Silicon - This study is an effort to utilize agricultural biomass rice husk for useful applications. The biomass has been milled and then pyrolysed at three different temperatures (800, 900 and... 相似文献
Multi-carrier waveforms have several advantages over single-carrier waveforms for radar communication. Employing multi-carrier complementary phase-coded (MCPC) waveforms in radar applications has recently attracted significant attention. MCPC radar signals take advantage of orthogonal frequency division multiplexing properties, and several authors have explored the use of MCPC signals and the difficulties associated with their implementation. The sidelobe level and peak-to-mean-envelope-power ratio (PMEPR) are the key issues that must be addressed to improve the performance of radar signals. We propose a scheme that applies pattern-based scaling and geometric progression methods to enhance sidelobe and PMEPR levels in MCPC radar signals. Numerical results demonstrate the improvement of sidelobe and PMEPR levels in the proposed scheme. Additionally, autocorrelations are obtained and analyzed by applying the proposed scheme in extensive simulation experiments. 相似文献
Journal of Materials Science: Materials in Electronics - The article focuses on the suitability of electrically characterized polypyrrole-banana carbon (PPy-BC) nanocomposites for broadband... 相似文献
Measurements of surface ozone and its precursor gases (NOx and CO) have been made at a semi‐arid site Anantapur (14.62°N, 77.65°E, 331 m asl) in tropical Indian region for the period, 2001–2003. NOx and CO levels were the highest during morning and late night hours at this site. Diurnal variations of ozone concentrations varied from 25 ppbv to 50 ppbv and were observed to increase gradually after sunrise, attaining a maximum value by the evening and decreasing gradually thereafter. During monsoon months, the diurnal amplitude of ozone was found to be small (20–25 ppbv). Seasonal variation in ozone showed a pronounced maximum (40–50 ppbv) in the winter and summer. Local pollutants were major contributors to the ozone levels during this period. Ozone shows a yearly mean mixing ratio of about 35.9 ± 8.8 ppbv. The daytime concentration of CO and NOx varied between 200 to 1200 ppbv and 3 to 20 ppbv respectively for the period studied. Annual average mixing ratios of oxides of nitrogen (NOx) and CO were observed to be 3.9±0.6 ppbv and 436±64 ppbv, respectively. 相似文献
Polycarbazole (PCz) has been synthesized by chemical oxidation method using APS as an oxidizing agent and PCz/CuO and PCz/Fe2O3 nanocomposites by in situ polymerization method for different wt% of CuO and Fe2O3 at room temperature. XRD patterns confirmed crystalline nature of samples. FTIR indicated strong interaction between PCz and nano fillers. The morphological and optical absorption studies were carried out using SEM and UV–Vis respectively. Addition of CuO or Fe2O3 to PCz decreased its direct and indirect band gaps. However, band gap showed a small change with dopant contents up to 30%. Urbach energy decreased with the addition of dopants. But Urbach energy of the composites increased with increasing dopants content from 10 to 30%. DC conductivity of PCz and its nanocomposites has been measured by following two probe technique in the temperature range 300–423 K. The conductivity of both the nanocomposites is found to be less than the pure PCz and it is found to increase with wt% of CuO or Fe2O3 as the case may be. The activation energy has been determined by fitting Arrhenius expression to the dc conductivity data at high temperature. The activation energy of polycarbazole is determined to be less than that of the composites. In both the composites, activation energy decreased and conductivity increased with the increase of dopant content.
Hydrogen fuel is a promising alternative to fossil fuels because of its energy content, clean nature, and fuel efficiency. However, it is not readily available. Most current producion processes are very energy intensive and emit carbon dioxide. Therefore, this article reviews technological options for hydrogen production that are eco-friendly and generate clean hydrogen fuel. Biological methods, such different fermentation processes and photolysis are discussed together with the required substrates and the process efficiency. 相似文献
This research relates to the design, modelling and fabrication of 3D metal printed heat sinks. The heat sinks presented in the research are the commonly used longitudinal fin solid heat sink (LFSHS) and three LFSHS lattice structure designs, differing only in their lattice sizes, fabricated using the Direct Metal Laser Sintering (DMLS) technique in Maraging Steel (MS1), on an EOSINT M280 system. In order to increase the heat sink surface area, the heat sinks are manufactured with mesh lattices along the length of the fins, while keeping the overall heat sink volume constant. The research is focused on pushing the limitations of the DMLS technique for the development of repeating unit, lattice structures heat sinks, and to examine the effect of incrementally varying the lattice sizes with regards to the resultant surface area of the heat sink and the thermal performance of the system. The results obtained under natural convection show that the thermal performance of the LFSHS outperformed all lattice structure heat sinks. This is due to the fact that, the pressure drop across the lattice heat sinks were so high, due to lattice meshes that it negated the positive effect of the greater surface area. 相似文献
The surface and microstructure stability of experimental W- and Re-rich Ni-based alloys in an impure-helium environment containing only CO and CO2 as impurities (ppm level) have been investigated at 1000 °C. All the alloys carburized during 50 h of exposure, and, depending on the alloy composition, different carbides of the type M6C, M7C3 and M23C6 formed on the alloy surface, in grain interiors and at grain boundaries. Microprobe analysis and Calphad-based calculations indicated that the chromium carbides (particularly Cr23C6) were enriched by rhenium. Extended exposure (225 h) led to the disappearance of surface transient carbides and the growth of surface oxide Cr2O3 occurred. 相似文献