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Results for "C. H. K. Chen"

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Recent progress in astrophysical plasma turbulence from solar wind observationsNov 10 2016This paper summarises some of the recent progress that has been made in understanding astrophysical plasma turbulence in the solar wind, from in situ spacecraft observations. At large scales, where the turbulence is predominantly Alfvenic, measurements ... More
Parallel Electric Field Spectrum of Solar Wind TurbulenceApr 03 2013By searching through more than 10 satellite-years of THEMIS and Cluster data, three reliable examples of parallel electric field turbulence in the undisturbed solar wind have been found. The perpendicular and parallel electric field spectra in these examples ... More
Analysis of Asymmetric Piezoelectric Composite BeamFeb 21 2008This paper deals with the vibration analysis of an asymmetric composite beam composed of glass a piezoelectric material. The Bernoulli's beam theory is adopted for mechanical deformations, and the electric potential field of the piezoelectric material ... More
Evidence for Electron Landau Damping in Space Plasma TurbulenceFeb 15 2019How turbulent energy is dissipated in weakly collisional space and astrophysical plasmas is a major open question. Here, we present the application of a field-particle correlation technique to directly measure the transfer of energy between the turbulent ... More
Spin Excitation in d-wave Superconductors : A Fermi Liquid PictureJun 21 2000Jan 12 2001A detailed study of the Inelastic Neutron Scattering (INS) spectra of the high-$T_c$ cuprates based on the Fermi liquid (FL) picture is given. We focus on the issue of the transformation between the commensurate and incommensurate (IC) excitation driven ... More
Orbit Feedback System for the Storage Ring of SRRCNov 09 2001Orbit feedback system plays crucial roles for the operation of the 3rd generation light source. There are various issues in orbit feedback system should be addressed to achieve ultimate performance. The orbit feedback system in SRRC is upgraded recently ... More
Data Acquisition and Uesr Interface of Beam Instrumentation System at SRRCNov 09 2001Data acquisition systems for the accelerator complex at SRRC composed various hardware and software components. Beam signals are processed by related processing electronics, and connect to control system by various type of interfaces in data acquisition ... More
A Spitzer Study of Dusty Disks in the Scorpius-Centaurus OB AssociationJan 06 2005We have obtained Spitzer Space Telescope MIPS observations of 40 F- and G-type common proper motion members of the Scorpius-Centaurus OB Association with ages between 5 and 20 Myr at 24 micron and 70 micron. We report the detection of fourteen objects ... More
Temperature Effect and Fermi Surface Investigation in the Scanning Tunneling Microscopy of Bi$_2$Sr$_2$CaCu$_2$O$_8$Aug 07 2003Based on a Fermi liquid picture, the temperature effect on the impurity-induced spatial modulation of local density of states (LDOS) is investigated for the d-wave superconductor Bi$_2$Sr$_2$CaCu$_2$O$_8$, in the context of scanning tunneling microscopy ... More
Broad-band Optical Polarimetric Studies toward the Galactic young star cluster Be 59Sep 28 2011We present multiwavelength optical linear polarimetric observations of 69 stars toward the young open cluster Be 59. The observations reveal the presence of three dust layers located at the distances of \sim300, \sim500 and \sim700 pc. The dust layers ... More
Mechanism of recrystallization process in epitaxial GaN under dynamic stress field - Atomistic origin of planar defect formationJul 05 2008May 02 2009The mechanism of recrystallization in epitaxial (1000) GaN film, introduced by indentation technique, is probed by lattice dynamic studies using Raman spectroscopy. The recrystallized region is identified by Micro-Raman area mapping. Pop-in bursts in ... More
Recrystallization of epitaxial GaN under indentationApr 11 2008Apr 15 2008We report recrystallization of epitaxial (epi-) GaN(0001) film under indentation.Hardness value is measured close to 10 GPa, using a Berkovich indenter. Pop-in burst in the loading line indicates nucleation of dislocations setting in plastic motion of ... More
