Txt2vz: a new tool for generating graph clouds

We present txt2vz (txt2vz.appspot.com), a new tool for automatically generating a visual summary of unstructured text data found in documents or web sites. The main purpose of the tool is to give the user information about the text so that they can quickly get a good idea about the topics covered. Txt2vz is able to identify important concepts from unstructured text data and to reveal relationships between those concepts. We discuss other approaches to generating diagrams from text and highlight the differences between tag clouds, word clouds, tree clouds and graph clouds

A new model for the double well potential

A new model for the double well potential is presented in the paper. In the new potential, the exchanging rate could be easily calculated by the perturbation method in supersymmetric quantum mechanics. It gives good results whether the barrier is high or sallow. The new model have many merits and may be used in the double well problem.Comment: 3pages, 3figure

Universal Quantum Degeneracy Point for Superconducting Qubits

The quantum degeneracy point approach [D. Vion et al., Science 296, 886 (2002)] effectively protects superconducting qubits from low-frequency noise that couples with the qubits as transverse noise. However, low-frequency noise in superconducting qubits can originate from various mechanisms and can couple with the qubits either as transverse or as longitudinal noise. Here, we present a quantum circuit containing a universal quantum degeneracy point that protects an encoded qubit from arbitrary low-frequency noise. We further show that universal quantum logic gates can be performed on the encoded qubit with high gate fidelity. The proposed scheme is robust against small parameter spreads due to fabrication errors in the superconducting qubits.Comment: 7 pages, 4 figure

The effect of tube diameter on vertical two-phase flow regimes in small tubes

Flow boiling flow patterns in four circular tubes with internal diameters of 1.10, 2.01, 2.88 and 4.26 mm were investigated in the present project. The experiments were conducted in vertical upward two-phase flow using R134a as the working fluid. The observed flow patterns include dispersed bubble, bubbly, confined bubble, slug, churn, annular and mist flow. The flow characteristics in the 2.88 and 4.26 mm tubes are similar to those typically described in normal size tubes. The smaller diameter tubes, 1.10 and 2.01 mm, exhibit strong "small tube characteristics" as described in earlier studies. The sketched flow maps show that the transition boundaries of slug-churn and churn-annular depend strongly on diameter. On the contrary, the dispersed bubble to churn and bubbly to slug boundaries are less affected. The transition boundaries are compared with existing models for normal size tubes showing poor agreement

Pulsars identified from the NRAO VLA Sky Survey

We identified 97 strong pulsars from the NRAO VLA Sky Survey (NVSS) at 1.4 GHz north of Dec(J2000) >-40\degr. The total flux density, linear polarization intensity and polarization angle (PA) of all pulsars are extracted from the NVSS catalog. The well-calibrated PA measurement of 5 pulsars can be used for absolute PA calibrations in other observations. Comparing the source positions with those in the pulsar catalog, we got the first measurement of the proper motion upper limit of PSR B0031-07, which is $\mu_{\alpha}\cos\delta = -102 \pm 74 mas/yr$ and $\mu_{\delta} = -105 \pm 78 mas/yr$.Comment: 7 pages; 3 figures; one big table; To appear in A&A Supplement

Disturbance Attenuation in a Magnetic Levitation System with Acceleration Feedback

The objective of this work is to demonstrate the use of acceleration feedback to improve the performance of a maglev system, especially in disturbance attenuation. In the single degree-of-freedom (DOF) system studied here, acceleration feedback has the effect of virtually increasing inertia, damping and stiffness. It is shown that it can be used to increase disturbance rejection without sacrificing tracking performance. Both analytical and experimental results demonstrate that disturbance rejection can be improved with acceleration feedback

Correcting low-frequency noise with continuous measurement

Low-frequency noise presents a serious source of decoherence in solid-state qubits. When combined with a continuous weak measurement of the eigenstates, the low-frequency noise induces a second-order relaxation between the qubit states. Here we show that the relaxation provides a unique approach to calibrate the low-frequency noise in the time-domain. By encoding one qubit with two physical qubits that are alternatively calibrated, quantum logic gates with high fidelity can be performed.Comment: 10 pages, 3 figures, submitte

QCD description of backward vector meson hard electroproduction

We consider backward vector meson exclusive electroproduction off nucleons in the framework of collinear QCD factorization. Nucleon to vector meson transition distribution amplitudes arise as building blocks for the corresponding factorized amplitudes. In the near-backward kinematics, the suggested factorization mechanism results in the dominance of the transverse cross section of vector meson production ($\sigma_T \gg \sigma_L$) and in the characteristic $1/Q^8$-scaling behavior of the cross section. We evaluate nucleon to vector meson TDAs in the cross-channel nucleon exchange model and present estimates of the differential cross section for backward $\rho^0$, $\omega$ and $\phi$ meson production off protons. The resulting cross sections are shown to be measurable in the forthcoming JLab@12 GeV experiments.Comment: 37 pages, 8 figures, 1 tabl