The band edge structure of Pbsub(1-x)Snsub(x)Te is derived in detail using a two band ellipsoidal model and compared with a more rigorous calculation based on six bands. A quantitative comparison is made for two values of the energy gap, corresponding to the cases where x=0 and x=0.17. It was found that, for the occupied states in nondegenerate materials, both models are practically equivalent. Discrepancies may occur only in high degeneracies or deep inversion layers. The agreement between both models was significantly improved by introducing an effective energy gap in the two band model. It is suggested that the use of the effective energy gap may improve the agreement between the two band model and experiment whenever the details of the band edge structure enter the interpretation of the experimental results. (author)
Band structure of semiconductors
Tsidilkovski, I M
2013-01-01
Band Structure of Semiconductors provides a review of the theoretical and experimental methods of investigating band structure and an analysis of the results of the developments in this field. The book presents the problems, methods, and applications in the study of band structure. Topics on the computational methods of band structure; band structures of important semiconducting materials; behavior of an electron in a perturbed periodic field; effective masses and g-factors for the most commonly encountered band structures; and the treatment of cyclotron resonance, Shubnikov-de Haas oscillatio
Microstrip microwave band gap structures
V Subramanian
2008-04-01
Microwave band gap structures exhibit certain stop band characteristics based on the periodicity, impedance contrast and effective refractive index contrast. These structures though formed in one-, two- and three-dimensional periodicity, are huge in size. In this paper, microstrip-based microwave band gap structures are formed by removing the substrate material in a periodic manner. This paper also demonstrates that these structures can serve as a non-destructive characterization tool for materials, a duplexor and frequency selective coupler. The paper presents both experimental results and theoretical simulation based on a commercially available finite element methodology for comparison.
Zerveas, George; Caruso, Enrico; Baccarani, Giorgio; Czornomaz, Lukas; Daix, Nicolas; Esseni, David; Gnani, Elena; Gnudi, Antonio; Grassi, Roberto; Luisier, Mathieu; Markussen, Troels; Osgnach, Patrik; Palestri, Pierpaolo; Schenk, Andreas; Selmi, Luca; Sousa, Marilyne; Stokbro, Kurt; Visciarelli, Michele
2016-01-01
We present and thoroughly compare band-structures computed with density functional theory, tight-binding, k · p and non-parabolic effective mass models. Parameter sets for the non-parabolic Γ, the L and X valleys and intervalley bandgaps are extracted for bulk InAs, GaAs and InGaAs. We then consider quantum-wells with thickness ranging from 3 nm to 10 nm and the bandgap dependence on film thickness is compared with experiments for In0.53Ga0.47 As quantum-wells. The impact of the band-structure on the drain current of nanoscale MOSFETs is simulated with ballistic transport models, the results provide a rigorous assessment of III-V semiconductor band structure calculation methods and calibrated band parameters for device simulations.
In this work we present a comparison of the experimental results, which have been obtained by the resonant photoelectron spectroscopy for a set of selected diluted magnetic semiconductors based on GeTe, doped with manganese. The photoemission spectra are acquired for the photon energy range of 40-60 eV, corresponding to the Mn 3p → 3d resonances. The spectral features related to Mn 3d states are revealed in the emission from the valence band. The Mn 3d states contribution manifests itself in the whole valence band with a maximum at the binding energy of 3.8 eV. (authors)
Band structure and nuclear dynamics
The relation between the Variable Moment of Inertia model and the Interacting Boson Model are discussed from a phenomenological viewpoint. New results on ground state mean-square radii in nuclei far from stability are reported, and a discussion of band structure extending to high angular momentum states and methods of extracting information on the underlying dynamics is given
Band structure of 158Gd in DPPQ and IBM
The band structure of 158Gd has been studied extensively in the decay of 158Eu and in reaction work. The Kumar-Baranger semimicroscopic DPPQ model yields the parameters of the collective Hamiltonian and predicts the band structure. The Interacting Boson Model (IBM-1) was also used for comparison
Photonic band gap structure simulator
Chen, Chiping; Shapiro, Michael A.; Smirnova, Evgenya I.; Temkin, Richard J.; Sirigiri, Jagadishwar R.
2006-10-03
A system and method for designing photonic band gap structures. The system and method provide a user with the capability to produce a model of a two-dimensional array of conductors corresponding to a unit cell. The model involves a linear equation. Boundary conditions representative of conditions at the boundary of the unit cell are applied to a solution of the Helmholtz equation defined for the unit cell. The linear equation can be approximated by a Hermitian matrix. An eigenvalue of the Helmholtz equation is calculated. One computation approach involves calculating finite differences. The model can include a symmetry element, such as a center of inversion, a rotation axis, and a mirror plane. A graphical user interface is provided for the user's convenience. A display is provided to display to a user the calculated eigenvalue, corresponding to a photonic energy level in the Brilloin zone of the unit cell.
High-energy band structure of gold
Christensen, N. Egede
1976-01-01
The band structure of gold for energies far above the Fermi level has been calculated using the relativistic augmented-plane-wave method. The calculated f-band edge (Γ6-) lies 15.6 eV above the Fermi level is agreement with recent photoemission work. The band model is applied to interpret...
High-spin states of 79Br have been studied in the reaction 76Ge(7Li, 4nγ) at 32 MeV. A gamma-detector array with twelve Compton-suppressed HPGe detectors was used. The positive-parity yrast states, interpreted as a rotationally aligned g(9(2)) proton band, and the negative-parity ground state band have been extended to spins of (33(2+)) and (25(2-)), respectively. Lifetime measurements indicate that both bands have a similar quadrupole deformation of β2 ∼ 0.2. The positive-parity α = -(1(2)) band has been identified. Several new inter-band transitions are observed. A cranked-shell model analysis shows that the νg(9(2)) and πg(9(2)) alignments occur in the positive-parity and the negative-parity bands at rotational frequencies of ℎω ∼ 0.6 and 0.4 MeV, respectively. The level energies and the electromagnetic properties of the g(9(2)) band can be well reproduced by a particle-rotor model calculation with an axially symmetric core
Maximizing band gaps in plate structures
Halkjær, Søren; Sigmund, Ole; Jensen, Jakob Søndergaard
2006-01-01
Band gaps, i.e., frequency ranges in which waves cannot propagate, can be found in elastic structures for which there is a certain periodic modulation of the material properties or structure. In this paper, we maximize the band gap size for bending waves in a Mindlin plate. We analyze an infinite...
Band structures and localization properties of aperiodic layered phononic crystals
Yan Zhizhong, E-mail: zzyan@bit.edu.cn [Department of Applied Mathematics, Beijing Institute of Technology, Beijing 100081 (China); Zhang Chuanzeng [Department of Civil Engineering, University of Siegen, D-57078 Siegen (Germany)
2012-03-15
The band structures and localization properties of in-plane elastic waves with coupling of longitudinal and transverse modes oblique propagating in aperiodic phononic crystals based on Thue-Morse and Rudin-Shapiro sequences are studied. Using transfer matrix method, the concept of the localization factor is introduced and the correctness is testified through the Rytov dispersion relation. For comparison, the perfect periodic structure and the quasi-periodic Fibonacci system are also considered. In addition, the influences of the random disorder, local resonance, translational and/or mirror symmetries on the band structures of the aperiodic phononic crystals are analyzed in this paper.
One-Dimensional Anisotropic Band Gap Structure
无
2000-01-01
The band gap structure of one-dimensional anisotropic photonic crystal has been studied by means of the transfer matrix formalism. From the analytic expressions and numeric calculations we see some general characteristics of the band gap structure of anisotropic photonic crystals, each band separates into two branches and the two branches react to polarization sensitively. In the practical case of oblique incidence, gaps move towards high frequency when the angle of incidence increases. Under some special conditions, the two branches become degenerate again.
Phononic band gap structures as optimal designs
Jensen, Jakob Søndergaard; Sigmund, Ole
2003-01-01
In this paper we use topology optimization to design phononic band gap structures. We consider 2D structures subjected to periodic loading and obtain the distribution of two materials with high contrast in material properties that gives the minimal vibrational response of the structure. Both in...
Electronic band structure of beryllium oxide
Sashin, V A; Kheifets, A S; Ford, M J
2003-01-01
The energy-momentum resolved valence band structure of beryllium oxide has been measured by electron momentum spectroscopy (EMS). Band dispersions, bandwidths and intervalence bandgap, electron momentum density (EMD) and density of occupied states have been extracted from the EMS data. The experimental results are compared with band structure calculations performed within the full potential linear muffin-tin orbital approximation. Our experimental bandwidths of 2.1 +- 0.2 and 4.8 +- 0.3 eV for the oxygen s and p bands, respectively, are in accord with theoretical predictions, as is the s-band EMD after background subtraction. Contrary to the calculations, however, the measured p-band EMD shows large intensity at the GAMMA point. The measured full valence bandwidth of 19.4 +- 0.3 eV is at least 1.4 eV larger than the theory. The experiment also finds a significantly higher value for the p-to-s-band EMD ratio in a broad momentum range compared to the theory.
Development of S-band accelerating structure
In Pohang Accelerator Laboratory (PAL) in Korea construction of XFEL (X-ray Free electron Lazar) institution is under construction aiming at the completion in 2014. Energy 10 GeV of the linac part of this institution and main frequency are planned in S-band (2856 MHz), and about 178 S-band 3m accelerating structures are due to be used for this linac. The oscillation of an X-ray laser requires very low emittance electron beam. On the other hand, since the accelerating structure which accelerates an electron beam has a feed port of microwave (iris), the electromagnetic field asymmetry of the microwave feeding device called coupler worsens the emittance of an electron beam. MHI manufactured two kinds of S-band accelerating structures with which the electromagnetic field asymmetry of coupler cavity was compensated for PALXFEL linac. We report these accelerating structures. (author)
Band Structure Based Analysis of Certain Photonic Crystal Structures
Wolff, Christian
2011-01-01
Photonic crystals are periodic dielectric structures that may exhibit a complete photonic band gap. First, I discuss geometric properties of the band structure such as band edges. In a second part, I present work on photonic Wannier functions and their use for solving the wave equation. The third part is devoted to applications of the presented methods: A polarization resolved transmission experiment of opel films and an analogy experiment for spontaneous emission inside a photonic crystal.
The band structures of 121,123I nuclei have been studied using a version of the particle-rotor-model in which the experimental excitation energies of the neighbouring (A-1) cores can be fed directly as input parameters. The calculations have been carried out with axially symmetric Nilsson potential with both prolate and oblate deformations. The parameters of the model have been chosen from earlier theoretical work and experimental odd-even mass differences. Only the Coriolis attenuation factor has been treated as adjustable parameter. The theoretical band structures are in very good agreement with the available experimental data. (orig.)
Band structure engineering in organic semiconductors.
Schwarze, Martin; Tress, Wolfgang; Beyer, Beatrice; Gao, Feng; Scholz, Reinhard; Poelking, Carl; Ortstein, Katrin; Günther, Alrun A; Kasemann, Daniel; Andrienko, Denis; Leo, Karl
2016-06-17
A key breakthrough in modern electronics was the introduction of band structure engineering, the design of almost arbitrary electronic potential structures by alloying different semiconductors to continuously tune the band gap and band-edge energies. Implementation of this approach in organic semiconductors has been hindered by strong localization of the electronic states in these materials. We show that the influence of so far largely ignored long-range Coulomb interactions provides a workaround. Photoelectron spectroscopy confirms that the ionization energies of crystalline organic semiconductors can be continuously tuned over a wide range by blending them with their halogenated derivatives. Correspondingly, the photovoltaic gap and open-circuit voltage of organic solar cells can be continuously tuned by the blending ratio of these donors. PMID:27313043
Design of smooth orthogonal wavelets with beautiful structure from 2-band to 4-band
无
2006-01-01
A complete algorithm to design 4-band orthogonal wavelets with beautiful structure from 2-band orthogonal wavelets is presented. For more smoothness, the conception of transfer vanishing moment is introduced by transplanting the requirements of vanishing moment from the 4-band wavelets to the 2-band ones. Consequently, the design of 4-band orthogonal wavelets with P vanishing moments and beautiful structure from 2-band ones with P transfer vanishing moments is completed.
High spin band structure in 139Nd
XU Qiang; ZHU Sheng-Jiang; CHE Xing-Lai; DING Huai-Bo; GU Long; ZHU Li-Hua; WU Xiao-Guang; LIU Ying; HE Chuang-Ye; LI Li-Hua; PAN Bo; HAO Xin; LI Guang-Sheng
2009-01-01
High-spin states in 139Nd nucleus have been reinvestigated with the reaction 128Te (16O, 5n) at a beam energy of 90 MeV. The level scheme has been expanded with spin up to 47/2 h. At the low spin states,the yrast collective structure built on the vh(-1)(11/2) multiplet shows a transitional shape with γ≈32° according to calculations of the triaxial rotor-plus-particle model. Three collective oblate bands with γ～-60° at the high spin states were identified for the first time. A band crossing is observed around hw ～0.4 MeV in one oblate band based on the 25/2- level.
The band-gap enhanced photovoltaic structure
Tessler, Nir
2016-05-01
We critically examine the recently suggested structure that was postulated to potentially add 50% to the photo-conversion efficiency of organic solar cells. We find that the structure could be realized using stepwise increase in the gap as long as the steps are not above 0.1 eV. We also show that the charge extraction is not compromised due to an interplay between the contact's space charge and the energy level modification, which result in a flat energy band at the extracting contact.
New linear accelerator (Linac) design based on C-band accelerating structures for SXFEL facility
ZHANG Meng; GU Qiang
2011-01-01
A C-band accelerator structure is one promising technique for a compact XFEL facility.It is also attractive in beam dynamics in maintaining a high quality electron beam,which is an important factor in the performance of a free electron laser.In this paper,a comparison between traditional S-band and C-band accelerating structures is made based on the linac configuration of a Shanghai Soft X-ray Free Electron Laser (SXFEL) facility.Throughout the comprehensive simulation,we conclude that the C-band structure is much more competitive.
Electronic band structures of binary skutterudites
The electronic properties of complex binary skutterudites, MX3 (M = Co, Rh, Ir; X = P, As, Sb) are explored, using various density functional theory (DFT) based theoretical approaches including Green's Function (GW) as well as regular and non-regular Tran Blaha modified Becke Jhonson (TB-mBJ) methods. The wide range of calculated bandgap values for each compound of this skutterudites family confirm that they are theoretically as challenging as their experimental studies. The computationally expensive GW method, which is generally assume to be efficient in the reproduction of the experimental bandgaps, is also not very successful in the calculation of bandgaps. In this article, the issue of the theoretical bandgaps of these compounds is resolved by reproducing the accurate experimental bandgaps, using the recently developed non-regular TB-mBJ approach, based on DFT. The effectiveness of this technique is due to the fact that a large volume of the binary skutterudite crystal is empty and hence quite large proportion of electrons lie outside of the atomic spheres, where unlike LDA and GGA which are poor in the treatment of these electrons, this technique properly treats these electrons and hence reproduces the clear electronic picture of these compounds. - Highlights: • Theoretical and experimental electronic band structures of binary skutterudites are reviewed. • The literature reveals that none of the existing theoretical results are consistent with the experiments. • GW, regular and non-regular TB-mBJ methods are used to reproduce the correct results. • The GW and regular TB-mBJ results are better than the available results in literature. • However, non-regular TB-mBJ reproduces the correct experimental band structures
Electronic band structures of binary skutterudites
Khan, Banaras [Center for Computational Materials Science, University of Malakand, Chakdara (Pakistan); Department of Physics, University of Malakand, Chakdara (Pakistan); Aliabad, H.A. Rahnamaye [Department of Physics, Hakim Sabzevari University, Sabzevar (Iran, Islamic Republic of); Saifullah [Center for Computational Materials Science, University of Malakand, Chakdara (Pakistan); Department of Physics, University of Malakand, Chakdara (Pakistan); Jalali-Asadabadi, S. [Department of Physics, Faculty of Science, University of Isfahan (UI), 81744 Isfahan (Iran, Islamic Republic of); Khan, Imad [Center for Computational Materials Science, University of Malakand, Chakdara (Pakistan); Department of Physics, University of Malakand, Chakdara (Pakistan); Ahmad, Iftikhar, E-mail: ahma5532@gmail.com [Center for Computational Materials Science, University of Malakand, Chakdara (Pakistan); Department of Physics, University of Malakand, Chakdara (Pakistan)
2015-10-25
The electronic properties of complex binary skutterudites, MX{sub 3} (M = Co, Rh, Ir; X = P, As, Sb) are explored, using various density functional theory (DFT) based theoretical approaches including Green's Function (GW) as well as regular and non-regular Tran Blaha modified Becke Jhonson (TB-mBJ) methods. The wide range of calculated bandgap values for each compound of this skutterudites family confirm that they are theoretically as challenging as their experimental studies. The computationally expensive GW method, which is generally assume to be efficient in the reproduction of the experimental bandgaps, is also not very successful in the calculation of bandgaps. In this article, the issue of the theoretical bandgaps of these compounds is resolved by reproducing the accurate experimental bandgaps, using the recently developed non-regular TB-mBJ approach, based on DFT. The effectiveness of this technique is due to the fact that a large volume of the binary skutterudite crystal is empty and hence quite large proportion of electrons lie outside of the atomic spheres, where unlike LDA and GGA which are poor in the treatment of these electrons, this technique properly treats these electrons and hence reproduces the clear electronic picture of these compounds. - Highlights: • Theoretical and experimental electronic band structures of binary skutterudites are reviewed. • The literature reveals that none of the existing theoretical results are consistent with the experiments. • GW, regular and non-regular TB-mBJ methods are used to reproduce the correct results. • The GW and regular TB-mBJ results are better than the available results in literature. • However, non-regular TB-mBJ reproduces the correct experimental band structures.
A Theoretical Structure of High School Concert Band Performance
Bergee, Martin J.
2015-01-01
This study used exploratory (EFA) and confirmatory factor analysis (CFA) to verify a theoretical structure for high school concert band performance and to test that structure for viability, generality, and invariance. A total of 101 university students enrolled in two different bands rated two high school band performances (a "first"…
Band-Structure of Thallium by the LMTO Method
Holtham, P. M.; Jan, J. P.; Skriver, Hans Lomholt
1977-01-01
The relativistic band structure of thallium has been calculated using the linear muffin-tin orbital (LMTO) method. The positions and extents of the bands were found to follow the Wigner-Seitz rule approximately, and the origin of the dispersion of the bands was established from the canonical s and...
Kink Band Instability and Propagation in Layered Structures
Wadee, M.A.; Hunt, G.W.; Peletier, M.A.
2003-01-01
A recent two-dimensional prototype model for the initiation of kink banding in compressed layered structures is extended to embrace the two propagation mechanisms of band broadening and band progression. As well as interlayer friction, overburden pressure and layer bending energy, the characteristic
Dual-band electromagnetic band gap structure for noise isolation in mixed signal SiP
Rotaru, M. D.; Sykulski, J. K.
2010-01-01
A compact dual-band electromagnetic band-gap (EBG) structure is proposed. It is shown through numerical simulation using 3D electromagnetic finite element modelling that by adding a slit to the classical mushroom shape an extra resonance is introduced and thus dual-band EBG structures can be built by cascading these new elements. It is also demonstrated that this novel approach can be used to isolate noise in a system such as a dual band transceiver integrated into a mixed signal system in a ...
Elucidating the stop bands of structurally colored systems through recursion
Amir, Ariel
2012-01-01
Interference phenomena are the source of some of the spectacular colors of animals and plants in nature. In some of these systems, the physical structure consists of an ordered array of layers with alternating high and low refractive indices. This periodicity leads to an optical band structure that is analogous to the electronic band structure encountered in semiconductor physics; namely, specific bands of wavelengths (the stop bands) are perfectly reflected. Here, we present a minimal model for optical band structure in a periodic multilayer and solve it using recursion relations. We present experimental data for various beetles, whose optical structure resembles the proposed model. The stop bands emerge in the limit of an infinite number of layers by finding the fixed point of the recursive relations. In order for these to converge, an infinitesimal amount of absorption needs to be present, reminiscent of the regularization procedures commonly used in physics calculations. Thus, using only the phenomenon of...
Band-structure calculations and structure-factor estimates of Cu - their complementarity
Rather than an uncritical comparison of experimental and theoretical values, the various sets of structure-factor values of copper metal derived from experimental diffraction procedures are mutally compared as also are the various sets of theoretical values derived from band-structure calculations. This approach reveals the presence of outlier sets in each group and allows recognition of their condition before any attempt is made to intercompare the groups. Within the experimental group, the γ-ray values do not appear to sustain the absolute status originally claimed from them. Within the theoretical group, an inadequacy in defining the core contribution is indicated. The latter conclusion suggests that it is an inappropriate operation to make direct comparison between diffraction-sourced experimental values of structure factors and theoretical values from band-structure calculations. Instead, the latter should be used on a complementary basis with the full (sin θ)/λ range of experimental values to establish the best core contribution. The minor valence-bond contribution to scattering, which is largely restricted to the low (sin θ)/λ region, is most sensitively defined by reference to band-structure prediction of photoemission spectral distribution. Attention is drawn to the possible significance of the form-factor curve versus (sin θ)/λ being dependent on the unit-cell dimension. (orig.)
Band Structure Characteristics of Nacreous Composite Materials with Various Defects
Yin, J.; Zhang, S.; Zhang, H. W.; Chen, B. S.
2016-06-01
Nacreous composite materials have excellent mechanical properties, such as high strength, high toughness, and wide phononic band gap. In order to research band structure characteristics of nacreous composite materials with various defects, supercell models with the Brick-and-Mortar microstructure are considered. An efficient multi-level substructure algorithm is employed to discuss the band structure. Furthermore, two common systems with point and line defects and varied material parameters are discussed. In addition, band structures concerning straight and deflected crack defects are calculated by changing the shear modulus of the mortar. Finally, the sensitivity of band structures to the random material distribution is presented by considering different volume ratios of the brick. The results reveal that the first band gap of a nacreous composite material is insensitive to defects under certain conditions. It will be of great value to the design and synthesis of new nacreous composite materials for better dynamic properties.
The complex band structure for armchair graphene nanoribbons
Zhang Liu-Jun; Xia Tong-Sheng
2010-01-01
Using a tight binding transfer matrix method, we calculate the complex band structure of armchair graphene nanoribbons. The real part of the complex band structure calculated by the transfer matrix method fits well with the bulk band structure calculated by a Hermitian matrix. The complex band structure gives extra information on carrier's decay behaviour. The imaginary loop connects the conduction and valence band, and can profoundly affect the characteristics of nanoscale electronic device made with graphene nanoribbons. In this work, the complex band structure calculation includes not only the first nearest neighbour interaction, but also the effects of edge bond relaxation and the third nearest neighbour interaction. The band gap is classified into three classes. Due to the edge bond relaxation and the third nearest neighbour interaction term, it opens a band gap for N= 3M-1. The band gap is almost unchanged for N = 3M + 1, but decreased for N = 3M. The maximum imaginary wave vector length provides additional information about the electrical characteristics of graphene nmaoribbons, and is also classified into three classes.
Pressure effects on band structures in dense lithium
We studied the change of the band structures in some structures of Li predicted at high pressures, using GGA and GW calculations. The width of the 1s band coming from the 1s electron of Li shows broadening by the pressurization, which is the normal behavior of bands at high pressure. The width of the band just below the Fermi level decreases by the pressurization, which is an opposite behavior to the normal bands. The character of this narrowing band is mostly p-like with a little s-like portion. The band gaps in some structures are really observed even by the GGA calculations. The gaps by the GW calculations increase to about 1.5 times the GGA values. Generally the one-shot GW calculation (diagonal only calculations) gives more reliable values than the GGA, but it may fail to predict band gaps for the case where band dispersion shows complex crossing near the Fermi level. There remains some structures for which GW calculations with off-diagonal elements taken into account are needed to identify the phase to be metallic or semiconducting.
Vargas, W. E.; Hernández-Jiménez, M.; Libby, E.; Azofeifa, D. E.; Solis, Á.; Barboza-Aguilar, C.
2015-09-01
Under normal illumination with non-polarized light, reflection spectra of the cuticle of golden-like and red Chrysina aurigans scarabs show a structured broad band of left-handed circularly polarized light. The polarization of the reflected light is attributed to a Bouligand-type left-handed chiral structure found through the scarab's cuticle. By considering these twisted structures as one-dimensional photonic crystals, a novel approach is developed from the dispersion relation of circularly polarized electromagnetic waves traveling through chiral media, to show how the broad band characterizing these spectra arises from an intrinsic narrow photonic band gap whose spectral position moves through visible and near-infrared wavelengths.
Atomic structure of amorphous shear bands in boron carbide.
Reddy, K Madhav; Liu, P; Hirata, A; Fujita, T; Chen, M W
2013-01-01
Amorphous shear bands are the main deformation and failure mode of super-hard boron carbide subjected to shock loading and high pressures at room temperature. Nevertheless, the formation mechanisms of the amorphous shear bands remain a long-standing scientific curiosity mainly because of the lack of experimental structure information of the disordered shear bands, comprising light elements of carbon and boron only. Here we report the atomic structure of the amorphous shear bands in boron carbide characterized by state-of-the-art aberration-corrected transmission electron microscopy. Distorted icosahedra, displaced from the crystalline matrix, were observed in nano-sized amorphous bands that produce dislocation-like local shear strains. These experimental results provide direct experimental evidence that the formation of amorphous shear bands in boron carbide results from the disassembly of the icosahedra, driven by shear stresses. PMID:24052052
W. Liu; Hayter, A. J.; Piegorsch, W W; Ah-Kine, P.
2008-01-01
A simultaneous confidence band provides useful information on the plausible range of the unknown regression model, and different confidence bands can often be constructed for the same regression model. For a simple regression line, Liu and Hayter (2007) propose use of the area of the confidence set corresponding to a confidence band as an optimality criterion in comparison of confidence bands; the smaller the area of the confidence set, the better the corresponding confidence band. This minim...
