonic devices. In this sense we believe it might be of interest to enlarge the knowledge on the dynamical class of two-dimensional plasmonic Dirac systems. According to the recurrence relations method, different systems are said to be dynamically equivalent if they have identical relaxation functions at all times, and such commonality may lead to deep connections between seemingly unrelated physical systems. We employ the recurrence relations approach to obtain relaxation and memory functions of density fluctuations and show that a two-dimensional plasmonic Dirac system at long wavelength and zero temperature belongs to the same dynamical class of standard two-dimensional electron gas and classical harmonic oscillator chain with an impurity mass.

  8. Hamiltonian formalism of two-dimensional Vlasov kinetic equation.

    Science.gov (United States)

    Pavlov, Maxim V

    2014-12-08

    In this paper, the two-dimensional Benney system describing long wave propagation of a finite depth fluid motion and the multi-dimensional Russo-Smereka kinetic equation describing a bubbly flow are considered. The Hamiltonian approach established by J. Gibbons for the one-dimensional Vlasov kinetic equation is extended to a multi-dimensional case. A local Hamiltonian structure associated with the hydrodynamic lattice of moments derived by D. J. Benney is constructed. A relationship between this hydrodynamic lattice of moments and the two-dimensional Vlasov kinetic equation is found. In the two-dimensional case, a Hamiltonian hydrodynamic lattice for the Russo-Smereka kinetic model is constructed. Simple hydrodynamic reductions are presented.

  9. Control Operator for the Two-Dimensional Energized Wave Equation

    Directory of Open Access Journals (Sweden)

    Sunday Augustus REJU

    2006-07-01

    Full Text Available This paper studies the analytical model for the construction of the two-dimensional Energized wave equation. The control operator is given in term of space and time t independent variables. The integral quadratic objective cost functional is subject to the constraint of two-dimensional Energized diffusion, Heat and a source. The operator that shall be obtained extends the Conjugate Gradient method (ECGM as developed by Hestenes et al (1952, [1]. The new operator enables the computation of the penalty cost, optimal controls and state trajectories of the two-dimensional energized wave equation when apply to the Conjugate Gradient methods in (Waziri & Reju, LEJPT & LJS, Issues 9, 2006, [2-4] to appear in this series.

  10. Velocity and Dispersion for a Two-Dimensional Random Walk

    International Nuclear Information System (INIS)

    Li Jinghui

    2009-01-01

    In the paper, we consider the transport of a two-dimensional random walk. The velocity and the dispersion of this two-dimensional random walk are derived. It mainly show that: (i) by controlling the values of the transition rates, the direction of the random walk can be reversed; (ii) for some suitably selected transition rates, our two-dimensional random walk can be efficient in comparison with the one-dimensional random walk. Our work is motivated in part by the challenge to explain the unidirectional transport of motor proteins. When the motor proteins move at the turn points of their tracks (i.e., the cytoskeleton filaments and the DNA molecular tubes), some of our results in this paper can be used to deal with the problem. (general)

  11. Oblique propagation of nonlinear hydromagnetic waves: One- and two-dimensional behavior

    International Nuclear Information System (INIS)

    Malara, F.; Elaoufir, J.

    1991-01-01

    The one- and two-dimensional behavior of obliquely propagating hydromagnetic waves is analyzed by means of analytical theory and numerical simulations. It is shown that the nonlinear evolution of a one-dimensional MHD wave leads to the formation of a rotational discontinuity and a compressive steepened quasi-linearly polarized pulse whose structure is similar to that of a finite amplitude magnetosonic simple wave. For small propagation angles, the pulse mode (fast or slow) depends on the value of β with respect to unity while for large propagation angles the wave mode is fixed by the sign of the initial density-field correlation. The two-dimensional evolution shows that an MHD wave is unstable against a small-amplitude long-wavelength modulation in the direction transverse to the wave propagation direction. A two-dimensional magnetosonic wave solution is found, in which the density fluctuation is driven by the corresponding total pressure fluctuation, exactly as in the one-dimensional simple wave. Along with the steepening effect, the wave experiences both wave front deformation and a self-focusing effect which may eventually lead to the collapse of the wave. The results compare well with observations of MHD waves in the Earth's foreshock and at comets

  12. Two-dimensional nonlinear equations of supersymmetric gauge theories

    International Nuclear Information System (INIS)

    Savel'ev, M.V.

    1985-01-01

    Supersymmetric generalization of two-dimensional nonlinear dynamical equations of gauge theories is presented. The nontrivial dynamics of a physical system in the supersymmetry and supergravity theories for (2+2)-dimensions is described by the integrable embeddings of Vsub(2/2) superspace into the flat enveloping superspace Rsub(N/M), supplied with the structure of a Lie superalgebra. An equation is derived which describes a supersymmetric generalization of the two-dimensional Toda lattice. It contains both super-Liouville and Sinh-Gordon equations

  13. Spin dynamics in a two-dimensional quantum gas

    DEFF Research Database (Denmark)

    Pedersen, Poul Lindholm; Gajdacz, Miroslav; Deuretzbacher, Frank

    2014-01-01

    We have investigated spin dynamics in a two-dimensional quantum gas. Through spin-changing collisions, two clouds with opposite spin orientations are spontaneously created in a Bose-Einstein condensate. After ballistic expansion, both clouds acquire ring-shaped density distributions with superimp......We have investigated spin dynamics in a two-dimensional quantum gas. Through spin-changing collisions, two clouds with opposite spin orientations are spontaneously created in a Bose-Einstein condensate. After ballistic expansion, both clouds acquire ring-shaped density distributions...

  14. Pair Interaction of Dislocations in Two-Dimensional Crystals

    Science.gov (United States)

    Eisenmann, C.; Gasser, U.; Keim, P.; Maret, G.; von Grünberg, H. H.

    2005-10-01

    The pair interaction between crystal dislocations is systematically explored by analyzing particle trajectories of two-dimensional colloidal crystals measured by video microscopy. The resulting pair energies are compared to Monte Carlo data and to predictions derived from the standard Hamiltonian of the elastic theory of dislocations. Good agreement is found with respect to the distance and temperature dependence of the interaction potential, but not regarding the angle dependence where discrete lattice effects become important. Our results on the whole confirm that the dislocation Hamiltonian allows a quantitative understanding of the formation and interaction energies of dislocations in two-dimensional crystals.

  15. Two dimensional nonlinear spectral estimation techniques for breast cancer localization

    International Nuclear Information System (INIS)

    Stathaki, P.T.; Constantinides, A.G.

    1994-01-01

    In this paper the problem of image texture analysis in the presence of noise is examined from a higher-order statistical perspective. The approach taken involves the use of two dimensional second order Volterra filters where the filter weights are derived from third order cumulants of the two dimensional signal. The specific application contained in this contribution is in mammography, an area in which it is difficult to discern the appropriate features. The paper describes the fundamental issues of the various components of the approach. The results of the entire texture modelling, classification and segmentation scheme contained in this paper are very encouraging

  16. Densis. Densimetric representation of two-dimensional matrices

    International Nuclear Information System (INIS)

    Los Arcos Merino, J.M.

    1978-01-01

    Densis is a Fortran V program which allows off-line control of a Calcomp digital plotter, to represent a two-dimensional matrix of numerical elements in the form of a variable shading intensity map in two colours. Each matrix element is associated to a square of a grid which is traced over by lines whose number is a function of the element value according to a selected scale. Program features, subroutine structure and running instructions, are described. Some typical results, for gamma-gamma coincidence experimental data and a sampled two-dimensional function, are indicated. (author)

  17. Two-dimensional QCD in the Coulomb gauge

    International Nuclear Information System (INIS)

    Kalashnikova, Yu.S.; Nefed'ev, A.V.

    2002-01-01

    Various aspects of the 't Hooft model for two-dimensional QCD in the limit of infinite number of colours in the Coulomb gauge are discussed. The properties of mesonic excitations are studied, with special emphasis on the pion. Attention is paid to the dual role of the pion. which, while a genuine qq-bar state, is a Goldstone boson of two-dimensional QCD as well. In particular, the validity of the soft-pion theorems is demonstrated. It is shown that the Coulomb gauge is the most suitable choice for the study of hadronic observables involving pions [ru

  18. Quantum Communication Through a Two-Dimensional Spin Network

    International Nuclear Information System (INIS)

    Wang Zhaoming; Gu Yongjian

    2012-01-01

    We investigate the state or entanglement transfer through a two-dimensional spin network. We show that for state transfer, better fidelity can be gained along the diagonal direction but for entanglement transfer, when the initial entanglement is created along the boundary, the concurrence is more inclined to propagate along the boundary. This behavior is produced by quantum mechanical interference and the communication quality depends on the precise size of the network. For some number of sites, the fidelity in a two-dimensional channel is higher than one-dimensional case. This is an important result for realizing quantum communication through high dimension spin chain networks.

  19. Critical Behaviour of a Two-Dimensional Random Antiferromagnet

    DEFF Research Database (Denmark)

    Als-Nielsen, Jens Aage; Birgeneau, R. J.; Guggenheim, H. J.

    1976-01-01

    A neutron scattering study of the order parameter, correlation length and staggered susceptibility of the two-dimensional random antiferromagnet Rb2Mn0.5Ni0.5F4 is reported. The system is found to exhibit a well-defined phase transition with critical exponents identical to those of the isomorphou...... pure materials K2NiF4 and K2MnF4. Thus, in these systems, which have the asymptotic critical behaviour of the two-dimensional Ising model, randomness has no measurable effect on the phase-transition behaviour....

  20. Two dimensional nonlinear spectral estimation techniques for breast cancer localization

    Energy Technology Data Exchange (ETDEWEB)

    Stathaki, P T; Constantinides, A G [Signal Processing Section, Department of Electrical and Electronic Engineering, Imperial College, Exhibition Road, London SW7 2BT, UK (United Kingdom)

    1994-12-31

    In this paper the problem of image texture analysis in the presence of noise is examined from a higher-order statistical perspective. The approach taken involves the use of two dimensional second order Volterra filters where the filter weights are derived from third order cumulants of the two dimensional signal. The specific application contained in this contribution is in mammography, an area in which it is difficult to discern the appropriate features. The paper describes the fundamental issues of the various components of the approach. The results of the entire texture modelling, classification and segmentation scheme contained in this paper are very encouraging. 7 refs, 2 figs.

  1. Finite element solution of two dimensional time dependent heat equation

    International Nuclear Information System (INIS)

    Maaz

    1999-01-01

    A Microsoft Windows based computer code, named FHEAT, has been developed for solving two dimensional heat problems in Cartesian and Cylindrical geometries. The programming language is Microsoft Visual Basic 3.0. The code makes use of Finite element formulation for spatial domain and Finite difference formulation for time domain. Presently the code is capable of solving two dimensional steady state and transient problems in xy- and rz-geometries. The code is capable excepting both triangular and rectangular elements. Validation and benchmarking was done against hand calculations and published results. (author)

  2. Chaotic dynamics in two-dimensional noninvertible maps

    CERN Document Server

    Mira, Christian; Cathala, Jean-Claude; Gardini, Laura

    1996-01-01

    This book is essentially devoted to complex properties (Phase plane structure and bifurcations) of two-dimensional noninvertible maps, i.e. maps having either a non-unique inverse, or no real inverse, according to the plane point. They constitute models of sets of discrete dynamical systems encountered in Engineering (Control, Signal Processing, Electronics), Physics, Economics, Life Sciences. Compared to the studies made in the one-dimensional case, the two-dimensional situation remained a long time in an underdeveloped state. It is only since these last years that the interest for this resea

  3. Chiral anomaly, fermionic determinant and two dimensional models

    International Nuclear Information System (INIS)

    Rego Monteiro, M.A. do.

    1985-01-01

    The chiral anomaly in random pair dimension is analysed. This anomaly is perturbatively calculated by dimensional regularization method. A new method for non-perturbative Jacobian calculation of a general chiral transformation, 1.e., finite and non-Abelian, is developed. This method is used for non-perturbative chiral anomaly calculation, as an alternative to bosonization of two-dimensional theories for massless fermions and to study the phenomenum of fermion number fractionalization. The fermionic determinant from two-dimensional quantum chromodynamics is also studied, and calculated, exactly, as in decoupling gauge as with out reference to a particular gauge. (M.C.K.) [pt

  4. Growth modes of individual ferrite grains in the austenite to ferrite transformation of low carbon steels

    International Nuclear Information System (INIS)

    Li, D.Z.; Xiao, N.M.; Lan, Y.J.; Zheng, C.W.; Li, Y.Y.

    2007-01-01

    The mesoscale deterministic cellular automaton (CA) method and probabilistic Q-state Potts-based Monte Carlo (MC) model have been adopted to investigate independently the individual growth behavior of ferrite grain during the austenite (γ)-ferrite (α) transformation. In these models, the γ-α phase transformation and ferrite grain coarsening induced by α/α grain boundary migration could be simulated simultaneously. The simulations demonstrated that both the hard impingement (ferrite grain coarsening) and the soft impingement (overlapping carbon concentration field) have a great influence on the individual ferrite growth behavior. Generally, ferrite grains displayed six modes of growth behavior: parabolic growth, delayed nucleation and growth, temporary shrinkage, partial shrinkage, complete shrinkage and accelerated growth in the transformation. Some modes have been observed before by the synchrotron X-ray diffraction experiment. The mesoscopic simulation provides an alternative tool for investigating both the individual grain growth behavior and the overall transformation behavior simultaneously during transformation

  5. Fatigue Debond Growth in Sandwich Structures Loaded in Mixed Mode Bending (MMB)

    DEFF Research Database (Denmark)

    Quispitupa, Amilcar; Berggreen, Christian; Carlsson, Leif A.

    2008-01-01

    Static and cyclic debond growth in sandwich specimens loaded in mixed mode bending (MMB) is examined. The MMB sandwich specimens were manufactured using H100 PVC foam core and E-glass/polyester non-crimp quadro-axial [0/45/90/-45]s DBLT-850 face sheets. Static test were performed to determine...... the fracture toughness of the debonded sandwich specimens at different mixed mode loadings. The mixed mode ratio (mode I to mode II) was controlled by changing the lever arm distance of the MMB test rig. Compliance technique and visual inspection was employed to measure the crack length during fatigue. Fatigue...... tests were performed at 90% of the static fracture toughness at a loading ratio of R=0.1. Fatigue results revealed higher debond crack growth rates when the lever arm distance was increased. For some specimens, the crack propagated just below the face/core interface in the foam core and for others...

  6. The growth of the tearing mode - Boundary and scaling effects

    Science.gov (United States)

    Steinolfson, R. S.; Van Hoven, G.

    1983-01-01

    A numerical model of resistive magnetic tearing is developed in order to verify and relate the results of the principal approximations used in analytic analyses and to investigate the solutions and their growth-rate scalings over a large range of primary parameters which include parametric values applicable to the solar atmosphere. The computations cover the linear behavior for a variety of boundary conditions, emphasizing effects which differentiate magnetic tearing in astrophysical situations from that in laboratory devices. Eigenfunction profiles for long and short wavelengths are computed and the applicability of the 'constant psi' approximation is investigated. The growth rate is computed for values of the magnetic Reynolds number up to a trillion and of the dimensionless wavelength parameter down to 0.001. The analysis predicts significant effects due to differing values of the magnetic Reynolds number.

  7. Control of growth mode of multiwalled carbon nanotubes

    International Nuclear Information System (INIS)

    Nguyen Hong Quang; Kim, Do-Hyung

    2009-01-01

    We have conducted an experimental study to investigate the synthesis of multi-walled carbon nanotubes (CNTs) by a dc plasma-enhanced chemical vapour deposition (PECVD) technique. The synthesis of base and tip-type of CNTs was selectively controlled by changing the catalyst size, catalyst film thickness correlated with altering the NH 3 pretreatment plasma current. These types of CNT showed distinctive properties in nanotube structure, growth rate and vertical alignment, which were confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and in situ optical interference measurement. The vertically aligned behaviour of CNT was systematically studied by using a fine-patterned catalyst layer with diverse critical dimensions. Freestanding single CNT was successfully realized by optimum tip-type CNT growth, conventional photolithography and wet-etch process.

  8. Vectorized Matlab Codes for Linear Two-Dimensional Elasticity

    Directory of Open Access Journals (Sweden)

    Jonas Koko

    2007-01-01

    Full Text Available A vectorized Matlab implementation for the linear finite element is provided for the two-dimensional linear elasticity with mixed boundary conditions. Vectorization means that there is no loop over triangles. Numerical experiments show that our implementation is more efficient than the standard implementation with a loop over all triangles.

  9. Level crossings in complex two-dimensional potentials

    Indian Academy of Sciences (India)

    Two-dimensional P T -symmetric quantum-mechanical systems with the complex cubic potential 12 = 2 + 2 + 2 and the complex Hénon–Heiles potential HH = 2 + 2 + (2 − 3/3) are investigated. Using numerical and perturbative methods, energy spectra are obtained to high levels. Although both ...

  10. Zero sound in a two-dimensional dipolar Fermi gas

    NARCIS (Netherlands)

    Lu, Z.K.; Matveenko, S.I.; Shlyapnikov, G.V.

    2013-01-01

    We study zero sound in a weakly interacting two-dimensional (2D) gas of single-component fermionic dipoles (polar molecules or atoms with a large magnetic moment) tilted with respect to the plane of their translational motion. It is shown that the propagation of zero sound is provided by both

  11. Interior design of a two-dimensional semiclassical black hole

    Science.gov (United States)

    Levanony, Dana; Ori, Amos

    2009-10-01

    We look into the inner structure of a two-dimensional dilatonic evaporating black hole. We establish and employ the homogenous approximation for the black-hole interior. Two kinds of spacelike singularities are found inside the black hole, and their structure is investigated. We also study the evolution of spacetime from the horizon to the singularity.

  12. On final states of two-dimensional decaying turbulence

    NARCIS (Netherlands)

    Yin, Z.

    2004-01-01

    Numerical and analytical studies of final states of two-dimensional (2D) decaying turbulence are carried out. The first part of this work is trying to give a definition for final states of 2D decaying turbulence. The functional relation of ¿-¿, which is frequently adopted as the characterization of

  13. Vibrations of thin piezoelectric shallow shells: Two-dimensional ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    In this paper we consider the eigenvalue problem for piezoelectric shallow shells and we show that, as the thickness of the shell goes to zero, the eigensolutions of the three-dimensional piezoelectric shells converge to the eigensolutions of a two- dimensional eigenvalue problem. Keywords. Vibrations; piezoelectricity ...

  14. Inter-layer Cooper pairing of two-dimensional electrons

    International Nuclear Information System (INIS)

    Inoue, Masahiro; Takemori, Tadashi; Yoshizaki, Ryozo; Sakudo, Tunetaro; Ohtaka, Kazuo

    1987-01-01

    The authors point out the possibility that the high transition temperatures of the recently discovered oxide superconductors are dominantly caused by the inter-layer Cooper pairing of two-dimensional electrons that are coupled through the exchange of three-dimensional phonons. (author)

  15. Solitary wave solutions of two-dimensional nonlinear Kadomtsev ...

    Indian Academy of Sciences (India)

    Aly R Seadawy

    2017-09-13

    Sep 13, 2017 ... We considered the two-dimensional DASWs in colli- sionless, unmagnetized cold plasma consisting of dust fluid, ions and electrons. The dynamics of DASWs is governed by the normalized fluid equations of nonlin- ear continuity (1), nonlinear motion of system (2) and. (3) and linear Poisson equation (4) as.

