Showing papers on "Energy (signal processing) published in 1999"

Band Anticrossing in GaInNAs Alloys

Abstract: We present evidence for a strong interaction between the conduction band and a narrow resonant band formed by nitrogen states in $\mathrm{Ga}{}_{1\ensuremath{-}x}\mathrm{In}{}_{x}\mathrm{N}{}_{y}\mathrm{As}{}_{1\ensuremath{-}y}$ alloys. The interaction leads to a splitting of the conduction band into two subbands and a reduction of the fundamental band gap. An anticrossing of the extended states of the conduction band of the $\mathrm{Ga}{}_{1\ensuremath{-}x}\mathrm{In}{}_{x}\mathrm{As}$ matrix and the localized nitrogen resonant states is used to model the interaction. Optical transitions associated with the energy minima of the two subbands and the characteristic anticrossing behavior of the transitions under applied hydrostatic pressure have been unambiguously observed using photomodulation spectroscopy. The experimental results are in excellent quantitative agreement with the model.

Atomic-scale magnetic modeling of oxide nanoparticles

Abstract: We present a method for atomic-scale modeling of the magnetic behavior of ionic magnetic solids. Spin distributions and net magnetic moments are calculated for nanoparticles of ferrimagnetic ${\mathrm{NiFe}}_{2}{\mathrm{O}}_{4}$ and $\ensuremath{\gamma}\ensuremath{-}{\mathrm{Fe}}_{2}{\mathrm{O}}_{3},$ and antiferromagnetic NiO as a function of applied field. Calculations incorporate crystal structures and exchange parameters determined from bulk data, bulk anisotropy for core spins, reasonable estimates for the anisotropy of surface spins, and finite temperatures simulated by random perturbations of spins. Surface spin disorder was found in the case of ferrimagnetic spinel nanoparticles, due to broken exchange bonds at the surface. The calculations also demonstrate that surface anisotropy enhances the coercivity of such particles only when surface spin disorder is present. Simulated thermal perturbations were used to characterize the distribution of energy barriers between surface spin states of such particles. The distribution of barriers can explain the macroscopic quantum tunneling like magnetic relaxation at low temperatures found experimentally. Calculations on NiO nanoparticles predict eight, six, or four-sublattice spin configurations in contrast to the two-sublattice configuration accepted for bulk NiO. Relatively weak coupling between the multiple sublattices allows a variety of reversal paths for the spins upon cycling the applied field, resulting in large coercivities and loop shifts, in qualitative agreement with experiment.

Chemical and thermal freeze-out parameters from 1 A to 2 0 0 A GeV

Abstract: The present knowledge about hadrons produced in relativistic heavy ion collisions is compatible with chemical freeze-out happening when the energy density divided by the particle density reaches the value of 1 GeV. This observation is used to determine the energy dependence of the chemical freeze-out parameters ${T}_{\mathrm{ch}}$ and ${\ensuremath{\mu}}_{B}^{\mathrm{ch}}$ for beam energies varying between 1 and $200A$ GeV. The consequences of this energy dependence are studied for various particle ratios. Predictions for particle ratios at beam energy $40A$ GeV are presented. The conditions for thermal freeze-out are also determined. These correspond either to an energy density of 45 ${\mathrm{M}\mathrm{e}\mathrm{V}/\mathrm{f}\mathrm{m}}^{3}$ or to a particle density of $0.05/{\mathrm{fm}}^{3}.$

Energetics of self-interstitial clusters in si

Abstract: The transient supersaturation in a system undergoing Ostwald ripening is related to the cluster formation energy ${E}_{\mathrm{fc}}$ as a function of cluster size $n$. We use this relation to study the energetics of self-interstitial clusters in Si. Measurements of transient enhanced diffusion of B in Si-implanted Si are used to determine $S(t)$, and inverse modeling is used to derive ${E}_{\mathrm{fc}}(n)$. For clusters with $ng15$, ${E}_{\mathrm{fc}}\ensuremath{\approx}0.8\mathrm{eV}$, close to the fault energy of ${113}$ defects. For clusters with $nl10$, ${E}_{\mathrm{fc}}$ is typically 0.5 eV higher, but stabler clusters exist at $n\ensuremath{\approx}4$ ( ${E}_{\mathrm{fc}}\ensuremath{\approx}1.0\mathrm{eV}$) and $n\ensuremath{\approx}8$ ( ${E}_{\mathrm{fc}}\ensuremath{\approx}0.6\mathrm{eV}$).

