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21.
Anirban Sengupta Chandan Mazumdar Aditya Bagchi 《Journal of Network and Systems Management》2011,19(3):319-342
From information security point of view, an enterprise is considered as a collection of assets and their interrelationships.
These interrelationships may be built into the enterprise information infrastructure, as in the case of connection of hardware
elements in network architecture, or in the installation of software or in the information assets. As a result, access to
one element may enable access to another if they are connected. An enterprise may specify conditions on the access of certain
assets in certain mode (read, write etc.) as policies. The interconnection of assets, along with specified policies, may lead
to managerial vulnerabilities in the enterprise information system. These vulnerabilities, if exploited by threats, may cause
disruption to the normal functioning of information systems. This paper presents a formal methodology for detection of managerial
vulnerabilities of, and threats to, enterprise information systems in linear time. 相似文献
22.
Kalman Filter (KF) is the optimal state estimator for linear dynamical systems in the presence of zero mean white Gaussian noise. It is a minimum mean square error (MMSE) estimator. In the present work a recursive maximum a posteriori estimator (RMAPE) has been developed from basic principles of estimation. This estimator may be used for realtime state estimation of linear dynamical systems in presence of zero mean white Gaussian noise. It is further shown here that the KF can be derived from this RMAPE algorithm, i.e. this work shows an alternative method way to derive the KF. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society 相似文献
23.
Santosh Ghosh Author Vitae Monjur Alam Author Vitae Author Vitae Indranil Sen Gupta Author Vitae 《Computers & Electrical Engineering》2009,35(2):329-338
All elliptic curve cryptographic schemes are based on scalar multiplication of points, and hence its faster computation signifies faster operation. This paper proposes two different parallelization techniques to speedup the GF(p) elliptic curve multiplication in affine coordinates and the corresponding architectures. The proposed implementations are capable of resisting different side channel attacks based on time and power analysis. The 160, 192, 224 and 256 bits implementations of both the architectures have been synthesized and simulated for both FPGA and 0.13μ CMOS ASIC. The final designs have been prototyped on a Xilinx Virtex-4 xc4vlx200-12ff1513 FPGA board and performance analyzes carried out. The experimental result and performance comparison show better throughput of the proposed implementations as compared to existing reported architectures. 相似文献
24.
In the recent years, we have seen that Grover search algorithm (Proceedings, 28th annual ACM symposium on the theory of computing, pp. 212–219, 1996) by using quantum parallelism has revolutionized the field of solving huge class of NP problems in comparisons to classical systems. In this work, we explore the idea of extending Grover search algorithm to approximate algorithms. Here we try to analyze the applicability of Grover search to process an unstructured database with a dynamic selection function in contrast to the static selection function used in the original work (Grover in Proceedings, 28th annual ACM symposium on the theory of computing, pp. 212–219, 1996). We show that this alteration facilitates us to extend the application of Grover search to the field of randomized search algorithms. Further, we use the dynamic Grover search algorithm to define the goals for a recommendation system based on which we propose a recommendation algorithm which uses binomial similarity distribution space giving us a quadratic speedup over traditional classical unstructured recommendation systems. Finally, we see how dynamic Grover search can be used to tackle a wide range of optimization problems where we improve complexity over existing optimization algorithms. 相似文献
25.
Two prototypical external and internal flows have been studied which display linear temporal instability followed by nonlinear saturation taking the flows to a new equilibrium state. Direct simulation results are obtained using a specific formulation and numerical methods with very high accuracy. These results are analyzed via proper orthogonal decomposition (POD), which reveal similar modes for flow past a circular cylinder and flow inside a lid-driven cavity, indicating universality of such modes. Unlike many other efforts on reduced order modeling via POD, here the emphasis has been on understanding the physical aspect of the flow instability which requires very high accuracy of the simulation. Then, the obtained POD modes are related to the instability modes (in the classical sense of defining the latter) and new generic types of instability modes are identified in the studied external and internal flows. These new modes have been reported for flow past a circular cylinder [Sengupta TK, Singh N, Suman VK. Dynamical system approach to instability of flow past a circular cylinder. J Fluid Mech 2010;656:82–115] which help one in understanding the instability sequence and the relative importance of these modes in the flow evolution starting from an impulsive start. Present comparative study, furthermore, reveals universality of such instability modes by showing their presence for the flow inside a lid-driven cavity as well. Despite seeming dissimilarities between these two flows, similarities between the instability portrait of these two flows suggest universality of such modes. From the equilibrium amplitude of vorticity time-series, we establish the presence of multiple modes and multiple bifurcation sequences for these flows in parameter space. Existing theory due to Landau and Stuart that considers only a single dominant mode and its self-interaction does not explain all these features. We invoke a multi-modal interaction model in the cited reference above, termed as Landau–Stuart–Eckhaus (LSE) equation in recognition of Eckhaus’ work in modifying the classical Stuart–Landau equation. We also show that the new instability modes do not follow either the classical Stuart–Landau or the newly proposed LSE model equations and for this reason we call these as anomalous modes. Two specific classes of anomalous modes are identified and classified in the present work. Empirical expressions for the evolution of these anomalous modes are presented and their unambiguous role during instabilities is discussed. 相似文献
26.