  16. Two-dimensional generalized harmonic oscillators and their Darboux partners

    International Nuclear Information System (INIS)

    Schulze-Halberg, Axel

    2011-01-01

    We construct two-dimensional Darboux partners of the shifted harmonic oscillator potential and of an isotonic oscillator potential belonging to the Smorodinsky–Winternitz class of superintegrable systems. The transformed solutions, their potentials and the corresponding discrete energy spectra are computed in explicit form. (paper)

  17. First principles calculation of two dimensional antimony and antimony arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Pillai, Sharad Babu, E-mail: sbpillai001@gmail.com; Narayan, Som; Jha, Prafulla K. [Department. of Physics, Faculty of Science, The M. S. University of Baroda, Vadodara-390002 (India); Dabhi, Shweta D. [Department of Physics, Maharaja Krishnakumarsinhji Bhavnagar University, Bhavnagar-364001 (India)

    2016-05-23

    This work focuses on the strain dependence of the electronic properties of two dimensional antimony (Sb) material and its alloy with As (SbAs) using density functional theory based first principles calculations. Both systems show indirect bandgap semiconducting character which can be transformed into a direct bandgap material with the application of relatively small strain.

  18. Two-dimensional models in statistical mechanics and field theory

    International Nuclear Information System (INIS)

    Koberle, R.

    1980-01-01

    Several features of two-dimensional models in statistical mechanics and Field theory, such as, lattice quantum chromodynamics, Z(N), Gross-Neveu and CP N-1 are discussed. The problems of confinement and dynamical mass generation are also analyzed. (L.C.) [pt

  19. Theory of the one- and two-dimensional electron gas

    International Nuclear Information System (INIS)

    Emery, V.J.

    1987-01-01

    Two topics are discussed: (1) the competition between 2k/sub F/ and 4k/sub F/ charge state waves in a one-dimensional electron gas and (2) a two-dimensional model of high T/sub c/ superconductivity in the oxides

  20. Two-dimensional turbulent flows on a bounded domain

    NARCIS (Netherlands)

    Kramer, W.

    2006-01-01

    Large-scale flows in the oceans and the atmosphere reveal strong similarities with purely two-dimensional flows. One of the most typical features is the cascade of energy from smaller flow scales towards larger scales. This is opposed to three-dimensional turbulence where larger flow structures

  1. Exterior calculus and two-dimensional supersymmetric models

    International Nuclear Information System (INIS)

    Sciuto, S.

    1980-01-01

    An important property of the calculus of differential forms on superspace is pointed out, and an economical way to treat the linear problem associated with certain supersymmetric two-dimensional models is discussed. A generalization of the super sine-Gordon model is proposed; its bosonic limit is a new model whose associate linear set has an SU(3) structure. (orig.)

  2. Second invariant for two-dimensional classical super systems

    Indian Academy of Sciences (India)

    Construction of superpotentials for two-dimensional classical super systems (for N. 2) is carried ... extensively used for the case of non-linear partial differential equation by various authors. [3,4–7,12 ..... found to be integrable just by accident.

  3. Quantitative optical mapping of two-dimensional materials

    DEFF Research Database (Denmark)

    Jessen, Bjarke S.; Whelan, Patrick R.; Mackenzie, David M. A.

    2018-01-01

    The pace of two-dimensional materials (2DM) research has been greatly accelerated by the ability to identify exfoliated thicknesses down to a monolayer from their optical contrast. Since this process requires time-consuming and error-prone manual assignment to avoid false-positives from image...

  4. Temperature maxima in stable two-dimensional shock waves

    International Nuclear Information System (INIS)

    Kum, O.; Hoover, W.G.; Hoover, C.G.

    1997-01-01

    We use molecular dynamics to study the structure of moderately strong shock waves in dense two-dimensional fluids, using Lucy pair potential. The stationary profiles show relatively broad temperature maxima, for both the longitudinal and the average kinetic temperatures, just as does Mott-Smith model for strong shock waves in dilute three-dimensional gases. copyright 1997 The American Physical Society

  5. Two-dimensional molecular line transfer for a cometary coma

    Science.gov (United States)

    Szutowicz, S.

    2017-09-01

    In the proposed axisymmetric model of the cometary coma the gas density profile is described by an angular density function. Three methods for treating two-dimensional radiative transfer are compared: the Large Velocity Gradient (LVG) (the Sobolev method), Accelerated Lambda Iteration (ALI) and accelerated Monte Carlo (MC).

  6. Sub-Nanometer Channels Embedded in Two-Dimensional Materials

    KAUST Repository

    Han, Yimo; Li, Ming-yang; Jung, Gang-Seob; Marsalis, Mark A.; Qin, Zhao; Buehler, Markus J.; Li, Lain-Jong; Muller, David A.

    2017-01-01

    Two-dimensional (2D) materials are among the most promising candidates for next-generation electronics due to their atomic thinness, allowing for flexible transparent electronics and ultimate length scaling1. Thus far, atomically-thin p-n junctions2

  7. Complex dynamical invariants for two-dimensional complex potentials

    Indian Academy of Sciences (India)

    Abstract. Complex dynamical invariants are searched out for two-dimensional complex poten- tials using rationalization method within the framework of an extended complex phase space characterized by x = x1 + ip3, y = x2 + ip4, px = p1 + ix3, py = p2 + ix4. It is found that the cubic oscillator and shifted harmonic oscillator ...

  8. Coherent Electron Focussing in a Two-Dimensional Electron Gas.

    NARCIS (Netherlands)

    Houten, H. van; Wees, B.J. van; Mooij, J.E.; Beenakker, C.W.J.; Williamson, J.G.; Foxon, C.T.

    1988-01-01

    The first experimental realization of ballistic point contacts in a two-dimensional electron gas for the study of transverse electron focussing by a magnetic field is reported. Multiple peaks associated with skipping orbits of electrons reflected specularly by the channel boundary are observed. At

  9. Two-dimensional ion effects in relativistic diodes

    International Nuclear Information System (INIS)

    Poukey, J.W.

    1975-01-01

    In relativistic diodes, ions are emitted from the anode plasma. The effects and properties of these ions are studied via a two-dimensional particle simulation code. The space charge of these ions enhances the electron emission, and this additional current (including that of the ions, themselves) aids in obtaining superpinched electron beams for use in pellet fusion studies. (U.S.)

  10. Bounds on the capacity of constrained two-dimensional codes

    DEFF Research Database (Denmark)

    Forchhammer, Søren; Justesen, Jørn

    2000-01-01

    Bounds on the capacity of constrained two-dimensional (2-D) codes are presented. The bounds of Calkin and Wilf apply to first-order symmetric constraints. The bounds are generalized in a weaker form to higher order and nonsymmetric constraints. Results are given for constraints specified by run-l...

  11. Interior design of a two-dimensional semiclassical black hole

    International Nuclear Information System (INIS)

    Levanony, Dana; Ori, Amos

    2009-01-01

    We look into the inner structure of a two-dimensional dilatonic evaporating black hole. We establish and employ the homogenous approximation for the black-hole interior. Two kinds of spacelike singularities are found inside the black hole, and their structure is investigated. We also study the evolution of spacetime from the horizon to the singularity.

  12. Two-dimensional profiling of Xanthomonas campestris pv. viticola ...

    African Journals Online (AJOL)

    However, the analysis of the 2D-PAGE gel images revealed a larger number of spots in the lysis method when compared to the others. Taking ... Keywords: Bacterial canker, Vitis vinifera, proteomics, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), two-dimensional gel electrophoresis (2D-PAGE).

  13. Image Making in Two Dimensional Art; Experiences with Straw and ...

    African Journals Online (AJOL)

    Image making in art is professionally referred to as bust in Sculpture andPortraiture in Painting. ... havebeen used to achieve these forms of art; like clay cement, marble, stone,different metals and, fibre glass in the three dimensional form; We also have Pencil, Charcoal Pastel and, Acrylic oil-paint in two dimensional form.

  14. Image Making in Two Dimensional Art; Experiences with Straw and ...

    African Journals Online (AJOL)

    Image making in art is professionally referred to as bust in Sculpture andPortraiture in Painting. It is an art form executed in three dimensional (3D)and two dimensional (2D) formats respectively. Uncountable materials havebeen used to achieve these forms of art; like clay cement, marble, stone,different metals and, fibre ...

  15. Mass relations for two-dimensional classical configurations

    International Nuclear Information System (INIS)

    Tataru-Mihai, P.

    1980-01-01

    Using the two-dimensional sigma-nonlinear models as a framework mass relations for classical configurations of instanton/soliton type are derived. Our results suggest an interesting differential-geometric interpretation of the mass of a classical configuration in terms of the topological characteristics of an associated manifold. (orig.)

  16. Seismically constrained two-dimensional crustal thermal structure of ...

    Indian Academy of Sciences (India)

    The temperature field within the crust is closely related to tectonic history as well as many other geological processes inside the earth. Therefore, knowledge of the crustal thermal structure of a region is of great importance for its tectonophysical studies. This work deals with the two-dimensional thermal modelling to ...

  17. Waiting Time Dynamics in Two-Dimensional Infrared Spectroscopy

    NARCIS (Netherlands)

    Jansen, Thomas L. C.; Knoester, Jasper

    We review recent work on the waiting time dynamics of coherent two-dimensional infrared (2DIR) spectroscopy. This dynamics can reveal chemical and physical processes that take place on the femto- and picosecond time scale, which is faster than the time scale that may be probed by, for example,

  18. Two-dimensional NMR studies of allyl palladium complexes of ...

    Indian Academy of Sciences (India)

    Administrator

    h3-Allyl complexes are intermediates in organic synthetic reactions such as allylic alkylation and amination. There is growing interest in understanding the structures of chiral h3-allyl intermediates as this would help to unravel the mechanism of enantioselective C–C bond forming reactions. Two-dimensional NMR study is a.

  19. Two-dimensional effects in nonlinear Kronig-Penney models

    DEFF Research Database (Denmark)

    Gaididei, Yuri Borisovich; Christiansen, Peter Leth; Rasmussen, Kim

    1997-01-01

    An analysis of two-dimensional (2D) effects in the nonlinear Kronig-Penney model is presented. We establish an effective one-dimensional description of the 2D effects, resulting in a set of pseudodifferential equations. The stationary states of the 2D system and their stability is studied...

  20. Two-dimensional position sensitive Si(Li) detector

    International Nuclear Information System (INIS)

    Walton, J.T.; Hubbard, G.S.; Haller, E.E.; Sommer, H.A.

    1978-11-01

    Circular, large-area two-dimensional Si(Li) position sensitive detectors have been fabricated. The detectors employ a thin lithium-diffused n + resisitive layer for one contact and a boron implanted p + resistive layer for the second contact. A position resolution of the order of 100 μm is indicated

  1. A TWO-DIMENSIONAL POSITION SENSITIVE SI(LI) DETECTOR

    Energy Technology Data Exchange (ETDEWEB)

    Walton, Jack T.; Hubbard, G. Scott; Haller, Eugene E.; Sommer, Heinrich A.

    1978-11-01

    Circular, large-area two-dimensional Si(Li) position sensitive detectors have been fabricated. The detectors employ a thin lithium-diffused n{sup +} resistive layer for one contact and a boron implanted p{sup +} resistive layer for the second contact. A position resolution of the order of 100 {micro}m is indicated.

  2. Solar Internal Rotation and Dynamo Waves: A Two Dimensional ...

    Indian Academy of Sciences (India)

    tribpo

    Solar Internal Rotation and Dynamo Waves: A Two Dimensional. Asymptotic Solution in the Convection Zone ... We calculate here a spatial 2 D structure of the mean magnetic field, adopting real profiles of the solar internal ... of the asymptotic solution in low (middle) and high (right panel) latitudes. field is shifted towards the ...

  3. Linkage analysis by two-dimensional DNA typing

    NARCIS (Netherlands)

    te Meerman, G J; Mullaart, E; Meulen ,van der Martin; den Daas, J H; Morolli, B; Uitterlinden, A G; Vijg, J

    1993-01-01

    In two-dimensional (2-D) DNA typing, genomic DNA fragments are separated, first according to size by electrophoresis in a neutral polyacrylamide gel and second according to sequence by denaturing gradient gel electrophoresis, followed by hybridization analysis using micro- and minisatellite core

  4. Proximity Induced Superconducting Properties in One and Two Dimensional Semiconductors

    DEFF Research Database (Denmark)

    Kjærgaard, Morten

    This report is concerned with the properties of one and two dimensional semiconducting materials when brought into contact with a superconductor. Experimentally we study the 2D electron gas in an InGaAs/InAs heterostructure with aluminum grown in situ on the surface, and theoretically we show tha...

  5. Two-Dimensional Charge Transport in Disordered Organic Semiconductors

    NARCIS (Netherlands)

    Brondijk, J. J.; Roelofs, W. S. C.; Mathijssen, S. G. J.; Shehu, A.; Cramer, T.; Biscarini, F.; Blom, P. W. M.; de Leeuw, D. M.

    2012-01-01

    We analyze the effect of carrier confinement on the charge-transport properties of organic field-effect transistors. Confinement is achieved experimentally by the use of semiconductors of which the active layer is only one molecule thick. The two-dimensional confinement of charge carriers provides

  6. Noninteracting beams of ballistic two-dimensional electrons

    International Nuclear Information System (INIS)

    Spector, J.; Stormer, H.L.; Baldwin, K.W.; Pfeiffer, L.N.; West, K.W.

    1991-01-01

    We demonstrate that two beams of two-dimensional ballistic electrons in a GaAs-AlGaAs heterostructure can penetrate each other with negligible mutual interaction analogous to the penetration of two optical beams. This allows electrical signal channels to intersect in the same plane with negligible crosstalk between the channels

  7. Two-dimensional dissipation in third sound resonance

    International Nuclear Information System (INIS)

    Buck, A.L.; Mochel, J.M.; Illinois Univ., Urbana

    1981-01-01

    The first determination of non-linear superflow dissipation in a truly two-dimensional helium film is reported. Superfluid velocities were measured using third sound resonance on a closed superfluid film. The predicted power law dissipation function, with exponent of approximately eight, is observed at three temperatures in a film of 0.58 mobile superfluid layers. (orig.)

  8. Graphene: a promising two-dimensional support for heterogeneous catalysts

    Directory of Open Access Journals (Sweden)

    Xiaobin eFan

    2015-01-01

    Full Text Available Graphene has many advantages that make it an attractive two-dimensional (2D support for heterogeneous catalysts. It not only allows the high loading of targeted catalytic species, but also facilitates the mass transfer during the reaction processes. These advantages, along with its unique physical and chemical properties, endow graphene great potential as catalyst support in heterogeneous catalysis.

  9. Two-dimensional interpolation with experimental data smoothing

    International Nuclear Information System (INIS)

    Trejbal, Z.

    1989-01-01

    A method of two-dimensional interpolation with smoothing of time statistically deflected points is developed for processing of magnetic field measurements at the U-120M field measurements at the U-120M cyclotron. Mathematical statement of initial requirements and the final result of relevant algebraic transformations are given. 3 refs

  10. Tunneling between parallel two-dimensional electron liquids

    Czech Academy of Sciences Publication Activity Database

    Jungwirth, Tomáš; MacDonald, A. H.

    361/362, - (1996), s. 167-170 ISSN 0039-6028. [International Conference on the Electronic Properties of Two Dimensional Systems /11./. Nottingham, 07.08.1995-11.08.1995] R&D Projects: GA ČR GA202/94/1278 Grant - others:INT(XX) 9106888 Impact factor: 2.783, year: 1996

  11. Two-Dimensional Tellurene as Excellent Thermoelectric Material

    KAUST Repository

    Sharma, Sitansh; Singh, Nirpendra; Schwingenschlö gl, Udo

    2018-01-01

    We study the thermoelectric properties of two-dimensional tellurene by first-principles calculations and semiclassical Boltzmann transport theory. The HSE06 hybrid functional results in a moderate direct band gap of 1.48 eV at the Γ point. A high

  12. Analysis of Two-Dimensional Electrophoresis Gel Images

    DEFF Research Database (Denmark)

    Pedersen, Lars

    2002-01-01

    This thesis describes and proposes solutions to some of the currently most important problems in pattern recognition and image analysis of two-dimensional gel electrophoresis (2DGE) images. 2DGE is the leading technique to separate individual proteins in biological samples with many biological...

  13. Patched Green's function techniques for two-dimensional systems

    DEFF Research Database (Denmark)

    Settnes, Mikkel; Power, Stephen; Lin, Jun

    2015-01-01

    We present a numerically efficient technique to evaluate the Green's function for extended two-dimensional systems without relying on periodic boundary conditions. Different regions of interest, or “patches,” are connected using self-energy terms which encode the information of the extended parts...

  14. Nonlinear dynamic characterization of two-dimensional materials

    NARCIS (Netherlands)

    Davidovikj, D.; Alijani, F.; Cartamil Bueno, S.J.; van der Zant, H.S.J.; Amabili, M.; Steeneken, P.G.

    2017-01-01

    Owing to their atomic-scale thickness, the resonances of two-dimensional (2D) material membranes show signatures of nonlinearities at forces of only a few picoNewtons. Although the linear dynamics of membranes is well understood, the exact relation between the nonlinear response and the resonator's

  15. Transient two-dimensional flow in porous media

    International Nuclear Information System (INIS)

    Sharpe, L. Jr.

    1979-01-01

    The transient flow of an isothermal ideal gas from the cavity formed by an underground nuclear explosion is investigated. A two-dimensional finite element method is used in analyzing the gas flow. Numerical results of the pressure distribution are obtained for both the stemming column and the surrounding porous media

  16. Two-dimensional QCD as a model for strong interaction

    International Nuclear Information System (INIS)

    Ellis, J.

    1977-01-01

    After an introduction to the formalism of two-dimensional QCD, its applications to various strong interaction processes are reviewed. Among the topics discussed are spectroscopy, deep inelastic cross-sections, ''hard'' processes involving hadrons, ''Regge'' behaviour, the existence of the Pomeron, and inclusive hadron cross-sections. Attempts are made to abstracts features useful for four-dimensional QCD phenomenology. (author)

  17. Two-dimensional gel electrophoresis analysis of different parts of ...

    African Journals Online (AJOL)

    Two-dimensional gel electrophoresis analysis of different parts of Panax quinquefolius L. root. ... From these results it was concluded that proteomic analysis method was an effective way to identify the different parts of quinquefolius L. root. These findings may contribute to further understanding of the physiological ...

  18. Two-dimensional optimization of free-electron-laser designs

    Science.gov (United States)

    Prosnitz, D.; Haas, R.A.

    1982-05-04

    Off-axis, two-dimensional designs for free electron lasers are described that maintain correspondence of a light beam with a synchronous electron at an optimal transverse radius r > 0 to achieve increased beam trapping efficiency and enhanced laser beam wavefront control so as to decrease optical beam diffraction and other deleterious effects.

  19. Kubo conductivity of a strongly magnetized two-dimensional plasma.

    Science.gov (United States)

    Montgomery, D.; Tappert, F.

    1971-01-01

    The Kubo formula is used to evaluate the bulk electrical conductivity of a two-dimensional guiding-center plasma in a strong dc magnetic field. The particles interact only electrostatically. An ?anomalous' electrical conductivity is derived for this system, which parallels a recent result of Taylor and McNamara for the coefficient of spatial diffusion.

  20. Bayesian approach for peak detection in two-dimensional chromatography

    NARCIS (Netherlands)

    Vivó-Truyols, G.

    2012-01-01

    A new method for peak detection in two-dimensional chromatography is presented. In a first step, the method starts with a conventional one-dimensional peak detection algorithm to detect modulated peaks. In a second step, a sophisticated algorithm is constructed to decide which of the individual

  1. Equilibrium spherically curved two-dimensional Lennard-Jones systems

    NARCIS (Netherlands)

    Voogd, J.M.; Sloot, P.M.A.; van Dantzig, R.

