Room‐Temperature Mesoscopic Fluctuations and Coulomb Drag in Multilayer WSe2

Mesoscopic fluctuations, manifesting the quantum interference (QI) of electrons, have been theoretically proposed in bilayer Coulomb drag systems. Unfortunately, these phenomena are usually observed at cryogenic temperatures, which severely limits their novel physics for pragmatic applications. In this paper, observation of room‐temperature QI and Coulomb drag in a multilayer WSe₂ transistor is reported via graphene contacts separately at its top and bottom layers. The central layers of WSe₂ act as an insulating region with a width of few nanometers, which spatially separates the top and bottom conducting channels and provides a strong Coulomb interaction between them, leading to large conductance oscillations at room temperature. The gradual suppression of the oscillations with the increase in the applied magnetic field and/or injected current further confirms the QI phenomenon. With the decrease in temperature, the Coulomb drag effect is exhibited in the system owing to the increased thickness of the insulating region. This study reveals a novel approach for realization of advanced quantum electronics operating at high temperatures.     

Effect of Sintering Temperature on Properties of CNT/Al Composite Prepared by Capsule-Free Hot Isostatic Pressing Technique

Carbon nanotube (CNT)/Al composite powders were prepared by high energy ball milling technique. CNTs were well dispersed in Al matrix but the graphite structure of CNTs was significantly damaged during the mixing process. Dense composite was prepared by capsule free hot isostatic pressing technique. The best sintering temperature was determined to be 620 °C, at which relative density of sintered specimens increased to 92 % and decreased with the increase of CNT content due to the formation of CNT clusters. Microhardness of the composite could be improved by increasing CNT content up to 1 wt% with the highest value of 56.7 HV which was nearly two times higher than that of pure Al. Electrical resistivity was increased in proportion to the CNT content. The increase of resistivity was due to the effect of porosity, electron scattering at particle boundaries and existence of oxidation phase.     

Large-Eddy Simulations of Staggered Parallel-Plate Fin Heat Exchangers: Effect of Reynolds Number on Flow Topology

A large-eddy simulation (LES) with dynamic subgrid-scale modeling is conducted to investigate flow over staggered parallel-plate fins and to depict turbulence effect on heat and mass transfer efficiency. Navier-Stokes equations for a low-Mach-number, weakly compressible formulation are solved using a second-order-accurate scheme in space and time. Calculations are carried out for Reynolds numbers Re ranging from 500 to 10,000. The results facilitate estimation of the flow topology and its evolution with regard to Re. Identification of coherent structures may bring about clear depiction of a particularly close relationship between heat transfer and turbulent flow field development. In addition, global heat and mass transfer correlations are estimated numerically and are found to be in reasonable agreement with previous experimental correlations.     

Combined electrochemical and biological treatment of industrial wastewater using porous electrodes

Zn²⁺, Ni²⁺ and propylene glycol methyl ether were simultaneously removed from simulated wastewater in a column consisting of an aerated packed bed and an electrochemical cell with a porous aluminium foam cathode and a porous stainless steel anode. After 48 h of sole electrochemical treatment at a liquid rate of 0.00183 m³ m^?2 s^?1, Zn²⁺ and Ni²⁺ were reduced by 95 and 80% respectively. In the turbulent flow regime with liquid rates varied from 0.0137 to 0.0366 m³ m^?2 s^?1, both Zn²⁺ and Ni²⁺ removal decreased by about 15% rather than increased as expected for a mass transfer‐controlled process. This can be attributed to bubble formation at the cathode surface under turbulent flow, which led to a lower active surface area for the electrodeposition of metal ions. Porous electrodes enhanced the metal removal by 17 and 60% for Zn²⁺ and Ni²⁺ respectively as compared with flat plate electrodes. Using combined biological and electrochemical treatment at a water rate of 0.00183 m³ m^?2 s^?1 and an air rate of 0.0518 m³ m^?2 s^?1, 99% of Zn²⁺ and 95% of Ni²⁺ were removed. In addition, the 5 day biological oxygen demand (BOD₅) was reduced by 58% concurrently over 72 h of treatment. Copyright © 2006 Society of Chemical Industry     

Max–min fairness in multi-commodity flows

In this paper, we provide a study of Max–Min Fair (MMF) multi-commodity flows and focus on some of their applications to multi-commodity networks. We first present the theoretical background for the problem of MMF and recall its relations with lexicographic optimization as well as a polynomial approach for achieving leximin maximization. We next describe two applications to telecommunication networks, one on routing and the second on load-balancing. We provide some deeper theoretical analysis of MMF multi-commodity flows, show how to solve the lexicographically minimum load network problem for the link load functions most frequently used in telecommunication networks. Some computational results illustrate the behavior of the obtained solutions and the required CPU time for a range of random and well-dimensioned networks.     

