Showing papers on "Energy (signal processing) published in 2001"
TL;DR: In this paper, the Lagrangian was constructed for an effective theory of highly energetic quarks with energy Q, interacting with collinear and soft gluons, and the heavy to light currents were matched onto operators in the effective theory at one loop.
Abstract: We construct the Lagrangian for an effective theory of highly energetic quarks with energy Q, interacting with collinear and soft gluons. This theory has two low energy scales, the transverse momentum of the collinear particles, ${p}_{\ensuremath{\perp}},$ and the scale ${p}_{\ensuremath{\perp}}^{2}/Q.$ The heavy to light currents are matched onto operators in the effective theory at one loop and the renormalization group equations for the corresponding Wilson coefficients are solved. This running is used to sum Sudakov logarithms in inclusive $\stackrel{\ensuremath{\rightarrow}}{B}{X}_{s}\ensuremath{\gamma}$ and $\stackrel{\ensuremath{\rightarrow}}{B}{X}_{u}l\overline{\ensuremath{
u}}$ decays. We also show that the interactions with collinear gluons preserve the relations for the soft part of the form factors for heavy-to-light decays found by Charles et al. [Phys. Rev. D 60, 014001 (1999)], establishing these relations in the large energy limit of QCD.
1,538 citations
TL;DR: In this article, a local exchange functional called OPTX was proposed to approximate the Hartree-Fock (HF) energies of the 18 first and second row atoms. But it was shown that neither δ p or t = Σ δ i |2 improves the fit to these atomic energies.
Abstract: We first attempt to determine a local exchange functional Ex[p] which accurately reproduces the Hartree-Fock (HF) energies of the 18 first and second row atoms. Ex[p is determined from p and |δp|, and we find that we can improve significantly upon Becke's original generalized gradient approximation functional (commonly called B88X) by allowing the coefficient of the Dirac exchange term to be optimized (it is argued that molecules do not behave like the uniform electron gas). We call this new two parameter exchange functional OPTX. We find that neither δ p or t = Σ δ i |2 improve the fit to these atomic energies. These exchange functionals include not only exchange, but also left-right correlation. It is therefore proposed that this functional provides a definition for exchange energy plus left-right correlation energy when used in Kohn-Sham (KS) calculations. We call this energy the Kohn-Sham exchange (or KSX) energy. It is shown that for nearly all molecules studied these KSX energies are lower than the ...
1,467 citations
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TL;DR: A geometric phase interpretation that is based on the relation between the 1-D analytic signal and the 2-D monogenic signal established by the Radon (1986) transform is introduced.
Abstract: This paper introduces a two-dimensional (2-D) generalization of the analytic signal This novel approach is based on the Riesz transform, which is used instead of the Hilbert transform The combination of a 2-D signal with the Riesz transformed one yields a sophisticated 2-D analytic signal: the monogenic signal The approach is derived analytically from irrotational and solenoidal vector fields Based on local amplitude and local phase, an appropriate local signal representation that preserves the split of identity, ie, the invariance-equivariance property of signal decomposition, is presented This is one of the central properties of the one-dimensional (1-D) analytic signal that decomposes a signal into structural and energetic information We show that further properties of the analytic signal concerning symmetry, energy, allpass transfer function, and orthogonality are also preserved, and we compare this with the behavior of other approaches for a 2-D analytic signal As a central topic of this paper, a geometric phase interpretation that is based on the relation between the 1-D analytic signal and the 2-D monogenic signal established by the Radon (1986) transform is introduced Possible applications of this relationship are sketched, and references to other applications of the monogenic signal are given
852 citations
TL;DR: Analysis showed that the photoluminescence peak energy E was related to the size of the a-Si QD, a (nm) by E(eV) = 1.56+2.40/a(2), which is a clear evidence for the quantum confinement effect in a- Si QDs.