    2005-01-01

    To learn about basic aspects of nano-scale spherical molecular shells during their formation, spherically curved two-dimensional N-particle Lennard-Jones systems are simulated, studying curvature evolution paths at zero-temperature. For many N-values (N < 800) equilibrium configu- rations are traced

  2. Giant 1/f noise in two-dimensional polycrystalline media

    International Nuclear Information System (INIS)

    Snarskii, A.; Bezsudnov, I.

    2008-01-01

    The behaviour of excess (1/f noise) in two-dimensional polycrystalline media is investigated. On the base of current trap model, it is shown that there exists a certain anisotropy value of conductivity tensor for polycrystalline media when the amplitude of 1/f noise becomes giant

  3. Non-linear self-reinforced growth of tearing modes with multiple rational surfaces

    International Nuclear Information System (INIS)

    Maschke, E.K.; Persson, M.; Dewar, R.L.; Australian National Univ., Canberra, ACT

    1993-06-01

    The non-linear evolution of tearing modes with multiple rational surfaces is discussed. It is demonstrated that, in the presence of small differential rotation, the non-linear growth might be faster than exponential. This growth occurs as the rotation frequencies of the plasma at the different rational surfaces go into equilibrium

  4. Control of growth mode in SrTiO3 homoepitaxy under 500 deg. C

    International Nuclear Information System (INIS)

    Li Yanrong; Li Jinlong; Zhang Ying; Wei Xianhua; Deng Xinwu; Liu Xingzhao

    2004-01-01

    Homoepitaxial SrTiO 3 thin films were grown by laser molecular beam epitaxy. The growth mode was determined by in-situ reflective high energy electron diffraction, and the surface of the films was studied by ex-situ atomic force microscopy. At the deposition rate of 0.16A ring /sec and the laser energy density of 6J/cm 2 , layer-by-layer growth was observed above 460 deg. C substrate temperature, while the Stranski-Krastanov growth mode, that is layer-by-layer growth plus island growth mode, prevailed between 460 deg. C and 410 deg. C. On further decreasing the substrate temperature, the island growth was determined under 410 deg. C. With the optimization of deposition process in terms of laser energy density and deposition rate, the lowest crystallization temperatures of SrTiO 3 films grown in layer-by-layer growth mode were obtained as low as 280 deg. C. The effects of laser energy density on growth temperature were studied

  5. [Effects of different trophic modes on growth characteristics, metabolism and cellular components of Chlorella vulgaris].

    Science.gov (United States)

    Kong, Weibao; Wang, Yang; Yang, Hong; Xi, Yuqin; Han, Rui; Niu, Shiquan

    2015-03-04

    We studied the effects of trophic modes related to glucose and light (photoautotrophy, mixotrophy and heterotrophy) on growth, cellular components and carbon metabolic pathway of Chlorella vulgaris. The parameters about growth of algal cells were investigated by using spectroscopy and chromatography techniques. When trophic mode changed from photoautotrophy to mixotrophy and to heterotrophy successively, the concentrations of soluble sugar, lipid and saturated C16/C18 fatty acids in C. vulgaris increased, whereas the concentrations of unsaturated C16, C18 fatty acids, proteins, photosynthetic pigments and 18 relative amino acids decreased. Light and glucose affect the growth, metabolism and the biochemical components biosynthesis of C. vulgaris. Addition of glucose can promote algal biomass accumulation, stimulate the synthesis of carbonaceous components, but inhibit nitrogenous components. Under illumination cultivation, concentration and consumption level of glucose decided the main trophic modes of C. vulgaris. Mixotrophic and heterotrophic cultivation could promote the growth of algal cells.

  6. Approximate solutions for the two-dimensional integral transport equation. Solution of complex two-dimensional transport problems

    International Nuclear Information System (INIS)

    Sanchez, Richard.

    1980-11-01

    This work is divided into two parts: the first part deals with the solution of complex two-dimensional transport problems, the second one (note CEA-N-2166) treats the critically mixed methods of resolution. A set of approximate solutions for the isotropic two-dimensional neutron transport problem has been developed using the interface current formalism. The method has been applied to regular lattices of rectangular cells containing a fuel pin, cladding, and water, or homogenized structural material. The cells are divided into zones that are homogeneous. A zone-wise flux expansion is used to formulate a direct collision probability problem within a cell. The coupling of the cells is effected by making extra assumptions on the currents entering and leaving the interfaces. Two codes have been written: CALLIOPE uses a cylindrical cell model and one or three terms for the flux expansion, and NAUSICAA uses a two-dimensional flux representation and does a truly two-dimensional calculation inside each cell. In both codes, one or three terms can be used to make a space-independent expansion of the angular fluxes entering and leaving each side of the cell. The accuracies and computing times achieved with the different approximations are illustrated by numerical studies on two benchmark problems and by calculations performed in the APOLLO multigroup code [fr

  7. The one-particle scenario for the metal-insulator transition in two-dimensional systems at T = 0

    CERN Document Server

    Tarasov, Y V

    2003-01-01

    The conductance of bounded disordered electron systems is calculated by reducing the original dynamic problem of arbitrary dimensionality to a set of strictly one-dimensional problems for one-particle mode propagators. The metallic ground state of a two-dimensional conductor, which is considered as a limiting case of three-dimensional quantum waveguide, is shown to result from its multi-modeness. As the waveguide thickness is reduced, e.g., by applying a 'pressing' potential, the electron system undergoes a set of continuous phase transitions related to discrete variations of the number of extended modes. The closing of the last current carrying mode is regarded as a phase transition of the electron system from metallic to dielectric state. The obtained results agree qualitatively with the observed 'anomalies' of resistivity of different two-dimensional electron and hole systems.

  8. A Two-Dimensional Micro Scanner Integrated with a Piezoelectric Actuator and Piezoresistors

    Directory of Open Access Journals (Sweden)

    Zheng You

    2009-01-01

    Full Text Available A compact two-dimensional micro scanner with small volume, large deflection angles and high frequency is presented and the two-dimensional laser scanning is achieved by specular reflection. To achieve large deflection angles, the micro scanner excited by a piezoelectric actuator operates in the resonance mode. The scanning frequencies and the maximum scanning angles of the two degrees of freedom are analyzed by modeling and simulation of the structure. For the deflection angle measurement, piezoresistors are integrated in the micro scanner. The appropriate directions and crystal orientations of the piezoresistors are designed to obtain the large piezoresistive coefficients for the high sensitivities. Wheatstone bridges are used to measure the deflection angles of each direction independently and precisely. The scanner is fabricated and packaged with the piezoelectric actuator and the piezoresistors detection circuits in a size of 28 mm×20 mm×18 mm. The experiment shows that the two scanning frequencies are 216.8 Hz and 464.8 Hz, respectively. By an actuation displacement of 10 μm, the scanning range of the two-dimensional micro scanner is above 26º × 23º. The deflection angle measurement sensitivities for two directions are 59 mV/deg and 30 mV/deg, respectively.

  9. A two-dimensional micro scanner integrated with a piezoelectric actuator and piezoresistors.

    Science.gov (United States)

    Zhang, Chi; Zhang, Gaofei; You, Zheng

    2009-01-01

    A compact two-dimensional micro scanner with small volume, large deflection angles and high frequency is presented and the two-dimensional laser scanning is achieved by specular reflection. To achieve large deflection angles, the micro scanner excited by a piezoelectric actuator operates in the resonance mode. The scanning frequencies and the maximum scanning angles of the two degrees of freedom are analyzed by modeling and simulation of the structure. For the deflection angle measurement, piezoresistors are integrated in the micro scanner. The appropriate directions and crystal orientations of the piezoresistors are designed to obtain the large piezoresistive coefficients for the high sensitivities. Wheatstone bridges are used to measure the deflection angles of each direction independently and precisely. The scanner is fabricated and packaged with the piezoelectric actuator and the piezoresistors detection circuits in a size of 28 mm×20 mm×18 mm. The experiment shows that the two scanning frequencies are 216.8 Hz and 464.8 Hz, respectively. By an actuation displacement of 10 μm, the scanning range of the two-dimensional micro scanner is above 26° × 23°. The deflection angle measurement sensitivities for two directions are 59 mV/deg and 30 mV/deg, respectively.

  10. Two-Dimensional Planar Lightwave Circuit Integrated Spatial Filter Array and Method of Use Thereof

    Science.gov (United States)

    Ai, Jun (Inventor); Dimov, Fedor (Inventor)

    2015-01-01

    A large coherent two-dimensional (2D) spatial filter array (SFA), 30 by 30 or larger, is produced by coupling a 2D planar lightwave circuit (PLC) array with a pair of lenslet arrays at the input and output side. The 2D PLC array is produced by stacking a plurality of chips, each chip with a plural number of straight PLC waveguides. A pupil array is coated onto the focal plane of the lenslet array. The PLC waveguides are produced by deposition of a plural number of silica layers on the silicon wafer, followed by photolithography and reactive ion etching (RIE) processes. A plural number of mode filters are included in the silica-on-silicon waveguide such that the PLC waveguide is transparent to the fundamental mode but higher order modes are attenuated by 40 dB or more.

  11. Two dimensional analytical model for a reconfigurable field effect transistor

    Science.gov (United States)

    Ranjith, R.; Jayachandran, Remya; Suja, K. J.; Komaragiri, Rama S.

    2018-02-01

    This paper presents two-dimensional potential and current models for a reconfigurable field effect transistor (RFET). Two potential models which describe subthreshold and above-threshold channel potentials are developed by solving two-dimensional (2D) Poisson's equation. In the first potential model, 2D Poisson's equation is solved by considering constant/zero charge density in the channel region of the device to get the subthreshold potential characteristics. In the second model, accumulation charge density is considered to get above-threshold potential characteristics of the device. The proposed models are applicable for the device having lightly doped or intrinsic channel. While obtaining the mathematical model, whole body area is divided into two regions: gated region and un-gated region. The analytical models are compared with technology computer-aided design (TCAD) simulation results and are in complete agreement for different lengths of the gated regions as well as at various supply voltage levels.

  12. Boron nitride as two dimensional dielectric: Reliability and dielectric breakdown

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Yanfeng; Pan, Chengbin; Hui, Fei; Shi, Yuanyuan; Lanza, Mario, E-mail: mlanza@suda.edu.cn [Institute of Functional Nano and Soft Materials, Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, 199 Ren-Ai Road, Suzhou 215123 (China); Zhang, Meiyun; Long, Shibing [Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China); Lian, Xiaojuan; Miao, Feng [National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); Larcher, Luca [DISMI, Università di Modena e Reggio Emilia, 42122 Reggio Emilia (Italy); Wu, Ernest [IBM Research Division, Essex Junction, Vermont 05452 (United States)

    2016-01-04

    Boron Nitride (BN) is a two dimensional insulator with excellent chemical, thermal, mechanical, and optical properties, which make it especially attractive for logic device applications. Nevertheless, its insulating properties and reliability as a dielectric material have never been analyzed in-depth. Here, we present the first thorough characterization of BN as dielectric film using nanoscale and device level experiments complementing with theoretical study. Our results reveal that BN is extremely stable against voltage stress, and it does not show the reliability problems related to conventional dielectrics like HfO{sub 2}, such as charge trapping and detrapping, stress induced leakage current, and untimely dielectric breakdown. Moreover, we observe a unique layer-by-layer dielectric breakdown, both at the nanoscale and device level. These findings may be of interest for many materials scientists and could open a new pathway towards two dimensional logic device applications.

  13. Quasi-two-dimensional thermoelectricity in SnSe

    Science.gov (United States)

    Tayari, V.; Senkovskiy, B. V.; Rybkovskiy, D.; Ehlen, N.; Fedorov, A.; Chen, C.-Y.; Avila, J.; Asensio, M.; Perucchi, A.; di Pietro, P.; Yashina, L.; Fakih, I.; Hemsworth, N.; Petrescu, M.; Gervais, G.; Grüneis, A.; Szkopek, T.

    2018-01-01

    Stannous selenide is a layered semiconductor that is a polar analog of black phosphorus and of great interest as a thermoelectric material. Unusually, hole doped SnSe supports a large Seebeck coefficient at high conductivity, which has not been explained to date. Angle-resolved photoemission spectroscopy, optical reflection spectroscopy, and magnetotransport measurements reveal a multiple-valley valence-band structure and a quasi-two-dimensional dispersion, realizing a Hicks-Dresselhaus thermoelectric contributing to the high Seebeck coefficient at high carrier density. We further demonstrate that the hole accumulation layer in exfoliated SnSe transistors exhibits a field effect mobility of up to 250 cm2/V s at T =1.3 K . SnSe is thus found to be a high-quality quasi-two-dimensional semiconductor ideal for thermoelectric applications.

  14. Folding two dimensional crystals by swift heavy ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Ochedowski, Oliver; Bukowska, Hanna [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany); Freire Soler, Victor M. [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany); Departament de Fisica Aplicada i Optica, Universitat de Barcelona, E08028 Barcelona (Spain); Brökers, Lara [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany); Ban-d' Etat, Brigitte; Lebius, Henning [CIMAP (CEA-CNRS-ENSICAEN-UCBN), 14070 Caen Cedex 5 (France); Schleberger, Marika, E-mail: marika.schleberger@uni-due.de [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany)

    2014-12-01

    Ion irradiation of graphene, the showcase model of two dimensional crystals, has been successfully applied to induce various modifications in the graphene crystal. One of these modifications is the formation of origami like foldings in graphene which are created by swift heavy ion irradiation under glancing incidence angle. These foldings can be applied to locally alter the physical properties of graphene like mechanical strength or chemical reactivity. In this work we show that the formation of foldings in two dimensional crystals is not restricted to graphene but can be applied for other materials like MoS{sub 2} and hexagonal BN as well. Further we show that chemical vapour deposited graphene forms foldings after swift heavy ion irradiation while chemical vapour deposited MoS{sub 2} does not.

  15. Folding two dimensional crystals by swift heavy ion irradiation

    International Nuclear Information System (INIS)

    Ochedowski, Oliver; Bukowska, Hanna; Freire Soler, Victor M.; Brökers, Lara; Ban-d'Etat, Brigitte; Lebius, Henning; Schleberger, Marika

    2014-01-01

    Ion irradiation of graphene, the showcase model of two dimensional crystals, has been successfully applied to induce various modifications in the graphene crystal. One of these modifications is the formation of origami like foldings in graphene which are created by swift heavy ion irradiation under glancing incidence angle. These foldings can be applied to locally alter the physical properties of graphene like mechanical strength or chemical reactivity. In this work we show that the formation of foldings in two dimensional crystals is not restricted to graphene but can be applied for other materials like MoS 2 and hexagonal BN as well. Further we show that chemical vapour deposited graphene forms foldings after swift heavy ion irradiation while chemical vapour deposited MoS 2 does not

  16. Two-dimensional time dependent Riemann solvers for neutron transport

    International Nuclear Information System (INIS)

    Brunner, Thomas A.; Holloway, James Paul

    2005-01-01

    A two-dimensional Riemann solver is developed for the spherical harmonics approximation to the time dependent neutron transport equation. The eigenstructure of the resulting equations is explored, giving insight into both the spherical harmonics approximation and the Riemann solver. The classic Roe-type Riemann solver used here was developed for one-dimensional problems, but can be used in multidimensional problems by treating each face of a two-dimensional computation cell in a locally one-dimensional way. Several test problems are used to explore the capabilities of both the Riemann solver and the spherical harmonics approximation. The numerical solution for a simple line source problem is compared to the analytic solution to both the P 1 equation and the full transport solution. A lattice problem is used to test the method on a more challenging problem

  17. Dynamics of vortex interactions in two-dimensional flows

    DEFF Research Database (Denmark)

    Juul Rasmussen, J.; Nielsen, A.H.; Naulin, V.

    2002-01-01

    The dynamics and interaction of like-signed vortex structures in two dimensional flows are investigated by means of direct numerical solutions of the two-dimensional Navier-Stokes equations. Two vortices with distributed vorticity merge when their distance relative to their radius, d/R-0l. is below...... a critical value, a(c). Using the Weiss-field, a(c) is estimated for vortex patches. Introducing an effective radius for vortices with distributed vorticity, we find that 3.3 ... is effectively producing small scale structures and the relation to the enstrophy "cascade" in developed 2D turbulence is discussed. The influence of finite viscosity on the merging is also investigated. Additionally, we examine vortex interactions on a finite domain, and discuss the results in connection...

  18. Quantum vacuum energy in two dimensional space-times

    International Nuclear Information System (INIS)

    Davies, P.C.W.; Fulling, S.A.

    1977-01-01

    The paper presents in detail the renormalization theory of the energy-momentum tensor of a two dimensional massless scalar field which has been used elsewhere to study the local physics in a model of black hole evaporation. The treatment is generalized to include the Casimir effect occurring in spatially finite models. The essence of the method is evaluation of the field products in the tensor as functions of two points, followed by covariant subtraction of the discontinuous terms arising as the points coalesce. In two dimensional massless theories, conformal transformations permit exact calculations to be performed. The results are applied here to some special cases, primarily space-times of constant curvature, with emphasis on the existence of distinct 'vacuum' states associated naturally with different conformal coordinate systems. The relevance of the work to the general problems of defining observables and of classifying and interpreting states in curved-space quantum field theory is discussed. (author)

  19. Explorative data analysis of two-dimensional electrophoresis gels

    DEFF Research Database (Denmark)

    Schultz, J.; Gottlieb, D.M.; Petersen, Marianne Kjerstine

    2004-01-01

    of gels is presented. First, an approach is demonstrated in which no prior knowledge of the separated proteins is used. Alignment of the gels followed by a simple transformation of data makes it possible to analyze the gels in an automated explorative manner by principal component analysis, to determine......Methods for classification of two-dimensional (2-DE) electrophoresis gels based on multivariate data analysis are demonstrated. Two-dimensional gels of ten wheat varieties are analyzed and it is demonstrated how to classify the wheat varieties in two qualities and a method for initial screening...... if the gels should be further analyzed. A more detailed approach is done by analyzing spot volume lists by principal components analysis and partial least square regression. The use of spot volume data offers a mean to investigate the spot pattern and link the classified protein patterns to distinct spots...

  20. Tuning spin transport across two-dimensional organometallic junctions

    Science.gov (United States)

    Liu, Shuanglong; Wang, Yun-Peng; Li, Xiangguo; Fry, James N.; Cheng, Hai-Ping

    2018-01-01

    We study via first-principles modeling and simulation two-dimensional spintronic junctions made of metal-organic frameworks consisting of two Mn-phthalocyanine ferromagnetic metal leads and semiconducting Ni-phthalocyanine channels of various lengths. These systems exhibit a large tunneling magnetoresistance ratio; the transmission functions of such junctions can be tuned using gate voltage by three orders of magnitude. We find that the origin of this drastic change lies in the orbital alignment and hybridization between the leads and the center electronic states. With physical insight into the observed on-off phenomenon, we predict a gate-controlled spin current switch based on two-dimensional crystallines and offer general guidelines for designing spin junctions using 2D materials.

  1. Two-dimensional Simulations of Correlation Reflectometry in Fusion Plasmas

    International Nuclear Information System (INIS)

    Valeo, E.J.; Kramer, G.J.; Nazikian, R.

    2001-01-01

    A two-dimensional wave propagation code, developed specifically to simulate correlation reflectometry in large-scale fusion plasmas is described. The code makes use of separate computational methods in the vacuum, underdense and reflection regions of the plasma in order to obtain the high computational efficiency necessary for correlation analysis. Simulations of Tokamak Fusion Test Reactor (TFTR) plasma with internal transport barriers are presented and compared with one-dimensional full-wave simulations. It is shown that the two-dimensional simulations are remarkably similar to the results of the one-dimensional full-wave analysis for a wide range of turbulent correlation lengths. Implications for the interpretation of correlation reflectometer measurements in fusion plasma are discussed

  2. Directional detection of dark matter with two-dimensional targets

    Science.gov (United States)

    Hochberg, Yonit; Kahn, Yonatan; Lisanti, Mariangela; Tully, Christopher G.; Zurek, Kathryn M.

