Enhancement of thermal,mechanical, ignition and damping response of magnesium using nano-ceria particles

Magnesium (Mg)-based nanocomposites owing to their low density and biocompatibility are being targeted for transportation and biomedical sectors. In order to support a sustainable environment, the prime aim of this study was to develop non-toxic magnesium-based nanocomposites for a wide spectrum of applications. To support this objective, cerium oxide nanoparticles (0.5?vol%, 1?vol%, and 1.5?vol%) reinforced Mg composites are developed in this study using blend-press-sinter powder metallurgy technique. The microstructural studies exhibited limited amounts of porosity in Mg and Mg-CeO₂ samples (< 1%). Increasing presence of CeO₂ nanoparticles (up to 1.5?vol%) led to a progressive increase in microhardness, dimensional stability, damping capacity and ignition resistance of magnesium. The compressive strengths increased with the increasing addition of the nanoparticles with a significant enhancement in the fracture strain (up to ~48%). Superior energy absorption was observed for all the composite samples prior to compressive fracture. Further, enhancement in thermal, mechanical and damping characteristics of pure Mg is correlated with microstructural changes due to the presence of the CeO₂ nanoparticles.     

A survey of sensory data boundary estimation,covering and tracking techniques using collaborating sensors

Boundary estimation and tracking have important applications in the areas of environmental monitoring and disaster management. A boundary separates two regions of interest in a phenomenon. It can be visualized as an edge if there is a sharp change in the field value between the two regions or alternatively, as a contour with a field value $f=\tau$ separating two regions with field values $f>\tau$ and $f<\tau$. Examples include contours/boundaries of hazardous concentration in a pollutant spill, frontal boundary of a forest fire, isotherms, isohalines etc. Recent advances in the area of embedded sensor devices and robotics have led to deployments of networks of sensors capable of sensing, computing, communication and mobility. They are used to estimate the boundaries of interest in physical phenomena, monitor or track them over time and also in some cases, mitigate the spatial spread of the phenomena. Since these sensors work autonomously in the environment, minimizing the energy consumed while maximizing the accuracy of estimation or tracking is the main challenge for algorithms for boundary estimation and tracking. Several algorithms with these objectives have been proposed in the literature. In this work, we focus on the algorithms that estimate and cover boundaries found in the sensory data in a field and not the topological boundary of the sensor network per se, which is beyond the scope of this paper.Here, our objective is to provide a comprehensive survey of the algorithms for boundary estimation and tracking by providing a taxonomy based on two broad categories — (i) Boundary estimation and tracking, where the sensors estimate the boundary without physically covering the boundary and (ii) Boundary covering — where the sensors not only predict the location and estimate the entire boundary but also physically cover the boundary by surrounding and bounding it. We further classify the techniques based on (a) sensing capabilities —in situ, range or remote sensing (b) movement capabilities — static or mobile sensors and (c) boundary type — static or dynamic and (d) type of estimation — field estimation where the entire field is sampled to search for contours and localized estimation where sampling is done near the boundary and (e) different types of mobility models in the case of mobile sensors. We believe that such a survey has not been performed before. By capturing and classifying the current state-of-the-art and identifying open research problems, we hope to ignite interest and stimulate efforts towards promising solutions for real-world boundary estimation and tracking problems.     

Scientific basis for establishing country greenhouse gas estimates for rice-based agriculture: An Indian case study

