Modified Sonine approximation for the Navier-Stokes transport coefficients of a granular gas

Motivated by the disagreement found at high dissipation between simulation data for the heat flux transport coefficients and the expressions derived from the Boltzmann equation by the standard first Sonine approximation [Brey et al., Phys. Rev. E 70, 051301 (2004); J. Phys.: Condens. Matter 17, S2489 (2005)], we implement in this paper a modified version of the first Sonine approximation in which the Maxwell-Boltzmann weight function is replaced by the homogeneous cooling state distribution. The structure of the transport coefficients is common in both approximations, the distinction appearing in the coefficient of the fourth cumulant $a_2$. Comparison with computer simulations shows that the modified approximation significantly improves the estimates for the heat flux transport coefficients at strong dissipation. In addition, the slight discrepancies between simulation and the standard first Sonine estimates for the shear viscosity and the self-diffusion coefficient are also partially corrected by the modified approximation. Finally, the extension of the modified first Sonine approximation to the transport coefficients of the Enskog kinetic theory is presented.Comment: 10 pages, 6 figures; v2: slightly shortene

Spin Orbit Coupling in Graphene Induced by Heavy Adatoms with Electrons in the Outer-Shell pp Orbitals

Many of the exotic properties proposed to occur in graphene rely on the possibility of increasing the spin orbit coupling (SOC). By combining analytical and numerical tight binding calculations, in this work we study the SOC induced by heavy adatoms with active electrons living in $p$ orbitals. Depending on the position of the adatoms on graphene different kinds of SOC appear. Adatoms located in hollow position induce spin conserving intrinsic like SOC whereas a random distribution of adatoms induces a spin flipping Rashba like SOC. The induced SOC is linearly proportional to the adatoms concentration, indicating the inexistent interference effects between different adatoms. By computing the Hall conductivity we have proved the stability of the topological quantum Hall phases created by the adatoms against inhomogeneous spin orbit coupling . For the case of Pb adatoms, we find that a concentration of 0.1 adatom per carbon atom generates SOC's of the order of $\sim$40$meV$

Foreword

Preface to the Volume by O. Rak on the Neolithic Rhyta, cult vessels distributed in most of the Balkan peninsul

Frequency division multiplex technique

A system for monitoring a plurality of condition responsive devices is described. It consists of a master control station and a remote station. The master control station is capable of transmitting command signals which includes a parity signal to a remote station which transmits the signals back to the command station so that such can be compared with the original signals in order to determine if there are any transmission errors. The system utilizes frequency sources which are 1.21 multiples of each other so that no linear combination of any harmonics will interfere with another frequency

A frequency division multiplex technique for transmitting commands

Reliable random access multiplexer is controlled and operated over two twisted-pair telephone lines at distances of 5.6 to 8.0 km with control signals of less than 10 volts rms. Technique adapts to any process or environmental control system where data source is necessary

New Media and the Quality of Life

We are currently in the middle of a revolution. This revolution, sometimes called the digital revolution, is the revolutionary transformation brought about in the information and communication structure of society by the advent of the digital computer, with most of the major transformations having taken place in the past thirty years. Digital computing technology has generated the mainframe and personal computer, the multimedia computer, and computer networks. It has also transformed the telephone system and the monetary system, it is transforming all kinds of conventional products ranging from washing machines to automobiles, and it is on its way to change television as well. More than ever, contemporary society is an Information Society, in which the importance of information and communication is much greater than in past societies, and of which technologies that facilitate information and communication processes are a central societal feature. In this paper, I want to evaluate the implications of contemporary information and communication media for the quality of life, including both the new media from the digital revolution and the older media that still remain in use. My evaluation of contemporary media will proceed in three parts. In the section to follow, the benefits of contemporary media will be discussed, with special emphasis given to their immediate functional benefits. The section thereafter is devoted to a discussion of four potential threats posed by contemporary media. In a final major section, I look at the future of digital media and the possibilities available to us in shaping that future. A short concluding section ends the paper