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Showing papers on "Energy (signal processing) published in 1998"


Journal ArticleDOI
TL;DR: In this paper, the expectation values of an operator similar to the Wilson loop in the large $N$ limit of field theories were calculated for supersymmetric Yang-Mills theory.
Abstract: We propose a method to calculate the expectation values of an operator similar to the Wilson loop in the large $N$ limit of field theories. We consider $N\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}4$ $(3+1)$-dimensional supersymmetric Yang-Mills theory. The prescription involves calculating the area of a fundamental string world sheet in certain supergravity backgrounds. We also consider the case of coincident $M$-theory five-branes where one is led to calculating the area of $M$-theory two-branes. We briefly discuss the computation for $(2+1)$-dimensional supersymmetric Yang-Mills theory with 16 supercharges which is nonconformal. In all of these cases, we calculate the energy of a quark-antiquark pair.

2,117 citations


Journal ArticleDOI
TL;DR: In this article, a model-independent upper bound was established for neutrino production by either AGN jets or GRBs, which is consistent with our predictions from GRB models.
Abstract: We show that cosmic-ray observations set a model-independent upper bound of ${E}_{\ensuremath{ u}}^{2}{\ensuremath{\Phi}}_{\ensuremath{ u}}l2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}{\mathrm{G}\mathrm{e}\mathrm{V}/\mathrm{c}\mathrm{m}}^{2}\mathrm{}\mathrm{s}\mathrm{}\mathrm{sr}$ to the intensity of high-energy neutrinos produced by photo-meson (or $p\ensuremath{-}p)$ interactions in sources of size not much larger than the proton photo-meson (or $p\ensuremath{-}p)$ mean-free-path. This bound applies, in particular, to neutrino production by either AGN jets or GRBs. The upper limit is two orders of magnitude below the intensity predicted in some popular AGN jet models and therefore contradicts the theory that the cosmic gamma-ray background is due to photo-pion interactions in AGN jets. The upper bound is consistent with our predictions from GRB models. The predicted intensity from GRBs is ${E}^{2}dN/dE\ensuremath{\sim}0.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}{\mathrm{G}\mathrm{e}\mathrm{V}/\mathrm{c}\mathrm{m}}^{2}\mathrm{}\mathrm{s}\mathrm{}\mathrm{sr}$ for ${10}^{14}\mathrm{eV}lEl{10}^{16}\mathrm{eV};$ we also derive the expected intensity at higher energy.

849 citations


Journal ArticleDOI
TL;DR: In this article, a weakly coupled scalar field with a simple exponential potential was proposed to model the early universe and the evolution of the structure formation in a cosmological model of the universe, which is consistent with large angle cosmic microwave background anisotropies.
Abstract: A weakly coupled scalar field \ensuremath{\Phi} with a simple exponential potential ${V=M}_{P}^{4}\mathrm{exp}(\ensuremath{-}\ensuremath{\lambda}\ensuremath{\Phi}{/M}_{P})$ where ${M}_{P}$ is the reduced Planck mass, and $\ensuremath{\lambda}g2,$ has an attractor solution in a radiation or matter dominated universe in which it mimics the scaling of the dominant component, contributing a fixed fraction ${\ensuremath{\Omega}}_{\ensuremath{\varphi}}$ (determined by \ensuremath{\lambda}) to the energy density. Such fields arise generically in particle physics theories involving compactified dimensions, with values of \ensuremath{\lambda} which give a cosmologically relevant ${\ensuremath{\Omega}}_{\ensuremath{\varphi}}.$ For natural initial conditions on the scalar field in the early universe the attractor solution is established long before the epoch of structure formation, and in contrast with the solutions used in other scalar field cosmologies, it is one which does not involve an energy scale for the scalar field characteristic of late times. We study in some detail the evolution of matter and radiation perturbations in a standard inflation-motivated $\ensuremath{\Omega}=1$ dark-matter dominated cosmology with this extra field. Using a full Einstein-Boltzmann calculation we compare observable quantities with current data. We find that, for ${\ensuremath{\Omega}}_{\ensuremath{\varphi}}\ensuremath{\simeq}0.08\char21{}0.12,$ these models are consistent with large angle cosmic microwave background anisotropies as detected by COBE, the linear mass variance as compiled from galaxy surveys, big bang nucleosynthesis, the abundance of rich clusters and constraints from the Lyman-\ensuremath{\alpha} systems at high redshift. Given the simplicity of the model, its theoretical motivation and its success in matching observations, we argue that it should be taken on a par with other currently viable models of structure formation.

776 citations


Journal ArticleDOI
TL;DR: Bounds on information processing rates implied by the bound on the speed of dynamical evolution are discussed, which suggests that adding 1 J of energy to a given computer can never increase its processing rate by more than about 3 × 1033 operations per second.