A complete Raman mapping of phase transitions in Si under indentationJul 05 2008Jul 14 2008Crystalline Si substrates are studied for pressure induced phase transformation under indentation at room temperature using Berkovich tip. Raman scattering study is used for the identification of the transformed phases. Raman line as well as area mapping ... More
Deformation potential dominated phonons in ZnS quantum dotsSep 12 2007Jul 06 2008Strong deformation potential (DP) dominated Raman spectra are reported for quantum confined cubic ZnS nanoclusters under off-resonance conditions allowed only in quantum dots. A flurry of zone boundary phonons is demonstrated in the scattering process. ... More
Strongly exchange-coupled and surface-state-modulated magnetization dynamics in Bi2Se3/YIG heterostructuresAug 02 2017We report strong interfacial exchange coupling in Bi2Se3/yttrium iron garnet (YIG) bilayers manifested as large in-plane interfacial magnetic anisotropy (IMA) and enhancement of damping probed by ferromagnetic resonance (FMR). The IMA and spin mixing ... More
Thermal Conductivity of Graphene Laminate: Making Plastic Thermally ConductiveJul 05 2014We have investigated thermal conductivity of graphene laminate films deposited on polyethylene terephthalate substrates. Two types of graphene laminate were studied - as deposited and compressed - in order to determine the physical parameters affecting ... More
Kinetic Turbulence in Astrophysical Plasmas: Waves and/or Structures?Jun 14 2018The question of the relative importance of coherent structures and waves has for a long time attracted a great deal of interest in astrophysical plasma turbulence research, with a more recent focus on kinetic scale dynamics. Here we utilize high-resolution ... More
Electron heat conduction in the solar wind: transition from Spitzer-Härm to the collisionless limitMar 05 2013Apr 29 2013We use a statistically significant set of measurements to show that the field-aligned electron heat flux $q_\parallel$ in the solar wind at 1 AU is consistent with the Spitzer-H\"{a}rm collisional heat flux $q_{sh}$ for temperature gradient scales larger ... More
Non-line-of-sight Node Localization based on Semi-Definite Programming in Wireless Sensor NetworksDec 31 2009An unknown-position sensor can be localized if there are three or more anchors making time-of-arrival (TOA) measurements of a signal from it. However, the location errors can be very large due to the fact that some of the measurements are from non-line-of-sight ... More
A Search for Subkilometer-sized Ordinary Chondrite Like Asteroids in the Main-BeltApr 07 2015The size-dependent effects of asteroids on surface regolith and collisional lifetimes suggest that small asteroids are younger than large asteroids. In this study, we performed multicolor main-belt asteroid (MBA) survey by Subaru telescope/Suprime-Cam ... More
Blue shift of yellow luminescence band in self-ion-implanted n-GaN nanowireFeb 02 2004Optical photoluminescence studies are performed in self-ion (Ga+)-implanted nominally doped n-GaN nanowires. A 50-keV Ga+ focused ion beam (FIB) in the fluence range of 1x1014 -2x10^16 ions cm^-2 is used for the irradiation process. A blueshift is observed ... More
Residual Energy Spectrum of Solar Wind TurbulenceApr 29 2013It has long been known that the energy in velocity and magnetic field fluctuations in the solar wind is not in equipartition. In this paper, we present an analysis of 5 years of Wind data at 1 AU to investigate the reason for this. The residual energy ... More
Density Fluctuation Spectrum of Solar Wind Turbulence between Ion and Electron ScalesMay 22 2012We present a measurement of the spectral index of density fluctuations between ion and electron scales in solar wind turbulence using the EFI instrument on the ARTEMIS spacecraft. The mean spectral index at 1 AU was found to be -2.75 +/- 0.06, steeper ... More
Low energy excitations of the t-J model in 1D and 2DJul 15 1996We present an exact diagonalization study of the low energy singlet and triplet states for both 1D and 2D t-J model. A scan of the parameter ratio J/t shows that for nearly all low energy states in both 1D and 2D the excitation energy takes the linear ... More
d-Wave Pairing Correlation in the Two-Dimensional t-J ModelJul 02 1998The pair-pair correlation function of the two-dimensional t-J model is studied by using the power-Lanczos method and an assumption of monotonic behavior. In comparison with the results of the ideal Fermi gas, we conclude that the 2D t-J model does not ... More
