Dynamic response of thick laminated annular sector plates subjected to moving load

The dynamic response of thick laminated annular sector plates with simply supported radial edges subjected to a radially distributed line load, which moves along the circumferential direction, is studied. A three-dimensional hybrid method composed of series solution, the layerwise theory and the differential quadrature method in conjunction with the finite difference method is employed. The fast rate of convergence and high accuracy of the method are demonstrated through different examples. Additionally, as a limit case, the out-of-plane dynamic responses of circular curved beams is obtained and compared with those of an unconstrained higher order shear deformation curved beam theory, which is formulated here. Then, the effects of different parameters such as the sector angle, thickness-to-outer radius ratio, ply lay out and the load velocity on the out-of-plane response of the symmetric and antisymmetric cross-ply laminated sector plates are investigated. The results can be used as benchmark solutions for future works.     

Heat transfer in power transformer windings with oil-forced cooling

Power transformer outages have a considerable economic impact on the operation of an electrical network. One of the most important parameters governing a transformer?s life expectancy is the hot-spot temperature (HST) value. The classical approach has been to consider the HST as the sum of the ambient temperature, the top-oil temperature rise and the hot-spot-to-top-oil temperature gradient. Temperature distribution is solved using the heat conduction equation. Finite element method is used in the numerical solution. The transformer selected for simulation is 32 MVA transformer with non-directed oil-forced cooling and directed oil-forced cooling. Comparing the results with those obtained from finite integral transform and experimental test checks the validity and accuracy of the proposed method.     

Mitigation of switching‐induced transient electromagnetic interference on control cable using Ni–Zn ferrite rings over cable sheath in gas‐insulated substations

The transient electromagnetic fields during switching operation in gas‐insulated substations (GISs) have rise times on the order of nanoseconds. These fields leak into the external environment through the discontinuities of gas‐insulated modules and affect the control cables and induce the transient voltage on cables, which results in malfunctioning of the equipment. The amplitudes of the electric and magnetic fields could be a few tens of kilovolts per meter and a few hundred amperes per meter according to layout of GIS, respectively. In this work, the induced voltage in the central conductor of a control cable and the induced current in its sheath, which is parallel to bus duct in a GIS with rated voltage of 230 kV, are calculated. Influence of the sheath material on the induced voltage and the type of its grounding on the induced current are analyzed. Furthermore, the impact of installing ferrite rings over the control cable sheath in mitigating the induced voltage and current is investigated. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Effectiveness of different surface cleaning methods on the shear bond strength of resin cement to contaminated zirconia: an in vitro study

The purpose of this in vitro study was to evaluate and compare the effectiveness of different surface cleaning methods on the shear bond strength (SBS) of zirconia ceramic surfaces. Seventy polished and cleaned zirconia disk specimens of 8 mm in diameter and 3.4 mm in thickness were immersed in fresh saliva. They were then pressed into a freshly mixed silicone disclosing medium. Six different cleaning methods were applied to the tested groups; they were airborne-particle abraded (AA), covered with a cleaning paste (Ivoclean®) (IV), etched with orthophosphoric acid (PA), immersed in alcohol (AL), rinsed with tap water only (WA), or cleaned with steam (SC). No surface cleaning was done after saliva immersion and silicone disclosing medium contamination to the control group (CC). The specimens were then bonded to an adhesive resin cement using polyethylene tubes. SBS was determined using a universal testing machine at a crosshead speed of 1 mm/min. The specimens were also examined with a scanning electron microscope and a stereomicroscope. Group AA yielded the highest SBS value (7.01 ± 1.4 MPa) among the groups, while Group WA had the lowest SBS value (3.03 ± 0.8 MPa). The SBS values of Group AA (7.01 ± 1.4 MPa) and IV (6.2 ± 1.7 MPa) were also significantly higher than those of the remaining four groups (p < 0.05). Within the limitations of this in vitro study, it was concluded that among the various cleaning methods tested, airborne-particle abrasion and Ivoclean® paste were effective in cleaning the zirconia surface.     

Natural vs. Synthetic Phosphate as Efficient Heterogeneous Compounds for Synthesis of Quinoxalines

Natural phosphate (NP) and synthetic fluorapatite phosphate (SFAP) were proposed as stable, inexpensive, readily available and recyclable catalysts for the condensation of 1,2-diamines with 1,2-dicarbonyls in methanol to afford quinoxaline at room temperature. NP provided as high as 92–99% yield for quinoxalines in short reaction times (i.e., 1–45 min), while SFAP created quinoxalines with 87–97% yield in 60–120 min. From the chemical analyses, X-ray fluoresecency, X-ray diffraction, energy dispersive X-ray and Fourier-transform infrared spectroscopy methods, two main phases (CaO, P₂O₅) appeared in NP together with other low content phases (SiO₂, Fe₂O₃). Compared to other phases, apatite (CaO and P₂O₅ as Ca10(PO₄)₆) played a major role in the catalytic activity of NP. SFAP with similar Ca/P atomic ratio showed a relatively lower catalytic activity than NP for the condensation of 1,2-diamine with 1,2-dicarbonyl in methanol at ambient temperature. To investigate the recyclability of catalysts, the surface properties of NP and 6-recycled NP were investigated using scanning electron microscopy, energy dispersive X-ray and Brunauer–Emmett–Teller and Barrett–Joyner–Halenda methods. Some differences were observed in NP and 6-recycled NP’s particle size, surface area, the volume and size of pores, and the content of elements; nevertheless, the use–reuse process did not noticeably change the catalytic property of NP.     

