Molecular dynamics modeling of cavity strengthening in irradiated iron

One of the most important problems in the field of nuclear industry is the relationship between irradiation-induced damage and the resulting induced mechanical response of the target metal and in particular ferritic base steels. In this work molecular dynamics simulation is used to simulate the nanoscale interaction between a moving dislocation and a defect, such as a cavity, as void or He bubble. The stress–strain curves are obtained under imposed strain rate condition using the atomic potentials based on the Fe potential of Ackland et al. 1997 for a void and He bubble as a function of He content and temperature. It appears that a 2 nm void is a stronger obstacle than a He bubble at low He contents, whereas at high He contents, the He bubble becomes a stronger obstacle. With increasing temperature the escape stress decreases and at the same time there is increasing degeneracy in the type of interaction.     

Low-power high-speed operation of submicron InP-InGaAs SHBTs at 1 mA

Scaling of submicron InP-InGaAs HBTs is investigated for low-power high-speed applications in mixed signal circuits. Device performance for transistors fabricated with a 0.5-/spl mu/m emitter width and varying emitter lengths are studied. The 0.5 /spl mu/m/spl times/2 /spl mu/m devices yielded excellent low-current RF performance, with an f/sub T/=173 GHz and an f/sub MAX/=187 GHz at 1 mA, the highest values reported for InP-based devices to date.     

Improved numerical simulations of incompressible flows based on viscous/inviscid interaction procedures

Viscous/inviscid interaction procedures consist usually of coupling potential flow and boundary layer calculations. In this study, the interaction is modeled using Helmholtz-type velocity decomposition where the gradient of the potential is augmented with a correction accounting for the vorticity effects in the viscous layers. Different ways to calculate the rotational components are discussed and methods to systematically improve the model are studied. Numerical results are compared with standard Navier–Stokes calculations to justify the present approach.     

The dynamic effects in vibrating-plate and pulsed extractors—II. The forces under the steady and pulsating single-phase flow

The experimental results are presented of the friction losses under the steady flow of liquid through plates of various construction. Under the laminar and fully turbulent regime of the flow the experimental data agree well with the derived relations and an empirical relation is given for the transition regime. The measurements are carried out of the forces and pressures existing under plate vibrations and an analysis of the experimental data shows that the equivalent thickness of the plate, expressing the effect on inertia forces under pulsating flow, is a periodic function of time. An empirical correlation for this quantity is found and the set of equations for the calculation of the forces, pressures and the instantaneous and average power input thus completed. A simple empirical relation for the average power input is provided.     

Occurrence of toxic cyanobacterial blooms for the first time in Lake Karaoun,Lebanon

The increasing occurrence of cyanobacterial bloom in freshwaters worldwide is of great importance because of public health risks. In addition, they are very likely to have negative impact on ecological and economic aspects. In this study, the seasonal succession of phytoplankton population in Lake Karaoun in Lebanon was monitored from May 2009 to June 2011. The physicochemical parameters of lake water were then monitored for 1 year, from June 2010 until June 2011, to correlate the physicochemical parameters with the phytoplankton population in the lake. Our results showed, for the first time in Lebanon, that the eutrophied Lake Karaoun has been under the invasion of toxic cyanobacterial blooms since May 2009. The cyanobacterial bloom was persistent from late spring (May) until late fall (December) for 2 consecutive years. The high water temperature in the summer season is the main factor that has been affecting the growth of the cyanobacteria. The most frequently encountered bloom‐forming species were Microcystis aeruginosa and Aphanizomenon ovalisporum, which were either present individually or coexistent. The obtained results showed that during the period of cyanobacterial bloom, a deterioration of water quality defined by low levels of dissolved oxygen, total dissolved solids, and electric conductivity was reported. During cyanobacterial bloom period, the concentration of the orthophosphate–P (PO4‐P) was very minimal. The measured high value of chlorophyll‐a concentration during cyanobacterial bloom period (48.6 μg/L) was attributed to high photosynthetic activity. Cyanobacterial blooms can cause a variety of water‐quality problems in Lake Karaoun in addition to human health risk.     

Removal and preconcentration of lead (II), copper (II), chromium (III) and iron (III) from wastewaters by surface developed alumina adsorbents with immobilized 1-nitroso-2-naphthol

The potential removal and preconcentration of lead (II), copper (II), chromium (III) and iron (III) from wastewaters were investigated and explored. Three new alumina adsorbents of acidic, neutral and basic nature (I–III) were synthesized via physical adsorption and surface loading of 1-nitroso-2-naphthol as a possible chelating ion-exchanger. The modified alumina adsorbents are characterized by strong thermal stability as well as resistance to acidic medium leaching processes. High metal up-take was found providing this order: Cu(II) > Cr(III) > Pb(II) owing to the strong contribution of surface loaded 1-nitroso-2-naphthol. The outlined results from the distribution coefficient and separation factor evaluations (low metal ion concentration levels) were found to denote to a different selectivity order: Pb(II) > Cu(II) > Cr(III)) due to the strong contribution of alumina matrix in the metal binding processes. The potential applications of alumina adsorbents for removal and preconcentration of Pb(II), Cu(II), Cr(III) from wastewaters as well as drinking tap water samples were successfully accomplished giving recovery values of (89–100 ± 1–3%) and (93–99 ± 3–4%), respectively without any noticeable interference of the wastewater or drinking tap water matrices.     

A Novel IDFT/DFT Based Transceiver for Faster than Nyquist Signaling Optimization

Wireless Personal Communications - Future radio communication systems become user-centric and lay more emphasize on individual quality-of-service (QoS) experience than system-wide performance....