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Sample records for valence-band maximum vbm

  1. Location of the valence band maximum in the band structure of anisotropic 1 T'-ReSe2

    Science.gov (United States)

    Eickholt, P.; Noky, J.; Schwier, E. F.; Shimada, K.; Miyamoto, K.; Okuda, T.; Datzer, C.; Drüppel, M.; Krüger, P.; Rohlfing, M.; Donath, M.

    2018-04-01

    Transition-metal dichalcogenides (TMDCs) are a focus of current research due to their fascinating optical and electronic properties with possible technical applications. ReSe2 is an interesting material of the TMDC family, with unique anisotropic properties originating from its distorted 1 T structure (1 T '). To develop a fundamental understanding of the optical and electric properties, we studied the underlying electronic structure with angle-resolved photoemission (ARPES) as well as band-structure calculations within the density functional theory (DFT)-local density approximation (LDA) and GdW approximations. We identified the Γ ¯M¯1 direction, which is perpendicular to the a axis, as a distinct direction in k space with the smallest bandwidth of the highest valence band. Using photon-energy-dependent ARPES, two valence band maxima are identified within experimental limits of about 50 meV: one at the high-symmetry point Z , and a second one at a non-high-symmetry point in the Brillouin zone. Thus, the position in k space of the global valence band maximum is undecided experimentally. Theoretically, an indirect band gap is predicted on a DFT-LDA level, while quasiparticle corrections lead to a direct band gap at the Z point.

  2. The localized effect of the Bi level on the valence band in the dilute bismuth GaBixAs1-x alloy

    Science.gov (United States)

    Zhao, Chuan-Zhen; Zhu, Min-Min; Wang, Jun; Wang, Sha-Sha; Lu, Ke-Qing

    2018-05-01

    The research on the temperature dependence of the band gap energy of the dilute bismuth GaBixAs1-x alloy has been done. It is found that its temperature insensitiveness is due to the enhanced localized character of the valence band state and the small decrease of the temperature coefficient for the conduction band minimum (CBM). The enhanced localized character of the valence band state is the main factor. In order to describe the localized effect of the Bi levels on the valence band, the localized energy is introduced into the Varshni's equation. It is found that the effect of the localized Bi level on the valence band becomes strong with increasing Bi content. In addition, it is found that the pressure dependence of the band gap energy of GaBixAs1-x does not seem to be influenced by the localized Bi levels. It is due to two factors. One is that the pressure dependence of the band gap energy is mainly determined by the D CBM of GaBixAs1-x. The D CBM of GaBixAs1-x is not influenced by the localized Bi levels. The other is that the small variation of the pressure coefficient for the D valence band maximum (VBM) state of GaBixAs1-x can be cancelled by the variation of the pressure coefficient for the D CBM state of GaBixAs1-x.

  3. Hole energy and momentum distributions in valence bands

    International Nuclear Information System (INIS)

    Laan, G. van der.

    1982-01-01

    In order to understand the electrical and magnetic properties of solids, the knowledge of the density of states and the dispersion relation of the valence bands is indispensable. This thesis offers some alternative methods to obtain information about the nature of the valence band. Part A deals with the energy distribution of the photoelectrons. A simple model, which explains the core hole satellite structure in compounds with large correlation effects between the valence band holes and the created photo-hole, is outlined. CuCl, CuX 2 (X = F Cl and Br) are studied, by photoemission and Auger electron spectroscopies in determining the valence band properties. Part B deals with the simultaneous measurement of the energy and the wave vector of the emitted electrons. A practical example is given for the determination of the dispersion relation in copper. The measurements of a surface resonance band and the distribution of the secondary electrons are also reported. (Auth.)

  4. Determination of a natural valence-band offset - The case of HgTe and CdTe

    Science.gov (United States)

    Shih, C. K.; Spicer, W. E.

    1987-01-01

    A method to determine a natural valence-band offset (NVBO), i.e., the change in the valence-band maximum energy which is intrinsic to the bulk band structures of semiconductors is proposed. The HgTe-CdTe system is used as an example in which it is found that the valence-band maximum of HgTe lies 0.35 + or - 0.06 eV above that of CdTe. The NVBO of 0.35 eV is in good agreement with the X-ray photoemission spectroscopy measurement of the heterojunction offset. The procedure to determine the NVBO between semiconductors, and its implication on the heterojunction band lineup and the electronic structures of semiconductor alloys, are discussed.

  5. Spin-dependent electron-phonon coupling in the valence band of single-layer WS2

    DEFF Research Database (Denmark)

    Hinsche, Nicki Frank; Ngankeu, Arlette S.; Guilloy, Kevin

    2017-01-01

    The absence of inversion symmetry leads to a strong spin-orbit splitting of the upper valence band of semiconducting single-layer transition-metal dichalchogenides such as MoS2 or WS2. This permits a direct comparison of the electron-phonon coupling strength in states that only differ by their spin....... Here, the electron-phonon coupling in the valence band maximum of single-layer WS2 is studied by first-principles calculations and angle-resolved photoemission. The coupling strength is found to be drastically different for the two spin-split branches, with calculated values of λK=0.0021 and 0.......40 for the upper and lower spin-split valence band of the freestanding layer, respectively. This difference is somewhat reduced when including scattering processes involving the Au(111) substrate present in the experiment but it remains significant, in good agreement with the experimental results....

  6. Optical verification of the valence band structure of cadmium arsenide

    NARCIS (Netherlands)

    Gelten, M.J.; Es, van C.M.; Blom, F.A.P.; Jongeneelen, J.W.F.

    1980-01-01

    Optical absorption measurements were performed on thin single crystalline samples of Cd3As2 at temperatures of 300 K and 10 K. At low temperature the interband absorption coefficient shows clearly two steps due to direct transitions from the heavy hole and light hole valence bands to the conduction

  7. A Comparison of the Valence Band Structure of Bulk and Epitaxial GeTe-based Diluted Magnetic Semiconductors

    International Nuclear Information System (INIS)

    Pietrzyk, M.A.; Kowalski, B.J.; Orlowski, B.A.; Knoff, W.; Story, T.; Dobrowolski, W.; Slynko, V.E.; Slynko, E.I.; Johnson, R.L.

    2010-01-01

    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)

  8. Spectroscopic determination of valence band parameters in InP

    International Nuclear Information System (INIS)

    Lewis, R.A.; Lough, B.C.C.

    2003-01-01

    Full text: The general form of the Hamiltonian for an electron or hole in a semiconductor has been given by Luttinger. The valence band is characterised by three parameters - γ 1 , γ 2 , γ 3 -now commonly known as the Luttinger parameters. Despite many investigations there is still considerable uncertainty regarding the Luttinger parameters of InP. The situation has been reviewed by Hackenberg et al. These authors themselves sought to determine the Luttinger parameters by hot-electron luminescence and discovered that many Luttinger parameter triplets were consistent with their data. We employ a spectroscopic approach to estimating valence-band parameters in InP. Calculations have been made for both the unperturbed energy levels and the energy levels in a magnetic field of acceptor impurities in semiconductors characterised by different Luttinger parameters. We compare our recent experimental data for the transitions associated with the Zn acceptor impurity in InP in magnetic fields up to 30 T to determine the most appropriate set of valence-band parameters for InP

  9. Determination of valence band parameters in ZnTe

    Energy Technology Data Exchange (ETDEWEB)

    Froehlich, D.; Noethe, A.; Reimann, K. (Duesseldorf Univ. (Germany, F.R.). Physikalisches Inst. - Lehrstuhl 2)

    1984-10-01

    The fine structure of the 2P exciton in ZnTe is studied by two-photon-absorption. The energy splitting into four states, caused by the envelope-hole coupling, allows the determination of the Luttinger parameters ..gamma../sub 2/ and ..gamma../sub 3/, which describe the complex valence band. ..gamma../sub 2/ = 0.8 and ..gamma../sub 3/ = 1.7 are obtained. These values are compared to results of other experiments mainly on 1S excitons.

  10. Relaxation and cross section effects in valence band photoemission spectroscopy

    International Nuclear Information System (INIS)

    McFeely, F.R.

    1976-09-01

    Various problems relating to the interpretation of valence band x-ray photoemission (XPS) spectra of solids are discussed. The experiments and calculations reported herein deal with the following questions: (1) To what extent do many-body effects manifest themselves in an XPS valence band spectrum, and thus invalidate a direct comparison between the photoemission energy distribution, I(E), and the density of states, N(E), calculated on the basis of ground-state one-electron theory. (2) The effect of the binding-energy-dependent photoemission cross section on I(E) at XPS energies. (3) In favorable cases indicated by (1) and (2) we examine the effect of the interaction of the crystal field with the apparent spin-orbit splittings of core levels observed in XPS spectra. (4) The use of tight binding band structure calculations to parameterize the electronic band structure from XPS and other data is described. (5) The use of high energy angle-resolved photoemission on oriented single crystals to gain orbital symmetry information is discussed. (6) The evolution of the shape of the photoemission energy distribution (of polycrystalline Cu) as a function of photon energy from 50 less than or equal h ω less than or equal 175 is discussed

  11. Valence band electronic structure of Pd based ternary chalcogenide superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Lohani, H. [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India); Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400085 (India); Mishra, P. [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India); Goyal, R.; Awana, V.P.S. [National Physical Laboratory(CSIR), Dr. K. S. Krishnan Road, New Delhi 110012 (India); Sekhar, B.R., E-mail: sekhar@iopb.res.in [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India); Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400085 (India)

    2016-12-15

    Highlights: • VB Photoemission study and DFT calculations on Pd based ternary superconductors are presented. • Nb{sub 2}Pd{sub 0.95}S{sub 5} shows a temperature dependent pseudogap. • VB spectral features of ternary superconductors are correlated to their structural geometry. - Abstract: We present a comparative study of the valence band electronic structure of Pd based ternary chalcogenide superconductors Nb{sub 2}Pd{sub 0.95}S{sub 5}, Ta{sub 2}Pd{sub 0.97}S{sub 6} and Ta{sub 2}Pd{sub 0.97}Te{sub 6} using experimental photoemission spectroscopy and density functional based theoretical calculations. We observe a qualitatively similarity between valence band (VB) spectra of Nb{sub 2}Pd{sub 0.95}S{sub 5} and Ta{sub 2}Pd{sub 0.97}S{sub 6}. Further, we find a pseudogap feature in Nb{sub 2}Pd{sub 0.95}S{sub 5} at low temperature, unlike other two compounds. We have correlated the structural geometry with the differences in VB spectra of these compounds. The different atomic packing in these compounds could vary the strength of inter-orbital hybridization among various atoms which leads to difference in their electronic structure as clearly observed in our DOS calculations.

  12. Measurement of valence band structure in arbitrary dielectric films

    International Nuclear Information System (INIS)

    Uhm, Han S.; Choi, Eun H.

    2012-01-01

    A new way of measuring the band structure of various dielectric materials using the secondary electron emission from Auger neutralization of ions is introduced. The first example of this measurement scheme is the magnesium oxide (MgO) films with respect to the application of the films in the display industries. The density of state in the valence bands of MgO film and MgO film with a functional layer (FL) deposited over a dielectric surface reveals that the density peak of film with a FL is considerably less than that of film, thereby indicating a better performance of MgO film with functional layer in display devices. The second example of the measurement is the boron-zinc oxide (BZO) films with respect to the application of the films to the development of solar cells. The measurement of density of state in BZO film suggests that a high concentration of boron impurity in BZO films may enhance the transition of electrons and holes through the band gap from the valence to the conduction band in zinc oxide crystals; thereby improving the conductivity of the film. Secondary electron emission by the Auger neutralization of ions is highly instrumental for the determination of the density of states in the valence band of dielectric materials.

  13. Valence band structure of binary chalcogenide vitreous semiconductors by high-resolution XPS

    International Nuclear Information System (INIS)

    Kozyukhin, S.; Golovchak, R.; Kovalskiy, A.; Shpotyuk, O.; Jain, H.

    2011-01-01

    High-resolution X-ray photoelectron spectroscopy (XPS) is used to study regularities in the formation of valence band electronic structure in binary As x Se 100−x , As x S 100−x , Ge x Se 100−x and Ge x S 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.

  14. Valence band structure of binary chalcogenide vitreous semiconductors by high-resolution XPS

    Energy Technology Data Exchange (ETDEWEB)

    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.

  15. Electronic structures and valence band splittings of transition metals doped GaNs

    International Nuclear Information System (INIS)

    Lee, Seung-Cheol; Lee, Kwang-Ryeol; Lee, Kyu-Hwan

    2007-01-01

    For a practical viewpoint, presence of spin splitting of valence band in host semiconductors by the doping of transition metal (TM) ions is an essential property when designing a diluted magnetic semiconductors (DMS) material. The first principle calculations were performed on the electronic and magnetic structure of 3d transition metal doped GaN. V, Cr, and Mn doped GaNs could not be candidates for DMS materials since most of their magnetic moments is concentrated on the TM ions and the splittings of valence band were negligible. In the cases of Fe, Co, Ni, and Cu doped GaNs, on the contrary, long-ranged spin splitting of valence band was found, which could be candidates for DMS materials

  16. Atomic contributions to the valence band photoelectron spectra of metal-free, iron and manganese phthalocyanines

    Energy Technology Data Exchange (ETDEWEB)

    Bidermane, I., E-mail: ieva.bidermane@physics.uu.se [Department of Physics and Astronomy, Uppsala University, Box-516, 75120 Uppsala (Sweden); Institut des Nanosciences de Paris, UPMC Univ. Paris 06, CNRS UMR 7588, F-75005 Paris (France); Brumboiu, I.E. [Department of Physics and Astronomy, Uppsala University, Box-516, 75120 Uppsala (Sweden); Totani, R. [Department of Physical and Chemical Sciences, University of L’Aquila, Via Vetoio, Coppito, I-67010 L’Aquila (Italy); Grazioli, C. [CNR-IOM, Laboratorio TASC, ss. 14 km. 163.5, Basovizza, 34149 Trieste (Italy); Departement of Chemical and Pharmaceutical Sciences, University of Trieste (Italy); Shariati-Nilsson, M.N.; Herper, H.C.; Eriksson, O.; Sanyal, B. [Department of Physics and Astronomy, Uppsala University, Box-516, 75120 Uppsala (Sweden); Ressel, B. [University of Nova Gorica, Vipavska Cesta 11c, 5270 Ajdovščina (Slovenia); Simone, M. de [CNR-IOM, Laboratorio TASC, ss. 14 km. 163.5, Basovizza, 34149 Trieste (Italy); Lozzi, L. [Department of Physical and Chemical Sciences, University of L’Aquila, Via Vetoio, Coppito, I-67010 L’Aquila (Italy); Brena, B.; Puglia, C. [Department of Physics and Astronomy, Uppsala University, Box-516, 75120 Uppsala (Sweden)

    2015-11-15

    Highlights: • In detail comparison between the valence band structure of H{sub 2}Pc, FePc and MnPc. • Comparison between the gas phase samples and thin evaporated films on Au (1 1 1). • Detailed analysis of the atomic orbital contributions to the valence band features. • DFT/HSE06 study of the valence band electronic structure of H{sub 2}Pc, FePc and MnPc. - Abstract: The present work reports a photoelectron spectroscopy study of the low-energy region of the valence band of metal-free phthalocyanine (H{sub 2}Pc) compared with those of iron phthalocyanine (FePc) and manganese phthalocyanine (MnPc). We have analysed in detail the atomic orbital composition of the valence band both experimentally, by making use of the variation in photoionization cross-sections with photon energy, and theoretically, by means of density functional theory. The atomic character of the Highest Occupied Molecular Orbital (HOMO), reflected on the outermost valence band binding energy region, is different for MnPc as compared to the other two molecules. The peaks related to the C 2p contributions, result in the HOMO for H{sub 2}Pc and FePc and in the HOMO-1 for MnPc as described by the theoretical predictions, in very good agreement with the experimental results. The DFT simulations, discerning the atomic contribution to the density of states, indicate how the central metal atom interacts with the C and N atoms of the molecule, giving rise to different partial and total density of states for these three Pc molecules.

  17. The Synthesis of NiO/TiO2 Heterostructures and Their Valence Band Offset Determination

    Directory of Open Access Journals (Sweden)

    Z. H. Ibupoto

    2014-01-01

    Full Text Available In this work, a heterojunction based on p-type NiO/n-type TiO2 nanostructures has been prepared on the fluorine doped tin oxide (FTO glass substrate by hydrothermal method. Scanning electron microscopy (SEM and X-Ray diffraction techniques were used for the morphological and crystalline arrays characterization. The X-ray photoelectron spectroscopy was employed to determine the valence-band offset (VBO of the NiO/TiO2 heterojunction prepared on FTO glass substrate. The core levels of Ni 2p and Ti 2p were utilized to align the valence-band offset of p-type NiO/n-type TiO2 heterojunction. The valence band offset was found to be ∼0.41 eV and the conduction band was calculated about ∼0.91 eV. The ratio of conduction band offset and the valence-band offset was found to be 2.21.

  18. Giant Cu 2p Resonances in CuO Valence-Band Photoemission

    NARCIS (Netherlands)

    Tjeng, L.H.; Chen, C.T.; Ghijsen, J.; Rudolf, P.; Sette, F.

    1991-01-01

    We report the observation of a giant resonance in the Cu 2p resonant-photoemission spectra of CuO. The study allows the unambiguous identification of the local Cu 3d8 configuration in the valence-band photoemission spectrum, providing conclusive evidence for the charge-transfer nature of the

  19. Theory of two-photon absorption by exciton states in cubic semiconductors with degenerate valence bands

    International Nuclear Information System (INIS)

    Nguyen Ai Viet; Nguyen Toan Thang.

    1987-06-01

    The coefficient of the absorption of two polarized photons is calculated for direct band gap semiconductors with degenerate valence bands. Wannier-Mott exciton states are included in both the intermediate and final states. Numerical calculations are performed for ZnSe and are compared with Sondergeld's experimental and theoretical results. (author). 11 refs, 2 tabs

  20. Nature of the valence band states in Bi2(Ca, Sr, La)3Cu2O8

    International Nuclear Information System (INIS)

    Wells, B.O.; Lindberg, P.A.P.; Shen, Z.; Dessau, D.S.; Spicer, W.E.; Lindau, I.; Mitzi, D.B.; Kapitulnik, A.

    1990-01-01

    We have used photoemission spectroscopy to examine the symmetry of the occupied states of the valence band for the La doped superconductor Bi 2 (Ca, Sr, La) 3 Cu 2 O 8 . While the oxygen states near the bottom of the 7 eV wide valence band exhibit predominantly O 2p z symmetry, the states at the top of the valence band extending to the Fermi level are found to have primarily O 2p x and O 2p y character. We have also examined anomalous intensity enhancements in the valence band feature for photon energies near 18 eV. These enhancements, which occur at photon energies ranging from 15.8 to 18.0 eV for the different valence band features, are not consistent with either simple final state effects or direct O2s transitions to unoccupied O2p states

  1. Tunneling emission of electrons from semiconductors' valence bands in high electric fields

    International Nuclear Information System (INIS)

    Kalganov, V. D.; Mileshkina, N. V.; Ostroumova, E. V.

    2006-01-01

    Tunneling emission currents of electrons from semiconductors to vacuum (needle-shaped GaAs photodetectors) and to a metal (silicon metal-insulator-semiconductor diodes with a tunneling-transparent insulator layer) are studied in high and ultrahigh electric fields. It is shown that, in semiconductors with the n-type conductivity, the major contribution to the emission current is made by the tunneling emission of electrons from the valence band of the semiconductor, rather than from the conduction band

  2. Instanton contributions to the valence band of the double Sine-Gordon potential

    International Nuclear Information System (INIS)

    Ricotta, R.M.; Escobar, C.O.

    1982-01-01

    The energy dispersion relation for the valence band of the double sine-Gordon potential is calculated, approximating the tunneling amplitude by a sum of contributions of multi-instantons and anti-instatons trajectories. The interesting feature of this potential is that they have to deal with two types of instantons, as there are two different potential barriers within one period of the potential. The results with the standard WKB approximation are compared. (Author) [pt

  3. Valence band variation in Si (110) nanowire induced by a covered insulator

    International Nuclear Information System (INIS)

    Hong-Hua, Xu; Xiao-Yan, Liu; Yu-Hui, He; Gang, Du; Ru-Qi, Han; Jin-Feng, Kang; Chun, Fan; Ai-Dong, Sun

    2010-01-01

    In this work, we investigate strain effects induced by the deposition of gate dielectrics on the valence band structures in Si (110) nanowire via the simulation of strain distribution and the calculation of a generalized 6×6k·p strained valence band. The nanowire is surrounded by the gate dielectric. Our simulation indicates that the strain of the amorphous SiO 2 insulator is negligible without considering temperature factors. On the other hand, the thermal residual strain in a nanowire with amorphous SiO 2 insulator which has negligible lattice misfit strain pushes the valence subbands upwards by chemical vapour deposition and downwards by thermal oxidation treatment. In contrast with the strain of the amorphous SiO 2 insulator, the strain of the HfO 2 gate insulator in Si (110) nanowire pushes the valence subbands upwards remarkably. The thermal residual strain by HfO 2 insulator contributes to the up-shifting tendency. Our simulation results for valence band shifting and warping in Si nanowires can provide useful guidance for further nanowire device design. (classical areas of phenomenology)

  4. Systematic study on intermolecular valence-band dispersion in molecular crystalline films

    International Nuclear Information System (INIS)

    Yamane, Hiroyuki; Kosugi, Nobuhiro

    2015-01-01

    Highlights: • Intermolecular valence-band dispersion of crystalline films of phthalocyanines. • Intermolecular transfer integral versus lattice constant. • Site-specific intermolecular interaction and resultant valence-band dispersion. • Band narrowing effect induced by elevated temperature. - Abstract: Functionalities of organic semiconductors are governed not only by individual properties of constituent molecules but also by solid-state electronic states near the Fermi level such as frontier molecular orbitals, depending on weak intermolecular interactions in various conformations. The individual molecular property has been widely investigated in detail; on the other hand, the weak intermolecular interaction is difficult to investigate precisely due to the presence of the structural and thermal energy broadenings in organic solids. Here we show quite small but essential intermolecular valence band dispersions and their temperature dependence of sub-0.1-eV scale in crystalline films of metal phthalocyanines (H_2Pc, ZnPc, CoPc, MnPc, and F_1_6ZnPc) by using angle-resolved photoemission spectroscopy (ARPES) with synchrotron radiation. The observed bands show intermolecular and site dependent dispersion widths, phases, and periodicities, for different chemical substitution of terminal groups and central metals in the phthalocyanine molecule. The precise and systematic band-dispersion measurement would be a credible approach toward the comprehensive understanding of intermolecular interactions and resultant charge transport properties as well as their tuning by substituents in organic molecular systems.

  5. Accounting for many-body correlation effects in the calculation of the valence band photoelectron emission spectra of ferromagnets

    International Nuclear Information System (INIS)

    Minar, J.; Chadov, S.; Ebert, H.; Chioncel, L.; Lichtenstein, A.; De Nadai, C.; Brookes, N.B.

    2005-01-01

    The influence of dynamical correlation effects on the valence band photoelectron emission of ferromagnetic Fe, Co and Ni has been investigated. Angle-resolved as well as angle-integrated valence band photoelectron emission spectra were calculated on the basis of the one-particle Green's function, which was obtained by using the fully relativistic Korringa-Kohn-Rostoker method. The correlation effects have been included in terms of the electronic self-energy which was calculated self-consistently within Dynamical Mean-Field Theory (DMFT). In addition a theoretical approach to calculate high-energy angle-resolved valence band photoelectron emission spectra is presented

  6. Valence Band Structure of InAs1-xBix and InSb1-xBix Alloy Semiconductors Calculated Using Valence Band Anticrossing Model

    Directory of Open Access Journals (Sweden)

    D. P. Samajdar

    2014-01-01

    Full Text Available The valence band anticrossing model has been used to calculate the heavy/light hole and spin-orbit split-off energies in InAs1-xBix and InSb1-xBix alloy systems. It is found that both the heavy/light hole, and spin-orbit split E+ levels move upwards in energy with an increase in Bi content in the alloy, whereas the split E− energy for the holes shows a reverse trend. The model is also used to calculate the reduction of band gap energy with an increase in Bi mole fraction. The calculated values of band gap variation agree well with the available experimental data.

  7. On the theory of phonoriton in cubic semiconductors with a degenerate valence band

    International Nuclear Information System (INIS)

    Nguyen Ai Viet; Nguyen Thi Que Huong; Le Qui Thong

    1992-10-01

    The ''phonoriton'' is an elementary excitation constructed from an exciton polariton and phonon in semiconductors under intense excitation by an electromagnetic wave near the exciton resonance (L.V. Keldysh and A.L. Ivanov, 1982). In this paper we develop a theory of phonoriton in direct band gap cubic semiconductor with a degenerate valence band using the simple model of J.L. Birman and B.S. Wang (1990). In addition to experimental proofs of the existence of phonoriton we propose an experiment to measure its flight time. (author). 33 refs

  8. Optical gain and gain suppression of quantum-well lasers with valence band mixing

    International Nuclear Information System (INIS)

    Ahn, D.; Chuang, S.L.

    1990-01-01

    The effects of valence band mixing on the nonlinear gains of quantum-well lasers are studied theoretically. The authors' analysis is based on the multiband effective-mass theory and the density matrix formalism with intraband relaxation taken into account. The gain and the gain-suppression coefficient of a quantum-well laser are calculated from the complex optical susceptibility obtained by the density matrix formulation with the theoretical dipole moments obtained from the multiband effective-mass theory. The calculated gain spectrum shows that there are remarkable differences (both in peak amplitude and spectral shape) between our model with valence band mixing and the conventional parabolic band model. The shape of the gain spectrum calculated by the authors' model becomes more symmetric due to intraband relaxation together with nonparabolic energy dispersions and is closer to the experimental observations when compared with the conventional method using the parabolic band model and the multiband effective-mass calculation without intraband relaxation. Both give quite asymmetric gain spectra. Optical intensity in the GaAs active region is estimated by solving rate equations for the stationary states with nonlinear gain suppression. The authors calculate the mode gain for the resonant mode including the gain suppression, which results in spectral hole burning of the gain spectrum

  9. Convergence of valence bands for high thermoelectric performance for p-type InN

    International Nuclear Information System (INIS)

    Li, Hai-Zhu; Li, Ruo-Ping; Liu, Jun-Hui; Huang, Ming-Ju

    2015-01-01

    Band engineering to converge the bands to achieve high valley degeneracy is one of effective approaches for designing ideal thermoelectric materials. Convergence of many valleys in the valence band may lead to a high Seebeck coefficient, and induce promising thermoelectric performance of p-type InN. In the current work, we have systematically investigated the electronic structure and thermoelectric performance of wurtzite InN by using the density functional theory combined with semiclassical Boltzmann transport theory. Form the results, it can be found that intrinsic InN has a large Seebeck coefficient (254 μV/K) and the largest value of Z e T is 0.77. The transport properties of p-type InN are better than that of n-type one at the optimum carrier concentration, which mainly due to the large Seebeck coefficient for p-type InN, although the electrical conductivity of n-type InN is larger than that of p-type one. We found that the larger Seebeck coefficient for p-type InN may originate from the large valley degeneracy in the valence band. Moreover, the low minimum lattice thermal conductivity for InN is one key factor to become a good thermoelectric material. Therefore, p-type InN could be a potential material for further applications in the thermoelectric area.

  10. Auger electron emission initiated by the creation of valence-band holes in graphene by positron annihilation.

    Science.gov (United States)

    Chirayath, V A; Callewaert, V; Fairchild, A J; Chrysler, M D; Gladen, R W; Mcdonald, A D; Imam, S K; Shastry, K; Koymen, A R; Saniz, R; Barbiellini, B; Rajeshwar, K; Partoens, B; Weiss, A H

    2017-07-13

    Auger processes involving the filling of holes in the valence band are thought to make important contributions to the low-energy photoelectron and secondary electron spectrum from many solids. However, measurements of the energy spectrum and the efficiency with which electrons are emitted in this process remain elusive due to a large unrelated background resulting from primary beam-induced secondary electrons. Here, we report the direct measurement of the energy spectra of electrons emitted from single layer graphene as a result of the decay of deep holes in the valence band. These measurements were made possible by eliminating competing backgrounds by employing low-energy positrons (holes by annihilation. Our experimental results, supported by theoretical calculations, indicate that between 80 and 100% of the deep valence-band holes in graphene are filled via an Auger transition.

  11. Valence-band splitting energies in wurtzite InP nanowires: Photoluminescence spectroscopy and ab initio calculations

    Science.gov (United States)

    Gadret, E. G.; Dias, G. O.; Dacal, L. C. O.; de Lima, M. M., Jr.; Ruffo, C. V. R. S.; Iikawa, F.; Brasil, M. J. S. P.; Chiaramonte, T.; Cotta, M. A.; Tizei, L. H. G.; Ugarte, D.; Cantarero, A.

    2010-09-01

    We investigated experimentally and theoretically the valence-band structure of wurtzite InP nanowires. The wurtzite phase, which usually is not stable for III-V phosphide compounds, has been observed in InP nanowires. We present results on the electronic properties of these nanowires using the photoluminescence excitation technique. Spectra from an ensemble of nanowires show three clear absorption edges separated by 44 meV and 143 meV, respectively. The band edges are attributed to excitonic absorptions involving three distinct valence-bands labeled: A, B, and C. Theoretical results based on “ab initio” calculation gives corresponding valence-band energy separations of 50 meV and 200 meV, respectively, which are in good agreement with the experimental results.

  12. Valence band structures of InAs/GaAs quantum rings using the Fourier transform method

    International Nuclear Information System (INIS)

    Jia Boyong; Yu Zhongyuan; Liu Yumin

    2009-01-01

    The valence band structures of strained InAs/GaAs quantum rings are calculated, with the four-band k · p model, in the framework of effective-mass envelope function theory. When determining the Hamiltonian matrix elements, we develop the Fourier transform method instead of the widely used analytical integral method. Using Fourier transform, we have investigated the energy levels as functions of the geometrical parameters of the rings and compared our results with those obtained by the analytical integral method. The results show that the energy levels in the quantum rings change dramatically with the inner radius, outer radius, average radius, width, height of the ring and the distance between two adjacent rings. Our method can be adopted in low-dimensional structures with arbitrary shape. Our results are consistent with those in the literature and should be helpful for studying and fabricating optoelectronic devices

  13. Resonant photoemission at core-level shake-up thresholds: Valence-band satellites in nickel

    International Nuclear Information System (INIS)

    Bjoerneholm, O.; Andersen, J.N.; Wigren, C.; Nilsson, A.; Nyholm, R.; Ma; Ortensson, N.

    1990-01-01

    Three-hole satellites (3d 7 final-state configuration) in the nickel valence-band photoelectron spectrum have been identified at 13 and 18 eV binding energy with use of synchrotron radiation from the MAX storage ring. The three-hole satellites show resonances at photon energies close to the threshold for excitation of 3p 5 3d 9 core-hole shake-up states. The 13-eV satellite also shows a resonance directly at the 3p threshold. This is interpreted as an interference between the direct three-hole ionization and a shake-up transition in the Auger decay of the 3p hole. This shake-up process is also identified directly in the M 2,3 M 4,5 M 4,5 Auger spectrum

  14. Decay of Wannier-Mott excitons interacting with acoustic phonon in semiconductors with a degenerate valence band

    International Nuclear Information System (INIS)

    Nguyen Toan Thang; Nguyen Ai Viet; Nguyen Hong Quang

    1987-06-01

    Decay probabilities of light and heavy excitons interacting with acoustic phonons in cubic semiconductors with a degenerate valence band are calculated. The numerical results for GaAs showed that the decay probability of the light exciton is much greater than that of the heavy one. (author). 10 refs, 1 fig

  15. Experimental determination of conduction and valence bands of semiconductor nanoparticles using Kelvin probe force microscopy

    International Nuclear Information System (INIS)

    Zhang Wen; Chen Yongsheng

    2013-01-01

    The ability to determine a semiconductor’s band edge positions is important for the design of new photocatalyst materials. In this paper, we introduced an experimental method based on Kelvin probe force microscopy to determine the conduction and valence band edge energies of semiconductor nanomaterials, which has rarely been demonstrated. We tested the method on six semiconductor nanoparticles (α-Fe 2 O 3 , CeO 2 , Al 2 O 3 , CuO, TiO 2 , and ZnO) with known electronic structures. The experimentally determined band edge positions for α-Fe 2 O 3 , Al 2 O 3 , and CuO well matched the literature values with no statistical difference. Except CeO 2 , all other metal oxides had a consistent upward bias in the experimental measurements of band edge positions because of the shielding effect of the adsorbed surface water layer. This experimental approach may outstand as a unique alternative way of probing the band edge energy positions of semiconductor materials to complement the current computational methods, which often find limitations in new synthetic or complex materials. Ultimately, this work provides scientific foundation for developing experimental tools to probe nanoscale electronic properties of photocatalytic materials, which will drive breakthroughs in the design of novel photocatalytic systems and advance the fundamental understanding of material properties.

  16. Crossover and valence band Kβ X-rays of chromium oxides

    International Nuclear Information System (INIS)

    Fazinic, Stjepko; Mandic, Luka; Kavcic, Matjaz; Bozicevic, Iva

    2011-01-01

    Kβ X-ray spectra of chromium metal and selected chromium oxides were measured twice using medium resolution flat crystal spectrometer and high resolution spectrometer employing Johansson geometry after excitation with 2 MeV proton beams. The positions and intensities of crossover (Kβ'') and valence (Kβ 2,5 ) band X-rays relative to the primary Kβ X-ray components were extracted in a consistent way. The results were compared with the existing data obtained by proton and photon induced ionization mechanisms and theoretical predictions. The obtained results in peak relative positions and intensities were analyzed in order to study dependence on the chromium oxidation states and chromium-oxygen bond lengths in selected chromium oxides. Our results obtained by both spectrometers confirm that the linear trend observed for the valence peak relative energy shift as a function of chromium oxidation number does not depend on the experimental resolution. Experimental results for normalized intensities (i.e. relative intensities divided with the number of chromium-oxygen pairs) of crossover and valence band X-rays obtained by both spectrometers are in very good agreement, and follow exponential relationship with the average Cr-O bond lengths in corresponding chromium oxides. The observed trends in crossover and valence X-rays normalized intensities could be used to measure the average chromium-oxygen bond length in various chromium oxides, with the sum of both crossover and valence X-ray normalized intensities being the most sensitive measure.

  17. Simultaneous Conduction and Valence Band Quantization in Ultrashallow High-Density Doping Profiles in Semiconductors

    Science.gov (United States)

    Mazzola, F.; Wells, J. W.; Pakpour-Tabrizi, A. C.; Jackman, R. B.; Thiagarajan, B.; Hofmann, Ph.; Miwa, J. A.

    2018-01-01

    We demonstrate simultaneous quantization of conduction band (CB) and valence band (VB) states in silicon using ultrashallow, high-density, phosphorus doping profiles (so-called Si:P δ layers). We show that, in addition to the well-known quantization of CB states within the dopant plane, the confinement of VB-derived states between the subsurface P dopant layer and the Si surface gives rise to a simultaneous quantization of VB states in this narrow region. We also show that the VB quantization can be explained using a simple particle-in-a-box model, and that the number and energy separation of the quantized VB states depend on the depth of the P dopant layer beneath the Si surface. Since the quantized CB states do not show a strong dependence on the dopant depth (but rather on the dopant density), it is straightforward to exhibit control over the properties of the quantized CB and VB states independently of each other by choosing the dopant density and depth accordingly, thus offering new possibilities for engineering quantum matter.

  18. Energy shift and conduction-to-valence band transition mediated by a time-dependent potential barrier in graphene

    Science.gov (United States)

    Chaves, Andrey; da Costa, D. R.; de Sousa, G. O.; Pereira, J. M.; Farias, G. A.

    2015-09-01

    We investigate the scattering of a wave packet describing low-energy electrons in graphene by a time-dependent finite-step potential barrier. Our results demonstrate that, after Klein tunneling through the barrier, the electron acquires an extra energy which depends on the rate of change of the barrier height with time. If this rate is negative, the electron loses energy and ends up as a valence band state after leaving the barrier, which effectively behaves as a positively charged quasiparticle.

  19. Characterization of MBE-grown InAlN/GaN heterostructure valence band offsets with varying In composition

    Energy Technology Data Exchange (ETDEWEB)

    Jiao, Wenyuan, E-mail: wyjiaonju@gmail.com; Kong, Wei; Li, Jincheng; Kim, Tong-Ho; Brown, April S. [Department of Electrical and Computer Engineering, Duke University, Durham, NC, 27708 (United States); Collar, Kristen [Department of Physics, Duke University, Durham, NC, 27708 (United States); Losurdo, Maria [CNR-NANOTEC, Istituto di Nanotecnologia, via Orabona, 4-70126 Bari (Italy)

    2016-03-15

    Angle-resolved X-ray photoelectron spectroscopy (XPS) is used in this work to experimentally determine the valence band offsets of molecular beam epitaxy (MBE)-grown InAlN/GaN heterostructures with varying indium composition. We find that the internal electric field resulting from polarization must be taken into account when analyzing the XPS data. Valence band offsets of 0.12 eV for In{sub 0.18}Al{sub 0.82}N, 0.15 eV for In{sub 0.17}Al{sub 0.83}N, and 0.23 eV for In{sub 0.098}Al{sub 0.902}N with GaN are obtained. The results show that a compositional-depended bowing parameter is needed in order to estimate the valence band energies of InAlN as a function of composition in relation to those of the binary endpoints, AlN and InN.

  20. Characterization of MBE-grown InAlN/GaN heterostructure valence band offsets with varying In composition

    Directory of Open Access Journals (Sweden)

    Wenyuan Jiao

    2016-03-01

    Full Text Available Angle-resolved X-ray photoelectron spectroscopy (XPS is used in this work to experimentally determine the valence band offsets of molecular beam epitaxy (MBE-grown InAlN/GaN heterostructures with varying indium composition. We find that the internal electric field resulting from polarization must be taken into account when analyzing the XPS data. Valence band offsets of 0.12 eV for In0.18Al0.82N, 0.15 eV for In0.17Al0.83N, and 0.23 eV for In0.098Al0.902N with GaN are obtained. The results show that a compositional-depended bowing parameter is needed in order to estimate the valence band energies of InAlN as a function of composition in relation to those of the binary endpoints, AlN and InN.

  1. Valence band offset of wurtzite InN/SrTiO3 heterojunction measured by x-ray photoelectron spectroscopy

    Directory of Open Access Journals (Sweden)

    Li Zhiwei

    2011-01-01

    Full Text Available Abstract The valence band offset (VBO of wurtzite indium nitride/strontium titanate (InN/SrTiO3 heterojunction has been directly measured by x-ray photoelectron spectroscopy. The VBO is determined to be 1.26 ± 0.23 eV and the conduction band offset is deduced to be 1.30 ± 0.23 eV, indicating the heterojunction has a type-I band alignment. The accurate determination of the valence and conduction band offsets paves a way to the applications of integrating InN with the functional oxide SrTiO3.

  2. Ab-initio calculation of the valence-band offset at strained GaAs/InAs (001) heterojunction

    International Nuclear Information System (INIS)

    Tit, N.; Peressi, M.

    1993-06-01

    We present a self consistent pseudopotential calculation of the valence band offset (VBO) at GaAs/InAs (001) strained heterojunction, which is chose as an example of the isovalent polar with common-anion lattice mismatched heterojunctions. The effects of strain are studied by looking at the variation of the VBO versus the in plane lattice constant, which is imposed by the substrate. Our results show that the VBO can be tuned by about 0.17 eV going from GaAs to InAs substrates. Comparison of our work with the available experimental and theoretical results is also discussed. (author). 25 refs, 3 figs, 5 tabs

  3. Valence band structure of PDMS surface and a blend with MWCNTs: A UPS and MIES study of an insulating polymer

    Energy Technology Data Exchange (ETDEWEB)

    Schmerl, Natalya M.; Khodakov, Dmitriy A.; Stapleton, Andrew J.; Ellis, Amanda V.; Andersson, Gunther G., E-mail: gunther.andersson@flinders.edu.au

    2015-10-30

    Graphical abstract: - Highlights: • Valence electron spectroscopy was performed on an insulating polymer using different charge compensation methods. • MWCNT were embedded in PDMS and found to be the most effective method for reducing the charging of the insulating polymer. • The valence band spectrum of PDMS was obtained via MIES and UPS. • Ion scattering spectroscopy was used to determine the concentration depth profile of the PDMS in the sample. - Abstract: The use of polydimethylsiloxane (PDMS) is increasing with new technologies working toward compact, flexible and transparent devices for use in medical and microfluidic systems. Electronic characterization of PDMS and other insulating materials is difficult due to charging, yet necessary for many applications where the interfacial structure is vital to device function or further modification. The outermost layer in particular is of importance as this is the area where chemical reactions such as surface functionalization will occur. Here, we investigate the valence band structure of the outermost layer and near surface area of PDMS through the use of metastable induced photoelectron spectroscopy (MIES) paired with ultraviolet photoelectron spectroscopy (UPS). The chemical composition of the samples under investigation were measured via X-ray photoelectron spectroscopy (XPS), and the vertical distribution of the polymer was shown with neutral impact collision ion scattering spectroscopy (NICISS). Three separate methods for charge compensation are used for the samples, and their effectiveness is compared.

  4. Internal-strain effect on the valence band of strained silicon and its correlation with the bond angles

    Energy Technology Data Exchange (ETDEWEB)

    Inaoka, Takeshi, E-mail: inaoka@phys.u-ryukyu.ac.jp; Yanagisawa, Susumu; Kadekawa, Yukihiro [Department of Physics and Earth Sciences, Faculty of Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213 (Japan)

    2014-02-14

    By means of the first-principles density-functional theory, we investigate the effect of relative atom displacement in the crystal unit cell, namely, internal strain on the valence-band dispersion of strained silicon, and find close correlation of this effect with variation in the specific bond angles due to internal strain. We consider the [111] ([110]) band dispersion for (111) ((110)) biaxial tensility and [111] ([110]) uniaxial compression, because remarkably small values of hole effective mass m* can be obtained in this dispersion. Under the practical condition of no normal stress, biaxial tensility (uniaxial compression) involves additional normal compression (tensility) and internal strain. With an increase in the internal-strain parameter, the energy separation between the highest and second-highest valence bands becomes strikingly larger, and the highest band with conspicuously small m* extends remarkably down to a lower energy region, until it intersects or becomes admixed with the second band. This is closely correlated with the change in the specific bond angles, and this change can reasonably explain the above enlargement of the band separation.

  5. Valence Band Structure of InAs1−xBix and InSb1−xBix Alloy Semiconductors Calculated Using Valence Band Anticrossing Model

    Science.gov (United States)

    Samajdar, D. P.; Dhar, S.

    2014-01-01

    The valence band anticrossing model has been used to calculate the heavy/light hole and spin-orbit split-off energies in InAs1−xBix and InSb1−xBix alloy systems. It is found that both the heavy/light hole, and spin-orbit split E + levels move upwards in energy with an increase in Bi content in the alloy, whereas the split E − energy for the holes shows a reverse trend. The model is also used to calculate the reduction of band gap energy with an increase in Bi mole fraction. The calculated values of band gap variation agree well with the available experimental data. PMID:24592181

  6. Valence band structure of InAs(1-x)Bi(x) and InSb(1-x)Bi(x) alloy semiconductors calculated using valence band anticrossing model.

    Science.gov (United States)

    Samajdar, D P; Dhar, S

    2014-01-01

    The valence band anticrossing model has been used to calculate the heavy/light hole and spin-orbit split-off energies in InAs(1-x)Bi(x) and InSb(1-x)Bi(x) alloy systems. It is found that both the heavy/light hole, and spin-orbit split E + levels move upwards in energy with an increase in Bi content in the alloy, whereas the split E - energy for the holes shows a reverse trend. The model is also used to calculate the reduction of band gap energy with an increase in Bi mole fraction. The calculated values of band gap variation agree well with the available experimental data.

  7. Determination of the impact of Bi content on the valence band energy of GaAsBi using x-ray photoelectron spectroscopy

    Directory of Open Access Journals (Sweden)

    K. Collar

    2017-07-01

    Full Text Available We investigate the change of the valence band energy of GaAs1-xBix (0valence band energy per addition of 1 % Bi is determined for strained and unstrained thin films using a linear approximation applicable to the dilute regime. Spectroscopic ellipsometry (SE was used as a complementary technique to determine the change in GaAsBi bandgap resulting from Bi addition. Analysis of SE and XPS data together supports the conclusion that ∼75% of the reduction in the bandgap is in the valence band for a compressively strained, dilute GaAsBi thin film at room temperature.

  8. Determination of the valence-band offset of CdS/CIS solar cell devices by target factor analysis

    Energy Technology Data Exchange (ETDEWEB)

    Niles, D.W.; Contreras, M.; Ramanathan, K.; Noufi, R. [National Renewable Energy Lab., Golden, CO (United States)

    1996-05-01

    X-ray photoemission spectroscopy (XPS) is used to determine and compare the valence-band offsets ({Delta}E{sub v}) for CdS grown by chemical bath deposition on single-crystal and thin-film CuInSe{sub 2} (CIS). The thin-film CIS device was suitable for photovoltaic energy production. By sputtering through the CdS/CIS interface and reducing the depth profile with target factor analysis, the magnitude of {Delta}E{sub v} was determined to be {Delta}E{sub v} = 1.06 {+-} 0.15 eV for both the single-crystal and thin-film interfaces. This determination of {Delta}E{sub v} is about 0.25 eV larger than many previously reported estimations CdS grown by physical vapor deposition on CIS and helps explain the record performance of CdS/CIS photovoltaic devices.

  9. Electronic properties and bonding in Zr Hx thin films investigated by valence-band x-ray photoelectron spectroscopy

    Science.gov (United States)

    Magnuson, Martin; Schmidt, Susann; Hultman, Lars; Högberg, Hans

    2017-11-01

    The electronic structure and chemical bonding in reactively magnetron sputtered Zr Hx (x =0.15 , 0.30, 1.16) thin films with oxygen content as low as 0.2 at.% are investigated by 4d valence band, shallow 4p core-level, and 3d core-level x-ray photoelectron spectroscopy. With increasing hydrogen content, we observe significant reduction of the 4d valence states close to the Fermi level as a result of redistribution of intensity toward the H 1s-Zr 4d hybridization region at ˜6 eV below the Fermi level. For low hydrogen content (x =0.15 , 0.30), the films consist of a superposition of hexagonal closest-packed metal (α phase) and understoichiometric δ -Zr Hx (Ca F2 -type structure) phases, while for x =1.16 , the films form single-phase Zr Hx that largely resembles that of stoichiometric δ -Zr H2 phase. We show that the cubic δ -Zr Hx phase is metastable as thin film up to x =1.16 , while for higher H contents the structure is predicted to be tetragonally distorted. For the investigated Zr H1.16 film, we find chemical shifts of 0.68 and 0.51 eV toward higher binding energies for the Zr 4 p3 /2 and 3 d5 /2 peak positions, respectively. Compared to the Zr metal binding energies of 27.26 and 178.87 eV, this signifies a charge transfer from Zr to H atoms. The change in the electronic structure, spectral line shapes, and chemical shifts as a function of hydrogen content is discussed in relation to the charge transfer from Zr to H that affects the conductivity by charge redistribution in the valence band.

  10. Valence band offset of β-Ga2O3/wurtzite GaN heterostructure measured by X-ray photoelectron spectroscopy.

    Science.gov (United States)

    Wei, Wei; Qin, Zhixin; Fan, Shunfei; Li, Zhiwei; Shi, Kai; Zhu, Qinsheng; Zhang, Guoyi

    2012-10-10

    A sample of the β-Ga2O3/wurtzite GaN heterostructure has been grown by dry thermal oxidation of GaN on a sapphire substrate. X-ray diffraction measurements show that the β-Ga2O3 layer was formed epitaxially on GaN. The valence band offset of the β-Ga2O3/wurtzite GaN heterostructure is measured by X-ray photoelectron spectroscopy. It is demonstrated that the valence band of the β-Ga2O3/GaN structure is 1.40 ± 0.08 eV.

  11. State density of valence-band tail and photoconductivity amorphous hydrogenated silicon

    International Nuclear Information System (INIS)

    Golikova, O.A.; Domashevskaya, Eh.P.; Mezdrogina, M.M.; Sorokina, K.L.; Terekhov, V.A.; Trostyanskij, S.N.

    1991-01-01

    Relation between photoconductivity and g(ε) mobility gap within the range adjoining to the top (mobility end) of valent zone (VZ tail) in a-Si:H film is studied. Stationary photoconductivity within spectral maximum range (χ=0.63μm) at Φ=10 17 photxcm -2 s -1 flow is measured. Density of g(ε) states are controlled using ultrasoft X-ray emission spectroscopy. It is shown, that correlation between photoconductivity and width of VZ tail may reflect the fact of their similar dependence o film heterogeneity: at the increase of share of microholes there occur both expansion of VZ tail and growth of number of respective hydrogen complexes and torn relations which results in drop of photoconductivity

  12. Effects of surface condition on the work function and valence-band position of ZnSnN2

    Science.gov (United States)

    Shing, Amanda M.; Tolstova, Yulia; Lewis, Nathan S.; Atwater, Harry A.

    2017-12-01

    ZnSnN2 is an emerging wide band gap earth-abundant semiconductor with potential applications in photonic devices such as solar cells, LEDs, and optical sensors. We report the characterization by ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy of reactively radio-frequency sputtered II-IV-nitride ZnSnN2 thin films. For samples transferred in high vacuum, the ZnSnN2 surface work function was 4.0 ± 0.1 eV below the vacuum level, with a valence-band onset of 1.2 ± 0.1 eV below the Fermi level. The resulting band diagram indicates that the degenerate bulk Fermi level position in ZnSnN2 shifts to mid-gap at the surface due to band bending that results from equilibration with delocalized surface states within the gap. Brief (< 10 s) exposures to air, a nitrogen-plasma treatment, or argon-ion sputtering caused significant chemical changes at the surface, both in surface composition and interfacial energetics. The relative band positioning of the n-type semiconductor against standard redox potentials indicated that ZnSnN2 has an appropriate energy band alignment for use as a photoanode to effect the oxygen-evolution reaction.

  13. Polarization Dependent Bulk-sensitive Valence Band Photoemission Spectroscopy and Density Functional Theory Calculations: Part I. 3d Transition Metals

    Science.gov (United States)

    Ueda, Shigenori; Hamada, Ikutaro

    2017-12-01

    The X-ray polarization dependent valence band HAXPES spectra of 3d transition metals (TMs) of Ti-Zn were measured to investigate the orbital resolved electronic structures by utilizing that the fact the photoionization cross-section of the atomic orbitals strongly depends on the experimental geometry. We have calculated the HAXPES spectra, which correspond to the cross-section weighted densities of states (CSW-DOSs), where the DOSs were obtained by the density functional theory calculations, and we have determined the relative photoionization cross-sections of the 4s and 4p orbitals to the 3d orbital in the 3d TMs. The experimentally obtained bulk-sensitive 3d and 4s DOSs were good agreement with the calculated DOSs in Ti, V, Cr, and Cu. In contrast, the deviations between the experimental and calculated 3d DOSs for Mn, Fe, Co, Ni were found, suggesting that the electron correlation plays an important role in the electronic structures for these materials.

  14. Valence-band and core-level photoemission study of single-crystal Bi2CaSr2Cu2O8 superconductors

    International Nuclear Information System (INIS)

    Shen, Z.; Lindberg, P.A.P.; Wells, B.O.; Mitzi, D.B.; Lindau, I.; Spicer, W.E.; Kapitulnik, A.

    1988-01-01

    High-quality single crystals of Bi 2 CaSr 2 Cu 2 O 8 superconductors have been prepared and cleaved in ultrahigh vacuum. Low-energy electron diffraction measurements show that the surface structure is consistent with the bulk crystal structure. Ultraviolet photoemission and x-ray photoemission experiments were performed on these well-characterized sample surfaces. The valence-band and the core-level spectra obtained from the single-crystal surfaces are in agreement with spectra recorded from polycrystalline samples, justifying earlier results from polycrystalline samples. Cu satellites are observed both in the valence band and Cu 2p core level, signaling the strong correlation among the Cu 3d electrons. The O 1s core-level data exhibit a sharp, single peak at 529-eV binding energy without any clear satellite structures

  15. Features of carrier tunneling between the silicon valence band and metal in devices based on the Al/high-K oxide/SiO_2/Si structure

    International Nuclear Information System (INIS)

    Vexler, M. I.; Grekhov, I. V.

    2016-01-01

    The features of electron tunneling from or into the silicon valence band in a metal–insulator–semiconductor system with the HfO_2(ZrO_2)/SiO_2 double-layer insulator are theoretically analyzed for different modes. It is demonstrated that the valence-band current plays a less important role in structures with HfO_2(ZrO_2)/SiO_2 than in structures containing only silicon dioxide. In the case of a very wide-gap high-K oxide ZrO_2, nonmonotonic behavior related to tunneling through the upper barrier is predicted for the valence-band–metal current component. The use of an insulator stack can offer certain advantages for some devices, including diodes, bipolar tunnel-emitter transistors, and resonant-tunneling diodes, along with the traditional use of high-K insulators in a field-effect transistor.

  16. Validation of voxel-based morphometry (VBM) based on MRI

    Science.gov (United States)

    Yang, Xueyu; Chen, Kewei; Guo, Xiaojuan; Yao, Li

    2007-03-01

    Voxel-based morphometry (VBM) is an automated and objective image analysis technique for detecting differences in regional concentration or volume of brain tissue composition based on structural magnetic resonance (MR) images. VBM has been used widely to evaluate brain morphometric differences between different populations, but there isn't an evaluation system for its validation until now. In this study, a quantitative and objective evaluation system was established in order to assess VBM performance. We recruited twenty normal volunteers (10 males and 10 females, age range 20-26 years, mean age 22.6 years). Firstly, several focal lesions (hippocampus, frontal lobe, anterior cingulate, back of hippocampus, back of anterior cingulate) were simulated in selected brain regions using real MRI data. Secondly, optimized VBM was performed to detect structural differences between groups. Thirdly, one-way ANOVA and post-hoc test were used to assess the accuracy and sensitivity of VBM analysis. The results revealed that VBM was a good detective tool in majority of brain regions, even in controversial brain region such as hippocampus in VBM study. Generally speaking, much more severity of focal lesion was, better VBM performance was. However size of focal lesion had little effects on VBM analysis.

  17. Effect of phase formation on valence band photoemission and photoresonance study of Ti/Ni multilayers using synchrotron radiation

    International Nuclear Information System (INIS)

    Bhatt, Pramod; Chaudhari, S.M.

    2006-01-01

    This paper presents investigation of Ti-Ni alloy phase formation and its effect on valence band (VB) photoemission and photoresonance study of as-deposited as well as annealed Ti/Ni multilayers (MLs) up to 600 deg. C using synchrotron radiation. For this purpose [Ti (50 A)/Ni (50 A)]X 10 ML structures were deposited by using electron-beam evaporation technique under ultra-high vacuum (UHV) conditions. Formation of different phases of Ti-Ni alloy due to annealing treatment has been confirmed by the X-ray diffraction (XRD) technique. The XRD pattern corresponding as-deposited ML sample shows crystalline nature of both Ti and Ni deposited layers, whereas 300 deg. C annealed ML sample show solid-state reaction (SSR) leading to amorphization and subsequent recrystallisation at higher temperatures of annealing (≥400 deg. C) with the formation of TiNi, TiNi 3 and Ti 2 Ni alloy phases. The survey scans corresponding to 400, 500 and 600 deg. C annealed ML sample shows interdiffusion and intermixing of Ni atoms into Ti layers leading to chemical Ti-Ni alloys phase formation at interface. The corresponding recorded VB spectra using synchrotron radiation at 134 eV on as-deposited ML sample with successive sputtering shows alternately photoemission bands due to Ti 3d and Ni 3d, respectively, indicating there is no mixing of the consequent layers and any phase formation at the interface during deposition. However, ML samples annealed at higher temperatures of annealing, particularly at 400, 500 and 600 deg. C show a clear shift in Ni 3d band and its satellite peak position to higher BE side indicates Ti-Ni alloy phase formation. In addition to this, reduction of satellite peak intensity and Ni 3d density of states (DOS) near Fermi level is also observed due to Ti-Ni phase formation with higher annealing temperatures. The variable photon energy VB measurements on as-deposited and ML samples annealed at 400 deg. C confirms existence and BE position of observed Ni 3d satellite

  18. First determination of the valence band dispersion of CH3NH3PbI3 hybrid organic-inorganic perovskite

    Science.gov (United States)

    Lee, Min-I.; Barragán, Ana; Nair, Maya N.; Jacques, Vincent L. R.; Le Bolloc'h, David; Fertey, Pierre; Jemli, Khaoula; Lédée, Ferdinand; Trippé-Allard, Gaëlle; Deleporte, Emmanuelle; Taleb-Ibrahimi, Amina; Tejeda, Antonio

    2017-07-01

    The family of hybrid organic-inorganic halide perovskites is in the limelight because of their recently discovered high photovoltaic efficiency. These materials combine photovoltaic energy conversion efficiencies exceeding 22% and low-temperature and low-cost processing in solution; a breakthrough in the panorama of renewable energy. Solar cell operation relies on the excitation of the valence band electrons to the conduction band by solar photons. One factor strongly impacting the absorption efficiency is the band dispersion. The band dispersion has been extensively studied theoretically, but no experimental information was available. Herein, we present the first experimental determination of the valence band dispersion of methylammonium lead halide in the tetragonal phase. Our results pave the way for contrasting the electronic hopping or the electron effective masses in different theories by comparing to our experimental bands. We also show a significant broadening of the electronic states, promoting relaxed conditions for photon absorption, and demonstrate that the tetragonal structure associated to the octahedra network distortion below 50 °C induces only a minor modification of the electronic bands, with respect to the cubic phase at high temperature, thus minimizing the impact of the cubic-tetragonal transition on solar cell efficiencies.

