Natural radioactivity measurements in beach-rock samples of south-east coast of Tamilnadu, India

The concentration of primordial radionuclides in beach-rock samples of the south-east coast of Tamilnadu, India has been measured using gamma ray spectrum of rock. The mean activities of 232Th, 238U and 40K are 144.18, 29.25 and 267.48 Bq kg(-1) respectively. In situ measurements were also carried out using environmental radiation dosemeter. The linear correlation coefficient was obtained. The average activity of concentration of 232Th in the present study is 2.5 times higher than the world median value while the activity of 238U and 40K were found to be lower. This may be due to the heavy minerals present in the study area. In the present study, the calculated activity ratio (Th/U) is higher than the crustal rocks. This may be due to changes in the crustal composition through time (mafic to felsic) that are reflected by a change in the Th and U abundances in sedimentary rocks, and also increase in carbon content with time resulted in the decrease in U content and increase in Th/U ratio.     

Complete exchange on the CM-5 and Touchstone Delta

The complete exchange (or all-to-all personalized) communication pattern occurs frequently in many important parallel computing applications. It is the densest form of communication because all processors need to communicate with all other processors. This can result in severe link contention and degrade performance considerably. Hence, it is necessary to use efficient algorithms in order to get good performance over a wide range of message and multiprocessor sizes. In this paper we present several algorithms to perform complete exchange on the Thinking Machines CM-5 and the Intel Touchstone Delta multiprocessors. Since these machines have different architectures and communication capabilities, different algorithms are needed to get the best performance on each of them. We present four algorithms for the CM-5 and six algorithms for the Delta. Complete exchange algorithms generally assume that the number of processors is a power of two. However, on the Delta the number of processors allocated by a user need not be a power of two. We propose algorithms that are even applicable to non-power-of-two meshes on the Delta. We have developed analytical models to estimate the performance of the algorithms on the basis of system parameters. Performance results on the CM-5 and Delta are also presented and analyzed.     

Solvothermal synthesis of nickel nanorods and its magnetic, structural and surface morphological behavior

One-dimensional rod-like nickel nanostructure was fabricated through a simple, efficient and one pot solvothermal approach with hydrazine hydrate and trimethylamine as reducing and morphology directing agents. The phase structure, morphology and magnetic properties of the as-prepared product were extensively characterized by X-ray diffraction, transmission electron microscopy and superconducting quantum interference device magnetometer. X-ray diffraction pattern indicated that the as-synthesized product was nickel with well-crystallized face-centered cubic structure. TEM observation showed that the nickel product consists of rod-like shape with size around 10 nm. Magnetic measurements revealed that the coercive forces of nickel nanorods at 300 K and 4.2 K are 198 Oe and 250 Oe, respectively. Compared with bulk nickel, the nanorods exhibit significant increase in coercive force as a reflection of shape anisotropy. A possible mechanism for the formation of rod-like nanostructure is proposed.     

Synthesis and vibrational properties of hematite (α-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>) nanoparticles

α- Fe₂O₃ nanoparticles have been synthesized by gel evaporation method in air at 300°C. The average size of as synthesized α-Fe₂O₃ nanoparticle was estimated to be 30 nm and the particles were of good crystalline nature. Shape of the nanoparticles were slightly deviated from spherical which is attributed to the asymmetric growth of primary nuclei. MicroRaman and X-ray diffraction results have shown mixed phases of α-Fe₂O₃ and γ-Fe₂O₃. However, the α-Fe₂O₃ phase is more predominant than γ-Fe₂O₃ due to the incomplete nucleation of α-Fe₂O₃ particles at the size of 30 nm. The vibrating sample magnetometer measurement shows that the nanoparticles possess ferromagnetic property.     

Nanostructured ZnO Films for Room Temperature Ammonia Sensing

Zinc oxide (ZnO) thin films have been deposited by a reactive dc magnetron sputtering technique onto a thoroughly cleaned glass substrate at room temperature. X-ray diffraction revealed that the deposited film was polycrystalline in nature. The field emission scanning electron micrograph (FE-SEM) showed the uniform formation of a rugby ball-shaped ZnO nanostructure. Energy dispersive x-ray analysis (EDX) confirmed that the film was stoichiometric and the direct band gap of the film, determined using UV–Vis spectroscopy, was 3.29 eV. The ZnO nanostructured film exhibited better sensing towards ammonia (NH₃) at room temperature (～30°C). The fabricated ZnO film based sensor was capable of detecting NH₃ at as low as 5 ppm, and its parameters, such as response, selectivity, stability, and response/recovery time, were also investigated.     

Analysis of GSM-SM Over $$kappa -mu$$ κ - μ , $$eta -mu$$ η - μ and $$alpha -mu$$ α - μ Fading Channels

Wireless Personal Communications - Spatial multiplexing increases the throughput by sending multiple data bits parallelly while generalized spatial modulation (GSM) increases the spectral...     

A critical review on global trends in biogas scenario with its up-gradation techniques for fuel cell and future perspectives

Renewable biogas production technology is an excellent method for eradication of greenhouse gas emission and thereby reducing global warming. This review discusses extensively on global biomass potential, energy need and method of satisfying the energy demand through sustainable techniques. One of the best alternative technological developments for the conversion of waste into useful energy is anaerobic digestion to produce biogas. It is recognized as one among leading green energy to manage the environmental and meet the current energy tasks to tackle globally. Generally, biogas can be utilized for cooking, heat and electricity generation. In order to extend the scope of application, traces of carbon dioxide, hydrogen sulphide has to be removed by several upgrading technologies to produce high purity methane (90%). This study discusses on biogas up-gradation using physical and chemical absorption, membrane separation, cryogenic separation, hybrid technology etc. Among the various up-gradation techniques, hybrid technology yields methane purity of 97%. In addition, this work reviews about benefits and problems in anaerobic integrated Solid Oxide Fuel Cell (SOFC) with latest real-world achievement in SOFC. Several SOFC systems with dynamic model development were reviewed based on efficiency of power generation. SOFC generates 45% more electricity than generator with heat engine. This review extends the scope for further research in biogas upgradation and global warming mitigation potential with carbon credits.     

An innovative Azadirachta indica gum-mediated synthesis of cocoon-shaped nano-AgHAp from Lamellidens marginalis shells

In this work, the evaluations of noble nanoparticles for the structural and morphological characteristics are focused. The control of desired particles size and morphology for hydroxyapatite (HAp) and Ag-substituted hydroxyapatite (AgHAp) derived from Lamellidens marginalis shells using Azadirachta Indica (AI) gum as a potential surfactant for the synthesis of stable nanoparticles are reported. The morphological change with respect to the concentration of AI gum is analyzed. The functional group (FTIR) and crystallographic (XRD) characterization of the HAp and AgHAp nanoparticles confirm the presence of HAp with desired apatite functional peaks. The morphological evaluation (FE-SEM) exhibited the formation of cocoon-shaped nanoparticles for the AI gum-medicated synthesis. Higher AI gum concentration reduces the particle size along with the formation of unique surface morphology. The average diameter of the synthesized AgHAp nanoparticles was found to be ≤30 nm which is revealed from HR-TEM. The bacterial investigation against bacterial strains substantiates the higher resistance of bacterial growth for Staphylococcus aureus was observed than Escherichia coli for the AgHAp particles. Hence, embedding silver nanoparticles in the HAp is an efficient approach to enhance the long-term antibacterial effect of the orthopedic and dental applications.