Triglyceride composition of chrysalis oil,an insect lipid 总被引:1,自引:0,他引:1
Chrysalis oil, an insect fat obtained from the spent silk worm pupae, Bombyx mori, is a by-product of sericultural industry
and represents a potential source of 1750 tons of linolenic-rich oil per annum for India. Fatty acid and triglyceride compositions
of chrysalis oil have been determined by the combination of the techniques of lower temperature segregation, lipolysis, thin
layer and gas liquid chromatography. Percentage contents of the component acids are: C14:0, 0.6; C16:0, 19.3; C18:0 3.9; C18:1, 17.7; C18:2, 9.8, and C18:3, 48.7. Major component triglycerides are, LLnLn, 5.2%; PLnO, 6.4%;OLnLn, 9.6%; LnLnLn, 10.5% and PLnLn, 14.0% (P, palmitic;
O, oleic; L, linoleic and Ln, linolenic acids. On low temperature crystallization, Chrysalis oil yielded two fractions amounting
together to 40% of the total with composition quite similar to that of linseed oil. 相似文献
27.
Partha Pratim Sengupta Satyananda Barik Basudam Adhikari 《Materials and Manufacturing Processes》2006,21(3):263-270
Polyaniline (PANI) was synthesized by oxidative polymerization of aniline using ammonium persulfate in an acid medium. The polyaniline salt was converted to base form by treatment with ammonium hydroxide. The polyaniline base was dissolved in N-methyl pyrrolidone (NMP) for film casting. The cast film was doped with HCl for obtaining higher conductivity. Both doped and undoped PANI films were characterized by UV-visible, FTIR, and XRD analyses. The electrical conductivity of the PANI film was studied by a four-point probe method at room temperature. Finally, ammonia gas-sensing characteristics of the prepared polyaniline film were studied by measuring the change in electrical conductivity on exposure to ammonia gas at different concentrations. The influence of concentration of acid during polymerization of aniline and dopant concentration on the gas sensing characteristics of PANI film are reported in this paper. 相似文献
28.
The extraction of copper from aqueous sulfate media into ELMs using the extractant LIX 984N-C was studied. Appropriately characterized emulsions on the basis of viscosity and internal drop sizes were used to study the effect of different parameters on extraction. The effects of stirring speed, surfactant concentration, pH of the external continuous phase, carrier concentration, internal phase stripping acid concentration and initial copper concentration are reported. These results show that LIX 984N-C efficiently extracts copper at low pH values typical of leach solutions. It was found that LIX 984N-C could extract up to 80% copper from aqueous solutions at pH value of 1. Performance of LIX 984N-C was also compared with LIX 84 and LIX 84-I at different pH values. Results indicate that LIX 984N-C could open up new avenues for extraction of copper into ELMs, not only from dilute solutions, but also from sulfuric acid leach solutions. 相似文献
29.
The rapid evolution of computing and communication technologies and their standardizations have made the boom in e-commerce
possible. Lowering of the cost of operation, increase in the speed of transactions, and easy global reach to customers and
vendors have been the reasons for the overwhelming popularity of this new way of commerce. This article examines the issues
related to the security of the assets and transactions in the e-commerce components and activities. Since large public money
is involved in the transactions, the role of information security and privacy is not exaggerated in this kind of business.
After examining the technologies used in e-commerce, the article goes on to identify the security requirement of e-commerce
systems from perceived threats and vulnerabilities. Then e-commerce security is viewed as an engineering management problem
and a life cycle approach is put forward. How the e-commerce systems can be made secure using the life cycle approach is outlined.
The relevant standards and laws are also discussed in the perspective of e-commerce. The article closes with some future research
directions and conclusions. 相似文献
30.
Vinay Singh K. Uvanesh Rashmi Rekha Behera Samrat Baruah Tarun Agarwal Indranil Banerjee 《Polymer-Plastics Technology and Engineering》2016,55(9):879-888
This study discusses about the effect of polysaccharides (agar, gum tragacanth, and guar gum) on the properties of the core (organogel)–shell [poly(vinyl alcohol)] microparticles. The size, swelling, and mucoadhesive properties of the poly(vinyl alcohol) microparticles were altered in the presence of the polysaccharides. Thermal analysis confirmed the presence of organogels within the microparticles. Fourier transform infrared spectroscopy confirmed the presence of the polysaccharides within the microparticles. The microparticles were biocompatible in nature. Drug release indicated that an alteration in the shell composition can be used for altering drug release. Ciprofloxacin-loaded microparticles showed sufficient antimicrobial efficiency. 相似文献