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1.
A major task of a Web GIS (Geographic Information Systems) system is to transfer map data to client applications over the
Internet, which may be too costly. To improve this inefficient process, various solutions are available. Caching the responses
of the requests on the client side is the most commonly implemented solution. However, this method may not be adequate by
itself. Besides caching the responses, predicting the next possible requests from a client and updating the cache with responses
for those requests together provide a remarkable performance improvement. This procedure is called “prefetching” and makes
caching mechanisms more effective and efficient. This paper proposes an efficient prefetching algorithm called Retrospective
Adaptive Prefetch (RAP), which is constructed over a heuristic method that considers the former actions of a given user. The
algorithm reduces the user-perceived response time and improves user navigation efficiency. Additionally, it adjusts the cache
size automatically, based on the memory size of the client’s machine. RAP is compared with four other prefetching algorithms.
The experiments show that RAP provides better performance enhancements than the other methods. 相似文献
2.
Cem??zdemir Ayse?Nilgün?Akin Ramazan?YildirimEmail author 《Korean Journal of Chemical Engineering》2003,20(5):840-843
The maximization of the total surface area of Pt-SnO2/Al2O3 catalyst was studied by using the Taguchi method of experimental design. The catalysts were prepared by sol-gel method. The
effects of HNO3, H2O and aluminum nitrate concentrations and the stirring rate on the total surface area were studied at three levels of each.
L9 orthogonal array leading nine experiments was used in the experimental design. The parameter levels that give maximum total
surface area were determined and experimentally verified. In the range of conditions studied it was found that, medium levels
of HNO3 and H2O concentration and lower levels of aluminum nitrate concentration and stirring rate maximize the total surface area. 相似文献
3.
Daniel?ZemanEmail author Ond?ej?Du?ek David?Mare?ek Martin?Popel Loganathan?Ramasamy Jan??těpánek Zdeněk??abokrtsky Jan?Haji? 《Language Resources and Evaluation》2014,48(4):601-637
We present HamleDT—a HArmonized Multi-LanguagE Dependency Treebank. HamleDT is a compilation of existing dependency treebanks (or dependency conversions of other treebanks), transformed so that they all conform to the same annotation style. In the present article, we provide a thorough investigation and discussion of a number of phenomena that are comparable across languages, though their annotation in treebanks often differs. We claim that transformation procedures can be designed to automatically identify most such phenomena and convert them to a unified annotation style. This unification is beneficial both to comparative corpus linguistics and to machine learning of syntactic parsing. 相似文献
4.
Lu??s Antunes Armando Matos Alexandre Pinto Andr?? Souto Andreia Teixeira 《Theory of Computing Systems》2013,52(1):162-178
We prove several results relating injective one-way functions, time-bounded conditional Kolmogorov complexity, and time-bounded conditional entropy. First we establish a connection between injective, strong and weak one-way functions and the expected value of the polynomial time-bounded Kolmogorov complexity, denoted here by?E(K t (x|f(x))). These results are in both directions. More precisely, conditions on?E(K t (x|f(x))) that imply that?f is a weak one-way function, and properties of?E(K t (x|f(x))) that are implied by the fact that?f is a strong one-way function. In particular, we prove a separation result: based on the concept of time-bounded Kolmogorov complexity, we find an interval in which every function?f is a necessarily weak but not a strong one-way function. Then we propose an individual approach to injective one-way functions based on Kolmogorov complexity, defining Kolmogorov one-way functions and prove some relationships between the new proposal and the classical definition of one-way functions, showing that a Kolmogorov one-way function is also a deterministic one-way function. A relationship between Kolmogorov one-way functions and the conjecture of polynomial time symmetry of information is also proved. Finally, we relate?E(K t (x|f(x))) and two forms of time-bounded entropy, the unpredictable entropy?H unp, in which ??one-wayness?? of a function can be easily expressed, and the Yao+ entropy, a measure based on compression/decompression schema in which only the decompressor is restricted to be time-bounded. 相似文献
5.