  19. Valence-band discontinuities of wurtzite GaN, AlN, and InN heterojunctions measured by x-ray photoemission spectroscopy

    International Nuclear Information System (INIS)

    Martin, G.; Botchkarev, A.; Rockett, A.; Morkoc, H.

    1996-01-01

    The valence-band discontinuities at various wurtzite GaN, AlN, and InN heterojunctions were measured by means of x-ray photoemission spectroscopy. A significant forward endash backward asymmetry was observed in the InN/GaN endash GaN/InN and InN/AlN endash AlN/InN heterojunctions. The asymmetry was understood as a piezoelectric strain effect. We report the valence band discontinuities for InN/GaN=1.05±0.25 eV, GaN/AlN=0.70±0.24 eV, and InN/AlN=1.81±0.20 eV, all in the standard type I lineup. These values obey transitivity to within the experimental accuracy. Tables of photoemission core level binding energies are reported for wurtzite GaN, AlN, and InN. copyright 1996 American Institute of Physics

  20. Advancing a Distributive-Bargaining and Integrative-Negotiation Integral System: A Values-Based Negotiation Model (VBM

    Directory of Open Access Journals (Sweden)

    Ivan Gan

    2017-09-01

    Full Text Available The proposed values-based negotiation model (VBM agrees with and extends principled negotiation’s recognition of personal values and emotions as important negotiation elements. First, building upon Martin Buber’s existentialist treatment of religion and secularism, VBM centers on religion as one of many possible sources of personal values that informs respectful and mutually beneficial interactions without needing one to necessarily be religious. Just as one need not be a Buddhist or a Hindu to practice yoga, negotiators of any theological outlook can profit from a model grounded in broad, common tenets drawn from a range of organized religions. Second, VBM distinguishes feelings from emotions because the long-lasting and intrinsically stimulated effects of feelings have greater implications on the perception of negotiated outcomes. VBM negotiators view negotiations as a constitutive prosocial process whereby parties consider the outcome important enough to invest time and energy. Negotiators who use VBM appeal to the goodness of their counterparts by doing good first so that both parties avoid a win-lose outcome. This counterintuitive move contradicts the self-centered but understandably normal human behavior of prioritizing one’s own interests before others’ interests. However, when one appeals to the goodness of one’s Buberian Thou counterparts, he or she stimulates positive emotions that promote understanding. Third, VBM provides a framework that draws upon an individual’s personal values (religious or otherwise and reconfigures the distributive-bargaining-and-integrative-negotiation distinction so that negotiators can freely apply distributive tactics to claim maximum intangible and tangible outcomes without compromising on their personal values or valuable relationships.

  1. Measurement of the valence band-offset in a PbSe/ZnO heterojunction by x-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Li Lin; Qiu Jijun; Weng Binbin; Yuan Zijian; Shi Zhisheng [School of Electrical and Computer Engineering, University of Oklahoma, Norman, Oklahoma 73019 (United States); Li Xiaomin; Gan Xiaoyan [State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Sellers, Ian R. [Deparment of Physics, University of Oklahoma, Norman, Oklahoma 73019 (United States)

    2012-12-24

    A heterojunction of PbSe/ZnO has been grown by molecular beam epitaxy. X-ray photoelectron spectroscopy was used to directly measure the valence-band offset (VBO) of the heterojunction. The VBO, {Delta}E{sub V}, was determined as 2.51 {+-} 0.05 eV using the Pb 4p{sup 3/2} and Zn 2p{sup 3/2} core levels as a reference. The conduction-band offset, {Delta}E{sub C}, was, therefore, determined to be 0.59 {+-} 0.05 eV based on the above {Delta}E{sub V} value. This analysis indicates that the PbSe/ZnO heterojunction forms a type I (Straddling Gap) heterostructure.

  2. Chemical state analysis of heat-treated 6, 13-bis(triisopropylsilylethynyl) pentacene investigated by XPS valence band spectra, XANES spectra and first-principles calculation

    International Nuclear Information System (INIS)

    Muro, Maiko; Natsume, Yutaka; Kikuma, Jun; Setoyama, Hiroyuki

    2014-01-01

    X-ray photoelectron spectroscopy (XPS) valence band spectra reflect the chemical bonding states. To take this advantage, we tried to interpret experimental spectra by the occupied density of states (DOS) based on first principles calculation. In this work, we discussed XPS and X-ray Absorption Near Edge Structure (XANES) spectra of 6, 13-bis(triisopropylsilylethynyl) pentacene (TIPS-Pen), which is well known as an organic semiconductor. We studied chemical structure change of TIPS-Pen caused by heat-treatment at 300degC under nitrogen and under the air. It has been suggested that the structural change of pentacene skeleton by Diels-Alder type reaction occurs in both cases. In addition, the sample heat-treated under the air showed desorption of the isopropyl group and increase of oxygen concentration. (author)

  3. Valence band electronic structure of Ho-doped La0.67Ca0.33MnO3 using ultra-violet photoemission spectroscopy

    Science.gov (United States)

    Rout, S. K.; Mukharjee, R. N.; Mishra, D. K.; Roul, B. K.; Sekhar, B. R.; Dalai, M. K.

    2017-05-01

    In this manuscript we report the valence band electronic structure of Ho doped La0.67Ca0.33MnO3 using ultraviolet photoemission spectroscopy. We compared the density of states of La0.67Ca0.33MnO3, La0.67Ca0.3Ho0.03MnO3 and La0.64Ho0.03Ca0.33MnO3 near the Fermi level at various temperatures. Significant amount of changes have been observed at higher temperatures (220 K and 300 K) where the near Fermi level density of states increases with Ho doping into La0.67Ca0.33MnO3 indicating the enhancement of magnitude of change in metallicity (conductivity).

  4. Valence band structure and density of states effective mass model of biaxial tensile strained silicon based on k · p theory

    International Nuclear Information System (INIS)

    Kuang Qian-Wei; Liu Hong-Xia; Wang Shu-Long; Qin Shan-Shan; Wang Zhi-Lin

    2011-01-01

    After constructing a stress and strain model, the valence bands of in-plane biaxial tensile strained Si is calculated by k · p method. In the paper we calculate the accurate anisotropy valance bands and the splitting energy between light and heavy hole bands. The results show that the valance bands are highly distorted, and the anisotropy is more obvious. To obtain the density of states (DOS) effective mass, which is a very important parameter for device modeling, a DOS effective mass model of biaxial tensile strained Si is constructed based on the valance band calculation. This model can be directly used in the device model of metal—oxide semiconductor field effect transistor (MOSFET). It also a provides valuable reference for biaxial tensile strained silicon MOSFET design. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  5. Interplay of Coulomb interactions and disorder in three-dimensional quadratic band crossings without time-reversal symmetry and with unequal masses for conduction and valence bands

    Science.gov (United States)

    Mandal, Ipsita; Nandkishore, Rahul M.

    2018-03-01

    Coulomb interactions famously drive three-dimensional quadratic band crossing semimetals into a non-Fermi liquid phase of matter. In a previous work [Nandkishore and Parameswaran, Phys. Rev. B 95, 205106 (2017), 10.1103/PhysRevB.95.205106], the effect of disorder on this non-Fermi liquid phase was investigated, assuming that the band structure was isotropic, assuming that the conduction and valence bands had the same band mass, and assuming that the disorder preserved exact time-reversal symmetry and statistical isotropy. It was shown that the non-Fermi liquid fixed point is unstable to disorder and that a runaway flow to strong disorder occurs. In this paper, we extend that analysis by relaxing the assumption of time-reversal symmetry and allowing the electron and hole masses to differ (but continuing to assume isotropy of the low energy band structure). We first incorporate time-reversal symmetry breaking disorder and demonstrate that there do not appear any new fixed points. Moreover, while the system continues to flow to strong disorder, time-reversal-symmetry-breaking disorder grows asymptotically more slowly than time-reversal-symmetry-preserving disorder, which we therefore expect should dominate the strong-coupling phase. We then allow for unequal electron and hole masses. We show that whereas asymmetry in the two masses is irrelevant in the clean system, it is relevant in the presence of disorder, such that the `effective masses' of the conduction and valence bands should become sharply distinct in the low-energy limit. We calculate the RG flow equations for the disordered interacting system with unequal band masses and demonstrate that the problem exhibits a runaway flow to strong disorder. Along the runaway flow, time-reversal-symmetry-preserving disorder grows asymptotically more rapidly than both time-reversal-symmetry-breaking disorder and the Coulomb interaction.

  6. Thickness-dependent change in the valence band offset of the SiO{sub 2}/Si interface studied using synchrotron-radiation photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Toyoda, S., E-mail: toyoda.satoshi.4w@kyoto-u.ac.jp; Oshima, M. [Department of Applied Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2016-08-28

    We have studied the thickness-dependent change in the valence band offset (VBO) of the SiO{sub 2}/Si(001) interface using synchrotron-radiation photoemission spectroscopy with soft and hard X-rays. The SiO{sub 2}-film thickness (T{sub ox}) and X-ray irradiation time (t{sub irrad}) were systematically parameterized to distinguish between the “intrinsic” T{sub ox} effects in the VBOs and the “extrinsic” differential charging phenomena in SiO{sub 2} films on Si substrates. The results revealed that at a spontaneous time (t{sub irrad} ≈ 5 s) that suppresses the differential charging phenomena as much as possible, the experimental VBO abruptly increases as a function of T{sub ox} and gradually saturates to the traditional VBO value range determined by the internal photoemission and photoconduction measurements. This effect is not attributed to the differential charging phenomena, but rather it is attributed to the “intrinsic” T{sub ox}-dependent change in the VBO. The two possible physical behaviors include electronic polarization and image charge. We have derived the electronic polarization contribution from experimental data by carefully describing the effects of the long-range image charges based on the classical dielectric-screening model.

  7. Large shift and small broadening of Br2 valence band upon dimer formation with H2O: an ab initio study.

    Science.gov (United States)

    Franklin-Mergarejo, Ricardo; Rubayo-Soneira, Jesus; Halberstadt, Nadine; Ayed, Tahra; Bernal-Uruchurtu, Margarita I; Hernández-Lamoneda, Ramón; Janda, Kenneth C

    2011-06-16

    Valence electronic excitation spectra are calculated for the H(2)O···Br(2) complex using highly correlated ab initio potentials for both the ground and the valence electronic excited states and a 2-D approximation for vibrational motion. Due to the strong interaction between the O-Br and the Br-Br stretching motions, inclusion of these vibrations is the minimum necessary for the spectrum calculation. A basis set calculation is performed to determine the vibrational wave functions for the ground electronic state and a wave packet simulation is conducted for the nuclear dynamics on the excited state surfaces. The effects of both the spin-orbit interaction and temperature on the spectra are explored. The interaction of Br(2) with a single water molecule induces nearly as large a shift in the spectrum as is observed for an aqueous solution. In contrast, complex formation has a remarkably small effect on the T = 0 K width of the valence bands due to the fast dissociation of the dihalogen bond upon excitation. We therefore conclude that the widths of the spectra in aqueous solution are mostly due to inhomogeneous broadening. © 2011 American Chemical Society

  8. Valence band electronic structure and band alignment of LaAlO{sub 3}/SrTiO{sub 3}(111) heterointerfaces

    Energy Technology Data Exchange (ETDEWEB)

    Gabel, J.; Scheiderer, P.; Zapf, M.; Schuetz, P.; Sing, M.; Claessen, R. [Physikalisches Institut and Roentgen Center for Complex Material Systems (RCCM), Universitaet Wuerzburg (Germany); Schlueter, C.; Lee, T.L. [Diamond Light Source, Didcot (United Kingdom)

    2015-07-01

    As in the famous LaAlO{sub 3}(LAO)/SrTiO{sub 3}(STO) (001) a two-dimensional electron system (2DES) also forms at the interface between LAO and STO in (111) orientation. A distinct feature of the (111) interface is its peculiar real space topology. Each bilayer represents a buckled honeycomb lattice similar to graphene which is known theoretically to host various topologically non-trivial states. Bilayer STO in proximity to the interface can be regarded as a three-orbital generalization of graphene with enhanced electron correlations making it a promising candidate for the realization of strongly correlated topological phases. We have investigated the electronic structure of the LAO/STO (111) heterostructure in relation to the oxygen vacancy concentration which we can control by synchrotron light irradiation and oxygen dosing. With hard X-ray photoemission we study the core levels, whereas resonant soft X-ray photoemission is used to probe the interfacial valence band (VB) states. Two VB features are found: a peak at the Fermi level associated with the 2DES and in-gap states at higher binding energies attributed to oxygen vacancies. By varying the oxygen vacancy contribution we can tune the emergence of the VB states and engineer the interfacial band alignment.

  9. Relation between plasmons and the valence-band density-of-states in polymethylmethacrylate - influence of ion irradiation on damage selectivity

    International Nuclear Information System (INIS)

    Moliton, J.P.; Jussiaux, C.; Trigaud, T.; Lazzaroni, R.; Lhost, O.; Bredas, J.L.; Kihn, Y.; Sevely, J.

    1996-01-01

    A physical model is presented that aims at rationalizing the selectivity of bond breakage observed when polymethylmethacrylate is irradiated by ions in the 10-500 keV energy range. This model, previously proposed by Brandt and Ritchie, is based on electronic collective effects. The coupling between the pure plasma oscillation at omega(p) and the oscillation of free electrons at [omega(k0)(2)](1/2) makes the whole electronic population resonant at the frequency omega(rp) = (omega(p)(2) + [omega(k0)(2)])(1/2). By computing the valence-band density of states, we calculate [omega(k0)(2)] and then deduce the theoretical value of omega(rp). On the other hand, we provide an experimental measurement of omega(rp) and study its dependence on ion fluence by electron-energy-loss spectroscopy. The validity of the model of Brandt and Ritchie is then discussed in the light of both theoretical and experimental data. (author)

  10. Comparing CAT12 and VBM8 for Detecting Brain Morphological Abnormalities in Temporal Lobe Epilepsy

    Directory of Open Access Journals (Sweden)

    Farnaz Farokhian

    2017-08-01

    Full Text Available The identification of the brain morphological alterations that play important roles in neurodegenerative/neurological diseases will contribute to our understanding of the causes of these diseases. Various automated software programs are designed to provide an automatic framework to detect brain morphological changes in structural magnetic resonance imaging (MRI data. A voxel-based morphometry (VBM analysis can also be used for the detection of brain volumetric abnormalities. Here, we compared gray matter (GM and white matter (WM abnormality results obtained by a VBM analysis using the Computational Anatomy Toolbox (CAT12 via the current version of Statistical Parametric Mapping software (SPM12 with the results obtained by a VBM analysis using the VBM8 toolbox implemented in the older software SPM8, in adult temporal lobe epilepsy (TLE patients with (n = 51 and without (n = 57 hippocampus sclerosis (HS, compared to healthy adult controls (n = 28. The VBM analysis using CAT12 showed that compared to the healthy controls, significant GM and WM reductions were located in ipsilateral mesial temporal lobes in the TLE-HS patients, and slight GM amygdala swelling was present in the right TLE-no patients (n = 27. In contrast, the VBM analysis via the VBM8 toolbox showed significant GM and WM reductions only in the left TLE-HS patients (n = 25 compared to the healthy controls. Our findings thus demonstrate that compared to VBM8, a VBM analysis using CAT12 provides a more accurate volumetric analysis of the brain regions in TLE. Our results further indicate that a VBM analysis using CAT12 is more robust and accurate against volumetric alterations than the VBM8 toolbox.

  11. Deduction of the chemical state and the electronic structure of Nd{sub 2}Fe{sub 14}B compound from X-ray photoelectron spectroscopy core-level and valence-band spectra

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jing; Liang, Le [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Zhang, Lanting, E-mail: lantingzh@sjtu.edu.cn, E-mail: lmsun@sjtu.edu.cn [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Hirano Institute for Materials Innovation, Shanghai Jiao Tong University, Shanghai 200240 (China); Sun, Limin, E-mail: lantingzh@sjtu.edu.cn, E-mail: lmsun@sjtu.edu.cn [Instrumental Analysis Center, Shanghai Jiao Tong University, Shanghai 200240 (China); Hirano, Shinichi [Hirano Institute for Materials Innovation, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2014-10-28

    Characterization of chemical state and electronic structure of the technologically important Nd{sub 2}Fe{sub 14}B compound is attractive for understanding the physical nature of its excellent magnetic properties. X-ray photoelectron spectroscopy (XPS) study of such rare-earth compound is important and also challenging due to the easy oxidation of surface and small photoelectron cross-sections of rare-earth 4f electrons and B 2p electrons, etc. Here, we reported an investigation based on XPS spectra of Nd{sub 2}Fe{sub 14}B compound as a function of Ar ion sputtering time. The chemical state of Fe and that of B in Nd{sub 2}Fe{sub 14}B compound can be clearly determined to be 0 and −3, respectively. The Nd in Nd{sub 2}Fe{sub 14}B compound is found to have the chemical state of close to +3 instead of +3 as compared with the Nd in Nd{sub 2}O{sub 3}. In addition, by comparing the valence-band spectrum of Nd{sub 2}Fe{sub 14}B compound to that of the pure Fe, the contributions from Nd, Fe, and B to the valence-band structure of Nd{sub 2}Fe{sub 14}B compound is made more clear. The B 2p states and B 2s states are identified to be at ∼11.2 eV and ∼24.6 eV, respectively, which is reported for the first time. The contribution from Nd 4f states can be identified both in XPS core-level spectrum and XPS valence-band spectrum. Although Nd 4f states partially hybridize with Fe 3d states, Nd 4f states are mainly localized in Nd{sub 2}Fe{sub 14}B compound.

  12. The observation of valence band change on resistive switching of epitaxial Pr{sub 0.7}Ca{sub 0.3}MnO{sub 3} film using removable liquid electrode

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hong-Sub; Park, Hyung-Ho, E-mail: hhpark@yonsei.ac.kr [Department of Materials Science and Engineering, Yonsei University, Seodaemun-Ku, Seoul 120-749 (Korea, Republic of)

    2015-12-07

    The resistive switching (RS) phenomenon in transition metal oxides (TMOs) has received a great deal of attention for non-volatile memory applications. Various RS mechanisms have been suggested as to explain the observed RS characteristics. Many reports suggest that changes of interface and the role of oxygen vacancies originate in RS phenomena; therefore, in this study, we use a liquid drop of mercury as the top electrode (TE), epitaxial Pr{sub 0.7}Ca{sub 0.3}MnO{sub 3} (PCMO) (110) film of the perovskite manganite family for RS material, and an Nb-doped (0.7 at. %) SrTiO{sub 3} (100) single crystal as the substrate to observe changes in the interface between the TE and TMOs. The use of removable liquid electrode Hg drop as TE not only enables observation of the RS characteristic as a bipolar RS curve (counterclockwise) but also facilitates analysis of the valence band of the PCMO surface after resistive switching via photoelectron spectroscopy. The observed I-V behaviors of the low and high resistance states (HRS) are explained with an electrochemical migration model in PCMO film where accumulated oxygen vacancies at the interface between the Hg TE and PCMO (110) surface induce the HRS. The interpreted RS mechanism is directly confirmed via valence band spectrum analysis.

  13. Change in the conversion rate for the E3-isomer sup(235m)U (76,8 eV; 1/2+ → 7/2-) at variation of configurations of the valence band of the atomic shell

    International Nuclear Information System (INIS)

    Grechukhin, D.P.; Soldatov, A.A.

    1983-01-01

    In the framework of the relativistic Hartree-Fock-Slater method, a change of the conversion rate lambda for the E3 isomer (at the transition energy of h/2πω=77 eV) with respect to the rate lambda for the normal configuration of uranium atom, (7ssup(1/2)sup(2)(6dsup(3/2))sup(1)(5fsup(5/2))sup(3), is calcUlated for 14 configurations of the valence band of the atomic shell, including considerable variations of the occupation numbers in 6d, 7s, and 5f orbits. A very strong change Δlambda/lambda 1 is found to be due to variation of the occupation number for the 5f orbit (ΔN(5f) not equal to 0); the change amounts to about 8% per ΔN(5f)=+-1, that is an order of magnitude higher than Δlambda/lambda 1 due to variations of the occupation numbers for other orbits in the cases where N(5f)=const. Though the direct contribution from the 5f electrons to the conversion is very small ( 1 for ΔN(5f) not equal to 0. A rigid correlation between the partial conversion rate and the r. m. s. radius of the orbit is obtained for 6p orbits

  14. Valence band electronic structure of Nb{sub 2}Pd{sub 1.2}Se{sub 5} and Nb{sub 2}Pd{sub 0.95}S{sub 5} superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Lohani, H. [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India); Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400085 (India); Mishra, P. [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India); Goyal, R.; Awana, V.P.S. [National Physical Laboratory(CSIR), Dr. K. S. Krishnan Road, New Delhi 110012 (India); Sekhar, B.R., E-mail: sekhar@iopb.res.in [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India); Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400085 (India)

    2017-03-15

    We present a comparative study of our valence band photoemission results on Nb{sub 2}Pd{sub 1.2}Se{sub 5} and Nb{sub 2}Pd{sub 0.95}S{sub 5} superconductors which are supported by our DFT based electronic structure calculations. We observe that the VB spectra of both the compounds are qualitatively similar, except for some slight differences in the binding energy positions of all the features. This could be due to the unequal electronegativities of Se and S atom. The calculated density of states (DOS) reveals that the VB features are mainly composed of Pd-Se/S hybridized states. The nature of DOS originating from the distinctly coordinated Pd atoms is different. Further, various Pd-4d and Nb-4d states crossing the Fermi level (E{sub f}) signifies the multiband character of these compounds. In addition, we find a temperature dependent pseudogap in Nb{sub 2}Pd{sub 0.95}S{sub 5} which is absent in Nb{sub 2}Pd{sub 1.2}Se{sub 5}.

  15. #DDOD Use Case: Make VBM (Value-Based Payment Modifier) reporting for all groups publicly available

    Data.gov (United States)

    U.S. Department of Health & Human Services — SUMMARY DDOD use case request to make Value-Based Payment Modifier (VBM) reporting more transparent for everyone. WHAT IS A USE CASE? A “Use Case” is a request that...

  16. VBM with viscous fluid registration of grey matter segments in SPM.

    Directory of Open Access Journals (Sweden)

    João M. S. Pereira

    2013-07-01

    Full Text Available Improved registration of grey matter segments in SPM has been achieved with the DARTEL algorithm. Previous work from our group suggested, however, that such improvements may not translate to studies of clinical groups. To address the registration issue in atrophic brains, this paper relaxed the condition of diffeomorphism, central to DARTEL, and made use of a viscous fluid registration model with limited regularisation constraints to register the modulated grey matter probability maps to an intra-population template. Quantitative analysis of the registration results after the additional viscous fluid step showed no worsening of co-localisation of fiducials compared to DARTEL or unified segmentation methods, and the resulting voxel based morphometry (VBM analyses were able to better identify atrophic regions and to produce results with fewer apparent false positives. DARTEL showed great sensitivity to atrophy, but the resulting VBM maps presented broad, amorphous regions of significance that are hard to interpret. We propose that the condition of diffeomorphism is not necessary for basic VBM studies in atrophic populations, but also that it has disadvantages that must be taken into consideration before a study. The presented viscous fluid registration method is proposed for VBM studies to enhance sensitivity and localizing power.

  17. Valence band photoemission studies of clean metals

    International Nuclear Information System (INIS)

    Wehner, P.S.

    1978-04-01

    The application of Angle-Resolved Photoelectron Spectroscopy (ARPES) to crystalline solids and the utilization of such studies to illuminate several questions concerning the detailed electronic structure of such materials, are discussed. Specifically, by construction of a Direct Transition (DT) model and the utilization of energy-dependent angle-resolved normal photoemission in the photon energy range 32 eV < or = hν < or = 200 eV, the bulk band structure of copper is experimentally mapped out along three different directions in the Brillouin Zone; GAMMA to K, GAMMA to L, and GAMMA to X. In addition, various effects which influence the obtainable resolution in vector k-space, namely, thermal disorder, momentum broadening, and band mixing, are discussed and are shown to place severe limitations on the applicability of the DT model. Finally, a model for Angle-Resolved X-ray Photoelectron Spectroscopy (ARXPS) based on the symmetry of the initial-state wavefunctions is presented and compared to experimental results obtained from copper single crystals

  18. Brain structure in narcissistic personality disorder: a VBM and DTI pilot study.

    Science.gov (United States)

    Nenadic, Igor; Güllmar, Daniel; Dietzek, Maren; Langbein, Kerstin; Steinke, Johanna; Gaser, Christian

    2015-02-28

    We analysed T1-weighted MRI scans using voxel-based morphometry (VBM) and tract-based spatial statistics (TBBS) on diffusion tensor images (DTI) in narcissistic personality disorder (NaPD) patients and healthy controls. Grey matter deficits include right prefrontal and bilateral medial prefrontal/anterior cingulate cortices, and decreased fractional anisotropy in right frontal lobe white matter. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  19. Gender and hemispheric differences in temporal lobe epilepsy: a VBM study.

    Science.gov (United States)

    Santana, Maria Teresa Castilho Garcia; Jackowski, Andrea Parolin; Britto, Fernanda Dos Santos; Sandim, Gabriel Barbosa; Caboclo, Luís Otávio Sales Ferreira; Centeno, Ricardo Silva; Carrete, Henrique; Yacubian, Elza Márcia Targas

    2014-04-01

    Gender differences are recognized in the functional and anatomical organization of the human brain. Differences between genders are probably expressed early in life, when differential rates of cerebral maturation occur. Sexual dimorphism has been described in temporal lobe epilepsy with mesial temporal sclerosis (TLE-MTS). Several voxel-based morphometry (VBM) studies have shown that TLE-MTS extends beyond mesial temporal structures, and that there are differences in the extent of anatomical damage between hemispheres, although none have approached gender differences. Our aim was to investigate gender differences and anatomical abnormalities in TLE-MTS. VBM5 was employed to analyze gender and hemispheric differences in 120 patients with TLE-MTS and 50 controls. VBM abnormalities were more widespread in left-TLE; while in women changes were mostly seen in temporal areas, frontal regions were more affected in men. Our study confirmed that gender and laterality are important factors determining the nature and severity of brain damage in TLE-MTS. Differential rates of maturation between gender and hemispheres may explain the distinct areas of anatomical damage in men and women. Copyright © 2013 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.

  20. Advancing a Distributive-Bargaining and Integrative-Negotiation Integral System: A Values-Based Negotiation Model (VBM)

    OpenAIRE

    Ivan Gan

    2017-01-01

    The proposed values-based negotiation model (VBM) agrees with and extends principled negotiation’s recognition of personal values and emotions as important negotiation elements. First, building upon Martin Buber’s existentialist treatment of religion and secularism, VBM centers on religion as one of many possible sources of personal values that informs respectful and mutually beneficial interactions without needing one to necessarily be religious. Just as one need not be a Buddhist or a Hindu...

  1. Motor function deficits in schizophrenia: an fMRI and VBM study

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Sadhana; Modi, Shilpi; Kumar, Pawan; Singh, Namita; Khushu, Subash [Institute of Nuclear Medicine and Allied Sciences (INMAS), NMR Research Center, Delhi (India); Goyal, Satnam; Bhatia, Triptish; Deshpande, Smita N. [RML Hospital, PGIMER, New Delhi (India)

    2014-05-15

    To investigate whether the motor functional alterations in schizophrenia (SZ) are also associated with structural changes in the related brain areas using functional magnetic resonance imaging (fMRI) and voxel-based morphometry (VBM). A sample of 14 right-handed SZ patients and 14 right-handed healthy control subjects matched for age, sex, and education were examined with structural high-resolution T1-weighted MRI; fMRI images were obtained during right index finger-tapping task in the same session. fMRI results showed reduced functional activation in the motor areas (contralateral precentral and postcentral gyrus) and ipsilateral cerebellum in SZ subjects as compared to healthy controls (n = 14). VBM analysis also revealed reduced grey matter in motor areas and white matter reduction in cerebellum of SZ subjects as compared to controls. The present study provides an evidence for a possible association between structural alterations in the motor cortex and disturbed functional activation in the motor areas in persons affected with SZ during a simple finger-tapping task. (orig.)

  2. Motor function deficits in schizophrenia: an fMRI and VBM study

    International Nuclear Information System (INIS)

    Singh, Sadhana; Modi, Shilpi; Kumar, Pawan; Singh, Namita; Khushu, Subash; Goyal, Satnam; Bhatia, Triptish; Deshpande, Smita N.

    2014-01-01

    To investigate whether the motor functional alterations in schizophrenia (SZ) are also associated with structural changes in the related brain areas using functional magnetic resonance imaging (fMRI) and voxel-based morphometry (VBM). A sample of 14 right-handed SZ patients and 14 right-handed healthy control subjects matched for age, sex, and education were examined with structural high-resolution T1-weighted MRI; fMRI images were obtained during right index finger-tapping task in the same session. fMRI results showed reduced functional activation in the motor areas (contralateral precentral and postcentral gyrus) and ipsilateral cerebellum in SZ subjects as compared to healthy controls (n = 14). VBM analysis also revealed reduced grey matter in motor areas and white matter reduction in cerebellum of SZ subjects as compared to controls. The present study provides an evidence for a possible association between structural alterations in the motor cortex and disturbed functional activation in the motor areas in persons affected with SZ during a simple finger-tapping task. (orig.)

  3. Changes of brain structure in Parkinson's disease patients with mild cognitive impairment analyzed via VBM technology.

    Science.gov (United States)

    Gao, Yuyuan; Nie, Kun; Huang, Biao; Mei, Mingjin; Guo, Manli; Xie, Sifen; Huang, Zhiheng; Wang, Limin; Zhao, Jiehao; Zhang, Yuhu; Wang, Lijuan

    2017-09-29

    To analyze changes in cerebral grey matter volume and white matter density in non-dementia Parkinson's disease patients using voxel-based morphometry (VBM) technology; to investigate features of brain structure changes in Parkinson's disease patients with mild cognitive impairment (PD-MCI), and reveal their intrinsic pathological changes. Based on the diagnostic criteria of PD-MCI, 23 PD-MCI patients, 23 Parkinson's disease patients with normal cognition (PD-NC), and 21 age- and gender-matched healthy people were recruited for the study. Scans were performed on all subjects on a 3.0T MR scanner to obtain brain structural magnetic resonance images. Images were preprocessed using the VBM8 tool from SPM8 software package on the Matlab R2008a platform, and data were then analyzed using the SPM statistical software package to compare the differences of grey matter volume and white matter density between groups, and to evaluate the brain structural changes corresponding to the overall cognitive function. Compared to the control group, the PD-NC group suffered from grey matter atrophy, mainly found in the prefrontal lobe, limbic lobe and left temporal gyrus. The PD-MCI group suffered from grey matter atrophy found in the frontal lobe, limbic lobe, basal ganglia and cerebellum. Compared to the PD-NC group, the PD-MCI group suffered from grey matter atrophy found in the left-side middle temporal gyrus, inferior temporal gyrus and frontal lobe. The grey matter regions correlated with MMSE score (mainly memory related) including the right cingulate gyrus and the limbic lobe. The grey matter regions correlated with MoCA score (mainly non-memory related) including the frontal lobe, basal ganglia, parahippocampal gyrus, occipital lobe and the cerebellum. Additionally, overall cognitive function in non-dementia PD was mainly located in the frontal and limbic system, and was dominated by subcortical atrophy. Structural changes in PD-MCI patients are associated with overall

  4. Brain structure in schizophrenia vs. psychotic bipolar I disorder: A VBM study.

    Science.gov (United States)

    Nenadic, Igor; Maitra, Raka; Langbein, Kerstin; Dietzek, Maren; Lorenz, Carsten; Smesny, Stefan; Reichenbach, Jürgen R; Sauer, Heinrich; Gaser, Christian

    2015-07-01

    While schizophrenia and bipolar disorder have been assumed to share phenotypic and genotypic features, there is also evidence for overlapping brain structural correlates, although it is unclear whether these relate to shared psychotic features. In this study, we used voxel-based morphometry (VBM8) in 34 schizophrenia patients, 17 euthymic bipolar I disorder patients (with a history of psychotic symptoms), and 34 healthy controls. Our results indicate that compared to healthy controls schizophrenia patients show grey matter deficits (pright dorsolateral prefrontal, as well as bilaterally in ventrolateral prefrontal and insular cortical areas, thalamus (bilaterally), left superior temporal cortex, and minor medial parietal and parietooccipital areas. Comparing schizophrenia vs. bipolar I patients (pleft dorsolateral prefrontal cortex, and left cerebellum. Compared to healthy controls, the deficits in bipolar I patients only reached significance at prights reserved.

  5. Structural MRI research in patients with nasopharyngeal carcinoma following radiotherapy: A DTI and VBM study.

    Science.gov (United States)

    Leng, Xi; Fang, Peng; Lin, Huan; An, Jie; Tan, Xin; Zhang, Chi; Wu, Donglin; Shen, Wen; Qiu, Shijun

    2017-11-01

    The aim of the present study was to investigate the microstructural characteristics of the brain lobes following radiotherapy (RT) for patients with nasopharyngeal carcinoma (NPC) at distinct times. Diffusion tensor imaging (DTI) and 3D-T1-weighted imaging was performed in 70 age- and sex-matched subjects, 24 of whom were pre-treatment patients. The patients were divided into three groups, according to the time following completion of RT. Fractional anisotropy (FA) and gray matter (GM) volume were determined. The DTI data were analyzed using tract-based spatial statistics and the GM volume was analyzed using voxel-based morphometry (VBM). Compared with the pre-RT group, the mean FA values in the left parietal lobe white matter (WM) and right cerebellum decreased significantly in the post-RT 0-6 month group (P<0.05). In addition, the mean FA values in the right parietal lobe WM decreased significantly in the post-RT 6-12 month group (P<0.05), compared with the pre-RT group. The FA level in the right temporal lobe remained significantly decreased, compared with that in the pre-RT group (P<0.05) for 1 year after RT. Furthermore, compared with pre-RT group, the GM volume in the bilateral frontal lobe, right occipital lobe, left parietal lobe, right temporal lobe and left cerebellum decreased significantly in the post-RT 0-6 month group (P<0.05), and in the bilateral temporal lobe, parietal lobe, right frontal lobe and left cerebellum, the GM volume decreased significantly in the post-RT 6-12 month group (P<0.05). The GM volume in the right temporal lobe, bilateral frontal lobe and bilateral cerebellum remained significantly decreased compared with that in the pre-RT group (P<0.05) for 1 year after RT. A combination of DTI and VBM may be used to determine radiation-induced brain injury in patients treated for NPC.

  6. The self-liking brain: a VBM study on the structural substrate of self-esteem.

    Science.gov (United States)

    Agroskin, Dmitrij; Klackl, Johannes; Jonas, Eva

    2014-01-01

    Abundant evidence suggests that self-esteem is an important personality resource for emotion regulation in response to stressful experiences. It was thus hypothesized that the relative grey matter volume of brain regions involved in responding to and coping with stress is related to individual differences in trait self-esteem. Using structural magnetic resonance imaging of 48 healthy adults in conjunction with voxel-based morphometry and diffeomorphic anatomical registration using exponentiated lie algebra (VBM-DARTEL), positive associations between self-esteem and regional grey matter volume were indeed found in the anterior cingulate cortex (ACC), right lateral prefrontal cortex (LPFC), right hippocampus, and left hypothalamus. In addition, self-esteem positively covaried with grey matter volume in the right temporo-parietal junction (TPJ), which has been implicated in pride and theory of mind. The results suggest that persons with low self-esteem have reduced grey matter volume in brain regions that contribute to emotion/stress regulation, pride, and theory of mind. The findings provide novel neuroanatomical evidence for the view that self-esteem constitutes a vital coping resource.

  7. The Self-Liking Brain: A VBM Study on the Structural Substrate of Self-Esteem

    Science.gov (United States)

    Agroskin, Dmitrij; Klackl, Johannes; Jonas, Eva

    2014-01-01

    Abundant evidence suggests that self-esteem is an important personality resource for emotion regulation in response to stressful experiences. It was thus hypothesized that the relative grey matter volume of brain regions involved in responding to and coping with stress is related to individual differences in trait self-esteem. Using structural magnetic resonance imaging of 48 healthy adults in conjunction with voxel-based morphometry and diffeomorphic anatomical registration using exponentiated lie algebra (VBM-DARTEL), positive associations between self-esteem and regional grey matter volume were indeed found in the anterior cingulate cortex (ACC), right lateral prefrontal cortex (LPFC), right hippocampus, and left hypothalamus. In addition, self-esteem positively covaried with grey matter volume in the right temporo-parietal junction (TPJ), which has been implicated in pride and theory of mind. The results suggest that persons with low self-esteem have reduced grey matter volume in brain regions that contribute to emotion/stress regulation, pride, and theory of mind. The findings provide novel neuroanatomical evidence for the view that self-esteem constitutes a vital coping resource. PMID:24489727

  8. Lateral frontal cortex volume reduction in Tourette syndrome revealed by VBM

    Directory of Open Access Journals (Sweden)

    Wittfoth Matthias

    2012-02-01

    Full Text Available Abstract Background Structural changes have been found predominantly in the frontal cortex and in the striatum in children and adolescents with Gilles de la Tourette syndrome (GTS. The influence of comorbid symptomatology is unclear. Here we sought to address the question of gray matter abnormalities in GTS patients with co-morbid obsessive-compulsive disorder (OCD and/or attention deficit hyperactivity disorder (ADHD using voxel-based morphometry (VBM in twenty-nine adult actually unmedicated GTS patients and twenty-five healthy control subjects. Results In GTS we detected a cluster of decreased gray matter volume in the left inferior frontal gyrus (IFG, but no regions demonstrating volume increases. By comparing subgroups of GTS with comorbid ADHD to the subgroup with comorbid OCD, we found a left-sided amygdalar volume increase. Conclusions From our results it is suggested that the left IFG may constitute a common underlying structural correlate of GTS with co-morbid OCD/ADHD. A volume reduction in this brain region that has been previously identified as a key region in OCD and was associated with the active inhibition of attentional processes may reflect the failure to control behavior. Amygdala volume increase is discussed on the background of a linkage of this structure with ADHD symptomatology. Correlations with clinical data revealed gray matter volume changes in specific brain areas that have been described in these conditions each.

  9. The self-liking brain: a VBM study on the structural substrate of self-esteem.

    Directory of Open Access Journals (Sweden)

    Dmitrij Agroskin

    Full Text Available Abundant evidence suggests that self-esteem is an important personality resource for emotion regulation in response to stressful experiences. It was thus hypothesized that the relative grey matter volume of brain regions involved in responding to and coping with stress is related to individual differences in trait self-esteem. Using structural magnetic resonance imaging of 48 healthy adults in conjunction with voxel-based morphometry and diffeomorphic anatomical registration using exponentiated lie algebra (VBM-DARTEL, positive associations between self-esteem and regional grey matter volume were indeed found in the anterior cingulate cortex (ACC, right lateral prefrontal cortex (LPFC, right hippocampus, and left hypothalamus. In addition, self-esteem positively covaried with grey matter volume in the right temporo-parietal junction (TPJ, which has been implicated in pride and theory of mind. The results suggest that persons with low self-esteem have reduced grey matter volume in brain regions that contribute to emotion/stress regulation, pride, and theory of mind. The findings provide novel neuroanatomical evidence for the view that self-esteem constitutes a vital coping resource.

  10. Voxel-based morphometry (VBM) based assessment of gray matter loss in medial temporal lobe epilepsy; comparison with FDG PET

    International Nuclear Information System (INIS)

    Kang, Hye Jin; Lee, Ho Young; Lee, Jae Sung; Kang, Eun Joo; Lee, Sang Gun; Chang, Kee Hyun; Lee, Dong Soo

    2004-01-01

    The aims of this study were to find brain regions in which gray matter volume was reduced and to show the capability of voxel-based morphometry (VBM) analysis for lateralizing epileptogenic zones in medial temporal lobe epilepsy (mTLE). The findings were compared with fluorodeoxyglucose positron emission tomography (FDG PET). MR T1-weighted images of 12 left mTLE and 11 right mTLE patients were compared with those of 37 normal controls. Images were transformed to standard MNI space and averaged in order to create study-specific brain template. Each image was normalized to this local template and brain tissues were segmented. Modulation VBM analysis was performed in order to observe gray matter volume change. Gray matter was smoothed with a Gaussian kernel. After these preprocessing, statistical analysis was performed using statistical parametric mapping software (SPM99). FDG PET images were compared with those of 22 normal controls using SPM. Gray matter volume was significantly reduced in the left amygdala and hippocampus in left mTLE. In addition, volume of cerebellum, anterior cingulate, and fusiform gyrus in both sides and left insula was reduced. In right mTLE, volume was reduced significantly in right hippocampus. In contrast, FDG uptake was decreased in broad areas of left or right temporal lobes in left TLE and right TLE, respectively. Gray matter loss was found in the ipsilateral hippocampus by modulation VBM analysis in medial temporal lobe epilepsy. This VBM analysis might be useful in lateralizing the epileptogenic zones in medial temporal lobe epilepsy, while SPM analysis of FDG PET disclosed hypometabolic epileptogenic zones

  11. Functional and structural abnormalities associated with empathy in patients with schizophrenia: An fMRI and VBM study

    OpenAIRE

    Singh, Sadhana; Modi, Shilpi; Goyal, Satnam; Kaur, Prabhjot; Singh, Namita; Bhatia, Triptish; Deshpande, Smita N; Khushu, Subash

    2015-01-01

    Empathy deficit is a core feature of schizophrenia which may lead to social dysfunction. The present study was carried out to investigate functional and structural abnormalities associated with empathy in patients with schizophrenia using functional magnetic resonance imaging (fMRI) and voxel-based morphometry (VBM). A sample of 14 schizophrenia patients and 14 healthy control subjects matched for age, sex and education were examined with structural high-resolution T1-weighted MRI; fMRI image...

  12. Voxel-based morphometry (VBM) based assessment of gray matter loss in medial temporal lobe epilepsy; comparison with FDG PET

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Hye Jin; Lee, Ho Young; Lee, Jae Sung; Kang, Eun Joo; Lee, Sang Gun; Chang, Kee Hyun; Lee, Dong Soo [College of Medicine, Seoul National Univ., Seoul (Korea, Republic of)

    2004-02-01

    The aims of this study were to find brain regions in which gray matter volume was reduced and to show the capability of voxel-based morphometry (VBM) analysis for lateralizing epileptogenic zones in medial temporal lobe epilepsy (mTLE). The findings were compared with fluorodeoxyglucose positron emission tomography (FDG PET). MR T1-weighted images of 12 left mTLE and 11 right mTLE patients were compared with those of 37 normal controls. Images were transformed to standard MNI space and averaged in order to create study-specific brain template. Each image was normalized to this local template and brain tissues were segmented. Modulation VBM analysis was performed in order to observe gray matter volume change. Gray matter was smoothed with a Gaussian kernel. After these preprocessing, statistical analysis was performed using statistical parametric mapping software (SPM99). FDG PET images were compared with those of 22 normal controls using SPM. Gray matter volume was significantly reduced in the left amygdala and hippocampus in left mTLE. In addition, volume of cerebellum, anterior cingulate, and fusiform gyrus in both sides and left insula was reduced. In right mTLE, volume was reduced significantly in right hippocampus. In contrast, FDG uptake was decreased in broad areas of left or right temporal lobes in left TLE and right TLE, respectively. Gray matter loss was found in the ipsilateral hippocampus by modulation VBM analysis in medial temporal lobe epilepsy. This VBM analysis might be useful in lateralizing the epileptogenic zones in medial temporal lobe epilepsy, while SPM analysis of FDG PET disclosed hypometabolic epileptogenic zones.

  13. Structural brain alterations in bipolar disorder II: a combined voxel-based morphometry (VBM) and diffusion tensor imaging (DTI) study.

    Science.gov (United States)

    Ambrosi, Elisa; Rossi-Espagnet, Maria Camilla; Kotzalidis, Georgios D; Comparelli, Anna; Del Casale, Antonio; Carducci, Filippo; Romano, Andrea; Manfredi, Giovanni; Tatarelli, Roberto; Bozzao, Alessandro; Girardi, Paolo

    2013-09-05

    Brain structural changes have been described in bipolar disorder (BP), but usually studies focused on both I and II subtypes indiscriminately and investigated changes in either brain volume or white matter (WM) integrity. We used combined voxel-based morphometry (VBM) and diffusion tensor imaging (DTI) analysis to track changes in the grey matter (GM) and WM in the brains of patients affected by BPII, as compared to healthy controls. Using VBM and DTI, we scanned 20 DSM-IV-TR BPII patients in their euthymic phase and 21 healthy, age- and gender-matched volunteers with no psychiatric history. VBM showed decreases in GM of BPII patients, compared to controls, which were diffuse in nature and most prominent in the right middle frontal gyrus and in the right superior temporal gurus. DTI showed significant and widespread FA reduction in BPII patients in all major WM tracts, including cortico-cortical association tracts. The small sample size limits the generalisability of our findings. Reduced GM volumes and WM integrity changes in BPII patients are not prominent like those previously reported in bipolar disorder type-I and involve cortical structures and their related association tracts. Copyright © 2013 Elsevier B.V. All rights reserved.

  14. Optimized VBM in patients with Alzheimer's disease: gray matter loss and its correlation with cognitive function

    International Nuclear Information System (INIS)

    Choi, Seon Hyeong; Moon, Won Jin; Chung, Eun Chul; Lee, Min Hee; Roh, Hong Gee; Park, Kwang Bo; Na, Duck Ryul

    2005-01-01

    To investigate the regional changes in gray matter volume by using optimized voxel based morphometry in the whole brain of patients with Alzheimer's disease (AD) and to determine its correlation with cognitive function. Nineteen patients with AD (mean mini mental state examination (MMSE) score = 20.4) and 19 age-matched control subjects (mean MMSE score 29) participated in this prospective study. T1-weighted 3D-SPGR scans were obtained for each subject. These T1-weighted images were spatially normalized into study-specific T1 template and segmented into gray matter, white matter and CSF. After the images were modulated and smoothed, all of the gray matter images were compared with control images by using voxel-wise statistical parametric test (two-sample-test). In patients with AD, total gray matter volume was significantly smaller than normal control (552 ± 39 mL vs. 632 ± 51 mL, ρ 0.001). Significant gray matter loss was seen in both the hippocampus and amygdala complexs, and the parahippocampi and frontoparietal cortices (ρ < 0.01, family wise error corrected). Left cerebral atrophy was more prominent than the right. Loss of gray matter volume in both the superior frontal gyri and left inferior temporal gyrus had a strong correlation with lower MMSE score. Optimized VBM was able to visualize pathologic changes of AD in vivo. In AD there was widespread gray matter volume loss in the frontoparietal lobes as well as the medial temporal lobes and had a strong correlation between volume loss of specific cortical areas and MMSE score

  15. Regional gray matter volume increases following 7days of voluntary wheel running exercise: a longitudinal VBM study in rats.

    Science.gov (United States)

    Sumiyoshi, Akira; Taki, Yasuyuki; Nonaka, Hiroi; Takeuchi, Hikaru; Kawashima, Ryuta

    2014-09-01

    The effects of physical exercise on brain morphology in rodents have been well documented in histological studies. However, to further understand when and where morphological changes occur in the whole brain, a noninvasive neuroimaging method allowing an unbiased, comprehensive, and longitudinal investigation of brain morphology should be used. In this study, we investigated the effects of 7days of voluntary wheel running exercise on regional gray matter volume (rGMV) using longitudinal voxel-based morphometry (VBM) in rats. Eighteen pairs of adult male naïve Wistar rats were randomized to the exercise or control condition (one rat for each condition from each pair). Each rat was scanned in a 7.0-T MRI scanner at three time points: before exercise, after 7days of exercise, and after 7days of follow-up. The T2-weighted MRI images were segmented using the rat brain tissue priors that were recently published by our laboratory, and the intra- and inter-subject template creation steps were followed. Longitudinal VBM analysis revealed significant increases in rGMV in the motor, somatosensory, association, and visual cortices in the exercise group. Among these brain regions, rGMV changes in the motor cortex were positively correlated with the total distance that was run during the 7days of exercise. In addition, the effects of 7days of exercise on rGMV persisted after 7days of follow-up. These results support the utility of a longitudinal VBM study in rats and provide new insights into experience-dependent structural brain plasticity in naïve adult animals. Copyright © 2014 Elsevier Inc. All rights reserved.

  16. Boron Doped diamond films as electron donors in photovoltaics: An X-ray absorption and hard X-ray photoemission study

    Energy Technology Data Exchange (ETDEWEB)

    Kapilashrami, M.; Zegkinoglou, I. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Department of Physics, University of Wisconsin Madison, Madison, Wisconsin 53706 (United States); Conti, G.; Nemšák, S.; Conlon, C. S.; Fadley, C. S. [Department of Physics, University of California, Davis, California 95616 (United States); Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Törndahl, T.; Fjällström, V. [Ångström Solar Center, Uppsala University, Box 534, SE-751 21 Uppsala (Sweden); Lischner, J. [Department of Physics, University of California, Berkeley, California 94720 (United States); Louie, Steven G. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Department of Physics, University of California, Berkeley, California 94720 (United States); Hamers, R. J.; Zhang, L. [Department of Chemistry, University of Wisconsin Madison, Madison, Wisconsin 53706 (United States); Guo, J.-H. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Himpsel, F. J., E-mail: fhimpsel@wisc.edu [Department of Physics, University of Wisconsin Madison, Madison, Wisconsin 53706 (United States)

    2014-10-14

    Highly boron-doped diamond films are investigated for their potential as transparent electron donors in solar cells. Specifically, the valence band offset between a diamond film (as electron donor) and Cu(In,Ga)Se₂ (CIGS) as light absorber is determined by a combination of soft X-ray absorption spectroscopy and hard X-ray photoelectron spectroscopy, which is more depth-penetrating than standard soft X-ray photoelectron spectroscopy. In addition, a theoretical analysis of the valence band is performed, based on GW quasiparticle band calculations. The valence band offset is found to be small: VBO=VBM{sub CIGS} – VBM{sub diamond}=0.3 eV±0.1 eV at the CIGS/Diamond interface and 0.0 eV±0.1 eV from CIGS to bulk diamond. These results provide a promising starting point for optimizing the band offset by choosing absorber materials with a slightly lower valence band maximum.

  17. Boron Doped diamond films as electron donors in photovoltaics: An X-ray absorption and hard X-ray photoemission study

    International Nuclear Information System (INIS)

    Kapilashrami, M.; Zegkinoglou, I.; Conti, G.; Nemšák, S.; Conlon, C. S.; Fadley, C. S.; Törndahl, T.; Fjällström, V.; Lischner, J.; Louie, Steven G.; Hamers, R. J.; Zhang, L.; Guo, J.-H.; Himpsel, F. J.

    2014-01-01

    Highly boron-doped diamond films are investigated for their potential as transparent electron donors in solar cells. Specifically, the valence band offset between a diamond film (as electron donor) and Cu(In,Ga)Se 2 (CIGS) as light absorber is determined by a combination of soft X-ray absorption spectroscopy and hard X-ray photoelectron spectroscopy, which is more depth-penetrating than standard soft X-ray photoelectron spectroscopy. In addition, a theoretical analysis of the valence band is performed, based on GW quasiparticle band calculations. The valence band offset is found to be small: VBO = VBM CIGS – VBM diamond  = 0.3 eV ± 0.1 eV at the CIGS/Diamond interface and 0.0 eV ± 0.1 eV from CIGS to bulk diamond. These results provide a promising starting point for optimizing the band offset by choosing absorber materials with a slightly lower valence band maximum.

  18. Cerebral asymmetry in patients with schizophrenia: a voxel-based morphometry (VBM) and diffusion tensor imaging (DTI) study.

    Science.gov (United States)

    Takao, Hidemasa; Abe, Osamu; Yamasue, Hidenori; Aoki, Shigeki; Kasai, Kiyoto; Ohtomo, Kuni

    2010-01-01

    To evaluate the differences in gray- and white-matter asymmetry between schizophrenia patients and normal subjects. Forty-eight right-handed patients with chronic schizophrenia (24 males and 24 females) and 48 right-handed age- and sex-matched healthy controls (24 males and 24 females) were included in this study. The effects of diagnosis on gray-matter volume asymmetry and white-matter fractional anisotropy (FA) asymmetry were evaluated with use of voxel-based morphometry (VBM) and voxel-based analysis of FA maps derived from diffusion tensor imaging (DTI), respectively. The mean gray- and white-matter volumes were significantly smaller in the schizophrenia group than in the control group. The voxel-based morphometry (VBM) showed no significant effect of diagnosis on gray-matter volume asymmetry. The voxel-based analysis of DTI also showed no significant effect of diagnosis on white-matter FA asymmetry. Our results of voxel-based analyses showed no significant differences in either gray-matter volume asymmetry or white-matter FA asymmetry between schizophrenia patients and normal subjects. (c) 2009 Wiley-Liss, Inc.

  19. Functional and structural abnormalities associated with empathy in patients with schizophrenia: An fMRI and VBM study.

    Science.gov (United States)

    Singh, Sadhana; Modi, Shilpi; Goyal, Satnam; Kaur, Prabhjot; Singh, Namita; Bhatia, Triptish; Deshpande, Smita N; Khushu, Subash

    2015-06-01

    Empathy deficit is a core feature of schizophrenia which may lead to social dysfunction. The present study was carried out to investigate functional and structural abnormalities associated with empathy in patients with schizophrenia using functional magnetic resonance imaging (fMRI) and voxel-based morphometry (VBM). A sample of 14 schizophrenia patients and 14 healthy control subjects matched for age, sex and education were examined with structural highresolution T1-weighted MRI; fMRI images were obtained during empathy task in the same session. The analysis was carried out using SPM8 software. On behavioural assessment, schizophrenic patients (83.00+-29.04) showed less scores for sadness compared to healthy controls (128.70+-22.26) (p less than 0.001). fMRI results also showed reduced clusters of activation in the bilateral fusiform gyrus, left lingual gyrus, left middle and inferior occipital gyrus in schizophrenic subjects as compared to controls during empathy task. In the same brain areas, VBM results also showed reduced grey and white matter volumes. The present study provides an evidence for an association between structural alterations and disturbed functional brain activation during empathy task in persons affected with schizophrenia. These findings suggest a biological basis for social cognition deficits in schizophrenics.

  20. Comparison of the diagnostic performance of FDG-PET and VBM-MRI in very mild Alzheimer's disease

    Energy Technology Data Exchange (ETDEWEB)

    Kawachi, Takashi [Division of Neuroimaging Research, HIABCD, Himeji, Hyogo (Japan); Kobe University Graduate School of Medicine, Department of Psychiatry, Kobe, Hyogo (Japan); Ishii, Kazunari; Mori, Tetsuya [Division of Neuroimaging Research, HIABCD, Himeji, Hyogo (Japan); Hyogo Brain and Heart Center, Department of Radiology and Nuclear Medicine, Himeji, Hyogo (Japan); Sakamoto, Setsu; Sasaki, Masahiro [Division of Neuroimaging Research, HIABCD, Himeji, Hyogo (Japan); Yamashita, Fumio; Matsuda, Hiroshi [National Center Hospital for Mental, Nervous and Muscular Disorders, National Center of Neurology and Psychiatry, Department of Radiology, Kodaira, Tokyo (Japan); Mori, Etsuro [Institute for Aging Brain and Cognitive Disorders, Hyogo Brain and Heart Center, Himeji, Hyogo (Japan)

    2006-07-15

    The aim of this study was to compare the diagnostic performance of{sup 18}F-fluorodeoxyglucose (FDG) positron emission tomography (PET) and voxel-based morphometry (VBM) on magnetic resonance imaging (MRI) in the same group of patients with very mild Alzheimer's disease (AD). Thirty patients with very mild AD (age 67.0{+-}5.8 years; MMSE score 25.5{+-}1.2, range 24-28), 32 patients with mild AD (age 67.0{+-}4.5 years, MMSE score 22.1{+-}0.8, range 21-23) and 60 age- and sex-matched normal volunteers underwent both FDG-PET and three-dimensional spoiled gradient echo MRI. Statistical parametric mapping was used to conduct voxel by voxel analysis and Z score mapping. First, the region of interest (ROI) maps of significant reductions in glucose metabolism and grey matter density in the mild AD patients were defined. Secondly, analysis of receiver operating characteristic (ROC) curves for Z scores in the ROI maps discriminating very mild AD patients and normal controls was performed. In mild AD patients, FDG-PET indicated significant reductions in glucose metabolism in the bilateral posterior cingulate gyri and the right parietotemporal area, while VBM analysis showed a significant decrease in grey matter volume density in the bilateral amygdala/hippocampus complex, compared with the normal control group. ROC analysis showed that in very mild AD patients the accuracy of FDG-PET diagnosis was 89% and that of VBM-MRI diagnosis was 83%. The accuracy of the combination of FDG-PET and VBM-MRI diagnosis was 94%. In very mild AD, both FDG-PET and VBM-MRI had high accuracy for diagnosis, but FDG-PET showed slightly higher accuracy than VBM-MRI. Combination of the two techniques will yield a higher diagnostic accuracy in very mild AD by making full use of functional and morphological images. (orig.)