Abstract: Amorphous silicon quantum dots ( $a\ensuremath{-}\mathrm{Si}$ QDs) were grown in a silicon nitride film by plasma enhanced chemical vapor deposition. Transmission electron micrographs clearly demonstrated that $a\ensuremath{-}\mathrm{Si}$ QDs were formed in the silicon nitride. Photoluminescence and optical absorption energy measurement of $a\ensuremath{-}\mathrm{Si}$ QDs with various sizes revealed that tuning of the photoluminescence emission from 2.0 to 2.76 eV is possible by controlling the size of the $a\ensuremath{-}\mathrm{Si}$ QD. Analysis also showed that the photoluminescence peak energy $E$ was related to the size of the $a\ensuremath{-}\mathrm{Si}$ QD, $a$ (nm) by $E(\mathrm{eV}){\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.56+2.40/a}^{2}$, which is a clear evidence for the quantum confinement effect in $a\ensuremath{-}\mathrm{Si}$ QDs.
483 citations
TL;DR: In this paper, realistic models of pion-exchange three-nucleon interactions obtained by fitting the energies of all the 17 bound or narrow states of $3l~Al~8$ nucleons, calculated with less than 2% error using the Green's function Monte Carlo method.
Abstract: We present realistic models of pion-exchange three-nucleon interactions obtained by fitting the energies of all the 17 bound or narrow states of $3l~Al~8$ nucleons, calculated with less than 2% error using the Green's function Monte Carlo method. The models contain two-pion-exchange terms due to $\ensuremath{\pi}N$ scattering in S and P waves, three-pion-exchange terms due to ring diagrams with one $\ensuremath{\Delta}$ in the intermediate states, and a phenomenological repulsive term to take into account relativistic effects, the suppression of the two-pion-exchange two-nucleon interaction by the third nucleon, and other effects. The models have five parameters, consisting of the strength of the four interactions and the short-range cutoff. The 17 fitted energies are insufficient to determine all of them uniquely. We consider five models, each having three adjustable parameters and assumed values for the other two. They reproduce the observed energies with an rms error $l1%$ when used together with the Argonne ${v}_{18}$ two-nucleon interaction. In one of the models the $\ensuremath{\pi}N$ S-wave scattering interaction is set to zero; in all others it is assumed to have the strength suggested by chiral effective-field theory. One of the models also assumes that the $\ensuremath{\pi}N$ P-wave scattering interaction has the strength suggested by effective-field theories, and the cutoff is adjusted to fit the data. In all other models the cutoff is taken to be the same as in the ${v}_{18}$ interaction. The effect of relativistic boost correction to the two-nucleon interaction on the strength of the repulsive three-nucleon interaction is estimated. Many calculated properties of $Al~8$ nuclei, including radii, magnetic dipole, and electric quadrupole moments, isobaric analog energy differences, etc., are tabulated. Results obtained with only Argonne ${v}_{8}^{\ensuremath{'}}$ and ${v}_{18}$ interactions are also reported. In addition, we present results for seven- and eight-body neutron drops in external potential wells.
458 citations
Patent•
19 Dec 2001TL;DR: In this paper, a processor provides signal quality based limits to a signal strength operating region of a pulse oximeter, which are superimposed on the typical gain dependent signal strength limits.
Abstract: A processor provides signal quality based limits to a signal strength operating region of a pulse oximeter. These limits are superimposed on the typical gain dependent signal strength limits. If a sensor signal appears physiologically generated, the pulse oximeter is allowed to operate with minimal signal strength, maximizing low perfusion performance. If a sensor signal is potentially due to a signal induced by a dislodged sensor, signal strength requirements are raised. Thus, signal quality limitations enhance probe off detection without significantly impacting low perfusion performance. One signal quality measure used is pulse rate density, which defines the percentage of time physiologically acceptable pulses are occurring. If the detected signal contains a significant percentage of unacceptable pulses, the minimum required signal strength is raised proportionately. Another signal quality measure used in conjunction with pulse rate density is energy ratio, computed as the percentage of total energy contained in the pulse rate fundamental and associated harmonics.
435 citations
TL;DR: Metal-encapsulated caged clusters of silicon from ab initio pseudopotential plane wave calculations using generalized gradient approximation for the exchange-correlation energy are reported, making them attractive for cluster-assembled materials.