    2017-09-01

    We propose two-dimensional materials as targets for direct detection of dark matter. Using graphene as an example, we focus on the case where dark matter scattering deposits sufficient energy on a valence-band electron to eject it from the target. We show that the sensitivity of graphene to dark matter of MeV to GeV mass can be comparable, for similar exposure and background levels, to that of semiconductor targets such as silicon and germanium. Moreover, a two-dimensional target is an excellent directional detector, as the ejected electron retains information about the angular dependence of the incident dark matter particle. This proposal can be implemented by the PTOLEMY experiment, presenting for the first time an opportunity for directional detection of sub-GeV dark matter.

  3. Linear negative magnetoresistance in two-dimensional Lorentz gases

    Science.gov (United States)

    Schluck, J.; Hund, M.; Heckenthaler, T.; Heinzel, T.; Siboni, N. H.; Horbach, J.; Pierz, K.; Schumacher, H. W.; Kazazis, D.; Gennser, U.; Mailly, D.

    2018-03-01

    Two-dimensional Lorentz gases formed by obstacles in the shape of circles, squares, and retroreflectors are reported to show a pronounced linear negative magnetoresistance at small magnetic fields. For circular obstacles at low number densities, our results agree with the predictions of a model based on classical retroreflection. In extension to the existing theoretical models, we find that the normalized magnetoresistance slope depends on the obstacle shape and increases as the number density of the obstacles is increased. The peaks are furthermore suppressed by in-plane magnetic fields as well as by elevated temperatures. These results suggest that classical retroreflection can form a significant contribution to the magnetoresistivity of two-dimensional Lorentz gases, while contributions from weak localization cannot be excluded, in particular for large obstacle densities.

  4. Quantum vacuum energy in two dimensional space-times

    Energy Technology Data Exchange (ETDEWEB)

    Davies, P C.W.; Fulling, S A [King' s Coll., London (UK). Dept. of Mathematics

    1977-04-21

    The paper presents in detail the renormalization theory of the energy-momentum tensor of a two dimensional massless scalar field which has been used elsewhere to study the local physics in a model of black hole evaporation. The treatment is generalized to include the Casimir effect occurring in spatially finite models. The essence of the method is evaluation of the field products in the tensor as functions of two points, followed by covariant subtraction of the discontinuous terms arising as the points coalesce. In two dimensional massless theories, conformal transformations permit exact calculations to be performed. The results are applied here to some special cases, primarily space-times of constant curvature, with emphasis on the existence of distinct 'vacuum' states associated naturally with different conformal coordinate systems. The relevance of the work to the general problems of defining observables and of classifying and interpreting states in curved-space quantum field theory is discussed.

  5. CORPORATE VALUATION USING TWO-DIMENSIONAL MONTE CARLO SIMULATION

    Directory of Open Access Journals (Sweden)

    Toth Reka

    2010-12-01

    Full Text Available In this paper, we have presented a corporate valuation model. The model combine several valuation methods in order to get more accurate results. To determine the corporate asset value we have used the Gordon-like two-stage asset valuation model based on the calculation of the free cash flow to the firm. We have used the free cash flow to the firm to determine the corporate market value, which was calculated with use of the Black-Scholes option pricing model in frame of the two-dimensional Monte Carlo simulation method. The combined model and the use of the two-dimensional simulation model provides a better opportunity for the corporate value estimation.

  6. Transport behavior of water molecules through two-dimensional nanopores

    International Nuclear Information System (INIS)

    Zhu, Chongqin; Li, Hui; Meng, Sheng

    2014-01-01

    Water transport through a two-dimensional nanoporous membrane has attracted increasing attention in recent years thanks to great demands in water purification and desalination applications. However, few studies have been reported on the microscopic mechanisms of water transport through structured nanopores, especially at the atomistic scale. Here we investigate the microstructure of water flow through two-dimensional model graphene membrane containing a variety of nanopores of different size by using molecular dynamics simulations. Our results clearly indicate that the continuum flow transits to discrete molecular flow patterns with decreasing pore sizes. While for pores with a diameter ≥15 Å water flux exhibits a linear dependence on the pore area, a nonlinear relationship between water flux and pore area has been identified for smaller pores. We attribute this deviation from linear behavior to the presence of discrete water flow, which is strongly influenced by the water-membrane interaction and hydrogen bonding between water molecules

  7. Two-dimensional superconductivity in ultrathin disordered thin films

    International Nuclear Information System (INIS)

    Beasley, M.R.

    1992-01-01

    The status of the understanding of two-dimensional superconductivity in ultrathin, disordered thin films is reviewed. The different consequences of microscopic versus macroscopic disorder are stressed. It is shown that microscopic disorder leads to a rapid suppression of the mean-field transition temperature. The consequences of macroscopic disorder are not well understood, but a universal behavior of the zero-bias resistance as a function of field and temperature has been observed. (orig.)

  8. Two-dimensional heat conducting simulation of plasma armatures

    International Nuclear Information System (INIS)

    Huerta, M.A.; Boynton, G.

    1991-01-01

    This paper reports on our development of a two-dimensional MHD code to simulate internal motions in a railgun plasma armature. The authors use the equations of resistive MHD, with Ohmic heating, and radiation heat transport. The authors use a Flux Corrected Transport code to advance all quantities in time. Our runs show the development of complex flows, subsequent shedding of secondary arcs, and a drop in the acceleration of the armature

  9. Topological field theories and two-dimensional instantons

    International Nuclear Information System (INIS)

    Schaposnik, F.A.

    1990-01-01

    In this paper, the author discusses some topics related to the recently developed Topological Field Theories (TFTs). The first part is devoted to a discussion on how a TFT can be quantized using techniques which are well-known from the study of gauge theories. Then the author describes the results that we have obtained in collaboration with George Thompson in the study of a two-dimensional TFT related to the Abelian Higgs model

  10. Two-dimensional color-code quantum computation

    International Nuclear Information System (INIS)

    Fowler, Austin G.

    2011-01-01

    We describe in detail how to perform universal fault-tolerant quantum computation on a two-dimensional color code, making use of only nearest neighbor interactions. Three defects (holes) in the code are used to represent logical qubits. Triple-defect logical qubits are deformed into isolated triangular sections of color code to enable transversal implementation of all single logical qubit Clifford group gates. Controlled-NOT (CNOT) is implemented between pairs of triple-defect logical qubits via braiding.

  11. Collision dynamics of two-dimensional non-Abelian vortices

    Science.gov (United States)

    Mawson, Thomas; Petersen, Timothy C.; Simula, Tapio

    2017-09-01

    We study computationally the collision dynamics of vortices in a two-dimensional spin-2 Bose-Einstein condensate. In contrast to Abelian vortex pairs, which annihilate or pass through each other, we observe non-Abelian vortex pairs to undergo rungihilation—an event that converts the colliding vortices into a rung vortex. The resulting rung defect subsequently decays to another pair of non-Abelian vortices of different type, accompanied by a magnetization reversal.

  12. An energy principle for two-dimensional collisionless relativistic plasmas

    International Nuclear Information System (INIS)

    Otto, A.; Schindler, K.

    1984-01-01

    Using relativistic Vlasov theory an energy principle for two-dimensional plasmas is derived, which provides a sufficient and necessary criterion for the stability of relativistic plasma equilibria. This energy principle includes charge separating effects since the exact Poisson equation was taken into consideration. Applying the variational principle to the case of the relativistic plane plasma sheet, the same marginal wave length is found as in the non-relativistic case. (author)

  13. Graphene – A Two-Dimensional Dirac Material

    OpenAIRE

    Liu, Danny; Wicklund, Johan

    2014-01-01

    Graphene is a two-dimensional material, whose popularity has soared in both condensedmatter physics and material science the past decade. Due to its unique properties, graphene can be used in a vast array of new and interesting applications that could fundamentally change the material industry. This report reviews the current research and literature in order to trace the historical development of graphene. Then, in order to better understand the material, the unique properties of graphene are...

  14. Resistive-strips micromegas detectors with two-dimensional readout

    Science.gov (United States)

    Byszewski, M.; Wotschack, J.

    2012-02-01

    Micromegas detectors show very good performance for charged particle tracking in high rate environments as for example at the LHC. It is shown that two coordinates can be extracted from a single gas gap in these detectors. Several micromegas chambers with spark protection by resistive strips and two-dimensional readout have been tested in the context of the R&D work for the ATLAS Muon System upgrade.

  15. Hall effect in the two-dimensional Luttinger liquid

    International Nuclear Information System (INIS)

    Anderson, P.W.

    1991-01-01

    The temperature dependence of the Hall effect in the normal state is a commom theme of all the cuprate superconductors and has been one of the more puzzling observations on these puzzling materials. We describe a general scheme within the Luttinger liquid theory of these two-dimensional quantum fluids which corrrelates the anomalous Hall and resistivity observations on a wide variety of both pure and doped single crystals, especially the data in the accompanying Letter of Chien, Wang, and Ong

  16. Theory of a Nearly Two-Dimensional Dipolar Bose Gas

    Science.gov (United States)

    2016-05-11

    order to be published, he sent the paper to Einstein to translate it. The other contributing scientist is world famous physicist Albert Einstein , maybe...mechanical state, a Bose- Einstein condensate (BEC), where the atoms cease to behave like distinguishable entities, and instead form a single macroscopic...model in both three- and two-dimensional geometries. 15. SUBJECT TERMS Bose Einstein condensation, ultracold physics, condensed matter, dipoles 16

  17. SU(1,2) invariance in two-dimensional oscillator

    Energy Technology Data Exchange (ETDEWEB)

    Krivonos, Sergey [Bogoliubov Laboratory of Theoretical Physics,Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Nersessian, Armen [Yerevan State University,1 Alex Manoogian St., Yerevan, 0025 (Armenia); Tomsk Polytechnic University,Lenin Ave. 30, 634050 Tomsk (Russian Federation)

    2017-02-01

    Performing the Hamiltonian analysis we explicitly established the canonical equivalence of the deformed oscillator, constructed in arXiv:1607.03756, with the ordinary one. As an immediate consequence, we proved that the SU(1,2) symmetry is the dynamical symmetry of the ordinary two-dimensional oscillator. The characteristic feature of this SU(1,2) symmetry is a non-polynomial structure of its generators written in terms of the oscillator variables.

  18. Decaying Two-Dimensional Turbulence in a Circular Container

    OpenAIRE

    Schneider, Kai; Farge, Marie

    2005-01-01

    We present direct numerical simulations of two-dimensional decaying turbulence at initial Reynolds number 5×104 in a circular container with no-slip boundary conditions. Starting with random initial conditions the flow rapidly exhibits self-organization into coherent vortices. We study their formation and the role of the viscous boundary layer on the production and decay of integral quantities. The no-slip wall produces vortices which are injected into the bulk flow and tend to compensate the...

  19. Two-dimensional readout in a liquid xenon ionisation chamber

    CERN Document Server

    Solovov, V; Ferreira-Marques, R; Lopes, M I; Pereira, A; Policarpo, Armando

    2002-01-01

    A two-dimensional readout with metal strips deposited on both sides of a glass plate is investigated aiming to assess the possibility of its use in a liquid xenon ionisation chamber for positron emission tomography. Here, we present results obtained with an alpha-source. It is shown that position resolution of <=1 mm, fwhm, can be achieved for free charge depositions equivalent to those due to gamma-rays with energy from 220 down to 110 keV.

  20. Stochastic and collisional diffusion in two-dimensional periodic flows

    International Nuclear Information System (INIS)

    Doxas, I.; Horton, W.; Berk, H.L.

    1990-05-01

    The global effective diffusion coefficient D* for a two-dimensional system of convective rolls with a time dependent perturbation added, is calculated. The perturbation produces a background diffusion coefficient D, which is calculated analytically using the Menlikov-Arnold integral. This intrinsic diffusion coefficient is then enhanced by the unperturbed flow, to produce the global effective diffusion coefficient D*, which we can calculate theoretically for a certain range of parameters. The theoretical value agrees well with numerical simulations. 23 refs., 4 figs

  1. The Convergence Acceleration of Two-Dimensional Fourier Interpolation

    Directory of Open Access Journals (Sweden)

    Anry Nersessian

    2008-07-01

    Full Text Available Hereby, the convergence acceleration of two-dimensional trigonometric interpolation for a smooth functions on a uniform mesh is considered. Together with theoretical estimates some numerical results are presented and discussed that reveal the potential of this method for application in image processing. Experiments show that suggested algorithm allows acceleration of conventional Fourier interpolation even for sparse meshes that can lead to an efficient image compression/decompression algorithms and also to applications in image zooming procedures.

  2. Two-dimensional correlation spectroscopy in polymer study

    Science.gov (United States)

    Park, Yeonju; Noda, Isao; Jung, Young Mee

    2015-01-01

    This review outlines the recent works of two-dimensional correlation spectroscopy (2DCOS) in polymer study. 2DCOS is a powerful technique applicable to the in-depth analysis of various spectral data of polymers obtained under some type of perturbation. The powerful utility of 2DCOS combined with various analytical techniques in polymer studies and noteworthy developments of 2DCOS used in this field are also highlighted. PMID:25815286

  3. Spatial Discrete Soliton in Two dimensional with Kerr medium

    International Nuclear Information System (INIS)

    Aghdami, M.; Mostafavi, D.; Mokhtari, F.; Keradmand, R.

    2012-01-01

    In this theoretical work propagation of the Gaussian beam through a two dimensional waveguides array is numerically investigated, in which each waveguide contains medium with Kerr nonlinearity considering coupling to vertical, horizontal and diagonal neighbor through light electric field. Different values of intensity, nonlinear coefficient Kerr and Gaussian beam width of incident Gaussian beam are examined and finally suitable parameters for providing central spatial solitons are obtained.

  4. GEPOIS: a two dimensional nonuniform mesh Poisson solver

    International Nuclear Information System (INIS)

    Quintenz, J.P.; Freeman, J.R.

    1979-06-01

    A computer code is described which solves Poisson's equation for the electric potential over a two dimensional cylindrical (r,z) nonuniform mesh which can contain internal electrodes. Poisson's equation is solved over a given region subject to a specified charge distribution with either Neumann or Dirichlet perimeter boundary conditions and with Dirichlet boundary conditions on internal surfaces. The static electric field is also computed over the region with special care given to normal electric field components at boundary surfaces

  5. Acoustic transparency in two-dimensional sonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Dehesa, Jose; Torrent, Daniel [Wave Phenomena Group, Department of Electronic Engineering, Polytechnic University of Valencia, C/ Camino de Vera s/n, E-46022 Valencia (Spain); Cai Liangwu [Department of Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506 (United States)], E-mail: jsdehesa@upvnet.upv.es

    2009-01-15

    Acoustic transparency is studied in two-dimensional sonic crystals consisting of hexagonal distributions of cylinders with continuously varying properties. The transparency condition is achieved by selectively closing the acoustic bandgaps, which are governed by the structure factor of the cylindrical scatterers. It is shown here that cylindrical scatterers with the proposed continuously varying properties are physically realizable by using metafluids based on sonic crystals. The feasibility of this proposal is analyzed by a numerical experiment based on multiple scattering theory.

  6. Two-dimensional manifolds with metrics of revolution

    International Nuclear Information System (INIS)

    Sabitov, I Kh

    2000-01-01

    This is a study of the topological and metric structure of two-dimensional manifolds with a metric that is locally a metric of revolution. In the case of compact manifolds this problem can be thoroughly investigated, and in particular it is explained why there are no closed analytic surfaces of revolution in R 3 other than a sphere and a torus (moreover, in the smoothness class C ∞ such surfaces, understood in a certain generalized sense, exist in any topological class)

  7. Warranty menu design for a two-dimensional warranty

    International Nuclear Information System (INIS)

    Ye, Zhi-Sheng; Murthy, D.N. Pra

    2016-01-01

    Fierce competitions in the commercial product market have forced manufacturers to provide customer-friendly warranties with a view to achieving higher customer satisfaction and increasing the market share. This study proposes a strategy that offers customers a two-dimensional warranty menu with a number of warranty choices, called a flexible warranty policy. We investigate the design of a flexible two-dimensional warranty policy that contains a number of rectangular regions. This warranty policy is obtained by dividing customers into several groups according to their use rates and providing each group a germane warranty region. Consumers choose a favorable one from the menu according to their usage behaviors. Evidently, this flexible warranty policy is attractive to users of different usage behaviors, and thus, it gives the manufacturer a good position in advertising the product. When consumers are unaware about their use rates upon purchase, we consider a fixed two-dimensional warranty policy with a stair-case warranty region and show that it is equivalent to the flexible policy. Such an equivalence reveals the inherent relationship between the rectangular warranty policy, the L-shape warranty policy, the step-stair warranty policy and the iso-probability of failure warranty policy that were extensively discussed in the literature. - Highlights: • We design a two-dimensional warranty menu with a number of warranty choices. • Consumers can choose a favorable one from the menu as per their usage behavior. • We further consider a fixed 2D warranty policy with a stair-case warranty region. • We show the equivalence of the two warranty policies.

  8. Two-dimensional simulation of the MHD stability, (1)

    International Nuclear Information System (INIS)

    Kurita, Gen-ichi; Amano, Tsuneo.

    1976-03-01

    The two-dimensional computer code has been prepared to study MHD stability of an axisymmetric toroidal plasma with and without the surrounding vacuum region. It also includes the effect of magnetic surfaces with non-circular cross sections. The linearized equations of motion are solved as an initial value problem. The results by computer simulation are compared with those by the theory for the cylindrical plasma; they are in good agreement. (auth.)

  9. Analysis of two dimensional signals via curvelet transform

    Science.gov (United States)

    Lech, W.; Wójcik, W.; Kotyra, A.; Popiel, P.; Duk, M.

    2007-04-01

    This paper describes an application of curvelet transform analysis problem of interferometric images. Comparing to two-dimensional wavelet transform, curvelet transform has higher time-frequency resolution. This article includes numerical experiments, which were executed on random interferometric image. In the result of nonlinear approximations, curvelet transform obtains matrix with smaller number of coefficients than is guaranteed by wavelet transform. Additionally, denoising simulations show that curvelet could be a very good tool to remove noise from images.

  10. One- and two-dimensional chemical exchange nuclear magnetic resonance studies of the creatine kinase catalyzed reaction

    International Nuclear Information System (INIS)

    Gober, J.R.

    1988-01-01

    The equilibrium chemical exchange dynamics of the creatine kinase enzyme system were studied by one- and two-dimensional 31 P NMR techniques. Pseudo-first-order reaction rate constants were measured by the saturation transfer method under an array of experimental conditions of pH and temperature. Quantitative one-dimensional spectra were collected under the same conditions in order to calculate the forward and reverse reaction rates, the K eq , the hydrogen ion stoichiometry, and the standard thermodynamic functions. The pure absorption mode in four quadrant two-dimensional chemical exchange experiment was employed so that the complete kinetic matrix showing all of the chemical exchange process could be realized

  11. Spin-orbit torque in two-dimensional antiferromagnetic topological insulators

    KAUST Repository

    Ghosh, Sumit; Manchon, Aurelien

    2017-01-01

    We investigate spin transport in two-dimensional ferromagnetic (FTI) and antiferromagnetic (AFTI) topological insulators. In the presence of an in-plane magnetization AFTI supports zero energy modes, which enables topologically protected edge conduction at low energy. We address the nature of current-driven spin torque in these structures and study the impact of spin-independent disorder. Interestingly, upon strong disorder the spin torque develops an antidamping component (i.e., even upon magnetization reversal) along the edges, which could enable current-driven manipulation of the antiferromagnetic order parameter. This antidamping torque decreases when increasing the system size and when the system enters the trivial insulator regime.

  12. Hybrid surface waves in two-dimensional Rashba-Dresselhaus materials

    Science.gov (United States)

    Yudin, Dmitry; Gulevich, Dmitry R.; Shelykh, Ivan A.

