Effects of marble powder as a partial replacement of cement on some engineering properties of self-compacting concrete

Self-compacting concretes (SCC) are highly fluid concretes that can flow and be placed in formwork under their own weight without the requirement of internal or external energy. This fluidity is obtained with the use of high paste volume and superplasticizer. The paste of SCC is made principally of cement, which is the most expensive component of concrete. As a result, the production cost of SCC is higher than conventional concrete. However, to make the manufacture of SCC more practical and economical, the binder is often a binary, ternary even quaternary compound: Portland cement mixed with mineral additions. The primary aim of this work is to study the effect of incorporating the marble powder as a supplementary cementations material on the rheological and mechanical properties of SCC. The fresh properties were measured using the slump flow, J-Ring, V-funnel, and modified slump flow. The properties of hardened SCC such as strengths and ultrasonic pulse velocity (UPV) were determined at age of 3, 28, and 90 days. The results have shown that using of marble powder in SCC enhances their fresh properties. At hardened state, the incorporation of marble powder decreases the mechanical strengths and UPV. It can be noted that it is possible to produce an economical SCC when the cement is partially substituted by the marble powder.     

A two-dimensional analytical model of subthreshold behavior to study the scaling capability of deep submicron double-gate GaN-MESFETs

In this paper, a new deep submicron double-gate (DG) Gallium Nitride (GaN)-MESFET design and its 2-D analytical model have been proposed, investigated and expected to suppress the short-channel-effects (SCEs) and improve the subthreshold behavior for deep submicron GaN-MESFET-based applications. The model predicts that the threshold voltage roll-off, DIBL effects and the subthreshold swing are greatly improved in comparison with the conventional Single-Gate (SG) GaN-MESFETs. The developed approaches are verified and validated by the good agreement found with the 2D numerical simulations for wide range of device parameters and bias conditions. DG GaN-MESFET can alleviate the critical problem and further improve the immunity of SCEs of deep submicron GaN-MESFET-based circuit for future power switching and digital gate devices.     

Bond graph modeling approach development for fuel cell PEMFC systems

This paper addresses the problem of bond graph methodology as a graphical approach for modeling fuel cell systems. The system consists of a Proton Exchange Membrane Fuel Cell (PEMFC) stack, an interleaved boost converter, battery pack connected via a buck converter.     

Effect of municipal solid waste compost and sewage sludge use on wheat (Triticum durum): growth,heavy metal accumulation,and antioxidant activity

BACKGROUND: Inappropriate utilisation of biosolids may adversely impact agrosystem productivity. Here, we address the response of wheat (Triticum durum) to different doses (0, 40, 100, 200 and 300 t ha^?1) of either municipal solid waste (MSW) compost or sewage sludge in a greenhouse pot experiment. Plant growth, heavy metal uptake, and antioxidant activity were considered. RESULTS: Biomass production of treated plants was significantly enhanced at 40 t ha^?1 and 100 t ha^?1 of MSW compost (+48% and +78% relative to the control, respectively). At the same doses of sewage sludge, the increase was only 18%. Higher doses of both biosolids restricted significantly the plant growth, in concomitance with the significant accumulation of heavy metals (Ni²⁺, Pb²⁺, Cu²⁺ and Zn²⁺), especially in leaves. Leaf activities of antioxidant enzymes (ascorbate peroxidase, glutathione reductase, catalase and superoxide dismutase) were unchanged at 40 t ha^?1 MSW compost or sewage sludge, but were significantly stimulated at higher doses (200–300 t ha^?1), together with higher leaf concentration of reduced glutathione. CONCLUSION: This preliminary study suggests that a MSW supply at moderate doses (100 t ha^?1) could be highly beneficial for wheat productivity. Copyright © 2010 Society of Chemical Industry     

Modeling and control of a permanent magnet synchronous generator dedicated to standalone wind energy conversion system

The interest for the use of renewable energies has increased, because of the increasing concerns of the environmental problems. Among renewable energies, wind energy is now widely used. Wind turbines based on an asynchronous generator with a wound rotor present the inconvenience of requiring a system of rings and brooms and a multiplier, inferring significant costs of maintenance. To limit these inconveniences, certain manufacturers developed wind turbines based on synchronous machines with large number of pairs of poles coupled directly with the turbine, avoiding using the multiplier. If the generator is equipped with permanent magnets, the system of rings and brooms is eliminated. The control of the permanent magnet synchronous generator (PMSG) can be affected with the implementation of various techniques of control. This paper presented a new approach mainly based on the control strategy of power production system based on the PMSG. In fact, a mathematical model that simulates the Matlab chain was established with the introduction of control techniques, such as direct control of the torque (DTC) to control the load side converter (LSC), the control of the speed of the turbine and the DC-bus voltage ensured by PI regulators. To show the performance of the correctors used, some simulation results of the system were presented and analyzed.     