  1. Determination of conduction and valence band electronic structure ...

    Indian Academy of Sciences (India)

    shifts in the rutile Ti d-band to lower energy with respect to anatase, i.e., ... requires excitation with UV light due to its wide band ... RIXS maps were compared to the theoretical results .... optical methods are insufficient, such as dark samples.

  2. Photoemission from valence bands of transition metal-phthalocyanines

    International Nuclear Information System (INIS)

    Shang, Ming-Hui; Nagaosa, Mayumi; Nagamatsu, Shin-ichi; Hosoumi, Shunsuke; Kera, Satoshi; Fujikawa, Takashi; Ueno, Nobuo

    2011-01-01

    Research highlights: → The HOMO mainly comes from the carbon atoms of Pc rings and the central metal atoms almost have no contribution on the highest occupied molecular orbital (HOMO: a 1u ) distribution of CoPc as well as NiPc. → Influence by central metal atom on the photoemission intensities from the HOMO of two single molecule systems is negligible for the major. → The modification of the distribution for π-orbital upon adsorption as well as the scattering effects of the central metal on the photoemission intensities are negligible for the major. - Abstract: Angular dependencies of ultraviolet photoelectron spectrum of transition metal-phthalocyanines (TM-Pcs), NiPc and CoPc, have been studied by using multiple-scattering theory to explore the electronic structure of the organometallic complexes influenced by central metal atom. The calculated angular distributions of photoelectrons for the highest occupied molecular orbital (HOMO: a 1u ) from the two single systems are nearly the same and represent well the experimental results obtained for the well-ordered monolayer on the highly oriented pyrolytic graphite substrate. The central metal atoms almost have no contribution on the HOMO distribution, which mainly comes from the carbon atoms of Pc ring. Moreover, the modification of the distribution for π orbital upon adsorption as well as the scattering effects of the central metal on the photoemission intensities are negligible for the major.

  3. DTI and VBM reveal white matter changes without associated gray matter changes in patients with idiopathic restless legs syndrome

    Science.gov (United States)

    Belke, Marcus; Heverhagen, Johannes T; Keil, Boris; Rosenow, Felix; Oertel, Wolfgang H; Stiasny-Kolster, Karin; Knake, Susanne; Menzler, Katja

    2015-01-01

    Background and Purpose We evaluated cerebral white and gray matter changes in patients with iRLS in order to shed light on the pathophysiology of this disease. Methods Twelve patients with iRLS were compared to 12 age- and sex-matched controls using whole-head diffusion tensor imaging (DTI) and voxel-based morphometry (VBM) techniques. Evaluation of the DTI scans included the voxelwise analysis of the fractional anisotropy (FA), radial diffusivity (RD), and axial diffusivity (AD). Results Diffusion tensor imaging revealed areas of altered FA in subcortical white matter bilaterally, mainly in temporal regions as well as in the right internal capsule, the pons, and the right cerebellum. These changes overlapped with changes in RD. Voxel-based morphometry did not reveal any gray matter alterations. Conclusions We showed altered diffusion properties in several white matter regions in patients with iRLS. White matter changes could mainly be attributed to changes in RD, a parameter thought to reflect altered myelination. Areas with altered white matter microstructure included areas in the internal capsule which include the corticospinal tract to the lower limbs, thereby supporting studies that suggest changes in sensorimotor pathways associated with RLS. PMID:26442748

  4. Optimized VBM in patients with Alzheimer's disease: gray matter loss and its correlation with cognitive function

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Seon Hyeong; Moon, Won Jin; Chung, Eun Chul; Lee, Min Hee; Roh, Hong Gee; Park, Kwang Bo; Na, Duck Ryul [Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of)

    2005-11-15

    To investigate the regional changes in gray matter volume by using optimized voxel based morphometry in the whole brain of patients with Alzheimer's disease (AD) and to determine its correlation with cognitive function. Nineteen patients with AD (mean mini mental state examination (MMSE) score = 20.4) and 19 age-matched control subjects (mean MMSE score 29) participated in this prospective study. T1-weighted 3D-SPGR scans were obtained for each subject. These T1-weighted images were spatially normalized into study-specific T1 template and segmented into gray matter, white matter and CSF. After the images were modulated and smoothed, all of the gray matter images were compared with control images by using voxel-wise statistical parametric test (two-sample-test). In patients with AD, total gray matter volume was significantly smaller than normal control (552 {+-} 39 mL vs. 632 {+-} 51 mL, {rho} 0.001). Significant gray matter loss was seen in both the hippocampus and amygdala complexs, and the parahippocampi and frontoparietal cortices ({rho} < 0.01, family wise error corrected). Left cerebral atrophy was more prominent than the right. Loss of gray matter volume in both the superior frontal gyri and left inferior temporal gyrus had a strong correlation with lower MMSE score. Optimized VBM was able to visualize pathologic changes of AD in vivo. In AD there was widespread gray matter volume loss in the frontoparietal lobes as well as the medial temporal lobes and had a strong correlation between volume loss of specific cortical areas and MMSE score.

  5. Effect of temperature on the valency bands of HDO in water in the liquid and solid states. Effects on the analysis of heavy water using infra-red absorption; Effet de temperature sur les bandes de valence de HDO dans l'eau a l'etat liquide et a l'etat solide - consequences pour l'analyse de l'eau lourde par absorption infra-rouge

    Energy Technology Data Exchange (ETDEWEB)

    Ceccaldi, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-07-01

    After, a description of the technique used, a qualitative examination is made of the influence of the temperature on the {nu}{sub OH}(3,400 cm{sup -1}) and {nu}{sub OD} (2,500 cm{sup -1}) valence bands of HDO in the liquid state and then during the passage to the solid state. Quantitative examination with two cells of different thickness makes it possible to define the influence of temperature on the residual absorption of the pure liquid (D{sub 2}O or H{sub 2}O and on the valency bands ({nu}{sub OH} and {nu}{sub OD} respectively). It is found that a similar change occurs in the two bands but that the changes in the background are very different. During the passage from the liquid to the solid state the shape of the bands varies considerably but little change occurs in the total intensity. It has been possible to express these results in a simple form which is directly applicable to analytical problems. (authors) [French] Apres un rappel de la technique utilisee, on examine qualitativement l'influence de la temperature sur les bandes de valence {nu}{sub OH} (3400 cm{sup -1}) et {nu}{sub OD} (2500 cm{sup -1}) de HDO a l'etat liquide puis le passage a l'etat solide. L'examen quantitatif, avec deux cuves d'epaisseurs differentes, permet de preciser l'influence de la temperature sur l'absorption residuelle du liquide pur (D{sub 2}O ou H{sub 2}O) et sur les bandes de valence ( {nu}{sub OH} et {nu}{sub OD} respectivement). On constate une evolution parallele de ces bandes mais un comportement tres different du fond continu. Lors du passage de l'etat liquide a l'etat solide, la forme des bandes varie considerablement mais non l'intensite totale. On a pu formuler ces resultats sous une forme simple applicable directement aux problemes analytiques. (auteurs)

  6. Sex-related difference in human white matter volumes studied: Inspection of the corpus callosum and other white matter by VBM

    Science.gov (United States)

    Shiino, Akihiko; Chen, Yen-Wei; Tanigaki, Kenji; Yamada, Atsushi; Vigers, Piers; Watanabe, Toshiyuki; Tooyama, Ikuo; Akiguchi, Ichiro

    2017-01-01

    It has been contended that any observed difference of the corpus callosum (CC) size between men and women is not sex-related but brain-size-related. A recent report, however, showed that the midsagittal CC area was significantly larger in women in 37 brain-size-matched pairs of normal young adults. Since this constituted strong evidence of sexual dimorphism and was obtained from publicly available data in OASIS, we examined volume differences within the CC and in other white matter using voxel-based morphometry (VBM). We created a three-dimensional region of interest of the CC and measured its volume. The VBM statistics were analyzed by permutation test and threshold-free cluster enhancement (TFCE) with the significance levels at FWER women in the same 37 brain-size-matched pairs. We found that the CC genu was the subregion showing the most significant sex-related difference. We also found that white matter in the bilateral anterior frontal regions and the left lateral white matter near to Broca’s area were larger in women, whereas there were no significant larger regions in men. Since we used brain-size-matched subjects, our results gave strong volumetric evidence of localized sexual dimorphism of white matter.

  7. Substitutional Co dopant on the GaAs(110) surface: A first principles study

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Zhou; Yi, Zhijun, E-mail: zhijunyi@cumt.edu.cn

    2016-12-01

    Using the first principles ground state method, the electronic properties of single Co dopant replacing one Ga atom on the GaAs(110) surface are studied. Our calculated local density of states (LDOS) at Co site presents several distinct peaks above the valence band maximum (VBM), and this agrees with recent experiments. Moreover, the calculated STM images at bias voltages of 2 eV and −2 eV also agree with experiments. We discussed the origin of Co impurity induced distinct peaks, which can be characterized with the hybridization between Co d orbitals and p-like orbitals of surface As and Ga atoms.

  8. The neuroanatomy of subthreshold depressive symptoms in Huntington's disease: a combined diffusion tensor imaging (DTI) and voxel-based morphometry (VBM) study.

    Science.gov (United States)

    Sprengelmeyer, R; Orth, M; Müller, H-P; Wolf, R C; Grön, G; Depping, M S; Kassubek, J; Justo, D; Rees, E M; Haider, S; Cole, J H; Hobbs, N Z; Roos, R A C; Dürr, A; Tabrizi, S J; Süssmuth, S D; Landwehrmeyer, G B

    2014-07-01

    Depressive symptoms are prominent psychopathological features of Huntington's disease (HD), making a negative impact on social functioning and well-being. We compared the frequencies of a history of depression, previous suicide attempts and current subthreshold depression between 61 early-stage HD participants and 40 matched controls. The HD group was then split based on the overall HD group's median Hospital Anxiety and Depression Scale-depression score into a group of 30 non-depressed participants (mean 0.8, s.d. = 0.7) and a group of 31 participants with subthreshold depressive symptoms (mean 7.3, s.d. = 3.5) to explore the neuroanatomy underlying subthreshold depressive symptoms in HD using voxel-based morphometry (VBM) and diffusion tensor imaging (DTI). Frequencies of history of depression, previous suicide attempts or current subthreshold depressive symptoms were higher in HD than in controls. The severity of current depressive symptoms was also higher in HD, but not associated with the severity of HD motor signs or disease burden. Compared with the non-depressed HD group DTI revealed lower fractional anisotropy (FA) values in the frontal cortex, anterior cingulate cortex, insula and cerebellum of the HD group with subthreshold depressive symptoms. In contrast, VBM measures were similar in both HD groups. A history of depression, the severity of HD motor signs or disease burden did not correlate with FA values of these regions. Current subthreshold depressive symptoms in early HD are associated with microstructural changes - without concomitant brain volume loss - in brain regions known to be involved in major depressive disorder, but not those typically associated with HD pathology.

  9. Approximate maximum parsimony and ancestral maximum likelihood.

    Science.gov (United States)

    Alon, Noga; Chor, Benny; Pardi, Fabio; Rapoport, Anat

    2010-01-01

    We explore the maximum parsimony (MP) and ancestral maximum likelihood (AML) criteria in phylogenetic tree reconstruction. Both problems are NP-hard, so we seek approximate solutions. We formulate the two problems as Steiner tree problems under appropriate distances. The gist of our approach is the succinct characterization of Steiner trees for a small number of leaves for the two distances. This enables the use of known Steiner tree approximation algorithms. The approach leads to a 16/9 approximation ratio for AML and asymptotically to a 1.55 approximation ratio for MP.

  10. Maximum permissible dose

    International Nuclear Information System (INIS)

    Anon.

    1979-01-01

    This chapter presents a historic overview of the establishment of radiation guidelines by various national and international agencies. The use of maximum permissible dose and maximum permissible body burden limits to derive working standards is discussed

  11. Highly conductive p-type amorphous oxides from low-temperature solution processing

    International Nuclear Information System (INIS)

    Li Jinwang; Tokumitsu, Eisuke; Koyano, Mikio; Mitani, Tadaoki; Shimoda, Tatsuya

    2012-01-01

    We report solution-processed, highly conductive (resistivity 1.3-3.8 mΩ cm), p-type amorphous A-B-O (A = Bi, Pb; B = Ru, Ir), processable at temperatures (down to 240 °C) that are compatible with plastic substrates. The film surfaces are smooth on the atomic scale. Bi-Ru-O was analyzed in detail. A small optical bandgap (0.2 eV) with a valence band maximum (VBM) below but very close to the Fermi level (binding energy E VBM = 0.04 eV) explains the high conductivity and suggests that they are degenerated semiconductors. The conductivity changes from three-dimensional to two-dimensional with decreasing temperature across 25 K.

  12. Maximum Acceleration Recording Circuit

    Science.gov (United States)

    Bozeman, Richard J., Jr.

    1995-01-01

    Coarsely digitized maximum levels recorded in blown fuses. Circuit feeds power to accelerometer and makes nonvolatile record of maximum level to which output of accelerometer rises during measurement interval. In comparison with inertia-type single-preset-trip-point mechanical maximum-acceleration-recording devices, circuit weighs less, occupies less space, and records accelerations within narrower bands of uncertainty. In comparison with prior electronic data-acquisition systems designed for same purpose, circuit simpler, less bulky, consumes less power, costs and analysis of data recorded in magnetic or electronic memory devices. Circuit used, for example, to record accelerations to which commodities subjected during transportation on trucks.

  13. Maximum Quantum Entropy Method

    OpenAIRE

    Sim, Jae-Hoon; Han, Myung Joon

    2018-01-01

    Maximum entropy method for analytic continuation is extended by introducing quantum relative entropy. This new method is formulated in terms of matrix-valued functions and therefore invariant under arbitrary unitary transformation of input matrix. As a result, the continuation of off-diagonal elements becomes straightforward. Without introducing any further ambiguity, the Bayesian probabilistic interpretation is maintained just as in the conventional maximum entropy method. The applications o...

  14. Maximum power demand cost

    International Nuclear Information System (INIS)

    Biondi, L.

    1998-01-01

    The charging for a service is a supplier's remuneration for the expenses incurred in providing it. There are currently two charges for electricity: consumption and maximum demand. While no problem arises about the former, the issue is more complicated for the latter and the analysis in this article tends to show that the annual charge for maximum demand arbitrarily discriminates among consumer groups, to the disadvantage of some [it

  15. Determination of 4f energy levels for trivalent lanthanide ions in YAlO{sub 3} by X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, Yuhei; Ueda, Kazushige, E-mail: kueda@che.kyutech.ac.jp

    2016-09-01

    A simple method to analyze 4f energy levels of trivalent lanthanide (Ln) ions was demonstrated by conventional X-ray photoelectron spectroscopy (XPS) measurements using Ln ions doped YAlO{sub 3} sintered polycrystalline samples. Although XPS peaks derived from Ln 4f states overlapped with the host's valence band consisting of O 2p states, the difference XPS spectra between Ln doped and non-doped samples showed only the Ln 4f peaks due to the large difference of photoionization cross sections between Ln 4f and O 2p orbitals. The difference spectra showing Ln 4f states were aligned at the valence band maximum (VBM) making use of the peaks of Al 2p inner shells, and the Ln{sup 3+} 4f energy levels referred to the VBM were determined from the Ln{sup 3+} 4f peak energies. The Ln{sup 3+} 4f energy levels obtained by this simple method were in good agreement with those previously obtained by resonant ultraviolet photoelectron spectroscopy measurements using single crystal samples. - Highlights: • Lanthanide (Ln) 4f energy in YAlO{sub 3} was studied by X-ray photoelectron spectroscopy. • The method used differences in photoionization probability between Ln 4f and O 2p. • Ln 4f states were obtained by difference spectra between Ln- and non-doped samples. • Obtained 4f energy levels agreed with those reported by a sophisticated method.

  16. Maximum likely scale estimation

    DEFF Research Database (Denmark)

    Loog, Marco; Pedersen, Kim Steenstrup; Markussen, Bo

    2005-01-01

    A maximum likelihood local scale estimation principle is presented. An actual implementation of the estimation principle uses second order moments of multiple measurements at a fixed location in the image. These measurements consist of Gaussian derivatives possibly taken at several scales and/or ...

  17. Robust Maximum Association Estimators

    NARCIS (Netherlands)

    A. Alfons (Andreas); C. Croux (Christophe); P. Filzmoser (Peter)

    2017-01-01

    textabstractThe maximum association between two multivariate variables X and Y is defined as the maximal value that a bivariate association measure between one-dimensional projections αX and αY can attain. Taking the Pearson correlation as projection index results in the first canonical correlation

  18. Brain structure in people at ultra-high risk of psychosis, patients with first-episode schizophrenia, and healthy controls: a VBM study.

    Science.gov (United States)

    Nenadic, Igor; Dietzek, Maren; Schönfeld, Nils; Lorenz, Carsten; Gussew, Alexander; Reichenbach, Jürgen R; Sauer, Heinrich; Gaser, Christian; Smesny, Stefan

    2015-02-01

    Early intervention research in schizophrenia has suggested that brain structural alterations might be present in subjects at high risk of developing psychosis. The heterogeneity of regional effects of these changes, which is established in schizophrenia, however, has not been explored in prodromal or high-risk populations. We used high-resolution MRI and voxel-based morphometry (VBM8) to analyze grey matter differences in 43 ultra high-risk subjects for psychosis (meeting ARMS criteria, identified through CAARMS interviews), 24 antipsychotic-naïve first-episode schizophrenia patients and 49 healthy controls (groups matched for age and gender). Compared to healthy controls, resp., first-episode schizophrenia patients had reduced regional grey matter in left prefrontal, insula, right parietal and left temporal cortices, while the high-risk group showed reductions in right middle temporal and left anterior frontal cortices. When dividing the ultra-high-risk group in those with a genetic risk vs. those with attenuated psychotic symptoms, the former showed left anterior frontal, right caudate, as well as a smaller right hippocampus, and amygdala reduction, while the latter subgroup showed right middle temporal cortical reductions (each compared to healthy controls). Our findings in a clinical psychosis high-risk cohort demonstrate variability of brain structural changes according to subgroup and background of elevated risk, suggesting frontal and possibly also hippocampal/amygdala changes in individuals with genetic susceptibility. Heterogeneity of structural brain changes (as seen in schizophrenia) appears evident even at high-risk stage, prior to potential onset of psychosis. Copyright © 2014 Elsevier B.V. All rights reserved.

  19. Electronic structures and optical properties of GaN nanotubes with MgGa–ON co-doping

    International Nuclear Information System (INIS)

    Yang, Mao; Shi, Jun-jie; Zhang, Min; Zhang, Shuai; Bao, Zhi-qiang; Luo, Shao-jun; Zhou, Tie-Cheng; Zhu, Tian-cong; Li, Xiang; Li, Jia

    2013-01-01

    Both the electronic structures and the optical properties of single-walled zigzag GaN nanotubes (NTs) with Mg Ga –O N co-doping are investigated using first-principles calculations. We find that the Mg Ga –O N defect complex can exist stably in GaN NTs. The direct band gap width of the GaN NTs can be reduced by means of the Mg Ga –O N co-doping. The electrons of the valence band maximum (VBM) state are localized around the N atoms bonded with the Mg atom. The imaginary part ε 2 of the complex dielectric function of GaN NTs with Mg Ga –O N co-doping has a sharp peak closely related to the optical transitions between the VBM and conduction band minimum states. - Highlights: ► The Mg Ga –O N defect complex can exist stably in GaN NTs. ► The band gap of the GaN NTs can be reduced due to the Mg Ga –O N co-doping. ► The VBM states are localized around the N atoms bonded with the Mg atom. ► The ε 2 -plot has a peak related to the optical transition from the VBM to CBM state

  20. Maximum power point tracking

    International Nuclear Information System (INIS)

    Enslin, J.H.R.

    1990-01-01

    A well engineered renewable remote energy system, utilizing the principal of Maximum Power Point Tracking can be m ore cost effective, has a higher reliability and can improve the quality of life in remote areas. This paper reports that a high-efficient power electronic converter, for converting the output voltage of a solar panel, or wind generator, to the required DC battery bus voltage has been realized. The converter is controlled to track the maximum power point of the input source under varying input and output parameters. Maximum power point tracking for relative small systems is achieved by maximization of the output current in a battery charging regulator, using an optimized hill-climbing, inexpensive microprocessor based algorithm. Through practical field measurements it is shown that a minimum input source saving of 15% on 3-5 kWh/day systems can easily be achieved. A total cost saving of at least 10-15% on the capital cost of these systems are achievable for relative small rating Remote Area Power Supply systems. The advantages at larger temperature variations and larger power rated systems are much higher. Other advantages include optimal sizing and system monitor and control

  1. Maximum entropy methods

    International Nuclear Information System (INIS)

    Ponman, T.J.

    1984-01-01

    For some years now two different expressions have been in use for maximum entropy image restoration and there has been some controversy over which one is appropriate for a given problem. Here two further entropies are presented and it is argued that there is no single correct algorithm. The properties of the four different methods are compared using simple 1D simulations with a view to showing how they can be used together to gain as much information as possible about the original object. (orig.)

  2. The last glacial maximum

    Science.gov (United States)

    Clark, P.U.; Dyke, A.S.; Shakun, J.D.; Carlson, A.E.; Clark, J.; Wohlfarth, B.; Mitrovica, J.X.; Hostetler, S.W.; McCabe, A.M.

    2009-01-01

    We used 5704 14C, 10Be, and 3He ages that span the interval from 10,000 to 50,000 years ago (10 to 50 ka) to constrain the timing of the Last Glacial Maximum (LGM) in terms of global ice-sheet and mountain-glacier extent. Growth of the ice sheets to their maximum positions occurred between 33.0 and 26.5 ka in response to climate forcing from decreases in northern summer insolation, tropical Pacific sea surface temperatures, and atmospheric CO2. Nearly all ice sheets were at their LGM positions from 26.5 ka to 19 to 20 ka, corresponding to minima in these forcings. The onset of Northern Hemisphere deglaciation 19 to 20 ka was induced by an increase in northern summer insolation, providing the source for an abrupt rise in sea level. The onset of deglaciation of the West Antarctic Ice Sheet occurred between 14 and 15 ka, consistent with evidence that this was the primary source for an abrupt rise in sea level ???14.5 ka.

  3. Maximum Entropy Fundamentals

    Directory of Open Access Journals (Sweden)

    F. Topsøe

    2001-09-01

    Full Text Available Abstract: In its modern formulation, the Maximum Entropy Principle was promoted by E.T. Jaynes, starting in the mid-fifties. The principle dictates that one should look for a distribution, consistent with available information, which maximizes the entropy. However, this principle focuses only on distributions and it appears advantageous to bring information theoretical thinking more prominently into play by also focusing on the "observer" and on coding. This view was brought forward by the second named author in the late seventies and is the view we will follow-up on here. It leads to the consideration of a certain game, the Code Length Game and, via standard game theoretical thinking, to a principle of Game Theoretical Equilibrium. This principle is more basic than the Maximum Entropy Principle in the sense that the search for one type of optimal strategies in the Code Length Game translates directly into the search for distributions with maximum entropy. In the present paper we offer a self-contained and comprehensive treatment of fundamentals of both principles mentioned, based on a study of the Code Length Game. Though new concepts and results are presented, the reading should be instructional and accessible to a rather wide audience, at least if certain mathematical details are left aside at a rst reading. The most frequently studied instance of entropy maximization pertains to the Mean Energy Model which involves a moment constraint related to a given function, here taken to represent "energy". This type of application is very well known from the literature with hundreds of applications pertaining to several different elds and will also here serve as important illustration of the theory. But our approach reaches further, especially regarding the study of continuity properties of the entropy function, and this leads to new results which allow a discussion of models with so-called entropy loss. These results have tempted us to speculate over

  4. Probable maximum flood control

    International Nuclear Information System (INIS)

    DeGabriele, C.E.; Wu, C.L.

    1991-11-01

    This study proposes preliminary design concepts to protect the waste-handling facilities and all shaft and ramp entries to the underground from the probable maximum flood (PMF) in the current design configuration for the proposed Nevada Nuclear Waste Storage Investigation (NNWSI) repository protection provisions were furnished by the United States Bureau of Reclamation (USSR) or developed from USSR data. Proposed flood protection provisions include site grading, drainage channels, and diversion dikes. Figures are provided to show these proposed flood protection provisions at each area investigated. These areas are the central surface facilities (including the waste-handling building and waste treatment building), tuff ramp portal, waste ramp portal, men-and-materials shaft, emplacement exhaust shaft, and exploratory shafts facility

  5. Introduction to maximum entropy

    International Nuclear Information System (INIS)

    Sivia, D.S.

    1988-01-01

    The maximum entropy (MaxEnt) principle has been successfully used in image reconstruction in a wide variety of fields. We review the need for such methods in data analysis and show, by use of a very simple example, why MaxEnt is to be preferred over other regularizing functions. This leads to a more general interpretation of the MaxEnt method, and its use is illustrated with several different examples. Practical difficulties with non-linear problems still remain, this being highlighted by the notorious phase problem in crystallography. We conclude with an example from neutron scattering, using data from a filter difference spectrometer to contrast MaxEnt with a conventional deconvolution. 12 refs., 8 figs., 1 tab

  6. Solar maximum observatory

    International Nuclear Information System (INIS)

    Rust, D.M.

    1984-01-01

    The successful retrieval and repair of the Solar Maximum Mission (SMM) satellite by Shuttle astronauts in April 1984 permitted continuance of solar flare observations that began in 1980. The SMM carries a soft X ray polychromator, gamma ray, UV and hard X ray imaging spectrometers, a coronagraph/polarimeter and particle counters. The data gathered thus far indicated that electrical potentials of 25 MeV develop in flares within 2 sec of onset. X ray data show that flares are composed of compressed magnetic loops that have come too close together. Other data have been taken on mass ejection, impacts of electron beams and conduction fronts with the chromosphere and changes in the solar radiant flux due to sunspots. 13 references

  7. Introduction to maximum entropy

    International Nuclear Information System (INIS)

    Sivia, D.S.

    1989-01-01

    The maximum entropy (MaxEnt) principle has been successfully used in image reconstruction in a wide variety of fields. The author reviews the need for such methods in data analysis and shows, by use of a very simple example, why MaxEnt is to be preferred over other regularizing functions. This leads to a more general interpretation of the MaxEnt method, and its use is illustrated with several different examples. Practical difficulties with non-linear problems still remain, this being highlighted by the notorious phase problem in crystallography. He concludes with an example from neutron scattering, using data from a filter difference spectrometer to contrast MaxEnt with a conventional deconvolution. 12 refs., 8 figs., 1 tab

  8. Functional Maximum Autocorrelation Factors

    DEFF Research Database (Denmark)

    Larsen, Rasmus; Nielsen, Allan Aasbjerg

    2005-01-01

    MAF outperforms the functional PCA in concentrating the interesting' spectra/shape variation in one end of the eigenvalue spectrum and allows for easier interpretation of effects. Conclusions. Functional MAF analysis is a useful methods for extracting low dimensional models of temporally or spatially......Purpose. We aim at data where samples of an underlying function are observed in a spatial or temporal layout. Examples of underlying functions are reflectance spectra and biological shapes. We apply functional models based on smoothing splines and generalize the functional PCA in......\\verb+~+\\$\\backslash\\$cite{ramsay97} to functional maximum autocorrelation factors (MAF)\\verb+~+\\$\\backslash\\$cite{switzer85,larsen2001d}. We apply the method to biological shapes as well as reflectance spectra. {\\$\\backslash\\$bf Methods}. MAF seeks linear combination of the original variables that maximize autocorrelation between...

  9. Regularized maximum correntropy machine

    KAUST Repository

    Wang, Jim Jing-Yan; Wang, Yunji; Jing, Bing-Yi; Gao, Xin

    2015-01-01

    In this paper we investigate the usage of regularized correntropy framework for learning of classifiers from noisy labels. The class label predictors learned by minimizing transitional loss functions are sensitive to the noisy and outlying labels of training samples, because the transitional loss functions are equally applied to all the samples. To solve this problem, we propose to learn the class label predictors by maximizing the correntropy between the predicted labels and the true labels of the training samples, under the regularized Maximum Correntropy Criteria (MCC) framework. Moreover, we regularize the predictor parameter to control the complexity of the predictor. The learning problem is formulated by an objective function considering the parameter regularization and MCC simultaneously. By optimizing the objective function alternately, we develop a novel predictor learning algorithm. The experiments on two challenging pattern classification tasks show that it significantly outperforms the machines with transitional loss functions.

  10. Regularized maximum correntropy machine

    KAUST Repository

    Wang, Jim Jing-Yan

    2015-02-12

    In this paper we investigate the usage of regularized correntropy framework for learning of classifiers from noisy labels. The class label predictors learned by minimizing transitional loss functions are sensitive to the noisy and outlying labels of training samples, because the transitional loss functions are equally applied to all the samples. To solve this problem, we propose to learn the class label predictors by maximizing the correntropy between the predicted labels and the true labels of the training samples, under the regularized Maximum Correntropy Criteria (MCC) framework. Moreover, we regularize the predictor parameter to control the complexity of the predictor. The learning problem is formulated by an objective function considering the parameter regularization and MCC simultaneously. By optimizing the objective function alternately, we develop a novel predictor learning algorithm. The experiments on two challenging pattern classification tasks show that it significantly outperforms the machines with transitional loss functions.

  11. Valence band photoemission from in-situ grown GaAs(100)-c(4 x 4)

    Czech Academy of Sciences Publication Activity Database

    Jiříček, Petr; Cukr, Miroslav; Bartoš, Igor; Adell, M.; Strasser, T.; Schattke, W.

    2006-01-01

    Roč. 56, č. 1 (2006), s. 21-26 ISSN 0011-4626. [Symposium on Surface Physics /10./. Praha, 11.07.2005-15.07.2005] R&D Projects: GA ČR(CZ) GA202/04/0994 Institutional research plan: CEZ:AV0Z10100521 Keywords : GaAs(100)-c(4X4) * surface states * band structure * structure plot Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.568, year: 2006

  12. Multiband model of the valence-band electronic structure in cylindrical GaAs nanowires

    Directory of Open Access Journals (Sweden)

    Čukarić Nemanja A.

    2010-01-01

    Full Text Available We compute the hole states in the GaAs free-standing nanowires, and in the GaAs/(Al,GaAs core-shell nanowires of type I-s, which are grown along the [100] direction. The hole states are extracted from the 4-band Luttinger-Kohn Hamiltonian, which explicitly takes into account mixing between the light and heavy holes. The axial aproximation is adopted, which allowed classification of states according to the total angular monentum (fz when expressed in units of the Planck constant. The envelope functions are expanded in Bessel functions of the first kind. The dispersion relations of the subbands E(kz obtained by the devised method do not resemble parabolas, which is otherwise a feature of the dispersion relations of the conduction subbands. Furthermore, the energy levels of holes whose total orbital momentum is fz=1/2 are shown to cross for a free-standing wire. The low energy fz=1/2 states are found to anticross, but these anticrossings turn into crossings when the ratio of the inner and outer radius of the core-shell wire takes a certain value. The influence of the geometric parameters on the dispersion relations is considered for both free standing and core-shell nanowires.

  13. Valence band states in Si-based p-type delta-doped field effect transistors

    International Nuclear Information System (INIS)

    Martinez-Orozco, J C; Vlaev, Stoyan J

    2009-01-01

    We present tight-binding calculations of the hole level structure of δ-doped Field Effect Transistor in a Si matrix within the first neighbors sp 3 s* semi-empirical tight-binding model including spin. We employ analytical expressions for Schottky barrier potential and the p-type δ-doped well based on a Thomas-Fermi approximation, we consider these potentials as external ones, so in the computations they are added to the diagonal terms of the tight-binding Hamiltonian, by this way we have the possibility to study the energy levels behavior as we vary the backbone parameters in the system: the two-dimensional impurity density (p 2d ) of the p-type δ-doped well and the contact voltage (V c ). The aim of this calculation is to demonstrate that the tight-binding approximation is suitable for device characterization that permits us to propose optimal values for the input parameters involved in the device design.

  14. Pressure variation of the valence band width in Ge: A self-consistent GW study

    DEFF Research Database (Denmark)

    Modak, Paritosh; Svane, Axel; Christensen, Niels Egede

    2009-01-01

    . In the present work we report results of quasiparticle self-consistent GW  (QSGW) band calculations for diamond- as well as β-tin-type Ge under pressure. For both phases we find that the band width increases with pressure. For β-tin Ge this agrees with experiment and density-functional theory, but for diamond Ge...

  15. Microscopic analysis of the valence band and impurity band theories of (Ga,Mn)As

    Czech Academy of Sciences Publication Activity Database

    Mašek, Jan; Máca, František; Kudrnovský, Josef; Makarovský, O.; Eaves, L.; Campion, R. P.; Edmonds, K. W.; Rushforth, A.W.; Foxon, C. T.; Gallagher, B. L.; Novák, Vít; Sinova, Jairo; Jungwirth, Tomáš

    2010-01-01

    Roč. 105, č. 22 (2010), 227202/1-227202/4 ISSN 0031-9007 R&D Projects: GA ČR GA202/07/0456; GA MŠk LC510; GA AV ČR KAN400100652 EU Projects: European Commission(XE) 215368 - SemiSpinNet; European Commission(XE) 214499 - NAMASTE Grant - others:AV ČR(CZ) AP0801 Program:Akademická prémie - Praemium Academiae Institutional research plan: CEZ:AV0Z10100520 Keywords : gallium arsenide * semiconductors Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 7.621, year: 2010

  16. Ab-initio valence band spectra of Al, In doped ZnO

    International Nuclear Information System (INIS)

    Palacios, P.; Sanchez, K.; Wahnon, P.

    2009-01-01

    We present the structural and electronic characterization of n-doped (Aluminium or Indium) ZnO and the effect of the doping on the calculated photoelectron spectroscopy (PES) spectra. The fully-relaxed calculations have been made using the density functional theory, including a Hubbard correlation term that increases the Zn-3d states binding energy, and which matches the experimental values. The effect of Oxygen vacancies is also included in our study. Our results show that the new Al or In-donor levels appearing in the conduction band hybridize with the Oxygen-2p states and help decrease the resistivity of these doped systems as was found experimentally. The calculated PES spectra show a small enhancement in the intensity close to the chemical potential as a result of these new Al or In levels

  17. Magnetic dichroism in UV photoemission at off-normal emission: Study of the valence bands

    International Nuclear Information System (INIS)

    Venus, D.; Kuch, W.; Lin, M.; Schneider, C.M.; Ebert, H.; Kirschner, J.

    1997-01-01

    Magnetic dichroism of angle-resolved UV photoemission from fcc Co/Cu(001) thin films has been measured using linearly p-polarized light, and a coplanar geometry where the light and photoelectron wave vectors are antiparallel, and both are perpendicular to the in-plane sample magnetization. This geometry emphasizes information about state dispersion due to the crystalline symmetry. An orderly dispersion of the features in the magnetic dichroism over a wide range of off-normal angles of electron emission is related in detail to the bulk band structure of fcc Co. The measurements confirm the practical utility of magnetic dichroism experiments as a relatively simple complement to spin-resolved photoemission. copyright 1997 The American Physical Society

  18. Photoemission intensity oscillations in the valence bands of C70 film

    International Nuclear Information System (INIS)

    Li Yanjun; Wang Peng; Ni Jingfu; Meng Liang; Wang Xiaobo; Sheng Chunqi; Li Hongnian; Zhang Wenhua; Xu Yang; Xu Faqiang; Zhu Junfa

    2011-01-01

    Highlights: → The article develops a procedure for obtaining the accurate spectral intensities in the studies of the photoionization cross-section oscillation of C 70 . → The article fulfills the observation of all oscillating periods of the cross-section oscillation of C 70 . → The article reports the oscillating data for more molecular orbitals (feature C in the article) as compared with the published works. → The article reveals that some simple theoretical models based on the spherical symmetric approximation survive for the ellipsoidally shaped C 70 . - Abstract: We have measured and analyzed the photoemission spectra (PES) of a C 70 film in the photon energy region from 13.4 eV to 98.4 eV. The photoelectron intensities of two C 2p π-derived features (denoted by A and B) oscillate regularly in the whole energy region with some fine structures below ∼30 eV. To obtain the detailed information of the oscillations, we have developed a sophisticated but practical procedure for intensity calculation. The procedure consists of two core concepts. The first is ascribing the PES features to their corresponding molecular orbitals with the help of density functional calculations. The second is a background subtraction algorithm. With this procedure, we obtained the oscillating behavior for individual features (A and B), which is by and large consistent with the predictions based on the spherical symmetric approximation although C 70 has the ellipsoidal shape. Owing to the solid state effect, the oscillating amplitudes of the A/B intensity ratios are smaller than those of gas phase C 70 , but an orbital shift reported recently was not observed on our sample. The oscillating curve of a deeper feature, which consists of both σ and π states, are also reported.

  19. Valence band states in Si-based p-type delta-doped field effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Orozco, J C; Vlaev, Stoyan J, E-mail: jcmover@correo.unam.m [Unidad Academica de Fisica, Universidad Autonoma de Zacatecas, Calzada Solidaridad esquina con Paseo la Bufa S/N, C.P. 98060, Zacatecas, Zac. (Mexico)

    2009-05-01

    We present tight-binding calculations of the hole level structure of delta-doped Field Effect Transistor in a Si matrix within the first neighbors sp{sup 3}s* semi-empirical tight-binding model including spin. We employ analytical expressions for Schottky barrier potential and the p-type delta-doped well based on a Thomas-Fermi approximation, we consider these potentials as external ones, so in the computations they are added to the diagonal terms of the tight-binding Hamiltonian, by this way we have the possibility to study the energy levels behavior as we vary the backbone parameters in the system: the two-dimensional impurity density (p{sub 2d}) of the p-type delta-doped well and the contact voltage (V{sub c}). The aim of this calculation is to demonstrate that the tight-binding approximation is suitable for device characterization that permits us to propose optimal values for the input parameters involved in the device design.

  20. Thermal evolution of the band edges of 6H-SiC: X-ray methods compared to the optical band gap

    International Nuclear Information System (INIS)

    Miedema, P.S.; Beye, M.; Könnecke, R.; Schiwietz, G.; Föhlisch, A.

    2014-01-01

    Highlights: • Conduction band minima (CBM) of 6H-SiC are estimated with Si 2p XAS. • Valence band maxima (VBM) of 6H-SiC are estimated with non-resonant Si 2p XES. • Temperature-dependent VBM and CBM of 6H-SiC show asymmetric band gap closing. • XAS, XES and RIXS band gap estimates are compared with the optical band gap. • XAS + XES versus optical band gap provides core-excitonic screening energies. - Abstract: The band gap of semiconductors like silicon and silicon carbide (SiC) is the key for their device properties. In this research, the band gap of 6H-SiC and its temperature dependence were analyzed with silicon 2p X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS) allowing for a separate analysis of the conduction-band minimum (CBM) and valence-band maximum (VBM) components of the band gap. The temperature-dependent asymmetric band gap shrinking of 6H-SiC was determined with a valence-band slope of +2.45 × 10 −4 eV/K and a conduction-band slope of −1.334 × 10 −4 eV/K. The apparent asymmetry, e.g., that two thirds of the band-gap shrinking with increasing temperature is due to the VBM evolution in 6H-SiC, is similar to the asymmetry obtained for pure silicon before. The overall band gap temperature-dependence determined with XAS and non-resonant XES is compared to temperature-dependent optical studies. The core-excitonic binding energy appearing in the Si 2p XAS is extracted as the main difference. In addition, the energy loss of the onset of the first band in RIXS yields to values similar to the optical band gap over the tested temperature range

  1. Solar maximum mission

    International Nuclear Information System (INIS)

    Ryan, J.

    1981-01-01

    By understanding the sun, astrophysicists hope to expand this knowledge to understanding other stars. To study the sun, NASA launched a satellite on February 14, 1980. The project is named the Solar Maximum Mission (SMM). The satellite conducted detailed observations of the sun in collaboration with other satellites and ground-based optical and radio observations until its failure 10 months into the mission. The main objective of the SMM was to investigate one aspect of solar activity: solar flares. A brief description of the flare mechanism is given. The SMM satellite was valuable in providing information on where and how a solar flare occurs. A sequence of photographs of a solar flare taken from SMM satellite shows how a solar flare develops in a particular layer of the solar atmosphere. Two flares especially suitable for detailed observations by a joint effort occurred on April 30 and May 21 of 1980. These flares and observations of the flares are discussed. Also discussed are significant discoveries made by individual experiments

  2. Credal Networks under Maximum Entropy

    OpenAIRE

    Lukasiewicz, Thomas

    2013-01-01

    We apply the principle of maximum entropy to select a unique joint probability distribution from the set of all joint probability distributions specified by a credal network. In detail, we start by showing that the unique joint distribution of a Bayesian tree coincides with the maximum entropy model of its conditional distributions. This result, however, does not hold anymore for general Bayesian networks. We thus present a new kind of maximum entropy models, which are computed sequentially. ...

  3. Investigation of the surface chemical and electronic states of pyridine-capped CdSe nanocrystal films after plasma treatments using H2, O2, and Ar gases

    International Nuclear Information System (INIS)

    Wang, Seok-Joo; Kim, Hyuncheol; Park, Hyung-Ho; Lee, Young-Su; Jeon, Hyeongtag; Chang, Ho Jung

    2010-01-01

    Surface chemical bonding and the electronic states of pyridine-capped CdSe nanocrystal films were evaluated using x-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy before and after plasma treatments using H 2 , O 2 , and Ar gases from the viewpoint of studying the effects of surface capping organic molecules and surface oxidation. Surface capping organic molecules could be removed during the plasma treatment due to the chemical reactivity, ion energy transfer, and vacuum UV (VUV) of the plasma gases. With O 2 plasma treatment, surface capping organic molecules were effectively removed but substantial oxidation of CdSe occurred during the plasma treatment. The valence band maximum energy (E VBM ) of CdSe nanocrystal films mainly depends on the apparent size of pyridine-capped CdSe nanocrystals, which controls the interparticle distance, and also on the oxidation of CdSe nanocrystals. Cd-rich surface in O 2 and H 2 plasma treatments partially would compensate for the decrease in E VBM . After Ar plasma treatment, the smallest value of E VBM resulted from high VUV photon flux, short wavelength, and ion energy transfer. The surface bonding states of CdSe had a strong influence on the electronic structure with the efficient strip of capping molecules as well as different surface oxidations and surface capping molecule contents.

  4. Maximum Entropy in Drug Discovery

    Directory of Open Access Journals (Sweden)

    Chih-Yuan Tseng

    2014-07-01

    Full Text Available Drug discovery applies multidisciplinary approaches either experimentally, computationally or both ways to identify lead compounds to treat various diseases. While conventional approaches have yielded many US Food and Drug Administration (FDA-approved drugs, researchers continue investigating and designing better approaches to increase the success rate in the discovery process. In this article, we provide an overview of the current strategies and point out where and how the method of maximum entropy has been introduced in this area. The maximum entropy principle has its root in thermodynamics, yet since Jaynes’ pioneering work in the 1950s, the maximum entropy principle has not only been used as a physics law, but also as a reasoning tool that allows us to process information in hand with the least bias. Its applicability in various disciplines has been abundantly demonstrated. We give several examples of applications of maximum entropy in different stages of drug discovery. Finally, we discuss a promising new direction in drug discovery that is likely to hinge on the ways of utilizing maximum entropy.

  5. Maximum stellar iron core mass

    Indian Academy of Sciences (India)

    60, No. 3. — journal of. March 2003 physics pp. 415–422. Maximum stellar iron core mass. F W GIACOBBE. Chicago Research Center/American Air Liquide ... iron core compression due to the weight of non-ferrous matter overlying the iron cores within large .... thermal equilibrium velocities will tend to be non-relativistic.

  6. Maximum entropy beam diagnostic tomography

    International Nuclear Information System (INIS)

    Mottershead, C.T.

    1985-01-01

    This paper reviews the formalism of maximum entropy beam diagnostic tomography as applied to the Fusion Materials Irradiation Test (FMIT) prototype accelerator. The same formalism has also been used with streak camera data to produce an ultrahigh speed movie of the beam profile of the Experimental Test Accelerator (ETA) at Livermore. 11 refs., 4 figs

  7. Maximum entropy beam diagnostic tomography

    International Nuclear Information System (INIS)

    Mottershead, C.T.

    1985-01-01

    This paper reviews the formalism of maximum entropy beam diagnostic tomography as applied to the Fusion Materials Irradiation Test (FMIT) prototype accelerator. The same formalism has also been used with streak camera data to produce an ultrahigh speed movie of the beam profile of the Experimental Test Accelerator (ETA) at Livermore

  8. A portable storage maximum thermometer

    International Nuclear Information System (INIS)

    Fayart, Gerard.

    1976-01-01

    A clinical thermometer storing the voltage corresponding to the maximum temperature in an analog memory is described. End of the measurement is shown by a lamp switch out. The measurement time is shortened by means of a low thermal inertia platinum probe. This portable thermometer is fitted with cell test and calibration system [fr

  9. Neutron spectra unfolding with maximum entropy and maximum likelihood

    International Nuclear Information System (INIS)

    Itoh, Shikoh; Tsunoda, Toshiharu

    1989-01-01

    A new unfolding theory has been established on the basis of the maximum entropy principle and the maximum likelihood method. This theory correctly embodies the Poisson statistics of neutron detection, and always brings a positive solution over the whole energy range. Moreover, the theory unifies both problems of overdetermined and of underdetermined. For the latter, the ambiguity in assigning a prior probability, i.e. the initial guess in the Bayesian sense, has become extinct by virtue of the principle. An approximate expression of the covariance matrix for the resultant spectra is also presented. An efficient algorithm to solve the nonlinear system, which appears in the present study, has been established. Results of computer simulation showed the effectiveness of the present theory. (author)

  10. Highly Efficient Photocatalytic Water Splitting over Edge-Modified Phosphorene Nanoribbons.

    Science.gov (United States)

    Hu, Wei; Lin, Lin; Zhang, Ruiqi; Yang, Chao; Yang, Jinlong

    2017-11-01

    Two-dimensional phosphorene with desirable optoelectronic properties (ideal band gap, high carrier mobility, and strong visible light absorption) is a promising metal-free photocatalyst for water splitting. However, the band edge positions of the valence band maximum (VBM) and conduction band maximum (CBM) of phosphorene are higher than the redox potentials in photocatalytic water splitting reactions. Thus, phosphorene can only be used as the photocathode for hydrogen evolution reaction as a low-efficiency visible-light-driven photocatalyst for hydrogen production in solar water splitting cells. Here, we propose a new mechanism to improve the photocatalytic efficiency of phosphorene nanoribbons (PNRs) by modifying their edges for full reactions in photocatalytic water splitting. By employing first-principles density functional theory calculations, we find that pseudohalogen (CN and OCN) passivated PNRs not only show desired VBM and CBM band edge positions induced by edge electric dipole layer, but also possess intrinsic optoelectronic properties of phosphorene, for both water oxidation and hydrogen reduction in photocatalytic water splitting without using extra energy. Furthermore, our calculations also predict that the maximum energy conversion efficiency of heterojunction solar cells consisting of different edge-modified PNRs can be as high as 20% for photocatalytic water splitting.

  11. On Maximum Entropy and Inference

    Directory of Open Access Journals (Sweden)

    Luigi Gresele

    2017-11-01

    Full Text Available Maximum entropy is a powerful concept that entails a sharp separation between relevant and irrelevant variables. It is typically invoked in inference, once an assumption is made on what the relevant variables are, in order to estimate a model from data, that affords predictions on all other (dependent variables. Conversely, maximum entropy can be invoked to retrieve the relevant variables (sufficient statistics directly from the data, once a model is identified by Bayesian model selection. We explore this approach in the case of spin models with interactions of arbitrary order, and we discuss how relevant interactions can be inferred. In this perspective, the dimensionality of the inference problem is not set by the number of parameters in the model, but by the frequency distribution of the data. We illustrate the method showing its ability to recover the correct model in a few prototype cases and discuss its application on a real dataset.

  12. Maximum Water Hammer Sensitivity Analysis

    OpenAIRE

    Jalil Emadi; Abbas Solemani

    2011-01-01

    Pressure waves and Water Hammer occur in a pumping system when valves are closed or opened suddenly or in the case of sudden failure of pumps. Determination of maximum water hammer is considered one of the most important technical and economical items of which engineers and designers of pumping stations and conveyance pipelines should take care. Hammer Software is a recent application used to simulate water hammer. The present study focuses on determining significance of ...

  13. Maximum Gene-Support Tree

    Directory of Open Access Journals (Sweden)

    Yunfeng Shan

    2008-01-01

    Full Text Available Genomes and genes diversify during evolution; however, it is unclear to what extent genes still retain the relationship among species. Model species for molecular phylogenetic studies include yeasts and viruses whose genomes were sequenced as well as plants that have the fossil-supported true phylogenetic trees available. In this study, we generated single gene trees of seven yeast species as well as single gene trees of nine baculovirus species using all the orthologous genes among the species compared. Homologous genes among seven known plants were used for validation of the finding. Four algorithms—maximum parsimony (MP, minimum evolution (ME, maximum likelihood (ML, and neighbor-joining (NJ—were used. Trees were reconstructed before and after weighting the DNA and protein sequence lengths among genes. Rarely a gene can always generate the “true tree” by all the four algorithms. However, the most frequent gene tree, termed “maximum gene-support tree” (MGS tree, or WMGS tree for the weighted one, in yeasts, baculoviruses, or plants was consistently found to be the “true tree” among the species. The results provide insights into the overall degree of divergence of orthologous genes of the genomes analyzed and suggest the following: 1 The true tree relationship among the species studied is still maintained by the largest group of orthologous genes; 2 There are usually more orthologous genes with higher similarities between genetically closer species than between genetically more distant ones; and 3 The maximum gene-support tree reflects the phylogenetic relationship among species in comparison.

  14. LCLS Maximum Credible Beam Power

    International Nuclear Information System (INIS)

    Clendenin, J.

    2005-01-01

    The maximum credible beam power is defined as the highest credible average beam power that the accelerator can deliver to the point in question, given the laws of physics, the beam line design, and assuming all protection devices have failed. For a new accelerator project, the official maximum credible beam power is determined by project staff in consultation with the Radiation Physics Department, after examining the arguments and evidence presented by the appropriate accelerator physicist(s) and beam line engineers. The definitive parameter becomes part of the project's safety envelope. This technical note will first review the studies that were done for the Gun Test Facility (GTF) at SSRL, where a photoinjector similar to the one proposed for the LCLS is being tested. In Section 3 the maximum charge out of the gun for a single rf pulse is calculated. In Section 4, PARMELA simulations are used to track the beam from the gun to the end of the photoinjector. Finally in Section 5 the beam through the matching section and injected into Linac-1 is discussed

  15. Effects of residual hydrogen in sputtering atmosphere on structures and properties of amorphous In-Ga-Zn-O thin films

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Haochun; Ishikawa, Kyohei; Ide, Keisuke [Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Hiramatsu, Hidenori; Hosono, Hideo; Kamiya, Toshio, E-mail: kamiya.t.aa@m.titech.ac.jp [Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Ueda, Shigenori [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba-city, Ibaraki 305-0047 (Japan); Ohashi, Naoki [Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); National Institute for Materials Science, 1-2-1 Sengen, Tsukuba-city, Ibaraki 305-0047 (Japan); Kumomi, Hideya [Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan)

    2015-11-28

    We investigated the effects of residual hydrogen in sputtering atmosphere on subgap states and carrier transport in amorphous In-Ga-Zn-O (a-IGZO) using two sputtering systems with different base pressures of ∼10{sup −4} and 10{sup −7 }Pa (standard (STD) and ultrahigh vacuum (UHV) sputtering, respectively), which produce a-IGZO films with impurity hydrogen contents at the orders of 10{sup 20} and 10{sup 19 }cm{sup −3}, respectively. Several subgap states were observed by hard X-ray photoemission spectroscopy, i.e., peak-shape near-valence band maximum (near-VBM) states, shoulder-shape near-VBM states, peak-shape near-conduction band minimum (near-CBM) states, and step-wise near-CBM states. It was confirmed that the formation of these subgap states were affected strongly by the residual hydrogen (possibly H{sub 2}O). The step-wise near-CBM states were observed only in the STD films deposited without O{sub 2} gas flow and attributed to metallic In. Such step-wise near-CBM state was not detected in the other films including the UHV films even deposited without O{sub 2} flow, substantiating that the metallic In is segregated by the strong reduction effect of the hydrogen/H{sub 2}O. Similarly, the density of the near-VBM states was very high for the STD films deposited without O{sub 2}. These films had low film density and are consistent with a model that voids in the amorphous structure form a part of the near-VBM states. On the other hand, the UHV films had high film densities and much less near-VBM states, keeping the possibility that some of the near-VBM states, in particular, of the peak-shape ones, originate from –OH and weakly bonded oxygen. These results indicate that 2% of excess O{sub 2} flow is required for the STD sputtering to compensate the effects of the residual hydrogen/H{sub 2}O. The high-density near-VBM states and the metallic In segregation deteriorated the electron mobility to 0.4 cm{sup 2}/(V s)

  16. Generic maximum likely scale selection

    DEFF Research Database (Denmark)

    Pedersen, Kim Steenstrup; Loog, Marco; Markussen, Bo

    2007-01-01

    in this work is on applying this selection principle under a Brownian image model. This image model provides a simple scale invariant prior for natural images and we provide illustrative examples of the behavior of our scale estimation on such images. In these illustrative examples, estimation is based......The fundamental problem of local scale selection is addressed by means of a novel principle, which is based on maximum likelihood estimation. The principle is generally applicable to a broad variety of image models and descriptors, and provides a generic scale estimation methodology. The focus...

  17. Extreme Maximum Land Surface Temperatures.

    Science.gov (United States)

    Garratt, J. R.

    1992-09-01

    There are numerous reports in the literature of observations of land surface temperatures. Some of these, almost all made in situ, reveal maximum values in the 50°-70°C range, with a few, made in desert regions, near 80°C. Consideration of a simplified form of the surface energy balance equation, utilizing likely upper values of absorbed shortwave flux (1000 W m2) and screen air temperature (55°C), that surface temperatures in the vicinity of 90°-100°C may occur for dry, darkish soils of low thermal conductivity (0.1-0.2 W m1 K1). Numerical simulations confirm this and suggest that temperature gradients in the first few centimeters of soil may reach 0.5°-1°C mm1 under these extreme conditions. The study bears upon the intrinsic interest of identifying extreme maximum temperatures and yields interesting information regarding the comfort zone of animals (including man).

  18. System for memorizing maximum values

    Science.gov (United States)

    Bozeman, Richard J., Jr.

    1992-08-01

    The invention discloses a system capable of memorizing maximum sensed values. The system includes conditioning circuitry which receives the analog output signal from a sensor transducer. The conditioning circuitry rectifies and filters the analog signal and provides an input signal to a digital driver, which may be either linear or logarithmic. The driver converts the analog signal to discrete digital values, which in turn triggers an output signal on one of a plurality of driver output lines n. The particular output lines selected is dependent on the converted digital value. A microfuse memory device connects across the driver output lines, with n segments. Each segment is associated with one driver output line, and includes a microfuse that is blown when a signal appears on the associated driver output line.

  19. Remarks on the maximum luminosity

    Science.gov (United States)

    Cardoso, Vitor; Ikeda, Taishi; Moore, Christopher J.; Yoo, Chul-Moon

    2018-04-01

    The quest for fundamental limitations on physical processes is old and venerable. Here, we investigate the maximum possible power, or luminosity, that any event can produce. We show, via full nonlinear simulations of Einstein's equations, that there exist initial conditions which give rise to arbitrarily large luminosities. However, the requirement that there is no past horizon in the spacetime seems to limit the luminosity to below the Planck value, LP=c5/G . Numerical relativity simulations of critical collapse yield the largest luminosities observed to date, ≈ 0.2 LP . We also present an analytic solution to the Einstein equations which seems to give an unboundedly large luminosity; this will guide future numerical efforts to investigate super-Planckian luminosities.

  20. Maximum mutual information regularized classification

    KAUST Repository

    Wang, Jim Jing-Yan

    2014-09-07

    In this paper, a novel pattern classification approach is proposed by regularizing the classifier learning to maximize mutual information between the classification response and the true class label. We argue that, with the learned classifier, the uncertainty of the true class label of a data sample should be reduced by knowing its classification response as much as possible. The reduced uncertainty is measured by the mutual information between the classification response and the true class label. To this end, when learning a linear classifier, we propose to maximize the mutual information between classification responses and true class labels of training samples, besides minimizing the classification error and reducing the classifier complexity. An objective function is constructed by modeling mutual information with entropy estimation, and it is optimized by a gradient descend method in an iterative algorithm. Experiments on two real world pattern classification problems show the significant improvements achieved by maximum mutual information regularization.

  1. Scintillation counter, maximum gamma aspect

    International Nuclear Information System (INIS)

    Thumim, A.D.

    1975-01-01

    A scintillation counter, particularly for counting gamma ray photons, includes a massive lead radiation shield surrounding a sample-receiving zone. The shield is disassembleable into a plurality of segments to allow facile installation and removal of a photomultiplier tube assembly, the segments being so constructed as to prevent straight-line access of external radiation through the shield into radiation-responsive areas. Provisions are made for accurately aligning the photomultiplier tube with respect to one or more sample-transmitting bores extending through the shield to the sample receiving zone. A sample elevator, used in transporting samples into the zone, is designed to provide a maximum gamma-receiving aspect to maximize the gamma detecting efficiency. (U.S.)