Limits to Quantum Gravity Effects on Energy Dependence of the Speed of Light from Observations of TeV Flares in Active Galaxies

Abstract: We have used data from a TeV {gamma} -ray flare associated with the active galaxy Markarian 421 to place bounds on the possible energy dependence of the speed of light in the context of an effective quantum gravitational energy scale. Recent theoretical work suggests that such an energy scale could be less than the Planck mass and perhaps as low as 10{sup 16} thinspthinspGeV. The limits derived here indicate this energy scale to be in excess of 6{times}10{sup 16} thinspthinspGeV for at least one approach to quantum gravity in the context of D-brane string theory. To the best of our knowledge, this constitutes the first convincing limit on such phenomena in this energy regime. {copyright} {ital 1999} {ital The American Physical Society}

Velocity structure functions, scaling, and transitions in high-Reynolds-number Couette-Taylor flow.

Abstract: Flow between concentric cylinders with a rotating inner cylinder is studied for Reynolds numbers in the range $2\ifmmode\times\else\texttimes\fi{}{10}^{3}lRl{10}^{6}$ (Taylor Reynolds numbers, $10l{R}_{\ensuremath{\lambda}}l290)$ for a system with radius ratio $\ensuremath{\eta}=0.724$. Even at the highest Reynolds number studied, the energy spectra do not show power law scaling (i.e., there is no inertial range), and the dissipation length scale is surprisingly large. Nevertheless, the velocity structure functions calculated using extended self-similarity exhibit clear power-law scaling. The structure function exponents ${\ensuremath{\zeta}}_{p}$ fit Kolmogorov's log-normal model within the experimental uncertainty, ${\ensuremath{\zeta}}_{p}=(p/3)[1+(\ensuremath{\mu}/6)(3\ensuremath{-}p)]$ (for $pl~10)$ with $\ensuremath{\mu}=0.27$. These ${\ensuremath{\zeta}}_{p}$ values are close to those found in other flows. Measurements of torque scaling are presented that are an order of magnitude more accurate than those previously reported [Lathrop et al., Phys Rev. A 46, 6390 (1992)]. Measurements of velocity in the fluid core reveal the presence of azimuthal traveling waves up to the highest Reynolds numbers examined. These waves show evidence of a transition at ${R}_{T}=1.3\ifmmode\times\else\texttimes\fi{}{10}^{4}$; this transition was observed previously in measurements of torque, but our wave velocity and wall shear stress measurements provide the first evidence from local quantities of the transition at ${R}_{T}.$ Velocity measurements indicate that at ${R}_{T}$ there is a change in the coherent structures of the core flow; this is consistent with our analyses of the scaling of the torque. Our measurements were made at two aspect ratios, and no significant dependence on aspect ratio was observable for $Rg{R}_{T}.$

Production and detection of relic gravitons in quintessential inflationary models

