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981.
A genetic algorithm (GA) has control parameters that must be determined before execution. We propose a self-organizing genetic
algorithm (SOGA) as a multimodal function optimizer which sets GA parameters such as population size, crossover probability,
and mutation probability adaptively during the execution of a genetic algorithm. In SOGA, GA parameters change according to
the fitnesses of individuals. SOGA and other approaches for adapting operator probabilities in GAs are discussed. The validity
of the proposed algorithm is verified in simulation examples, including system identification.
This work was presented, in part, at the International Symposium on Artificial Life and Robotics, Oita, Japan, February 18–20,
1996 相似文献
982.
Throughout this study on information processing using an artificial neural network (ANN) and chaos we are attempting to devise
a memory model that resembles human behavioral characteristics. For that purpose we construct a framework of the macroscopic
model of the responding process in biological systems. Incoming stimuli are applied to the sensory receptors and preprocessed.
A pattern-matching block allows one of the chaotic memories to find a feasible response in an associative way. After the chaotic
memory is stabilized on one of the stable equilibrium points or limit cycles, its performance is evaluated. Since chaotic
memory and the performance evaluation block form a feedback loop, they can handle features of the information blocks and store
newly updated information blocks. Two kinds of chaotic memories are established in this paper: one is a 1-D map in which many
information blocks can be stored as unstable periodic orbits, and the other is the famous Lozi attractor with rich dynamics.
Simulations are performed for the mobile robot navigation problem in each case.
This work was presented, in part, at the Second International Symposium on Artificial Life and Robotics, Oita, Japan, February
18–20, 1997 相似文献
983.
Robust control designs for a discrete Takagi and Sugeno (T-S) fuzzy model are proposed. The T-S fuzzy model contains (possibly fast) time-varying uncertainty. First, a switching-type robust control is shown to stabilize the T-S fuzzy model asymptotically. Second, a saturation-type robust control is shown to render the T-S model practically stable. In both designs, only the bound of uncertainty is needed. The effectiveness of proposed designs is analyzed rigorously and illustrated by simulations. 相似文献
984.
A handwritten Chinese character recognition method based on primitive and compound fuzzy features using the SEART neural network model is proposed. The primitive features are extracted in local and global view. Since handwritten Chinese characters vary a great deal, the fuzzy concept is used to extract the compound features in structural view. We combine the two categories of features and use a fast classifier, called the Supervised Extended ART (SEART) neural network model, to recognize handwritten Chinese characters. The SEART classifier has excellent performance, is fast, and has good generalization and exception handling abilities in complex problems. Using the fuzzy set theory in feature extraction and the neural network model as a classifier is helpful for reducing distortions, noise and variations. In spite of the poor thinning, a 90.24% recognition rate on average for the 605 test character categories was obtained. The database used is CCL/HCCR3 (provided by CCL, ITRI, Taiwan). The experiment not only confirms the feasibility of the proposed system, but also suggests that applying the fuzzy set theory and neural networks to recognition of handwritten Chinese characters is an efficient and promising approach. 相似文献
985.
Fu-Lai Chung Tong Lee 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》1998,28(6):919-924
Since Sanchez's seminal paper on fuzzy relational equations, both their theories and applications have been continuously exploited by researchers. However, the solvable conditions of a system of fuzzy relational equations, also known as a fuzzy relational system (FRS), are still poorly established and their relationship with the methods for obtaining approximate solutions are unclear. When the FRS is adopted to model a fuzzy system, most of the existing identification algorithms focus on parameter estimation and less on the structure identification. In this paper, these two issues are addressed. New theoretical understandings on solving a system of fuzzy relational equations exactly and approximately are presented and their implications on the use of FRS to encode fuzzy rulebases are highlighted. Based upon the guided evolutionary simulated annealing (GESA) algorithm, an evolutionary identification formulation called EVIDENT capable for both parameter and structure identifications in fuzzy system models is proposed. As demonstrated by the simulation results, the new algorithm not only is effective in determining the structure of the systems, but also identifies a better parametric solution, as compared with that of the existing FRS identification algorithms. 相似文献
986.
Application of fuzzy logic structures in CAD of digital electronics substantially improves quality of design solutions by providing designers with flexibility in formulating goals and selecting tradeoffs. In addition, the following aspects of a design process are positively impacted by application of fuzzy logic: utilization of domain knowledge, interpretation of uncertainties in design data, and adaptation of design algorithms. We successfully applied fuzzy logic structures in conjunction with constructive and iterative algorithms for selecting of design solutions for different stages of the design process. We also introduced fuzzy logic software development tool to be used in CAD applications 相似文献
987.