Abstract: We report metal-encapsulated caged clusters of silicon from ab initio pseudopotential plane wave calculations using generalized gradient approximation for the exchange-correlation energy. Depending upon the size of the metal ( $M$) atom, silicon forms fullerenelike $M@{\mathrm{Si}}_{16}$, $M\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\mathrm{Hf}$, Zr, and cubic $M@{\mathrm{Si}}_{14}$, $M\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\mathrm{Fe}$, Ru, Os, caged clusters. The embedding energy of the $M$ atom is $\ensuremath{\approx}12\mathrm{eV}$ due to strong $M\ensuremath{-}\mathrm{Si}$ interactions that make the cage compact. Bonding in these clusters is predominantly covalent and the highest-occupied--lowest-unoccupied molecular orbital gap is $\ensuremath{\approx}1.5\mathrm{eV}$. However, an exceptionally large gap (2.35 eV) is obtained for $\mathrm{Ti}@{\mathrm{Si}}_{16}$ Frank-Kasper polyhedron. Interaction between these clusters is weak, making them attractive for cluster-assembled materials.
333 citations
TL;DR: In this paper, the corrections to neutrino mixing parameters in the presence of matter of constant density are calculated systematically as series expansions in terms of the mass hierarchy, and the parameter mapping obtained is then used to find simple, but nevertheless accurate formulas for oscillation probabilities in matter including $\mathrm{CP}$ effects.
Abstract: The corrections to neutrino mixing parameters in the presence of matter of constant density are calculated systematically as series expansions in terms of the mass hierarchy $\ensuremath{\Delta}{m}_{21}^{2}/\ensuremath{\Delta}{m}_{31}^{2}.$ The parameter mapping obtained is then used to find simple, but nevertheless accurate formulas for oscillation probabilities in matter including $\mathrm{CP}$ effects. Expressions with one to one correspondence to the vacuum case are derived, which are valid for neutrino energies above the solar resonance energy. Two applications are given to show that these results are a useful and powerful tool for analytical studies of neutrino beams passing through the Earth mantle or core: First, the ``disentanglement problem'' of matter and $\mathrm{CP}$ effects in $\mathrm{CP}$ asymmetry is discussed and second, estimations of the statistical sensitivity to the $\mathrm{CP}$ terms of the oscillation probabilities in neutrino factory experiments are presented.
292 citations
TL;DR: In this article, the complex dielectric tensor components of four chalcopyrite semiconductors in an optical energy range (1.4-5.2 eV) were determined at room temperature by spectroscopic ellipsometry.
Abstract: We report on the complex dielectric tensor components of four chalcopyrite semiconductors in an optical energy range (1.4--5.2 eV, from 0.9 eV for ${\mathrm{CuInSe}}_{2})$ determined at room temperature by spectroscopic ellipsometry. Our results were obtained on single crystals of ${\mathrm{CuInSe}}_{2},$ ${\mathrm{CuGaSe}}_{2},$ ${\mathrm{CuInS}}_{2},$ and ${\mathrm{CuGaS}}_{2}.$ Values of refractive indices n, extinction coefficients k, and normal-incidence reflectivity R in the two different polarizations are given and compared with earlier data where available. We analyze in detail the structures of the dielectric function observed in the studied energy region. Critical-point parameters of electronic transitions are obtained from a fitting of numerically calculated second-derivative spectra ${d}^{2}\ensuremath{\varepsilon}(\ensuremath{\omega})/d{\ensuremath{\omega}}^{2}.$ Experimental energies and polarizations are discussed on the basis of published band-structure calculations.
289 citations
Ruhr University Bochum1, Kyushu University2, Oak Ridge National Laboratory3, Niigata University4, University of Pisa5, Los Alamos National Laboratory6, Argonne National Laboratory7, Lawrence Livermore National Laboratory8, Academy of Sciences of the Czech Republic9, University of Arizona10, Hebrew University of Jerusalem11, University of Trento12
TL;DR: In this article, the energy eigenvalue results and some wave function properties using the realistic four-nucleon interaction were compared, showing the high accuracy of their present ability to calculate the four-Nucleon bound state.
Abstract: In the past, several efficient methods have been developed to solve the Schr\"odinger equation for four-nucleon bound states accurately. These are the Faddeev-Yakubovsky, the coupled-rearrangement-channel Gaussian-basis variational, the stochastic variational, the hyperspherical variational, the Green's function Monte Carlo, the no-core shell model, and the effective interaction hyperspherical harmonic methods. In this article we compare the energy eigenvalue results and some wave function properties using the realistic $\mathrm{AV}{8}^{\ensuremath{'}}$ NN interaction. The results of all schemes agree very well showing the high accuracy of our present ability to calculate the four-nucleon bound state.