Abstract: A large class of quintessential inflationary models, recently proposed by Peebles and Vilenkin, leads to post-inflationary phases whose effective equation of state is stiffer than radiation. The expected gravitational wave logarithmic energy spectra are tilted towards high frequencies and characterized by two parameters: the inflationary curvature scale at which the transition to the stiff phase occurs and the number of (nonconformally coupled) scalar degrees of freedom whose decay into fermions triggers the onset of a gravitational reheating of the Universe. Depending upon the parameters of the model and upon the different inflationary dynamics (prior to the onset of the stiff evolution), the relic gravitons energy density can be much more sizable than in standard inflationary models, for frequencies larger than $1$ Hz. We estimate the required sensitivity for detection of the predicted spectral amplitude and show that the allowed region of our parameter space leads to a signal smaller (by one $1.5$ orders of magnitude) than the advanced laser interferometric gravitational wave observatory sensitivity at a frequency of $0.1$ kHz. The maximal signal, in our context, is expected in the GHz region where the energy density of relic gravitons in critical units (i.e., ${h}_{0}^{2}{\ensuremath{\Omega}}_{\mathrm{GW}})$ is of the order of ${10}^{\ensuremath{-}6},$ roughly eight orders of magnitude larger than in ordinary inflationary models. Smaller detectors (not necessarily interferometers) can be relevant for detection purposes in the GHz frequency window. We suggest or speculate that future measurements through microwave cavities can offer interesting perspectives.

Decision feedback multiuser detection: a systematic approach

Abstract: A systematic approach to decision feedback multiuser detection is introduced for the joint detection of symbols of K simultaneously transmitting users of a synchronous correlated waveform multiple-access (CWMA) channel with Gaussian noise. A new performance criterion called symmetric energy is defined which is a low-noise indicator of the joint error rate that at least one user is detected erroneously. Even the best linear detectors can perform poorly in terms of symmetric energy compared to the maximum-likelihood detector. A general class of decision feedback detectors (DFDs) is defined with O(K) implementational complexity per user. The symmetric energy of arbitrary DFD and bounds on their asymptotic effective energy (AEE) performance are obtained along with an exact bit-error rate and AEE analysis for the decorrelating DFD. The optimum DFD that maximizes symmetric energy is obtained. Each one of the K! optimum, decorrelating, and conventional DFDs, that correspond to the K! orders in which the users can be detected, are shown to outperform the linear optimum, decorrelating, and conventional detectors, respectively, in terms of symmetric energy. Moreover, algorithms are obtained for determining the choice of order of detection for the three DFDs which guarantee that they uniformly (user-wise) outperform their linear counterparts. In addition to optimality in symmetric energy, it is also shown that under certain conditions, the optimum DFD achieves the AEE performance of the exponentially complex maximum-likelihood detector for all users simultaneously. None of the results of this paper make the perfect feedback assumption. The implications of our work on power control for multiuser detection are also discussed.

Supersymmetry and generalized calibrations

Abstract: A static minimal energy configuration of a super p-brane in a supersymmetric $(n+1)$-dimensional spacetime is shown to be a ``generalized calibrated'' submanifold. Calibrations in ${E}^{(1,n)}$ and ${\mathrm{AdS}}_{n+1}$ are special cases. We present several M-brane examples.

Low-Energy Magnetic Excitations of the Mn 12 -Acetate Spin Cluster Observed by Neutron Scattering

Abstract: We studied ${\mathrm{Mn}}_{12}$-acetate by inelastic neutron scattering and diffraction. We separated the energy levels corresponding to the splitting of the lowest $S$ multiplet ( $S\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}10$ ground state). The irregular spacing of the transition energies unambiguously shows the presence of high-order terms in the spin Hamiltonian [ $D\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}0.457(2){\mathrm{cm}}^{\ensuremath{-}1}$, ${B}_{4}^{0}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}2.33(4)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}{\mathrm{cm}}^{\ensuremath{-}1}$]. The relative intensity of the lowest energy peaks is very sensitive to the small transverse term that is responsible for quantum tunneling, providing the first determination of this term in zero magnetic field $[{B}_{4}^{4}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ifmmode\pm\else\textpm\fi{}3.0(5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}{\mathrm{cm}}^{\ensuremath{-}1}]$.

