STUDIES ON THE PERCENTAGE VARIATION OF RESISTANCE OF PVC-GRAPHITE THICK FILM RESISTORS

The percentage variation of resistance of PVC-graphite thick film resistors has been studied. Two different grain sizes of graphite, as well as four different compositions of PVC- graphite are adopted in the preparation of thick film resistors. Among the four different compositions of PVC-graphite i.e. 90%:10% to 60%:40%, 90%:10% PVC-graphite composite thick film resistor shows the least variation with temperature changes. This can be attributed to high composition of graphite. The variation will be lowered down with a decrease in the loading fraction of PVC in thick film resistors. The percentage variations of resistance of PVC-graphite thick film resistors, after 700C for 1000 hours, or after 30 cycles thermal shock tests as well as the variations after the short term overload tests, have been measured and studied. A possible explanation on these experiments is also presented

Influence of thermomechanical processing on the grain size, texture and mechanical properties of Mg-Al alloys

El título de la revista en eslovaco es "Kovové Materiály"The work carried out by the authors over the last decade on the processing, microstructural characterization and the mechanical behaviour of Mg alloys is reviewed. In particular, the potential for grain refinement and for the development of specific textures of large strain hot rolling (LSHR), equal channel angular pressing (ECAP) and accumulative roll bonding (ARB) is discussed. The recrystallization and the deformation mechanisms predominant in Mg alloys are analyzed as a function of the grain size and the texture in a wide range of stresses, strain rates and temperatures. Finally, the the feasibility of superplatic forming of Mg alloys was examined, taking into account the influence of factors such as grain size stability and microstructural heterogeneities.The authors acknowledge financial support from CICYT under program MAT 2003/1172Peer reviewe

Influence of thermomechanical processing on the grain size, texture and mechanical properties of Mg-Al alloys

El título de la revista en eslovaco es "Kovové Materiály"The work carried out by the authors over the last decade on the processing, microstructural characterization and the mechanical behaviour of Mg alloys is reviewed. In particular, the potential for grain refinement and for the development of specific textures of large strain hot rolling (LSHR), equal channel angular pressing (ECAP) and accumulative roll bonding (ARB) is discussed. The recrystallization and the deformation mechanisms predominant in Mg alloys are analyzed as a function of the grain size and the texture in a wide range of stresses, strain rates and temperatures. Finally, the the feasibility of superplatic forming of Mg alloys was examined, taking into account the influence of factors such as grain size stability and microstructural heterogeneities.The authors acknowledge financial support from CICYT under program MAT 2003/1172Peer reviewe

Microstructural development and mechanical properties of PM Ti-45Al-2Nb-2Mn-0.8vol.%TiB₂ processed by field assisted hot pressing

A gamma-TiAl intermetallic alloy, Ti-45Al-2Nb-2Mn(at.%)-0.8vol.%TiB₂, has been processed from gas atomized prealloyed powder by field assisted hot pressing (FAHP). An initial analysis of the prealloyed powder helped on the understanding of the intermetallic sintering behavior. Atomized powder consisted of alfa metastable phase that transformed into alfa2+gamma equilibrium phases by thermal treating. Different powder particle microstructures were found, which influence the microstructure development of the FAHP gamma-TiAl material depending on the sintering temperature. Duplex, nearly lamellar and fully lamellar microstructures were obtained at the sintering temperatures above 1000°C. Lower consolidation temperatures, below 1000°C, led to the formation of an Al rich phase at powder particle boundaries, which is deleterious to the mechanical properties. High compressive yield strength of 1050MPa was observed in samples with FAHP duplex microstructures at room temperature. Whereas nearly lamellar and fully lamellar microstructures showed yield strength values of 655 and 626MPa at room temperature and 440 and 425MPa at 750°C, respectively, which are superior in comparison to similar alloys processed by other techniques. These excellent properties can be explained due to the different volume fractions of the alfa2 and gamma phases and the refinement of the PM microstructures.Funding from the Spanish Ministry of Science and Innovation through projects MAT2009-14547-C02-01 and MAT2009-14547-C02-02 is acknowledged. The Madrid Regional Government partially supported this project through the ESTRUMAT grant (P2009/MAT-1585).Publicad

Applying Three Port Converter with Dual Battery Storage System for Hybrid Power Generation