A comprehensive scientific assessment of CH₄ budget estimation for Indian rice paddies, based on a decade of measurements in India, is presented. Indian paddy cultivation areas contain soils that have low to medium levels of soil organic carbon. The average seasonally integrated CH₄ flux (E _sif) values calculated from these measurements were 15.3 ± 2.6 g m^–2 for continuously flooded (CF), 6.9 ± 4.3 g m^–2 for intermittently flooded (IF) single aeration (SA) and 2.2 ± 1.5 g m^–2 for IF multiple aeration (MA) rice ecosystems. For CF and IF (MA) rice ecosystems having high soil organic carbon, without organic amendments, the CH₄ flux (E _sif) may be increased by 1.7 times relative to low soil organic carbon, whereas it may enhance by 5.3 for CF if amended organically. Organic amendment and high soil organic carbon paddy areas do not alter the methane budget estimates for India (3.6±1.4 TgY^–1) much, due to their small paddy harvested area. Methane estimated using average emission factors (E _sif) for all paddy water regimes, which include harvested areas having soils with high organic carbon and organic amendments, may give a budget of 5 TgY^–1 for India.     

Thermally induced crosslinking between polyacrylic acid and epoxidized natural rubber. III. Effect of carbon black filler and mixer rotor speed

High-temperature molding of Brabender-mixed blend of polyacrylic acid (PAA) and epoxidized natural rubber (ENR) causes thermally induced crosslinking between PAA and ENR. Studies on Monsanto rheometry of the blend and physical properties, solvent swelling, and dynamic mechanical properties of the molded blend show that both mixer rotor speed and carbon black filler influence the crosslinking between the component polymers. For example, the extent of crosslinking for the 50–50 PAA–ENR blend was found maximum when the component polymers were mixed at 40 rpm, but the same blend filled with 30 phr HAF carbon black filler showed maximum crosslinking when mixing was carried out at 120 rpm. The results have been explained on the basis of formation of network on the filler surface, which in turn depends on two competing factors: increase in bound rubber formation with increase in filler loading at a fixed rotor speed and enhanced degradation of ENR at higher mixer rotor speed at a fixed filler loading. © 1994 John Wiley & Sons, Inc.     

The Effect of Temperature on the Strength of Adhesively-Bonded Composite-Aluminium Joints

Different materials have different coefficients of thermal expansion, which is a measure of the change in length for a given change in temperature. When different materials are combined structurally, as in a bonded joint, a temperature change leads to stresses being set up. These stresses are present even in an unloaded joint which has been cured at say 150°C and cooled to room temperature. Further stresses result from operations at even lower temperatures.

In addition to temperature-induced stresses, account also has to be taken of changes in adhesive properties. Low temperatures cause the adhesive to become more brittle (reduced strain to failure), while high temperatures cause the adhesive to become more ductile, but make it less strong and more liable to creep.

Theoretical predictions are made of the strength of a series of aluminium/CFRP joints using three different adhesives at 20°C and 55°C. Various failure criteria are used to show good correlation with experimental results.     

Color Subspaces as Photometric Invariants

Complex reflectance phenomena such as specular reflections confound many vision problems since they produce image ‘features’ that do not correspond directly to intrinsic surface properties such as shape and spectral reflectance. A common approach to mitigate these effects is to explore functions of an image that are invariant to these photometric events. In this paper we describe a class of such invariants that result from exploiting color information in images of dichromatic surfaces. These invariants are derived from illuminant-dependent ‘subspaces’ of RGB color space, and they enable the application of Lambertian-based vision techniques to a broad class of specular, non-Lambertian scenes. Using implementations of recent algorithms taken from the literature, we demonstrate the practical utility of these invariants for a wide variety of applications, including stereo, shape from shading, photometric stereo, material-based segmentation, and motion estimation.     

Inorganic-Based Printed Thermoelectric Materials and Devices

One of the simplest ways to generate electric power from waste heat is thermoelectric (TE) energy conversion. So far, most of the research on thermoelectrics has focused on inorganic bulk TE materials and their device applications. However, high production costs per power output and limited shape conformity hinder applications of state-of-the-art thermoelectric devices (TEDs). In recent years, printed thermoelectrics has emerged as an exciting pathway for their potential in the production of low-cost shape-conformable TEDs. Although several inorganic bulk TE materials with high performance are successfully developed, achieving high performance in inorganic-based printed TE materials is still a challenge. Nevertheless, significant progress has been made in printed thermoelectrics in recent years. In this review article, it is started with an introduction signifying the importance of printed thermoelectrics followed by a discussion of theoretical concepts of thermoelectricity, from fundamental transport phenomena to device efficiency. Afterward, the general process of inorganic TE ink formulation is summarized, and the current development of the inorganic and hybrid inks with the mention of their TE properties and their influencing factors is elaborated. In the end, TEDs with different architecture and geometries are highlighted by documenting their performance and fabrication techniques.     