Shell model description of band structure in 48Cr
The band structure for normal and abnormal parity bands in 48Cr are described using the m-scheme shell model. In addition to full fp-shell, two particles in the 1d3/2 orbital are allowed in order to describe intruder states. The interaction includes fp-, sd- and mixed matrix elements
Fractional Band Filling in an Atomic Chain Structure
Crain, J. N.; Kirakosian, A.; Altmann, K. N.; Bromberger, C.; Erwin, S. C.; McChesney, J. L.; Lin, J.-L.; Himpsel, F. J.
2003-05-01
A new chain structure of Au is found on stepped Si(111) which exhibits a 1/4-filled band and a pair of ≥1/2-filled bands with a combined filling of 4/3. Band dispersions and Fermi surfaces for Si(553)-Au are obtained by photoemission and compared to that of Si(557)-Au. The dimensionality of both systems is determined using a tight binding fit. The fractional band filling makes it possible to preserve metallicity in the presence of strong correlations.
Structure of nearly degenerate dipole bands in {sup 108}Ag
Sethi, J. [Tata Institute of Fundamental Research, Colaba, Mumbai 400 005 (India); Palit, R., E-mail: palit@tifr.res.in [Tata Institute of Fundamental Research, Colaba, Mumbai 400 005 (India); Saha, S.; Trivedi, T. [Tata Institute of Fundamental Research, Colaba, Mumbai 400 005 (India); Bhat, G.H.; Sheikh, J.A. [Department of Physics, University of Kashmir, Srinagar 190 006 (India); Datta, P. [Ananda Mohan College, Kolkata 700009 (India); Carroll, J.J. [US Army Research Laboratory, Adelphi, MD 20783 (United States); Chattopadhyay, S. [Saha Institute of Nuclear Physics, Kolkata 700064 (India); Donthi, R. [Tata Institute of Fundamental Research, Colaba, Mumbai 400 005 (India); Garg, U. [University of Notre Dame, Notre Dame, IN 46556 (United States); Jadhav, S.; Jain, H.C. [Tata Institute of Fundamental Research, Colaba, Mumbai 400 005 (India); Karamian, S. [Joint Institute for Nuclear Research, Dubna 141980 (Russian Federation); Kumar, S. [University of Delhi, Delhi 110007 (India); Litz, M.S. [US Army Research Laboratory, Adelphi, MD 20783 (United States); Mehta, D. [Panjab University, Chandigarh 160014 (India); Naidu, B.S. [Tata Institute of Fundamental Research, Colaba, Mumbai 400 005 (India); Naik, Z. [Sambalpur University, Sambalpur 143005 (India); Sihotra, S. [Panjab University, Chandigarh 160014 (India); and others
2013-08-09
The high spin negative parity states of {sup 108}Ag have been investigated with the {sup 11}B + {sup 100}Mo reaction at 39 MeV beam energy using the INGA facility at TIFR, Mumbai. From the γ–γ coincidence analysis, an excited negative parity band has been established and found to be nearly degenerate with the ground state band. The spin and parity of the levels are assigned using angular correlation and polarization measurements. This pair of degenerate bands in {sup 108}Ag is studied using the recently developed microscopic triaxial projected shell model approach. The observed energy levels and the ratio of the electromagnetic transition probabilities of these bands in this isotope are well reproduced by the present model. Further, it is shown that the partner band has a different quasiparticle structure as compared to the yrast band.
Structure of nearly degenerate dipole bands in 108Ag
The high spin negative parity states of 108Ag have been investigated with the 11B + 100Mo reaction at 39 MeV beam energy using the INGA facility at TIFR, Mumbai. From the γ–γ coincidence analysis, an excited negative parity band has been established and found to be nearly degenerate with the ground state band. The spin and parity of the levels are assigned using angular correlation and polarization measurements. This pair of degenerate bands in 108Ag is studied using the recently developed microscopic triaxial projected shell model approach. The observed energy levels and the ratio of the electromagnetic transition probabilities of these bands in this isotope are well reproduced by the present model. Further, it is shown that the partner band has a different quasiparticle structure as compared to the yrast band
Nonequilibrium band structure of nano-devices
Hackenbuchner, S.; Sabathil, M.; Majewski, J. A.; Zandler, G.; Vogl, P.; Beham, E.; Zrenner, A.; Lugli, P.
2002-03-01
A method is developed for calculating, in a consistent manner, the realistic electronic structure of three-dimensional (3-D) heterostructure quantum devices under bias and its current density close to equilibrium. The nonequilibrium electronic structure is characterized by local Fermi levels that are calculated self-consistently. We have applied this scheme to predict asymmetric Stark shifts and tunneling of confined electrons and holes in single-dot GaAs/InGaAs photodiodes.
Motagh, Mahdi; Haghshenas Haghighi, Mahmud; Shamshiri, Roghaye; Esmaeili, Mustapha
2015-05-01
The ongoing pattern of groundwater induced land subsidence in major valleys and agricultural regions of Iran has been recently documented by several studies (e.g. [1-4]) using C-band Interferometric Synthetic Aperture Radar (InSAR) observations. In this article we present the results of our research in which we evaluated the performance of C-band, L-band and X-band SAR data, using time-series method of small baseline subset (SBAS), to retrieve long time series of ground subsidence in agricultural regions in the country. Two major groundwater basins have been selected for this purpose: (1) Rafsanjan Valley in the Kerman province of central Iran and (2) Tehran Plain (capital of Iran). We also report on our experience using dualpolarimetry (HH/VV) X-band SAR data for Persistent Scatterer (PS) deformation analysis in natural terrains subject to high rate of deformation.
W. Liu; Hayter, A. J.; Piegorsch, W W
2009-01-01
A simultaneous confidence band provides useful information on the plausible range of the unknown regression model, and different confidence bands can often be constructed for the same regression model. For a simple regression line, it is proposed in Liu and Hayter (2007) to use the area of the confidence set that corresponds to a confidence band as an optimality criterion in comparison of confidence bands; the smaller is the area of the confidence set, the better is the corresponding confiden...
Design for maximum band-gaps in beam structures
Olhoff, Niels; Niu, Bin; Cheng, Gengdong
2012-01-01
This paper aims to extend earlier optimum design results for transversely vibrating Bernoulli-Euler beams by determining new optimum band-gap beam structures for (i) different combinations of classical boundary conditions, (ii) much larger values of the orders n and n-1 of adjacent upper and lower...... eigenfrequencies of maximized band-gaps, and (iii) different values of a minimum cross-sectional area constraint. The periodicity of the optimum beams and the attenuation of their band-gaps are also discussed....
Markos, Peter
2016-01-01
Frequency and transmission spectrum of two-dimensional array of metallic rods is investigated numerically. Based on the recent analysis of the band structure of two-dimensional photonic crystal with dielectric rods [P. Marko\\v{s}, Phys. Rev. A 92 043814 (2015)] we identify two types of bands in the frequency spectrum: Bragg (P) bands resulting from a periodicity and Fano (F) bands which arise from Fano resonances associated with each of the cylinders within the periodic structure. It is shown that the existence of Fano band in a certain frequency range is manifested by a Fano resonance in the transmittance. In particular, we re-examine the symmetry properties of the H- polarized band structure in the frequency range where the spectrum consists of the localized modes associated with the single scatterer resonances and we explore process of formation of Fano bands by identifying individual terms in the expansion of the LCAO states. We demonstrate how the interplay between the two scattering mechanisms affects p...
Band formation in coupled-resonator slow-wave structures.
Möller, Björn M; Woggon, Ulrike; Artemyev, Mikhail V
2007-12-10
Sequences of coupled-resonator optical waveguides (CROWs) have been examined as slow-wave structures. The formation of photonic bands in finite systems is studied in the frame of a coupled oscillator model. Several types of resonator size tuning in the system are evaluated in a systematical manner. We show that aperiodicities in sequences of coupled microspheres provide an additional degree of freedom for the design of photonic bands. PMID:19551030
Comparison of broad-band and narrow-band red and near-infrared vegetation indices
An experiment has been conducted in which narrow-band field reflectance spectra were acquired of a rooted pinyon pine canopy with five different gravel backgrounds. Leaf area was successively removed as the measurements were repeated. From these reflectance spectra, narrow-band and broad-band (AVHRR, TM, MSS) red and near-infrared (NIR) vegetation index values were calculated. The performance of the vegetation indices was evaluated based on their capability to accurately estimate leaf area index (LAI) and percent green cover. Background effects were found for each of the tested vegetation indices. However, the background effects are most pronounced in the normalized difference vegetation index (NDVI) and ratio vegetation index (RVI). Background effects can be reduced using either the perpendicular vegetation index (PVI) or soil adjusted vegetation index (SAVI) formulations. The narrow-band versions of these vegetation indices had only slightly better accuracy than their broad-band counterparts. The background effects were minimized using derivative based vegetation indices, which measure the amplitude of the chlorophyll red-edge using continuous narrow-band spectra from 626 nm to 795 nm. (author)
Tuning the electronic band structure of PCBM by electron irradiation
Yoo Seung
2011-01-01
Full Text Available Abstract Tuning the electronic band structures such as band-edge position and bandgap of organic semiconductors is crucial to maximize the performance of organic photovoltaic devices. We present a simple yet effective electron irradiation approach to tune the band structure of [6, 6]-phenyl-C61-butyric acid methyl ester (PCBM that is the most widely used organic acceptor material. We have found that the lowest unoccupied molecular orbital (LUMO level of PCBM up-shifts toward the vacuum energy level, while the highest occupied molecular orbital (HOMO level down-shifts when PCBM is electron-irradiated. The shift of the HOMO and the LUMO levels increases as the irradiated electron fluence increases. Accordingly, the band-edge position and the bandgap of PCBM can be controlled by adjusting the electron fluence. Characterization of electron-irradiated PCBM reveals that the variation of the band structure is attributed to the molecular structural change of PCBM by electron irradiation.
Michiardi, Matteo; Aguilera, Irene; Bianchi, Marco;
2014-01-01
The bulk band structure of Bi2Te3 has been determined by angle-resolved photoemission spectroscopy and compared to first-principles calculations. We have performed calculations using the local density approximation (LDA) of density functional theory and the one-shot GW approximation within the all......-electron full-potential linearized augmented-plane-wave (FLAPW) formalism, fully taking into account spin-orbit coupling. Quasiparticle effects produce significant changes in the band structure of Bi2Te3 when compared to LDA. Experimental and calculated results are compared in the spectral regions where...... distinct differences between the LDA and GW results are present. Overall a superior agreement with GW is found, highlighting the importance of many-body effects in the band structure of this family of topological insulators....
Simulation of the Band Structure of Graphene and Carbon Nanotube
Simulation technique has been performed to simulate the band structure of both graphene and carbon nanotube. Accordingly, the dispersion relations for graphene and carbon nanotube are deduced analytically, using the tight binding model and LCAO scheme. The results from the simulation of the dispersion relation of both graphene and carbon nanotube were found to be consistent with those in the literature which indicates the correctness of the process of simulation technique. The present research is very important for tailoring graphene and carbon nanotube with specific band structure, in order to satisfy the required electronic properties of them.
Simulation of the Band Structure of Graphene and Carbon Nanotube
Mina, Aziz N.; Awadallah, Attia A.; Phillips, Adel H.; Ahmed, Riham R.
2012-02-01
Simulation technique has been performed to simulate the band structure of both graphene and carbon nanotube. Accordingly, the dispersion relations for graphene and carbon nanotube are deduced analytically, using the tight binding model & LCAO scheme. The results from the simulation of the dispersion relation of both graphene and carbon nanotube were found to be consistent with those in the literature which indicates the correctness of the process of simulation technique. The present research is very important for tailoring graphene and carbon nanotube with specific band structure, in order to satisfy the required electronic properties of them.
Band structure of CdTe under high pressure
The band structures and density of states of cadmium telluride (CdTe) under various pressures ranging from normal to 4.5 Mbar are obtained. The electronic band structure at normal pressure of CdTe (ZnS structure) is analyzed and the direct band gap value is found to be 1.654 eV. CdTe becomes metal and superconductor under high pressure but before that it undergoes structural phase transition from ZnS phase to NaCl phase. The equilibrium lattice constant, bulk modulus and the phase transition pressure at which the compounds undergo structural phase transition from ZnS to NaCl are predicted from the total energy calculations. The density of states at the Fermi level (N(EF)) gets enhanced after metallization, which leads to the superconductivity in CdTe. In our calculation, the metallization pressure (PM = 1.935 Mbar) and the corresponding reduced volume ((V/V0)M = 0.458) are estimated. Metallization occurs via direct closing of band gap at Γ point. (author)
Optimum design of band-gap beam structures
Olhoff, Niels; Niu, Bin; Cheng, Gengdong
2012-01-01
of a single, linearly elastic material without damping. Numerical results are presented for different combinations of classical boundary conditions, prescribed orders of the upper and lower natural frequencies of maximized natural frequency gaps, and a given minimum constraint value for the beam......The design of band-gap structures receives increasing attention for many applications in mitigation of undesirable vibration and noise emission levels. A band-gap structure usually consists of a periodic distribution of elastic materials or segments, where the propagation of waves is impeded or...... significantly suppressed for a range of external excitation frequencies. Maximization of the band-gap is therefore an obvious objective for optimum design. This problem is sometimes formulated by optimizing a parameterized design model which assumes multiple periodicity in the design. However, it is shown in...
Reconfigurable wave band structure of an artificial square ice
Iacocca, Ezio; Gliga, Sebastian; Stamps, Robert L.; Heinonen, Olle
2016-04-01
Artificial square ices are structures composed of magnetic nanoelements arranged on the sites of a two-dimensional square lattice, such that there are four interacting magnetic elements at each vertex, leading to geometrical frustration. Using a semianalytical approach, we show that square ices exhibit a rich spin-wave band structure that is tunable both by external magnetic fields and the magnetization configuration of individual elements. Internal degrees of freedom can give rise to equilibrium states with bent magnetization at the element edges leading to characteristic excitations; in the presence of magnetostatic interactions these form separate bands analogous to impurity bands in semiconductors. Full-scale micromagnetic simulations corroborate our semianalytical approach. Our results show that artificial square ices can be viewed as reconfigurable and tunable magnonic crystals that can be used as metamaterials for spin-wave-based applications at the nanoscale.
Photonic Band Gap structures: A new approach to accelerator cavities
Kroll, N. [California Univ., San Diego, La Jolla, CA (United States). Dept. of Physics]|[Stanford Linear Accelerator Center, Menlo Park, CA (United States); Smith, D.R.; Schultz, S. [California Univ., San Diego, La Jolla, CA (United States). Dept. of Physics
1992-12-31
We introduce a new accelerator cavity design based on Photonic Band Gap (PGB) structures. The PGB cavity consists of a two-dimensional periodic array of high dielectric, low loss cylinders with a single removal defect, bounded on top and bottom by conducting sheets. We present the results of both numerical simulations and experimental measurements on the PGB cavity.
Photonic Band Gap structures: A new approach to accelerator cavities
We introduce a new accelerator cavity design based on Photonic Band Gap (PGB) structures. The PGB cavity consists of a two-dimensional periodic array of high dielectric, low loss cylinders with a single removal defect, bounded on top and bottom by conducting sheets. We present the results of both numerical simulations and experimental measurements on the PGB cavity
Emission bands of phosphorus and calculation of band structure of rare earth phosphides
The method of x-ray emission spectroscopy has been used to investigate the electronic structure of monophosphides of rare-earth metals (REM). The fluorescence K bands of phosphorus have been obtained in LaP, PrP, SmP, GdP, TbP, DyP, HoP, ErP, TmP, YbP, and LuP and also the Lsub(2,3) bands of phosphorus in ErP, TmP, YbP, and LuP. Using the Green function technique involving the muffin-tin potential, the energy spectrum for ErP has been calculated in the single-electron approximation. The hystogram of electronic state distribution N(E) is compared with the experimental K and Lsub(2,3) bands of phosphorus in ErP. The agreement between the main details of N(E) and that of x-ray spectra allows to state that the model used provides a good description of the electron density distribution in crystals of REM monophosphides. In accordance with the character of the N(E) distribution the compounds under study are classified as semimetals or semiconductors with a very narrow forbidden band
Hubbard-U band-structure methods
Albers, R.C.; Christensen, Niels Egede; Svane, Axel
2009-01-01
The last decade has seen a large increase in the number of electronic-structure calculations that involve adding a Hubbard term to the local-density approximation band-structure Hamiltonian. The Hubbard term is then determined either at the mean-field level or with sophisticated many...... inconsistent with what the calculations actually do. Although many of these calculations are often treated as essentially first-principles calculations, in fact, we argue that they should be viewed from an entirely different point of view, namely, as based on phenomenological many-body corrections to band-structure......-body techniques such as using dynamical mean-field theory. We review the physics underlying these approaches and discuss their strengths and weaknesses in terms of the larger issues of electronic structure that they involve. In particular, we argue that the common assumptions made to justify such calculations are...
X-Band Photonic Band-Gap Accelerator Structure Breakdown Experiment
Marsh, Roark A.; /MIT /MIT /NIFS, Gifu /JAERI, Kyoto /LLNL, Livermore; Shapiro, Michael A.; Temkin, Richard J.; /MIT; Dolgashev, Valery A.; Laurent, Lisa L.; Lewandowski, James R.; Yeremian, A.Dian; Tantawi, Sami G.; /SLAC
2012-06-11
In order to understand the performance of photonic band-gap (PBG) structures under realistic high gradient, high power, high repetition rate operation, a PBG accelerator structure was designed and tested at X band (11.424 GHz). The structure consisted of a single test cell with matching cells before and after the structure. The design followed principles previously established in testing a series of conventional pillbox structures. The PBG structure was tested at an accelerating gradient of 65 MV/m yielding a breakdown rate of two breakdowns per hour at 60 Hz. An accelerating gradient above 110 MV/m was demonstrated at a higher breakdown rate. Significant pulsed heating occurred on the surface of the inner rods of the PBG structure, with a temperature rise of 85 K estimated when operating in 100 ns pulses at a gradient of 100 MV/m and a surface magnetic field of 890 kA/m. A temperature rise of up to 250 K was estimated for some shots. The iris surfaces, the location of peak electric field, surprisingly had no damage, but the inner rods, the location of the peak magnetic fields and a large temperature rise, had significant damage. Breakdown in accelerator structures is generally understood in terms of electric field effects. These PBG structure results highlight the unexpected role of magnetic fields in breakdown. The hypothesis is presented that the moderate level electric field on the inner rods, about 14 MV/m, is enhanced at small tips and projections caused by pulsed heating, leading to breakdown. Future PBG structures should be built to minimize pulsed surface heating and temperature rise.
The band structure of metallic sodium is calculated, using for the first time the self-consistent field variational cellular method. In order to implement the self-consistency in the variational cellular theory, the crystal electronic charge density was calculated within the muffin-tin approximation. The comparison between our results and those derived from other calculations leads to the conclusion that the proposed self-consistent version of the variational cellular method is fast and accurate. (author)
Structure of superdeformed bands in the A ≅ 150 mass region
The structure of superdeformed rotational bands recently discovered around 152Dy is discussed within the deformed shell model based on an average Woods-Saxon potential with a monopole pairing force. A comparison with available experimental data is provided and detailed predictions for yet unobserved cases are given. Pronounced variations in the observed rotational pattern are attributed to the angular momentum alignment of the high-N intruder (quasi)particles. (orig.)
Band Structure Modifications in Deformed InP Quantum Wires
V.V. Kuryliuk
2014-11-01
Full Text Available The work describes the features of the band structure of deformed InP nanowires with different diameters. It is shown that the bending of quantum wires is capable of creating local minima in the conduction and valence bands which are separated from the surface of the cylindrical wire. This result opens up new possibilities for controlling both the lifetime of photoexcited carriers by keeping them at these minima and the magnitude of the photovoltage in solar energy conversion devices based on quantum wires. The work lies within a common goal aiming to develop new methods of functionalization of nanostructured surfaces using mechanical deformations.
Multi-band and broadband acoustic metamaterial with resonant structures
We design an acoustic metamaterial (AM) with multi-band of negative modulus composed of different sized split hollow spheres (SHSs). From acoustic transmitted experiment, the AM exhibits simultaneously negative modulus at frequencies 914, 1298 and 1514 Hz. Based on the multi-band designed concept, broadband AM is fabricated by arraying gradually sized SHS. The transmission results indicate that this medium can achieve negative modulus at the frequency range from 900 to 1500 Hz. This kind of broadband AM is very convenient to couple with other structures to gain the double-negative AM.
Inter-band optoelectronic properties in quantum dot structure of low band gap III-V semiconductors
A generalized theory is developed to study inter-band optical absorption coefficient (IOAC) and material gain (MG) in quantum dot structures of narrow gap III-V compound semiconductor considering the wave-vector (k→) dependence of the optical transition matrix element. The band structures of these low band gap semiconducting materials with sufficiently separated split-off valance band are frequently described by the three energy band model of Kane. This has been adopted for analysis of the IOAC and MG taking InAs, InSb, Hg1−xCdxTe, and In1−xGaxAsyP1−y lattice matched to InP, as example of III–V compound semiconductors, having varied split-off energy band compared to their bulk band gap energy. It has been found that magnitude of the IOAC for quantum dots increases with increasing incident photon energy and the lines of absorption are more closely spaced in the three band model of Kane than those with parabolic energy band approximations reflecting the direct the influence of energy band parameters. The results show a significant deviation to the MG spectrum of narrow-gap materials having band nonparabolicity compared to the parabolic band model approximations. The results reflect the important role of valence band split-off energies in these narrow gap semiconductors
Coupling effect of quantum wells on band structure
Jie, Chen; Weiyou, Zeng
2015-10-01
The coupling effects of quantum wells on band structure are numerically investigated by using the Matlab programming language. In a one dimensional finite quantum well with the potential barrier V0, the calculation is performed by increasing the number of inserted barriers with the same height Vb, and by, respectively, varying the thickness ratio of separated wells to inserted barriers and the height ratio of Vb to V0. Our calculations show that coupling is strongly influenced by the above parameters of the inserted barriers and wells. When these variables change, the width of the energy bands and gaps can be tuned. Our investigation shows that it is possible for quantum wells to achieve the desired width of the bands and gaps.
Coupling effect of quantum wells on band structure
The coupling effects of quantum wells on band structure are numerically investigated by using the Matlab programming language. In a one dimensional finite quantum well with the potential barrier V0, the calculation is performed by increasing the number of inserted barriers with the same height Vb, and by, respectively, varying the thickness ratio of separated wells to inserted barriers and the height ratio of Vb to V0. Our calculations show that coupling is strongly influenced by the above parameters of the inserted barriers and wells. When these variables change, the width of the energy bands and gaps can be tuned. Our investigation shows that it is possible for quantum wells to achieve the desired width of the bands and gaps. (paper)
QUANTITATIVE ANALYSIS OF BANDED STRUCTURES IN DUAL-PHASE STEELS
Benoit Krebs
2011-05-01
Full Text Available Dual-Phase (DP steels are composed of martensite islands dispersed in a ductile ferrite matrix, which provides a good balance between strength and ductility. Current processing conditions (continuous casting followed by hot and cold rolling generate 'banded structures' i.e., irregular, parallel and alternating bands of ferrite and martensite, which are detrimental to mechanical properties and especially for in-use properties. We present an original and simple method to quantify the intensity and wavelength of these bands. This method, based on the analysis of covariance function of binary images, is firstly tested on model images. It is compared with ASTM E-1268 standard and appears to be more robust. Then it is applied on real DP steel microstructures and proves to be sufficiently sensitive to discriminate samples resulting from different thermo-mechanical routes.
Mid-frequency Band Dynamics of Large Space Structures
Coppolino, Robert N.; Adams, Douglas S.
2004-01-01
High and low intensity dynamic environments experienced by a spacecraft during launch and on-orbit operations, respectively, induce structural loads and motions, which are difficult to reliably predict. Structural dynamics in low- and mid-frequency bands are sensitive to component interface uncertainty and non-linearity as evidenced in laboratory testing and flight operations. Analytical tools for prediction of linear system response are not necessarily adequate for reliable prediction of mid-frequency band dynamics and analysis of measured laboratory and flight data. A new MATLAB toolbox, designed to address the key challenges of mid-frequency band dynamics, is introduced in this paper. Finite-element models of major subassemblies are defined following rational frequency-wavelength guidelines. For computational efficiency, these subassemblies are described as linear, component mode models. The complete structural system model is composed of component mode subassemblies and linear or non-linear joint descriptions. Computation and display of structural dynamic responses are accomplished employing well-established, stable numerical methods, modern signal processing procedures and descriptive graphical tools. Parametric sensitivity and Monte-Carlo based system identification tools are used to reconcile models with experimental data and investigate the effects of uncertainties. Models and dynamic responses are exported for employment in applications, such as detailed structural integrity and mechanical-optical-control performance analyses.
Development of X-band accelerating structures for high gradients
S. Bini; M. G. Grimaldi; L. Romano; F. Ruffino; R. Parodi; V. Chimenti; A. Marcelli; L. Palumbo; B. Spataro; V. A. Dolgashev; S. Tantawi; A.D. Yeremian; Y. Higashi
2012-01-01
Short copper standing wave (SW) structures operating at an X-band frequency have been recently designed and manufactured at the Laboratori Nazionali di Frascati of the Istituto Nazionale di Fisica Nucleare (INFN) using the vacuum brazing technique.High power tests of the structures have been performed at the SLAC National Accelerator Laboratory.In this manuscript we report the results of these tests and the activity in progress to enhance the high gradient performance of the next generation of structures,particularly the technological characterization of high performance coatings obtained via molybdenum sputtering.
