SLANT SUBMANIFOLDS OF A RIEMANNIAN PRODUCT MANIFOLD

In this article, the geometry of the slant submanifolds of a Riemannian product manifold is studied. Some necessary and sufficient conditions on slant, bi-slant and semi-slant submanifolds are given. We research fundamental properties of the distributions which are involved in definitions of semi- and bi-slant submanifolds in a Riemannian product manifold.     

Subgroup separability of certain generalized free products of nilpotent-by-finite groups

In this paper, we show that certain generalized free products of nilpotent-by-finite groups are subgroup separable when the amalgamated subgroup is h× D where D is in the center of both factors.     

L（j,k）-number of Direct Product of Path and Cycle

For positive numbers j and k, an L(j,k)-labeling f of G is an assignment of numbers to vertices of G such that |f(u)-f(v)|≥j if uv∈E(G), and |f(u)-f(v)|≥k if d(u,v)=2. Then the span of f is the difference between the maximum and the minimum numbers assigned by f. The L(j,k)-number of G, denoted by λj,k(G), is the minimum span over all L(j,k)-labelings of G. In this paper, we give some results about the L(j,k)-number of the direct product of a path and a cycle for j≤k.     

f-Harmonic maps of doubly warped product manifolds

In this paper, we study f-harmonicity of some special maps from or into a doubly warped product manifold. First we recall some properties of doubly twisted product manifolds. After showing that the inclusion maps from Riemannian manifolds M and N into the doubly warped product manifold M × _μ,λ N can not be proper f-harmonic maps, we use projection maps and product maps to construct nontrivial f-harmonic maps. Thus we obtain some similar results given in [21], such as the conditions for f-harmonicity of projection maps and some characterizations for non-trivial f-harmonicity of the special product maps. Furthermore, we investigate non-trivial f-harmonicity of the product of two harmonic maps.     

基于产品生命周期的闭环供应链回收量预测方法

针对马尔科夫预测方法存在的误差,根据产品在生命周期不同阶段的特点,提出了产品生命周期转化系数和状态转移矩阵,并利用该系数和矩阵对马尔科夫预测方法进行了改进:当相邻两期的产品处于不同的生命周期阶段,用产品生命周期转化系数修正预测值.在此基础上,结合闭环供应链的物品回收特点,提出了相应的预测方法,通过算例对模型的验证与分析得出:改进后的预测方法在一定程度上提高了预测精度.     

石油产品酸值测定仪校准方法

通过分析石油产品酸值测定仪工作原理,参考相应的国家技术规范,建立石油产品酸值测定仪的校准方法。使用酸值(以KOH计)为(0.11±0.03) mg/g的酸值标准物质对以颜色指示剂法为原理的石油产品酸值测定仪进行校准,设定校准项目:示值误差为–0.01 mg/g;重复性为0.02 mg/g。对石油产品酸值测定仪示值误差测量结果的不确定度进行评定,扩展不确定度为0.04 mg/g(k=2)。该校准方法计量特性满足校准要求,可用于评价石油产品酸值测定仪的性能。     

“光纸”开启灯光新纪元

如果光也可以像纸一样打印,还能被运用到任何物体表面,你会如何使用它?来自美国的Rohinni公司发明了一种"光纸",它是一种打印光的形式,可以把光打印成任何形状,从而运用到不同物体表面和不同场景中去。是不是觉得这有点像3D打印?Rohinni公司的CMOSmoot说:"我们不知道将来光纸在相关平台上会有怎样的应用,我们所知道仅仅是如何开启制造光的大门。"     

量子点电视搭载ColorIQ光学技术

TCL多媒体和QDVision公司宣布向中国市场推出一款搭载ColorIQ光学技术的55寸4K超高清量子点电视。这款全新的电视拥有绝佳的色彩、时尚的造型以及卓越的图像表现,将很快在中国2,000多家店面开售,并将把产业带入全新的量子点显示技术时代。作为高端旗舰产品,TV+量子点电视H9700的发布是TCLTV+家庭娱乐电视家族的又一次重磅硬件升级。全新的量子点电视经QDVision公司与TCL联合开发,在     

一款教育类移动应用程序“爱猜元素”的开发

北京大学化学国家级实验教学示范中心开发了一款名为"爱猜元素"的教育类移动应用程序。它是以元素周期表为框架,"猜谜游戏"为逻辑主线,围绕元素知识及相关原理而设计的科普资源平台。本文主要介绍了该化学教育类app的设计理念、产品特点及其应用场景。