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The fabrication of aluminium AA7075 and AA7075/SiC composite foams employ the stir casting method, incorporating calcium carbonate (CaCO3) as a blowing agent at a concentration constituting 2.5wt. % of the alloy. Notably, no viscosity-enhancing component was included in the process. The compressive parameters, including the yield strength (σc), plateau stress (σpl) and energy absorption (Eab), of the foam materials were examined to investigate the influence of Silicon Carbide (SiC) on the microstructure, namely the cell size and cell wall thickness. The incorporation of Silicon Carbide particles (SiC) into the cell wall imparts enhanced hardness and strength. The findings indicate that the inclusion of SiC particles may enhance the mechanical properties like σc, σp and Eab, of composite foams. The porosity of the composite foam increases from 59.07% to 68.68% with the incorporation of SiC particles. The cell dimensions fluctuated between 1.12 and 1.45mm as the relative density of the AA7075/SiC composite foam decreased from 0.4 to 0.31. [ABSTRACT FROM AUTHOR]

In this study, AA7075/SiC/TiB2 closed-cell aluminium hybrid composite foams (AHCFs) with different densities were fabricated by top-loaded bottom-pouring stir casting technique. This technique uses oyster-shell powders (CaCO3 2.5 wt% of composite with 60 μm size) as blowing agents and no viscosity-enhancing ingredient. The silicon carbide (SiC 0, 3, 6, 9, and 12 wt% with 25 μm) and titanium diboride (TiB2 3 wt% with particle size 15 μm) are used as primary and secondary reinforcement agents. It has been noted that the addition of TiB2 and SiC enhanced the mechanical properties (modulus of elasticity, yield strength, and plateau strength) of AHCFs. The energy absorption capacity of AHCFs increases with the addition of SiC up to 3 wt%, and a further increase in SiC content leads to the reduction. It is observed that density and cell wall thickness increase with increasing the wt% of SiC and pore size, porosity decrease with an increase in wt%. of reinforcement. It is also noted that stirring temperature also strongly influenced the microstructural properties of AHCFs, and 750 °C of stirring temperature is sufficient for aluminium foaming. [ABSTRACT FROM AUTHOR]

This article addresses the issue of iterative learning control for a specific category of discrete linear singular time-delay systems. A new iterative learning control algorithm based on the p-accelerated normal S-iteration method is proposed, and convergence analysis of the corresponding learning control algorithm is studied. With certain assumptions, the proposed algorithm guarantees that the output of the system converges to the desired output trajectory within a finite time interval. The theoretical analysis is supported by numerical examples. The results indicate that the p-accelerated normal S-iterative learning control algorithm outperforms both the first-order PD-type iterative learning control and second-order PD-type iterative learning control algorithms for discrete linear singular systems theoretically and numerically. [ABSTRACT FROM AUTHOR]

Aluminium foams have been manufactured and discovered to have a variety of uses in automotive and structural applications. However, due to their varied characteristics, it is difficult to choose an appropriate material. In this context, the selection of material for good properties is a challenging task. This study attempted to identify materials from various combinations employing the Multiple Attribute Decision Making (MADM) technique based on their mechanical and physical properties. Complex Proportional Assessment (COPRAS) is a Multi-Criteria Decision Making (MCDM) technique employed for evaluating the ranking order of the aluminium composite foam’s formulations based on performance measures. The composite foam with 2.5 wt.% of Calcium carbonate as foaming agent demonstrated the best combination of mechanical properties. [ABSTRACT FROM AUTHOR]

The second-order ILC algorithm is studied for a class of linear discrete-time switched systems with model uncertainties, external noises and the time-delay for tracking reference trajectory by taking advantage of super-vector representation. This study is based on the assumption that the systems operate under finite intervals. A sufficient condition for convergence of the algorithms is deduced when the model uncertainties and external noises are absent. Then the convergence is analysed, when the model uncertainties are present but the external noises are absent and the robustness against the bounded external noises is discussed. The analysis manifests that the second-order ILC algorithm is feasible and effective when it is imposed on the linear switched systems specified by the arbitrarily present switching rules when they are imposed on the system. We have presented a simulation example to illustrate effectiveness of the proposed second-order ILC algorithm in the study of robustness of the considered SISO linear discrete time-invariant time delay switched system. [ABSTRACT FROM AUTHOR]