Engineering Design of a Multipurpose X-band Accelerating Structure
Gudkov, Dmitry; Samoshkin, Alexander; Zennaro, Riccardo; Dehler, Micha; Raguin, Jean-Yves
2010-01-01
Both FEL projects, SwissFEL and Fermi-Elettra each require an X-band RF accelerating structure for optimal bunch compression at the respective injectors. As the CLIC project is pursuing a program for producing and testing the X-band high-gradient RF structures, a collaboration between PSI, Elettra and CERN has been established to build a multipurpose X-band accelerating structure. This paper focuses on its engineering design, which is based on the disked cells jointed together by diffusion bonding. Vacuum brazing and laser beam welding is used for auxiliary components. The accelerating structure consists of two coupler subassemblies, 73 disks and includes a wakefield monitor and diagnostic waveguides. The engineering study includes the external cooling system, consisting of two parallel cooling circuits and an RF tuning system, which allows phase advance tuning of the cell by deforming the outer wall. The engineering solution for the installation and sealing of the wake field monitor feed-through devices that...
Ultrafast Band Structure Control of a Two-Dimensional Heterostructure.
Ulstrup, Søren; Čabo, Antonija Grubišić; Miwa, Jill A; Riley, Jonathon M; Grønborg, Signe S; Johannsen, Jens C; Cacho, Cephise; Alexander, Oliver; Chapman, Richard T; Springate, Emma; Bianchi, Marco; Dendzik, Maciej; Lauritsen, Jeppe V; King, Phil D C; Hofmann, Philip
2016-06-28
The electronic structure of two-dimensional (2D) semiconductors can be significantly altered by screening effects, either from free charge carriers in the material or by environmental screening from the surrounding medium. The physical properties of 2D semiconductors placed in a heterostructure with other 2D materials are therefore governed by a complex interplay of both intra- and interlayer interactions. Here, using time- and angle-resolved photoemission, we are able to isolate both the layer-resolved band structure and, more importantly, the transient band structure evolution of a model 2D heterostructure formed of a single layer of MoS2 on graphene. Our results reveal a pronounced renormalization of the quasiparticle gap of the MoS2 layer. Following optical excitation, the band gap is reduced by up to ∼400 meV on femtosecond time scales due to a persistence of strong electronic interactions despite the environmental screening by the n-doped graphene. This points to a large degree of tunability of both the electronic structure and the electron dynamics for 2D semiconductors embedded in a van der Waals-bonded heterostructure. PMID:27267820
Study of the band structures in 104Pd
Complete text of publication follows. During the past years, beside the A ∼ 130 mass region, chiral candidate twin bands have been found also in odd-odd and odd-mass rhodium isotopes with A ∼ 100. The role of triaxial deformation of the core in degeneracy of chiral band doubling has been pointed out in 102Ru and 103Rh. More recently, a study of 106Ag has revealed that gamma softness has marked implications for the phenomenon of nuclear chirality. In order to further examine this effect on the stability of chiral geometry we studied the band structures of 104Pd, the core nucleus of 106Ag. High-spin states in 104Pd have been studied through the 96Zr(13C,5n) reaction at beam energies of 51 and 58 MeV, using the Euroball IV γ-ray spectrometer. The γ rays were measured in coincidence with charged particles detected by the Diamant array in order to eliminate the contaminants from the stronger (13C,xn) reaction channels. A total of ∼ 2 x 109 triple- and higher-fold coincidence events were stored among which ∼ 4.5 x 108 belonged to the 104Pd reaction channel. On the basis of the analysis of γγγ-coincidence data, several new high-spin bands have been established. The ground state band has been extended up to Ex ∼12 MeV with Iπ=(26+), while the previously published negative-parity bands have been extended up to Ex ∼11 and ∼9 MeV with Iπ=(23-) and (20-), respectively. The theoretical interpretation of the experimental results obtained is in progress
Calculation of complex band structure for low symmetry lattices
Srivastava, Manoj; Zhang, Xiaoguang; Cheng, Hai-Ping
2009-03-01
Complex band structure calculation is an integral part of a first-principles plane-wave based quantum transport method. [1] The direction of decay for the complex wave vectors is also the transport direction. The existing algorithm [1] has the limitation that it only allows the transport direction along a lattice vector perpendicular to the basal plane formed by two other lattice vectors, e.g., the c-axis of a tetragonal lattice. We generalize this algorithm to nonorthogonal lattices with transport direction not aligned with any lattice vector. We show that this generalization leads to changes in the boundary conditions and the Schrodinger's equation projected to the transport direction. We present, as an example, the calculation of the complex band structure of fcc Cu along a direction perpendicular to the (111) basal plane. [1] Hyoung Joon Choi and Jisoon Ihm, Phys. Rev. B 59, 2267 (1999).
Parameterization and algebraic structure of 3-band orthogonal wavelet systems
无
2001-01-01
In this paper, a complete parameterization for the 3-band compact wavelet systems is presented. Using the parametric result, a program of the filterbank design is completed, which can give not only the filterbanks but also the graphs of all possible scaling functions and their corresponding wavelets. Especially some symmetric wavelets with small supports are given. Finally an algebraic structure for this kind of wavelet systems is characterized.
The structure of rotational bands in alpha-cluster nuclei
Bijker Roelof
2015-01-01
Full Text Available In this contribution, I discuss an algebraic treatment of alpha-cluster nuclei based on the introduction of a spectrum generating algebra for the relative motion of the alpha-clusters. Particular attention is paid to the discrete symmetry of the geometric arrangement of the α-particles, and the consequences for the structure of the rotational bands in the 12C and 16O nuclei.
Intermediate band solar cell structures grown by MOVPE
Vyskočil, Jan; Zíková, Markéta; Hospodková, Alice; Oswald, Jiří; Petříček, Otto; Pangrác, Jiří
Lund: Nanometer Structure Consortium, 2015 - (Ghalamestani, S.; Lundfald, L.), s. 191-194 [EWMOVPE XVI - 16th European Workshop on Metalorganic Vapor Phase Epitaxy. Lund (SE), 07.06.2015-10.06.2015] R&D Projects: GA ČR(CZ) GP14-21285P Institutional support: RVO:68378271 Keywords : InAs * GaAsSb * quantum dot * intermediate band solar cell s Subject RIV: BM - Solid Matter Physics ; Magnetism
Band structural properties of MoS2 (molybdenite)
Semiconductivity and superconductivity in MoS2 (molybdenite) can be understood in terms of the band structure of MoS2. The band structural properties of MoS2 are presented here. The energy dependence of nsub(eff) and epsilon(infinity)sub(eff) is investigated. Using calculated values of nsub(eff) and epsilon(infinity)sub(eff), the Penn gap has been determined. The value thus obtained is shown to be in good agreement with the reflectivity data and also with the value obtained from the band structure. The Ravindra and Srivastava formula has been shown to give values for the isobaric temperature gradient of Esub(G)[(deltaEsub(G)/deltaT)sub(P)], which are in agreement with the experimental data, and the contribution to (deltaEsub(G)/deltaT)sub(P) due to the electron lattice interaction has been evaluated. In addition, the electronic polarizability has been calculated using a modified Lorentz-Lorenz relation. (author)
Electronic band structure and photoemission: A review and projection
A brief review of electronic-structure calculations in solids, as a means of interpreting photoemission spectra, is presented. The calculations are, in general, of three types: ordinary one-electron-like band structures, which apply to bulk solids and are the basis of all other calculations; surface modified calculations, which take into account, self-consistently if at all possible, the presence of a vacuum-solid interface and of the electronic modifications caused thereby; and many-body calculations, which go beyond average-field approximations and consider dynamic rearrangement effects caused by electron-electron correlations during the photoemission process. 44 refs
Structure of high-spin bands in 104Pd
Complete text of publication follows. High-spin states of 104Pd were studied through the 96Zr(13C,5n) reaction at beam energies of 51 and 58 MeV, using the Euroball IV γ-ray spectrometer in conjunction with the Diamant charged particle array. On the basis of the analysis of γγγ-coincidence data, the previously known rotation-like structures (bands 1,2,3,4) have been extended up to Ex∼6, 13, 11 and 9 MeV with Iπ=(12+), (26+), (23-) and (20-), respectively. Besides the major sideband structures, two new negative parity cascades (bands 5,6) were found and built up to Ex∼8 MeV with Iπ=(17-) and (18-). The 104Pd nucleus with its 6 valence protons and 8 valence neutrons relative to 90Zr lies in the upper part of the g9/2 proton subshell and in the middle part of the d5/2, g7/2 neutron subshell where the low-Ωh11/2 orbitals intrude already at small deformations. To get a deeper insight into the structure of the observed bands, total routhian surface (trs) calculations based on the Woods-Saxon cranking formalism were performed. Comparing the experimental Routhians E' and aligned angular momenta Ix with the trs results (Fig. 1), we assign two-quasiparticle ν(h11/2)2 configuration to the positive-parity bands 1 and 2. According to this expectation, the alignment of a h11/2 neutron pair is clearly visible at ℎω∼0.4 MeV frequency with nearly the full possible alignment gain of ∼10ℎ. As in the negative-parity bands 3,4,5 and 6 the νh11/2 alignment seems to be blocked, their configuration contains one neutron in the h11/2 orbit. Furthermore, the second quasineutron is expected to have a g7/2, d5/2 origin due to their parity. This assumption is supported by the good agreement of the experimental data with the trs results and accordingly we suggest νh11/2(d5/2, g7/2) configurations for these bands.
Dual-band metamaterial with a windmill-like structure
A broadband negative refractive index metamaterial based on a windmill-like structure is proposed, and investigated numerically and experimentally at the microwave frequency range. From the numerical and experimental results, effect media parameters are retrieved, which clearly show that two broad frequency bands exist in which the permittivity and permeability are negative. The two negative bands are from 9.1 GHz to 10.5 GHz and from 12.05 GHz to 14.65 GHz respectively, and the negative bandwidth is 4 GHz. Due to the good bandwidth performance, the metallic cell with double negative property obtained in this paper is suitable for use in the design of multiband or broadband microwave devices. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)
Simple metamaterial structure enabling triple-band perfect absorber
Two resonators in metamaterial usually correspond only to two absorption peaks. In this report, by breaking the symmetry, we could create multi-fundamental resonances at GHz frequencies in both simulation and experiment. First, a dual-band metamaterial absorber (MA) was achieved for 4.6 and 10.6 GHz. Next, by modifying the relative position of inner square, the triple-band MA was obtained with enhanced absorption properties. In addition, dependence on the polarization of the incident electromagnetic (EM) wave was clarified. The mechanism is elucidated to be an alteration of the coupling strength, which is made by changing the geometrical configuration of the inner square and the outer ring. It is shown that our structural configuration can be applied to the fields where the interaction with a wide range of EM waves exists or is needed. (paper)
Wakefield Monitor Experiments with X-Band Accelerating Structures
Lillestøl, Reidar; Corsini, Roberto; Döbert, Steffen; Farabolini, Wilfrid; Malina, Lukas; Pfingstner, Juergen; Wuensch, Walter
2015-01-01
The accelerating structures for CLIC must be aligned with a precision of a few um with respect to the beam trajectory in order to mitigate emittance growth due to transverse wake fields. We report on first results from wake field monitor tests in an X-band structure, with a probe beam at the CLIC Test Facility. The monitors are currently installed in the CLIC Two-Beam Module. In order to fully demonstrate the feasibility of using wakefield monitors for CLIC, the precision of the monitors must be verified using a probe beam while simultaneously filling the structure with high power rf used to drive the accelerating mode. We outline plans to perform such a demonstration in the CLIC Test Facility.
Collective Band Structures in Neutron-Rich 108Mo Nucleus
DING Huai-Bo; WANG Jian-Guo; XU Qiang; ZHU Sheng-Jiang; J. H. Hamilton; A. V. Ramayya; J. K. Hwang; Y. X. Luo; J. O. Rasmussen; I. Y. Lee; CHE Xing-Lai
2007-01-01
High spin states in the neutron-rich 108Mo nucleus are studied by measuring prompt γ-rays following the spontaneous fission of 252Cf with a Gammasphere detector array. The ground-state band is confirmed, and the one-phonon γ-vibrational band is updated with spin up to 12 h. A new collective band with the band head level at 1422.4 keV is suggested as a two-phonon γ-vibrational band. Another new band is proposed as a two-quasi-proton excitation band. Systematic characteristics of the collective bands are discussed.
Analysis of photonic band-gap structures in stratified medium
Tong, Ming-Sze; Yinchao, Chen; Lu, Yilong;
2005-01-01
Purpose - To demonstrate the flexibility and advantages of a non-uniform pseudo-spectral time domain (nu-PSTD) method through studies of the wave propagation characteristics on photonic band-gap (PBG) structures in stratified medium Design/methodology/approach - A nu-PSTD method is proposed in...... the occasions where the spatial distributions contain step of up to five times larger than the original size, while simultaneously the flexibility of non-uniform sampling offers further savings on computational storage. Research limitations/implications - Research has been mainly limited to the simple...
Band structure in the polymer quantization of the harmonic oscillator
We discuss the detailed structure of the spectrum of the Hamiltonian for the polymerized harmonic oscillator and compare it with the spectrum in the standard quantization. As we will see the non-separability of the Hilbert space implies that the point spectrum consists of bands similar to the ones appearing in the treatment of periodic potentials. This feature of the spectrum of the polymeric harmonic oscillator may be relevant for the discussion of the polymer quantization of the scalar field and may have interesting consequences for the statistical mechanics of these models. (paper)
Determination of the band structure of LuNi{sub 2}B{sub 2}C
Bergk, B. [Hochfeld-Magnetlabor, Forschungszentrum Rossendorf, Dresden (Germany); Inst. fuer Festkoerperphysik, Technische Univ. Dresden (Germany); Bartkowiak, M.; Ignatchik, O. [Hochfeld-Magnetlabor, Forschungszentrum Rossendorf, Dresden (Germany); Jaeckel, M. [Inst. fuer Festkoerperphysik, Technische Univ. Dresden (Germany); Wosnitza, J.; Rosner, H.; Petzold, V. [MPI fuer chemische Physik fester Stoffe, Dresden (Germany); Canfield, P. [Iowa State Univ. of Science and Technology, Ames (United States). Ames Lab., Condensed Matter Physics
2007-07-01
We present de Haas-van Alphen (dHvA) investigations on the nonmagnetic borocarbide superconductor LuNi{sub 2}B{sub 2}C which have been performed by use of the torque method in high magnetic fields up to 32 T and at low temperatures down to 50 mK. The complex band structure is extracted from the quantum oscillations in the normal state. In comparison with full-potential-local-orbital calculations of the band structure we are able to assign the observed dHvA frequencies to the different bands. Temperature dependent dHvA investigations allowed the extraction of the effective band masses for the several Fermi-surface sheets. We observe an enhancement of the effective masses compared to the theoretical calculations which is due to electron-phonon interaction. Finally, we are able to examine the angular dependence of the electron-phonon coupling for the different Fermi-surface sheets. (orig.)
Quasiparticle band structure of thirteen semiconductors and insulators
By using a model dielectric matrix in electron self-energy evaluations the computational effort of a quasiparticle band-structure calculation for a semiconductor is greatly reduced. Applications to various systems with or without inversion symmetry, having narrow or wide band gaps, and semiconductor alloys demonstrate the reliability and accuracy of the method. Calculations have been performed for thirteen semiconducting or insulating materials: Si, LiCl, AlP, AlAs, AlSb, GaP, GaAs, GaSb, InP, InAs, InSb, and the Al0.5Ga0.5As and In0.53Ga0.47As alloys. Excellent agreement with experimental results is obtained for the quasiparticle energies for these materials. The only three exceptions, E(Γ1c) of AlP, E(L1c) of AlAs, and E(L1c) of AlSb are discussed and attributed to various experimental uncertainties. Several other quasiparticle-excitation-related properties are also examined in this work. The many-body corrections to the eigenvalues of the valence-band-maximum states obtained from the local-density approximation are calculated for the zinc-blende-structure semiconductors, which are widely used in semiconductor-interface studies. In the present approach, the static screening of the Coulomb interaction between two electrons in a crystal is determined using a model that depends only on the local charge densities at these two points. Since a direct quantitative modeling of the electron self-energy operator has proven difficult, the successful application of the present model-dielectric-function scheme in self-energy calculations makes possible detailed studies of the quasiparticle properties of rather complex systems, which would be otherwise computationally too demanding
Self energy corrections to the ''ab initio'' band structure: Chromium
We describe the effect of many particle corrections to improve the electronic energy spectrum calculated in the framework of the Density Functional Formalism (DFF). We show that it is possible to consider an n particle diagram like a correction to the DFF results for electronic structure, if we take into account the electron-electron interaction with non-zero transmitted momentum q or energy ε. The model is proposed for calculating the leading term of the self-energy expansion as a power series in interactions, i.e. the second order term under the conditions q=O and ε≠O. This model is illustrated by calculating the electronic band structure and optical properties of anti ferromagnetic chromium. The self-energy correction leads to a better agreement between the theoretical calculations and experimental measurements of electronic properties. (author). 40 refs, 5 figs, 3 tabs
We analyze the influence of conduction-band nonparabolicity on bound electronic states in the active region of a quantum cascade laser (QCL). Our model assumes expansion of the conduction-band dispersion relation up to a fourth order in wavevector and use of a suitable second boundary condition at the interface of two III-V semiconductor layers. Numerical results, obtained by the transfer matrix method, are presented for two mid-infrared GaAs/Al0.33Ga0.67As QCL active regions, and they are in very good agreement with experimental data found in the literature. Comparison with a different nonparabolicity model is presented for the example of a GaAs/Al0.38Ga0.62As-based mid-IR QCL. Calculations have also been carried out for one THz QCL structure to illustrate the possible application of the model in the terahertz part of the spectrum. (paper)
Electronic band structure of the layered compound Td-WTe2
Augustin, J.; Eyert, V.; Böker, Th.; Frentrup, W.; Dwelk, H.; Janowitz, C.; Manzke, R.
2000-10-01
We have studied the electronic structure of the layered compound Td-WTe2 experimentally using high-resolution angle-resolved photoelectron spectroscopy, and theoretically using density-functional based augmented spherical wave calculations. Comparison of the measured and calculated data shows in general good agreement. The theoretical results reveal the semimetallic as well as metallic character of Td-WTe2; the semimetallic character is due to a 0.5 eV overlap of Te 5p- and W 5d-like bands along Γ-Y, while the metallic character is due to two classical metallic bands. The rather low conductivity of Td-WTe2 is interpreted as resulting from a low density of states at the Fermi level.
Structure of negative parity yrast bands in odd mass 125-131Ce nuclei
Arun Bharti; Suram Singh; S K Khosa
2010-04-01
The negative parity yrast bands of neutron-deficient 125-131Ce nuclei are studied by using the projected shell model approach. Energy levels, transition energies and (1)/(2) ratios are calculated and compared with the available experimental data. The calculations reproduce the band-head spins of negative parity yrast bands and indicate the multi-quasiparticle structure for these bands.
Band Structure and Optical Properties of Ordered AuCu3
Skriver, Hans Lomholt; Lengkeek, H. P.
1979-01-01
initio band structure obtained by the relativistic linear muffin-tin orbitals method. The band calculation reveals that ordered AuCu3 has distinct copper and gold d bands positioned in and hybridizing with an s band common to copper and gold. The calculated state density is found to be in good agreement...
QUANTUM-MECHANICAL MODELING OF SPATIAL AND BAND STRUCTURE OF Y3AL5O12 SCINTILLATION CRYSTAL
I. I. Vrubel
2016-05-01
Full Text Available Spatial and electronic structures of a unit cell of yttrium-aluminum garnet have been studied. Quantum-mechanical model have been presented. Semi-empirical methods PM6 and PM7 have been used for geometry optimization of the crystal unit cell. Band structure has been calculated within density functional theory with the use of PBE exchange-correlation functional. Histograms of metal-oxygen distances for equilibrium geometry have been constructed. Comparison of the used methods has been carried out and recommendation about their applicability for such problems was given. The single-particle wave functions and energies have been calculated. The bandgap was estimated. The band structure was plotted. It was shown that the method gives reliable results for spatial and band structure of Y3Al5O12 scintillation crystal. The results of this work can be used for improvement of characteristics of garnet scintillation crystals.
Influence of Structural Parameters on a Novel Metamaterial Absorber Structure at K-band Frequency
Cuong, Tran Manh; Thuy, Nguyen Thi; Tuan, Le Anh
2016-05-01
Metamaterials nowadays continue to gain attention thanks to their special electromagnetic characteristics. An increasing number of studies are being conducted on the absolute electromagnetic absorber configurations of high impedance surface materials at a certain frequency band. These configurations are usually fabricated with a layer of metal structure based on a dielectric sheet. In this study, we present an optimal design of a novel electromagnetic absorber metamaterial configuration working at a 23-GHz frequency range (K band).
Analysis of the electronic structure of crystals through band structure unfolding
Gordienko, A. B.; Kosobutsky, A. V.
2016-03-01
In this work, we consider an alternative implementation of the band structure unfolding method within the framework of the density functional theory, which combines the advantages of the basis of localized functions and plane waves. This approach has been used to analyze the electronic structure of the ordered CuCl x Br1- x copper halide alloys and F 0 center in MgO that enables us to reveal qualitatively the features remaining hidden when using the standard supercell method, because of the complex band structure of systems with defects.
X-band coaxial standing-wave linear accelerator structure
A new high efficiency X-Band, standing-wave linear accelerator cavity structure has been developed. It utilizes a shaped coaxial cavity as the coupling cavity between accelerating cavities for π/2 mode operation, hence the overall diameter is extremely small while maintaining a very high shunt impedance. The coupling cavity and accelerating cavity are easily machined on opposite sides of a single cell, eliminating any subassembly steps. Cavity geometries were developed using the computer codes LACC and LALA. Prototype 1.5 MeV and 4.0 MeV, 20 cm long accelerators are now under development. The accelerators employ a stepped field focusing technique to keep the beam focused at low field levels. The beam dynamics code PARMELA was used to optimize the longitudinal bunching and transverse beam characteristics. The accelerator design parameters, as well as experimental results, are presented
Role of interface band structure on hot electron transport
Garramone, John J.
Knowledge of electron transport through materials and interfaces is fundamentally and technologically important. For example, metal interconnects within integrated circuits suffer increasingly from electromigration and signal delay due to an increase in resistance from grain boundary and sidewall scattering since their dimensions are becoming shorter than the electron mean free path. Additionally, all semiconductor based devices require the transport of electrons through materials and interfaces where scattering and parallel momentum conservation are important. In this thesis, the inelastic and elastic scattering of hot electrons are studied in nanometer thick copper, silver and gold films deposited on silicon substrates. Hot electrons are electron with energy greater than kBT above the Fermi level (EF). This work was performed utilizing ballistic electron emission microscopy (BEEM) which is a three terminal scanning tunneling microscopy (STM) technique that measures the percentage of hot electrons transmitted across a Schottky barrier interface. Hot electron attenuation lengths of the metals were extracted by measuring the BEEM current as a function of metal overlayer thickness for both hot electron and hot hole injection at 80 K and under ultra high vacuum. The inelastic and elastic scattering lengths were extracted by fitting the energetic dependence of the measured attenuation lengths to a Fermi liquid based model. A sharp increase in the attenuation length is observed at low injection energies, just above the Schottky barrier height, only for metals on Si(001) substrates. In contrast, the attenuation length measured on Si(111) substrates shows a sharp decrease. These results indicate that interface band structure and parallel momentum conservation have significant impact upon the transport of hot electrons across non epitaxial metal-semiconductor interfaces. In addition, they help to separate effects upon hot electron transport that are inherent to the metal
Photonic band gaps with layer-by-layer double-etched structures
Periodic layer-by-layer dielectric structures with full three-dimensional photonic band gaps have been designed and fabricated. In contrast to previous layer-by-layer structures the rods in each successive layer are at an angle of 70.5 degree to each other, achieved by etching both sides of a silicon wafer. Photonic band-structure calculations are utilized to optimize the photonic band gap by varying the structural geometry. The structure has been fabricated by double etching Si wafers producing millimeter wave photonic band gaps between 300 and 500 GHz, in excellent agreement with band calculations. Overetching this structure produces a multiply connected geometry and increases both the size and frequency of the photonic band gap, in very good agreement with experimental measurements. This new robust double-etched structure doubles the frequency possible from a single Si wafer, and can be scaled to produced band gaps at higher frequencies. copyright 1996 American Institute of Physics
Phononic Band Gaps in 2D Quadratic and 3D Cubic Cellular Structures
Franziska Warmuth
2015-12-01
Full Text Available The static and dynamic mechanical behaviour of cellular materials can be designed by the architecture of the underlying unit cell. In this paper, the phononic band structure of 2D and 3D cellular structures is investigated. It is shown how the geometry of the unit cell influences the band structure and eventually leads to full band gaps. The mechanism leading to full band gaps is elucidated. Based on this knowledge, a 3D cellular structure with a broad full band gap is identified. Furthermore, the dependence of the width of the gap on the geometry parameters of the unit cell is presented.
Enlargement of Photonic Band Gaps and Physical Picture of Photonic Band Structures
ZHANG Yan; SHI Jun-Jie
2006-01-01
@@ Light propagation in a one-dimensional photonic crystal (PC), consisting of alternative slabs with refractive indices (layer thicknesses) n1 (a) and n2 (b), is investigated. An important optimal parameter matching condition,n1a ≈ n2b, is obtained for the largest photonic band gap (PBG). Moreover, we find that the exact analytical solutions for the electric/magnetic field eigenmodes at the band edges are standing waves with odd or even symmetry about the centre of each layer. The electric/magnetic field eigenfunctions at the top and bottom of the nth band have n and n - 1 nodes in one period of PC, respectively. The PBG arises from the symmetric differences of the field eigenfunctions at the band edges.
Hyperspectral bands prediction based on inter-band spectral correlation structure
Ahmed, Ayman M.; Sharkawy, Mohamed El.; Elramly, Salwa H.