700 citations


Journal ArticleDOI
Y. Fukuda1, T. Hayakawa1, E. Ichihara1, Kunio Inoue1, K. Ishihara1, H. Ishino1, Yoshitaka Itow1, Takaaki Kajita1, J. Kameda1, S. Kasuga1, K. Kobayashi1, Yohei Kobayashi1, Yusuke Koshio1, K. Martens1, M. Miura1, Masayuki Nakahata1, S. Nakayama1, A. Okada1, M. Oketa1, Ko Okumura1, M. Ota1, N. Sakurai1, Masato Shiozawa1, Yasunari Suzuki1, Y. Takeuchi1, Y. Totsuka1, Shinya Yamada1, M. Earl2, Alec Habig2, J. T. Hong2, E. Kearns2, S. B. Kim2, S. B. Kim3, M. Masuzawa2, M. D. Messier2, Kate Scholberg2, J. L. Stone2, L. R. Sulak2, C. W. Walter2, M. Goldhaber4, T. Barszczak5, W. Gajewski5, P. G. Halverson5, J. Hsu5, W. R. Kropp5, L. R. Price5, Frederick Reines5, H. W. Sobel5, Mark R. Vagins5, K. S. Ganezer6, W. E. Keig6, R. W. Ellsworth7, S. Tasaka8, J. W. Flanagan9, A. Kibayashi9, John G. Learned9, S. Matsuno9, V. J. Stenger9, D. Takemori9, T. Ishii, Junichi Kanzaki, T. Kobayashi, K. Nakamura, K. Nishikawa, Yuichi Oyama, A. Sakai, Makoto Sakuda, Osamu Sasaki, S. Echigo10, M. Kohama10, A. T. Suzuki10, Todd Haines11, Todd Haines5, E. Blaufuss12, R. Sanford12, R. Svoboda12, M. L. Chen13, Z. Conner13, Z. Conner14, J. A. Goodman13, G. W. Sullivan13, Masaki Mori1, Masaki Mori15, J. Hill16, C. K. Jung16, C. Mauger16, C. McGrew16, E. Sharkey16, B. Viren16, C. Yanagisawa16, W. Doki17, T. Ishizuka18, T. Ishizuka17, Y. Kitaguchi17, H. Koga17, Kazumasa Miyano17, H. Okazawa17, C. Saji17, M. Takahata17, A. Kusano19, Y. Nagashima19, M. Takita19, T. Yamaguchi19, Minoru Yoshida19, M. Etoh20, K. Fujita20, Akira Hasegawa20, Takehisa Hasegawa20, S. Hatakeyama20, T. Iwamoto20, T. Kinebuchi20, M. Koga20, T. Maruyama20, Hiroshi Ogawa20, A. Suzuki20, F. Tsushima20, Masatoshi Koshiba1, M. Nemoto21, Kyoshi Nishijima21, T. Futagami22, Y. Hayato22, Y. Kanaya22, K. Kaneyuki22, Y. Watanabe22, D. Kielczewska23, D. Kielczewska5, R. A. Doyle24, J. S. George24, A. L. Stachyra24, L. Wai24, J. Wilkes24, K. K. Young24 
TL;DR: The first results of the solar neutrino flux measurement from Super-Kamiokande are presented in this article, where the results are obtained from data taken between 31 May 1996, and 23 June 1997.
Abstract: The first results of the solar neutrino flux measurement from Super-Kamiokande are presented. The results shown here are obtained from data taken between 31 May 1996, and 23 June 1997. Using our measurement of recoil electrons with energies above 6.5 MeV, we infer the total flux of ${}^{8}\mathrm{B}$ solar neutrinos to be $2.42\ifmmode\pm\else\textpm\fi{}0.06(\mathrm{stat}{)}_{\ensuremath{-}0.07}^{+0.10}(\mathrm{syst})\ifmmode\times\else\texttimes\fi{}{10}^{6}\mathrm{cm}{}^{\ensuremath{-}2}{\mathrm{s}}^{\ensuremath{-}1}$. This result is consistent with the Kamiokande measurement and is 36% of the flux predicted by the BP95 solar model. The flux is also measured in 1.5 month subsets and shown to be consistent with a constant rate.

677 citations


Journal ArticleDOI
TL;DR: In this article, the Akeno giant air shower array (AAGA) data set was used to investigate the spectral properties of the cosmic-ray energy spectrum above the 2.7 K cutoff.
Abstract: The cosmic-ray energy spectrum above ${10}^{18.5}\mathrm{eV}$ is reported using the updated data set of the Akeno Giant Air Shower Array from February 1990 to October 1997. The energy spectrum extends beyond ${10}^{20}\mathrm{eV}$ and the energy gap between the highest energy event and the others is being filled up with recently observed events. The spectral shape suggests the absence of the 2.7 K cutoff in the energy spectrum or a possible presence of a new component beyond the 2.7 K cutoff.

