Quadrature oscillator using CCCCTAs and grounded capacitors with amplitude controllability

The realisation of two electronically tunable current-mode quadrature oscillators using Current Controlled Current Conveyor Tranconductance Amplifiers (CCCCTAs) and grounded capacitors is presented. The proposed circuits offer the following advantages. The condition of oscillation and the frequency of oscillation can be orthogonally controlled. Availability of electronic control of amplitude of output current is achieved. The oscillators have high outputs impedance which facilitates easy driving an external load without additional current buffers. The proposed circuits are constructed by using two active elements and all grounded capacitors which are attractive for integration and have low active and passive sensitivities. The PSPICE simulation and experimental results are included to show the workability of the proposed circuit.     

Flexible,lead-free,gamma-shielding materials based on natural rubber/metal oxide composites

Properties such as gamma shielding, cure characteristics, and mechanical properties of natural rubber (NR) system with addition of oxides such as: iron (II, III) oxide (Fe₃O₄), tungsten (III) oxide (W₂O₃), or bismuth (III) oxide (Bi₂O₃) were studied for potential replacement of flexible lead (Pb), and introduced as gamma-shielding materials, to minimize risks caused by Pb. The results showed that increase in the content of oxides such as Fe₃O₄, W₂O₃, or Bi₂O₃ from 0 to 100, 300, and 500 parts/100 parts of rubber by weight (phr) increased the gamma attenuation coefficients, tensile modulus at 100% elongation, and hardness (Shore A), though they reduced the tensile strength and elongation-at-break. The composites also underwent thermal aging tests at 70 °C for 96 h. The results indicated slight reduction in the overall tensile properties. Specifically, for NR composites with 300 or 500 phr of Bi₂O₃, the mass attenuation coefficients (μ _m) of these composites were the highest among other composites and even higher than lead sheets that were measured using the same set-up. The outcome of the results imply great possibilities of replacing hazardous lead-containing gamma-shielding materials with the investigated composites, while still providing safe and efficient gamma-shielding properties for the users.     

Novel Recovery of Nano-Structured Ceria (CeO(2)) from Ce(III)-Benzoxazine Dimer Complexes via Thermal Decomposition

N,N-bis(2-hydroxybenzyl)alkylamines, benzoxazine dimers, are the major product produced from benzoxazine monomers on mono-functional phenol by the one step ring opening reaction. Due to the metal responsive property of benzoxazine dimers, in this present work, N,N-bis(5-methyl-2-hydroxybenzyl)methylamine (MMD), N,N-bis (5-ethyl-2-hydroxybenzyl)methylamine (EMD), and N,N-bis(5-methoxy-2-hydroxybenzyl) methyl amine (MeMD), are considered as novel ligands for rare earth metal ion, such as cerium(III) ion. The complex formed when the clear and colorless solutions of cerium nitrate and benzoxazine dimers were mixed, results in a brown colored solution. The metal-ligand ratios determined by the molar ratio and the Job's methods were found to be in a ratio of 1:6. To clarify the evidence of the complex formation mechanism, the interactions among protons in benzoxazine dimers both prior to and after the formation of complexes were determined by means of (1)H-NMR, 2D-NMR and a computational simulation. The single phase ceria (CeO(2)) was successfully prepared by thermal decomposition of the Ce(III)-benzoxazine dimer complexes at 600 °C for 2 h, was then characterized using XRD. In addition, the ceria powder investigated by TEM is spherical with an average diameter of 20 nm.     

Electrolyte materials for solid oxide fuel cells derived from metal complexes: Gadolinia-doped ceria

Gadolinia doped ceria (GDC) powders with different gadolinium contents were successfully prepared by the thermal decomposition of ceria complexes. All the calcined powder samples were found to be ceria-based solid-solutions having a fluorite-type structure. The powders were cold-isostatically pressed and sintered in air at 1500 °C for 5 h to attain a sintered density of about 90% of its theoretical value. The electrical conductivity of the GDC pellets in air was studied as a function of temperature in the 225–700 °C range, by using two-probe electrochemical impedance spectroscopy measurements. The highest total conductivity (σ_600 °C = 0.025 S/cm) was found for the Ce_0.85Gd_0.15O_1.925 composition.     

Mossar: motion segmentation by using splitting and remerging strategies

This paper presents a novel approach for motion segmentation by using strategies of splitting and remerging. The presented approach, Mossar, hybridizes two existing ones to obtain their potential advantages while covering weaknesses: (1) velocity-based, one of the most widely used approaches that has fairly low accuracy but provides computational simplicity and (2) graph-based, a state-of-the-art approach that provides outstanding accuracy, yet bears high computational complexity and a burden in setting of thresholds. An initial set of key frames is generated by a velocity-based splitting process and then fed into a graph-based remerging process for refinement. We present mechanisms that improve key-frames capturing in the velocity-based approach as well as details on how the graph-based approach is modified and later applied to remerging. The proposed approach also allows users to interactively add or reduce the number of key frames to control segmentation hierarchy without the need to change threshold values and re-run segmentation, as usually done in existing approaches. Our experimental results show that the presented hybrid approach, compared to both velocity-based and graph-based, demonstrates superior performance in terms of accuracy and in comparison to graph-based, our approach has not only less complexity but also a lesser number of thresholds, the values of which can be much more simply determined.     