  2. Maximum mutual information regularized classification

    KAUST Repository

    Wang, Jim Jing-Yan; Wang, Yi; Zhao, Shiguang; Gao, Xin

    2014-01-01

    In this paper, a novel pattern classification approach is proposed by regularizing the classifier learning to maximize mutual information between the classification response and the true class label. We argue that, with the learned classifier, the uncertainty of the true class label of a data sample should be reduced by knowing its classification response as much as possible. The reduced uncertainty is measured by the mutual information between the classification response and the true class label. To this end, when learning a linear classifier, we propose to maximize the mutual information between classification responses and true class labels of training samples, besides minimizing the classification error and reducing the classifier complexity. An objective function is constructed by modeling mutual information with entropy estimation, and it is optimized by a gradient descend method in an iterative algorithm. Experiments on two real world pattern classification problems show the significant improvements achieved by maximum mutual information regularization.

  3. Dynamics of Impurity and Valence Bands in Ga1-xMnxAs Within the Dynamical Mean-Field Approximation

    International Nuclear Information System (INIS)

    Majidi, M.A.; Moreno, Juana; Jarrell, Mark; Fishman, Randy Scott; Aryanpour, K.A.

    2006-01-01

    We calculate the density-of-states and the spectral function of Ga 1-x Mn x As within the dynamical mean-field approximation. Our model includes the competing effects of the strong spin-orbit coupling on the J=3/2 GaAs hole bands and the exchange interaction between the magnetic ions and the itinerant holes. We study the quasiparticle and impurity bands in the paramagnetic and ferromagnetic phases for different values of impurity-hole coupling J c at a Mn doping of x=0.05. By analyzing the anisotropic angular distribution of the impurity band carriers at T=0, we conclude that the carrier polarization is optimal when the carriers move along the direction parallel to the average magnetization.

  4. Size and alloying induced shift in core and valence bands of Pd-Ag and Pd-Cu nanoparticles

    International Nuclear Information System (INIS)

    Sengar, Saurabh K.; Mehta, B. R.; Govind

    2014-01-01

    In this report, X-ray photoelectron spectroscopy studies have been carried out on Pd, Ag, Cu, Pd-Ag, and Pd-Cu nanoparticles having identical sizes corresponding to mobility equivalent diameters of 60, 40, and 20 nm. The nanoparticles were prepared by the gas phase synthesis method. The effect of size on valence and core levels in metal and alloy nanoparticles has been studied by comparing the values to those with the 60 nm nanoparticles. The effect of alloying has been investigated by comparing the valence and core level binding energies of Pd-Cu and Pd-Ag alloy nanoparticles with the corresponding values for Pd, Ag, and Cu nanoparticles of identical sizes. These effects have been explained in terms of size induced lattice contractions, alloying induced charge transfer, and hybridization effects. The observation of alloying and size induced binding energy shifts in bimetallic nanoparticles is important from the point of view of hydrogen reactivity

  5. Character of states near the Fermi level in (Ga,Mn)As: impurity to valence band crossover

    Czech Academy of Sciences Publication Activity Database

    Jungwirth, Tomáš; Sinova, J.; MacDonald, A. H.; Gallagher, B. L.; Novák, Vít; Edmonds, K. W.; Rushforth, A.W.; Campion, R. P.; Foxon, C. T.; Eaves, L.; Olejník, Kamil; Mašek, Jan; Yang, E. S. R.; Wunderlich, J.; Gould, C.; Molenkamp, L. W.; Dietl, T.; Ohno, H.

    2007-01-01

    Roč. 76, č. 12 (2007), 125206/1-125206/8 ISSN 1098-0121 R&D Projects: GA ČR GA202/05/0575; GA ČR GA202/04/1519; GA AV ČR KAN400100652; GA MŠk LC510; GA ČR GEFON/06/E001; GA ČR GEFON/06/E002 EU Projects: European Commission(XE) 015728 - NANOSPIN Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z10100521 Keywords : ferromagnetic semiconductors, * metal-insulator transition Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.172, year: 2007

  6. Fine structure and energy spectrum of exciton in direct band gap cubic semiconductors with degenerate valence bands

    International Nuclear Information System (INIS)

    Nguyen Toan Thang; Nguyen Ai Viet; Nguyen Que Huong

    1987-06-01

    The influence of the cubic structure on the energy spectrum of direct exciton is investigated, using the new method suggested by Nguyen Van Hieu and co-workers. Explicit expressions of the exciton energy levels 1S, 2S and 2P are derived. A comparison with the experiments and the other theory is done for ZnSe. (author). 10 refs, 1 fig., 2 tabs

  7. Maximum entropy and Bayesian methods

    International Nuclear Information System (INIS)

    Smith, C.R.; Erickson, G.J.; Neudorfer, P.O.

    1992-01-01

    Bayesian probability theory and Maximum Entropy methods are at the core of a new view of scientific inference. These 'new' ideas, along with the revolution in computational methods afforded by modern computers allow astronomers, electrical engineers, image processors of any type, NMR chemists and physicists, and anyone at all who has to deal with incomplete and noisy data, to take advantage of methods that, in the past, have been applied only in some areas of theoretical physics. The title workshops have been the focus of a group of researchers from many different fields, and this diversity is evident in this book. There are tutorial and theoretical papers, and applications in a very wide variety of fields. Almost any instance of dealing with incomplete and noisy data can be usefully treated by these methods, and many areas of theoretical research are being enhanced by the thoughtful application of Bayes' theorem. Contributions contained in this volume present a state-of-the-art overview that will be influential and useful for many years to come

  8. Maximum entropy principal for transportation

    International Nuclear Information System (INIS)

    Bilich, F.; Da Silva, R.

    2008-01-01

    In this work we deal with modeling of the transportation phenomenon for use in the transportation planning process and policy-impact studies. The model developed is based on the dependence concept, i.e., the notion that the probability of a trip starting at origin i is dependent on the probability of a trip ending at destination j given that the factors (such as travel time, cost, etc.) which affect travel between origin i and destination j assume some specific values. The derivation of the solution of the model employs the maximum entropy principle combining a priori multinomial distribution with a trip utility concept. This model is utilized to forecast trip distributions under a variety of policy changes and scenarios. The dependence coefficients are obtained from a regression equation where the functional form is derived based on conditional probability and perception of factors from experimental psychology. The dependence coefficients encode all the information that was previously encoded in the form of constraints. In addition, the dependence coefficients encode information that cannot be expressed in the form of constraints for practical reasons, namely, computational tractability. The equivalence between the standard formulation (i.e., objective function with constraints) and the dependence formulation (i.e., without constraints) is demonstrated. The parameters of the dependence-based trip-distribution model are estimated, and the model is also validated using commercial air travel data in the U.S. In addition, policy impact analyses (such as allowance of supersonic flights inside the U.S. and user surcharge at noise-impacted airports) on air travel are performed.

  9. Last Glacial Maximum Salinity Reconstruction

    Science.gov (United States)

    Homola, K.; Spivack, A. J.

    2016-12-01

    It has been previously demonstrated that salinity can be reconstructed from sediment porewater. The goal of our study is to reconstruct high precision salinity during the Last Glacial Maximum (LGM). Salinity is usually determined at high precision via conductivity, which requires a larger volume of water than can be extracted from a sediment core, or via chloride titration, which yields lower than ideal precision. It has been demonstrated for water column samples that high precision density measurements can be used to determine salinity at the precision of a conductivity measurement using the equation of state of seawater. However, water column seawater has a relatively constant composition, in contrast to porewater, where variations from standard seawater composition occur. These deviations, which affect the equation of state, must be corrected for through precise measurements of each ion's concentration and knowledge of apparent partial molar density in seawater. We have developed a density-based method for determining porewater salinity that requires only 5 mL of sample, achieving density precisions of 10-6 g/mL. We have applied this method to porewater samples extracted from long cores collected along a N-S transect across the western North Atlantic (R/V Knorr cruise KN223). Density was determined to a precision of 2.3x10-6 g/mL, which translates to salinity uncertainty of 0.002 gms/kg if the effect of differences in composition is well constrained. Concentrations of anions (Cl-, and SO4-2) and cations (Na+, Mg+, Ca+2, and K+) were measured. To correct salinities at the precision required to unravel LGM Meridional Overturning Circulation, our ion precisions must be better than 0.1% for SO4-/Cl- and Mg+/Na+, and 0.4% for Ca+/Na+, and K+/Na+. Alkalinity, pH and Dissolved Inorganic Carbon of the porewater were determined to precisions better than 4% when ratioed to Cl-, and used to calculate HCO3-, and CO3-2. Apparent partial molar densities in seawater were

  10. Maximum Parsimony on Phylogenetic networks

    Science.gov (United States)

    2012-01-01

    Background Phylogenetic networks are generalizations of phylogenetic trees, that are used to model evolutionary events in various contexts. Several different methods and criteria have been introduced for reconstructing phylogenetic trees. Maximum Parsimony is a character-based approach that infers a phylogenetic tree by minimizing the total number of evolutionary steps required to explain a given set of data assigned on the leaves. Exact solutions for optimizing parsimony scores on phylogenetic trees have been introduced in the past. Results In this paper, we define the parsimony score on networks as the sum of the substitution costs along all the edges of the network; and show that certain well-known algorithms that calculate the optimum parsimony score on trees, such as Sankoff and Fitch algorithms extend naturally for networks, barring conflicting assignments at the reticulate vertices. We provide heuristics for finding the optimum parsimony scores on networks. Our algorithms can be applied for any cost matrix that may contain unequal substitution costs of transforming between different characters along different edges of the network. We analyzed this for experimental data on 10 leaves or fewer with at most 2 reticulations and found that for almost all networks, the bounds returned by the heuristics matched with the exhaustively determined optimum parsimony scores. Conclusion The parsimony score we define here does not directly reflect the cost of the best tree in the network that displays the evolution of the character. However, when searching for the most parsimonious network that describes a collection of characters, it becomes necessary to add additional cost considerations to prefer simpler structures, such as trees over networks. The parsimony score on a network that we describe here takes into account the substitution costs along the additional edges incident on each reticulate vertex, in addition to the substitution costs along the other edges which are

  11. Band gap and defect states of MgO thin films investigated using reflection electron energy loss spectroscopy

    Directory of Open Access Journals (Sweden)

    Sung Heo

    2015-07-01

    Full Text Available The band gap and defect states of MgO thin films were investigated by using reflection electron energy loss spectroscopy (REELS and high-energy resolution REELS (HR-REELS. HR-REELS with a primary electron energy of 0.3 keV revealed that the surface F center (FS energy was located at approximately 4.2 eV above the valence band maximum (VBM and the surface band gap width (EgS was approximately 6.3 eV. The bulk F center (FB energy was located approximately 4.9 eV above the VBM and the bulk band gap width was about 7.8 eV, when measured by REELS with 3 keV primary electrons. From a first-principles calculation, we confirmed that the 4.2 eV and 4.9 eV peaks were FS and FB, induced by oxygen vacancies. We also experimentally demonstrated that the HR-REELS peak height increases with increasing number of oxygen vacancies. Finally, we calculated the secondary electron emission yields (γ for various noble gases. He and Ne were not influenced by the defect states owing to their higher ionization energies, but Ar, Kr, and Xe exhibited a stronger dependence on the defect states owing to their small ionization energies.

  12. Performance enhancement of perovskite solar cells with Mg-doped TiO2 compact film as the hole-blocking layer

    International Nuclear Information System (INIS)

    Wang, Jing; Qin, Minchao; Tao, Hong; Ke, Weijun; Chen, Zhao; Wan, Jiawei; Qin, Pingli; Lei, Hongwei; Fang, Guojia; Xiong, Liangbin; Yu, Huaqing

    2015-01-01

    In this letter, we report perovskite solar cells with thin dense Mg-doped TiO 2 as hole-blocking layers (HBLs), which outperform cells using TiO 2 HBLs in several ways: higher open-circuit voltage (V oc ) (1.08 V), power conversion efficiency (12.28%), short-circuit current, and fill factor. These properties improvements are attributed to the better properties of Mg-modulated TiO 2 as compared to TiO 2 such as better optical transmission properties, upshifted conduction band minimum (CBM) and downshifted valence band maximum (VBM), better hole-blocking effect, and higher electron life time. The higher-lying CBM due to the modulation with wider band gap MgO and the formation of magnesium oxide and magnesium hydroxides together resulted in an increment of V oc . In addition, the Mg-modulated TiO 2 with lower VBM played a better role in the hole-blocking. The HBL with modulated band position provided better electron transport and hole blocking effects within the device

  13. Enhanced surface modification engineering (H, F, Cl, Br, and NO{sub 2}) of CdS nanowires with and without surface dangling bonds

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Yijie; Xing, Huaizhong, E-mail: xinghz@dhu.edu.cn; Lu, Aijiang; Wang, Chunrui; Xu, Xiaofeng [Department of Applied Physics and State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Ren Min Road 2999, Songjiang District, Shanghai 201620 (China); Huang, Yan; Chen, Xiaoshuang, E-mail: jqwang@ee.ecnu.edu.cn, E-mail: xschen@mail.sitp.ac.cn [National Lab. of Infrared Physics, Shanghai Institute for Technical Physics, Chinese Academy of Science, 500 Yu Tian Road, Shanghai 200083 (China); Wang, Jiqing, E-mail: jqwang@ee.ecnu.edu.cn, E-mail: xschen@mail.sitp.ac.cn [Key Laboratory of Polarized Materials and Devices, East China Normal University, Shanghai 200062 (China)

    2015-08-07

    Semiconductor nanowires (NWs) can be applied in gas sensing and cell detection, but the sensing mechanism is not clearly understood. In this study, surface modification effect on the electronic properties of CdS NWs for different diameters with several species (H, F, Cl, Br, and NO{sub 2}) is investigated by first principles calculations. The surface dangling bonds and halogen elements are chosen to represent the environment of the surface. Halogen passivation drastically changes the band gaps due to the strong electronegativity and the energy level of halogen atoms. Density of states analysis indicates that valence band maximum (VBM) of halogen-passivated NWs is formed by the p states of halogen atoms, while VBM of H-passivated NWs is originated from Cd 4d and S 3p orbitals. To illustrate that surface modification can be applied in gas sensing, NO{sub 2}-absorbed NWs with different coverage are calculated. Low coverage of NO{sub 2} introduces a deep p-type dopant-like level, while high coverage introduces a shallow n-type dopant-like level into the band structure. The transformation is due to that at low coverage the adsorption is chemical while at high coverage is physical. These findings might promote the understanding of surface modification effect and the sensing mechanism of NWs as gas sensors.

  14. Scaling Effect of Phosphorene Nanoribbon - Uncovering the Origin of Asymmetric Current Transport

    Science.gov (United States)

    Lv, Yawei; Chang, Sheng; Huang, Qijun; Wang, Hao; He, Jin

    2016-01-01

    In this paper, phosphorene nanoribbons (PNRs) are theoretically studied using a multiscale simulation flow from the ab initio level to the tight binding (TB) level. The scaling effects of both armchair PNRs (aPNRs) and zigzag PNRs (zPNRs) from material properties to device properties are explored. The much larger effective mass of holes compared to that of electrons in zPNR is responsible for its asymmetric transport. However, in aPNR, not only the effective mass difference but also the non-equal density of state (DOS) distributions near valence band maximum (VBM) and conduction band minimum (CBM) lead to the asymmetric transport. This non-equal distribution phenomenon is caused by energy band degeneracies near the VBM. Based on these two different mechanisms, PNRs’ asymmetric transport characteristics at the device level are explained, and it is shown that this behaviour can be ameliorated well by reducing the ribbon width in an aPNR MOSFET. Calculation results also indicate that aPNR’s effective mass is comparable to that of a graphene nanoribbon (GNR) at the same bandgap; however, aPNR’s band gap variation is more stable and regular than that of GNR, making it a good candidate for use in low-dimensional nano devices. PMID:27897230

  15. Electron–phonon interaction and scattering in phosphorene

    Science.gov (United States)

    Fan, Xiaolin; Zhao, Guojun; Wang, Shudong

    2018-04-01

    The electron–phonon scattering of phosphorene is investigated via performing first-principles calculations. Our results reveal that the scattering rates are negligible at the valence band maximum (VBM) and conduction band minimum, but they are much larger away from the band edges. The scattering rates increase with the rising temperature. The relaxation times run up to ~850 fs around the VBM at 1 K, and they will decrease with the increasing temperature. In addition, we find that the mean free paths (MFPs) are anisotropic. The MFPs along the armchair direction are two times larger than that along the zigzag direction near the band edges. According to our results, we predict that the extraction of hot holes is best achieved along the armchair direction in phosphorene with a 65 nm range at 1 K. The best extraction range of hot electrons is less than 30 nm along the armchair direction at 1 K. On the other hand, the extraction range of hot holes and hot electrons will decrease to 15 nm along both directions in phosphorene at 300 K.

  16. The structural, electronic and magnetic properties of CoS2 under pressure

    Science.gov (United States)

    Feng, Zhong-Ying; Yang, Yan; Zhang, Jian-Min

    2018-05-01

    The structural, electronic and magnetic properties of CoS2 under pressure have been investigated by the first-principles calculations. The lattice constant and volume decrease with increasing pressure. The CoS2 is stable and behaves a brittle characteristic under the pressures of 0-5 GPa. The CoS2 presents metallic characteristic under the pressures of 1-5 GPa although it is nearly half-metal (HM) under the pressure of 0 GPa. The lowest conduction bands for spin-up and spin-down channels shift towards higher and lower energy region, respectively, with the pressure increasing from 0 to 5 GPa. In spin-up channel the conduction band minimum (CBM) is mainly contributed by Co-3d(eg) orbitals at R point but the valence band maximum (VBM) is contributed by Co-3d(t2g) orbitals near M point. While in spin-down channel the CBM is contributed by S-3p orbitals at Γ point but the VBM is contributed by Co-3d(t2g) orbitals near X point. The CoS2 is still suitable to be used in the supercapacitor under the environmental pressures of 0-5 GPa due to the high conductivity.

  17. A Combined Theoretical and Experimental View on Valence and Conduction Band Densities of States of Lead Halide Perovskites

    Science.gov (United States)

    Kronik, Leeor; Endres, James; Egger, David A.; Kulbak, Michael; Kerner, Ross A.; Zhao, Lianfeng; Silver, Scott H.; Hodes, Gary; Rand, Barry P.; Cahen, David; Kahn, Antoine

    We present results for the valence and conduction band density of states (DOS), measured via ultraviolet and inverse photoemission spectroscopies for three lead halide perovskites. Specifically, the DOS of MAPbI3, MAPbBr3, and CsPbBr3, grown on different substrates, are compared. Theoretical DOS, calculated via hybrid density functional theory and including spin-orbit coupling, are compared to experimental data. The agreement between experiment and theory, obtained after correcting the latter for quantitative discrepancies, leads to the identification of valence and conduction band spectral features. In particular, this comparison allows for precise determination of the energy position of the band edges, namely ionization energies and electron affinities of these materials. We find an unusually low DOS at the valence band maximum (VBM) of these systems, which confirms and generalizes previous findings of strong band dispersion and low DOS at the VBM of MAPbI3. This calls for special attention when using electron spectroscopy to determine the frontier electronic states of lead halide perovskites.

  18. Maximum: Recent Implementation and Application to the Study of Corrosion-Induced Microstructures in Thin Films of Aluminum-Copper Metallization.

    Science.gov (United States)

    Liang, Shoudeng

    energy-specific photoelectrons from Cu 3d and O 2p valence bands. Such characteristic structures were observed only when the film was annealed below the solvus temperatures in the Al-Cu binary phase diagram, i.e., when a phase separation occurred. These results demonstrated the usefulness of spectromicroscopy in corrosion studies.

  19. Two-dimensional maximum entropy image restoration

    International Nuclear Information System (INIS)

    Brolley, J.E.; Lazarus, R.B.; Suydam, B.R.; Trussell, H.J.

    1977-07-01

    An optical check problem was constructed to test P LOG P maximum entropy restoration of an extremely distorted image. Useful recovery of the original image was obtained. Comparison with maximum a posteriori restoration is made. 7 figures

  20. Receiver function estimated by maximum entropy deconvolution

    Institute of Scientific and Technical Information of China (English)

    吴庆举; 田小波; 张乃铃; 李卫平; 曾融生

    2003-01-01

    Maximum entropy deconvolution is presented to estimate receiver function, with the maximum entropy as the rule to determine auto-correlation and cross-correlation functions. The Toeplitz equation and Levinson algorithm are used to calculate the iterative formula of error-predicting filter, and receiver function is then estimated. During extrapolation, reflective coefficient is always less than 1, which keeps maximum entropy deconvolution stable. The maximum entropy of the data outside window increases the resolution of receiver function. Both synthetic and real seismograms show that maximum entropy deconvolution is an effective method to measure receiver function in time-domain.

  1. Maximum Power from a Solar Panel

    Directory of Open Access Journals (Sweden)

    Michael Miller

    2010-01-01

    Full Text Available Solar energy has become a promising alternative to conventional fossil fuel sources. Solar panels are used to collect solar radiation and convert it into electricity. One of the techniques used to maximize the effectiveness of this energy alternative is to maximize the power output of the solar collector. In this project the maximum power is calculated by determining the voltage and the current of maximum power. These quantities are determined by finding the maximum value for the equation for power using differentiation. After the maximum values are found for each time of day, each individual quantity, voltage of maximum power, current of maximum power, and maximum power is plotted as a function of the time of day.

  2. Surface and bulk electronic structures of unintentionally and Mg-doped In0.7Ga0.3N epilayer by hard X-ray photoelectron spectroscopy

    Science.gov (United States)

    Imura, Masataka; Tsuda, Shunsuke; Takeda, Hiroyuki; Nagata, Takahiro; Banal, Ryan G.; Yoshikawa, Hideki; Yang, AnLi; Yamashita, Yoshiyuki; Kobayashi, Keisuke; Koide, Yasuo; Yamaguchi, Tomohiro; Kaneko, Masamitsu; Uematsu, Nao; Wang, Ke; Araki, Tsutomu; Nanishi, Yasushi

    2018-03-01

    The surface and bulk electronic structures of In0.7Ga0.3N epilayers are investigated by angle-resolved hard X-ray photoelectron spectroscopy (HX-PES) combined with soft X-PES. The unintentionally and Mg-doped In0.7Ga0.3N (u-In0.7Ga0.3N and In0.7Ga0.3N:Mg, respectively) epilayers are grown by radio-frequency plasma-assisted molecular beam epitaxy. Here three samples with different Mg concentrations ([Mg] = 0, 7 × 1019, and 4 × 1020 cm-3) are chosen for comparison. It is found that a large downward energy band bending exists in all samples due to the formation of a surface electron accumulation (SEA) layer. For u-In0.7Ga0.3N epilayer, band bending as large as 0.8 ± 0.05 eV occurs from bulk to surface. Judged from the valence band spectral edge and numerical analysis of energy band with a surface quantum well, the valence band maximum (VBM) with respect to Fermi energy (EF) level in the bulk is determined to be 1.22 ± 0.05 eV. In contrast, for In0.7Ga0.3N:Mg epilayers, the band bending increases and the VBM only in the bulk tends to shift toward the EF level owing to the Mg acceptor doping. Hence, the energy band is considered to exhibit a downward bending structure due to the coexistence of the n+ SEA layer and Mg-doped p layer formed in the bulk. When [Mg] changes from 7 × 1019 to 4 × 1020 cm-3, the peak split occurs in HX-PES spectra under the bulk sensitive condition. This result indicates that the energy band forms an anomalous downward bending structure with a singular point due to the generation of a thin depleted region at the n+ p interface. For In0.7Ga0.3N:Mg epilayers, the VBM in the bulk is assumed to be slightly lower than EF level within 0.1 eV.

  3. Maximum permissible voltage of YBCO coated conductors

    Energy Technology Data Exchange (ETDEWEB)

    Wen, J.; Lin, B.; Sheng, J.; Xu, J.; Jin, Z. [Department of Electrical Engineering, Shanghai Jiao Tong University, Shanghai (China); Hong, Z., E-mail: zhiyong.hong@sjtu.edu.cn [Department of Electrical Engineering, Shanghai Jiao Tong University, Shanghai (China); Wang, D.; Zhou, H.; Shen, X.; Shen, C. [Qingpu Power Supply Company, State Grid Shanghai Municipal Electric Power Company, Shanghai (China)

    2014-06-15

    Highlights: • We examine three kinds of tapes’ maximum permissible voltage. • We examine the relationship between quenching duration and maximum permissible voltage. • Continuous I{sub c} degradations under repetitive quenching where tapes reaching maximum permissible voltage. • The relationship between maximum permissible voltage and resistance, temperature. - Abstract: Superconducting fault current limiter (SFCL) could reduce short circuit currents in electrical power system. One of the most important thing in developing SFCL is to find out the maximum permissible voltage of each limiting element. The maximum permissible voltage is defined as the maximum voltage per unit length at which the YBCO coated conductors (CC) do not suffer from critical current (I{sub c}) degradation or burnout. In this research, the time of quenching process is changed and voltage is raised until the I{sub c} degradation or burnout happens. YBCO coated conductors test in the experiment are from American superconductor (AMSC) and Shanghai Jiao Tong University (SJTU). Along with the quenching duration increasing, the maximum permissible voltage of CC decreases. When quenching duration is 100 ms, the maximum permissible of SJTU CC, 12 mm AMSC CC and 4 mm AMSC CC are 0.72 V/cm, 0.52 V/cm and 1.2 V/cm respectively. Based on the results of samples, the whole length of CCs used in the design of a SFCL can be determined.

  4. Revealing the Maximum Strength in Nanotwinned Copper

    DEFF Research Database (Denmark)

    Lu, L.; Chen, X.; Huang, Xiaoxu

    2009-01-01

    boundary–related processes. We investigated the maximum strength of nanotwinned copper samples with different twin thicknesses. We found that the strength increases with decreasing twin thickness, reaching a maximum at 15 nanometers, followed by a softening at smaller values that is accompanied by enhanced...

  5. Modelling maximum canopy conductance and transpiration in ...

    African Journals Online (AJOL)

    There is much current interest in predicting the maximum amount of water that can be transpired by Eucalyptus trees. It is possible that industrial waste water may be applied as irrigation water to eucalypts and it is important to predict the maximum transpiration rates of these plantations in an attempt to dispose of this ...

  6. MXLKID: a maximum likelihood parameter identifier

    International Nuclear Information System (INIS)

    Gavel, D.T.

    1980-07-01

    MXLKID (MaXimum LiKelihood IDentifier) is a computer program designed to identify unknown parameters in a nonlinear dynamic system. Using noisy measurement data from the system, the maximum likelihood identifier computes a likelihood function (LF). Identification of system parameters is accomplished by maximizing the LF with respect to the parameters. The main body of this report briefly summarizes the maximum likelihood technique and gives instructions and examples for running the MXLKID program. MXLKID is implemented LRLTRAN on the CDC7600 computer at LLNL. A detailed mathematical description of the algorithm is given in the appendices. 24 figures, 6 tables

  7. Maximum neutron flux in thermal reactors

    International Nuclear Information System (INIS)

    Strugar, P.V.

    1968-12-01

    Direct approach to the problem is to calculate spatial distribution of fuel concentration if the reactor core directly using the condition of maximum neutron flux and comply with thermal limitations. This paper proved that the problem can be solved by applying the variational calculus, i.e. by using the maximum principle of Pontryagin. Mathematical model of reactor core is based on the two-group neutron diffusion theory with some simplifications which make it appropriate from maximum principle point of view. Here applied theory of maximum principle are suitable for application. The solution of optimum distribution of fuel concentration in the reactor core is obtained in explicit analytical form. The reactor critical dimensions are roots of a system of nonlinear equations and verification of optimum conditions can be done only for specific examples

  8. Maximum allowable load on wheeled mobile manipulators

    International Nuclear Information System (INIS)

    Habibnejad Korayem, M.; Ghariblu, H.

    2003-01-01

    This paper develops a computational technique for finding the maximum allowable load of mobile manipulator during a given trajectory. The maximum allowable loads which can be achieved by a mobile manipulator during a given trajectory are limited by the number of factors; probably the dynamic properties of mobile base and mounted manipulator, their actuator limitations and additional constraints applied to resolving the redundancy are the most important factors. To resolve extra D.O.F introduced by the base mobility, additional constraint functions are proposed directly in the task space of mobile manipulator. Finally, in two numerical examples involving a two-link planar manipulator mounted on a differentially driven mobile base, application of the method to determining maximum allowable load is verified. The simulation results demonstrates the maximum allowable load on a desired trajectory has not a unique value and directly depends on the additional constraint functions which applies to resolve the motion redundancy

  9. Maximum phytoplankton concentrations in the sea

    DEFF Research Database (Denmark)

    Jackson, G.A.; Kiørboe, Thomas

    2008-01-01

    A simplification of plankton dynamics using coagulation theory provides predictions of the maximum algal concentration sustainable in aquatic systems. These predictions have previously been tested successfully against results from iron fertilization experiments. We extend the test to data collect...

  10. Maximum-Likelihood Detection Of Noncoherent CPM

    Science.gov (United States)

    Divsalar, Dariush; Simon, Marvin K.

    1993-01-01

    Simplified detectors proposed for use in maximum-likelihood-sequence detection of symbols in alphabet of size M transmitted by uncoded, full-response continuous phase modulation over radio channel with additive white Gaussian noise. Structures of receivers derived from particular interpretation of maximum-likelihood metrics. Receivers include front ends, structures of which depends only on M, analogous to those in receivers of coherent CPM. Parts of receivers following front ends have structures, complexity of which would depend on N.

  11. Maximum gravitational redshift of white dwarfs

    International Nuclear Information System (INIS)

    Shapiro, S.L.; Teukolsky, S.A.

    1976-01-01

    The stability of uniformly rotating, cold white dwarfs is examined in the framework of the Parametrized Post-Newtonian (PPN) formalism of Will and Nordtvedt. The maximum central density and gravitational redshift of a white dwarf are determined as functions of five of the nine PPN parameters (γ, β, zeta 2 , zeta 3 , and zeta 4 ), the total angular momentum J, and the composition of the star. General relativity predicts that the maximum redshifts is 571 km s -1 for nonrotating carbon and helium dwarfs, but is lower for stars composed of heavier nuclei. Uniform rotation can increase the maximum redshift to 647 km s -1 for carbon stars (the neutronization limit) and to 893 km s -1 for helium stars (the uniform rotation limit). The redshift distribution of a larger sample of white dwarfs may help determine the composition of their cores

  12. Maximum entropy analysis of EGRET data

    DEFF Research Database (Denmark)

    Pohl, M.; Strong, A.W.

    1997-01-01

    EGRET data are usually analysed on the basis of the Maximum-Likelihood method \\cite{ma96} in a search for point sources in excess to a model for the background radiation (e.g. \\cite{hu97}). This method depends strongly on the quality of the background model, and thus may have high systematic unce...... uncertainties in region of strong and uncertain background like the Galactic Center region. Here we show images of such regions obtained by the quantified Maximum-Entropy method. We also discuss a possible further use of MEM in the analysis of problematic regions of the sky....

  13. The Maximum Resource Bin Packing Problem

    DEFF Research Database (Denmark)

    Boyar, J.; Epstein, L.; Favrholdt, L.M.

    2006-01-01

    Usually, for bin packing problems, we try to minimize the number of bins used or in the case of the dual bin packing problem, maximize the number or total size of accepted items. This paper presents results for the opposite problems, where we would like to maximize the number of bins used...... algorithms, First-Fit-Increasing and First-Fit-Decreasing for the maximum resource variant of classical bin packing. For the on-line variant, we define maximum resource variants of classical and dual bin packing. For dual bin packing, no on-line algorithm is competitive. For classical bin packing, we find...

  14. Shower maximum detector for SDC calorimetry

    International Nuclear Information System (INIS)

    Ernwein, J.

    1994-01-01

    A prototype for the SDC end-cap (EM) calorimeter complete with a pre-shower and a shower maximum detector was tested in beams of electrons and Π's at CERN by an SDC subsystem group. The prototype was manufactured from scintillator tiles and strips read out with 1 mm diameter wave-length shifting fibers. The design and construction of the shower maximum detector is described, and results of laboratory tests on light yield and performance of the scintillator-fiber system are given. Preliminary results on energy and position measurements with the shower max detector in the test beam are shown. (authors). 4 refs., 5 figs

  15. Topics in Bayesian statistics and maximum entropy

    International Nuclear Information System (INIS)

    Mutihac, R.; Cicuttin, A.; Cerdeira, A.; Stanciulescu, C.

    1998-12-01

    Notions of Bayesian decision theory and maximum entropy methods are reviewed with particular emphasis on probabilistic inference and Bayesian modeling. The axiomatic approach is considered as the best justification of Bayesian analysis and maximum entropy principle applied in natural sciences. Particular emphasis is put on solving the inverse problem in digital image restoration and Bayesian modeling of neural networks. Further topics addressed briefly include language modeling, neutron scattering, multiuser detection and channel equalization in digital communications, genetic information, and Bayesian court decision-making. (author)

  16. Density estimation by maximum quantum entropy

    International Nuclear Information System (INIS)

    Silver, R.N.; Wallstrom, T.; Martz, H.F.

    1993-01-01

    A new Bayesian method for non-parametric density estimation is proposed, based on a mathematical analogy to quantum statistical physics. The mathematical procedure is related to maximum entropy methods for inverse problems and image reconstruction. The information divergence enforces global smoothing toward default models, convexity, positivity, extensivity and normalization. The novel feature is the replacement of classical entropy by quantum entropy, so that local smoothing is enforced by constraints on differential operators. The linear response of the estimate is proportional to the covariance. The hyperparameters are estimated by type-II maximum likelihood (evidence). The method is demonstrated on textbook data sets

  17. Sodium beta-alumina thin films as gate dielectrics for AlGaN/GaN metal—insulator—semiconductor high-electron-mobility transistors

    International Nuclear Information System (INIS)

    Tian Ben-Lang; Chen Chao; Li Yan-Rong; Zhang Wan-Li; Liu Xing-Zhao

    2012-01-01

    Sodium beta-alumina (SBA) is deposited on AlGaN/GaN by using a co-deposition process with sodium and Al 2 O 3 as the precursors. The X-ray diffraction (XRD) spectrum reveals that the deposited thin film is amorphous. The binding energy and composition of the deposited thin film, obtained from the X-ray photoelectron spectroscopy (XPS) measurement, are consistent with those of SBA. The dielectric constant of the SBA thin film is about 50. Each of the capacitance—voltage characteristics obtained at five different frequencies shows a high-quality interface between SBA and AlGaN. The interface trap density of metal—insulator—semiconductor high-electron-mobility transistor (MISHEMT) is measured to be (3.5∼9.5)×10 10 cm −2 ·eV −1 by the conductance method. The fixed charge density of SBA dielectric is on the order of 2.7×10 12 cm −2 . Compared with the AlGaN/GaN metal—semiconductor heterostructure high-electron-mobility transistor (MESHEMT), the AlGaN/GaN MISHEMT usually has a threshold voltage that shifts negatively. However, the threshold voltage of the AlGaN/GaN MISHEMT using SBA as the gate dielectric shifts positively from −5.5 V to −3.5 V. From XPS results, the surface valence-band maximum (VBM-EF) of AlGaN is found to decrease from 2.56 eV to 2.25 eV after the SBA thin film deposition. The possible reasons why the threshold voltage of AlGaN/GaN MISHEMT with the SBA gate dielectric shifts positively are the influence of SBA on surface valence-band maximum (VBM-EF), the reduction of interface traps and the effects of sodium ions, and/or the fixed charges in SBA on the two-dimensional electron gas (2DEG). (condensed matter: structural, mechanical, and thermal properties)

  18. Nonsymmetric entropy and maximum nonsymmetric entropy principle

    International Nuclear Information System (INIS)

    Liu Chengshi

    2009-01-01

    Under the frame of a statistical model, the concept of nonsymmetric entropy which generalizes the concepts of Boltzmann's entropy and Shannon's entropy, is defined. Maximum nonsymmetric entropy principle is proved. Some important distribution laws such as power law, can be derived from this principle naturally. Especially, nonsymmetric entropy is more convenient than other entropy such as Tsallis's entropy in deriving power laws.

  19. Maximum speed of dewetting on a fiber

    NARCIS (Netherlands)

    Chan, Tak Shing; Gueudre, Thomas; Snoeijer, Jacobus Hendrikus

    2011-01-01

    A solid object can be coated by a nonwetting liquid since a receding contact line cannot exceed a critical speed. We theoretically investigate this forced wetting transition for axisymmetric menisci on fibers of varying radii. First, we use a matched asymptotic expansion and derive the maximum speed

  20. Maximum potential preventive effect of hip protectors

    NARCIS (Netherlands)

    van Schoor, N.M.; Smit, J.H.; Bouter, L.M.; Veenings, B.; Asma, G.B.; Lips, P.T.A.M.

    2007-01-01

    OBJECTIVES: To estimate the maximum potential preventive effect of hip protectors in older persons living in the community or homes for the elderly. DESIGN: Observational cohort study. SETTING: Emergency departments in the Netherlands. PARTICIPANTS: Hip fracture patients aged 70 and older who

  1. Maximum gain of Yagi-Uda arrays

    DEFF Research Database (Denmark)

    Bojsen, J.H.; Schjær-Jacobsen, Hans; Nilsson, E.

    1971-01-01

    Numerical optimisation techniques have been used to find the maximum gain of some specific parasitic arrays. The gain of an array of infinitely thin, equispaced dipoles loaded with arbitrary reactances has been optimised. The results show that standard travelling-wave design methods are not optimum....... Yagi–Uda arrays with equal and unequal spacing have also been optimised with experimental verification....

  2. correlation between maximum dry density and cohesion

    African Journals Online (AJOL)

    HOD

    represents maximum dry density, signifies plastic limit and is liquid limit. Researchers [6, 7] estimate compaction parameters. Aside from the correlation existing between compaction parameters and other physical quantities there are some other correlations that have been investigated by other researchers. The well-known.

  3. Weak scale from the maximum entropy principle

    Science.gov (United States)

    Hamada, Yuta; Kawai, Hikaru; Kawana, Kiyoharu

    2015-03-01

    The theory of the multiverse and wormholes suggests that the parameters of the Standard Model (SM) are fixed in such a way that the radiation of the S3 universe at the final stage S_rad becomes maximum, which we call the maximum entropy principle. Although it is difficult to confirm this principle generally, for a few parameters of the SM, we can check whether S_rad actually becomes maximum at the observed values. In this paper, we regard S_rad at the final stage as a function of the weak scale (the Higgs expectation value) vh, and show that it becomes maximum around vh = {{O}} (300 GeV) when the dimensionless couplings in the SM, i.e., the Higgs self-coupling, the gauge couplings, and the Yukawa couplings are fixed. Roughly speaking, we find that the weak scale is given by vh ˜ T_{BBN}2 / (M_{pl}ye5), where ye is the Yukawa coupling of electron, T_BBN is the temperature at which the Big Bang nucleosynthesis starts, and M_pl is the Planck mass.

  4. The maximum-entropy method in superspace

    Czech Academy of Sciences Publication Activity Database

    van Smaalen, S.; Palatinus, Lukáš; Schneider, M.

    2003-01-01

    Roč. 59, - (2003), s. 459-469 ISSN 0108-7673 Grant - others:DFG(DE) XX Institutional research plan: CEZ:AV0Z1010914 Keywords : maximum-entropy method, * aperiodic crystals * electron density Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.558, year: 2003

  5. Achieving maximum sustainable yield in mixed fisheries

    NARCIS (Netherlands)

    Ulrich, Clara; Vermard, Youen; Dolder, Paul J.; Brunel, Thomas; Jardim, Ernesto; Holmes, Steven J.; Kempf, Alexander; Mortensen, Lars O.; Poos, Jan Jaap; Rindorf, Anna

    2017-01-01

    Achieving single species maximum sustainable yield (MSY) in complex and dynamic fisheries targeting multiple species (mixed fisheries) is challenging because achieving the objective for one species may mean missing the objective for another. The North Sea mixed fisheries are a representative example

  6. 5 CFR 534.203 - Maximum stipends.

    Science.gov (United States)

    2010-01-01

    ... maximum stipend established under this section. (e) A trainee at a non-Federal hospital, clinic, or medical or dental laboratory who is assigned to a Federal hospital, clinic, or medical or dental... Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS PAY UNDER OTHER SYSTEMS Student...

  7. Minimal length, Friedmann equations and maximum density

    Energy Technology Data Exchange (ETDEWEB)

    Awad, Adel [Center for Theoretical Physics, British University of Egypt,Sherouk City 11837, P.O. Box 43 (Egypt); Department of Physics, Faculty of Science, Ain Shams University,Cairo, 11566 (Egypt); Ali, Ahmed Farag [Centre for Fundamental Physics, Zewail City of Science and Technology,Sheikh Zayed, 12588, Giza (Egypt); Department of Physics, Faculty of Science, Benha University,Benha, 13518 (Egypt)

    2014-06-16

    Inspired by Jacobson’s thermodynamic approach, Cai et al. have shown the emergence of Friedmann equations from the first law of thermodynamics. We extend Akbar-Cai derivation http://dx.doi.org/10.1103/PhysRevD.75.084003 of Friedmann equations to accommodate a general entropy-area law. Studying the resulted Friedmann equations using a specific entropy-area law, which is motivated by the generalized uncertainty principle (GUP), reveals the existence of a maximum energy density closed to Planck density. Allowing for a general continuous pressure p(ρ,a) leads to bounded curvature invariants and a general nonsingular evolution. In this case, the maximum energy density is reached in a finite time and there is no cosmological evolution beyond this point which leaves the big bang singularity inaccessible from a spacetime prospective. The existence of maximum energy density and a general nonsingular evolution is independent of the equation of state and the spacial curvature k. As an example we study the evolution of the equation of state p=ωρ through its phase-space diagram to show the existence of a maximum energy which is reachable in a finite time.

  8. Maximum concentrations at work and maximum biologically tolerable concentration for working materials 1991

    International Nuclear Information System (INIS)

    1991-01-01

    The meaning of the term 'maximum concentration at work' in regard of various pollutants is discussed. Specifically, a number of dusts and smokes are dealt with. The valuation criteria for maximum biologically tolerable concentrations for working materials are indicated. The working materials in question are corcinogeneous substances or substances liable to cause allergies or mutate the genome. (VT) [de

  9. 75 FR 43840 - Inflation Adjustment of the Ordinary Maximum and Aggravated Maximum Civil Monetary Penalties for...

    Science.gov (United States)

    2010-07-27

    ...-17530; Notice No. 2] RIN 2130-ZA03 Inflation Adjustment of the Ordinary Maximum and Aggravated Maximum... remains at $250. These adjustments are required by the Federal Civil Penalties Inflation Adjustment Act [email protected] . SUPPLEMENTARY INFORMATION: The Federal Civil Penalties Inflation Adjustment Act of 1990...

  10. Zipf's law, power laws and maximum entropy

    International Nuclear Information System (INIS)

    Visser, Matt

    2013-01-01

    Zipf's law, and power laws in general, have attracted and continue to attract considerable attention in a wide variety of disciplines—from astronomy to demographics to software structure to economics to linguistics to zoology, and even warfare. A recent model of random group formation (RGF) attempts a general explanation of such phenomena based on Jaynes' notion of maximum entropy applied to a particular choice of cost function. In the present paper I argue that the specific cost function used in the RGF model is in fact unnecessarily complicated, and that power laws can be obtained in a much simpler way by applying maximum entropy ideas directly to the Shannon entropy subject only to a single constraint: that the average of the logarithm of the observable quantity is specified. (paper)

  11. Maximum-entropy description of animal movement.

    Science.gov (United States)

    Fleming, Chris H; Subaşı, Yiğit; Calabrese, Justin M

    2015-03-01

    We introduce a class of maximum-entropy states that naturally includes within it all of the major continuous-time stochastic processes that have been applied to animal movement, including Brownian motion, Ornstein-Uhlenbeck motion, integrated Ornstein-Uhlenbeck motion, a recently discovered hybrid of the previous models, and a new model that describes central-place foraging. We are also able to predict a further hierarchy of new models that will emerge as data quality improves to better resolve the underlying continuity of animal movement. Finally, we also show that Langevin equations must obey a fluctuation-dissipation theorem to generate processes that fall from this class of maximum-entropy distributions when the constraints are purely kinematic.

  12. Pareto versus lognormal: a maximum entropy test.

    Science.gov (United States)

    Bee, Marco; Riccaboni, Massimo; Schiavo, Stefano

    2011-08-01

    It is commonly found that distributions that seem to be lognormal over a broad range change to a power-law (Pareto) distribution for the last few percentiles. The distributions of many physical, natural, and social events (earthquake size, species abundance, income and wealth, as well as file, city, and firm sizes) display this structure. We present a test for the occurrence of power-law tails in statistical distributions based on maximum entropy. This methodology allows one to identify the true data-generating processes even in the case when it is neither lognormal nor Pareto. The maximum entropy approach is then compared with other widely used methods and applied to different levels of aggregation of complex systems. Our results provide support for the theory that distributions with lognormal body and Pareto tail can be generated as mixtures of lognormally distributed units.

  13. Maximum likelihood estimation for integrated diffusion processes

    DEFF Research Database (Denmark)

    Baltazar-Larios, Fernando; Sørensen, Michael

    We propose a method for obtaining maximum likelihood estimates of parameters in diffusion models when the data is a discrete time sample of the integral of the process, while no direct observations of the process itself are available. The data are, moreover, assumed to be contaminated...... EM-algorithm to obtain maximum likelihood estimates of the parameters in the diffusion model. As part of the algorithm, we use a recent simple method for approximate simulation of diffusion bridges. In simulation studies for the Ornstein-Uhlenbeck process and the CIR process the proposed method works...... by measurement errors. Integrated volatility is an example of this type of observations. Another example is ice-core data on oxygen isotopes used to investigate paleo-temperatures. The data can be viewed as incomplete observations of a model with a tractable likelihood function. Therefore we propose a simulated...

  14. A Maximum Radius for Habitable Planets.

    Science.gov (United States)

    Alibert, Yann

    2015-09-01

    We compute the maximum radius a planet can have in order to fulfill two constraints that are likely necessary conditions for habitability: 1- surface temperature and pressure compatible with the existence of liquid water, and 2- no ice layer at the bottom of a putative global ocean, that would prevent the operation of the geologic carbon cycle to operate. We demonstrate that, above a given radius, these two constraints cannot be met: in the Super-Earth mass range (1-12 Mearth), the overall maximum that a planet can have varies between 1.8 and 2.3 Rearth. This radius is reduced when considering planets with higher Fe/Si ratios, and taking into account irradiation effects on the structure of the gas envelope.

  15. Maximum parsimony on subsets of taxa.

    Science.gov (United States)

    Fischer, Mareike; Thatte, Bhalchandra D

    2009-09-21

    In this paper we investigate mathematical questions concerning the reliability (reconstruction accuracy) of Fitch's maximum parsimony algorithm for reconstructing the ancestral state given a phylogenetic tree and a character. In particular, we consider the question whether the maximum parsimony method applied to a subset of taxa can reconstruct the ancestral state of the root more accurately than when applied to all taxa, and we give an example showing that this indeed is possible. A surprising feature of our example is that ignoring a taxon closer to the root improves the reliability of the method. On the other hand, in the case of the two-state symmetric substitution model, we answer affirmatively a conjecture of Li, Steel and Zhang which states that under a molecular clock the probability that the state at a single taxon is a correct guess of the ancestral state is a lower bound on the reconstruction accuracy of Fitch's method applied to all taxa.

  16. Maximum entropy analysis of liquid diffraction data

    International Nuclear Information System (INIS)

    Root, J.H.; Egelstaff, P.A.; Nickel, B.G.

    1986-01-01

    A maximum entropy method for reducing truncation effects in the inverse Fourier transform of structure factor, S(q), to pair correlation function, g(r), is described. The advantages and limitations of the method are explored with the PY hard sphere structure factor as model input data. An example using real data on liquid chlorine, is then presented. It is seen that spurious structure is greatly reduced in comparison to traditional Fourier transform methods. (author)

  17. A Maximum Resonant Set of Polyomino Graphs

    Directory of Open Access Journals (Sweden)

    Zhang Heping

    2016-05-01

    Full Text Available A polyomino graph P is a connected finite subgraph of the infinite plane grid such that each finite face is surrounded by a regular square of side length one and each edge belongs to at least one square. A dimer covering of P corresponds to a perfect matching. Different dimer coverings can interact via an alternating cycle (or square with respect to them. A set of disjoint squares of P is a resonant set if P has a perfect matching M so that each one of those squares is M-alternating. In this paper, we show that if K is a maximum resonant set of P, then P − K has a unique perfect matching. We further prove that the maximum forcing number of a polyomino graph is equal to the cardinality of a maximum resonant set. This confirms a conjecture of Xu et al. [26]. We also show that if K is a maximal alternating set of P, then P − K has a unique perfect matching.

  18. Automatic maximum entropy spectral reconstruction in NMR

    International Nuclear Information System (INIS)

    Mobli, Mehdi; Maciejewski, Mark W.; Gryk, Michael R.; Hoch, Jeffrey C.

    2007-01-01

    Developments in superconducting magnets, cryogenic probes, isotope labeling strategies, and sophisticated pulse sequences together have enabled the application, in principle, of high-resolution NMR spectroscopy to biomolecular systems approaching 1 megadalton. In practice, however, conventional approaches to NMR that utilize the fast Fourier transform, which require data collected at uniform time intervals, result in prohibitively lengthy data collection times in order to achieve the full resolution afforded by high field magnets. A variety of approaches that involve nonuniform sampling have been proposed, each utilizing a non-Fourier method of spectrum analysis. A very general non-Fourier method that is capable of utilizing data collected using any of the proposed nonuniform sampling strategies is maximum entropy reconstruction. A limiting factor in the adoption of maximum entropy reconstruction in NMR has been the need to specify non-intuitive parameters. Here we describe a fully automated system for maximum entropy reconstruction that requires no user-specified parameters. A web-accessible script generator provides the user interface to the system

  19. maximum neutron flux at thermal nuclear reactors

    International Nuclear Information System (INIS)

    Strugar, P.

    1968-10-01

    Since actual research reactors are technically complicated and expensive facilities it is important to achieve savings by appropriate reactor lattice configurations. There is a number of papers, and practical examples of reactors with central reflector, dealing with spatial distribution of fuel elements which would result in higher neutron flux. Common disadvantage of all the solutions is that the choice of best solution is done starting from the anticipated spatial distributions of fuel elements. The weakness of these approaches is lack of defined optimization criteria. Direct approach is defined as follows: determine the spatial distribution of fuel concentration starting from the condition of maximum neutron flux by fulfilling the thermal constraints. Thus the problem of determining the maximum neutron flux is solving a variational problem which is beyond the possibilities of classical variational calculation. This variational problem has been successfully solved by applying the maximum principle of Pontrjagin. Optimum distribution of fuel concentration was obtained in explicit analytical form. Thus, spatial distribution of the neutron flux and critical dimensions of quite complex reactor system are calculated in a relatively simple way. In addition to the fact that the results are innovative this approach is interesting because of the optimization procedure itself [sr

  20. Tunable Band Gap and Conductivity Type of ZnSe/Si Core-Shell Nanowire Heterostructures

    Directory of Open Access Journals (Sweden)

    Yijie Zeng

    2014-10-01

    Full Text Available The electronic properties of zincblende ZnSe/Si core-shell nanowires (NWs with a diameter of 1.1–2.8 nm are calculated by means of the first principle calculation. Band gaps of both ZnSe-core/Si-shell and Si-core/ZnSe-shell NWs are much smaller than those of pure ZnSe or Si NWs. Band alignment analysis reveals that the small band gaps of ZnSe/Si core-shell NWs are caused by the interface state. Fixing the ZnSe core size and enlarging the Si shell would turn the NWs from intrinsic to p-type, then to metallic. However, Fixing the Si core and enlarging the ZnSe shell would not change the band gap significantly. The partial charge distribution diagram shows that the conduction band maximum (CBM is confined in Si, while the valence band maximum (VBM is mainly distributed around the interface. Our findings also show that the band gap and conductivity type of ZnSe/Si core-shell NWs can be tuned by the concentration and diameter of the core-shell material, respectively.

  1. Maximum entropy decomposition of quadrupole mass spectra

    International Nuclear Information System (INIS)

    Toussaint, U. von; Dose, V.; Golan, A.

    2004-01-01

    We present an information-theoretic method called generalized maximum entropy (GME) for decomposing mass spectra of gas mixtures from noisy measurements. In this GME approach to the noisy, underdetermined inverse problem, the joint entropies of concentration, cracking, and noise probabilities are maximized subject to the measured data. This provides a robust estimation for the unknown cracking patterns and the concentrations of the contributing molecules. The method is applied to mass spectroscopic data of hydrocarbons, and the estimates are compared with those received from a Bayesian approach. We show that the GME method is efficient and is computationally fast

  2. Maximum power operation of interacting molecular motors

    DEFF Research Database (Denmark)

    Golubeva, Natalia; Imparato, Alberto

    2013-01-01

    , as compared to the non-interacting system, in a wide range of biologically compatible scenarios. We furthermore consider the case where the motor-motor interaction directly affects the internal chemical cycle and investigate the effect on the system dynamics and thermodynamics.......We study the mechanical and thermodynamic properties of different traffic models for kinesin which are relevant in biological and experimental contexts. We find that motor-motor interactions play a fundamental role by enhancing the thermodynamic efficiency at maximum power of the motors...

  3. Maximum entropy method in momentum density reconstruction

    International Nuclear Information System (INIS)

    Dobrzynski, L.; Holas, A.

    1997-01-01

    The Maximum Entropy Method (MEM) is applied to the reconstruction of the 3-dimensional electron momentum density distributions observed through the set of Compton profiles measured along various crystallographic directions. It is shown that the reconstruction of electron momentum density may be reliably carried out with the aid of simple iterative algorithm suggested originally by Collins. A number of distributions has been simulated in order to check the performance of MEM. It is shown that MEM can be recommended as a model-free approach. (author). 13 refs, 1 fig

  4. On the maximum drawdown during speculative bubbles

    Science.gov (United States)

    Rotundo, Giulia; Navarra, Mauro

    2007-08-01

    A taxonomy of large financial crashes proposed in the literature locates the burst of speculative bubbles due to endogenous causes in the framework of extreme stock market crashes, defined as falls of market prices that are outlier with respect to the bulk of drawdown price movement distribution. This paper goes on deeper in the analysis providing a further characterization of the rising part of such selected bubbles through the examination of drawdown and maximum drawdown movement of indices prices. The analysis of drawdown duration is also performed and it is the core of the risk measure estimated here.

  5. Multi-Channel Maximum Likelihood Pitch Estimation

    DEFF Research Database (Denmark)

    Christensen, Mads Græsbøll

    2012-01-01

    In this paper, a method for multi-channel pitch estimation is proposed. The method is a maximum likelihood estimator and is based on a parametric model where the signals in the various channels share the same fundamental frequency but can have different amplitudes, phases, and noise characteristics....... This essentially means that the model allows for different conditions in the various channels, like different signal-to-noise ratios, microphone characteristics and reverberation. Moreover, the method does not assume that a certain array structure is used but rather relies on a more general model and is hence...

  6. Conductivity maximum in a charged colloidal suspension

    Energy Technology Data Exchange (ETDEWEB)

    Bastea, S

    2009-01-27

    Molecular dynamics simulations of a charged colloidal suspension in the salt-free regime show that the system exhibits an electrical conductivity maximum as a function of colloid charge. We attribute this behavior to two main competing effects: colloid effective charge saturation due to counterion 'condensation' and diffusion slowdown due to the relaxation effect. In agreement with previous observations, we also find that the effective transported charge is larger than the one determined by the Stern layer and suggest that it corresponds to the boundary fluid layer at the surface of the colloidal particles.

  7. Dynamical maximum entropy approach to flocking.

    Science.gov (United States)

    Cavagna, Andrea; Giardina, Irene; Ginelli, Francesco; Mora, Thierry; Piovani, Duccio; Tavarone, Raffaele; Walczak, Aleksandra M

    2014-04-01

    We derive a new method to infer from data the out-of-equilibrium alignment dynamics of collectively moving animal groups, by considering the maximum entropy model distribution consistent with temporal and spatial correlations of flight direction. When bird neighborhoods evolve rapidly, this dynamical inference correctly learns the parameters of the model, while a static one relying only on the spatial correlations fails. When neighbors change slowly and the detailed balance is satisfied, we recover the static procedure. We demonstrate the validity of the method on simulated data. The approach is applicable to other systems of active matter.

  8. Maximum Temperature Detection System for Integrated Circuits

    Science.gov (United States)

    Frankiewicz, Maciej; Kos, Andrzej

    2015-03-01

    The paper describes structure and measurement results of the system detecting present maximum temperature on the surface of an integrated circuit. The system consists of the set of proportional to absolute temperature sensors, temperature processing path and a digital part designed in VHDL. Analogue parts of the circuit where designed with full-custom technique. The system is a part of temperature-controlled oscillator circuit - a power management system based on dynamic frequency scaling method. The oscillator cooperates with microprocessor dedicated for thermal experiments. The whole system is implemented in UMC CMOS 0.18 μm (1.8 V) technology.

  9. Maximum entropy PDF projection: A review

    Science.gov (United States)

    Baggenstoss, Paul M.

    2017-06-01

    We review maximum entropy (MaxEnt) PDF projection, a method with wide potential applications in statistical inference. The method constructs a sampling distribution for a high-dimensional vector x based on knowing the sampling distribution p(z) of a lower-dimensional feature z = T (x). Under mild conditions, the distribution p(x) having highest possible entropy among all distributions consistent with p(z) may be readily found. Furthermore, the MaxEnt p(x) may be sampled, making the approach useful in Monte Carlo methods. We review the theorem and present a case study in model order selection and classification for handwritten character recognition.