Reducing the impacts of intra-class spectral variability on the accuracy of soft classification and super-resolution mapping of shoreline

The main objective of this research is to assess the impact of intra-class spectral variation on the accuracy of soft classification and super-resolution mapping. The accuracy of both analyses was negatively related to the degree of intra-class spectral variation, but the effect could be reduced through the use of spectral sub-classes. The latter is illustrated in mapping the shoreline at a sub-pixel scale from Landsat ETM+ data. Reducing the degree of intra-class spectral variation increased the accuracy of soft classification, with the correlation between predicted and actual class coverage rising from 0.87 to 0.94, and super-resolution mapping, with the RMSE in shoreline location decreasing from 41.13 m to 35.22 m.     

Intermittent ultrasound-assisted ceramic membrane fouling control in ultrafiltration

In this study, remediation of ceramic membrane fouling by an in-line intermittent ultrasound system was investigated. A piezoelectric ultrasonic transducer was integrated into a membrane unit that provided ultrafiltration (UF) of a diluted skim milk solution containing 0.10 wt% of protein. The effects of ultrasound at varied frequencies (20, 28, and 40 kHz) and power intensities (1.44, 2.88, and 5.76 W/cm²) under continuous operation and intermittent mode at various intervals (0.50, 1.0, 1.5, 2.0, 2.5, and 3.0 minutes) on membrane fouling were studied. The quality and flow rate of the permeate stream were monitored for the evaluation of the UF process performance. Optimal conditions of continuous ultrasound were found at 28 kHz and 2.88 W/cm². Moreover, at optimal ultrasonic conditions, the optimal intermittent time was found at 0.50 minute. At optimal ultrasonic conditions, the permeate amount increased by 79.8% and 94.2% for 0.50 minute intermittent ultrasound and continuous ultrasound, respectively, as compared with that of the UF process without ultrasound. Also, intermittent ultrasound induced better fouling control at a lower protein concentration of 0.05% by weight. The cleaning effect of ultrasound could be attributed to the cavitation bubbles generated by the rarefaction and pressure cycles of the applied ultrasound.     

Energy-consistent theory of cylindrical shells

On the basis of the energy-consistent direction in the theory of shells, the deflected mode of circular cylindrical shells, considered as three-dimensional bodies, is studied. At that, two-dimensional equations of the boundary problem, obtained on the basis of the Lagrange principle by means of expansion of the sought relocations in polynomial series regarding the normal coordinate, are used. Equations are presented for the case when the approximation of the relocations in respect of the shell thickness retains summands that are by an order of magnitude higher than that in the Kirchhoff-Love classical theory of shells. The boundary problem formulated is solved with the help of the Laplace transform. As an example, a shell under the action of local loads is considered, for which the deflected mode is determined and a comparison is performed with the results obtained in accordance with the classical theory.     

Uniformity optimization techniques for rapid thermal processingsystems

This paper presents two efficient robust methods for uniformity optimization of rapid thermal processes. Both of these methods involve the reuse of empirical response surfaces linking zone powers to measured process data created on a baseline system. The first method uses fossilized gain matrices from the baseline system, while the second method involves customization of the baseline response surface for each system. The approaches use the response surfaces for iterative modification of zone powers to reduce the process nonuniformity on successively processed wafers. These methods are applied to the optimization of rapid thermal oxidation processes on several lamp-heated rapid thermal processing systems. Most of the uniformity improvement is obtained with the first two optimization runs; in some instances, the process is optimized to less than 1% 1-sigma nonuniformity with the use of just two wafers. Because the response surfaces from the baseline system can be reused for all similar systems, considerable savings in time and wafers are realized