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51.
Hoshiaki Iijima Osamu Taguchi Ken-Ichi Hirano 《Metallurgical and Materials Transactions A》1977,8(6):991-995
Interdiffusion coefficient
in cobalt-manganese alloys has been determined by Matano's method in the temperature range between 1133 and 1423 K on (pure
Co)-(Co-30.28 at. pct Mn alloy) and (pure Co)-(Co-51.76 at. pct Mn alloy) couples. This, ∼D, has been found to increase with the increase of manganese content. However, the activation energy (∼Q) and frequency factor (
0) show a maximum at about 10 at. pct Mn. The concentration dependence of
and
has been discussed taking into account the thermodynamic properties of the alloy. The difference in
between the ferro- and paramagnetic phases in Co-5 at. pct Mn alloy has been found to be 24 kJ/mol, which is larger, than
that for the diffusion of Mn54 in this alloy. Further it has been found that the Kirkendall marker moves toward manganese-rich side, showing that manganese
atoms diffuse faster than cobalt atoms. From the marker shift, the intrinsic diffusion coefficients,D
Co andD
Mn, at 33 at. pct Mn have been determined as follows:D
Co=0.22×10−4 exp(−263 kJ mol−1/RT) m2/s, andD
Mn=0.98×10−4 exp(−229 kJ mol−1/RT) m2/s. 相似文献
52.
53.
Osamu Watanabe 《Theory of Computing Systems》1991,24(1):1-10
The classUP [V] is the class of sets accepted by polynomial-time nondeterministic Turing machines which have at most one accepting path for every input. The complexity of this class closely relates to that of computing inverses ofone-way functions, where a one-way function is a one-to-one, length-increasing, and polynomial-time computable function whose inverse cannot be computed within polynomial time. It is known [GS], [K] that there exists a one-way function if and only ifP UP. In this paper the intractability of sets inUP is investigated in terms of polynomial-time reducibility to a sparse set. It is shown thatUP has a set that is
m
P
-reducible to no sparse set ifP UP. We interpret this structural property in the relation with approximation algorithms: it is shown that ifP UP, thenUP has a set with no 1-APT approximation and, furthermore,UP has a set that is not
m
P
-reducible to any set with a 1-APT approximation. The implication of this result in the study of one-way functions is also discussed. In order to prove the main theorem, we introduce a variation of tree-pruning methods.This paper was written while the author visited the Department of Mathematics, University of California, Santa Barbara. This research was supported in part by the National Science Foundation under Grant CCR-8611980. 相似文献
54.
An Extension of the Receiver Operating Characteristic Curve and AUC-Optimal Classification 总被引:1,自引:0,他引:1
While most proposed methods for solving classification problems focus on minimization of the classification error rate, we are interested in the receiver operating characteristic (ROC) curve, which provides more information about classification performance than the error rate does. The area under the ROC curve (AUC) is a natural measure for overall assessment of a classifier based on the ROC curve. We discuss a class of concave functions for AUC maximization in which a boosting-type algorithm including RankBoost is considered, and the Bayesian risk consistency and the lower bound of the optimum function are discussed. A procedure derived by maximizing a specific optimum function has high robustness, based on gross error sensitivity. Additionally, we focus on the partial AUC, which is the partial area under the ROC curve. For example, in medical screening, a high true-positive rate to the fixed lower false-positive rate is preferable and thus the partial AUC corresponding to lower false-positive rates is much more important than the remaining AUC. We extend the class of concave optimum functions for partial AUC optimality with the boosting algorithm. We investigated the validity of the proposed method through several experiments with data sets in the UCI repository. 相似文献
55.
