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101.
The d.c. and a.c. (100 Hz–1 MHz) conductivities of HCl-doped polyaniline have been measured in the temperature range 77–300 K. At 77 K, the a.c. conductivity data, (), can be described by the relation ()=As, where the parameter s lies close to unity and decreases with increase in the doping level. The ratio of measured a.c. to d.c. conductivity shows dispersion at 77 K, which decreases with increase in the doping level. This decrease is found to be sharp around pH3.0. In the temperature range 77–150 K, the observed d.c. conductivity data can be described by Mott's three dimensional variable range hopping (VRH) model. Scanning electron microscopy studies reveal a sharp change in structural morphology of HCl-doped polyaniline at a pH3.0. A strikingly remarkable structural morphology has been observed in the formc of a channel at this pH value. This change is accompanied by a rapid increase in d.c. conductivity, dielectric constant, along with sharp changes in structural morphology, which indicates the existence of a doping-induced structural conductivity correlation in this system. © 1998 Chapman & Hall 相似文献
102.
In this paper, we introduce a generalization of the polymatrix game (a nonzero sum noncooperativen-person game) considered by Howson and relate the problem of computing an equilibrium set of strategies for such a game to the generalized linear complementarity problem of Cottle and Dantzig. For an even more general version of the game we prove the existence of an-equilibrium set of strategies. We also present a result on the stability of the equilibria based on degree theory. 相似文献
103.
D. Sreenivasu N. Narsimlu G. S. Sastry V. Chandra Mouli 《Journal of Materials Science: Materials in Electronics》1996,7(4):283-284
Electron paramagnetic resonance (EPR) studies have been performed on the glass system (30–x) NaF-xNa2O-50B2O3-20Bi2O3 doped with CuO as a paramagnetic probe. The calculated g values indicate that Cu2+ is in a tetragonally elongated octahedral co-ordination, and the Jahn-Teller character gives rise to anisotropic hyperfine structure. The spin-Hamiltonian parameters and -bonding parameter, 2, are calculated. Varying the fluoride ion concentration and its effect on these parameters is also discussed. 相似文献
104.
We introduce a high order parameter-robust numerical method to solve a Dirichlet problem for one-dimensional time dependent singularly perturbed reaction-diffusion equation. A small parameter ε is multiplied with the second order spatial derivative in the equation. The parabolic boundary layers appear in the solution of the problem as the perturbation parameter ε tends to zero. To obtain the approximate solution of the problem we construct a numerical method by combining the Crank–Nicolson method on an uniform mesh in time direction, together with a hybrid scheme which is a suitable combination of a fourth order compact difference scheme and the standard central difference scheme on a generalized Shishkin mesh in spatial direction. We prove that the resulting method is parameter-robust or ε-uniform in the sense that its numerical solution converges to the exact solution uniformly well with respect to the singular perturbation parameter ε. More specifically, we prove that the numerical method is uniformly convergent of second order in time and almost fourth order in spatial variable, if the discretization parameters satisfy a non-restrictive relation. Numerical experiments are presented to validate the theoretical results and also indicate that the relation between the discretization parameters is not necessary in practice. 相似文献
105.
Advances in multimedia data acquisition and storage technology have led to the growth of very large multimedia databases.
Analyzing this huge amount of multimedia data to discover useful knowledge is a challenging problem. This challenge has opened
the opportunity for research in Multimedia Data Mining (MDM). Multimedia data mining can be defined as the process of finding
interesting patterns from media data such as audio, video, image and text that are not ordinarily accessible by basic queries
and associated results. The motivation for doing MDM is to use the discovered patterns to improve decision making. MDM has
therefore attracted significant research efforts in developing methods and tools to organize, manage, search and perform domain
specific tasks for data from domains such as surveillance, meetings, broadcast news, sports, archives, movies, medical data,
as well as personal and online media collections. This paper presents a survey on the problems and solutions in Multimedia
Data Mining, approached from the following angles: feature extraction, transformation and representation techniques, data
mining techniques, and current multimedia data mining systems in various application domains. We discuss main aspects of feature
extraction, transformation and representation techniques. These aspects are: level of feature extraction, feature fusion,
features synchronization, feature correlation discovery and accurate representation of multimedia data. Comparison of MDM
techniques with state of the art video processing, audio processing and image processing techniques is also provided. Similarly,
we compare MDM techniques with the state of the art data mining techniques involving clustering, classification, sequence
pattern mining, association rule mining and visualization. We review current multimedia data mining systems in detail, grouping
them according to problem formulations and approaches. The review includes supervised and unsupervised discovery of events
and actions from one or more continuous sequences. We also do a detailed analysis to understand what has been achieved and
what are the remaining gaps where future research efforts could be focussed. We then conclude this survey with a look at open
research directions. 相似文献
106.