    2017-01-01

    We address the electromagnetic properties of two-dimensional electron gas confined by a dielectric environment in the presence of both Rashba and Dresselhaus spin-orbit interactions. It is demonstrated that off-diagonal components of the conductivity tensor resulting from a delicate interplay between Rashba and Dresselhaus couplings lead to the hybridization of transverse electric and transverse magnetic surface electromagnetic modes localized at the interface. We show that the characteristics of these hybrid surface waves can be controlled by additional intense external off-resonant coherent pumping.

  13. Resonances in a two-dimensional electron waveguide with a single δ-function scatterer

    International Nuclear Information System (INIS)

    Boese, Daniel; Lischka, Markus; Reichl, L. E.

    2000-01-01

    We study the conductance properties of a straight two-dimensional electron waveguide with an s-like scatterer modeled by a single δ-function potential with a finite number of modes. Even such a simple system exhibits interesting resonance phenomena. These resonances are explained in terms of quasibound states both by using a direct solution of the Schroedinger equation and by studying the Green's function of the system. Using the Green's function we calculate the survival probability as well as the power absorption, and show the influence of the quasibound states on these two quantities. (c) 2000 The American Physical Society

  14. Selection rule for Dirac-like points in two-dimensional dielectric photonic crystals

    KAUST Repository

    Li, Yan

    2013-01-01

    We developed a selection rule for Dirac-like points in two-dimensional dielectric photonic crystals. The rule is derived from a perturbation theory and states that a non-zero, mode-coupling integral between the degenerate Bloch states guarantees a Dirac-like point, regardless of the type of the degeneracy. In fact, the selection rule can also be determined from the symmetry of the Bloch states even without computing the integral. Thus, the existence of Dirac-like points can be quickly and conclusively predicted for various photonic crystals independent of wave polarization, lattice structure, and composition. © 2013 Optical Society of America.

  15. Flame propagation in two-dimensional solids: Particle-resolved studies with complex plasmas

    Science.gov (United States)

    Yurchenko, S. O.; Yakovlev, E. V.; Couëdel, L.; Kryuchkov, N. P.; Lipaev, A. M.; Naumkin, V. N.; Kislov, A. Yu.; Ovcharov, P. V.; Zaytsev, K. I.; Vorob'ev, E. V.; Morfill, G. E.; Ivlev, A. V.

    2017-10-01

    Using two-dimensional (2D) complex plasmas as an experimental model system, particle-resolved studies of flame propagation in classical 2D solids are carried out. Combining experiments, theory, and molecular dynamics simulations, we demonstrate that the mode-coupling instability operating in 2D complex plasmas reveals all essential features of combustion, such as an activated heat release, two-zone structure of the self-similar temperature profile ("flame front"), as well as thermal expansion of the medium and temperature saturation behind the front. The presented results are of relevance for various fields ranging from combustion and thermochemistry, to chemical physics and synthesis of materials.

  16. Dispersion and damping of two-dimensional dust acoustic waves: theory and simulation

    International Nuclear Information System (INIS)

    Upadhyaya, Nitin; Miskovic, Z L; Hou, L-J

    2010-01-01

    A two-dimensional generalized hydrodynamics (GH) model is developed to study the full spectrum of both longitudinal and transverse dust acoustic waves (DAW) in strongly coupled complex (dusty) plasmas, with memory-function-formalism being implemented to enforce high-frequency sum rules. Results are compared with earlier theories (such as quasi-localized charge approximation and its extended version) and with a self-consistent Brownian dynamics simulation. It is found that the GH approach provides a good account, not only of dispersion relations, but also of damping rates of the DAW modes in a wide range of coupling strengths, an issue hitherto not fully addressed for dusty plasmas.

  17. Wave dispersion relation of two-dimensional plasma crystals in a magnetic field

    International Nuclear Information System (INIS)

    Uchida, G.; Konopka, U.; Morfill, G.

    2004-01-01

    The wave dispersion relation in a two-dimensional strongly coupled plasma crystal is studied by theoretical analysis and molecular dynamics simulation taking into account a constant magnetic field parallel to the crystal normal. The expression for the wave dispersion relation clearly shows that high-frequency and low-frequency branches exist as a result of the coupling of longitudinal and transverse modes due to the Lorenz force acting on the dust particles. The high-frequency and the low-frequency branches are found to belong to right-hand and left-hand polarized waves, respectively

  18. Symmetrical analysis of the defect level splitting in two-dimensional photonic crystals

    International Nuclear Information System (INIS)

    Malkova, N; Kim, S; Gopalan, V

    2003-01-01

    In this paper doubly degenerate defect states in the band gap of the two-dimensional photonic crystal are studied. These states can be split by a convenient distortion of the lattice. Through analogy with the Jahn-Teller effect in solids, we present a group theoretical analysis of the lifting of the degeneracy of doubly degenerate states in a square lattice by different vibronic modes. The effect is supported by the supercell plane-wave model and by the finite difference time domain technique. We suggest ways for using the effect in photonic switching devices and waveguides

  19. Decaying quasi-two-dimensional viscous flow on a square domain

    DEFF Research Database (Denmark)

    Konijnenberg, J.A. van de; Flor, J.B.; Heijst, G.J.F. van

    1998-01-01

    A comparison is made between experimental, numerical and analytical results for the two-dimensional flow on a square domain. The experiments concern the flow at the interface of a two-layer stratified fluid, evoked by either stirring the fluid with a rake, or by injecting additional fluid...... at the interface. Two numerical simulations were performed with initial conditions and boundary conditions that correspond approximately with those met in the experiments. The analytical results concern the calculation of the lowest modes of a decaying Stokes flow on a square domain. At late times...... relationship between vorticity and stream function in the experiments and the simulations. (C) 1998 American Institute of Physics....

  20. Spin-orbit torque in two-dimensional antiferromagnetic topological insulators

    KAUST Repository

    Ghosh, Sumit

    2017-01-24

    We investigate spin transport in two-dimensional ferromagnetic (FTI) and antiferromagnetic (AFTI) topological insulators. In the presence of an in-plane magnetization AFTI supports zero energy modes, which enables topologically protected edge conduction at low energy. We address the nature of current-driven spin torque in these structures and study the impact of spin-independent disorder. Interestingly, upon strong disorder the spin torque develops an antidamping component (i.e., even upon magnetization reversal) along the edges, which could enable current-driven manipulation of the antiferromagnetic order parameter. This antidamping torque decreases when increasing the system size and when the system enters the trivial insulator regime.

  1. Diffraction of a plane wave on two-dimensional conductive structures and a surface wave

    Science.gov (United States)

    Davidovich, Mikhael V.

    2018-04-01

    We consider the structures type of two-dimensional electron gas in the form of a thin conductive, in particular, graphene films described by tensor conductivity, which are isolated or located on the dielectric layers. The dispersion equation for hybrid modes, as well as scattering parameters. We show that free wave (eigenwaves) problem follow from the problem of diffraction when linking the amplitude of the current of the linear equations are unsolvable, i.e., the determinant of this system is zero. As a particular case the dispersion equation follow from the conditions of matching (with zero reflection coefficient).

  2. Two-dimensional shielding benchmarks for iron at YAYOI, (1)

    International Nuclear Information System (INIS)

    Oka, Yoshiaki; An, Shigehiro; Kasai, Shigeru; Miyasaka, Shun-ichi; Koyama, Kinji.

    The aim of this work is to assess the collapsed neutron and gamma multigroup cross sections for two dimensional discrete ordinate transport code. Two dimensional distributions of neutron flux and gamma ray dose through a 70cm thick and 94cm square iron shield were measured at the fast neutron source reactor ''YAYOI''. The iron shield was placed over the lead reflector in the vertical experimental column surrounded by heavy concrete wall. The detectors used in this experiment were threshold detectors In, Ni, Al, Mg, Fe and Zn, sandwitch resonance detectors Au, W and Co, activation foils Au for neutrons and thermoluminescence detectors for gamma ray dose. The experimental results were compared with the calculated ones by the discrete ordinate transport code ANISN and TWOTRAN. The region-wise, coupled neutron-gamma multigroup cross-sections (100n+20gamma, EURLIB structure) were generated from ENDF/B-IV library for neutrons and POPOP4 library for gamma-ray production cross-sections by using the code system RADHEAT. The effective microscopic neutron cross sections were obtained from the infinite dilution values applying ABBN type self-shielding factors. The gamma ray production multigroup cross-sections were calculated from these effective microscopic neutron cross-sections. For two-dimensional calculations the group constants were collapsed into 10 neutron groups and 3 gamma groups by using ANISN. (auth.)

  3. Electromagnetically induced two-dimensional grating assisted by incoherent pump

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yu-Yuan; Liu, Zhuan-Zhuan; Wan, Ren-Gang, E-mail: wrg@snnu.edu.cn

    2017-04-25

    We propose a scheme for realizing electromagnetically induced two-dimensional grating in a double-Λ system driven simultaneously by a coherent field and an incoherent pump field. In such an atomic configuration, the absorption is suppressed owing to the incoherent pumping process and the probe can be even amplified, while the refractivity is mainly attributed to the dynamically induced coherence. With the help of a standing-wave pattern coherent field, we obtain periodically modulated refractive index without or with gain, and therefore phase grating or gain-phase grating which diffracts a probe light into high-order direction efficiently can be formed in the medium via appropriate manipulation of the system parameters. The diffraction efficiency attainable by the present gratings can be controlled by tuning the coherent field intensity or the interaction length. Hence, the two-dimensional grating can be utilized as all-optical splitter or router in optical networking and communication. - Highlights: • Two-dimensional grating is coherently induced in four-level atoms. • Phase and gain-phase gratings are obtained assisted by incoherent pump. • The diffraction power is improved due to the enhanced refraction modulation. • The gratings can be utilized as multi-channel all-optical splitter and router.

  4. Procedures for two-dimensional electrophoresis of proteins

    Energy Technology Data Exchange (ETDEWEB)

    Tollaksen, S.L.; Giometti, C.S.

    1996-10-01

    High-resolution two-dimensional gel electrophoresis (2DE) of proteins, using isoelectric focusing in the first dimension and sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS-PAGE) in the second, was first described in 1975. In the 20 years since those publications, numerous modifications of the original method have evolved. The ISO-DALT system of 2DE is a high-throughput approach that has stood the test of time. The problem of casting many isoelectric focusing gels and SDS-PAGE slab gels (up to 20) in a reproducible manner has been solved by the use of the techniques and equipment described in this manual. The ISO-DALT system of two-dimensional gel electrophoresis originated in the late 1970s and has been modified many times to improve its high-resolution, high-throughput capabilities. This report provides the detailed procedures used with the current ISO-DALT system to prepare, run, stain, and photograph two-dimensional gels for protein analysis.

  5. Experimental two-dimensional quantum walk on a photonic chip.

    Science.gov (United States)

    Tang, Hao; Lin, Xiao-Feng; Feng, Zhen; Chen, Jing-Yuan; Gao, Jun; Sun, Ke; Wang, Chao-Yue; Lai, Peng-Cheng; Xu, Xiao-Yun; Wang, Yao; Qiao, Lu-Feng; Yang, Ai-Lin; Jin, Xian-Min

    2018-05-01

    Quantum walks, in virtue of the coherent superposition and quantum interference, have exponential superiority over their classical counterpart in applications of quantum searching and quantum simulation. The quantum-enhanced power is highly related to the state space of quantum walks, which can be expanded by enlarging the photon number and/or the dimensions of the evolution network, but the former is considerably challenging due to probabilistic generation of single photons and multiplicative loss. We demonstrate a two-dimensional continuous-time quantum walk by using the external geometry of photonic waveguide arrays, rather than the inner degree of freedoms of photons. Using femtosecond laser direct writing, we construct a large-scale three-dimensional structure that forms a two-dimensional lattice with up to 49 × 49 nodes on a photonic chip. We demonstrate spatial two-dimensional quantum walks using heralded single photons and single photon-level imaging. We analyze the quantum transport properties via observing the ballistic evolution pattern and the variance profile, which agree well with simulation results. We further reveal the transient nature that is the unique feature for quantum walks of beyond one dimension. An architecture that allows a quantum walk to freely evolve in all directions and at a large scale, combining with defect and disorder control, may bring up powerful and versatile quantum walk machines for classically intractable problems.

  6. Automated Processing of Two-Dimensional Correlation Spectra

    Science.gov (United States)

    Sengstschmid; Sterk; Freeman

    1998-04-01

    An automated scheme is described which locates the centers of cross peaks in two-dimensional correlation spectra, even under conditions of severe overlap. Double-quantum-filtered correlation (DQ-COSY) spectra have been investigated, but the method is also applicable to TOCSY and NOESY spectra. The search criterion is the intrinsic symmetry (or antisymmetry) of cross-peak multiplets. An initial global search provides the preliminary information to build up a two-dimensional "chemical shift grid." All genuine cross peaks must be centered at intersections of this grid, a fact that reduces the extent of the subsequent search program enormously. The program recognizes cross peaks by examining the symmetry of signals in a test zone centered at a grid intersection. This "symmetry filter" employs a "lowest value algorithm" to discriminate against overlapping responses from adjacent multiplets. A progressive multiplet subtraction scheme provides further suppression of overlap effects. The processed two-dimensional correlation spectrum represents cross peaks as points at the chemical shift coordinates, with some indication of their relative intensities. Alternatively, the information is presented in the form of a correlation table. The authenticity of a given cross peak is judged by a set of "confidence criteria" expressed as numerical parameters. Experimental results are presented for the 400-MHz double-quantum-filtered COSY spectrum of 4-androsten-3,17-dione, a case where there is severe overlap. Copyright 1998 Academic Press.

  7. Quantum oscillations in quasi-two-dimensional conductors

    CERN Document Server

    Galbova, O

    2002-01-01

    The electronic absorption of sound waves in quasi-two-dimensional conductors in strong magnetic fields, is investigated theoretically. A longitudinal acoustic wave, propagating along the normal n-> to the layer of quasi-two-dimensional conductor (k-> = left brace 0,0,k right brace; u-> = left brace 0,0,u right brace) in magnetic field (B-> = left brace 0, 0, B right brace), is considered. The quasiclassical approach for this geometry is of no interest, due to the absence of interaction between electromagnetic and acoustic waves. The problem is of interest in strong magnetic field when quantization of the charge carriers energy levels takes place. The quantum oscillations in the sound absorption coefficient, as a function of the magnetic field, are theoretically observed. The experimental study of the quantum oscillations in quasi-two-dimensional conductors makes it possible to solve the inverse problem of determining from experimental data the extrema closed sections of the Fermi surface by a plane p sub z = ...

  8. Sufficient Controllability Condition for Affine Systems with Two-Dimensional Control and Two-Dimensional Zero Dynamics

    Directory of Open Access Journals (Sweden)

    D. A. Fetisov

    2015-01-01

    Full Text Available The controllability conditions are well known if we speak about linear stationary systems: a linear stationary system is controllable if and only if the dimension of the state vector is equal to the rank of the controllability matrix. The concept of the controllability matrix is extended to affine systems, but relations between affine systems controllability and properties of this matrix are more complicated. Various controllability conditions are set for affine systems, but they deal as usual either with systems of some special form or with controllability in some small neighborhood of the concerned point. An affine system is known to be controllable if the system is equivalent to a system of a canonical form, which is defined and regular in the whole space of states. In this case, the system is said to be feedback linearizable in the space of states. However there are examples, which illustrate that a system can be controllable even if it is not feedback linearizable in any open subset in the space of states. In this article we deal with such systems.Affine systems with two-dimensional control are considered. The system in question is assumed to be equivalent to a system of a quasicanonical form with two-dimensional zero dynamics which is defined and regular in the whole space of states. Therefore the controllability of the original system is equivalent to the controllability of the received system of a quasicanonical form. In this article the sufficient condition for an available solution of the terminal problem is proven for systems of a quasicanonical form with two-dimensional control and two-dimensional zero dynamics. The condition is valid in the case of an arbitrary time interval and arbitrary initial and finite states of the system. Therefore the controllability condition is set for systems of a quasicanonical form with two-dimensional control and two-dimensional zero dynamics. An example is given which illustrates how the proved

  9. On a separating method for mixed-modes crack growth in wood material using image analysis

    Science.gov (United States)

    Moutou Pitti, R.; Dubois, F.; Pop, O.

    2010-06-01

    Due to the complex wood anatomy and the loading orientation, the timber elements are subjected to a mixed-mode fracture. In these conditions, the crack tip advance is characterized by mixed-mode kinematics. In order to characterize the fracture process function versus the loading orientation, a new mixed-mode crack growth timber specimen is proposed. In the present paper, the design process and the experimental validation of this specimen are proposed. Using experimental results, the energy release rate is calculated for several modes. The calculi consist on the separation of each fracture mode. The design of the specimen is based on the analytical approach and numerical simulation by finite element method. The specimen particularity is the stability of the crack propagation under a force control.

  10. Face/core debond fatigue crack growth characterization using the sandwich mixed mode bending specimen

    DEFF Research Database (Denmark)

    Manca, Marcello; Quispitupa, Amilcar; Berggreen, Christian

    2012-01-01

    Face/core fatigue crack growth in foam-cored sandwich composites is examined using the mixed mode bending (MMB) test method. The mixed mode loading at the debond crack tip is controlled by changing the load application point in the MMB test fixture. Sandwich specimens were manufactured using H45...... and H100 PVC foam cores and E-glass/polyester face sheets. All specimens were pre-cracked in order to define a sharp crack front. The static debond fracture toughness for each material configuration was measured at different mode-mixity phase angles. Fatigue tests were performed at 80% of the static...

  11. Curvature effects in the nonlinear growth of the cylindrical tearing mode

    International Nuclear Information System (INIS)

    Somon, J. P.

    1984-01-01

    The full set of the usual resistive massless equations is used to investigate the nonlinear growth of the helical perturbation to a cylindrical equilibrium with tokamak ordering. There is a curvature dependant critical magnetic island width xsub(T)sup(*) α set containing D/Δ' above which the Rutherford solution is recovered for the tearing mode as well as for the linear slow interchange modes with Δ' > 0. Non linearity stabilizes at this critical width the linearly unstable slow interchange modes with Δ' > 0

  12. Effect of Compressive Mode I on the Mixed Mode I/II Fatigue Crack Growth Rate of 42CrMo4

    Science.gov (United States)

    Heirani, Hasan; Farhangdoost, Khalil

    2018-01-01

    Subsurface cracks in mechanical contact loading components are subjected to mixed mode I/II, so it is necessary to evaluate the fatigue behavior of materials under mixed mode loading. For this purpose, fatigue crack propagation tests are performed with compact tension shear specimens for several stress intensity factor (SIF) ratios of mode I and mode II. The effect of compressive mode I loading on mixed mode I/II crack growth rate and fracture surface is investigated. Tests are carried out for the pure mode I, pure mode II, and two different mixed mode loading angles. On the basis of the experimental results, mixed mode crack growth rate parameters are proposed according to Tanaka and Richard with Paris' law. Results show neither Richard's nor Tanaka's equivalent SIFs are very useful because these SIFs depend strongly on the loading angle, but Richard's equivalent SIF formula is more suitable than Tanaka's formula. The compressive mode I causes the crack closure, and the friction force between the crack surfaces resists against the crack growth. In compressive loading with 45° angle, d a/d N increases as K eq decreases.

  13. On the two-dimensional Saigo-Maeda fractional calculus asociated with two-dimensional Aleph TRANSFORM

    Directory of Open Access Journals (Sweden)

    Dinesh Kumar

    2013-11-01

    Full Text Available This paper deals with the study of two-dimensional Saigo-Maeda operators of Weyl type associated with Aleph function defined in this paper. Two theorems on these defined operators are established. Some interesting results associated with the H-functions and generalized Mittag-Leffler functions are deduced from the derived results. One dimensional analog of the derived results is also obtained.

