به نام خدا
Title: Feasibility of SNMP OID compression
Authors: Hari TS Narayanan a, , Geetha Ilangovan a , Sumitra Narayanan b
Abstract: Simple network management protocol (SNMP) object identi?er (OID) compression can improve bandwidth usage and response time. The current literature includes several OID compres- sion algorithms to reduce redundancy in SNMP protocol data units (PDUs). The overhead of OID compression could outweigh the bene?ts it offers if its tradeoffs are not well understood. The main objective of this paper is to investigate the OID compression as a viable feature for SNMP libraries. This is done by adding an OID compression algorithm to Net-SNMP, which is one of the popular open source implementations of the SNMP framework. Change to image size, lines of code added, complexity of compression code, the effect of compression on response time, and testing effort required are the parameters presented to understand the viability of OID compression.
Publish Year: 2013
Number of Published in: Information Sciences - Science Direct
Pages: 8
موضوع: فشرده سازی تصویر، فشرده سازی داده ها
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Title: Accelerating Pollard’s Rho Algorithm on Finite Fields
Authors: Jung Hee Cheon, Jin Hong , and Minkyu Kim
Abstract: Most generic and memory efficient algorithms for solving the discrete logarithm problem construct a certain random graph consisting of group element nodes and return the solution when a collision is found among the graph nodes. In this work, we develop a technique for traveling through the random graph with- out fully computing each node and also provide an extension to the distinguished point collision detection method that is suitable for this new situation. Concrete constructions of this technique for multiplicative subgroups of the finite fields are given. Our implementations confirm that the proposed technique provides practical speedup over existing algorithms.
Publish Year: 2012
Publisher: Journal of Cryptography - Journal of Springer
Number of Pages: 48
موضوع: میدانهای متناهی، جبر مجرد، رمزنگاری
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به نام خدا
Title: Numerical simulation and optimization of CO2 sequestration in saline aquifers
Authors: Zheming Zhang, Ramesh Agarwal
Abstract: With heightened concerns on CO2 emissions from coal fired electricity generation plants, there has been major emphasis in recent years on the development of safe and economical Carbon Dioxide Capture and Sequestration (CCS) technology worldwide. Saline reservoirs are attractive geological sites for CO2 sequestration because of their huge capacity for long term sequestration. Over the last decade, numerical simulation codes have been developed in US, Europe and Japan to determine a priori the CO2 storage capacity of a saline aquifer and to provide risk assessment with reasonable confidence before the actual deployment of CO2 sequestration can proceed with enormous investment. In US, the 2nd version of Transport of Unsaturated Groundwater and Heat (TOUGH2) numerical simulator has been widely used for this purpose. However at present, it does not have the ability to determine optimal parameters such as injection rate, injection pressure, injection depth for vertical and horizontal wells, etc. for optimization of the CO2 storage capacity and for minimizing the leakage potential by confining the plume migration. This paper describes the development of a “Genetic Algorithm (GA)” based optimizer for TOUGH2 that can be used by the industry with good confidence to optimize the CO2 storage capacity in a saline aquifer of interest. This new code including the TOUGH2 and the GA optimizer is designated as “GATOUGH2”. It has been validated by conducting simulations of three widely used benchmark problems by the CCS researchers worldwide: (a) study of CO2 plume evolution and leakage through an abandoned well, (b) study of enhanced CH4 recovery in combination with CO2 storage in depleted gas reservoirs, and (c) study of CO2 injection into a heterogeneous geological formation. The results of these simulations are in excellent agreement with those of other researchers using different codes. The validated code has been employed to optimize the proposed water-alternating-gas (WAG) injection scheme for (a) a vertical CO2 injection well and (b) a horizontal CO2 injection well, in order to optimize the CO2 sequestration capacity of an aquifer. The optimized calculations from GATOUGH2 are compared with the brute force nearly optimized results obtained by performing a large number of calculations. These comparisons demonstrate the significant efficiency and accuracy of GATOUGH2 as an optimizer compared to using TOUGH2 in a brute force manner. This capability holds a great promise in studying a host of other problems in CO2 sequestration such as how to optimally accelerate the capillary trapping, accelerate the dissolution of CO2 in water or brine, and immobilize the CO2 plume.
Publish Year: 2013
Published in: Computers and Fluids - Science Direct
Number of Pages: 9
موضوع: مهندسی مواد، متالورژی
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به نام خدا
Title: Construction of fuzzy ontologies from fuzzy XML models
Authors: Fu Zhang, Z.M. Ma, Li Yan
Abstract: The success and proliferation of the Semantic Web depends heavily on construction of Web ontologies. However, classical ontology construction approaches are not sufficient for handling imprecise and uncertain information that is commonly found in many application domains. Therefore, great efforts on construction of fuzzy ontologies have been made in recent years. In particular, XML is imposing itself as a standard for representing and exchanging information on the Web, topics related to the modeling of fuzzy data have become very interesting in the XML data context. Therefore, constructing fuzzy ontologies from fuzzy XML data resources may make the existing fuzzy XML data upgrade to Semantic Web contents, and the constructed fuzzy ontologies may be useful for improving some fuzzy XML applications.This paper proposes a formal approach and an automated tool for constructing fuzzy ontologies from fuzzy XML data resources. Firstly, we propose a formal definition of fuzzy XML models (including the document structure fuzzy DTDs and the document content fuzzy XML documents). On this basis, we propose a formal approach for constructing fuzzy ontologies from fuzzy XML models, i.e., transforming a fuzzy XML model (including fuzzy DTD and fuzzy XML document) into a fuzzy ontology. Also, we give the proof of correctness of the construction approach, and provide a detailed construction example. Furthermore, we implement a prototype tool called FXML2FOnto, which can automatically construct fuzzy ontologies from fuzzy XML models. Finally, in order to show that the constructed fuzzy ontologies may be useful for improving some fuzzy XML applications, we focus on investigating how to reason on fuzzy XML models (e.g., conformance, inclusion, and equivalence) based on the constructed fuzzy ontologies, and it turns out that the reasoning tasks of fuzzy XML models can be checked by means of the reasoning mechanism of fuzzy ontologies.
Publish Year: 2013
Published in: Knowledge-Based Systems - Science Direct
Number of Pages: 20
موضوع: XML ، فازی
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به نام خدا
Title: A method for the coating of a polymer inclusion membrane with a monolayer of silver nanoparticles
Authors: Ya Ya N Bonggotgetsakul, Robert W Cattrall, Spas D Kolev
Abstract: The preparation of silver nanoparticles (AgNPs) is described using a polymer inclusion membrane (PIM) consisting of 45% (m/m) di-(2-ethylhexyl)phosphoric acid (D2EHPA) and 55% (m/m) poly(vinyl chloride) (PVC) as a template. The Ag(I) ion was ?rstly extracted into the membrane via cation-exchange and then subsequently reduced with NaBH , trisodium citrate, citric acid, or L-ascorbic acid to form AgNPs. The most effective reducing agent was found to be L-ascorbic acid which at pH 2.0 formed a uniform monolayer of AgNPs of an average size of 360 nm on the surface of the PIM. Citric acid also produced AgNPs but these were embedded in the bulk of the membrane and did not provide a good surface coverage. NaBH and trisodium citrate, on the other hand, gave rise to the formation of black silver oxide on the membrane surface. Factors such as the membrane loading with Ag(I), PIM composition, reduction time, temperature and shaking time were found to have a significant influence on the surface coverage and size of the AgNPs.
Publish Year: 2013
Published in: Journal of Membrane Science - Science Direct
Number of Pages: 8
موضوع: مهندسی شیمی
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