269 citations
TL;DR: In this paper, high-resolution photoemission is used to study the electronic structure of the cuprate superconductor as a function of hole doping and temperature, and a kink observed in the band dispersion in the nodal line in the superconducting state is associated with coupling to a resonant mode observed in neutron scattering.
Abstract: High-resolution photoemission is used to study the electronic structure of the cuprate superconductor, ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$, as a function of hole doping and temperature. A kink observed in the band dispersion in the nodal line in the superconducting state is associated with coupling to a resonant mode observed in neutron scattering. From the measured real part of the self-energy it is possible to extract a coupling constant which is largest in the underdoped regime, then decreasing continuously into the overdoped regime.
TL;DR: This Letter presents a wavelet technique for extracting coherent vortices from three-dimensional turbulent flows, which is applied to a homogeneous isotropic turbulent flow at resolution N = 256(3).
Abstract: This Letter presents a wavelet technique for extracting coherent vortices from three-dimensional turbulent flows, which is applied to a homogeneous isotropic turbulent flow at resolution ${N\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}256}^{3}$. The coherent flow is reconstructed from only $3%N$ wavelet coefficients that retain the vortex tubes, and $98.9%$ of the energy with the same ${k}^{\ensuremath{-}5/3}$ spectrum as the total flow. In contrast, the remaining $97%N$ wavelet coefficients correspond to the incoherent flow which is structureless, decorrelated, and whose effect can therefore be modeled statistically.
TL;DR: The experimental results are consistent with an electrostatic accelerating mechanism that requires an ultrashort scale length at the back of the target.
Abstract: The influence of the plasma density scale length on the production of MeV protons from thin foil targets irradiated at $I{\ensuremath{\lambda}}^{2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}5\ifmmode\times\else\texttimes\fi{}{10}^{19}\phantom{\rule{0ex}{0ex}}\mathrm{W}\mathrm{cm}{}^{\ensuremath{-}2}$ has been studied. With an unperturbed foil, protons with energy $g20\phantom{\rule{0ex}{0ex}}\mathrm{MeV}$ were formed in an exponential energy spectrum with a temperature of $2.5\ifmmode\pm\else\textpm\fi{}0.3\mathrm{MeV}$. When a plasma with a scale length of $100\ensuremath{\mu}\mathrm{m}$ was preformed on the back of the foil, the maximum proton energy was reduced to $l5\phantom{\rule{0ex}{0ex}}\mathrm{MeV}$ and the beam was essentially destroyed. The experimental results are consistent with an electrostatic accelerating mechanism that requires an ultrashort scale length at the back of the target.
TL;DR: In this article, the vibrational spectrum of AlN grown on Si(111) was studied and the Raman backscattering along the growth c axis and from a cleaved surface perpendicular to the wurtzite c direction was used to determine the phonon energies.
Abstract: We study the vibrational spectrum of AlN grown on Si(111). The AlN was deposited using gas-source molecular beam epitaxy. Raman backscattering along the growth c axis and from a cleaved surface perpendicular to the wurtzite c direction allows us to determine the ${E}_{2}^{1},$ ${E}_{2}^{2},$ ${A}_{1}(\mathrm{TO}),$ ${A}_{1}(\mathrm{LO}),$ and ${E}_{1}(\mathrm{TO})$ phonon energies. For a 0.8-\ensuremath{\mu}m-thick AlN layer under a biaxial tensile stress of 0.6 GPa, these are 249.0, 653.6, 607.3, 884.5, and 666.5 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, respectively. By combining the Raman and x-ray diffraction studies, the Raman stress factor of AlN is found to be $\ensuremath{-}6.3\ifmmode\pm\else\textpm\fi{}1.4{\mathrm{cm}}^{\ensuremath{-}1}/\mathrm{GPa}$ for the ${E}_{2}^{2}$ phonon. This factor depends on published values of the elastic constants of AlN, as discussed in the text. The zero-stress ${E}_{2}^{2}$ energy is determined to be $657.4\ifmmode\pm\else\textpm\fi{}0.2{\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}.$ Fourier-transform infrared reflectance and absorption techniques allow us to measure the ${E}_{1}(\mathrm{TO})$ and ${A}_{1}(\mathrm{LO})$ phonon energies. The film thickness (from 0.06 to 1.0 \ensuremath{\mu}m) results in great differences in the reflectance spectra, which are well described by a model using damped Lorentzian oscillators taking into account the crystal anisotropy and the film thickness.