2013-02-01
Hyperspectral imaging has been widely studied in many applications; notably in climate changes, vegetation, and desert studies. However, such kind of imaging brings a huge amount of data, which requires transmission, processing, and storage resources for both airborne and spaceborne imaging. Compression of hyperspectral data cubes is an effective solution for these problems. Lossless compression of the hyperspectral data usually results in low compression ratio, which may not meet the available resources; on the other hand, lossy compression may give the desired ratio, but with a significant degradation effect on object identification performance of the hyperspectral data. Moreover, most hyperspectral data compression techniques exploits the similarities in spectral dimensions; which requires bands reordering or regrouping, to make use of the spectral redundancy. In this paper, we analyze the spectral cross correlation between bands for AVIRIS and Hyperion hyperspectral data; spectral cross correlation matrix is calculated, assessing the strength of the spectral matrix, we propose new technique to find highly correlated groups of bands in the hyperspectral data cube based on "inter band correlation square", and finally, we propose a new technique of band regrouping based on correlation values weights for different group of bands as network of correlation.
Comparison of Model Prediction With Measurements of Galactic Background Noise at L-Band
Le Vine, David M.; Abraham, Saji; Kerr, Yann H.;
2005-01-01
The spectral window at L-band (1.413 GHz) is important for passive remote sensing of surface parameters such as soil moisture and sea surface salinity that are needed to understand the hydrological cycle and ocean circulation. Radiation from celestial sources (mostly galactic) is strong in this w......The spectral window at L-band (1.413 GHz) is important for passive remote sensing of surface parameters such as soil moisture and sea surface salinity that are needed to understand the hydrological cycle and ocean circulation. Radiation from celestial sources (mostly galactic) is strong...... in this window, and an accurate accounting of this background radiation is often needed for calibration. This paper presents a comparison of the background radiation predicted by a model developed from modern radio astronomy measurements with measurements made with several modern L-band remote sensing...
Comparison of High Performance Network Options: EDR InfiniBand vs.100Gb RDMA Capable Ethernet
Kachelmeier, Luke Anthony [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of New Mexico, Albuquerque, NM (United States); Van Wig, Faith Virginia [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Missouri Univ. of Science and Technology, Rolla, MO (United States); Erickson, Kari Natania [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); New Mexico Inst. of Mining and Technology, Socorro, NM (United States)
2016-08-08
These are the slides for a presentation at the HPC Mini Showcase. This is a comparison of two different high performance network options: EDR InfiniBand and 100Gb RDMA capable ethernet. The conclusion of this comparison is the following: there is good potential, as shown with the direct results; 100Gb technology is too new and not standardized, thus deployment effort is complex for both options; different companies are not necessarily compatible; if you want 100Gb/s, you must get it all from one place.
Band structure of surface barrier states and resonances
Full text: G. Binnig and H. Rohrer, Nobel Prize Winners for the invention of the Scanning Tunneling Microscope, write in the opening sentence of one of their papers, co-authored with others : 'One of the fundamental problems in surface physics is obtaining knowledge of the electron-metal-surface interaction potential.' Although it is known that the surface barrier has an 'image' asymptotic form and saturates or weakens closer to the crystal surface, the position of the image tail, momentum dependence of the barrier height and saturation closer to the surface have not been agreed upon by different workers and techniques to this day. Ab initio calculations using the density functional approximation produce locations for the position of the image tail which differ by ∼50% depending on whether the exiting or incoming electron is considered part of the crystal or a classical charge interacting with the electron gas. Very low energy electron diffraction (VLEED), k-resolved inverse photoemission spectroscopy (KRIPES) and 2-photon photoemission spectroscopy (2PPE) are sensitive to the barrier but analyses to date have not yielded consistent conclusions. In this work we have used our plane-wave scattering method to calculate the barrier energy band structure for Cu (001) over the whole SBZ to compare with experimental results from KRIPES and 2PPE data as well as the calculation of Smith et al. This calculation used a parameterized nearly-free-electron function to represent the substrate scattering and could only produce states not resonances which occur outside of bulk band gaps and above the barrier height. As well, no inelastic scattering could be included. We show that inelastic scattering, surface restructuring and an extended data-base must be included for definitive conclusions about details of the barrier. Also, our calculation shows above-barrier resonances are strong and should be measured by experimentalists to extract the momentum dependent saturation and
DeHaas-vanAlphen Effect and LMTO Band-structure of LaSn3
Boulet, R. M.; Jan, J. -P.; Skriver, Hans Lomholt
1982-01-01
Results of de Haas-van Alphen experiments in the intermetallic compound LaSn3 can be explained by a linear muffin-tin orbital band structure calculation without involving the f bands of lanthanum.......Results of de Haas-van Alphen experiments in the intermetallic compound LaSn3 can be explained by a linear muffin-tin orbital band structure calculation without involving the f bands of lanthanum....
True photonic band-gap mode-control in VCSEL structures
Romstad, F.; Madsen, M.; Birkedal, Dan;
2003-01-01
Photonic band-gap mode confinement in novel nano-structured large area VCSEL structures is confirmed by the amplified spontaneous emission spectrum. Both guide and anti-guide VCSEL structures are experimentally characterised to verify the photonic band-gap effect.......Photonic band-gap mode confinement in novel nano-structured large area VCSEL structures is confirmed by the amplified spontaneous emission spectrum. Both guide and anti-guide VCSEL structures are experimentally characterised to verify the photonic band-gap effect....
Hvatov, Alexander; Sorokin, Sergey
2013-01-01
cell with various boundary conditions. Two classical models of periodic structures are considered, for which closed form solutions are obtained and analyzed. The regular and irregular eigenfrequencies of periodicity cells and finite periodic structures are identified, and the eigenmodes are compared.......Analysis of wave-guide properties of infinite periodic structures is a well establish research subject. The existence of frequency stop-bands, in which transmission of the vibro-acoustic energy is impossible, suggests that these structures may be used for vibro-isolation. In any technical...... application, however, only a finite segment of such a structure can be used. This paper is concerned with comparison of the eigenfrequency spectra of finite periodic structures with location of stop-bands for their infinite counterparts. Special attention is paid to eigenfrequencies of a single periodicity...
Kohei Arai
2013-04-01
Full Text Available Accuracy evaluation of cross calibration through band-to-band data comparison for visible and near infrared radiometers which onboard earth observation satellites is conducted. The conventional cross calibration for visible to near infrared radiometers onboard earth observation satellites is conducted through comparisons of band-to-band data of which spectral response functions are overlapped mostly. There are the following major error sources due to observation time difference, spectral response function difference in conjunction of surface reflectance and atmospheric optical depth, observation area difference. These error sources are assessed with dataset acquired through ground measurements of surface reflectance and optical depth. Then the accuracy of the conventional cross calibration is evaluated with vicarious calibration data. The results show that cross calibration accuracy can be done more precisely if the influences due to the aforementioned three major error sources are taken into account.
Band structures of ZnTe:O alloys with isolated oxygen and with clustered oxygen impurities
Highlights: • Band structures of ZnTe:O alloy highly depends on the status of oxygen. • Clustered oxygen lowers the bandgap while isolated oxygen increases the bandgap. • The solar adsorption efficiency of ZnTe:O can be improved by oxygen clustering. -- Abstract: First-principles calculations reveal that band structures of ZnTe:O alloys highly depend on the configuration of oxygen in the alloy. For alloys with isolated oxygen, the calculated band structure shows the formation of intermediate states between valence and conduction band and the shift of conduction band to higher energy level. It expands the gap between valence and conduction band. For alloys with clustered oxygen, the formation of intermediate band is still observed, while the gap between valence and conduction band is decreased. For alloys with oxygen impurities adjacent to Zn vacancy, the band structure only shows the decrease of the gap between valence and conduction band without the formation of any intermediate band. These results suggest the critical role of Zn–O bonding in determining the energy level of the impurity states. On the basis of our results, a possible band engineering approach is suggested in order to improve the performance of ZnTe:O alloy as intermediate band solar adsorbent
Photonic band structure of two-dimensional metal/dielectric photonic crystals
An improved plane wave expansion method for the numerical calculation of photonic bands of metal/dielectric photonic crystal (PC) are presented. This method is applied to two-dimensional PCs with frequency-dependent dielectric constants. We obtained the photonic band structure of three kinds of structures: sawtooth, cylinder and hole PCs. The results show that the lowest band-1 is relatively flat, and does not approach zero. Also, there is no complete band-gap that extends throughout the first Brillouin zone for these three structures. However, there are partial band-gaps in different directions in the first Brillouin zone. For the complementary cylinder and hole PCs, their photonic bands are similar except for the lowest three bands; the hole PC’s lowest frequency of band-1 is larger than that of cylinder PC for the configuration R/d = 0.2. (paper)
Rietveld analysis and electronic bands structure on Tc superconductors systems
A procedure for simultaneous refinement of structural and micro-structural disorder parameters for polycrystalline YBa2Cu3O7-x system is proposed. It is based on Rietveld method combined with Fourier analysis for broadened peaks Another purpose of this paper consists in electronic structure determination studied by using the self-consistent Tight Binding Linear Muffin-Tin Orbital Atomic Spheres Approximation TB-LMTO-ASA methods. The Rietveld method uses an analytical function that describes the profiles, usually pseudo-Voigt (pV) or Pearson VII (PVII). The parameters of the analytical profiles describe its amplitude, position and peak shape. The full width at half maximum (FWHM) is supposed to vary with the diffraction angle in agreement with the Caglioti, Paoletti and Ricci's relationship. The best structural parameters are determined in the least squares sense by the minimisation a classical residual using the Marquardt method. In this case, the peak profiles were modelled by the pseudo-Voigt function corrected by the instrumental asymmetry. The physical information obtained are: scale factor, lattice parameters, atomic position and displacements, atomic occupation numbers, temperature factor (isotropy or anisotropy), preferred orientation parameter, crystalline size and micro-strain along different crystallographic directions, distributions of crystallite size and micro-strain functions. This procedure was implemented on computer code and it has a friendly graphical interface based on pull down menus technique. From the experimental point of view the X-ray diffraction data were collected using a horizontal powder diffractometer in the Bragg-Brentano (BB) geometry with a Ni filtered CuKα, λ = 1.54178 A, at room temperature using a DRON 2 set-up. The diffraction profiles were measured with a proportional gas detector, a single channel pulse-height discrimination and a standard associated counting circuit. The electronic band calculations are based on the TB
On the Design of Laser Structured Ka Band Multi-Chip Module
Ghulam Mehdi
2013-09-01
Full Text Available The rapid prototyping of millimeter wave (MMW multi-chip module (MCM on low-cost ceramic-polymer composite substrate using laser ablation process is presented. A Ka band MCM front-end receiver is designed, fabricated and tested. The complete front-end receiver module except the IF and power distribution sections is realized on the single prescribed substrate. The measured receiver gain, noise figure and image rejection is 37 dB, 4.25 dB and 40 dB respectively. However, it deduced from the experimental results of the two front-end modules that the complex permittivity characteristics of the substrate are altered after the laser ablation process. The effective permittivity alteration phenomenon is further validated through the characterization and comparison of various laser ablated and chemically etched Ka band parallel-coupled band-pass filters. A simple and experimentally verified method is worked out to utilize the laser ablation structuring process on the prescribed substrate. It is anticipated that the proposed method can be applied to other laminated substrates as well with the prescribed manufacturing process.
Miniaturization of electromagnetic band gap structures for mobile applications
Goussetis, G.; Feresidis, A. P.; Palikaras, G. K.; Kitra, M.; Vardaxoglou, J. C.
2005-12-01
It is well known that interference of the human body affects the performance of the antennas in mobile phone handsets. In this contribution, we investigate the use of miniaturized metallodielectric electromagnetic band gap (MEBG) structures embedded in the case of a mobile handset as a means of decoupling the antenna from the user's hand. The closely coupled MEBG concept is employed to achieve miniaturization of the order of 15:1. Full wave dispersion relations for planar closely coupled MEBG arrays are presented and are validated experimentally. The performance of a prototype handset with an embedded conformal MEBG is assessed experimentally and is compared to a similar prototype without the MEBG. Reduction in the detuning of the antenna because of the human hand by virtue of the MEBG is demonstrated. Moreover, the efficiency of the handset when loaded with a human hand model is shown to improve when the MEBG is in place. The improvements are attributed to the decoupling of the antenna from the user's hand, which is achieved by means of suppressing the fields in the locality of the hand.
Theoretical study of relative width of photonic band gap for the 3-D dielectric structure
G K Johri; Akhilesh Tiwari; Saumya Saxena; Rajesh Sharma; Kuldeep Srivastava; Manoj Johri
2002-03-01
Calculations for the relative width (/0) as a function of refractive index and relative radius of the photonic band gap for the fcc closed packed 3-D dielectric microstructure are reported and comparison of experimental observations and theoretical predictions are given. This work is useful for the understanding of photonic crystals and occurrence of the photonic band gap.
Comparisons of Aquarius Measurements over Oceans with Radiative Transfer Models at L-Band
Dinnat, E.; LeVine, D.; Abraham, S.; DeMattheis, P.; Utku, C.
2012-01-01
The Aquarius/SAC-D spacecraft includes three L-band (1.4 GHz) radiometers dedicated to measuring sea surface salinity. It was launched in June 2011 by NASA and CONAE (Argentine space agency). We report detailed comparisons of Aquarius measurements with radiative transfer model predictions. These comparisons are used as part of the initial assessment of Aquarius data and to estimate the radiometer calibration bias and stability. Comparisons are also being performed to assess the performance of models used in the retrieval algorithm for correcting the effect of various sources of geophysical "noise" (e.g. Faraday rotation, surface roughness). Such corrections are critical in bringing the error in retrieved salinity down to the required 0.2 practical salinity unit on monthly global maps at 150 km by 150 km resolution.
Band Structure and Fermi-Surface Properties of Ordered beta-Brass
Skriver, Hans Lomholt; Christensen, N. E.
1973-01-01
The band structure of ordered β-brass (β′-CuZn) has been calculated throughout the Brillouin zone by the augmented-plane-wave method. The present band model differs from previous calculations with respect to the position and width of the Cu 3d band. The derived dielectric function ε2(ω) and the...
Jung-Hwan Lee
2014-01-01
Full Text Available Understanding the biocompatibility of nanoparticles in dental materials is essential for their safe usage in the oral cavity. In this study, we investigated whether nanoparticles deposited on orthodontic latex rubber bands are involved in the induction of cytotoxicity. A method of stretching to three times (“3L” the length of the latex rubber bands was employed to detach the particles using the original length (“L” for comparison. The cytotoxicity tests were performed on extracts with mouse fibroblasts (L929 and human gingival fibroblasts (HGFs. Fourier transform infrared spectroscopy, ion chromatography, elemental analysis, and inductively coupled plasma mass spectrometry (ICP-MS were performed to detect the harmful components in the extracts from rubber bands. There was a significant decrease in the cell viability in the “L” samples compared with the “3L” samples (P<0.05 in the L929 and HGF cells. This was due to the Ni single crystal nanoparticles (~50nm from the inner surface of “L” samples that were detached in the “3L” samples as well as the Zn ion (~9 ppm detected in the extract. This study revealed that the Ni nanoparticles, as well as Zn ions, were involved in the induction of cytotoxicity from the latex rubber bands.
The motivation for this work is the study of thundercloud radio emission from extensive air showers. The ionization electrons from an extensive air shower constitute a current pulse whose amplitude is modulated by the thundercloud field. The concept of band comparison is investigated for white noise, and a modified form of band comparison is developed based on comparing the average, taken over a finite time interval, of the square of the signal amplitude at the output of one narrow band filter to that at the other. It is found that prefiltering of the signal with a filter having the same center frequency as the two band comparison filters, but a wider band pass than either one of them, has no effect on the band comparison properties of a pure transient, while for the noise, the Q of the prefilter is effectively added to the Q's of the two band comparison filters. After consideration of the properties of band comparison, a combined band comparison and signal-to-noise ratio test is developed for use in our measurements of shower ionization of radio emission from thundercloud fields. Data were taken during five thunderstorms which occurred during the summer of 1975. To the sensitivity of our instrumentation (about 105 V/m for the thundercloud field), there is no evidence of shower ionization radio emission in this data. One concludes that fields on the order of 105 V/m are either generally confined to small regions of a thundercloud, or that the field distribution in the cloud is so complicated as to obscure the modulation of the shower ionization electron current
Band structure of sup 7 sup 9 Br
Ray, I; Bhattacharya, S; Saha-Sarkar, M; Sethi, B; Chatterjee, J M; Chattopadhyay, S; Goswami, A; Muralithar, S; Singh, R P; Bhowmik, R K
1999-01-01
High-spin states of sup 7 sup 9 Br have been studied in the reaction sup 7 sup 6 Ge( sup 7 Li, 4n gamma) at 32 MeV. A gamma-detector array with twelve Compton-suppressed HPGe detectors was used. The positive-parity yrast states, interpreted as a rotationally aligned g sub ( sub 9 sub ( sub 2 sub ) sub ) proton band, and the negative-parity ground state band have been extended to spins of (33(2 sup +)) and (25(2 sup -)), respectively. Lifetime measurements indicate that both bands have a similar quadrupole deformation of beta sub 2 approx 0.2. The positive-parity alpha = -(1(2)) band has been identified. Several new inter-band transitions are observed. A cranked-shell model analysis shows that the nu g sub ( sub 9 sub ( sub 2 sub ) sub ) and pi g sub ( sub 9 sub ( sub 2 sub ) sub ) alignments occur in the positive-parity and the negative-parity bands at rotational frequencies of Planck constant omega approx 0.6 and 0.4 MeV, respectively. The level energies and the electromagnetic properties of the g sub ( sub ...
First principle study of band structure of SrMO3 perovskites
Daga, Avinash; Sharma, Smita
2016-05-01
First principle study of band structure calculations in the local density approximations (LDA) as well as in the generalized gradient approximations (GGA) have been used to determine the electronic structure of SrMO3 where M stands for Ti, Zr and Mo. Occurrence of band gap proves SrTiO3 and SrZrO3 to be insulating. A small band gap is observed in SrMoO3 perovskite signifies it to be metallic. Band structures are found to compare well with the available data in the literature showing the relevance of this approach. ABINIT computer code has been used to carry out all the calculations.
Broad-band detection and mass comparison between lithium ions by FT-ICR MS
Golzke, Hendrik [Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany); Institut fuer Experimentelle Kernphysik, Karlsruher Institut fuer Technologie, Karlsruhe (Germany); Blaum, Klaus; Heck, Michael; Ubieto-Diaz, Marta [Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany); Cakirli, R. Burcu [Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany); Department of Physics, University of Istanbul, Istanbul (Turkey); Rodriguez, Daniel [Departamento de Fisica Atomica Molecular y Nuclear, Universidad de Granada, Granada (Spain); Schweikhard, Lutz [Institute of Physics, Ernst-Moritz-Arndt-University Greifswald, Greifswald (Germany); Stahl, Stefan [Stahl Electronics, Kellerweg 23, 67528 Mettenheim (Germany)
2012-07-01
Penning traps are widely used as storage devices for charged particles. With such a trap a mass-spectrometry system for the KArlsruhe TRItium Neutrino (KATRIN) experiment has been developed and characterized at the Max-Planck-Institute for Nuclear Physics in Heidelberg. A broad-band non-destructive Fourier Transform Ion Cyclotron Resonance (FT-ICR) method which is able to record simultaneously the eigenfrequencies of different stored particles over a wide range is used. In this talk the dipolar and quadrupolar detection technique and a recent mass comparison between {sup 6}Li{sup +} and {sup 7}Li{sup +} are presented.
Relationships between magnetic foot points and G-band bright structures
Ishikawa, R.; Tsuneta, S.; Kitakoshi, Y.; Katsukawa, Y.; Bonet, J. A.; Domínguez, S. Vargas; van der Voort, L. H. M. Rouppe; Sakamoto, Y; Ebisuzaki, T.
2008-01-01
Magnetic elements are thought to be described by flux tube models, and are well reproduced by MHD simulations. However, these simulations are only partially constrained by observations. We observationally investigate the relationship between G-band bright points and magnetic structures to clarify conditions, which make magnetic structures bright in G-band. The G-band filtergrams together with magnetograms and dopplergrams were taken for a plage region covered by abnormal granules as well as u...
Comparison between Ultroid and Rubber Band Ligation in Treatment of Internal Hemorrhoids
Rasoul Azizi
2010-11-01
Full Text Available "nHemorrhoid is one of the most common surgical diseases and different methods are available for its treatment. This study is a comparison between two methods of treatment of internal hemorrhoid, Monopolar low voltage instrument (Ultroid and Rubber Band Ligation. This method has been carried out prospectively in which 50 patients who were treated with rubber band ligation and 50 patients with Ultroid were compared according to the incidence of complications, post-operative pain and treatment response. According to this study complete success rate with Ultroid was 82% and partial success rate was 10% and no response to treatment was seen in 8%. In Rubber Band method the complete response rate was 94% (P=0.2. With Ultroid, 74% of patient reported no postoperative pain, 24% reported mild and moderate pain and 2% of patients complained of severe pain. With Rubber band ligation, 72% of patients reported no post-operative pain, 26% reported mild and moderate pain and 1% complained of severe pain (P=0.00. Rubber Band ligation and Ultroid are both considered as outpatient procedures for treatment of hemorrhoids. Both methods are mostly used for grade 1, 2 and sometime grade 3 hemorrhoids. In Ultroid method the operator is required to hold the probe for a period of time, and in most cases, the surgeon should spend between 20-25 minutes for the coagulation of three piles. Some surgeons do not have patience for this modality of internal hemorrhoid treatment. In this study we achieved acceptable results comparable with those of other techniques.
Design and analysis of defected ground structure transformer for dual-band antenna
Wai-Wa Choi
2014-12-01
Full Text Available This study presents a novel dual-band antenna design methodology utilising a dual-frequency impedance transformer with defected ground structure (DGS. The proposed dual-frequency DGS impedance transformer generates a second resonant frequency from a conventional single-band antenna, resulting dual-band operation. Simulation studies illustrate that the adopted design achieves versatile configurations for arbitrary operating frequencies and diverse input impedance ranges in planar antenna structures. To experimentally verify the proposed design methodology, a dual-frequency DGS impedance transformer was implemented for a 2.4 GHz monopole antenna to obtain a 900/2400 MHz dual-band antenna. Measurement shows that the 10 dB return loss bandwidth in 900 MHz band is 34.4 MHz, whereas that in 2400 MHz band is wider than 530 MHz. Typical monopole radiation patterns are observed at both operating bands.
Band structures in silicene on monolayer gallium phosphide substrate
Ren, Miaojuan; Li, Mingming; Zhang, Changwen; Yuan, Min; Li, Ping; Li, Feng; Ji, Weixiao; Chen, Xinlian
2016-07-01
Opening a sizable band gap in the zero-gap silicene is a key issue for its application in nanoelectronics. We design new 2D silicene and GaP heterobilayer (Si/GaP HBL) composed of silicene and monolayer (ML) GaP. Based on first-principles calculations, we find that the interaction energies are in the range of -295.5 to -297.5 meV per unit cell, indicating a weak interaction between silicene and gallium phosphide (GaP) monolayer. The band gap changes ranging from 0.06 to 0.44 eV in hybrid HBLs. An unexpected indirect-direct band gap crossover is also observed in HBLs, dependent on the stacking pattern. These provide a possible way to design effective FETs out of silicene on GaP monolayer.
New bismuth borophosphate Bi4BPO10 was obtained by spontaneous crystallization from the melt of correspondent composition at 804 °C. Crystal structure with orthorhombic lattice parameters: a = 22.5731(3) Å, b = 14.0523(2) Å, c = 5.5149(1) Å, V = 1749.34(4), Z = 8, SG Pcab was determined by X-ray powder diffraction technique. The [Bi2O2]2+ -layers, which are typical for bismuth oxide compounds, transform into cationic endless strips of 4 bismuth atoms width directed along the c-axis in Bi4BPO10. The strips combining stacks are separated by flat triangle [BO3]3− -anions within stacks. Neighboring stacks are separated by tetrahedral [PO4]3−-anions and shifted relatively to each other. Bismuth atoms are placed in 5–7 vertex oxygen irregular polyhedra. Bi4BPO10 is stable up to 812 °C, then melts according to the peritectic law. The absorption spectrum in the range 350–700 nm was obtained and the width of the forbidden band was estimated as 3.46 eV. The band electronic structure of Bi4BPO10 was modeled using DFT approach. The calculated band gap (3.56 eV) is in good agreement with the experimentally obtained data. - Graphical abstract: Display Omitted - Highlights: • New bismuth borophosphate with composition Bi4BPO10 was synthesized. • The crystal structure was determined by X-ray powder diffraction technique. • Bismuth-oxygen part [Bi4O3]6+ forms endless strips of 4 bismuth atoms width. • Electronic structure was modeled by DFT method. • The calculated band gap (3.56 eV) is very close to the experimental one (3.46 eV)
Photonic band structures in one-dimensional photonic crystals containing Dirac materials
We have investigated the band structures of one-dimensional photonic crystals (1DPCs) composed of Dirac materials and ordinary dielectric media. It is found that there exist an omnidirectional passing band and a kind of special band, which result from the interaction of the evanescent and propagating waves. Due to the interface effect and strong dispersion, the electromagnetic fields inside the special bands are strongly enhanced. It is also shown that the properties of these bands are invariant upon the lattice constant but sensitive to the resonant conditions
Phononic First Band Gap of Quaternary Layered Periodic Structure with the Lumped-Mass Method
Chen Yuan
2014-01-01
Full Text Available Existing band gap analysis is mostly focused on the binary structure, while the researches on the quaternary layered periodic structure are still lacking. In this paper, the unidimensional lumped-mass method in the phonic crystal theory is firstly improved so that the material viscoelasticity can be taken into consideration. Then, the binary layered periodic structure is converted into a quaternary one and band gaps appear at low frequency range. Finally, the effects of density, elastic modulus, damping ratio, and the thickness of single material on the first band gap of the quaternary layered periodic structure are analyzed after the algorithm is promoted. The research findings show that effects of density, elastic modulus, and thickness of materials on the first band gap are considerable but those of damping ratio are not so distinct. This research provides theoretical bases for band gap design of the quaternary layered periodic structure.