640 citations


Journal ArticleDOI
TL;DR: A quasi-analytical experimental analysis is described in this paper to quantify the tradeoff between energy capture and diversity level in a RAKE receiver using measured received waveforms obtained from ultrawide bandwidth signal propagation experiments.
Abstract: A quasi-analytical experimental analysis is described in this paper to quantify the tradeoff between energy capture and diversity level in a RAKE receiver using measured received waveforms obtained from ultrawide bandwidth signal propagation experiments.

551 citations


Journal ArticleDOI
TL;DR: MDW velocity measurements down to the so called creep regime show that the average energy barrier scales as $(1/H{)}^{\ensuremath{\mu}phantom}\phantom{\rule{0ex}{0ex}}=\phantom¬0ex}2/3$.
Abstract: We have studied the motion of a magnetic domain wall (MDW) driven by a magnetic field H in a 2D ultrathin Pt/Co/Pt film showing perpendicular anisotropy and quenched disorder. MDW velocity measurements down to the so called creep regime show that the average energy barrier scales as $(1/H{)}^{\ensuremath{\mu}}$ with $\ensuremath{\mu}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.24\ifmmode\pm\else\textpm\fi{}0.04$ and that the correlation function along a MDW is governed by a wandering exponent $\ensuremath{\zeta}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.69\ifmmode\pm\else\textpm\fi{}0.07$, in very good agreement with theories giving $\ensuremath{\mu}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.25$ and $\ensuremath{\zeta}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2/3$. This is the first direct measurement of the creep regime for a moving interface in a disordered medium.

502 citations


Journal ArticleDOI
TL;DR: In this paper, a magnetically tunable Feshbach resonance was found for laser-cooled atoms with Zeeman-resolved photoassociation spectroscopy, and this resonance tunes to zero energy at a magnetic field of $164.7
Abstract: We probe $s$-wave collisions of laser-cooled ${}^{85}\mathrm{Rb}({f\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2,m}_{f}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}2)$ atoms with Zeeman-resolved photoassociation spectroscopy. We observe that these collisions exhibit a magnetically tunable Feshbach resonance, and determine that this resonance tunes to zero energy at a magnetic field of $164\ifmmode\pm\else\textpm\fi{}7\mathrm{G}$. This result indicates that the self-interaction energy of an ${}^{85}\mathrm{Rb}$ Bose-Einstein condensate can be magnetically tuned. We also demonstrate that Zeeman-resolved photoassociation spectroscopy provides a useful new tool for the study of ultracold atomic collisions.

424 citations


Journal ArticleDOI
TL;DR: In this article, the authors used the density matrix renormalization group to study the 2D 2D J model at a hole doping of $x\phantom{\rule{0ex}{0ex}}= \phantom{1}{8}$ on clusters as large as $19.
Abstract: Using the density matrix renormalization group, we study the 2D $t\ensuremath{-}J$ model at a hole doping of $x\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\frac{1}{8}$ on clusters as large as $19\ifmmode\times\else\texttimes\fi{}8$. We find a striped phase consistent with recent neutron scattering experiments. We find that bond-centered and site-centered stripes have nearly the same energy, suggesting that in the absence of pinning effects the domain walls can fluctuate.

351 citations


Journal ArticleDOI
TL;DR: The lowest energy structures of nanoclusters were obtained by unconstrained dynamical and genetic-symbiotic optimization methods, using a Gupta $n$-body potential.
Abstract: The lowest energy structures of ${\mathrm{Au}}_{n}$ ( $n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}38,55,75$) nanoclusters are obtained by unconstrained dynamical and genetic-symbiotic optimization methods, using a Gupta $n$-body potential. A set of amorphous structures, nearly degenerate in energy, are found as the most stable configurations. Some crystalline or quasicrystalline isomers are also minima of the cluster potential energy surface with similar energy. First principles calculations using density functional theory confirm these results and give different electronic properties for the ordered and disordered gold cluster isomers.

Journal ArticleDOI
TL;DR: In this article, the vibrational OH stretch spectra have been measured for size-selected pure water clusters in the size range $n\phantom{\rule{0ex}{0ex}} = \phantom{ 0ex}{ 0ex}}8--10$ and it was shown that the spectra originate from a small number of microcrystalline structures based on the cubic octamer.
Abstract: The vibrational OH stretch spectra have been measured for size-selected pure water clusters $({\mathrm{H}}_{2}\mathrm{O}{)}_{n}$, in the size range $n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}8--10$. Comparison between experiment and calculations suggests that the spectra originate from a small number of ``microcrystalline'' structures, based on the cubic octamer. The $n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}8$ spectra are caused by two isomers of ${D}_{2d}$ and ${S}_{4}$ symmetry. The proposed lowest energy nonamer and decamer structures are derived from the octamer by insertion of one and two two-coordinated molecules, respectively, into the cube edges.

