Analytical resolution and numerical identification of fuzzyrelational systems

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.     

A game theoretic fault detection filter

The fault detection process is approximated with a disturbance attenuation problem. The solution to this problem, for both linear time-varying and time-invariant systems, leads to a game theoretic filter which bounds the transmission of all exogenous signals except the fault to be detected. In the limit, when the disturbance attenuation bound is brought to zero, a complete transmission block is achieved by embedding the nuisance inputs into an unobservable, invariant subspace. Since this is the same invariant subspace structure seen in some types of detection filters, we can claim that the asymptotic game filter is itself a detection filter. One can also make use of this subspace structure to reduce the order of the limiting game theoretic filter by factoring this invariant subspace out of the state space. The resulting lower dimensional filter will then be sensitive only to the failure to be detected. A pair of examples given at the end of the paper demonstrate the effectiveness of the filter for time-invariant and time-varying problems in both full-order and reduced-order forms     

A basic-cycle calculation technique for efficient dynamic dataredistribution

Array redistribution is usually required to enhance algorithm performance in many parallel programs on distributed memory multicomputers. Since it is performed at run-time, there is a performance trade-off between the efficiency of the new data decomposition for a subsequent phase of an algorithm and the cost of redistributing data among processors. In this paper, we present a basic-cycle calculation technique to efficiently perform BLOCK-CYCLIC(S) to BLOCK-CYCLIC(t) redistribution. The main idea of the basic-cycle calculation technique is, first, to develop closed forms for computing source/destination processors of some specific array elements in a basic-cycle, which is defined as icm(s,t)/gcd(s,t). These closed forms are then used to efficiently determine the communication sets of a basic-cycle. From the source/destination processor/data sets of a basic-cycle, we can efficiently perform a BLOCK-CYCLIC(s) to BLOCK-CYCLIC(t) redistribution. To evaluate the performance of the basic-cycle calculation technique, we have implemented this technique on an IBM SP2 parallel machine, along with the PITFALLS method and the multiphase method. The cost models for these three methods are also presented. The experimental results show that the basic-cycle calculation technique outperforms the PITFALLS method and the multiphase method for most test samples     

An evolutionary approach to pattern-based time series segmentation

Time series data, due to their numerical and continuous nature, are difficult to process, analyze, and mine. However, these tasks become easier when the data can be transformed into meaningful symbols. Most recent works on time series only address how to identify a given pattern from a time series and do not consider the problem of identifying a suitable set of time points for segmenting the time series in accordance with a given set of pattern templates (e.g., a set of technical patterns for stock analysis). However, the use of fixed-length segmentation is an oversimplified approach to this problem; hence, a dynamic approach (with high controllability) is preferable so that the time series can be segmented flexibly and effectively according to the needs of the users and the applications. In view of the fact that this segmentation problem is an optimization problem and evolutionary computation is an appropriate tool to solve it, we propose an evolutionary time series segmentation algorithm. This approach allows a sizeable set of pattern templates to be generated for mining or query. In addition, defining similarity between time series (or time series segments) is of fundamental importance in fitness computation. By identifying the perceptually important points directly from the time domain, time series segments and templates of different lengths can be compared and intuitive pattern matching can be carried out in an effective and efficient manner. Encouraging experimental results are reported from tests that segment both artificial time series generated from the combinations of pattern templates and the time series of selected Hong Kong stocks.     

Evolution of textures and microstructures in IF-steel sheets during continuous confined strip shearing and subsequent recrystallization annealing

Interstitial free (IF) steel sheets were deformed by continuous confined strip shearing (CCSS) based on the equal channel angular pressing (ECAP). The samples were deformed by CCSS up to three passages and subsequently recrystallized at 700°C for 1 h. The strain history of IF steel sheets in the CCSS die-channel was tackled by finite element method (FEM) simulations. The deformation by CCSS led to the shear deformation and consequently the formation of shear texture components. With increasing number of CCSS passages, the intensity of the deformation texture was hardly increased. The recrystallization texture resembled the deformation texture. The orientation stability was discussed by mean of Taylor deformation model and the formation of recrystallization textures was discussed by occurrence of the discontinuous recrystallization. Observations by transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD) revealed the formation of ultra-fine grains in IF sheets deformed by CCSS.     