  10. Multiperiod Maximum Loss is time unit invariant.

    Science.gov (United States)

    Kovacevic, Raimund M; Breuer, Thomas

    2016-01-01

    Time unit invariance is introduced as an additional requirement for multiperiod risk measures: for a constant portfolio under an i.i.d. risk factor process, the multiperiod risk should equal the one period risk of the aggregated loss, for an appropriate choice of parameters and independent of the portfolio and its distribution. Multiperiod Maximum Loss over a sequence of Kullback-Leibler balls is time unit invariant. This is also the case for the entropic risk measure. On the other hand, multiperiod Value at Risk and multiperiod Expected Shortfall are not time unit invariant.

  11. Maximum a posteriori decoder for digital communications

    Science.gov (United States)

    Altes, Richard A. (Inventor)

    1997-01-01

    A system and method for decoding by identification of the most likely phase coded signal corresponding to received data. The present invention has particular application to communication with signals that experience spurious random phase perturbations. The generalized estimator-correlator uses a maximum a posteriori (MAP) estimator to generate phase estimates for correlation with incoming data samples and for correlation with mean phases indicative of unique hypothesized signals. The result is a MAP likelihood statistic for each hypothesized transmission, wherein the highest value statistic identifies the transmitted signal.

  12. Improved Maximum Parsimony Models for Phylogenetic Networks.

    Science.gov (United States)

    Van Iersel, Leo; Jones, Mark; Scornavacca, Celine

    2018-05-01

    Phylogenetic networks are well suited to represent evolutionary histories comprising reticulate evolution. Several methods aiming at reconstructing explicit phylogenetic networks have been developed in the last two decades. In this article, we propose a new definition of maximum parsimony for phylogenetic networks that permits to model biological scenarios that cannot be modeled by the definitions currently present in the literature (namely, the "hardwired" and "softwired" parsimony). Building on this new definition, we provide several algorithmic results that lay the foundations for new parsimony-based methods for phylogenetic network reconstruction.

  13. Ancestral sequence reconstruction with Maximum Parsimony

    OpenAIRE

    Herbst, Lina; Fischer, Mareike

    2017-01-01

    One of the main aims in phylogenetics is the estimation of ancestral sequences based on present-day data like, for instance, DNA alignments. One way to estimate the data of the last common ancestor of a given set of species is to first reconstruct a phylogenetic tree with some tree inference method and then to use some method of ancestral state inference based on that tree. One of the best-known methods both for tree inference as well as for ancestral sequence inference is Maximum Parsimony (...

  14. Objective Bayesianism and the Maximum Entropy Principle

    Directory of Open Access Journals (Sweden)

    Jon Williamson

    2013-09-01

    Full Text Available Objective Bayesian epistemology invokes three norms: the strengths of our beliefs should be probabilities; they should be calibrated to our evidence of physical probabilities; and they should otherwise equivocate sufficiently between the basic propositions that we can express. The three norms are sometimes explicated by appealing to the maximum entropy principle, which says that a belief function should be a probability function, from all those that are calibrated to evidence, that has maximum entropy. However, the three norms of objective Bayesianism are usually justified in different ways. In this paper, we show that the three norms can all be subsumed under a single justification in terms of minimising worst-case expected loss. This, in turn, is equivalent to maximising a generalised notion of entropy. We suggest that requiring language invariance, in addition to minimising worst-case expected loss, motivates maximisation of standard entropy as opposed to maximisation of other instances of generalised entropy. Our argument also provides a qualified justification for updating degrees of belief by Bayesian conditionalisation. However, conditional probabilities play a less central part in the objective Bayesian account than they do under the subjective view of Bayesianism, leading to a reduced role for Bayes’ Theorem.

  15. Efficient heuristics for maximum common substructure search.

    Science.gov (United States)

    Englert, Péter; Kovács, Péter

    2015-05-26

    Maximum common substructure search is a computationally hard optimization problem with diverse applications in the field of cheminformatics, including similarity search, lead optimization, molecule alignment, and clustering. Most of these applications have strict constraints on running time, so heuristic methods are often preferred. However, the development of an algorithm that is both fast enough and accurate enough for most practical purposes is still a challenge. Moreover, in some applications, the quality of a common substructure depends not only on its size but also on various topological features of the one-to-one atom correspondence it defines. Two state-of-the-art heuristic algorithms for finding maximum common substructures have been implemented at ChemAxon Ltd., and effective heuristics have been developed to improve both their efficiency and the relevance of the atom mappings they provide. The implementations have been thoroughly evaluated and compared with existing solutions (KCOMBU and Indigo). The heuristics have been found to greatly improve the performance and applicability of the algorithms. The purpose of this paper is to introduce the applied methods and present the experimental results.

  16. Hydraulic Limits on Maximum Plant Transpiration

    Science.gov (United States)

    Manzoni, S.; Vico, G.; Katul, G. G.; Palmroth, S.; Jackson, R. B.; Porporato, A. M.

    2011-12-01

    Photosynthesis occurs at the expense of water losses through transpiration. As a consequence of this basic carbon-water interaction at the leaf level, plant growth and ecosystem carbon exchanges are tightly coupled to transpiration. In this contribution, the hydraulic constraints that limit transpiration rates under well-watered conditions are examined across plant functional types and climates. The potential water flow through plants is proportional to both xylem hydraulic conductivity (which depends on plant carbon economy) and the difference in water potential between the soil and the atmosphere (the driving force that pulls water from the soil). Differently from previous works, we study how this potential flux changes with the amplitude of the driving force (i.e., we focus on xylem properties and not on stomatal regulation). Xylem hydraulic conductivity decreases as the driving force increases due to cavitation of the tissues. As a result of this negative feedback, more negative leaf (and xylem) water potentials would provide a stronger driving force for water transport, while at the same time limiting xylem hydraulic conductivity due to cavitation. Here, the leaf water potential value that allows an optimum balance between driving force and xylem conductivity is quantified, thus defining the maximum transpiration rate that can be sustained by the soil-to-leaf hydraulic system. To apply the proposed framework at the global scale, a novel database of xylem conductivity and cavitation vulnerability across plant types and biomes is developed. Conductivity and water potential at 50% cavitation are shown to be complementary (in particular between angiosperms and conifers), suggesting a tradeoff between transport efficiency and hydraulic safety. Plants from warmer and drier biomes tend to achieve larger maximum transpiration than plants growing in environments with lower atmospheric water demand. The predicted maximum transpiration and the corresponding leaf water

  17. Analogue of Pontryagin's maximum principle for multiple integrals minimization problems

    OpenAIRE

    Mikhail, Zelikin

    2016-01-01

    The theorem like Pontryagin's maximum principle for multiple integrals is proved. Unlike the usual maximum principle, the maximum should be taken not over all matrices, but only on matrices of rank one. Examples are given.

  18. Lake Basin Fetch and Maximum Length/Width

    Data.gov (United States)

    Minnesota Department of Natural Resources — Linear features representing the Fetch, Maximum Length and Maximum Width of a lake basin. Fetch, maximum length and average width are calcuated from the lake polygon...

  19. Maximum Likelihood Reconstruction for Magnetic Resonance Fingerprinting.

    Science.gov (United States)

    Zhao, Bo; Setsompop, Kawin; Ye, Huihui; Cauley, Stephen F; Wald, Lawrence L

    2016-08-01

    This paper introduces a statistical estimation framework for magnetic resonance (MR) fingerprinting, a recently proposed quantitative imaging paradigm. Within this framework, we present a maximum likelihood (ML) formalism to estimate multiple MR tissue parameter maps directly from highly undersampled, noisy k-space data. A novel algorithm, based on variable splitting, the alternating direction method of multipliers, and the variable projection method, is developed to solve the resulting optimization problem. Representative results from both simulations and in vivo experiments demonstrate that the proposed approach yields significantly improved accuracy in parameter estimation, compared to the conventional MR fingerprinting reconstruction. Moreover, the proposed framework provides new theoretical insights into the conventional approach. We show analytically that the conventional approach is an approximation to the ML reconstruction; more precisely, it is exactly equivalent to the first iteration of the proposed algorithm for the ML reconstruction, provided that a gridding reconstruction is used as an initialization.

  20. Maximum Profit Configurations of Commercial Engines

    Directory of Open Access Journals (Sweden)

    Yiran Chen

    2011-06-01

    Full Text Available An investigation of commercial engines with finite capacity low- and high-price economic subsystems and a generalized commodity transfer law [n ∝ Δ (P m] in commodity flow processes, in which effects of the price elasticities of supply and demand are introduced, is presented in this paper. Optimal cycle configurations of commercial engines for maximum profit are obtained by applying optimal control theory. In some special cases, the eventual state—market equilibrium—is solely determined by the initial conditions and the inherent characteristics of two subsystems; while the different ways of transfer affect the model in respects of the specific forms of the paths of prices and the instantaneous commodity flow, i.e., the optimal configuration.

  1. The worst case complexity of maximum parsimony.

    Science.gov (United States)

    Carmel, Amir; Musa-Lempel, Noa; Tsur, Dekel; Ziv-Ukelson, Michal

    2014-11-01

    One of the core classical problems in computational biology is that of constructing the most parsimonious phylogenetic tree interpreting an input set of sequences from the genomes of evolutionarily related organisms. We reexamine the classical maximum parsimony (MP) optimization problem for the general (asymmetric) scoring matrix case, where rooted phylogenies are implied, and analyze the worst case bounds of three approaches to MP: The approach of Cavalli-Sforza and Edwards, the approach of Hendy and Penny, and a new agglomerative, "bottom-up" approach we present in this article. We show that the second and third approaches are faster than the first one by a factor of Θ(√n) and Θ(n), respectively, where n is the number of species.

  2. Modelling maximum likelihood estimation of availability

    International Nuclear Information System (INIS)

    Waller, R.A.; Tietjen, G.L.; Rock, G.W.

    1975-01-01

    Suppose the performance of a nuclear powered electrical generating power plant is continuously monitored to record the sequence of failure and repairs during sustained operation. The purpose of this study is to assess one method of estimating the performance of the power plant when the measure of performance is availability. That is, we determine the probability that the plant is operational at time t. To study the availability of a power plant, we first assume statistical models for the variables, X and Y, which denote the time-to-failure and the time-to-repair variables, respectively. Once those statistical models are specified, the availability, A(t), can be expressed as a function of some or all of their parameters. Usually those parameters are unknown in practice and so A(t) is unknown. This paper discusses the maximum likelihood estimator of A(t) when the time-to-failure model for X is an exponential density with parameter, lambda, and the time-to-repair model for Y is an exponential density with parameter, theta. Under the assumption of exponential models for X and Y, it follows that the instantaneous availability at time t is A(t)=lambda/(lambda+theta)+theta/(lambda+theta)exp[-[(1/lambda)+(1/theta)]t] with t>0. Also, the steady-state availability is A(infinity)=lambda/(lambda+theta). We use the observations from n failure-repair cycles of the power plant, say X 1 , X 2 , ..., Xsub(n), Y 1 , Y 2 , ..., Ysub(n) to present the maximum likelihood estimators of A(t) and A(infinity). The exact sampling distributions for those estimators and some statistical properties are discussed before a simulation model is used to determine 95% simulation intervals for A(t). The methodology is applied to two examples which approximate the operating history of two nuclear power plants. (author)

  3. A maximum power point tracking for photovoltaic-SPE system using a maximum current controller

    Energy Technology Data Exchange (ETDEWEB)

    Muhida, Riza [Osaka Univ., Dept. of Physical Science, Toyonaka, Osaka (Japan); Osaka Univ., Dept. of Electrical Engineering, Suita, Osaka (Japan); Park, Minwon; Dakkak, Mohammed; Matsuura, Kenji [Osaka Univ., Dept. of Electrical Engineering, Suita, Osaka (Japan); Tsuyoshi, Akira; Michira, Masakazu [Kobe City College of Technology, Nishi-ku, Kobe (Japan)

    2003-02-01

    Processes to produce hydrogen from solar photovoltaic (PV)-powered water electrolysis using solid polymer electrolysis (SPE) are reported. An alternative control of maximum power point tracking (MPPT) in the PV-SPE system based on the maximum current searching methods has been designed and implemented. Based on the characteristics of voltage-current and theoretical analysis of SPE, it can be shown that the tracking of the maximum current output of DC-DC converter in SPE side will track the MPPT of photovoltaic panel simultaneously. This method uses a proportional integrator controller to control the duty factor of DC-DC converter with pulse-width modulator (PWM). The MPPT performance and hydrogen production performance of this method have been evaluated and discussed based on the results of the experiment. (Author)

  4. Electronic structure and electron dynamics at Si(100)

    Energy Technology Data Exchange (ETDEWEB)

    Weinelt, M. [Universitaet Erlangen-Nuernberg, Lehrstuhl fuer Festkoerperphysik, Erlangen (Germany); Max-Born-Institut, Berlin (Germany); Kutschera, M.; Schmidt, R.; Orth, C.; Fauster, T. [Universitaet Erlangen-Nuernberg, Lehrstuhl fuer Festkoerperphysik, Erlangen (Germany); Rohlfing, M. [International University Bremen, School of Engineering and Science, P.O. Box 750 561, Bremen (Germany)

    2005-02-01

    The electronic structure and electron dynamics at a Si(100) surface is studied by two-photon photoemission (2PPE). At 90 K the occupied D{sub up} dangling-bond state is located 150{+-}50 meV below the valence-band maximum (VBM) at the center of the surface Brillouin zone anti {gamma} and exhibits an effective hole mass of (0.5{+-}0.15)m{sub e}. The unoccupied D{sub down} band has a local minimum at anti {gamma} at 650{+-}50 meV above the VBM and shows strong dispersion along the dimer rows of the c(4 x 2) reconstructed surface. At 300 K the D{sub down} position shifts comparable to the Si conduction-band minimum by 40 meV to lower energies but the dispersion of the dangling-bond states is independent of temperature. The surface band bending for p-doped silicon is less than 30 meV, while acceptor-type defects cause significant and preparation-dependent band bending on n-doped samples. 2PPE spectra of Si(100) are dominated by interband transitions between the occupied and unoccupied surface states and emission out of transiently and permanently charged surface defects. Including electron-hole interaction in many-body calculations of the quasi-particle band structure leads us to assign a dangling-bond split-off state to a quasi-one-dimensional surface exciton with a binding energy of 130 meV. Electrons resonantly excited to the unoccupied D{sub down} dangling-bond band with an excess energy of about 350 meV need 1.5{+-}0.2 ps to scatter via phonon emission to the band bottom at anti {gamma} and relax within 5 ps with an excited hole in the occupied surface band to form an exciton living for nanoseconds. (orig.)

  5. Capacitance–voltage and current–voltage characteristics for the study of high background doping and conduction mechanisms in GaAsN grown by chemical beam epitaxy

    International Nuclear Information System (INIS)

    Bouzazi, Boussairi; Kojima, Nobuaki; Ohshita, Yoshio; Yamaguchi, Masafumi

    2013-01-01

    Highlights: ► The cause of high background doping was confirmed and characterized. ► The current–voltage characteristics deviate from the thermionic emission. ► The recombination current is attributed to a hole trap (E V + 0.52 eV). ► The hole trap (E V + 0.52 eV) was confirmed by DLTS measurements. -- Abstract: The temperature dependence of capacitance–voltage (C–V) and current voltage (I–V) characteristics were used to study the cause of high background doping and the underlying current transport mechanisms in GaAsN Schottky diode grown by chemical beam epitaxy (CBE). In one hand, a nitrogen-related sigmoid increase of junction capacitance and ionized acceptor concentration was observed in the temperature range 70–100 K and was attributed to the thermal ionization of a nitrogen–hydrogen-related deep acceptor-state, with thermal activation energy of approximately 0.11 eV above the valence band maximum (VBM) of GaAsN. This acceptor state is mainly responsible for the high background doping in unintentionally doped GaAsN grown by CBE. On the other hand, the I–V characteristics at different temperatures were found to deviate from the well known pure thermionic-emission mechanism. Based on their fitting at each temperature, the recombination current in the space charge region of GaAsN Schottky diode was mainly attributed to a hole trap, localized at 0.51 eV above the VBM. Given the accuracy of measurements, this result was confirmed by deep level transient spectroscopy measurements. Nevertheless, considering the Shockley–Read–Hall model of generation-recombination, the recombination activity of this defect was quantified and qualified to be weak compared with the markedly degradation of minority carrier lifetime in GaAsN material

  6. Difficulty of carrier generation in orthorhombic PbO

    Energy Technology Data Exchange (ETDEWEB)

    Liao, Min; Takemoto, Seiji; Toda, Yoshitake; Tada, Tomofumi [Materials Research Center for Element Strategy, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Xiao, Zewen; Kamiya, Toshio; Hosono, Hideo, E-mail: hosono@msl.titech.ac.jp [Materials Research Center for Element Strategy, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Ueda, Shigenori [Synchrotron X-ray Station at SPring-8, National Institute for Materials Science, Hyogo 679-5148 (Japan); Quantum Beam Unit, National Institute for Materials Science, Tsukuba 305-0047 (Japan)

    2016-04-28

    Polycrystalline β-PbO films were grown by pulsed laser deposition in atmospheres ranging from oxygen-poor (the oxygen pressure of 0.01 Pa) to oxygen-rich (13 Pa) conditions, and the oxygen chemical potential was further enhanced by ozone annealing to examine hole doping. It was found that each of the as-grown β-PbO films showed poor electrical conductivity, σ < 1.4 × 10{sup −7} S cm{sup −1}, regardless of the oxygen pressure. The density functional calculations revealed that native defects including Pb and O vacancies have deep transition levels and extremely high formation enthalpies, which indicates difficulty of carrier generation in β-PbO and explains the experimentally observed poor electrical conductivity. The analysis of the electronic structures showed that the interaction between Pb 6s and O 2p orbitals is weak due to the deep energy level of Pb 6s and does not raise the valence band maximum (VBM) level unlike that observed in SnO, which is also supported by ultraviolet photoemission spectroscopy measurements. The deep acceptor transition levels of the native defects are attributed to the deep VBM of β-PbO. On the other hand, annealing β-PbO films in reactive oxygen-containing atmospheres (i.e., O{sub 3}) led to a significantly enhanced electrical conductivity (i.e., σ > 7.1 × 10{sup 2} S cm{sup −1}) but it is the result of the formation of an n-type PbO{sub 2} phase because oxygen chemical potential exceeded the phase boundary limit. The striking difference in carrier generation between PbO and SnO is discussed based on the electronic structures calculated by density functional theory.

  7. Maximum mass of magnetic white dwarfs

    International Nuclear Information System (INIS)

    Paret, Daryel Manreza; Horvath, Jorge Ernesto; Martínez, Aurora Perez

    2015-01-01

    We revisit the problem of the maximum masses of magnetized white dwarfs (WDs). The impact of a strong magnetic field on the structure equations is addressed. The pressures become anisotropic due to the presence of the magnetic field and split into parallel and perpendicular components. We first construct stable solutions of the Tolman-Oppenheimer-Volkoff equations for parallel pressures and find that physical solutions vanish for the perpendicular pressure when B ≳ 10 13 G. This fact establishes an upper bound for a magnetic field and the stability of the configurations in the (quasi) spherical approximation. Our findings also indicate that it is not possible to obtain stable magnetized WDs with super-Chandrasekhar masses because the values of the magnetic field needed for them are higher than this bound. To proceed into the anisotropic regime, we can apply results for structure equations appropriate for a cylindrical metric with anisotropic pressures that were derived in our previous work. From the solutions of the structure equations in cylindrical symmetry we have confirmed the same bound for B ∼ 10 13 G, since beyond this value no physical solutions are possible. Our tentative conclusion is that massive WDs with masses well beyond the Chandrasekhar limit do not constitute stable solutions and should not exist. (paper)

  8. TRENDS IN ESTIMATED MIXING DEPTH DAILY MAXIMUMS

    Energy Technology Data Exchange (ETDEWEB)

    Buckley, R; Amy DuPont, A; Robert Kurzeja, R; Matt Parker, M

    2007-11-12

    Mixing depth is an important quantity in the determination of air pollution concentrations. Fireweather forecasts depend strongly on estimates of the mixing depth as a means of determining the altitude and dilution (ventilation rates) of smoke plumes. The Savannah River United States Forest Service (USFS) routinely conducts prescribed fires at the Savannah River Site (SRS), a heavily wooded Department of Energy (DOE) facility located in southwest South Carolina. For many years, the Savannah River National Laboratory (SRNL) has provided forecasts of weather conditions in support of the fire program, including an estimated mixing depth using potential temperature and turbulence change with height at a given location. This paper examines trends in the average estimated mixing depth daily maximum at the SRS over an extended period of time (4.75 years) derived from numerical atmospheric simulations using two versions of the Regional Atmospheric Modeling System (RAMS). This allows for differences to be seen between the model versions, as well as trends on a multi-year time frame. In addition, comparisons of predicted mixing depth for individual days in which special balloon soundings were released are also discussed.

  9. Mammographic image restoration using maximum entropy deconvolution

    International Nuclear Information System (INIS)

    Jannetta, A; Jackson, J C; Kotre, C J; Birch, I P; Robson, K J; Padgett, R

    2004-01-01

    An image restoration approach based on a Bayesian maximum entropy method (MEM) has been applied to a radiological image deconvolution problem, that of reduction of geometric blurring in magnification mammography. The aim of the work is to demonstrate an improvement in image spatial resolution in realistic noisy radiological images with no associated penalty in terms of reduction in the signal-to-noise ratio perceived by the observer. Images of the TORMAM mammographic image quality phantom were recorded using the standard magnification settings of 1.8 magnification/fine focus and also at 1.8 magnification/broad focus and 3.0 magnification/fine focus; the latter two arrangements would normally give rise to unacceptable geometric blurring. Measured point-spread functions were used in conjunction with the MEM image processing to de-blur these images. The results are presented as comparative images of phantom test features and as observer scores for the raw and processed images. Visualization of high resolution features and the total image scores for the test phantom were improved by the application of the MEM processing. It is argued that this successful demonstration of image de-blurring in noisy radiological images offers the possibility of weakening the link between focal spot size and geometric blurring in radiology, thus opening up new approaches to system optimization

  10. Maximum Margin Clustering of Hyperspectral Data

    Science.gov (United States)

    Niazmardi, S.; Safari, A.; Homayouni, S.

    2013-09-01

    In recent decades, large margin methods such as Support Vector Machines (SVMs) are supposed to be the state-of-the-art of supervised learning methods for classification of hyperspectral data. However, the results of these algorithms mainly depend on the quality and quantity of available training data. To tackle down the problems associated with the training data, the researcher put effort into extending the capability of large margin algorithms for unsupervised learning. One of the recent proposed algorithms is Maximum Margin Clustering (MMC). The MMC is an unsupervised SVMs algorithm that simultaneously estimates both the labels and the hyperplane parameters. Nevertheless, the optimization of the MMC algorithm is a non-convex problem. Most of the existing MMC methods rely on the reformulating and the relaxing of the non-convex optimization problem as semi-definite programs (SDP), which are computationally very expensive and only can handle small data sets. Moreover, most of these algorithms are two-class classification, which cannot be used for classification of remotely sensed data. In this paper, a new MMC algorithm is used that solve the original non-convex problem using Alternative Optimization method. This algorithm is also extended for multi-class classification and its performance is evaluated. The results of the proposed algorithm show that the algorithm has acceptable results for hyperspectral data clustering.

  11. Paving the road to maximum productivity.

    Science.gov (United States)

    Holland, C

    1998-01-01

    "Job security" is an oxymoron in today's environment of downsizing, mergers, and acquisitions. Workers find themselves living by new rules in the workplace that they may not understand. How do we cope? It is the leader's charge to take advantage of this chaos and create conditions under which his or her people can understand the need for change and come together with a shared purpose to effect that change. The clinical laboratory at Arkansas Children's Hospital has taken advantage of this chaos to down-size and to redesign how the work gets done to pave the road to maximum productivity. After initial hourly cutbacks, the workers accepted the cold, hard fact that they would never get their old world back. They set goals to proactively shape their new world through reorganizing, flexing staff with workload, creating a rapid response laboratory, exploiting information technology, and outsourcing. Today the laboratory is a lean, productive machine that accepts change as a way of life. We have learned to adapt, trust, and support each other as we have journeyed together over the rough roads. We are looking forward to paving a new fork in the road to the future.

  12. Maximum power flux of auroral kilometric radiation

    International Nuclear Information System (INIS)

    Benson, R.F.; Fainberg, J.

    1991-01-01

    The maximum auroral kilometric radiation (AKR) power flux observed by distant satellites has been increased by more than a factor of 10 from previously reported values. This increase has been achieved by a new data selection criterion and a new analysis of antenna spin modulated signals received by the radio astronomy instrument on ISEE 3. The method relies on selecting AKR events containing signals in the highest-frequency channel (1980, kHz), followed by a careful analysis that effectively increased the instrumental dynamic range by more than 20 dB by making use of the spacecraft antenna gain diagram during a spacecraft rotation. This analysis has allowed the separation of real signals from those created in the receiver by overloading. Many signals having the appearance of AKR harmonic signals were shown to be of spurious origin. During one event, however, real second harmonic AKR signals were detected even though the spacecraft was at a great distance (17 R E ) from Earth. During another event, when the spacecraft was at the orbital distance of the Moon and on the morning side of Earth, the power flux of fundamental AKR was greater than 3 x 10 -13 W m -2 Hz -1 at 360 kHz normalized to a radial distance r of 25 R E assuming the power falls off as r -2 . A comparison of these intense signal levels with the most intense source region values (obtained by ISIS 1 and Viking) suggests that multiple sources were observed by ISEE 3

  13. Maximum likelihood window for time delay estimation

    International Nuclear Information System (INIS)

    Lee, Young Sup; Yoon, Dong Jin; Kim, Chi Yup

    2004-01-01

    Time delay estimation for the detection of leak location in underground pipelines is critically important. Because the exact leak location depends upon the precision of the time delay between sensor signals due to leak noise and the speed of elastic waves, the research on the estimation of time delay has been one of the key issues in leak lovating with the time arrival difference method. In this study, an optimal Maximum Likelihood window is considered to obtain a better estimation of the time delay. This method has been proved in experiments, which can provide much clearer and more precise peaks in cross-correlation functions of leak signals. The leak location error has been less than 1 % of the distance between sensors, for example the error was not greater than 3 m for 300 m long underground pipelines. Apart from the experiment, an intensive theoretical analysis in terms of signal processing has been described. The improved leak locating with the suggested method is due to the windowing effect in frequency domain, which offers a weighting in significant frequencies.

  14. Ancestral Sequence Reconstruction with Maximum Parsimony.

    Science.gov (United States)

    Herbst, Lina; Fischer, Mareike

    2017-12-01

    One of the main aims in phylogenetics is the estimation of ancestral sequences based on present-day data like, for instance, DNA alignments. One way to estimate the data of the last common ancestor of a given set of species is to first reconstruct a phylogenetic tree with some tree inference method and then to use some method of ancestral state inference based on that tree. One of the best-known methods both for tree inference and for ancestral sequence inference is Maximum Parsimony (MP). In this manuscript, we focus on this method and on ancestral state inference for fully bifurcating trees. In particular, we investigate a conjecture published by Charleston and Steel in 1995 concerning the number of species which need to have a particular state, say a, at a particular site in order for MP to unambiguously return a as an estimate for the state of the last common ancestor. We prove the conjecture for all even numbers of character states, which is the most relevant case in biology. We also show that the conjecture does not hold in general for odd numbers of character states, but also present some positive results for this case.

  15. 49 CFR 230.24 - Maximum allowable stress.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Maximum allowable stress. 230.24 Section 230.24... Allowable Stress § 230.24 Maximum allowable stress. (a) Maximum allowable stress value. The maximum allowable stress value on any component of a steam locomotive boiler shall not exceed 1/4 of the ultimate...

  16. 20 CFR 226.52 - Total annuity subject to maximum.

    Science.gov (United States)

    2010-04-01

    ... 20 Employees' Benefits 1 2010-04-01 2010-04-01 false Total annuity subject to maximum. 226.52... COMPUTING EMPLOYEE, SPOUSE, AND DIVORCED SPOUSE ANNUITIES Railroad Retirement Family Maximum § 226.52 Total annuity subject to maximum. The total annuity amount which is compared to the maximum monthly amount to...

  17. Half-width at half-maximum, full-width at half-maximum analysis

    Indian Academy of Sciences (India)

    addition to the well-defined parameter full-width at half-maximum (FWHM). The distribution of ... optical side-lobes in the diffraction pattern resulting in steep central maxima [6], reduc- tion of effects of ... and broad central peak. The idea of.

  18. Effect of light illumination and temperature on P3HT films, n-type Si, and ITO

    Energy Technology Data Exchange (ETDEWEB)

    Scudiero, Louis, E-mail: scudiero@wsu.edu [Chemistry Department and Material Science and Engineering Program, Washington State University, Pullman, Washington 99164 (United States); Shen, Yang [Department of Electrical and Computer Engineering, University of Virginia, 351 McCormick Road, Charlottesville, Virginia 22904 (United States); Gupta, Mool C., E-mail: mgupta@virginia.edu [Department of Electrical and Computer Engineering, University of Virginia, 351 McCormick Road, Charlottesville, Virginia 22904 (United States)

    2014-02-15

    The secondary electron (SE) cutoff energy region spectra are recorded before (dark), during (light) and after laser exposure (dark) for P3HT, Si, and ITO. An SE cutoff energy shift is observed when the bare n-type doped Si substrate is exposed to 532 nm light. This is attributed to the presence of a thin native oxide layer (∼1.5 nm) on Si. No energy shift is detected on the Ar sputtered clean Si. Also, no shift was observed for ITO. When exposed to light, a net SE energy cutoff shift was measured for P3HT deposited on both Si and ITO substrates at room temperature. However, no significant valence band maximum (VBM) energy shifts were measured for P3HT that was spun cast on both substrates under dark and light illumination. Furthermore, light effect was investigated at three different temperatures; 25, 70, and 160{sup o}C and it is found that for P3HT, the magnitude of the SE cutoff energy change is not only substrate dependent but also depends on temperature.

  19. Density functional theory studies of TiO2 for photocatalysis and Li storage applications

    Science.gov (United States)

    Kim, Yong-Hoon; Lee, Ji Il; Lee, Dong Ki; Lee, Gyu Heon; Kang, Jeung Ku

    We present two theory-experiment collaboration studies of anatase TiO2 for energy applications. First, we discuss a hydrogen-nitrogen co-doped TiO2 (HN-TiO2) as a photocatalyst, and show that the interstitially introduced HN contributes to the increase of solar-to-fuel conversion efficiency. We find that the variation of valence band maximum (VBM) of NH-TiO2 extends the photoactive spectrum to the visible light, and argue that created mid-gap states produce efficient electron and hole conduction channels. Next, we consider experimentally fabricated hierarchical TiO2 nanocrystals integrated with binder-free porous graphene (PG) network foam for a Li storage application. It was found that the TiO2-PG facilitated rapid ionic transfer during the Li-ion insertion/extraction process. We clarify the mechanisms by showing that Li ion migration into the TiO2-PG interface stabilize the binder-free oxide-graphene interface. Atomistic mechanism of Li ion insertion and migration is discussed by comparing cases between an isolated Li ion, when the crowding effect is included, and when the surface Li ions are present. We found that the supply of additional surface Li ions significantly reduce the Li insertion barrier, driving a spontaneous domino-like concerted Li insertion at the oxide surface region.

  20. Investigation on thermal evaporated CH3NH3PbI3 thin films

    Directory of Open Access Journals (Sweden)

    Youzhen Li

    2015-09-01

    Full Text Available CH3NH3I, PbI2 and CH3NH3PbI3 films were fabricated by evaporation and characterized with X-ray Photoelectron Spectroscopy (XPS and X-ray diffraction (XRD. The XPS results indicate that the PbI2 and CH3NH3PbI3 films are more uniform and stable than the CH3NH3I film. The atomic ratio of the CH3NH3I, PbI2 and CH3NH3PbI3 films are C:N:I=1.00:1.01:0.70, Pb:I= 1.00:1.91 and C: N: Pb: I = 1.29:1.07:1.00:2.94, respectively. The atomic ratio of CH3NH3PbI3 is very close to that of the ideal perovskite. Small angle x-ray diffraction results demonstrate that the as evaporated CH3NH3PbI3 film is crystalline. The valence band maximum (VBM and work function (WF of the CH3NH3PbI3 film are about 0.85eV and 4.86eV, respectively.

  1. A facile and novel strategy to synthesize reduced TiO₂ nanotubes photoelectrode for photoelectrocatalytic degradation of diclofenac.

    Science.gov (United States)

    Cheng, Xiuwen; Cheng, Qingfeng; Deng, Xiaoyong; Wang, Pu; Liu, Huiling

    2016-02-01

    TiO2 nano-materials have been considered as a versatile candidate for the photoelectrochemical (PECH) applications. In this study, we reported a facile and novel strategy to synthesize reduced TiO2 nanotubes (TiO2 NTs) photoelectrode. The microwave reduction could introduce oxygen vacancy in the lattice of TiO2, while the rapid-production of oxygen vacancy facilitated the generation of impurity level between the forbidden band and greatly enhancement of visible light absorption, thereby resulting in an improved separation efficiency of photogenerated charge carriers and photocatalytic (PC) performance. Additionally, the derived valence band X-ray photoelectron spectroscopy (VBXPS) and photoluminescence (PL) spectra confirmed the existence of oxygen vacancy in the lattice of TiO2 NTs photoelectrode, in which the valence bond maximum (VBM) and charge carriers concentration of reduced TiO2 NTs photoelectrode was determined to be 1.75 eV and 5.36 × 10(19) cm(-3), respectively. Furthermore, the scavenging experiments revealed that ·OH radical was the dominated species for the degradation of diclofenac. The enhanced-visible-light PC mechanism could mainly be attributed to the generation of oxygen vacancy, which can provide not only the visible light absorption capacity but also charge separation efficiency. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. First-principles study of structural, electronic, linear and nonlinear optical properties of Ga{2}PSb ternary chalcopyrite

    Science.gov (United States)

    Ouahrani, T.; Reshak, A. H.; de La Roza, A. Otero; Mebrouki, M.; Luaña, V.; Khenata, R.; Amrani, B.

    2009-12-01

    We report results from first-principles density functional calculations using the full-potential linear augmented plane wave (FP-LAPW) method. The generalized gradient approximation (GGA) and the Engel-Vosko-generalized gradient approximation (EV-GGA) were used for the exchange-correlation energy of the structural, electronic, linear and nonlinear optical properties of the chalcopyrite Ga2PSb compound. The valence band maximum (VBM) is located at the Γv point, and the conduction band minimum (CBM) is located at the Γc point, resulting in a direct band gap of about 0.365 eV for GGA and 0.83 eV for EV-GGA. In comparison with the experimental one (1.2 eV) we found that EV-GGA calculation gives energy gap in reasonable agreement with the experiment. The spin orbit coupling has marginal influence on the optical properties. The ground state quantities such as lattice parameters (a, c and u), bulk modules B and its pressure derivative B^primeare evaluated.

  3. Robust indirect band gap and anisotropy of optical absorption in B-doped phosphorene.

    Science.gov (United States)

    Wu, Zhi-Feng; Gao, Peng-Fei; Guo, Lei; Kang, Jun; Fang, Dang-Qi; Zhang, Yang; Xia, Ming-Gang; Zhang, Sheng-Li; Wen, Yu-Hua

    2017-12-06

    A traditional doping technique plays an important role in the band structure engineering of two-dimensional nanostructures. Since electron interaction is changed by doping, the optical and electrochemical properties could also be significantly tuned. In this study, density functional theory calculations have been employed to explore the structural stability, and electronic and optical properties of B-doped phosphorene. The results show that all B-doped phosphorenes are stable with a relatively low binding energy. Of particular interest is that these B-doped systems exhibit an indirect band gap, which is distinct from the direct one of pure phosphorene. Despite the different concentrations and configurations of B dopants, such indirect band gaps are robust. The screened hybrid density functional HSE06 predicts that the band gap of B-doped phosphorene is slightly smaller than that of pure phosphorene. Spatial charge distributions at the valence band maximum (VBM) and the conduction band minimum (CBM) are analyzed to understand the features of an indirect band gap. By comparison with pure phosphorene, B-doped phosphorenes exhibit strong anisotropy and intensity of optical absorption. Moreover, B dopants could enhance the stability of Li adsorption on phosphorene with less sacrifice of the Li diffusion rate. Our results suggest that B-doping is an effective way of tuning the band gap, enhancing the intensity of optical absorption and improving the performances of Li adsorption, which could promote potential applications in novel optical devices and lithium-ion batteries.

  4. CuAlTe{sub 2}: A promising bulk thermoelectric material

    Energy Technology Data Exchange (ETDEWEB)

    Gudelli, Vijay Kumar [Department of Physics, Indian Institute of Technology Hyderabad, Ordnance Factory Estate, Yeddumailaram 502 205, Telangana (India); Kanchana, V., E-mail: kanchana@iith.ac.in [Department of Physics, Indian Institute of Technology Hyderabad, Ordnance Factory Estate, Yeddumailaram 502 205, Telangana (India); Vaitheeswaran, G. [Advanced Centre of Research in High Energy Materials (ACRHEM), University of Hyderabad, Prof. C. R. Rao Road, Gachibowli, Hyderabad 500 046, Telangana (India)

    2015-11-05

    Transport properties of Cu-based chalcopyrite materials are presented using the full potential linear augmented plane wave method and Boltzmann Semi-classical theory. All the studied compounds appear to be direct band gap semiconductors evaluated based on the Tran-Blaha modified Becke-Johnson potential. The heavy and light band combination found near the valence band maximum (VBM) drive these materials to possess good thermoelectric properties. Among the studied compounds, CuAlTe{sub 2} is found to be more promising, in comparison with CuGaTe{sub 2}, which is reported to be an efficient thermoelectric material with appreciable figure of merit. Another interesting fact about CuAlTe{sub 2} is the comparable thermoelectric properties possessed by both n- type and p-type carriers, which might attract good device applications and are explained in detail using the electronic structure calculations. - Highlights: • Band structure calculation of Cu(Al,Ga)Ch{sub 2} compounds with the TB-mBJ functional. • Mixed heavy-light bands near Fermi level might favour good thermoelectric properties. • Among the investigated compounds CuAlTe{sub 2} appears to be more promising. • Thermoelectric properties of CuAlTe{sub 2} are almost comparable with CuGaTe{sub 2}. • Both n,p-type thermoelectric properties of CuAlTe{sub 2} can attract device applications.

  5. Mechanical control of the electro-optical properties of monolayer and bilayer BC3 by applying the in-plane biaxial strain

    Science.gov (United States)

    Behzad, Somayeh

    2017-11-01

    Recently, a new two-dimensional (2D) material, the 2D BC3 crystal, has been synthesized. Here, the mechanical control of the electro-optical properties of monolayer and bilayer BC3 by applying the biaxial strain is investigated. The electronic structure calculations showed that the strain-free monolayer and bilayer BC3 are indirect band-gap semiconductors with band gap of 0.62 and 0.29 eV, respectively, where the conduction band minimum (CBM) is at the M point whereas the valence band maximum (VBM) is at the Γ point. The doubly degenerated bands in the monolayer BC3 are splitted in the bilayer BC3 due to the interlayer interactions. Both monolayer and bilayer BC3 remain indirect gap semiconductor under biaxial tensile strain and their band gaps increases with strain. On the other hand, by increasing the magnitude of tensile strain, the optical spectra shift to the lower energies and the static dielectric constant increases. These findings suggest the potential of strain-engineered 2D BC3 in electronic and optoelectronic device applications.

  6. Surface thermodynamic stability, electronic and magnetic properties in various (001) surfaces of Zr2CoSn Heusler alloy

    Science.gov (United States)

    Yang, Yan; Feng, Zhong-Ying; Zhang, Jian-Min

    2018-05-01

    The spin-polarized first-principles are used to study the surface thermodynamic stability, electronic and magnetic properties in various (001) surfaces of Zr2CoSn Heusler alloy, and the bulk Zr2CoSn Heusler alloy are also discussed to make comparison. The conduction band minimum (CBM) of half-metallic (HM) bulk Zr2CoSn alloy is contributed by ZrA, ZrB and Co atoms, while the valence band maximum (VBM) is contributed by ZrB and Co atoms. The SnSn termination is the most stable surface with the highest spin polarizations P = 77.1% among the CoCo, ZrCo, ZrZr, ZrSn and SnSn terminations of the Zr2CoSn (001) surface. In the SnSn termination of the Zr2CoSn (001) surface, the atomic partial density of states (APDOS) of atoms in the surface, subsurface and third layers are much influenced by the surface effect and the total magnetic moment (TMM) is mainly contributed by the atomic magnetic moments of atoms in fourth to ninth layers.

  7. Cosmic shear measurement with maximum likelihood and maximum a posteriori inference

    Science.gov (United States)

    Hall, Alex; Taylor, Andy

    2017-06-01

    We investigate the problem of noise bias in maximum likelihood and maximum a posteriori estimators for cosmic shear. We derive the leading and next-to-leading order biases and compute them in the context of galaxy ellipticity measurements, extending previous work on maximum likelihood inference for weak lensing. We show that a large part of the bias on these point estimators can be removed using information already contained in the likelihood when a galaxy model is specified, without the need for external calibration. We test these bias-corrected estimators on simulated galaxy images similar to those expected from planned space-based weak lensing surveys, with promising results. We find that the introduction of an intrinsic shape prior can help with mitigation of noise bias, such that the maximum a posteriori estimate can be made less biased than the maximum likelihood estimate. Second-order terms offer a check on the convergence of the estimators, but are largely subdominant. We show how biases propagate to shear estimates, demonstrating in our simple set-up that shear biases can be reduced by orders of magnitude and potentially to within the requirements of planned space-based surveys at mild signal-to-noise ratio. We find that second-order terms can exhibit significant cancellations at low signal-to-noise ratio when Gaussian noise is assumed, which has implications for inferring the performance of shear-measurement algorithms from simplified simulations. We discuss the viability of our point estimators as tools for lensing inference, arguing that they allow for the robust measurement of ellipticity and shear.

  8. Band Alignments, Valence Bands, and Core Levels in the Tin Sulfides SnS, SnS2, and Sn2S3: Experiment and Theory

    OpenAIRE

    Whittles, TJ; Burton, LA; Skelton, JM; Walsh, A; Veal, TD; Dhanak, VR

    2016-01-01

    Tin sulfide solar cells show relatively poor efficiencies despite attractive photovoltaic properties, and there is difficulty in identifying separate phases, which are also known to form during Cu2ZnSnS4 depositions. We present X-ray photoemission spectroscopy (XPS) and inverse photoemission spectroscopy measurements of single crystal SnS, SnS2, and Sn2S3, with electronic-structure calculations from density functional theory (DFT). Differences in the XPS spectra of the three phases, including...

  9. Dynamics of Impurity and Valence Bands in Ga1-xMnxAs Within the Dynamical Mean-Field Approximation

    Energy Technology Data Exchange (ETDEWEB)

    Majidi, M. A. [University of Cincinnati; Moreno, Juana [University of North Dakota, Grand Forks; Jarrell, Mark [University of Cincinnati; Fishman, Randy Scott [ORNL; Aryanpour, K. A. [University of California, Davis

    2006-08-01

    We calculate the density-of-states and the spectral function of Ga1−xMnxAs within the dynamical mean-field approximation. Our model includes the competing effects of the strong spin-orbit coupling on the J=3/2 GaAs hole bands and the exchange interaction between the magnetic ions and the itinerant holes. We study the quasiparticle and impurity bands in the paramagnetic and ferromagnetic phases for different values of impurity-hole coupling Jc at a Mn doping of x=0.05. By analyzing the anisotropic angular distribution of the impurity band carriers at T=0, we conclude that the carrier polarization is optimal when the carriers move along the direction parallel to the average magnetization.

  10. A maximum likelihood framework for protein design

    Directory of Open Access Journals (Sweden)

    Philippe Hervé

    2006-06-01

    Full Text Available Abstract Background The aim of protein design is to predict amino-acid sequences compatible with a given target structure. Traditionally envisioned as a purely thermodynamic question, this problem can also be understood in a wider context, where additional constraints are captured by learning the sequence patterns displayed by natural proteins of known conformation. In this latter perspective, however, we still need a theoretical formalization of the question, leading to general and efficient learning methods, and allowing for the selection of fast and accurate objective functions quantifying sequence/structure compatibility. Results We propose a formulation of the protein design problem in terms of model-based statistical inference. Our framework uses the maximum likelihood principle to optimize the unknown parameters of a statistical potential, which we call an inverse potential to contrast with classical potentials used for structure prediction. We propose an implementation based on Markov chain Monte Carlo, in which the likelihood is maximized by gradient descent and is numerically estimated by thermodynamic integration. The fit of the models is evaluated by cross-validation. We apply this to a simple pairwise contact potential, supplemented with a solvent-accessibility term, and show that the resulting models have a better predictive power than currently available pairwise potentials. Furthermore, the model comparison method presented here allows one to measure the relative contribution of each component of the potential, and to choose the optimal number of accessibility classes, which turns out to be much higher than classically considered. Conclusion Altogether, this reformulation makes it possible to test a wide diversity of models, using different forms of potentials, or accounting for other factors than just the constraint of thermodynamic stability. Ultimately, such model-based statistical analyses may help to understand the forces

  11. Maximum entropy production rate in quantum thermodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Beretta, Gian Paolo, E-mail: beretta@ing.unibs.i [Universita di Brescia, via Branze 38, 25123 Brescia (Italy)

    2010-06-01

    In the framework of the recent quest for well-behaved nonlinear extensions of the traditional Schroedinger-von Neumann unitary dynamics that could provide fundamental explanations of recent experimental evidence of loss of quantum coherence at the microscopic level, a recent paper [Gheorghiu-Svirschevski 2001 Phys. Rev. A 63 054102] reproposes the nonlinear equation of motion proposed by the present author [see Beretta G P 1987 Found. Phys. 17 365 and references therein] for quantum (thermo)dynamics of a single isolated indivisible constituent system, such as a single particle, qubit, qudit, spin or atomic system, or a Bose-Einstein or Fermi-Dirac field. As already proved, such nonlinear dynamics entails a fundamental unifying microscopic proof and extension of Onsager's reciprocity and Callen's fluctuation-dissipation relations to all nonequilibrium states, close and far from thermodynamic equilibrium. In this paper we propose a brief but self-contained review of the main results already proved, including the explicit geometrical construction of the equation of motion from the steepest-entropy-ascent ansatz and its exact mathematical and conceptual equivalence with the maximal-entropy-generation variational-principle formulation presented in Gheorghiu-Svirschevski S 2001 Phys. Rev. A 63 022105. Moreover, we show how it can be extended to the case of a composite system to obtain the general form of the equation of motion, consistent with the demanding requirements of strong separability and of compatibility with general thermodynamics principles. The irreversible term in the equation of motion describes the spontaneous attraction of the state operator in the direction of steepest entropy ascent, thus implementing the maximum entropy production principle in quantum theory. The time rate at which the path of steepest entropy ascent is followed has so far been left unspecified. As a step towards the identification of such rate, here we propose a possible

  12. Determination of the maximum-depth to potential field sources by a maximum structural index method

    Science.gov (United States)

    Fedi, M.; Florio, G.

    2013-01-01

    A simple and fast determination of the limiting depth to the sources may represent a significant help to the data interpretation. To this end we explore the possibility of determining those source parameters shared by all the classes of models fitting the data. One approach is to determine the maximum depth-to-source compatible with the measured data, by using for example the well-known Bott-Smith rules. These rules involve only the knowledge of the field and its horizontal gradient maxima, and are independent from the density contrast. Thanks to the direct relationship between structural index and depth to sources we work out a simple and fast strategy to obtain the maximum depth by using the semi-automated methods, such as Euler deconvolution or depth-from-extreme-points method (DEXP). The proposed method consists in estimating the maximum depth as the one obtained for the highest allowable value of the structural index (Nmax). Nmax may be easily determined, since it depends only on the dimensionality of the problem (2D/3D) and on the nature of the analyzed field (e.g., gravity field or magnetic field). We tested our approach on synthetic models against the results obtained by the classical Bott-Smith formulas and the results are in fact very similar, confirming the validity of this method. However, while Bott-Smith formulas are restricted to the gravity field only, our method is applicable also to the magnetic field and to any derivative of the gravity and magnetic field. Our method yields a useful criterion to assess the source model based on the (∂f/∂x)max/fmax ratio. The usefulness of the method in real cases is demonstrated for a salt wall in the Mississippi basin, where the estimation of the maximum depth agrees with the seismic information.

  13. Weighted Maximum-Clique Transversal Sets of Graphs

    OpenAIRE

    Chuan-Min Lee

    2011-01-01

    A maximum-clique transversal set of a graph G is a subset of vertices intersecting all maximum cliques of G. The maximum-clique transversal set problem is to find a maximum-clique transversal set of G of minimum cardinality. Motivated by the placement of transmitters for cellular telephones, Chang, Kloks, and Lee introduced the concept of maximum-clique transversal sets on graphs in 2001. In this paper, we study the weighted version of the maximum-clique transversal set problem for split grap...

  14. Pattern formation, logistics, and maximum path probability

    Science.gov (United States)

    Kirkaldy, J. S.

    1985-05-01

    The concept of pattern formation, which to current researchers is a synonym for self-organization, carries the connotation of deductive logic together with the process of spontaneous inference. Defining a pattern as an equivalence relation on a set of thermodynamic objects, we establish that a large class of irreversible pattern-forming systems, evolving along idealized quasisteady paths, approaches the stable steady state as a mapping upon the formal deductive imperatives of a propositional function calculus. In the preamble the classical reversible thermodynamics of composite systems is analyzed as an externally manipulated system of space partitioning and classification based on ideal enclosures and diaphragms. The diaphragms have discrete classification capabilities which are designated in relation to conserved quantities by descriptors such as impervious, diathermal, and adiabatic. Differentiability in the continuum thermodynamic calculus is invoked as equivalent to analyticity and consistency in the underlying class or sentential calculus. The seat of inference, however, rests with the thermodynamicist. In the transition to an irreversible pattern-forming system the defined nature of the composite reservoirs remains, but a given diaphragm is replaced by a pattern-forming system which by its nature is a spontaneously evolving volume partitioner and classifier of invariants. The seat of volition or inference for the classification system is thus transferred from the experimenter or theoretician to the diaphragm, and with it the full deductive facility. The equivalence relations or partitions associated with the emerging patterns may thus be associated with theorems of the natural pattern-forming calculus. The entropy function, together with its derivatives, is the vehicle which relates the logistics of reservoirs and diaphragms to the analog logistics of the continuum. Maximum path probability or second-order differentiability of the entropy in isolation are

  15. Accurate modeling and maximum power point detection of ...

    African Journals Online (AJOL)

    Accurate modeling and maximum power point detection of photovoltaic ... Determination of MPP enables the PV system to deliver maximum available power. ..... adaptive artificial neural network: Proposition for a new sizing procedure.

  16. Maximum power per VA control of vector controlled interior ...

    Indian Academy of Sciences (India)

    Thakur Sumeet Singh

    2018-04-11

    Apr 11, 2018 ... Department of Electrical Engineering, Indian Institute of Technology Delhi, New ... The MPVA operation allows maximum-utilization of the drive-system. ... Permanent magnet motor; unity power factor; maximum VA utilization; ...

  17. Electron density distribution in Si and Ge using multipole, maximum ...

    Indian Academy of Sciences (India)

    Si and Ge has been studied using multipole, maximum entropy method (MEM) and ... and electron density distribution using the currently available versatile ..... data should be subjected to maximum possible utility for the characterization of.

  18. 40 CFR 141.13 - Maximum contaminant levels for turbidity.

    Science.gov (United States)

    2010-07-01

    ... turbidity. 141.13 Section 141.13 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) WATER... Maximum contaminant levels for turbidity. The maximum contaminant levels for turbidity are applicable to... part. The maximum contaminant levels for turbidity in drinking water, measured at a representative...

  19. Maximum Power Training and Plyometrics for Cross-Country Running.

    Science.gov (United States)

    Ebben, William P.

    2001-01-01

    Provides a rationale for maximum power training and plyometrics as conditioning strategies for cross-country runners, examining: an evaluation of training methods (strength training and maximum power training and plyometrics); biomechanic and velocity specificity (role in preventing injury); and practical application of maximum power training and…

  20. 13 CFR 107.840 - Maximum term of Financing.

    Science.gov (United States)

    2010-01-01

    ... 13 Business Credit and Assistance 1 2010-01-01 2010-01-01 false Maximum term of Financing. 107.840... COMPANIES Financing of Small Businesses by Licensees Structuring Licensee's Financing of An Eligible Small Business: Terms and Conditions of Financing § 107.840 Maximum term of Financing. The maximum term of any...

  1. 7 CFR 3565.210 - Maximum interest rate.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 15 2010-01-01 2010-01-01 false Maximum interest rate. 3565.210 Section 3565.210... AGRICULTURE GUARANTEED RURAL RENTAL HOUSING PROGRAM Loan Requirements § 3565.210 Maximum interest rate. The interest rate for a guaranteed loan must not exceed the maximum allowable rate specified by the Agency in...

  2. Characterizing graphs of maximum matching width at most 2

    DEFF Research Database (Denmark)

    Jeong, Jisu; Ok, Seongmin; Suh, Geewon

    2017-01-01

    The maximum matching width is a width-parameter that is de ned on a branch-decomposition over the vertex set of a graph. The size of a maximum matching in the bipartite graph is used as a cut-function. In this paper, we characterize the graphs of maximum matching width at most 2 using the minor o...

  3. 40 CFR 1042.140 - Maximum engine power, displacement, power density, and maximum in-use engine speed.

    Science.gov (United States)

    2010-07-01

    ... cylinders having an internal diameter of 13.0 cm and a 15.5 cm stroke length, the rounded displacement would... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Maximum engine power, displacement... Maximum engine power, displacement, power density, and maximum in-use engine speed. This section describes...

  4. The maximum entropy production and maximum Shannon information entropy in enzyme kinetics

    Science.gov (United States)

    Dobovišek, Andrej; Markovič, Rene; Brumen, Milan; Fajmut, Aleš

    2018-04-01

    We demonstrate that the maximum entropy production principle (MEPP) serves as a physical selection principle for the description of the most probable non-equilibrium steady states in simple enzymatic reactions. A theoretical approach is developed, which enables maximization of the density of entropy production with respect to the enzyme rate constants for the enzyme reaction in a steady state. Mass and Gibbs free energy conservations are considered as optimization constraints. In such a way computed optimal enzyme rate constants in a steady state yield also the most uniform probability distribution of the enzyme states. This accounts for the maximal Shannon information entropy. By means of the stability analysis it is also demonstrated that maximal density of entropy production in that enzyme reaction requires flexible enzyme structure, which enables rapid transitions between different enzyme states. These results are supported by an example, in which density of entropy production and Shannon information entropy are numerically maximized for the enzyme Glucose Isomerase.

  5. Solar Maximum Mission Experiment - Ultraviolet Spectroscopy and Polarimetry on the Solar Maximum Mission

    Science.gov (United States)

    Tandberg-Hanssen, E.; Cheng, C. C.; Woodgate, B. E.; Brandt, J. C.; Chapman, R. D.; Athay, R. G.; Beckers, J. M.; Bruner, E. C.; Gurman, J. B.; Hyder, C. L.

    1981-01-01

    The Ultraviolet Spectrometer and Polarimeter on the Solar Maximum Mission spacecraft is described. It is pointed out that the instrument, which operates in the wavelength range 1150-3600 A, has a spatial resolution of 2-3 arcsec and a spectral resolution of 0.02 A FWHM in second order. A Gregorian telescope, with a focal length of 1.8 m, feeds a 1 m Ebert-Fastie spectrometer. A polarimeter comprising rotating Mg F2 waveplates can be inserted behind the spectrometer entrance slit; it permits all four Stokes parameters to be determined. Among the observing modes are rasters, spectral scans, velocity measurements, and polarimetry. Examples of initial observations made since launch are presented.

  6. Benefits of the maximum tolerated dose (MTD) and maximum tolerated concentration (MTC) concept in aquatic toxicology

    International Nuclear Information System (INIS)

    Hutchinson, Thomas H.; Boegi, Christian; Winter, Matthew J.; Owens, J. Willie

    2009-01-01

    There is increasing recognition of the need to identify specific sublethal effects of chemicals, such as reproductive toxicity, and specific modes of actions of the chemicals, such as interference with the endocrine system. To achieve these aims requires criteria which provide a basis to interpret study findings so as to separate these specific toxicities and modes of action from not only acute lethality per se but also from severe inanition and malaise that non-specifically compromise reproductive capacity and the response of endocrine endpoints. Mammalian toxicologists have recognized that very high dose levels are sometimes required to elicit both specific adverse effects and present the potential of non-specific 'systemic toxicity'. Mammalian toxicologists have developed the concept of a maximum tolerated dose (MTD) beyond which a specific toxicity or action cannot be attributed to a test substance due to the compromised state of the organism. Ecotoxicologists are now confronted by a similar challenge and must develop an analogous concept of a MTD and the respective criteria. As examples of this conundrum, we note recent developments in efforts to validate protocols for fish reproductive toxicity and endocrine screens (e.g. some chemicals originally selected as 'negatives' elicited decreases in fecundity or changes in endpoints intended to be biomarkers for endocrine modes of action). Unless analogous criteria can be developed, the potentially confounding effects of systemic toxicity may then undermine the reliable assessment of specific reproductive effects or biomarkers such as vitellogenin or spiggin. The same issue confronts other areas of aquatic toxicology (e.g., genotoxicity) and the use of aquatic animals for preclinical assessments of drugs (e.g., use of zebrafish for drug safety assessment). We propose that there are benefits to adopting the concept of an MTD for toxicology and pharmacology studies using fish and other aquatic organisms and the

  7. Microprocessor Controlled Maximum Power Point Tracker for Photovoltaic Application

    International Nuclear Information System (INIS)

    Jiya, J. D.; Tahirou, G.