Journal ArticleDOI
TL;DR: In this article, a detailed investigation on the excitation and deexcitation processes of Er in Si is reported, in particular, Er pumping through electron-hole pair recombination and Er de-excitation through Auger processes transferring energy to either free or bound electrons and holes.
Abstract: A detailed investigation on the excitation and deexcitation processes of ${\mathrm{Er}}^{3+}$ in Si is reported. In particular, we explored Er pumping through electron-hole pair recombination and Er deexcitation through Auger processes transferring energy to either free or bound electrons and holes. Since Er donor behavior would result in a free-carrier concentration varying along its profile, experiments have been performed by embedding the whole Er profile within previously prepared $n$-doped or $p$-doped regions. Multiple P (B) implants were performed in $n$-type ($p$-type) Czochralski Si samples in order to realize uniform dopant concentrations from $4\ifmmode\times\else\texttimes\fi{}{10}^{16}$ to $1.2\ifmmode\times\else\texttimes\fi{}{10}^{18}/{\mathrm{cm}}^{3}$ at depths between 0.5 and 2.5 \ensuremath{\mu}m below the surface. These samples have been subsequently implanted with 4 MeV $3.3\ifmmode\times\else\texttimes\fi{}{10}^{13}{\mathrm{E}\mathrm{r}/\mathrm{c}\mathrm{m}}^{2}$ and annealed at 900 \ifmmode^\circ\else\textdegree\fi{}C for 30 min. Free electrons or holes concentrations in the region where Er sits were measured by spreading resistance profiling. It has been found that the release of electrons or holes from shallow donors and acceptors, occurring at temperatures between 15 and 100 K, produces a strong reduction of both time decay and luminescence intensity at 1.54 \ensuremath{\mu}m. These phenomena are produced by Auger deexcitation of the ${\mathrm{Er}}^{3+}$ intra-$4f$ electrons with energy transfer to free carriers. The Auger coefficient of this process has been measured to be ${C}_{A}\ensuremath{\sim}5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}{\mathrm{cm}}^{3}{\mathrm{}\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$ for both free electrons and free holes. Moreover, at 15 K (when the free carriers are frozen and the donor and acceptor levels occupied) the ${\mathrm{Er}}^{3+}$ time decay has been found to depend on the P (or B) concentrations. This is attributed to an impurity Auger deexcitation to electrons (or holes) bound to shallow donors (acceptors): the efficiency of this process has been determined to be two orders of magnitude smaller with respect to the Auger deexcitation with free carriers. Furthermore, at temperatures above 100 K a nonradiative back-transfer decay process, characterized by an activation energy of 0.15 eV, is seen to set in for both $p$-type and $n$-type samples. This suggests that the back-transfer process, which severely limits the high-temperature luminescence efficiency, is always completed by a thermalization of an electron trapped at an Er-related level to the conduction band. Finally, by analysis of the pump power dependence of time decay and luminescence yield at 15 K, we have found that excitation of Er through the recombination of an electron-hole pair is a very efficient process, characterized by an effective cross section of $3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}{\mathrm{cm}}^{2}$ and able to provide an internal quantum efficiency as high as 10% at low temperatures (15 K) and pump powers (below 1 mW). This efficiency is significantly reduced when, at higher temperatures and/or high pump powers, strong nonradiative decay processes set in. These phenomena are investigated in detail and their impact on device operation perspectives are analyzed and discussed.

Journal ArticleDOI
TL;DR: In this paper, the authors numerically studied an inertial linear chain model with ferromagnetic couplings and showed that the energy per particle in such a model scales with distance.
Abstract: Within a microcanonical scenario we numerically study an $N$-sized linear chain classical inertial $\mathrm{XY}$ model including ferromagnetic couplings which decrease with distance as ${r}^{\ensuremath{-}\ensuremath{\alpha}}$ ( $\ensuremath{\alpha}\ensuremath{\ge}0$). We show that for $N\ensuremath{\rightarrow}\ensuremath{\infty}$ (thermodynamic limit): (i) The energy per particle ${E}_{N}/N$ scales like ${N}^{*}\ensuremath{\equiv}({N}^{1\ensuremath{-}\ensuremath{\alpha}}\ensuremath{-}1)/(1\ensuremath{-}\ensuremath{\alpha})$; (ii) The properly scaled maximum Lyapunov exponent ${\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\lambda}}}_{N}^{\mathrm{max}}$ tends, for ${E}_{N}/({\mathrm{NN}}^{*})$ above a threshold, to zero for and only for $\ensuremath{\alpha}\ensuremath{\le}1$. These results are analogous to those observed in low-dimensional and in self-organized critical dissipative systems. This entire picture suggests a connection with the nonextensive thermostatistics recently introduced by one of us.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the phonon-mediated electron relaxation in self-organized quantum dots and showed that the electron and hole relaxation time constants are 5.2 and 0.6 ps, respectively, consistent with a model of electrons scattering from holes which can relax rapidly via phonon emission.
Abstract: Carrier relaxation in self-organized ${\mathrm{In}}_{0.4}{\mathrm{Ga}}_{0.6}\mathrm{A}\mathrm{s}/\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}$ quantum dots is investigated by time-resolved differential transmission measurements. The dots have a base dimension of around 14 nm and a height of 7 nm, leading to an average energy separation of the ground and first excited electronic states much greater than the LO-phonon energy, so the phonon-mediated electron relaxation is expected to be slow. Our measurements indicate that, even at low carrier densities (less than one electron-hole pair per dot), the electron and hole relaxation time constants are 5.2 and 0.6 ps, respectively; this indicates a lack of any ``phonon bottleneck'' and is consistent with a model of electrons scattering from holes which can relax rapidly via phonon emission.