Self-focusing, channel formation, and high-energy ion generation in interaction of an intense short laser pulse with a He jet

Abstract: Using interferometry, we investigate the dynamics of interaction of a relativistically intense 4-TW, 400-fs laser pulse with a He gas jet. We observe a stable plasma channel 1 mm long and less than 30 $\ensuremath{\mu}$m in diameter, with a radial gradient of electron density $\ensuremath{\sim}5\ifmmode\times\else\texttimes\fi{}{10}^{22}$ ${\mathrm{cm}}^{\ensuremath{-}4}$ and with an on-axis electron density approximately ten times less than its maximum value of $8\ifmmode\times\else\texttimes\fi{}{10}^{19}$ ${\mathrm{cm}}^{\ensuremath{-}3}.$ A high radial velocity of the surrounding gas ionization of $\ensuremath{\sim}3.8\ifmmode\times\else\texttimes\fi{}{10}^{8}$ cm/s has been observed after the channel formation, and it is attributed to the fast ions expelled from the laser channel and propagating radially outward. We developed a kinetic model which describes the plasma channel formation and the subsequent ambient gas excitation and ionization. Comparing the model predictions with the interferometric data, we reconstructed the axial profile of laser channel and on-axis laser intensity. The estimated maximum energy of accelerated ions is about 500 keV, and the total energy of the fast ions is 5% of the laser pulse energy.

Evidence for a missing nucleon resonance in kaon photoproduction

Abstract: New SAPHIR $p(\ensuremath{\gamma}{,K}^{+})\ensuremath{\Lambda}$ total cross section data show a resonance structure at a total c.m. energy around 1900 MeV. We investigate this feature with an isobar model and find that the structure can be well explained by including a new ${D}_{13}$ resonance at 1895 MeV. Such a state has been predicted by a relativistic quark model at 1960 MeV with significant $\ensuremath{\gamma}N$ and $K\ensuremath{\Lambda}$ branching ratios. We demonstrate how the measurement of the photon asymmetry can be used to further study this resonance. In addition, verification of the predicted large decay widths into the $\ensuremath{\eta}N$ and ${\ensuremath{\eta}}^{\ensuremath{'}}N$ channels would allow distinguishing between other nearby ${D}_{13}$ states.

Predominantly Superconducting Origin of Large Energy Gaps in Underdoped Bi 2 Sr 2 CaCu 2 O 8+δ from Tunneling Spectroscopy

Abstract: New tunneling data are reported in ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ which show quasiparticle excitation gaps, \ensuremath{\Delta}, reaching values as high as 60 meV for underdoped crystals with ${T}_{c}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}70\mathrm{K}$. These energy gaps are nearly 3 times larger than those of overdoped crystals with similar ${T}_{c}$. Despite the large differences in gap magnitude, the tunneling spectra display qualitatively similar characteristics over the entire doping range. Detailed examination of the spectra, including the Josephson ${I}_{c}{R}_{n}$ product measured in break junctions, indicates that these energy gaps are predominantly of superconducting origin.

Microscopic descriptions of superdeformed bands with the Gogny force: Configuration mixing calculations in the A~190 mass region

Abstract: A quantal Hamiltonian ${\stackrel{^}{\mathcal{H}}}_{\mathrm{coll}}$ expressed in terms of the five collective quadrupole coordinates is built for eight nuclei ${(}^{190,192,194}$Hg, ${}^{192,194,196}$Pb, and ${}^{196,198}$Po) which display secondary minima at large elongation in their potential energy surface. These surfaces as well as the tensor of inertia entering ${\stackrel{^}{\mathcal{H}}}_{\mathrm{coll}}$ are deduced from constrained Hartree-Fock-Bogoliubov calculations based on Gogny force. A two-center basis method employed to solve ${\stackrel{^}{\mathcal{H}}}_{\mathrm{coll}}$ is presented. The stability of predicted collective spectra is discussed. Yrast and vibrational $\ensuremath{\pi}=+$ superdeformed (SD) bands are predicted together with collective bands at normal deformation (ND). The predicted yrast SD bands at low spin display properties which compare favorably with experimental information. Quite good agreement is in particular obtained for the isomeric energies of nuclei for which the link between SD and ND levels is experimentally known. Among the excited SD bands which are here predicted, those built on top of $\ensuremath{\beta}$ vibrations are lower in energy. Only for the ${}^{196,198}$Po isotopes are these excitation energies falling in the low energy range $E\ensuremath{\sim}$0.8--1.0 MeV. These properties should favor an experimental discovery of $\ensuremath{\beta}$-vibrational SD bands in the $A\ensuremath{\sim}$190 mass region.

