Effect of Doping of Zn and Ca into ErBa2Cu3O7?δ Superconductor Prepared via Co-precipitation Method

Zn- and Ca-doped ErBa₂Cu₃O_7−δ were successfully prepared via coprecipitation method using metal acetates as the starting salts. The precipitated samples were calcined for 20 h at 900 °C and sintered at 920 °C for 24 h. All heat treatments were carried out under oxygen environment. Results show that there is a selectivity of the doping site depending on the ionic radius of the dopant. Furthermore, increase in the critical temperature, T _c , was observed in 0.05 mole of calcium and zinc doped samples. The difference in ionic radius of the dopant led to the increase in porosity as the ionic radius decreases. On the other hand, structural distortion increased as the difference of ionic radius became larger.     

Optimizing acido-basic profile of support in Ni supported La2O3+Al2O3 catalyst for dry reforming of methane

The increasing alarm of global warming always draws interest in reactions like dry reforming of methane (DRM) where both global warming gases (CO₂ and CH₄) are converted into value-added chemical building blocks, such as syngas. Nickel catalyst active sites along with support acid-base profiles play a key role in DRM. Herein, xLa₂O₃+(100-x) Al₂O₃ (x = 0, 10, 15, 20%) supports are prepared and followed by NiO dispersion over the produced support by impregnation method. It was tested for DRM reaction and characterized with TGA, XRD, TEM, IR, Surface area and porosity measurement, H₂-TPR, CO₂-TPD and NH₃-TPD techniques. Upon increasing the basic lanthana proportion in the acidic alumina support, the crystallinity of alumina and acidity of total support decline. Up to 15% Lanthana addition in support claims a low acid and rich basic surface including super basic sites (related to unidentate carbonates) which governed optimum catalytic performance 64% CH₄ conversion, 79% CO₂ conversion and H₂/CO ~ 1 up to 460-min in time on stream test. 20% lanthanum oxide loading led to inferior performance due to rapid loss of surface area, pore-volume, pore diameter, acidity and medium basic strength sites. Fine-tuning of acid-base lanthana-alumina support with dispersed Ni species are a means for understanding DRM.     

The effect of oxide,carbide, nitride and boride additives on properties of pressureless sintered SiC: A review

Properties such as high hardness, low density, and high elastic modulus have made SiC ceramics proper choices for a variety of industrial applications. However, disadvantages such as low sinterability, and low fracture toughness have limited the fabrication of these ceramics. Past researches show that the use of Al₂O₃-Y₂O₃ additives play an important role in improving the sinterability and the properties of the composites. The use of oxide, carbide, nitride and boride additives results in improved sinterability, physical and mechanical properties. The investigations show that the microstructure, porosities, amount of additives, reaction of additives with the matrix, grain size and, finally, the sintering temperature are the most important factors affecting the properties of SiC ceramics. In this paper, the effect of using various additives, the sintering temperature and the annealing heat treatment on sinterability, microstructure and properties of the SiC matrix composites fabricated by pressureless sintering method have been investigated.     

Effects of Mangifera pajang Kostermans juice on plasma antioxidant status and liver and kidney function in normocholesterolemic subjects

The effects of a bambangan juice powder (BJP) drink on plasma vitamin and antioxidant enzyme levels and liver and kidney function were investigated. Thirty-two healthy subjects (12 male and 20 female) ages 24–28 years were recruited from the Faculty of Medicine and Health Sciences of University Putra Malaysia, Malaysia. Compared with consuming the placebo, consumption of the BJP drink daily for 9 weeks significantly increased the concentration of plasma β-carotene and ascorbic acid. Plasma total antioxidant status was increased, but liver and kidney functions were unaffected after consumption of the BJP drink. The consumption of a BJP drink resulted in a significant improvement in certain cardiovascular biochemical parameters and thus reduced the risk of cardiovascular disease.     

The effect of resin uptake on the flexural properties of compression molded sandwich composites

Resin uptake plays a critical role in the stiffness-to-weight ratio of wind turbine blades in which sandwich composites are used extensively. This work examines the flexural properties of nominally half-inch thick sandwich composites made with polyvinyl chloride (PVC) foam cores (H60 and H80; PSC and GPC) at several resin uptakes. We found that the specific flexural strength and modulus for the H80 GPC sandwich composites increase from 82.04 to 90.70 kN · m/kg and 6.03 to 7.13 MN · m/kg, respectively, with 11.0% resin uptake reduction, which stands out among the four core sandwich composites. Considering reaching a high stiffness-to-weight ratio while preventing resin starvation, 32% to 38% and 40% to 45% resin uptakes are adequate ranges for the H80 PSC and GPC sandwich composites, respectively. The H60 GPC sandwich composites have lower debonding toughness than H60 PSC due to stress concentration in the smooth side skin-core interphase region. The ailure mode of the sandwich composites depends on the core stiffness and surface texture. The H60 GPC sandwich composites exhibit core shearing and bottom skin-core debonding failure, while the H80 GPC and PSC sandwich composites show top skin cracking and core crushing failure. The findings indicate that an appropriate range of resin uptake exists for each type of core sandwich composite, and that within the range, a low-resin uptake leads to lighter blades and thus lower cyclic gravitational loads, beneficial for long blades.     

Fermentation and non-digestibility of Mangifera pajang fibrous pulp and its polysaccharides

Populations of Bifidobacterium longum BB536, Salmonella choleraesuis JCM 6977, Escherichia coli ATCC 35922 and B. pseudocatenulatum G4 were monitored over 24 and 48 h. The digestibility of Mangifera pajang fibrous (MPF) and its polysaccharides by human gastric juice and human α-amylase were also determined. MPF and its polysaccharides increased the number of bifidobacteria but did not affect the growth of S. choleraesuis JCM 6977 or E. coli ATCC 35922; moreover, their effects were comparable to those of the commercial prebiotic inulin. M. pajang fibrous polysaccharides showed the highest non-digestibility by human gastric juice and human α-amylase compared to MPF and inulin; MPF showed a higher non-digestibility than inulin. MPF and its polysaccharides showed strong fermentation and non-digestibility properties, and thus it might be a prospective prebiotic that could be incorporated into food products.     

A novel maximum power point tracking technique based on fuzzy logic for photovoltaic systems

Maximum power point tracking (MPPT) techniques are considered a crucial part in photovoltaic system design to maximise the output power of a photovoltaic array. Whilst several techniques have been designed, Perturb and Observe (P&O) is widely used for MPPT due to its low cost and simple implementation. Fuzzy logic (FL) is another common technique that achieves vastly improved performance for MPPT technique in terms of response speed and low fluctuation about the maximum power point. However, major issues of the conventional FL-MPPT are a drift problem associated with changing irradiance and complex implementation when compared with the P&O-MPPT. In this paper, a novel MPPT technique based on FL control and P&O algorithm is presented. The proposed method incorporates the advantages of the P&O-MPPT to account for slow and fast changes in solar irradiance and the reduced processing time for the FL-MPPT to address complex engineering problems when the membership functions are few. To evaluate the performance, the P&O-MPPT, FL-MPPT and the proposed method are simulated by a MATLAB-SIMULINK model for a grid-connected PV system. The EN 50530 standard test is used to calculate the efficiency of the proposed method under varying weather conditions. The simulation results demonstrate that the proposed technique accurately tracks the maximum power point and avoids the drift problem, whilst achieving efficiencies of greater than 99.6%.