Using X-ray diffraction data, the behaviour of Kevlar 49 fibres at low temperatures, up to –100°C, has been analysed. During cooling, the basal plane of the monoclinic unit cell shrinks whereas the c- (unique, chain axis) length is not significantly affected. In contrast, in the return heating cycle to ambient temperature, the basal plane expands and contraction occurs along the chain direction. The unit cell registers a reduction in volume in both the cooling and heating cycles. Conspicuously, after a cycle of cooling and heating, the unit cell does not return to its initial volume. 相似文献
Cutting of Y2O3-doped TZP rods by a low-speed diamond saw introduces an unidentified, metastable phase X (x -ZrO2) coexisting with the tetragonal ( t -ZrO2) and the monoclinic ( m -ZrO2) phases initially present in the sample. Further mechanical deformation of the cut surface by indentation or polishing sustains the x -ZrO2. Chemical etching removes the x -ZrO2 and increases the m -ZrO2content. 相似文献
Ontologies are currently emerging as representation techniques for overlapping compatibility context domains. The continuing need for more effective information retrieval has lead to the creation of the notions of the semantic web and personalized information management. Subsequently, the need for effective ontology visualization for design, management and browsing has arisen. Several ontology visualization tools have come out to strengthen the users’ cognitive support. The primary goal of this paper is to present a survey on recently implemented ontology visualization tools and their contributions in the enrichment of users’ cognitive support. This work also presents the preliminary results of an evaluation of three visualization tools to determine the suitability of each method for end user applications where ontologies are used as browsing aids. 相似文献
Experimental measurements were made of the pH, density, bulk viscosity and electrical conductivity of aqueous solutions of sodium lauryl sulphate for a wide range of concentrations at 25°C. Also, the time-dependent interfacial tension data of this system with mutually saturated benzene phases are reported. Comparison of these data with literature values shows fair agreement in the majority of the cases and further reveals the lack of data in the earlier investigations below the critical micelle concentration of sodium lauryl sulphate in water. A detailed compilation of the data, reported in the literature since 1937, of the pH, density, bulk viscosity, electrical conductivity, surface tension, interfacial tension with benzene, surface excess concentration, surface shear viscosity, diffusivity and critical micelle concentration of the sodium lauryl sulphate system is given. The importance of this anionic surfactant system together with the various factors which influence the physical properties is examined. 相似文献
Model simulations of the Ocean General Circulation Model (OGCM; MOM4p1), coupled with a state-of-the-art biogeochemical model TOPAZ (Tracers of Phytoplankton with Allometric Zooplankton), which includes multi-nutrient limitations including iron limitation, are used to study the seasonal variations of mixed-layer properties and their influence on nutrients and chlorophyll in the Arabian Sea. The spatial variation of nitrate during the Northeast Monsoon (NEM) and Southwest Monsoon (SWM), in the northern and western parts of the Arabian Sea and coast of Somalia, are very well captured by the model and compare well with observations. Modelled chlorophyll and primary productivity are validated with satellite-derived maps for the Arabian Sea. 相似文献
A novel image encryption framework is proposed in this article. A new chaotic map and a pseudorandom bit generator are proposed. Apart from this, a novel image encryption system is designed based on the proposed map and the proposed pseudorandom bit generator. These three are the major contributions of this work that makes a complete cryptosystem. The proposed new chaotic map is proposed which will be known as the ‘RCM map’ and its chaotic property is studied based on Devaney’s theory. The proposed pseudorandom bit generator is tested using the NIST test suite. The proposed method is simple to implement and does not involve any highly complex operations. Moreover, the proposed method is completely lossless, and therefore cent percent of data can be recovered from the encrypted image. The decryption process is also simple to implement i.e. just reverse of the encryption procedure. A scrambling algorithm is also proposed to further enhance the security of the overall system. The simulation, detailed analysis, and comparative studies of the proposed overall image encryption framework will help to understand the strengths and weaknesses of it. The experimental results are very promising and show the prospects of chaos theory and its usage in the field of data security.
Multidimensional Systems and Signal Processing - High-performance sonar systems mostly combine a large sensor array and an efficient beamformer for enhancing the overall detection capabilities and... 相似文献
This paper reflects the achievements and the challenges ahead in the field of organic light emitting diodes (OLEDs). The primary intention of this paper is to study different organic materials synthesized so far and the OLEDs fabricated for solid-state lighting. After deep review of literature we have synthesized and characterized rare earth based europium organic complexes Eu(TTA)3Phen, Eu(x)Y(1?x)(TTA)3Phen, and Eu(x)Tb(1?x)(TTA)3Phen, where x = 0.4 and 0.5 by solution technique maintaining stoichiometric ratio. Blended films of pure and doped Eu complexes that are molecularly doped into polymer resins namely polymethylmethacrylate (PMMA) and polystyrene (PS) are prepared according to weight percentage. Concentration effect on absorption and emission spectra of the blended films was studied for different weight percentages (10, 25, 50, 60%). All the complexes doped in PMMA showed an excellent transparency of 90–97% while the complexes doped in polystyrene showed a transparency of 85–90%, bit less than in PMMA. Energy gap of the synthesized complexes have been determined in PMMA and PS. Considering the facts that these complexes have good solubility in most of the organic solvents, the absorption spectra of Eu(TTA)3Phen, Eu0.5Y0.5(TTA)3Phen and Eu0.5Tb0.5(TTA)3Phen complexes are studied, and OLED devices having the structure ITO/m-MTDATA/α-NPD/TPBi:Eu(x)Y(1?x)(TTA)3Phen/Alq3/LiF:Al (where x = 0.4, 0.5) were fabricated and characterized. Significant red emission was observed from fabricated OLED devices at 612 nm when operated in a range of 10–18 V. Thus the synthesized rare earth based organic complexes are the best suitable candidates for fabrication of red OLED devices. The extensive review on OLEDS concludes that our present lighting system can be replaced with white OLEDS, recently developed energy saving lighting technology. 相似文献
Wireless Personal Communications - Applications of wireless sensor networks (WSNs) are increasing tremendously to facilitate and establish a link between the physical world and information system.... 相似文献