    2002-01-01

    This paper presents a microprocessor controlled maximum power point tracker for photovoltaic module. Input current and voltage are measured and multiplied within the microprocessor, which contains an algorithm to seek the maximum power point. The duly cycle of the DC-DC converter, at which the maximum power occurs is obtained, noted and adjusted. The microprocessor constantly seeks for improvement of obtained power by varying the duty cycle

  8. MEGA5: Molecular Evolutionary Genetics Analysis Using Maximum Likelihood, Evolutionary Distance, and Maximum Parsimony Methods

    Science.gov (United States)

    Tamura, Koichiro; Peterson, Daniel; Peterson, Nicholas; Stecher, Glen; Nei, Masatoshi; Kumar, Sudhir

    2011-01-01

    Comparative analysis of molecular sequence data is essential for reconstructing the evolutionary histories of species and inferring the nature and extent of selective forces shaping the evolution of genes and species. Here, we announce the release of Molecular Evolutionary Genetics Analysis version 5 (MEGA5), which is a user-friendly software for mining online databases, building sequence alignments and phylogenetic trees, and using methods of evolutionary bioinformatics in basic biology, biomedicine, and evolution. The newest addition in MEGA5 is a collection of maximum likelihood (ML) analyses for inferring evolutionary trees, selecting best-fit substitution models (nucleotide or amino acid), inferring ancestral states and sequences (along with probabilities), and estimating evolutionary rates site-by-site. In computer simulation analyses, ML tree inference algorithms in MEGA5 compared favorably with other software packages in terms of computational efficiency and the accuracy of the estimates of phylogenetic trees, substitution parameters, and rate variation among sites. The MEGA user interface has now been enhanced to be activity driven to make it easier for the use of both beginners and experienced scientists. This version of MEGA is intended for the Windows platform, and it has been configured for effective use on Mac OS X and Linux desktops. It is available free of charge from http://www.megasoftware.net. PMID:21546353

  9. 49 CFR 195.406 - Maximum operating pressure.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false Maximum operating pressure. 195.406 Section 195.406 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS... HAZARDOUS LIQUIDS BY PIPELINE Operation and Maintenance § 195.406 Maximum operating pressure. (a) Except for...

  10. 78 FR 49370 - Inflation Adjustment of Maximum Forfeiture Penalties

    Science.gov (United States)

    2013-08-14

    ... ``civil monetary penalties provided by law'' at least once every four years. DATES: Effective September 13... increases the maximum civil monetary forfeiture penalties available to the Commission under its rules... maximum civil penalties established in that section to account for inflation since the last adjustment to...

  11. 22 CFR 201.67 - Maximum freight charges.

    Science.gov (United States)

    2010-04-01

    ..., commodity rate classification, quantity, vessel flag category (U.S.-or foreign-flag), choice of ports, and... the United States. (2) Maximum charter rates. (i) USAID will not finance ocean freight under any... owner(s). (4) Maximum liner rates. USAID will not finance ocean freight for a cargo liner shipment at a...

  12. Maximum penetration level of distributed generation without violating voltage limits

    NARCIS (Netherlands)

    Morren, J.; Haan, de S.W.H.

    2009-01-01

    Connection of Distributed Generation (DG) units to a distribution network will result in a local voltage increase. As there will be a maximum on the allowable voltage increase, this will limit the maximum allowable penetration level of DG. By reactive power compensation (by the DG unit itself) a

  13. Particle Swarm Optimization Based of the Maximum Photovoltaic ...

    African Journals Online (AJOL)

    Photovoltaic electricity is seen as an important source of renewable energy. The photovoltaic array is an unstable source of power since the peak power point depends on the temperature and the irradiation level. A maximum peak power point tracking is then necessary for maximum efficiency. In this work, a Particle Swarm ...

  14. Maximum-entropy clustering algorithm and its global convergence analysis

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Constructing a batch of differentiable entropy functions touniformly approximate an objective function by means of the maximum-entropy principle, a new clustering algorithm, called maximum-entropy clustering algorithm, is proposed based on optimization theory. This algorithm is a soft generalization of the hard C-means algorithm and possesses global convergence. Its relations with other clustering algorithms are discussed.

  15. Application of maximum entropy to neutron tunneling spectroscopy

    International Nuclear Information System (INIS)

    Mukhopadhyay, R.; Silver, R.N.

    1990-01-01

    We demonstrate the maximum entropy method for the deconvolution of high resolution tunneling data acquired with a quasielastic spectrometer. Given a precise characterization of the instrument resolution function, a maximum entropy analysis of lutidine data obtained with the IRIS spectrometer at ISIS results in an effective factor of three improvement in resolution. 7 refs., 4 figs

  16. The regulation of starch accumulation in Panicum maximum Jacq ...

    African Journals Online (AJOL)

    ... decrease the starch level. These observations are discussed in relation to the photosynthetic characteristics of P. maximum. Keywords: accumulation; botany; carbon assimilation; co2 fixation; growth conditions; mesophyll; metabolites; nitrogen; nitrogen levels; nitrogen supply; panicum maximum; plant physiology; starch; ...

  17. 32 CFR 842.35 - Depreciation and maximum allowances.

    Science.gov (United States)

    2010-07-01

    ... 32 National Defense 6 2010-07-01 2010-07-01 false Depreciation and maximum allowances. 842.35... LITIGATION ADMINISTRATIVE CLAIMS Personnel Claims (31 U.S.C. 3701, 3721) § 842.35 Depreciation and maximum allowances. The military services have jointly established the “Allowance List-Depreciation Guide” to...

  18. The maximum significant wave height in the Southern North Sea

    NARCIS (Netherlands)

    Bouws, E.; Tolman, H.L.; Holthuijsen, L.H.; Eldeberky, Y.; Booij, N.; Ferier, P.

    1995-01-01

    The maximum possible wave conditions along the Dutch coast, which seem to be dominated by the limited water depth, have been estimated in the present study with numerical simulations. Discussions with meteorologists suggest that the maximum possible sustained wind speed in North Sea conditions is

  19. PTree: pattern-based, stochastic search for maximum parsimony phylogenies

    OpenAIRE

    Gregor, Ivan; Steinbr?ck, Lars; McHardy, Alice C.

    2013-01-01

    Phylogenetic reconstruction is vital to analyzing the evolutionary relationship of genes within and across populations of different species. Nowadays, with next generation sequencing technologies producing sets comprising thousands of sequences, robust identification of the tree topology, which is optimal according to standard criteria such as maximum parsimony, maximum likelihood or posterior probability, with phylogenetic inference methods is a computationally very demanding task. Here, we ...

  20. 5 CFR 838.711 - Maximum former spouse survivor annuity.

    Science.gov (United States)

    2010-01-01

    ... 5 Administrative Personnel 2 2010-01-01 2010-01-01 false Maximum former spouse survivor annuity... Orders Awarding Former Spouse Survivor Annuities Limitations on Survivor Annuities § 838.711 Maximum former spouse survivor annuity. (a) Under CSRS, payments under a court order may not exceed the amount...

  1. Maximum physical capacity testing in cancer patients undergoing chemotherapy

    DEFF Research Database (Denmark)

    Knutsen, L.; Quist, M; Midtgaard, J

    2006-01-01

    BACKGROUND: Over the past few years there has been a growing interest in the field of physical exercise in rehabilitation of cancer patients, leading to requirements for objective maximum physical capacity measurement (maximum oxygen uptake (VO(2max)) and one-repetition maximum (1RM)) to determin...... early in the treatment process. However, the patients were self-referred and thus highly motivated and as such are not necessarily representative of the whole population of cancer patients treated with chemotherapy....... in performing maximum physical capacity tests as these motivated them through self-perceived competitiveness and set a standard that served to encourage peak performance. CONCLUSION: The positive attitudes in this sample towards maximum physical capacity open the possibility of introducing physical testing...

  2. Maximum Principles for Discrete and Semidiscrete Reaction-Diffusion Equation

    Directory of Open Access Journals (Sweden)

    Petr Stehlík

    2015-01-01

    Full Text Available We study reaction-diffusion equations with a general reaction function f on one-dimensional lattices with continuous or discrete time ux′  (or  Δtux=k(ux-1-2ux+ux+1+f(ux, x∈Z. We prove weak and strong maximum and minimum principles for corresponding initial-boundary value problems. Whereas the maximum principles in the semidiscrete case (continuous time exhibit similar features to those of fully continuous reaction-diffusion model, in the discrete case the weak maximum principle holds for a smaller class of functions and the strong maximum principle is valid in a weaker sense. We describe in detail how the validity of maximum principles depends on the nonlinearity and the time step. We illustrate our results on the Nagumo equation with the bistable nonlinearity.

  3. 78 FR 9845 - Minimum and Ordinary Maximum and Aggravated Maximum Civil Monetary Penalties for a Violation of...

    Science.gov (United States)

    2013-02-12

    ... maximum penalty amount of $75,000 for each violation, except that if the violation results in death... the maximum civil penalty for a violation is $175,000 if the violation results in death, serious... Penalties for a Violation of the Hazardous Materials Transportation Laws or Regulations, Orders, Special...

  4. The power and robustness of maximum LOD score statistics.

    Science.gov (United States)

    Yoo, Y J; Mendell, N R

    2008-07-01

    The maximum LOD score statistic is extremely powerful for gene mapping when calculated using the correct genetic parameter value. When the mode of genetic transmission is unknown, the maximum of the LOD scores obtained using several genetic parameter values is reported. This latter statistic requires higher critical value than the maximum LOD score statistic calculated from a single genetic parameter value. In this paper, we compare the power of maximum LOD scores based on three fixed sets of genetic parameter values with the power of the LOD score obtained after maximizing over the entire range of genetic parameter values. We simulate family data under nine generating models. For generating models with non-zero phenocopy rates, LOD scores maximized over the entire range of genetic parameters yielded greater power than maximum LOD scores for fixed sets of parameter values with zero phenocopy rates. No maximum LOD score was consistently more powerful than the others for generating models with a zero phenocopy rate. The power loss of the LOD score maximized over the entire range of genetic parameters, relative to the maximum LOD score calculated using the correct genetic parameter value, appeared to be robust to the generating models.

  5. Parameters determining maximum wind velocity in a tropical cyclone

    International Nuclear Information System (INIS)

    Choudhury, A.M.

    1984-09-01

    The spiral structure of a tropical cyclone was earlier explained by a tangential velocity distribution which varies inversely as the distance from the cyclone centre outside the circle of maximum wind speed. The case has been extended in the present paper by adding a radial velocity. It has been found that a suitable combination of radial and tangential velocities can account for the spiral structure of a cyclone. This enables parametrization of the cyclone. Finally a formula has been derived relating maximum velocity in a tropical cyclone with angular momentum, radius of maximum wind speed and the spiral angle. The shapes of the spirals have been computed for various spiral angles. (author)

  6. Environmental Monitoring, Water Quality - Total Maximum Daily Load (TMDL)

    Data.gov (United States)

    NSGIC Education | GIS Inventory — The Clean Water Act Section 303(d) establishes the Total Maximum Daily Load (TMDL) program. The purpose of the TMDL program is to identify sources of pollution and...

  7. Probabilistic maximum-value wind prediction for offshore environments

    DEFF Research Database (Denmark)

    Staid, Andrea; Pinson, Pierre; Guikema, Seth D.

    2015-01-01

    statistical models to predict the full distribution of the maximum-value wind speeds in a 3 h interval. We take a detailed look at the performance of linear models, generalized additive models and multivariate adaptive regression splines models using meteorological covariates such as gust speed, wind speed......, convective available potential energy, Charnock, mean sea-level pressure and temperature, as given by the European Center for Medium-Range Weather Forecasts forecasts. The models are trained to predict the mean value of maximum wind speed, and the residuals from training the models are used to develop...... the full probabilistic distribution of maximum wind speed. Knowledge of the maximum wind speed for an offshore location within a given period can inform decision-making regarding turbine operations, planned maintenance operations and power grid scheduling in order to improve safety and reliability...

  8. Combining Experiments and Simulations Using the Maximum Entropy Principle

    DEFF Research Database (Denmark)

    Boomsma, Wouter; Ferkinghoff-Borg, Jesper; Lindorff-Larsen, Kresten

    2014-01-01

    are not in quantitative agreement with experimental data. The principle of maximum entropy is a general procedure for constructing probability distributions in the light of new data, making it a natural tool in cases when an initial model provides results that are at odds with experiments. The number of maximum entropy...... in the context of a simple example, after which we proceed with a real-world application in the field of molecular simulations, where the maximum entropy procedure has recently provided new insight. Given the limited accuracy of force fields, macromolecular simulations sometimes produce results....... Three very recent papers have explored this problem using the maximum entropy approach, providing both new theoretical and practical insights to the problem. We highlight each of these contributions in turn and conclude with a discussion on remaining challenges....

  9. Parametric optimization of thermoelectric elements footprint for maximum power generation

    DEFF Research Database (Denmark)

    Rezania, A.; Rosendahl, Lasse; Yin, Hao

    2014-01-01

    The development studies in thermoelectric generator (TEG) systems are mostly disconnected to parametric optimization of the module components. In this study, optimum footprint ratio of n- and p-type thermoelectric (TE) elements is explored to achieve maximum power generation, maximum cost......-performance, and variation of efficiency in the uni-couple over a wide range of the heat transfer coefficient on the cold junction. The three-dimensional (3D) governing equations of the thermoelectricity and the heat transfer are solved using the finite element method (FEM) for temperature dependent properties of TE...... materials. The results, which are in good agreement with the previous computational studies, show that the maximum power generation and the maximum cost-performance in the module occur at An/Ap

  10. Ethylene Production Maximum Achievable Control Technology (MACT) Compliance Manual

    Science.gov (United States)

    This July 2006 document is intended to help owners and operators of ethylene processes understand and comply with EPA's maximum achievable control technology standards promulgated on July 12, 2002, as amended on April 13, 2005 and April 20, 2006.

  11. ORIGINAL ARTICLES Surgical practice in a maximum security prison

    African Journals Online (AJOL)

    Prison Clinic, Mangaung Maximum Security Prison, Bloemfontein. F Kleinhans, BA (Cur) .... HIV positivity rate and the use of the rectum to store foreign objects. ... fruit in sunlight. Other positive health-promoting factors may also play a role,.

  12. A technique for estimating maximum harvesting effort in a stochastic ...

    Indian Academy of Sciences (India)

    Unknown

    Estimation of maximum harvesting effort has a great impact on the ... fluctuating environment has been developed in a two-species competitive system, which shows that under realistic .... The existence and local stability properties of the equi-.

  13. Water Quality Assessment and Total Maximum Daily Loads Information (ATTAINS)

    Data.gov (United States)

    U.S. Environmental Protection Agency — The Water Quality Assessment TMDL Tracking And Implementation System (ATTAINS) stores and tracks state water quality assessment decisions, Total Maximum Daily Loads...

  14. Post optimization paradigm in maximum 3-satisfiability logic programming

    Science.gov (United States)

    Mansor, Mohd. Asyraf; Sathasivam, Saratha; Kasihmuddin, Mohd Shareduwan Mohd

    2017-08-01

    Maximum 3-Satisfiability (MAX-3SAT) is a counterpart of the Boolean satisfiability problem that can be treated as a constraint optimization problem. It deals with a conundrum of searching the maximum number of satisfied clauses in a particular 3-SAT formula. This paper presents the implementation of enhanced Hopfield network in hastening the Maximum 3-Satisfiability (MAX-3SAT) logic programming. Four post optimization techniques are investigated, including the Elliot symmetric activation function, Gaussian activation function, Wavelet activation function and Hyperbolic tangent activation function. The performances of these post optimization techniques in accelerating MAX-3SAT logic programming will be discussed in terms of the ratio of maximum satisfied clauses, Hamming distance and the computation time. Dev-C++ was used as the platform for training, testing and validating our proposed techniques. The results depict the Hyperbolic tangent activation function and Elliot symmetric activation function can be used in doing MAX-3SAT logic programming.

  15. Maximum likelihood estimation of finite mixture model for economic data

    Science.gov (United States)

    Phoong, Seuk-Yen; Ismail, Mohd Tahir

    2014-06-01

    Finite mixture model is a mixture model with finite-dimension. This models are provides a natural representation of heterogeneity in a finite number of latent classes. In addition, finite mixture models also known as latent class models or unsupervised learning models. Recently, maximum likelihood estimation fitted finite mixture models has greatly drawn statistician's attention. The main reason is because maximum likelihood estimation is a powerful statistical method which provides consistent findings as the sample sizes increases to infinity. Thus, the application of maximum likelihood estimation is used to fit finite mixture model in the present paper in order to explore the relationship between nonlinear economic data. In this paper, a two-component normal mixture model is fitted by maximum likelihood estimation in order to investigate the relationship among stock market price and rubber price for sampled countries. Results described that there is a negative effect among rubber price and stock market price for Malaysia, Thailand, Philippines and Indonesia.

  16. Encoding Strategy for Maximum Noise Tolerance Bidirectional Associative Memory

    National Research Council Canada - National Science Library

    Shen, Dan

    2003-01-01

    In this paper, the Basic Bidirectional Associative Memory (BAM) is extended by choosing weights in the correlation matrix, for a given set of training pairs, which result in a maximum noise tolerance set for BAM...

  17. Narrow band interference cancelation in OFDM: Astructured maximum likelihood approach

    KAUST Repository

    Sohail, Muhammad Sadiq; Al-Naffouri, Tareq Y.; Al-Ghadhban, Samir N.

    2012-01-01

    This paper presents a maximum likelihood (ML) approach to mitigate the effect of narrow band interference (NBI) in a zero padded orthogonal frequency division multiplexing (ZP-OFDM) system. The NBI is assumed to be time variant and asynchronous

  18. Maximum entropy deconvolution of low count nuclear medicine images

    International Nuclear Information System (INIS)

    McGrath, D.M.

    1998-12-01

    Maximum entropy is applied to the problem of deconvolving nuclear medicine images, with special consideration for very low count data. The physics of the formation of scintigraphic images is described, illustrating the phenomena which degrade planar estimates of the tracer distribution. Various techniques which are used to restore these images are reviewed, outlining the relative merits of each. The development and theoretical justification of maximum entropy as an image processing technique is discussed. Maximum entropy is then applied to the problem of planar deconvolution, highlighting the question of the choice of error parameters for low count data. A novel iterative version of the algorithm is suggested which allows the errors to be estimated from the predicted Poisson mean values. This method is shown to produce the exact results predicted by combining Poisson statistics and a Bayesian interpretation of the maximum entropy approach. A facility for total count preservation has also been incorporated, leading to improved quantification. In order to evaluate this iterative maximum entropy technique, two comparable methods, Wiener filtering and a novel Bayesian maximum likelihood expectation maximisation technique, were implemented. The comparison of results obtained indicated that this maximum entropy approach may produce equivalent or better measures of image quality than the compared methods, depending upon the accuracy of the system model used. The novel Bayesian maximum likelihood expectation maximisation technique was shown to be preferable over many existing maximum a posteriori methods due to its simplicity of implementation. A single parameter is required to define the Bayesian prior, which suppresses noise in the solution and may reduce the processing time substantially. Finally, maximum entropy deconvolution was applied as a pre-processing step in single photon emission computed tomography reconstruction of low count data. Higher contrast results were

  19. What controls the maximum magnitude of injection-induced earthquakes?

    Science.gov (United States)

    Eaton, D. W. S.

    2017-12-01

    Three different approaches for estimation of maximum magnitude are considered here, along with their implications for managing risk. The first approach is based on a deterministic limit for seismic moment proposed by McGarr (1976), which was originally designed for application to mining-induced seismicity. This approach has since been reformulated for earthquakes induced by fluid injection (McGarr, 2014). In essence, this method assumes that the upper limit for seismic moment release is constrained by the pressure-induced stress change. A deterministic limit is given by the product of shear modulus and the net injected fluid volume. This method is based on the assumptions that the medium is fully saturated and in a state of incipient failure. An alternative geometrical approach was proposed by Shapiro et al. (2011), who postulated that the rupture area for an induced earthquake falls entirely within the stimulated volume. This assumption reduces the maximum-magnitude problem to one of estimating the largest potential slip surface area within a given stimulated volume. Finally, van der Elst et al. (2016) proposed that the maximum observed magnitude, statistically speaking, is the expected maximum value for a finite sample drawn from an unbounded Gutenberg-Richter distribution. These three models imply different approaches for risk management. The deterministic method proposed by McGarr (2014) implies that a ceiling on the maximum magnitude can be imposed by limiting the net injected volume, whereas the approach developed by Shapiro et al. (2011) implies that the time-dependent maximum magnitude is governed by the spatial size of the microseismic event cloud. Finally, the sample-size hypothesis of Van der Elst et al. (2016) implies that the best available estimate of the maximum magnitude is based upon observed seismicity rate. The latter two approaches suggest that real-time monitoring is essential for effective management of risk. A reliable estimate of maximum

  20. Maximum organic carbon limits at different melter feed rates (U)

    International Nuclear Information System (INIS)

    Choi, A.S.

    1995-01-01

    This report documents the results of a study to assess the impact of varying melter feed rates on the maximum total organic carbon (TOC) limits allowable in the DWPF melter feed. Topics discussed include: carbon content; feed rate; feed composition; melter vapor space temperature; combustion and dilution air; off-gas surges; earlier work on maximum TOC; overview of models; and the results of the work completed

  1. A tropospheric ozone maximum over the equatorial Southern Indian Ocean

    Directory of Open Access Journals (Sweden)

    L. Zhang

    2012-05-01

    Full Text Available We examine the distribution of tropical tropospheric ozone (O3 from the Microwave Limb Sounder (MLS and the Tropospheric Emission Spectrometer (TES by using a global three-dimensional model of tropospheric chemistry (GEOS-Chem. MLS and TES observations of tropospheric O3 during 2005 to 2009 reveal a distinct, persistent O3 maximum, both in mixing ratio and tropospheric column, in May over the Equatorial Southern Indian Ocean (ESIO. The maximum is most pronounced in 2006 and 2008 and less evident in the other three years. This feature is also consistent with the total column O3 observations from the Ozone Mapping Instrument (OMI and the Atmospheric Infrared Sounder (AIRS. Model results reproduce the observed May O3 maximum and the associated interannual variability. The origin of the maximum reflects a complex interplay of chemical and dynamic factors. The O3 maximum is dominated by the O3 production driven by lightning nitrogen oxides (NOx emissions, which accounts for 62% of the tropospheric column O3 in May 2006. We find the contribution from biomass burning, soil, anthropogenic and biogenic sources to the O3 maximum are rather small. The O3 productions in the lightning outflow from Central Africa and South America both peak in May and are directly responsible for the O3 maximum over the western ESIO. The lightning outflow from Equatorial Asia dominates over the eastern ESIO. The interannual variability of the O3 maximum is driven largely by the anomalous anti-cyclones over the southern Indian Ocean in May 2006 and 2008. The lightning outflow from Central Africa and South America is effectively entrained by the anti-cyclones followed by northward transport to the ESIO.

  2. Dinosaur Metabolism and the Allometry of Maximum Growth Rate

    OpenAIRE

    Myhrvold, Nathan P.

    2016-01-01

    The allometry of maximum somatic growth rate has been used in prior studies to classify the metabolic state of both extant vertebrates and dinosaurs. The most recent such studies are reviewed, and their data is reanalyzed. The results of allometric regressions on growth rate are shown to depend on the choice of independent variable; the typical choice used in prior studies introduces a geometric shear transformation that exaggerates the statistical power of the regressions. The maximum growth...

  3. MAXIMUM PRINCIPLE FOR SUBSONIC FLOW WITH VARIABLE ENTROPY

    Directory of Open Access Journals (Sweden)

    B. Sizykh Grigory

    2017-01-01

    Full Text Available Maximum principle for subsonic flow is fair for stationary irrotational subsonic gas flows. According to this prin- ciple, if the value of the velocity is not constant everywhere, then its maximum is achieved on the boundary and only on the boundary of the considered domain. This property is used when designing form of an aircraft with a maximum critical val- ue of the Mach number: it is believed that if the local Mach number is less than unit in the incoming flow and on the body surface, then the Mach number is less then unit in all points of flow. The known proof of maximum principle for subsonic flow is based on the assumption that in the whole considered area of the flow the pressure is a function of density. For the ideal and perfect gas (the role of diffusion is negligible, and the Mendeleev-Clapeyron law is fulfilled, the pressure is a function of density if entropy is constant in the entire considered area of the flow. Shows an example of a stationary sub- sonic irrotational flow, in which the entropy has different values on different stream lines, and the pressure is not a function of density. The application of the maximum principle for subsonic flow with respect to such a flow would be unreasonable. This example shows the relevance of the question about the place of the points of maximum value of the velocity, if the entropy is not a constant. To clarify the regularities of the location of these points, was performed the analysis of the com- plete Euler equations (without any simplifying assumptions in 3-D case. The new proof of the maximum principle for sub- sonic flow was proposed. This proof does not rely on the assumption that the pressure is a function of density. Thus, it is shown that the maximum principle for subsonic flow is true for stationary subsonic irrotational flows of ideal perfect gas with variable entropy.

  4. On semidefinite programming relaxations of maximum k-section

    NARCIS (Netherlands)

    de Klerk, E.; Pasechnik, D.V.; Sotirov, R.; Dobre, C.

    2012-01-01

    We derive a new semidefinite programming bound for the maximum k -section problem. For k=2 (i.e. for maximum bisection), the new bound is at least as strong as a well-known bound by Poljak and Rendl (SIAM J Optim 5(3):467–487, 1995). For k ≥ 3the new bound dominates a bound of Karisch and Rendl

  5. Direct maximum parsimony phylogeny reconstruction from genotype data

    OpenAIRE

    Sridhar, Srinath; Lam, Fumei; Blelloch, Guy E; Ravi, R; Schwartz, Russell

    2007-01-01

    Abstract Background Maximum parsimony phylogenetic tree reconstruction from genetic variation data is a fundamental problem in computational genetics with many practical applications in population genetics, whole genome analysis, and the search for genetic predictors of disease. Efficient methods are available for reconstruction of maximum parsimony trees from haplotype data, but such data are difficult to determine directly for autosomal DNA. Data more commonly is available in the form of ge...

  6. Maximum power point tracker based on fuzzy logic

    International Nuclear Information System (INIS)

    Daoud, A.; Midoun, A.

    2006-01-01

    The solar energy is used as power source in photovoltaic power systems and the need for an intelligent power management system is important to obtain the maximum power from the limited solar panels. With the changing of the sun illumination due to variation of angle of incidence of sun radiation and of the temperature of the panels, Maximum Power Point Tracker (MPPT) enables optimization of solar power generation. The MPPT is a sub-system designed to extract the maximum power from a power source. In the case of solar panels power source. the maximum power point varies as a result of changes in its electrical characteristics which in turn are functions of radiation dose, temperature, ageing and other effects. The MPPT maximum the power output from panels for a given set of conditions by detecting the best working point of the power characteristic and then controls the current through the panels or the voltage across them. Many MPPT methods have been reported in literature. These techniques of MPPT can be classified into three main categories that include: lookup table methods, hill climbing methods and computational methods. The techniques vary according to the degree of sophistication, processing time and memory requirements. The perturbation and observation algorithm (hill climbing technique) is commonly used due to its ease of implementation, and relative tracking efficiency. However, it has been shown that when the insolation changes rapidly, the perturbation and observation method is slow to track the maximum power point. In recent years, the fuzzy controllers are used for maximum power point tracking. This method only requires the linguistic control rules for maximum power point, the mathematical model is not required and therefore the implementation of this control method is easy to real control system. In this paper, we we present a simple robust MPPT using fuzzy set theory where the hardware consists of the microchip's microcontroller unit control card and

  7. Maximum spectral demands in the near-fault region

    Science.gov (United States)

    Huang, Yin-Nan; Whittaker, Andrew S.; Luco, Nicolas

    2008-01-01

    The Next Generation Attenuation (NGA) relationships for shallow crustal earthquakes in the western United States predict a rotated geometric mean of horizontal spectral demand, termed GMRotI50, and not maximum spectral demand. Differences between strike-normal, strike-parallel, geometric-mean, and maximum spectral demands in the near-fault region are investigated using 147 pairs of records selected from the NGA strong motion database. The selected records are for earthquakes with moment magnitude greater than 6.5 and for closest site-to-fault distance less than 15 km. Ratios of maximum spectral demand to NGA-predicted GMRotI50 for each pair of ground motions are presented. The ratio shows a clear dependence on period and the Somerville directivity parameters. Maximum demands can substantially exceed NGA-predicted GMRotI50 demands in the near-fault region, which has significant implications for seismic design, seismic performance assessment, and the next-generation seismic design maps. Strike-normal spectral demands are a significantly unconservative surrogate for maximum spectral demands for closest distance greater than 3 to 5 km. Scale factors that transform NGA-predicted GMRotI50 to a maximum spectral demand in the near-fault region are proposed.

  8. Maximum vehicle cabin temperatures under different meteorological conditions

    Science.gov (United States)

    Grundstein, Andrew; Meentemeyer, Vernon; Dowd, John

    2009-05-01

    A variety of studies have documented the dangerously high temperatures that may occur within the passenger compartment (cabin) of cars under clear sky conditions, even at relatively low ambient air temperatures. Our study, however, is the first to examine cabin temperatures under variable weather conditions. It uses a unique maximum vehicle cabin temperature dataset in conjunction with directly comparable ambient air temperature, solar radiation, and cloud cover data collected from April through August 2007 in Athens, GA. Maximum cabin temperatures, ranging from 41-76°C, varied considerably depending on the weather conditions and the time of year. Clear days had the highest cabin temperatures, with average values of 68°C in the summer and 61°C in the spring. Cloudy days in both the spring and summer were on average approximately 10°C cooler. Our findings indicate that even on cloudy days with lower ambient air temperatures, vehicle cabin temperatures may reach deadly levels. Additionally, two predictive models of maximum daily vehicle cabin temperatures were developed using commonly available meteorological data. One model uses maximum ambient air temperature and average daily solar radiation while the other uses cloud cover percentage as a surrogate for solar radiation. From these models, two maximum vehicle cabin temperature indices were developed to assess the level of danger. The models and indices may be useful for forecasting hazardous conditions, promoting public awareness, and to estimate past cabin temperatures for use in forensic analyses.

  9. Fractal Dimension and Maximum Sunspot Number in Solar Cycle

    Directory of Open Access Journals (Sweden)

    R.-S. Kim

    2006-09-01

    Full Text Available The fractal dimension is a quantitative parameter describing the characteristics of irregular time series. In this study, we use this parameter to analyze the irregular aspects of solar activity and to predict the maximum sunspot number in the following solar cycle by examining time series of the sunspot number. For this, we considered the daily sunspot number since 1850 from SIDC (Solar Influences Data analysis Center and then estimated cycle variation of the fractal dimension by using Higuchi's method. We examined the relationship between this fractal dimension and the maximum monthly sunspot number in each solar cycle. As a result, we found that there is a strong inverse relationship between the fractal dimension and the maximum monthly sunspot number. By using this relation we predicted the maximum sunspot number in the solar cycle from the fractal dimension of the sunspot numbers during the solar activity increasing phase. The successful prediction is proven by a good correlation (r=0.89 between the observed and predicted maximum sunspot numbers in the solar cycles.

  10. Size dependence of efficiency at maximum power of heat engine

    KAUST Repository

    Izumida, Y.; Ito, N.

    2013-01-01

    We perform a molecular dynamics computer simulation of a heat engine model to study how the engine size difference affects its performance. Upon tactically increasing the size of the model anisotropically, we determine that there exists an optimum size at which the model attains the maximum power for the shortest working period. This optimum size locates between the ballistic heat transport region and the diffusive heat transport one. We also study the size dependence of the efficiency at the maximum power. Interestingly, we find that the efficiency at the maximum power around the optimum size attains a value that has been proposed as a universal upper bound, and it even begins to exceed the bound as the size further increases. We explain this behavior of the efficiency at maximum power by using a linear response theory for the heat engine operating under a finite working period, which naturally extends the low-dissipation Carnot cycle model [M. Esposito, R. Kawai, K. Lindenberg, C. Van den Broeck, Phys. Rev. Lett. 105, 150603 (2010)]. The theory also shows that the efficiency at the maximum power under an extreme condition may reach the Carnot efficiency in principle.© EDP Sciences Società Italiana di Fisica Springer-Verlag 2013.

  11. Size dependence of efficiency at maximum power of heat engine

    KAUST Repository

    Izumida, Y.

    2013-10-01

    We perform a molecular dynamics computer simulation of a heat engine model to study how the engine size difference affects its performance. Upon tactically increasing the size of the model anisotropically, we determine that there exists an optimum size at which the model attains the maximum power for the shortest working period. This optimum size locates between the ballistic heat transport region and the diffusive heat transport one. We also study the size dependence of the efficiency at the maximum power. Interestingly, we find that the efficiency at the maximum power around the optimum size attains a value that has been proposed as a universal upper bound, and it even begins to exceed the bound as the size further increases. We explain this behavior of the efficiency at maximum power by using a linear response theory for the heat engine operating under a finite working period, which naturally extends the low-dissipation Carnot cycle model [M. Esposito, R. Kawai, K. Lindenberg, C. Van den Broeck, Phys. Rev. Lett. 105, 150603 (2010)]. The theory also shows that the efficiency at the maximum power under an extreme condition may reach the Carnot efficiency in principle.© EDP Sciences Società Italiana di Fisica Springer-Verlag 2013.

  12. How long do centenarians survive? Life expectancy and maximum lifespan.

    Science.gov (United States)

    Modig, K; Andersson, T; Vaupel, J; Rau, R; Ahlbom, A

    2017-08-01

    The purpose of this study was to explore the pattern of mortality above the age of 100 years. In particular, we aimed to examine whether Scandinavian data support the theory that mortality reaches a plateau at particularly old ages. Whether the maximum length of life increases with time was also investigated. The analyses were based on individual level data on all Swedish and Danish centenarians born from 1870 to 1901; in total 3006 men and 10 963 women were included. Birth cohort-specific probabilities of dying were calculated. Exact ages were used for calculations of maximum length of life. Whether maximum age changed over time was analysed taking into account increases in cohort size. The results confirm that there has not been any improvement in mortality amongst centenarians in the past 30 years and that the current rise in life expectancy is driven by reductions in mortality below the age of 100 years. The death risks seem to reach a plateau of around 50% at the age 103 years for men and 107 years for women. Despite the rising life expectancy, the maximum age does not appear to increase, in particular after accounting for the increasing number of individuals of advanced age. Mortality amongst centenarians is not changing despite improvements at younger ages. An extension of the maximum lifespan and a sizeable extension of life expectancy both require reductions in mortality above the age of 100 years. © 2017 The Association for the Publication of the Journal of Internal Medicine.

  13. Modeling multisite streamflow dependence with maximum entropy copula

    Science.gov (United States)

    Hao, Z.; Singh, V. P.

    2013-10-01

    Synthetic streamflows at different sites in a river basin are needed for planning, operation, and management of water resources projects. Modeling the temporal and spatial dependence structure of monthly streamflow at different sites is generally required. In this study, the maximum entropy copula method is proposed for multisite monthly streamflow simulation, in which the temporal and spatial dependence structure is imposed as constraints to derive the maximum entropy copula. The monthly streamflows at different sites are then generated by sampling from the conditional distribution. A case study for the generation of monthly streamflow at three sites in the Colorado River basin illustrates the application of the proposed method. Simulated streamflow from the maximum entropy copula is in satisfactory agreement with observed streamflow.

  14. Quality, precision and accuracy of the maximum No. 40 anemometer

    Energy Technology Data Exchange (ETDEWEB)

    Obermeir, J. [Otech Engineering, Davis, CA (United States); Blittersdorf, D. [NRG Systems Inc., Hinesburg, VT (United States)

    1996-12-31

    This paper synthesizes available calibration data for the Maximum No. 40 anemometer. Despite its long history in the wind industry, controversy surrounds the choice of transfer function for this anemometer. Many users are unaware that recent changes in default transfer functions in data loggers are producing output wind speed differences as large as 7.6%. Comparison of two calibration methods used for large samples of Maximum No. 40 anemometers shows a consistent difference of 4.6% in output speeds. This difference is significantly larger than estimated uncertainty levels. Testing, initially performed to investigate related issues, reveals that Gill and Maximum cup anemometers change their calibration transfer functions significantly when calibrated in the open atmosphere compared with calibration in a laminar wind tunnel. This indicates that atmospheric turbulence changes the calibration transfer function of cup anemometers. These results call into question the suitability of standard wind tunnel calibration testing for cup anemometers. 6 refs., 10 figs., 4 tabs.

  15. Beat the Deviations in Estimating Maximum Power of Thermoelectric Modules

    DEFF Research Database (Denmark)

    Gao, Junling; Chen, Min

    2013-01-01

    Under a certain temperature difference, the maximum power of a thermoelectric module can be estimated by the open-circuit voltage and the short-circuit current. In practical measurement, there exist two switch modes, either from open to short or from short to open, but the two modes can give...... different estimations on the maximum power. Using TEG-127-2.8-3.5-250 and TEG-127-1.4-1.6-250 as two examples, the difference is about 10%, leading to some deviations with the temperature change. This paper analyzes such differences by means of a nonlinear numerical model of thermoelectricity, and finds out...... that the main cause is the influence of various currents on the produced electromotive potential. A simple and effective calibration method is proposed to minimize the deviations in specifying the maximum power. Experimental results validate the method with improved estimation accuracy....

  16. Mass mortality of the vermetid gastropod Ceraesignum maximum

    Science.gov (United States)

    Brown, A. L.; Frazer, T. K.; Shima, J. S.; Osenberg, C. W.

    2016-09-01

    Ceraesignum maximum (G.B. Sowerby I, 1825), formerly Dendropoma maximum, was subject to a sudden, massive die-off in the Society Islands, French Polynesia, in 2015. On Mo'orea, where we have detailed documentation of the die-off, these gastropods were previously found in densities up to 165 m-2. In July 2015, we surveyed shallow back reefs of Mo'orea before, during and after the die-off, documenting their swift decline. All censused populations incurred 100% mortality. Additional surveys and observations from Mo'orea, Tahiti, Bora Bora, and Huahine (but not Taha'a) suggested a similar, and approximately simultaneous, die-off. The cause(s) of this cataclysmic mass mortality are currently unknown. Given the previously documented negative effects of C. maximum on corals, we expect the die-off will have cascading effects on the reef community.

  17. Stationary neutrino radiation transport by maximum entropy closure

    International Nuclear Information System (INIS)

    Bludman, S.A.

    1994-11-01

    The authors obtain the angular distributions that maximize the entropy functional for Maxwell-Boltzmann (classical), Bose-Einstein, and Fermi-Dirac radiation. In the low and high occupancy limits, the maximum entropy closure is bounded by previously known variable Eddington factors that depend only on the flux. For intermediate occupancy, the maximum entropy closure depends on both the occupation density and the flux. The Fermi-Dirac maximum entropy variable Eddington factor shows a scale invariance, which leads to a simple, exact analytic closure for fermions. This two-dimensional variable Eddington factor gives results that agree well with exact (Monte Carlo) neutrino transport calculations out of a collapse residue during early phases of hydrostatic neutron star formation

  18. Spatio-temporal observations of the tertiary ozone maximum

    Directory of Open Access Journals (Sweden)

    V. F. Sofieva

    2009-07-01

    Full Text Available We present spatio-temporal distributions of the tertiary ozone maximum (TOM, based on GOMOS (Global Ozone Monitoring by Occultation of Stars ozone measurements in 2002–2006. The tertiary ozone maximum is typically observed in the high-latitude winter mesosphere at an altitude of ~72 km. Although the explanation for this phenomenon has been found recently – low concentrations of odd-hydrogen cause the subsequent decrease in odd-oxygen losses – models have had significant deviations from existing observations until recently. Good coverage of polar night regions by GOMOS data has allowed for the first time to obtain spatial and temporal observational distributions of night-time ozone mixing ratio in the mesosphere.

    The distributions obtained from GOMOS data have specific features, which are variable from year to year. In particular, due to a long lifetime of ozone in polar night conditions, the downward transport of polar air by the meridional circulation is clearly observed in the tertiary ozone maximum time series. Although the maximum tertiary ozone mixing ratio is achieved close to the polar night terminator (as predicted by the theory, TOM can be observed also at very high latitudes, not only in the beginning and at the end, but also in the middle of winter. We have compared the observational spatio-temporal distributions of the tertiary ozone maximum with that obtained using WACCM (Whole Atmosphere Community Climate Model and found that the specific features are reproduced satisfactorily by the model.

    Since ozone in the mesosphere is very sensitive to HOx concentrations, energetic particle precipitation can significantly modify the shape of the ozone profiles. In particular, GOMOS observations have shown that the tertiary ozone maximum was temporarily destroyed during the January 2005 and December 2006 solar proton events as a result of the HOx enhancement from the increased ionization.

  19. Estimating the maximum potential revenue for grid connected electricity storage :

    Energy Technology Data Exchange (ETDEWEB)

    Byrne, Raymond Harry; Silva Monroy, Cesar Augusto.

    2012-12-01

    The valuation of an electricity storage device is based on the expected future cash flow generated by the device. Two potential sources of income for an electricity storage system are energy arbitrage and participation in the frequency regulation market. Energy arbitrage refers to purchasing (stor- ing) energy when electricity prices are low, and selling (discharging) energy when electricity prices are high. Frequency regulation is an ancillary service geared towards maintaining system frequency, and is typically procured by the independent system operator in some type of market. This paper outlines the calculations required to estimate the maximum potential revenue from participating in these two activities. First, a mathematical model is presented for the state of charge as a function of the storage device parameters and the quantities of electricity purchased/sold as well as the quantities o ered into the regulation market. Using this mathematical model, we present a linear programming optimization approach to calculating the maximum potential revenue from an elec- tricity storage device. The calculation of the maximum potential revenue is critical in developing an upper bound on the value of storage, as a benchmark for evaluating potential trading strate- gies, and a tool for capital nance risk assessment. Then, we use historical California Independent System Operator (CAISO) data from 2010-2011 to evaluate the maximum potential revenue from the Tehachapi wind energy storage project, an American Recovery and Reinvestment Act of 2009 (ARRA) energy storage demonstration project. We investigate the maximum potential revenue from two di erent scenarios: arbitrage only and arbitrage combined with the regulation market. Our analysis shows that participation in the regulation market produces four times the revenue compared to arbitrage in the CAISO market using 2010 and 2011 data. Then we evaluate several trading strategies to illustrate how they compare to the

  20. Discontinuity of maximum entropy inference and quantum phase transitions

    International Nuclear Information System (INIS)

    Chen, Jianxin; Ji, Zhengfeng; Yu, Nengkun; Zeng, Bei; Li, Chi-Kwong; Poon, Yiu-Tung; Shen, Yi; Zhou, Duanlu

    2015-01-01

    In this paper, we discuss the connection between two genuinely quantum phenomena—the discontinuity of quantum maximum entropy inference and quantum phase transitions at zero temperature. It is shown that the discontinuity of the maximum entropy inference of local observable measurements signals the non-local type of transitions, where local density matrices of the ground state change smoothly at the transition point. We then propose to use the quantum conditional mutual information of the ground state as an indicator to detect the discontinuity and the non-local type of quantum phase transitions in the thermodynamic limit. (paper)

  1. On an Objective Basis for the Maximum Entropy Principle

    Directory of Open Access Journals (Sweden)

    David J. Miller

    2015-01-01

    Full Text Available In this letter, we elaborate on some of the issues raised by a recent paper by Neapolitan and Jiang concerning the maximum entropy (ME principle and alternative principles for estimating probabilities consistent with known, measured constraint information. We argue that the ME solution for the “problematic” example introduced by Neapolitan and Jiang has stronger objective basis, rooted in results from information theory, than their alternative proposed solution. We also raise some technical concerns about the Bayesian analysis in their work, which was used to independently support their alternative to the ME solution. The letter concludes by noting some open problems involving maximum entropy statistical inference.

  2. The maximum economic depth of groundwater abstraction for irrigation

    Science.gov (United States)

    Bierkens, M. F.; Van Beek, L. P.; de Graaf, I. E. M.; Gleeson, T. P.

    2017-12-01

    Over recent decades, groundwater has become increasingly important for agriculture. Irrigation accounts for 40% of the global food production and its importance is expected to grow further in the near future. Already, about 70% of the globally abstracted water is used for irrigation, and nearly half of that is pumped groundwater. In many irrigated areas where groundwater is the primary source of irrigation water, groundwater abstraction is larger than recharge and we see massive groundwater head decline in these areas. An important question then is: to what maximum depth can groundwater be pumped for it to be still economically recoverable? The objective of this study is therefore to create a global map of the maximum depth of economically recoverable groundwater when used for irrigation. The maximum economic depth is the maximum depth at which revenues are still larger than pumping costs or the maximum depth at which initial investments become too large compared to yearly revenues. To this end we set up a simple economic model where costs of well drilling and the energy costs of pumping, which are a function of well depth and static head depth respectively, are compared with the revenues obtained for the irrigated crops. Parameters for the cost sub-model are obtained from several US-based studies and applied to other countries based on GDP/capita as an index of labour costs. The revenue sub-model is based on gross irrigation water demand calculated with a global hydrological and water resources model, areal coverage of crop types from MIRCA2000 and FAO-based statistics on crop yield and market price. We applied our method to irrigated areas in the world overlying productive aquifers. Estimated maximum economic depths range between 50 and 500 m. Most important factors explaining the maximum economic depth are the dominant crop type in the area and whether or not initial investments in well infrastructure are limiting. In subsequent research, our estimates of

  3. Efficiency of autonomous soft nanomachines at maximum power.

    Science.gov (United States)

    Seifert, Udo

    2011-01-14

    We consider nanosized artificial or biological machines working in steady state enforced by imposing nonequilibrium concentrations of solutes or by applying external forces, torques, or electric fields. For unicyclic and strongly coupled multicyclic machines, efficiency at maximum power is not bounded by the linear response value 1/2. For strong driving, it can even approach the thermodynamic limit 1. Quite generally, such machines fall into three different classes characterized, respectively, as "strong and efficient," "strong and inefficient," and "balanced." For weakly coupled multicyclic machines, efficiency at maximum power has lost any universality even in the linear response regime.

  4. A comparison of methods of predicting maximum oxygen uptake.

    OpenAIRE

    Grant, S; Corbett, K; Amjad, A M; Wilson, J; Aitchison, T

    1995-01-01

    The aim of this study was to compare the results from a Cooper walk run test, a multistage shuttle run test, and a submaximal cycle test with the direct measurement of maximum oxygen uptake on a treadmill. Three predictive tests of maximum oxygen uptake--linear extrapolation of heart rate of VO2 collected from a submaximal cycle ergometer test (predicted L/E), the Cooper 12 min walk, run test, and a multi-stage progressive shuttle run test (MST)--were performed by 22 young healthy males (mean...

  5. Maximum length scale in density based topology optimization

    DEFF Research Database (Denmark)

    Lazarov, Boyan Stefanov; Wang, Fengwen

    2017-01-01

    The focus of this work is on two new techniques for imposing maximum length scale in topology optimization. Restrictions on the maximum length scale provide designers with full control over the optimized structure and open possibilities to tailor the optimized design for broader range...... of manufacturing processes by fulfilling the associated technological constraints. One of the proposed methods is based on combination of several filters and builds on top of the classical density filtering which can be viewed as a low pass filter applied to the design parametrization. The main idea...

  6. A Maximum Entropy Method for a Robust Portfolio Problem

    Directory of Open Access Journals (Sweden)

    Yingying Xu

    2014-06-01

    Full Text Available We propose a continuous maximum entropy method to investigate the robustoptimal portfolio selection problem for the market with transaction costs and dividends.This robust model aims to maximize the worst-case portfolio return in the case that allof asset returns lie within some prescribed intervals. A numerical optimal solution tothe problem is obtained by using a continuous maximum entropy method. Furthermore,some numerical experiments indicate that the robust model in this paper can result in betterportfolio performance than a classical mean-variance model.

  7. MAXIMUM RUNOFF OF THE FLOOD ON WADIS OF NORTHERN ...

    African Journals Online (AJOL)

    lanez

    The technique of account the maximal runoff of flood for the rivers of northern part of Algeria based on the theory of ... north to south: 1) coastal Tel – fertile, high cultivated and sown zone; 2) territory of Atlas. Mountains ... In the first case the empiric dependence between maximum intensity of precipitation for some calculation ...

  8. Scientific substantination of maximum allowable concentration of fluopicolide in water

    Directory of Open Access Journals (Sweden)

    Pelo I.М.

    2014-03-01

    Full Text Available In order to substantiate fluopicolide maximum allowable concentration in the water of water reservoirs the research was carried out. Methods of study: laboratory hygienic experiment using organoleptic and sanitary-chemical, sanitary-toxicological, sanitary-microbiological and mathematical methods. The results of fluopicolide influence on organoleptic properties of water, sanitary regimen of reservoirs for household purposes were given and its subthreshold concentration in water by sanitary and toxicological hazard index was calculated. The threshold concentration of the substance by the main hazard criteria was established, the maximum allowable concentration in water was substantiated. The studies led to the following conclusions: fluopicolide threshold concentration in water by organoleptic hazard index (limiting criterion – the smell – 0.15 mg/dm3, general sanitary hazard index (limiting criteria – impact on the number of saprophytic microflora, biochemical oxygen demand and nitrification – 0.015 mg/dm3, the maximum noneffective concentration – 0.14 mg/dm3, the maximum allowable concentration - 0.015 mg/dm3.

  9. Image coding based on maximum entropy partitioning for identifying ...

    Indian Academy of Sciences (India)

    A new coding scheme based on maximum entropy partitioning is proposed in our work, particularly to identify the improbable intensities related to different emotions. The improbable intensities when used as a mask decode the facial expression correctly, providing an effectiveplatform for future emotion categorization ...

  10. Computing the maximum volume inscribed ellipsoid of a polytopic projection

    NARCIS (Netherlands)

    Zhen, Jianzhe; den Hertog, Dick

    We introduce a novel scheme based on a blending of Fourier-Motzkin elimination (FME) and adjustable robust optimization techniques to compute the maximum volume inscribed ellipsoid (MVE) in a polytopic projection. It is well-known that deriving an explicit description of a projected polytope is

  11. Computing the Maximum Volume Inscribed Ellipsoid of a Polytopic Projection

    NARCIS (Netherlands)

    Zhen, J.; den Hertog, D.

    2015-01-01

    We introduce a novel scheme based on a blending of Fourier-Motzkin elimination (FME) and adjustable robust optimization techniques to compute the maximum volume inscribed ellipsoid (MVE) in a polytopic projection. It is well-known that deriving an explicit description of a projected polytope is

  12. Maximum super angle optimization method for array antenna pattern synthesis

    DEFF Research Database (Denmark)

    Wu, Ji; Roederer, A. G

    1991-01-01

    Different optimization criteria related to antenna pattern synthesis are discussed. Based on the maximum criteria and vector space representation, a simple and efficient optimization method is presented for array and array fed reflector power pattern synthesis. A sector pattern synthesized by a 2...

  13. correlation between maximum dry density and cohesion of ...

    African Journals Online (AJOL)

    HOD

    investigation on sandy soils to determine the correlation between relative density and compaction test parameter. Using twenty soil samples, they were able to develop correlations between relative density, coefficient of uniformity and maximum dry density. Khafaji [5] using standard proctor compaction method carried out an ...

  14. Molecular markers linked to apomixis in Panicum maximum Jacq ...

    African Journals Online (AJOL)

    Panicum maximum Jacq. is an important forage grass of African origin largely used in the tropics. The genetic breeding of this species is based on the hybridization of sexual and apomictic genotypes and selection of apomictic F1 hybrids. The objective of this work was to identify molecular markers linked to apomixis in P.

  15. Maximum likelihood estimation of the attenuated ultrasound pulse

    DEFF Research Database (Denmark)

    Rasmussen, Klaus Bolding

    1994-01-01

    The attenuated ultrasound pulse is divided into two parts: a stationary basic pulse and a nonstationary attenuation pulse. A standard ARMA model is used for the basic pulse, and a nonstandard ARMA model is derived for the attenuation pulse. The maximum likelihood estimator of the attenuated...

  16. On a Weak Discrete Maximum Principle for hp-FEM

    Czech Academy of Sciences Publication Activity Database

    Šolín, Pavel; Vejchodský, Tomáš

    -, č. 209 (2007), s. 54-65 ISSN 0377-0427 R&D Projects: GA ČR(CZ) GA102/05/0629 Institutional research plan: CEZ:AV0Z20570509; CEZ:AV0Z10190503 Keywords : discrete maximum principle * hp-FEM Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 0.943, year: 2007

  17. Gamma-ray spectra deconvolution by maximum-entropy methods

    International Nuclear Information System (INIS)

    Los Arcos, J.M.

    1996-01-01

    A maximum-entropy method which includes the response of detectors and the statistical fluctuations of spectra is described and applied to the deconvolution of γ-ray spectra. Resolution enhancement of 25% can be reached for experimental peaks and up to 50% for simulated ones, while the intensities are conserved within 1-2%. (orig.)

  18. Modeling maximum daily temperature using a varying coefficient regression model

    Science.gov (United States)

    Han Li; Xinwei Deng; Dong-Yum Kim; Eric P. Smith

    2014-01-01

    Relationships between stream water and air temperatures are often modeled using linear or nonlinear regression methods. Despite a strong relationship between water and air temperatures and a variety of models that are effective for data summarized on a weekly basis, such models did not yield consistently good predictions for summaries such as daily maximum temperature...

  19. Maximum Interconnectedness and Availability for Directional Airborne Range Extension Networks

    Science.gov (United States)

    2016-08-29

    IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 1 Maximum Interconnectedness and Availability for Directional Airborne Range Extension Networks Thomas...2 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS I. INTRODUCTION Tactical military networks both on land and at sea often have restricted transmission...a standard definition in graph theoretic and networking literature that is related to, but different from, the metric we consider. August 29, 2016

  20. Maximum of difference assessment of typical semitrailers: a global study

    CSIR Research Space (South Africa)

    Kienhofer, F

    2016-11-01

    Full Text Available the maximum allowable width and frontal overhang as stipulated by legislation from Australia, the European Union, Canada, the United States and South Africa. The majority of the Australian, EU and Canadian semitrailer combinations and all of the South African...

  1. The constraint rule of the maximum entropy principle

    NARCIS (Netherlands)

    Uffink, J.

    1995-01-01

    The principle of maximum entropy is a method for assigning values to probability distributions on the basis of partial information. In usual formulations of this and related methods of inference one assumes that this partial information takes the form of a constraint on allowed probability

  2. 24 CFR 232.565 - Maximum loan amount.

    Science.gov (United States)

    2010-04-01

    ... URBAN DEVELOPMENT MORTGAGE AND LOAN INSURANCE PROGRAMS UNDER NATIONAL HOUSING ACT AND OTHER AUTHORITIES MORTGAGE INSURANCE FOR NURSING HOMES, INTERMEDIATE CARE FACILITIES, BOARD AND CARE HOMES, AND ASSISTED... Fire Safety Equipment Eligible Security Instruments § 232.565 Maximum loan amount. The principal amount...

  3. 5 CFR 531.221 - Maximum payable rate rule.

    Science.gov (United States)

    2010-01-01

    ... before the reassignment. (ii) If the rate resulting from the geographic conversion under paragraph (c)(2... previous rate (i.e., the former special rate after the geographic conversion) with the rates on the current... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Maximum payable rate rule. 531.221...

  4. Effects of bruxism on the maximum bite force

    Directory of Open Access Journals (Sweden)

    Todić Jelena T.

    2017-01-01

    Full Text Available Background/Aim. Bruxism is a parafunctional activity of the masticatory system, which is characterized by clenching or grinding of teeth. The purpose of this study was to determine whether the presence of bruxism has impact on maximum bite force, with particular reference to the potential impact of gender on bite force values. Methods. This study included two groups of subjects: without and with bruxism. The presence of bruxism in the subjects was registered using a specific clinical questionnaire on bruxism and physical examination. The subjects from both groups were submitted to the procedure of measuring the maximum bite pressure and occlusal contact area using a single-sheet pressure-sensitive films (Fuji Prescale MS and HS Film. Maximal bite force was obtained by multiplying maximal bite pressure and occlusal contact area values. Results. The average values of maximal bite force were significantly higher in the subjects with bruxism compared to those without bruxism (p 0.01. Maximal bite force was significantly higher in the males compared to the females in all segments of the research. Conclusion. The presence of bruxism influences the increase in the maximum bite force as shown in this study. Gender is a significant determinant of bite force. Registration of maximum bite force can be used in diagnosing and analysing pathophysiological events during bruxism.

  5. MAXIMUM-LIKELIHOOD-ESTIMATION OF THE ENTROPY OF AN ATTRACTOR

    NARCIS (Netherlands)

    SCHOUTEN, JC; TAKENS, F; VANDENBLEEK, CM

    In this paper, a maximum-likelihood estimate of the (Kolmogorov) entropy of an attractor is proposed that can be obtained directly from a time series. Also, the relative standard deviation of the entropy estimate is derived; it is dependent on the entropy and on the number of samples used in the

  6. Adaptive Unscented Kalman Filter using Maximum Likelihood Estimation

    DEFF Research Database (Denmark)

    Mahmoudi, Zeinab; Poulsen, Niels Kjølstad; Madsen, Henrik

    2017-01-01

    The purpose of this study is to develop an adaptive unscented Kalman filter (UKF) by tuning the measurement noise covariance. We use the maximum likelihood estimation (MLE) and the covariance matching (CM) method to estimate the noise covariance. The multi-step prediction errors generated...