Kyung-OhLee Jun-HoPark Yoon-YoungPark 《计算机科学技术学报》2004,19(6):0-0
When designing a multimedia server, several things must be decided: which scheduling scheme to adopt, how to allocate multimedia objects on storage devices, and the round length with which the streams will be serviced. Several problems in the designing of large-scale multimedia servers are addressed, with the following contributions: (1) a striping scheme is proposed that minimizes the number of seeks and hence maximizes the performance; (2) a simple and efficient mechanism is presented to find the optimal striping unit size as well as the optimal round length, which exploits both the characteristics of VBR streams and the situation of resources in the system; and (3) the characteristics and resource requirements of several scheduling schemes are investigated in order to obtain a clear indication as to which scheme shows the best performance in realtime multimedia servicing. Based on our analysis and experimental results, the CSCAN scheme outperforms the other schemes. It is believed that the results ar 相似文献
988.
Dong-Geun Lee You Hwan Lee Sunghak Lee Chong Soo Lee Sun-Moo Hur 《Metallurgical and Materials Transactions A》2004,35(10):3103-3112
Effects of microstructural morphology on dynamic deformation behavior and ballistic impact properties of Ti-6Al-4V alloy plates
were investigated in this study. Dynamic torsional and ballistic impact tests were conducted on equiaxed and bimodal microstructures,
which were processed by different heat treatments, and then the test data were analyzed in relation to microstructures and
tensile properties. According to the dynamic torsional test data, maximum shear stress and fracture shear strain of the bimodal
microstructure were higher than those of the equiaxed microstructure, and the possibility of the adiabatic shear band formation
was more likely in the equiaxed microstructure than in the bimodal microstructure. In the ballistically impacted region of
the equiaxed microstructure, a number of adiabatic shear bands and cracks were observed to be formed along plastic flow lines,
and delamination occurred because of cracking along the flow lines or shear bands. In the case of the bimodal microstructure,
shear bands were found in limited areas near the penetrated surface without occurring delamination, and their number was smaller
than that of the equiaxed microstructure. Thus, ballistic performance of the bimodal microstructure was better than that of
the equiaxed microstructure, which was consistent with the dynamic torsional test results. 相似文献
989.
G. Y. Kim L. M. He J. D. Meyer W. Y. Lee A. Quintero J. A. Haynes 《Metallurgical and Materials Transactions A》2004,35(11):3581-3593
A laboratory-scale chemical vapor deposition (CVD) reactor was used to perform “continuous” Hf doping experiments while the
surface of a single-crystal Ni alloy was being aluminized to form an aluminide (β-NiAl) coating matrix for 45 minutes at 1150 °C. The continuous doping procedure, in which HfCl4 and AlCl3 were simultaneously introduced with H2, required a high HfCl4/AlCl3 ratio (>∼0.6) to cause the precipitation of Hf-rich particles (∼0.1 μm) at grain boundaries of the coating layer, with the overall Hf concentration of ∼0.05 to 0.25 wt pct measured in the coating
layer by glow-discharge mass spectroscopy (GDMS). Below this ratio, Hf did not incorporate as a dopant into the growing coating
layer from the gas phase, as the coating matrix appeared to be “saturated” with other refractory elements partitioned from
the alloy substrate. In comparison, the Hf concentration in the aluminide coating layer formed on pure Ni was in the range
of ∼0.1 wt pct, which was close to the solubility of Hf estimated for bulk NiAl. Interestingly, the segregation of Hf and
the formation of a thin γ′-Ni3Al layer (∼0.5 μm) at the coating surface were consistently observed for both the alloy and pure-Ni substrates. The formation of the thin
γ′-Ni3Al layer was attributed to an increase in the elastic strain of the β-NiAl phase, associated with the segregation of Hf as well as other refractory alloying elements at the coating surface. This
phenomenon also implied that the coating layer was actually growing at the interface between the γ′-Ni3Al layer and the β-NiAl coating matrix, not at the gas/coating interface, during the early stage of the coating growth. 相似文献
990.
Cheng-Hsun Hsu Shen-Chih Lee Hwei-Yuan Teng 《Metallurgical and Materials Transactions A》2004,35(2):471-480
This research studied the effects of heat treatment and testing temperature on fracture mechanics behavior of Si-modified
CA-15 martensitic stainless steel (MSS), which is similar to AISI 403 grade stainless steel, which has been widely used in
wall and blanket structures and in the pipe of nuclear power plant reactors, turbine blades, and nozzles. The results indicated
that fracture toughness of low-Si CA-15 MSS is better than that of AISI 403. The specimens of the low-Si CA-15 MSS after austenitization
at 1010 °C and then tempering at 300 °C have higher plane-strain fracture toughness (K
IC
) values for both 25 °C and −150 °C testing temperatures. However, the specimens tested at 150 °C cannot satisfy the plane-strain
fracture toughness criteria. The fatigue crack growth rate is the slowest after austenitization at 1010 °C for 2 hours and
tempering at 400 °C. Observing the crack propagation paths using a metallographic test, it was found that the cracking paths
preferred orientation and branched along ferrite phase, owing to martensite-phase strengthening and grain-boundary-carbide
retarding after 300 °C to 400 °C tempering. Also, transmission electron microscopy (TEM), scanning electron microscopy (SEM),
and X-ray diffraction analysis were performed to correlate the properties attained to the microstructural observation. 相似文献