Journal ArticleDOI
TL;DR: In this article, the dynamics of excited carriers generated near a silicon surface were characterized on femtosecond time scales using the transient grating technique in the reflection configuration, and the lifetime for relaxation through phonon scattering at carrier densities below 1.4
Abstract: The dynamics of excited carriers generated near a silicon surface were characterized on femtosecond time scales using the transient grating technique in the reflection configuration. For electrons in the energy range $1.4\ifmmode\pm\else\textpm\fi{}0.6\mathrm{eV}$ above the conduction band edge and their corresponding holes, the lifetime for relaxation through phonon scattering at carrier densities below ${10}^{20}\phantom{\rule{0ex}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ was determined to be 240 fs. This relaxation time increased sharply for carrier densities higher than $5\ifmmode\times\else\texttimes\fi{}{10}^{20}\phantom{\rule{0ex}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$, providing the first direct evidence for charge screening of carrier-phonon scattering in Si.

Journal ArticleDOI
TL;DR: In this paper, the results obtained on nondeuterated samples provide the first direct measurement of the zero-field splitting in a large cluster nanomagnet, and a reliable and accurate determination of the composition of the cluster's spin wave functions and the spin-Hamiltonian parameters are deduced from the experimental observations, giving crucial information for the study of macroscopic quantum tunneling process.
Abstract: Neutron spectroscopy has been used to observe transitions between the energy levels for the 21 different orientations of the $S\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}10$ spin ground state of an octanuclear iron molecular cluster $({\mathrm{Fe}}_{8})$ exhibiting quantum tunneling of the magnetization. The results obtained on nondeuterated samples provide the first direct measurement of the zero-field splitting in a large cluster nanomagnet. A reliable and accurate determination of the composition of the cluster's spin wave functions and the spin-Hamiltonian parameters are deduced from the experimental observations, giving crucial information for the study of the macroscopic quantum tunneling process.

Journal ArticleDOI
TL;DR: In this article, the authors investigate the properties of a model of granular matter consisting of $N$ Brownian particles on a line, subject to inelastic mutual collisions, and display a genuine thermodynamic limit for the mean values of the energy, and the energy dissipation.
Abstract: We investigate the properties of a model of granular matter consisting of $N$ Brownian particles on a line, subject to inelastic mutual collisions. This model displays a genuine thermodynamic limit for the mean values of the energy, and the energy dissipation. When the typical relaxation time $\ensuremath{\tau}$ associated with the Brownian process is small compared with the mean collision time ${\ensuremath{\tau}}_{c}$ the spatial density is nearly homogeneous and the velocity probability distribution is Gaussian. In the opposite limit $\ensuremath{\tau}\ensuremath{\gg}{\ensuremath{\tau}}_{c}$ one has strong spatial clustering, with a fractal distribution of particles, and the velocity probability distribution strongly deviates from the Gaussian one.

Journal ArticleDOI
TL;DR: In this article, the authors performed measurements on forced and decaying 2D turbulence in flowing soap films and showed that the resulting turbulent steady state agrees with the ideas of an inverse energy cascade accompanied by a forward enstrophy cascade.
Abstract: We have performed measurements on forced and decaying 2D turbulence in flowing soap films. Unlike previous experiments, turbulence was excited by grids (arrays of cylinders) lining the walls of the flow channel. The resulting turbulent steady state agrees with the ideas of an inverse energy cascade accompanied by a forward enstrophy cascade. Energy spectra agree, respectively, with ${k}^{\ensuremath{-}5/3}$ and ${k}^{\ensuremath{-}3}$ power laws. Downstream from the forcing section of the channel, the turbulence decays freely, and the energy spectrum scales only as ${k}^{\ensuremath{-}3}$. Our observations unite the results of several theories, and a number of simulations and experiments, into a single self-consistent set of measurements.