A general topology-based framework for adaptive insertion of cohesive elements in finite element meshes 总被引:1,自引:1,他引:0
Glaucio?H.?PaulinoEmail author Waldemar?Celes Rodrigo?Espinha Zhengyu??Zhang 《Engineering with Computers》2008,24(1):59-78
Large-scale simulation of separation phenomena in solids such as fracture, branching, and fragmentation requires a scalable
data structure representation of the evolving model. Modeling of such phenomena can be successfully accomplished by means
of cohesive models of fracture, which are versatile and effective tools for computational analysis. A common approach to insert
cohesive elements in finite element meshes consists of adding discrete special interfaces (cohesive elements) between bulk
elements. The insertion of cohesive elements along bulk element interfaces for fragmentation simulation imposes changes in
the topology of the mesh. This paper presents a unified topology-based framework for supporting adaptive fragmentation simulations,
being able to handle two- and three-dimensional models, with finite elements of any order. We represent the finite element
model using a compact and “complete” topological data structure, which is capable of retrieving all adjacency relationships
needed for the simulation. Moreover, we introduce a new topology-based algorithm that systematically classifies fractured
facets (i.e., facets along which fracture has occurred). The algorithm follows a set of procedures that consistently perform
all the topological changes needed to update the model. The proposed topology-based framework is general and ensures that
the model representation remains always valid during fragmentation, even when very complex crack patterns are involved. The
framework correctness and efficiency are illustrated by arbitrary insertion of cohesive elements in various finite element
meshes of self-similar geometries, including both two- and three-dimensional models. These computational tests clearly show
linear scaling in time, which is a key feature of the present data-structure representation. The effectiveness of the proposed
approach is also demonstrated by dynamic fracture analysis through finite element simulations of actual engineering problems.
相似文献
Glaucio H. PaulinoEmail: |
6.
7.
Anthony?Etuk Timothy?J.?Norman Murat??ensoyEmail author Mudhakar?Srivatsa 《Autonomous Agents and Multi-Agent Systems》2017,31(3):531-560
The presence of numerous and disparate information sources available to support decision-making calls for efficient methods of harnessing their potential. Information sources may be unreliable, and misleading reports can affect decisions. Existing trust and reputation mechanisms typically rely on reports from as many sources as possible to mitigate the influence of misleading reports on decisions. In the real world, however, it is often the case that querying information sources can be costly in terms of energy, bandwidth, delay overheads, and other constraints. We present a model of source selection and fusion in resource-constrained environments, where there is uncertainty regarding the trustworthiness of sources. We exploit diversity among sources to stratify them into homogeneous subgroups to both minimise redundant sampling and mitigate the effect of certain biases. Through controlled experiments, we demonstrate that a diversity-based approach is robust to biases introduced due to dependencies among source reports, performs significantly better than existing approaches when sampling budget is limited and equally as good with an unlimited budget. 相似文献
8.
We thoroughly study the behavioural theory of epi, a ??-calculus extended with polyadic synchronisation. We show that the natural contextual equivalence, barbed congruence, coincides with early bisimilarity, which is thus its co-inductive characterisation. Moreover, we relate early bisimilarity with the other usual notions, ground, late and open, obtaining a lattice of equivalence relations that clarifies the relationship among the ??standard?? bisimilarities. Furthermore, we apply the theory developed to obtain an expressiveness result: epi extended with key encryption primitives may be fully abstractly encoded in the original epi calculus. The proposed encoding is sound and complete with respect to barbed congruence; hence, cryptographic epi (crypto-epi) gets behavioural theory for free, which contrasts with other process languages with cryptographic constructs that usually require a big effort to develop such theory. Therefore, it is possible to use crypto-epi to analyse and to verify properties of security protocols using equational reasoning. To illustrate this claim, we prove compliance with symmetric and asymmetric cryptographic system laws, and the correctness of a protocol of secure message exchange. 相似文献
9.
The study is focused on the external and internal mass transfers of lipids during their biodegradation process in a bioreactor with stationary basket bed of immobilized Bacillus spp. cells. By means of the lipid mass balance for a single particle of biocatalyst, considering the kinetic model adapted for the immobilized bacterial cells, specific mathematical models have been developed to estimate their mass flows in the liquid boundary layer surrounding the particle and inside the particle. The values of mass flows are significantly influenced by the internal diffusion velocity of lipids and the rate of their consumption, but also by the position inside the basket bed. These influences accumulated led to the appearance of a biological inactive region near the particle centre, its magnitude varying from 1.3 to 49.4% of the overall volume of particles. 相似文献
10.