Frame Dependence of the Electric Field Spectrum of Solar Wind TurbulenceMay 12 2011Aug 05 2011We present the first survey of electric field data using the ARTEMIS spacecraft in the solar wind to study inertial range turbulence. It was found that the average perpendicular spectral index of the electric field depends on the frame of measurement. ... More
The Nature of Subproton Scale Turbulence in the Solar WindMay 13 2013The nature of subproton scale fluctuations in the solar wind is an open question, partly because two similar types of electromagnetic turbulence can occur: kinetic Alfven turbulence and whistler turbulence. These two possibilities, however, have one key ... More
Inertial-Range Kinetic Turbulence in Pressure-Anisotropic Astrophysical PlasmasJan 27 2015Jun 05 2015A theoretical framework for low-frequency electromagnetic (drift-)kinetic turbulence in a collisionless, multi-species plasma is presented. The result generalises reduced magnetohydrodynamics (RMHD) and kinetic RMHD (Schekochihin et al. 2009) for pressure-anisotropic ... More
Fluctuations of Entropy Production in Partially Masked Electric Circuits: Theoretical AnalysisJan 19 2016Jan 28 2016In this work we perform theoretical analysis about a coupled RC circuit with constant driven currents. Starting from stochastic differential equations, where voltages are subject to thermal noises, we derive time-correlation functions, steady-state distributions ... More
Superconducting energy gap and c-axis plasma frequency of (Nd,Sm)O0.82F0.18FeAs superconductors from infrared ellipsometryMay 15 2008We present ellipsometric measurements of the far-infrared dielectric response of polycrystalline samples of the new pnictide superconductor RO0.82F0.18FeAs (R=Nd and Sm). We find evidence that the electronic properties are strongly anisotropic such that ... More
Surface optical Raman modes in InN nanostructuresJul 05 2008Raman spectroscopic investigations are carried out on one-dimensional nanostructures of InN,such as nanowires and nanobelts synthesized by chemical vapor deposition. In addition to the optical phonons allowed by symmetry; A1, E1 and E2(high) modes, two ... More
Beyond-limit light focusing in the intermediate zoneJan 13 2009We experimentally demonstrate that a new nanolens of designed plasmonic subwavelength aperture can focus light to a single-line with its width beyond the diffraction limit that sets the smallest achievable line width at half the wavelength. The measurements ... More
Using Synthetic Spacecraft Data to Interpret Compressible Fluctuations in Solar Wind TurbulenceJun 28 2012Kinetic plasma theory is used to generate synthetic spacecraft data to analyze and interpret the compressible fluctuations in the inertial range of solar wind turbulence. The kinetic counterparts of the three familiar linear MHD wave modes---the fast, ... More
The slow-mode nature of compressible wave power in solar wind turbulenceJun 21 2011We use a large, statistical set of measurements from the Wind spacecraft at 1 AU, and supporting synthetic spacecraft data based on kinetic plasma theory, to show that the compressible component of inertial range solar wind turbulence is primarily in ... More
Measurement of the electronic thermal conductance channels and heat capacity of graphene at low temperatureAug 10 2013The ability to transport energy is a fundamental property of the two-dimensional Dirac fermions in graphene. Electronic thermal transport in this system is relatively unexplored and is expected to show unique fundamental properties and to play an important ... More
Multi-phonon Raman scattering in GaN nanowiresAug 16 2007UV Raman scattering studies show longitudinal optical (LO) mode up to 4th order in wurtzite GaN nanowire system. Frohlich interaction of electron with the long range electrostatic field of ionic bonded GaN gives rise to enhancement in LO phonon modes. ... More
Low-Energy Charge-Density Excitations in MgB$_{2}$: Striking Interplay between Single-Particle and Collective Behavior for Large MomentaMay 12 2006Jul 13 2006A sharp feature in the charge-density excitation spectra of single-crystal MgB$_{2}$, displaying a remarkable cosine-like, periodic energy dispersion with momentum transfer ($q$) along the $c^{*}$-axis, has been observed for the first time by high-resolution ... More
