Rolling Friction in a Micro Tribosystem

Pin-on-disc apparatus was used to investigate the effect of temperature on the dry sliding friction characteristics of a Zr-based bulk metallic glass (BMG) near its glass transition temperature (T _g = 625 K) (an analogous phenomenon in crystalline metals called the ductile-brittle transition). Unexpected variation in frictional behavior was observed in the temperature range of 603–643 K, suggesting that the glass transition and formation of protective oxide layers played roles in the tribological properties of BMG. An explanation of the behavior is given based on Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) analysis.     

System co-optimization in wireless receiver design with TrACS

System co-optimization of the analog receiver front end circuit and the digital baseband processing could enable receiver designs with lower power budgets, as the signal processing in the digital receiver is asymmetric across circuit topologies. This paper presents a simulation tool that could assist with such co-optimized designs. TrACS (Transceiver Architecture and Channel Simulator) is an RF/DSP co-simulator, capable of providing an application-specific system-level perspective to receiver design. The simulator is especially relevant in the context of energy-constrained wireless sensor node design, where the simulator’s system perspective determines the compatibility of circuit topologies, modulation techniques and synchronization methods for various wireless scenarios. A few case studies are presented, which illustrate co-optimization of a ZigBEE receiver using TrACS.     

Unsteady conjugate forced convection heat/mass transfer in ensembles of spherical particles with cell models

Numerical methods are used to investigate the transient, conjugate, forced convection heat/mass transfer in multiparticle systems at low to moderate Reynolds numbers. The interparticle interactions have been accounted for by using the simple cell models. The momentum and heat/mass balance equations were solved numerically in spherical coordinates system by a finite difference method. The values considered for the sphere Reynolds number are Re < 100. The computations were focused on the influence of the voidage and physical properties ratios on the heat/mass transfer rate for sphere Peclet number, 10 ? Pe ? 1000.     

Evaluation of thermal and dielectric behaviour of some anionic nylon 612 copolymers

The anionic nylon 612 copolymers consisting of ?-caprolactam and 0.0–50.0 wt.% of laurolactam comonomer were synthesized and some of their characteristics were compared. The melting temperature, degree of crystallinity (first and second heating scan) and crystallization temperature of the nylon 612 copolymers are influenced by the presence of comonomer (laurolactam) decreasing proportionally to the amount of the laurolactam in the initial monomer mixture. The thermal stability of the copolyamides is good and equal to that of PA 6. Dielectric measurements performed on the polymers under study, over a frequency range of 10⁰–10⁶ Hz, at temperatures from 173 to 373 K have evidenced that modification of the dielectric permittivity and dielectric loss values occur in concordance with increase/decrease of the homogeneity in the polymer chains structure induced by incorporation of laurolactam segments.     

Activation Energy of Bi2Sr2Ca1−x Er x Cu2O8+d Epitaxial Thin Films

The scaling behavior of the effective activation energy U(T, H) of epitaxial oriented Bi₂Sr₂Ca_1–x Er _x Cu₂O_8+d thin films with 0x0.10 has been studied as function of temperature and magnetic field. It has been found that the activation energy scales as U(H, T)=U ₀(1–t)^m H ⁿ with exponent m=1.20±0.03 and n=–1/2. The field and temperature dependence of the activation energy, as well as its overall magnitude, is consistent with a model in which U(T, H) arises from plastic deformations of viscous flux liquid above the vortex-glass transition temperature.     

Evaluating parallel architectures for two real-time applicationswith 100 kHz repetition rate [hadron collider data]

In the context of research and development activities for future hadron colliders, competitive implementations of real-time algorithms for feature extraction have been made on various forms of commercial pipelined and parallel architectures. The algorithms used for benchmarking serve for decision making and are of relative complexity; they are required to run with a repetition rate of 100 kHz on data sets of kilobyte size. Results are reported and discussed in detail. Among the commercially available architectures, pipelined image processing systems can compete with custom-designed architectures. General-purpose processors with systolic mesh connectivity can also be used. Massively parallel systems of the SIMD type (many processors executing the same program on different data) are less suitable in the presently marketed form     

An adaptive strategy for solving kinetic model concomitant estimation — Reduction problems

In order to simultaneously estimate the parameters and to reduce a complex kinetic model, an adaptive strategy which combines effective adaptive random search (ARS) and statistical ridge analysis steps is developed. As demonstrated, this strategy can save computational time because the estimation is not repeated with each reduced model. The use of ARS is preferred for highly nonlinear models and cases having multiple parameter constraints, guaranteeing reliability for interactively obtaining the global reduced model parameter solution.     

Thermoelectric power and annealing effects in NbAl2O3 cermet-type films

The effects of annealing on the structure and electrical conduction in $\text{Nb}\text{Al}{}_2\text{O}{}_3$ semiconducting films were investigated. Annealing increases the product of the density of states and the mobility near the Fermi level, and this suggests that the mobility increases because of structural changes in the alumina matrix.Thermopower measurements allowed us to evaluate the asymmetry about the Fermi level of the product Nμ.     

On the structural changes during thermal oxidation of evaporated Zn thin films

Metallic Zn thin films (d = 200 nm-500 nm) were deposited in vacuum onto unheated glass substrate by quasi-closed volume technique at a source temperature of 723 K. Sets of samples simultaneously deposited on horizontally and vertically arranged substrates were prepared. The as-deposited Zn films were heated under ambient atmosphere at various temperatures ranged between 300 K and 650 K. By XRD and AFM techniques, the microstructural characteristics and their changes during Zn films heating were investigated. The influence of the deposition conditions on the structural changes during the oxidation process is also discussed.