Notizie da 5 fonti

09 feb 2016 17:00

Researchers have studied a membrane laser containing nanometer-sized holes to demonstrate how photon losses can be minimized.  [Physics] Published Tue Feb 09, 2016

fisica | physics - spotlighting exceptional research

08 feb 2016 17:00

Author(s): David A. Kosower A simplifying technique for calculating scattering amplitudes—the basis for predictions in particle physics experiments—has been extended to cover a class of effective quantum field theories. [Physics 9, 15] Published Mon Feb 08, 2016

fisica | physics - spotlighting exceptional research

05 feb 2016 17:00

Author(s): Tamela Maciel Carbon honeycomb, a new carbon structure, could store large amounts of hydrogen gas, which may benefit fuel cell technology. [Physics 9, 16] Published Fri Feb 05, 2016

fisica | physics - spotlighting exceptional research

04 feb 2016 17:00

New models show that neutron stars—and not dark matter—could be responsible for an excess of gamma rays from the Milky Way’s center. [Physics] Published Thu Feb 04, 2016

fisica | physics - spotlighting exceptional research

04 feb 2016 02:00

Analysis of dynamic features of pedestrian flows is one of the most exciting topics in pedestrian dynamics. This paper focuses on the effect of homogeneity and heterogeneity in three parameters of the social force model, namely desired velocity, reaction time, and body size, on the moving dynamics of bidirectional pedestrian flows in the corridors. The speed and its deviation in free flows are investigated. Simulation results show that the homogeneous higher desired speed which is less than a critical threshold, shorter reaction time or smaller body size results in higher speed of flows. The free dynamics is more sensitive to the heterogeneity in desired speed than that in reaction time or in body size. In particular, an inner lane formation is observed in normal lanes. Furthermore, the breakdown probability and the start time of breakdown are focused on. This study reveals that the sizes of homogeneous desired speed, reaction time or body size play more important roles in affect...

fisica | chinese physics b latest papers

04 feb 2016 02:00

In this work, the behavior of the three-dimensional (3D) jet coiling based on the viscoelastic Oldroyd-B model is investigated by a corrected particle scheme, which is named the smoothed particle hydrodynamics with corrected symmetric kernel gradient and shifting particle technique (SPH_CS_SP) method. The accuracy and stability of SPH_CS_SP method is first tested by solving Poiseuille flow and Taylor–Green flow. Then the capacity for the SPH_CS_SP method to solve the viscoelastic fluid is verified by the polymer flow through a periodic array of cylinders. Moreover, the convergence of the SPH_CS_SP method is also investigated. Finally, the proposed method is further applied to the 3D viscoelastic jet coiling problem, and the influences of macroscopic parameters on the jet coiling are discussed. The numerical results show that the SPH_CS_SP method has higher accuracy and better stability than the traditional SPH method and other corrected SPH method, and can improve the tensile ins...

fisica | chinese physics b latest papers

04 feb 2016 02:00

Sensitive detection of acetylene (C 2 H 2 ) is performed by absorption spectroscopy and wavelength modulation spectroscopy (WMS) based on Fiber Fabry–Perot tunable filter (FFP-TF) at 1530.32 nm. After being calibrated by Fiber Bragg Grating (FBG), FFP-TF is frequency-multiplexed and modulated at 20 Hz and 2.5 kHz respectively to achieve wavelength modulation. The linearity with 0.9907 fitting coefficient is obtained by measuring different concentrations in a 100 ppmv–400 ppmv range. Furthermore, the stability of the system is analyzed by detecting 50 ppmv and 100 ppmv standard gases for 2 h under room temperature and ambient pressure conditions respectively. The precision of 11 ppmv is achieved by calculating the standard deviation. Therefore, the measuring system of C 2 H 2 detection can be applied in practical applications.

fisica | chinese physics b latest papers

04 feb 2016 02:00

High- κ /Ge gate stack has recently attracted a great deal of attention as a potential candidate to replace planar silicon transistors for sub-22 generation. However, the desorption and volatilization of GeO hamper the development of Ge-based devices. To cope with this challenge, various techniques have been proposed to improve the high- κ /Ge interface. However, these techniques have not been developed perfectly yet to control the interface. Therefore, in this paper, we propose an improved stress relieved pre-oxide (SRPO) method to improve the thermodynamic stability of the high- κ /Ge interface. The x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) results indicate that the GeO volatilization of the high- κ /Ge gate stack is efficiently suppressed after 500 °C annealing, and the electrical characteristics are greatly improved.

fisica | chinese physics b latest papers

04 feb 2016 02:00

Raman spectra of confined water adsorbed in nanoporous TiO 2 are obtained in experiment. TiO 2 samples with different pore diameters under different humidity conditions are investigated. The results indicate that the symmetric vibrational mode of water molecule is destroyed when relative humidity decreases. This indicates that the interaction between water molecules and surface of TiO 2 becomes stronger when the distance between water molecules and surface turns smaller, and the interaction plays a major role in depressing the symmetric vibrational peak. The spectra of confined water in TiO 2 and Vycor are compared. When filling fractions are the same, their spectra show distinctions no matter whether they are in partial filling condition or in full filling condition. The spectra of HDO confined in TiO 2 with different filling fractions are compared with each other. There is no clear distinction among their vibrational peaks, and ...

fisica | chinese physics b latest papers

04 feb 2016 02:00

We have studied the characteristics of current-induced nonequilibrium spin polarization in semiconductor-nanowire/s-wave superconductor junctions with strong spin–orbit coupling. It was found that within some parameter regions the magnitude of the current-induced nonequilibrium spin polarization density in such structures will increase (or decrease) with the decrease (or increase) of the charge current density, in contrast to that found in normal spin–orbit coupled semiconductor structures. It was also found that the unusual characteristics of the current-induced nonequilibrium spin polarization in such structures can be well explained by the effect of the Andreev reflection.

fisica | chinese physics b latest papers