640-646The proposed research work used three power sources, namely wind energy, solar energy and grid. Wind and solar constitute the primary energy sources while the grid acted as the secondary one; added to that, we have the battery storage system. The priority between the two forms of energy in the primary source is determined by their availability. The solar irradiance is available during daytime, whereas during cloudy and night times, energy extraction is impossible; besides that wind energy is also not reliable. Thus the central level controller (CLC) is used, which serves as a deciding authority for the selection of primary source. When none of the energies in the primary sources are available the grid supplies the required power to the load. When there is a surplus energy from primary sources, it is stored in a battery or exported to the grid. In addition DBSS is also introduced for effective utilization of battery storage system. The proposed model is connected with micro grid to provide utilization path for surplus power. The overall design and simulation is performed by using MATLAB/SIMULINK

Regulation of Iron-Related Molecules In the Rat Hippocampus: Sex- and Age-Associated Differences

Iron accumulation, especially that of free oxidized ferrous iron, has been shown to induce tissue oxidative damage and contribute to brain aging and the development of neurodegenerative disease. Here we examine whether sex and advanced age affect the expression of iron-related molecules that participate in regulating free iron levels (heme oxygenase I (HOI), iron-regulatory protein I (IRPI), and ferritin heavy chain (FTH)) and whether changes in the expression of these molecules are associated with differences in the expression of alpha-synuclein (ASN) which is thought to be a critical regulator in the pathogenesis of neurodegeneration. Using a well-established aging animal model, we demonstrate that the expression of HOI, FTH, and IRPI mRNAs is higher in the female hippocampus than that observed in male Fischer 344/NNiaHSD x Brown Norway/BiNia (F344BN) rats, regardless of age group. Consistent with these sexassociated alterations in iron-related regulators, the expression of ASN mRNA and protein in the female hippocampus was lower than that found in male rats. These results suggest a sex-dependent difference in regulating the expression of molecules involved in iron metabolism and neurodegeneration. A similar finding in humans, if present, may help to shed light on why sex may affect the incidence of neurodegenerative disorders

Large spontaneous exchange bias in a weak ferromagnet Pb6Ni9(TeO6)5

We report the magnetic and dielectric behavior of Pb6Ni9(TeO6)5, a new compound comprising the honeycomb-like layers of S=1 spins, through detailed structural, magnetic and dielectric investigation. An antiferromagnetic-type transition at 25 K (TN) with weak-ferromagnetic behavior is revealed. Interestingly, a large value of coercive field of 1.32 T at 2 K is observed. The isothermal magnetization after zero-field-cooled condition, it exhibits the presence of large spontaneous exchange bias (SEB) with a magnitude of 0.19 T at 2 K; which is rare in single bulk materials, especially without external doping. The value of |HEB| further enhances to 0.24 T under 16 T field-cooled condition, confirming the presence of large exchange bias in the material. In addition, the dielectric constant shows an anomaly at the onset of TN, indicating the presence of magnetodielectric coupling.Comment: 16 pages, 6 figures, 2 supplimentory figures, under revision of Scientific Report

Microbial properties of soils as affected by cropping and nutrient management practices in several long-term manurial experiments in the semi-arid tropics of India

Microorganisms play a critical role in nutrient transformation, soil health and for sustaining the productivity of soils. Effects of long-term cropping, fertilization, manuring and their integration on microbial community were studied in soil samples from five long-term fertilizer experiments under various rainfed production systems in the semi-arid tropics (SAT) of India. Microbial population counts were analyzed by dilution plating and were in turn compared with different parameters such as soil treatments, soil type, soil microbial biomass C, soil organic C, rainfall and soil pH. The counts were high in treatments where combinations of organic and inorganic fertilizers were applied compared to control. Vertisols showed larger organic carbon levels than Alfisols. Fungal population was higher in acidic soils and in treatments under continuous inorganic fertilization treatments whereas a high number of bacteria were found in integrated use of organic and inorganic fertilizers. At most of the locations soil organic C and microbial biomass C showed significant positive ( p � 0.05) correlation with microbial populations. Thus, results suggest that even under arid and semi-arid tropical conditions, regular addition of nutrients in an integrated manner could improve soil organic carbon and microbial population counts. For each production system, better carbon sequestration management practices were identifie