Design and performance of compensator for decremental persistent current in HTS magnets using linear type magnetic flux pump

This paper has described the characteristics of a stationary linear type magnetic flux pump newly developed this time. The linear type flux pump aims to compensate a little decremental persistent current of the HTS magnet in NMR and MRI systems. The flux pump mainly consists of DC bias coil, 3-phase AC coil and Nb foil. Analytical results by the FEM are proved to nearly agree with experimental ones. In the experiment, it has been investigated that the flux pump can effectively charge the current in the load coil of 1.3 mH for various frequencies in 150 s under two following conditions: (1) DC bias of 10 A and AC of 4 A_rms, (2) DC bias of 10 A and AC of 5 A_rms. The maximum magnitudes of initial increasing rate of pumping current and load magnet voltage are: (1) 0.2 A/s and 25 mV and (2) 0.22 A/s and 34 mV, respectively.     

Effects of surface treatment of field emitter arrays on electrical characteristics of active matrix cathode

The effects of a wet chemical surface treatment of molybdenum-tip (Mo-tip) emitters on the electrical characteristics of an active matrix cathode composed of hydrogenated amorphous silicon thin film transistors and Mo-tip emitters are described. X-Ray photoelectron spectroscopy measurements showed that the surface treatment removed MoO₃ from the surface of the e-beam evaporated Mo film. In addition, the surface roughness of the Mo film was increased as the result of the surface treatment. The surface-treated active matrix cathode showed stable emission characteristics and immunity from emitter failures during its operation. The response time of the active matrix cathode was decreased by the surface treatment of the Mo-tip emitters. A change in surface composition and surface roughness appear to be responsible for the enhancement of the active matrix cathode.     

Effect of biaxial loads on elastic-plastic <Emphasis Type="Italic">J</Emphasis> and crack tip constraint for cracked plates: finite element study

Based on detailed two-dimensional (2-D) and three-dimensional (3-D) finite element (FE) analyses, this paper attempts to quantify in-plane and out-of-plane constraint effects on elastic-plastic J and crack tip stresses for a plate with a through-thickness crack and semi-elliptical surface crack under positive biaxial loading. For the plate with a through-thickness crack, plate thickness and relative crack length are systematically varied, whereas for the plate with a semi-elliptical surface crack, the relative crack depth and aspect ratio of the semi-elliptical crack are systematically varied. It is found that the reference stress based approach for uniaxial loading can be applied to estimate J under biaxial loading, provided that the limit load specific to biaxial loading is used, implying that quantification of the biaxiality effect on the limit load is important. Investigation on the effect of biaxiality on the limit load suggests that for relatively thin plates with small cracks, in particular with semi-elliptical surface cracks, the effect of biaxiality on the limit load can be neglected for positive biaxial loading, and thus elastic-plastic J for a biaxially loaded plate could be estimated, assuming that such plate is subject to uniaxial load. Regarding the effect of biaxiality on crack tip stress triaxiality, it is found that such effect is more pronounced for a thicker plate. For plates with semi-elliptical surface cracks, the crack aspect ratio is found to be more important than the relative crack depth, and the effect of biaxiality on crack tip stress triaxiality is found to be more pronounced near the surface points along the crack front.     

The effect of He or Ar/O2 plasma treatment on Si surface prior to chemical vapor deposition of SiO2

The effect of O₂ plasma pretreatment on the SiO₂/Si interface property was studied using direct plasma varying the plasma power, He or Ar/O₂ ratio and the pretreatment time. The decrease of the pretreatment plasma power decreased the plasma damage and improved the interface property. The addition of He in O₂ glow discharge improved the electrical and the interface properties and there was an optimum He/O₂ ratio. The improvement of the interface property by Ar/O₂-plasma pretreatment was better than that by He/O₂, which is believed to be due to the lower oxidation rate of the Si surface. C–V analysis showed that the P_b center defect density was influenced by plasma pretreatment process parameters. To investigate the oxidation states near to and at the SiO₂/Si interface, X-ray photoelectron spectroscopy depth analysis was used and the gas phase in the glow discharge was investigated using optical emission spectroscopy analysis at various experimental conditions.     

Effect of irradiation on the impact and seismic response of a spent fuel storage and transport cask

The spent fuel storage and transport cask must withstand various accident conditions such as fire, free drop and puncture in accordance with the requirement of the IAEA and domestic regulations. The spent fuel storage and transport cask should maintain the structural safety not to release radioactive material in any condition. And also the effects of the irradiation should be considered because the spent fuels stored in the cask for a long time and be possible to change the mechanical properties of the cask.In this study, the changed mechanical properties of the cask after irradiation for the 30 years storage periods are assumed and applied to the impact analysis using ABAQUS/Explicit code and seismic analysis using ANSYS code. The stress intensity on each part of the cask is calculated and the effects of irradiation are studied and structural integrity of the package is evaluated.