微孔和介孔材料中的热化学

这篇论文综述了美国加州大学戴维斯分校科学院院士Navrotsky课题组多年来在多孔材料上取得的一系列热化学研究结果。讨论了热化学对微孔、介孔材料的结构稳定性和合成过程的影响。借助多种测热手段对影响骨架结构的热焓、热熵和自由能进行了系统的测量和计算。研究数据表明一系列纯硅分子筛、介孔材料和磷酸铝多孔材料同相应的石英相和块磷铝矿相相比能量上最多只高出15 kJ·mol-1。一系列纯硅分子筛的熵值比石英相高出3.2—4.2 J·K-1·mol-1；在0—12.6 J·K-1·mol-1范围内相对应的自由能几乎没有差别。因此，对不同微孔、介孔材料，其骨架结构在能量上是几乎没有区别的。另外，本文通过介绍一种新型测热方法——原位测热，揭示了分子筛合成过程中的动力学和成核/结晶机理。     

SAPO-34处理方法对吸附性能的影响

以二乙胺为结构导向剂, 在微波条件下合成了SAPO-34分子筛材料, 并分别在空气和氮气氛下1073 K焙烧. 考察了氮气氛下分子筛表面碳改性后对材料表面及水、甲醇和乙醇吸附性能的影响. 结果表明: 碳改性后SAPO-34比表面、孔容下降, 但孔径趋于均一. 与SAPO-34样品相比, 碳改性后SAPO-34吸水量从0.295 g/g降低到0.180 g/g, 甲醇/乙醇的吸附比从1.42提高到2.81.     

SIM卡也可复制！

大家都知道在模拟蜂窝网中，作弊者将无线电扫瞄器调谐到蜂窝控制信道上．当一个合法手机的ＭＩＮ和ＥＳＮ在空中传播时，即可将它们记录下来。通过空中电波，可以盗取成千上万的模拟手机的识别码，因此复制欺诈的规模巨大。当复制的手机使用时，被欺骗的网络相信它们是合法手机，而它们的任何呼叫将记入合法用户的帐单。有的国家的模拟移动通信运营商，欺诈损失曾经占到营业额的３０％，以至影响到了通信网的正常运营。 后来，手机升级到了数字时代，引进了比模拟机更为先进的技术，大家都一致认为数字手机非常安全了，是不可复制的。难道真的就安全了吗？下面的文章将用事实来告诉你──     

MOSFET模型＆参数提取

器件模型及参数作为工艺和设计之间的接口，对保证集成电路设计的投片成功具有决定意义。本文介绍了电路模拟中常用的几种MOSFET模型，并着重探讨了使用自动参数提取软件提取一套准确的模型参数的具体工作步骤。     

平阳县南麂岛有线电视微波联网方案和实施

随着平阳县有线电视“村村通”工程的不断推进和数字微波技术的发展,我们经过再三论证决定采用8G数字微波用QPSK调制方式,以点对点的传输来解决南麂岛的有线电视联网问题。目前传送省台、市台及本地等12套电视节目和本地调频广播节目1套.     

A meshless model for transient heat conduction analyses of 3D axisymmetric functionally graded solids

A meshless numerical model is developed for analyzing transient heat conductions in three-dimensional （3D） axisymmetric continuously nonhomogeneous functionally graded materials （FGMs）. Axial symmetry of geometry and boundary conditions reduces the original 3D initial-boundary value problem into a two-dimensional （2D） problem. Local weak forms are derived for small polygonal sub-domains which surround nodal points distributed over the cross section. In order to simplify the treatment of the essential boundary conditions, spatial variations of the temperature and heat flux at discrete time instants are interpolated by the natural neighbor interpolation. Moreover, the using of three-node triangular finite element method （FEM） shape functions as test functions reduces the orders of integrands involved in domain integrals. The semi-discrete heat conduction equation is solved numerically with the traditional two-point difference technique in the time domain. Two numerical examples are investigated and excellent results are obtained, demonstrating the potential application of the proposed approach.     

提高新型大屏幕彩电开关稳压电源效率浅析

从提高开关稳压电源的效率着眼,对新型大屏幕彩电开关稳压电源电路进行了介绍,并结合应用实例对半桥式开关稳压电源的工作原理进行了分析.     

Human motion prediction using optimized sliding window polynomial fitting and recursive least squares

Human motion prediction is a critical issue in human-robot collaboration (HRC) tasks. In order to reduce thelocal error caused by the limitation of the capture range and sampling frequency of the depth sensor, a hybrid human motion prediction algorithm, optimized sliding window polynomial fitting and recursive least squares (OSWPF-RLS) was proposed. The OSWPF-RLS algorithm uses the human body joint data obtained under the HRC task as input, and uses recursive least squares (RLS) to predict the human movement trajectories within the time window. Then, the optimized sliding window polynomial fitting (OSWPF) is used to calculate the multi-step prediction value, and the increment of multi-step prediction value was appropriately constrained. Experimental results show that compared with the existing benchmark algorithms, the OSWPF-RLS algorithm improved the multi-