  14. Quantifying urban growth patterns in Hanoi using landscape expansion modes and time series spatial metrics.

    Science.gov (United States)

    Nong, Duong H; Lepczyk, Christopher A; Miura, Tomoaki; Fox, Jefferson M

    2018-01-01

    Urbanization has been driven by various social, economic, and political factors around the world for centuries. Because urbanization continues unabated in many places, it is crucial to understand patterns of urbanization and their potential ecological and environmental impacts. Given this need, the objectives of our study were to quantify urban growth rates, growth modes, and resultant changes in the landscape pattern of urbanization in Hanoi, Vietnam from 1993 to 2010 and to evaluate the extent to which the process of urban growth in Hanoi conformed to the diffusion-coalescence theory. We analyzed the spatiotemporal patterns and dynamics of the built-up land in Hanoi using landscape expansion modes, spatial metrics, and a gradient approach. Urbanization was most pronounced in the periods of 2001-2006 and 2006-2010 at a distance of 10 to 35 km around the urban center. Over the 17 year period urban expansion in Hanoi was dominated by infilling and edge expansion growth modes. Our findings support the diffusion-coalescence theory of urbanization. The shift of the urban growth areas over time and the dynamic nature of the spatial metrics revealed important information about our understanding of the urban growth process and cycle. Furthermore, our findings can be used to evaluate urban planning policies and aid in urbanization issues in rapidly urbanizing countries.

  15. Quantifying urban growth patterns in Hanoi using landscape expansion modes and time series spatial metrics

    Science.gov (United States)

    Lepczyk, Christopher A.; Miura, Tomoaki; Fox, Jefferson M.

    2018-01-01

    Urbanization has been driven by various social, economic, and political factors around the world for centuries. Because urbanization continues unabated in many places, it is crucial to understand patterns of urbanization and their potential ecological and environmental impacts. Given this need, the objectives of our study were to quantify urban growth rates, growth modes, and resultant changes in the landscape pattern of urbanization in Hanoi, Vietnam from 1993 to 2010 and to evaluate the extent to which the process of urban growth in Hanoi conformed to the diffusion-coalescence theory. We analyzed the spatiotemporal patterns and dynamics of the built-up land in Hanoi using landscape expansion modes, spatial metrics, and a gradient approach. Urbanization was most pronounced in the periods of 2001–2006 and 2006–2010 at a distance of 10 to 35 km around the urban center. Over the 17 year period urban expansion in Hanoi was dominated by infilling and edge expansion growth modes. Our findings support the diffusion-coalescence theory of urbanization. The shift of the urban growth areas over time and the dynamic nature of the spatial metrics revealed important information about our understanding of the urban growth process and cycle. Furthermore, our findings can be used to evaluate urban planning policies and aid in urbanization issues in rapidly urbanizing countries. PMID:29734346

  16. Two-dimensionally grown single-crystal silicon nanosheets with tunable visible-light emissions.

    Science.gov (United States)

    Kim, Sung Wook; Lee, Jaejun; Sung, Ji Ho; Seo, Dong-jae; Kim, Ilsoo; Jo, Moon-Ho; Kwon, Byoung Wook; Choi, Won Kook; Choi, Heon-Jin

    2014-07-22

    Since the discovery of graphene, growth of two-dimensional (2D) nanomaterials has greatly attracted attention. However, spontaneous growth of atomic two-dimensional (2D) materials is limitedly permitted for several layered-structure crystals, such as graphene, MoS2, and h-BN, and otherwise it is notoriously difficult. Here we report the gas-phase 2D growth of silicon (Si), that is cubic in symmetry, via dendritic growth and an interdendritic filling mechanism and to form Si nanosheets (SiNSs) of 1 to 13 nm in thickness. Thin SiNSs show strong thickness-dependent photoluminescence in visible range including red, green, and blue (RGB) emissions with the associated band gap energies ranging from 1.6 to 3.2 eV; these emission energies were greater than those from Si quantum dots (SiQDs) of the similar sizes. We also demonstrated that electrically driven white, as well as blue, emission in a conventional organic light-emitting diode (OLED) geometry with the SiNS assembly as the active emitting layers. Tunable light emissions in visible range in our observations suggest practical implications for novel 2D Si nanophotonics.

  17. Two-dimensional polyacrylamide gel electrophoresis of intracellular proteins

    International Nuclear Information System (INIS)

    Ojima, N.; Sakamoto, T.; Yamashita, M.

    1996-01-01

    Since two-dimensional electrophoresis was established by O'Farrell for analysis of intracellular proteins of Escherichia coli, it has been applied to separation of proteins of animal cells and tissues, and especially to identification of stress proteins. Using this technique, proteins are separated by isoelectric focusing containing 8 m urea in the first dimension and by SDS-PAGE in the second dimension. The gels are stained with Coomassie Blue R-250 dye, followed by silver staining. In the case of radio-labeled proteins, the gels are dried and then autoradiographed. In order to identify a specific protein separated by two-dimensional electrophoresis, a technique determining the N-terminal amino acid sequence of the protein has been developed recently. After the proteins in the gel were electrotransferred to a polyvinylidene difluoride membrane, the membrane was stained for protein with Commassie Blue and a stained membrane fragment was applied to a protein sequencer. Our recent studies demonstrated that fish cells newly synthesized various proteins in response to heat shock, cold nd osmotic stresses. For example, when cellular proteins extracted from cold-treated rainbow trout cells were subjected to two-dimensional gel electrophoresis, the 70 kDa protein was found to be synthesized during the cold-treatment. N-Terminal sequence analysis showed that the cold-inducible protein was a homolog of mammalian valosin-containing protein and yeast cell division cycle gene product CDC48p. Furthermore, the sequence data were useful for preparing PCR primers and a rabbit antibody against a synthetic peptide to analyze a role for the protein in the function of trout cells and mechanisms for regulation

  18. Statistical mechanics of two-dimensional and geophysical flows

    International Nuclear Information System (INIS)

    Bouchet, Freddy; Venaille, Antoine

    2012-01-01

    The theoretical study of the self-organization of two-dimensional and geophysical turbulent flows is addressed based on statistical mechanics methods. This review is a self-contained presentation of classical and recent works on this subject; from the statistical mechanics basis of the theory up to applications to Jupiter’s troposphere and ocean vortices and jets. Emphasize has been placed on examples with available analytical treatment in order to favor better understanding of the physics and dynamics. After a brief presentation of the 2D Euler and quasi-geostrophic equations, the specificity of two-dimensional and geophysical turbulence is emphasized. The equilibrium microcanonical measure is built from the Liouville theorem. Important statistical mechanics concepts (large deviations and mean field approach) and thermodynamic concepts (ensemble inequivalence and negative heat capacity) are briefly explained and described. On this theoretical basis, we predict the output of the long time evolution of complex turbulent flows as statistical equilibria. This is applied to make quantitative models of two-dimensional turbulence, the Great Red Spot and other Jovian vortices, ocean jets like the Gulf-Stream, and ocean vortices. A detailed comparison between these statistical equilibria and real flow observations is provided. We also present recent results for non-equilibrium situations, for the studies of either the relaxation towards equilibrium or non-equilibrium steady states. In this last case, forces and dissipation are in a statistical balance; fluxes of conserved quantity characterize the system and microcanonical or other equilibrium measures no longer describe the system.

  19. Two-dimensional photonic crystal bandedge laser with hybrid perovskite thin film for optical gain

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Hyungrae [Department of Biophysics and Chemical Biology, Seoul National University, Seoul 08826 (Korea, Republic of); Inter-University Semiconductor Research Center, Seoul National University, Seoul 08826 (Korea, Republic of); Bae, Seunghwan [Department of Materials Science and Engineering, Seoul National University, Seoul 08826 (Korea, Republic of); Lee, Myungjae [Inter-University Semiconductor Research Center, Seoul National University, Seoul 08826 (Korea, Republic of); Department of Physics and Astronomy, Seoul National University, Seoul 08826 (Korea, Republic of); Jeon, Heonsu, E-mail: hsjeon@snu.ac.kr [Department of Biophysics and Chemical Biology, Seoul National University, Seoul 08826 (Korea, Republic of); Inter-University Semiconductor Research Center, Seoul National University, Seoul 08826 (Korea, Republic of); Department of Physics and Astronomy, Seoul National University, Seoul 08826 (Korea, Republic of)

    2016-05-02

    We report optically pumped room temperature single mode laser that contains a thin film of hybrid perovskite, an emerging photonic material, as gain medium. Two-dimensional square lattice photonic crystal (PhC) backbone structure enables single mode laser operation via a photonic bandedge mode, while a thin film of methyl-ammonium lead iodide (CH{sub 3}NH{sub 3}PbI{sub 3}) spin-coated atop provides optical gain for lasing. Two kinds of bandedge modes, Γ and M, are employed, and both devices laser in single mode at similar laser thresholds of ∼200 μJ/cm{sup 2} in pulse energy density. Polarization dependence measurements reveal a clear difference between the two kinds of bandedge lasers: isotropic for the Γ-point laser and highly anisotropic for the M-point laser. These observations are consistent with expected modal properties, confirming that the lasing actions indeed originate from the corresponding PhC bandedge modes.

  20. Introduction to two dimensional conformal and superconformal field theory

    International Nuclear Information System (INIS)

    Shenker, S.H.

    1986-01-01

    Some of the basic properties of conformal and superconformal field theories in two dimensions are discussed in connection with the string and superstring theories built from them. In the first lecture the stress-energy tensor, the Virasoro algebra, highest weight states, primary fields, operator products coefficients, bootstrap ideas, and unitary and degenerate representations of the Virasoro algebra are discussed. In the second lecture the basic structure of superconformal two dimensional field theory is sketched and then the Ramond Neveu-Schwarz formulation of the superstring is described. Some of the issues involved in constructing the fermion vertex in this formalism are discussed

  1. Quasi-integrability and two-dimensional QCD

    International Nuclear Information System (INIS)

    Abdalla, E.; Mohayaee, R.

    1996-10-01

    The notion of integrability in two-dimensional QCD is discussed. We show that in spite of an infinite number of conserved charges, particle production is not entirely suppressed. This phenomenon, which we call quasi-integrability, is explained in terms of quantum corrections to the combined algebra of higher-conserved and spectrum-generating currents. We predict the qualitative form of particle production probabilities and verify that they are in agreement with numerical data. We also discuss four-dimensional self-dual Yang-Mills theory in the light of our results. (author). 25 refs, 4 figs, 1 tab

  2. Two dimensional hybrid simulation of a curved bow shock

    International Nuclear Information System (INIS)

    Thomas, V.A.; Winske, D.

    1990-01-01

    Results are presented from two dimensional hybrid simulations of curved collisionless supercritical shocks, retaining both quasi-perpendicular and quasi-parallel sections of the shock in order to study the character and origin of the foreshock ion population. The simulations demonstrate that the foreshock ion population is dominated by ions impinging upon the quasi-parallel side of the shock, while nonlocal transport from the quasi-perpendicular side of the shock into the foreshock region is minimal. Further, it is shown that the ions gain energy by drifting significantly in the direction of the convection electric field through multiple shock encounters

  3. Focused two-dimensional antiscatter grid for mammography

    International Nuclear Information System (INIS)

    Makarova, O.V.; Moldovan, N.; Tang, C.-M.; Mancini, D.C.; Divan, R.; Zyryanov, V.N.; Ryding, D.C.; Yaeger, J.; Liu, C.

    2002-01-01

    We are developing freestanding high-aspect-ratio, focused, two-dimensional antiscatter grids for mammography using deep x-ray lithography and copper electroforming. The exposure is performed using x-rays from bending magnet beamline 2-BM at the Advanced Photon Source (APS) of Argonne National Laboratory. A 2.8-mm-thick prototype freestanding copper antiscatter grid with 25 (micro)m-wide parallel cell walls and 550 (micro)m periodicity has been fabricated. The progress in developing a dynamic double-exposure technique to create the grid with the cell walls aligned to a point x-ray source of the mammography system is discussed

  4. Two-dimensional 220 MHz Fourier transform EPR imaging

    International Nuclear Information System (INIS)

    Placidi, Giuseppe; Brivati, John A.; Alecci, Marcello; Testa, Luca; Sotgiu, Antonello

    1998-01-01

    In the last decade radiofrequency continuous-wave EPR spectrometers have been developed to detect and localize free radicals in vivo. Only recently, pulsed radiofrequency EPR spectrometers have been described for imaging applications with small samples. In the present work, we show the first two-dimensional image obtained at 220 MHz on a large phantom (40 ml) that simulates typical conditions of in vivo EPR imaging. This pulsed EPR apparatus has the potential to make the time required for three-dimensional imaging compatible with the biological half-life of normally used paramagnetic probes. (author)

  5. Voltage quantization by ballistic vortices in two-dimensional superconductors

    International Nuclear Information System (INIS)

    Orlando, T.P.; Delin, K.A.

    1991-01-01

    The voltage generated by moving ballistic vortices with a mass m ν in a two-dimensional superconducting ring is quantized, and this quantization depends on the amount of charge enclosed by the ring. The quantization of the voltage is the dual to flux quantization in a superconductor, and is a manifestation of the Aharonov-Casher effect. The quantization is obtained by applying the Bohr-Sommerfeld criterion to the canonical momentum of the ballistic vortices. The results of this quantization condition can also be used to understand the persistent voltage predicted by van Wees for an array of Josephson junctions

  6. Two-dimensional beam profiles and one-dimensional projections

    Science.gov (United States)

    Findlay, D. J. S.; Jones, B.; Adams, D. J.

    2018-05-01

    One-dimensional projections of improved two-dimensional representations of transverse profiles of particle beams are proposed for fitting to data from harp-type monitors measuring beam profiles on particle accelerators. Composite distributions, with tails smoothly matched on to a central (inverted) parabola, are shown to give noticeably better fits than single gaussian and single parabolic distributions to data from harp-type beam profile monitors all along the proton beam transport lines to the two target stations on the ISIS Spallation Neutron Source. Some implications for inferring beam current densities on the beam axis are noted.

  7. Two-dimensionally confined topological edge states in photonic crystals

    International Nuclear Information System (INIS)

    Barik, Sabyasachi; Miyake, Hirokazu; DeGottardi, Wade; Waks, Edo; Hafezi, Mohammad

    2016-01-01

    We present an all-dielectric photonic crystal structure that supports two-dimensionally confined helical topological edge states. The topological properties of the system are controlled by the crystal parameters. An interface between two regions of differing band topologies gives rise to topological edge states confined in a dielectric slab that propagate around sharp corners without backscattering. Three-dimensional finite-difference time-domain calculations show these edges to be confined in the out-of-plane direction by total internal reflection. Such nanoscale photonic crystal architectures could enable strong interactions between photonic edge states and quantum emitters. (paper)

  8. Nonlinear aerodynamics of two-dimensional airfoils in severe maneuver

    Science.gov (United States)

    Scott, Matthew T.; Mccune, James E.

    1988-01-01

    This paper presents a nonlinear theory of forces and moment acting on a two-dimensional airfoil in unsteady potential flow. Results are obtained for cases of both large and small amplitude motion. The analysis, which is based on an extension of Wagner's integral equation to the nonlinear regime, takes full advantage of the trailing wake's tendency to deform under local velocities. Interactive computational results are presented that show examples of wake-induced lift and moment augmentation on the order of 20 percent of quasi-static values. The expandability and flexibility of the present computational method are noted, as well as the relative speed with which solutions are obtained.

  9. Two-dimensional unsteady lift problems in supersonic flight

    Science.gov (United States)

    Heaslet, Max A; Lomax, Harvard

    1949-01-01

    The variation of pressure distribution is calculated for a two-dimensional supersonic airfoil either experiencing a sudden angle-of-attack change or entering a sharp-edge gust. From these pressure distributions the indicial lift functions applicable to unsteady lift problems are determined for two cases. Results are presented which permit the determination of maximum increment in lift coefficient attained by an unrestrained airfoil during its flight through a gust. As an application of these results, the minimum altitude for safe flight through a specific gust is calculated for a particular supersonic wing of given strength and wing loading.

  10. Engineering topological edge states in two dimensional magnetic photonic crystal

    Science.gov (United States)

    Yang, Bing; Wu, Tong; Zhang, Xiangdong

    2017-01-01

    Based on a perturbative approach, we propose a simple and efficient method to engineer the topological edge states in two dimensional magnetic photonic crystals. The topological edge states in the microstructures can be constructed and varied by altering the parameters of the microstructure according to the field-energy distributions of the Bloch states at the related Bloch wave vectors. The validity of the proposed method has been demonstrated by exact numerical calculations through three concrete examples. Our method makes the topological edge states "designable."

  11. Synthesis of borophenes: Anisotropic, two-dimensional boron polymorphs

    Energy Technology Data Exchange (ETDEWEB)

    Mannix, A. J.; Zhou, X. -F.; Kiraly, B.; Wood, J. D.; Alducin, D.; Myers, B. D.; Liu, X.; Fisher, B. L.; Santiago, U.; Guest, J. R.; Yacaman, M. J.; Ponce, A.; Oganov, A. R.; Hersam, M. C.; Guisinger, N. P.

    2015-12-17

    At the atomic-cluster scale, pure boron is markedly similar to carbon, forming simple planar molecules and cage-like fullerenes. Theoretical studies predict that two-dimensional (2D) boron sheets will adopt an atomic configuration similar to that of boron atomic clusters. We synthesized atomically thin, crystalline 2D boron sheets (i.e., borophene) on silver surfaces under ultrahigh-vacuum conditions. Atomic-scale characterization, supported by theoretical calculations, revealed structures reminiscent of fused boron clusters with multiple scales of anisotropic, out-of-plane buckling. Unlike bulk boron allotropes, borophene shows metallic characteristics that are consistent with predictions of a highly anisotropic, 2D metal.

  12. Field analysis of two-dimensional focusing grating

    OpenAIRE

    Borsboom, P.P.; Frankena, H.J.

    1995-01-01

    The method that we have developed [P-P. Borsboom, Ph.D. dissertation (Delft University of Technology, Delft, The Netherlands); P-P. Borsboom and H. J. Frankena, J. Opt. Soc. Am. A 12, 1134–1141 (1995)] is successfully applied to a two-dimensional focusing grating coupler. The field in the focal region has been determined for symmetrical chirped gratings consisting of as many as 124 corrugations. The intensity distribution in the focal region agrees well with the approximate predictions of geo...

  13. Wigner functions from the two-dimensional wavelet group.

    Science.gov (United States)

    Ali, S T; Krasowska, A E; Murenzi, R

    2000-12-01

    Following a general procedure developed previously [Ann. Henri Poincaré 1, 685 (2000)], here we construct Wigner functions on a phase space related to the similitude group in two dimensions. Since the group space in this case is topologically homeomorphic to the phase space in question, the Wigner functions so constructed may also be considered as being functions on the group space itself. Previously the similitude group was used to construct wavelets for two-dimensional image analysis; we discuss here the connection between the wavelet transform and the Wigner function.

  14. Pattern formation in two-dimensional square-shoulder systems

    International Nuclear Information System (INIS)

    Fornleitner, Julia; Kahl, Gerhard

    2010-01-01

    Using a highly efficient and reliable optimization tool that is based on ideas of genetic algorithms, we have systematically studied the pattern formation of the two-dimensional square-shoulder system. An overwhelming wealth of complex ordered equilibrium structures emerge from this investigation as we vary the shoulder width. With increasing pressure three structural archetypes could be identified: cluster lattices, where clusters of particles occupy the sites of distorted hexagonal lattices, lane formation, and compact particle arrangements with high coordination numbers. The internal complexity of these structures increases with increasing shoulder width.

