arXiv subjects

Jing Liu

Publications and source records attributed to Jing Liu.

715 records · Page 40Linked to original sources

arXiv2013

Brillouin cavity optomechanics with microfluidic devices

Cavity optomechanics allows the parametric coupling of phonon- and photon-modes in microresonators and is presently investigated in a broad variety of solid-state systems. Optomechanics with superfluids has been proposed as a path towards ultra-low optical- and mechanical-dissipation. However, there have been no optomechanics experiments reported with non-solid phases of matter. Direct liquid immersion of optomechanics experiments is challenging since the acoustic energy simply leaks out to the higher-impedance liquid surrounding the device. Conversely, here we confine liquids inside hollow resonators thereby enabling optical excitation of mechanical whispering-gallery modes at frequencies ranging from 2 MHz to 11,000 MHz (for example, with mechanical Q = 4700 at 99 MHz). Vibrations are sustained even when we increase the fluid viscosity to be higher than that of blood. Our device enables optomechanical investigation with liquids, while light is conventionally coupled from the outer dry side of the capillary, and liquids are provided by means of a standard microfluidic inlet.

physics.optics↗

arXiv2012

Cavity optomechanics on a microfluidic resonator with water and viscous liquids

Currently, optical- or mechanical-resonances are commonly used in microfluidic research. However, optomechanical oscillations by light pressure were not shown with liquids. This is because replacing the surrounding air with water inherently increases the acoustical impedance and hence the associated acoustical radiation-losses. Here, we bridge between microfluidics and optomechanics by fabricating hollow bubble resonators with liquid inside and optically exciting 100-MHz vibrations with only mW optical-input power. This constitutes the first time that any microfluidic system is optomechanically actuated. We further prove the feasibility of microfluidic optomechanics on liquids by demonstrating vibrations on organic fluids with viscous-dissipation higher than blood viscosity while measuring density changes in the liquid via the vibration frequency shift. Our device will enable using cavity optomechanics for studying non-solid phases of matter.

physics.optics↗

arXiv2012

Pressure tuning of Fermi surface topology of optimally doped BaFe$_{1.9}$Ni$_{0.1}$As$_{2}$

The superconducting, transport, and structural properties of optimally electron-doped BaFe$_{1.9}$Ni$_{0.1}$As$_{2}$ are investigated by combining the electrical resistance and synchrotron X-ray diffraction measurements at high pressures. The superconducting transition temperature of this system is found to decrease in a similar way of the axial ratio of $c/a$ with increasing pressure but vanishing at a critical pressure of 7.5 GPa where $c/a$ has a dip and an isostructural transformation from a tetragonal to a collapsed tetragonal phase takes place. The resistance is found to obey a linear temperature dependence, evidencing the antiferromagnetic spin-fluctuations transport mechanism. The pressure effects are interpreted within the framework of pressure-induced Fermi surface topology modification in which pressure suppresses both the quasiparticle effective mass and the strength of the antiferromagnetic spin fluctuations leading to the reduction of superconductivity, accordingly. The absent superconductivity in the collapsed tetragonal phase is suggested to result from the complete suppression of the antiferromagnetic spin fluctuations.

cond-mat.supr-con↗

arXiv2012

A Novel Video Compression Approach Based on Underdetermined Blind Source Separation

This paper develops a new video compression approach based on underdetermined blind source separation. Underdetermined blind source separation, which can be used to efficiently enhance the video compression ratio, is combined with various off-the-shelf codecs in this paper. Combining with MPEG-2, video compression ratio could be improved slightly more than 33%. As for combing with H.264, 4X~12X more compression ratio could be achieved with acceptable PSNR, according to different kinds of video sequences.

cs.MM↗

arXiv2012

Pressure-induced amorphization and polyamorphism in one-dimensional single crystal TiO2 nanomaterials

