基于DPSK调制的光学物理层网络编码安全研究

将物理层网络编码引入光网络中,研究了在3Gb/s的传输速率下基于差分相移键控(DPSK)调制的物理层网络安全编码的光网络.将两路同频信号通过光纤传输到中继,在中继处混合在一起后同时再通过光纤传给两个用户,在接收端将混合信号通过解码出来得到两个用户信号比特的异或,最后通过与其中一个用户的信息进行异或就可以得到另一个用户的信息.由于两路信号为同频信号,混合后必会发生干涉,利用DPSK将两路信号占空比分别调制为33％与67％,解决了信号混合后的干涉问题.由于在中继处两个信号混合后,发出的是两个用户的混合信号,具有一次一密效果,在利用物理层网络编码提高网络的吞吐量的同时,也增加了从中继到用户的链路的安全性.     

浅析北京市城市污水处理与再生利用

分析了目前北京市的污水处理与再生利用状况,提出一些建设性的意见,以增进对北京市及中国污水处理与再生业的认识。     

3ds Max辅助平法识图课程的教学实践

将3ds Max三维动画和平面效果制作软件引入《平法识图》课堂教学,通过介绍钢筋排布构造模型的制作方法,把构件的3D图和内部构造等直观的展现给学生,从而达到了教师方便描述,学生理解到位,计算思路明确的良好教学效果。     

Constrained multi-objective optimization using constrained non-dominated sorting combined with an improved hybrid multi-objective evolutionary algorithm

Constrained multi-objective optimization problems (cMOPs) are complex because the optimizer should balance not only between exploration and exploitation, but also between feasibility and optimality. This article suggests a parameter-free constraint handling approach called constrained non-dominated sorting (CNS). In CNS, each solution in a population is assigned a constrained non-dominated rank based on its constraint violation degree and Pareto rank. An improved hybrid multi-objective optimization algorithm called cMOEA/H for solving cMOPs is proposed. Additionally, a dynamic resource allocation mechanism is adopted by cMOEA/H to spare more computational efforts for those relatively hard sub-problems. cMOEA/H is first compared with the baseline algorithm using an existing constraint handling mechanism, verifying the advantages of the proposed constraint handling mechanism. Then cMOEA/H is compared with some classic constrained multi-objective optimizers, experimental results indicating that cMOEA/H could be a competitive alternative for solving cMOPs. Finally, the characteristics of cMOEA/H are studied.     

高层综合写字楼外部环境的整合设计

随着高层写字楼的迅速发展,其外部环境也变得复杂。本文针对西安现有高层写字楼外部环境问题,把握建筑、城市、景观和心理设计的几大原则,提出高层写字楼外部环境的整合设计,较好地解决城市交通和城市形象的问题。     

Controlled oxidative nanopatterning of microrough titanium surfaces for improving osteogenic activity

To further enhance the biological properties of acid-etched microrough titanium surfaces, titania nanotextured thin films were produced by simple chemical oxidation, without significantly altering the existing topographical and roughness features. The nanotextured layers on titanium surfaces can be controllably varied by tuning the oxidation duration time. The oxidation treatment significantly reduced water contact angles and increased the surface energy compared to the surfaces prior to oxidation. The murine bone marrow stromal cells (BMSCs) were used to evaluate the bioactivity. In comparison, oxidative nanopatterning of microrough titanium surfaces led to improved attachment and proliferation of BMSCs. The rate of osteoblastic differentiation was also represented by the increased levels of alkaline phosphatase activity and mineral deposition. These data indicated that oxidative nanopatterning enhanced the biological properties of the microrough titanium surfaces by modulating their surface chemistry and nanotopography. Based on the proven mechanical interlocking ability of microtopographies, enhancement of multiple osteoblast functions attained by this oxidative nanopatterning is expected to lead to better implant osseointegration in vivo.     

Microstructure and texture evolution in fully pearlitic steel during wire drawing

The evolution of morphology of pearlite and crystallographic texture of ferrite matrix in fully pearlitic steels during wire drawing were quantitatively investigated.The study revealed that a fiber structure of the pearlite morphology and a <110> fiber texture of the ferrite matrix begin to take shape and develop gradually with increasing strain.The growth rates of the fiber structure and the <110> texture are different in different regions within the wires with increasing drawing strain.There is a close relationship between the pearlite morphology and the crystalline texture during wire drawing.The pearlite interlamellar spacing(ILS) and thickness of cementite lamellae(T) decrease gradually both in longitudinal and transverse sections.The definition of pearlite colony should be reconsidered for describing microstructure of the wire drawing deformed pearlitic steels.     

以分子氧为氧源催化丙烯环氧化制环氧丙烷研究进展

环氧丙烷是重要的基础化工原料。主要工业生产方法有氯醇法和Halcon法。氯醇法环境污染严重 ,急待改进 ;Halcon法产生大量联产品 ,且基本建设投资巨大。为了满足环境和经济等方面的要求 ,以分子氧为氧源的丙烯催化环氧化是最理想的生产方法 ,目前正处于研究阶段。文中对近十年来的研究进展做了综述     

Synthesis of Co2SnO4@C core-shell nanostructures with reversible lithium storage

This paper reports the synthesis of Co₂SnO₄@C core-shell nanostructures through a simple glucose hydrothermal and subsequent carbonization approach. The as-synthesized Co₂SnO₄@C core-shell nanostructures have been applied as anode materials for lithium-ion batteries, which exhibit improved cyclic performance compared to pure Co₂SnO₄ nanocrystals. The carbon matrix has good volume buffering effect and high electronic conductivity, which may be responsible for the improved cyclic performance.     

表面机械研磨处理Mg-Gd-Y合金不同应变层的时效硬化行为和机理

采用表面机械研磨处理(SMAT)在Mg-Gd-Y合金中获得了梯度组织结构,通过维氏硬度计和透射电子显微镜对试样中不同应变层的时效硬化行为和机理进行了研究。结果表明,SMAT后合金表面梯度组织可以分为3层:剧烈应变层、中等应变层和无影响层。在225℃时效,不同应变层的时效硬化行为表现出明显差异。出现峰时效的时间由剧烈应变层、中等应变层到无影响层依次延长;而峰时效时的硬度增量则依次增大。这与不同应变层中沉淀相的形态、分布以及与位错等缺陷的相互作用有关。剧烈应变层显示了最短的峰时效时间和最高的峰时效硬度,说明SMAT表面纳米化对促进Mg-Gd-Y合金的时效硬化有显著效果。