Patent
31 Jul 1998
TL;DR: In this article, the authors proposed a method to interface a device to a bus carrying power and a signal while simultaneously complying with bus-standard current draw limits, storing power for the device in an energy storage device located in the interface apparatus, and conditioning the bus signal as a function of the energy level of the signal received by the interface device from the bus and the level of energy measured in the energy storage devices in interface apparatus.
Abstract: The object of the invention is to interface a device to a bus carrying power and a signal while simultaneously complying with bus-standard current draw limits, storing power for the device in an energy storage device located in the interface apparatus, and conditioning the bus signal as a function of the energy level of the signal received by the interface device from the bus and the level of energy measured in the energy storage device in the interface apparatus. As shown in FIG. 29 , according to one aspect of the invention the interface apparatus ( 472 ) includes an input filter ( 480 ), a current limiter ( 482 ), a power converter ( 483 ), an energy storage device ( 484 ), a signal decoder/controller ( 486 ) and a signal conditioner ( 488 ). In operation, power flows from the bus through input filter ( 480 ) through the current limiter ( 482 ) to the power converter ( 483 ), which converts the power to a form suitable for charging the energy storage device ( 484 ). The output of the energy storage device provides power to the device. The bus signal is received by the signal decoder/controller ( 486 ), which performs any necessary decoding before sending the signal onto the signal conditioner ( 488 ). Signal decoder/controller ( 486 ) also is connected to and controls power converter 483 . Signal conditioner ( 488 ) measures the level of energy stored in energy storage device ( 484 ) then generates and conveys to the signal input of the device an output signal that is a function of the energy level of the bus signal and the measured level of energy in the energy storage device ( 484 ).

Patent
28 Aug 1998
TL;DR: In this paper, the authors describe a stand-alone device that responds to a signal by storing energy retrieved from the signal, and using the stored energy to generate another signal encoded with information provided by a data source (such as a memory or a sensor depending on the implementation) that is included in the device.
Abstract: A stand-alone device includes an integrated circuit (IC) die (optionally free of conventional IC packaging and bond pads) that responds to a signal by (1) storing energy retrieved from the signal, and (2) using the stored energy to generate another signal that is encoded with information provided by a data source (such as a memory or a sensor depending on the implementation) that is included in the device. The IC die includes a power supply, a signal transmitter, and optionally includes an antenna. During operation of one embodiment, the power supply receives from the antenna electrical energy extracted from a portion of a radio frequency signal incident on the IC die. The power supply stores the energy in an energy store over a period of time, and thereafter supplies at least a portion of the stored energy to the signal transmitter. The signal transmitter uses the energy to generate an electrical signal carrying the information from the data source, and on receipt of the electrical signal the antenna transmits another radio frequency signal containing the information. All parts of the IC die are coupled to each other by electrical conductors formed within the IC die. The device is used as a stand-alone component, i.e. free of connections to other electronic components. In one such case the IC die includes the antenna, and all interactions with the device are performed by wireless signals.

Journal ArticleDOI
TL;DR: In this article, a matching relation between the vector current in full QCD and in non-relativistic QCD was obtained, where the energy of the reaction is such that both the perturbative expansion in the strong coupling constant and the velocity of the heavy quarks can be used.
Abstract: We present $O({\ensuremath{\alpha}}_{s}^{2})$ corrections to the cross section for ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\gamma}}^{*}\ensuremath{\rightarrow}Q\overline{Q}$ close to threshold. We assume that the energy of the reaction is such that both the perturbative expansion in the strong coupling constant ${\ensuremath{\alpha}}_{s}$ and expansion in the velocity $\ensuremath{\beta}$ of the heavy quarks can be used. We obtain terms $O({\ensuremath{\alpha}}_{s}^{2}/{\ensuremath{\beta}}^{2},{\ensuremath{\alpha}}_{s}^{2}/\ensuremath{\beta},{\ensuremath{\alpha}}_{s}^{2})$ in the relative correction. We demonstrate how an expansion of Feynman diagrams in the threshold region is constructed. We obtain a matching relation between the vector current in full QCD and in nonrelativistic QCD.

Journal ArticleDOI
TL;DR: In this article, the decay of axion walls bounded by strings in axion models was studied and it was shown that the main decay mechanism is into barely relativistic axions, and that the contribution to the cosmological energy density of axions from wall decay is of the same order of magnitude as that from vacuum realignment, with however large uncertainties.
Abstract: We discuss the appearance at the QCD phase transition, and the subsequent decay, of axion walls bounded by strings in $N=1$ axion models. We argue on intuitive grounds that the main decay mechanism is into barely relativistic axions. We present numerical simulations of the decay process. In these simulations, the decay happens immediately, in a time scale of order the light travel time, and the average energy of the radiated axions is $〈{\ensuremath{\omega}}_{a}〉\ensuremath{\simeq}{7m}_{a}$ for ${v}_{a}{/m}_{a}\ensuremath{\simeq}500.$ $〈{\ensuremath{\omega}}_{a}〉$ is found to increase approximately linearly with $\mathrm{ln}{(v}_{a}{/m}_{a}).$ Extrapolation of this behavior yields $〈{\ensuremath{\omega}}_{a}〉\ensuremath{\sim}{60m}_{a}$ in axion models of interest. We find that the contribution to the cosmological energy density of axions from wall decay is of the same order of magnitude as that from vacuum realignment, with however large uncertainties. The velocity dispersion of axions from wall decay is found to be larger, by a factor ${10}^{3}$ or so, than that of axions from vacuum realignment and string decay. We discuss the implications of this for the formation and evolution of axion miniclusters and for the direct detection of axion dark matter on Earth. Finally we discuss the cosmology of axion models with $Ng1$ in which the domain wall problem is solved by introducing a small ${U}_{\mathrm{PQ}}$(1) breaking interaction. We find that in this case the walls decay into gravitational waves.