TL;DR: Two-pion correlation functions in Au+Au collisions at s{sub NN} =130 GeV have been measured by the STAR (solenoidal tracker at RHIC) detector as mentioned in this paper.
Abstract: Two-pion correlation functions in Au+Au collisions at s{sub NN}=130 GeV have been measured by the STAR (solenoidal tracker at RHIC) detector. The source size extracted by fitting the correlations grows with event multiplicity and decreases with transverse momentum. Anomalously large sizes or emission durations, which have been suggested as signals of quark-gluon plasma formation and rehadronization, are not observed. The Hanbury Brown--Twiss parameters display a weak energy dependence over a broad range in s{sub NN}.
TL;DR: In contrast to previous attempts to find an alternative mechanism for a small m(nu), it is shown how a solution may be obtained in a simple extension of the standard model, without using any ingredient supplied by the large extra dimensions.
Abstract: If there is no new physics beyond the TeV energy scale, such as in a theory of large extra dimensions, the smallness of the seesaw neutrino mass, i.e., ${m}_{\ensuremath{
u}}{\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}m}_{D}^{2}/{m}_{N}$, cannot be explained by a very large ${m}_{N}$. In contrast to previous attempts to find an alternative mechanism for a small ${m}_{\ensuremath{
u}}$, I show how a solution may be obtained in a simple extension of the standard model, without using any ingredient supplied by the large extra dimensions. It is also experimentally testable at future accelerators.
TL;DR: In this article, a scaling field has been shown to not support the presence of such a field, providing the strong constraint that the energy density in quintessence could be a significant fraction of the overall energy even in the early universe while the cosmological constant will be dynamically relevant only at late times.
Abstract: In the past years ``quintessence'' models have been considered which can produce the accelerated expansion in the universe suggested by recent astronomical observations. One of the key differences between quintessence and a cosmological constant is that the energy density in quintessence, ${\ensuremath{\Omega}}_{\ensuremath{\varphi}},$ could be a significant fraction of the overall energy even in the early universe, while the cosmological constant will be dynamically relevant only at late times. We use standard big bang nucleosynthesis and the observed abundances of primordial nuclides to put constraints on ${\ensuremath{\Omega}}_{\ensuremath{\varphi}}$ at temperatures near $T\ensuremath{\sim}1 \mathrm{MeV}.$ We point out that current experimental data do not support the presence of such a field, providing the strong constraint ${\ensuremath{\Omega}}_{\ensuremath{\varphi}}$ $(\mathrm{MeV})l0.045$ at $2\ensuremath{\sigma}$ C.L. and strengthening previous results. We also consider the effect a scaling field has on cosmic microwave background (CMB) anisotropies using the recent data from BOOMERANG and DASI combined with SNIa data, providing the CMB constraint ${\ensuremath{\Omega}}_{\ensuremath{\varphi}}l~0.39$ at $2\ensuremath{\sigma}$ during the radiation dominated epoch.
TL;DR: In this article, a detailed scan over parameter space was performed to find solutions which satisfy the current experimental limits on the electric dipole moments of the electron, neutron and ${}^{199}{Hg}$ atom, exploring the allowed configurations of phases and masses.
Abstract: We reexamine large CP-violating phases in the general minimal supersymmetric standard model, as well as more restricted models. We perform a detailed scan over parameter space to find solutions which satisfy the current experimental limits on the electric dipole moments of the electron, neutron and ${}^{199}\mathrm{Hg}$ atom, exploring the allowed configurations of phases and masses, and we attempt to quantify the level of tuning of the parameters necessary to populate the regions of cancellations. We then consider the measurement of CP-violating phases at a future linear collider. We find that measurements of chargino and neutralino masses and production cross sections allow for a determination of ${\ensuremath{\varphi}}_{1}$ (the phase of ${M}_{1})$ to a precision of $\ensuremath{\pi}/30,$ while the EDM constraints require that ${\ensuremath{\theta}}_{\ensuremath{\mu}}$ be too small to be measured. Using the EDM constraints we find that the CP-even model parameters and the phase ${\ensuremath{\varphi}}_{1}$ can be determined at a linear collider with $400\mathrm{GeV}$ c.m. energy. As long as some information on the size of $|\ensuremath{\mu}|$ is included in the observables, a measurement of ${\ensuremath{\varphi}}_{1}$ is guaranteed for ${\ensuremath{\varphi}}_{1}g\ensuremath{\pi}/10.$ To unambiguously identify $\mathrm{CP}$ violation, we construct CP-odd kinematical variables at a linear collider. However, the $\mathrm{CP}$ asymmetries are rather small, typically about 0.1--1.5 %, and it will be challenging to experimentally observe the predicted asymmetries.