Power and spectral index anisotropy of the entire inertial range of turbulence in the fast solar windFeb 10 2010We measure the power and spectral index anisotropy of high speed solar wind turbulence from scales larger than the outer scale down to the ion gyroscale, thus covering the entire inertial range. We show that the power and spectral indices at the outer ... More
Dipole and quadrupole solitons in optically-induced two-dimensional defocusing photonic latticesMay 17 2008Dipole and quadrupole solitons in a two-dimensional optically induced defocus- ing photonic lattice are theoretically predicted and experimentally observed. It is shown that in-phase nearest-neighbor dipole and out-of-phase next-nearest-neighbor dipoles ... More
Notions of double for Lie algebroidsNov 24 2000We define an abstract notion of double Lie algebroid, which includes as particular cases: (1) the double Lie algebroid of a double Lie groupoid in the sense of the author, such as the iterated tangent bundle of an ordinary manifold, and various iterated ... More
Ehresmann doubles and Drinfel'd doubles for Lie algebroids and Lie bialgebroidsNov 26 2006Dec 22 2006The word `double' was used by Ehresmann to mean `an object X in the category of all X'. Double categories, double groupoids and double vector bundles are instances, but the notion of Lie algebroid cannot readily be doubled in the Ehresmann sense, since ... More
Physical Structure and Nature of Supernova Remnants in M101Feb 23 2012Supernova remnant (SNR) candidates in the giant spiral galaxy M101 have been previously identified from ground-based H-alpha and [SII] images. We have used archival Hubble Space Telescope (HST) H-alpha and broad-band images as well as stellar photometry ... More
Intermittency of Solar Wind Density Fluctuations From Ion to Electron ScalesMay 28 2014The intermittency of density fluctuations in the solar wind at kinetic scales has been examined using high time resolution Faraday cup measurements from the Spektr-R spacecraft. It was found that the probability density functions (PDFs) of the fluctuations ... More
The t system: a new system for estimating the total magnitudes of galaxiesDec 09 1997We present a new, but simple, procedure for estimating the total magnitudes of galaxies. This procedure involves the out-focusing of digital galaxy images numerically, the fitting of the resulting surface-brightness profiles with a single generalised ... More
Experimental determination of whistler wave dispersion relation in the solar windSep 10 2016The origins and properties of large amplitude whistler wave packets in the solar wind are still unclear. In this Letter we utilise single spacecraft electric and magnetic field waveform measurements from the ARTEMIS mission to calculate the plasma frame ... More
A Critical Examination of Hypernova Remnant Candidates in M101. I. MF83Sep 15 2000The SNR candidate MF83 in M101 is coincident with a very luminous X-ray source. Based on the high X-ray luminosity, it has been suggested that MF83 is a "hypernova remnant" requiring an explosion energy about two orders of magnitude higher than normal ... More
Surface plasmon polariton assisted optical switching in noble bimetallic nanoparticle systemAug 31 2015Photoresponse of bimetallic Au-Ag nanoparticle embedded soda glass (Au-Ag@SG) substrate is reported for surface plasmon assisted optical switching using 808 nm excitation. Au-Ag@SG system is made by an ion beam technique where Ag^+ is introduced first ... More
Are Giant Planets Forming Around HR 4796A?Nov 03 2003We have obtained FUSE and HST STIS spectra of HR 4796A, a nearby 8 Myr old main sequence star that possesses a dusty circumstellar disk whose inclination has been constrained from high resolution near-infrared observations to be ~17 deg from edge-on. ... More
The Low Velocity Wind from the Circumstellar Matter Around the B9V Star sigma HerculisSep 04 2002We have obtained FUSE spectra of sigma Her, a nearby binary system, with a main sequence primary, that has a Vega-like infrared excess. We observe absorption in the excited fine structure lines C II* at 1037 A, N II* at 1085 A, and N II** at 1086 A that ... More
A Possible Massive Asteroid Belt Around zeta LepSep 14 2001We have used the Keck I telescope to image at 11.7 microns and 17.9 microns the dust emission around zeta Lep, a main sequence A-type star at 21.5 pc from the Sun with an infrared excess. The excess is at most marginally resolved at 17.9 microns. The ... More
