A nonlinear reaction diffusion equations for activator inhibitor systems is considered. Under suitable conditions, firstly, the outer solution of the original problem is obtained, secondly, using the variables of mult...A nonlinear reaction diffusion equations for activator inhibitor systems is considered. Under suitable conditions, firstly, the outer solution of the original problem is obtained, secondly, using the variables of multiple scales and the expanding theory of power series the formal asymptotic expansions of the solution are constructed, and finally, using the theory of differential inequalities the uniform validity and asymptotic behavior of the solution are studied.展开更多
作为解决信息过载问题的有效方式,推荐系统能够根据用户偏好对海量信息进行过滤,为用户提供个性化的推荐.但在推荐过程中,性能表现优异的协同过滤模型并没有充分利用上下文信息,这在一定程度上使系统面临性能瓶颈.为了进一步提高系统性...作为解决信息过载问题的有效方式,推荐系统能够根据用户偏好对海量信息进行过滤,为用户提供个性化的推荐.但在推荐过程中,性能表现优异的协同过滤模型并没有充分利用上下文信息,这在一定程度上使系统面临性能瓶颈.为了进一步提高系统性能,从评分上下文信息着手,通过对项目评分进行分类统计获得评分奇异性,同时借鉴多渠道扩散相似性模型将推荐系统作为用户-项目二分网络的思想,提出了融合奇异性和扩散过程的协同过滤模型(collaborative filtering model fusing singularity and diffusion process,简称CFSDP).为了表明模型的优越性,比较实验基于MovieLens,NetFlix和Jester这3个不同的数据集展开.实验结果表明,该模型不仅具有良好的扩展性,而且在合理的时间开销下,可以显著提高系统的预测和推荐质量.展开更多
The effect of Si on the growth kinetics of intermetallic compounds during the reaction of solid iron and molten aluminum was investigated with a scanning electron microscope coupled with an energy dispersive X-ray spe...The effect of Si on the growth kinetics of intermetallic compounds during the reaction of solid iron and molten aluminum was investigated with a scanning electron microscope coupled with an energy dispersive X-ray spectroscope, and hot-dip aluminized experiments. The results show that the intermetallic layer is composed of major Fe2Al5 and minor FeAl3. The Al-Fe-Si ternary phase, rl/rg, is formed in the Fe2Al5 layer. The tongue-like morphology of the Fe2Als layer becomes less distinct and disappears finally as the content of Si in aluminum bath increases. Si in the bath improves the prohibiting ability to the growth of Fe2Als and FeAl3. When the contents of Si are 0, 0.5%, 1.0%, 1.5%, 2.0% and 3.0%, the activation energies of Fe2Al5 are evaluated to be 207, 186, 169, 168, 167 and 172 kJ/mol, respectively. The reduction of the activation energy might result from the lattice distortion caused by Si atom penetrating into the Fe2Al5 phase. When Si atom occupies the vacancy site, it blocks easy diffusion path and results in the disappearance of tongue-like morphology.展开更多
为克服实验手段的不足,用分子动力学方法模拟丁羟推进剂粘接体系中增塑剂癸二酸二辛酯(DOS)的扩散行为。利用分子模拟软件Materials Studio 4.3构建增塑剂和粘接体系的分子模型,选用COMPASS力场,对经几何优化后的混合体系进行分子动力...为克服实验手段的不足,用分子动力学方法模拟丁羟推进剂粘接体系中增塑剂癸二酸二辛酯(DOS)的扩散行为。利用分子模拟软件Materials Studio 4.3构建增塑剂和粘接体系的分子模型,选用COMPASS力场,对经几何优化后的混合体系进行分子动力学模拟,得到增塑剂在粘接体系中的均方位移,通过爱因斯坦方程得到其扩散系数。环境温度为273,298,310,323,348K时,DOS在丁羟推进剂粘接体系中的扩散系数分别为0.0010,0.0020,0.0025,0.0031,0.0043;DOS含量为23%,37.5%,47%,60%时,扩散系数分别为0.0025,0.0020,0.0018,0.0015(单位10-4cm2.s-1)。结果表明:随着温度的升高,扩散系数逐渐增大;随着增塑剂含量的增加,扩散系数依次略有下降。展开更多
基金the National Natural Science Foundation of China under Grant Nos.40676016 and 10471039the National Key Project for Basics Research under Grant Nos.2003CB415101-03 and 2004CB418304+1 种基金the Key Project of the Chinese Academy of Sciences under Grant No.KZCX3-SW-221in part by E-Insitutes of Shanghai Municipal Education Commission under Grant No.E03004
文摘A nonlinear reaction diffusion equations for activator inhibitor systems is considered. Under suitable conditions, firstly, the outer solution of the original problem is obtained, secondly, using the variables of multiple scales and the expanding theory of power series the formal asymptotic expansions of the solution are constructed, and finally, using the theory of differential inequalities the uniform validity and asymptotic behavior of the solution are studied.