Electron Microscopy Study of γ-Al2O3 Supported Cobalt Fischer–Tropsch Synthesis Catalysts

Three supported catalysts containing 20 wt% cobalt and 0.5 wt% rhenium were subjected to electron microscopy studies in their calcined state. The catalysts were prepared by incipient wetness impregnation of γ-Al₂O₃ supports of different pore characteristics with aqueous solutions of cobalt nitrate hexahydrate and perrhenic acid. The influence of the support on the Co₃O₄ crystallite size and distribution was studied by X-ray diffraction and electron microscopy. There was a positive correlation between the pore diameter of the support and the post calcination Co₃O₄ crystallite size. On all three γ-Al₂O₃ supports, Co₃O₄ was present as aggregates of many crystallites (20–270 nm in size). Cobalt oxide did not crystallise as independent crystallites, but as an interconnected network, with a roughly common crystallographic orientation, within the matrix pore structure. The internal variations in crystallite size between the catalysts were maintained after reduction. Fischer–Tropsch synthesis was carried out in a fixed-bed reactor at industrial conditions (T = 483 K, P = 20 bar, H₂/CO = 2.1). Although the cobalt-time yields varied significantly (4.6–6.7 × 10^?3 mol CO/mol Co s), the site-time yields were constant (63–68 × 10^?3 s^?1) for the three samples. The C₅₊ selectivity could not be correlated to the cobalt oxide aggregate size and is more likely related to the cobalt particle size and chemical properties of the γ-Al₂O₃ support.     

Nanotechnology-based combinational drug delivery systems for breast cancer treatment

Modern chemotherapeutic anticancer treatments have come a long way in the fight against breast cancer, thus bringing science closer to a cure. However, the nature of these drugs is to attack both cancerous and non-cancerous cells at the same time. In our studies, we synthesized Magnetic Cyclodextrin-polyurethane based nano-composite (Fe₃O₄-ECA-PU-CD) which is a drug delivery system using a biocompatible magnetic polymer that directs chemotherapeutic drugs to cancerous regions in the body with an external magnet. This nano-composite was able to facilitate the loading and simultaneous release of the hydrophilic antitumor drug Doxorubicin (DOX) along with the hydrophobic antitumor drug docetaxel. The composite was made using a simple co-precipitation method with magnetic nano-particles (MNPs) followed by a silica coating process and an in situ polymerization process. Verification of synthesis for the drug carrier was carried out using techniques such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Thermogravimetric Analysis (TGA), and a vibrating sample magnetometer (VSM) to measure magnetic properties. Drug loading and release efficiencies were monitored using an HPLC-UV detector. Finally, an MTT assay was performed in order to evaluate the biocompatibility and toxicity of the synthetic nano-composite on MCF7 cell lines. Our findings present a new biocompatible drug delivery system with a high capacity for loading and directing two different chemotherapeutic drugs simultaneously to cancer sites with little to no toxicity to the surrounding non-cancerous cells. These studies present a viable tool for cancer treatment and research where the cancer is efficiently removed while the patient remains healthy.     

Investigation of the creep behavior of graphene oxide nanoplatelet-reinforced adhesively bonded joints

In this paper, the effect of adding graphene oxide nano-platelets (GONPs) into the adhesive layer was investigated on the creep behavior of adhesively bonded joints. The neat and GONP-reinforced adhesive joints were manufactured and tested under creep loading with different stress and temperature levels. 0.1?wt% GONPs revealed the highest improvement on the adhesive joint creep behavior amongst the studied weight percentages. Furthermore, the effect of GONPs on the creep behavior of adhesive joints was more significant at higher temperatures. It was found that adding 0.1?wt% of GONPs into the adhesive layer imposed reductions of 21%, 31% and 34% in the elastic shear strains and reductions of 24%, 31% and 37% in the creep shear strains of SLJs under testing temperatures of 30, 40 and 50?°C, respectively. The Burgers rheological model was employed for simulating the creep behavior of the neat and GONP-reinforced adhesive joints. The Burgers model parameters were obtained as functions of testing temperature, creep shear stress and GONP weight percentage using a response surface methodology. Reasonable agreement was obtained between the modeled and experimental creep behaviors of the adhesive joints.     

Magnetic immobilization of recombinant E. coli producing extracellular asparaginase: An effective way to intensify downstream process

Purification is one of the most important steps in biotechnological downstream process. This procedure is associated with some difficulties including several separation steps. Common cell separation procedures are usually time and energy consuming that also compromises cell growth, viability and reusability. Magnetic immobilization was introduced as a novel separation technique to provide a quick, easy and convenient alternative vs. traditional cell harvesting methods. In this study, recombinant E. coli producing extracellular asparaginase was decorated by synthesized L-lysine coated iron oxide nanoparticles and cell growth, immobilization efficiency and asparaginase productivity was evaluated.