The structural phase transitions of single crystal TiO2-B nanoribbons were investigated in-situ at high-pressure using the synchrotron X-ray diffraction and the Raman scattering. Our results have shown a pressure-induced amorphization (PIA) occurred in TiO2-B nanoribbons upon compression, resulting in a high density amorphous (HDA) form related to the baddeleyite structure. Upon decompression, the HDA form transforms to a low density amorphous (LDA) form while the samples still maintain their pristine nanoribbon shape. HRTEM imaging reveals that the LDA phase has an α-PbO2 structure with short range order. We propose a homogeneous nucleation mechanism to explain the pressure-induced amorphous phase transitions in the TiO2-B nanoribbons. Our study demonstrates for the first time that PIA and polyamorphism occurred in the one-dimensional (1D) TiO2 nanomaterials and provides a new method for preparing 1D amorphous nanomaterials from crystalline nanomaterials.

cond-mat.mtrl-sci↗

arXiv2010

\textsc{MaGe} - a {\sc Geant4}-based Monte Carlo Application Framework for Low-background Germanium Experiments

We describe a physics simulation software framework, MAGE, that is based on the GEANT4 simulation toolkit. MAGE is used to simulate the response of ultra-low radioactive background radiation detectors to ionizing radiation, specifically the MAJORANA and GERDA neutrinoless double-beta decay experiments. MAJORANA and GERDA use high-purity germanium detectors to search for the neutrinoless double-beta decay of 76Ge, and MAGE is jointly developed between these two collaborations. The MAGE framework contains the geometry models of common objects, prototypes, test stands, and the actual experiments. It also implements customized event generators, GEANT4 physics lists, and output formats. All of these features are available as class libraries that are typically compiled into a single executable. The user selects the particular experimental setup implementation at run-time via macros. The combination of all these common classes into one framework reduces duplication of efforts, eases comparison between simulated data and experiment, and simplifies the addition of new detectors to be simulated. This paper focuses on the software framework, custom event generators, and physics lists.

nucl-ex↗

arXiv2010

Evidence for Competition between Superconductivity and Kondo Effect in CeFeAsO0.7F0.3 under High Pressure

We discover a pressure induced quantum phase transition from the superconducting state to the non-superconducting Kondo screened phase associated with a 2% volume collapse in CeFeAsO0.7F0.3 through measurements of high-pressure resistance, synchrotron x-ray diffraction, and x-ray absorption spectroscopy (XAS) in a diamond anvil cell. Our XAS data of Ce-L3 in CeFeAsO0.7F0.3 clearly show a spectral weight transfer from the main line to the satellite line after the transition, demonstrating the formation of the Kondo singlets under pressure in CeFeAsO1-xFx. Our results have revealed a physical picture of a pressure-induce competition between Kondo singlets and BCS singlets in the Ce-pnictide superconductors.

cond-mat.supr-con↗

arXiv2009

Pressure-induced lattice collapse in tetragonal phase and structural phase transition in single crystalline Fe1.05Te

We report studies of in-situ x-ray diffraction (XRD) and electronic properties on the single crystalline of Fe1.05Te compound under high pressure. The results demonstrated that the sample undergoes a pressure-induced lattice collapse in tetragonal phase (cT) at 4 GPa at room temperature. The cT phase in turn transfers to monoclinic (M) phase with increasing pressure to 14 GPa. The resistance measurements under pressures show that the onset temperature of structural phase transition (TSTR) decreases upon transformation from the tetragonal (T) to the cT phase and turns up at the 4 GPa where is the boundary pressure of T-cT phase. The onset of antiferromagnetic transition (TAF) shows little change up to 0.8 GPa by magnetization measurements. In the domain of M phase, the sample behaves like semiconductor at low temperature. No superconductivity is observed under the pressure investigated.

cond-mat.supr-con↗

arXiv2009

Approximating Scheduling Machines with Capacity Constraints

In the Scheduling Machines with Capacity Constraints problem, we are given k identical machines, each of which can process at most m_i jobs. M jobs are also given, where job j has a non-negative processing time length t_j >= 0. The task is to find a schedule such that the makespan is minimized and the capacity constraints are met. In this paper, we present a 3-approximation algorithm using an extension of Iterative Rounding Method introduced by Jain. To the best of the authors' knowledge, this is the first attempt to apply Iterative Rounding Method to scheduling problem with capacity constraints.