05 Sep 2001
TL;DR: In this paper, the design of a nonlinear controller for the double inverted pendulum (DIP) system consisting of two inverted pendulums mounted on a cart is considered.
Abstract: The paper considers the design of a nonlinear controller for the double inverted pendulum (DIP), a system consisting of two inverted pendulums mounted on a cart. The swingup controller bringing the pendulums from any initial position to the unstable up-up position is designed based on passivity properties and energy shaping. While the swingup controller drives the DIP into a region of attraction around the unstable up-up position, the balance controller designed on the basis of the linearized model stabilizes the DIP at the unstable equilibrium. The simulation results show the effectiveness of the proposed nonlinear design method for the DIP system.
TL;DR: In this article, a methodology for the assessment of the seismic energy demands imposed on structures is proposed, which is carried out through two consecutive phases inelastic design input energy spectra for systems with a prescribed displacement ductility ratio.
TL;DR: It is demonstrated that the relative entropy from information theory, Sigma(k)p( k) ln(p(k)/p(*)(k), has a natural role in the energetics of equilibrium and nonequilibrium conformational fluctuations of the single molecule.
Abstract: Using a one-dimensional macromolecule in aqueous solution as an illustration, we demonstrate that the relative entropy from information theory, ${\ensuremath{\sum}}_{k}{p}_{k}\mathrm{ln}{(p}_{k}{/p}_{k}^{*}),$ has a natural role in the energetics of equilibrium and nonequilibrium conformational fluctuations of the single molecule. It is identified as the free energy difference associated with a fluctuating density in equilibrium, and is associated with the distribution deviate from the equilibrium in nonequilibrium relaxation. This result can be generalized to any other isothermal macromolecular system using the mathematical theories of large deviations and Markov processes, and at the same time provides the well-known mathematical results with interesting physical interpretations.
TL;DR: In this article, the SKS spectrometer at the K6 beam line in the KEK 12-GeV Proton Synchrotron was used to obtain an energy resolution of 1.65 MeV (FWHM).
Abstract: Excitation energy spectra of ${}_{\mathrm{\ensuremath{\Lambda}}}^{89}\mathrm{Y},$ ${}_{\mathrm{\ensuremath{\Lambda}}}^{51}\mathrm{V},$ and ${}_{\mathrm{\ensuremath{\Lambda}}}^{12}\mathrm{C}$ have been measured via the $({\ensuremath{\pi}}^{+}{,K}^{+})$ reaction by using the SKS spectrometer at the K6 beam line in the KEK 12-GeV Proton Synchrotron. In the ${}_{\mathrm{\ensuremath{\Lambda}}}^{89}\mathrm{Y}$ spectrum, obtained with an energy resolution of 1.65 MeV (FWHM) and in the highest statistics so far, we have succeeded in clearly observing a characteristic fine structure in heavy \ensuremath{\Lambda} hypernuclear systems and precisely obtaining a series of \ensuremath{\Lambda} single-particle energies in the very wide excitation energy range of more than 20 MeV, for the first time. Also in the ${}_{\mathrm{\ensuremath{\Lambda}}}^{51}\mathrm{V}$ spectrum, a similar structure to that of ${}_{\mathrm{\ensuremath{\Lambda}}}^{89}\mathrm{Y}$ was observed. In the ${}_{\mathrm{\ensuremath{\Lambda}}}^{12}\mathrm{C}$ spectrum, new core-excited states were clearly resolved thanks to the best energy resolution of 1.45 MeV so far achieved by using the SKS spectrometer.
TL;DR: In this article, the first-principles molecular-dynamics method was used to study the interface structures of three crystalline phases of the Si(001) substrate: cristobalite, quartz, and tridymite.