Er3+-Yb3+ doped 22[3SrO.2TiO2].30[2SiO2.B2O3] glass and glass-ceramics are developed and investigated for their electrical properties. The degree of crystallization is varied by means of crystallization temperature ranging from 600 to 1000°C. In glass-ceramic samples, two major crystalline phases, Sr3Ti2O7 and TiO2, are confirmed by diffraction analysis. The best crystallized glass-ceramic (crystallization temperature 950°C) sample shows 100-1 50 times lower impedance in temperature range, 200-300°C, than the uncrystallized glass. Electrical relaxation corresponding to the crystalline phase can be isolated in frequency domain. The glass-ceramic shows a 10-100 times higher dielectric constant than the glass in lower frequency range. This dielectric constant and dissipation factor increase with increasing temperature beyond a threshold value. Curie temperature was not visible in the measured temperature range. [ABSTRACT FROM AUTHOR]

Abstract: In this work, copper oxide-doped (1, 3 and 5 wt%) tin oxide powders have been synthesised by sol–gel method and thick film sensor array has been developed by screen printing technique for the detection of H2S gas. Powder X-ray diffraction pattern shows that the tin oxide (SnO2) doped with 3 wt% copper oxide (CuO) has smaller crystallite size in comparison to 0, 1 and 5 wt% CuO-doped SnO2. Furthermore, field emission scanning electron microscopy manifests the formation of porous film consisting of loosely interconnected small crystallites. The effect of various amounts of CuO dopant has been studied on the sensing properties of sensor array with respect to hydrogen sulfide (H2S) gas. It is found that the SnO2 doped with 3 wt% CuO is extremely sensitive (82%) to H2S gas at 150 °C, while it is almost insensitive to many other gases, i.e., hydrogen (H2), carbon monoxide (CO), sulphur dioxide (SO2) and liquefied petroleum gas (LPG). Moreover, at low concentration of gas, it shows fast recovery as compared to response time. Such high performance of 3 wt% CuO-doped SnO2 thick film sensor is probably due to the diminishing of the p–n junction and the smallest crystallite size (11 nm) along with porous structure. [Copyright &y& Elsevier]

Abstract: Tantalum (Ta5+) doped CaCu3Ti4−x Ta x O12 (x =0.05 and 0.10) ceramics were prepared by semi-wet route using solid Ta2O5 powder and metal nitrate solutions. Powder X-ray diffraction confirmed the major phase formation of cubic CaCu3Ti4O12 ceramic in the doped samples sintered at 900°C for 6h. Microstructure has been studied using field-emission scanning electron microscopy. The grain size is in the range of 150nm to 1μm for both compositions. Dielectric constant of the samples increases with increasing tantalum concentrations. [Copyright &y& Elsevier]

Abstract: The aim of present investigation is to study the effect of co-doping of lanthanum and magnesium on the ionic conductivity of CeO2 for its use as a solid electrolyte in the intermediate temperature solid oxide fuel cells (IT SOFC). Attempts have been made to synthesize compositions with x =0.075, 0.07, 0.06, 0.05 and 0.00 and y =0.00, 0.01, 0.03, 0.05 and 0.15 in the system Ce1−x−y Mg x La y O2−x−y/2 (CML) by auto-combustion method. X-ray diffraction patterns show that all the samples have fluorite structure similar to undoped ceria. Microstructures of thermally etched samples have been studied by scanning electron microscopy (SEM). In order to evaluate the contributions of grains σ g, grainboundaries σ gb and electrode–specimen interface to the total conductivity σ t, use is made of AC impedance analysis. Impedance measurements are made in the frequency range 1Hz to 1MHz and temperature range 250–500°C. The results show that the conductivity of the system increases with increasing lanthanum content. There is no enhancement in conductivity due to co-doping with La and Mg. [Copyright &y& Elsevier]

