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11.
It is important to verify assumptions and methods of image retrieval against actual human behavior. A study was conducted to compare similarity methods of color histograms against human assessment of similarity. The similarity methods tested include basic histogram intersection, center histogram matching, locality histogram matching, and size-weighted histogram matching. 161 subjects participated in the empirical study. The findings, based on Spearman correlation analysis, showed that both the basic histogram intersection method and size-weighted histogram are very close to human assessment of similarity (Spearman correlation coefficient of 0.915). The other two are not close to human judgment on similarity. This study illustrates an alternative approach to evaluating matching algorithms. Unlike the usual measures of recall and precision, this approach emphasizes human validation. Fewer images are required with the use of statistical testing. 相似文献
12.
A planar double-gate SOI MOSFET (DG-SOI) with thin channel and thick source/drain (S/D) was successfully fabricated. Using both experimental data and simulation results, the S/D asymmetric effect induced by gate misalignment was studied. For a misaligned DG-SOI, there is gate nonoverlapped region on one side and extra gate overlapped region on the other side. The nonoverlapped region introduces extra series resistance and weakly controlled channel, while the extra overlapped region introduces additional overlap capacitance and gate leakage current. We compared two cases: bottom gate shift to source side (DG/spl I.bar/S) and bottom gate shift to drain side (DG/spl I.bar/D). At the same gate misalignment value, DG/spl I.bar/S resulted in a larger drain-induced barrier lowering effect and smaller overlap capacitance at drain side than DG/spl I.bar/D. Because of reduced drain-side capacitance, the speed of three-stage ring oscillator of DG/spl I.bar/S, with 20% gate misalignment length (L/sub mis/) over gate length (L/sub g/), or L/sub mis//L/sub g/=20%, was faster than that of two-gate aligned DG-SOI. 相似文献
13.
Axial-field electrical machines offer an alternative to the conventional machines. In the axial-field machine, the airgap flux is axial in direction and the active current carrying conductors are radially positioned. This paper presents the design characteristics, special features, manufacturing aspects and potential applications for axial-field electrical machines. The experimental results from several prototypes, including d.c. machines, synchronous machines and single-phase machines are given. The special features of the axial-field machine, such as its planar and adjustable airgap, flat shape, ease of diversification, etc., enable axial-field machines to have distinct advantages over conventional machines in certain applications, especially in special-purpose applications. 相似文献
14.
Zhang Z.G. Chan S.C. Tsui K.M. 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2008,55(6):576-580
This paper proposes a new Kalman-filter-based recursive frequency estimator for discrete-time multicomponent sinusoidal signals whose frequencies may be time-varying. The frequency estimator is based on the linear prediction approach and it employs the Kalman filter to track the linear prediction coefficients (LPCs) recursively. Frequencies of the sinusoids can then be computed using the estimated LPCs. Due to the coloredness of the linear prediction error, an iterative algorithm is employed to estimate the covariance matrix of the prediction error and the LPCs alternately in the Kalman filter in order to improve the tracking performance. Simulation results show that the proposed Kalman-filter-based iterative frequency estimator can achieve better tracking results than the conventional recursive least-squares-based estimators. 相似文献
15.
Min Chan Kim Dong Won Lee Chang Kyun Choi 《Korean Journal of Chemical Engineering》2008,25(6):1239-1244
When a horizontal homogeneous solid is melted from below, convection can be induced in a thermally unstable melt layer. In
this study the onset of buoyancy-driven convection during time-dependent melting is investigated by using similarly transformed
disturbance equations. The critical Rayleigh numbers based on the melt-layer thickness are found numerically for various conditions.
For small superheats, the present predictions approach the well known results of classical Rayleigh-Bénard problems, that
is, critical Rayleigh numbers are located between 1,296 and 1,708, regardless of the Prandtl number. However, for high superheats
the critical Rayleigh number increases with an increase in phase change rate but with decrease in Prandtl number. 相似文献
16.
Cyclic oxidation response of multiphase niobium-based alloys 总被引:4,自引:0,他引:4
Kwai S. Chan 《Metallurgical and Materials Transactions A》2004,35(2):589-597
Cyclic oxidation tests were performed on multiphase Nb-based alloys containing silicide, Laves, and Nb solid solution phases.
In particular, the oxidation resistance of six alloys with various compositions (Nb, Ti, Hf, Cr, Ge, and Si) and microstructures
was characterized by thermal cycling from ambient temperature to a peak temperature that ranges from 900 °C to 1400 °C. Weight
change data were obtained and the corresponding spalled oxides were collected and identified by X-ray diffraction. The results
indicated that Nb-based alloys formed a mixture of CrNbO4, Nb2O5, and Nb2O5 · TiO2, with possibly small amounts of SiO2 or GeO2. The oxidation resistance was improved when CrNbO4 formed instead of Nb2O5 and Nb2O5 · TiO2. These results were used to assess the influence of microstructure and composition on the oxidation resistance of multiphase
Nb-based alloys. 相似文献
17.
18.
19.
Control of calcium hexaluminate grain morphology in in-situ toughened ceramic composites 总被引:2,自引:0,他引:2
The influence of processing conditions on the morphology of calcium hexaluminate (CA6) grains in Al2O3: 30 vol% CaO·6Al2O3 (CA6) ceramic composites was investigated. Specimens were prepared by in-situ reaction sintering using precursor powders of alumina, and either calcium carbonate or calcium oxide. In some samples, 1 vol% anorthite glass was added as a sintering aid. X-ray diffraction was used to study the phase development in the as-calcined and sintered states. The resultant microstructures were characterized using both scanning electron microscopy (SEM), and imaging secondary ion mass spectrometry (SIMS). It was found that the CA6 grains developed a platelike morphology when CaCO3 was used as the starting calcium-rich powder. In contrast, samples prepared using CaO resulted in equiaxed CA6 grains. This result was observed to be independent of the anorthite glass addition. The findings are rationalized in terms of distinct CA6 reaction mechanisms, resulting from differences in the reactivity of the powders during the early stages of calcining.Cement Nomenclature C
CaO
- A
Al2O3 相似文献
20.
K. Y. Sze W. K. Chan T. H. H. Pian 《International journal for numerical methods in engineering》2002,55(7):853-878
This paper presents eight‐node solid‐shell elements for geometric non‐linear analysis of elastic shells. To subdue shear, trapezoidal and thickness locking, the assumed natural strain method and an ad hoc modified generalized laminate stiffness matrix are employed. A selectively reduced integrated element is formulated with its membrane and bending shear strain components taken to be constant and equal to the ones evaluated at the element centroid. With the generalized stresses arising from the modified generalized laminate stiffness matrix assumed to be independent from the ones obtained from the displacement, an extended Hellinger–Reissner functional can be derived. By choosing the assumed generalized stresses similar to the assumed stresses of a previous solid element, a hybrid‐stress solid‐shell element is formulated. Commonly employed geometric non‐linear homogeneous and laminated shell problems are attempted and our results are close to those of other state‐of‐the‐art elements. Moreover, the hybrid‐stress element converges more readily than the selectively reduced integrated element in all benchmark problems. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献