Abstract: Interface structures of ${\mathrm{SiO}}_{2}/\mathrm{Si}(001)$ are studied by using the first-principles molecular-dynamics method. Three crystalline phases of the ${\mathrm{SiO}}_{2},$ cristobalite, quartz, and tridymite, are stacked on the Si(001) substrate and are fully relaxed. When the ${\mathrm{SiO}}_{2}$ layer is very thin (\ensuremath{\sim}7 \AA{}), the lowest-energy structure is the tridymite, followed by the quartz phase. As the ${\mathrm{SiO}}_{2}$ layer becomes thicker (\ensuremath{\sim}15 \AA{}), the quartz phase has lower energy than the tridymite phase. The cristobalite phase on Si(001) is unstable due to large lattice mismatch, and transforms into a different crystal structure. No defects appear at the interface after the successive bond breaking and rebonding, but the energy of the resulting structure is the highest irrespective of the thickness. Calculations of the local density of states show that the band-gap change occurs on the ${\mathrm{SiO}}_{2}$ side, resulting in an effective decrease of the oxide thickness by 2--5 \AA{}.
TL;DR: In this article, the authors used the coupled discretized continuum channels approach to calculate the angular distribution of the fragments and their energy distributions compared with those measured at several laboratory angles, revealing the importance of higher-order continuum state couplings for understanding of the measurements.
Abstract: We discuss calculations of three-body observables for the breakup of ${}^{8}\mathrm{B}$ on a ${}^{58}\mathrm{Ni}$ target at low energy using the coupled discretized continuum channels approach. Calculations of both the angular distribution of the ${}^{7}\mathrm{Be}$ fragments and their energy distributions are compared with those measured at several laboratory angles. In these observables there is interference between the breakup amplitudes from different spin-parity excitations of the projectile. The resulting angle and the energy distributions reveal the importance of the higher-order continuum state couplings for an understanding of the measurements.
Patent•
18 Dec 2001TL;DR: In this paper, a particle size distribution monitor is proposed for monitoring the particle size distributions of particles in a suspension under dynamic conditions. But the method is not suitable for the detection of particle sizes.
Abstract: A particle size distribution monitor, comprising: a transducer adapted to be a source of ultrasonic energy and positioned in contact with a suspension containing a percent by volume of particles in a liquid, the transducer transmitting ultrasonic energy through the suspension wherein the energy comprises a wideband pulse containing a range of frequency components; a transducer adapted to be a receiver of ultrasonic energy and positioned in contact with said suspension to receive said wideband range of ultrasonic energy which has passed through the suspension; a first means adapted to accept a signal from said receiver and make an instantaneous determination of the attenuation of the wideband ultrasonic energy in passing through the suspension. A method of monitoring the particle size distribution of particles in a suspension under dynamic conditions, comprising the steps of: transmitting a first pulse of ultrasonic energy containing a wideband range of frequency components through the suspension which attenuates the pulse; receiving the attenuated pulse after it has passed through the suspension; developing a first signal representative of the attenuated first pulse; digitizing the first signal with a high speed analog-to-digital converter to form a time domain signal; applying a Fourier transform to convert the time domain signal to an equivalent frequency domain signal, or spectrum, for each signal; converting the spectrum into dB to express the attenuation as a function of frequency.
TL;DR: The results indicate that at this RHIC energy, although the p-p pair production becomes important at midrapidity, a significant excess of baryons over antibaryons is still present.
Abstract: We report results on the ratio of mid-rapidity anti-proton to proton yields in Au+Au collisions at $\rts = 130$ GeV per nucleon pair as measured by the STAR experiment at RHIC. Within the rapidity and transverse momentum range of $|y|<0.5$ and 0.4 $
TL;DR: Vinokur et al. as discussed by the authors derived a different expression for the vortex pinning potential, which is valid for all defect sizes and describes its renormalization due to thermal fluctuations, and showed that natural linear defects in thin films form an analogous system to columnar tracks in irradiated samples.