  15. Pattern formation in two-dimensional square-shoulder systems

    Energy Technology Data Exchange (ETDEWEB)

    Fornleitner, Julia [Institut fuer Festkoerperforschung, Forschungsszentrum Juelich, D-52425 Juelich (Germany); Kahl, Gerhard, E-mail: fornleitner@cmt.tuwien.ac.a [Institut fuer Theoretische Physik and Centre for Computational Materials Science (CMS), Technische Universitaet Wien, Wiedner Hauptstrasse 8-10, A-1040 Wien (Austria)

    2010-03-17

    Using a highly efficient and reliable optimization tool that is based on ideas of genetic algorithms, we have systematically studied the pattern formation of the two-dimensional square-shoulder system. An overwhelming wealth of complex ordered equilibrium structures emerge from this investigation as we vary the shoulder width. With increasing pressure three structural archetypes could be identified: cluster lattices, where clusters of particles occupy the sites of distorted hexagonal lattices, lane formation, and compact particle arrangements with high coordination numbers. The internal complexity of these structures increases with increasing shoulder width.

  16. Decay of homogeneous two-dimensional quantum turbulence

    Science.gov (United States)

    Baggaley, Andrew W.; Barenghi, Carlo F.

    2018-03-01

    We numerically simulate the free decay of two-dimensional quantum turbulence in a large, homogeneous Bose-Einstein condensate. The large number of vortices, the uniformity of the density profile, and the absence of boundaries (where vortices can drift out of the condensate) isolate the annihilation of vortex-antivortex pairs as the only mechanism which reduces the number of vortices, Nv, during the turbulence decay. The results clearly reveal that vortex annihilation is a four-vortex process, confirming the decay law Nv˜t-1 /3 where t is time, which was inferred from experiments with relatively few vortices in small harmonically trapped condensates.

  17. Human muscle proteins: analysis by two-dimensional electrophoresis

    Energy Technology Data Exchange (ETDEWEB)

    Giometti, C.S.; Danon, M.J.; Anderson, N.G.

    1983-09-01

    Proteins from single frozen sections of human muscle were separated by two-dimensional gel electrophoresis and detected by fluorography or Coomassie Blue staining. The major proteins were identical in different normal muscles obtained from either sex at different ages, and in Duchenne and myotonic dystrophy samples. Congenital myopathy denervation atrophy, polymyositis, and Becker's muscular dystrophy samples, however, showed abnormal myosin light chain compositions, some with a decrease of fast-fiber myosin light chains and others with a decrease of slow-fiber light chains. These protein alterations did not correlate with any specific disease, and may be cause by generalized muscle-fiber damage.

  18. Cavalier perspective plots of two-dimensional matrices. Program Stereo

    International Nuclear Information System (INIS)

    Los Arcos Merino, J.M.

    1978-01-01

    The program Stereo allows representation of a two-dimensional matrix containing numerical data, in the form of a cavalier perspective, isometric or not, with an angle variable between 0 deg and 180 deg. The representation is in histogram form for each matrix row and those curves which fall behind higher curves and therefore would not be seen are suppressed. It has been written in Fortran V for a Calcomp-936 digital plotter operating off-line with a Univac 1106 computer. Drawing method, subroutine structure and running instructions are described in this paper. (author)

  19. Bosonization in a two-dimensional Riemann Cartan geometry

    International Nuclear Information System (INIS)

    Denardo, G.; Spallucci, E.

    1987-01-01

    We study the vacuum functional for a Dirac field in a two dimensional Riemann-Cartan geometry. Torsion is treated as a quantum variable while the metric is considered as a classical background field. Decoupling spinors from the non-Riemannian part of the geometry introduces a chiral Jacobian into the vacuum generating functional. We compute this functional Jacobian determinant by means of the Alvarez method. Finally, we show that the effective action for the background geometry is of the Liouville type and does not preserve any memory of the initial torsion field. (author)

  20. Periodic trajectories for two-dimensional nonintegrable Hamiltonians

    International Nuclear Information System (INIS)

    Davies, K.T.R.

    1990-02-01

    I want to report on some calculations of classical periodic trajectories in a two-dimensional nonintegrable potential. After a brief introduction, I will present some details of the theory. The main part of this report will be devoted to showing pictures of the various families of trajectories and to discussing the topology (in E-τ space) and branching behavior of these families. Then I will demonstrate the connection between periodic trajectories and ''nearby'' nonperiodic trajectories, which nicely illustrates the relationship of this work to chaos. Finally, I will discuss very briefly how periodic trajectories can be used to calculate tori. 12 refs., 40 figs

  1. Optical Two Dimensional Fourier Transform Spectroscopy of Layered Metal Dichalcogenides

    Science.gov (United States)

    Dey, P.; Paul, J.; Stevens, C. E.; Kovalyuk, Z. D.; Kudrynskyi, Z. R.; Romero, A. H.; Cantarero, A.; Hilton, D. J.; Shan, J.; Karaiskaj, D.; Z. D. Kovalyuk; Z. R. Kudrynskyi Collaboration; A. H. Romero Collaboration; A. Cantarero Collaboration; D. J. Hilton Collaboration; J. Shan Collaboration

    2015-03-01

    Nonlinear two-dimensional Fourier transform (2DFT) measurements were used to study the mechanism of excitonic dephasing and probe the electronic structure of the excitonic ground state in layered metal dichalcogenides. Temperature-dependent 2DFT measurements were performed to probe exciton-phonon interactions. Excitation density dependent 2DFT measurements reveal exciton-exciton and exciton-carrier scattering, and the lower limit for the homogeneous linewidth of excitons on positively and negatively doped samples. U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-SC0012635.

  2. Two-dimensional collapse calculations of cylindrical clouds

    International Nuclear Information System (INIS)

    Bastien, P.; Mitalas, R.

    1979-01-01

    A two-dimensional hydrodynamic computer code has been extensively modified and expanded to study the collapse of non-rotating interstellar clouds. The physics and the numerical methods involved are discussed. The results are presented and discussed in terms of the Jeans number. The critical Jeans number for collapse of non-rotating cylindrical clouds whose length is the same as their diameter is 1.00. No evidence for fragmentation has been found for these clouds, but fragmentation seems quite likely for more elongated cylindrical clouds. (author)

  3. Poincare' maps of impulsed oscillators and two-dimensional dynamics

    International Nuclear Information System (INIS)

    Lupini, R.; Lenci, S.; Gardini, L.; Urbino Univ.

    1996-01-01

    The Poincare' map of one-dimensional linear oscillators subject to periodic, non-linear and time-delayed impulses is shown to reduce to a family of plane maps with possible non-uniqueness of the inverse. By restricting the analysis to a convenient form of the impulse function, a variety of interesting dynamical behaviours in this family are pointed out, including multistability and homoclinic bifurcations. Critical curves of two-dimensional endomorphisms are used to identify the structure of absorbing areas and their bifurcations

  4. Inverse radiative transfer problems in two-dimensional heterogeneous media

    International Nuclear Information System (INIS)

    Tito, Mariella Janette Berrocal

    2001-01-01

    The analysis of inverse problems in participating media where emission, absorption and scattering take place has several relevant applications in engineering and medicine. Some of the techniques developed for the solution of inverse problems have as a first step the solution of the direct problem. In this work the discrete ordinates method has been used for the solution of the linearized Boltzmann equation in two dimensional cartesian geometry. The Levenberg - Marquardt method has been used for the solution of the inverse problem of internal source and absorption and scattering coefficient estimation. (author)

  5. Two-Dimensional One-Component Plasma on Flamm's Paraboloid

    Science.gov (United States)

    Fantoni, Riccardo; Téllez, Gabriel

    2008-11-01

    We study the classical non-relativistic two-dimensional one-component plasma at Coulomb coupling Γ=2 on the Riemannian surface known as Flamm's paraboloid which is obtained from the spatial part of the Schwarzschild metric. At this special value of the coupling constant, the statistical mechanics of the system are exactly solvable analytically. The Helmholtz free energy asymptotic expansion for the large system has been found. The density of the plasma, in the thermodynamic limit, has been carefully studied in various situations.

  6. Morphology of bipolar planetary nebulae. I. Two-dimensional spectrophotometry

    International Nuclear Information System (INIS)

    Pascoli, G.

    1990-01-01

    Two-dimensional spectrophotometric observations of bipolar planetary nebulae were performed by using a CCD detector mounted at the Cassegrain focus of either 1.54 m Danish Telescope or 2.2 m German Telescope at La Silla (ESO) in Chile. Emission lines have been selected with the help of narrow band-pass interference filters (Δλ∼ 10 - 20 A). Isophotal maps in various lines Hα, [NII] λ 6584, [OIII] λ 5007 and [SII] λλ 6717-6731 are presented. Particular attention has been given to scrutinize the symmetries inside a few bipolar planetary nebulae, in order to subsequently investigate their space structure

  7. Gibbs perturbations of a two-dimensional gauge field

    International Nuclear Information System (INIS)

    Petrova, E.N.

    1981-01-01

    Small Gibbs perturbations of random fields have been investigated up to now for a few initial fields only. Among them there are independent fields, Gaussian fields and some others. The possibility for the investigation of Gibbs modifications of a random field depends essentially on the existence of good estimates for semiinvariants of this field. This is the reason why the class of random fields for which the investigation of Gibbs perturbations with arbitrary potential of bounded support is possible is rather small. The author takes as initial a well-known model: a two-dimensional gauge field. (Auth.)

  8. Saddle-points of a two dimensional random lattice theory

    International Nuclear Information System (INIS)

    Pertermann, D.

    1985-07-01

    A two dimensional random lattice theory with a free massless scalar field is considered. We analyse the field theoretic generating functional for any given choice of positions of the lattice sites. Asking for saddle-points of this generating functional with respect to the positions we find the hexagonal lattice and a triangulated version of the hypercubic lattice as candidates. The investigation of the neighbourhood of a single lattice site yields triangulated rectangles and regular polygons extremizing the above generating functional on the local level. (author)

  9. Minimal quantization of two-dimensional models with chiral anomalies

    International Nuclear Information System (INIS)

    Ilieva, N.

    1987-01-01

    Two-dimensional gauge models with chiral anomalies - ''left-handed'' QED and the chiral Schwinger model, are quantized consistently in the frames of the minimal quantization method. The choice of the cone time as a physical time for system of quantization is motivated. The well-known mass spectrum is found but with a fixed value of the regularization parameter a=2. Such a unique solution is obtained due to the strong requirement of consistency of the minimal quantization that reflects in the physically motivated choice of the time axis

  10. Two-dimensional N = 2 Super-Yang-Mills Theory

    Science.gov (United States)

    August, Daniel; Wellegehausen, Björn; Wipf, Andreas

    2018-03-01

    Supersymmetry is one of the possible scenarios for physics beyond the standard model. The building blocks of this scenario are supersymmetric gauge theories. In our work we study the N = 1 Super-Yang-Mills (SYM) theory with gauge group SU(2) dimensionally reduced to two-dimensional N = 2 SYM theory. In our lattice formulation we break supersymmetry and chiral symmetry explicitly while preserving R symmetry. By fine tuning the bar-mass of the fermions in the Lagrangian we construct a supersymmetric continuum theory. To this aim we carefully investigate mass spectra and Ward identities, which both show a clear signal of supersymmetry restoration in the continuum limit.

  11. Mixed-symmetry superconductivity in two-dimensional Fermi liquids

    International Nuclear Information System (INIS)

    Musaelian, K.A.; Betouras, J.; Chubukov, A.V.; Joynt, R.

    1996-01-01

    We consider a two-dimensional (2D) isotropic Fermi liquid with attraction in both s and d channels and examine the possibility of a superconducting state with mixed s and d symmetry of the gap function. We show that both in the weak-coupling limit and at strong coupling, a mixed s+id symmetry state is realized in a certain range of interaction. Phase transitions between the mixed and the pure symmetry states are second order. We also show that there is no stable mixed s+d symmetry state at any coupling. copyright 1996 The American Physical Society

  12. Magnus force in discrete and continuous two-dimensional superfluids

    International Nuclear Information System (INIS)

    Gecse, Z.; Khlebnikov, S.

    2005-01-01

    Motion of vortices in two-dimensional superfluids in the classical limit is studied by solving the Gross-Pitaevskii equation numerically on a uniform lattice. We find that, in the presence of a superflow directed along one of the main lattice periods, vortices move with the superflow on fine lattices but perpendicular to it on coarse ones. We interpret this result as a transition from the full Magnus force in a Galilean-invariant limit to vanishing effective Magnus force in a discrete system, in agreement with the existing experiments on vortex motion in Josephson junction arrays

  13. Two dimensional topological insulator in quantizing magnetic fields

    Science.gov (United States)

    Olshanetsky, E. B.; Kvon, Z. D.; Gusev, G. M.; Mikhailov, N. N.; Dvoretsky, S. A.

    2018-05-01

    The effect of quantizing magnetic field on the electron transport is investigated in a two dimensional topological insulator (2D TI) based on a 8 nm (013) HgTe quantum well (QW). The local resistance behavior is indicative of a metal-insulator transition at B ≈ 6 T. On the whole the experimental data agrees with the theory according to which the helical edge states transport in a 2D TI persists from zero up to a critical magnetic field Bc after which a gap opens up in the 2D TI spectrum.

  14. Anisotropic mass density by two-dimensional acoustic metamaterials

    Energy Technology Data Exchange (ETDEWEB)

    Torrent, Daniel; Sanchez-Dehesa, Jose [Wave Phenomena Group, Department of Electronic Engineering, Polytechnic University of Valencia, C/Camino de Vera s/n, E-46022 Valencia (Spain)], E-mail: jsdehesa@upvnet.upv.es

    2008-02-15

    We show that specially designed two-dimensional arrangements of full elastic cylinders embedded in a nonviscous fluid or gas define (in the homogenization limit) a new class of acoustic metamaterials characterized by a dynamical effective mass density that is anisotropic. Here, analytic expressions for the dynamical mass density and the effective sound velocity tensors are derived in the long wavelength limit. Both show an explicit dependence on the lattice filling fraction, the elastic properties of cylinders relative to the background, their positions in the unit cell, and their multiple scattering interactions. Several examples of these metamaterials are reported and discussed.

  15. The Penalty Cost Functional for the Two-Dimensional

    Directory of Open Access Journals (Sweden)

    Victor Onomza WAZIRI

    2006-07-01

    Full Text Available This paper constructs the penalty cost functional for optimizing the two-dimensional control operator of the energized wave equation. In some multiplier methods such as the Lagrange multipliers and Pontrygean maximum principle, the cost of merging the constraint equation to the integral quadratic objective functional to obtain an unconstraint equation is normally guessed or obtained from the first partial derivatives of the unconstrained equation. The Extended Conjugate Gradient Method (ECGM necessitates that the penalty cost be sequentially obtained algebraically. The ECGM problem contains a functional which is completely given in terms of state and time spatial dependent variables.

  16. Autocorrelation based reconstruction of two-dimensional binary objects

    International Nuclear Information System (INIS)

    Mejia-Barbosa, Y.; Castaneda, R.

    2005-10-01

    A method for reconstructing two-dimensional binary objects from its autocorrelation function is discussed. The objects consist of a finite set of identical elements. The reconstruction algorithm is based on the concept of class of element pairs, defined as the set of element pairs with the same separation vector. This concept allows to solve the redundancy introduced by the element pairs of each class. It is also shown that different objects, consisting of an equal number of elements and the same classes of pairs, provide Fraunhofer diffraction patterns with identical intensity distributions. However, the method predicts all the possible objects that produce the same Fraunhofer pattern. (author)

  17. BRST quantization of Polyakov's two-dimensional gravity

    International Nuclear Information System (INIS)

    Itoh, Katsumi

    1990-01-01

    Two-dimensional gravity coupled to minimal models is quantized in the chiral gauge by the BRST method. By using the Wakimoto construction for the gravity sector, we show how the quartet mechanism of Kugo and Ojima works and solve the physical state condition. As a result the positive semi-definiteness of the physical subspace is shown. The formula of Knizhnik et al. for gravitational scaling dimensions is rederived from the physical state condition. We also observe a relation between the chiral gauge and the conformal gauge. (orig.)

  18. Confinement and dynamical regulation in two-dimensional convective turbulence

    DEFF Research Database (Denmark)

    Bian, N.H.; Garcia, O.E.

    2003-01-01

    In this work the nature of confinement improvement implied by the self-consistent generation of mean flows in two-dimensional convective turbulence is studied. The confinement variations are linked to two distinct regulation mechanisms which are also shown to be at the origin of low......-frequency bursting in the fluctuation level and the convective heat flux integral, both resulting in a state of large-scale intermittency. The first one involves the control of convective transport by sheared mean flows. This regulation relies on the conservative transfer of kinetic energy from tilted fluctuations...

  19. Two-dimensional approach to relativistic positioning systems

    International Nuclear Information System (INIS)

    Coll, Bartolome; Ferrando, Joan Josep; Morales, Juan Antonio

    2006-01-01

    A relativistic positioning system is a physical realization of a coordinate system consisting in four clocks in arbitrary motion broadcasting their proper times. The basic elements of the relativistic positioning systems are presented in the two-dimensional case. This simplified approach allows to explain and to analyze the properties and interest of these new systems. The positioning system defined by geodesic emitters in flat metric is developed in detail. The information that the data generated by a relativistic positioning system give on the space-time metric interval is analyzed, and the interest of these results in gravimetry is pointed out

  20. Nonlinear excitations in two-dimensional molecular structures with impurities

    DEFF Research Database (Denmark)

    Gaididei, Yuri Borisovich; Rasmussen, Kim; Christiansen, Peter Leth

    1995-01-01

    We study the nonlinear dynamics of electronic excitations interacting with acoustic phonons in two-dimensional molecular structures with impurities. We show that the problem is reduced to the nonlinear Schrodinger equation with a varying coefficient. The latter represents the influence...... of the impurity. Transforming the equation to the noninertial frame of reference coupled with the center of mass we investigate the soliton behavior in the close vicinity of the impurity. With the help of the lens transformation we show that the soliton width is governed by an Ermakov-Pinney equation. We also...... excitations. Analytical results are in good agreement with numerical simulations of the nonlinear Schrodinger equation....

  1. Functional Parallel Factor Analysis for Functions of One- and Two-dimensional Arguments.

    Science.gov (United States)

    Choi, Ji Yeh; Hwang, Heungsun; Timmerman, Marieke E

    2018-03-01

    Parallel factor analysis (PARAFAC) is a useful multivariate method for decomposing three-way data that consist of three different types of entities simultaneously. This method estimates trilinear components, each of which is a low-dimensional representation of a set of entities, often called a mode, to explain the maximum variance of the data. Functional PARAFAC permits the entities in different modes to be smooth functions or curves, varying over a continuum, rather than a collection of unconnected responses. The existing functional PARAFAC methods handle functions of a one-dimensional argument (e.g., time) only. In this paper, we propose a new extension of functional PARAFAC for handling three-way data whose responses are sequenced along both a two-dimensional domain (e.g., a plane with x- and y-axis coordinates) and a one-dimensional argument. Technically, the proposed method combines PARAFAC with basis function expansion approximations, using a set of piecewise quadratic finite element basis functions for estimating two-dimensional smooth functions and a set of one-dimensional basis functions for estimating one-dimensional smooth functions. In a simulation study, the proposed method appeared to outperform the conventional PARAFAC. We apply the method to EEG data to demonstrate its empirical usefulness.

