Thermal Behavior of a Multi-layered Thin Slab Carrying Periodic Signals Under the Effect of the Dual-Phase-Lag Heat Conduction Model

The thermal behavior of a two–layered thin slab carrying periodic signals under the effect of the dual-phase-lag heat conduction model is investigated. Two types of periodic signals are considered, a periodic heating source and a periodic imposed temperature at the boundary. The deviations among the predictions of the classical diffusion model, the wave mode, and the dual-phase-lag model are investigated. Analytical closed-form solutions are obtained for the temperature distribution within the slab. The effect of the angular frequency, thickness of the plate, dimensionless thermal relaxation time, dimensionless phase-lag in temperature gradient, thermal conductivity, and thermal diffusivity on the temperature distribution of the slab was studied. It is found that the deviations among the three models increase as the frequency of the signals increases and as the thickness of the plate decreases. It is found that the use of the dual-phase-lag heat conduction model is necessary when the metal film thickness is of order 10^–6 m and the angular frequency of the signals is of order 10¹²rad · s^–1.     

Remedial measures to control seepage problems in the Kafrein dam, Jordan

The Kafrein dam, 480 m long and 30 m high, is located on the Wadi Kafrein, a few kilometres from the active Jordan Valley fault. The Jordan Valley Authority proposed raising the crest of the existing dam by approximately 7 m and extending the length of the embankment to 554 m, in order to increase its storage capacity by 6 million m³ to a total of 8.5 million m³. The paper discusses the likelihood that existing seepage problems will be exacerbated when the dam is raised and proposes some remedial actions to increase the safety of the dam and minimise both the amount of seepage and any adverse effects. Electronic Publication     

Miscibility characterization of SMA/SAN and SMA/PMMA blends by differential scanning calorimetry and fluorescence techniques

In this study, styrene‐maleic anhydride (SMA) copolymer was modified by monoesterification method with 9‐(hydroxymethyl)anthracene fluorophore to prepare a fluorescent anthracene labeled SMA (SMA‐An) material. The latter was then characterized by attenuated total reflection (ATR) and thermogravimetric analysis (TGA) techniques. In the second step of this work, SMA‐An was added to SMA/[Styrene‐Acrylonitrile Copolymer (SAN)] and SMA/[Poly(methyl methacrylate) (PMMA)] blends to investigate the miscibility of these blends at the molecular level. The miscibility of SMA/PMMA blends was characterized using fluorescence quenching of anthracene by the succinic anhydride and succinic acid functions on SMA macromolecule itself. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Passivation of silicon by silicon nitride films

It is shown by contactless transient photoconductivity measurements in the microwave frequency range that Si₃N₄ films are an outstanding passivation of the n-type c-Si surface. Si₃N₄ on n-type Si forms an accumulation layer, which acts as an ideally reflecting potential barrier for minority carriers (holes). Due to the small space charge layer capacitance, minority carrier storage at this interface is very limited.In contrast to the latter measurements on p-type Si wafers covered with Si₃N₄ are characterized by storage of excess charge carriers in the surface depletion layer. The stored charge carriers decay slowly. The minority carriers (electrons) collected at the surface show a reduced mobility.     

Watershed characteristics, land use and fabric: The application of remote sensing and geographical information systems

Integrated watershed assessment, especially relying on remote sensing (RS), is a newly established procedure in developing countries. It is proving to be a major component in river‐basin environmental management. The recurrence of environmental problems in the Akkar El Kabir River watershed, as well as the lack of proper data on sources and sinks of pollutants, and the extent of human interference, led to the current study. Advanced geoinformation tools, such as RS and geographical information systems (GIS), prove to be a valuable asset in securing data on the fabric of the Akkar watershed in relation to its natural setting and anthropic interference. This is particularly true in the current study as the river constitutes the boundary between Lebanon and Syria. Remote sensing captures the watershed characteristics and land use on both sides without constraints. The natural fabric includes geology, drainage, hydrogeology, forest and soil. The anthropic fabric includes settlements, utilities, roads, agriculture and land use. If it were not for geoinformation techniques, the task of securing such data would be difficult. Also, these techniques show the impact of malpractices from excessive human interference that result in degradation of land and water quality. Changes in the watershed, such as environmental deterioration, are observed as water pollution, soil erosion, forest decline and socioeconomic imbalance. Obviously, this is the outcome of malpractices in a multisectorial system. A major challenge for RS and GIS is to quantify, model and predict, if possible, the extent of these changes. Remote sensing inherently captures the impact of interaction between nature and human beings. Detection of change is a major indicator that RS can contribute to the evaluation of the state of the environment. The application of it on this watershed reveals that significant changes have occurred over the last 10–15 years, most of which are anthropic.     

Rosemary oil as a corrosion inhibitor for carbon steel in 0.5 M sulfuric acid solution

The possibility of using rosemary oil as a corrosion inhibitor of carbon steel in 0.5 M sulfuric acid solution was investigated by determination of weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy. It was shown that the inhibition effectiveness increases with an increase in the concentration of oil and a decrease in the temperature. The inhibiting effect of the investigated oil is due to its adsorption on the surface of the steel and complexation. Adsorption is described by a Langmuir isotherm. The effect of the temperature on the corrosion rate was studied in the presence and absence of the oil and the thermodynamic parameters of the corrosion process were calculated.     

Ethoxylated fatty alcohols as corrosion inhibitors for dissolution of zinc in hydrochloric acid

The effect of some ethoxylated fatty alcohols, with different numbers of ethylene oxide units, on the corrosion of zinc in 0.5 M HCl has been studied using weight loss and polarization measurements. The inhibition efficiency was found to increase with increasing concentration, number of ethylene oxide units per molecule and with decreasing the temperature. Inhibition was explained on the basis of adsorption of ethoxylated fatty alcohols molecules on the metal surface through their ethoxy groups. The degree of surface coverage varied linearly with logarithm of inhibitor concentration fitting Temkin isotherm. The thermodynamic parameters were calculated for the tested system from the data obtained at different temperatures.     

The Effect of Annealing Temperature on the Magnetic Properties of Mn x Co1?x Fe2O4 Ferrites Nanoparticles

Mn _x Co_1?x Fe₂O₄ ferrites compounds (0??x??0.6) have been synthesized by a glycol-thermal method from high-purity metals chlorides. Single phase spinel structure of the nanoparticles has been confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. The diameters of the as-prepared powders were estimated from XRD and TEM and were found to be in the range: 7 to 13?nm. Room temperature magnetizations were obtained using a vibrating sample magnetometer (VSM) on the as-prepared samples and on samples annealed at 500 and 700?°C. The variation of coercive fields, saturation and remnant magnetizations as a function of composition (x) and grain size have been investigated. ⁵⁷Co M?ssbauer spectra for as-prepared samples were also measured at different temperatures (27, 100, and 200?°C). Significant changes in magnetization properties and M?ssbauer parameters are observed across the composition range studied. The variation of coercive fields and saturation magnetizations appear to critically depend on the particle sizes as the compounds evolve from single domain to multidomain structure.