Abstract: The behavior of the superconducting current density ${j}_{s}(B,T)$ and the dynamical relaxation rate $Q(B,T)$ of ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ thin films exhibits a number of features typical for strong pinning of vortices by growth induced linear defects. At low magnetic fields ${j}_{s}(B)$ and $Q(B)$ are constant up to a characteristic field ${B}^{*},$ that is directly proportional to the linear defect density ${n}_{\mathrm{disl}}.$ The pinning energy ${U}_{c}(B=0)\ensuremath{\approx}600\mathrm{K}$ can be explained by half-loop excitations determining the thermal activation of vortices at low magnetic fields. Extending the Bose glass theory [D. R. Nelson and V. M. Vinokur, Phys. Rev. B 48, 13 060 (1993)], we derive a different expression for the vortex pinning potential ${\ensuremath{\varepsilon}}_{r}(R),$ which is valid for all defect sizes and describes its renormalization due to thermal fluctuations. With this expression we explain the temperature dependence of the true critical current density ${j}_{c}(0,T)$ and of the pinning energy ${U}_{c}(0,T)$ at low magnetic fields. At high magnetic fields ${\ensuremath{\mu}}_{0}H\ensuremath{\gg}{B}^{*}$ the current density experiences a power law behavior ${j}_{s}(B)\ensuremath{\sim}{B}^{\ensuremath{\alpha}},$ with $\ensuremath{\alpha}\ensuremath{\approx}\ensuremath{-}0.58$ for films with low ${n}_{\mathrm{disl}}$ and $\ensuremath{\alpha}\ensuremath{\approx}\ensuremath{-}0.8$ to -1.1 for films with high ${n}_{\mathrm{disl}}.$ The pinning energy in this regime, ${U}_{c}(\mathrm{high}B)\ensuremath{\approx}60--200\mathrm{K}$ is independent of magnetic field, but depends on the dislocation density. This implies that vortex pinning is still largely determined by the linear defects, even when the vortex density is much larger than the linear defect density. Our results show that natural linear defects in thin films form an analogous system to columnar tracks in irradiated samples. There are, however, three essential differences: (i) typical matching fields are at least one order of magnitude smaller, (ii) linear defects are smaller than columnar tracks, and (iii) the distribution of natural linear defects is nonrandom, whereas columnar tracks are randomly distributed. Nevertheless the Bose glass theory, that has successfully described many properties of pinning by columnar tracks, can be applied also to thin films. A better understanding of pinning in thin films is thus useful to put the properties of irradiated samples in a broader perspective.
TL;DR: In this article, ordered quantum dot patterns are generated on GaSb and InSb surfaces due to a surface instability induced by ion sputtering at normal incidence, and the characteristic length of the generated patterns scales with the square root of the ion energy over the energy range of 75\char21{}1800 eV.
Abstract: Ordered quantum dot patterns are generated on GaSb and InSb surfaces due to a surface instability induced by ${\mathrm{Ar}}^{+}$-ion sputtering at normal incidence. The characteristic length of the generated patterns scales with the square root of the ion energy over the energy range of 75\char21{}1800 eV. This energy dependence is compared to the solutions of the isotropic Kuramoto-Sivashinsky equation and allows the determination of the lateral width of the energy distribution deposited by the incident ions in the very-low-energy range. We show that the observed energy dependence is in agreement with the linear continuum theory under the assumption that the dominant smoothing process is due to effective ion-induced diffusion without mass transport on the surface.
TL;DR: In this paper, the authors performed a systematic analysis of the nonionizing energy losses (NIEL) for electrons, protons, neutrons and γ-rays in Si and GaAs for a wide range of particle energies.
TL;DR: In this article, the Gruneisen parameters of phonon modes as a function of their energy, averaged over the whole Brillouin zone, were determined by means of high pressure inelastic neutron scattering measurements.
Abstract: Isotropic negative thermal expansion has been reported in cubic ${\mathrm{ZrW}}_{2}{\mathrm{O}}_{8}$ over a wide range of temperatures (0--1050 K). Here we report the direct experimental determination of the Gr\"uneisen parameters of phonon modes as a function of their energy, averaged over the whole Brillouin zone, by means of high pressure inelastic neutron scattering measurements. We observe a pronounced softening of the phonon spectrum at $P\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.7\mathrm{kbar}$ compared to that at ambient pressure by about 0.1--0.2 meV for phonons of energy below 8 meV. This unusual phonon softening on compression, corresponding to large negative Gr\"uneisen parameters, is able to account for the observed large negative thermal expansion.