The observed $Ω_{c}^{0}$ resonances as pentaquark statesMay 24 2017Jul 26 2017In present work, we investigate the spectrum of several low-lying $sscq\bar{q}$ pentaquark configurations employing the constituent quark model, within which the hyperfine interaction between quarks is taken to be mediated by Goldstone boson exchange. ... More
The Molecular Clouds Fueling a 1/5 Solar Metallicity StarburstJul 06 2016Sep 02 2016Using the Atacama Large Millimeter/submillimeter Array, we have made the first high spatial and spectral resolution observations of the molecular gas and dust in the prototypical blue compact dwarf galaxy II Zw 40. The CO(2-1) and CO(3-2) emission is ... More
Fabrication and characterization of an induced GaAs single hole transistorFeb 16 2010We have fabricated and characterized a single hole transistor in an undoped AlGaAs-GaAs heterostructure. Our device consists of a p-type quantum dot, populated using an electric field rather than modulation doping. Low temperature transport measurements ... More
Congruences of Multipartition Functions Modulo Powers of PrimesJun 28 2012Let $p_r(n)$ denote the number of $r$-component multipartitions of $n$, and let $S_{\gamma,\lambda}$ be the space spanned by $\eta(24z)^\gamma \phi(24z)$, where $\eta(z)$ is the Dedekind's eta function and $\phi(z)$ is a holomorphic modular form in $M_\lambda({\rm ... More
Impurity effects on s+g-wave superconductivity in borocarbides Y(Lu)Ni_2B_2CJun 11 2003Recently a hybrid s+g-wave pairing is proposed to describe the experimental observation for a nodal structure of the superconducting gap in borocarbide YNi$_2$B$_2$C and possibly LuNi$_2$B$_2$C. In this paper the impurity effects on the s+g-wave superconductivity ... More
Magnetic Field Rotations in the Solar Wind at Kinetic ScalesJul 28 2015Sep 15 2015The solar wind magnetic field contains rotations at a broad range of scales, which have been extensively studied in the MHD range. Here we present an extension of this analysis to the range between ion and electron kinetic scales. The distribution of ... More
Anisotropy of Alfvénic Turbulence in the Solar Wind and Numerical SimulationsSep 03 2010Jun 08 2011We investigate the anisotropy of Alfv\'enic turbulence in the inertial range of slow solar wind and in both driven and decaying reduced magnetohydrodynamic simulations. A direct comparison is made by measuring the anisotropic second-order structure functions ... More
Anisotropy of Imbalanced Alfvenic Turbulence in Fast Solar WindSep 13 2010Dec 09 2010We present the first measurement of the scale-dependent power anisotropy of Elsasser variables in imbalanced fast solar wind turbulence. The dominant Elsasser mode is isotropic at lower spacecraft frequencies but becomes increasingly anisotropic at higher ... More
Interpreting Power Anisotropy Measurements in Plasma TurbulenceSep 14 2009Feb 22 2010A relationship is derived between power anisotropy and wavevector anisotropy in turbulent fluctuations. This can be used to interpret plasma turbulence measurements, for example in the solar wind. If fluctuations are anisotropic in shape then the ion ... More
Electrical Autonomous Brownian GyratorMar 31 2017Sep 18 2017We study experimentally and theoretically the steady-state dynamics of a simple stochastic electronic system featuring two resistor-capacitor circuits coupled by a third capacitor. The resistors are subject to thermal noises at real temperatures. The ... More
Photometric Redshift Techniques: Reliability and ApplicationsSep 27 1998This article describes the various photometric techniques currently being used, including some preliminary results from the large CNOC2 redshift survey. It also presents a critical look at the reliability of the photometric redshift technique, in part ... More
Double Lie algebroids and the double of a Lie bialgebroidAug 17 1998We define a general notion of abstract double Lie algebroid. We show (1) that the double Lie algebroid of a double Lie groupoid is a double Lie algebroid in this sense; (2) that the double cotangent constructed from Lie algebroid structures on a vector ... More
On certain canonical diffeomorphisms in symplectic and Poisson geometryOct 24 2002The canonical involution of a double (=iterated) tangent bundle may be dualized in different ways to yield relations between the Tulczyjew diffeomorphism, the Poisson anchor associated with the standard symplectic structure on the cotangent space,and ... More
