Stationary and dynamical properties of a zero range process on scale-free networks

We study the condensation phenomenon in a zero range process on scale-free networks. We show that the stationary state property depends only on the degree distribution of underlying networks. The model displays a stationary state phase transition between a condensed phase and an uncondensed phase, and the phase diagram is obtained analytically. As for the dynamical property, we find that the relaxation dynamics depends on the global structure of underlying networks. The relaxation time follows the power law $\tau \sim L^z$ with the network size $L$ in the condensed phase. The dynamic exponent $z$ is found to take a different value depending on whether underlying networks have a tree structure or not.Comment: 9 pages, 6 eps figures, accepted version in PR

Coulomb Drag near the metal-insulator transition in two-dimensions

We studied the drag resistivity between dilute two-dimensional hole systems, near the apparent metal-insulator transition. We find the deviations from the $T^{2}$ dependence of the drag to be independent of layer spacing and correlated with the metalliclike behavior in the single layer resistivity, suggesting they both arise from the same origin. In addition, layer spacing dependence measurements suggest that while the screening properties of the system remain relatively independent of temperature, they weaken significantly as the carrier density is reduced. Finally, we demonstrate that the drag itself significantly enhances the metallic $T$ dependence in the single layer resistivity.Comment: 6 pages, 5 figures; revisions to text, to appear in Phys. Rev.

Vertical variation of optical properties of mixed Asian dust/pollution plumes according to pathway of air mass transport over East Asia

© Author(s) 2015. This is an Open Access article made available under the terms of the Creative Commons Attribution License 3.0 https://creativecommons.org/licenses/by/3.0/We use five years (2009-2013) of multiwavelength Raman lidar measurements at Gwangju, South Korea (35.10° N, 126.53° E) for the identification of changes of optical properties of East Asian dust depending on its transport path over China. Profiles of backscatter and extinction coefficients, lidar ratios, and backscatter-related Ångström exponents (wavelength pair 355/532 nm) were measured at Gwangju. Linear particle depolarization ratios were used to identify East Asian dust layers. We used backward trajectory modeling to identify the pathway and the vertical position of dust-laden air masses over China during long-range transport. Most cases of Asian dust events can be described by the emission of dust in desert areas and subsequent transport over highly polluted regions of China. The Asian dust plumes could be categorized into two classes according to the height above ground at which these plumes were transported: (case I) the dust layers passed over China at high altitude levels (> 3 km) until arrival over Gwangju, and (case II) the Asian dust layers were transported near the surface and within the lower troposphere (< 3 km) over industrialized areas before they arrived over Gwangju. We find that the optical characteristics of these mixed Asian dust layers over Gwangju differ depending on their vertical position above ground over China and the change of height above ground during transport. The mean linear particle depolarization ratio was 0.21 ± 0.06 (at 532 nm), the mean lidar ratios were 52 ± 7 sr at 355 nm and 53 ± 8 sr at 532 nm, and the mean Ångström exponent was 0.74 ± 0.31 for case I. In contrast, plumes transported at lower altitudes (case II) showed low depolarization ratios (0.13 ± 0.04 at 532 nm), and higher lidar ratio (63 ± 9 sr at 355 nm and 62 ± 8 sr at 532 nm) and Ångström exponents (0.98 ± 0.51). These numbers show that the optical characteristics of mixed Asian plumes are more similar to optical characteristics of urban pollution. We find a decrease of the linear depolarization ratio of the mixed dust/pollution plume depending on transport time if the pollution layer traveled over China at low heights, i.e., below approximately 3 km above ground. In contrast, we do not find such a trend if the dust plumes traveled at heights above 3 km over China. We need a longer time series of lidar measurements in order to determine in a quantitative way the change of optical properties of dust with transport time.Peer reviewedFinal Published versio

Soft fluidic rotary actuator with improved actuation properties

The constantly increasing amount of machines operating in the vicinity of humans makes it necessary to rethink the design approach for such machines to ensure that they are safe when interacting with humans. Traditional mechanisms are rigid and heavy and as such considered unsuitable, even dangerous when a controlled physical contact with humans is desired. A huge improvement in terms of safe human-robot interaction has been achieved by a radically new approach to robotics - soft material robotics. These new robots are made of compliant materials that render them safe when compared to the conventional rigid-link robots. This undeniable advantage of compliance and softness is paired with a number of drawbacks. One of them is that a complex and sophisticated controller is required to move a soft robot into the desired positions or along a desired trajectory, especially with external forces being present. In this paper we propose an improved soft fluidic rotary actuator composed of silicone rubber and fiber-based reinforcement. The actuator is cheap and easily manufactured providing near linear actuation properties when compared to pneumatic actuators presented elsewhere. The paper presents the actuator design, manufacturing process and a mathematical model of the actuator behavior as well as an experimental validation of the model. Four different actuator types are compared including a square-shaped and three differently reinforced cylindrical actuators

Conserved cosmological structures in the one-loop superstring effective action

A generic form of low-energy effective action of superstring theories with one-loop quantum correction is well known. Based on this action we derive the complete perturbation equations and general analytic solutions in the cosmological spacetime. Using the solutions we identify conserved quantities characterizing the perturbations: the amplitude of gravitational wave and the perturbed three-space curvature in the uniform-field gauge both in the large-scale limit, and the angular-momentum of rotational perturbation are conserved independently of changing gravity sector. Implications for calculating perturbation spectra generated in the inflation era based on the string action are presented.Comment: 5 pages, no figure, To appear in Phys. Rev.

Infrared Hall conductivity of Na0.7_{0.7}CoO2_2

We report infrared Hall conductivity $\sigma_{xy}(\omega)$ of Na$_{0.7}$CoO$_2$ thin films determined from Faraday rotation angle $\theta_{F}$ measurements. $\sigma_{xy}(\omega)$ exhibits two types of hole conduction, Drude and incoherent carriers. The coherent Drude carrier shows a large renormalized mass and Fermi liquid-like behavior of Hall scattering rate, $\gamma_{H} \sim aT^{2}$. The spectral weight is suppressed and disappears at T = 120K. The incoherent carrier response is centered at mid-IR frequency and shifts to lower energy with increasing T. Infrared Hall constant is positive and almost independent of temperature in sharp contrast with the dc-Hall constant.Comment: 5 Pages, 5 Figures. Author list corrected in metadata only, paper is unchange

Frictional Drag between Two Dilute Two-Dimensional Hole Layers

We report drag measurements on dilute double layer two-dimensional hole systems in the regime of r_s=19~39. We observed a strong enhancement of the drag over the simple Boltzmann calculations of Coulomb interaction, and deviations from the T^2 dependence which cannot be explained by phonon-mediated, plasmon-enhanced, or disorder-related processes. We suggest that this deviation results from interaction effects in the dilute regime.Comment: 4 pages, 3 figures, accepted in Phys. Rev. Lett. Added single layer transport dat