Neyman–Pearson Test for Fault Detection in the Process Dynamics

Fault detection in industrial plants plays an important role for ensuring the product quality, safety, and reliability of plant equipment. The purpose of this work is to propose a fault detection technique with a black-box modeling and a statistical module based on Neyman–Pearson test (NPT). In fact, Nonlinear Auto-Regressive Moving Average with eXogenous input (NARMAX) model is used to obtain a model for the normal condition operation. To detect a fault, The NPT has been applied to the residual of NARMAX model. The efficiency of the technique is illustrated through its application to monitor product quality in a distillation unit.     

Stability,magnetic, electronic,elastic, thermodynamic,optical, and thermoelectric properties of Co2TiSn,Co2ZrSn and Co2HfSn Heusler alloys from calculations using generalized gradient approximation techniques

Structural, magnetic, electronic, elastic, thermodynamic, optical, and thermoelectric properties of full-Heusler alloys Co₂YSn (Y?=?Ti; Zr; Hf) were determined using density functional theory-based WIEN2k code within GGA and GGA?+?U approximations for exchange correlation functions. The calculated formation energies and elastic parameters demonstrate the stability of these alloys. It was also observed that the studied compounds have a ductile structure and exhibit anisotropic behavior. The magnetic moment of these systems is equal to 2 μ_B, which conforms to the Slater–Pauling rule. In addition, the half-metallic ferrimagnetic behavior and good bandgap in the minority spin are showed for all compounds. The optical properties are systematically studied by computing the optical parameters. The existence of bandgaps with minimal energy loss in IR and visible regions makes these materials suitable candidates for optoelectronic devices. The thermoelectric properties of these systems were also examined in terms of temperature and chemical potential.

     

Analytical analysis of nanoscale multiple gate MOSFETs including effects of hot-carrier induced interface charges

As the channel length rapidly shrinks down to the nanoscale regime, the multiple gate MOSFETs structures have been considered as potential candidates for a CMOS device scaling due to its good short-channel-effects (SCEs) immunity. Therefore, in this work we investigate the scaling capability of Double Gate (DG) and Gate All Around (GAA) MOSFETs using an analytical analysis of the two dimensional Poisson equation in which the hot-carrier induced interface charge effects have been considered. Basing on this analysis, we have found that the degradation becomes more important when the channel length gets shorter, and the minimum surface potential position is affected by the hot-carrier induced localized interface charge density. Using this analysis, we have studied the scaling limits of DG and GAA MOSFETs and compared their performances including the hot-carrier effects. Our obtained results showed that the analytical analysis is in close agreement with the 2-D numerical simulation over a wide range of devices parameters. The proposed analytical approach may provide a theoretical basis and physical insights for multiple gate MOSFETs design including the hot-carrier degradation effects.     

Finite-time stability and stabilization of time-delay systems

Finite-time stability and stabilization of retarded-type functional differential equations are developed. First, a theoretical result on finite-time stability inspired by the theory of differential equations, using Lyapunov functionals, is given. As it may appear not easily usable in practice, we show how to obtain finite-time stabilization of linear systems with delays in the input by using an extension of Artstein’s model reduction to nonlinear feedback. With this approach, we give an explicit finite-time controller for scalar linear systems and for the chain of integrators with delays in the input.     

2.45-GHz-CMOS temperature compensated multi-controlled oscillator for IEEE 802.15 wireless PAN

A 2.45 GHz Multi-Controlled Oscillator (MCO) has been designed using a CMOS 0.28 μm STMicroelectronics technology for use in frequency synthesizer and open loop FSK modulation circuit in multi-band IEEE 802.15 Wireless Personal Area Network (PAN) applications. Simple structure allowing multiple frequency control has been adopted so that the VCO maintains its center frequency and tuning range throughout ?40°C to 120°C by the way of a Proportional To Absolute Temperature (PTAT) biasing scheme. Simulations and measurements show the sensitivity of the VCO center frequency has been reduced from 1300 ppm/°C to 73 ppm/°C, while a phase noise of ?96 dBc/Hz @ 1 MHz offset with a power consumption of 18 mW have been achieved.