Direct Observation of Coexistence of Ferromagnetism and Superconductivity in RuSr2(Gd0.7Ce0.3)2Cu2O10May 26 2001Recent reports of the detecting of ferromagnetism and superconductivity in ruthenium-cuprates have aroused great interest. Unfortunately, whether the two antagonistic phenomena coexist in the same space in the compounds remains unresolved. By employing ... More
Topological insulator Bi2Se3 films on rare earth iron garnets and their high-quality interfacesSep 12 2018The integration of quantum materials like topological insulators (TIs) with magnetic insulators (MIs) has important technological implications for spintronics and quantum computing. Here we report excellent crystallinity of c-axis oriented epitaxial TI ... More
Spectral Shaping of Cascade Emissions from Multiplexed Cold Atomic EnsemblesOct 07 2015We investigate the spectral properties of the biphoton state from the cascade emissions of cold atomic ensembles, which composes of a telecommunication photon (signal) followed by an infrared one (idler) via four-wave mixing.\ With adiabatic conditions ... More
Nitrogen ion beam synthesis of InN in InP (100) at elevated temperatureAug 16 2007InN phase is grown in crystalline InP(100) substrates by 50 keV N+ implantation at an elevated temperature of 400 deg C followed by annealing at 525 deg C in N2 ambient. Crystallographic structural and Raman scattering studies are performed for the characterization ... More
Ferromagnetism in cobalt doped n-GaNAug 16 2007Ferromagnetic ordering is reported in the post-annealed samples of Co doped n-GaN formed by Co+ implantation. A maximum Curie temperature ~ 250K is recorded for the sample with 8 atomic percent Co. Particle induced x-ray emission-channeling study confirmed ... More
Optical characterization of GaN by N+ implantation into GaAs at elevated temperatureAug 16 2007Both hexagonal wurtzite and cubic zinc blend GaN phases were synthesized in GaAs by 50 keV N+ implantation at 400 deg C and subsequent annealing at 900 deg C for 15 min in N2 ambient. Crystallographic structural and Raman scattering studies revealed that ... More
Star Formation and Galaxy EnvironmentApr 05 2000The dependence of star formation rate on galaxian environment is a key issue in the understanding of galaxy formation and evolution. However, the study of this subject is complex and observationally challenging. This paper reviews some of the current ... More
THz Generation and Detection on Dirac Fermions in Topological InsulatorsJan 26 2013This study shows that a terahertz (THz) wave can be generated from the (001) surface of cleaved Bi$_{\textrm{2}}$Se$_{\textrm{3}}$ and Cu-doped Bi$_{\textrm{2}}$Se$_{\textrm{3}}$ single crystals using 800 nm femtosecond pulses. The generated THz power ... More
Linear and Nonlinear Fano Resonance on two-dimensional Magnetic MetamaterialsJan 05 2012We demonstrate that both linear and nonlinear Fano resonances can be realized on two dimensional magnetic metamaterials. The Fano resonance comes from the interference between localized magnetic plasmon resonance and propagating surface plasmon polaritons. ... More
Specific heat of the iron-based high-$T_c$ superconductor SmO$_{1-x}$F$_x$FeAsApr 23 2008May 23 2008The specific heat $C(T)$ of new iron-based high-$T_c$ superconductor SmO$_{1-x}$F$_x$FeAs ($0 \leq x \leq 0.2$) was systematically studied. For undoped $x$ = 0 sample, a specific heat jump was observed at 130 K. This is attributed to the structural or ... More
Symmetric Versus Nonsymmetric Structure of the Phosphorus Vacancy on InP(110)Jun 08 2000The atomic and electronic structure of positively charged P vacancies on InP(110) surfaces is determined by combining scanning tunneling microscopy, photoelectron spectroscopy, and density-functional theory calculations. The vacancy exhibits a nonsymmetric ... More
New Debris Disks Around Young, Low Mass Stars Discovered With The Spitzer Space TelescopeApr 05 2009(abridged) We present 24 and 70 micron MIPS observations of 70 A through M-type dwarfs with estimated ages from 8 Myr to 1.1 Gyr, as part of a Spitzer guaranteed time program. Our sample is selected from stars with common youth indicators such as lithium ... More
Neutral B Flavor Tagging for the Measurement of Mixing-induced CP Violation at BelleMar 13 2004We describe a flavor tagging algorithm used in measurements of the CP violation parameter sin2phi_1 at the Belle experiment. Efficiencies and wrong tag fractions are evaluated using flavor-specific B meson decays into hadronic and semileptonic modes. ... More