OTIS-MOT: an efficient interconnection network for parallel processing

Mesh of trees (MOT) is well known for its small diameter, high bisection width, simple decomposability and area universality. On the other hand, OTIS (Optical Transpose Interconnection System) provides an efficient optoelectronic model for massively parallel processing system. In this paper, we present OTIS-MOT as a competent candidate for a two-tier architecture that can take the advantages of both the OTIS and the MOT. We show that an n⁴_-n^{4}_{-} processor OTIS-MOT has diameter 8log n ^∗+1 (The base of the logarithm is assumed to be 2 throughout this paper.) and fault diameter 8log n+2 under single node failure. We establish other topological properties such as bisection width, multiple paths and the modularity. We show that many communication as well as application algorithms can run on this network in comparable time or even faster than other similar tree-based two-tier architectures. The communication algorithms including row/column-group broadcast and one-to-all broadcast are shown to require O(log n) time, multicast in O(n ²log n) time and the bit-reverse permutation in O(n) time. Many parallel algorithms for various problems such as finding polynomial zeros, sales forecasting, matrix-vector multiplication and the DFT computation are proposed to map in O(log n) time. Sorting and prefix computation are also shown to run in O(log n) time.     

Green microalga Chlorella vulgaris as a potential feedstock for biodiesel

BACKGROUND: A major bottleneck in microalgal biodiesel production is lipid content, which is often low in microalgal species. The present study examines Chlorella vulgaris as a potential feedstock for biodiesel by identifying and evaluating the relationships between the critical variables that enhance the lipid yield, and characterizes the biodiesel produced for various properties. RESULTS: Factors affecting lipid accumulation in a green microalga, Chlorella vulgaris were examined. Multifactor optimization raised the lipid pool to 55% dry cell weight against 9% control. When C. vulgaris cells pre‐grown in glucose (0.7%)‐supplemented medium were transferred to the optimized condition at the second stage, the lipid yield was boosted to 1974 mg L^?1, a value almost 20‐fold higher than for the control. The transesterified C. vulgaris oil showed the presence of ～82% saturated fatty acids, with palmitate and stearate as major components, thus highlighting the oxidative stability of C. vulgaris biodiesel. The fuel properties (density, viscosity, acid value, iodine value, calorific value, cetane index, ash and water contents) are comparable with the international (ASTM and EN) and Indian (IS) biodiesel standards. CONCLUSION: C. vulgaris biomass with 55% lipid content and adequate fuel properties is potentially a renewable feedstock for biodiesel. Copyright © 2011 Society of Chemical Industry     

Non-uniform illumination in concentrating solar cells

After a gap of more than two decades, Concentrator Photovoltaics (CPV) technology is once again under spotlight for making use of the best available solar cell technologies and improving the overall performance. CPV finds its use in a number of applications ranging from building integration to huge power generation units. Although the principles of solar concentration are well understood, many practical design, operation, control issues require further understanding and research. A particular issue for CPV technology is the non-uniformity of the incident flux which tends to cause hot spots, current mismatch and reduce the overall efficiency of the system. Understanding of this effect requires further research, and shall help to employ the most successful means of using solar concentrators. This study reviews the causes and effects of the non-uniformity in the CPV systems. It highlights the importance of this issue in solar cell design and reviews the methods for the solar cell characterization under non-uniform flux conditions. Finally, it puts forward a few methods of improving the CPV performance by reducing the non-uniformity effect on the concentrator solar cells.