Abstract: A few compositions in the system Ce1−x Sr x O2−x with 0.05≤ x ≤0.20 have been prepared by auto-combustion method. More than 93% of theoretical density has been achieved by sintering at 1350°C for 4h. Solid solution has formed in the composition with x =0.05. All other compositions have been found to contain XRD lines of SrCeO3 beside the major fluorite phase. Complex plane impedance analysis has clearly revealed the contribution of grains, grain boundaries, and electrode specimen interface to the total observed resistance of the sample. Conduction occurs mainly due to diffusion of O2− ions through oxygen vacancies as indicated by values of activation energy of conduction. Composition, Ce0.95 Sr0.05 O1.95 exhibits the highest ionic conductivity 3.26×10−3 Scm−1 at 500°C among the series. Ionic conductivity decreases gradually with increasing x. This is due to the formation of a second phase SrCeO3 and increasing probability of formation of neutral associated defect pairs, . [Copyright &y& Elsevier]

Abstract: CaCu2.9Fe0.1Ti4O12 (CCFTO) has been prepared by a novel semi-wet route and its dielectric properties have been studied in the temperature range 300–500K. It is found that dielectric constant (ɛ) decreases drastically in the frequency range 100Hz to 1MHz. Complex plane impedance and modulus analysis was done to understand this drastic decrease in ɛ. Oxidation state of various ions was studied using X-ray photoelectron spectroscopy (XPS). The decrease in the permittivity of CCFTO can be attributed to two factors: the suppression of the Ca/Cu disorder in CCFTO which is observed in CaCu3Ti4O12 (CCTO) and the absence of the grain boundary internal barrier layer capacitance mechanism. [Copyright &y& Elsevier]

Abstract: A typical composition of the system Ce1 − x Gd x O2 − δ with x =0.15 (CGO15) has been synthesized by auto-combustion method. DTA/TGA of the precursor compound indicated the completion of reaction at about 270°C. Greater than 95% of the theoretical density has been achieved by sintering at 1300°C for 10h. Single phase formation in as-burnt stage has been confirmed by its powder X-ray diffraction (XRD) pattern. The structural morphology was studied employing bright field transmission electron micrograph (BFTEM) and high resolution transmission electron micrograph (HRTEM). BFTEM image indicates that particles are highly agglomerated and appear to be dispersed in amorphous matrix. Also BFTEM image reveals that the average particle size is 26±5nm. The presence of amorphous phase in as-prepared ash was also confirmed by HRTEM and selected area diffraction (SAD). The scanning electron micrograph (SEM) of the thermally etched system shows grains having an average size of 400nm. Impedance measurements have been made in the frequency range 1Hz to 1.3MHz between 200 and 500°C and the total conductivity was measured. An enhanced conductivity value is observed which may make this system suitable for application as a solid electrolyte material for intermediate temperature solid oxide fuel cells (IT-SOFCs). [Copyright &y& Elsevier]

Researchers wanted to develop skin liposomal formulations that would carry 5-fluorouracil to the cancer site in an adjuvant way, as well as enhancing the health of basal cell carcinoma patients who were experiencing unfavorable consequences. Using Strat-M films in vitro, the detailed skin-damaging potential of the synthesized skin liposomes and the sensitivity to 5-fluorouracil were evaluated. It was found that the Korsmeyer-Pepas condition was the best one for controlling drug administration. Additionally, it is unknown if it might irritate skin. The vitality and hemolytic potential of the cytostatic effect on the recommended anti-tumor therapy were also examined in in vitro investigations. Our findings suggest that a sodium alginate and hyaluronic acid crosslinked gel containing AS1411 aptamer liposomes coated with 5-fluorouracil is the optimal liposome solution. This liposome characterization appears to have good biological safety implications and may be exploited as a different approach to basal cell carcinoma skin treatments. [ABSTRACT FROM AUTHOR]

