Three-dimensional generalized thermoelastic diffusion and application for a thermoelastic half-space subjected to rectangular thermal pulse

In this article, a model of three-dimensional generalized thermo-diffusion in a half-space thermoelastic medium subjected to permeating gas and the rectangular thermal pulse has been constructed. The half-space is considered to be made of an isotropic homogeneous thermoelastic material. The chemical potential is also assumed to be known on the bounding plane. Laplace transform techniques have been applied, and the solution is obtained in the Laplace transform domain using a direct approach. The solution of the problem in the physical domain is obtained numerically using a numerical method based on a Riemann-sum approximation for the inversion of Laplace transform. The temperature increment, stress, strain, diffusion concentration, and chemical potential distributions are represented graphically. The nonzero value of the relaxation time parameter predicts the finite speed of thermal, mechanical, diffusion waves.     

Role of alloyed silicon and some inorganic inhibitors in the inhibition of meta-stable and stable pitting of Al in perchlorate solutions

The study of both meta-stable and stable pitting events on the surface of pure Al and three Al–Si alloys, namely (Al + 6%Si), (Al + 12%Si) and (Al + 18%Si) alloys, was carried out in deaerated neutral NaClO₄ solutions of various concentrations (10⁻⁴–10⁻² M). Measurements were carried out under the effect of various experimental conditions using potentiodynamic anodic polarization and potentiostatic techniques. The results presented below showed that meta-stable pits (appeared as oscillations in current) form at potentials close to the pitting potential (E _pit) and during the induction time for stable pit formation. Various factors affecting the rate of meta-stable and stable pits were studied. The presence of Si as an alloying element in Al reduces the rate of formation of meta-stable pits, corresponding to a reduction in the probability of developing stable pits, and an increase in the pitting potential results. The inhibitive effects of chromate, silicate, molybdate and tungstate on pitting corrosion in Al were also studied. Results obtained showed that these known inhibitors retard both meta-stable and stable pitting events. This makes attainment of stable pit growth more difficult in presence of these inhibitors.

Deflection Prediction of Steel and FRP-Reinforced Concrete-Filled FRP Tube Beams

This paper presents the results of experimental and theoretical investigations that study the flexural behavior of reinforced concrete-filled fiber-reinforced polymer (FRP) tubes (RCFFTs) beams. The experimental program consists of 10 circular beams [6 RCFFT and 4 control reinforced concrete (RC) beams] with a total length of 2,000?mm, tested under four-point bending load. The experimental results were used to review and verify the applicability of various North American code provisions and some available equations in the literature to predict deflection of RCFFT beams. The measured deflections and the experimental values of the effective moment of inertia were analyzed and compared with those predicted using available models. The results of the analysis indicated that the behavior of steel and FRP-RCFFT beams under the flexural load was significantly different than that of steel and FRP-RC members. This is attributed to the confining effect of the FRP tubes and their axial contribution. This confining behavior in turn enhanced the overall flexural behavior and improved the tension stiffening of RCFFT beams. For that, the predicted tension stiffening of steel and FRP-RCFFT beams using the conventional equations (steel or FRP-RC member) underestimates the flexural response; therefore, the predicted deflections are overestimated. Based on the analysis of the test results, the Branson’s equation for the effective moment of inertia of RC structures is modified, and new equations are developed to accurately predict the deflection of concrete-filled FRP tube (CFFT) beams reinforced with steel or FRP bars.     

Thermodynamic,adsorption and electrochemical studies for corrosion inhibition of carbon steel by henna extract in acid medium

Corrosion inhibition of carbon steel in the presence of different concentrations of aqueous extract from henna leaves in 1 M HCl solution has been studied using the weight loss and potentiodynamic polarization techniques. The effect of temperature on the corrosion behavior of carbon steel was studied in the temperature range 293–333 K. The inhibition efficiency increases with increasing inhibitor concentration but decreases with increasing temperature. The activation and free energies for the inhibition reactions support the mechanism of physical adsorption. The adsorption of henna extract on C-steel surface is endothermic, spontaneous and consistent with the Langmuir adsorption isotherm. The potentiodynamic polarization measurements indicate that henna extract acts as a mixed inhibitor. Surface and protective film analysis have been carried out using; energy dispersive X-ray (EDX), scanning electron microscopy (SEM), Fourier transforms infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) analysis.     

