We perceive big data with massive datasets of complex and variegated structures in the modern era. Such attributes formulate hindrances while analyzing and storing the data to generate apt aftermaths. Privacy and security are the colossal perturb in the domain space of extensive data analysis. In this paper, our foremost priority is the computing technologies that focus on big data, IoT (Internet of Things), Cloud Computing, Blockchain, and fog computing. Among these, Cloud Computing follows the role of providing on-demand services to their customers by optimizing the cost factor. AWS, Azure, Google Cloud are the major cloud providers today. Fog computing offers new insights into the extension of cloud computing systems by procuring services to the edges of the network. In collaboration with multiple technologies, the Internet of Things takes this into effect, which solves the labyrinth of dealing with advanced services considering its significance in varied application domains. The Blockchain is a dataset that entertains many applications ranging from the fields of crypto-currency to smart contracts. The prospect of this research paper is to present the critical analysis and review it under the umbrella of existing extensive data systems. In this paper, we attend to critics' reviews and address the existing threats to the security of extensive data systems. Moreover, we scrutinize the security attacks on computing systems based upon Cloud, Blockchain, IoT, and fog. This paper lucidly illustrates the different threat behaviour and their impacts on complementary computational technologies. The authors have mooted a precise analysis of cloud-based technologies and discussed their defense mechanism and the security issues of mobile healthcare.
The effect of dose, dose rate, monomer type, and monomer concentration on the water transport behavior in grafted cellulose pulp and hand sheets was studied. At low dose rates, grafting rates of styrene onto wood pulp were less with hand sheets than with the pulp itself. Grafting was also found to be decreased by increasing the dose rate. Grafting mixtures of styrene and acrylonitrile gave better yields than styrene alone. Excellent grafting yields were obtained by treating the pulp or hand sheets with water before adding vinyl monomers. In this way, solvents such as dioxane could be eliminated from the grafting mixture. The hand sheets, grafted with mixtures of acrylonitrile and styrene, had good mechanical properties although less than the corresponding ungrafted sheets. Grafting decreased the moisture regain in pulp and hand sheets. Gamma irradiation of wood pulp under ambient conditions without additives reduced the water sorption considerably. 相似文献
This paper presents a simple and efficient multiple access interference (MAI) cancelation technique in optical code division multiple access (OCDMA) system. The proposed technique is based on hybrid frequency shift keying (FSK) with an enhanced modified prime code as a signature sequence for coding techniques. Coherent FSK modulation along with incoherent demodulation using Arrayed-Waveguide Grating has been examined in the transceiver structure. In the proposed technique, a reference signal is constructed by using one of the addressed spreading sequences, and MAI cancelation is performed by subtracting the reference signal from the received signal of the desired user. The performance of the proposed FSK-OCDMA system is compared with the performance of the existing pulse position modulation (PPM)–OCDMA system. The simulation results reveal that the bit-error rate performance of the proposed technique is superior to the performance of the pulse position modulation (PPM) technique. Also, the results indicate that the proposed technique is very power efficient, and when the bit rate is constant, the network capacity can be expanded to accommodate a large number of simultaneous active users with low error rate. Moreover, the proposed technique simplifies the hardware of the receiver design. 相似文献
Journal of Materials Science - Polymer nanocomposite films were prepared using the casting method through filling a polymer mixture of carboxymethyl cellulose (CMC) and polyethylene oxide (PEO)... 相似文献
The radiation-induced polymerization of methyl methacrylate was investigated with radiation sources of cobalt 60 and accelerated electrons at dose rates up to 3 Mrads/sec. Extrapolation of previous rates of polymerization at dose rates of 0.01–200 rads/sec coincided with the present results, the rates being approximately proportional to the square root of the dose rate throughout the entire set of dose rates measured. The molecular weights seemed to be independent of dose rate at the highest dose rates investigated. A combination of high polymer with a much higher molecular weight than expected was formed, together with a substantial portion of low molecular weight polymer. The reason for this behavior is not clear at this time. The G(M·) calculated from the molecular weights and fraction of polymer and resin was 6.0, which approaches that reported in previous investigations at low dose rates. There was no significant effect of air on the polymerization kinetics of methyl methacrylate at above 1 Mrad/sec. Nitrogen also did not influence the measured rates. Conversions to polymer were not substantially reduced by the presence of inhibitor at above 1.26 × 105 rads/sec. Water did not influence the rates of polymerization, except at the highest temperature (50°C) investigated. A large posteffect was observed in sealed degassed ampoules after 25% conversion to polymer. Only 3.4% additional polymer was formed in 24 hr after irradiation in the presence of air. The activation energy for the electron beam polymerization of methyl methacrylate was about 7.0 kcal/mole. This value, considering the complications in technique such as beam heating, did not differ from literature data enough to suggest any mechanistic difference in the polymerization at high dose rates. 相似文献
The design is reported of a compact three-component tool-shank dynamometer. It is based on a design in which the load bearing section has its stiffness reduced by two holes symmetrically positioned about the centre-line, and connected by a narrow slit. The holes are positioned to enable strain gauges to record the highest local strains' and, hence to maximize sensitivity and to minimize cross-sensitivity. Experimental analysis has identified the critical location, relative to the hole, at which the maximum surface strain is attained. Improvement of the dynamometer accuracy has been achieved by accurate location of the point of force application to eliminate the cross-sensitivity between the different components. Further improvement of the dynamometer sensitivity has been achieved by appropriate design of the electrical circuits. Force signals have been captured and processed using a micro-computer through specially designed strain-gauge amplifiers and analogue-to-digital converter ADC. A series of tests have been carried out to determine the dynamometer static and dynamic characteristics. Mathematical models have been developed to characterize and formulate the dynamometer performance. 相似文献
Refractive indices and birefringence for skin and core changes with strain, produced by different stresses in undrawn vestan fibres, were measured interferometrically. Applications were carried out using multiple-beam Fizeau fringes in transmission to determine the Cauchy's constants and dispersive coefficient for the fibre layers. The resulting data were used to calculate the polarizability per unit volume for each layer. The scanning electron microscope (SEM), optical microscope and He-Ne laser beam were applied to estimate the geometrical parameters of the fibre cross-section. A comparative study between the three methods used for measuring the fibre diameter was made. The effect of temperature on the refractive index and birefringence for each fibre layer has been also investigated. The relationship between temperature and birefringence of the fibres was studied and the thermal coefficient of the refractive index was determined. An empirical formula is suggested to relate temperature and birefringence. Illustrations are given using microinterferograms. 相似文献