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31.
Microsystem Technologies - Single-Walled Carbon Nanotubes (SWCNTs) are widely used as potential carriers in drug delivery systems. The objective of this work was to observe the effects of pristine,...  相似文献   
32.
A mathematical model for the transient heat flow analysis in arc-welding processes is proposed, based on a unique set of boundary conditions. The model attempts to make use of the relative advantages of analytical as well as numerical techniques in order to reduce the problem size for providing a quicker solution without sacrificing the accuracy of prediction. The variation of thermo-physical properties with temperature has been incorporated into the model to improve the thermal analysis in the weld and heat-affected zones. The model has been evaluated using a five-point explicit finite difference method for analysing the welding heat flow in thin plates of two different geometric configurations. The temperature distribution closer to the heat source, primarily in the weld zone and the heat-affected zones, are predicted by the numerical technique. The thermal characteristics beyond the heat-affected zone are amenable to standard analytical techniques. The behaviour of the boundary condition in the model has been investigated in detail.Nomenclature q Rate of heat per unit thickness (Wm–1) - d Plate thickness (m) - v Velocity of source (m s–1) - t Time (s) - T Temperature value at the desired point (K) - T 0 Initial temperature (K) - K Thermal conductivity (W m–1 K–1) - Density (kg m–3) - c p Specific heat (J kg–1 K–1) - Thermal diffusivity (m2 s–1) - n - Distance of point considered from the source (=x–vt) (m) - K 0 Modified Bessel function of second kind and zero order - r Radial distance from the source (r=(x 2+y 2)1/2) (m) - Model width (m) - a Plate width (m) - Distance from the source =(2+4 ×10–4)1/2 (m) - n   相似文献   
33.
Multiprocessor systems which afford a high degree of parallelism are used in a variety of applications. The extremely stringent reliability requirement has made the provision of fault-tolerance an important aspect in the design of such systems. This paper presents a review of the various approaches towards tolerating hardware faults in multiprocessor systems. It emphasizes the basic concepts of fault tolerant design and the various problems to be taken care of by the designer. An indepth survey of the various models, techniques and methods for fault diagnosis is given. Further, we consider the strategies for fault-tolerance in specialized multiprocessor architectures which have the ability of dynamic reconfiguration and are suited tovlsi implementation. An analysis of the state-of-the-art is given which points out the major aspects of fault-tolerance in such architectures.  相似文献   
34.
Silicon - In the present report, a photonic crystal based micro-ring resonator (MRR) structure is proposed which is very compact in size and has very fast response and is employed for temperature...  相似文献   
35.
In cancer therapy, the application of (fractionated) harsh radiation treatment is state of the art for many types of tumors. However, ionizing radiation is a “double-edged sword”—it can kill the tumor but can also promote the selection of radioresistant tumor cell clones or even initiate carcinogenesis in the normal irradiated tissue. Individualized radiotherapy would reduce these risks and boost the treatment, but its development requires a deep understanding of DNA damage and repair processes and the corresponding control mechanisms. DNA double strand breaks (DSBs) and their repair play a critical role in the cellular response to radiation. In previous years, it has become apparent that, beyond genetic and epigenetic determinants, the structural aspects of damaged chromatin (i.e., not only of DSBs themselves but also of the whole damage-surrounding chromatin domains) form another layer of complex DSB regulation. In the present article, we summarize the application of super-resolution single molecule localization microscopy (SMLM) for investigations of these structural aspects with emphasis on the relationship between the nano-architecture of radiation-induced repair foci (IRIFs), represented here by γH2AX foci, and their chromatin environment. Using irradiated HeLa cell cultures as an example, we show repair-dependent rearrangements of damaged chromatin and analyze the architecture of γH2AX repair clusters according to topological similarities. Although HeLa cells are known to have highly aberrant genomes, the topological similarity of γH2AX was high, indicating a functional, presumptively genome type-independent relevance of structural aspects in DSB repair. Remarkably, nano-scaled chromatin rearrangements during repair depended both on the chromatin domain type and the treatment. Based on these results, we demonstrate how the nano-architecture and topology of IRIFs and chromatin can be determined, point to the methodological relevance of SMLM, and discuss the consequences of the observed phenomena for the DSB repair network regulation or, for instance, radiation treatment outcomes.  相似文献   
36.