Morphological analysis on the coherence of kHz QPOsNov 23 2010Oct 31 2012We take the recently published data of twin kHz quasi-period oscillations (QPOs) in neutron star (NS) lowmass X-ray binaries (LMXBs) as the samples, and investigate the morphology of the samples, which focuses on the quality factor, peak frequency of ... More
Optimizing the spectro-temporal properties of photon pairs from Bragg-reflection waveguidesSep 10 2018Mar 03 2019Bragg-reflection waveguides (BRWs) fabricated from AlGaAs provide an interesting non-linear optical platform for photon-pair generation via parametric down-conversion (PDC). In contrast to many conventional PDC sources, BRWs are made of high refractive ... More
Kinetic Scale Density Fluctuations in the Solar WindSep 29 2012We motivate the importance of studying kinetic scale turbulence for understanding the macroscopic properties of the heliosphere, such as the heating of the solar wind. We then discuss the technique by which kinetic scale density fluctuations can be measured ... More
Pressure Effects on the Superconducting and Spin-Density-Wave States of the Newly Discovered Sm(O1-xFx)FeAsApr 10 2008Aug 04 2008High temperature superconductors with a Tc above 40 K have been found to be strongly correlated electron systems and to have a layered structure. Guided by these rules, Kamihara et al. discovered a Tc up to 26 K in the layered La(O1-xFx)FeAs. By replacing ... More
T violation in $B\to K φφ$ decaysDec 14 2004We present the general form of the decay width angular distributions with T-odd terms in $B\to K \phi \phi$ decays. We concentrate on the T violating effects by considering various possible T-odd momentum correlations. In a generic class of CP violating ... More
Spin-orbital-angular-momentum coupled Bose-Einstein condensatesMar 21 2018Aug 06 2018We demonstrate coupling between the atomic spin and orbital-angular-momentum (OAM) of the atom's center-of-mass motion in a Bose-Einstein condensate (BEC). The coupling is induced by Raman-dressing lasers with a Laguerre-Gaussian beam, and creates coreless ... More
Nitrogen-Functionalized Graphene Nanoflakes (GNFs:N): Tunable Photoluminescence and Electronic StructuresAug 04 2012This study investigates the strong photoluminescence (PL) and X-ray excited optical luminescence observed in nitrogen-functionalized 2D graphene nanoflakes (GNFs:N), which arise from the significantly enhanced density of states in the region of {\pi} ... More
Network Topology of an Experimental Futures ExchangeMay 17 2007Many systems of different nature exhibit scale free behaviors. Economic systems with power law distribution in the wealth is one of the examples. To better understand the working behind the complexity, we undertook an empirical study measuring the interactions ... More
Hole concentration and phonon renormalization in Ca-doped YBa_2Cu_3O_y (6.76 < y < 7.00)Nov 07 2002In order to access the overdoped regime of the YBa_2Cu_3O_y phase diagram, 2% Ca is substituted for Y in YBa_2Cu_3O_y (y = 7.00,6.93,6.88,6.76). Raman scattering studies have been carried out on these four single crystals. Measurements of the superconductivity-induced ... More
Measurement of Cosmic-ray Muons and Muon-induced Neutrons in the Aberdeen Tunnel Underground LaboratorySep 30 2015Nov 26 2016We have measured the muon flux and production rate of muon-induced neutrons at a depth of 611 m water equivalent. Our apparatus comprises three layers of crossed plastic scintillator hodoscopes for tracking the incident cosmic-ray muons and 760 L of gadolinium-doped ... More
Study of two-subband population in Fe-doped AlxGa1-xN/GaN heterostructures by persistent photoconductivity effectSep 15 2006The electronic properties of Fe-doped Al0.31Ga0.69N/GaN heterostructures have been studied by Shubnikov-de Haas measurement. Two subbands of the two-dimensional electron gas in the hetero-interface were populated. After the low temperature illumination, ... More
Spatial Symmetry of Superconducting Gap in YBa2Cu3O7-δObtained from Femtosecond SpectroscopyNov 19 2003Nov 25 2003The polarized femtosecond spectroscopies obtained from well characterized (100) and (110) YBa2Cu3O7-\delta thin films are reported. This bulk-sensitive spectroscopy, combining with the well-textured samples, serves as an effective probe to quasiparticle ... More