Synthesis of uranium nitride by a mechanically induced gas-solid reaction

A high energy, low-temperature, ball-milling route was used to directly produce uranium nitride. Pure uranium metal particles (∼100 μm) were ball milled under a 420 kPa nitrogen atmosphere for 24 h at ambient temperature to yield phase pure U₂N₃ powder as confirmed by X-ray diffraction and energy dispersive spectroscopy. The median particle size was measured to be approximately 6 μm.     

Passivity and passivity breakdown of zinc anode in alkaline medium

The electrochemical behaviour of zinc in NaOH solutions has been investigated by using potentiodynamic technique and complemented by X-ray analysis. The E/i curves exhibit active, passive and transpassive regions prior to oxygen evolution. The active region displays two anodic peaks. The passivity is due to the Formation of a compact Zn(OH)₂ film on the anode surface. The transpassive region is assigned to the electroformation of ZnO₂. The reverse sweep shows an activation anodic peak and one catholic peak prior to hydrogen evolution. The influence of increasing additives of NaCl, NaBr and Nal on the anodic behaviour of zinc in NaOH solutions has been studied. The halides stimulate the active dissolution of zinc and tend to break down the passive film, leading to pitting corrosion. The aggressiveness of the halide anions towards the stability of the passive film decreases in the order: I^? > Br^? > Cl^?. The susceptibility of zinc anode to pitting corrosion enhances with increasing the halide ion concentration but decreases with increasing both the alkali concentration and the sweep rate.     

Liquid-Phase Oxidation of Cyclohexane over Co-TUD-1

Cobalt was successfully incorporated into TUD-1 and characterized by means of X-ray powder diffraction, UV–Vis spectroscopy, N₂ adsorption and elemental analysis. The catalyst is highly efficient in the oxidation of cyclohexane with TBHP under solvent-free and mild oxidation conditions.     

Reliability analysis of photovoltaic systems

Reliability is an important parameter for the user of photovoltaic (PV) power systems. A methodology for the analytical treatment of the reliability of PV systems is proposed in this paper. The method depends upon the logic of the fault-tree technique. The reliabilities of the different components of a PV system are used to predict the reliability of the overall system. Today's most commonly known systems are considered and a reliability formula is developed for each system. The methodology presented is appropriate for a wide range of applications and system types.     

The role of the nurse practitioner in a urology service

OBJECTIVE: To evaluate the role of the nurse practitioner in urology and to determine the impact on the work of junior doctors. METHODS: Written criteria were defined before the postholder was appointed and subsequent performance was assessed against these criteria. Training was provided and the quality of work was assessed by direct observation. Senior House Officers (SHOs) were asked whether the post had increased their opportunities to attend theatre, outpatients and post-graduate training sessions and had decreased the number of 'inappropriate' tasks they had to perform. RESULTS: The nurse practitioner accomplished all the tasks that were defined before the appointment. The assessment of patients in pre-admission and haematuria clinics was satisfactory. The continuity of information, care of patients and counselling for patients receiving complex surgery were improved. Sixty-three per cent of all patients seen in the pre-admission clinic and all patients in a haematuria clinic were assessed initially by the nurse practitioner. Because the nurse practitioner was involved in setting up intravenous drug administration and infusions, administrative tasks and in obtaining results from the laboratory, the number of 'inappropriate' tasks performed by the SHOs decreased and they were able to attend more sessions of training and education. CONCLUSIONS: The nurse practitioner in clinical urological practice constitutes an effective use of resources and relieves junior medical staff from other tasks, allowing them to receive a more focused training. In addition, the quality of patient care was thought to be improved in some areas. The framework of a job plan for a nurse practitioner is described.     

Distribution of Mercury,Trace Organics,and Other Heavy Metals in Detroit River Sediments

In 1980 the Ontario Ministry of the Environment carried out a surficial bottom sediment survey of the Detroit River. The survey was designed to update changes in sediment mercury levels from a 1970 study, and to determine the spatial distribution of trace organics and other heavy metals as a baseline for future investigations. The contamination of sediments along the Ontario shoreline of the river was localized near known inputs such as Little River, the West Windsor sewage treatment plant, Turkey Creek, and Riviere aux Canards. Almost the entire U.S. shoreline sediments exhibited elevated levels (above provincial dredging guidelines) of contaminants such as heavy metals and PCBs. Levels of one order of magnitude higher than those on the Canadian shore were prevalent along the U.S. shore. Mercury levels exhibited a substantial decline during the period 1970–1980. Increases in chromium, copper, lead, and zinc in the vicinity of the mouth of the Rouge River along the U.S. shoreline during the same period suggest both recent and continuing inputs from industrial and municipal sources.