Abstract: The aim of the present investigation was to study the effect of doping of magnesium and calcium on the ionic conductivity of CeO2 in the system Ce1−xCax−yMgyO2−x (x=0.150) for its use as a solid electrolyte in the intermediate temperature solid oxide fuel cells (IT SOFC).Attempts have been made to synthesize a few compositions in this system with x=0.150 and y=0.000, 0.050, 0.060, 0.065 and 0.070. The precursor materials have been synthesized by auto-combustion method. Solid solution forms in compositions with y≤0.060. Microstructures of thermally etched samples have been studied by scanning electron microscopy (SEM). In order to evaluate the total electrical conductivity, σt, use is made of complex plane impedance analysis. Impedance measurements were made in the frequency range 1Hz–1MHz and temperature range 250–500°C. It is found that co-doped samples show higher conductivity than undoped and singly doped samples. [Copyright &y& Elsevier]

Abstract: Co-doping effect of Sm3+ and Ca2+ ions in ceria has been studied using the microwave assisted synthesis (MAS) technique. Thermal response of the prepared compositions was studied using differential thermal and thermo-gravimetric techniques (DTA/TG). Structural studies were performed using X-ray diffraction (XRD) and fourier transform infrared spectroscopy (FT-IR). The impedance analyses were performed over a wide range of temperatures (200–500°C) and frequency (100Hz to 1MHz). The conductivity data show that 10% doping of both Sm3+ and Ca2+ in ceria provides a significant rise in the conductivity value of pure ceria. [Copyright &y& Elsevier]

Abstract: An efficient synthesis is used for the first time to prepare CuO/reduced graphene oxide nanocomposite anode materials for lithium ion batteries. Initially, copper oxide (CuO) nanoparticles are synthesized via a simple, facile and inexpensive microwave-assisted method within short reaction times (<20 min) and subsequent heat treatment at 500 °C for 5 h. The obtained pure CuO nanoparticles are mixed with 10 wt% of graphene nanosheets by the use of spex mill for 1 min. By short-time spex-milling, a unique CuO/reduced graphene oxide nanocomposite is obtained with a microstructure of multi-scale CuO nanoparticles homogeneously dispersed in a graphene matrix. The synthesized samples are characterized using X-ray diffraction and field-emission transmission electron microscopy studies. The spex-milled nanocomposite anode exhibits better electrochemical performance with higher reversible capacity and excellent cyclability in comparison with pure CuO nanoparticles. The initial discharge capacity of the pure CuO nanoparticles and their nanocomposite are 785.2 mAh g−1 and 1043.3 mAh g−1 with reversible capacity retention of 392.1 mAh g−1 and 516.4 mAh g−1 after 45 cycles respectively. The excellent electrochemical performance of CuO/reduced graphene oxide nanocomposite can be attributed to their unique structures, which intimately combine the conductive graphene nanosheets network with uniformly dispersed CuO nanoparticles. [Copyright &y& Elsevier]

Abstract: Present investigation provides experimental studies on cylindrical dielectric resonator antennas (CDRAs) fabricated from (Zn1−x Mg x )TiO3 (ZMT) ceramic material with different substitution of Mg in place of Zn (x =0.1, 0.2, 0.3, 0.4 and 0.5) along with measurement of material permittivity in C-band of microwave frequencies. The dielectric properties of the ZMT ceramic materials with different x values (x =0.1–0.5) have been measured at microwave frequencies using Hakki–Coleman method modified by Courtney. The value of dielectric constant and loss tangent decreases with the increase in Mg content. The dielectric constant is minimum for x =0.3 and loss tangent is minimum for x =0.5. The variations of return loss and input impedance versus frequency and radiation patterns of CDRAs at their respective resonant frequencies are studied experimentally. The measured results for resonant frequency and return loss bandwidth of the CDRAs are also compared with theoretical ones. The measured resonant frequencies of all the four CDRAs are nearly in agreement with respective theoretical values and the values of input resistance at respective resonant frequencies of the CDRAs match well with the coaxial feed impedance of 50Ω. The designed CDRAs have broad beam, low side lobe and cross-polarized lobe levels. [Copyright &y& Elsevier]