This letter presents a new algorithm for blind dereverberation and echo cancellation based on independent component analysis (ICA) for actual acoustic signals. We focus on frequency domain ICA (FD-ICA) because its computational cost and speed of learning convergence are sufficiently reasonable for practical applications such as hands-free speech recognition. In applying conventional FD-ICA as a preprocessing of automatic speech recognition in noisy environments, one of the most critical problems is how to cope with reverberations. To extract a clean signal from the reverberant observation, we model the separation process in the short-time Fourier transform domain and apply the multiple input/output inverse-filtering theorem (MINT) to the FD-ICA separation model. A naive implementation of this method is computationally expensive, because its time complexity is the second order of reverberation time. Therefore, the main issue in dereverberation is to reduce the high computational cost of ICA. In this letter, we reduce the computational complexity to the linear order of the reverberation time by using two techniques: (1) a separation model based on the independence of delayed observed signals with MINT and (2) spatial sphering for preprocessing. Experiments show that the computational cost grows in proportion to the linear order of the reverberation time and that our method improves the word correctness of automatic speech recognition by 10 to 20 points in a RT??= 670 ms reverberant environment. 相似文献
56.
Eight subjects participated in a subjective experiment of eight conditions to investigate the effects of heated seats in vehicles on skin temperature, thermal sensation and thermal comfort during the initial warm-up period. The experimental conditions were designed as a combination of air temperature in the test room (5, 10, 15, or 20 °C) and heated seat (on/off). The heated seat was effective for improving thermal comfort during the initial warm-up period when air temperature was lower than 15 °C. Use of heated seats prevented decreases in or increased toe skin temperature. Heated seats also increased foot thermal sensation at 15 and 20 °C. Optimal thermal sensation in contact with the seat was higher when air temperature was lower. Optimal skin temperature in contact with the seat back was higher than that with the seat cushion. Moreover, these optimal skin temperatures were higher when air temperature was lower. 相似文献
57.
Several- Ni-Al and Ni-Al-Ti two-phase bicrystals were made by the solid-state diffusion couple method. Each couple consisted of a-phase single crystal and a pure-Ni polycrystal, and was annealed at 1473 K in an Ar gas atmosphere. Single crystal layers of-phase with uniform thickness always grow into the parent-phase single crystals. The resultant/ interface has no voids or facets regardless of the orientation of interface and the chemical composition of the-phase. Porosity formation due to the Kirkendall effect is observed in the diffused region. Concentration profiles exhibit nearly constant gradients in-phase. The orientation relationship between both phases is found to be 001//001, that is, the-phase grows epitaxially along the crystal orientation of-phase. 相似文献
58.
Crystallite size distribution and the lattice distortions in highly γ-irradiated linear polyethylene
Crystallite size distributions and lattice distortions have been analysed for highly-irradiated linear polyethylene in the direction normal to 1 1 0 and 0 0 1 lattice planes through X-ray line profile analysis. It has been found that the lateral crystallite size is little affected irradiation greater than 1000 Mrad, whereas that in the chain direction decreases almost linearly with the dose of irradiation. A minor difference in the crystallite size between irradiation atmospheres, i.e. irradiation in air or in vacuum, has been disclosed at a very high dose of irradiation. The above degradation behaviour of crystallites and the change in lattice distortions have proved that radiation cross-links are mainly formed in the amorphous region near the lamellar surface of polyethylene. 相似文献
59.
Koji Ishida Ken Hirota Osamu Yamaguchi Hideki Kume Suguru Inamura Hiroki Miyamoto 《Journal of the American Ceramic Society》1994,77(5):1391-1395
In the system ZrO2 –Al2 O3 , a new method for preparing ZrO2 solid solutions from ZrCl4 and AlCl3 using hydrazine monohydrate is investigated. c -ZrO2 solid solutions containing up to ∼40 mol% Al2 O3 crystallize at low temperatures from amorphous materials. The formation mechanism is discussed from IR spectral data. The values of the lattice parameter α increase linearly from 0.5072 to 0.5105 nm with increasing Al2 O3 content. At higher temperatures, transformation of the solid solutions proceeds as follows: c ( SS ) → t ( ss ) → t ( ss ) +α-Al2 O3 → m +α-Al2 O3 . m -ZrO2 –α-Al2 O3 composite ceramics are fabricated by hot isostatic pressing for 2 h at 1250°C and 196 MPa. Microstructures and mechanical properties are examined, in connection with increasing Al2 O3 content. 相似文献
60.