Electronic band structure of tetracene-TCNQ and perylene-TCNQ compounds
Shokaryev, I.; Buurma, A. J. C.; Jurchescu, O. D.; Uijttewaal, M. A.; de Wijs, G.A.; Palstra, T. T. M.; Groot, R.A. de
2008-01-01
The relationship between the crystal structures, band structures, and electronic properties of acene-TCNQ complexes has been investigated. We focus on the newly synthesized crystals of the charge-transfer salt tetracene-TCNQ and similar to it. perylene-TCNQ, potentially interesting for realization of ambipolar transport. The band structures were calculated from first principles using density-functional theory (DFT). Despite the similarity in the crystal structures of the acene-TCNQ complexes ...
Structural comparison of contractile nanomachines
Sebastian Kube
2015-05-01
Full Text Available Contractile molecular machines are a common feature among bacteriophages and prokaryotes. Due to their stability and the large size, contractile-tailed bacteriophages are traditionally investigated by electron microscopic methods. Complemented by crystallographic studies, a molecular model of contraction for the T4 phage was developed. Lately, also related contractile structures like the Photorhabdus virulence cassette-like particles, the R-Type pyocins and the contractile tubule of the bacterial Type VI secretion system have been analyzed by cryo electron microscopy. Photorhabdus virulence cassette particles and R-Type pyocins are toxin complexes reminiscent of bacteriophage tails that are secreted by bacteria to kill their insect host or competing bacteria. In contrast, the Type VI secretion system is an intracellular apparatus for injection of effector proteins into bacterial and eukaryotic cells. Although it shares homology with other contractile systems, the Type VI secretion system is additionally equipped with a recycling function, which makes it suitable for multiple rounds of action. Starting from the 3D reconstructions, we compare these molecular machines structurally and functionally to their viral counterparts and summarize the current knowledge on their respective mode of action.
The band structures of BSb and BxGa1-xSb alloys
无
2009-01-01
The band structures of BSb and BxGa1-xSb alloys are studied using first-principles calculations in the generalized gradient approximation. By SQS-8 supercells to model a random alloy, the direct transition energy-gap (Γ15v- Γ1c) bowing of 3.0 eV is obtained for BxGa1-xSb alloys in x = 0-50%, in x = 0-11% the energy-gap is the band-gap and increases by 7 meV/%B with boron composition increasing; by SQS-16 supercells the bowing parameter is about 1.9 eV in x = 0-12.5%. The formation enthalpies of mixing, ΔH, are calculated for BxGa1-xAs and BxGa1-xSb alloys. A comparison of enthalpies indicates that BxGa1-xSb films with boron composition of 7% may be possible.
The band structures of BSb and BxGa1-xSb alloys
XIONG DePing; ZHOU ShouLi; WANG Qi; LUO Li; HUANG YongQing; REN XiaoMin
2009-01-01
The band structures of BSb and BxGa1-xSb alloys are studied using first-principles calculations in the generalized gradient approximation. By SQS-8 supercells to model a random alloy, the direct transition energy-gap (Γ15v-Γ1c) bowing of 3.0 eV is obtained for BxGa1-xSb alloys in x=0-50%, in x=0-11% the energy-gap is the band-gap and increases by 7 meV/%B with boron composition increasing; by SQS-16 supercells the bowing parameter is about 1.9 eV in x= 0-12.5%. The formation enthalpies of mixing, ΔH,are calculated for BxGa1-xAs and BxGa1-xSb alloys. A comparison of enthalpies indicates that BxGa1-xSb films with boron composition of 7% may be possible.
Phononic band gaps and vibrations in one- and two-dimensional mass-spring structures
Jensen, Jakob Søndergaard
2003-01-01
The vibrational response of finite periodic lattice structures subjected to periodic loading is investigated. Special attention is devoted to the response in frequency ranges with gaps in the band structure for the corresponding infinite periodic lattice. The effects of boundaries, viscous damping......, and imperfections are studied by analyzing two examples; a 1-D filter and a 2-D wave guide. In 1-D the structural response in the band gap is shown to be insensitive to damping and small imperfections. In 2-D the similar effect of damping is noted for one type of periodic structure, whereas for...... another type the band gap effect is nearly eliminated by damping. In both 1-D and 2-D it is demonstrated how the free structural boundaries affect the response in the band gap due to local resonances. Finally, 2-D wave guides are considered by replacing the periodic structure with a homogeneous structure...
High-Pressure Crystal Structure, Lattice Vibrations, and Band Structure of BiSbO4.
Errandonea, Daniel; Muñoz, Alfonso; Rodríguez-Hernández, Placida; Gomis, Oscar; Achary, S Nagabhusan; Popescu, Catalin; Patwe, Sadeque J; Tyagi, Avesh K
2016-05-16
The high-pressure crystal structure, lattice-vibrations, and electronic band structure of BiSbO4 were studied by ab initio simulations. We also performed Raman spectroscopy, infrared spectroscopy, and diffuse-reflectance measurements, as well as synchrotron powder X-ray diffraction. High-pressure X-ray diffraction measurements show that the crystal structure of BiSbO4 remains stable up to at least 70 GPa, unlike other known MTO4-type ternary oxides. These experiments also give information on the pressure dependence of the unit-cell parameters. Calculations properly describe the crystal structure of BiSbO4 and the changes induced by pressure on it. They also predict a possible high-pressure phase. A room-temperature pressure-volume equation of state is determined, and the effect of pressure on the coordination polyhedron of Bi and Sb is discussed. Raman- and infrared-active phonons were measured and calculated. In particular, calculations provide assignments for all the vibrational modes as well as their pressure dependence. In addition, the band structure and electronic density of states under pressure were also calculated. The calculations combined with the optical measurements allow us to conclude that BiSbO4 is an indirect-gap semiconductor, with an electronic band gap of 2.9(1) eV. Finally, the isothermal compressibility tensor for BiSbO4 is given at 1.8 GPa. The experimental (theoretical) data revealed that the direction of maximum compressibility is in the (0 1 0) plane at ∼33° (38°) to the c-axis and 47° (42°) to the a-axis. The reliability of the reported results is supported by the consistency between experiments and calculations. PMID:27128858
Recent Results from Broad-Band Intensity Mapping Measurements of Cosmic Large Scale Structure
Zemcov, Michael B.; CIBER, Herschel-SPIRE
2016-01-01
Intensity mapping integrates the total emission in a given spectral band over the universe's history. Tomographic measurements of cosmic structure can be performed using specific line tracers observed in narrow bands, but a wealth of information is also available from broad-band observations performed by instruments capable of capturing high-fidelity, wide-angle images of extragalactic emission. Sensitive to the continuum emission from faint and diffuse sources, these broad-band measurements provide a view on cosmic structure traced by components not readily detected in point source surveys. After accounting for measurement effects and astrophysical foregrounds, the angular power spectra of such data can be compared to predictions from models to yield powerful insights into the history of cosmic structure formation. This talk will highlight some recent measurements of large scale structure performed using broad-band intensity mapping methods that have given new insights on faint, distant, and diffuse components in the extragalactic background light.
Band structures of TiO2 doped with N, C and B
无
2006-01-01
This study on the band structures and charge densities of nitrogen (N)-, carbon (C)- and boron (B)-doped titanium dioxide (TiO2) by first-principles simulation with the CASTEP code (Segall et al., 2002) showed that the three 2p bands of impurity atom are located above the valence-band maximum and below the Ti 3d bands, and that along with the decreasing of impurity atomic number, the fluctuations become more intensive. We cannot observe obvious band-gap narrowing in our result.Therefore, the cause of absorption in visible light might be the isolated impurity atom 2p states in band-gap rather than the band-gap narrowing.
Novel structure for magnetic rotation bands in 60Ni
Zhao, P. W.; Zhang, S.Q.; Peng, J.; H.Z. Liang; Ring, P.; Meng, J
2011-01-01
The self-consistent tilted axis cranking relativistic mean-field theory based on a point-coupling interaction has been established and applied to investigate systematically the newly observed shears bands in 60Ni. The tilted angles, deformation parameters, energy spectra, and reduced M1 and $E2$ transition probabilities have been studied in a fully microscopic and self-consistent way for various configurations and rotational frequencies. It is found the competition between the configurations ...
Band structures in 98Ru and 99Ru
The level schemes of 98sup(,)99Ru were studied with the reactions 8Mo(α,3nγ) and 98Mo(α,4nγ) at Esub(α) = 35 to 55 MeV, using a large variety of in-beam γ-ray detection techniques and conversion-electron measurements. A search for the 3- state was carried out with the reaction 98Ru(p,p'). The ground-state band of 98Ru was excited up to Jsup(π) = (12)+ and a negative-parity band up to (15)-. New levels in 98Ru were found at Esub(x) = 2285 (Jsup(π) = 4+), 2435 (Jsup(π) = (3-,4+), 2671, 3540, 4224, 4847, 4915 (Jsup(π) = (12)sup()), 4989 (Jsup(π) = (12sup())), 5521 (Jsup(π) = (13)-), 5889, 6591 (Jsup(π) = (15)-), and 7621 keV. New unambiguous spin and parity assignments were made for the levels at Esub(x) = 2014 and 3852 keV, as Jsup(π) = 3+ and 9-, respectivley. New levels in 99Ru were found at Esub(x) = 1976, 2021 (Jsup(π) = (15/2+)), 2393, 2401 (Jsup(π) = (17/2+)), 2875 (π = (+)), 3037, 3201 (Jsup(π) = (23/2)-), 3460 (J = (17/2)), 3484 (Jsup(π) = (21/2+)), 3985, 4224 (Jsup(π) = (27/2-)), and 5359 keV. The 1070 keV, Jsup(π) = 11/2- level in 99Ru has a half-life of 2.8 ns. A strongly excited negative-parity band is built on this level. A positive-parity band based on the ground state was excited up to Jsup(π) = (21/2+). The level schemes are well reproduced by the interacting boson model in the vibrational limit. (orig.)
Electron momentum density, band structure, and structural properties of SrS
Sharma, G., E-mail: gsphysics@gmail.com [University of Kota, Department of Pure and Applied Physics (India); Munjal, N.; Vyas, V. [Banasthali University, Department of Physics (India); Kumar, R.; Sharma, B. K. [University of Rajasthan, Department of Physics (India); Joshi, K. B. [MLS University, Department of Physics (India)
2013-10-15
The electron momentum density, the electronic band structure, and the structural properties of SrS are presented in this paper. The isotropic Compton profile, anisotropies in the directional Compton profiles, the electronic band structure and density of states are calculated using the ab initio periodic linear combination of atomic orbitals method with the CRYSTAL06 code. Structural parameters of SrS-lattice constants and bulk moduli in the B1 and B2 phases-are computed together with the transition pressure. The computed parameters are well in agreement with earlier investigations. To compare the calculated isotropic Compton profile, measurement on polycrystalline SrS is performed using 5Ci-{sup 241}Am Compton spectrometer. Additionally, charge transfer is studied by means of the Compton profiles computed from the ionic model. The nature of bonding in the isovalent SrS and SrO compounds is compared on the basis of equal-valenceelectron-density profiles and the bonding in SrS is found to be more covalent than in SrO.
Study of III-V semiconductor band structure by synchrotron photoemission
Angle-resolved synchrotron photoemission studies of six III-V semiconductors have been carried out. For emission normal to the (110) plane of these materials, peaks in the experimental spectra were identified with the bands involved in the transitions, and the critical point energies X3, X5, and Σ1/sup min/, were determined. The data indicate that k perpendicular is conserved in the transitions. Comparison of the data with theoretical bands permits an evaluation of k perpendicular associated with the experimentally observed transition, and from this information the bands were plotted out
Obtaining the band structure of a complicated photonic crystal by linear operations
吴良; 叶卓; 何赛灵
2003-01-01
Absolute band gaps can be created by lifting the degeneracy in the bands of a photonic crystal.To calculate the band structure of a complicated photonic crystal generated by e.g.symmetry breaking,general forms of all possible linear operations are presented in terms of matrices and a procedure to combine these operations is given.Other forms of linear operations(such as the addition,subtraction,and translation transforms) are also presented to obtain an explicit expression for the Fourier coefficient of the dielectric function in the plane-wave expansion method.With the present method,band structures for various complicated photonic crystals(related through these linear operations) can be obtained easily and quickly.As a numerical example,a large absolute band gap for a complicated photonic crystal structure of GaAs is found in the high region of normalized frequency.
Valence band structure of binary chalcogenide vitreous semiconductors by high-resolution XPS
Kozyukhin, S., E-mail: sergkoz@igic.ras.ru [Russian Academy of Science, Institute of General and Inorganic Chemistry (Russian Federation); Golovchak, R. [Lviv Scientific Research Institute of Materials of SRC ' Carat' (Ukraine); Kovalskiy, A. [Lehigh University, Department of Materials Science and Engineering (United States); Shpotyuk, O. [Lviv Scientific Research Institute of Materials of SRC ' Carat' (Ukraine); Jain, H. [Lehigh University, Department of Materials Science and Engineering (United States)
2011-04-15
High-resolution X-ray photoelectron spectroscopy (XPS) is used to study regularities in the formation of valence band electronic structure in binary As{sub x}Se{sub 100-x}, As{sub x}S{sub 100-x}, Ge{sub x}Se{sub 100-x} and Ge{sub x}S{sub 100-x} chalcogenide vitreous semiconductors. It is shown that the highest occupied energetic states in the valence band of these materials are formed by lone pair electrons of chalcogen atoms, which play dominant role in the formation of valence band electronic structure of chalcogen-rich glasses. A well-expressed contribution from chalcogen bonding p electrons and more deep s orbitals are also recorded in the experimental valence band XPS spectra. Compositional dependences of the observed bands are qualitatively analyzed from structural and compositional points of view.
By virtue of the efficiency of the Dirichlet-to-Neumann map method, we have calculated, for H-polarization (TE mode), the band structure of 2D photonic crystals with a square lattice composed of metallic rods embedded in an air background. The rod in the unit cell is chosen to be circular in shape. Here, from a practical point of view, in order to obtain maximum band gaps, we have studied the band structure as a function of the size of the rods. We have also studied the flat bands appearing in the band structures and have shown that for frequencies around the surface plasmon frequency, the modes are highly localized at the interface between the metallic rods and the air background.
Structure of Dipole Bands in 112In: Through Lifetime Measurement
High-spin states of the 112In nucleus have been populated via 100Mo(16O, p3n) reaction at 80 MeV beam energy. Lifetimes of excited states of dipole bands have been measured using Doppler-shift attenuation method. The B(M1) transition rates deduced from the measured lifetimes show a rapid decrease with increasing angular momentum. The decrease in B(M1) values are well accounted by the prediction of tilted axis cranking calculations. These measurements confirm the presence of shears mechanism in this nuclei.
Quasiparticle electronic band structure of the alkali metal chalcogenides
S.V. Syrotyuk
2015-09-01
Full Text Available The electronic energy band spectra of the alkali metal chalcogenides M2A (M: Li, Na, K, Rb; A: O, S, Se, Te have been evaluated within the projector augmented waves (PAW approach by means of the ABINIT code. The Kohn-Sham single-particle states have been found in the GGA framework. Further, on the basis of these results the quasiparticle energies of electrons as well as the dielectric constants were obtained in the approximation GW. The calculations based on the Green's function have been originally done for all the considered M2A crystals, except Li2O.
Determination of conduction and valence band electronic structure of anatase and rutile TiO2
Jakub Szlachetko; Katarzyna Michalow-Mauke; Maarten Nachtegaal; Jacinto Sá
2014-03-01
Electronic structures of rutile and anatase polymorph of TiO2 were determined by resonant inelastic X-ray scattering measurements and FEFF9.0 calculations. Difference between crystalline structures led to shifts in the rutile Ti -band to lower energy with respect to anatase, i.e., decrease in band gap. Anatase possesses localized states located in the band gap where electrons can be trapped, which are almost absent in the rutile structure. This could well explain the reported longer lifetimes in anatase. It was revealed that HR-XAS is insufficient to study in-depth unoccupied states of investigated materials because it overlooks the shallow traps.
Compact electromagnetic bandgap structures for notch band in ultra-wideband applications.
Rotaru, Mihai; Sykulski, Jan
2010-01-01
This paper introduces a novel approach to create notch band filters in the front-end of ultra-wideband (UWB) communication systems based on electromagnetic bandgap (EBG) structures. The concept presented here can be implemented in any structure that has a microstrip in its configuration. The EBG structure is first analyzed using a full wave electromagnetic solver and then optimized to work at WLAN band (5.15-5.825 GHz). Two UWB passband filters are used to demonstrate the applicability and effectiveness of the novel EBG notch band feature. Simulation results are provided for two cases studied. PMID:22163430
Band gap structure modification of amorphous anodic Al oxide film by Ti-alloying
Canulescu, Stela; Rechendorff, K.; Borca, C. N.;
2014-01-01
The band structure of pure and Ti-alloyed anodic aluminum oxide has been examined as a function of Ti concentration varying from 2 to 20 at. %. The band gap energy of Ti-alloyed anodic Al oxide decreases with increasing Ti concentration. X-ray absorption spectroscopy reveals that Ti atoms are not...
Band Structure and Quantum Confined Stark Effect in InN/GaN superlattices
Gorczyca, I.; Suski, T.; Christensen, Niels Egede;
2012-01-01
InN/GaN superlattices offer an important way of band gap engineering in the blue-green range of the spectrum. This approach represents a more controlled method than the band gap tuning in quantum well systems by application of InGaN alloys. The electronic structures of short-period wurtzite InN/G...
Acoustic band pinning in the phononic crystal plates of anti-symmetric structure
Cai Chen; Zhu Xue-Feng; Chen Qian; Yuan Ying; Liang Bin; Cheng Jian-Chun
2011-01-01
Acoustic bands are studied numerically for a Lamb wave propagating in an anti-symmetric structure of a onedimensional periodic plate by using the method of supercell plane-wave expansion.The results show that all the bands are pinned in pairs at the Brillouin zone boundary as long as the anti-symmetry remains and acoustic band gaps (ABGs) only appear between certain bands.In order to reveal the relationship between the band pinning and the anti-symmetry,the method of eigenmode analysis is introduced to calculate the displacement fields of different plate structures.Further,the method of harmony response analysis is employed to calculate the reference spectra to verify the accuracy of numerical calculations of acoustic band map,and both the locations and widths of ABGs in the acoustic band map are in good agreement with those of the reference spectra.The investigations show that the pinning effect is very sensitive to the anti-symmetry of periodic plates,and by introducing different types of breakages,more ABGs or narrow pass bands will appear,which is meaningful in band gap engineering.
Multi-large low-frequency band gaps in a periodic hybrid structure
Wang, T.; Sheng, M. P.; Guo, H. B.
2016-03-01
A hybrid structure composed of a local resonance mass and an external oscillator is proposed in this paper for restraining the elastic longitudinal wave propagation. Theoretical model has been established to investigate the dispersion relation and band gaps of the structure. The results show that the hybrid structure can produce multi-band gaps wider than the multi-resonator acoustic metamaterials. It is much easier for the hybrid structure to yield wide and low band gaps by adjusting the mass and stiffness of the external oscillator. Small series spring constant ratio results in low-frequency band gaps, in which the external oscillator acts as a resonator and replaces the original local resonator to hold the band gaps in low frequency range. Compared with the one-dimensional phononic crystal (PC) lattice, a new band gap emerges in lower frequency range in the hybrid structure because of the added local resonance, which will be a significant assistance in low-frequency vibration and noise reduction. Further, harmonic response analysis using finite element method (FEM) has been performed, and results show that elastic longitudinal waves are efficiently forbidden within the band gaps.
Yan, Zhi-zhong; Wei, Chun-qiu; Zheng, Hui; Zhang, Chuanzeng
2016-05-01
In this paper, a meshless radial basis function (RBF) collocation method is developed to calculate the phononic band structures taking account of different interface models. The present method is validated by using the analytical results in the case of perfect interfaces. The stability is fully discussed based on the types of RBFs, the shape parameters and the node numbers. And the advantages of the proposed RBF method compared to the finite element method (FEM) are also illustrated. In addition, the influences of the spring-interface model and the three-phase model on the wave band gaps are investigated by comparing with the perfect interfaces. For different interface models, the effects of various interface conditions, length ratios and density ratios on the band gap width are analyzed. The comparison results of the two models show that the weakly bonded interface has a significant effect on the properties of phononic crystals. Besides, the band structures of the spring-interface model have certain similarities and differences with those of the three-phase model.
Band structure engineering through orbital interaction for enhanced thermoelectric power factor
Band structure engineering for specific electronic or optical properties is essential for the further development of many important technologies including thermoelectrics, optoelectronics, and microelectronics. In this work, we report orbital interaction as a powerful tool to finetune the band structure and the transport properties of charge carriers in bulk crystalline semiconductors. The proposed mechanism of orbital interaction on band structure is demonstrated for IV-VI thermoelectric semiconductors. For IV-VI materials, we find that the convergence of multiple carrier pockets not only displays a strong correlation with the s-p and spin-orbit coupling but also coincides with the enhancement of power factor. Our results suggest a useful path to engineer the band structure and an enticing solid-solution design principle to enhance thermoelectric performance
Banded structure and its distribution in friction stir processing of 316L austenitic stainless steel
Highlights: ► Friction stir processing (FSP) as a repair method. ► Sigma phase formed in the FSP zone. ► Low heat input contributes to restrain sigma phase precipitation. - Abstract: Banded structures, which vary with welding parameters, were observed in friction stir processing of 316L austenite stainless steel. Sigma phase precipitation was detected in banded structures by transmission electron microscopy. The amount of banded structure had direct ratio relations with heat input. The higher the heat input, the larger the area of banded structures. This is attributable to slower cooling rate at high heat input, which results in longer exposure to the temperature range for precipitation. The formation of sigma phase produced Cr depletion, which resulted in largely degraded corrosion resistance. The present study suggests that low heat input (i.e. low rotation speeds, low working loads and high welding speed) contributes to restrain sigma phase precipitation.
The impurity optical absorption and structure of conduction band in 6H-SiC
The investigation of absorption spectra in n-type nitrogen doped 6H-SiC crystals from the near infrared up to fundamental band region at polarization of electric field (E) of the light wave relatively the optical axis (C) for E parallel to C and E perpendicular to C has been carried out. It is for the first time that at E parallel to C a slight absorption band with maximum at 2.85 eV has been investigated. All absorption bands observed were caused by photoionization of donors (nitrogen) with electron transition in to above-lying minima of the conduction band situated at different critical points of the Brillouin zone. The analysis of data obtained and experimental data available on the photoionization of nitrogen, alongside with theoretical data on the structure of the conduction band make it possible to propose the structure and symmetry of additional extrema in Brillouin zone for 6H-SiC
Simple inverted band structure model for cadmium arsenide (Cd3As2)
The development of a simple Hamiltonian yielding the inverted band structure of Cd3As2 in the 4 mm (C4v12) low-temperature phase is proposed. The presented theory takes into account the spin orbit interaction and tetragonal distortion of lattice in the low symmetry. The authors obtain k-linear terms in the band structure and therefore a splitting in k-space of spin degenerate energy bands. The reported band model contains only one new crystal field parameter d = cr|Z> in addition to well known Kildal's set. The first evaluation of this shows that (0.028 < d < 0.072) eV using optical absorption edge data. The finite width of the anisotropic heavy and light hole bands is pointed out. (authors)
Efficient VLSI Architecture For CSD Basedsub-Band Tree Structure Using 4-Tap Filter
Radhe Kant Mishra,; Dr. Subbaratnam Kumar
2014-01-01
A sub-band tree structure hardware design based on canonic signed digit (CSD) architecture is presented in this paper. We have proposed based on canonic signed digit (CSD) arithmetic for low complexity and efficient implementation of sub-band tree structure. The canonic signed digit (CSD) technique has been applied to reduce the number of full adders required by 2’s complement based deigns. This architecture is suitable for high speed on-line applications. With this architectu...
Dual-Band Terahertz Left-Handed Metamaterial with Fishnet Structure
We present the design of a dual-band left-handed metamaterial with fishnet structure in the terahertz regime. Its left-handed properties are described by the retrieved effective electromagnetic parameters. We introduce an equivalent circuit which offers a theoretical explanation for the left-handed behavior of the dual-band fishnet metamaterial, and investigate its losses receiving higher figure of merit. The design is beneficial to the development of frequency agile and broadband THz materials and devices. The dual-band fishnet metamaterial can be extended to infrared and optical frequency ranges by regulating the structural parameters. (fundamental areas of phenomenology (including applications))
Hao Liu; Ziqiang Xu
2013-01-01
A modified electromagnetic-bandgap (M-EBG) structure and its application to planar monopole ultra-wideband (UWB) antenna are presented. The proposed M-EBG which comprises two strip patch and an edge-located via can perform dual notched bands. By properly designing and placing strip patch near the feedline, the proposed M-EBG not only possesses a simple structure and compact size but also exhibits good band rejection. Moreover, it is easy to tune the dual notched bands by altering the dimensio...
