MAGNETOTHERMOELASTICITY WITH THERMAL RELAXATION IN A CONDUCTING MEDIUM WITH VARIABLE ELECTRICAL AND THERMAL CONDUCTIVITY

The equations of magnetothermoelasticity with one relaxation time and with variable electrical and thermal conductivity for one-dimensional problems including heat sources are cast into matrix form using the state-space and Laplace transform techniques. The resulting formulation is applied to a problem for the whole conducting space with a plane distribution of heat sources. It also is applied to a semispace problem with a traction-free surface and plane distribution of heat sources located inside the conducting medium. The inversion of the Laplace transforms is carried out using a numerical approach. Numerical results for the temperature, displacement, and stress distributions are given and illustrated graphically for both problems. A comparison is made with the results obtained in the following cases: (i) the electrical and thermal conductivities have constant values, (ii) the absence of magnetic field, and (iii) the coupled theory in magnetothermoelasticity.     

On the Two-Temperature Green–Naghdi Thermoelasticity Theories

The constitutive laws for two-temperature Green–Naghdi theories are given. It is proved that the two-temperature thermoelasticity theory admits dissipation of energy and the theory of elasticity without energy dissipation is valid only when the two-temperatures coincide. The uniqueness and reciprocal theorems are proved for a linear anisotropic and inhomogeneous thermoelastic centro-symmetric solid in the frame of two-temperature Green–Naghdi theories. The convolutional variational principle is established for the two-temperature Green–Naghdi theory of type III. A continuous dependence result is given for an isotropic solid.     

Thermal and morphological behavior of irradiated composite materials based on injection‐moulded recycled polyethylene terephthalate

The effect of gamma irradiation and short glass fiber (SGF) on the thermal and morphological behavior of the recycled poly (ethylene terephthalate) (rPET) in the presence of reactive additive (epoxy resin, 2 wt %) has been investigated. Characterization of the resulted composites to evaluate the effect of incorporation the SGF and irradiation by means of differential scanning calorimetry, X‐ray diffraction, thermal gravimetric analysis, and scanning electron microscopy (SEM). The results show that the SGF and epoxy resin behave as nucleating agents for the crystallization of rPET. A noticeable increase in the rPET thermal stability in the presence of both SGF and epoxy resin has been observed. Furthermore, the rPET melting temperature (T_m) slightly decrease in the presence of the SGF and remains nearly constant with the incorporation of the epoxy resin. On the other hand, the rPET crystallinity percent (X%) decreases in the presence of SGF and gamma irradiation. The SEM showed that a layer of epoxy resin was coated onto the SGF in the rPET matrix. This coating layer raises the interfacial shear strength between the fiber and polymer matrix and also increases with gamma irradiation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Thermal degradation behavior of poly(vinyl chloride) in the presence of poly(glycidyl methacrylate)

The thermal degradation behavior of poly(vinyl chloride) (PVC) in presence of poly(glycidyl methacrylate) (PGMA) has been studied using continuous potentiometric determination of the evolved HCl gas from the degradation process from one hand and by evaluating the extent of discoloration of the degraded samples from the other. The efficiency of blending PGMA with dibasic lead carbonate (DBLC) conventional thermal stabilizer has also been investigated. A probable radical mechanism for the effect of PGMA on the thermal stabilization of PVC has been suggested based on data reported by FTIR and elemental analyses. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Design of fault simulator

Fault simulator is proposed to understand and evaluate all possible fault propagation scenarios, which is an essential part of safety design and operation design and support of chemical/production processes. Process models are constructed and integrated with fault models, which are formulated in qualitative manner using fault semantic networks (FSN). Trend analysis techniques are used to map real time and simulation quantitative data into qualitative fault models for better decision support and tuning of FSN. The design of the proposed fault simulator is described and applied on experimental plant (G-Plant) to diagnose several fault scenarios. The proposed fault simulator will enable industrial plants to specify and validate safety requirements as part of safety system design as well as to support recovery and shutdown operation and disaster management.     

Failure behavior of Cu–Ti–Zr-based bulk metallic glass alloys

Microstructure fracture and mechanical properties of Cu-based bulk metallic glass alloys were investigated. Centrifugal casting into copper molds were used to manufacture basic Cu₄₇Ti₃₃Zr₁₁Ni₉, and modified Cu₄₇Ti₃₃Zr₁₁Ni₇Si₁Sn₁ alloys. Although the alloys show an amorphous structure, TEM images revealed the formation of nanoparticles. At room temperature compression tests reveal fracture strength of 2000 MPa, elastic modulus of 127 GPa, and 1.8% fracture strain for the unmodified basic alloy. Whereas the modified alloy exhibits a fracture strength of 2179 MPa, elastic modulus reaches 123 GPa, and 2.4% fracture strain. So, with the addition of 1 at.% Si and Sn, the fracture strength improves by 9% and the fracture strain improves by 25%, but the fracture behavior under compression conditions exhibits a conical shape similar to that produced by tensile testing of ductile alloys. A proposed fracture mechanism explaining the formation of the conical fracture surface was adopted. The formation of homogeneously distributed nano-size (2–5 nm) precipitates changes the mode of fracture of the metallic glass from single to multiple shear plane modes leading to the conical shape fracture surface morphology.     