Multiple tabu search algorithm for economic dispatch problem considering valve-point effects

This paper presents a multiple tabu search (MTS) algorithm to solve the economic dispatch (ED) problem by taking valve-point effects into consideration. The practical ED problem with valve-point effects is represented as a non-smooth optimization problem with equality and inequality constraints that make the problem of finding the global or near global optimum difficult. The proposed MTS algorithm is the sequential execution of individual tabu search (TS) algorithm simultaneously by only one personal microcomputer. The MTS algorithm introduces additional techniques for improvement of search process, such as initialization, adaptive searches, multiple searches, replacing and restarting process. To show its effectiveness, the MTS is applied to test two studied systems consisting of 13 and 40 power generating units with valve-point effects. The optimized results by MTS are compared with those of conventional approaches, such as simulated annealing (SA), genetic algorithm (GA), TS algorithm and particle swarm optimization (PSO). Studied results confirm that the proposed MTS approach is capable of obtaining higher quality solution efficiently and lowest computational time.     

A 10.7-MHz fully balanced,high-Q, 87-dB-dynamic-range current-tunable Gm-C bandpass filter

A 10.7-MHz fully balanced, high-Q, wide-dynamic-range current-tunable Gm-C bandpass filter is presented. The technique is relatively simple based on two fully balanced components, i.e. an adder and a low-Q-based bandpass filter. The Q factor is approximately equal to a typically high and constant value of a common-emitter current gain (β) and is, for the first time, independent of variables such as a center frequency. Possible solutions for good stability of the Q factor with temperature are suggested. Not only can the need for additional Q-tunable circuits be greatly reduced, the sensitivity of the Q factor can be greatly improved. Sensitivities of either the Q factor or the center frequency are constant between 1 and −1 and are no longer strongly affected by the Q factor or variables. As a simple example at 10.7 MHz, the paper demonstrates the high-Q factor of 121, the low total output noise of 5.303 μV_rms, the 3rd-order intermodulation-free dynamic range (IMFDR₃) of 74.45 dB and the wide dynamic range of 87.45 dB at 1% IM₃. The center frequency is current tunable over three orders of magnitude. Comparisons to other 10.7-MHz Gm-C approaches are also included.     

Development of novel hybrid materials from polylactic acid and nano-silver coated carbon black with distinct antimicrobial and electrical properties

This work aims to prepare nanosilver coated carbon black via benzoxazine oxidation as a filler for polylactic acid (PLA) to produce novel hybrid materials with improved electrical and antimicrobial properties. Nanosilver coated carbon black exhibited antimicrobial activity against S.aureus, B.subtilis, M.luteus, E.coli, P.aeruginosa and C.albicans. It was found that the nanosilver coated carbon black (10CB-Ag) was the most effective filler since it showed largest inhibition zones. Thermogravimetric analysis (TGA) showed that the silver content in 10CB-Ag was 5.68% by weight. The hybrid materials of PLA with uncoated carbon black and nanosilver coated carbon black fillers were prepared by injection molding. The optimal composition of the prepared hybrid materials was found to be 15 phr of nanosilver coated carbon black in PLA (15AgCB-PLA). This material showed quite good properties, e.g. tensile strength of 50 MPa, % elongation at break of 1.68 and electrical conductivity of 2.78 × 10^?9 S?m^?1. Moreover, it exhibited the S. aureus inhibition of about 99%. This work revealed the possibility of using this material for anti-electrostatic and antimicrobial applications.     

Evaluation of antioxidant activities and phenolic subtype contents of ethanolic bran extracts of Thai pigmented rice varieties through chemical and cellular assays

This study revealed that the ethanolic bran extracts of 11 Thai pigmented (red and purple) and 2 nonpigmented rice varieties exerted scavenging activity against DPPH and ABTS radicals and ROS in HL‐60 cells in the following order: red > purple > nonpigmented rice. These rice extracts also showed the same order of phenolic and flavonoid contents, which were strongly correlated with their scavenging activity. Phenolic subtype analysis further indicated that proanthocyanidins as well as anthocyanins and protocatechuic acid contributed directly to antioxidant capacity in red and purple rice bran, respectively. In contrast, these pigmented rice bran extracts possessed moderate chelating activity partly attributed to their contents of phenolics and flavonoids, especially proanthocyanidins in red rice bran. Moreover, rice bran extracts significantly restored SOD and CAT activities in oxidative stress‐induced A549 cells. This study provides new insights on the intracellular potent antioxidant capacity of pigmented rice bran extracts in the cell‐based systems.