Realization of Band-Notch UWB Monopole Antenna Using AMC Structure
Pradeep Kumar
2013-06-01
Full Text Available This article presents the design, simulation and testing of an Ultra Wide Band (UWB planar monopole antenna with WLAN band-notch characteristic. The proposed antenna consists, the combination of planar monopole antenna with partial ground and a pair of AMC structures. The AMC structure used for the design is mushroom-like. Design equation of EBG parameters is also proposed for FR4 substrate using transmission line model. Using proposed equations, Mushroom-like EBG structure is integrated along the feed line of a monopole antenna for WLAN (5 GHz – 6 GHz band rejection. TheCurrent distribution and equivalent circuit model of antenna is used to explain band-notch characteristic of EBG resonator. The proposed antenna is fabricated on an FR4 substrate with a thickness of 1.6 mmand εr = 4.4. The measured VSWR characteristic is less than 2 for complete UWB band except for WLAN band i.e. 5 GHz – 6 GHz. The gain of the proposed structure is around 2 dBi – 6.7 dBi for complete UWBband except for WLAN band where it is reduced to -4 dBi. The measured radiation pattern of proposed antenna is omnidirectional along H plane and bidirectional in E plane. A nearly constant group delaywith variations < 2ns, except for the notched bandwidth makes proposed antenna suitable for UWB application.
Band structure of hydrogenated silicene on Ag(111): Evidence for half-silicane
Wang, W.; Olovsson, W.; Uhrberg, R. I. G.
2016-02-01
In the case of graphene, hydrogenation removes the conductivity due to the bands forming the Dirac cone by opening up a band gap. This type of chemical functionalization is of the utmost importance for electronic applications. As predicted by theoretical studies, a similar change in the band structure is expected for silicene, the closest analog to graphene. We here report a study of the atomic and electronic structures of hydrogenated silicene with hydrogen on one side, the so-called half-silicane. The ("2 √{3 }×2 √{3 } ") phase of silicene on Ag(111) was used in this Rapid Communication since it can be formed homogeneously across the entire surface of the Ag substrate. Low-energy electron diffraction and scanning tunneling microscopy data clearly show that hydrogenation changes the structure of silicene on Ag(111) resulting in a (1 × 1) periodicity with respect to the silicene lattice. The hydrogenated silicene also exhibits a quasiregular (2 √{3 }×2 √{3 } )-like arrangement of vacancies. Angle-resolved photoelectron spectroscopy revealed two dispersive bands which can be unambiguously assigned to half-silicane. The common top of these bands is located at ˜0.9 eV below the Fermi level. We find that the experimental bands are closely reproduced by the theoretical band structure of free-standing silicene with H adsorbed on the upper hexagonal sublattice.
On the structure of collective bands in 78Kr
Using 16O, 19F, and 12C induced reactions high spin states in 78Kr were excited. The targets consisted of 65Cu, 69Ni, and 68Zn. On the base of gamma spectroscopic methods as γγ-coincidences, angular distributions and excitation functions a level scheme of 78Kr is proposed. Four bands could be identified, which decay mostly by stretched E2-transitions. From recoil distance Doppler shift as well as Doppler shift attenuation measurements lifetimes of about 20 states were measured. The β-decay of the 103 keV isomeric state and the ground state in 78Rb was observed and the half-lifes determined. Altogether a very good agreement of the level scheme and the E2- and E1-transition strength with predictions of the interacting boson model were found. Using a Monte Carlo code the γ-decay of the continuum of highly excited nuclei is described. Entry states, mean γ-energies, γ-spectra, mean multiplicities, multipolarities, and mean feeding times as well as e.g. their second moments were calculated for the reactions 58Ni(16O,2p)72Se and 68Zn(12C,2n)78Kr. The results are discussed and compared with experimental data. (HSI)
Łoś, H.; Osińska-Skotak, K.; Pluto-Kossakowska, J.; Bernier, M.; Gauthier, Y.; Jasek, M.; Roth, A.
2016-06-01
In this study, synthetic aperture radar (SAR) data from TerraSAR-X were compared with RADARSAT-2 data to evaluate their effectiveness for river ice monitoring on the Peace River. For several years RADARSAT-2 data have been successfully used for river ice observation. However, it is important to take into account data from other satellites as they may provide solutions when it is not possible to obtain images from the preferred system (e.g., in the case of acquisition priority conflicts). In this study we compared three TerraSAR-X (X-band) and three RADARSAT-2 (C-band) datasets acquired in December 2013 on a section of the Peace River, Canada. For selected classes (open water, skim ice, juxtaposed skim ice, agglomerated skim ice, frazil run and consolidated ice) we compared backscattering values in HH and VV polarisation and performed Wishart supervised classification. Covariance matrices that were previously filtered using a refined Lee filter were used as input data for classification. For all data sets the overall accuracy was higher than 80%. Similar errors associated with classification output were observed for data from both satellite systems.
Photonic band gap of superconductor-medium structure: Two-dimensional triangular lattice
Liu, Wan-guo; Pan, Feng-ming, E-mail: fmpan@nuaa.edu.cn; Cai, Li-wei
2014-05-15
Highlights: • Plane wave expansion is generalized to superconductor-medium periodic structure. • A wider band gap appears than that in conventional photonic crystals. • Part of original energy levels are rearranged upon consideration of the superconductivity. • Band gap width decreases monotonically with penetration length, but not with the filling factor. • Band gaps can be partially shut down or opened by adjusting filling factor. - Abstract: Based on London theory a general form of wave equation is formulated for both dielectric medium and superconductor. Using the wave equation and applying plane wave expansion, we have numerically calculated the band structures and density of states of a photonic crystal, whose intersection is constructed by a two-dimensional triangular lattice of superconductor padding in dielectric medium. Results indicate a wider band gap in the superconductor-medium photonic crystal than that in conventional photonic crystals. And part of original energy levels are found to be rearranged upon consideration of the superconductivity. The dependence of band gap on penetration length and filling factor is also discussed. Band gap width decreases monotonically with the penetration length, but not with the filling factor. Band gaps can be partially shut down or opened by adjusting filling factor.
Rotational band structures in N=89 153Gd
The reactions 152Sm(α,3n) at 37 MeV and 124Sn(36S,α3n) at 165 MeV were used to produce high-spin states in the transitional rare-earth nucleus 153Gd. Significant extensions in angular momentum and excitation energy with respect to earlier work were achieved and several new rotational sequences were observed. The rotational behavior of 153Gd is described in terms of quasiparticle assignments and the observed alignment properties are analyzed within the framework of the cranked shell model. Detailed comparisons with other N=89 nuclei are presented. These have led to corrections to the 157Er level scheme
Precise fabrication of X-band accelerating structure
An accelerating structure with a/λ=0.16 is being fabricated to study a precise fabrication method. A frequency control of each cell better than 10-4 level is required to realize a detuned structure. The present machining level is nearly 1 MHz/11.4 GHz in relative frequency error, which just satisfies the above requirement. To keep this machining precision, the diffusion bonding technique is found preferable to join the cells. Various diffusion conditions were tried. The frequency change can be less than 1 MHz/11.4 GHz and it can be controlled well better than that. (author)
Shank, Joshua C.; Tellekamp, M. Brooks; Doolittle, W. Alan, E-mail: alan.doolittle@ece.gatech.edu [Department of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)
2015-01-21
The theoretically suggested band structure of the novel p-type semiconductor lithium niobite (LiNbO{sub 2}), the direct coupling of photons to ion motion, and optically induced band structure modifications are investigated by temperature dependent photoluminescence. LiNbO{sub 2} has previously been used as a memristor material but is shown here to be useful as a sensor owing to the electrical, optical, and chemical ease of lithium removal and insertion. Despite the high concentration of vacancies present in lithium niobite due to the intentional removal of lithium atoms, strong photoluminescence spectra are observed even at room temperature that experimentally confirm the suggested band structure implying transitions from a flat conduction band to a degenerate valence band. Removal of small amounts of lithium significantly modifies the photoluminescence spectra including additional larger than stoichiometric-band gap features. Sufficient removal of lithium results in the elimination of the photoluminescence response supporting the predicted transition from a direct to indirect band gap semiconductor. In addition, non-thermal coupling between the incident laser and lithium ions is observed and results in modulation of the electrical impedance.
Valence band structure of the Si(331)-(12 x 1) surface reconstruction
Battaglia, Corsin [Ecole Polytechnique Federale de Lausanne (EPFL), Institute of Microengineering (IMT), Photovoltaics and Thin Film Electronics Laboratory, Rue A-L Breguet 2, 2000 Neuchatel (Switzerland); Fabian Schwier, Eike; Monney, Claude; Didiot, Clement; Mariotti, Nicolas; Gunnar Garnier, Michael; Aebi, Philipp [Department of Physics and Fribourg Center for Nanomaterials, Universite de Fribourg, Chemin du Musee 3, 1700 Fribourg (Switzerland); Gaal-Nagy, Katalin; Onida, Giovanni, E-mail: corsin.battaglia@epfl.ch [Dipartimento di Fisica and European Theoretical Spectroscopy Facility (ETSF), Universita degli Studi di Milano, Via Celoria 16, 20133 Milano (Italy)
2011-04-06
Using angle-resolved photoelectron spectroscopy we investigate the electronic valence band structure of the Si(331)-(12 x 1) surface reconstruction for which we recently proposed a structural model containing silicon pentamers as elementary structural building blocks. We find that this surface, reported to be metallic in a previous study, shows a clear band gap at the Fermi energy, indicating semiconducting behavior. An occupied surface state, presumably containing several spectral components, is found centered at - 0.6 eV exhibiting a flat energy dispersion. These results are confirmed by scanning tunneling spectroscopy and are consistent with recent first-principles calculations for our structural model.
Valence band structure of the Si(331)-(12 x 1) surface reconstruction
Using angle-resolved photoelectron spectroscopy we investigate the electronic valence band structure of the Si(331)-(12 x 1) surface reconstruction for which we recently proposed a structural model containing silicon pentamers as elementary structural building blocks. We find that this surface, reported to be metallic in a previous study, shows a clear band gap at the Fermi energy, indicating semiconducting behavior. An occupied surface state, presumably containing several spectral components, is found centered at - 0.6 eV exhibiting a flat energy dispersion. These results are confirmed by scanning tunneling spectroscopy and are consistent with recent first-principles calculations for our structural model.
Reducing support loss in micromechanical ring resonators using phononic band-gap structures
Hsu, Feng-Chia; Huang, Tsun-Che; Wang, Chin-Hung; Chang, Pin [Industrial Technology Research Institute-South, Tainan 709, Taiwan (China); Hsu, Jin-Chen, E-mail: fengchiahsu@itri.org.t, E-mail: hsujc@yuntech.edu.t [Department of Mechanical Engineering, National Yunlin University of Science and Technology, Douliou, Yunlin 64002, Taiwan (China)
2011-09-21
In micromechanical resonators, energy loss via supports into the substrates may lead to a low quality factor. To eliminate the support loss, in this paper a phononic band-gap structure is employed. We demonstrate a design of phononic-crystal (PC) strips used to support extensional wine-glass mode ring resonators to increase the quality factor. The PC strips are introduced to stop elastic-wave propagation by the band-gap and deaf-band effects. Analyses of resonant characteristics of the ring resonators and the dispersion relations, eigenmodes, and transmission properties of the PC strips are presented. With the proposed resonator architecture, the finite-element simulations show that the leaky power is effectively reduced and the stored energy inside the resonators is enhanced simultaneously as the operating frequencies of the resonators are within the band gap or deaf bands. Realization of a high quality factor micromechanical ring resonator with minimized support loss is expected.
Electronic Band Structures of TiO2 with Heavy Nitrogen Doping
XUE Jinbo; LI Qi; LIANG Wei; SHANG Jianku
2008-01-01
The first-principles density-functional calculation was conducted to investigate the electronic band structures of titanium dioxide with heavy nitrogen doping (TiO2-xNx).The calculation results indicate that when x≤0.25,isolated N 2p states appear above the valence-band maximum of TiO2 without a band-gap narrowing between O 2p and Ti 3d states.When x≥0.50,an obvious band gap narrowing between O 2p and Ti 3d states was observed along with the existence of isolated N 2p states above the valence-band of TiO2,indicating that the mechanism proposed by Asahi et al operates under heavy nitrogen doping condition.
Superlattice band structure: New and simple energy quantification condition
Assuming an approximated effective mass and using Bastard's boundary conditions, a simple method is used to calculate the subband structure for periodic semiconducting heterostructures. Our method consists to derive and solve the energy quantification condition (EQC), this is a simple real equation, composed of trigonometric and hyperbolic functions, and does not need any programming effort or sophistic machine to solve it. For less than ten wells heterostructures, we have derived and simplified the energy quantification conditions. The subband is build point by point; each point presents an energy level. Our simple energy quantification condition is used to calculate the subband structure of the GaAs/Ga0.5Al0.5As heterostructures, and build its subband point by point for 4 and 20 wells. Our finding shows a good agreement with previously published results
Superlattice band structure: New and simple energy quantification condition
Maiz, F.
2014-10-01
Assuming an approximated effective mass and using Bastard's boundary conditions, a simple method is used to calculate the subband structure for periodic semiconducting heterostructures. Our method consists to derive and solve the energy quantification condition (EQC), this is a simple real equation, composed of trigonometric and hyperbolic functions, and does not need any programming effort or sophistic machine to solve it. For less than ten wells heterostructures, we have derived and simplified the energy quantification conditions. The subband is build point by point; each point presents an energy level. Our simple energy quantification condition is used to calculate the subband structure of the GaAs/Ga0.5Al0.5As heterostructures, and build its subband point by point for 4 and 20 wells. Our finding shows a good agreement with previously published results.
Superlattice band structure: New and simple energy quantification condition
Maiz, F., E-mail: fethimaiz@gmail.com [University of Cartage, Nabeul Engineering Preparatory Institute, Merazka, 8000 Nabeul (Tunisia); King Khalid University, Faculty of Science, Physics Department, P.O. Box 9004, Abha 61413 (Saudi Arabia)
2014-10-01
Assuming an approximated effective mass and using Bastard's boundary conditions, a simple method is used to calculate the subband structure for periodic semiconducting heterostructures. Our method consists to derive and solve the energy quantification condition (EQC), this is a simple real equation, composed of trigonometric and hyperbolic functions, and does not need any programming effort or sophistic machine to solve it. For less than ten wells heterostructures, we have derived and simplified the energy quantification conditions. The subband is build point by point; each point presents an energy level. Our simple energy quantification condition is used to calculate the subband structure of the GaAs/Ga{sub 0.5}Al{sub 0.5}As heterostructures, and build its subband point by point for 4 and 20 wells. Our finding shows a good agreement with previously published results.
New enumeration algorithm for protein structure comparison and classification
2013-01-01
Background Protein structure comparison and classification is an effective method for exploring protein structure-function relations. This problem is computationally challenging. Many different computational approaches for protein structure comparison apply the secondary structure elements (SSEs) representation of protein structures. Results We study the complexity of the protein structure comparison problem based on a mixed-graph model with respect to different computational frameworks. We d...
F. Phillips
2004-04-01
Full Text Available Rotational temperatures derived from the OH(8–3 band may vary by ~18K depending on the choice of transition probabilities. This is of concern when absolute temperatures or trends determined in combination with measurements of other hydroxyl bands are important. In this paper, measurements of the OH(8–3 temperature-insensitive Q/P and R/P line intensity ratios are used to select the most appropriate transition probabilities for use with this band. Aurora, airglow and solar and telluric absorption in the OH(8–3 band are also investigated. Water vapour absorption of P_{1}(4, airglow or auroral contamination of P_{1}(2 and solar absorption in the vicinity of P_{1}(5 are concerns to be considered when deriving rotational temperatures from this band.
A comparison is made of temperatures derived from OH(6–2 and OH(8–3 spectra collected alternately at Davis (69° S, 78° E in 1990. An average difference of ~4K is found, with OH(8–3 temperatures being warmer, but a difference of this magnitude is within the two sigma uncertainty limit of the measurements.
Key words. Atmospheric composition and structure airglow and aurora; pressure, density, and temperature
Structure of positive parity bands in odd-odd 108Ag
Nuclei in the transitional A ∼ 110 region near the Z = 50 shell closure are known to exhibit a variety of phenomena like magnetic rotation, anti-magnetic rotation, chiral rotation and collective behavior as well. The present work provides significant new information on the spectroscopic levels of the positive parity bands in 108Ag nucleus. The comparison of the experimental data of high spin states of a ΔI = 1 band with Tilted Axis Cranking (TAC) model calculations suggests its origin is due to magnetic rotation
Structure sensitive bands in the vibrational spectra of metal complexes of tetraphenylporphine
Oshio, Hiroki; Ama, Tomoharu; Watanabe, Takeshi; Kincaid, James; Nakamoto, Kazuo
The i.r. and RR spectra of twenty Fe(TPP)LL' type complexes have been measured to locate structure-sensitive bands. In i.r. spectra, band I (1350-1330 cm -1) and band III (469-432 cm -1) are spin-state sensitive whereas band II (806-790 cm -1) is oxidation-state sensitive and slightly spin-state sensitive in the Fe(II) state. To examine the nature of these bands, the i.r. spectra of Co(TPP), (Fe(TPP)) 2O and their d8 and d20 analogs have been measured, and empirical assignments proposed. In RR spectra, band C (1545-1498 cm -1, ap) and band D (1565-1540 cm -1, p) are spin-state sensitive whereas band E (391-376 cm -1, p) is sensitive to both spin and oxidation states. These results on RR spectra are in good agreement with those of previous workers.
Electronic structure and band alignment at an epitaxial spinel/perovskite heterojunction.
Qiao, Liang; Li, Wei; Xiao, Haiyan; Meyer, Harry M; Liang, Xuelei; Nguyen, N V; Weber, William J; Biegalski, Michael D
2014-08-27
The electronic properties of solid-solid interfaces play critical roles in a variety of technological applications. Recent advances of film epitaxy and characterization techniques have demonstrated a wealth of exotic phenomena at interfaces of oxide materials, which are critically dependent on the alignment of their energy bands across the interface. Here we report a combined photoemission and electrical investigation of the electronic structures across a prototypical spinel/perovskite heterojunction. Energy-level band alignment at an epitaxial Co3O4/SrTiO3(001) heterointerface indicates a chemically abrupt, type I heterojunction without detectable band bending at both the film and substrate. The unexpected band alignment for this typical p-type semiconductor on SrTiO3 is attributed to its intrinsic d-d interband excitation, which significantly narrows the fundamental band gap between the top of the valence band and the bottom of the conduction band. The formation of the type I heterojunction with a flat-band state results in a simultaneous confinement of both electrons and holes inside the Co3O4 layer, thus rendering the epitaxial Co3O4/SrTiO3(001) heterostructure to be a very promising material for high-efficiency luminescence and optoelectronic device applications. PMID:25075939
Strain effects on band structure of wurtzite ZnO: a GGA + U study
Band structures in wurtzite bulk ZnO/Zn1−xMgxO are calculated using first-principles based on the framework of generalized gradient approximation to density functional theory with the introduction of the on-site Coulomb interaction. Strain effects on band gap, splitting energies of valence bands, electron and hole effective masses in strained bulk ZnO are discussed. According to the results, the band gap increases gradually with increasing stress in strained ZnO as an Mg content of Zn1−xMgxO substrate less than 0.3, which is consistent with the experimental results. It is further demonstrated that electron mass of conduction band (CB) under stress increases slightly. There are almost no changes in effective masses of light hole band (LHB) and heavy hole band (HHB) along [00k] and [k00] directions under stress, and stress leads to an obvious decrease in effective masses of crystal splitting band (CSB) along the same directions. (semiconductor materials)
Relationships between magnetic foot points and G-band bright structures
Ishikawa, R; Kitakoshi, Y; Katsukawa, Y; Bonet, J A; Domínguez, S Vargas; van der Voort, L H M Rouppe; Sakamoto, Y; Ebisuzaki, T
2008-01-01
Magnetic elements are thought to be described by flux tube models, and are well reproduced by MHD simulations. However, these simulations are only partially constrained by observations. We observationally investigate the relationship between G-band bright points and magnetic structures to clarify conditions, which make magnetic structures bright in G-band. The G-band filtergrams together with magnetograms and dopplergrams were taken for a plage region covered by abnormal granules as well as ubiquitous G-band bright points, using the Swedish 1-m Solar Telescope (SST) under very good seeing conditions. High magnetic flux density regions are not necessarily associated with G-band bright points. We refer to the observed extended areas with high magnetic flux density as magnetic islands to separate them from magnetic elements. We discover that G-band bright points tend to be located near the boundary of such magnetic islands. The concentration of G-band bright points decreases with inward distance from the boundar...
Tunable band structures of polycrystalline graphene by external and mismatch strains
Jiang-Tao Wu; Xing-Hua Shi; Yu-Jie Wei
2012-01-01
Lacking a band gap largely limits the application of graphene in electronic devices.Previous study shows that grain boundaries (GBs) in polycrystalline graphene can dramatically alter the electrical properties of graphene.Here,we investigate the band structure of polycrystalline graphene tuned by externally imposed strains and intrinsic mismatch strains at the GB by density functional theory (DFT) calculations.We found that graphene with symmetrical GBs typically has zero band gap even with large uniaxial and biaxial strain.However,some particular asymmetrical GBs can open a band gap in graphene and their band structures can be substantially tuned by external strains.A maximum band gap about 0.19 eV was observed in matched-armchair GB (5,5) | (3,7) with a misorientation of θ =13° when the applied uniaxial strain increases to 9％.Although mismatch strain is inevitable in asymmetrical GBs,it has a small influence on the band gap of polycrystalline graphene.
Liu, Hao; Xu, Ziqiang
2013-01-01
A modified electromagnetic-bandgap (M-EBG) structure and its application to planar monopole ultra-wideband (UWB) antenna are presented. The proposed M-EBG which comprises two strip patch and an edge-located via can perform dual notched bands. By properly designing and placing strip patch near the feedline, the proposed M-EBG not only possesses a simple structure and compact size but also exhibits good band rejection. Moreover, it is easy to tune the dual notched bands by altering the dimensions of the M-EBG. A demonstration antenna with dual band-notched characteristics is designed and fabricated to validate the proposed method. The results show that the proposed antenna can satisfy the requirements of VSWR WiMAX) and the wireless local area network (WLAN) at 3.5 GHz and 5.5 GHz, respectively. PMID:24170984
Gorczyca,, I.; Łepkowski, S. P.; Suski, T.;
2009-01-01
atomic arrangements are examined. Particular attention is paid to the magnitude of and trends in bowing of the band gaps. Indium composition fluctuation (clustering) is simulated by different distributions of In atoms and it is shown that it strongly influences the band gaps. The gaps are considerably......The electronic band structures of InxGa1-xN, InxAl1-xN, and InxGayAl1-x-yN alloys are calculated by ab initio methods using a supercell geometry, and the effects of varying the composition and atomic arrangements methods using a supercell geometry, and the effects of varying the composition and...
Band structure properties of (BGa)P semiconductors for lattice matched integration on (001) silicon
Hossain, Nadir; Sweeney, Stephen [Advanced Technology Institute and Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); Hosea, Jeff [Advanced Technology Institute and Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH, UK and Ibnu Sina Institute for Fundamental Science Studies, Universiti Teknologi Malaysia, Johor Bahru 81310 (Malaysia); Liebich, Sven; Zimprich, Martin; Volz, Kerstin; Stolz, Wolfgang [Material Sciences Center and Faculty of Physics, Philipps-University, 35032 Marburg (Germany); Kunert, Bernerdette [NAsP III/V GmbH, Am Knechtacker 19, 35041 Marburg (Germany)
2013-12-04
We report the band structure properties of (BGa)P layers grown on silicon substrate using metal-organic vapour-phase epitaxy. Using surface photo-voltage spectroscopy we find that both the direct and indirect band gaps of (BGa)P alloys (strained and unstrained) decrease with Boron content. Our experimental results suggest that the band gap of (BGa)P layers up to 6% Boron is large and suitable to be used as cladding and contact layers in GaP-based quantum well heterostructures on silicon substrates.
Study of periodic band gap structure of the magnetized plasma photonic crystals
ZHANG Hai-feng; MA Li; LIU Shao-bin
2009-01-01
The characteristics of the periodic band gaps of the one dimension magnetized plasma photonic crystals are studied with the piecewise linear current density recursive convolution (PLCDRC) finite-differential time-domain (FDTD) method. In fre-quency-domain, the transmission coefficients of electromagnetic Gaussian pulses are computed, and the effects of the periodic structure constant, plasma layer thickness and parameters of plasma on the properties of periodic band gaps of magnetized photonic crystals are analyzed. The results show that the periodic band gaps depend strongly on the plasma parameters.
Photonic band structures of two-dimensional photonic crystals with deformed lattices
Cai Xiang-Hua; Zheng Wan-Hua; Ma Xiao-Tao; Ren Gang; Xia Jian-Bai
2005-01-01
Using the plane-wave expansion method, we have calculated and analysed the changes of photonic band structures arising from two kinds of deformed lattices, including the stretching and shrinking of lattices. The square lattice with square air holes and the triangular lattice with circular air holes are both studied. Calculated results show that the change of lattice size in some special ranges can enlarge the band gap, which depends strongly on the filling factor of air holes in photonic crystals; and besides, the asymmetric band edges will appear with the broken symmetry of lattices.
Chegel, Raad
2016-06-01
By using the third nearest neighbor modified tight binding (3NN-TB) method, the electronic structure and band gap of BNNRs under transverse electric fields are explored. The band gap of the BNNRs has a decreasing with increasing the intensity of the applied electric field, independent on the ribbon edge types. Furthermore, an analytic model for the dependence of the band gap in armchair and zigzag BNNRs on the electric field is proposed. The reduction of E g is similar for some N a armchair and N z zigzag BNNRs independent of their edges.
Tight-binding modelling of the electronic band structure of layered superconducting perovskites
Mishonov, T.; Penev, E.
2000-01-01
A detailed tight-binding analysis of the electron band structure of the CuO_2 plane of layered cuprates is performed within a sigma-band Hamiltonian including four orbitals - Cu3d_x^2-y^2, Cu4s, O2p_x, and O2p_y. Both the experimental and theoretical hints in favor of Fermi level located in a Cu or O band, respectively, are considered. For these two alternatives analytical expressions are obtained for the LCAO electron wave functions suitable for the treatment of electron superexchange. Simpl...
Promoting Photochemical Water Oxidation with Metallic Band Structures.