Journal ArticleDOI
TL;DR: In this paper, a measurement of the x-ray transition in trapped Li-like ions was made that resolved the $0.026\mathrm{eV}$ hyperfine splitting.
Abstract: A measurement of the ${2s}_{1/2}\ensuremath{-}{2p}_{3/2}$ x-ray transition in trapped Li-like ${\mathrm{Bi}}^{80+}$ ions was made that resolved the $0.820\ifmmode\pm\else\textpm\fi{}0.026\mathrm{eV}$ hyperfine splitting of the $({1s}^{2}2s{)}_{F\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}4,5}$ ground configuration, providing the first such measurement in a multielectron highly charged ion. The intensity ratio of the two components is shown to be a new electron density diagnostic. The statistically averaged $2788.139\ifmmode\pm\else\textpm\fi{}0.039\mathrm{eV}$ energy of the ${2s}_{1/2}\ensuremath{-}{2p}_{3/2}$ transition provides the most accurate test of QED in a high- $Z$ ion to date, demonstrating the need for including higher-order terms in the Lamb shift calculations.

Journal ArticleDOI
TL;DR: In this article, the Ni-like transient collisional excitation scheme was shown to achieve a gain of 35 cm{sup {minus}1} and a gL product of 12.5 on the 4d{r_arrow}4p J=0{r _arrow}1 transition for Ni-Like Pd at 147{Angstrom} with an 8mm line focus.
Abstract: We report experimental results of x-ray amplification of spontaneous emission in a Ni-like transient collisional excitation scheme. The Ni-like plasma formation, ionization, and collisional excitation requires irradiation of a slab target by two laser pulses: a formation beam with 5J energy of 800ps duration and a pump beam of 5J energy in 1.1ps. A gain of 35 cm{sup {minus}1} and a gL product of 12.5 are measured on the 4d{r_arrow}4p J=0{r_arrow}1 transition for Ni-like Pd at 147{Angstrom} with an 8mm line focus. The high efficiency of this scheme at {open_quotes}table-top{close_quotes} laser energies is a direct consequence of the nonstationary population inversion produced by the high intensity picosecond pulse. {copyright} {ital 1998} {ital The American Physical Society}

Journal ArticleDOI
TL;DR: In this paper, the largest Lyapunov exponent and the finite size effects of a system of $N$ fully coupled classical particles, which shows a second order phase transition were studied.
Abstract: We study the largest Lyapunov exponent $\ensuremath{\lambda}$ and the finite size effects of a system of $N$ fully coupled classical particles, which shows a second order phase transition. Slightly below the critical energy density ${U}_{c}$, $\ensuremath{\lambda}$ shows a peak which persists for very large $N$ values $(N\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}20000)$. We show, both numerically and analytically, that chaoticity is strongly related to kinetic energy fluctuations. In the limit of small energy, $\ensuremath{\lambda}$ goes to zero with an $N$-independent power law: $\ensuremath{\lambda}\ensuremath{\sim}\sqrt{U}$. In the continuum limit the system is integrable in the whole high temperature phase. More precisely, the behavior $\ensuremath{\lambda}\ensuremath{\sim}{N}^{\ensuremath{-}1/3}$ is found numerically for $Ug{U}_{c}$ and justified on the basis of a random matrix approximation.

