Synthesis and characterization of low cost willemite based glass–ceramic for opto-electronic applications

This paper presents a comprehensive study on thermal, structural and optical properties of novel willemite glass–ceramics. The precursor glass in the ZnO–SLS glass system was successfully prepared using conventional melt-quenching technique and willemite (Zn₂SiO₄) glass–ceramics were derived from this precursor glass by a control crystallization process. The effect of heat-treatment temperature on the phase transformation, morphology and size of Zn₂SiO₄ crystal phase was examined using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) techniques. Furthermore, fourier transform infrared reflection (FTIR) spectroscopy was used to evaluate the Zn₂SiO₄ crystal structural evolution. The average size of Zn₂SiO₄ crystallite obtained from calculation of XRD is found to be in the range 30–60 nm, whereas the grain size observed in FESEM is in range of 200–400 nm. The appearance of SiO₂, ZnO₄ and Zn–O–Si bands detected from FTIR indicate the formation of Zn₂SiO₄ crystal phase. Besides, the study of the optical band gap has found that optical band gap of the glass–ceramics decreased as the heat treatment temperature increased. The photoluminescence spectra of willemite glass–ceramics exhibit two different emissions around 525 nm (green) and 585 nm (yellow); exhibit a characteristic of broad absorption band around 260 nm. These two different spectra reveal that the luminescence performance of the willemite glass–ceramics was enhanced with the progression of heat treatment temperature due to different located energy levels of the β-Zn₂SiO₄ and α-Zn₂SiO₄ crystalline phase. Such luminescent glass–ceramics was expected to find potential applications in phosphors and opto-electronic devices.     

Fixed versus sun tracking solar panels: an economic analysis

The performance of photovoltaic panels depends on many factors. One factor involves the light reception angles at the panels in which the intensity of the received solar radiation from the sun at the earth is affected significantly by the diurnal and seasonal movement of the earth. The maximum output of the panels is achieved when the panels are perpendicular to the sun’s rays. This research is an empirical financial assessment of the benefit of using a dual-axis sun tracker versus a fixed-flat position, as well as a comparison of the performance of the two panels under such settings. The experiment was conducted using 190 W panels, a manual dual-axis sun tracker, and a data acquisition system, which collected and stored the experimental data. A significant improvement in output was noticed in the tracked panel. The overall average improvement for the entire data collection time interval was 82 %. The financial assessment was performed based on the energy market rate in Texas and the average price and operative expenses of the dual-axis sun trackers. The breakeven point for the dual-axis sun tracking system was found to be “never,” 13, and 6 years for 1-, 4-, and 9-panel configurations, respectively, in each system.     

Fabrication and Determination of an Aluminium Fixed Point Cell as a Secondary Standard in Thermocouple Calibration

A new open-type aluminium (Al) fixed-point cell has been fabricated in Puslit Metrologi-LIPI. The cell was successfully characterized by direct comparison with a commercial Al cell. The cell plateau lasted for four hours with a flatness of 0.014 °C, measured as the difference between the beginning and the end of the plateau using a type S thermocouple. The reproducibility of realizations is 0.04 °C; the immersion profile of the cell was measured for 30 mm depth, from the bottom of the cell, and the variation was found to be 0.02 °C. A good agreement within 0.16 °C was measured at the freezing point. Furthermore, the cell improves the entry in Appendix C, calibration and measurement capability (CMC) by 0.24 °C, allowing the cell to be included as a secondary standard of the international temperature scale of 1990 realization in Puslit Metrologi-LIPI.     