Plasmon-enhanced multi-ionization of small metal clusters in strong femtosecond laser fields

Abstract: The multiply charging process of platinum cluster ions under intense field conditions show a strong dependence on the width of the femtosecond laser pulse. Increasing the pulse width from 140 to 600 fs while keeping the energy per pulse constant leads to an increase in the highest observed charge state ${z}^{*}$ of the ejected atoms from ${z}^{*}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}13$ to ${z}^{*}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}20$. This increased charging efficiency is explained by the evolution of the plasmon energy of the metal cluster upon the change in electron density during the Coulomb explosion process. Thus the time dependence of the charging of a cluster in an intense light field has been observed in real time.

Fast neutron emission from a high-energy ion beam produced by a high-intensity subpicosecond laser pulse

Abstract: Neutron emission as high as ${10}^{7}$ is observed when a high intensity (a few ${10}^{19}\mathrm{W}/{\mathrm{cm}}^{2}$) subpicosecond laser pulse at 529 nm wavelength is focused on a deuterated polyethylene target. Neutron emission is also measured in different directions. The emission of neutrons along the laser axis is higher than in the transverse direction. Nonisotropic emission is consistent with neutrons generated by $\mathrm{D}(d,n){\ensuremath{-}}^{3}\mathrm{He}$ reaction for 0.3--1 MeV deuterons accelerated in the direction of the laser beam. The energy transferred to the ions is roughly estimated and compared with the energy carried out by the electrons.

Method and system for down-converting an electromagnetic signal

Abstract: Methods for down converting a modulated carrier signal to a demodulated baseband signal are described herein The method requires that a first portion of energy is transferred from the modulated carrier signal, and stored at a first storage device when a first switch is on At least some of the energy stored in the first storage device is discharged when the first switch is off The method further comprises transferring a second portion of energy from the modulated carrier signal, storing at a second storage device the second portion of transferred energy when a second switch is on, and discharging at least some of the energy stored in the second storage device when the second switch is off A down-converted in-phase baseband signal portion is generated from the energy accumulated in the first storage device while both the charging and the discharging occurs, and a down-converted inverted in-phase baseband signal portion is generated from the energy accumulated in the second storage device while both the charging and the discharging occurs, and the two portions are combined with a first differential amplifier circuit to form a down-converted differential in-phase baseband signal

Stationary H-Mode Discharges with Internal Transport Barrier on ASDEX Upgrade

Abstract: Stationary discharges with $H$-mode edge and internal transport barrier for energy, momentum, and particle transport have been obtained on ASDEX Upgrade. At a line averaged density of $4\ifmmode\times\else\texttimes\fi{}{10}^{19}{\mathrm{m}}^{\ensuremath{-}3}$ an $H$ factor of ${H}_{\mathrm{ITER}89\ensuremath{-}P}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2.4$ and ${\ensuremath{\beta}}_{N}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2$ could be maintained for 6 s corresponding to 40 confinement times, limited only by the possible discharge duration. The $q$ profile is flat in the center and close to 1. Current diffusion calculations suggest that reconnection is required to clamp the safety factor at 1, which in the absence of sawteeth is explained by the strong fishbone activity.

Slave Boson Approach to Neutron Scattering in YBa 2 Cu 3 O 6 + y Superconductors

Abstract: The evolution of the so-called ``41 meV resonance'' in the magnetic response of YBCO cuprates is studied with slave boson theory for the $t\ensuremath{-}{t}^{\ensuremath{'}}\ensuremath{-}J$ model. The resonance appears as a collective spin fluctuation in the $d$-wave superconducting (SC) state. It is undamped at optimal doping due to a threshold in the excitation energies of particle-hole pairs with relative wave vector $(\ensuremath{\pi},\ensuremath{\pi})$. When hole filling is reduced, the resonance moves to lower energies and broadens. Below the resonance energy we find a crossover to an incommensurate response in agreement with a recent experiment on ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6.6}$. We show that dynamic nesting in the $d$-wave SC state causes this effect.