Stellar contents and star formation in the young open cluster Stock 8Dec 13 2007We present $UBVI_c$ CCD photometry of the young open cluster Stock 8 with the aim to study the basic properties and star formation scenario in this region. The radius of the cluster is found to be $\sim 6^{\prime}$ ($\sim 3.6$ pc) and the reddening within ... More
X-ray absorption spectroscopy (XAS) investigation of the electronic structure of superconducting FeSex single crystalsMay 05 2010Jul 26 2010X-ray absorption spectroscopy (XAS) Fe K-edge spectra of the FeSex (x=1-0.8) single crystals cleaved in situ in vacuum reveal characteristic Fe 4sp states, a lattice distortion and the Se K-edge spectra point to a strong Fe 3d-Se 4p hybridization giving ... More
Spatially-resolved relaxation dynamics of photoinduced quasiparticles in underdoped YBa$sub 2$Cu$sub 3$O$sub {7-delta}$Aug 20 2005The spatially-resolved relaxation characteristics of photoinduced quasiparticles (QPs) in CuO$sub 2$ planes of underdoped YBCO are disclosed by polarized fs time-resolved spectroscopy. The relaxation time (tau) along b axis diverges at Tc, and appears ... More
Dynamic magnetic-transformation-induced exchange bias in (Fe2O3)0.1-(FeTiO3)0.9Jan 08 2018Up to now, for the conventional exchange bias (EB) systems there has been one pinning phase and one pinned phase, and the pinning and pinned phases are inherent to the material and do not mutually transform into each other. Interestingly, we show here ... More
Extended calculations of energy levels, radiative properties, $A_{J}$, $B_{J}$ hyperfine interaction constants, and Landé $g_{J}$-factors for nitrogen-like \mbox{Ge XXVI}Jan 11 2018Employing two state-of-the-art methods, multiconfiguration Dirac--Hartree--Fock and second-order many-body perturbation theory, highly accurate calculations are performed for the lowest 272 fine-structure levels arising from the $2s^{2} 2p^{3}$, $2s 2p^{4}$, ... More
Decay Spectrum of $K^+ \to e^+ ν_{e}γ$Jan 07 2008The form factors of the $K^+ \to \gamma$ transition are studied in the light-front quark model and chiral perturbation theory of $O(p^6)$. The decay spectrum of $K^+ \to e^+ \nu_{e}\gamma$, dominated by the structure dependent contribution, is illustrated ... More
Correlation effects of exchange splitting and coexistence of spin-density-wave and superconductivity in single crystalline Sr1-xKxFe2As2Aug 20 2008The nature of spin-density wave and its relation with superconductivity are crucial issues in the newly discovered Fe-based high temperature superconductors. Particularly it is unclear whether the superconducting phase and spin density wave (SDW) are ... More
Planets and IR Excesses: Preliminary Results from a Spitzer/MIPS Survey of Solar-Type StarsDec 10 2004As part of a large Spitzer/MIPS GTO program, we have searched for infrared excesses due to debris disks toward 26 FGK field stars known from radial velocity (RV) studies to have one or more planets. While none of these stars show excesses at 24um, we ... More
Blue luminescence of Au nanoclusters embedded in silica matrixSep 29 2004Photoluminescence study using the 325 nm He-Cd excitation is reported for the Au nanoclusters embedded in SiO2 matrix. Au clusters are grown by ion beam mixing with 100 KeV Ar+ irradiation on Au [40 nm]/SiO2 at various fluences and subsequent annealing ... More
The Design and Testing of the Address in Real Time Data Driver Card for the Micromegas Detector of the ATLAS New Small Wheel UpgradeJun 18 2018The Address in Real Time Data Driver Card (ADDC) is designed to transmit the trigger data in the Micromegas detector of the ATLAS New Small Wheel (NSW) upgrade. The ART signals are generated by the front end ASIC, named VMM chip, to indicate the address ... More
The orbital characters of bands in iron-based superconductor BaFe1.85Co0.15As2Apr 26 2009Nov 17 2010The unconventional superconductivity in the newly discovered iron-based superconductors is intimately related to its multi-band/multi-orbital nature. Here we report the comprehensive orbital characters of the low-energy three-dimensional electronic structure ... More
Effect of co-doping of donor and acceptor impurities in the ferromagnetic semiconductor Zn1-xCrxTe studied by soft x-ray magnetic circular dichroismMar 25 2011We have performed x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) studies of the diluted ferromagnetic semiconductor Zn$_{1-\textit{x}}$Cr$_\textit{x}$Te doped with iodine (I) or nitrogen (N), corresponding to electron ... More