Performance optimization of integrated gas and power within microgrids using hybrid PSO–PS algorithm

In this paper, a hybrid algorithm consisting of particle swarm optimization and pattern search algorithm is proposed to evaluate and optimize the design and operation of microgrids (MGs) in combined gas and power networks. Key performance indicators (KPIs) are modeled and proposed to evaluate and assess MGs. The paper begins by proposing a comprehensive study to define KPIs, which are used to evaluate the following MG parameters: economical efficiency, reliability, environmental conservation, and power quality. Multi‐objective evaluation functions are then developed by building a relationship matrix of MG and KPI components. The results are then displayed as optimized power generation percentages for each technology with values for four KPI categories: cost, quality, reliability and environmental friendliness. Two case studies are examined in this paper; both the province of Ontario and Toronto regional zone under all system parameters with varying percentage of generation via gas technology. Results indicated that the optimal scenario for both Ontario and Toronto was achieved at hybrid PSO–patern search percentage generation via gas technology with improved cost KPI and other KPIs remaining approximately constant. Copyright © 2016 John Wiley & Sons, Ltd.     

Integration of PV system with SMES based on model predictive control for utility grid reliability improvement.

This paper describes the integration of a photovoltaic (PV) renewable energy source with a superconducting magnetic energy storage (SMES) system. The integrated system can improve the voltage stability of the utility grid and achieve power leveling. The control schemes employ model predictive control (MPC), which has gained significant attention in recent years because of its advantages such as fast response and simple implementation. The PV system provides maximum power at various irradiation levels using the incremental conductance technique (INC). The interfaced grid side converter of the SMES can control the grid voltage by regulating its injected reactive power to the grid, while the charge and discharge operation of the SMES coil can be managed by the system operator to inject/absorb active power to/from the grid to achieve the power leveling strategy. Simulation results based on MATLAB/Simulink® software prove the fast response of the system control objectives in tracking the setpoints at different loading scenarios and PV irradiance levels, while the SMES injects/absorbs active and reactive power to/from the grid during various events to improve the voltage response and achieve power leveling strategy.     

Freezing time calculations for various products

This article presents a numerical simulation that estimates the freezing time for different products. In this regard, the freezing process is mathematically modelled by transient heat conduction equations that incorporate the physical properties of the three distinct regions that exist during a freezing process. These regions are namely, the solid phase region, the liquid phase region and the interface region. This model is experimentally validated and used to estimate the freezing time for three different food products, which are namely, fish balls, cherry juice and peas balls. The freezing times estimated numerically through the present model agree well with those reported in the literature and are in excellent agreement with the experimental data. Copyright © 2003 John Wiley & Sons, Ltd.     

Reduction of aqueous carbonate photocatalysed by treated semiconductors

Heterogeneous photocatalysed reduction of aqueous Na₂CO₃ solution (1 m) was achieved by using phthalocyanine-coated semiconductor powders (1–3% coating) as well as bare semiconductors. The suspensions were irradiated with 254 nm light from a low-pressure mercury lamp in a nitrogen atmosphere. The phthalocyanine dyes (Fe²⁺-Pc or Co²⁺-Pc) absorb > 80% of the 254 nm radiation and thus sensitize the semiconductor. The products of reduction (CH₃OH and HCHO) were determined spectrophotometrically. The CH₃OH yields obtained are much higher than the HCHO yields, due to a photocatalysed reduction of HCHO to CH₃OH. The CH₃OH yields from coated titania increased linearly with irradiation time over the period 6–18 h. However, the straight line does not pass through the origin, and it seems that a slowing-down occurs at times > 6 h. Titania coated with both dyes gave an optimum CH₃OH yield at 2% surface coating. At higher coating percentages, phthalocyanine screens the surface, thus reducing the light reaching the semiconductor. Changing the redox potential of the phthalocyanine dye by changing its central metal from Fe to Co affects the CH₃OH yields. The bare MoS₂ photocatalyst gave a much higher CH₃OH yield due to the characteristic behaviour of the semiconducting layer-type disulphide, distinguished from that of classical semiconducting materials. In the various semiconductors studied, it seems that there is no correlation between the position of the conduction band and the yield of CH₃OH. Such correlation was argued. Generally, a decrease in the yield of CH₃OH was observed as the band gap width of the semiconductor increased. The yields of the photoproduced CH₃OH generally increased with the percentage of light absorbed at 254 nm by the various semiconductors. Irradiation leads to the production of electrons in the conduction band of the semiconductor. It is likely that the photoproduced electrons reduce CO₃²- initially to HCOO- and then to HCHO and CH₃OH.