Decay laws for three-dimensional magnetohydrodynamic turbulence

Abstract: Novel decay laws in three-dimensional incompressible magnetohydrodynamic turbulence are obtained by high-resolution numerical simulations with up to ${512}^{3}$ modes and explained by a simple theoretical model. For the typical case of finite magnetic helicity $H$ the energy decay is governed by the conservation of $H$ and the decay of the energy ratio $\ensuremath{\Gamma}{\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}E}^{V}/{E}^{M}$. One finds the relation $({E}^{5/2}/\ensuremath{\epsilon}H){\ensuremath{\Gamma}}^{1/2}/(1+\ensuremath{\Gamma}{)}^{3/2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\mathrm{const}$, where $\ensuremath{\epsilon}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}dE/\mathrm{dt}$. Use of the numerical result that $\ensuremath{\Gamma}(t)\ensuremath{\propto}E(t)$ gives the asymptotic law $E\ensuremath{\sim}{t}^{\ensuremath{-}0.5}$ in good agreement with the numerical observations. For the special case $H\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0$ the energy decreases more rapidly $E\ensuremath{\sim}{t}^{\ensuremath{-}1}$.

Temperature Dependent Photoemission Studies of Optimally Doped Bi 2 Sr 2 CaCu 2 O 8

Abstract: High resolution angle-resolved photoemission is used to study the electronic structure of optimally doped ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8}$. These studies, with an energy resolution of 8 meV, show that the sharp peak observed in the superconducting state has an intrinsic width of the order of 14 meV. Detailed temperature dependent studies reveal that this peak is fixed in binding energy at all temperatures at which it is observable and further that it exists at temperatures even above the superconducting transition temperature ${T}_{c}$. However, our analysis indicates that with the onset of long range phase coherence a gap emerges in the spectral response between the main incoherent peak and the Fermi level.

Tip-induced band bending by scanning tunneling spectroscopy of the states of the tip-induced quantum dot on inas(110)

Abstract: We analyze the quantized states of the tip-induced quantum dot appearing in scanning tunneling spectroscopy (STS) on n-type InAs(110) ${(N}_{D}=2\ifmmode\times\else\texttimes\fi{}{10}^{16}{\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}).$ STS at negative sample bias (-200--0 mV) is used to determine the state energies. The analysis of the spectra indicates that the z-quantization leads to one or two quantized states while a ladder of states due to the lateral confinement is observed. The magnetic-field dependence (0--6 T) shows the expected splitting of the first excited state in quantitative agreement with Hartree calculations. If an ionized dopant is located in the center of the quantum dot, a reduction in energy and a change in intensity of the single-particle ground state is found, which is also in quantitative agreement with Hartree calculations. The analysis of the tip-induced states can be used to reconstruct the shape of the tip-induced band bending.

Josephson Coupling through a Magnetic Impurity

Abstract: We analyze nonperturbatively the behavior of a Josephson junction in which two BCS superconductors are coupled through an Anderson impurity. We recover earlier perturbative results which found that a $\ensuremath{\delta}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{\pi}$ phase difference is preferred when the impurity is singly occupied and the on-site Coulomb interaction is large. We find a novel intermediate phase in which one of $\ensuremath{\delta}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0$ and $\ensuremath{\delta}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{\pi}$ is stable while the other is metastable, with the energy $E(\ensuremath{\delta})$ having a kink somewhere in between. As a consequence of the kink, the $I\ensuremath{-}V$ characteristics of the junction are modified at low voltages.

