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Nguyen Huy Dan Pham Thi ThanhNguyen Hai Yen Nguyen Thi Thanh Huyen Duong Dinh Thang Luu Tien Hung 《Journal of magnetism and magnetic materials》2012,324(7):1435-1439
We have observed magnetic anisotropy in bulk Nd55−xCoxFe30Al10B5 (x=10, 15 and 20) alloys prepared by copper mold suction casting method with a presence of external magnetic field (quenching field) μ0H=0.25 T. By changing direction of the measuring field from perpendicular to parallel one in comparison with that of the quenching field, coercive force of the alloys slightly decreases while remanent magnetization and squareness of hysteresis loop increase more clearly. It is also found that the higher Co-concentration in the alloys the larger magnetic anisotropy is induced. The structure analyses manifest nanocrystalline particles embedded in residual amorphous matrix of the alloys. The size of the particles is in range of 10-30 nm and their crystalline phases consist of Nd2(Fe,Co)14B, Nd3Co, Nd3Al, NdAl2 and Nd. 相似文献
95.
The Alperin Weight Conjecture was stated by J. Alperin in 1986 and constitutes one of the main problems in the representation
theory of finite groups. In this paper, we provide a reduction to simple groups and as an application we prove the conjecture
in several cases. 相似文献
96.
Globally solving a nonlinear UAV task assignment problem by stochastic and deterministic optimization approaches 总被引:1,自引:0,他引:1
In this paper, we consider a task allocation model that consists of assigning a set of m unmanned aerial vehicles (UAVs) to a set of n tasks in an optimal way. The optimality is quantified by target scores. The mission is to maximize the target score while
satisfying capacity constraints of both the UAVs and the tasks. This problem is known to be NP-hard. Existing algorithms are
not suitable for the large scale setting. Scalability and robustness are recognized as two main issues. We deal with these
issues by two optimization approaches. The first approach is the Cross-Entropy (CE) method, a generic and practical tool of
stochastic optimization for solving NP-hard problem. The second one is Branch and Bound algorithm, an efficient classical
tool of global deterministic optimization. The numerical results show the efficiency of our approaches, in particular the
CE method for very large scale setting. 相似文献
97.
Nguyen Van Hieu Nguyen Van Duy Pham Thanh Huy Nguyen Duc Chien 《Physica E: Low-dimensional Systems and Nanostructures》2008,40(9):2950-2958
Nb-Pt co-doped TiO2 and the hybrid SWCNTs/Nb-Pt co-doped TiO2 thin films have been prepared by the sol–gel spin-coating process for gas-sensor fabrication. Field emission scanning electron microscope (FE-SEM, TEM and X-ray diffraction (XRD) characterizations indicated that the SWCNTs inclusion did not affect the morphology of the TiO2 thin film and the particle size. Additionally, the SWCNTs were well embedded in the TiO2 matrix. The gas-sensing properties of Nb–Pt co-doped TiO2 thin films with and without SWCNTs inclusion were investigated. The hybrid sensors with the inclusion of different SWCNTs contents are examined to elucidate the effect of SWCNTs content on the gas-sensing properties. Experimental results revealed that the responses to ethanol of Nb–Pt co-doped TiO2 sensors with SWNCTs inclusion increase by factors of 2–5 depending on the operating temperature and the ethanol concentration, compared to that of the sensor without SWCNTs inclusion. Moreover, all hybrid sensors can operate with high sensitivity and stability at a relatively low operating temperature (<335 °C). The responses of the hybrid sensors are greatly affected by SWCNTs content inclusion. The optimized SWCNTs content of 0.01% by weight was obtained for our experiment. The improved gas-sensing performance should be attributed to the additional formation of the p/n junction between SWCNTs (p-type) and TiO2 (n-type). 相似文献
98.
Pham Anh Minh 《Proceedings of the American Mathematical Society》2002,130(2):307-310
The purpose of this note is to provide a -group whose mod-3 cohomology ring has a nilpotent element satisfying .
99.
This paper describes the synthesis and study of the mesomorphic properties (by DSC, microscopic observation and X-ray diffraction) of three new series of semi-perfluorinated liquid crystals: 4-(2,2,3,3,4,4,4-heptafluorobutyloxycarbonyl)phenyl, 4-(2,2,3,3,4,4,5,5-octafluoropentyloxycarbonyl)phenyl, and 4-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-octyloxy-carbonyl)phenyl 4-(n-alkyloxy)benzoates. One compound of the second family crystallizes in the P1 space group with Z ' 2. The molecule adopts a slightly bent conformation with a fully extended alkyloxy and semi-perfluorinated chain in a smectic C-like structure. The comparison of the present structure is made with that of a similar compound of the first family with a longer alkyloxy chain (this latter crystallizes in the P1 space group with two independent molecules in the unit cell). Comparison of the molecular packing shows the importance of the chain lengths in the molecular arrangement and molecular interactions in both structures. 相似文献
100.
Simultaneous analyses of inclusive and semi-inclusive reactionns in neutrino-nucleon collisions and elastic neutrino-proton scattering uniquely determine the neutral-current couplings between neutrinos and hadrons up to a two-fold “vector-axial-vector ambiguity”. One of the preferred solutions coincides with the Salam-Weinberg model within errors while the other solution, also compatible with SU(2) ? U(1) models with the simplest Higgs mechanism, may be helpful in understanding the bismuth puzzle. 相似文献