cs.DS↗

arXiv2008

$B_{s} \to PP $ decays and the NLO contributions in the pQCD Approach

By employing the perturbative QCD(pQCD) factorization approach, we calculated the partial next-to-leading order (NLO) contributions to $B_s \to P P$ decays ($P= π, K, \etap $), coming from the QCD vertex corrections, the quark-loops and the chromo-magnetic penguins. we found numerically that (a) for three measured decays $\bar{B}_s \to K^+ π^-, K^+K^-$ and $π^+π^-$, the consistency between the pQCD predictions and the measured values are improved effectively by the inclusion of the NLO contributions; (b) for $\bar{B}_s \to K^0\etap$ and $K^0π^0$ decays, the NLO enhancements to the branching ratios can be significant, from $\sim 50%$ to 170%, to be tested by the LHC experiments; (c) for the CP-violating asymmetries, the leading order pQCD predictions can also be changed significantly by the inclusion of the NLO contributions; (d) for $\bar{B}_s \to K^+π^-$ decay, the pQCD prediction for the direct CP asymmetry is $\acp^{dir}(\bar{B}_s \to K^+π^-)=0.26\pm 0.06$, which agrees very well with the only measured value available currently.

hep-ph↗

arXiv2008

Network Motifs in Object-Oriented Software Systems

Nowadays, software has become a complex piece of work that may be beyond our control. Understanding how software evolves over time plays an important role in controlling software development processes. Recently, a few researchers found the quantitative evidence of structural duplication in software systems or web applications, which is similar to the evolutionary trend found in biological systems. To investigate the principles or rules of software evolution, we introduce the relevant theories and methods of complex networks into structural evolution and change of software systems. According to the results of our experiment on network motifs, we find that the stability of a motif shows positive correlation with its abundance and a motif with high Z score tends to have stable structure. These findings imply that the evolution of software systems is based on functional cloning as well as structural duplication and tends to be structurally stable. So, the work presented in this paper will be useful for the analysis of structural changes of software systems in reverse engineering.

cs.SE↗

arXiv2008

Full Diversity Codes for MISO Systems Equipped with Linear or ML Detectors

In this paper, a general criterion for space time block codes (STBC) to achieve full-diversity with a linear receiver is proposed for a wireless communication system having multiple transmitter and single receiver antennas (MISO). Particularly, the STBC with Toeplitz structure satisfies this criterion and therefore, enables full-diversity. Further examination of this Toeplitz STBC reveals the following important properties: a) The symbol transmission rate can be made to approach unity. b) Applying the Toeplitz code to any signalling scheme having nonzero distance between the nearest constellation points results in a non-vanishing determinant. In addition, if QAM is used as the signalling scheme, then for independent MISO flat fading channels, the Toeplitz codes is proved to approach the optimal diversity-vs-multiplexing tradeoff with a ZF receiver when the number of channel uses is large. This is, so far, the first non-orthogonal STBC shown to achieve the optimal tradeoff for such a receiver. On the other hand, when ML detection is employed in a MISO system, the Toeplitz STBC achieves the maximum coding gain for independent channels. When the channel fading coefficients are correlated, the inherent transmission matrix in the Toeplitz STBC can be designed to minimize the average worst case pair-wise error probability.

cs.IT↗

arXiv2008

MaGe - a Geant4-based Monte Carlo framework for low-background experiments

A Monte Carlo framework, MaGe, has been developed based on the Geant4 simulation toolkit. Its purpose is to simulate physics processes in low-energy and low-background radiation detectors, specifically for the Majorana and Gerda $^{76}$Ge neutrinoless double-beta decay experiments. This jointly-developed tool is also used to verify the simulation of physics processes relevant to other low-background experiments in Geant4. The MaGe framework contains simulations of prototype experiments and test stands, and is easily extended to incorporate new geometries and configurations while still using the same verified physics processes, tunings, and code framework. This reduces duplication of efforts and improves the robustness of and confidence in the simulation output.

nucl-ex↗