Reduction of sidelobe levels in multicarrier radar signals via the fusion of hill patterns and geometric progression

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.     

Extraction and Characterization of Carbon from Bio Waste

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...     

Biohydrogen Production from Organic Waste – A Review

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.     

Corrosion-resistant polypyrrole-banana carbon (PPy-BC) nanocomposites for protection against electromagnetic interference: a green approach

Journal of Materials Science: Materials in Electronics - The article focuses on the suitability of electrically characterized polypyrrole-banana carbon (PPy-BC) nanocomposites for broadband...     

Structural,Optical and Electrical Conductivity Studies in Polycarbazole and its Metal Oxide Nano Composites

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.

     

Optimization of infrared radiation cure process parameters for glass fiber reinforced polymer composites

Elevated temperature post curing is one of the most critical step in the processing of polymer composites. It ensures that the complete cross-linking takes place to produce the targeted properties of composites. In this work infrared radiation (IR) post curing process for glass fiber reinforced polymer composite laminates is studied as an alternative to conventional thermal cure. Distance from the IR source, curing schedule and volume of the composite were selected as the IR cure parameters for optimization. Design of experiments (DOE) approach was adopted for conducting the experiments. Tensile strength and flexural strength of the composite laminate were the responses measured to select the final cure parameters. Analysis of variance (ANOVA), surface plots and contour plots clearly demonstrate that the distance from the IR source and volume of the composite contribute nearly 70% to the response functions. This establishes that polymer composites cured using IR technique can achieve the same properties using only 25% of the total time compared to that of conventional thermal curing.     

Chromia-Assisted Decarburization of W-Rich Ni-Based Alloys in Impure Helium at 1273 K (1000 °C)

The microstructure and surface stability of two experimental W-rich Ni-based alloys have been studied at 1273 K (1000 °C) in an impure-He environment containing only CO and CO₂ as impurities. The alloy Ni-2.3Al-12Cr-12W contained 0.08 wt pct carbon in solution, whereas the second alloy Ni-2.3Al-3Mo-12Cr-12Co-12W contained M₆C carbides at the same carbon level. Both alloys, which were preoxidized with ~2.3 μm Cr₂O₃ layer, were decarburized completely within 50 hours of exposure to the helium gas mixture at 1273 K (1000 °C) via the following chromia-assisted decarburization reaction: Cr₂O₃ (s) + 3C_alloy (s) → 2Cr (s) + 3CO (g). Microstructural observations, bulk carbon analysis, and microprobe measurements confirmed that the carbon in solid solution reacted with the surface chromium oxide resulting in the simultaneous loss of chromia and carbon. The Cr produced by the decomposition of the Cr₂O₃ diffused back into the alloy, whereas CO gas was released and detected by a gas chromatograph. Once the alloy carbon content was reduced to negligible levels, subsequent exposure led to the uninterrupted growth of Cr₂O₃ layer in both alloys. In the preoxidized alloys, chromia-assisted decarburization rates were slower for an alloy containing carbides compared with the alloy with carbon in solid solution only. The formation of Cr₂O₃ is shown to be the rate-limiting step in the chromia-assisted decarburization reaction. Exposure of as-fabricated alloys to the impure-He environment led to the formation of a thin layer of Al₂O₃ (<1 μm) between the substrate and surface Cr₂O₃ oxide that inhibited this decarburization process by acting as a diffusion barrier.     

Aqueous Extraction and Enzymatic Destabilization of Coconut Milk Emulsions

Fresh and mature coconuts were subjected to deshelling, paring and disintegration. The coconut milk was extracted, treated with an enzyme (protease) at different concentrations and centrifuged, in order to separate it into coconut cream and aqueous phases. Subsequently, coconut cream was subjected to chilling (different temperatures) and thawing to ambient temperature (29 ± 2 °C) followed by centrifugation to obtain a clear virgin coconut oil (VCO). Coconut milk treated with aspartic protease at concentration of 0.02 mg/g, resulted in 90.4 ± 1.2% yield. A maximum yield of 95.3 ± 1.0% was obtained when the treatment of coconut milk with aspartic protease at concentration of 0.02 mg/g was followed by chilling (5 °C) and thawing. Physicochemical properties and fatty acid compositions were evaluated and compared with commercial coconut oil samples. It was found that the oil obtained from present study is low with respect to free fatty acids (0.31%) and peroxide value (0.81 mequiv O₂/kg) when compared with the commercial coconut oil samples. Sensory evaluation was also carried out to ensure the product acceptability.