Long lasting instabilities in granular mixtures

We have performed experiments of axial segregation in the Oyama's drum. We have tested binary granular mixtures during very long times. The segregation patterns have been captured by a CCD camera and spatio-temporal graphs are created. We report the occurence of instabilities which can last several hours. We stress that those instabilities originate from the competition between axial and radial segregations. We put into evidence the occurence of giant fluctuations in the fraction of grain species along the surface during the unstable periods.Comment: 10 pages, 10 figures, (2002

Design of small CRPA arrays with circular microstrip loops for electromagnetically coupled feed

This paper proposes a design of small controlled reception pattern antenna (CRPA) arrays using circular microstrip loops with frequencyinsensitive characteristics. The proposed array consists of seven identical upper and lower circular loops that are electromagnetically coupled, which results in a frequency-insensitive behavior. To demonstrate the feasibility of the proposed feeding mechanism, the proposed array is fabricated, and its antenna characteristics are measured in a full-anechoic chamber. The operating principle of the proposed feeding mechanism is then interpreted using an equivalent circuit model, and the effectiveness of the circular loop shape is demonstrated by calculating near electromagnetic fields in proximity to the radiator. The results confirm that the proposed feeding mechanism is suitable to have frequency- insensitive behavior and induces strong electric and magnetic field strengths for higher radiation gain in extremely small antenna arrays

Dynamics of axial separation in long rotating drums

We propose a continuum description for the axial separation of granular materials in a long rotating drum. The model, operating with two local variables, concentration difference and the dynamic angle of repose, describes both initial transient traveling wave dynamics and long-term segregation of the binary mixture. Segregation proceeds through ultra-slow logarithmic coarsening.Comment: 4 pages, 3 Postscript figures; submitted to PR

Development of PAN (personal area network) for Mobile Robot Using Bluetooth Transceiver

In recent years, wireless applications using radio frequency (RF) have been rapidly evolving in personal computing and communications devices. Bluetooth technology was created to replace the cables used on mobile devices. Bluetooth is an open specification and encompasses a simple low-cost, low power solution for integration into devices. This research work aim was to provide a PAN (personal area network) for computer based mobile robot that supports real-time control of four mobile robots from a host mobile robot. With ad hoc topology, mobile robots may request and establish a connection when it is within the range or terminated the connection when it leaves the area. A system that contains both hardware and software is designed to enable the robots to participate in multi-agent robotics system (MARS). Computer based mobile robot provide operating system that enabled development of wireless connection via IP address

Live Migration in Emerging Cloud Paradigms

The elastic provisioning of resources and the capability to adapt to changing resource demand and environmental conditions on-the-fly are, probably, key success factors of cloud computing. Live migration of virtual resources is of pivotal importance in achieving such key properties. However, the ability to effectively and efficiently determine which resource to be migrated and where, by satisfying proper objectives and constraints, remains a research challenge. The existing literature is generally based on metaheuristics running a central resolver. Such an approach is not suitable because it only considers the quality-of-service aspect during the decision-making performance while ignoring the regulatory challenges. This column highlights the regulatory challenges associated with the cross-border dataflow implication of migration and stresses the need to adopt alternative decision approaches.postprin

Thermophysical and elastic properties of Cu50Zr50 and (Cu50Zr50)95Al5 bulk-metallic-glass-forming alloys

By employing a containerless high-temperature high-vacuum electrostatic levitation technique, the thermophysical properties, including the ratio between the specific heat capacity and the hemispherical total emissivity, the specific volume, and the viscosity, of Cu50Zr50 and (Cu50Zr50)95Al5 bulk-metallic-glass (BMG)-forming liquids have been measured. Compared with Cu50Zr50, the improved glass-forming ability of (Cu50Zr50)95Al5 can be attributed to its dense liquid structure and its high value of viscosity. Additionally, the relationship between the viscosity of various BMG forming liquids at the melting temperature and the elastic properties of the corresponding glasses at room temperature will be compared

Thermophysical properties of a Cu46Zr42Al7Y5 bulk metallic glass-forming liquid

The thermophysical properties, including the specific volume V, the surface tension sigma, and the viscosity eta, of a Cu46Zr42Al7Y5 bulk metallic glass in the molten state were investigated using a containerless high-temperature high-vacuum electrostatic levitation technique. The viscosity measurements indicate that the Cu46Zr42Al7Y5 alloy exhibits an intermediate fragility with the fragility index m=49

Chemical Raman Enhancement of Organic Adsorbates on Metal Surfaces

Using a combination of first-principles theory and experiments, we provide a quantitative explanation for chemical contributions to surface-enhanced Raman spectroscopy for a well-studied organic molecule, benzene thiol, chemisorbed on planar Au(111) surfaces. With density functional theory calculations of the static Raman tensor, we demonstrate and quantify a strong mode-dependent modification of benzene thiol Raman spectra by Au substrates. Raman active modes with the largest enhancements result from stronger contributions from Au to their electron-vibron coupling, as quantified through a deformation potential, a well-defined property of each vibrational mode. A straightforward and general analysis is introduced that allows extraction of chemical enhancement from experiments for specific vibrational modes; measured values are in excellent agreement with our calculations.Comment: 5 pages, 4 figures and Supplementary material included as ancillary fil