Pradeep K. Atrey M. Anwar Hossain Abdulmotaleb El Saddik Mohan S. Kankanhalli 《Multimedia Systems》2010,16(6):345-379
This survey aims at providing multimedia researchers with a state-of-the-art overview of fusion strategies, which are used
for combining multiple modalities in order to accomplish various multimedia analysis tasks. The existing literature on multimodal
fusion research is presented through several classifications based on the fusion methodology and the level of fusion (feature,
decision, and hybrid). The fusion methods are described from the perspective of the basic concept, advantages, weaknesses,
and their usage in various analysis tasks as reported in the literature. Moreover, several distinctive issues that influence
a multimodal fusion process such as, the use of correlation and independence, confidence level, contextual information, synchronization
between different modalities, and the optimal modality selection are also highlighted. Finally, we present the open issues
for further research in the area of multimodal fusion. 相似文献
107.
The core nodes in an optical burst switching (OBS) network are normally equipped with wavelength converters (WCs) to reduce the burst loss probability. Since WCs are expensive and still immature technologically, it is desirable to reduce the number of WCs in the network and to have partial wavelength conversion capability at the core nodes. Nevertheless, a majority of algorithms in the literature are proposed under the full wavelength conversion assumption. As a result, they do not consider the burst loss caused by insufficient WCs, i.e., bursts dropped due to the unavailability of free WCs to convert them to unused wavelengths. In this paper, we demonstrate how to use burst rescheduling to decrease the burst loss due to insufficient WCs and hence cut down on the overall burst loss probability in OBS networks. Two burst rescheduling algorithms are proposed. Their effectiveness in reducing the overall burst loss probability is verified through simulation experiments. 相似文献
108.
Ganapati Panda Pyari Mohan Pradhan Babita Majhi 《Expert systems with applications》2011,38(10):12671-12683
Conventional derivative based learning rule poses stability problem when used in adaptive identification of infinite impulse response (IIR) systems. In addition the performance of these methods substantially deteriorates when reduced order adaptive models are used for such identification. In this paper the IIR system identification task is formulated as an optimization problem and a recently introduced cat swarm optimization (CSO) is used to develop a new population based learning rule for the model. Both actual and reduced order identification of few benchmarked IIR plants is carried out through simulation study. The results demonstrate superior identification performance of the new method compared to that achieved by genetic algorithm (GA) and particle swarm optimization (PSO) based identification. 相似文献
109.
Classical data mining algorithms require expensive passes over the entire database to generate frequent items and hence to generate association rules. With the increase in the size of database, it is becoming very difficult to handle large amount of data for computation. One of the solutions to this problem is to generate sample from the database that acts as representative of the entire database for finding association rules in such a way that the distance of the sample from the complete database is minimal. Choosing correct sample that could represent data is not an easy task. Many algorithms have been proposed in the past. Some of them are computationally fast while others give better accuracy. In this paper, we present an algorithm for generating a sample from the database that can replace the entire database for generating association rules and is aimed at keeping a balance between accuracy and speed. The algorithm that is proposed takes into account the average number of small, medium and large 1-itemset in the database and average weight of the transactions to define threshold condition for the transactions. Set of transactions that satisfy the threshold condition is chosen as the representative for the entire database. The effectiveness of the proposed algorithm has been tested over several runs of database generated by IBM synthetic data generator. A vivid comparative performance evaluation of the proposed technique with the existing sampling techniques for comparing the accuracy and speed has also been carried out. 相似文献
110.
Majority of the mesh-partitioning algorithms attempt to optimise the interprocessor communications, while balancing the computational load among the processors. However, it is desirable to simultaneously optimise the submesh aspect ratios in order to significantly improve the convergence characteristics of the domain decomposition based Preconditioned-conjugate-gradient algorithms, being used extensively in the state-of-the-art parallel finite element codes. Keeping this in view, a new distributed multi-objective mesh-partitioning algorithm using evolutionary computing techniques is proposed in this paper. Effectiveness of the proposed distributed mesh-partitioning algorithm is demonstrated by solving several unstructured meshes of practical-engineering problems and also benchmark problems. 相似文献