Liu, Hongfei; Moré, René; Grundmann, Henrik; Cui, Chunhua; Erni, Rolf; Patzke, Greta R
2016-02-10
The development of economic water oxidation catalysts is a key step toward large-scale water splitting. However, their current exploration remains empirical to a large extent. Elucidating the correlations between electronic properties and catalytic activity is crucial for deriving general and straightforward catalyst design principles. Herein, strongly correlated electronic systems with abundant and easily tunable electronic properties, namely La(1-x)Sr(x)BO3 perovskites and La(2-x)Sr(x)BO4 layered perovskites (B = Fe, Co, Ni, or Mn), were employed as model systems to identify favorable electronic structures for water oxidation. We established a direct correlation between the enhancement of catalytic activity and the insulator to metal transition through tuning the electronic properties of the target perovskite families via the La(3+)/Sr(2+) ratio. Their improved photochemical water oxidation performance was clearly linked to the increasingly metallic character. These electronic structure-activity relations provide a promising guideline for constructing efficient water oxidation catalysts. PMID:26771537
Esparza López, Nuria; Alcón García, Pablo; Herrán Ontañón, Luis Fernando; Las Heras Andrés, Fernando Luis
2016-01-01
A novel Substrate Integrated Waveguide (SIW) is proposed using Frequency Selective Surfaces (FSS) operating in Stop- Band (SBFSS-SIW) as metal conductor plates. These structures preserve the propagation properties and the dimensions of the conventional SIW, and have periodic isolated pads that could allow the direct integration of biased active and passive devices on the SIW surface. A set of SBFSS-SIW for X-band have been designed, simulated and experimentally measured to demonstrat...
Band structure analysis of (1 × 2)-H/Pd(110)-pr
Shuttleworth, I. G.
2013-09-01
A novel method of band structure analysis based on the atomic orbital (AO) coefficients in LCAO-DFT has been applied to the (1 × 2)-H/Pd(110)-pr system. The analysis has revealed symmetry-dependent Pd 4d band splitting due to H ligand effects; ensemble effects due to the (1 × 2) Pd reconstruction are shown to be relatively minor.
Berne, A.D.; Delrieu, G.; Andrieu, H.
2005-01-01
The present study aims at a preliminary approach of multiradar compositing applied to the estimation of the vertical structure of precipitation¿an important issue for radar rainfall measurement and prediction. During the HYDROMET Integrated Radar Experiment (HIRE¿98), the vertical profile of reflectivity was measured, on the one hand, with an X-band vertically pointing radar system, and, on the other hand, with an X-band RHI scanning protocol radar. The analysis of the raw data highlights the...
We have performed a numerical solution for band structure of an Abrikosov vortex lattice in type-II superconductors forming a periodic array in two dimensions for applications of incorporating the photonic crystals concept into superconducting materials with possibilities for optical electronics. The implemented numerical method is based on the extensive numerical solution of the Ginzburg-Landau equation for calculating the parameters of the two-fluid model and obtaining the band structure from the permittivity, which depends on the above parameters and the frequency. This is while the characteristics of such crystals highly vary with an externally applied static normal magnetic field, leading to nonlinear behavior of the band structure, which also has nonlinear dependence on the temperature. The similar analysis for every arbitrary lattice structure is also possible to be developed by this approach as presented in this work. We also present some examples and discuss the results
Modeling the band structure of the higher manganese silicides starting from Mn$_4$Si$_7$
V., Vijay Shankar; Tseng, Yu-Chih; Kee, Hae-Young
2016-01-01
The higher manganese silicides (HMS), with the chemical formula MnSi$_x$($x \\approx 1.73 - 1.75$), have been attracted a lot of attention due to their potential application as thermoelectric materials. While the electronic band structures of HMS have been previously studied using first principle calculations, the relation between crystal structures of Mn and Si atoms and their band structures is not well understood. Here we study Mn$_4$Si$_7$ using first principle calculations and show that a...
Research on the large band gaps in multilayer radial phononic crystal structure
Gao, Nansha; Wu, Jiu Hui; Guan, Dong
2016-04-01
In this paper, we study the band gaps (BGs) of new proposed radial phononic crystal (RPC) structure composed of multilayer sections. The band structure, transmission spectra and eigenmode displacement fields of the multilayer RPC are calculated by using finite element method (FEM). Due to the vibration coupling effects between thin circular plate and intermediate mass, the RPC structure can exhibit large BGs, which can be effectively shifted by changing the different geometry values. This study shows that multilayer RPC can unfold larger and lower BGs than traditional phononic crystals (PCs) and RPC can be composed of single material.
Polarization-dependent diffraction in all-dielectric, twisted-band structures
Kardaś, Tomasz M.; Jagodnicka, Anna; Wasylczyk, Piotr, E-mail: pwasylcz@fuw.edu.pl [Photonic Nanostructure Facility, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warszawa (Poland)
2015-11-23
We propose a concept for light polarization management: polarization-dependent diffraction in all-dielectric microstructures. Numerical simulations of light propagation show that with an appropriately configured array of twisted bands, such structures may exhibit zero birefringence and at the same time diffract two circular polarizations with different efficiencies. Non-birefringent structures as thin as 3 μm have a significant difference in diffraction efficiency for left- and right-hand circular polarizations. We identify the structural parameters of such twisted-band matrices for optimum performance as circular polarizers.
Polarization-dependent diffraction in all-dielectric, twisted-band structures
Kardaś, Tomasz M.; Jagodnicka, Anna; Wasylczyk, Piotr
2015-11-01
We propose a concept for light polarization management: polarization-dependent diffraction in all-dielectric microstructures. Numerical simulations of light propagation show that with an appropriately configured array of twisted bands, such structures may exhibit zero birefringence and at the same time diffract two circular polarizations with different efficiencies. Non-birefringent structures as thin as 3 μm have a significant difference in diffraction efficiency for left- and right-hand circular polarizations. We identify the structural parameters of such twisted-band matrices for optimum performance as circular polarizers.
Analysis of photonic band-gap (PBG) structures using the FDTD method
Tong, M.S.; Cheng, M.; Lu, Y.L.;
2004-01-01
In this paper, a number of photonic band-gap (PBG) structures, which are formed by periodic circuit elements printed oil transmission-line circuits, are studied by using a well-known numerical method, the finite-difference time-domain (FDTD) method. The results validate the band-stop filter...... behavior of these structures, and the computed results generally match well with ones published in the literature. It is also found that the FDTD method is a robust, versatile, and powerful numerical technique to perform such numerical studies. The proposed PBG filter structures may be applied in microwave...
Photonic stop bands in quasi-random nanoporous anodic alumina structures
Maksymov, Ivan; Pallares, Josep; Marsal, Lluis F
2011-01-01
The existence of photonic stop bands in the self-assembled arrangement of pores in porous anodic alumina structures is investigated by means of rigorous 2D finite- difference time-domain calculations. Self-assembled porous anodic alumina shows a random distribution of domains, each of them with a very definite triangular pattern, constituting a quasi-random structure. The observed stop bands are similar to those of photonic quasicrystals or random structures. As the pores of nanoporous anodic alumina can be infiltrated with noble metals, nonlinear or active media, it makes this material very attractive and cost-effective for applications including inhibition of spontaneous emission, random lasing, LEDs and biosensors.
Frontera, T.; Deschamps, A.; Ugalde, A.; Jara, J. A.; Hello, Y.; Goula, X.; Olivera, C.
2009-04-01
deployment of an opto-electrical cable to provide power and data transmission from the coast to a recording point at 2550 m in depth and 15km south to Porquerolles Island in the frame of the Antares neutrino telescope project. The program was founded in the 2002-2006 CPER (State-Region Research plan) by PACA region and CNRS/INSU and in the Antares collaboration which is responsible of all the marine operations on the site. The OBS and the DPG were set up by the ROV "Victor" from Ifremer (French Research Institute for Exploitation of the Sea) and partially buried; levelling and orientation were performed directly on the site. The instrument was running from April 2005 to April 2007. In April 2006 the sensor was completely buried. Data transmitted in quasi real time to Geoazur were integrated to the regional data center. In April 2007 the sensor was retrieved and reinstalled with data transmission protocol modification in October 2008. A water leak detected in December forced to cut the alimentation in January 2009. Because both sensors have not operated over the same time period, two different periods have been analysed: 2006 for the Antares OBS and 2008 for the Casablanca's one. In this way we are able to make a comparison of the noise behaviour by observing also the seasonal evolution. As observed on most of the ocean floor observatories, the noise is quite large on all components for both OBS. In general, the Antares OBS shows a better behaviour than the Casablanca OBS, due to the more favourable site conditions. Both OBS have been reinstalled to ameliorate some site condition deficiencies, which has basically affected the low frequency band, between 0.008 and 0.07 Hz. After the reinstallations, the noise conditions have improved at least 10 dB. A comparison of the power spectral density (PSD) curves for both stations concerning the periods after the reinstallations of the OBS show that, at low frequencies, the vertical component PSD curve for the Casablanca OBS is about
Band structure of the quasi two-dimensional purple molybdenum bronze
Guyot, H.; Balaska, H.; Perrier, P.; Marcus, J.
2006-09-01
The molybdenum purple bronze KMo 6O 17 is quasi two-dimensional (2D) metallic oxide that shows a Peierls transition towards a metallic charge density wave state. Since this specific transition is directly related to the electron properties of the normal state, we have investigated the electronic structure of this bronze at room temperature. The shape of the Mo K1s absorption edge reveals the presence of distorted MoO 6 octahedra in the crystallographic structure. Photoemission experiments evidence a large conduction band, with a bandwidth of 800 meV and confirm the metallic character of this bronze. A wide depleted zone separates the conduction band from the valence band that exhibits a fourfold structure, directly connected to the octahedral symmetry of the Mo sites. The band structure is determined by ARUPS in two main directions of the (0 0 1) Brillouin zone. It exhibits some unpredicted features but corroborates the earlier theoretical band structure and Fermi surface. It confirms the hidden one-dimensionality of KMo 6O 17 that has been proposed to explain the origin of the Peierls transition in this 2D compound.
Bulk and surface band structure of the new family of semiconductors BiTeX (X=I, Br, Cl)
Moreschini, L., E-mail: lmoreschini@lbl.gov [Advanced Light Source (ALS), Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Autès, G. [Institute of Theoretical Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Crepaldi, A. [Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Moser, S. [Advanced Light Source (ALS), Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Johannsen, J.C. [Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Kim, K.S. [Advanced Light Source (ALS), Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Department of Physics, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science, Pohang 790-784 (Korea, Republic of); Berger, H.; Bugnon, Ph.; Magrez, A. [Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Denlinger, J.; Rotenberg, E.; Bostwick, A. [Advanced Light Source (ALS), Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Yazyev, O.V. [Institute of Theoretical Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); and others
2015-05-15
Highlights: • We provide an ARPES comparison between the three tellurohalides BiTeX (X = I, Br, Cl). • They present a similar band structure with namely spin-split bulk and surface states. • They offer, except for BiTeCl, the possibility of ambipolar conduction. • They can be easily doped. • From the data appeared so far, BiTeBr may be the most appealing for applications. - Abstract: We present an overview of the new family of semiconductors BiTeX (X = I, Br, Cl) from the perspective of angle resolved photoemission spectroscopy. The strong band bending occurring at the surface potentially endows them with a large flexibility, as they are capable of hosting both hole and electron conduction, and can be modified by inclusion or adsorption of foreign atoms. In addition, their trigonal crystal structure lacks a center of symmetry and allows for both bulk and surface spin-split bands at the Fermi level. We elucidate analogies and differences among the three materials, also in the light of recent theoretical and experimental work.
Bulk and surface band structure of the new family of semiconductors BiTeX (X=I, Br, Cl)
Highlights: • We provide an ARPES comparison between the three tellurohalides BiTeX (X = I, Br, Cl). • They present a similar band structure with namely spin-split bulk and surface states. • They offer, except for BiTeCl, the possibility of ambipolar conduction. • They can be easily doped. • From the data appeared so far, BiTeBr may be the most appealing for applications. - Abstract: We present an overview of the new family of semiconductors BiTeX (X = I, Br, Cl) from the perspective of angle resolved photoemission spectroscopy. The strong band bending occurring at the surface potentially endows them with a large flexibility, as they are capable of hosting both hole and electron conduction, and can be modified by inclusion or adsorption of foreign atoms. In addition, their trigonal crystal structure lacks a center of symmetry and allows for both bulk and surface spin-split bands at the Fermi level. We elucidate analogies and differences among the three materials, also in the light of recent theoretical and experimental work
Structural alphabets for protein structure classification: a comparison study.
Le, Quan; Pollastri, Gianluca; Koehl, Patrice
2009-03-27
Finding structural similarities between proteins often helps reveal shared functionality, which otherwise might not be detected by native sequence information alone. Such similarity is usually detected and quantified by protein structure alignment. Determining the optimal alignment between two protein structures, however, remains a hard problem. An alternative approach is to approximate each three-dimensional protein structure using a sequence of motifs derived from a structural alphabet. Using this approach, structure comparison is performed by comparing the corresponding motif sequences or structural sequences. In this article, we measure the performance of such alphabets in the context of the protein structure classification problem. We consider both local and global structural sequences. Each letter of a local structural sequence corresponds to the best matching fragment to the corresponding local segment of the protein structure. The global structural sequence is designed to generate the best possible complete chain that matches the full protein structure. We use an alphabet of 20 letters, corresponding to a library of 20 motifs or protein fragments having four residues. We show that the global structural sequences approximate well the native structures of proteins, with an average coordinate root mean square of 0.69 A over 2225 test proteins. The approximation is best for all alpha-proteins, while relatively poorer for all beta-proteins. We then test the performance of four different sequence representations of proteins (their native sequence, the sequence of their secondary-structure elements, and the local and global structural sequences based on our fragment library) with different classifiers in their ability to classify proteins that belong to five distinct folds of CATH. Without surprise, the primary sequence alone performs poorly as a structure classifier. We show that addition of either secondary-structure information or local information from the
Effects of weak nonlinearity on dispersion relations and frequency band-gaps of periodic structures
Sorokin, Vladislav; Thomsen, Jon Juel
2015-01-01
The analysis of the behaviour of linear periodic structures can be traced back over 300 years, to Sir Isaac Newton, and still attracts much attention. An essential feature of periodic struc-tures is the presence of frequency band-gaps, i.e. frequency ranges in which waves cannot propagate....... Determination of band-gaps and the corresponding attenuation levels is an im-portant practical problem. Most existing analytical methods in the field are based on Floquet theory; e.g. this holds for the classical Hill’s method of infinite determinants, and the method of space-harmonics. However, application of...... accounted for. The present work deals with analytically predicting dynamic responses for nonlinear continuous elastic periodic structures. Specifically, the effects of weak nonlinearity on the dispersion re-lation and frequency band-gaps of a periodic Bernoulli-Euler beam performing bending os...
Microscopic structure of deformed and superdeformed collective bands in rotating nuclei
We investigate in self-consistent cranked Nilsson plus quasiparticle random-phase approximation the structure of 190,192,194Hg in their evolution from normal to superdeformation and from low to high rotational frequencies. The analysis of the energy levels suggests a splitting of few normally deformed bands into two or more branches. The investigation of the dynamical moments of inertia supports the octupole character of the low-lying negative parity superdeformed bands, in agreement with previous theoretical predictions and experimental findings. As a more direct confirm of their octupole nature, we obtain strong E1 transitions linking those bands to the yrast superdeformed band, in agreement with experiments. A similar result is shown to hold also for 152Dy. Like in 152Dy, the collectivity of the low-lying scissors mode gets enhanced with the onset of superdeformation
Energy band structure of Cr by the Slater-Koster interpolation scheme
The matrix elements of the Hamiltonian between nine localized wave-functions in tight-binding formalism are derived. The symmetry adapted wave-functions and the secular equations are formed by the group theory method for high symmetry points in the Brillouin zone. A set of interaction integrals is chosen on physical ground and fitted via the Slater-Koster interpolation scheme to the abinito band structure of chromium calculated by the Green function method. Then the energy band structure of chromium is interpolated and extrapolated in the Brillouin zone. (author)
Numerical study of the effect of permeability on square and triangular microwave band gap structures
We report the theoretical work on the photonic band gap structures suitable for microwave frequency region formed by magnetic materials (ε=9.87 and μ=2.17) using plane wave expansion method. The structures under analysis are two-dimensional square and triangular lattices. The calculated band gap between 10 and 20GHz region is anlaysed for the effect due to lattice spacing and the property of the material. The results are also compared with that of pure dielectric case. Obtained results indicate that both impedance and effective refractive index are responsible for the gap width and mid-gap frequency
Improvement of protein structure comparison using a structural alphabet.
Joseph, Agnel Praveen; Srinivasan, N; de Brevern, Alexandre G
2011-09-01
The three dimensional structure of a protein provides major insights into its function. Protein structure comparison has implications in functional and evolutionary studies. A structural alphabet (SA) is a library of local protein structure prototypes that can abstract every part of protein main chain conformation. Protein Blocks (PBs) is a widely used SA, composed of 16 prototypes, each representing a pentapeptide backbone conformation defined in terms of dihedral angles. Through this description, the 3D structural information can be translated into a 1D sequence of PBs. In a previous study, we have used this approach to compare protein structures encoded in terms of PBs. A classical sequence alignment procedure based on dynamic programming was used, with a dedicated PB Substitution Matrix (SM). PB-based pairwise structural alignment method gave an excellent performance, when compared to other established methods for mining. In this study, we have (i) refined the SMs and (ii) improved the Protein Block Alignment methodology (named as iPBA). The SM was normalized in regards to sequence and structural similarity. Alignment of protein structures often involves similar structural regions separated by dissimilar stretches. A dynamic programming algorithm that weighs these local similar stretches has been designed. Amino acid substitutions scores were also coupled linearly with the PB substitutions. iPBA improves (i) the mining efficiency rate by 6.8% and (ii) more than 82% of the alignments have a better quality. A higher efficiency in aligning multi-domain proteins could be also demonstrated. The quality of alignment is better than DALI and MUSTANG in 81.3% of the cases. Thus our study has resulted in an impressive improvement in the quality of protein structural alignment. PMID:21569819
The calculation of the band structure in 3D phononic crystal with hexagonal lattice
Aryadoust, Mahrokh; Salehi, H. [University of Shahid Chamran, Ahvaz (Iran, Islamic Republic of). Dept. of Physics
2015-07-01
In this article, the propagation of acoustic waves in the phononic crystals (PCs) of three dimensions with the hexagonal (HEX) lattice is studied theoretically. The PCs are constituted of nickel (Ni) spheres embedded in epoxy. The calculations of the band structure and the density of states are performed using the plane wave expansion (PWE) method in the irreducible part of the Brillouin zone (BZ). In this study, we analyse the dependence of the band structures inside (the complete band gap width) on c/a and filling fraction in the irreducible part of the first BZ. Also, we have analysed the band structure of the ALHA and MLHKM planes. The results show that the maximum width of absolute elastic band gap (AEBG) (0.045) in the irreducible part of the BZ of HEX lattice is formed for c/a=6 and filling fraction equal to 0.01. In addition, the maximum of the first and second AEBG widths are 0.0884 and 0.0474, respectively, in the MLHKM plane, and the maximum of the first and second AEBG widths are 0.0851 and 0.0431, respectively, in the ALHA plane.
Complete multipactor suppression in an X-band dielectric-loaded accelerating structure
Jing, C.; Gold, S. H.; Fischer, Richard; Gai, W.
2016-05-01
Multipactor is a major issue limiting the gradient of rf-driven Dielectric-Loaded Accelerating (DLA) structures. Theoretical models have predicted that an axial magnetic field applied to DLA structures may completely block the multipactor discharge. However, previous attempts to demonstrate this magnetic field effect in an X-band traveling-wave DLA structure were inconclusive, due to the axial variation of the applied magnetic field, and showed only partial suppression of the multipactor loading [Jing et al., Appl. Phys. Lett. 103, 213503 (2013)]. The present experiment has been performed under improved conditions with a uniform axial magnetic field extending along the length of an X-band standing-wave DLA structure. Multipactor loading began to be continuously reduced starting from 3.5 kG applied magnetic field and was completely suppressed at ˜8 kG. Dependence of multipactor suppression on the rf gradient inside the DLA structure was also measured.
The Development of Layered Photonic Band Gap Structures Using a Micro-Transfer Molding Technique
Kevin Jerome Sutherland
2001-05-01
Photonic band gap (PBG) crystals are periodic dielectric structures that manipulate electromagnetic radiation in a manner similar to semiconductor devices manipulating electrons. Whereas a semiconductor material exhibits an electronic band gap in which electrons cannot exist, similarly, a photonic crystal containing a photonic band gap does not allow the propagation of specific frequencies of electromagnetic radiation. This phenomenon results from the destructive Bragg diffraction interference that a wave propagating at a specific frequency will experience because of the periodic change in dielectric permitivity. This gives rise to a variety of optical applications for improving the efficiency and effectiveness of opto-electronic devices. These applications are reviewed later. Several methods are currently used to fabricate photonic crystals, which are also discussed in detail. This research involves a layer-by-layer micro-transfer molding ({mu}TM) and stacking method to create three-dimensional FCC structures of epoxy or titania. The structures, once reduced significantly in size can be infiltrated with an organic gain media and stacked on a semiconductor to improve the efficiency of an electronically pumped light-emitting diode. Photonic band gap structures have been proven to effectively create a band gap for certain frequencies of electro-magnetic radiation in the microwave and near-infrared ranges. The objective of this research project was originally two-fold: to fabricate a three dimensional (3-D) structure of a size scaled to prohibit electromagnetic propagation within the visible wavelength range, and then to characterize that structure using laser dye emission spectra. As a master mold has not yet been developed for the micro transfer molding technique in the visible range, the research was limited to scaling down the length scale as much as possible with the current available technology and characterizing these structures with other methods.
Electron-Phonon Renormalization of Electronic Band Structures of C Allotropes and BN Polymorphs
Tutchton, Roxanne M.; Marchbanks, Christopher; Wu, Zhigang
The effect of lattice vibration on electronic band structures has been mostly neglected in first-principles calculations because the electron-phonon (e-ph) renormalization of quasi-particle energies is often small (zero-point renormalizations of band gaps in these materials, except for graphene, are larger than 100 meV, and (2) there are large variations in e-ph renormalization of band gaps due to differences in crystal structure. This work was supported by a U.S. DOE Early Career Award (Grant No. DE-SC0006433). Computations were carried out at the Golden Energy Computing Organization at CSM and the National Energy Research Scientific Computing Center (NERSC).
Study on temperature property of band structures in onedimensional photonic crystals
无
2007-01-01
Using transfer matrix method, the optical transmission properties in one-dimensional (1-D) photonic crystal is analyzed.When the temperature varies, not only the refractive index of the optical medium is changed because of the thermo-optical effect, but also the thickness of the optical medium is changed due to the thermal-expansion effect. Thus, the structure of 1/4 wave-plate stack in original photonic crystal is destroyed and the band structure varies. In this work, the effects of the temperature variation on the first and second band gap in a 1-D photonic crystal are analyzed in detail. It is found that the changes of the starting wavelength, the cut-off wavelength and the forbidden band width depend linearly on the temperature.
P. Kovacs
2010-04-01
Full Text Available The paper is focused on the automated design and optimization of electromagnetic band gap structures suppressing the propagation of surface waves. For the optimization, we use different global evolutionary algorithms like the genetic algorithm with the single-point crossover (GAs and the multi-point (GAm one, the differential evolution (DE and particle swarm optimization (PSO. The algorithms are mutually compared in terms of convergence velocity and accuracy. The developed technique is universal (applicable for any unit cell geometry. The method is based on the dispersion diagram calculation in CST Microwave Studio (CST MWS and optimization in Matlab. A design example of a mushroom structure with simultaneous electromagnetic band gap properties (EBG and the artificial magnetic conductor ones (AMC in the required frequency band is presented.
Dielectric band structure of crystals: General properties, and calculations for silicon
We shift the dielectric band structure method, orginially proposed by Baldereschi and Tosatti for the description of microscopic electronic screening in crystals. Some general properties are examined first, including the requirements of causality and stability. The specific test case of silicon is then considered. Dielectric bands are calculated, according to several different prescriptions for the construction of the dielectric matrix. It is shown that the results allow a very direct appraisal of the screening properties of the system, as well as of the quality of the dielectric model adopted. The electronic charge displacement induced by γsub(25') and X3 phonon-like displacements of the atoms is also calculated and compared with the results of existent full self-consistent calculations. Conclusions are drawn on the relative accuracies of the dielectric band structures. (author)
Mini-Dirac cones in the band structure of a copper intercalated epitaxial graphene superlattice
Forti, S.; Stöhr, A.; Zakharov, A. A.; Coletti, C.; Emtsev, K. V.; Starke, U.
2016-09-01
The electronic band structure of an epitaxial graphene superlattice, generated by intercalating a monolayer of Cu atoms, is directly imaged by angle-resolved photoelectron spectroscopy. The 3.2 nm lateral period of the superlattice is induced by a varying registry between the graphene honeycomb and the Cu atoms as imposed by the heteroepitaxial interface Cu/SiC. The carbon atoms experience a lateral potential across the supercell of an estimated value of about 65 meV. The potential leads to strong energy renormalization in the band structure of the graphene layer and the emergence of mini-Dirac cones. The mini-cones’ band velocity is reduced to about half of graphene's Fermi velocity. Notably, the ordering of the interfacial Cu atoms can be reversibly blocked by mild annealing. The superlattice indeed disappears at ∼220 °C.