Ethylene vinyl acetate rubber (45% vinyl acetate content, EVA‐45) and organomodified clay (12Me‐MMT) composites were prepared by solution blending of the rubber and the clay. A combination of X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy studies showed that the composites obtained are on the nanometer scale. The measurements of the dynamic mechanical properties for different compositions over a temperature range (?100 to +100°C) showed that the storage moduli of these rubber–clay nanocomposites are higher above the glass to rubber transition temperature compared to the neat rubber. The tensile strength of the nanocomposites is about 1.6 times higher than that of the EVA‐45. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2216–2220, 2003  相似文献   
37.
Detailed statistical trend analysis of thermoplastic elastomers based on poly (phenylene ether) (PPE), polystyrene (PS), ethylene vinyl acetate (EVA) and styrene‐ethylene‐butylene‐styrene (SEBS) was done through Design Expert software by Stat‐Ease. D optimal crossed design was followed to capture the interaction with the parameters. Effect of blend ratio, vinyl acetate (VA) content of EVA, molecular weight (MW) of SEBS and intrinsic viscosity (IV) of PPE on the blend performance (response) was studied in detail. Design of Experiment (DOE) analysis showed the “optimized formulation” of the blend. Increase in PPE‐polystyrene (PS) content increased tensile strength and modulus of the blend, followed by a decrease in strain at break. However, EVA had a reverse effect on tensile strength and modulus. Strain at break increased significantly with increasing SEBS content in the blend. Graphical and numerical optimization showed that superior mechanical properties (tensile strength, strain at break and modulus) could be achieved at VA content ~ 50% at a particular loading of EVA. Low MW SEBS was found to be more compatible with the other components of the blend. Mechanical properties of the quaternary blend were marginally affected with change in IV of PPE in the range of 0.33 to 0.46. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007  相似文献   
38.
Different structured activated carbons were prepared from Terminalia arjuna nuts, an agricultural waste, by chemical activation with zinc chloride for the adsorption of Cr(VI) from dilute aqueous solutions. The most important parameter in chemical activation was found to be the chemical ratio (activating agent/precursor, g/g). Carbonization temperature and time are the other two important variables, which had significant effect on the pore structure of carbon. A high surface area of was obtained at a chemical ratio of 300%, carbonization time and temperature of 1 h and 500 °C, respectively. The activated carbon developed shows substantial capability to adsorb Cr(VI) from dilute aqueous solutions. The parameters studied include pH, adsorbent dosage, contact time, and initial concentrations. The kinetic data were best fitted to the Lagergren pseudo-first-order model. The isotherm equilibrium data were well fitted by the Langmuir and Freundlich models. The maximum removal of chromium was obtained at pH 1.0 (about 99% for adsorbent dose of 2 g/l and 10 mg/l initial concentration).  相似文献   
39.
The rates of absorption of CO2 into water and 0.1 kmol/m3 aqueous solutions of MEA, DEA and AMP were measured in a stirred cell with a flat gas-liquid interface in the presence of fine activated carbon particles. Experiments showed that the rates of absorption increased significantly with increases in the loading of activated carbon up to about 6 kg/m3 and thereafter remained constant.  相似文献   
40.
Recognizing a subject given a set of biometrics is a fundamental pattern recognition problem. This paper builds novel statistical models for multibiometric systems using geometric and multinomial distributions. These models are generic as they are only based on the similarity scores produced by a recognition system. They predict the bounds on the range of indices within which a test subject is likely to be present in a sorted set of similarity scores. These bounds are then used in the multibiometric recognition system to predict a smaller subset of subjects from the database as probable candidates for a given test subject. Experimental results show that the proposed models enhance the recognition rate beyond the underlying matching algorithms for multiple face views, fingerprints, palm prints, irises and their combinations.  相似文献   
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