  7. Handelman's hierarchy for the maximum stable set problem

    NARCIS (Netherlands)

    Laurent, M.; Sun, Z.

    2014-01-01

    The maximum stable set problem is a well-known NP-hard problem in combinatorial optimization, which can be formulated as the maximization of a quadratic square-free polynomial over the (Boolean) hypercube. We investigate a hierarchy of linear programming relaxations for this problem, based on a

  8. New shower maximum trigger for electrons and photons at CDF

    International Nuclear Information System (INIS)

    Amidei, D.; Burkett, K.; Gerdes, D.; Miao, C.; Wolinski, D.

    1994-01-01

    For the 1994 Tevatron collider run, CDF has upgraded the electron and photo trigger hardware to make use of shower position and size information from the central shower maximum detector. For electrons, the upgrade has resulted in a 50% reduction in backgrounds while retaining approximately 90% of the signal. The new trigger also eliminates the background to photon triggers from single-phototube spikes

  9. New shower maximum trigger for electrons and photons at CDF

    International Nuclear Information System (INIS)

    Gerdes, D.

    1994-08-01

    For the 1994 Tevatron collider run, CDF has upgraded the electron and photon trigger hardware to make use of shower position and size information from the central shower maximum detector. For electrons, the upgrade has resulted in a 50% reduction in backgrounds while retaining approximately 90% of the signal. The new trigger also eliminates the background to photon triggers from single-phototube discharge

  10. Maximum drawdown and the allocation to real estate

    NARCIS (Netherlands)

    Hamelink, F.; Hoesli, M.

    2004-01-01

    The role of real estate in a mixed-asset portfolio is investigated when the maximum drawdown (hereafter MaxDD), rather than the standard deviation, is used as the measure of risk. In particular, it is analysed whether the discrepancy between the optimal allocation to real estate and the actual

  11. A Family of Maximum SNR Filters for Noise Reduction

    DEFF Research Database (Denmark)

    Huang, Gongping; Benesty, Jacob; Long, Tao

    2014-01-01

    significantly increase the SNR but at the expense of tremendous speech distortion. As a consequence, the speech quality improvement, measured by the perceptual evaluation of speech quality (PESQ) algorithm, is marginal if any, regardless of the number of microphones used. In the STFT domain, the maximum SNR...

  12. 5 CFR 581.402 - Maximum garnishment limitations.

    Science.gov (United States)

    2010-01-01

    ... PROCESSING GARNISHMENT ORDERS FOR CHILD SUPPORT AND/OR ALIMONY Consumer Credit Protection Act Restrictions..., pursuant to section 1673(b)(2) (A) and (B) of title 15 of the United States Code (the Consumer Credit... local law, the maximum part of the aggregate disposable earnings subject to garnishment to enforce any...

  13. Distribution of phytoplankton groups within the deep chlorophyll maximum

    KAUST Repository

    Latasa, Mikel; Cabello, Ana Marí a; Moran, Xose Anxelu G.; Massana, Ramon; Scharek, Renate

    2016-01-01

    and optical and FISH microscopy. All groups presented minimum abundances at the surface and a maximum in the DCM layer. The cell distribution was not vertically symmetrical around the DCM peak and cells tended to accumulate in the upper part of the DCM layer

  14. 44 CFR 208.12 - Maximum Pay Rate Table.

    Science.gov (United States)

    2010-10-01

    ...) Physicians. DHS uses the latest Special Salary Rate Table Number 0290 for Medical Officers (Clinical... Personnel, in which case the Maximum Pay Rate Table would not apply. (3) Compensation for Sponsoring Agency... organizations, e.g., HMOs or medical or engineering professional associations, under the revised definition of...

  15. Anti-nutrient components of guinea grass ( Panicum maximum ...

    African Journals Online (AJOL)

    Yomi

    2012-01-31

    Jan 31, 2012 ... A true measure of forage quality is animal ... The anti-nutritional contents of a pasture could be ... nutrient factors in P. maximum; (2) assess the effect of nitrogen ..... 3. http://www.clemson.edu/Fairfield/local/news/quality.

  16. SIMULATION OF NEW SIMPLE FUZZY LOGIC MAXIMUM POWER ...

    African Journals Online (AJOL)

    2010-06-30

    Jun 30, 2010 ... Basic structure photovoltaic system Solar array mathematic ... The equivalent circuit model of a solar cell consists of a current generator and a diode .... control of boost converter (tracker) such that maximum power is achieved at the output of the solar panel. Fig.11. The membership function of input. Fig.12.

  17. Sur les estimateurs du maximum de vraisemblance dans les mod& ...

    African Journals Online (AJOL)

    Abstract. We are interested in the existence and uniqueness of maximum likelihood estimators of parameters in the two multiplicative regression models, with Poisson or negative binomial probability distributions. Following its work on the multiplicative Poisson model with two factors without repeated measures, Haberman ...

  18. Gravitational Waves and the Maximum Spin Frequency of Neutron Stars

    NARCIS (Netherlands)

    Patruno, A.; Haskell, B.; D'Angelo, C.

    2012-01-01

    In this paper, we re-examine the idea that gravitational waves are required as a braking mechanism to explain the observed maximum spin frequency of neutron stars. We show that for millisecond X-ray pulsars, the existence of spin equilibrium as set by the disk/magnetosphere interaction is sufficient

  19. Applications of the Maximum Entropy Method in superspace

    Czech Academy of Sciences Publication Activity Database

    van Smaalen, S.; Palatinus, Lukáš

    2004-01-01

    Roč. 305, - (2004), s. 57-62 ISSN 0015-0193 Grant - others:DFG and FCI(DE) XX Institutional research plan: CEZ:AV0Z1010914 Keywords : Maximum Entropy Method * modulated structures * charge density Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.517, year: 2004

  20. Phytophthora stricta isolated from Rhododendron maximum in Pennsylvania

    Science.gov (United States)

    During a survey in October 2013, in the Michaux State Forest in Pennsylvania , necrotic Rhododendron maximum leaves were noticed on mature plants alongside a stream. Symptoms were nondescript necrotic lesions at the tips of mature leaves. Colonies resembling a Phytophthora sp. were observed from c...

  1. Transversals and independence in linear hypergraphs with maximum degree two

    DEFF Research Database (Denmark)

    Henning, Michael A.; Yeo, Anders

    2017-01-01

    , k-uniform hypergraphs with maximum degree 2. It is known [European J. Combin. 36 (2014), 231–236] that if H ∈ Hk, then (k + 1)τ (H) 6 ≤ n + m, and there are only two hypergraphs that achieve equality in the bound. In this paper, we prove a much more powerful result, and establish tight upper bounds...

  2. A conrparison of optirnunl and maximum reproduction using the rat ...

    African Journals Online (AJOL)

    of pigs to increase reproduction rate of sows (te Brake,. 1978; Walker et at., 1979; Kemm et at., 1980). However, no experimental evidence exists that this strategy would in fact improve biological efficiency. In this pilot experiment, an attempt was made to compare systems of optimum or maximum reproduction using the rat.

  3. Revision of regional maximum flood (RMF) estimation in Namibia ...

    African Journals Online (AJOL)

    Extreme flood hydrology in Namibia for the past 30 years has largely been based on the South African Department of Water Affairs Technical Report 137 (TR 137) of 1988. This report proposes an empirically established upper limit of flood peaks for regions called the regional maximum flood (RMF), which could be ...

  4. Maximum entropy estimation via Gauss-LP quadratures

    NARCIS (Netherlands)

    Thély, Maxime; Sutter, Tobias; Mohajerin Esfahani, P.; Lygeros, John; Dochain, Denis; Henrion, Didier; Peaucelle, Dimitri

    2017-01-01

    We present an approximation method to a class of parametric integration problems that naturally appear when solving the dual of the maximum entropy estimation problem. Our method builds up on a recent generalization of Gauss quadratures via an infinite-dimensional linear program, and utilizes a

  5. On the maximum entropy distributions of inherently positive nuclear data

    Energy Technology Data Exchange (ETDEWEB)

    Taavitsainen, A., E-mail: aapo.taavitsainen@gmail.com; Vanhanen, R.

    2017-05-11

    The multivariate log-normal distribution is used by many authors and statistical uncertainty propagation programs for inherently positive quantities. Sometimes it is claimed that the log-normal distribution results from the maximum entropy principle, if only means, covariances and inherent positiveness of quantities are known or assumed to be known. In this article we show that this is not true. Assuming a constant prior distribution, the maximum entropy distribution is in fact a truncated multivariate normal distribution – whenever it exists. However, its practical application to multidimensional cases is hindered by lack of a method to compute its location and scale parameters from means and covariances. Therefore, regardless of its theoretical disadvantage, use of other distributions seems to be a practical necessity. - Highlights: • Statistical uncertainty propagation requires a sampling distribution. • The objective distribution of inherently positive quantities is determined. • The objectivity is based on the maximum entropy principle. • The maximum entropy distribution is the truncated normal distribution. • Applicability of log-normal or normal distribution approximation is limited.

  6. Current opinion about maximum entropy methods in Moessbauer spectroscopy

    International Nuclear Information System (INIS)

    Szymanski, K

    2009-01-01

    Current opinion about Maximum Entropy Methods in Moessbauer Spectroscopy is presented. The most important advantage offered by the method is the correct data processing under circumstances of incomplete information. Disadvantage is the sophisticated algorithm and its application to the specific problems.

  7. The maximum number of minimal codewords in long codes

    DEFF Research Database (Denmark)

    Alahmadi, A.; Aldred, R.E.L.; dela Cruz, R.

    2013-01-01

    Upper bounds on the maximum number of minimal codewords in a binary code follow from the theory of matroids. Random coding provides lower bounds. In this paper, we compare these bounds with analogous bounds for the cycle code of graphs. This problem (in the graphic case) was considered in 1981 by...

  8. Inverse feasibility problems of the inverse maximum flow problems

    Indian Academy of Sciences (India)

    199–209. c Indian Academy of Sciences. Inverse feasibility problems of the inverse maximum flow problems. ADRIAN DEACONU. ∗ and ELEONOR CIUREA. Department of Mathematics and Computer Science, Faculty of Mathematics and Informatics, Transilvania University of Brasov, Brasov, Iuliu Maniu st. 50,. Romania.

  9. Maximum Permissible Concentrations and Negligible Concentrations for pesticides

    NARCIS (Netherlands)

    Crommentuijn T; Kalf DF; Polder MD; Posthumus R; Plassche EJ van de; CSR

    1997-01-01

    Maximum Permissible Concentrations (MPCs) and Negligible Concentrations (NCs) derived for a series of pesticides are presented in this report. These MPCs and NCs are used by the Ministry of Housing, Spatial Planning and the Environment (VROM) to set Environmental Quality Objectives. For some of the

  10. Maximum Safety Regenerative Power Tracking for DC Traction Power Systems

    Directory of Open Access Journals (Sweden)

    Guifu Du

    2017-02-01

    Full Text Available Direct current (DC traction power systems are widely used in metro transport systems, with running rails usually being used as return conductors. When traction current flows through the running rails, a potential voltage known as “rail potential” is generated between the rails and ground. Currently, abnormal rises of rail potential exist in many railway lines during the operation of railway systems. Excessively high rail potentials pose a threat to human life and to devices connected to the rails. In this paper, the effect of regenerative power distribution on rail potential is analyzed. Maximum safety regenerative power tracking is proposed for the control of maximum absolute rail potential and energy consumption during the operation of DC traction power systems. The dwell time of multiple trains at each station and the trigger voltage of the regenerative energy absorbing device (READ are optimized based on an improved particle swarm optimization (PSO algorithm to manage the distribution of regenerative power. In this way, the maximum absolute rail potential and energy consumption of DC traction power systems can be reduced. The operation data of Guangzhou Metro Line 2 are used in the simulations, and the results show that the scheme can reduce the maximum absolute rail potential and energy consumption effectively and guarantee the safety in energy saving of DC traction power systems.

  11. Maximum Mass of Hybrid Stars in the Quark Bag Model

    Science.gov (United States)

    Alaverdyan, G. B.; Vartanyan, Yu. L.

    2017-12-01

    The effect of model parameters in the equation of state for quark matter on the magnitude of the maximum mass of hybrid stars is examined. Quark matter is described in terms of the extended MIT bag model including corrections for one-gluon exchange. For nucleon matter in the range of densities corresponding to the phase transition, a relativistic equation of state is used that is calculated with two-particle correlations taken into account based on using the Bonn meson-exchange potential. The Maxwell construction is used to calculate the characteristics of the first order phase transition and it is shown that for a fixed value of the strong interaction constant αs, the baryon concentrations of the coexisting phases grow monotonically as the bag constant B increases. It is shown that for a fixed value of the strong interaction constant αs, the maximum mass of a hybrid star increases as the bag constant B decreases. For a given value of the bag parameter B, the maximum mass rises as the strong interaction constant αs increases. It is shown that the configurations of hybrid stars with maximum masses equal to or exceeding the mass of the currently known most massive pulsar are possible for values of the strong interaction constant αs > 0.6 and sufficiently low values of the bag constant.

  12. Maximum-Entropy Inference with a Programmable Annealer

    Science.gov (United States)

    Chancellor, Nicholas; Szoke, Szilard; Vinci, Walter; Aeppli, Gabriel; Warburton, Paul A.

    2016-03-01

    Optimisation problems typically involve finding the ground state (i.e. the minimum energy configuration) of a cost function with respect to many variables. If the variables are corrupted by noise then this maximises the likelihood that the solution is correct. The maximum entropy solution on the other hand takes the form of a Boltzmann distribution over the ground and excited states of the cost function to correct for noise. Here we use a programmable annealer for the information decoding problem which we simulate as a random Ising model in a field. We show experimentally that finite temperature maximum entropy decoding can give slightly better bit-error-rates than the maximum likelihood approach, confirming that useful information can be extracted from the excited states of the annealer. Furthermore we introduce a bit-by-bit analytical method which is agnostic to the specific application and use it to show that the annealer samples from a highly Boltzmann-like distribution. Machines of this kind are therefore candidates for use in a variety of machine learning applications which exploit maximum entropy inference, including language processing and image recognition.

  13. Direct maximum parsimony phylogeny reconstruction from genotype data.

    Science.gov (United States)

    Sridhar, Srinath; Lam, Fumei; Blelloch, Guy E; Ravi, R; Schwartz, Russell

    2007-12-05

    Maximum parsimony phylogenetic tree reconstruction from genetic variation data is a fundamental problem in computational genetics with many practical applications in population genetics, whole genome analysis, and the search for genetic predictors of disease. Efficient methods are available for reconstruction of maximum parsimony trees from haplotype data, but such data are difficult to determine directly for autosomal DNA. Data more commonly is available in the form of genotypes, which consist of conflated combinations of pairs of haplotypes from homologous chromosomes. Currently, there are no general algorithms for the direct reconstruction of maximum parsimony phylogenies from genotype data. Hence phylogenetic applications for autosomal data must therefore rely on other methods for first computationally inferring haplotypes from genotypes. In this work, we develop the first practical method for computing maximum parsimony phylogenies directly from genotype data. We show that the standard practice of first inferring haplotypes from genotypes and then reconstructing a phylogeny on the haplotypes often substantially overestimates phylogeny size. As an immediate application, our method can be used to determine the minimum number of mutations required to explain a given set of observed genotypes. Phylogeny reconstruction directly from unphased data is computationally feasible for moderate-sized problem instances and can lead to substantially more accurate tree size inferences than the standard practice of treating phasing and phylogeny construction as two separate analysis stages. The difference between the approaches is particularly important for downstream applications that require a lower-bound on the number of mutations that the genetic region has undergone.

  14. Multilevel maximum likelihood estimation with application to covariance matrices

    Czech Academy of Sciences Publication Activity Database

    Turčičová, Marie; Mandel, J.; Eben, Kryštof

    Published online: 23 January ( 2018 ) ISSN 0361-0926 R&D Projects: GA ČR GA13-34856S Institutional support: RVO:67985807 Keywords : Fisher information * High dimension * Hierarchical maximum likelihood * Nested parameter spaces * Spectral diagonal covariance model * Sparse inverse covariance model Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 0.311, year: 2016

  15. Heat Convection at the Density Maximum Point of Water

    Science.gov (United States)

    Balta, Nuri; Korganci, Nuri

    2018-01-01

    Water exhibits a maximum in density at normal pressure at around 4° degree temperature. This paper demonstrates that during cooling, at around 4 °C, the temperature remains constant for a while because of heat exchange associated with convective currents inside the water. Superficial approach implies it as a new anomaly of water, but actually it…

  16. Combining Experiments and Simulations Using the Maximum Entropy Principle

    DEFF Research Database (Denmark)

    Boomsma, Wouter; Ferkinghoff-Borg, Jesper; Lindorff-Larsen, Kresten

    2014-01-01

    in the context of a simple example, after which we proceed with a real-world application in the field of molecular simulations, where the maximum entropy procedure has recently provided new insight. Given the limited accuracy of force fields, macromolecular simulations sometimes produce results...

  17. Optimal item discrimination and maximum information for logistic IRT models

    NARCIS (Netherlands)

    Veerkamp, W.J.J.; Veerkamp, Wim J.J.; Berger, Martijn P.F.; Berger, Martijn

    1999-01-01

    Items with the highest discrimination parameter values in a logistic item response theory model do not necessarily give maximum information. This paper derives discrimination parameter values, as functions of the guessing parameter and distances between person parameters and item difficulty, that

  18. Effect of Training Frequency on Maximum Expiratory Pressure

    Science.gov (United States)

    Anand, Supraja; El-Bashiti, Nour; Sapienza, Christine

    2012-01-01

    Purpose: To determine the effects of expiratory muscle strength training (EMST) frequency on maximum expiratory pressure (MEP). Method: We assigned 12 healthy participants to 2 groups of training frequency (3 days per week and 5 days per week). They completed a 4-week training program on an EMST trainer (Aspire Products, LLC). MEP was the primary…

  19. Assessment of the phytoremediation potential of Panicum maximum ...

    African Journals Online (AJOL)

    Obvious signs of phyto-toxicity however appeared in plants exposed to 120 ppm Pb2+ and Cd2+ at day twenty-three, suggesting that P. maximum may be a moderate metal accumulator. Keywords: phytoremediation, heavy metals, uptake, tissues, accumulator. African Journal of Biotechnology, Vol 13(19), 1979-1984 ...

  20. Atlantic Meridional Overturning Circulation During the Last Glacial Maximum.

    NARCIS (Netherlands)

    Lynch-Stieglitz, J.; Adkins, J.F.; Curry, W.B.; Dokken, T.; Hall, I.R.; Herguera, J.C.; Hirschi, J.J.-M.; Ivanova, E.V.; Kissel, C.; Marchal, O.; Marchitto, T.M.; McCave, I.N.; McManus, J.F.; Mulitza, S.; Ninnemann, U.; Peeters, F.J.C.; Yu, E.-F.; Zahn, R.

    2007-01-01

    The circulation of the deep Atlantic Ocean during the height of the last ice age appears to have been quite different from today. We review observations implying that Atlantic meridional overturning circulation during the Last Glacial Maximum was neither extremely sluggish nor an enhanced version of

  1. MPBoot: fast phylogenetic maximum parsimony tree inference and bootstrap approximation.

    Science.gov (United States)

    Hoang, Diep Thi; Vinh, Le Sy; Flouri, Tomáš; Stamatakis, Alexandros; von Haeseler, Arndt; Minh, Bui Quang

    2018-02-02

    The nonparametric bootstrap is widely used to measure the branch support of phylogenetic trees. However, bootstrapping is computationally expensive and remains a bottleneck in phylogenetic analyses. Recently, an ultrafast bootstrap approximation (UFBoot) approach was proposed for maximum likelihood analyses. However, such an approach is still missing for maximum parsimony. To close this gap we present MPBoot, an adaptation and extension of UFBoot to compute branch supports under the maximum parsimony principle. MPBoot works for both uniform and non-uniform cost matrices. Our analyses on biological DNA and protein showed that under uniform cost matrices, MPBoot runs on average 4.7 (DNA) to 7 times (protein data) (range: 1.2-20.7) faster than the standard parsimony bootstrap implemented in PAUP*; but 1.6 (DNA) to 4.1 times (protein data) slower than the standard bootstrap with a fast search routine in TNT (fast-TNT). However, for non-uniform cost matrices MPBoot is 5 (DNA) to 13 times (protein data) (range:0.3-63.9) faster than fast-TNT. We note that MPBoot achieves better scores more frequently than PAUP* and fast-TNT. However, this effect is less pronounced if an intensive but slower search in TNT is invoked. Moreover, experiments on large-scale simulated data show that while both PAUP* and TNT bootstrap estimates are too conservative, MPBoot bootstrap estimates appear more unbiased. MPBoot provides an efficient alternative to the standard maximum parsimony bootstrap procedure. It shows favorable performance in terms of run time, the capability of finding a maximum parsimony tree, and high bootstrap accuracy on simulated as well as empirical data sets. MPBoot is easy-to-use, open-source and available at http://www.cibiv.at/software/mpboot .

  2. Modelling information flow along the human connectome using maximum flow.

    Science.gov (United States)

    Lyoo, Youngwook; Kim, Jieun E; Yoon, Sujung

    2018-01-01

    The human connectome is a complex network that transmits information between interlinked brain regions. Using graph theory, previously well-known network measures of integration between brain regions have been constructed under the key assumption that information flows strictly along the shortest paths possible between two nodes. However, it is now apparent that information does flow through non-shortest paths in many real-world networks such as cellular networks, social networks, and the internet. In the current hypothesis, we present a novel framework using the maximum flow to quantify information flow along all possible paths within the brain, so as to implement an analogy to network traffic. We hypothesize that the connection strengths of brain networks represent a limit on the amount of information that can flow through the connections per unit of time. This allows us to compute the maximum amount of information flow between two brain regions along all possible paths. Using this novel framework of maximum flow, previous network topological measures are expanded to account for information flow through non-shortest paths. The most important advantage of the current approach using maximum flow is that it can integrate the weighted connectivity data in a way that better reflects the real information flow of the brain network. The current framework and its concept regarding maximum flow provides insight on how network structure shapes information flow in contrast to graph theory, and suggests future applications such as investigating structural and functional connectomes at a neuronal level. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Novel TPPO Based Maximum Power Point Method for Photovoltaic System

    Directory of Open Access Journals (Sweden)

    ABBASI, M. A.

    2017-08-01

    Full Text Available Photovoltaic (PV system has a great potential and it is installed more when compared with other renewable energy sources nowadays. However, the PV system cannot perform optimally due to its solid reliance on climate conditions. Due to this dependency, PV system does not operate at its maximum power point (MPP. Many MPP tracking methods have been proposed for this purpose. One of these is the Perturb and Observe Method (P&O which is the most famous due to its simplicity, less cost and fast track. But it deviates from MPP in continuously changing weather conditions, especially in rapidly changing irradiance conditions. A new Maximum Power Point Tracking (MPPT method, Tetra Point Perturb and Observe (TPPO, has been proposed to improve PV system performance in changing irradiance conditions and the effects on characteristic curves of PV array module due to varying irradiance are delineated. The Proposed MPPT method has shown better results in increasing the efficiency of a PV system.

  4. Maximum power point tracker for photovoltaic power plants

    Science.gov (United States)

    Arcidiacono, V.; Corsi, S.; Lambri, L.

    The paper describes two different closed-loop control criteria for the maximum power point tracking of the voltage-current characteristic of a photovoltaic generator. The two criteria are discussed and compared, inter alia, with regard to the setting-up problems that they pose. Although a detailed analysis is not embarked upon, the paper also provides some quantitative information on the energy advantages obtained by using electronic maximum power point tracking systems, as compared with the situation in which the point of operation of the photovoltaic generator is not controlled at all. Lastly, the paper presents two high-efficiency MPPT converters for experimental photovoltaic plants of the stand-alone and the grid-interconnected type.

  5. On the maximum of wave surface of sea waves

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, B

    1980-01-01

    This article considers wave surface as a normal stationary random process to solve the estimation of the maximum of wave surface in a given time interval by means of the theoretical results of probability theory. The results are represented by formulas (13) to (19) in this article. It was proved in this article that when time interval approaches infinite, the formulas (3), (6) of E )eta max) that were derived from the references (Cartwright, Longuet-Higgins) can also be derived by asymptotic distribution of the maximum of wave surface provided by the article. The advantage of the results obtained from this point of view as compared with the results obtained from the references was discussed.

  6. Einstein-Dirac theory in spin maximum I

    International Nuclear Information System (INIS)

    Crumeyrolle, A.

    1975-01-01

    An unitary Einstein-Dirac theory, first in spin maximum 1, is constructed. An original feature of this article is that it is written without any tetrapod technics; basic notions and existence conditions for spinor structures on pseudo-Riemannian fibre bundles are only used. A coupling gravitation-electromagnetic field is pointed out, in the geometric setting of the tangent bundle over space-time. Generalized Maxwell equations for inductive media in presence of gravitational field are obtained. Enlarged Einstein-Schroedinger theory, gives a particular case of this E.D. theory. E. S. theory is a truncated E.D. theory in spin maximum 1. A close relation between torsion-vector and Schroedinger's potential exists and nullity of torsion-vector has a spinor meaning. Finally the Petiau-Duffin-Kemmer theory is incorporated in this geometric setting [fr

  7. GENERALIZATION OF RAYLEIGH MAXIMUM LIKELIHOOD DESPECKLING FILTER USING QUADRILATERAL KERNELS

    Directory of Open Access Journals (Sweden)

    S. Sridevi

    2013-02-01

    Full Text Available Speckle noise is the most prevalent noise in clinical ultrasound images. It visibly looks like light and dark spots and deduce the pixel intensity as murkiest. Gazing at fetal ultrasound images, the impact of edge and local fine details are more palpable for obstetricians and gynecologists to carry out prenatal diagnosis of congenital heart disease. A robust despeckling filter has to be contrived to proficiently suppress speckle noise and simultaneously preserve the features. The proposed filter is the generalization of Rayleigh maximum likelihood filter by the exploitation of statistical tools as tuning parameters and use different shapes of quadrilateral kernels to estimate the noise free pixel from neighborhood. The performance of various filters namely Median, Kuwahura, Frost, Homogenous mask filter and Rayleigh maximum likelihood filter are compared with the proposed filter in terms PSNR and image profile. Comparatively the proposed filters surpass the conventional filters.

  8. Thermoelectric cooler concepts and the limit for maximum cooling

    International Nuclear Information System (INIS)

    Seifert, W; Hinsche, N F; Pluschke, V

    2014-01-01

    The conventional analysis of a Peltier cooler approximates the material properties as independent of temperature using a constant properties model (CPM). Alternative concepts have been published by Bian and Shakouri (2006 Appl. Phys. Lett. 89 212101), Bian (et al 2007 Phys. Rev. B 75 245208) and Snyder et al (2012 Phys. Rev. B 86 045202). While Snyder's Thomson cooler concept results from a consideration of compatibility, the method of Bian et al focuses on the redistribution of heat. Thus, both approaches are based on different principles. In this paper we compare the new concepts to CPM and we reconsider the limit for maximum cooling. The results provide a new perspective on maximum cooling. (paper)

  9. Peyronie's Reconstruction for Maximum Length and Girth Gain: Geometrical Principles

    Directory of Open Access Journals (Sweden)

    Paulo H. Egydio

    2008-01-01

    Full Text Available Peyronie's disease has been associated with penile shortening and some degree of erectile dysfunction. Surgical reconstruction should be based on giving a functional penis, that is, rectifying the penis with rigidity enough to make the sexual intercourse. The procedure should be discussed preoperatively in terms of length and girth reconstruction in order to improve patient satisfaction. The tunical reconstruction for maximum penile length and girth restoration should be based on the maximum length of the dissected neurovascular bundle possible and the application of geometrical principles to define the precise site and size of tunical incision and grafting procedure. As penile rectification and rigidity are required to achieve complete functional restoration of the penis and 20 to 54% of patients experience associated erectile dysfunction, penile straightening alone may not be enough to provide complete functional restoration. Therefore, phosphodiesterase inhibitors, self-injection, or penile prosthesis may need to be added in some cases.

  10. On the maximum Q in feedback controlled subignited plasmas

    International Nuclear Information System (INIS)

    Anderson, D.; Hamnen, H.; Lisak, M.

    1990-01-01

    High Q operation in feedback controlled subignited fusion plasma requires the operating temperature to be close to the ignition temperature. In the present work we discuss technological and physical effects which may restrict this temperature difference. The investigation is based on a simplified, but still accurate, 0=D analytical analysis of the maximum Q of a subignited system. Particular emphasis is given to sawtooth ocsillations which complicate the interpretation of diagnostic neutron emission data into plasma temperatures and may imply an inherent lower bound on the temperature deviation from the ignition point. The estimated maximum Q is found to be marginal (Q = 10-20) from the point of view of a fusion reactor. (authors)

  11. Maximum Likelihood Compton Polarimetry with the Compton Spectrometer and Imager

    Energy Technology Data Exchange (ETDEWEB)

    Lowell, A. W.; Boggs, S. E; Chiu, C. L.; Kierans, C. A.; Sleator, C.; Tomsick, J. A.; Zoglauer, A. C. [Space Sciences Laboratory, University of California, Berkeley (United States); Chang, H.-K.; Tseng, C.-H.; Yang, C.-Y. [Institute of Astronomy, National Tsing Hua University, Taiwan (China); Jean, P.; Ballmoos, P. von [IRAP Toulouse (France); Lin, C.-H. [Institute of Physics, Academia Sinica, Taiwan (China); Amman, M. [Lawrence Berkeley National Laboratory (United States)

    2017-10-20

    Astrophysical polarization measurements in the soft gamma-ray band are becoming more feasible as detectors with high position and energy resolution are deployed. Previous work has shown that the minimum detectable polarization (MDP) of an ideal Compton polarimeter can be improved by ∼21% when an unbinned, maximum likelihood method (MLM) is used instead of the standard approach of fitting a sinusoid to a histogram of azimuthal scattering angles. Here we outline a procedure for implementing this maximum likelihood approach for real, nonideal polarimeters. As an example, we use the recent observation of GRB 160530A with the Compton Spectrometer and Imager. We find that the MDP for this observation is reduced by 20% when the MLM is used instead of the standard method.

  12. Optimal Portfolio Strategy under Rolling Economic Maximum Drawdown Constraints

    Directory of Open Access Journals (Sweden)

    Xiaojian Yu

    2014-01-01

    Full Text Available This paper deals with the problem of optimal portfolio strategy under the constraints of rolling economic maximum drawdown. A more practical strategy is developed by using rolling Sharpe ratio in computing the allocation proportion in contrast to existing models. Besides, another novel strategy named “REDP strategy” is further proposed, which replaces the rolling economic drawdown of the portfolio with the rolling economic drawdown of the risky asset. The simulation tests prove that REDP strategy can ensure the portfolio to satisfy the drawdown constraint and outperforms other strategies significantly. An empirical comparison research on the performances of different strategies is carried out by using the 23-year monthly data of SPTR, DJUBS, and 3-month T-bill. The investment cases of single risky asset and two risky assets are both studied in this paper. Empirical results indicate that the REDP strategy successfully controls the maximum drawdown within the given limit and performs best in both return and risk.

  13. Optimum detection for extracting maximum information from symmetric qubit sets

    International Nuclear Information System (INIS)

    Mizuno, Jun; Fujiwara, Mikio; Sasaki, Masahide; Akiba, Makoto; Kawanishi, Tetsuya; Barnett, Stephen M.

    2002-01-01

    We demonstrate a class of optimum detection strategies for extracting the maximum information from sets of equiprobable real symmetric qubit states of a single photon. These optimum strategies have been predicted by Sasaki et al. [Phys. Rev. A 59, 3325 (1999)]. The peculiar aspect is that the detections with at least three outputs suffice for optimum extraction of information regardless of the number of signal elements. The cases of ternary (or trine), quinary, and septenary polarization signals are studied where a standard von Neumann detection (a projection onto a binary orthogonal basis) fails to access the maximum information. Our experiments demonstrate that it is possible with present technologies to attain about 96% of the theoretical limit

  14. Effect of current on the maximum possible reward.

    Science.gov (United States)

    Gallistel, C R; Leon, M; Waraczynski, M; Hanau, M S

    1991-12-01

    Using a 2-lever choice paradigm with concurrent variable interval schedules of reward, it was found that when pulse frequency is increased, the preference-determining rewarding effect of 0.5-s trains of brief cathodal pulses delivered to the medial forebrain bundle of the rat saturates (stops increasing) at values ranging from 200 to 631 pulses/s (pps). Raising the current lowered the saturation frequency, which confirms earlier, more extensive findings showing that the rewarding effect of short trains saturates at pulse frequencies that vary from less than 100 pps to more than 800 pps, depending on the current. It was also found that the maximum possible reward--the magnitude of the reward at or beyond the saturation pulse frequency--increases with increasing current. Thus, increasing the current reduces the saturation frequency but increases the subjective magnitude of the maximum possible reward.

  15. Jarzynski equality in the context of maximum path entropy

    Science.gov (United States)

    González, Diego; Davis, Sergio

    2017-06-01

    In the global framework of finding an axiomatic derivation of nonequilibrium Statistical Mechanics from fundamental principles, such as the maximum path entropy - also known as Maximum Caliber principle -, this work proposes an alternative derivation of the well-known Jarzynski equality, a nonequilibrium identity of great importance today due to its applications to irreversible processes: biological systems (protein folding), mechanical systems, among others. This equality relates the free energy differences between two equilibrium thermodynamic states with the work performed when going between those states, through an average over a path ensemble. In this work the analysis of Jarzynski's equality will be performed using the formalism of inference over path space. This derivation highlights the wide generality of Jarzynski's original result, which could even be used in non-thermodynamical settings such as social systems, financial and ecological systems.

  16. Maximum mass-particle velocities in Kantor's information mechanics

    International Nuclear Information System (INIS)

    Sverdlik, D.I.

    1989-01-01

    Kantor's information mechanics links phenomena previously regarded as not treatable by a single theory. It is used here to calculate the maximum velocities υ m of single particles. For the electron, υ m /c ∼ 1 - 1.253814 x 10 -77 . The maximum υ m corresponds to υ m /c ∼ 1 -1.097864 x 10 -122 for a single mass particle with a rest mass of 3.078496 x 10 -5 g. This is the fastest that matter can move. Either information mechanics or classical mechanics can be used to show that υ m is less for heavier particles. That υ m is less for lighter particles can be deduced from an information mechanics argument alone

  17. Maximum field capability of energy saver superconducting magnets

    International Nuclear Information System (INIS)

    Turkot, F.; Cooper, W.E.; Hanft, R.; McInturff, A.

    1983-01-01

    At an energy of 1 TeV the superconducting cable in the Energy Saver dipole magnets will be operating at ca. 96% of its nominal short sample limit; the corresponding number in the quadrupole magnets will be 81%. All magnets for the Saver are individually tested for maximum current capability under two modes of operation; some 900 dipoles and 275 quadrupoles have now been measured. The dipole winding is composed of four individually wound coils which in general come from four different reels of cable. As part of the magnet fabrication quality control a short piece of cable from both ends of each reel has its critical current measured at 5T and 4.3K. In this paper the authors describe and present the statistical results of the maximum field tests (including quench and cycle) on Saver dipole and quadrupole magnets and explore the correlation of these tests with cable critical current

  18. Algorithms of maximum likelihood data clustering with applications

    Science.gov (United States)

    Giada, Lorenzo; Marsili, Matteo

    2002-12-01

    We address the problem of data clustering by introducing an unsupervised, parameter-free approach based on maximum likelihood principle. Starting from the observation that data sets belonging to the same cluster share a common information, we construct an expression for the likelihood of any possible cluster structure. The likelihood in turn depends only on the Pearson's coefficient of the data. We discuss clustering algorithms that provide a fast and reliable approximation to maximum likelihood configurations. Compared to standard clustering methods, our approach has the advantages that (i) it is parameter free, (ii) the number of clusters need not be fixed in advance and (iii) the interpretation of the results is transparent. In order to test our approach and compare it with standard clustering algorithms, we analyze two very different data sets: time series of financial market returns and gene expression data. We find that different maximization algorithms produce similar cluster structures whereas the outcome of standard algorithms has a much wider variability.

  19. Optimal Control of Polymer Flooding Based on Maximum Principle

    Directory of Open Access Journals (Sweden)

    Yang Lei

    2012-01-01

    Full Text Available Polymer flooding is one of the most important technologies for enhanced oil recovery (EOR. In this paper, an optimal control model of distributed parameter systems (DPSs for polymer injection strategies is established, which involves the performance index as maximum of the profit, the governing equations as the fluid flow equations of polymer flooding, and the inequality constraint as the polymer concentration limitation. To cope with the optimal control problem (OCP of this DPS, the necessary conditions for optimality are obtained through application of the calculus of variations and Pontryagin’s weak maximum principle. A gradient method is proposed for the computation of optimal injection strategies. The numerical results of an example illustrate the effectiveness of the proposed method.

  20. Maximum heat flux in boiling in a large volume

    International Nuclear Information System (INIS)

    Bergmans, Dzh.

    1976-01-01

    Relationships are derived for the maximum heat flux qsub(max) without basing on the assumptions of both the critical vapor velocity corresponding to the zero growth rate, and planar interface. The Helmholz nonstability analysis of vapor column has been made to this end. The results of this examination have been used to find maximum heat flux for spherical, cylindric and flat plate heaters. The conventional hydrodynamic theory was found to be incapable of producing a satisfactory explanation of qsub(max) for small heaters. The occurrence of qsub(max) in the present case can be explained by inadequate removal of vapor output from the heater (the force of gravity for cylindrical heaters and surface tension for the spherical ones). In case of flat plate heater the qsub(max) value can be explained with the help of the hydrodynamic theory

  1. A Maximum Principle for SDEs of Mean-Field Type

    Energy Technology Data Exchange (ETDEWEB)

    Andersson, Daniel, E-mail: danieand@math.kth.se; Djehiche, Boualem, E-mail: boualem@math.kth.se [Royal Institute of Technology, Department of Mathematics (Sweden)

    2011-06-15

    We study the optimal control of a stochastic differential equation (SDE) of mean-field type, where the coefficients are allowed to depend on some functional of the law as well as the state of the process. Moreover the cost functional is also of mean-field type, which makes the control problem time inconsistent in the sense that the Bellman optimality principle does not hold. Under the assumption of a convex action space a maximum principle of local form is derived, specifying the necessary conditions for optimality. These are also shown to be sufficient under additional assumptions. This maximum principle differs from the classical one, where the adjoint equation is a linear backward SDE, since here the adjoint equation turns out to be a linear mean-field backward SDE. As an illustration, we apply the result to the mean-variance portfolio selection problem.

  2. A Maximum Principle for SDEs of Mean-Field Type

    International Nuclear Information System (INIS)

    Andersson, Daniel; Djehiche, Boualem

    2011-01-01

    We study the optimal control of a stochastic differential equation (SDE) of mean-field type, where the coefficients are allowed to depend on some functional of the law as well as the state of the process. Moreover the cost functional is also of mean-field type, which makes the control problem time inconsistent in the sense that the Bellman optimality principle does not hold. Under the assumption of a convex action space a maximum principle of local form is derived, specifying the necessary conditions for optimality. These are also shown to be sufficient under additional assumptions. This maximum principle differs from the classical one, where the adjoint equation is a linear backward SDE, since here the adjoint equation turns out to be a linear mean-field backward SDE. As an illustration, we apply the result to the mean-variance portfolio selection problem.

  3. Rumor Identification with Maximum Entropy in MicroNet

    Directory of Open Access Journals (Sweden)

    Suisheng Yu

    2017-01-01

    Full Text Available The widely used applications of Microblog, WeChat, and other social networking platforms (that we call MicroNet shorten the period of information dissemination and expand the range of information dissemination, which allows rumors to cause greater harm and have more influence. A hot topic in the information dissemination field is how to identify and block rumors. Based on the maximum entropy model, this paper constructs the recognition mechanism of rumor information in the micronetwork environment. First, based on the information entropy theory, we obtained the characteristics of rumor information using the maximum entropy model. Next, we optimized the original classifier training set and the feature function to divide the information into rumors and nonrumors. Finally, the experimental simulation results show that the rumor identification results using this method are better than the original classifier and other related classification methods.

  4. Maximum Power Point Tracking Based on Sliding Mode Control

    Directory of Open Access Journals (Sweden)

    Nimrod Vázquez

    2015-01-01

    Full Text Available Solar panels, which have become a good choice, are used to generate and supply electricity in commercial and residential applications. This generated power starts with the solar cells, which have a complex relationship between solar irradiation, temperature, and output power. For this reason a tracking of the maximum power point is required. Traditionally, this has been made by considering just current and voltage conditions at the photovoltaic panel; however, temperature also influences the process. In this paper the voltage, current, and temperature in the PV system are considered to be a part of a sliding surface for the proposed maximum power point tracking; this means a sliding mode controller is applied. Obtained results gave a good dynamic response, as a difference from traditional schemes, which are only based on computational algorithms. A traditional algorithm based on MPPT was added in order to assure a low steady state error.

  5. Design and Implementation of Photovoltaic Maximum Power Point Tracking Controller

    Directory of Open Access Journals (Sweden)

    Fawaz S. Abdullah

    2018-03-01

    Full Text Available  The power supplied by any solar array depends upon the environmental conditions as weather conditions (temperature and radiation intensity and the incident angle of the radiant source. The work aims to study the maximum power tracking schemes that used to compare the system performance without and with different types of controllers. The maximum power points of the solar panel under test studied and compared with two controller's types.  The first controller is the proportional- integral - derivative controller type and the second is the perturbation and observation algorithm controller. The associated converter system is a microcontroller based type, whereas the results studied and compared of greatest power point of the Photovoltaic panels under the different two controllers. The experimental tests results compared with simulation results to verify accurate performance.

  6. Maximum credible accident analysis for TR-2 reactor conceptual design

    International Nuclear Information System (INIS)

    Manopulo, E.

    1981-01-01

    A new reactor, TR-2, of 5 MW, designed in cooperation with CEN/GRENOBLE is under construction in the open pool of TR-1 reactor of 1 MW set up by AMF atomics at the Cekmece Nuclear Research and Training Center. In this report the fission product inventory and doses released after the maximum credible accident have been studied. The diffusion of the gaseous fission products to the environment and the potential radiation risks to the population have been evaluated

  7. Maximum Entropy Estimation of Transition Probabilities of Reversible Markov Chains

    Directory of Open Access Journals (Sweden)

    Erik Van der Straeten

    2009-11-01

    Full Text Available In this paper, we develop a general theory for the estimation of the transition probabilities of reversible Markov chains using the maximum entropy principle. A broad range of physical models can be studied within this approach. We use one-dimensional classical spin systems to illustrate the theoretical ideas. The examples studied in this paper are: the Ising model, the Potts model and the Blume-Emery-Griffiths model.

  8. Precise charge density studies by maximum entropy method

    CERN Document Server

    Takata, M

    2003-01-01

    For the production research and development of nanomaterials, their structural information is indispensable. Recently, a sophisticated analytical method, which is based on information theory, the Maximum Entropy Method (MEM) using synchrotron radiation powder data, has been successfully applied to determine precise charge densities of metallofullerenes and nanochannel microporous compounds. The results revealed various endohedral natures of metallofullerenes and one-dimensional array formation of adsorbed gas molecules in nanochannel microporous compounds. The concept of MEM analysis was also described briefly. (author)

  9. PNNL: A Supervised Maximum Entropy Approach to Word Sense Disambiguation

    Energy Technology Data Exchange (ETDEWEB)

    Tratz, Stephen C.; Sanfilippo, Antonio P.; Gregory, Michelle L.; Chappell, Alan R.; Posse, Christian; Whitney, Paul D.

    2007-06-23

    In this paper, we described the PNNL Word Sense Disambiguation system as applied to the English All-Word task in Se-mEval 2007. We use a supervised learning approach, employing a large number of features and using Information Gain for dimension reduction. Our Maximum Entropy approach combined with a rich set of features produced results that are significantly better than baseline and are the highest F-score for the fined-grained English All-Words subtask.

  10. The maximum entropy method of moments and Bayesian probability theory

    Science.gov (United States)

    Bretthorst, G. Larry

    2013-08-01

    The problem of density estimation occurs in many disciplines. For example, in MRI it is often necessary to classify the types of tissues in an image. To perform this classification one must first identify the characteristics of the tissues to be classified. These characteristics might be the intensity of a T1 weighted image and in MRI many other types of characteristic weightings (classifiers) may be generated. In a given tissue type there is no single intensity that characterizes the tissue, rather there is a distribution of intensities. Often this distributions can be characterized by a Gaussian, but just as often it is much more complicated. Either way, estimating the distribution of intensities is an inference problem. In the case of a Gaussian distribution, one must estimate the mean and standard deviation. However, in the Non-Gaussian case the shape of the density function itself must be inferred. Three common techniques for estimating density functions are binned histograms [1, 2], kernel density estimation [3, 4], and the maximum entropy method of moments [5, 6]. In the introduction, the maximum entropy method of moments will be reviewed. Some of its problems and conditions under which it fails will be discussed. Then in later sections, the functional form of the maximum entropy method of moments probability distribution will be incorporated into Bayesian probability theory. It will be shown that Bayesian probability theory solves all of the problems with the maximum entropy method of moments. One gets posterior probabilities for the Lagrange multipliers, and, finally, one can put error bars on the resulting estimated density function.

  11. Bayesian interpretation of Generalized empirical likelihood by maximum entropy

    OpenAIRE

    Rochet , Paul

    2011-01-01

    We study a parametric estimation problem related to moment condition models. As an alternative to the generalized empirical likelihood (GEL) and the generalized method of moments (GMM), a Bayesian approach to the problem can be adopted, extending the MEM procedure to parametric moment conditions. We show in particular that a large number of GEL estimators can be interpreted as a maximum entropy solution. Moreover, we provide a more general field of applications by proving the method to be rob...

  12. The calculation of maximum permissible exposure levels for laser radiation

    International Nuclear Information System (INIS)

    Tozer, B.A.

    1979-01-01

    The maximum permissible exposure data of the revised standard BS 4803 are presented as a set of decision charts which ensure that the user automatically takes into account such details as pulse length and pulse pattern, limiting angular subtense, combinations of multiple wavelength and/or multiple pulse lengths, etc. The two decision charts given are for the calculation of radiation hazards to skin and eye respectively. (author)

  13. The discrete maximum principle for Galerkin solutions of elliptic problems

    Czech Academy of Sciences Publication Activity Database

    Vejchodský, Tomáš

    2012-01-01

    Roč. 10, č. 1 (2012), s. 25-43 ISSN 1895-1074 R&D Projects: GA AV ČR IAA100760702 Institutional research plan: CEZ:AV0Z10190503 Keywords : discrete maximum principle * monotone methods * Galerkin solution Subject RIV: BA - General Mathematics Impact factor: 0.405, year: 2012 http://www.springerlink.com/content/x73624wm23x4wj26

  14. ON A GENERALIZATION OF THE MAXIMUM ENTROPY THEOREM OF BURG

    Directory of Open Access Journals (Sweden)

    JOSÉ MARCANO

    2017-01-01

    Full Text Available In this article we introduce some matrix manipulations that allow us to obtain a version of the original Christoffel-Darboux formula, which is of interest in many applications of linear algebra. Using these developments matrix and Jensen’s inequality, we obtain the main result of this proposal, which is the generalization of the maximum entropy theorem of Burg for multivariate processes.

  15. Determing and monitoring of maximum permissible power for HWRR-3

    International Nuclear Information System (INIS)

    Jia Zhanli; Xiao Shigang; Jin Huajin; Lu Changshen

    1987-01-01

    The operating power of a reactor is an important parameter to be monitored. This report briefly describes the determining and monitoring of maximum permissiable power for HWRR-3. The calculating method is described, and the result of calculation and analysis of error are also given. On-line calculation and real time monitoring have been realized at the heavy water reactor. It provides the reactor with a real time and reliable supervision. This makes operation convenient and increases reliability

  16. Maximum Likelihood, Consistency and Data Envelopment Analysis: A Statistical Foundation

    OpenAIRE

    Rajiv D. Banker

    1993-01-01

    This paper provides a formal statistical basis for the efficiency evaluation techniques of data envelopment analysis (DEA). DEA estimators of the best practice monotone increasing and concave production function are shown to be also maximum likelihood estimators if the deviation of actual output from the efficient output is regarded as a stochastic variable with a monotone decreasing probability density function. While the best practice frontier estimator is biased below the theoretical front...

  17. A maximum modulus theorem for the Oseen problem

    Czech Academy of Sciences Publication Activity Database

    Kračmar, S.; Medková, Dagmar; Nečasová, Šárka; Varnhorn, W.

    2013-01-01

    Roč. 192, č. 6 (2013), s. 1059-1076 ISSN 0373-3114 R&D Projects: GA ČR(CZ) GAP201/11/1304; GA MŠk LC06052 Institutional research plan: CEZ:AV0Z10190503 Keywords : Oseen problem * maximum modulus theorem * Oseen potentials Subject RIV: BA - General Mathematics Impact factor: 0.909, year: 2013 http://link.springer.com/article/10.1007%2Fs10231-012-0258-x

  18. Seeking the epoch of maximum luminosity for dusty quasars

    International Nuclear Information System (INIS)

    Vardanyan, Valeri; Weedman, Daniel; Sargsyan, Lusine

    2014-01-01

    Infrared luminosities νL ν (7.8 μm) arising from dust reradiation are determined for Sloan Digital Sky Survey (SDSS) quasars with 1.4 maximum at any redshift z < 5, reaching a plateau for z ≳ 3 with maximum luminosity νL ν (7.8 μm) ≳ 10 47 erg s –1 ; luminosity functions show one quasar Gpc –3 having νL ν (7.8 μm) > 10 46.6 erg s –1 for all 2 maximum luminosity has not yet been identified at any redshift below 5. The most ultraviolet luminous quasars, defined by rest frame νL ν (0.25 μm), have the largest values of the ratio νL ν (0.25 μm)/νL ν (7.8 μm) with a maximum ratio at z = 2.9. From these results, we conclude that the quasars most luminous in the ultraviolet have the smallest dust content and appear luminous primarily because of lessened extinction. Observed ultraviolet/infrared luminosity ratios are used to define 'obscured' quasars as those having >5 mag of ultraviolet extinction. We present a new summary of obscured quasars discovered with the Spitzer Infrared Spectrograph and determine the infrared luminosity function of these obscured quasars at z ∼ 2.1. This is compared with infrared luminosity functions of optically discovered, unobscured quasars in the SDSS and in the AGN and Galaxy Evolution Survey. The comparison indicates comparable numbers of obscured and unobscured quasars at z ∼ 2.1 with a possible excess of obscured quasars at fainter luminosities.

  19. Industry guidelines for the calibration of maximum anemometers

    Energy Technology Data Exchange (ETDEWEB)

    Bailey, B.H. [AWS Scientific, Inc., Albany, NY (United States)

    1996-12-31

    The purpose of this paper is to report on a framework of guidelines for the calibration of the Maximum Type 40 anemometer. This anemometer model is the wind speed sensor of choice in the majority of wind resource assessment programs in the U.S. These guidelines were established by the Utility Wind Resource Assessment Program. In addition to providing guidelines for anemometers, the appropriate use of non-calibrated anemometers is also discussed. 14 refs., 1 tab.

  20. Max '91: Flare research at the next solar maximum

    Science.gov (United States)

    Dennis, Brian; Canfield, Richard; Bruner, Marilyn; Emslie, Gordon; Hildner, Ernest; Hudson, Hugh; Hurford, Gordon; Lin, Robert; Novick, Robert; Tarbell, Ted

    1988-01-01

    To address the central scientific questions surrounding solar flares, coordinated observations of electromagnetic radiation and energetic particles must be made from spacecraft, balloons, rockets, and ground-based observatories. A program to enhance capabilities in these areas in preparation for the next solar maximum in 1991 is recommended. The major scientific issues are described, and required observations and coordination of observations and analyses are detailed. A program plan and conceptual budgets are provided.

  1. Max '91: flare research at the next solar maximum

    International Nuclear Information System (INIS)

    Dennis, B.; Canfield, R.; Bruner, M.

    1988-01-01

    To address the central scientific questions surrounding solar flares, coordinated observations of electromagnetic radiation and energetic particles must be made from spacecraft, balloons, rockets, and ground-based observatories. A program to enhance capabilities in these areas in preparation for the next solar maximum in 1991 is recommended. The major scientific issues are described, and required observations and coordination of observations and analyses are detailed. A program plan and conceptual budgets are provided

  2. Maximum likelihood convolutional decoding (MCD) performance due to system losses

    Science.gov (United States)

    Webster, L.

    1976-01-01

    A model for predicting the computational performance of a maximum likelihood convolutional decoder (MCD) operating in a noisy carrier reference environment is described. This model is used to develop a subroutine that will be utilized by the Telemetry Analysis Program to compute the MCD bit error rate. When this computational model is averaged over noisy reference phase errors using a high-rate interpolation scheme, the results are found to agree quite favorably with experimental measurements.

  3. Maximum total organic carbon limit for DWPF melter feed

    International Nuclear Information System (INIS)

    Choi, A.S.

    1995-01-01

    DWPF recently decided to control the potential flammability of melter off-gas by limiting the total carbon content in the melter feed and maintaining adequate conditions for combustion in the melter plenum. With this new strategy, all the LFL analyzers and associated interlocks and alarms were removed from both the primary and backup melter off-gas systems. Subsequently, D. Iverson of DWPF- T ampersand E requested that SRTC determine the maximum allowable total organic carbon (TOC) content in the melter feed which can be implemented as part of the Process Requirements for melter feed preparation (PR-S04). The maximum TOC limit thus determined in this study was about 24,000 ppm on an aqueous slurry basis. At the TOC levels below this, the peak concentration of combustible components in the quenched off-gas will not exceed 60 percent of the LFL during off-gas surges of magnitudes up to three times nominal, provided that the melter plenum temperature and the air purge rate to the BUFC are monitored and controlled above 650 degrees C and 220 lb/hr, respectively. Appropriate interlocks should discontinue the feeding when one or both of these conditions are not met. Both the magnitude and duration of an off-gas surge have a major impact on the maximum TOC limit, since they directly affect the melter plenum temperature and combustion. Although the data obtained during recent DWPF melter startup tests showed that the peak magnitude of a surge can be greater than three times nominal, the observed duration was considerably shorter, on the order of several seconds. The long surge duration assumed in this study has a greater impact on the plenum temperature than the peak magnitude, thus making the maximum TOC estimate conservative. Two models were used to make the necessary calculations to determine the TOC limit

  4. The Maximum Entropy Principle and the Modern Portfolio Theory

    Directory of Open Access Journals (Sweden)

    Ailton Cassetari

    2003-12-01

    Full Text Available In this work, a capital allocation methodology base don the Principle of Maximum Entropy was developed. The Shannons entropy is used as a measure, concerning the Modern Portfolio Theory, are also discuted. Particularly, the methodology is tested making a systematic comparison to: 1 the mean-variance (Markovitz approach and 2 the mean VaR approach (capital allocations based on the Value at Risk concept. In principle, such confrontations show the plausibility and effectiveness of the developed method.

  5. Occurrence and Impact of Insects in Maximum Growth Plantations

    Energy Technology Data Exchange (ETDEWEB)

    Nowak, J.T.; Berisford, C.W.

    2001-01-01

    Investigation of the relationships between intensive management practices and insect infestation using maximum growth potential studies of loblolly pine constructed over five years using a hierarchy of cultural treatments-monitoring differences in growth and insect infestation levels related to the increasing management intensities. This study shows that tree fertilization can increase coneworm infestation and demonstrated that tip moth management tree growth, at least initially.

  6. Statistical Bias in Maximum Likelihood Estimators of Item Parameters.

    Science.gov (United States)

    1982-04-01

    34 a> E r’r~e r ,C Ie I# ne,..,.rVi rnd Id.,flfv b1 - bindk numb.r) I; ,t-i i-cd I ’ tiie bias in the maximum likelihood ,st i- i;, ’ t iIeiIrs in...NTC, IL 60088 Psychometric Laboratory University of North Carolina I ERIC Facility-Acquisitions Davie Hall 013A 4833 Rugby Avenue Chapel Hill, NC

  7. Direct maximum parsimony phylogeny reconstruction from genotype data

    Directory of Open Access Journals (Sweden)

    Ravi R

    2007-12-01

    Full Text Available Abstract Background Maximum parsimony phylogenetic tree reconstruction from genetic variation data is a fundamental problem in computational genetics with many practical applications in population genetics, whole genome analysis, and the search for genetic predictors of disease. Efficient methods are available for reconstruction of maximum parsimony trees from haplotype data, but such data are difficult to determine directly for autosomal DNA. Data more commonly is available in the form of genotypes, which consist of conflated combinations of pairs of haplotypes from homologous chromosomes. Currently, there are no general algorithms for the direct reconstruction of maximum parsimony phylogenies from genotype data. Hence phylogenetic applications for autosomal data must therefore rely on other methods for first computationally inferring haplotypes from genotypes. Results In this work, we develop the first practical method for computing maximum parsimony phylogenies directly from genotype data. We show that the standard practice of first inferring haplotypes from genotypes and then reconstructing a phylogeny on the haplotypes often substantially overestimates phylogeny size. As an immediate application, our method can be used to determine the minimum number of mutations required to explain a given set of observed genotypes. Conclusion Phylogeny reconstruction directly from unphased data is computationally feasible for moderate-sized problem instances and can lead to substantially more accurate tree size inferences than the standard practice of treating phasing and phylogeny construction as two separate analysis stages. The difference between the approaches is particularly important for downstream applications that require a lower-bound on the number of mutations that the genetic region has undergone.

