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91.
In this paper, a fuzzy c‐means clustering algorithm based on interval‐valued weights is proposed for improving clustering performance. In the proposed algorithm, the interval‐valued weights are first constructed by synergy of the ReliefF algorithm and the analytic hierarchy process (AHP) method, and then they are transformed into a constraint condition associating with each weight variable in the weighted clustering objective function. In the sequence, the weighted clustering objective function is solved by combining the Lagrange multiplier method with the gradient‐based iteration computation. In the whole process of algorithm iteration, a compulsion strategy with human–computer cooperation is adopted to ensure each weight variable satisfies interval constraint itself. Three well‐known data set are used to perform profound experiments. Experimental results clearly show that the proposed algorithm has better clustering performance than other the weighted fuzzy c‐means clustering algorithm. 相似文献
92.
In this paper, we introduce a new category of fuzzy models called a fuzzy ensemble of parallel polynomial neural network (FEP2N2), which consist of a series of polynomial neural networks weighted by activation levels of information granules formed with the use of fuzzy clustering. The two underlying design mechanisms of the proposed networks rely on information granules resulting from the use of fuzzy C-means clustering (FCM) and take advantage of polynomial neural networks (PNNs).The resulting model comes in the form of parallel polynomial neural networks. In the design procedure, in order to estimate the optimal values of the coefficients of polynomial neural networks we use a weighted least square estimation algorithm. We incorporate various types of structures as the consequent part of the fuzzy model when using the learning algorithm. Among the diverse structures being available, we consider polynomial neural networks, which exhibit highly nonlinear characteristics when being viewed as local learning models.We use FCM to form information granules and to overcome the high dimensionality problem. We adopt PNNs to find the optimal local models, which can describe the relationship between the input variables and output variable within some local region of the input space.We show that the generalization capabilities as well as the approximation abilities of the proposed model are improved as a result of using polynomial neural networks. The performance of the network is quantified through experimentation in which we use a number of benchmarks already exploited within the realm of fuzzy or neurofuzzy modeling. 相似文献
93.
Alloys from the solid solution Ce1−xThxPt3Si (x = 0.0, 0.02, 0.04, 0.08, 0.1, 0.2 and 1.0) were prepared by arc-melting. X-ray Rietveld powder analyses revealed that alloys in the compositional range 0 ≤ x ≤ 0.2 crystallize with the CePt3B-type with a random distribution of Ce and Th atoms in positions 1(b) (1/2, 1/2, z) of the noncentrosymmetric space group P4mm. Th-doping results in a rapid suppression of the superconductivity. The alloy with x = 0.02 shows the onset of superconducting state at Tc = 400 mK, while that with x = 0.04 remains in normal metallic state at least down to 70 mK. 相似文献
94.
A new series of R2PdIn8 intermetallics, where R = Pr, Nd, and Sm, was prepared by arc-melting the constituents under argon atmosphere and studied by means of X-ray diffraction and magnetic measurements. The compounds crystallize with a tetragonal structure of the Ho2CoGa8 type (space group P4/mmm). At very low temperatures, they order antiferromagnetically, and the Nd-based indide presumably exhibits an additional magnetic phase transition in the ordered region. 相似文献
95.
The very high temperature reactor (VHTR) has been selected as among the Generation IV nuclear power system. The coolant, namely helium, has been shown to contain low level of oxidizing as well as carbon‐bearing impurities (such as H2, CO (and CO2), CH4, N2 ranging from a few microbars to hundreds of microbars and water vapour in the microbar range) that can interact with metals at high temperature. In this specific gas phase, there is a competition between the formation of protective oxide scales and deleterious reactions towards carbon. A possible oxide layer reduction could be observed in a particular case detailed in this paper. This destruction of the oxide can imply consequences on the behaviour of the alloy as strong carburization or deep internal oxidation could occur. The influence of the level of impurities was analysed through a parametric approach. The experiments were carried out in a purpose‐designed device that allows the control of low impurity partial pressures. 相似文献
96.
A. Szytua B. Penc D. Kaczorowski A. Arulraj S. Baran N. Stüsser K. Tomala 《Journal of Alloys and Compounds》2008,460(1-2):120-124
Magnetization, magnetic susceptibility, neutron diffraction and X-ray photoemission spectroscopy measurements were performed on polycrystalline samples: PrCo0.85Ge2 and NdCo0.82Ge2, crystallizing in an orthorhombic structure of the CeNiSi2-type. The magnetometric data indicate that both compounds are antiferromagnetic at low temperatures, PrCo0.85Ge2 below 5 K and NdCo0.82Ge2 below 2.1 K. The neutron diffraction data indicate an antiferromagnetic structure in PrCo0.85Ge2 at 1.5 K and give no evidence of any magnetic ordering in NdCo0.82Ge2. The X-ray photoemission data indicate that the valence bands are formed predominantly by R 4f5d6s and Co 3d bands. The spin-orbit splitting values determined from the Pr and Nd, 3d5/2 and 3d3/2 XPS spectra are equal to 20.9 eV for the Pr compound and 23.0 eV for the Nd compound. The analysis of these spectra performed on the basis of the Gunnarsson–Schönhammer model revealed a small hybridization between 4f-electrons of the rare earths with the conduction band which implies rather good stability of the f shell in these compounds. 相似文献
97.