Watermark encoding method exploiting biases inherent in original signal

Abstract: Source materials to be watermarked already have variations in their characteristics that may tend to aid the watermark encoding. Where such favorable variations exist, relatively less watermark energy can be applied.

A Solution of the Odderon Problem

Abstract: The intercept of the odderon trajectory is derived by finding the spectrum of the second integral of motion of the three Reggeon system in high energy QCD. When combined with an earlier solution of the appropriate Baxter equation, this leads to the determination of the low lying states of that system. In particular, the energy of the lowest state gives the intercept of the odderon ${\ensuremath{\alpha}}_{O}(0)\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1\ensuremath{-}0.2472{\ensuremath{\alpha}}_{s}{N}_{c}/\ensuremath{\pi}$.

Elimination of self-absorption in fluorescence hard-x-ray absorption spectra

Abstract: Fluorescence detection is a convenient way to measure x-ray absorption spectra in situations where samples cannot be made in the required configuration. However, self-absorption effects cause considerable distortion of spectra measured in fluorescence. We describe a straightforward procedure to correct for such distortion in the hard-x-ray region using the known energy dependence of the x-ray absorption coefficients. This procedure is used to obtain the vanadium K-edge spectrum of single crystal ${\mathrm{V}}_{2}{\mathrm{O}}_{3}$ and we demonstrate that self-absorption is properly corrected. This facilitates the use of fluorescence detection even in the hard-x-ray region.

Self-trapping and multiplication of electronic excitations in Al 2 O 3 and Al 2 O 3 : S c crystals

Abstract: The processes of intrinsic and extrinsic luminescence excitation by synchrotron radiation of 4\char21{}40 eV or electron pulses have been studied in $\ensuremath{\alpha}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ single crystals at 8 K. The intrinsic A (7.6 eV) and E emissions (3.77 eV) can be effectively excited in the region of long-wavelength (8.85\char21{}9.1 eV) and short-wavelength (9.1\char21{}9.3 eV) components of exciton absorption doublet, respectively. Fast (\ensuremath{\sim}6 and \ensuremath{\sim}20 ns) and slow (\ensuremath{\sim}150 ns) components of the A emission correspond to the creation of singlet and triplet ${p}^{5}s$ excitons. The efficiency of the A emission in the region of band-to-band transitions is low. The intensity of A emission sharply increases (approximately quadratically) with a rise of the excitation density by nanosecond electron pulses. In ${\mathrm{Al}}_{2}{\mathrm{O}}_{3}:\mathrm{S}\mathrm{c},$ the 5.6-eV luminescence is caused by the decay of near-impurity electronic excitations (\ensuremath{\sim}8.5 eV) as well as by the electron recombination with holes localized near ${\mathrm{Sc}}^{3+}$ centers. The efficiency of 7.6-, 5.6-, and 3.8-eV emission sharply increases at the energy of exciting photons of $h\ensuremath{ u}g25\mathrm{eV}.$ One photon of 26\char21{}29 and 30\char21{}37 eV causes the ionization of the ${2p}^{6}$ or ${2s}^{2}$ shell of the oxygen ion and provides the creation of two or three electron-hole pairs, respectively. Long-term investigations of $\ensuremath{\alpha}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ crystals did not lead to the detection of immobile self-trapped holes or electrons. The A emission excited at the direct photocreation of excitons or at the recombination of free electrons and free holes is interpreted by us as the radiative decay of self-shrunk excitons. The theoretical model of Sumi allows the existence of such immobile self-shrunk excitons even if an electron and a hole do not separately undergo the self-trapping.