  8. Investigation on maximum transition temperature of phonon mediated superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Fusui, L; Yi, S; Yinlong, S [Physics Department, Beijing University (CN)

    1989-05-01

    Three model effective phonon spectra are proposed to get plots of {ital T}{sub {ital c}}-{omega} adn {lambda}-{omega}. It can be concluded that there is no maximum limit of {ital T}{sub {ital c}} in phonon mediated superconductivity for reasonable values of {lambda}. The importance of high frequency LO phonon is also emphasized. Some discussions on high {ital T}{sub {ital c}} are given.

  9. Study of forecasting maximum demand of electric power

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, B.C.; Hwang, Y.J. [Korea Energy Economics Institute, Euiwang (Korea, Republic of)

    1997-08-01

    As far as the past performances of power supply and demand in Korea is concerned, one of the striking phenomena is that there have been repeated periodic surpluses and shortages of power generation facilities. Precise assumption and prediction of power demands is the basic work in establishing a supply plan and carrying out the right policy since facilities investment of the power generation industry requires a tremendous amount of capital and a long construction period. The purpose of this study is to study a model for the inference and prediction of a more precise maximum demand under these backgrounds. The non-parametric model considered in this study, paying attention to meteorological factors such as temperature and humidity, does not have a simple proportionate relationship with the maximum power demand, but affects it through mutual complicated nonlinear interaction. I used the non-parametric inference technique by introducing meteorological effects without importing any literal assumption on the interaction of temperature and humidity preliminarily. According to the analysis result, it is found that the non-parametric model that introduces the number of tropical nights which shows the continuity of the meteorological effect has better prediction power than the linear model. The non- parametric model that considers both the number of tropical nights and the number of cooling days at the same time is a model for predicting maximum demand. 7 refs., 6 figs., 9 tabs.

  10. Maximum Work of Free-Piston Stirling Engine Generators

    Science.gov (United States)

    Kojima, Shinji

    2017-04-01

    Using the method of adjoint equations described in Ref. [1], we have calculated the maximum thermal efficiencies that are theoretically attainable by free-piston Stirling and Carnot engine generators by considering the work loss due to friction and Joule heat. The net work done by the Carnot cycle is negative even when the duration of heat addition is optimized to give the maximum amount of heat addition, which is the same situation for the Brayton cycle described in our previous paper. For the Stirling cycle, the net work done is positive, and the thermal efficiency is greater than that of the Otto cycle described in our previous paper by a factor of about 2.7-1.4 for compression ratios of 5-30. The Stirling cycle is much better than the Otto, Brayton, and Carnot cycles. We have found that the optimized piston trajectories of the isothermal, isobaric, and adiabatic processes are the same when the compression ratio and the maximum volume of the same working fluid of the three processes are the same, which has facilitated the present analysis because the optimized piston trajectories of the Carnot and Stirling cycles are the same as those of the Brayton and Otto cycles, respectively.

  11. Erich Regener and the ionisation maximum of the atmosphere

    Science.gov (United States)

    Carlson, P.; Watson, A. A.

    2014-12-01

    In the 1930s the German physicist Erich Regener (1881-1955) did important work on the measurement of the rate of production of ionisation deep under water and in the atmosphere. Along with one of his students, Georg Pfotzer, he discovered the altitude at which the production of ionisation in the atmosphere reaches a maximum, often, but misleadingly, called the Pfotzer maximum. Regener was one of the first to estimate the energy density of cosmic rays, an estimate that was used by Baade and Zwicky to bolster their postulate that supernovae might be their source. Yet Regener's name is less recognised by present-day cosmic ray physicists than it should be, largely because in 1937 he was forced to take early retirement by the National Socialists as his wife had Jewish ancestors. In this paper we briefly review his work on cosmic rays and recommend an alternative naming of the ionisation maximum. The influence that Regener had on the field through his son, his son-in-law, his grandsons and his students, and through his links with Rutherford's group in Cambridge, is discussed in an appendix. Regener was nominated for the Nobel Prize in Physics by Schrödinger in 1938. He died in 1955 at the age of 73.

  12. Mid-depth temperature maximum in an estuarine lake

    Science.gov (United States)

    Stepanenko, V. M.; Repina, I. A.; Artamonov, A. Yu; Gorin, S. L.; Lykossov, V. N.; Kulyamin, D. V.

    2018-03-01

    The mid-depth temperature maximum (TeM) was measured in an estuarine Bol’shoi Vilyui Lake (Kamchatka peninsula, Russia) in summer 2015. We applied 1D k-ɛ model LAKE to the case, and found it successfully simulating the phenomenon. We argue that the main prerequisite for mid-depth TeM development is a salinity increase below the freshwater mixed layer, sharp enough in order to increase the temperature with depth not to cause convective mixing and double diffusion there. Given that this condition is satisfied, the TeM magnitude is controlled by physical factors which we identified as: radiation absorption below the mixed layer, mixed-layer temperature dynamics, vertical heat conduction and water-sediments heat exchange. In addition to these, we formulate the mechanism of temperature maximum ‘pumping’, resulting from the phase shift between diurnal cycles of mixed-layer depth and temperature maximum magnitude. Based on the LAKE model results we quantify the contribution of the above listed mechanisms and find their individual significance highly sensitive to water turbidity. Relying on physical mechanisms identified we define environmental conditions favouring the summertime TeM development in salinity-stratified lakes as: small-mixed layer depth (roughly, ~wind and cloudless weather. We exemplify the effect of mixed-layer depth on TeM by a set of selected lakes.

  13. An Efficient Algorithm for the Maximum Distance Problem

    Directory of Open Access Journals (Sweden)

    Gabrielle Assunta Grün

    2001-12-01

    Full Text Available Efficient algorithms for temporal reasoning are essential in knowledge-based systems. This is central in many areas of Artificial Intelligence including scheduling, planning, plan recognition, and natural language understanding. As such, scalability is a crucial consideration in temporal reasoning. While reasoning in the interval algebra is NP-complete, reasoning in the less expressive point algebra is tractable. In this paper, we explore an extension to the work of Gerevini and Schubert which is based on the point algebra. In their seminal framework, temporal relations are expressed as a directed acyclic graph partitioned into chains and supported by a metagraph data structure, where time points or events are represented by vertices, and directed edges are labelled with < or ≤. They are interested in fast algorithms for determining the strongest relation between two events. They begin by developing fast algorithms for the case where all points lie on a chain. In this paper, we are interested in a generalization of this, namely we consider the problem of finding the maximum ``distance'' between two vertices in a chain ; this problem arises in real world applications such as in process control and crew scheduling. We describe an O(n time preprocessing algorithm for the maximum distance problem on chains. It allows queries for the maximum number of < edges between two vertices to be answered in O(1 time. This matches the performance of the algorithm of Gerevini and Schubert for determining the strongest relation holding between two vertices in a chain.

  14. Maximum Aerobic Capacity of Underground Coal Miners in India

    Directory of Open Access Journals (Sweden)

    Ratnadeep Saha

    2011-01-01

    Full Text Available Miners fitness test was assessed in terms of determination of maximum aerobic capacity by an indirect method following a standard step test protocol before going down to mine by taking into consideration of heart rates (Telemetric recording and oxygen consumption of the subjects (Oxylog-II during exercise at different working rates. Maximal heart rate was derived as 220−age. Coal miners reported a maximum aerobic capacity within a range of 35–38.3 mL/kg/min. It also revealed that oldest miners (50–59 yrs had a lowest maximal oxygen uptake (34.2±3.38 mL/kg/min compared to (42.4±2.03 mL/kg/min compared to (42.4±2.03 mL/kg/min the youngest group (20–29 yrs. It was found to be negatively correlated with age (r=−0.55 and −0.33 for younger and older groups respectively and directly associated with the body weight of the subjects (r=0.57 – 0.68, P≤0.001. Carriers showed maximum cardio respiratory capacity compared to other miners. Indian miners VO2max was found to be lower both compared to their abroad mining counterparts and various other non-mining occupational working groups in India.

  15. Exact parallel maximum clique algorithm for general and protein graphs.

    Science.gov (United States)

    Depolli, Matjaž; Konc, Janez; Rozman, Kati; Trobec, Roman; Janežič, Dušanka

    2013-09-23

    A new exact parallel maximum clique algorithm MaxCliquePara, which finds the maximum clique (the fully connected subgraph) in undirected general and protein graphs, is presented. First, a new branch and bound algorithm for finding a maximum clique on a single computer core, which builds on ideas presented in two published state of the art sequential algorithms is implemented. The new sequential MaxCliqueSeq algorithm is faster than the reference algorithms on both DIMACS benchmark graphs as well as on protein-derived product graphs used for protein structural comparisons. Next, the MaxCliqueSeq algorithm is parallelized by splitting the branch-and-bound search tree to multiple cores, resulting in MaxCliquePara algorithm. The ability to exploit all cores efficiently makes the new parallel MaxCliquePara algorithm markedly superior to other tested algorithms. On a 12-core computer, the parallelization provides up to 2 orders of magnitude faster execution on the large DIMACS benchmark graphs and up to an order of magnitude faster execution on protein product graphs. The algorithms are freely accessible on http://commsys.ijs.si/~matjaz/maxclique.

  16. Maximum likelihood as a common computational framework in tomotherapy

    International Nuclear Information System (INIS)

    Olivera, G.H.; Shepard, D.M.; Reckwerdt, P.J.; Ruchala, K.; Zachman, J.; Fitchard, E.E.; Mackie, T.R.

    1998-01-01

    Tomotherapy is a dose delivery technique using helical or axial intensity modulated beams. One of the strengths of the tomotherapy concept is that it can incorporate a number of processes into a single piece of equipment. These processes include treatment optimization planning, dose reconstruction and kilovoltage/megavoltage image reconstruction. A common computational technique that could be used for all of these processes would be very appealing. The maximum likelihood estimator, originally developed for emission tomography, can serve as a useful tool in imaging and radiotherapy. We believe that this approach can play an important role in the processes of optimization planning, dose reconstruction and kilovoltage and/or megavoltage image reconstruction. These processes involve computations that require comparable physical methods. They are also based on equivalent assumptions, and they have similar mathematical solutions. As a result, the maximum likelihood approach is able to provide a common framework for all three of these computational problems. We will demonstrate how maximum likelihood methods can be applied to optimization planning, dose reconstruction and megavoltage image reconstruction in tomotherapy. Results for planning optimization, dose reconstruction and megavoltage image reconstruction will be presented. Strengths and weaknesses of the methodology are analysed. Future directions for this work are also suggested. (author)

  17. Maximum-confidence discrimination among symmetric qudit states

    International Nuclear Information System (INIS)

    Jimenez, O.; Solis-Prosser, M. A.; Delgado, A.; Neves, L.

    2011-01-01

    We study the maximum-confidence (MC) measurement strategy for discriminating among nonorthogonal symmetric qudit states. Restricting to linearly dependent and equally likely pure states, we find the optimal positive operator valued measure (POVM) that maximizes our confidence in identifying each state in the set and minimizes the probability of obtaining inconclusive results. The physical realization of this POVM is completely determined and it is shown that after an inconclusive outcome, the input states may be mapped into a new set of equiprobable symmetric states, restricted, however, to a subspace of the original qudit Hilbert space. By applying the MC measurement again onto this new set, we can still gain some information about the input states, although with less confidence than before. This leads us to introduce the concept of sequential maximum-confidence (SMC) measurements, where the optimized MC strategy is iterated in as many stages as allowed by the input set, until no further information can be extracted from an inconclusive result. Within each stage of this measurement our confidence in identifying the input states is the highest possible, although it decreases from one stage to the next. In addition, the more stages we accomplish within the maximum allowed, the higher will be the probability of correct identification. We will discuss an explicit example of the optimal SMC measurement applied in the discrimination among four symmetric qutrit states and propose an optical network to implement it.

  18. Maximum nondiffracting propagation distance of aperture-truncated Airy beams

    Science.gov (United States)

    Chu, Xingchun; Zhao, Shanghong; Fang, Yingwu

    2018-05-01

    Airy beams have called attention of many researchers due to their non-diffracting, self-healing and transverse accelerating properties. A key issue in research of Airy beams and its applications is how to evaluate their nondiffracting propagation distance. In this paper, the critical transverse extent of physically realizable Airy beams is analyzed under the local spatial frequency methodology. The maximum nondiffracting propagation distance of aperture-truncated Airy beams is formulated and analyzed based on their local spatial frequency. The validity of the formula is verified by comparing the maximum nondiffracting propagation distance of an aperture-truncated ideal Airy beam, aperture-truncated exponentially decaying Airy beam and exponentially decaying Airy beam. Results show that the formula can be used to evaluate accurately the maximum nondiffracting propagation distance of an aperture-truncated ideal Airy beam. Therefore, it can guide us to select appropriate parameters to generate Airy beams with long nondiffracting propagation distance that have potential application in the fields of laser weapons or optical communications.

  19. Extending the maximum operation time of the MNSR reactor.

    Science.gov (United States)

    Dawahra, S; Khattab, K; Saba, G

    2016-09-01

    An effective modification to extend the maximum operation time of the Miniature Neutron Source Reactor (MNSR) to enhance the utilization of the reactor has been tested using the MCNP4C code. This modification consisted of inserting manually in each of the reactor inner irradiation tube a chain of three polyethylene-connected containers filled of water. The total height of the chain was 11.5cm. The replacement of the actual cadmium absorber with B(10) absorber was needed as well. The rest of the core structure materials and dimensions remained unchanged. A 3-D neutronic model with the new modifications was developed to compare the neutronic parameters of the old and modified cores. The results of the old and modified core excess reactivities (ρex) were: 3.954, 6.241 mk respectively. The maximum reactor operation times were: 428, 1025min and the safety reactivity factors were: 1.654 and 1.595 respectively. Therefore, a 139% increase in the maximum reactor operation time was noticed for the modified core. This increase enhanced the utilization of the MNSR reactor to conduct a long time irradiation of the unknown samples using the NAA technique and increase the amount of radioisotope production in the reactor. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. PTree: pattern-based, stochastic search for maximum parsimony phylogenies

    Directory of Open Access Journals (Sweden)

    Ivan Gregor

    2013-06-01

    Full Text Available Phylogenetic reconstruction is vital to analyzing the evolutionary relationship of genes within and across populations of different species. Nowadays, with next generation sequencing technologies producing sets comprising thousands of sequences, robust identification of the tree topology, which is optimal according to standard criteria such as maximum parsimony, maximum likelihood or posterior probability, with phylogenetic inference methods is a computationally very demanding task. Here, we describe a stochastic search method for a maximum parsimony tree, implemented in a software package we named PTree. Our method is based on a new pattern-based technique that enables us to infer intermediate sequences efficiently where the incorporation of these sequences in the current tree topology yields a phylogenetic tree with a lower cost. Evaluation across multiple datasets showed that our method is comparable to the algorithms implemented in PAUP* or TNT, which are widely used by the bioinformatics community, in terms of topological accuracy and runtime. We show that our method can process large-scale datasets of 1,000–8,000 sequences. We believe that our novel pattern-based method enriches the current set of tools and methods for phylogenetic tree inference. The software is available under: http://algbio.cs.uni-duesseldorf.de/webapps/wa-download/.

  1. Cases in which ancestral maximum likelihood will be confusingly misleading.

    Science.gov (United States)

    Handelman, Tomer; Chor, Benny

    2017-05-07

    Ancestral maximum likelihood (AML) is a phylogenetic tree reconstruction criteria that "lies between" maximum parsimony (MP) and maximum likelihood (ML). ML has long been known to be statistically consistent. On the other hand, Felsenstein (1978) showed that MP is statistically inconsistent, and even positively misleading: There are cases where the parsimony criteria, applied to data generated according to one tree topology, will be optimized on a different tree topology. The question of weather AML is statistically consistent or not has been open for a long time. Mossel et al. (2009) have shown that AML can "shrink" short tree edges, resulting in a star tree with no internal resolution, which yields a better AML score than the original (resolved) model. This result implies that AML is statistically inconsistent, but not that it is positively misleading, because the star tree is compatible with any other topology. We show that AML is confusingly misleading: For some simple, four taxa (resolved) tree, the ancestral likelihood optimization criteria is maximized on an incorrect (resolved) tree topology, as well as on a star tree (both with specific edge lengths), while the tree with the original, correct topology, has strictly lower ancestral likelihood. Interestingly, the two short edges in the incorrect, resolved tree topology are of length zero, and are not adjacent, so this resolved tree is in fact a simple path. While for MP, the underlying phenomenon can be described as long edge attraction, it turns out that here we have long edge repulsion. Copyright © 2017. Published by Elsevier Ltd.

  2. PTree: pattern-based, stochastic search for maximum parsimony phylogenies.

    Science.gov (United States)

    Gregor, Ivan; Steinbrück, Lars; McHardy, Alice C

    2013-01-01

    Phylogenetic reconstruction is vital to analyzing the evolutionary relationship of genes within and across populations of different species. Nowadays, with next generation sequencing technologies producing sets comprising thousands of sequences, robust identification of the tree topology, which is optimal according to standard criteria such as maximum parsimony, maximum likelihood or posterior probability, with phylogenetic inference methods is a computationally very demanding task. Here, we describe a stochastic search method for a maximum parsimony tree, implemented in a software package we named PTree. Our method is based on a new pattern-based technique that enables us to infer intermediate sequences efficiently where the incorporation of these sequences in the current tree topology yields a phylogenetic tree with a lower cost. Evaluation across multiple datasets showed that our method is comparable to the algorithms implemented in PAUP* or TNT, which are widely used by the bioinformatics community, in terms of topological accuracy and runtime. We show that our method can process large-scale datasets of 1,000-8,000 sequences. We believe that our novel pattern-based method enriches the current set of tools and methods for phylogenetic tree inference. The software is available under: http://algbio.cs.uni-duesseldorf.de/webapps/wa-download/.

  3. MAXIMUM POWEWR POINT TRACKING SYSTEM FOR PHOTOVOLTAIC STATION: A REVIEW

    Directory of Open Access Journals (Sweden)

    I. Elzein

    2015-01-01

    Full Text Available In recent years there has been a growing attention towards the use of renewable energy sources. Among them solar energy is one of the most promising green energy resources due to its environment sustainability and inexhaustibility. However photovoltaic systems (PhV suffer from big cost of equipment and low efficiency. Moreover, the solar cell V-I characteristic is nonlinear and varies with irradiation and temperature. In general, there is a unique point of PhV operation, called the Maximum Power Point (MPP, in which the PV system operates with maximum efficiency and produces its maximum output power. The location of the MPP is not known in advance, but can be located, either through calculation models or by search algorithms. Therefore MPPT techniques are important to maintain the PV array’s high efficiency. Many different techniques for MPPT are discussed. This review paper hopefully will serve as a convenient tool for future work in PhV power conversion.

  4. Maximum Entropy and Theory Construction: A Reply to Favretti

    Directory of Open Access Journals (Sweden)

    John Harte

    2018-04-01

    Full Text Available In the maximum entropy theory of ecology (METE, the form of a function describing the distribution of abundances over species and metabolic rates over individuals in an ecosystem is inferred using the maximum entropy inference procedure. Favretti shows that an alternative maximum entropy model exists that assumes the same prior knowledge and makes predictions that differ from METE’s. He shows that both cannot be correct and asserts that his is the correct one because it can be derived from a classic microstate-counting calculation. I clarify here exactly what the core entities and definitions are for METE, and discuss the relevance of two critical issues raised by Favretti: the existence of a counting procedure for microstates and the choices of definition of the core elements of a theory. I emphasize that a theorist controls how the core entities of his or her theory are defined, and that nature is the final arbiter of the validity of a theory.

  5. Maximum entropy reconstructions for crystallographic imaging; Cristallographie et reconstruction d`images par maximum d`entropie

    Energy Technology Data Exchange (ETDEWEB)

    Papoular, R

    1997-07-01

    The Fourier Transform is of central importance to Crystallography since it allows the visualization in real space of tridimensional scattering densities pertaining to physical systems from diffraction data (powder or single-crystal diffraction, using x-rays, neutrons, electrons or else). In turn, this visualization makes it possible to model and parametrize these systems, the crystal structures of which are eventually refined by Least-Squares techniques (e.g., the Rietveld method in the case of Powder Diffraction). The Maximum Entropy Method (sometimes called MEM or MaxEnt) is a general imaging technique, related to solving ill-conditioned inverse problems. It is ideally suited for tackling undetermined systems of linear questions (for which the number of variables is much larger than the number of equations). It is already being applied successfully in Astronomy, Radioastronomy and Medical Imaging. The advantages of using MAXIMUM Entropy over conventional Fourier and `difference Fourier` syntheses stem from the following facts: MaxEnt takes the experimental error bars into account; MaxEnt incorporate Prior Knowledge (e.g., the positivity of the scattering density in some instances); MaxEnt allows density reconstructions from incompletely phased data, as well as from overlapping Bragg reflections; MaxEnt substantially reduces truncation errors to which conventional experimental Fourier reconstructions are usually prone. The principles of Maximum Entropy imaging as applied to Crystallography are first presented. The method is then illustrated by a detailed example specific to Neutron Diffraction: the search for proton in solids. (author). 17 refs.

  6. Solution-processed n-ZnO nanorod/p-Co{sub 3}O{sub 4} nanoplate heterojunction light-emitting diode

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jong-Woo; Lee, Su Jeong; Biswas, Pranab [Department of Materials Science and Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722 (Korea, Republic of); Lee, Tae Il [Department of BioNano Technology, Gachon University, 1342 Seongnam Daero, Seongnam 13120 (Korea, Republic of); Myoung, Jae-Min, E-mail: jmmyoung@yonsei.ac.kr [Department of Materials Science and Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722 (Korea, Republic of)

    2017-06-01

    Highlights: • The n-ZnO nanorods were epitaxially grown on p-Co{sub 3}O{sub 4} nanoplates. • The heteroepitaxial p-n junction was fabricated by using hydrothermal process. • The LEDs emitted reddish-orange and violet light related to ZnO point defects. • The Co{sub 3}O{sub 4} nanoplates function as a hole injection layer. • Junction between 1D NRs and 2D NPs provides a new approach to design nanostructures. - Abstract: A heterojunction light-emitting diode (LED) based on p-type cobalt oxide (Co{sub 3}O{sub 4}) nanoplates (NPs)/n-type zinc oxide (ZnO) nanorods (NRs) is demonstrated. Using a low-temperature aqueous solution process, the n-type ZnO NRs were epitaxially grown on Co{sub 3}O{sub 4} NPs which were two-dimensionally assembled by a modified Langmuir-Blodgett process. The heterojunction LEDs exhibited a typical rectifying behavior with a turn-on voltage of about 2 V and emitted not only reddish-orange light at 610 nm but also violet light at about 400 nm. From the comparative analyses of electroluminescence and photoluminescence, it was determined that the reddish-orange light emission was related to the electronic transitions from zinc interstitials (Zn{sub i}) to oxygen interstitials (O{sub i}) or conduction-band minimum (CBM) to oxygen vacancies (V{sub O}), and the violet light emission was attribute to the transition from CBM to valence-band maximum (VBM) or Zn{sub i} to zinc vacancies (V{sub Zn}).

  7. Holistic electronic response underlying the development of magnetism in co-doped diluted magnetic semiconductors

    Science.gov (United States)

    Andriotis, Antonis N.; Menon, Madhu

    2018-05-01

    A systematic analysis of the properties of codoped diluted magnetic semiconductors (DMSs) reveals the role and the effect of the codopants in dictating the magnetic features of the DMSs. Our results indicate that the magnetic features of a codoped DMS is the outcome of synergistic electronic processes of the whole system rather than a local hybridization process isolated from the rest of the system. Specifically, the d-orbital hybridization of the (co)dopants and the introduction of their impurity bands lead to the readjustment of the position of the p-band center of the host’s anions and that of the valence band maximum (VBM). The overall effect of these is to pull the hybridized d-bands of the (co)dopants relative to the Fermi energy, E F , which in turn dictate the value of the magnetic moment of both the dopant as well as the codopant. More precisely, the magnetic moment of a dopant shows an almost linearly increasing (decreasing) variation as the dopant’s d-band center (the latter dictated by the codopant) moves away from (gets closer to) E F . Our results thus suggest a completely new approach in the investigation and understanding of the origin of the defect induced magnetism and support previous reports suggesting the Fermi-energy engineering as a mean for developing high T C DMSs. These trends are demonstrated with results obtained for GaN, GaP, and CdS doped with one of the V, Mn, Co and Cu dopants and codoped with the transition metals of the 3d-series.

  8. Effect of dynamic surface polarization on the oxidative stability of solvents in nonaqueous Li-O 2 batteries

    Science.gov (United States)

    Khetan, Abhishek; Pitsch, Heinz; Viswanathan, Venkatasubramanian

    2017-09-01

    Polarization-induced renormalization of the frontier energy levels of interacting molecules and surfaces can cause significant shifts in the excitation and transport behavior of electrons. This phenomenon is crucial in determining the oxidative stability of nonaqueous electrolytes in high-energy density electrochemical systems such as the Li-O2 battery. On the basis of partially self-consistent first-principles Sc G W0 calculations, we systematically study how the electronic energy levels of four commonly used solvent molecules, namely, dimethylsulfoxide (DMSO), dimethoxyethane (DME), tetrahydrofuran (THF), and acetonitrile (ACN), renormalize when physisorbed on the different stable surfaces of Li2O2 , the main discharge product. Using band level alignment arguments, we propose that the difference between the solvent's highest occupied molecular orbital (HOMO) level and the surface's valence-band maximum (VBM) is a refined metric of oxidative stability. This metric and a previously used descriptor, solvent's gas phase HOMO level, agree quite well for physisorbed cases on pristine surfaces where ACN is oxidatively most stable followed by DME, THF, and DMSO. However, this effect is intrinsically linked to the surface chemistry of the solvent's interaction with the surface states and defects, and depends strongly on their nature. We conclusively show that the propensity of solvent molecules to oxidize will be significantly higher on Li2O2 surfaces with defects as compared to pristine surfaces. This suggests that the oxidative stability of a solvent is dynamic and is a strong function of surface electronic properties. Thus, while gas phase HOMO levels could be used for preliminary solvent candidate screening, a more refined picture of solvent stability requires mapping out the solvent stability as a function of the state of the surface under operating conditions.

  9. Energetic, structural and electronic properties of metal vacancies in strained AlN/GaN interfaces.

    Science.gov (United States)

    Kioseoglou, J; Pontikis, V; Komninou, Ph; Pavloudis, Th; Chen, J; Karakostas, Th

    2015-04-01

    AlN/GaN heterostructures have been studied using density-functional pseudopotential calculations yielding the formation energies of metal vacancies under the influence of local interfacial strains, the associated charge distribution and the energies of vacancy-induced electronic states. Interfaces are built normal to the polar direction of the wurtzite structure by joining two single crystals of AlN and GaN that are a few atomic layers thick; thus, periodic boundary conditions generate two distinct heterophase interfaces. We show that the formation energy of vacancies is a function of their distance from the interfaces: the vacancy-interface interaction is found repulsive or attractive, depending on the type of the interface. When the interaction is attractive, the vacancy formation energy decreases with increasing the associated electric charge, and hence the equilibrium vacancy concentration at the interface is greater. This finding can reveal the well-known morphological differences existing between the two types of investigated interfaces. Moreover, we found that the electric charge is strongly localized around the Ga vacancy, while in the case of Al vacancies is almost uniformly distributed throughout the AlN/GaN heterostructure. Crucially, for the applications of heterostructures, metal vacancies introduce deep states in the calculated bandgap at energy levels from 0.5 to 1 eV above the valence band maximum (VBM). It is, therefore, predicted that vacancies could initiate 'green luminescence' i.e. light emission in the energy range of 2.5 eV stemming from electronic transitions between these extra levels, and the conduction band, or energy levels, due to shallow donors.

  10. Solution-processed n-ZnO nanorod/p-Co_3O_4 nanoplate heterojunction light-emitting diode

    International Nuclear Information System (INIS)

    Kim, Jong-Woo; Lee, Su Jeong; Biswas, Pranab; Lee, Tae Il; Myoung, Jae-Min

    2017-01-01

    Highlights: • The n-ZnO nanorods were epitaxially grown on p-Co_3O_4 nanoplates. • The heteroepitaxial p-n junction was fabricated by using hydrothermal process. • The LEDs emitted reddish-orange and violet light related to ZnO point defects. • The Co_3O_4 nanoplates function as a hole injection layer. • Junction between 1D NRs and 2D NPs provides a new approach to design nanostructures. - Abstract: A heterojunction light-emitting diode (LED) based on p-type cobalt oxide (Co_3O_4) nanoplates (NPs)/n-type zinc oxide (ZnO) nanorods (NRs) is demonstrated. Using a low-temperature aqueous solution process, the n-type ZnO NRs were epitaxially grown on Co_3O_4 NPs which were two-dimensionally assembled by a modified Langmuir-Blodgett process. The heterojunction LEDs exhibited a typical rectifying behavior with a turn-on voltage of about 2 V and emitted not only reddish-orange light at 610 nm but also violet light at about 400 nm. From the comparative analyses of electroluminescence and photoluminescence, it was determined that the reddish-orange light emission was related to the electronic transitions from zinc interstitials (Zn_i) to oxygen interstitials (O_i) or conduction-band minimum (CBM) to oxygen vacancies (V_O), and the violet light emission was attribute to the transition from CBM to valence-band maximum (VBM) or Zn_i to zinc vacancies (V_Z_n).

  11. Electronic structure of the amorphous oxide semiconductor a-InGaZnO4-x: Tauc-Lorentz optical model and origins of subgap states

    International Nuclear Information System (INIS)

    Kamiya, Toshio; Nomura, Kenji; Hosono, Hideo

    2009-01-01

    This paper discusses an optical model and subgap electronic states for a representative amorphous oxide semiconductor, InGaZnO 4 (a-IGZO). Parameterized optical models were developed based on the Tauc-Lorentz model combined with a Lorentz-type oscillator. The measured optical absorption spectra exhibit nearly linear dependences on photon energy (E) between 3 eV 0,TL ) being around 4 eV. The optimized parameters for the fixed E 0,TL of 3.7 eV are provided for four different a-IGZO films with root-mean-square errors less than 1%. Formation energies of crystalline IGZO, stoichiometric a-IGZO, oxygen deficient a-IGZO and their constituent oxides were calculated by the density functional theory using the local density approximation (LDA) and generalized gradient approximation with PBE96 functionals (PBE). PBE gives larger unit cell volumes at the ground states and better agreement in the formation energies than LDA does. The formation energies of an oxygen deficiency in a-IGZO were calculated to be 3.2-3.5 eV. The calculated electronic structures of stoichiometric a-IGZO models exhibit somewhat large dispersions for conduction bands (CB), which are not largely affected by the disordered structure in a-IGZO, while the dispersions of the valence bands (VBs) are very small, unlike the crystalline IGZO, showing that a-IGZO have strongly localized states at the VB maximums (VBMs). Oxygen-deficient a-IGZO models showed that oxygen deficiencies form both a deep localized state at 0.4-1 eV above VBM and a shallow donor state depending on local atomic configurations. An oxygen deficiency that forms a deep state breaks the dispersion of the CB, which could be an origin of the subgap states observed near CB. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Interfacial electronic structures revealed at the rubrene/CH3NH3PbI3 interface.

    Science.gov (United States)

    Ji, Gengwu; Zheng, Guanhaojie; Zhao, Bin; Song, Fei; Zhang, Xiaonan; Shen, Kongchao; Yang, Yingguo; Xiong, Yimin; Gao, Xingyu; Cao, Liang; Qi, Dong-Chen

    2017-03-01

    The electronic structures of rubrene films deposited on CH 3 NH 3 PbI 3 perovskite have been investigated using in situ ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS). It was found that rubrene molecules interacted weakly with the perovskite substrate. Due to charge redistribution at their interface, a downward 'band bending'-like energy shift of ∼0.3 eV and an upward band bending of ∼0.1 eV were identified at the upper rubrene side and the CH 3 NH 3 PbI 3 substrate side, respectively. After the energy level alignment was established at the rubrene/CH 3 NH 3 PbI 3 interface, its highest occupied molecular orbital (HOMO)-valence band maximum (VBM) offset was found to be as low as ∼0.1 eV favoring the hole extraction with its lowest unoccupied molecular orbital (LUMO)-conduction band minimum (CBM) offset as large as ∼1.4 eV effectively blocking the undesired electron transfer from perovskite to rubrene. As a demonstration, simple inverted planar solar cell devices incorporating rubrene and rubrene/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole transport layers (HTLs) were fabricated in this work and yielded a champion power conversion efficiency of 8.76% and 13.52%, respectively. Thus, the present work suggests that a rubrene thin film could serve as a promising hole transport layer for efficient perovskite-based solar cells.

  13. Maximum entropy reconstruction of spin densities involving non uniform prior

    International Nuclear Information System (INIS)

    Schweizer, J.; Ressouche, E.; Papoular, R.J.; Zheludev, A.I.

    1997-01-01

    Diffraction experiments give microscopic information on structures in crystals. A method which uses the concept of maximum of entropy (MaxEnt), appears to be a formidable improvement in the treatment of diffraction data. This method is based on a bayesian approach: among all the maps compatible with the experimental data, it selects that one which has the highest prior (intrinsic) probability. Considering that all the points of the map are equally probable, this probability (flat prior) is expressed via the Boltzman entropy of the distribution. This method has been used for the reconstruction of charge densities from X-ray data, for maps of nuclear densities from unpolarized neutron data as well as for distributions of spin density. The density maps obtained by this method, as compared to those resulting from the usual inverse Fourier transformation, are tremendously improved. In particular, any substantial deviation from the background is really contained in the data, as it costs entropy compared to a map that would ignore such features. However, in most of the cases, before the measurements are performed, some knowledge exists about the distribution which is investigated. It can range from the simple information of the type of scattering electrons to an elaborate theoretical model. In these cases, the uniform prior which considers all the different pixels as equally likely, is too weak a requirement and has to be replaced. In a rigorous bayesian analysis, Skilling has shown that prior knowledge can be encoded into the Maximum Entropy formalism through a model m(rvec r), via a new definition for the entropy given in this paper. In the absence of any data, the maximum of the entropy functional is reached for ρ(rvec r) = m(rvec r). Any substantial departure from the model, observed in the final map, is really contained in the data as, with the new definition, it costs entropy. This paper presents illustrations of model testing

  14. Maximum margin semi-supervised learning with irrelevant data.

    Science.gov (United States)

    Yang, Haiqin; Huang, Kaizhu; King, Irwin; Lyu, Michael R

    2015-10-01

    Semi-supervised learning (SSL) is a typical learning paradigms training a model from both labeled and unlabeled data. The traditional SSL models usually assume unlabeled data are relevant to the labeled data, i.e., following the same distributions of the targeted labeled data. In this paper, we address a different, yet formidable scenario in semi-supervised classification, where the unlabeled data may contain irrelevant data to the labeled data. To tackle this problem, we develop a maximum margin model, named tri-class support vector machine (3C-SVM), to utilize the available training data, while seeking a hyperplane for separating the targeted data well. Our 3C-SVM exhibits several characteristics and advantages. First, it does not need any prior knowledge and explicit assumption on the data relatedness. On the contrary, it can relieve the effect of irrelevant unlabeled data based on the logistic principle and maximum entropy principle. That is, 3C-SVM approaches an ideal classifier. This classifier relies heavily on labeled data and is confident on the relevant data lying far away from the decision hyperplane, while maximally ignoring the irrelevant data, which are hardly distinguished. Second, theoretical analysis is provided to prove that in what condition, the irrelevant data can help to seek the hyperplane. Third, 3C-SVM is a generalized model that unifies several popular maximum margin models, including standard SVMs, Semi-supervised SVMs (S(3)VMs), and SVMs learned from the universum (U-SVMs) as its special cases. More importantly, we deploy a concave-convex produce to solve the proposed 3C-SVM, transforming the original mixed integer programming, to a semi-definite programming relaxation, and finally to a sequence of quadratic programming subproblems, which yields the same worst case time complexity as that of S(3)VMs. Finally, we demonstrate the effectiveness and efficiency of our proposed 3C-SVM through systematical experimental comparisons. Copyright

  15. Catastrophic Disruption Threshold and Maximum Deflection from Kinetic Impact

    Science.gov (United States)

    Cheng, A. F.

    2017-12-01

    The use of a kinetic impactor to deflect an asteroid on a collision course with Earth was described in the NASA Near-Earth Object Survey and Deflection Analysis of Alternatives (2007) as the most mature approach for asteroid deflection and mitigation. The NASA DART mission will demonstrate asteroid deflection by kinetic impact at the Potentially Hazardous Asteroid 65803 Didymos in October, 2022. The kinetic impactor approach is considered to be applicable with warning times of 10 years or more and with hazardous asteroid diameters of 400 m or less. In principle, a larger kinetic impactor bringing greater kinetic energy could cause a larger deflection, but input of excessive kinetic energy will cause catastrophic disruption of the target, leaving possibly large fragments still on collision course with Earth. Thus the catastrophic disruption threshold limits the maximum deflection from a kinetic impactor. An often-cited rule of thumb states that the maximum deflection is 0.1 times the escape velocity before the target will be disrupted. It turns out this rule of thumb does not work well. A comparison to numerical simulation results shows that a similar rule applies in the gravity limit, for large targets more than 300 m, where the maximum deflection is roughly the escape velocity at momentum enhancement factor β=2. In the gravity limit, the rule of thumb corresponds to pure momentum coupling (μ=1/3), but simulations find a slightly different scaling μ=0.43. In the smaller target size range that kinetic impactors would apply to, the catastrophic disruption limit is strength-controlled. A DART-like impactor won't disrupt any target asteroid down to significantly smaller size than the 50 m below which a hazardous object would not penetrate the atmosphere in any case unless it is unusually strong.

  16. Interface termination and band alignment of epitaxially grown alumina films on Cu-Al alloy

    Science.gov (United States)

    Yoshitake, Michiko; Song, Weijie; Libra, Jiří; Mašek, Karel; Šutara, František; Matolín, Vladimír; Prince, Kevin C.

    2008-02-01

    Epitaxial ultrathin alumina films were grown on a Cu-9 at. % Al(111) substrate by selective oxidation of Al in the alloy in ultrahigh vacuum. The photoelectron spectra of Al 2p and valence band were measured in situ during oxidation. By analyzing multiple peaks of Al 2p, the interface atomic structure was discussed. The energy difference between the Fermi level of the substrate and the valence band maximum of alumina (band offset) was obtained. The relation between the interface atomic structure and the band offset was compared with the reported first-principles calculations. A novel method for controlling the band offset was proposed.

  17. Maximum-likelihood method for numerical inversion of Mellin transform

    International Nuclear Information System (INIS)

    Iqbal, M.

    1997-01-01

    A method is described for inverting the Mellin transform which uses an expansion in Laguerre polynomials and converts the Mellin transform to Laplace transform, then the maximum-likelihood regularization method is used to recover the original function of the Mellin transform. The performance of the method is illustrated by the inversion of the test functions available in the literature (J. Inst. Math. Appl., 20 (1977) 73; Math. Comput., 53 (1989) 589). Effectiveness of the method is shown by results obtained through demonstration by means of tables and diagrams

  18. Observations of Halley's Comet by the Solar Maximum Mission (SMM)

    Science.gov (United States)

    Niedner, M. B.

    1986-01-01

    Solar Maximum Mission coronagraph/polarimeter observations of large scale phenomena in Halley's Comet are discussed. Observations of the hydrogen coma with the UV spectrometer are considered. It is concluded that coronograph/polarimeter observations of the disconnection event, in which the entire plasma tail uproots itself from the head of the comet, is convected away in the solar wind at speeds in the 50 to 100 km/sec range (relative to the head), and is replaced by a plasma tail constructed from folding ion-tail rays, are the most interesting.

  19. Maximum entropy principle and hydrodynamic models in statistical mechanics

    International Nuclear Information System (INIS)

    Trovato, M.; Reggiani, L.

    2012-01-01

    This review presents the state of the art of the maximum entropy principle (MEP) in its classical and quantum (QMEP) formulation. Within the classical MEP we overview a general theory able to provide, in a dynamical context, the macroscopic relevant variables for carrier transport in the presence of electric fields of arbitrary strength. For the macroscopic variables the linearized maximum entropy approach is developed including full-band effects within a total energy scheme. Under spatially homogeneous conditions, we construct a closed set of hydrodynamic equations for the small-signal (dynamic) response of the macroscopic variables. The coupling between the driving field and the energy dissipation is analyzed quantitatively by using an arbitrary number of moments of the distribution function. Analogously, the theoretical approach is applied to many one-dimensional n + nn + submicron Si structures by using different band structure models, different doping profiles, different applied biases and is validated by comparing numerical calculations with ensemble Monte Carlo simulations and with available experimental data. Within the quantum MEP we introduce a quantum entropy functional of the reduced density matrix, the principle of quantum maximum entropy is then asserted as fundamental principle of quantum statistical mechanics. Accordingly, we have developed a comprehensive theoretical formalism to construct rigorously a closed quantum hydrodynamic transport within a Wigner function approach. The theory is formulated both in thermodynamic equilibrium and nonequilibrium conditions, and the quantum contributions are obtained by only assuming that the Lagrange multipliers can be expanded in powers of ħ 2 , being ħ the reduced Planck constant. In particular, by using an arbitrary number of moments, we prove that: i) on a macroscopic scale all nonlocal effects, compatible with the uncertainty principle, are imputable to high-order spatial derivatives both of the

  20. Twenty-five years of maximum-entropy principle

    Science.gov (United States)

    Kapur, J. N.

    1983-04-01

    The strengths and weaknesses of the maximum entropy principle (MEP) are examined and some challenging problems that remain outstanding at the end of the first quarter century of the principle are discussed. The original formalism of the MEP is presented and its relationship to statistical mechanics is set forth. The use of MEP for characterizing statistical distributions, in statistical inference, nonlinear spectral analysis, transportation models, population density models, models for brand-switching in marketing and vote-switching in elections is discussed. Its application to finance, insurance, image reconstruction, pattern recognition, operations research and engineering, biology and medicine, and nonparametric density estimation is considered.

  1. Gentile statistics with a large maximum occupation number

    International Nuclear Information System (INIS)

    Dai Wusheng; Xie Mi

    2004-01-01

    In Gentile statistics the maximum occupation number can take on unrestricted integers: 1 1 the Bose-Einstein case is not recovered from Gentile statistics as n goes to N. Attention is also concentrated on the contribution of the ground state which was ignored in related literature. The thermodynamic behavior of a ν-dimensional Gentile ideal gas of particle of dispersion E=p s /2m, where ν and s are arbitrary, is analyzed in detail. Moreover, we provide an alternative derivation of the partition function for Gentile statistics

  2. Solar maximum mission panel jettison analysis remote manipulator system

    Science.gov (United States)

    Bauer, R. B.

    1980-01-01

    A study is presented of the development of the Remote Manipulator System (RMS) configurations for jettison of the solar panels on the Solar Maximum Mission/Multimission Satellite. A valid RMS maneuver between jettison configurations was developed. Arm and longeron loads and effector excursions due to the solar panel jettison were determined to see if they were within acceptable limits. These loads and end effector excursions were analyzed under two RMS modes, servos active in position hold submode, and in the brakes on mode.

  3. Penalized Maximum Likelihood Estimation for univariate normal mixture distributions

    International Nuclear Information System (INIS)

    Ridolfi, A.; Idier, J.

    2001-01-01

    Due to singularities of the likelihood function, the maximum likelihood approach for the estimation of the parameters of normal mixture models is an acknowledged ill posed optimization problem. Ill posedness is solved by penalizing the likelihood function. In the Bayesian framework, it amounts to incorporating an inverted gamma prior in the likelihood function. A penalized version of the EM algorithm is derived, which is still explicit and which intrinsically assures that the estimates are not singular. Numerical evidence of the latter property is put forward with a test

  4. Maximum Likelihood and Bayes Estimation in Randomly Censored Geometric Distribution

    Directory of Open Access Journals (Sweden)

    Hare Krishna

    2017-01-01

    Full Text Available In this article, we study the geometric distribution under randomly censored data. Maximum likelihood estimators and confidence intervals based on Fisher information matrix are derived for the unknown parameters with randomly censored data. Bayes estimators are also developed using beta priors under generalized entropy and LINEX loss functions. Also, Bayesian credible and highest posterior density (HPD credible intervals are obtained for the parameters. Expected time on test and reliability characteristics are also analyzed in this article. To compare various estimates developed in the article, a Monte Carlo simulation study is carried out. Finally, for illustration purpose, a randomly censored real data set is discussed.

  5. Maximum discharge rate of liquid-vapor mixtures from vessels

    International Nuclear Information System (INIS)

    Moody, F.J.

    1975-09-01

    A discrepancy exists in theoretical predictions of the two-phase equilibrium discharge rate from pipes attached to vessels. Theory which predicts critical flow data in terms of pipe exit pressure and quality severely overpredicts flow rates in terms of vessel fluid properties. This study shows that the discrepancy is explained by the flow pattern. Due to decompression and flashing as fluid accelerates into the pipe entrance, the maximum discharge rate from a vessel is limited by choking of a homogeneous bubbly mixture. The mixture tends toward a slip flow pattern as it travels through the pipe, finally reaching a different choked condition at the pipe exit

  6. Maximum entropy technique in the doublet structure analysis

    International Nuclear Information System (INIS)

    Belashev, B.Z.; Panebrattsev, Yu.A.; Shakhaliev, Eh.I.; Soroko, L.M.

    1998-01-01

    The Maximum Entropy Technique (MENT) for solution of the inverse problems is explained. The effective computer program for resolution of the nonlinear equations system encountered in the MENT has been developed and tested. The possibilities of the MENT have been demonstrated on the example of the MENT in the doublet structure analysis of noisy experimental data. The comparison of the MENT results with results of the Fourier algorithm technique without regularization is presented. The tolerant noise level is equal to 30% for MENT and only 0.1% for the Fourier algorithm

  7. Distributed maximum power point tracking in wind micro-grids

    Directory of Open Access Journals (Sweden)

    Carlos Andrés Ramos-Paja

    2012-06-01

    Full Text Available With the aim of reducing the hardware requirements in micro-grids based on wind generators, a distributed maximum power point tracking algorithm is proposed. Such a solution reduces the amount of current sensors and processing devices to maximize the power extracted from the micro-grid, reducing the application cost. The analysis of the optimal operating points of the wind generator was performed experimentally, which in addition provides realistic model parameters. Finally, the proposed solution was validated by means of detailed simulations performed in the power electronics software PSIM, contrasting the achieved performance with traditional solutions.

  8. Rectangular maximum-volume submatrices and their applications

    KAUST Repository

    Mikhalev, Aleksandr; Oseledets, I.V.

    2017-01-01

    We introduce a definition of the volume of a general rectangular matrix, which is equivalent to an absolute value of the determinant for square matrices. We generalize results of square maximum-volume submatrices to the rectangular case, show a connection of the rectangular volume with an optimal experimental design and provide estimates for a growth of coefficients and an approximation error in spectral and Chebyshev norms. Three promising applications of such submatrices are presented: recommender systems, finding maximal elements in low-rank matrices and preconditioning of overdetermined linear systems. The code is available online.

  9. Global Harmonization of Maximum Residue Limits for Pesticides.

    Science.gov (United States)

    Ambrus, Árpád; Yang, Yong Zhen

    2016-01-13

    International trade plays an important role in national economics. The Codex Alimentarius Commission develops harmonized international food standards, guidelines, and codes of practice to protect the health of consumers and to ensure fair practices in the food trade. The Codex maximum residue limits (MRLs) elaborated by the Codex Committee on Pesticide Residues are based on the recommendations of the FAO/WHO Joint Meeting on Pesticides (JMPR). The basic principles applied currently by the JMPR for the evaluation of experimental data and related information are described together with some of the areas in which further developments are needed.

  10. Nuclear Reactor RA Safety Report, Vol. 16, Maximum hypothetical accident

    International Nuclear Information System (INIS)

    1986-11-01

    Fault tree analysis of the maximum hypothetical accident covers the basic elements: accident initiation, phase development phases - scheme of possible accident flow. Cause of the accident initiation is the break of primary cooling pipe, heavy water system. Loss of primary coolant causes loss of pressure in the primary circuit at the coolant input in the reactor vessel. This initiates safety protection system which should automatically shutdown the reactor. Separate chapters are devoted to: after-heat removal, coolant and moderator loss; accident effects on the reactor core, effects in the reactor building, and release of radioactive wastes [sr

  11. Theory and application of maximum magnetic energy in toroidal plasmas

    International Nuclear Information System (INIS)

    Chu, T.K.

    1992-02-01

    The magnetic energy in an inductively driven steady-state toroidal plasma is a maximum for a given rate of dissipation of energy (Poynting flux). A purely resistive steady state of the piecewise force-free configuration, however, cannot exist, as the periodic removal of the excess poloidal flux and pressure, due to heating, ruptures the static equilibrium of the partitioning rational surfaces intermittently. The rupture necessitates a plasma with a negative q'/q (as in reverse field pinches and spheromaks) to have the same α in all its force-free regions and with a positive q'/q (as in tokamaks) to have centrally peaked α's

  12. Elemental composition of cosmic rays using a maximum likelihood method

    International Nuclear Information System (INIS)

    Ruddick, K.

    1996-01-01

    We present a progress report on our attempts to determine the composition of cosmic rays in the knee region of the energy spectrum. We have used three different devices to measure properties of the extensive air showers produced by primary cosmic rays: the Soudan 2 underground detector measures the muon flux deep underground, a proportional tube array samples shower density at the surface of the earth, and a Cherenkov array observes light produced high in the atmosphere. We have begun maximum likelihood fits to these measurements with the hope of determining the nuclear mass number A on an event by event basis. (orig.)

  13. Approximation for maximum pressure calculation in containment of PWR reactors

    International Nuclear Information System (INIS)

    Souza, A.L. de

    1989-01-01

    A correlation was developed to estimate the maximum pressure of dry containment of PWR following a Loss-of-Coolant Accident - LOCA. The expression proposed is a function of the total energy released to the containment by the primary circuit, of the free volume of the containment building and of the total surface are of the heat-conducting structures. The results show good agreement with those present in Final Safety Analysis Report - FSAR of several PWR's plants. The errors are in the order of ± 12%. (author) [pt

  14. Maximum wind energy extraction strategies using power electronic converters

    Science.gov (United States)

    Wang, Quincy Qing

    2003-10-01

    This thesis focuses on maximum wind energy extraction strategies for achieving the highest energy output of variable speed wind turbine power generation systems. Power electronic converters and controls provide the basic platform to accomplish the research of this thesis in both hardware and software aspects. In order to send wind energy to a utility grid, a variable speed wind turbine requires a power electronic converter to convert a variable voltage variable frequency source into a fixed voltage fixed frequency supply. Generic single-phase and three-phase converter topologies, converter control methods for wind power generation, as well as the developed direct drive generator, are introduced in the thesis for establishing variable-speed wind energy conversion systems. Variable speed wind power generation system modeling and simulation are essential methods both for understanding the system behavior and for developing advanced system control strategies. Wind generation system components, including wind turbine, 1-phase IGBT inverter, 3-phase IGBT inverter, synchronous generator, and rectifier, are modeled in this thesis using MATLAB/SIMULINK. The simulation results have been verified by a commercial simulation software package, PSIM, and confirmed by field test results. Since the dynamic time constants for these individual models are much different, a creative approach has also been developed in this thesis to combine these models for entire wind power generation system simulation. An advanced maximum wind energy extraction strategy relies not only on proper system hardware design, but also on sophisticated software control algorithms. Based on literature review and computer simulation on wind turbine control algorithms, an intelligent maximum wind energy extraction control algorithm is proposed in this thesis. This algorithm has a unique on-line adaptation and optimization capability, which is able to achieve maximum wind energy conversion efficiency through

  15. The Ultraviolet Spectrometer and Polarimeter on the Solar Maximum Mission

    Science.gov (United States)

    Woodgate, B. E.; Brandt, J. C.; Kalet, M. W.; Kenny, P. J.; Tandberg-Hanssen, E. A.; Bruner, E. C.; Beckers, J. M.; Henze, W.; Knox, E. D.; Hyder, C. L.

    1980-01-01

    The Ultraviolet Spectrometer and Polarimeter (UVSP) on the Solar Maximum Mission spacecraft is described, including the experiment objectives, system design, performance, and modes of operation. The instrument operates in the wavelength range 1150-3600 A with better than 2 arcsec spatial resolution, raster range 256 x 256 sq arcsec, and 20 mA spectral resolution in second order. Observations can be made with specific sets of four lines simultaneously, or with both sides of two lines simultaneously for velocity and polarization. A rotatable retarder can be inserted into the spectrometer beam for measurement of Zeeman splitting and linear polarization in the transition region and chromosphere.

  16. The ultraviolet spectrometer and polarimeter on the solar maximum mission

    International Nuclear Information System (INIS)

    Woodgate, B.E.; Brandt, J.C.; Kalet, M.W.; Kenny, P.J.; Beckers, J.M.; Henze, W.; Hyder, C.L.; Knox, E.D.

    1980-01-01

    The Ultraviolet Spectrometer and Polarimeter (UVSP) on the Solar Maximum Mission spacecraft is described, including the experiment objectives, system design. performance, and modes of operation. The instrument operates in the wavelength range 1150-3600 Angstreom with better than 2 arc sec spatial resolution, raster range 256 x 256 arc sec 2 , and 20 m Angstroem spectral resolution in second order. Observations can be made with specific sets of 4 lines simultaneously, or with both sides of 2 lines simultaneously for velocity and polarization. A rotatable retarder can be inserted into the spectrometer beam for measurement of Zeeman splitting and linear polarization in the transition region and chromosphere. (orig.)

  17. Rectangular maximum-volume submatrices and their applications

    KAUST Repository

    Mikhalev, Aleksandr

    2017-10-18

    We introduce a definition of the volume of a general rectangular matrix, which is equivalent to an absolute value of the determinant for square matrices. We generalize results of square maximum-volume submatrices to the rectangular case, show a connection of the rectangular volume with an optimal experimental design and provide estimates for a growth of coefficients and an approximation error in spectral and Chebyshev norms. Three promising applications of such submatrices are presented: recommender systems, finding maximal elements in low-rank matrices and preconditioning of overdetermined linear systems. The code is available online.

  18. Variable Step Size Maximum Correntropy Criteria Based Adaptive Filtering Algorithm

    Directory of Open Access Journals (Sweden)

    S. Radhika

    2016-04-01

    Full Text Available Maximum correntropy criterion (MCC based adaptive filters are found to be robust against impulsive interference. This paper proposes a novel MCC based adaptive filter with variable step size in order to obtain improved performance in terms of both convergence rate and steady state error with robustness against impulsive interference. The optimal variable step size is obtained by minimizing the Mean Square Deviation (MSD error from one iteration to the other. Simulation results in the context of a highly impulsive system identification scenario show that the proposed algorithm has faster convergence and lesser steady state error than the conventional MCC based adaptive filters.

  19. ON THE MAXIMUM MASS OF STELLAR BLACK HOLES

    International Nuclear Information System (INIS)

    Belczynski, Krzysztof; Fryer, Chris L.; Bulik, Tomasz; Ruiter, Ashley; Valsecchi, Francesca; Vink, Jorick S.; Hurley, Jarrod R.

    2010-01-01

    We present the spectrum of compact object masses: neutron stars and black holes (BHs) that originate from single stars in different environments. In particular, we calculate the dependence of maximum BH mass on metallicity and on some specific wind mass loss rates (e.g., Hurley et al. and Vink et al.). Our calculations show that the highest mass BHs observed in the Galaxy M bh ∼ 15 M sun in the high metallicity environment (Z = Z sun = 0.02) can be explained with stellar models and the wind mass loss rates adopted here. To reach this result we had to set luminous blue variable mass loss rates at the level of ∼10 -4 M sun yr -1 and to employ metallicity-dependent Wolf-Rayet winds. With such winds, calibrated on Galactic BH mass measurements, the maximum BH mass obtained for moderate metallicity (Z = 0.3 Z sun = 0.006) is M bh,max = 30 M sun . This is a rather striking finding as the mass of the most massive known stellar BH is M bh = 23-34 M sun and, in fact, it is located in a small star-forming galaxy with moderate metallicity. We find that in the very low (globular cluster-like) metallicity environment the maximum BH mass can be as high as M bh,max = 80 M sun (Z = 0.01 Z sun = 0.0002). It is interesting to note that X-ray luminosity from Eddington-limited accretion onto an 80 M sun BH is of the order of ∼10 40 erg s -1 and is comparable to luminosities of some known ultra-luminous X-ray sources. We emphasize that our results were obtained for single stars only and that binary interactions may alter these maximum BH masses (e.g., accretion from a close companion). This is strictly a proof-of-principle study which demonstrates that stellar models can naturally explain even the most massive known stellar BHs.

  20. Maximum allowable heat flux for a submerged horizontal tube bundle

    International Nuclear Information System (INIS)

    McEligot, D.M.

    1995-01-01

    For application to industrial heating of large pools by immersed heat exchangers, the socalled maximum allowable (or open-quotes criticalclose quotes) heat flux is studied for unconfined tube bundles aligned horizontally in a pool without forced flow. In general, we are considering boiling after the pool reaches its saturation temperature rather than sub-cooled pool boiling which should occur during early stages of transient operation. A combination of literature review and simple approximate analysis has been used. To date our main conclusion is that estimates of q inch chf are highly uncertain for this configuration