Julian Chojnowski Slawomir Rubinsztajn Witold Fortuniak Jan Kurjata 《Journal of Inorganic and Organometallic Polymers and Materials》2007,17(1):173-187
Summary Reactions of hexamethylcyclotrisiloxane, D3, with 1,1,3,3-tetramethyldisiloxane, HMMH, 1,1,1,3,3-pentamethyldisiloxane, HMM, phenyldimethylsilane and phenylmethylsilane catalyzed by tris(pentafluorophenyl)borane were studied. These reactions lead
to ring opening of D3 by the SiH reactant producing open chain oligomers with hydrosilane functionality at one or both chain ends. The reactivity
of the hydrosilanes toward D3 decreases in the series: PhMeSiH2 > HMMH > PhMe2SiH > HMM. Competitive self-oligomerization of HMMH and HMM also occurs. Primary products of these processes are able to enter into reactions with the SiH and D3 reactants; some also undergo cyclization. Thus, consecutive and competitive processes lead to a series of various oligohomologues.
Gas chromatography in conjunction with chemical ionization mass spectroscopy permitted identification of structure and determination
of the basic directions of these oligomerization processes. Polysiloxanes of higher molecular weight may be also formed in
some of these systems. The reactions, which occur in the systems studied, are rationalized on the basis of the mechanism involving
the hydride transfer from silicon to trivalent boron. This includes the transient formation of tertiary trisilyloxonium borate
which decomposes by the hydride transfer to one of the silicon atoms of the trisilyloxonium center.
Footnote: This paper is dedicated to Professor Ian Manners in recognition of his significant contributions to the field of
organometallic polymers. 相似文献
98.
Brittleness of materials—whether it occurs naturally or with aging—affects significantly performance and manifests itself
in various properties. In the past, brittleness was defined qualitatively, but now a definition of brittleness for viscoelastic
materials exists, enabling analysis of all types of polymer-based materials. The quantity brittleness, B, has been evaluated for neat thermoplastics, but here composites and metal alloys are also assessed. The physical significance
of brittleness is connected to the dimensional stability of materials. The connections of brittleness to tensile elongation
and to fatigue are explored while its relationship to surface properties—specifically wear by repetitive scratching—is examined
more closely. The economic impact of wear results in monetary loss associated with failure and reduced service life of plastic
parts—thus its connection to brittleness finds use across a broad spectrum of industrial applications which utilize plastics
for manufacturing, processing, etc. We also demonstrate a correspondence between impact strength (Charpy or Izod) and brittleness
of polymers. It is shown that the assumption hardness is equivalent to brittleness is inaccurate; this fact has important
implications for interpreting the results of mechanical testing of viscoelastic materials. 相似文献
99.
Urolithiasis is a common diagnostic and therapeutic problem in small-animal veterinary practice. The traditional diagnostic approach usually consists of clinical, radiological and ultrasonographic examination of the patient. The main diagnostic material is still urine sediment, ignoring the fact that presence of crystalluria is not always of pathological significance. In order to establish the most effective therapeutic and preventative strategies, especially in the case of multicomponent stone, it is crucial to define the exact elemental composition of the given stone including crystallization nidus chemical contents. In the course of the research, the usefulness of scanning electron microscopy combined with X-ray-dispersive spectrometry in analysis of canine mixed and compound stones was investigated. The obtained results indicated that the tested method allows one to trace the dynamics of the crystallization process, including crystallization nucleus detection, and concurrently and quantitatively assess the elemental composition of the given urinary concrement. Moreover, the conducted research showed epidemiological data of urolithiasis occurrence in a population of dogs coming from the southern part of Poland. 相似文献
100.
Krystyna A Skibniewska Witold Kozirok Lucja Fornal Kazimierz Markiewicz 《Journal of the science of food and agriculture》2002,82(14):1676-1681
The content of macroelements P, Mg and Ca and microelements Mn, Fe, Zn and Cu was determined in 10 commercially sold oat products made by different technological processes (dehulling, instantinising, extrusion, flaking). Phosphorus was the most prevalent of the macroelements (from 240.8 ± 2.2 to 845.5 ± 8.1 mg per 100 g), followed by magnesium (from 73.2 ± 0.7 to 271.9 ± 2.7 mg per 100 g) and calcium (from 30.69 ± 0.01 to 112.7 ± 0.3 mg per 100 g). The Ca/P ratio ranged from 1:5.3 in crushed oat to 1:8.2 in oat flakes. Regarding the microelements, manganese was present at the highest concentrations (from 2.62 ± 0.02 to 8.69 ± 0.01 mg per 100 g). The content of iron was similar and that of zinc not much lower, whereas the amount of copper was considerably smaller (from 0.23 ± 0.002 to 0.59 ± 0.002 mg per 100 g). The highest concentrations of mineral elements were found in instant oat bran flakes and the lowest in extruded oat and corn crisps containing 50% corn grouts. Samples of the products analysed were subjected to in vitro enzymatic digestion, simulating the digestive process occurring in the human alimentary tract. The supernatants thus obtained were analysed for their content of the previously determined mineral components; the percentage of minerals released from the products was calculated. The following sequence of mineral components released was observed: Cu (57.2–95.6%) > P (39.7–60.9%) > Ca (18.2–39.5%) > Mg (16.4–39.8%) > Mn (6.4–24.7%) > Fe (6.5–29%) > Zn (11–17.2%). The Ca/P ratio in the supernatant worsened from 1:8.2 in crushed oat to 1:23.3 in extruded oat and corn crisps. Crushed oat released the highest amounts of mineral elements during enzymatic hydrolysis, with oat grouts coming second. As regards the other products, it is difficult to establish their relative sequence in the release of minerals. © 2002 Society of Chemical Industry 相似文献