Energy management system and method

Abstract: A method is provided for managing the energy usage of an energy consuming system adapted to determine the energy of a controlled space, the energy consuming system including a plurality of operating components having on and off states and a plurality of differing noise levels when making transitions between the on and off states. The method includes determining the noise levels of the components of the energy consuming system, selecting a relatively low noise level component of the energy consuming system to provide a selected noise masking component, and causing a relatively high noise level component of the energy consuming system differing from the selected noise masking component to make a transition between on and off states. The method further includes causing the selected noise masking component to make a transition between its on and off states after the transition of high noise level component. The noise level of the selected noise masking component prior is increased prior to the transition of the high noise level component and decreased thereafter. The noise level of the selected noise masking component is gradually increased and gradually decreased. The operations are performed according to the occupancy of the controlled space. A parameter band of control is determined for controlling a selected parameter of the controlled space and the selected parameter of the controlled space is determined. A parameter drift of the selected parameter within the controlled space is determined in order to determine whether the parameter drift is adjusting the parameter toward the band of control. The energy of the controlled space is determined accordingly. Energy is applied to the energy system if the drift of the selected parameter of the controlled space is not adjusting the parameter toward the band of control.

Electronic structure, phase stability, and magnetic properties of La 1 − x Sr x CoO 3 from first-principles full-potential calculations

Abstract: In order to understand the role of hole doping on electronic structure, phase stability and magnetic properties of ${\mathrm{LaCoO}}_{3}$ generalized-gradient-corrected, relativistic first-principles full-potential density functional calculations have been performed for ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CoO}}_{3}$ as a function of x, using the supercell approach as well as the virtual crystal approximation (VCA). It has been shown that the rhombohedral distortion is stabilizing the nonmagnetic (i.e., diamagnetic or paramagnetic) ground state in ${\mathrm{LaCoO}}_{3}.$ Spin-polarized calculation on the hypothetical cubic perovskite phase of ${\mathrm{LaCoO}}_{3}$ shows that the ferromagnetic phase is lower in energy than the corresponding nonmagnetic phase. The analysis of the electronic structures show that a Peierls-Jahn-Teller-like instability arises in the ferromagnetic cubic phase and leads to the rhombohedral distortion in ${\mathrm{LaCoO}}_{3}.$ The calculated magnetic moment for ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CoO}}_{3}$ as a function of Sr substitution is found to be in very good agreement with recent neutron scattering measurements. We have successfully explained the hole-doping induced, nonmagnetic-to-ferromagnetic transition as well as the rhombohedral-to-cubic structural transition as a function of Sr substitution in ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CoO}}_{3}.$ Due to the failure of the density functional theory to predict the semiconducting nature of ${\mathrm{LaCoO}}_{3},$ we are unable to explain the experimentally observed semiconductor-to-metal transition in ${\mathrm{LaCoO}}_{3}$ by Sr substitution. The origin of the ferromagnetism in ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CoO}}_{3}$ has been explained through itinerant-band ferromagnetism.

Extraction of the spin glass correlation length

Abstract: The peak of the spin glass relaxation rate, $S(t)\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}d[{\ensuremath{-}M}_{\mathrm{TRM}}({t,t}_{w})/H]/d\mathrm{ln}t$, is directly related to the typical value of the free energy barrier which can be explored over experimental time scales. A change in magnetic field $H$ generates an energy ${E}_{z}{\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}N}_{s}{\ensuremath{\chi}}_{\mathrm{fc}}{H}^{2}$ by which the barrier heights are reduced, where ${\ensuremath{\chi}}_{\mathrm{fc}}$ is the field cooled susceptibility per spin, and ${N}_{s}$ is the number of correlated spins. The shift of the peak of $S(t)$ gives ${E}_{z}$, generating the correlation length, $\ensuremath{\xi}(t,T)$ for $\mathrm{Cu}:\mathrm{Mn}6\mathrm{at}.%$ and ${\mathrm{CdCr}}_{1.7}{\mathrm{In}}_{0.3}{\mathrm{S}}_{4}$. Fits to power law dynamics, $\ensuremath{\xi}(t,T)\ensuremath{\propto}{t}^{\ensuremath{\alpha}(T)}$ and activated dynamics $\ensuremath{\xi}(t,T)\ensuremath{\propto}(\mathrm{ln}t{)}^{1/\ensuremath{\psi}}$ compare well with simulation fits but possess too small a prefactor for activated dynamics.