  2. Ground-state and dynamical properties of two-dimensional dipolar Fermi liquids

    International Nuclear Information System (INIS)

    Abedinpour, Saeed H.; Asgari, Reza; Tanatar, B.; Polini, Marco

    2014-01-01

    We study the ground-state properties of a two-dimensional spin-polarized fluid of dipolar fermions within the Euler–Lagrange Fermi-hypernetted-chain approximation. Our method is based on the solution of a scattering Schrödinger equation for the “pair amplitude” √(g(r)), where g(r) is the pair distribution function. A key ingredient in our theory is the effective pair potential, which includes a bosonic term from Jastrow–Feenberg correlations and a fermionic contribution from kinetic energy and exchange, which is tailored to reproduce the Hartree–Fock limit at weak coupling. Very good agreement with recent results based on quantum Monte Carlo simulations is achieved over a wide range of coupling constants up to the liquid-to-crystal quantum phase transition. Using the fluctuation–dissipation theorem and a static approximation for the effective inter-particle interactions, we calculate the dynamical density–density response function, and furthermore demonstrate that an undamped zero-sound mode exists for any value of the interaction strength, down to infinitesimally weak couplings. -- Highlights: •We have studied the ground state properties of a strongly correlated two-dimensional fluid of dipolar fermions. •We have calculated the effective inter-particle interaction and the dynamical density–density response function. •We have shown that an undamped zero sound mode exists at any value of the interaction strength

  3. On some classes of two-dimensional local models in discrete two-dimensional monatomic FPU lattice with cubic and quartic potential

    International Nuclear Information System (INIS)

    Quan, Xu; Qiang, Tian

    2009-01-01

    This paper discusses the two-dimensional discrete monatomic Fermi–Pasta–Ulam lattice, by using the method of multiple-scale and the quasi-discreteness approach. By taking into account the interaction between the atoms in the lattice and their nearest neighbours, it obtains some classes of two-dimensional local models as follows: two-dimensional bright and dark discrete soliton trains, two-dimensional bright and dark line discrete breathers, and two-dimensional bright and dark discrete breather. (condensed matter: structure, thermal and mechanical properties)

  4. Surface Reconstruction-Induced Coincidence Lattice Formation Between Two-Dimensionally Bonded Materials and a Three-Dimensionally Bonded Substrate

    NARCIS (Netherlands)

    Boschker, Jos E.; Momand, Jamo; Bragaglia, Valeria; Wang, Ruining; Perumal, Karthick; Giussani, Alessandro; Kooi, Bart J.; Riechert, Henning; Calarco, Raffaella

    Sb2Te3 films are used for studying the epitaxial registry between two-dimensionally bonded (2D) materials and three-dimensional bonded (3D) substrates. In contrast to the growth of 3D materials, it is found that the formation of coincidence lattices between Sb2Te3 and Si(111) depends on the geometry

  5. Spectral properties near the Mott transition in the two-dimensional Hubbard model

    Science.gov (United States)

    Kohno, Masanori

    2013-03-01

    Single-particle excitations near the Mott transition in the two-dimensional (2D) Hubbard model are investigated by using cluster perturbation theory. The Mott transition is characterized by the loss of the spectral weight from the dispersing mode that leads continuously to the spin-wave excitation of the Mott insulator. The origins of the dominant modes of the 2D Hubbard model near the Mott transition can be traced back to those of the one-dimensional Hubbard model. Various anomalous spectral features observed in cuprate high-temperature superconductors, such as the pseudogap, Fermi arc, flat band, doping-induced states, hole pockets, and spinon-like and holon-like branches, as well as giant kink and waterfall in the dispersion relation, are explained in a unified manner as properties near the Mott transition in a 2D system.

  6. Application of Nondimensional Dynamic Influence Function Method for Eigenmode Analysis of Two-Dimensional Acoustic Cavities

    Directory of Open Access Journals (Sweden)

    S. W. Kang

    2014-04-01

    Full Text Available This paper establishes an improved NDIF method for the eigenvalue extraction of two-dimensional acoustic cavities with arbitrary shapes. The NDIF method, which was introduced by the authors in 1999, gives highly accurate eigenvalues despite employing a small number of nodes. However, it needs the inefficient procedure of calculating the singularity of a system matrix in the frequency range of interest for extracting eigenvalues and mode shapes. The paper proposes a practical approach for overcoming the inefficient procedure by making the final system matrix equation of the NDIF method into a form of algebraic eigenvalue problem. The solution quality of the proposed method is investigated by obtaining the eigenvalues and mode shapes of a circular, a rectangular, and an arbitrarily shaped cavity.

  7. A low threshold nanocavity in a two-dimensional 12-fold photonic quasicrystal

    Science.gov (United States)

    Ren, Jie; Sun, XiaoHong; Wang, Shuai

    2018-05-01

    In this article, a low threshold nanocavity is built and investigated in a two-dimensional 12-fold holographic photonic quasicrystal (PQC). The cavity is formed by using the method of multi-beam common-path interference. By finely adjusting the structure parameters of the cavity, the Q factor and the mode volume are optimized, which are two keys to low-threshold on the basis of Purcell effect. Finally, an optimal cavity is obtained with Q value of 6023 and mode volume of 1.24 ×10-12cm3 . On the other hand, by Fourier Transformation of the electric field components in the cavity, the in-plane wave vectors are calculated and fitted to evaluate the cavity performance. The performance analysis of the cavity further proves the effectiveness of the optimization process. This has a guiding significance for the research of low threshold nano-laser.

  8. Dynamics of wave packets in two-dimensional random systems with anisotropic disorder.

    Science.gov (United States)

    Samelsohn, Gregory; Gruzdev, Eugene

    2008-09-01

    A theoretical model is proposed to describe narrowband pulse dynamics in two-dimensional systems with arbitrary correlated disorder. In anisotropic systems with elongated cigarlike inhomogeneities, fast propagation is predicted in the direction across the structure where the wave is exponentially localized and tunneling of evanescent modes plays a dominant role in typical realizations. Along the structure, where the wave is channeled as in a waveguide, the motion of the wave energy is relatively slow. Numerical simulations performed for ultra-wide-band pulses show that even at the initial stage of wave evolution, the radiation diffuses predominantly in the direction along the major axis of the correlation ellipse. Spectral analysis of the results relates the long tail of the wave observed in the transverse direction to a number of frequency domain "lucky shots" associated with the long-living resonant modes localized inside the sample.

  9. Low frequency phononic band structures in two-dimensional arc-shaped phononic crystals

    International Nuclear Information System (INIS)

    Xu, Zhenlong; Wu, Fugen; Guo, Zhongning

    2012-01-01

    The low frequency phononic band structures of two-dimensional arc-shaped phononic crystals (APCs) were studied by the transfer matrix method in cylindrical coordinates. The results showed the first phononic band gaps (PBGs) of APCs from zero Hz with low modes. Locally resonant (LR) gaps were obtained with higher-order rotation symmetry, due to LR frequencies corresponding to the speeds of acoustic waves in the materials. These properties can be efficiently used in a structure for low frequencies that are forbidden, or in a device that permits a narrow window of frequencies. -- Highlights: ► We report a new class of quasi-periodic hetero-structures, arc-shaped phononic crystals (APCs). ► The results show the first PBGs start with zero Hz with low modes. ► Locally resonant (LR) gaps were obtained with higher-order rotation symmetry, due to LR frequencies corresponding to the speeds of acoustic waves in the materials.

  10. Modes of long crack growth under non-stationary temperature fields

    International Nuclear Information System (INIS)

    Tereshin, D.A.

    2012-01-01

    Highlights: ► Moving thermal stresses can result in much lengthier cracks than usually expected. ► Codirectional crack grows gradually along with thermal zone movement. ► Oppositely directed crack grows stepwise towards thermal tension movement. ► The total crack increment can be up to the whole region of thermal tension travel. - Abstract: The exploitation practice of structures under thermal loads evidences that the final length of a quasistatic crack can be considerably greater than the thermal tension zone, sometimes causing that the structure approaches complete fracture. This occurs in one or several cycles of a gradual crack growth due to the evolution of thermal field in time resulting in that fracture zone follows the moving tension zone. By the extreme example of quasistationary thermal stress field the set of quasistatic crack growth modes and their peculiarities for the case of moving thermal stresses are described here. These are modes developing both in the direction of the thermal stress field propagation and in the opposite direction. The critical condition of each mode is described, and the crack growth rates are estimated. The rational crack growth evaluation procedure is also proposed. The theoretical conclusions are supported by the experiment, which demonstrates the growth of long thermal cracks.

  11. Airborne measurements of nucleation mode particles I: coastal nucleation and growth rates

    Directory of Open Access Journals (Sweden)

    C. D. O'Dowd

    2007-01-01

    Full Text Available A light aircraft was equipped with a bank of Condensation Particle Counters (CPCs (50% cut from 3–5.4–9.6 nm and a nano-Scanning Mobility Particle Sizer (nSMPS and deployed along the west coast of Ireland, in the vicinity of Mace Head. The objective of the exercise was to provide high resolution micro-physical measurements of the coastal nucleation mode in order to map the spatial extent of new particle production regions and to evaluate the evolution, and associated growth rates of the coastal nucleation-mode aerosol plume. Results indicate that coastal new particle production is occurring over most areas along the land-sea interface with peak concentrations at the coastal plume-head in excess of 106 cm−3. Pseudo-Lagrangian studies of the coastal plume evolution illustrated significant growth of new particles to sizes in excess of 8 nm approximately 10 km downwind of the source region. Close to the plume head (<1 km growth rates can be as high as 123–171 nm h−1, decreasing gradually to 53–72 nm h−1 at 3 km. Further along the plume, at distances up to 10 km, the growth rates are calculated to be 17–32 nm h−1. Growth rates of this magnitude suggest that after a couple of hours, coastal nucleation mode particles can reach significant sizes where they can contribution to the regional aerosol loading.

  12. A microprocessor based on a two-dimensional semiconductor

    Science.gov (United States)

    Wachter, Stefan; Polyushkin, Dmitry K.; Bethge, Ole; Mueller, Thomas

    2017-04-01

    The advent of microcomputers in the 1970s has dramatically changed our society. Since then, microprocessors have been made almost exclusively from silicon, but the ever-increasing demand for higher integration density and speed, lower power consumption and better integrability with everyday goods has prompted the search for alternatives. Germanium and III-V compound semiconductors are being considered promising candidates for future high-performance processor generations and chips based on thin-film plastic technology or carbon nanotubes could allow for embedding electronic intelligence into arbitrary objects for the Internet-of-Things. Here, we present a 1-bit implementation of a microprocessor using a two-dimensional semiconductor--molybdenum disulfide. The device can execute user-defined programs stored in an external memory, perform logical operations and communicate with its periphery. Our 1-bit design is readily scalable to multi-bit data. The device consists of 115 transistors and constitutes the most complex circuitry so far made from a two-dimensional material.

  13. Thermal expansion of two-dimensional itinerant nearly ferromagnetic metal

    International Nuclear Information System (INIS)

    Konno, R; Hatayama, N; Takahashi, Y; Nakano, H

    2009-01-01

    Thermal expansion of two-dimensional itinerant nearly ferromagnetic metal is investigated according to the recent theoretical development of magneto-volume effect for the three-dimensional weak ferromagnets. We particularly focus on the T 2 -linear thermal expansion of magnetic origin at low temperatures, so far disregarded by conventional theories. As the effect of thermal spin fluctuations we have found that the T-linear thermal expansion coefficient shows strong enhancement by assuming the double Lorentzian form of the non-interacting dynamical susceptibility justified in the small wave-number and low frequency region. It grows faster in proportional to y -1/2 as we approach the magnetic instability point than two-dimensional nearly antiferromagnetic metals with ln(1/y s ) dependence, where y and y s are the inverses of the reduced uniform and staggered magnetic susceptibilities, respectively. Our result is consistent with the Grueneisen's relation between the thermal expansion coefficient and the specific heat at low temperatures. In 2-dimensional electron gas we find that the thermal expansion coefficient is divergent with a finite y when the higher order term of non-interacting dynamical susceptibility is taken into account.

  14. Emergence of geometry: A two-dimensional toy model

    International Nuclear Information System (INIS)

    Alfaro, Jorge; Espriu, Domene; Puigdomenech, Daniel

    2010-01-01

    We review the similarities between the effective chiral Lagrangrian, relevant for low-energy strong interactions, and the Einstein-Hilbert action. We use these analogies to suggest a specific mechanism whereby gravitons would emerge as Goldstone bosons of a global SO(D)xGL(D) symmetry broken down to SO(D) by fermion condensation. We propose a two-dimensional toy model where a dynamical zweibein is generated from a topological theory without any preexisting metric structure, the space being endowed only with an affine connection. A metric appears only after the symmetry breaking; thus the notion of distance is an induced effective one. In spite of several nonstandard features this simple toy model appears to be renormalizable and at long distances is described by an effective Lagrangian that corresponds to that of two-dimensional gravity (Liouville theory). The induced cosmological constant is related to the dynamical mass M acquired by the fermion fields in the breaking, which also acts as an infrared regulator. The low-energy expansion is valid for momenta k>M, i.e. for supra-horizon scales. We briefly discuss a possible implementation of a similar mechanism in four dimensions.

  15. Chimera patterns in two-dimensional networks of coupled neurons

    Science.gov (United States)

    Schmidt, Alexander; Kasimatis, Theodoros; Hizanidis, Johanne; Provata, Astero; Hövel, Philipp

    2017-03-01

    We discuss synchronization patterns in networks of FitzHugh-Nagumo and leaky integrate-and-fire oscillators coupled in a two-dimensional toroidal geometry. A common feature between the two models is the presence of fast and slow dynamics, a typical characteristic of neurons. Earlier studies have demonstrated that both models when coupled nonlocally in one-dimensional ring networks produce chimera states for a large range of parameter values. In this study, we give evidence of a plethora of two-dimensional chimera patterns of various shapes, including spots, rings, stripes, and grids, observed in both models, as well as additional patterns found mainly in the FitzHugh-Nagumo system. Both systems exhibit multistability: For the same parameter values, different initial conditions give rise to different dynamical states. Transitions occur between various patterns when the parameters (coupling range, coupling strength, refractory period, and coupling phase) are varied. Many patterns observed in the two models follow similar rules. For example, the diameter of the rings grows linearly with the coupling radius.

  16. Comprehensive two-dimensional liquid chromatographic analysis of poloxamers.

    Science.gov (United States)

    Malik, Muhammad Imran; Lee, Sanghoon; Chang, Taihyun

    2016-04-15

    Poloxamers are low molar mass triblock copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO), having number of applications as non-ionic surfactants. Comprehensive one and two-dimensional liquid chromatographic (LC) analysis of these materials is proposed in this study. The separation of oligomers of both types (PEO and PPO) is demonstrated for several commercial poloxamers. This is accomplished at the critical conditions for one of the block while interaction for the other block. Reversed phase LC at CAP of PEO allowed for oligomeric separation of triblock copolymers with regard to PPO block whereas normal phase LC at CAP of PPO renders oligomeric separation with respect to PEO block. The oligomeric separation with regard to PEO and PPO are coupled online (comprehensive 2D-LC) to reveal two-dimensional contour plots by unconventional 2D IC×IC (interaction chromatography) coupling. The study provides chemical composition mapping of both PEO and PPO, equivalent to combined molar mass and chemical composition mapping for several commercial poloxamers. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Evidence for two-dimensional ising structure in atomic nuclei

    International Nuclear Information System (INIS)

    MacGregor, M.H.

    1976-01-01

    Although the unpaired nucleons in an atomic nucleus exhibit pronounced shell-model-like behavior, the situation with respect to the paired-off ''core region'' nucleons is considerably more obscure. Several recent ''multi-alpha knockout'' and ''quasi-fission'' experiments indicate that nucleon clustering is prevalent throughout the core region of the nucleus; this same conclusion is suggested by nuclear-binding-energy systematics, by the evidence for a ''neutron halo'' in heavy nuclei and by the magnetic-moment systematics of low-mass odd-A nuclei. A number of arguments suggests, in turn, that this nucleon clustering is not spherical or spheroidal in shape, as has generally been assumed, but instead is in the form of two-dimensional Ising-like layers, with the layers arrayed perpendicular to the symmetry axis of the nucleus. The effects of this two-dimensional layering are observed most clearly in low-energy-induced fission, where nuclei with an even (odd) number of Ising layers fission symmetrically (asymmetrically). This picture of the nucleus gives an immediate quantitative explanation for the observed asymmetry in the fission of uranium, and also for the transition from symmetric to asymmetric and back to symmetric fission as the atomic number of the fissioning nuclues increase from A = 197 up to A = 258. These results suggest that, in the shell model formulation of the atomic nucleus, the basis states for the paired-off nucleon core region should be modified so as to contain laminar nucleon cluster correlations

  18. Aspects of jamming in two-dimensional athermal frictionless systems.

    Science.gov (United States)

    Reichhardt, C; Reichhardt, C J Olson

    2014-05-07

    In this work we provide an overview of jamming transitions in two dimensional systems focusing on the limit of frictionless particle interactions in the absence of thermal fluctuations. We first discuss jamming in systems with short range repulsive interactions, where the onset of jamming occurs at a critical packing density and where certain quantities show a divergence indicative of critical behavior. We describe how aspects of the dynamics change as the jamming density is approached and how these dynamics can be explored using externally driven probes. Different particle shapes can produce jamming densities much lower than those observed for disk-shaped particles, and we show how jamming exhibits fragility for some shapes while for other shapes this is absent. Next we describe the effects of long range interactions and jamming behavior in systems such as charged colloids, vortices in type-II superconductors, and dislocations. We consider the effect of adding obstacles to frictionless jamming systems and discuss connections between this type of jamming and systems that exhibit depinning transitions. Finally, we discuss open questions such as whether the jamming transition in all these different systems can be described by the same or a small subset of universal behaviors, as well as future directions for studies of jamming transitions in two dimensional systems, such as jamming in self-driven or active matter systems.

  19. Two-dimensional nuclear magnetic resonance of quadrupolar systems

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Shuanhu [Univ. of California, Berkeley, CA (United States)

    1997-09-01

    This dissertation describes two-dimensional nuclear magnetic resonance theory and experiments which have been developed to study quadruples in the solid state. The technique of multiple-quantum magic-angle spinning (MQMAS) is extensively reviewed and expanded upon in this thesis. Specifically, MQMAS is first compared with another technique, dynamic-angle spinning (DAS). The similarity between the two techniques allows us to extend much of the DAS work to the MQMAS case. Application of MQMAS to a series of aluminum containing materials is then presented. The superior resolution enhancement through MQMAS is exploited to detect the five- and six-coordinated aluminum in many aluminosilicate glasses. Combining the MQMAS method with other experiments, such as HETCOR, greatly expands the possibility of the use of MQMAS to study a large range of problems and is demonstrated in Chapter 5. Finally, the technique switching-angle spinning (SAS) is applied to quadrupolar nuclei to fully characterize a quadrupolar spin system in which all of the 8 NMR parameters are accurately determined. This dissertation is meant to demonstrate that with the combination of two-dimensional NMR concepts and new advanced spinning technologies, a series of multiple-dimensional NMR techniques can be designed to allow a detailed study of quadrupolar nuclei in the solid state.

  20. Two-Dimensional Impact Reconstruction Method for Rail Defect Inspection

    Directory of Open Access Journals (Sweden)

    Jie Zhao

    2014-01-01

    Full Text Available The safety of train operating is seriously menaced by the rail defects, so it is of great significance to inspect rail defects dynamically while the train is operating. This paper presents a two-dimensional impact reconstruction method to realize the on-line inspection of rail defects. The proposed method utilizes preprocessing technology to convert time domain vertical vibration signals acquired by wireless sensor network to space signals. The modern time-frequency analysis method is improved to reconstruct the obtained multisensor information. Then, the image fusion processing technology based on spectrum threshold processing and node color labeling is proposed to reduce the noise, and blank the periodic impact signal caused by rail joints and locomotive running gear. This method can convert the aperiodic impact signals caused by rail defects to partial periodic impact signals, and locate the rail defects. An application indicates that the two-dimensional impact reconstruction method could display the impact caused by rail defects obviously, and is an effective on-line rail defects inspection method.