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31.
In this paper we give a geometric interpretation of the notion of the horizontal mean curvature which is introduced by Danielli Garofalo-Nhieu and Pauls who recently introduced sub- Riemannian minimal surfaces in Carnot groups. This will be done by introducing a natural nonholonomic connection which is the restriction (projection) of the natural Riemannian connection on the horizontal bundle. For this nonholonomic connection and (intrinsic) regular hypersurfaces we introduce the notions of the horizontal second fundamental form and the horizontal shape operator. It turns out that the horizontal mean curvature is the trace of the horizontal shape operator.  相似文献   
32.
模拟退火法在吸收薄膜的椭偏反演算法中的应用   总被引:18,自引:4,他引:14  
将一种广泛用于求解复杂系统优化问题的技术--模拟退火法--用来求解椭偏反演方程。首先假设一个薄膜模型,计算出其相应的椭偏参数(Ψ,Δ)的值,在这个计算值的基础上加入不同标准偏差的高斯噪声;然后将加入噪声后的值(Ψm,Δm)作为模拟的测量数据,采用模拟退火算法进行求解,验证得知这种方法求得的薄膜参数很接近于假设的薄膜模型参数的真值,与其他文献的报道结果一致,而且在扩大搜寻范围时,仍然可以得到准确解,从而证明了该方法的可行性以及有效性。  相似文献   
33.
研究了Rb(5PJ)+Rb(5PJ)→Rb(nlJ')+Rb(5S)碰撞能量合并过程,利用单模半导体激光器分别共振激发Rb原子的5P1/2或5P3/2态,利用另一与泵浦激光束反向平行的单模激光束作为吸收线探测激发态原子密度及其空间分布,吸收线分别调至5P1/2→5D3/2和5P3/2→7S1/2跃迁.由激发态原子密度和谱线荧光比得到碰撞能量合并过程的截面,对5P3/2激发,碰撞转移得到5D5/2,5D3/2和7S1/2的截面分别是(1.32士0.59)×10-14,(1.18士0.53)×10-14和(3.21士1.44)×10-15cm2;对5P1/2激发,碰撞转移到5D5/2和5D3/2的截面分别是(6.57士2.96)×10-15和(5.90士2.66)×10-15cm2.与其他的实验结果进行了比较.  相似文献   
34.
Polyvinyl alcohol (PVA) nanofibers containing Ag nanoparticles were prepared by electrospinning PVA/silver nitrate (AgNO3) aqueous solutions, followed by short heat treatment, and their antimicrobial activity was investigated for wound dressing applications. Since PVA is a water soluble and biocompatible polymer, it is one of the best materials for the preparation of wound dressing nanofibers. After heat treatment at 155 °C for 3 min, the PVA/AgNO3 nanofibers became insoluble, while the Ag+ ions therein were reduced so as to produce a large number of Ag nanoparticles situated preferentially on their surface. The residual Ag+ ions were reduced by subsequent UV irradiation for 3 h. The average diameter of the Ag nanoparticles after the heat treatment was 5.9 nm and this value increased slightly to 6.3 nm after UV irradiation. It was found that most of the Ag+ ions were reduced by the simple heat treatment. The PVA nanofibers containing Ag nanoparticles showed very strong antimicrobial activity. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2468–2474, 2006  相似文献   
35.
Methylene-bridged bis-imidazolium receptor 1 has been synthesized. Anion binding studies carried out using 1H NMR revealed that this compound displayed good affinities for acetate, while binding spherical halide anions weakly.  相似文献   
36.
We consider a stowage-planning problem of arranging containers on a container ship in the maritime transportation system. Since containers are accessible only from the top of the stack, temporary unloading and reloading of containers, called shifting, is unavoidable if a container required to be unloaded at the current port is stacked under containers to be unloaded at later ports on the route of the ship. The objective of the stowage planning problem is to minimize the time required for shifting and crane movements on a tour of a container ship while maintaining the stability of the ship. For the problem, we develop a heuristic solution method in which the problem is divided into two subproblems, one for assigning container groups into the holds and one for determining a loading pattern of containers assigned to each hold. The former subproblem is solved by a greedy heuristic based on the transportation simplex method, while the latter is solved by a tree search method. These two subproblems are solved iteratively using information obtained from solutions of each other. To see the performance of the suggested algorithm, computational tests are performed on problem instances generated based on information obtained from an ocean container liner. Results show that the suggested algorithm works better than existing algorithms.  相似文献   
37.
In this paper, we give a recursive construction from an LTTS(v + 2) to an LTTS(16v + 2) for v 3. Furthermore, the existence of LTTS(2n + 2) is proved. Thereby, we completely solve the existence problem of LTTS)(v) (large set of pairwise disjoint transitive triple systems of order v).  相似文献   
38.
以~1H NMR谱学和磁化率对一些含邻苯二硫酚或巯基苯酚配体的钴化合物的磁性作了研究,并讨论了它们的电子结构。  相似文献   
39.
测定了二个顺磁性化合物(Ph_1P)[V_2(mp)_6](Ⅰ)和(Ph_4P)_2[NaV(mp)_3 (MeCN)(MeOH)](Ⅱ)(H_2mp=邻巯基苯酚,o-HO_1C_6H_4SH)的固态和/或溶液中的顺磁波谱。(Ⅰ)的77K固态谱及(Ⅱ)的室温固态谱均经模拟计算,认为它们的钒原子处在S=l/2的Ⅰ=7/2状态,(Ⅱ)的低温(77K)溶液谱(乙腈)与Ⅱ的固态谱相同,均有特征的八条精细结构,认为非配对电子基本上定域在钒原子的周围。  相似文献   
40.
We study the Bloch oscillations of two-component Bose-Einstein condensates trapped in spin-dependent optical lattices. The influence of the intercomponent atom interaction on the system is discussed in detail Accelerated breakdown of the Bloch oscillations and revival phenomena are found respectively for the repulsive and attractive case. For both the cases, the system will finally be set in a quantum self-trapping state due to dynamical instability.  相似文献   
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