Band structure and optical properties of highly anisotropic LiBa2[B10O16(OH)3] decaborate crystal
The band structure (BS), charge density distribution and linear-optical properties of the anisotropic crystal LiBa2[B10O16(OH)3] (LBBOH) are calculated using a self-consistent norm-conserving pseudopotential method within the framework of the local-density approximation theory. A high anisotropy of the band energy gap (4.22 eV for the E parallel b, 4.46 eV for the E parallel c) and giant birefringence (up to 0.20) are found. Comparison of the theoretically calculated and the experimentally measured polarised spectra of the imaginary part of the dielectric susceptibility ε2 shows a good agreement. The anisotropy of the charge density distribution, BS dispersion and of the optical spectra originate from anisotropy between the 2pzB-2pzO and 2py,xB-2py,yO bonding orbitals. The observed anisotropy in the LBBOH is principally different from that of β-BaB2O4 (BBO) single crystals. In the LBBOH single crystals the anisotropy of optical and charge density distribution is caused by different projection of the orbitals originating from particular borate clusters on the particular crystallographic axes, contrary to the BBO, where the anisotropy is caused prevailingly by a different local site symmetry of oxygen within the borate planes. The observed anisotropy is analysed in terms of the band energy dispersion and space charge density distribution
Hybrid functional band gap calculation of SnO6 containing perovskites and their derived structures
We have studied the properties of SnO6 octahedra-containing perovskites and their derived structures using ab initio calculations with different density functionals. In order to predict the correct band gap of the materials, we have used B3LYP hybrid density functional, and the results of B3LYP were compared with those obtained using the local density approximation and generalized gradient approximation data. The calculations have been conducted for the orthorhombic ground state of the SnO6 containing perovskites. We also have expended the hybrid density functional calculation to the ASnO3/A'SnO3 system with different cation orderings. We propose an empirical relationship between the tolerance factor and the band gap of SnO6 containing oxide materials based on first principles calculation. - Graphical abstract: (a) Structure of ASnO3 for orthorhombic ground state. The green ball is A (Ba, Sr, Ca) cation and the small (red) ball on edge is oxygen. SnO6 octahedrons are plotted as polyhedron. (b) Band gap of ASnO3 as a function of the tolerance factor for different density functionals. The experimental values of the band gap are marked as green pentagons. (c) ASnO3/A'SnO3 superlattices with two types cation arrangement: [001] layered structure and [111] rocksalt structure, respectively. (d) B3LYP hybrid functional band gaps of ASnO3, [001] ordered superlattices, and [111] ordered superlattices of ASnO3/A'SnO3 as a function of the effective tolerance factor. Note the empirical linear relationship between the band gap and effective tolerance factor. - Highlights: • We report the hybrid functional band gap calculation of ASnO3 and ASnO3/A'SnO3. • The band gap of ASnO3 using B3LYP functional reproduces the experimental value. • We propose the linear relationship between the tolerance factor and the band gap
Band structure, cohesive properties, and Compton profile of γ- and α-cerium
Podloucky, R.; Glötzel, D.
1983-03-01
Recent Compton scattering experiments on the high-volume (γ) and low-volume (α) phases of fcc cerium and their interpretation in terms of the renormalized-free-atom model cast severe doubts on the promotional model of Pauling and Zachariasen for the γ-α transition. Stimulated by these results, we have extended a previous self-consistent local-density band-structure investigation to study the Compton profiles of γ- and α-cerium. For the band structure, Bloch functions, and their Fourier transforms we use the linear muffin-tin orbital method in the atomic-sphere approximation. We analyze the calculated Compton profiles in terms of band structure and local angular momentum character of the wave functions. The change in band structure and wave functions under compression (with approximately one electron per atom in the 4f band of both phases) accounts well for the observed change in the Compton profile. This provides further evidence against the promotional model in agreement with the analysis of Kornstädt et al. In addition, we study the cohesive energy of fcc cerium as a function of volume in the local-density approximation. For α-cerium in the 4f1(5d 6s)3 configuration we find a cohesive energy of 5.4 eV/atom in good agreement with experiment, whereas the "promotional" 4f0(5d 6s)4 state yields a binding energy of 0.6 eV/atom only. Therefore the fourth valence electron has to be a 4f electron, and α-cerium has to be regarded as an f-band metal.
Crystal structure, energy band and optical properties of dysprosium monophosphate DyPO{sub 4}
Khadraoui, Z.; Bouzidi, C., E-mail: bouzidtc@yahoo.fr; Horchani-Naifer, K.; Ferid, M.
2014-12-25
Graphical abstract: The monophosphate DyPO{sub 4} has been synthesized by high temperature solid-state reaction method and was structurally characterized by single crystal X-ray diffraction. DyPO{sub 4} crystallizes in the tetragonal system (I4{sub 1}/Iamd). The energy-band structure, density of states and the chemical bonds have been investigated by density functional methods (DFT). - Highlights: • The DyPO{sub 4} has been synthesized by high temperature solid-state reaction method. • DFT was used to determine the electronic structure and optical properties of DyPO{sub 4}. • The monophosphate DyPO{sub 4} is an insulator with direct band gap (6.38 eV). - Abstract: A rare earth monophosphate crystal of DyPO{sub 4} has been synthesized by high temperature solid-state reaction method and was structurally characterized by single crystal X-ray diffraction. Atomic arrangement of DyPO{sub 4} structure is based on corner and edge sharing PO{sub 4} tetrahedra and DyO{sub 8} polyhedra. The FTIR, Raman, Scanning electron microscopy, diffuse reflectance and emission spectra of the compound have been investigated. Density functional calculation using a Generalized Gradient Approximation was used to determine the electronic structure and optical properties. The calculated total and partial densities of states indicate that the top of valance band is mainly built upon O-2p states with P-3p states via σ (P–O) interactions, and the low conduction bands mostly originates from Dy-5d. The results show that the monophosphate DyPO{sub 4} is an insulator with a calculated band gap (5.8 eV) closer to the experimental value (6.38 eV)
Structure and Evolution of Convection Band Occurred over the Korean Peninsula
Kim, W.; Lee, T.
2011-12-01
A significant portion of the annual precipitation on the Korean peninsula is produced by heavy precipitation systems (HPSs) during summer. HPSs over the Korean peninsula could be classified into four major types (convection bands, cloud clusters, isolated thunderstorms, and squall lines) by phenomenological analysis. Among four major types of HPSs, convection bands (CBs) tend to concentrate a large amount of rainfall over limited area due to their quasi-stationary behavior for several hours. Convective cells embedded in CB move along the band and new cells are continuously formed in the upstream of the band. In this study, the structure and evolution of CB have been investigated using NCEP Climate Forecast System Reanalysis (CFSR) data and Weather Research and Forecasting (WRF) model. Thirty CB cases occurred during 2000-2010 were selected to conduct composite analysis. We obtained several profiles which represent northern area (NA), southern area (SA), and upstream area (UA) of CB by composite analysis. Modest band-perpendicular wind component (5 m s-1) is found in the level of 925-1000 hPa in SA, while band-perpendicular wind component of NA is nearly zero. Additionally, equivalent potential temperature in the lower-troposphere of SA is about 10 K larger than that of NA. Low-level band-perpendicular wind component of SA seems to play an important role in the development of CB by providing the environment for large-scale convergence and transporting warm and moist air from southern area of CB. Band-parallel wind component is predominant in the middle- and lower-troposphere. On the basis of the results of composite analysis, ideal simulation for the evolution of CB was set up. The analysis for the evolution of CB is in progress.
k.p Parameters with Accuracy Control from Preexistent First-Principles Band Structure Calculations
Sipahi, Guilherme; Bastos, Carlos M. O.; Sabino, Fernando P.; Faria Junior, Paulo E.; de Campos, Tiago; da Silva, Juarez L. F.
The k.p method is a successful approach to obtain band structure, optical and transport properties of semiconductors. It overtakes the ab initio methods in confined systems due to its low computational cost since it is a continuum method that does not require all the atoms' orbital information. From an effective one-electron Hamiltonian, the k.p matrix representation can be calculated using perturbation theory and the parameters identified by symmetry arguments. The parameters determination, however, needs a complementary approach. In this paper, we developed a general method to extract the k.p parameters from preexistent band structures of bulk materials that is not limited by the crystal symmetry or by the model. To demonstrate our approach, we applied it to zinc blende GaAs band structure calculated by hybrid density functional theory within the Heyd-Scuseria-Ernzerhof functional (DFT-HSE), for the usual 8 ×8 k.p Hamiltonian. Our parameters reproduced the DFT-HSE band structure with great accuracy up to 20% of the first Brillouin zone (FBZ). Furthermore, for fitting regions ranging from 7-20% of FBZ, the parameters lie inside the range of values reported by the most reliable studies in the literature. The authors acknowledge financial support from the Brazilian agencies CNPq (Grant #246549/2012-2) and FAPESP (Grants #2011/19333-4, #2012/05618-0 and #2013/23393-8).
A Review of Electronic Band Structure of Graphene and Carbon Nanotubes Using Tight Binding
Davood Fathi
2011-01-01
Full Text Available The electronic band structure variations of single-walled carbon nanotubes (SWCNTs using Huckle/tight binding approximation theory are studied. According to the chirality indices, the related expressions for energy dispersion variations of these elements are derived and plotted for zigzag and chiral nanotubes.
NiO: correlated band structure of a charge-transfer insulator
Kuneš, Jan; Anisimov, V.I.; Skornyakov, S.L.; Lukoyanov, A.V.; Vollhardt, D.
2007-01-01
Roč. 99, č. 15 (2007), 156404/1-156404/4. ISSN 0031-9007 Institutional research plan: CEZ:AV0Z10100521 Keywords : band structure * dynamical mean field * charge transfer insulators Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 6.944, year: 2007
Band structure and optical properties of LiKB4O7 single crystal
Smok, P; Seinert, H; Kityk, [No Value; Berdowski, J
2003-01-01
The band structure (BS), electronic charge density distribution and linear optical properties of the LiKB4O7 (LKB4) single crystal are calculated using a self-consistent norm-conserving pseudo-potential method within the framework of the local density approximation theory. Dispersion of the imaginar
Photonic Band Structure of Dispersive Metamaterials Formulated as a Hermitian Eigenvalue Problem
Raman, Aaswath
2010-02-26
We formulate the photonic band structure calculation of any lossless dispersive photonic crystal and optical metamaterial as a Hermitian eigenvalue problem. We further show that the eigenmodes of such lossless systems provide an orthonormal basis, which can be used to rigorously describe the behavior of lossy dispersive systems in general. © 2010 The American Physical Society.
Band structure of ZrS{sub x}Se{sub 2-x} by ARPES
Moustafa, Mohamed; Paulheim, Alexander; Janowitz, Christoph; Manzke, Recardo [Institut fuer Physik, Humboldt-Universitaet Berlin, Berlin (Germany)
2011-07-01
The valence band structure of mixed samples of ZrS{sub x} Se{sub 2-x} single crystals, where x varies from 0 to 2, has been studied by means of high-resolution angle-resolved photoelectron spectroscopy (ARPES) using synchrotron radiation. The crystals were found to be extrinsic n-type semiconductors with indirect bandgap. The composition dependence of the band structure is presented and discussed. A characteristic splitting of the chalcogen p-derived valence bands at the symmetric point A is observed. The size of the splitting shows to increases almost linearly as progressing from ZrS{sub 2} to ZrSe{sub 2} reaching 320 meV. Further, the energy gap values are estimated from the valence band maximum to the observed emission close to the conduction band minimum. The gaps are found to vary from 1.78 eV to 1.16 eV for ZrS{sub 2} to ZrSe{sub 2}, respectively, and are compared to our previously reported optical values.
Hao Liu
2013-01-01
Full Text Available A modified electromagnetic-bandgap (M-EBG structure and its application to planar monopole ultra-wideband (UWB antenna are presented. The proposed M-EBG which comprises two strip patch and an edge-located via can perform dual notched bands. By properly designing and placing strip patch near the feedline, the proposed M-EBG not only possesses a simple structure and compact size but also exhibits good band rejection. Moreover, it is easy to tune the dual notched bands by altering the dimensions of the M-EBG. A demonstration antenna with dual band-notched characteristics is designed and fabricated to validate the proposed method. The results show that the proposed antenna can satisfy the requirements of VSWR < 2 over UWB 3.1–10.6 GHz, except for the rejected bands of the world interoperability for microwave access (WiMAX and the wireless local area network (WLAN at 3.5 GHz and 5.5 GHz, respectively.
Valley-dependent band structure and valley polarization in periodically modulated graphene
Lu, Wei-Tao
2016-08-01
The valley-dependent energy band and transport property of graphene under a periodic magnetic-strained field are studied, where the time-reversal symmetry is broken and the valley degeneracy is lifted. The considered superlattice is composed of two different barriers, providing more degrees of freedom for engineering the electronic structure. The electrons near the K and K' valleys are dominated by different effective superlattices. It is found that the energy bands for both valleys are symmetric with respect to ky=-(AM+ξ AS) /4 under the symmetric superlattices. More finite-energy Dirac points, more prominent collimation behavior, and new crossing points are found for K' valley. The degenerate miniband near the K valley splits into two subminibands and produces a new band gap under the asymmetric superlattices. The velocity for the K' valley is greatly renormalized compared with the K valley, and so we can achieve a finite velocity for the K valley while the velocity for the K' valley is zero. Especially, the miniband and band gap could be manipulated independently, leading to an increase of the conductance. The characteristics of the band structure are reflected in the transmission spectra. The Dirac points and the crossing points appear as pronounced peaks in transmission. A remarkable valley polarization is obtained which is robust to the disorder and can be controlled by the strain, the period, and the voltage.
Observation of dark-current signals from the S-band structures of the SLAC linac
It is well known that the electro-magnetic fields in high-gradient RF structures can cause electron emission from the metallic structure walls. If the emitted electrons are captured and accelerated by the accelerating fields so-called dark-current is induced. Dark-currents have been measured and studied for various RF-structures. In this paper the authors present measurements of RF induced signals for the SLC S-band structures. For nominal gradients of 17 MV/m it is shown that the dark-current can be strong enough to significantly reduce the signal-to-noise ratio of the SLC beam wire scanners. They also show results from RF measurements in the dipole band. The measurements are compared to more direct observations of dark-current and it is tried to connect the results to possible effects on the accelerated particle beam
Ferromagnetism and the electronic band structure in (Ga,Mn)(Bi,As) epitaxial layers
Impact of Bi incorporation into (Ga,Mn)As layers on their electronic- and band-structures as well as their magnetic and structural properties has been studied. Homogenous (Ga,Mn)(Bi,As) layers of high structural perfection have been grown by the low-temperature molecular-beam epitaxy technique. Post-growth annealing treatment of the layers results in an improvement of their structural and magnetic properties and an increase in the hole concentration in the layers. The modulation photoreflectance spectroscopy results are consistent with the valence-band model of hole-mediated ferromagnetism in the layers. This material combines the properties of (Ga,Mn)As and Ga(Bi,As) ternary compounds and offers the possibility of tuning its electrical and magnetic properties by controlling the alloy composition.
Dyadic Green's function study of band structures of dispersive photonic crystals
We present here in terms of a dyadic Green's function (DGF) a general description of optical phenomena in photonic crystal (PC) structures, described particularly by frequency-dependent components, assuming that PC structures are decomposed into their relatively simple constituent parts via conductivity tensors. We demonstrate this approach by explicitly calculating the DGFs for electromagnetic waves propagating in the one- and two-dimensional dispersive PCs consisting of a periodic array of identical metallic quantum wells and a periodic square array of identical metallic quantum wires, each embedded in a three-dimensional dispersive medium. By means of the explicit analytic dispersion relations, which result from the frequency poles of the corresponding DGFs, we also calculate the band structures of these dispersive PCs by simple numerical means. Our analysis shows that the band structures calculated from our DGF approach conform well with those calculated from the traditional computational methods.
The interpenetrating network structure provides an interesting avenue to novel materials. Locally resonant phononic crystal (LRPC) exhibits excellent sound attenuation performance based on the periodical arrangement of sound wave scatters. Combining the LRPC concept and interpenetrating network glassy structure, this paper has developed a new material which can achieve a wide band underwater strong acoustic absorption. Underwater absorption coefficients of different samples were measured by the pulse tube. Measurement results show that the new material possesses excellent underwater acoustic effects in a wide frequency range. Moreover, in order to investigate impacts of locally resonant units, some defects are introduced into the sample. The experimental result and the theoretical calculation both show that locally resonant units being connected to a network structure play an important role in achieving a wide band strong acoustic absorption. (condensed matter: structure, thermal and mechanical properties)
Band structure effects in nitrogen K-edge resonant inelastic X ray scattering from GaN
Strocov, V. N.; Schmitt, T.; Rubensson, J.-E.; Blaha, P; Paskova, T.; Nilsson, P. O.
2004-01-01
Systematic experimental data on resonant inelastic X-ray scattering (RIXS) in GaN near the N K-edge are presented for the first time. Excitation energy dependence of the spectral structures manifests the band structure effects originating from momentum selectivity of the RIXS process. This finding allows obtaining k-resolved band structure information for GaN crystals and nanostructures.
RF breakdown studies on an S-band disk-loaded structure
RF breakdown test in an S-band traveling wave accelerating structure were studied by use of a resonant ring. The accelerating structure with a surface roughness of 300 nm was used without any special treatment after the fabrication. The maximum field gradient on the beam axis was 104.5 MV/m with a peak field-emission current of 24 mA. This current level, however, was decreasing by the RF processing. (author)
Electromagnetic wave band structure due to surface plasmon resonances in a complex plasma
Vladimirov, S. V.; Ishihara, O.
2016-07-01
The dielectric properties of complex plasma containing either metal or dielectric spherical inclusions (macroparticles, dust) are investigated. We focus on surface plasmon resonances on the macroparticle surfaces and their effect on electromagnetic wave propagation. It is demonstrated that the presence of surface plasmon oscillations can significantly modify plasma electromagnetic properties by resonances and cutoffs in the effective permittivity. This leads to related branches of electromagnetic waves and to the wave band gaps. The conditions necessary to observe the band-gap structure in laboratory dusty plasma and/or space (cosmic) dusty plasmas are discussed.
Investigation of band structure of {sup 103,105}Rh using microscopic computational technique
Kumar, Amit, E-mail: akbcw2@gmail.com [Research Scholar, Department of Physics and Electronics, University of Jammu, Jammu-180006 (India); Singh, Suram, E-mail: suramsingh@gmail.com [Assistant Professor, Department of Physics Govt. Degree College, Kathua-184142 (India); Bharti, Arun, E-mail: arunbharti-2003@yahoo.co.in [Professor, Department of Physics and Electronics, University of Jammu, Jammu-180006 (India)
2015-08-28
The high-spin structure in {sup 61}Cu nucleus is studied in terms of effective two body interaction. In order to take into account the deformed BCS basis, the basis states are expanded in terms of the core eigenfunctions. Yrast band with some other bands havew been obtained and back-bending in moment of inertia has also been calculated and compared with the available experimental data for {sup 61}Cu nucleus. On comparing the available experimental as well as other theoretical data, it is found that the treatment with PSM provides a satisfactory explanation of the available data.
Dual Band and Beam-Steering Antennas Using Reconfigurable Feed on Sierpinski Structure
Seonghun Kang; Chang Won Jung
2015-01-01
Fractal patch antennas based on the Sierpinski structure are studied in this paper. The antennas operate at dual bands (around 2 and 5 GHz) and are designed to steer the beam directions at around 5 GHz band (the first harmonic). The antennas use reconfigurable triple feeds on the same antenna plane to have three beam directions. The same scale factor defines the geometrical self-similarity of the Sierpinski fractal. The proposed antennas are fabricated through three iterations from 1st order ...
Electromagnetic wave band structure due to surface plasmon resonances in a complex plasma.
Vladimirov, S V; Ishihara, O
2016-07-01
The dielectric properties of complex plasma containing either metal or dielectric spherical inclusions (macroparticles, dust) are investigated. We focus on surface plasmon resonances on the macroparticle surfaces and their effect on electromagnetic wave propagation. It is demonstrated that the presence of surface plasmon oscillations can significantly modify plasma electromagnetic properties by resonances and cutoffs in the effective permittivity. This leads to related branches of electromagnetic waves and to the wave band gaps. The conditions necessary to observe the band-gap structure in laboratory dusty plasma and/or space (cosmic) dusty plasmas are discussed. PMID:27575225
Narimani, M.; Nourbakhsh, Z.
2016-05-01
In this paper, the structural, electronic and optical properties of LuPdBi and ScPdBi compounds are investigated using the density functional theory by WIEN2K package within the generalized gradient approximation, local density approximation, Engel-Vosco generalized gradient approximations and modified Becke-Johnson potential approaches. The topological phases and band orders of these compounds are studied. The effect of pressure on band inversion strength, electron density of states and the linear coefficient of the electronic specific heat of these compounds is investigated. Furthermore, the effect of pressure on real and imaginary parts of dielectric function, absorption and reflectivity coefficients of these compounds is studied.
Investigation of band structure of 103,105Rh using microscopic computational technique
The high-spin structure in 61Cu nucleus is studied in terms of effective two body interaction. In order to take into account the deformed BCS basis, the basis states are expanded in terms of the core eigenfunctions. Yrast band with some other bands havew been obtained and back-bending in moment of inertia has also been calculated and compared with the available experimental data for 61Cu nucleus. On comparing the available experimental as well as other theoretical data, it is found that the treatment with PSM provides a satisfactory explanation of the available data
Junquera, Javier; Aguado-Puente, Pablo
2013-03-01
At metal-isulator interfaces, the metallic wave functions with an energy eigenvalue within the band gap decay exponentially inside the dielectric (metal-induced gap states, MIGS). These MIGS can be actually regarded as Bloch functions with an associated complex wave vector. Usually only real values of the wave vectors are discussed in text books, since infinite periodicity is assumed and, in that situation, wave functions growing exponentially in any direction would not be physically valid. However, localized wave functions with an exponential decay are indeed perfectly valid solution of the Schrodinger equation in the presence of defects, surfaces or interfaces. For this reason, properties of MIGS have been typically discussed in terms of the complex band structure of bulk materials. The probable dependence on the interface particulars has been rarely taken into account explicitly due to the difficulties to include them into the model or simulations. We aim to characterize from first-principles simulations the MIGS in realistic ferroelectric capacitors and their connection with the complex band structure of the ferroelectric material. We emphasize the influence of the real interface beyond the complex band structure of bulk materials. Financial support provided by MICINN Grant FIS2009-12721-C04-02, and by the European Union Grant No. CP-FP 228989-2 ``OxIDes''. Computer resources provided by the RES.
Structural characteristic correlated to the electronic band gap in Mo S2
Chu, Shengqi; Park, Changyong; Shen, Guoyin
2016-07-01
The structural evolution with pressure in bulk Mo S2 has been investigated by high-pressure x-ray diffraction using synchrotron radiation. We found that the out-of-plane S-Mo-S bond angle θ increases and that in in-plane angle ϕ decreases linearly with increasing pressure across the known semiconducting-to-metal phase transition, whereas the Mo-S bond length and the S-Mo-S trilayer thickness display only little change. Extrapolating the experimental result along the in-plane lattice parameter with pressure, both S-Mo-S bond angles trend to those found in monolayer Mo S2 , which manifests as a structural characteristic closely correlating the electronic band gap of Mo S2 to its physical forms and phases, e.g., monolayer as direct band gap semiconductor, multilayer or bulk as indirect band gap semiconductor, and high-pressure (>19 GPa ) bulk form as metal. Combined with the effects of bond strength and van der Waals interlayer interactions, the structural correlations between the characteristic bond angle and electronic band gaps are readily extendible to other transition metal dichalcogenide systems (M X2 , where M =Mo , W and X =S , Se, Te).
SRTM mission-cross comparison of X adn C band data properties
Rosen, P.; Eineder, M.; Rabus, B.; Gurrola, E.; Hensley, S.; Knopfle, W.; Breit, H.; Roth, A.; Werner, M.
2001-01-01
This paper compares the specific properties of the X and C band data sets with respect to global coverage, height accuracy, sensor specific errors, product definition, product format and availability.
Comparison of the chromosome banding patterns in Dryomys laniger and D. nitedula from Turkey
Arslan, A.; Kankilic, T.; Yorulmaz, T.; Kankilic, T.; Zima, Jan
2016-01-01
Roč. 40, č. 3 (2016), s. 363-368. ISSN 1300-0179 Institutional support: RVO:68081766 Keywords : dormice * karyotype * C-banding * AgNOR staining Subject RIV: EG - Zoology Impact factor: 0.630, year: 2014
Evidence is now quite strong that the elementary hybridization model is the correct way to understand the lattice-coherent Fermi liquid regime at very low temperatures. Many-body theory leads to significant renormalizations of the input parameters, and many of the band-theoretic channels for hybridization are suppressed by the combined effects of Hund's-rule coupling, crystal-field splitting, and the f-f Coulomb repulsion U. Some exploratory calculations based on this picture are described, and some inferences are drawn about the band structures of several heavy-fermion materials. These inferences can and should be tested by suitably modified band-theoretic calculations. We find evidence for a significant Baber-scattering contribution in the very-low-temperature resistivity. A new mechanism is proposed for crossover from the coherent Fermi-liquid regime to the incoherent dense-Kondo regime. 28 refs
Band structures of carbon nanotube with spin-orbit coupling interaction
Liu Hong, E-mail: liuhong3@njnu.edu.c [Physics Department, Nanjing Normal University, Nanjing 210046 (China)
2011-01-01
We explore the band structures of single-walled carbon nanotubes (SWCNTs) with two types of spin-orbit couplings. The obtained results indicate that weak Rashba spin-orbit coupling interaction can lead to the breaking of four-fold degeneracy in all tubes even though without the intrinsic SO coupling. The asymmetric splitting between conduction bands and valence bands is caused by both SO couplings at the same time. When the ratio of Rashba spin-orbit coupling to the intrinsic spin-orbit coupling is larger than 3, metallic zigzag nanotube is always metallic conductor, on the contrary it becomes semiconducting properties. However, only when this ratio is equal to about 3 or the intrinsic spin-orbit coupling is much weak, the metallic armchair nanotube still holds the metallic behavior in transport.