Adsorptive recovery of phenolic compounds from apple juice

The recovery of phenolic compounds from apple juice was studied on a laboratory scale using a food grade polymethylmethacrylate adsorption resin. The work was carried out to understand how the processing parameters of the adsorption process can be manipulated to optimise production of apple phenolics as functional food ingredients. Adsorption was determined by mixing weighed amounts of the polymer with a diluted apple juice concentrate at 20–80 °C and at pH values ranging from 2.0 to 3.9. At regular intervals samples were withdrawn from the aqueous phase. Total phenolics, absorbance values at 280 and 420 nm, and the amounts of individual phenolics remaining in the liquid phase were determined. The analytical data were fitted to the Langmuir and Freundlich isotherms. In contrast to previous findings, the pH value significantly affected the adsorption onto the resin. HPLC analyses revealed different affinities of individual compounds, which enabled selective enrichment of certain phenolics in the liquid phase or on the sorbent surface. Desorption studies were performed using a resin with known amounts of adsorbed phenolic compounds. Elution was carried out by an automated pressurised liquid extraction system, studying the effects of temperature (40–180 °C) and solvents (water, ethanol, methanol). Here again, individual compounds showed different behaviours depending on their hydrophobicity. Therefore, a systematic change of parameters for the sorption and desorption process can be helpful for the recovery of purified plant extracts enriched in certain target compounds.     

Acute urine retention. Another presentation of a hydatid cyst of the kidney

We report on a case of hydatic cyst of the kidney, in a 12 year-old male, revealed by an acute urinary retention. After a brief report of the common signs of this parasitic disease, we emphasize the importance of hydaturia and acute urinary retention as another revealing sign of this disease.     

An examination of the perforation of a mild steel plate by a flat-ended cylindrical projectile

Results of tests are presented in which flat-ended cylindrical projectiles, of varying length, were projected normally at high speed against a thin mild steel plate, to examine the impact conditions relevant to their containment.A diagram of the equipment used, a photograph and photomicrographs of typical perforated plates are provided. Final profiles and thickness strains for various impact conditions, along with further derived information, are presented and discussed.Comparison is made with the results of static tests.     

Statistical Prediction Model for the HAPS Gateway Link and Fixed Satellite Service Interoperability at 5850–7075 MHz

High altitude platform station (HAPS) is a new airborne technology suited in the stratosphere layer, which is expected to remain quasi-stationary while delivering a host of wireless services for the next generation of mobile and fixed devices. The theoretical basis behind the spectrum planning for this new emerging technology is classified under the worst case (WC) prediction model, which insures protection for existing services, but in contrast it deprives achieving spectrum efficiency. However, a new spectrum allocation for HAPS in the reliable band 5850–7075 MHz is on the table of the International Telecommunications Union (ITU) under the agenda item 1.20 of the World Radio Conference-2012 (WRC-12). In this article, a comprehensive intersystem interference transformation technique for the WC prediction model to the minimum coupling loss (MCL) approach is proposed to define the technical compatibility between HAPS and Fixed Satellite Service (FSS) gateways. In advance; the interference probability has been performed to investigate the impact on sharing constrains between systems; by using Monte-Carlo statistical simulation. The paper presents an accomplished statistical simulation model that has proved the ability to convey the interference probability into an unwanted range of parameters; which achieves practical, actual and optimum spectrum sharing.     

Triple-helix directed cleavage of double-stranded DNA by benzoquinoquinoxaline-1,10-phenanthroline conjugates

Oligonucleotide-directed triple-helix formation provides a rational means to interfere with genomic DNA targets and to direct modifications at specific sites. We have developed a new class of compounds that, at low concentrations, efficiently targets and damages double-stranded DNA specifically at the site where a triple-helical structure is formed. In these new compounds, a triple-helix-specific intercalator-benzoquinoquinoxaline (BQQ)-was coupled to one of two isomeric 1,10-phenanthrolinecarboxaldehyde derivatives. 1,10-Phenanthroline derivatives are known to cleave DNA in the presence of copper ions. The obtained BQQ-1,10-phenanthroline (BQQ-OP) conjugates were compared with regard to their ability to cleave triple-helix DNA. Both conjugates displayed a sequence preference inside the triple-helical site, as judged from the more pronounced cleavage obtained at stretches of TAxT base triplets.     

Multi-objective flower pollination algorithm: a new technique for EEG signal denoising

Neural Computing and Applications - The electroencephalogram (EEG) signal denoising problem has been considered a challenging task because of several artifact noises, such as eye blinking, eye...