文摘作为解决信息过载问题的有效方式,推荐系统能够根据用户偏好对海量信息进行过滤,为用户提供个性化的推荐.但在推荐过程中,性能表现优异的协同过滤模型并没有充分利用上下文信息,这在一定程度上使系统面临性能瓶颈.为了进一步提高系统性能,从评分上下文信息着手,通过对项目评分进行分类统计获得评分奇异性,同时借鉴多渠道扩散相似性模型将推荐系统作为用户-项目二分网络的思想,提出了融合奇异性和扩散过程的协同过滤模型(collaborative filtering model fusing singularity and diffusion process,简称CFSDP).为了表明模型的优越性,比较实验基于MovieLens,NetFlix和Jester这3个不同的数据集展开.实验结果表明,该模型不仅具有良好的扩展性,而且在合理的时间开销下,可以显著提高系统的预测和推荐质量.
基金Project (51071135) supported by the National Natural Science Foundation of ChinaProject (20114301110005) supported by the Ph. D.Programs Foundation of Ministry of Education of ChinaProject (10XZX15) supported by the Science Foundation of Xiangtan University,China
文摘The effect of Si on the growth kinetics of intermetallic compounds during the reaction of solid iron and molten aluminum was investigated with a scanning electron microscope coupled with an energy dispersive X-ray spectroscope, and hot-dip aluminized experiments. The results show that the intermetallic layer is composed of major Fe2Al5 and minor FeAl3. The Al-Fe-Si ternary phase, rl/rg, is formed in the Fe2Al5 layer. The tongue-like morphology of the Fe2Als layer becomes less distinct and disappears finally as the content of Si in aluminum bath increases. Si in the bath improves the prohibiting ability to the growth of Fe2Als and FeAl3. When the contents of Si are 0, 0.5%, 1.0%, 1.5%, 2.0% and 3.0%, the activation energies of Fe2Al5 are evaluated to be 207, 186, 169, 168, 167 and 172 kJ/mol, respectively. The reduction of the activation energy might result from the lattice distortion caused by Si atom penetrating into the Fe2Al5 phase. When Si atom occupies the vacancy site, it blocks easy diffusion path and results in the disappearance of tongue-like morphology.
文摘为克服实验手段的不足,用分子动力学方法模拟丁羟推进剂粘接体系中增塑剂癸二酸二辛酯(DOS)的扩散行为。利用分子模拟软件Materials Studio 4.3构建增塑剂和粘接体系的分子模型,选用COMPASS力场,对经几何优化后的混合体系进行分子动力学模拟,得到增塑剂在粘接体系中的均方位移,通过爱因斯坦方程得到其扩散系数。环境温度为273,298,310,323,348K时,DOS在丁羟推进剂粘接体系中的扩散系数分别为0.0010,0.0020,0.0025,0.0031,0.0043;DOS含量为23%,37.5%,47%,60%时,扩散系数分别为0.0025,0.0020,0.0018,0.0015(单位10-4cm2.s-1)。结果表明:随着温度的升高,扩散系数逐渐增大;随着增塑剂含量的增加,扩散系数依次略有下降。