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TL;DR: In this article, the band-gap energy of II-VI compound semiconductors was calculated using a modified dielectric theory and the calculated bandgap energies of MgS and MgSe were 4.62 and 3.67 eV.
Abstract: The band-gap energy of II-VI compound semiconductors was simply calculated using a modified dielectric theory. The calculated band-gap energies of MgS and MgSe were 4.62 and 3.67 eV. From the extrapolation of the band-gap energies of ${\mathrm{Zn}}_{1\ensuremath{-}x}{\mathrm{Mg}}_{x}\mathrm{Se}$ and ${\mathrm{Zn}}_{1\ensuremath{-}x}{\mathrm{Mg}}_{x}\mathrm{S},$ the band-gap energies of MgSe and MgS of zinc blende at room temperature were determined to be 3.59 and $4.45\ifmmode\pm\else\textpm\fi{}0.2\mathrm{eV},$ almost the same as the value calculated using the modified dielectric theory. The bowing parameter of the ${\mathrm{Zn}}_{1\ensuremath{-}x}{\mathrm{Mg}}_{x}\mathrm{Se}$ ternary alloy was experimentally obtained as 0 eV, which can be explained in terms of the modified dielectric theory. The lattice constant of the quaternary alloy ${\mathrm{Zn}}_{1\ensuremath{-}x}{\mathrm{Mg}}_{x}{\mathrm{S}}_{y}{\mathrm{Se}}_{1\ensuremath{-}y}$ can be expressed by Vegard's law [Z. Phys. 5, 17 (1921)]. The band-gap energy of ${\mathrm{Zn}}_{1\ensuremath{-}x}{\mathrm{Mg}}_{x}{\mathrm{S}}_{y}{\mathrm{Se}}_{1\ensuremath{-}y}$ can be expressed by the parabolic function of the composition considering the bowing parameter, where we use of 4.65, 3.59, 3.68, and 2.69 eV as the band-gap energies of MgS, MgSe, ZnS, and ZnSe, respectively.

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TL;DR: In this paper, the existence of post-inflationary phases stiffer than radiation leads to the production of stochastic gravitational wave (GW) backgrounds whose logarithmic energy spectra are typically "blue" at high frequencies.
Abstract: We point out that the existence of post-inflationary phases stiffer than radiation leads to the production of stochastic gravitational wave (GW) backgrounds whose logarithmic energy spectra (in critical units) are typically ``blue'' at high frequencies The maximal spectral slope (for present frequencies larger than ${10}^{\ensuremath{-}16}$ Hz) is of order 1 and is related to the maximal sound velocity of the stiff plasma governing the evolution of the geometry The duration of the stiff phase is crucially determined by the back reaction of the GW leaving the horizon during the de Sitter phase and reentering during the stiff phase Therefore, the maximal (inflationary) curvature scale has to be fine-tuned to a value smaller than the limits set by the large scale measurements ${(H}_{\mathrm{dS}}\ensuremath{\lesssim}{10}^{\ensuremath{-}6} {M}_{P})$ in order to have a sufficiently long stiff phase reaching an energy scale of the order of $1 \mathrm{TeV}$ and even lower if we want the stiff phase to touch the hadronic era (corresponding to ${T}_{\mathrm{had}}\ensuremath{\sim}140 \mathrm{MeV})$ By looking more positively at our exercise we see that, if an inflationary phase is followed by a stiff phase, there exists the appealing possibility of ``graviton reheating'' whose effective temperature can be generally quite low

Patent
Kirk H. Drees1
27 Jan 1998
TL;DR: In this paper, a method and apparatus for controlling an energy storage medium connected to an environmental control system that is providing environmental conditioning is provided. But the controller does not specify the optimal control trajectories of an energy cost function.
Abstract: A method and apparatus is provided for controlling an energy storage medium connected to an environmental control system that is providing environmental conditioning. The controller includes an energy pricing data structure for storing a real-time energy pricing profile indicative of energy rates corresponding to time-varying production costs of energy. The controller also includes a storage medium containing rules that approximate optimal control trajectories of an energy cost function that is dependent upon the real-time energy pricing profile, with the rules governing the operation of the energy storage medium. In addition, the controller has an engine for generating a storage medium control signal based upon the real-time energy pricing profile and the rules whereby the energy storage medium is controlled with the storage medium control signal in order to minimize energy costs associated with environmental control system.

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TL;DR: In this article, the authors used the lowest order constrained variational method to calculate the properties of asymmetrical nuclear matter with the new charge-independent breaking, Argonne ${V}_{18}$ ${(AV}-18}),$ as well as Argonne${V}{14}$${(AV]-14})$ potentials, for a wide range of density and proton to neutron ratio.
Abstract: The lowest order constrained variational method is used to calculate the properties of asymmetrical nuclear matter with the new charge-independent breaking, Argonne ${V}_{18}$ ${(AV}_{18}),$ as well as Argonne ${V}_{14}$ ${(AV}_{14})$ potentials, for a wide range of density and proton to neutron ratio. The new ${\mathrm{AV}}_{18}$ potential, unlike ${\mathrm{AV}}_{14}$ and \ensuremath{\Delta}-Reid interactions, overbinds nuclear matter at a saturation density of about $0.31{\mathrm{fm}}^{\mathrm{\ensuremath{-}}3}$ which agrees well with the variational method based on hypernetted chain summation techniques. It is shown that it is not a good approximation to use the result of nuclear and neutron matter to get the equation of state of asymmetrical nuclear matter with an empirical parabolic approximation. Finally, various properties of asymmetrical nuclear matter such as incompressibility, symmetry energy, etc., are given and a comparison is made with the other many-body techniques.